f \ the small systems journal $2.40 in CANADA Jt^ MULTI-USER SYSTEM ■^ ^ OPERATES - Up to 4 terminals running INDEPENDENT programs HARDWARE TIME SHARE- Requires no modifications to computer IDEAL FOR — All multi-terminal applications The SwTPC multi-user system converts our standard 6800 single user computer into a multi-user time share system that may be operated with up to four terminals. The four terminals operate independently and may be running four different programs. No modifications to the computer are necessary, you sim- ply plug in the multi-user board and add an interface for each additional terminal. The multi-user system is ideal for program training, multi- station business applications and for computer aided in- struction (CAI). Speed reduction from a single user system is negligible because all switching is done in hardware. Multi-user BASIC, suitable for program instruction and sim- ple business applications, is included with the multi-user board. An 8K disc BASIC is also available for systems in which disc drives are used. This software has a complete nine digit floating point math package, full string features and data files. For computer aided instruction applications, a full feature version of PILOT is available. It includes math operators, misspelling match features and all other proposed for the ANSI! standard version. The 6800 multi-user system is just as economical, but far more flexible and powerful than multiple small machines for CAI applications. MUB-68 Multi-User Board and BASIC Software Assembled and tested $150.00 Kit $129.95 SOUTHWEST TECHNICAL PRODUCTS CORPORATION 219 W. RHAPSODY SAN ANTONIO, TEXAS 78216 Circle 350 on inquiry card. .4 Model Z-2 Up to 51ZK of RAM/ROM Fill your Model Z-2D One or two disks Up to 512K of RAM/ROM Up to 184K of disk kill System Two Dual disk Up to 512K of RAM/ROM Up to 184K of disk needs with the indiistryls mostprofessloiial :¥A ii ■ #1 IN RELIABILITY When you choose Cromemco you get not only the industry's finest microcomputers but also the indus- try's widest microcomputer selec- tion. What's more, you get a computer from the manufacturer that compu- ter dealers rate #1 in product re- liability.* Your range of choice includes our advanced System Three with up to four 8" disk drives. Or choose from the System Two and Z-2D with 5" drives. Then for ROM-based work there's the Z2. Each of these com- puters further offers up to V2 mega- byte of RAM (or ROM). We say these are the industry's most professional microcomputers because they have outstanding fea- tures like these: • Z-80A microprocessor — oper- ates at 250 nanosecond cycle time — nearly twice the speed of most others. 'Rated in The 1977 Computer Store Survey by Image Resources, Westlake Village, CA. Up to 512 kilobytes of RAM and 1 megabyte of disk storage System Three Two to four disks Up to 51 2K of RAM/ ROM Up to 1 megabyte of disk 21 card slots to allow for un- paralleled system expansion us- ing industry-standard S-100 cards. S-100 bus — don't overlook how important this is. It has the in- dustry's widest support and Cro- memco has professionally imple- mented it in a fully-shielded design. Q • Cromemco card support of more than a dozen circuit cards for process control, business sys- tems, and data acquisition in- cluding cards for A-D and D-A conversion, for interfacing daisy- wheel or dot-matrix printers, even a card for programming PROIVIs. • The industry's most professional software support, including FOR- TRAN IV, 16K Disk-Extended BASIC, Z-80 Macro Assembler, Cromemco Multi-User Operating System — and more coming. • Rugged, professional all-metal construction for rack (or bench or floor cabinet) mounting. Cab- inets available. FOR TODAY AND TOMORROW Cromemco computers, will meet your needs now and in the future because of their unquestioned tech- nical leadership, professionalism and enormous expandability. See them today at your dealer. There's no substitute for getting the best. see next Circle 80 on inquiry card. Crontenteo Incorporated Specialists in computers and peripherals 260 BERNARDO AVE., MOUNTAIN VIEW, CA 94040 • (415) 964-7400 BYTE )ulv 1978 SEE YOUR LOCAL DEALER Anchodie. AK 99501 ALASKA DIVERSIFIED DIGITAL ITOOWniHiiKDAvtrnw (907) 2T7-63I2 Hunlwllle. AL31WS COMPUTERLAND OF HUNTSVILLE 3020 Unlvcrlily Drtvi. N.W. (20S) 539-1200 *Llltle Rock, AR 72206 COMPUTER PRODUCTS UNLIMITED 2412Si>uihBr(Mdwiv {501) }T1 4)449 Ph«ni>..AZ 85021 COMPUTER RESEARCH CORP ZZ25 W Mm. View Ro^ - No, G (601)943-ST19 PhMnU,AZB5029 COMPUTER WORLD 2230 Wnl LirkxHir [6021 943-S925 laaan.Kiii'oraiSnt 8VTE SHOP OF TUCSON 26T2 E»t B'Bxfwiv (602) 327-4579 • CuKin, CA 90746 SUNSHINE COMPUTER COMPANY 20710 Soulh Ltapwood AMOue (213)327.2118 BYTE SHOP SACRAMENTO 6041 Gi«enbick Low (91G|961.BYTE El Cerrllo, CA 94530 COMPUTERLAND EL CERRITO 1 1074 Sm Piblo Avenue (415)233-5010 • FMinUin Valley, CA 92708 ADVENTURES IN COMPUTING 8TS6 WiriKi Avtniw (714) 848-83SS FrtMio, CA 93703 BYTE SHOP OF FRESNO 3139 t. McKinley Axniw (209)485-2417 Hiy*iid, CA 94S42 COMPUTERLAND OF HAYWARO 22634 Foothill Boulevird (415) 138-8080 ALGORITHM PERSONAL COMPUTERS 7561 RhiTw Drive (714)751-8080 lotfcwood, CA 90302 COMPUTERLAND OF W. LOS ANGELES 6840 Li CIciHii Boulcvird (213) 776-8080 Lawndile. CA 93060 BYTE SHOP OF LAWNDALE 6S08 Hiwlhomc Boulrvud (2131371 2421 •Lownti. CA 95650 KINGMONT ENTERPRISES. INC. 9900 KIni Roid (916)988-8189 Los AnidM, CA 90025 AMERICAN RECORDER COMPANY 1655 Siwlclle Boulevard (213)477-2063 McnIoPirk.CA 94025 COMPUTADATA PROCESSING SERVICE 2225 Shiion Roid - No. 224 MlulonVlefo.CA 92630 COMPUTERLAND SADDLEBACK VLV 24001 Vij FjbrkBiM ~ No 904 (714)7700131 • Mounutn Virw. CA 94040 BYTE OF Mt VIEW 1063 W El Cjmino Reil (415)969-5464 Oiutft. CA 92667 COMPUTER MART 633-a W«l KiltUt Bojlnard {714)633.1222 Palo Alto, CA 94306 BYTE SHOP PALO ALTO 2227 El Camino Rnl (415) 327-8080 Palo Alio. CA 94301 MICROTECH EXPORTS 912Cowp« SliHi (415)328-1712 Paud>ni,CA9ll01 BYTE SHOP PASADENA 496 South Lake Avenue (213)684-3311 Placcrville, CA 95667 GRANITE BUSINESS SYSTEMS 670 Plcaunl Valley Rud (916)626-1161 Sacramento, CA 95816 MICROCOMPUTER APPLICATIONS SYS 2322 Capital AMniM (916) 433-4944 San Diego. CA 92211 COMPUTERLAND OF SAN DIEGO 4233 Canroy Street (714) 560-9912 THE CW4PUTER CENTER 8205 Ronton Road (714) 192-5302 San Fran(lico,CA 94105 COMPUTERLAND OF SAN F RANCISCO 117 Fremont Street (415) 546-1592 • San FranclKO, CA 94103 THE COMPUTER STORE OF S.F. 1093 Motion Street (415)431-0640 SanFraiH:iico.CA9411S THE NETWORK: 495 Third Avenue -No. 8 (415)221-1112 •DENOTES SYSTEM THREE' DEALER San Joie.CA9SI14 BYTE SHOP Mi ol SAN (OSt 2626 Union Avenue (408) 377-4685 San|ote.CA95123 THE COMPUTER ROOM I24-HBIaiiamHi1l Road (408) 226-8383 San(o»e,CA'9S132 PLANE DATA WORKS 3 584 Minio Court (408) 2624566 (415)895-9363 • San Mateo, CA 94401 COMPUTER TERMINAL 309 S. San Maleo Drive (415) 347-9894 * Sania Ana, CA 92705 ADVANCED MICROCOMPUTER PROD 1310 £aii Edinger (714)558-881) Santa Oar a. CA 95051 THE BYTE SHOP OF SANTA CLARA 3400 El Cam.no Real (408) 249-4221 THE COMPUTER STORE BZO Broadway (213)451-0713 Sunnwak. CA 94086 BYTE INDUSTRIES 910 W Miudf (415)719-8000 RECREATIONAL COMPUTER CENTER 1324 South Mary Avenue (408) 712-)1IH Tinlin. CA 92680 COMPUTERLAND OF TUSTIN 104 Weil Flrtl Street (714) 544-0542 •Van Nuyi.CA 91411 COMPUTER COMPONENTS 5848 Sepulveda Boulevard Walnut Creek. CA 94596 BYTE SHOP COMPUTERS OF DIABLO VLY 2989 N Main Street (415)933-6152 EnflewDod, CO 80110 BYTE SHOPOF ARAF _ _ 3463 South Acoma Street (101) 76I4IZ1 Fairfield, CT*06430 COMPUTERLAND OF FAIRFIELD 2475 Black Rock Turnpike (203) 374-2227 WindMTLockt.CT 06096 THE COMPUTER STORE 61 South Main Street (203) 6174188 Newark. DE 19711 COMPUTERLAND OF NEWCASTLE CITY ^ttro Shopping Cenler Kirkwood Highway (302) 738-9656 Ft. Laudt.dak, FL J33J4 BYTE OF FT LAUDERDALE 1044 E Oakland Park Blvd. (105) 561 2983 Ft. Lauderdale, FL 13312 COMPUTERS FOR YOU, INC, 3608 W Broward Blvd. (305) 581-8945 • Ft Meyert.FL 33901 MICROCOMPUTER SYSTEMS, INC 12800 US 41 South (813)481-3376 Planlallon.FL 33317 COMPUTERAGE 1400 SW. 70th Avenue (305) 791-8080 (813) 879-4225 • Atlanta, GA 30340 ATLANTA COMPUTER MART S09t-B Buford Highway Marietta, GA 30060 EDUCATIONAL DATA SERVICES 79 On ford Road •Halku.Maui, HI 96708 CAPACITY, INC P,0. Box A (808) 5752930 •Honolulu. HI 96815 COMPACT COMPUTERS 305 Royal Hawaiian, Ste. 407 18081 373 2751 Kiilua, Oahu, HI 96734 MICROCOMPUTER ENTERPRISES 1450 Mokulua Drive (808) 261-3281 Arlington Heigh ti, IL 60004 COMPUTERLAND ARLINGTON HTS. 50 Eati Rand Road (112)255-6488 Champaign, I L 61820 BYTE SHOP CHAMPAIGN 1602 S Neil Street [217)352-2313 Chicago. IL 60632 BRONSON 1 BRATTON. INC. 5161 S. Millard Avenue (312)735«20D Lide.lL 60532 COMPUTER A CONTROL AFFILIATE 4315 A>aiea.No.40l 1312)9684548 Lombard. IL 60148 MIDWEST MICROCOMPUTERS, INC, 708 South Main Street (312) 495-9889 Napcrvillt, IL 60540 ILLINI MICROCOMPUTERS 61 2 Eati Olden Avenue (312)420UI3 NHet. IL 60648 COMPUTERLAND NILES 9511 N. Milwaukee Avanut (311)967.1714 BYTE luly 1978 □ Oak Lawn. IL 60453 COMPUTERLAND OF OAK LAWN 10935 Soulh Citno Avenue (312)422-8080 Roeet (911)649.5942 Lexington, KV 40501 DATA DOMAIN OF LEXINGTON 506-1/2 Euclid Avenue (606) 233-3346 Louifville, KY 40222 COMPUTERLAND OF LOUISVILLE 813-8 Lyndon Lane (502) 425-8308 Louisville. KY 40220 DATA DOMAIN OF LOUISVILLE 3028 Hunlinger Lane (502) 456-5242 Louisville, KV 40206 PRAGMATECH 2310 Hellwnod Avenue (S02) 89!-1230 •Surtington, MA 01803 THE COMPUTER STORE (617)272-8m College Park. MD 20740 INTELLIGENT BUSINESS MACHINES 7318 Baltimore. Avenue. Suite 100 (301 ) 779-7998 • P>kesville.MD21108 MODULAR SYSTEMS, INC 4005 Seven Mile Lane (301)4844322 • Rockville, MD 20852 COMPUTER WORKSHOP 1776 east ttfferMn (301)468-0463 Rockville, MD 20855 COMPUTERLAND Of GAITHERSBURG 16065 Frederick Road. Route 355 (301) 948-7616 Silver SpCing. MD 20901 CAM ENGINEERING. INC 9318 Worth Avenue (301) 589-1779 •Tow«>n.MO*2I204 COMPUTERS ETC. 1 3-A Allegheny Avenue (301) 296-0520 Ann ArtKH, Ml 48104 NEWMAN COMPUTER EXCHANGE 1250 North Main Sirect (113) 994-4445 Ann Arboi, Ml 48104 THE COMPUTER STORE Ann Arbor. Ml 48104 UNITED MICROSYSTEMS CORP 2601 South SUie Sireel (313) 6684806 •Berrien Sprinp. Ml 49103 THE ABACUS Route No 1, Box 191.(Nilet Avenue) (616) 429-3034 Grand Rapidt. Ml 49508 )EPSAN. GROUP K 4706 Morningtlde Drive. S.E. (616)698-9057 Royal Oak, Ml 48073 COMPUTER MART OF ROYAL OAK 1800 Weil 14 Mile Road (313)576-0900 Edina, MN 55435 COMPUTER DEPOT, INC 3511 Wnf 70th Street (612) 927-5601 Chettertield. MO 63017 COMPUTER SYSTEMS CTR ST. LOUIS 13461 Olive Boulevard (314) 576-5020 COMPUTERLAND OF NASHUA 419 Amhertt (603) 889-5238 Hoboken. N) 07030 HOBOKEN COMPUTER WORKS No, 20 Hudson Place (201)420-1644 •itelln.NI 08830 COMPUTER MART OF NEW JERSEY 501 Rout* No 27 (201) 2834)600 Morriiio 1978 § §!• ly Circle 305 on inquiry card. Letters DESIGNERS BEWARE: SOME 2716 CONFUSION I just came across a very untidy situ- ation involving read only memory num- bers which may be of interest to a great number of readers. We are all familiar by now with the advantages of the 2716 erasable read only memory; however, everyone should be aware that while the Intel version (and possibly others) re- quires only a single +5 V supply, Texas Instruments makes a similar device with identical memory organization, number TMS2716 that requires ±5 V and +12 V supplies. This part is designed to be pin compatible with the older 2708s. Texas Instruments has another part labeled TMS2516 which is pin compatible with an Intel type 2716, requiring only a +5 V supply. While this is assuredly somewhat bizarre, there seems to be argument amongst the two companies as to who claimed the name 2716 first. It is definitely something that many will be in need to be aware of. David Marke Solar Dynamics Ltd 3904 Warehouse Row, Suite C Austin TX 78704 HOW TO STAY IN CIRCULATION I was somewhat astonished (an un- derstatement) to find, wrapped in the splendor of the March 1978 (I think) plain brown BYTE wrapper, an April 1978 Playboy. Now don't get me wrong, I enjoy looking at lovely ladies; in fact it is one of my most time consuming hobbies. However, 1 can pick up Hef's rag anywhere in Ottawa, and right now my computer needs more tips on oper- ating than I do. So, if you would, I'd appreciate an issue of BYTE that matches the enclosed mailing sticker. Thank you. Kevin Szabo Box 86, Hillcrest Dr RR #1, Manotick Ontario CANADA KOA 2N0 WHERE TO GETTECO Carl Helmers' editorial in the March 1978 BYTE, page 6, was interesting to me, since the LSI-11 can run the RT11 operating system, for which there is a version of real TECO (a superset of the old PDP6/PDP10 TECO) with most or all of the features he wants, plus ability to use floppies, etc. Sources for said TECO are available from DECUS for a minimal charge. I've worked on the Continued on page 120 YOURS FOR ONLY ^149.95 Now, the first complete software oriented video system (theVB-IB.) is even morG versatile. The newly improved VB-1B Video Interface Board gives you 128 possible characters to play with. Graphics galore. Horizontal and vertical oscillators that operate within 1.6% of actual TV standards to get rid of wiggle, rolling and jitters. The VB-1B cuts snow by up to 50% and provides 8% left and right margins. And we'll give you a "Doodle" program so you can play around with graphic shapes on your own screen. Easy connection and adjustments . . , with the new VB-1B. Available— along with all our other S-100 bus compatible products— either from your local computer store or from us diroctiy. r^r CI iu i.^.^L 2116 Walsh Avenue B 95050 Circle 335 on inquiry card A Division of Solid State Music Telephone (408) 246-2707 |uly 1978eiBYTt Publications Inc 11 ,■4 KIMER: A KIM-1 Timer Listing J: Combination digital cloc/i and timer program written for tine MOS Teclinology KIM-1 computer. The LED readout is used to display hours, minutes and seconds. Address Hexadecimal Label Op Code Comments Code 00 00 00 SETHR: #00 01 00 SETMIN: #00 02 00 CNTR; #00 02 00 A5 00 START: LDA SETHR Set starting time. 02 02 85 FB STA POINTH 02 04 A5 01 LDA SETMIN 02 06 85 FA STA POINTL 02 08 A9 00 LDA #00 02 OA 85 F9 STA INH 02 OC 8D 03 17 STA 1703 Set PB7 as input. 02 OF A9 04 LDA #04 Set timer loop count. 02 11 85 02 STA CNTR 02 13 A2 20 TIMER: LDX #20 Timer calibration. 02 15 CA DELAY: DEX 02 16 DO FD BNE DELAY 02 18 A9 F1 LDA #F1 Start timer. 02 1A 8D OF 17 STA 170F 02 ID 20 IF IF WAIT: JSR SCANDS Display current time. 02 20 2C 07 17 BIT 1707 Wait for timer interrupt. 02 23 10 F8 BPL WAIT 02 25 C6 02 DEC CNTR Decrement counter. 02 27 DO EA BNE TIMER Finish second timeout. 02 29 F8 SEP Set decimal mode. 02 2A 18 CLC Clear carry. 02 2B AO 00 LDY #00 02 2D A5 F9 LDA INH Get seconds. 02 2F 69 01 ADC #01 Add 1. 02 31 85 F9 STA INH 02 33 C9 60 CMP #60 Check if next minute. 02 35 FO 04 BEQ MIN Branch if yes. 02 37 A2 19 LDX #19 Set delay count. 02 39 DO 23 BNE SET Wait for next timer start 02 3B 84 F9 MIN: STY INH Clear seconds. 02 3D 18 CLC 02 3E A5 FA LDA POINTL Get minutes. 02 40 69 01 ADC #01 Add 1. 02 42 85 FA STA POINTL 02 44 C9 60 CMP #60 Check if next hour. 02 46 FO 04 BEQ HRS Branch if yes. 02 48 A2 14 LDX #14 Set delay count. 02 4A DO 12 BNE SET Wait for next timer start 02 4C 84 FA HRS: STY POINTL Clear minutes. 02 4E A2 10 LDX #10 Set delay count. 02 50 18 CLC 02 51 A5 FB LDA POINTH Get hours digits. 02 53 69 01 ADC #01 Add 1. 02 55 85 FB STA POINTH 02 57 C9 24 CMP #24 Check if next day. 02 59 DO 03 BNE SET Branch if not. 02 5B 84 FB STY POINTH Clear hours. 02 5D CA DEX Adjust delay count. 02 5E D8 SET: CLD Clear decimal mode. 02 5F A9 04 LDA #04 Reset loop count. 02 61 85 02 STA CNTR 02 63 4C 15 02 JMP DELAY Start next cycle. Robert Baker 15 Windsor Dr Atco NJ 08004 This short program converts your KIM-l into a 24 hour digital clocl< and illustrates the use of the built-in timer for long time delays, and the use of instruction loops for shorter delays. The 7 segment displays are used for output, and are used in con- junction with one of the routines in the read only memory which drives them. To use the internal timer, 10 pin PB7 of 6530-003 must be set as an input pin to allow testing of the timer interrupt. This is accomplished by setting bit 7 of the direc- tion register (location 1 703) to before using the timer. The timer is started by loading it with the desired delay count, and the address used determines the timer frequency and whether or not to enable the timer interrupt. Bits and 1 of the address select the timer frequency as 1, 8, 64, or 1024 us per timer count while bit 3 enables the timer interrupt if set to 1 . This clock program uses the internal timer for a time delay of approximately 250 ms. After four time delays (1 second), the current time is incremented by 1 and the timing cycle continues. Whenever the time count is being incremented, instruction timing delays are added where needed to keep all time delays constant for whatever program route is taken. An additional instruction delay is added within the 1 second timer to calibrate the timer to exactly 1 second. If your system clock is slightly slower or faster, you may have to adjust the timer count (location 0219) for about 1 ms increments and the calibration count (location 0214) for 4 jis increments. To set the clock, enter the desired start- ing time hours in location 0000 and minutes in location 0001. To start the clock, set the program starting address (0200) and depress "GO" at the desired starting time (as set in locations 0000 and 0001). If the starting time is set as 0000 (hours and minutes), the program can be used to measure elapsed times for special applications by using the "ST" button to stop the program. For even fancier applications, you can add testing of an external switch to start and stop the clock. If you would rather have a 12 hour clock, simply change the contents of loca- tion 0258 from 24 to 1 2.» «: > * I 12 July 1978 O BYTE Publication! Inc Hie Computer for the Professional The 8813 was built with you, the professional, in mind. It quickly and easily processes cost estimates, payrolls, accounts, inventory, patient/ client records and much more. You can write reports, briefs, and proposals on the 8813's typewriter keyboard, see them on the video screen, and instantly correct, revise, or print them. Using the 8813, one person can process what would normally require many secretaries, several bookkeepers, and a great deal of time. And data storage takes a small fraction of the space used by previous methods. You don't need to learn complicated computer lan- guages. The 8813 understands commands in EngUsh. If you want to write your own programs, the 8813 includes a simple computer language, BASIC, that you can master in a few days. The 8813 slashes the professional's overhead. It's a powerful time and money-saving ally. Prices for complete systems including printer start at less than $8,000. See the 8813 at your local dealer or contact PolyMorphic Systems, 460 Ward Drive, Santa Barbara, California, 93111, (805) 967-0468, for the name of the dealer nearest you. PolyMorphic Systems BYTE July 1978 13 WliyApplel] St selling pei h the VTorlcTs l>iial comimter. rhich personal computer will be most enjoyable and rewarding for you? Since we delivered our first Apple® II in April, 1977, more people have chosen our computer than all other personal computers combined. Here are the reasons Apple has become such an overwhelming favorite. Apple is a fully tested and assembled mainframe computer. You won't need to spend weeks and months in assembly. Just take an Apple home, plug it in, hook up your color TV* and any cassette tape deck — -and the fun begins. To ensure that the fun never stops, and to keep Apple working hard, we've spent the last year expanding the Apple system. There are new peripherals, new software, and the Apple II Basic Programming Manual. And wait till you see the Apple magazine to keep owners on top of what's new. Apple is so powerful and easy to use that you'll find dozens of applications. There are Apples in major universities, helping teach computer skills. There are Apples in the office, where they're being programmed to control inven- tories, chart stocks and balance the books. And there are Apples at home, where they can help manage the family budget, control your home's environ- ment, teach arithmetic and foreign languages and, of course, enable you to create hundreds of sound and action video games. When you buy an Apple II you're investing in the leading edge of tech- nology. Apple was the first computer to come with BASIC in ROM, for example. And the first computer with up to 48K bytes RAM on one board, using advanced, high density 16K devices. We're working to keep Apple the most up-to-date personal computer money can buy. Apple II delivers the features you need to enjoy the real satisfaction a personal computer can bring, today and in the future. * & hi-resolutjon « graiihics.too. Don't settle for a black and white display! Connect your^ Apple to a color TV and BASIC gives you instant , command of three display modes: Text, 40h x 48v * Color-graphics in 15 colors,, and a 280h x 192v High Resolution " array that lets you plot graphs and compose ' 3-D images. ^ Apple gives you the added- capability of combining text and graphics, too. Back to basics, and assembly lan^ua^ too. Apple speaks three languages: fast ^ integer BASIC, floating point BASIC ^ for scientific and financial applications, and 6502 assembly language. That's ■" maximum programming flexibility. And, a to preserve user's space, both integer BASIC and monitor are permanently stored in 8K bytes of ROM, so you < have an easy-to-use, universal language instantly available. BASIC gives you graphic commands: COLOR=, VLIN, ^ HLIN, PLOT and SCRN. And direct memory access, with PEEK, POKE and CALL commands. -• Software: Oufs and yotns. There's a growing selection of pre- programmed software from the Apple , Software Bank — Basic Finance, Checkbook, High Resolution Graphics and more. Now there's a User Section in our bank, to make it easy for you to obtain programs developed A / ^ by other Apple owners. Our Software Bank is your link to Apple owners all over the world. Alive with the sound of music. Apple's ex- clusive built-in speaker delivers the added dimension of sound to your programs. Sound to compose electronic music. Sound to liven up games and educational programs. Sound, so that any program can "talk" back to you. That's an example of Apple's "people compatible" design. Another is its light, durable injection- molded case, so you can take Apple with you. And the professional quality, typewriter-style keyboard has n-key rollover, for fast, error-free operator interaction. Apple is tiie proven computer. Apple is a state-of-the-art single board computer, with advanced LSI design to keep component count to a minimum. That makes it more reliable. If glitches do occur, the fully socketed board and built-in diagnostics sim- plify troubleshooting. In fact, on our assembly line, we use Apples to test new Apples. *Apple II plugs into any standard TV using / an inexpensive modulator (not included). *ln California, call 408/996-1010. 4 Apple peripherals are smart peripherals. Watch the far right column of this ad each month for the latest in our grow- ing family of peripherals. We call them "intelligent interfaces." They're smart peripherals, so you can plug them in and run them from BASIC without having to develop custom software. No other personal computer comes close to Apple's expandability. In addi- tion to the built-in video interface, cas- sette I/O, and four A/D inputs with two continuously variable game paddles, Apple has eight peripheral slots, three TTL inputs and four TTL outputs. Plus a powerful, state-of-the-art switching power supply that can drive all your Apple peripherals. Available now. Apple is in stock and ready for delivery at a store near you. Call us for the dealer nearest you. Or, for more details and a copy of our "Consumer's Guide to Personal Computers," call 800/538-9696** or write Apple Computer, Inc., 10260 Bandley Drive, Cuper- tino, CA 95014. ulry card. g|npplG computer Programming is a snap! I'm halfway through Apple's BASIC manual and already I've programmed my own space wars game. Those math programs I wrote last week- 1 just rewrote them using Apple's mini-assembler and got them to run a hundred times faster New from Apple. Introducing Disk IP : instant access to your files. Our newest peripheral is Disk II, a high-deiisity 5V4" floppy disk drive for fast, lowcost data retrieval. It's perfect for storing large bodies of data such as household finances, address files and in- ventories; you can find any record in just half a second. No more searching through stacks of cassettes; with a few keystrokes, your system will load, store and run any file by name. Disk II consists of interface cards and fourteen drives, for control of nearly 1.6 megabytes of data, with no expansion chassis. The com- bination of ROM-based bootstrap loader and an operating system in RAM provides complete disk handling capability, includ- ing these special features: • Soft sectored • Random or sequential file access • Program chaining capability • Universal DOS command processor works with existing languages and monitor • Full disk capability in systems with as little as 16K RAM • Storage capacity : 113 kilobytes/diskette. See Disk II now at your Apple dealer. Sold complete with controller and DOS at $495.t Peripherals in stock Hobby Board (A2B0001X), Parallel Print( Interface (A2B0002X), Communication Ii terface (A2B0003X), Disk II (A2M0004X Coming soon High speed Serial Interface, Printer II, Printer IIA, Monitor II, Modem IIA. ' Price subject to change without notice. Circle 1 5 on inquiry c Apple's smart peripherals make expansion easy. Just plug 'em in ai they're ready to run. I've already added two disks, a printer and f^ communications card. The Second West Coast Computer Faire Photo 1: Some of the 14,000+ crowd amble by a young hacker program- ming music on a Video Brain computer. By Chris Morgan, Editor San Jose was the place to be last March 3, 4 and 5 for the Second West Coast Com- puter Faire. The Convention Center was easily able to handle the crowd of 14,169 who came to see the latest developments in personal computing. A quick examination of some of the hun- dreds of manufacturers' booths revealed some trends: floppy disks are on the in- crease, with new models being shown or promised by Heathkit, Apple, Radio Shack and many others; more and more personal computers are now being offered with built- in floppy disks; peripherals and add-ons are 2: Robot trials at mabyte booth, a attraction at the West Coast Com- re. ,rd. id e it f 13: IBM's booth, an [us addition to the ■4 ^ .^,. ., I Circle 351 on in"" ^eliSblc business pro !*■" (♦**>**'■ mmfmi^mncse fV/IAISIMAI. 1(1.*«T11» V*"' -> > ;;::::ra;:;;;;;T:=- -^ .'.VlK'tV ^'1 K.ith Persons P^^;^^-;^^^^,5^^,,„p,„.nt A"«^J£. to USl' '>!'>'■' ' .,. una to no,u'- VV'^' ^^^*;f;^\5, avaUabU' to pro^ > t.chnuaUss>sta>K. ^ ^^^^ ,,,,,,. uvr.ntK:^ ,,-lud..-. ^ifJ-*''),\) inu. ana Aaav.ss b U (If udured l^sXetta 6c All svstenis are conip. ^.^0 ,v 8oao Photo 4: Ira Baxter's chess playing system dis- play, which competed in the Microcomputer Chess Tournament at the Faire. \ ^ ri Photo 5: Apple Computer's new minifloppy drive. 's Larry Weinstein displays Star Wars graphics. now available for a wide variety of computer buses. I enjoyed the many special features of the show, particularly the excellent computer generated art on display in the lobby. The microcomputer chess tournament proved to be one of the hits of the show. Larry Wagner from Atari presided over the 3 day battle of the processors, taking time out to give me a guided tour of the tournament. The level of play was impressive, and the winning pro- gram, called S ARGON, was a 16 K byte Z-80 assembler program written by a hus- band and wife team, Kathe and Dan Spracklen. It beat some highly touted com- ♦ ^jmmm U P^ --"— , t. ^^^^^^^y ^ fi ^^^^^^^^^^ f^t . . . in software too! Hardware. Software. Peripherals. We've got the best in the business! P.O. Box 6528 Denver, CO 80206 (303) 777-7133 Photo 7: Heath's new H27 dual floppy drive, sched- uled to be available later this year. .1 4 Photo 8: Students from Mills College Center for Contemporary Music in Oakland demonstrate- a digital and analog hybrid music synthesizer system, one of many special exhibits at the Faire. petition. (A copy of the SARGON program is available for $15 postpaid from the SpraclIMMI«IIIMIIMIMMIIIIII)M The North Star 16K RAM board is a star performer in our HORIZON computer. Just as important, it is the ideal memory for most other S-100 bus systems. No other RAM board can surpass the speed, reliability, and quality features of the North Star 16K RAM at any price. SPEED — The North Star 16K RAM is the fastest S-100 bus memory board available. No wait states are required, even with a Z80 at 4MHz. And, of course, this outstand- ing 16K RAM will operate with both 8080 and Z80 proc- essors at 2MHz. Industry standard 200ns dynamic RAM chips are used. Invisible on-board refresh circuitry allows the processor to run at full speed. RELIABILITY — The North Star 16K RAM is designed to match the same high standards as our MICRO DISK SYSTEM and HORIZON computer. For example, all ad- dress and data signals are fully buffered. A parity check option is available with the 16K RAM for applications re- quiring immediate hardware error detection. If a memory error occurs, a status flip/flop is set and an interrupt can inform the processor. Or, if preferred, an error status light will go on. FEATURES —The North Star 16K RAM offers many de- sirable features. Addressability is switch-selectable to start at any 8K boundary. The board can perform bank switching for special software applications, such as time- sharing. Also, bank switching can be used to expand the amount of RAM beyond 64K bytes. Power consumption is minimal — the maximum power requirements are: .6A @ 8V; .4A @ -h16V, and .1A @ -16V. PRICES — $399 kit. $459 assembled, tested and burned- in. Parity option: $39 Kit. $59 assembled, tested and burned-in. Write for free color catalog or visit your local computer store. North Star * Computers 2547 Ninth Street • Berkeley, California 94710 • (415) 549-0858 Circle 285 on inquiry card. BYTE luly 1978 21 fe,*f;.'> .■:'-•■ Apfrficatlons Programs for your p®fs programs available. j^ Soon you'll see G2 program tapes in many other fields of interest Including advanced programs to challenge [ the interest of even the most serious computer usen The G2 IVogram i Library is available for most popular brands of personal computers. Just select the package marked for the computer you own. Start building your G2 Program Library now. And put the full power of your computer to . work for you. THE REASON ^ YOU BOUGHT ^ YOUR COMPUTER. I CRT A product of GRT Corporation Custom Products Division 1286 North Lawrence Station Road r^^ „i„ i/io „ • _i nn Sunnyvale, California94086 Circle 148 on inquiry card. BYTE |uiy W8 23 There's an Ohio Scientific dealer near you. ALABAMA M.C.S. Corp. Pelham Mall Pelham, AL 35124 (205)663-1287 ALASKA Scientific Business Instr's 500 W. 27th Anchorage, AK 99503 (907) 277-2650 CALIFORNIA Expansion Techniques 2534 Ganesha Altadena, CA 91001 (213) 794-0476 Shuey Aircraft 1009 E. Vermont Anaheim, CA 92805 (714)991-3940 Olson Electronics 11332 East South Cerritos, CA 90701 (213)860-0060 Computer Power 1276 Via Rancho Escondido, CA 92025 (714)746-0064 Adventures in Computing 8756 Warner Fountain Valley, CA 92706 (714)848-8388 Olson Electronics 4642 West Century Inglewood, CA 90304 (213)674-5740 Olson Electronics Kearny Mesa, 4840 Convoy San Diego, CA 92111 (714)292-1100 Systems Engineering 900 3rd Street San Francisco, CA 94107 (415)777-3150 Olson Electronics 2125 El Camino Real Santa Clara, CA 95051 (408) 248-4886 COLORADO Total Data Systems 125 Fairway Lane Fort Collins, CO 80521 (303)491-5692 Tricomp/Computer Country 7115 N. Federal Westminster, CO 80030 (303) 426-7743 Delaware Microsystems 92 East Main #1 Newark, DE 19711 (302) 738-3700 (after 7 PM) FLORIDA Olson Electronics 5833 Ponce de Leon Coral Gables, FL 33146 (305) 666-3327 Olson Electronics 1644 N. E. Second Miami, FL 33132 (305)374-4121 Calculator Place 12 South Orange Sarasota, FL 33577 (813)366-7449 Olson Electronics 6901 22nd Avenue, N, Tyrone Square Mall St. Petersburg, FL 33710 (813)345-9119 Olson Electronics 1215 South Dale Mabry Tampa, FL 33609 (813)253-3129 GEORGIA Electronic Information 120 Heatherwood Athens, GA 30601 (404) 353-2858 Secom Systems 5241-F New Peach Tree Chamblee, GA 30341 (404) 455-0672 Olson Electronics 2571 N. Decatur Decatur, GA 30033 (404) 378-4201 HAWAII Small Computer Systems 3140 Wailalae Honolulu, HI 96816 (808) 732-5246 ILLINOIS American Microprocessors 1100 E. Broadway Alton, IL 62002 (618)465-4489 Tech-Tronics 714 S. University Carbondale, IL 62901 (618)549-8495 Adonis Computing 2855 W. Nelson Chicago, IL 60618 (312)463-0847 Electronic Systems 611 N.Wells Chicago, IL 60610 (312)944-6565 Olson Electronics 4101 N. Milwaukee Chicago. IL 60641 (312)545-7336 Olson Electronics 1734 0gden Downers Grove, IL 60515 (312)852-9650 A & H Associates, Ltd. 2530 Crawford Evanston, IL 60602 (312)328-2800 No-Name 2701 Grand Galesburg, IL 61401 (309)343-6135 CompuTermlnal Systems, Inc. 1132 Waukegan Glenview, IL 60025 (312) 724-3690 Tek-Aids Industries 1711 Chestnut Glenview, IL 60025 (312)724-2620 American Microprocessors 6934 N. University Peoria. IL 61614 (309) 692-5852 American Microprocessors 20 N. Milwaukee Pralrieview, IL 60069 (312)634-0076 Wysocki Electric 3080 South Blvd. Rockford, IL 61109 (815)874-4846 Data Domain 1612 E. Algonquin Schaumburg, IL 60195 (312)397-8700 INDIANA American Microprocessors 146 N. Broad Griffith, IN 46319 (219)924-7901 American Microprocessors 3602 East Washington Indianapolis, IN 46201 (317)359-7445 American Microprocessors 2655 Irving Portage, IN 46368 (219) 760-2278 Computer Management 610 Monroe LaPorle, IN 46350 (219)362-5812 Data Domain 406 S. College Bloomington.lN 46401 (812)334-3607 Data Domain 7027 N. Michigan Indianapolis, IN 46268 (317)251-3139 Data Domain 10 N. Third LaFayette, IN 47902 (317)423-2548 Olson Electronics 5353 N. Keystone Indianapolis, IN 46220 (317)253-1584 IOWA American Microprocessors 102 E. 4th Waterloo, lA 50703 (319) 296-2255 John E. Chllds 1201 E. Second Ohumwa, lA 52501 (515)682-2165 Microbus 1910Mt. Vernon, S. E. Cedar Rapids, lA 52403 (319) 364-5075 KANSAS Barney & Associates 425 N. Broadway Pittsburg, KS 66762 (316)231-1970 Technigraphics 5911 Claredon Wichita, KA 67220 (316) 744-2443 KENTUCKY Data Domain 3028 Hunslnger Louisville, KY 40220 (502) 456-5242 Olson Electronics 117 Southland Lexington, KY 40503 (606)278-9413 Olson Electronics 4137Shelbyville Louisville, KY 40207 (502) 893-2562 MARYLAND Systems Engineering 1749 Rockvllle Pike #307 Rockville, MD 20842 (301)468-1822 The Mathbox 4431 Lehigh College Park, MD 20740 (301)277-6828 MASSACHUSETTS Bradshaw Enterprises 18 Harborvlew Hingham, MA 02043 (617)749-6844 Computer Shop-Aircom 288 Norfolk Cambridge, MA 02139 (617)661-2670 MICHIGAN The Abacus Route 1, Box 193 Niles Road Berrien Springs, Ml 49103 (616)429-3034 Concept Engineering 3706 Mallbu Lansing, Ml 48910 (517)394-0585 Great Lakes Photo 5001 Eastman Midland, Ml 48640 (517)631-5461 Microcomputer World 313 Michigan N. E. Grand Rapids, Ml 49503 (616)451-8972 Olson Electronics 29121 DeQuindre Madison Heights, Ml 48071 (313)546-0190 MINNESOTA Custom Computer Systems 1823 Lowry Minneapolis, MN 55411 (612)588-3944 Micro Business Sales 4345 Lyndale N. Minneapolis, MN 55412 (612)871-9230 MISSISSIPPI Jack Fisher Sales 100 Main Michigan City, MS 38647 (601)224-6470 MISSOURI The Computer Bit 1320 S. Glenstone Springfield, MO 65804 (417)883-2709 Computer Place Rt. #4, Box 91 -D Joplin, MO 64801 (417)781-1986 Futureworld 1909 Seven Pines St. Louis, MO 63141 (314)434-1121 Impact Systems Decker Building 613 W. 3rd P.O. Box 478 Lee's Summit, MO 66463 (816)524-5919 Norman Electronics 402 Wall Joplin, MO 74801 (417)724-0368 MONTANA Linco P.O Box 2418 Cut Bank, MT 59427 (406)336-3117 NEBRASKA Omaha Computer Store 4540 South 84th Omaha, NB 68127 (402) 592-3590 NEW JERSEY Computer Corner 224 Passaic Fairfield, NJ 07006 (201)835-7080 Computer Power 235 Nutley Nutley, NJ 07110 (201) 667-5502 NEW YORK Associated Consultants 33 Ogden East Williston, NY 11596 (516)746-1079 Brag Microcomputers 19 (Cambridge Rochester, NY 14607 (716)442-5861 Computer Mart of N. Y. 118 Madison New York, NY 10016 (212)686-7923 Microcomputer Workshop 234 Tennyson Terrace Williamsvllle, NY 14221 (716) 632-8270 Ylngco Two World Trade Center Penthouse 107th Floor New York, NY 10048 (212)775-9000 OHIO Byte Shop 2432 Chester Columbus, OH 43221 (614)486-7761 Johnson Computer 123 W.Washington Medina, OH 44256 (216)725-4560 Lucas Office Equipment & Service 869 E. Franklin Centerville. OH 45469 (513)433-8484 Olson Electronics 69 West State Akron, OH 44308 (216) 7620301 Olson Electronics 1994 Brittaln Akron, OH 44310 (216)633-4338 Olson Electronics 3265 W. Market Akron, OH 44313 (216)864-3407 Olson Electronics 2020 Euclid Cleveland, OH 44115 (216)621-6387 Olson Electronics 6813 Pearl Cleveland, OH 44130 (216)845-2424 Olson Electronics 6153Mayfleld Cleveland, OH 44124 (216)449-2690 Olson Electronics 21850 Center Ridge Cleveland, OH 44116 (216)331-4600 Olson Electronics 1975 Henderson Columbus, OH 43220 (614)451-3245 Otson Electronics 7401 Market Southern Park Mall Youngstown, OH 44512 (216)758-3828 OKLAHOMA Accounting Systems 2709 Orlando Oklahoma City, OK 73120 (405)751-1537 Gauger Engineering 910 Orient Clinton, OK 73601 Gauger Engineering 3824 S. 79th East Tulsa, OK 74145 (918)627-1064 OREGON Flal Computer 11013 S. E. 52nd Milwaukle, OR 97222 (503) 654-9574 PENNSYLVANIA Abacus Data Systems Route 8 Reno, PA 16343 (814)677-6502 Olson Electronics 5918 Penn Pittsburgh, PA 15206 (412)362-1333 Olson Electronics 3405 Saw Mill Run Pittsburgh, PA 15227 (412)881-0702 Olson Electronics 4778McKnlght Pittsburgh, PA 15237 (412)366-7298 TENNESSEE Computer Power of Memphis 3065 James Memphis, TN 38128 (901)386-9905 Computer Powerof Oak Ridge 800 Oak Ridge Turnpike Oak Ridge, TN 38730 (615)4829031 Smart Machine Mart Sd 5151 Hlllson { Nashville, TN 37211 i (615)833-9773 A SOUTH DAKOTA Exe Engineering 804 E. Lewis Vermillion, SD 57069 (605)624-6411 TEXAS Mr. Computer 744 FM 1960 W, Suite E Houston, TX 77090 (713)444-7419 UTAH Small Computer Systems 4450 Trinity Salt Lake City, UT 84120 (801)967-7635 VIRGINIA H/B Computers 217 E. Main Charlottesville, VA 22101 (804)295-1975 Microsystems, Inc. 5320 Williamson Roanoke, VA 24012 (703) 563-0693 WASHINGTON Ye Olde Computer Shoppe 1301 George Washington Richland, V\iA 99352 (509) 946-3330 WISCONSIN Madison Computer Store 1863 Monroe Madison, Wl 53711 (608) 255-5552 MicroComp 785 S. Main Fond du Lac, Wl 54935 (414)922-2515 Olson Electronics 3125 South 108th West Allls, Wl 53227 (414)541-1406 WYOMING Control Technology 204 Crazy Horse Lane Gillette, WY 82716 (307) 682-0300 CANADA Omega Computing Ltd. Box 220 Station P Toronto, Ontario Canada M5S 2F7 (416) 425-9200 Robo-Tronics 509 16th N. W. Calgary, Alberta Canada T2M 0J6 (403) 282-9468 f IIROPF Pan Atlantic Computer System GmbH 61 Armstadt Frankfurterstrasse 78 West Germany ^ 24 BYTE July 1978 Circle 290 on inquiry card. The C2-8P * An exceptional value in personal computing ennuBuan n If you are interested in an ultra high per- [formance personal computer which can be fully expanded to a mainframe class micro- somputer system, consider the C2-8P. Features: Minimally equipped with 8K BASIC-in-ROM, 4K RAM, lachine code monitor, video display interface, cassette iterface and keyboard with upper and lower case |haracters. (Video monitor and cassette recorder optional K Y ci a I! i_ d t T y h t -3 k I !i! T! -_! s --- 1 ! - i i ^ 5—= f- 5^-? r^- -== I _3 ri L m Ti O F' '^ r" :S "t Figure I: A sample printout of the Axiom EX800 printer. This sample was made by photographically reproducing the original silver colored paper image ata J:l scale. 28 July 1978 © BYTE Publicjtions Inc R J Bosen POB93 Magna UT 84044 Some time ago I decided I needed a hard copy printer to make my computer system really useful, but as I looked over the possi- bilities on the market I concluded that every alternative was either too expensive, too slow, or too limited in capability for my needs (which included good legibility and lower case printing). Just as I was about to abandon my plans, I saw a press release concerning a company called "Axiom" and a printer that appeared to solve all of my problems. It was adver- tised at $660, could print up to 160 char- acters per second (including upper and lower case letters) with an 80 column page width, and offered double and quadruple width characters as a bonus. 1 immediately wrote to Axiom and was surprised to receive a thick information packet within a week. My first (and only) disappointment came as I discovered that the 80 column page width was squeezed onto a 5 inch roll of special paper which was a little hard to read, but other features of the printer looked promising enough to justify further investigation, so I experimented with the printout sample they sent me to see if ! could find ways around these annoyances. I went to a photocopy center and found it was quite easy to get very sharp copies which were much more readable than the original. I decided that if the narrow page width became a serious problem I could write software to split a wide page into two 5 inch columns and print a page in two passes. Experimenting with the photocopier confirmed the feasibility of this idea as I successfullly laid two 5 inch pieces of the sample printout side by side and obtained the illusion of a 9 inch page width. I phoned the desk at Axiom to place my order; ten days later the printer was in my hands. I opened it up to reveal an Intel 4004 processor controlling an electrosensitive printing mechanism that works with special paper, consisting of a layer of paper, a layer of ink, and an aluminum upper layer. The print head strokes across the paper and burns the aluminum off in tiny dots, exposing the ink underneath in patterns stored in the processor read only memory. The processor controls character size and line length, allowing very flexible mixing of character sizes anywhere on any line and giving automatic line feeds when the end of the line has been reached. Other benefits of the I 3 i *■ f t microprocessor control include a self-test feature activated by pushing a button on the back panel which prints a test pattern on the paper, and a convenient parallel interface with simple handshait5v.ll* 205 639 1?00 4333 Convoy Suwt San Diego 714. 5609912 1816 Vgnacio Valiev Road SrT406 Kentwood 616-942 2931 Buffalo 716fl36-6511 Wilfiul Creek 416-935-6502 ILLINOIS 29673 Nonhwtttern Highway 225 Elmiia Road CALIFORNIA 6743 Dublin Blxd 117 F.emoniStieel SanF.anosco415 546 1592 6840 LaCicno«iBlvd Ioglewood213 776«)80 50 Eaii Rand Road Arlington Meighis 31 2 255-6488 Soijint.aid313356-8111 MINNESOTA Ithaca 607-277-4888 OHIO Dubl>n41583a8090 1077 Saratoga Sunnyvale Ho»d COLORADO 961 1 No. M.lwsukM Avenue 9070 Morgan CirclaDr'M 1 288 SOM Canter Ho.0 11074 San Pablo Avenue El Ce"iio<16.333 5010 San JoM 408 253-8080 2422 So CoiO'ado Blvd Nilei3129671714 BlooTiington 612-884-1474 Mayliald Haighii 216-461 42 42nd Avenue Denver 303 759-4685 10936 S Cicero Avenue N6W HAMPSHIRE OREGON 22634 Fooifiill Blvd Mavward 415 536 8080 San Maieo416672fl080 CONNECTICUT Oak Lawn 312-422 8080 419 Amneni 12020S W MainStraai 4S46 El Cam.no H^al Loi Alioi 4)5941 8I5J 6S40 La Ctegega Blvd KENTUCKY Nashua 603-889 5238 T.jard 503-620-61 70 Santa Rosa 707 52B 1775 16720 So Hawihorne BivO 24 75 Slack Rock Turnpike Fairtieid203 374 2227 813 6 Lyndon Lane Louiiville 502426 8308 NEW JERSEY 1442 E Route 70 TEXAS 3300Andarton Lane lnglewood?13 7 76 8080 Lawndale 213 371 7144 DELAWARE MARYLAND Cherry Hill 609 795-5900 Austin 612-452 5701 24001 Vis Fabnonte =904 ElCidPUza Suite 104 Ajtro Shopping Centet 16065 frede-ick Road, IRi. 3551 2 De Haft Siratt 6439 Wetthaimar MiHion Vieio 714 770-0131 Thousand Oaks 805-495-3554 Newark 302 738 9566 Rockville 301 948-7676 Morritlown 201 539-4077 HousTon 713-977-0909 WASHINGTON 1500 South 336th Slrsel Parkway Center. Suite 12 Federal Way 206-838-9363 WISCONSIN 690 5. Whitney Way Madison IDiiactory Aisisiani INTERNATIONAL 52 58 Clarence Strati Svdfiey NSW 2000 AultraLaTLX AA 24757 "SEE US AT PERSONAL COMPUTING '78 IN PHILADELPHIA, AUGUST 24-27" Circle 75 on inquiry card. BYTE July 1978 33 The New WHl7 ''Mini'' Floppy- a Giant Leap Forward in H8 Systems Sopliistication! pNow you can give your H8 the power and versatility only a floppy disk system can provide! The WH17 lets you load programs in seconds instead of minutes, store hundreds of programs on a single disk with immediate access, update files virtually instantly. It's far more versatile and reliable than paper tape or cassette storage and really makes your H8 a "total capa^ bility" computer system! Storage media for the WH17 consists of the standard, hard- sectored, 40-track diskette. Mea- suring just 5.25" in diameter, each disk offers the user access to 400 sectors (10 per track) oi better than 102K* bytes of available program and data storage area. Supplied fully assembled, the WH17's model 82 WANGCO drive posts a conservative 30' ms track seek specification, and random sector typical access times of less than 350* ms. (A figure considerably better than that of many equivalent com- letitive drives.) A diskette containing all re- quired H8 operating systems is sold separately. This software includes the Heath Disk Operat ing System (HDOS), with its unique diagnostic, BUG-8, console debugger, TED-8, a powerful text editor, HASL-8, and extended Benton Harbor BASIC. The fully assembled WH17, with dual-drive, controller and systems software, wrill be available in June, 1978, for S975. f HEATHKIT COMPUTERS Systems Engineered for Personal Computing petit; Uniis of Schlumbergef Pioducts Coiporatton Rsidij pr-ces ort somo producls may be slightly ABBONA-PhooniK, 2727 w Indian School Hd. (602) 279-6247 CAUFOBNIA-Anahelm, 330 E Ba« Rd |714) 776-9420. El CKrIto, 6000 Poltoro Avs 1415) 236-6870, Los Ana«lM. Z30S 8 Flowm SI. (213) 749-0261 : Pommn. 1 555 Orango GrovB AV8. N. (714) 623-3543; RMwxxl Cll». 2001 MiddMwId Rd. (415) 363-8156: SacranMnlD, 1960 Fullon Avs i»16) 486-1575: S«n DIagD (U M(u),S363 Center Or (714)461-0110; S«llJo»eoll«,2112E 62nd SI (317)257-4321 KANS,« - Kansas CHy (Mission), 5960 Lamar Ave 1913) 362-4486 KENTUCKY-Loulsvlllo. 12401 Shelbyville Rd (502)245-7811 LOUISIANA -Naw Orleans (Kenner), 1900 Veterans Memorial Hwy. (604) 722-6321. l«ARYLAND-Bsitlmors,1713E JoppaRd 1301) 661-4446: RockVllle, 5542 Nicholson Larra (301) 861-5420. ^ BASSACHUSETTS-Boston (Psaboijy), 242 Anaover SI (617) 531 -9330; Boston (Wslluley). 165 Worcester Ave. (Rt. 9 lUSt vrest ol Rt. 128) (617) 237-1 510. MICMIOAN-0«ro8.l8B45W.Ei9htMileRd i3l3i 535-6460; E.D«1rott, 181496 EiaWMIIeHd (313)772-0416 HINNESOTA-Mlnneaiiolls (Hopkins), 101 Shady Oak Rd. r612| 938-6371 MISSOURI- St. Louis (BridgeJon). 3794 McKelvey Rd (314)291-1850 NEBRASKA-Omaha, 9207 Maple St (4021 391-2071. NEW JERSEY-Fslr Lawn, 35-07 Sroadviay (Rte. 4) (201) 791-6936; Ocean. 1013 Slate Hwy. 35(201) 775-1231 NEW YORK- Buflaki (Amhersl). 3476 Sheridan Dr (716) 835-3090: Jerlclio. Long island, IS Jericho Turnpike (5l6)334-8l8l;Roohsatsr,937Je(lersonHd (7161244-5470 White Plains (North White Plains). 7 Reservoir Bd (914) 761-7690 OHIO-anclnna« (Woodlawn). 10133 Spnnqtiekl Pike (513) 771-8850; Clevelana. 5444 Peail Bd (2161 686-2590. Columbus, 250O Morse Rd. (814)475-7200: Tolatlo, 48 S Byrne Rd. (419) 537-1887 PENNSYLVANIA-PtlllsiMphIa, 6316 Roosevelt Blvd (215) 288-0180. Frsior (Chester Co.). 630 Uncasler Pike HI 30) (215) 847-5555; Plttslwrgh, 3482 Wm PennHlvy. (412)824-3664 RHODE ISLAND- Providence (Warwick), 556 Greenwich Ave (4011 738-5150 TEXAS - Dallas, 2715 Ross Ave. (214) 826-4063; Houslon,370S Westheimer (713) 623-2090. San Antonio, 71 1 1 Blanco HO. (512) 341-8676 VIROINIA-Ale«»nr, Ml 49022 Please send me my FREE Catalog. I am not on your mailing list. City . .State _ _Zip^ "Prices and specitications subject to change wittiout notice. I I I .J 34 BYTE July 1978 HEATHKIT CATALOG Read about nearly 400 money-saving, fun-to-build electronic kits. Use coupon to send for your mail order catalog or bring coupon to a Heathkit Electronic Center for your catalog. Get Your Copy Today! Circle 160 on inquiry card. Figure 7: A basic top- down design diagram is a structure like tiiis. The number ofieveis may vary, and the number of boxes may vary, but the basic idea is given by this prototype. level I (highest) level 2 level 3 (lowest) Figure 2: The first level of design is the act of saying "I want a program to do thus and so." Here "thus and so " Is defined to mean checkbook balancing. checkbook bank stmt deposit slips checks implied inputs balance checkbook implied outputs comparison ot checkbook and bank balances errors corrections The basic principle of top-down design procedure says that you start at a very high level of function definition and then pro- gressively expand that function into more and more detail until you're at a low enough level to begin coding your program. Actually, this is a very natural way to design solutions to any problem, but, for some reason, this method was very slowly applied to programming. The top-down method is different from bottom-up, where the concern is for coding and details before a real program design has been done. Bot- tom-up methods work on the "how" aspects of the program before the "what" aspects. An analogy of this method would be the building of a house, using no structural plans, by first laying down a convenient foundation and then gradually adding wood and stone until some desirable struc- ture has evolved. Let's take an example of a function that could be performed on a microproc- essor system for the purpose of illustrating the technique of modular, top-down pro- gram design. The function, monthly check- book balancing, was selected because it is a process that is familiar to most of us and it contains all of the elements which make it a good example. In order to design what you want the program to do, begin by drawing a multi- level design diagram like the one shown in figure 1. The diagram will describe what the program does at a number of different levels of detail, starting with the highest level which is a single block describing the overall function. The next lower level of blocks breaks the higher level function into a number of more detailed subfunctions. The next level takes those blocks and breaks them into even greater detail, and so on. An important point to remember is that the total function of the program is represented at each level. Figure 2 illustrates the first steps in the top-down design of your checkbook balanc- ing program. The first block simply states that the program will balance your check- book. There are no details in that block and it certainly doesn't invite coding at this point in the design. For input, you know that you will have your checkbook entries, monthly statement from the bank, deposit slips and cancelled checks. The output you want is a comparison of your checkbook balance (adjusted for recent deposits, ser- vice charges and outstanding checks) and the balance shown on the bank statement. You also want to know where any errors were made and what corrections are required. The second level of design, shown in figure 3, breaks the first level block into three major subfunctions. Although this sub- division could have been done differently in terms of the content of the second level blocks, the sum total of those functions always adds up to the entire function of the program. The idea is that you start the process slowly and don't attempt to develop too much detail too soon. Keep the number of subfunctions small, five or fewer, under July 1978 O BYTE Publications Inc 35 Figure 3: Once the first level of design has been determined, the next level is specified by breaking up the task into parts which are fundamentally inde- pendent of one another. Here, checkbook balancing is viewed as three separate modules of function. balance checkbook balance deposits bolance checks and charges compare bonk and checkbook bolonces ( stort j match deposits in checkbook against bank statement adjust bonk balance for any late deposits match concelled checks to check- book entries and bonk statement adjust check- book balance for any bonk charges adjust bank balance for any outstand- ing checks compare bonk balance to checkbook balance determine any differences and correct mistakes C end J Figure 5: After the modu- lar structure of the ap- plication is determined in a hierarchy such as those exemplified In figures I to 4, then attention can be given to sequencing of functions. This flowchart shows general level se- quencing of the checkbook balancing application. balance checkbook balance checks and charges match cancelled checks to check- book entries and bank statement adjust check- book balance for any bank charges adjust bank balance for any outstand- ing checks Figure 4: Carrying the process one step further, the next level is shown here for one of the branches of the structure of the programs. each function block. Don't worry about the order in which these subfunctions will be performed in your program. Remember, you're only concerned at this point about what is to be done, not how it is to be done. Next, take the design to the next lower level by further subdividing each of the second level blocks. Figure 4 illustrates a portion of this step. Just make sure that each subblock represents a complete sub- function and that the subfunctions at any level are equivalent to the program function. You might ask at this point, "How many levels must I go through?", or "How do I know when to stop?" There is no precise answer to these questions, although the fol- lowing guidelines should help. In general, you will find that you should stop when the lowest level of functions is so simple that you can easily write a program module to do each one. A module should be considered to have about 50 program instructions, or less. Experience will help you to know when you have reached this point. Also, you will find that the more complex the program, the more design levels you will need; general- ly, about three or four levels will be sufficient. Another method of determining if you've carried the design to a low enough level comes about almost automatically. If you are attempting to complete one of the lower levels and you find that the order of sub- function execution is becoming difficult to ignore, then you've probably gone far enough. Also, if you find that it is becoming necessary to show that program branching or decision making is required (top-down de- sign diagrams should show no decision logic), then you know that you have about the right level of design. You are now ready to start thinking about the how of your program. Modular Construction. If you try to make each block at the lowest level of your design diagram into a module, you might determine that some blocks are simple and can be combined into fewer modules. On the other hand, there will probably be blocks which would result in modules larger than the minimum size of 50 instructions we have established. In this case, take the blocks through one or more additional levels of design. Now decide what sequence the functions should be performed in. Begin drawing a 36 luly 1978 © BYTE Publicitions Inc Rackets or Racquets? Software systems from TSC serve — whether your racket is business or pleasure. TSC's software is designed for business and industrial uses as well as for recreation. Off the job or at work, TSC ^ software serves your needs. Assembly Language Programs (Includes Source Listings) With Object Code Cassette SL68-5C 6800 Space Voyage SL68-24C 6800 Text Editing System SL68-26C 6800 Mnemonic Assembler SL68-29C 6800 Text Processing System $18.95 $30.45 $30.45 $38.95 With Object Code Paper Tape SL68-24P 6800 Text Editing System $31.50 SL68-26P 6800 Mnemonic Assembler SL68-29P 6800 Text Processing System SL80-10P 8080 Text Editing System SL80-1 IP 8080 Text Processing System $31.50 $40.00 $37.50 $41.00 Cassettes are in the Kansas City Standard format. Many other programs are available. Send 25c for a complete catalog. Technical Systems Consultants, Inc. Box 2574 W. Lafayette, Indiana 47906 317-423-5465 Specialists in Software & Hardware for Industry & the Hobbyist Circle 370 on inquiry card. To Order: Include 3% postage, $1.00 handling on orders under $10.00, and Indiana residents add 4% sales tax. Check your dealer! TSC Monthly Feature: 8080 Mnemonic Assemblei This is the most complete resident non-macro assembler available lor the 8080 and the com- plete source listing is included! The assembler is fully Intel compatible except tor logical expression operators. All standard pseudo-ops are supported plus features such as paging, titling, spacing, listing suppression, sorted symbol table, Intel format tape generation, hex or octal output, decimal line numbers, auto field formatting, hex, decimal, octal or binary constants, and more. 5.5K of RAM is required beginning at 1000 hex, plus source and symbol table space. An object code paper tape in Intel ASCII format is available SL80-12 8080 Mnemonic Assembler $25.00 SL80-12P Assembler with paper tape $34.00 BYTE lulv 1578 37 executive f start J return yes call return yes call return call yes call return r end j processing details call input and format all required data match concelled checKs to check- booK and bank statement subtract charges from checkbook subtract checks from bank balance compare bank balance to checkbook indicate amt. of mis- match and locate error processmg subroutine modules Figure 6: While the sequencing of the diagram shown in figure 5 is adequate, it is often usefui to explicitly partition all sequencing of execution in a separate module called the "executive" for the application. This flowchart shows a simple example of such an executive program which sequences the major operations of the application. flowchart showing the required sequence. Will each function be performed for each pass through the program? If not, add deci- sion blocks showing the conditions under which each such function is executed. Also add any function blocks which may be necessary to initialize data, clear tables, lO data, etc. Figure 5 shows a sequence of functions which results from the design of your exam- ple checkbook balancing program. Actually, the functions shown are probably too high level for this step, but for the sake of illustra- tion, the diagram should make the point. At this time, I would recommend that you consider making use of a special pro- gram structure called an executive routine, which offers some significant advantages. The executive is the main routine in the program and primarily contains calls to the function modules which do all the processing duties. It makes all decisions about the sequence of execution, it also contains the starting and ending points of the program. The objective of the executive is to concentrate most of the decision logic and common function of the program into a separate routine which becomes another program module. In this way, the function modules need not, and should not, make sequencing deci- sions. They should never directly pass con- trol to another function module. This should be done only through the executive. A func- tion module's only responsibility is to be given control by the executive, do its assigned job, and then return control back to the executive. Function modules are written in the form of subroutines using the call and return facilities of the programming language being used. They should also contain a generous sprinkling of comment statements to insure a high degree of understandability, as well as a well-defined lO interface to the outside world and the rest of the program. Figure 6 illustrates the final step in the modular, top-down design of your check- book balancing program. You have added an executive routine and some necessary house- keeping routines. You could begin coding the program from this flowchart by first writing the executive and the associated subroutine calls for each of the processing modules. By writing dummy subroutines which simply return control when they are called, you can test your executive for cor- rect operation without the need for the real processing modules. The next step, of course, is writing the processing routines. This is simplified by the design approach described in this article because it allows you to work on each routine as a separate unit which can be written and tested independently of all other routines in the program. When all routines are com- pleted, they simply plug into the executive to form a total program. Later, if you want to change the sequence of execution, add or delete functions, it can be simply a matter of manipulating modular routines. ■ 38 |uly 1978 ® BYTE Publications Inc HOW TO BEAT THE SYSTEM WITH SYNCHRO-SOUND High-performance, low cost complete Microcomputer Business Systems (plus Software) at EXTRA savings only Synchro-Sound can offer! ^SYSTEMl No. 1 J P'G'TAL SYSTEMS DSj;;2 _|»i|L^ ^ fSYSTEMMMSAI VDP 80 No. 2 Z-80 COMPUTER SYSTEM! 32K RAM, 4 RS-232 serial interfaces; 16 bits of parallel I/O. Double density floppy disk, Shugart dual-drive. Regular price $4995.00 CENTRONICS 700 PRINTER With RS-232 Interface 60 characters per second, 132 col- umn line, tractor feed. Regular price $1720.00 HAZELTINE 1500 VIDEO TERMINAL 80 cfiaracter lines, 24 line page, line and page editing. Separate numeric keypad. Regular price $1149.00 $7864.00 THE COMPLETE SYSTEM ^-yi^m- nn ONLY $7495.00 SAVE $369.00! DATA PROCESSING COMPUTER SYSTEM 32K RAM, expandable to 196K. Parallel and serial I/O. Megabyte mass storage, alphanumeric in- telligent keyboard. Regular Price $6995.00 OKIDATA 22 PRINTER With RS-232 Interface Tractor feed, 132 column, 125 Ipm, upper and lower case. 12 different fonts on command. Regular price $2888.00 $9883.00 THE COMPLETE SYSTEM ^niiliC nr\ ONLY Q944d.UU SAVE $438.00! CROMEMCO SYSTEM 3 Z-80 COMPUTER SYSTEM 32K RAM, dual disk drive, RS-232 In terface. S-100 bus. Regular price $5990.00 MODEL 3703 LINE PRINTER 180 characters per second, print line width 132 cols., bi-directional print- ing. Regular price $2995.00 CRT TERMINAL MODEL 3100 80 characters per line, 24 lines, up to 19,200 baud, upper and lower case. Regular price $1595.00 $10,580.00 SAVE $485.00! Three software packages* that enable you to profitably make full use of your Microcomputer Business System ACCOUNTS RECEIVABLE PACKAGE Creates transaction file of charges, credits and payments. Batch mode for monthly statements and aged schedules. Operators manual and disk, single copy $500.00 INVENTORY PACKAGE Maintains current listing of stock items, master inventory listing with price and cost data. Operators manual and disk, single copy $500.00 ORDER-ENTRY PACKAGE (Requires Accounts Receivable and/or Inventory Package) Links Accounts Receivable and Inventory packages into one coherent, easy-to-use, time- saving system. Operators manual and disk, single copy $500.00 Buy any of our 3 MICROCOMPUTER SYSTEMS and any combination of these 3 SOFTWARE PACKAGES ARE YOURS FOR HALF PRICE! * Require 48K Memory and Microsoft Basic Terminal and Printer substitutions may be made on any of the above Systems CUSTOMIZED HARDWARE SYSTEMS ARE AVAILABLE Complete modern servicing and consulting facilities on premises SYNCHRO-SOUND ENTERPRISES INC The Computer People 193-25 Jamaica Avenue, Jamaica, New York 11423 212/468-7067 TWX: 710-582-5886 Hours 9-4 daily Visit ournew showroom and Saturday Working units on display DeptBSY BankAmericard* Master Charge Circle 355 on inquiry card. BYTE luJy 1978 39 SYNCHROSOUND ENTERPRISES, INC.I One-Stop shopping for Hardware and Software Everything you need in small computer systems with special emphasis on TERMINALS! Look at these units. ..compare price, quality, delivery, service. ..and you'll see why you don't have to look anyplace else! LEAR SIEGLER ADM 3A TERMINAL • Full addressable cursor • Display format— 24 lines of 80 characters per line • Communications rates— 75 to 19,200 Baud • Computer interfaces — EIA standard ADM3A Kit ADM3A Assembled . Lower Case option $759.95 854.95 69.00 ADDS REGENT 100 VIDEO DISPLAY TERMINAL Display Format— 80 characters per line by 24 lines. 25th line reserved for terminal status. Re- verse video, underline, half and zero intensity and blinking are all standard features. Zio "Ed OKIDATA MODEL 110 LINE PRINTER • 110 CPS dot matrix Feed°" $1199.00 Fe'ed" 1349.00 RS 232C Interface.. 260.00 i4' $1325.00 TELETYPE MODEL 43 PRINTER • 132 Characters per line • 110 or 300 Baud switch selectable • Full keyboard • RS 232C Serial Interface standard $1299.00 OKIDATA MODEL 22 LINE PRINTER 125 lines per minute 132-column print line • Upper/lower case • 8 different character sizes • 12 IPS paper slew Tractor Feed $2449.00 RS232C Serial Interface. ..379.00 DECWRITER II • 132 column printing • 10-30 CPS • Full keyboard • Tractor feed $1495.00 40 BYTE July 1978 SYNCHROMUND ENTERPRISES, INC.I CENTRONICS 703 SERIAL PRINTER \ • Low cost of ownership • Bidirectional logic seeking printing • Microprocessor electronics ^^Q^_ /\/\ • Excellent print quality «)>^OUOaUU CENTRONICS 761 PRINTER • 300 Baud serial transnnission • Bidirectional and incremental printing • RS232, CCITT-V24, or current loop interface • Baud selection (110/150/300) $2025.001 KSR with Keyboard. Receive only version 1895.001 IMSAI 8080 MICROCOMPUTER • Powerful • Low cost • Easy to use IMSAI 8080 ^PEIaim With 22 Slot Mother Board $649.95 PCS-80/15 Kit 699.00 HAZELTINE 1500 VIDEO TERMINAL • Reverse video • 24 X 80 display • Programmable brightness levels • RS232 and current loop and much more"" Assembled $ 1 1 49.00 /Kit:^95.oo FLOPPY DISK SYSTEM Fully IBM 3740 media and format compatible Full formatter and controller $2475.00 Digital Systems Dual Drive System BfujiiiiiMiiiTimiHiii Dual Density Version 12745.00 HAZELTINE MODULAR 1 INTELLIGENT TERMINAL • 1920 character display • 8 different video levels • Full editing capability • Removable keyboard and much more Assembled .... $1659.00 SPECIAL BUYS Vista V80 Floppy Disk System $619.95 Cromemco Z-2 Kit 565.25 Compucolor8001 ColorComputer 2595.00 IMS 16K Static Memory 525.00 North Star Microfloppy Disk Kit 599.00 North Star Horizon 1 Kit 1499.00 North Star Horizon 2 Kit 1899.00 Javelin 9" Video Monitor 159.95 Livermore Modem Model 76 299.00 Micropolis Model 1053MOD 2 1799.00 IMSAI AP44-44 Col. Printer Kit 299.00 TDLXitan Alpha 1 Assembled 939.95 We carry a full line of the following: TDL, Centronics, Seals, Hazeltine, Micropolis, Vista, Hayden, IMSAI, Cromemco, Digital Systems, Compucolor, Icom, LearSiegler, Okidata, DEC, Javelin, North Star, Peripheral Vision. Same day delivery and shipping on most items. Full modern repair facilities on premises for complete servicing of everything we sell. SYNCHRO-SOUND ENTERPRISES INC The Computer People 193-25 Jamaica Avenue, Jamaica, New York 11423 212/468-7067 TWX: 710-582-5886 Hours 9-4 daily Visit our new showroom and Saturday Working units on display Dept. BBB BankAmericard • Master Charge Circle 356 on Inquiry card. BYTE July 1978 41 Who's Afraid of Dynamic Memories? It is not necessary to re- fresh euery cell of the dynamic programmable memory individually, but only the rows of the memory matrix. (Conversation overheard in local com- puter store): Customer: What's the difference be- tween static and dynamic memory? Salesman: Static memory worlds and ■ dynamic memory doesn 't. It is unfortunate that the dynamic memory has had a rocky start in the small systems world, but it is not really surprising. The dynamic programmable memory is a part generally avoided by most designers because it is not nearly as simple to use as static memory. But taking the extra trouble and design care can pay handsome cost and performance dividends, since the dynamic memory is inherently a lower cost part than its static counterpart (by present standards of technology). The purpose of this article is to remove some of the mystery about dynamic mem- ory parts. In order to best cover all the trade-offs involved in a dynamic memory design, the discussion centers around the design of an actual dynamic programmable memory with the following specifications: 1 . 32 K bytes on one card. 2. Altair (S-100) bus compatible (an elusive specification, as we'll see later). 3. Refresh mechanism invisible to the processor. 4. Lowest power dissipation possible with current integrated circuits. 5. Full speed operation in a 2 mHz sys- tem (no wait states). 6. Foolproof operation: refresh main- tained despite halted processor and direct memory access operations, interrupts and prolonged wait states. Note: A commonly seen misnomer is the abbreviation "RAM" used to refer to a typical volatile programmable memory part such as those dis- cussed in this article. RAM stands for "random access memory, "which is descriptive of any memory part which addresses a unique memory cell given a set of binary inputs. A "read only memory " for example is also a random access memory, yet it is quite different In function from the vola- tile programmable memories. Thus in reading advertisements and manu- facturers' literature, be aware that the term RAM as used really means "volatile programmable memory, " a resource for the programmer who uses the system. . .CH Lane T Hauck Director of Research and Development Noval Inc 8401 Aero Dr San Diego CA 92123 Figure 1 is the usual starting point in any discussion of programmable memory. It is shown here only to point out that the static programmable memory cell uses six MOS transistors, while the dynamic cell uses only one (end of cost advantage argument). The dynamic programmable memory ceil uses a charge storage technique to store digi- tal information. The capacitor C^- in figure lb is charged for one logic state and dis- charged for the opposite state. Capacitors, being what they are, don't hold charge for- ever (due to leakage), so the cell shown works fine, but only for a few milliseconds. After that, the charge decays below a usable value. This is the reason for the mechanism called refresh. A refresh operation reads the value of the charge on the capacitor, ampli- fies it to its initial value, and dumps it back into the capacitor. Life would really be difficult if the de- signer had to implement the entire refresh operation (read, amplify, write) in a dy- namic memory system. Dynamic memory designers have made things simple by estab- lishing the following refresh "rules": 1 . It is not necessary to refresh every cell in the dynamic memory individually, but only the rows of the memory matrix. 2. A refresh operation is accomplished by simply accessing the required number of rows with any type of memory operation (read, write, or do nothing but set up the correct addresses ac- companied by a "strobe" or timing pulse). Programmable memories are organized in an XY matrix of rows and columns. The matrix is generally square, so it is possible to deduce the number of rows in the memory that must be accessed during 42 July 1978 ©BYTE Publicitions Inc TARBELL SETS STANDARDS For Hobbyists and Systems Developers Sales to thousands of hobbyists over the past two years have proven the Tarbell Cassette Interface to be a microcomputer industry standard. Tarbell Electronics continues research and development to produce new and efficient components to fill hobbyists' changing needs. TARBELL CASSETTE INTERFACE • Plugs directly into your IMSAI or ALT AIR * • Fastest transfer rate: 187 (standard) to 540 bytes/second • Extremely Reliable— Phase encoded (self-clocking) • 4 Extra Status Lines, 4 Extra Control Lines • 37-page manual included • Device Code Selectable by DIP-switch • Capable of Generating Kansas City tapes also • No modification required on audio cassette recorder • Complete kit $120, Assembled $175, Manual $4 • Full 6 month warranty on kit and assembled units TARBELL FLOPPY INTERFACE • Plugs directly into your IMSAI or ALT AIR* and handles up to 4 standard single drives in daisy- chain. • Operates at standard 250K bits per second on normal disc format capacity of 256K bytes. • Works with modified CP/M* Operating System and BASIC-E Compiler. • Hardware includes 4 extra IC slots, built-in phantom bootstrap and on-board crystal clock. Uses WD 1771 LSI Chip. • Full 6-month warranty and exten- sive documentation. • PRICE: Kit $190 Assembled $265 TARBELL PROTOTYPE BOARD Model 1010 DISC . niiHljiiiit ^iiifjilmiiK| IMSAI 8080 Mniiii iiHiiii^liiir CP/M with BASIC-E and manuals: $100 I Compatible Disc Drives Ask about our disc drives priced as low as $525. • Gold plated edge pins • Takes 33 14-pin ICs or • Mix 40-pin, 18-pin, 16-pin and 14-pin ICs • Location for 5 volt regulator • Suitable for solder and wire wrap • ALTAIR/IMSAI compatible Price: $28.00 For fast, off the shelf delivery, ail Tarbell Electronics products may be purchased from computer store dealers across the country. Or write Tarbell Electronics direct for complete information. ' ALTAIR is a trademark/ tradename of MITS, Inc. CP/M is a trademark/tradename of Digital Research 20620 South Leapwood Avenue, Suite P Carson, California 90746 (213) 538-4251 Circle 360 on inquiry card. BYTE luly 1978 43 VDD (a) ROW SEL (b) CC Figure 1 : Comparison of static and dynamic memory cells. The static mem- ory cell (figure la) Is actually a flip flop (or bistable multivibrator) made up of six MOS transistors and capable of storing one bit of information. The dynamic memory cell (figure lb) uses one MOS transistor and a capacitor to store one bit of information. The major differences between the two memory storage techniques are cost (dynamic memories are significantly cheaper than static memories) and the fact that dynamic memories must be "refreshed" regularly to maintain the charges on the capacitors. CESSOR ADDRESS LINES REFRESH COUNTER r MULTIP LEXER , A 6 MULTIPLEXER REFRESH ARBITRATION LOGIC CONTROL ADDRESS LINES nYNAMir MTMnRY D.u ARf (AY Figure 2: Refresh implementation block diagram. Dynamic memory cells must be refreshed periodically, or the capacitors used to store the bits of information will discharge. Refreshing is done by simply accessing the cells in question with any type of memory operation (read, write, or do nothing but set up and strobe the correct addresses). Because dynamic memory cells share common lines, it Is necessary to access only the rows of the memory matrix. All dynamic memories are set up so that the row decoders are fed by the least significant address lines (AO thru A 5 for a 4 K part, for instance). The mem- ory address lines are fed by a multiplexer that selects either the A lines (proc- essor address lines) or the B lines (refresh counter lines) as directed by the refresh arbitration logic. The selected lines are then fed into the dynamic memory array. The refresh arbitration logic insures that the refresh opera- tions and the processor operations do not interfere with each other. a refresh interval. For example, a 4 K by 1 bit memory is 64 by 64, so 64 memory cycles must be performed for refresh; a 16 K by 1 bit memory is 128 by 128 and requires 128 refresh cycles. The specification for refresh interval is generally 2 ms. This means that all rows of the memory matrix must be "exercised" at least once every 2 ms. Hovk' do you knovk" v^'here the "rows" are? All dynamic memories are set up so that the row decoders are fed by the least significant address lines; for a 4 K part, this means the six low order address lines, or AO, A1, A2, A3, A4 and A5. During the refresh opera- tion, the remaining address lines A6 thru All are in "don't care" states. For a 16 K part, the seven low order address lines AO thru A6 constitute the row address lines. Figure 2 shows how refresh is accom- plished. The memory address lines are fed by a multiplexer that selects address inputs from multiple sources. When the A inputs are selected, the processor accesses the mem- ory; when the B inputs are selected, the refresh address counter accesses the mem- ory. The role of the refresh arbitration logic is to insure that the refresh operations and processor access operations do not interfere with each other. The block diagram in figure 2 shows a 2 input multiplexer. A later section of this article shows how the number of inputs may be expanded to accommodate a multiplexed address programmable memory. Some system designs allow the use of dy- namic memories without having to imple- ment any refresh circuitry whatsoever. The most common system of this type is a video system that uses raster scanning. In order to present a stable image on the video display, all information is stored in a refresh mem- ory. As the electron beam scans the screen, a digital address that identifies the beam posi- tion is developed by the video display's tim- ing circuitry and fed to the memory address lines. The memory thus sequences continu- ously through its addresses. This satisfies the refresh requirement automatically, since the refresh counter of figure 2 is in effect re- placed by the video display's counters. The 4 K dynamic memory is currently available in three different packages: 22 pin, 18 pin and 16 pin. The survivor of the in- compatibility battle is clearly the 16 pin package, due largely to its superior design, low power and true compatibility between multiple sources. Ironically, the smallest package, the 16 pinner, was the easiest one to convert to a 16 K memory part. [Several manufacturers of personal computers take advantage of this to offer memory in differ- ent combinations of 4 K and 16 K byte blocks . . .CM/ We'll see how this was done 44 July 1978©BYTE Publicalions Inc The AJ 841 l/Q A completely refurbished IBM Selectrk ASCII terminal with RS232 or parallel interface. FEATURES: • ASCII code. • 14.9 characters per second printout. • Speciolintroductory price — $995 [regularly $1,195]. 75% discount tronn original price of new unit. • Serial RS 232 or parallel interface. • Order direct from factory • Documentation included. • 30-day warranty — ports and labor • Higti quality Selecthc printing. Full warranty information available upon request • Reliable, heavy duty Selectric mechanism. • Off-line use as typewriter AJ 841 WARRANTY AND SERVICE IS AVAILABLE IN THE FOLLOWING CITIES: Los Angeles/ Cincinnati Philadelptnia/ Detroit l-lGckensact RAS CAS "IHC- V|L - ADDRESSES WRITE 'OUT K 'RAS '^RCD • n: ••RAH ROW ADDRESS COLUMN ADDRESS Irsh 'gas A '.rj' m TTMMUm ■ rcs \ 'RCH "OH - VOL- OPEN -c VALID DATA 'off > Figure 3: Dynamic memory timing for tfie l\10STEK /VIK4176 16 K dynamic memory (Courtesy MOSTEK). Tlie foilowing steps are necessary for a memory cycie: set up tiie low order 7 bit address on tfie address line (for tiie case of the 16 K memory) by setting tiie address multiplexer to state 2; wait for tiie address lines to settle; drop the row address strobe (RAS) line to the low state to latch the low address into the port; wait the "row address hold time"; set up the high order 7 bit address on the address lines; finally, drop the column address line to the low state, which latches the high address into the port. <•: 46 July 1978 © BYTE Publicilions Inc GET THE ^^ LOW DOWN BEFORE YOU BUY SO YOU WANT TO BUY A COMPUTER?? This new book presents an objective look at the top 24 micro systems sold throughout the world. It discusses the Pros and Cons of each system in No Uncertain Terms and takes a straightforward look at the micro computer industry as it relates to YOU. Written especially for the layman in a language he can understand. Profit from the mistakes of others. Includes hundreds of references. Table of Contents 1 . Introduction 2. Don't get hung up on the chips 3. Which category do you fit into 4. Now -About the Hardware 5. Peripherials that plug in? 6. What? No Software! 7. Helpful Suggestions before spending money 8. Addresses master charge $4.50 per Volume Volume discounts available SCIENTIFIC RESEARCH P.O. Box 490099-B Key Biscayne, Florida 33149 Phone Orders Call 800-327-6543 Add $1 handling, all domestic shipments sent U.P.S. except APO and P.O. Box which go parcel post. Foreign orders add $4 for air shipment and make payable in U.S. funds. BYTE luly 1978 47 ^ Antique Mechanical Computers Part 1: Early Automata Dr James M Williams 58 Trumbull St New Haven CT 06510 There is a high technology in every age, not just our own. My purpose in writing these articles Is to remind computer enthusiasts that there is a high technology in every age, not just our own. Described herein are some of the stellar accomplishments of earlier times. The technology of electronics is merely the latest link in a continuous chain of technological developments spanning 20,000 years. Before that, there was a mechanical technology. Part 1 of this three part series describes some highlights in the development of auto- mata up to the 18th century. Part 2 contin- ues with 18th and 19th century develop- ments, and part 3 concludes with a descrip- tion of Torres' 1 91 1 chess automaton. I am not going to speak here of those in- candescent moments long ago when the truly great and critical achievements of mechanics were discovered: that day when an ancient man hooked a stick under one large stone and over another to invent the lever. Nor will I consider the wheel, which, however it came about, multiplied mechan- ical possibilities so manyfold (pulley, cam, gear, crank, escapement) that as the know- ledge spread humanity was irrevocably changed. We simply do not know the story of mechanical knowledge and its spread, so we must spin scenarios instead of histories. We will also have to concentrate on high- lights, since an exhaustive treatment of mechanical computers would fill many books. We do know most of the latest chapter, however. It has taken place in the past 350 years, beginning in Renaissance times, flourishing in the Industrial Revolution, and finally levelling off in the early years of this century. The mechanisms that are now commonplace were being born back then, and what exciting times they must have been. Glance through a compilation of mechanisms and note the dates of first appearances in machinery. You will be sur- prised to see how many basic movements date from two centuries ago. And with study and application, a man could learn them, make them his own, and employ them in mechanisms of his own. Consider the thrill of the obscure local blacksmith in, say, Saxony 400 years ago who copied in wood the mechanism of the town clock's striking- jack — the clock, a wonder that was the envy of other towns, imported at great expense from Italy — and discovered for himself the means of transforming rotary motion into intermittent linear motion, via a cam. (Medieval cathedral clocks generally had a life-size figure, man, angel, or devil, which carried a mace to strike hours on a bell: the "striking-Jacques" or "striking- jack.") Imagine the challenge and excite- ment in realizing that one could construct a clock that would strike noon fairly consis- tently when the shadow of the church steeple touches a particular joint of flagstone in the village square. Could one compress this wonderous mechanism into a container small enough to carry, and be able to see the time whenever he wished? Could one construct a clock for the pocket? The first ones showed up around 1650, bulky as an ostrich egg and not much better at keeping reliable time. A little over two centuries ago a carpenter from York- shire, England, James Harrison, who had taught himself mechanics over a period of 30 years, constructed his fourth highly 48 luly 1978®BYTE Publicitionsinc COMPUTER Js ^'J(n.- ■// '^n-i >»t, For Homeowners, Businessmen, Engineers, Hobbyists, Doctors, Lawyers, Men and mjii9. Vol. We have been in business for over nine years buifding a rep9%flrtft>n for providing a quality product at nomir\^|,prtces — NOT what the traffic will bear. Our soft**ai& '^ » ;- . X^^W f*^ L^**^. Business & Per- sonal Bookkeep' ing Programs \>vVO('^^ • Versatile - operation. - as most programs atf^w for rnultiple modes of Tutorial — as each program ^ s^H'jpromfttn t r\^a y eyre ry^ et setf^roffipting ttld le^ you through the program {most contained right in their source code,. - ^^^ ^m. » • Comprehensive — as an example our PSD program not only computes Power Spectral Densities but also includes FFT's. Inverse-transforms, Windowing, Stidmg Windows, simultaneous FFT's variable data sizes, etc and as a last word our software is: • Readable — as all of our programs are reproduced full size for ease in reading. 9 • Virtually Machine Independent — these programs are wn'1 in a subset of Dartmouth Basic but are not oriented for any particular system. Just in case your Basic might not use one o particular system. Just in case your Basic might not use o our functions we have included an appendix in Volume V wl gives conversion algorithms for 19 different Basic's; that's right, just look it up and make the substitution for your particular version. If you would like to convert your favorite program in to Fortran or ApLor any other language, the appendix in Volume M will define the statements and their parameters as used in our Over 85% of our programs in the first five volumes will execute i JK Basic's with 16K of free user RAM. If you only have 4K ^because of its lack of string functions only about 60% of our programs '^in Volumes I through V wou|{^^'ua»9Jjle^however they should execute in only 8K of user RAWP^ v.j* ^ '■<• v For those that have specific needs, we can ta'TISr anyfef our-OT^r; Pfiju r you or we can write one to fit your specific needs ^ - ?^inH»»«*Vfvol. I - $24.95 ^nt i<* *»•* iBookkeeping ' __ . . • TSames »0Z Vol. IV Bingo Bonds Bull Enterprise Football Funds 1 Funds 2 Go-Moku Ufe Loans Mazes Poker Popul Profits Qubic Rates Retire Savings SBA T?c-Tac-Toe Vol. V Andy Cap Baseball Compare Confid 10 Descrip Differ Engine Fourier Horse Integers LOO'C / -., Playboy O Primes Probal Quadrac Red Baron Regression 2 Road Runner Roulette Santa Stat 10 Stat 1 1 Steel Top Vary Xmas t APPENDIX B ts and generates financial reports. nv. Depr. A/R. A/P. '^ ^ O 0( "11^::. Designed to challenge the average player, fairly comprehensive. ->Q Great fun for-aW, offers aiinique opportunity for beginners in need of |For Doctors and Dentists alike, a complete patient billing system which also permits the maintaining of a patient history record. j VVordprocessing for lawyers, publishers, writers, etc. Write, store, and change from rough draft to final copy in a variety of formats. «\ form l^>^cfures l^~~ torn «"• ^ «nV>r JVol. Ill — $39.95 jj flftal^ Investments /Advanced Business .Billing, Inventory on ' '^\ and de^'^Payroll ■*!**•• *^ Vol, V — $9.95 , • • ' Experimenter's vij^— InC^'**'^ Program Vol. VII — $39.96 Professiofwl" PrograjT\s,. 7 Disk utility program with memory testing "J Tajcpayers return, itemized deductions or standard "'Reconciles bank statements Balances your checkbook Computes real cost on bank financed items: cars, boats, etc 42 .Computes depreciation, 4 methods, any time period ^6. d4 erC— FAVORITE PROGRAM CONVERSIONS t,M»»C ^- \ 5rL\- p»? » 2* '°., j.„ter. ** ::Ld'»"«'«"SCIENTIFIC RESEARCH tjfiot y««P.O. Box 490099-B, Key Biscayne, FL 33149 ^n» t»<»«*Phone orders call 800-327-6543 ' '-r «nd_o^f^yip^^en^-^05) ^6J-1153__ Add SI^Hper volume handling, otraSmestic shipnnents sent U.P.S. except APO and P.O. Box which go parcel post. Foreign orders add $8.00/volume for air shipnnent and make payable in U.S. ,pnDUi»-iiollars QfjJy-tniel **; yrlghted i^^ ts% thon AVAILABLE AT MOST COMPUTER STORES [laUer • iviastar Ghiirge and Bank Arnericar^ ^ccepted. .re|prQcbicfid-Qr sold^ BYTE July 1978 49 * Photo 1 : The bird organ, a popular novelty of the 18th and 19th centuries. The device is a sophisticated automaton capable of imitating the sound and movements of a real bird: the wings flap, the head turns, and the beak moves to the accompaniment of assorted bird whistles. PIVOT POINTS PITCH PISTON VOLUME VALVE Figure 7 ; Schematic diagram of a typical bird organ mechanism. Two metal cams control the bird's voice: the far cam controls the pitch piston (located in the body of the bird whistle), and the near cam controls the volume valve (located inside the wind chest). accurate watch (chronometer) and won a prize of X20,000 from the British govern- ment in 1760. Determined to make the British Navy the master of the seas, the Admiralty offered a prize for a watch that would permit a ship to calculate its longi- tude with an accuracy of 60 nautical miles after being at sea for six weeks. (Latitude is relatively easy to calculate by accurately measuring the elevation above the horizon of any celestial body. Longitude is more difficult, and requires knowing the elevation at a time known relative to a fixed ref- erence, the zero meridian at Greenwich, England.) Mechanicians (an excellent name for the practitioners of this craft) chose to work in the field for much the same reasons we all choose a field today: because it was an absorbing and genteel means of earning a living, because it offered accomplishments one could show with pride, and because it was the area for future expansion, the grow- ing edge of the technology. Look at the legacy of machines they have left us: the Linotype, the typewriter and its relatives, the reproducing piano (and its less intel- ligent cousin, the player piano), clocks and watches of every description. They are all fine mechanisms, but most of them were perfected and essentially attained their present configuration 80 years ago and more. Electronic devices have displaced most of them. The flowering of mechanical technology had other branches that have now died out, though, leaving only accounts in books and a few decaying museum specimens of machinery which once stirred general admiration and brought fame to their creators: the Orrery, a clockwork model of the solar system, complete with moons, that once stood proudly in the exhibition room of every significant university; the dazzling variety of music boxes which once were found in every parlor; and so on. And who nowadays recalls the bird organ (see photo 1 and figure 1)? The bird organ was a mechanical device that produced a very close simulation of a bird's song; 200 years ago it was a very expensive and much cherished ornament in the parlor of every gentle home. I have seen electronic versions of circuits for such a device and have built one, but together with its transformer and loudspeaker it occupies most of the space in a small bird- house. A commercial version I purchased is slightly smaller, housed in a 3 inch plastic sphere. Around the year 1800 there was a bird organ made for sale to replace the 50 luly 1978 <^ BYTE Publicalions Inc THIRD *3r- ' ■>«» Intelligent Machines for Home, Business & Industry SsSVTT C9 AJE#LL* (Call for Papers) deadline for final paper: September 1st (request instructions, now!) tell everyone of your latest project and results {partial list of topics - suggest others/ Tutorials for the Absolute Novice Interactive Stained Glass (Art & Film) Electronic Music Systems Community Memory & Electronic News Computer Networking for the Public Intelligent Typewriters (Word Processing for All) Exotic Games & Simulations Amateur Radio & Logic Machines Applications: Plain & Fancy The Business of Small Computing Computers for Small Business IntelUgent Prostheses for the Physically Impaired Personal Computing in Education & Learning Legal & Tax Aspects of Home Computers System Software for Everyone Hardware Hackers' Delights Bus & Interface Standards Speech Synthesis & Speech Recognition The Future of Consumer Computers be an exhibitor — homebrew or commercial Propose Exhibiting your Homebrewed System or Widget Request a Commercial Product Exhibitors' Prospectus IN LOS ANGELES FOR THE FIRST TIME using the humongous Los Angeles Convention Center NOVEMBER 3 - 4 - S ,1:978 9am-6pm 9am-6pm noon-Spm for all the details, request your FREE Silicon Gulch Gazette Computer Faire Box 1579, Palo Alto, CA 94302 (415) 851-7075 Circle 393 on inquiry card. BYTE |ulv 1978 51 In computer terms, the bird organ can be de- scribed as a spring driven power train controlled by a mechanical read only memory. head of a gentleman's walking stick. A hinged lid sprang open by a concealed catch, and out popped a minute feather covered bird model that opened its beak, spread its wings and sang. The entire device, except for its winding key, was housed in a gold ornamented cylinder 114 by 2 inches (3.8 by 5 cm) long. How's that for miniatur- ization? And I'll wager it made a better song than my blocking oscillator version. There were bird organs, or accounts of them, in antiquity. The Greeks used steam or air to drive whistles mounted in bird figures; the Arabs and Persians supposedly did the same. The mechanism was some- times a cluster of tuned whistles like a bank of miniature organ pipes, and this arrange- ment is found in a clock from 1 750, but the modern bird organ dates from about 1770 and was likely devised as a means of teaching domesticated songbirds to sing. Soon minia- turized, it was incorporated into decorative objets d'art of all sorts: snuff boxes, per- fume flasks, table centerpieces (these often had small fountains of water and other dis- tractions built in), clocks, even watches (but these were very rare), and free standing forms. One delightful version of the latter, perhaps 9 inches (23 cm) high, depicts a lady seated at her desk and a bird on a perch pole nearby. Her hand is on a (mock) bird organ, which she cranks while her pet listens attentively. The bird then tries to copy the song, but makes errors, which she corrects by playing the lesson again so that the bird "learns" and repeats it accurately, with much enthusiastic flapping of wings, pivot- ing on the perch, etc. Large or small, the mechanism of bird organs was always the same (see figure 1): a main spring drove a gear train which oper- ated a bellows to compress air in a wind box, and another gear train drove an intricately cut cam which, via a piston, varied the pitch of a whistle connected to the air supply. A similar cam operated a valve to control the volume of the whistle tone. More gears drove cams that controlled the beak, wings, and pivoting actions via push wires ascending the perch pole and the bird's hollow legs. Songs of eight or nine species are to be found among bird organ mechanisms (some elaborate devices had double or triple songs), and the nightingale was most popular. Remember the fairy tale about the mechan- ical nightingale by brothers Grimm, about 1855? It lived in a jewelled tree, and some devices were made in this form, but the objet d'art was perhaps most popular, being finished in enamel and gold and frequently decorated with precious stones. While bird organs were essentially one of a kind machines, there was a sort of produc- tion line for them maintained by the most famous makers, and many thousands of them exist in museums. A great many were exported from France and Switzerland to the Orient. They are still made, and, while expensive, they are no longer the luxury of rich men. [A German bird organ about the size of a pocket calculator Is currently avail- able for under $400 ... CM] In computer terms, the complete mecha- nism might be described as a spring driven power train controlled by a mechanical read only memory whose values are stored as a distance of the edge of the cam from the cam's center of rotation. In 45 seconds of singing, there might be a fair number of places where the notes sound, perhaps, six to eight per second (during a trill). Referring to figure 1 , if we have two cams which rotate in 45 seconds, and we allow a time division of ten samples per second, and if we allow eight bits of precision per sample, we would require 900 bytes of read only memory to simulate the control func- tions of these cams. A longer song, as in the tutorial automa- ton described above, might require three times as many bytes together with a smaller number to control bird and figure motion. This gives a total of 3 K bytes of mechanical read only memory divided unequally among several cams (something approaching the storage capacity of contemporary read only memory parts). A better way to look at this sort of mech- anism might be as a computer with analog storage (varying cam curves) and analog output (varying positions of the volume valve and pitch piston). Information is stored in the intricate curves of the cams. The information is fixed there for all time, or until wear or rust alter it, and may be recovered whenever it is needed by rotating the cam while the cam-follower rides on its periphery. It is in every way an "analog" of the desired sound, but it is not a recording, because it has been distorted in storage to suit the particular readout mechanism being employed (the cam-follower). (I have de- scribed the stored information as digital in order to facilitate the comparison; this has validity because of the relatively small number of analog positions and their re- solvability into bytes of restricted number.) Even in the 1770 to 1850 era the cam was not a new invention, but this application was novel. It was a benchmark in the field of mechanics. Storage of information had now become a tool of the mechanician, where formerly mere repetitive movement, the regular back and forth movement of a 52 luly 1978 @ BYTE Publicitiom Inc clock's mechanism, was known to be available. With the possibility of storing informa- tion comes the possibility of crafting com- plex and seemingly nonrepetitive movement. If it is the desire of the builder of the mecha- nism, these movements may be arranged to mimic the movements of living organisms. This is the basis of more complex mechan- ical toys like the rabbit that walks about beating on a drum. (Incidentally, in 1880 a minute gold rabbit, perhaps an inch high, who also played his drum, was sold as a brooch. Not to mention a 3 inch gold caterpillar that sedately crawled its path, circa 1850.) However engaging, these were funda- mentally simple and regular movements that did not tax the designer. Mechanicians have constructed far more complex ma- chines designed to duplicate the most intricate and coordinated movements per- formed by living creatures and to produce an effect of illusory life for the few minutes the mechanism operates. Why would clever, dedicated people do such a thing? Why build an automaton? Machines That Imitate Life: a Rationale Until modern times there was a pervasive and unchallengeable view that the bodies of human beings were not fit subjects for in- vestigation. Death was the penalty for human dissection during the middle ages, except for rare occasions when the Church sponsored demonstrations of the corpses of criminals. Clearly, anything so sternly for- bidden must have been well worth investi- gating; could it have been that the secret of life lay concealed in the structure of the body? There were some who took the risk, and they always found that animal and human structure were very similar. Since, in the influential and respected view of Rene Descartes (1596-1650), animals were ma- chines that differed from humans chiefly in their lack of divine inspiration, it is easy to see the framework for a "mechanistic" view of living organisms. The notion held much appeal. It explained in terms that were comprehensible to the average edu- cated man how living creatures were con- structed by substituting mechanism for mystery. Popular expositions of science from the 1890s right up to the 1940s typically de- picted drawings of a person cut away to reveal bellows and pump rooms in the chest, the chemical factory in the abdomen, the telephone switchboard in the skull, the pistons and gears in the limbs, and so on. I suggest that this conception of orga- nisms as chains of mechanisms, and the corollary, of a god as the divine watchmaker who constructed and set them in motion, was perhaps the most influential factor lead- ing to the construction of machines designed to imitate life. Note the variety of literature in which the attempt to create life is central to the theme: from ballads and fairy tales dating back to the beginning of language to Mary Shelley's Frankenstein (1818); from Offenbach's opera with the clockwork ballerina. Tales of Hoffman (1881), through countless science fiction works, to tales such as Shaw's Pygmalion. And of course there is recombinant DNA research, the leading edge of biochemical investigation at this moment where the purpose is, manifestly, to explore the mechanisms of life in living cells. The impulse is still there in us although the metaphor is different in different ages, and the mechanisms employed are de- pendent on available technology. Astonishing Automata About 1709, in Grenoble, the Edison of automata, Jacques de Vaucanson, was born. Little is known of his early life, except that he was something of a rake and a seminary dropout who disrupted affairs at the monas- tery by making wood and paper wings that flew about. But much is remembered of his automata, which, though they no longer exist, were the marvel of their age, the object of admiration by all gentlemen who saw them, and the envy of mechanicians ever since. Vaucanson was not a showman, but a philosopher and inventor. He often spoke of "moving anatomy," his expression for the concept that life, especially life in lower animals, was in fact a series of undirected movements (what we would today call "reflex movements"), and that by duplicat- ing the movements and actions of a live creature, one might succeed in duplicating the life of the creature. While such a notion seems absurd to us (it is, according to cur- rent understandings of the formation of ideas, magical, and therefore primitive) there is precedent for it from a character no less important than St Thomas Aquinas. Vaucan- son had a splendid opportunity to come across St Thomas's writings, since he lived in a monastery for perhaps 1 5 years. Books were expensive treasures in 1709, and mon- asteries were the main places where collec- tions existed. St Thomas's works would probably have been among them. In the Summa Theologica (Q13; Art 2; Reply obj 3; Part II) there is a passage: "Animals About 1 709, In Grenoble, the Edison of automata, Jacques de Vaucanson, was born. July 197aOBYTE Publications Inc 53 show orderly behavior and are machines, as distinct from man who has been endowed with a rational soul and therefore acts by reason." If animals are orderly machines, it might be possible to make a machine that looks and behaves like an animal. If one took special pains to reproduce vital details like respiration, digestion and excretion, etc (so runs the argument), one would then have created the next best thing to a real living animal. Vaucanson arrived in Paris in 1735 at the age of 26 to pursue his moving anatomy con- AVEC PERMISSION | DU MAGISTRAT DE LA VILLE, | On expofera a la vue dn Pttblique les^. chefs etOeuvres Mechaniques du Celibre Mon- H fieitr VAUCANSON,. Membre de PAcademie Royale des Sciences de Paris, m qui confiftent en trois Figures Automates. S SC A V O 1 R: m 'A premiere, Un hoinme de Grandeur naturellc habiliti en SAUVAGEqui joui Onzc airs fur la Flute travcrficrc par 'cs^« menies mouvemenis des Levres dcs doiu & le fouBle de fa bouche comme I'homme vivanc. e^ ^^ L,A fcconde, un hommc au(Ti de Grandeur naturelle. habillcen BERGER PROVENCAL qji joue 20. airsdiffercns fur leFIutetdeija ^y Provence d'une main & du Tambourtn de Pautrc avec route la prc^ifion & perfcftion de nwme qu'un habile joiieur. (|^ ^LAtroifi^mc un CANARD artifijiel en Cuivre d'orc ^ui B&is , Mange , CrqiiafTe Barbotc dans I'cau & fait la digcflicn comm» un^S ^ Canard vivant. m QR l^Es 3. Pieces qui ont fait meriter une Recompenfc a I'Authcur d*une Penfion de 8- m'"e & ?■ cent Litres par Ic Roy , Ji qui ont en- Sw Hi gag^ un grand nombre des Pcrfonnes de diftinflion a des longs & penibles Voyages pour les voir . marque micux Icur mcrite qu'un plus ^J ^£ long detail. On Efpere que dans cette Ville un chacun fera charm^ de propter de Toccafion de les voir & qu'its en feront la dilTerence ^5 ^S du nombre des bagatels, que I'on fait voir tous les jours au publique- Coin.'nelePi-oprictairedoit fctrouver le 12. a Francfurt il donnera ak maA pendanr 8- jours a commenccr ce jourd'huy 2. Reprcfen rations pjr jour a 3. & 5. hcures apres midy au Poii du Miroir > Ton payera 94. {^ jWj Sols au premi^ , 16. au fecond & 6. au croiilcTTie place , & comme 11 07 a aucune rrichexic dam ccs beaux ouvrages Ton enfeta voir S^ ^$ fintericur a de.couvert en payant 24. Sols par perToniie , l^n vend aulH dans la n>^mc Sate le m^naire prefentc par TAuteur a Meffieurs^P gde I'Academie Royale qui concJcnt un ample detail des pieces contcn6es dans ces ouvrages & aufli TApprobation des RkfTteursdc ''Aca-^^ _demie. g M Les Compagnies parciculicres pourroa: les voir a couc heute , en avertiHanc d'avoncc & pajcroot 3. Livres par Perfonne etaqt au m JB moin au nombre des huics. SB iiSS16ilfiSiiStSiilt8i£iitll«tiSfiS@SliSllliitiiSii6£Si§iiiSSisi Figure 2a: Three automata invented by Jacques de Vaucanson in the mid-1 8th century. Shown are a flute player, mechanical duck, and a flageolet (whistle) and drum player. The novelty of these figures caused a sensation in their time (from an 18th century engraving, courtesy Bettmann Archive). 54 luly l978SBYTt Publicjtionslnc A = FOUR FINGERS OF RIGHT HAND B" = THREE FINGERS OF LEFT HAND DISTRIBUTOR LOW PRESSURE MEDIUM PRESSURE — HIGH PRESSURE cepts. He promptly ran out of money. There is documentation to show he had the idea ". . . of getting assistance by producing some machines that could excite public curi- osity . . ." as a means of raising funds. He excited plenty of public curiosity, for in 1738 he simultaneously displayed three automata (see figure 2a). An automaton duck ". . . made of gilded copper who dtiiiks, eats, quacks, splashes about on the water, and digests his food like a living duck" was one, and a pair of automata musicians who played flute and drums were the others. The machines were life-size and were mounted on cubical pedestals about three feet on a side, which contained the bulky mechanism. They were unique and original, and they created a public sensation for 50 years. To me, the flute player seems the most remarkable mechanism of the three. De Juvigny, a friend of Vaucanson's, wrote in 1777, "At first many people would not believe that the sounds were produced by the flute the automaton was holding. These people believed that the sounds must come from a bird organ or German organ enclosed in the body of the figure. The most incredu- lous, however, were soon convinced that the automaton was in fact blowing the flute, that the breath coming from his lips made it play and that the movement of his fingers determined the different notes. . . The pec- tators were permitted to see even the inner- most springs and to follow their move- ments." Figure 2b shows the mechanism in outline form. All that needs mention is the weight motor (not shown), and the fact that different weights were added to each bellows in the set of three to provide different pres- sures of air. High, medium and low pressures provided the designer with the possibility of playing notes loudly or softly in the lowest register, or of shifting the flute to a higher register by employing greater pressures. The distributor valve selected the correct pres- sure for a given note. Ihe illustration merely hints at the head mechanism, which must have been extremely complex. This description of flute playing is from the Encyclopedia Brittanica: "The flute is held sideways to the right of the player, who forms his lips to make an aper- ture and directs his breath stream across the mouth hole and onto its further edge, where it breaks up into eddies that alternate regu- larly above and below this edge and so excite the air column of the flute into vibration. Stability of the notes in the various registers and at different loudnesses is achieved by Figure 2b: Details of Vaucanson 's remarkably sophisticated flute player automaton. A music box- like drum with pro- grammed pins controlled the motion of the fingers, volume of air and shape of the mouth (made of rubber) so that the device actually played a standard flute. luly 1978 ; BYTL Publiialioni Inc 55 "(Vaucanson's mechanical duck) is the most admi- rable thing imaginable, a piece of human work- manship almost passing understanding." control of lip aperture, angle of breath im- pact, and breath force. The compass is three octaves. . . ." Vaucanson's complications came from his decision to use the true flute, blown from the side, and not a recorder, which is an air pipe instrument blown from one end like a pennywhistle or organ pipe. In both instruments, air column length is varied by closing the appropriate holes in the body. To some degree Vaucanson simplified his task by employing seven active fingers (instead of eight, the modern standard: or maybe his particular flute had only seven fingerholes), but he took on and overcame the challenge of providing means to produce the proper size of lip aperture and the proper angle of breath stream to mouth hole. It seems quite likely that Vaucanson used actual rubber, first seen in France in 1736, in the lip mechanism, for there is evi- dence (in another automaton) that he knew how to fabricate rubber. Now, I can imagine a mechanism that would dilate and contract the aperture in a set of rubber lips, and vary somewhat the angle of a stream of air blown through the hole, but I have the considerable advantage of being able to draw on two centuries' accu- Figure 2c: Details of Vaucanson's mechanical duck, showing the intestine- like tubing within. The duck could drink, quack and splash about, and was able to eat, digest and eliminate food (from an 18th century engraving, courtesy Bettmann Archive). mulation of mechanical knowledge. Vaucan- son was starting from scratch, building a mechanism never before seen, to produce a motion never before defined, to perform a task never before attempted. That he suc- ceeded so well is astonishing; that he did it within 36 months is staggering. And remem- ber, he employed mainly hand tools. There was no local machine shop he could call on to mill a part. We have no record of where Vaucanson learned his mechanics, but his skills were prodigious. The combination tabor (drum) and flageolet (pennywhistle) player shown at the right in figure 2a was undoubtedly con- structed along similar lines; I have not seen an explanation of its mechanism. It would have been simpler, since the flageolet is easier to play than a flute (only four or five finger holes, blown from one end), and ma- chinery to make the right arm beat the drum would be relatively simple to figure out. It seems unlikely the two automata could have been so well synchronized that they played together. Vaucanson's Mechanical Duck It always startles me to read things like this anonymous appreciation of Vaucanson's duck: "It is the most admirable thing imaginable, a piece of human worksmanship almost passing understanding." I try to ac- count for the powerful attraction that con- structing simulacra of lower animals held for men 200 years ago. Still, it catches me off guard to see the adulation the duck evoked. Dr G C Beireis, the fourth owner of the ma- chine in 1785, rhapsodizes, "It was in this duck that Vaucanson's genius reached its highest point. I have still not got over my astonishment at this work. (He had seen it thirty years earlier.) One single wing con- tains more than 400 articulated pieces." I doubt we would feel that way today about an automated Scottie, say, but maybe ducks make better pets. It was, from all accounts, a singular like- ness to a duck, and here is what it did: After a light touch on a point on the base, the duck in the most natural way in the world begins to look around him, eyeing the audience with an intel- ligent air. His lord and master, how- ever, apparently interprets this differ- ently, for soon he goes off to look for something for the bird to eat. No sooner has he filled a dish with oat- meal porridge than our famished friend plunges his beak deep into it, showing his satisfaction by some char- acteristic movements of his tail. The 56 July 1978 @ BYTE Publicilions Inc way in which he takes the porridge and swallows it greedily is extraordi- narily true to life. In next to no time the basin has been half emptied, al- though on several occasions the bird, as if alarmed by some unfamiliar noises, has raised his head and glanced curiously around him. After this, satisfied with his frugal meal, he stands up and begins to flap his wings and to stretch himself while expressing his gratitude by several con- tented quacks. But most astonishing of all are the contractions of the bird's body clearly showing that his stomach is a little upset by this rapid meal and the effects of a painful digestion be- come obvious. However, the brave bird holds out, and after a few moments we are convinced in the most concrete manner that he has overcome his in- ternal difficulties. The truth is that the smell which now spreads through the room becomes almost unbearable. We wish to express to the artist inventor the pleasure which his demonstration gave to us. (From Chapuis' book, Automata: Historical and Teclinical Study, see detailed bibliography in part 3 of this article.) Something here for everyone, isn't there? Passion, satisfaction, and a dash of slapstick. The mechanicians in the audience were dazzled by Vaucanson's skill in building a duck that could swivel its neck in every direction while sitting or standing; this does suggest some remarkable techniques for managing the pushwires ascending the legs, maybe even some internal mechanisms within the body. Probably written by Vaucanson and cer- tainly based on data only he could have pro- vided, the following passage from an article in a 1777 dictionary of science shows how proud he was of the internal mechanisms that caused grain to be ". . . digested as in real animals by dissolution and not by (grinding) . . . the inventor does not set this up as a perfect digestive system capable of manufacturing blood and nourishing juices to support the animal, and it would be un- fair to reproach him with this shortcoming." But it is clear how well he knew the 18th century idea that blood comes from food, and he implies he was trying to follow it. Indeed, in some accounts the body was covered by latticework so the interior mechanisms could be viewed as they did their job. Vaucanson had good reason to be proud, for the body contained his new invention, the rubber tube. Any machine capable of making that kind of smell had to be alive! One wonders what the "...chemical lab- oratory where the principal part of the food could be decomposed..." mentioned in the article might refer to. It may have been that his rubber tube intestine actually con- tained some chemicals or enzymes that attacked the starch in oat porridge, causing it "...to leave the body in markedly changed form." But there was hardly time enough in a performance of a few minutes to convert anything. More likely the operator between performances drained the stomach of its contents and loaded the nether-part of the intestine with the imitation duck dung that so impressed audiences. The duck and the two musicians probably made a good deal of money for Vaucanson, but because it was necessary to transport them to other capitals of Europe for further exhibition he sold them all in 1743 to show- men who took them to England, Russia, and finally to Germany. In St Petersburg in 1782 the third owners tinkered with the mecha- nisms, interchanging parts so they would break if anyone else tried to show them. Dr Beireis had this partly repaired, but when Goethe viewed the duck in 1805, he found, "Vaucanson's automata were para- lyzed. The duck had lost its feathers and, reduced to a skeleton, would still bravely eat its oats, but could no longer digest them." The duck was 108 years old when Rechsteiner, a skilled mechanician, was hired to repair it. It was exhibited in Italy in 1844 and in London two years later. After that it dropped out of sight. Some photographs turned up in the early 1950s, evidently left by the former curator of the Paris Museum of Arts and Crafts. They are glass plate negatives that probably date from before 1900. The skeleton they reveal, together with the appearance of the mecha- nism, strongly suggests the wreckage of Vaucanson's duck, as they were labelled. The plates were said to be from Dresden, and if the duck survived World War II, one hopes it is in a dry attic. The musicians were lost from sight sometime around 1800. None of the imitations of Vaucanson's automata, including mekaniker Rechsteiner's duplicate duck, now survives. These won- drous mechanisms are altogether lost. Vaucanson himself seems to have pros- pered (he was a member of the Academy of Science in 1777) and continued inventing. In 1741 he devised the system of punched cards that controlled looms in the jacquard tapestry factory. This is generally considered to be the first digital number storage and readout system. In 1760 he invented the Satisfied with his frugal meal, the mechanical duck stands up and begins to flap his wings and to stretch himself while ex- pressing his gratitude with several contented quacks. luly 1978 ra BYTE Publications Inc 57 Note: A complete bibliography for this part of "Antique Mechanical Computers" will appear with "Part 3: Human and Machine Action and the Torres Chess Automaton" in September 1978 BYTE. modern metal-cutting lathe, with a shaped guideway to prevent chatter and twisting of the tool. Mechanism of the Automata While relatively simple to explain and easy to grasp when explained, Vaucanson's machines really are very sophisticated in performance and embody concepts easily 100 years ahead of their time. The weight- motor is a heavy weight suspended from a rope wrapped around a drum windlass, which, while slowly falling, drives a gear- train (speed controlled by a governor). These gears slowly turn a cam-drum, the master controller "memory" mechanism, one rotation of which equals one perfor- mance of the automaton. This drum, per- haps the diameter of a small keg and three feet long, has on its surface an array of rows of studs of some sort, nails or wooden knobs. Cam-followers, some sort of spring loaded levers, ride on the drum surface, one for each row (circle) of studs in the array, and each cam-follower is for a moment pushed out of place if a stud rotates by to push on it. There are as many circles of studs on the drum as there are functions of the automaton to be controlled, and the cam-follower unique to that circle of studs does the controlling. Thus, one row, say, controls the dilation and contraction mechanism of the lips, and another row might manage the movements of the first finger, left hand, and so on. There would be about 1 2 functions to be controlled, so about 12 rows or circles of studs are on the drum. It is rather like a giant music box movement, except that instead of steel needles being plucked, cam-followers are displaced, and with displacement each fol- lower pulls on a flexible cable which is linked by its own pulley system to the finger, lip, or valve that is unique to it. In some cases, like the lip control mechanism, the require- ment to produce music is for smooth varia- tion from one size to another, so the row of studs for that function is replaced by a smoothly varying curve, a cam. In other cases, the fingering mechanism, a finger either does or does not cover a flute hole. This is digital control (the word comes from counting on the fingers); the former is ana- log, meaning that a little movement here causes a proportional movement there. When it is all put together and regulated carefully, the machine will play the flute using wind pressures as selected by the distributor valve. For the sake of impressive appearance, the machine is covered with a wooden framework in human shape and is clothed, but it would do its job bare. How- ever, it would look like a machine and not a person. The tabor and flageolet player is similar, but probably only two levels of wind were employed, and the fingering is simpler, probably four fingers. The duck was essentially a giant version of the mechanism that operated the bird figures described earlier but with many more, and more complex, movements. While it is possible that some weight sensitive area was built into the pedestal so that the duck started to gobble the food only when a plate was placed before it, it seems much more likely that the operator carefully mem- orized the duck's movements (which, of course, are identical every time) and returned with the plate at just the right moment. Otherwise the bird would have been gulping down thin air. If they still existed, these machines would provide an intriguing catalog of early 18th century movements, probably including some that Vaucanson devised for special purposes that would not be rediscovered for 75 years or more. But, as computers, the machines were incredible. Here, 240 years ago, was a digital and analog computer preprogrammed with perhaps 300 to 500 bytes of read only memory, each byte 10 or 12 bits wide. Vaucanson appears to be the first person to have seen the need for synchronous control of multiple functions (how else could you play a flute except by regulating breath angle and pressure while simultaneously fingering the proper notes?) as well as the first who saw \hQ possibility of designing mechanisms to effect such con- trol. That he used the music box spindle approach to his problem is not to his dis- credit, for that mechanism was known to function reliably over long periods while undergoing little wear. His incorporation of music box memory devices into an array on a single drum (the master controller) enabled him to produce some remarkable results. He could control a variety of simul- taneous, interdependent functions because they were all driven by the same "clock." This was parallel data processing, in rela- tively small chunks, to be sure, but parallel beyond doubt. The likes of it were not seen again in mechanics until the player piano with its paper tape. It is not so very different from the way the central nervous system deals with data in many parallel channels simultaneously. But why is this surprising? Jacques de Vaucanson was attempting to create life. It was his genius to approach the task in the manner of living things." ,1 58 July 1978 '0 BYTE Publicilions Inc DESIGN a voice command system with theSiliconix CODEC &WIN an Appier Enter the Siliconix CODEC Design Contest and win an Apple II — the world's best -selling personal computer — or another great prize. All you have to do is use Siliconix' CODEC to design a microprocessor- based system which responds to your spoken words (or talks back to you). Our CODEC is a two-chip set: the DF331 coder is a high-speed serial output A/D converter — a complete subsystem- on-a- chip; the DF332 decoder con- verts high-speed digital bit streams into analog signals. The system you design must be capable of understanding or speaking at least 16 words. Here's what you can win: 1st prize: Apple II personal computer (retail value $1,445). A completely self-contained computer system with high resolution color graphics m 15 colors (with color TV); BASIC m ROM, 16K bytes of RAM, built-in video interface, cassette I/O, four A/D inputs with two game paddles supplied, eight peripheral slots, three TTL inputs and four TTL outputs. Apple 11 plugs into any standard TV using a modulator . 2nd prize: Silicomx LCD Stopwatch-In-A-Wristwatch Features time, day, date, plus split timing stopwatch functions. 3rd prize: Silicomx LED Stopwatch. Includes split timing function. 4th prize : Siliconix Telephone Timer Includes start/ stop and timeout. 5tn prize: Siliconix LED Stopwatch Features a digital start/stop timer All entries must be accompanied by our official entry blank. Get yours, along with complete contest rules, data sheets and other information, by filling out the ^°"""'*"iZrSiliconix Mail to: Siliconix CODEC Design Contest 2201 Laurelwood Road Santa Clara, CA 95054 Yes, I want to know more about the Silicomx CODEC Design Contest. Please send me details and the official entry blank. Name:. _Title:- Company: Address: _ City: (Optional) .Mail Station:- _State:. -Zip:. Circle 31 7 on inquiry card. BYTE July 1978 59 The Z-80 in Parallel Bob Loewer Micro Diversions Inc 7900 Westpark Dr Suite 308 McLean VA 22101 PROCESSOR . I 1 PROCESSOR, Many design engineers have introduced various types of parallel processing into systems in order to achieve higher through- put rates. Almost without exception though, these applications have been limited to medium and large scale computers due to price and complexity. In the past two years, microprocessors have reached a level of sophistication which makes them candidates for parallel processing systems. Such systems could conceivably offer minicomputer performance at micro- P ME MOR V I 32K a SHARED MEMORY (52KI MEMORY (32K) J DATA BUS I ADDRESS BUS I CONTROL BUS Figure 1 : The author's parallel Z-80 system. Both processors work indepen- dently, each supported by 32 K bytes of programmable memory. The proces- sors are linked by 32 K bytes of shared programmable memory. The shared memory, addressable by either processor as the upper 32 K, has its own address and data buses. Shared memory conflicts are resolved by the arbiter circuit shown in figure 2a. computer cost. This article is an investiga- tion of that idea. The Z-80 The Z-80 microprocessor, manufactured by Zilog, is a third generation LSI device which offers full software compatibility with the 8080 processor. Upgraded features provided by the Z-80 include: two sets of exchangeable registers, indexing, a full range instruction set (including register or memory bit operations), eleven addressing modes, a nonmaskable interrupt, dynamic memory refresh address generation, and an Interrupt register to provide a high speed vectored interrupt response to any location in memory. The Z-80's minimum number of control bus signals makes it easy to interface in multiple processor configurations. System Layout My design consists largely of two Z-80 microprocessors (processor X and processor Y) operating independently, each supported by 32 K bytes of programmable memory (see figure 1). The processors are indirectly linked by 32 K bytes of common memory, making a system total of 96 K bytes. The shared memory, addressable by either processor as the upper 32 K, has its own address and data buses. Data or address signals are gated onto their respective bus when (1) either processor performs an opera- tion involving a read or write against the shared memory, or (2) either processor attempts an op code fetch from the shared memory, or (3) machine instructions com- bine (1) and (2). Shared memory bus conflicts are resolved by the arbiter (see figure 2a). Since the processors use opposite phases of the clock, requests for bus access can never be initiated at exactly the same time. However, depen- ding upon the instruction sequences being executed, bus request conflicts can occur. This problem, summarized in table 3, has been carefully examined and is represented by figure 3b. It illustrates what is assumed to 60 July 19780BYTE Publications Inc \ ^ X SELECT {^^ Y SELECT ^l> ^ About the Author Bob Loewer is an employee of the Telenet Communications Corpora- tion and a graduate stu- dent at the University of Maryland at College Park. He is cofounder of Micro Diversions Inc, a company Involved with microcom- puters and microcomputer education. This article de- scribes Bob's early re- search on parallel micro- processor systems. \ ^ Y WAIT Figure 2a: The shared memory arbiter. This circuit resolves conflicts between the two proces- sors if both attempt to gai n simult aneous access to the shared mem ory bus. Fo r example, a request from processor X (XMREQ low) will cause IC3a to drive the XSELECT line low and will also disable IC3b. Processor Y will be locked out during X's memory reque st. If Y m akes a memory request while locked out, the output of IC4a will go low, activating the YWAIT line. be the worst possible case of bus conflict; both processors simultaneously executing shared memory read or write instructions from the shared memory. Of course, one cannot predict when each processor will attempt to access the shared memory, so all possible interprocessor state relationships have been investigated. The basic memory read or write instruc- tion has seven "T" cycles (T is defined as the duration of one clock period). The T states and their functions are: M1,T1 IVI1,T2 M1,T3 M1,T4 M2,T1 1V12,T2 M2,T3 Instruction decoding Op code fetch Memory read or write operation The M cycles are machine cycles. Table 3 shows the seven interprocessor T state align- ments: M1,T1 active for one processor when states Ml.TI thru M2,T3 for the other are active. Figure 3b illustrates an example of the processor request signals and signals from the conflict arbitration logic. Note that after a very short period (maximum of seven clock cycles) the arbiter synchronizes and thereby provides complete cooperation between the two processors' fetch and execution cycles by putting one of the processors into one or two wait states. Further, in the seven possible interprocessor T state relationships, there are two in which opposing shared memory access request signals are synchronized, in which case the arbiter does nothing. This means that, regardless of the processors' instruction Number Type + 5 V GND IC1 74S04 14 7 IC2 74S10 14 7 IC3 74S1 26 14 7 IC4 74S32 14 7 IC5 74125 14 7 IC6 74125 14 7 IC7 74125 14 7 IC8 74125 14 7 IC9 74125 14 7 IC10 74125 14 7 IC11 74125 14 7 IC12 74125 14 7 IC13 7432 14 7 IC14 7408 14 7 IC15 74S157 16 8 IC16 74S157 16 8 IC17 74S157 16 8 IC18 74S157 16 8 Table I: Power wiring table for figures 2a and 2b. July 1978 ® BYTE Publicalions Inc 61 SHARED MEMORY DATa BUS Figure 2b: Control cir- cuitry for tlie siiared memory parallel Z-80 system. The respective processor data buses and the shared memory data bus are shown at the top. The shared memory address bus is at the right. The shared memory arbiter is shown in the center (see figure 2a for a de- tailed schematic). This circuit works on a first come, first served basis to resolve all conflicts between the two pro- cessors. <;> «o^<±> - o- o yi5 O 0.2 ez A! B3 fl4 B4 % n a> MD WD MO MD MD MD MD MD 1 2 3 4 5 6 7 in> t> a> ICI4 7408 E>- VXI^ Yl Y? yj Y4 se ST (CI6 74SI57 A2 B2 A3 B3 A4 B4 2 3 5 6 M te 13^ SHARED MEMORY ARBITER Yl V2 V3 Y4 SE ST ICI7 74S(57 Al fli A2 82 A3 83 A4 B' 2 3 5 6 Yl Y2 V3 Y4 SE ST ICI8 74SI57 AZ B2 A3 B3 A4 84 2 3 5 6 l]hmht)h^Al)h^hhm- AhmhcAc}- mamahh <^ <^ ■ "« SHARED 1 MEMORY / ADDRESS -C!l> "«2 -(j;> M«a PROCESSOR PROCESSOR PROCESSOR PROCESSOR PROCESSOR PROCESSOR PROCESSOR PROCESSOR 62 luly 1978 © BYTE Publications Inc Ml -OP CODE FETCH- -IVIEMORY READ (OR WRITE)- Figure 3a: The basic Z-80 memory read or write cycle. Clock periods are referred to as T cycles and the basic operations are referred to as M (for machine) cycles. The first machine cycle of any instruction is a fetch cycle (Ml). Subsequent M cycles move data to or from the memory. sequences, 86 percent of the time the system is at most one wait state away from syn- chronization. Thereafter, both processors can execute read and write instructions from the shared memory at 100 percent processor utilization, assuming the instruction syn- chronization is not lost. Certainly opposing software will not consist solely of instructions which offer no bus interference. But it is clear that the most efficient method of solving the shared mem- ory bus conflict problem is the one that will achieve short term interprocessor synchroni- zation whenever possible. Arbitration Logic Each processor provides signals to the arbiter which identify a valid shared memory access request. IC2a and IC2b receive RFSH, MREQ, and A15 (the high order address bit signal) from their respective processors. MREQ indicates that a memory read or write operation is underway: either A1 5 line going high identifies the shared memory as the object of the request; and the RFSH lines insure that the dynamic memory refresh strobe from one processor will not interfere with the shared memory access request of the other. IC3a and IC3b provide an opposing grant or deny shared memory bus access proviso that is strictly first come, first served. A request from, say, processor X will cause IC3a to drive XSELECT low, and coinciden- tally disable IC3b. Processor Y will be locked out for the length of processor X's memory request. Now suppose processor Y does make a request for bus access when processor X is using the bus. This condition will forc e IC4a to its low state, activating the YWAIT line. The wait signal will continue until processor X concludes its memory access. Under no circumstances, however, will processor Y be forced into more than one wait st ate for this p rocessor X access. When XMREQ goes high, XSELECT follows Continued on page 174 Beginning Event Finishing Event Stipulation Delay Before Occurrence (ns) XA15 high XRFSH high XMREQ low XAIBhigh XRFSH high XMREQ low YA15 high YRFSH high YMREQIow YAlShigh YRFSH high YMREQIow XA15 high XRFSH high XMREQ low YA15 high YRFSH high YMREQIow 28 to XSELECT low YSELECT high to XSELECT low YSELECT low 25 after YSELECT goes high 28 to YSELECTlow XSELECT high to YSELECT low XSELECT low 25 after XSELECT goes high 53 53 22 22 to XWAIT low YSELECT low To YWAIT low XSELECT low XSELECT high to YWAIT high YSELECT low YSELECThigh to YWAIT high XSELECT low Table 2: Timing considera- tions in the arbiter cir- cuitry. The arbiter takes a finite amount of time for its logic circuits to effect the changes shown. The corresponding delays are shown at the right. )uly I978©BYTE Publications Inc 63 Photo 7: Hal Chamberlin's home built HAL-4096 computer system, built in 1972. This system, which is still In service handling lO for an IIVIP-16 micro- computer system, features TTL logic, a 16 bit word length, 16 registers, 4 K bytes of magnetic core memory (a surplus IBIVI 1620), and priority interrupt. The First Ten Years of Amateur Computing If one could find a specific date for the birth of personal computing, it would be May 5 1966. Sol Libes President, Amateur Computer Group of New Jersey 995 Chimney Ridge Springfield NJ 07081 Most people I meet are under the mis- taken notion that personal computing started only two or three years ago, with the introduction of the Altair 8800 by MITS. Nothing could be further from the truth. In fact, the amateur computing hobby was then almost ten years old. I therefore decided to write this article to set the record straight, give credit to the early pioneers in this hobby and shed some light on the early history of microprocessors. If one could find a specific date for the birth of personal computing, it would be May 5 1966. For it was on that date that Steven B Gray founded the Amateur Computer Society and began publishing a quarterly called \he ACS Newsletter. The newsletter exchanged information on where to get surplus computer gear, how to build not too complicated circuits, where to get integrated circuits, tips, experiences and where to get help. By the end of 1966, the Society reported that it had over 70 members. 1966 also saw the publication of the first books on how to build a home computer. Typical was We Built Our Own Computers by A B Bolt and published by Cambridge University Press. In January 1968, a survey in the ACS Newsletter reported that two amateurs had their home built systems up and running and that many others were actively working on their systems. The survey indicated that programmable memory sizes ranged from 4 to 8 K with some as high as 20 K, all magnetic core of course. Tele- types and Flexowriters were popular for 10. Clock speeds ranged from 500 kHz to 1 MHz, with the average 500 kHz. Most used discrete transistors, and a few reported using those new and hard to come by RTL integrated circuits. Instruction sets were small, ranging from 11 to 34 instructions. Word sizes were from four to 32 bits, with 12 bits the typical number. Registers ranged from two to 11, with three most common. Most reported that they had been working on their machines for about two years. The April 1968 issue of Popular Me- chanics reported on ECHO IV (Electronic Computing Home Operator), a home built computer constructed by Jim Sutherland. It had four registers, used a 4 bit word, had 8 K bytes of core memory, 18 instructions and a clock speed of 160 kHz. In December 1968 Don Tarbell (now 64 July 1978 © BYTE Publications Inc THE FULL POWER OF THE 1 6-BIT TMS 9900 MICROPROCESSOR IS NOW AVAILABLE WITH THE UNIQUE COMBINA- TION OF RELIABLE HARDWARD AND FAST, EASY TO USE SOFTWARE IN THE TECHNICO SS-1 6. WITH MINICOMPUTER PERFORMANCE THE TECHNICO 16-BIT MICROCOMPUTERS ARE AVAILABLE FROM THE SINGLE BOARD SUPER STARTER SYSTEM AT UNDER $400 TO THE FULL SS-1 6 WITH UP TO 65K BYTES OF MEMORY, MINI-FLOPPY OR FULL FLOPPY DISKS, A 4800 BAUD DIGITAL CASSETTE, 64 COLOR VIDEO BOARD OPTION, RS232 AND 20 MA CURRENT LOOP ALL COMBINED WITH ONE OF THE INDUSTRVS FASTEST BASICS AND A FULL ASSEMBLER, EDITOR, LINKING LOADER PACKAGE. SYSTEMS ARE AVAILABLE COMPLETELY ASSEMBLED AND TESTED OR IN UNASSEMBLED TEC-KIT^"* FORM. EXPLICIT MANUAL INCLUDED OR AVAILABLE SEPARATELY AT $35. TO LEARN MORE... JUST TEAR OFF A PIECE OF THIS AD AND RETURN TO TECHNICO OR CALL OUR HOTLINE 1-800/638-2893 OR YOUR LOCAL DEALER. EUROPEAN MODELS AVAILABLE THROUGH TECHNICO INTERNATIONAL TECHNICO INCORPORATED 9130 RED BRANCH RD COLUMBIA, MD 21045 PHONE 301-596-4100 TECHNICO INTERNATIONAL 2442 N LEXINGTON ST ARLINGTON. VA 22207 PHONE 703-538 4000 TELEX 64100 SOLIDSTA DOMESTIC SALES Circle 372 on inquiry card. SALES OUTSIDE CONTINENTAL U.S. BYTE July 1978 65 The first computer kit was introduced in 1971. It featured 52 TTL inte- grated circuits, a 32 by 8 bit programmable memory, and 15 instruc- tions for $503. Photo 2: The author's TVT-1, designed by Don Lancaster and built in late 1973. Intended only as a TV typewriter, it was interfaced to a modem and used with an IBM timesharing system. known for his high speed tape cassette interface) reported on his home built com- puter in the ACS Newsletter. It had a 4 bit word size, four registers, 10 kHz clock and was constructed using RTL integrated circuit logic. He used a Teletype for 10. In 1967, Dave Digby ran an ad in CQ magazine offering a computer kit. It was advertised as featuring RTL logic, four registers, a 512 to 1024 byte delay line memory, and serial input and output. The price was $1000. As far as I know, he never delivered any units. Most early builders constructed copies of the Digital Equipment Corporation's PDP-8 minicomputer with their own modifi- cations. In the surplus area, 1000 Minute- men I missile guidance processors became available in 1971. 1971 also saw the introduction of the first computer kit. It was part of the National Radio Institute's course on com- puter electronics. It used 52 TTL integrated circuits, had a 32 by 8 bit integrated circuit memory, 15 instructions and an operator's panel, and it sold for $503. Louis E Frenzel, then of NRI and now at Heathkit, was the designer. In late 1971, the Kenback Corporation The Kenback-1 computer featured a 1 K byte MOS shift register memory made by a small, young manufacturer called Intel. introduced the Kenback-1 computer for $750. It was intended primarily for educa- tional use. It had a 1 K byte MOS shift register memory made by a small, young integrated circuit manufacturer called Intel. It also had three registers, an 8 bit word size, 65 instructions, operator's panel, and an audio cassette for program storage. The December 1971 issue oi Computers and Automation described five home built computer systems. And by the end of the year 1971, there were reported to be 195 members in the Amateur Computer Society. In 1972 things continued to pick up. In June Don Tarbell reported that he had written an editor program for his new home built system and was working on an as- sembler program. His system used an 8 bit word, 16 registers, and 4 K bytes of core memory. Early 1972 saw the introduction of the 8008 microprocessor, by Intel, the opening of a number of used computer equipment stores, large price drops in TTL logic and the availability of the 1101 programmable memory at low cost. All of this proved to be a tremendous stimulus for amateur com- puter experimenters. In the September 1972 issue of the ACS Newsletter Hal Chamberlin reported on his home built HAL-4096. This 16 bit machine utilized surplus IBM 1620 core memories. Hal furnished a complete set of construction plans for $2. The system had 16 registers, priority interrupt, Selectric and paper tape 10, and many other very advanced features. The September 14 1972 issue of Elec- tronic Design carried an article on how to build a circuit which would display 1024 ASCII characters on a TV set. In 1973 amateur computing advanced in several areas. In May, the EPD company advertised the System One computer kit for $695. It had 1 K bytes of memory with expansion to 8 K and contained 82 integrated circuits. It had 57 instructions encoded in a diode matrix read only memory. The September 1973 issue of Radio Electronics published Don Lancaster's plans for the construction of the TVT-1 . Although intended as a TV typewriter, many enter- prising experimenters interfaced it to modems and home built computers. In late 1973, the Sceibi Computer Consulting Company introduced the first computer kit using a microprocessor. The kit was called the Scelbi-8H and it sold for $565. It used the Intel 8008 and had 66 luly 1978 © BYTE Publications Inc see TURNOFF RELRV 6 : DELflV 300: REM STOP ARM.. WRIT sense inputs liiiwmiihimtiiiiiiitiifc 210 TURf-40N LITE 4 : REM Expansion bus Socl(ets for up to 16l( of on-board RAM 8 user definable indicator lites ZIBLTM Lite port in PROIM displays an 8-bltword Programming slots for 2 TMS 2716s; stores user's programs 4 3/4-amp reed relays 4 general purpose relays, 5 amp at 115 VAC Dynabyte*s new Basic Controller: Check out its capabilities and imagine your applications The Basic Controller^'^ is a powerful, versatile and easy to use single board microcomputer system designed for control applications. It is heavily into control I/O: relays, flags and sense inputs. What makes controlling these l/Os (and the external devices they control) so easy is our ZIBL^"^ (Z-80 Industrial Basic Language). It is a superset of NIBL, National Semiconduc- tor's control BASIC, and was written by us specifically for control applications. We've divided the control world into six categories: sense inputs, flag outputs, lites, relays, A/Ds and D/As. ZIBL implements 64 channels of each in such a way that you need not know anything more about them than their names. In ZIBL it is valid to say: 1 00 IF TIME = 053010 AND SENSE (18) = OTURNON RELAYS Simple, isn't it! Some but not all of the Basic Controller's mouth watering features Circle 1 10 on inquiry card. include: • File structures that allow multiple programs written in ZIBL to reside concurrently in RAM. Each program may be individually LOADed, RENAMEd, or RUN. Any program may access another program as though it were a subroutine, while still retaining its own line numbers and variables. • Complete communication versatility. LISTing, PRINTing and INPUTing may be done to or from any serial or parallel I/O channel or the self-contained CRT I/O. • Single key SAVE or LOAD to and from cassette. • Single key SAVE to EPROM. No worry about PROM addressing or programming routines, it is handled by ZIBL — automatically — even if there are other programs already in PROM. • ZIBL in ROM: TURNON, TORNOFF DEUW, TIME, REM, IF THEN, DO GNTIL, GOTO, GOSGB, @(exp), TRACE MODE, UNK, READ, DATA, DIR, RND(x,y), strings triple precision integer arithmetic, plus the usual statements. • Onboard: Z-80 MPU, 32 flags, 32 sense, 8 relays, 8 lites, 2 serial, 1 parallel, cassette I/O, 64x16 video, keyboard port, two 2716 sockets with programming capability, up to 16k on-board RAM, up to 48k off-board RAM, real time clock, vectored interrupts, Lite Port on board, a kitchen sink, and an Expansion Bus. $750 assembled, tested, warranted 1 year. You add power supply, keyboard and monitor. Available now — see your computer retailer. 1 005 ElwellCt, Palo Alto, CA 94303 (415)965-1010 BYTE luly 1978 67 1 K bytes of integrated circuit program- mable memory. It was expandable to 16 K bytes of programmable memory ($2760) and had options such as cassette 10, ASCII keyboard input, oscilloscope output and serial 10. In 1973, Digital Equipment Corporation offered the PDP-8A with 1 K words of 1 2 bit programmable memory for $875. Also in 1973, a small publishing house catering to computer and digital electronics hobby- ists began publishing with a book on wire wrap construction techniques. It was called M P Publishing Company and was a part time activity of Carl Helmers (who later began a monthly called Experimenters' Computer System which after five issues was transformed into BYTE in 1975). 1974 marked a year of substantial in- crease in amateur computing. In July, Radio-Electronics magazine carried a con- struction article by Jonathan Titus on building the Mark-S processor, which used the Intel 8008 microprocessor. It is estimated that over 500 of these units were built by avid experimenters. In October, Southwest Technical Pro- ducts Company (SwTPC) introduced the TVT-II kit for $180 and an ASCII key- board kit for $40. In September, Hal Singer started the IVIicro-8 Newsletter to exchange information Photo 3: The author's Mark-8 processor, built in late 1974. Designed by Jonathan Titus, it uses the Intel 8008 microprocessor and has I K bytes of programmable memory. among hundreds of experimenters who were building the Mark-8 unit. In November 1974, Hal Chamberlin and some associates began another very popular but short-lived magazine called The Com- puter Hobbyist. 1975 was the year that personal com- puting exploded. It began, in January, when Popular Electronics carried an article on the Altair 8800 microcomputer by MITS. First deliveries were in April 1975. The kit sold for $375 and included 1 K bytes of pro- grammable memory, but no 10. MITS claims that by the end of 1976 they had sold over 10,000 Altair 8800s (80% to hobbyists). In April, the first computer club held its meeting. Started by Bob Reiling and Gordon French, and calling itself The Homebrew Computer Club, it met in Menio Park CA. One month later the Amateur Computer Group of New Jersey was formed. In the fall of 1975, MITS released its 4 K and 8 K BASIC interpreters, SwTPC introduced their 6800 based microcomputer, and the first decade of amateur computing was complete. Since then, the field as we know it today has rapidly matured and expanded. Some Microprocessor History Intel Corporation must be credited with developing the microprocessor, the single chip integrated circuit which performs the basic functions of a central processing unit. In 1969, a Japanese company, Busicom, contracted with Intel to develop a chip set for a printer-calculator. It used a 4 bit data bus and consisted of four integrated circuits in a set: a processor, read only memory with 10, programmable memory with lO, and a shift register type memory. Busicom per- mitted Intel to market the chip set for noncalculator applications, and the first generation of microprocessors was born. The processor chip was designated the 4004, and it sold for $200. It came in an 18 pin dual in line package (DIP) and would interface only with the other chips in the family. Programs had to be stored in the erasable read only memory. Data and address information was multiplexed on the 4 bit bus. Since program could only be executed out of read only memory, and since progammable memory was used only to store data, debugging software proved to be difficult. Further, a great deal of support logic was required. At nearly the same time, Datapoint, a manufacturer of intelligent terminals, contracted with Intel and Texas Instru- ments to produce a true processor on a 68 July 1978 @ BYTE Publlcitiom Inc An IMFO 2000 DISK SYSTEM gives you a lot less than you expected: Less Cost Less Hassle The DISCOMEM Controller board costs us less to manufacture. So your complete INFO 2000 Disk System costs you less - at least $400 less than com- perable disk systems. Less Hardware Only three S-100 boards are needed to create a com- plete, high-performance disk-based microcomputer system-the DISCOMEM Controller Board, a 32K memory board, and any 8080, 8085 or Z80 CPU board. You don't need extra interface or EPROM boards since DISCOMEM contains 2 serial ports, 3 parallel ports and provision for 7K of EPROM and IK of RAM. LessTime The INFO 2000 Disk Sys- tem is incredibly fast! Disk seek times are up to 8 times faster than with other drives. A full disk-to- disk copy and verification takes well under a minute. Formatting and verifying a new diskette takes less than half a minute. Reload- ing CP/M* from diskette takes a fraction of a se- cond. Less Space The system is remarkably compact, requiring only 1/2 to 1/3 the space taken by other 2-drive disk sys- tems. The INFO 2000 Disk System eliminates the "I/O configuration blues" by incorporating all necessary interface ports. A CP/M Loader and all I/O drivers are contained in EPROM so there is no need for special software customization. Just plug the system into your S-100 microcomputer and begin immediate operation using the CP/M disk operating system. The INFO 2000 Disk System is supported by the most extensive library of software available, including 3 different BASICS, 2 ANSI FORTRAN IVs, several assemblers, text editors, de- bugging tools, utilities and numerous applications packages. Less Errors This disk system uses full size 8" diskettes and standard IBM 3740 recording format. So you're assured superior protection against errors, and full interchangeability with other CP/M-based systems. ffliuuuiiuiiiUttiiii It all adds up to more capability for your money. The complete INFO 2000 Disk System comes completely assembled and tested. It includes dual diskette drives, the DISCOMEM Controller, power supply, cabinet, cables and the CP/M disk operating system — everything you need for immediate plug-in-and-go operation with your | microcomputer. This means less time, hassle, hardware, space, errors and less money than for CORPORATION comparable equipment. Now, isn't that a lot less than you'd expected in a dual disk system? 20630 South Leapwood Avenue Full price of S-100 Disk System is $2,600. Model without input/output facilities also available for $2,450. Delivery two Carsoa California 90746 weeks from receipt of order. INFO 2000 Disk Systems also available for Digital Group and Heath H8 microcomputers. /■213) 532-1702 Dealer inquiries welcomed. •Cp/M is a registered trademark of Digital Research. Circle 178 on inquiry card. BYTE |ulv 1978 69 .m^' t mn ^;':. ,N.^ ^^. • A' ■'-/ ■i-«ff*\- .^ ^ / /'//o^o 4; /?o^er Amidon's 4 bit processor, built in 1972 and fondly referred to as the "Spider. " It was built with TTL logic and used to control an amateur radio (R TTY). The Spider was featured on the cover of April 1977 BYTE. chip. Intel succeeded in doing this. Un- fortunately, the device proved to be too slov/ for Datapoint's use. Intel decided, therefore, in 1971, to market the device for $200 and call it the 8008. It marked the first generation of "true" microprocessor integrated circuits. The 8008 used an 8 bit data word with a more powerful instruction set than the 4004, but it still had many of the disadvan- tages of the 4004. It required considerable support logic. The 8008 however was a more general purpose device. For example, it contained a set of logical operations that the 4004 did not have. Its instruction set was similar to a minicomputer's, and it could directly address 16 K bytes of pro- grammable memory. It even had interrupt capability. At the same time, Intel introduced the 1101, a 256 by 1 bit programmable memory (which enabled the experimenter to build a 1 K by 8 bit memory with only 32 integrated circuits!), and the 1702 256 by 8 bit EROM. With the 8008, 1101 and 1702 integrated circuits, general purpose computers could now be built. In 1972 several other manufacturers recognized this emerging market. Most notable was National Semiconductor who introduced the IMP-16, a chip set which may have been a little ahead of its time. It was a bit slice system of variable word length and user definable instruction set. It later developed into the third generation Pace microprocessor. In late 1973, Intel introduced the 8080 processor, and, soon after. Motorola intro- duced the 6800. The 8080 has become the de facto industry standard, used in more applications than any other processor. The 8080 is basically an enhancement of the 8008. It came in a 40 pin dual in line package and could directly address 64 K bytes of programmable memory and read only memory. It had a true bidirectional data bus and an expanded instruction set. However, it still required an external clock and multiple power supplies. The 6800 on the other hand required only one TTL compatible power supply, had simpler control circuitry, and an instruction set more compatible with larger computers. 1975 and 1976 saw the introduction of enhanced third generation micro- processors. The Zilog Z-80, an enhanced 8080, featured a larger instruction set, more registers, on chip clock, and more. The 6502, from MOS Technology, was an enhancement of the 6800. The Texas Instruments TMS9900 and TMS9980 became the first widely available single chip 16 bit microprocessors. 1977 marked the introduction of the fourth generation of microprocessors. In fact, these devices now could be called 70 luly 1978 © BYTE Publicitions Inc microcomputers in a single integrated circuit. Tliese new devices include the complete microprocessor, read only memory, programmable memory, and 10 circuitry on one chip. A minimum of support logic is required. The future promises an increase in word size, functions, speed and memory capacity. (It looks like the single chip processor that runs BASIC may soon be a reality.) The next ten years in microprocessors and personal computing should be even more amazing than the past decade." Photo 5: The Scelbi-SH processor. This was the first kit to utiiize a microprocessor. It employed an Intel 8008 processor and was introduced in late 1973; design work began on the unit in August 1972. The prototype featured an oscilloscope display and audio tape unit. Sceibi has since discontinued their hardware line to concentrate on software and applications publications. The last Scelbi-8H was sold in December 1974. TURTLES Small home robots controllable by your computer. Attachable to any computer via parallel interface (not included) Terrapin^" Turtles can: • 'walk' (on 2" radius wheels) • 'talk' (via 2-tone speaker) • 'blink' (with lights as eyes) • 'draw' (with solenoid-controlled pen) • 'feel' (using S'/?" radius dome as touch sensor) Use your Turtle to map rooms, solve mazes, dance, ex- plore Artificial Intelligence, teach geometry or programming. A unique peripheral to keep you "in touch" with your computer. Limited delivery from stock • Brochures available Kit $300 Assembled $500 Terrapin, Inc. S-100 Interface $40 Shipping $5 Mass. residents add 5% sales tax 33 Edinborough Street, 6th Floor Boston, MA 02111 (617) 482-1033 Circle 374 on inquiry card. July 197g@BYTE Publications Inc 71 f5V GO [I> dirO 560ii (TYPICAL FOR 6) Figure 1: Schematic diagram for t/ie motor driver. The 7400, Id, has +5 V connected to pin 14 and pin 7 is connected to ground. Controlling DC Motors Robert L Walton 5616 Houston Rd Eaton Rapids Ml 48827 About the Author; Robert Walton is a process computer engineer employed by Consumers Power Company. He has designed and homebrewed an 8008 based system with 9 K of memory, Kansas City audio tape interface, ASCII keyboard, 128 by 128 dot graphic video interface, and a front panel which allows exam- ination and modification of contents in memory during program execution. More recently he has been experimenting with a KIM-1. This article wilt explain one inexpensive way to control the position of asnnall 1.5 V to 3 V hobby DC motor to within a quarter turn out of a total range of 16,384 turns. Various types of mechanical apparatus may be attached to this shaft for accurate posi- tioning. The feedback portion of this circuit may be used alone for position sensing of shafts which reverse direction during opera- tion. Modifications to obtain resolution better than a quarter turn and to drive higher powered DC motors will be discussed. The impetus for developing this circuit came while estimating the cost and com- plexity of implementing the circuit shown by Leon Sweer, Thomas Dwyer and Margot Critchfield in the article "Controlling Small DC Motors with Analog Signals" (August 1977 BYTE, page 18). My lack of a digital to analog converter, the apparently high power dissipation in the power op amp, and the mechanical complexity of the feedback potentiometer gear reduction were all negative factors. An "all digital" scheme was devised to overcome these problems. The motor driver circuit is shown in figure 1. The circuit is simplified consider- ably by the presence of only three modes of operation: full forward, full reverse, and completely stopped. All transistors are in cutoff or sat uration at all times. The signals labeled FOR and REV are at a high l evel, + 5 V, while the motor is stopped. When FOR is brought low, Q1, Q4, and Q6 become saturated, or "turned on." This effectively connects motor pin 1 to+5 V and motor pin 2 to ground. When REV is brought low, Q2, Q3, and Q5 conduct, connecting motor pin 1 to ground and motor pin 2 to -i-5 V. Note that FOR and REV must never be grounded simultaneously; if this situation occurs, heavy current will flow through Q1, Q2, Q3, and Q4, potentially damaging the devices. To eliminate the possibility of this happening due to a programming bug while the moto r dri ve is connected to a computer, the FOR and REV signals have been modified to GO and DIR signals by the gate logic of ICl. The motor will be stopped as long as the GO signal is low. It will run forward 72 luly 1978 e-BYTE Publicilions Inc p= ^^ \L^^^ M 'f^^ ^um(^iim ^ MODEL CC-8 $185.00 (4800 Baud) $195.00 (9600 Baud and 220V/50 Hz) 9600 BAUD CASSETTE RECORDER An ASYNCHRONOUS NRZ type Recorder with remote motor start/stop. Error rate 108 at 4800 BAUD. Can be used from 110 to 9600 BAUD into a UART - no clocking required. This is not an audio recorder. It takes RS232 or TTL signals from the terminal or computer and gives back the same signals. No audio interface is used. Motor start/stop is manual or through TTL or RS232 signals. Tape speeds are 1.6" / 3.0" and 6.0" per second. 110 volt, 60 Hz, 5 v/atts. (220 Volts on special order). Can use high quality audio cassettes (Philips Type) or certified data cassettes. Can be used in remote locations from a 12 Volt battery. Recommended for DATA LOGGING, WORD PROCESSING, COMPUTER PROGRAM RELOADING and DATA STORAGE. Manual control except for motor start/stop. 6800, 8080 or Z80 software for file or record searching available on request with order. Used by major computer manufacturers. Bell Telephone and U.S. Government for program reloading and field servicing. AVAILABILITY - Off the shelf. PROVIDES MONITOR AND TAPE SOFTWARE in ROM. TERMINAL and TAPE PORTS on SAME BOARD. CONTROLS ONE or TWO TAPE UNITS (CC-8 or 3M3B). This is a complete 8080, 8085, or Z80 system controller. It provides the terminal I/O (RS232, 20 mA or TTL) and the data cartridge I/O, plus the motor controlling parallel I/O latches. Two kilobytes of on board ROM provide turn on and go control of your Altair or IMSAI. NO MORE BOOTSTRAPPING. Loads and Dumps memory in hex on the terminal, formats tape cartridge files, has word processing and paper tape routines. Best of all, it has the search routines to locate files and records by means of six, five, and four letter strings. Just type in the file name and the recorder and software do the rest. Can be used in the BiSync (IBM), BiPhase (Phase encoded) or NRZ modes with suitable recorders, interfaces and software. This is Revision 8 of this controller. This version features 2708 type EPROM's so that you can write your own software or relocate it as desired. One 2708 preprogrammed is supplied with the board. A socket is available for the second ROM allowing up to a full 2K of monitor programs. Fits all SI 00 bus computers using 8080 or Z80 MPU's. Requires 2 MHz clock from bus. Cannot be used with audio cassettes without an interface. Cassette or cartridge inputs are TTL or RS232 level. AVAILABILITY - Off the shelf. 2SIO (R) CONTROLLER $190.00, Tested & Assmb. itiiiiii"*'"'"'* 6800 CONTROLLER for SWTP $190.00, Tested & Assmb. PROVIDES MONITOR AND TAPE SOFTWARE in EPROM. EXPANDS MIKBUG with IK of ADDITIONAL ROM PROGRAM This is a complete tape controller for the SWTP 6800 system. Has 3K of EPROM space for your own programs. A 1 K ROM (2708) is provided with all tape and monitor functions. The ROM program is identical to our extensive 8080 ROM program. Has one ACIA for one or two tape drives, one UART for an additional Serial port and a 4 bit parallel port for motor control. Will control one or two CC-8 or 3M3B drives with the software provided. Can be used with other tape drives controllable with 4 TTL bits if appropriate software changes are made. Extra serial port is provided for your use with a second terminal or printer (RS232, TTL or 20 ma). The ROM program supplements the MIKbug program and is entered automatically on reset. SWTbug compatible ROM is also available. AVAILABILITY - Off the shelf. Z 80 BOARD for SWTP COMPUTER Now you can use the 8080/Z80 software programs in your SWTP 6800 machine. Re- places your MPU board with a Z80 and ROM so that you are up and running with your present SWTP memory and MPS card. 1 K ROM on board replaces MIKBUG. AVAILABILITY - Off the shelf. _$190.00, Tested & Assmb. For U.P.S. delivery, add $3.00. Overseas and air shipments charges collect, N.J. Residents add 5% Sales Tax. WRITE or CALL for further information. Phone Orders on Master Charge and BankAmericard accepted. Naticnal Multiplex Cerpcraticn j 3474 Rand Avenue, South Plainfield NJ 07080 Box 288 Phone (201) 561-3600 TWX 710-997-9530 c^^,^^. Circle 275 on inquiry card. BYTE July 1978 73 Figure 2: Opaque disk to be attaclied to motor stiaft. Two gaps are cut so ttie disl^ will be rota- tionaiiy balanced. when GO and DIR are high, and reverse when GO is high and DIR is low. The DIR signal may be reversed with GO remaining high without damage. This reversal may occur as often as desired, even many times per second, without electronic damage. Diodes D1, D2, D3 and D4 are used to suppress switching transients from the motor. Higher powered motors or higher voltage motors may be accommodated by using 7426 open collector gates in place of the 7400 gates or by using additional transistor driver stages, as appropriate. Position Feedback Determining how many times a shaft has turned in one direction is simple. Attach an opaque disk with periodic gaps in it to the shaft as shown in figure 2. Shine a beam of light on one side of the disk and place a phototransistor on the other side. Apply the TOP VIEW MOTOR SlOe VIEW Figure 3: Placement of phototransistors A and B. Thie ptiototransistors should be within an eighth of an inch of the disk. The disk should be opaque and painted flat black. The 60° gap size and 30° placement of the photo- transistors will provide a steady count once every 90 of rotation. DARK fl LIGHT DARK B DARK A LIGHT r 4a COUNTERCLOCKWISE ROTATION r 4t: CLOCKWISE ROTATION 30» ROTATION Figure 4: Phototransistor timing diagram. Note that the counter must count up when a dark to light transition occurs on A and B is dark, or when a light to dark transition occurs on B and A is dark. The counter must count down when a dark to light transition occurs on B and A is dark or when a light to dark transition occurs on A and B is dark. This assumes that a counterclock- wise rotation causes an increase in count. output of the phototransistor to a Schmitt trigger and count the high to low transitions. Note that it is not possible to determine the direction the shaft is rotating by observ- ing the electrical signals generated. By adding another phototransistor, it is possible to determine the direction the shaft is turning. The two phototransistors, identi- fied as A and B, must be arranged as shown in figure 3. The direction of rotation can be determined by observing which photo- transistor is the first one on when the gap is encountered as shown in figure 4. The direction can also be determined by observ- ing which phototransistor is the last one off. It is really necessary to use both of these transitions in order to avoid miscounting when the oscillating situation explained in the caption of figure 5 is encountered. The circuit to detect and register the shaft turns is shown in figure 6. This circuit functions by propagation delay. Signals A and B are high when their respective photo- transistors are on. Signals AD and BD are signals A and B, respectively, delayed by passing through four inverters. Similar terminology applies to A-hB and (A+B)D. These signals are then "anded" and "ored" together to make up and down counting signals for the four cascaded counters. The four counters provide 16 bits of position information, or one part in 65,536. In the unlikely event that additional preci- sion is required, more counters may be added. Note that the circuit generates four counts per revolution. If more counts per revolution are required, additional narrower gaps may be cut in the opaque disk and the phototransistors may be placed closer together. Construction The opaque disk may be made from a sandwich of two index cards and aluminum foil glued together. The disk may then be drilled to fit the motor shaft and fastened with a drop of epoxy. If the motor shaft is mounted vertically with the disk up, the phototransistor may be mounted beneath the disk. An incandescent desk lamp may be used to illuminate the disk. The photo- transistors may have to be adjusted a little to get the unit functioning. Be sure the collector of each phototransistor reads over 4 V when dark and under 0.5 V when illuminated. Be sure this is true all the way around the disk. Note: you will not be able to see the up and down counter inputs or the outputs of the four "and" gates on any but the very fastest oscilloscopes. To test the circuit, wire the GO motor input high and wire pin 7 of IC7 (figure 6) 74 )ulv 1978©BYTE Publications Inc EDP books you can't affoid to be without MICROPROCESSOR APPLICATIONS MANUAL by Motorola, Inc. 435/278 Pub. Pr., $28.50 Club Pr., $22.50 PROGRAMMING LANGUAGES by A. B. Tucker, Jr. 654/158 Pub. Pr., $17.50 Club Pr., $13.50 ILLUSTRATING BASIC (A Simple Programming; Language) by D. Alcock 771/928 Pub. Pr., $10.95 Club Pr., $8.95 AUTOMATIC DATA PROCESSING HANDBOOK by The Diebold Group, Inc. 168/075 Pub. Pr., $33.50 Club Pr., $23.75 MICROPROCESSOR PROGRAMMING FOR COMPUTER HOBBYISTS by N. Graham 783/S6X Pub. Pr., $12.95 Club Pr., $10.95 THE COMPULATOR BOOK Building Super Calculators & Minicomputer Hardware with Calculator Chips by R. P. Haviland 783/578 Pub. Pr., $10.95 Club Pr.. $9.30 MICROCOMPUTERS/MICROPROCESSORS: Hardware, Software and Applications by J. L. HilburnA P. N. Julich 771/499 Pub. Pr., $19.50 Club Pr., $15.60 INTERACTIVE COMPUTER GRAPHICS by B. S. Walker, G. R. Grund & E. A. Drawneck 767/661 Pub. Pr., $14.50 Club Pr., $12.30 THE INFORMATION SYSTEMS HANDBOOK by F. W. McFarlan & R. L. Nolan 769/29X Pub. Pr., $35.00 Club Pr., $25.50 MINICOMPUTERS: Structures and Programming by T. G. Lewis & J. W. Doerr 773/009 Pub. Pr., $13.95 Club Pr., $10.95 GETTING INVOLVED WITH YOUR OWN COMPUTER A Guide for Beginners by L. Solomon & S. Veit 771/952 Pub. Pr., $9.95 Club Pr., $8.35 ALGORITHMS + DATA STRUCTURES^ PROGRAMS by N. Wirth 769/664 Pub. Pr., $19.00 Club Pr., $13.75 ADVANCED ANS COBOL WITH STRUCTURED PROGRAMMING by G. D. Brown 772/118 Pub. Pr., $19.95 Club Pr., $15.95 APPLYING MICROPROCESSORS New Hardware, Software & Applications Edited by L. Altman & S. E. Scrupski 191/603 Pub. Pr., $19.50 Club Pr., $12.50 MICROPROGRAMMING PRIMER by H. Katzan, Jr. 333/874 Pub. Pr., $17.95 Club Pr., $13.95 A DISCIPLINE OF PROGRAMMING by E. W. Dijkstra 770/115 Pub. Pr., $18.95 Club Pr., $15.75 any one of these great professional books for $489 only t values up to $35.00 Introductory offer to new members of the Computer Professionals' Book Club Special $1.89 bonus book comes to you with your first club selection THIS new professional club is designed to meet your day-to-day on-the-job needs by providing practical books in your field on a regular basis at below publisher prices. If you're missing out on important technical literature — if today's high cost of reading curbs the growth of your library — here's the solution to your problem. The Computer Professionals' Book Club was organized for you, to provide an economical reading program that cannot fail to be of value. Administered by the McGraw-Hill Book Cbmpany, all books are chosen by qualified editors and consultants. Their understanding of the standards and values of the literature in your field guarantees the appropriateness of the selections. How the Club operates: Every month you receive free of charge The Computer Profes- sionals' Book Club Bulletin. This announces and describes the Club's featured book of the month as well as alternate selections available at special members' prices. If you want to examine the Club's feature of the month, you do nothing. If you prefer one of the alternate selections — or if you want no book at all — you notify the club by returning the card en- closed with each Bulletin. As a Club Member, you agree only to the purchase of four books (including your first selection) over a two-year period. Considering the many books published annually, there will surely be at least four you would want to own anyway. By joining the club, you save both money and the trouble of searching for the best books. VALUES UP TO $35.00 WITH MAJOR DISCOUNTS ON ALL OTHER CLUB SE- LECTIONS. Your bonus books come with the first selection, and you may choose both of them fromi the books described in this special introductory offer. EXTRA SAVINGS: Remit in full with your order, plus any local and state tax, and McGraw-Hill will pay all regular postage and handling charges. NO RISK GUARANTEE: If not completely satisfied return selections for full refund and membership cancellation. MAIL THIS COUPON TODAY COMPUTER PROFESSIONALS/Book Club P.O. Box 582 Princeton Road. Hightstown, NewJersey 08520 Please enroll me as a member and send me the two books indicated, I am to receive the- bonus book at the intro- ductory price ol $1.89 plus my first selection, plus tax, postage, and handling If not completely satisfied, I may return |he books within 10 days and request that my member- ship be cancelled. If I keep the books, I agree to take a minimum ol three additional books during the next two years at special Club prices (guaranteed 15% discount, often more). I will receive the Club Bulletin 13 times a year. If I want to examine the featured selection, I need take no action. It will be shipped automatically. If, however, I want an alternate selection— or no book at all— I simply notify the Club by returning the convenient card always enclosed, I will always have a minimum of 10 days in which to return the card and you will credit my account fully, including postage, it this is not the case. Membership in the club is continuous but cancellable by me at any time after the four- book purchase requirement has been filled. This order subject to acceptance by McGraw-Hill. Orders from outside the continental U.S. must be prepaid. Company, business, or Institutional tax exemption status Is not appliable to pur- chases made through individual Club memberships. All prices subiect to change without notice. Offer good for new mem- bers only. A shipping and handling charge is added to all shipments. Members are billed when books arrive. Write Code tt of $1 89 bonus book selection here Write code # of first selection here P39299 Circle 219 on inquiry card. BYTE luly 1978 75 Photo J: A breadboard of the motor controller. The photocells may be seen In front of the motor. • . to the motor DIR input. Tie tine LOAD input (figure 6) to +5 V. The motor should seel< one end of one of the gaps and "chatter" there. The rate of chatter may be anywhere from five to 100 times per second. The angle the disk turns during this chatter should be only a few degrees. Experiment with the lighting to obtain the fastest chatter rate. Passing your hand in front of the lamp will cause the motor to run away. When your hand is removed, the shaft will again seek a position. Use It is wise to have a mechanical arrange- ment using a slipclutch or a similar device to prevent mechanical or electrical damage if the motor runs away. Such an accident could result from a program problem or a burnt out light source. Such an arrangement also provides the facility for automatically zeroing the position when power is first applied to the circuit. The motor is driven in one direction long enough to ensure that the slipclutch is slipping, and then the LOAD line is momentarily lowered to load the counters with the known position. The counters will then contain the correct ab- solute position until power is turned off or the slipclutch operates again. To set the motor to a specific position, perform the program in listing 1 (flowchart POSITION OF A -,, POSITION OF A--_ POSITION OF B--' nttBK A LIGHT nABK- p Figure 5: Reason for decoding trailing edge of signals. A 30° oscillation of the disk between the positions shown will create the above waveform. If the trailing edge was not decoded, the counter would be decremented once for each oscillation and lose track of the correct position. 76 )uly 1978 ©BYTE Publicaliom Inc the electric pencil II ^^ e 1Q78 Mirhafil ?ihraver TM "Hie Electric Pencil II is a Character Oriented Word Processing System. This means that text is entered as a string of continuous characters and is manipulated as such. This allows the user enormous freedom and ease in the movement and handling of text. Since line endings are never delineated, any number of characters, words, lines or paragraphs may be inserted or deleted anywhere in the text. The entirety of the text shifts and opens up or closes as needed in full view of the user. The typing of carriage returns as well as word hyphenation is not required since lines of text are formatted automatically. 1978 Michael Shrayer As text is typed in and the end of a screen line is reached, a partially completed word is shifted to the beginning of the following line. Whenever text is inserted or deleted, existing text is pushed down or pulled up in a wrap around fashion. Everything appears on the video display screen as it occurs which eliminates any guesswork. Text may be reviewed at will by variable speed scrolling both in the forward and reverse directions. By using the search or the search and replace function, any string of characters may be located and/or replaced with any other string of characters as desired. When text is printed. The Electric Pencil II automatically inserts carriage returns where they are needed. Numerous combinations of line length, page length, line spacing and page spacing allow for any form to be handled. Character spacing, BOLD PACE, multicolumn as well as bidirectional printing are included in the Diablo versions. Right justification gives right-hand margins that are even. Pages may be numbered as well as titled. This entire page (excepting the large titles and logo) was printed by the Diablo version of The Electric Pencil II in one pass. NowonCP/M You've probably seen The Electric Pencil in action by now. It's the most powerful 8080/Z80 character oriented word processor on the market today. Michael Shrayer is now proud to present the new Electric Pencil II. NEW FEATURES : !! Supports Four Disk Drives Disk Storage and Retrieva Printing !!! Print Value Bidirectional Multispeed Print Value Scoreboard Cassette Backup Capabili Control !!! Non-Print Indentation !!! Centering ! CP/M Compatible 1!! Disk Operating System ! ! ! Simple File Management ! ! ! Quick and Easy 1 !!! Dynamic Print Formatting !!! Multicolumn Chaining !!! Page-at-a-time Scrolling !!! New Scrolling Controls 1!! New Subsystem with ! ! ! Automatic Word and Record Number Tally ! ! ! ty ! ! ! Full Margin Control !!! End-of-Page ing Text Commenting ! ! ! Line and Paragraph ! ! ! Underlining ! ! ! BOLD FACE ! ! ! WIDE SCREEN VIDEO!!! Available to Imsai VIO video users for a huge 80x24 character screen !! HAVE WE GOT A VERSION FOR YOU ? The Electric Pencil II operates with any 8080/Z80 based microcomputer that supports a CP/M disk system and uses a Imsai VIO, Processor Technology VDM-1, Polymorphic VTI, Solid State Music VB-IB, Vector Graphic Flashwriter or any similar memory mapped video interface. Specify when using CP/M that has been modified for Micropolis or North Star disk systems as follows: For North Star add suffix A to version number, for Micropolis add suffix B to version number, e.g. SS-IIA, DV-IIB. Vers. Video Printer TTY or similar Price SS-II SOL $225. SP-II VTI TTY or similar $225. SV-II VDM TTY or similar $225. SI-II VIO TTY or similar $250. DS-II SOL Diablo 1610/20 $275. DP-II VTI Diablo 1610/20 $275. DV-II VDM Diablo 1610/20 $275. DI-II VIO Diablo 1610/20 $300. ss MICHAEL SHRAYER SOFTWARE 1253 Vista Superba Drive GLendaLe, CA 91205 (213) 956-1593 The Electric Pencil I is still available for non CP/M users: coming attractions Sort & Merge Utility !!! The NEC printer package !!! The HELIOS Electric Pencil ! ! ! Pencil to CP/M file conversion ! ! ! CP/M to Pencil file conversion ! ! ! Vers. Video Printer Cassette Disk Drive Price SS SOL TTY or similar CUTS $ioo. SP VTI TTY or similar Tarbell $ioo. sv VDM TTY or similar Tarbell $100. SSN SOL TTY or similar CUTS North Star $125. SPN VTI TTY or similar Tarbell North Star $125. SVN VDM TTY or similar Tarbell North Star $125. DS SOL Diablo 1610/20 CUTS $150. DP VTI Diablo 1610/20 Tarbell $150. DV VDM Diablo 1610/20 Tarbell $150. DSN SOL Diablo 1610/20 CUTS North Star $175. DPN VTI Diablo 1610/20 Tarbell North Star $175. DVN VDM Diablo 1610/20 Tarbell North Star $175. Demand a demo Srom your dealer I Circle 316 on inquiry card. BYTE jury 1978 77 in figure 7) at least twenty times per second. On an 8 bit machine, reading a 16 bit real time quantity poses a problem. If one byte is read and then the other, there is a real possibility that the 16 bit input may have changed between the two operations. Therefore the position is read twice and checked for agreement before proceeding. With a 16 bit machine, only a single input operation need be performed. The motor will race at top speed toward the desired setting. When it goes past the setting, it will turn around and race back, again overshooting. After a couple of quick oscillations, the desired position will have been reached and the motor will shut off. A better algorithm could be devised by estimating the speed of the motor and anticipating the overshoot, causing the motor to approach zero speed very close to Figure 6: Schematic dia- gram for the encoder cir- cuit. The data input lines should be wired to the state corresponding to the desired initial position of the motor. The dotted in capacitors may be required to obtain sufficiently wide clock pulses for the up and down counters. TIME DELAY t>M>4>M> 12 ap I rh 104 7404 ^{>M>^ r^ LOAD [3>- I DATA [~>- INPUT I LINES Q>- I np>- I o- I I o- I I I t^M^H^^-^ rf7 .001 "-2 7404 (A + B)D IC6 7408 6a V TTXi U 10 IC7 4 74193 Vd LD A B C D ON OA 08 OC CD CL GND CAR BOL L 14 I o I I I IDATA OUTPUT Vd LD A B C D ON OA OB OC OD CL GND (TO 3 I COMPUTER) IC8 I 74193 I I I I -o I /77 -U .DATA /77 Iqutput Kto I computer) 78 July 1978©BYTE Publications Inc Personal Computers & Microprocessing Here are two inexpensive programmed learning courses designed to keep you up-to-date in digital electronics. Design of Digital Systems - six volumes The products of digital electronics techno- logy will play an important role in your future. Calculators, digital watches and TV games are already commonplace. Now, microprocessors are generating a whole new range of products. Personal computers will be in widespread use very soon. Your TV, telephone and computer will combine to change your children's education, your job— your entire way of life. WRITTEN BY EXPERTS These courses were written by experts in electronics and learning systems so that you could teach yourself the theory and appli- cation of digital logic. Learning by self- instruction has the advantages of being faster and more thorough than classroom learning. You work at your own pace and respond by answering questions on each new piece of information before proceeding. After completing these courses you will have broadened your career prospects as well as your understanding of the rapidly chang- ing technological world around you. The courses are designed as much for the professional engineer as for the amateur enthusiast. You'll learn about microprocess- ing as well as personal computing — not to mention all the other aspects of digital electronics design. ADVANCED COURSE DESIGN OF DIGITAL SYSTEMS Design of Digital Systems is written for the engineer and serious hobbyist who wants to learn more about digital electronics. Its six large-format volumes— each 11%" x 8%" are packed with information, diagrams and questions designed to lead you step by step through number systems and Boolean algebra to memories, counters and simple arithmetic circuits, and finally to a complete understand- ing of the design and operation of micro- processors and computers. CONTENTS The contents of Design of Digital Systems include: Book 1: Octal, hexadecimal and binary number systems; representation of negative numbers; complementary systems; binary mulitplication and division. Book 2: OR and AND functions; logic gates; NOT, exclusive-OR, NAND.NOR and exclusive - NOR functions; multiple input gates; truth tables; DeMorgan's Laws; canon- ical forms; logic conventions; Karnaugh map- ping; three-state and wired logic. Also aviilabU at laadtng computer itoras: Campuler Mdrt ot New Yurk. 1 18 Mddisun Ave . New Vurk, NY Erie Computer Co., 1253 West 8th Si . Erie, PA. Interactive Compulets. 7646'/, Dastiwoud. Houston, TX Interactive Computers, 16440 Et Camino Real, Housloii, TX, Interactive Computers, 217 W, Salt Franuisco, Same Ee, NM, Readout Computer Slores, 6 Winspear Ave,, Buffalo, NY Imperial Computer Systems, liK ,2105 23rd Ave . Rixkford, IL Home Computer Center. 6101 Yoiiije SI,, Wiltowdale, Oni.rrio, Canada artd inanv othort. Ask your dealer. Book 3: Half adders and full adders; sub- tractors; serial and parallel adders; processors and arithmetic logic units (ALUs); multi- plication and division systems. Book 4: Flip-flops; shift registers; asynch- ronous counters; ring, Johnson and exclusive -OR feedback counter; random access mem- ories (RAMs); read-only memories (ROMs). Book 5: Structure of calculators; keyboard encoding; decoding display data; register systems; control unit; program ROM; address decoding; instruction sets; instruction decod- ing; control program structure. Book 6: Central processing unit (CPU); memory organization; character represen- tation; program storage; address modes; input/output systems; program interrupts; interrupt priorities; programming; assemblers; executive programs, operating systems, and time-sharing. BASIC COURSE NO RISK GUARANTEE There's absolutely no risk to you. if you're not completely satisfied with your courses, simply return them to GFN within 30 days. We'll send you a prompt, full refund. Plus return postage. TAX DEDUCTIBLE In most cases, the full cost of GFN's courses can be a tax deductible expense. HOWTO ORDER To order by credit card, call GFN's toll- free number - (800)331-1000; or send your check or money order (payable to GFN Industries, Inc.) to the address below. Prices include overseas surface mail post- age. Air iVIaii: additional costs (10 volumes); Caribbean S10; Europe $15; Africa, South America S20; Australia, Asia $25; or write for exact quote Write for educational discounts, quantity discounts and dealer costs. LOW PRICES -SAVE $5 We ship promptly from stock. There are no extras— we pay all shipping costs; we even pay your sales tax where required. And if you order both courses, you save $5. Order at no obligation today. Design of Digital Systems $79.95 - 6 volumes Digital Computer Logic $14.95 & Electronics - 4 volumes Both courses - 10 volumes $29.90 Digital Computer Logic & Electronics CONTENTS Digital Computer Logi: and Electronics is designed for the beginner. No mathmetical knowledge other than simple arithmetic is assumed, though you should have an aptitude for logical thought, it consists of 4 volumes- each 1 r/2" X 8%"— and serves as an intro- duction to the subject of digital electronics. Contents include: Binary, octal and decimal number systems; conversion between number systems; AND, OR, NOR and NAND gates and inverters; Boolean algebra and truth tables; DeMorgan's Laws; design of logical circuits using NOR gates; R-S and J-K flip- flops; binary counters, shift registers and half-adders. ^ GFN Industries, Inc. Suite 400-B 888 Seventh Ave. New York N.Y. 10019 Call TOLL-FREE (800)331-1000 (orders only) BYTE luly 1978 79 Octal Address Operation Codes 001 000 001 002 066 056 aaa bbb 001 004 101 001 005 001 006 310 107 001 007 001 010 001 Oil 320 101 271 001 012 001 015 001 016 110 107 272 004 001 001 017 001 022 110 277 004 001 001 023 001 026 001 031 140 110 301 047 054 001 001 001 032 061 Commentary set memory address registers to location of high byte of desired position get low byte of current position save in B register get high byte of current position save in C register read low byte again compare to previous read re-read if not same read high byte again compare to previous read re-read if not same compare high byte with desired high byte jump if less jump if greater high byte equal-recall low byte to A decrement address registers to point to low byte of desired position compare low byte to desired low byte jump if less jump if greater equal, set A for DIR and GO = go output DIR & GO position low — set GO = 1, DIR = go output GO & DIR position high — set GO= I.DIR = 1 output GO and DIR Listing 1: Intel 8008 program for motor control. This segment of code should be executed at least 20 times per second. The desired position is in location bbb-aaa (high byte) and the next previous location (low byte). The two locations must be on the same page. Input port is the low byte of the counter and port 3 is the high byte. Output port has DIR in its least significant bit and GO in the next bit. 001 033 277 Mnemonic LLI aaa LHI bbb READ INP LBA INP 3 LCA INP CPB JFZ READ INP 3 CPC JFZ READ CPM JTC LOW JFZ HIGH LAB DCL CPM 001 001 001 034 037 042 140 047 110 054 006 000 001 001 JTC LOW JFZ HIGH LAI 001 001 044 047 104 056 006 002 001 LOW JMP OUT LAI 2 001 001 051 054 104 056 006 003 001 HIGH JMP OUT LAI 3 001 056 127 OUT OUT3 Figure 7: Program flow- chart Variables DU and DL hold the upper and lower bytes of the de- sired position. This pro- gram must be executed at least 20 times per second. If the motor runs away, complement the DIR bit outputs. Do not attempt to reach positions closer than 50 turns to or 65535 with this algorithm because of the counter overflow which occurs. the desired position. Such a scheme would reduce the settling time of the system to a minimum. Modifications For those purists who insist on doing everything in software, the Schmitt trigger outputs may be tied directly to two com- puter input lines, or even interrupt lines, and the decoding and counting may be done in the computer. For those other purists who prefer not to tie their machine up with repetitive loops such as the one in figure 7, this positioning scheme may be implemented in hardware by installing four 4 bit compara- tors on the counter outputs. Cascade the comparators together and connect two output ports from a computer to the other comparator inputs. Invert the "equal" comparator output and connect it to GO. Connect the "greater than" comparator output to DIR. If the motor runs away connect the "less than" comparator output to DIR. Now the computer outputs 16 bit position values and the circuit positions the motor to follow the computer output." ( BEGIN J . NPUT LOWER BYTE OF COUNTER INTO LI 1 INPUT UPPER BYTE OF COUNTER INTO Ul 1 ' INPUT LOWER BYTE OF COUNTER INTO L2 1 INPUT UPPER BYTE OF COUNTER INTO U2 — 5!0c Ij ± I ifl continues where the TV Typewriter Cookbook leaves off. New, inexpensive video display circuits (and the software to drive them) are described. The designs allow a variety of alpha- numeric and graphics formats to be implemented, including high resolution graphics. The circuits are designed for use on 6500 or 6800 systems, but can be adapted to other proces- sors. Chapters also cover methods for displaying memory contents and a description of transparency techniques. 256 pp. $5.95. BASIC: A Hands-on Method by Herbert D Peckham is a light-hearted but thorough self-study course in BASIC, designed for people new to the subject. The introduction defines what BASIC is, gives some background on its origins, and tells you how to get started. Chapters cover: computer arithmetic and program management; input, output and simple applications; decisions and branching; looping; working with collections of numbers; subroutines; and more. Although the book is oriented towards the implementation of BASIC on time sharing terminals, the ideas and techniques are applicable to the personal computer. 244 pp. $7.95. Not Just a Good Buy But An Investment Microprocessor Lexicon, Acronyms and Definitions by SYBEX. 1 10 pp. This little book is a necessity to anyone who wants an explanation of those hard-to- fathom acronyms and other micro terms. Included are sections on signals in the main standards, functions of essential chips, and more. At 414" x 5Vs" it can be pocketed easily. For only $2.95 every microcomputerphile should have a copy. The 8080 Programmer's Pocket Guide written by Sceibi Computer Consulting Inc is a handy 3" x 4" com- pendium of 8080 facts. Included are detailed descriptions of the 8080 in- struction set, information about an 8080 paper tape loader program, and an in- struction set summary and index. 8080 programmers will want a copy of this useful book. 130 pp. Only $2.95. jT^iS^^ Computer Science: A First Course, Second Edition, by Forsythe, Keenan, Organick, and Stenberg. Over 760 pp. $18.25 hardcover. Computer Science: Projects and Study Problems by A I Forsythe, E I Organick, and R C Plummer. This companion text to Computer Science: A First Course is a series of work problems designed to intrigue the reader. Problems include plotting graphs, simultaneous equations, the eight queens problem, designing a perceptron (a machine that learns), as well as a series of problems specifically designed to complement the chapters of Computer Science: A First Course. 292 pp. $9.75. Computer Science: Programming in FORTRAN IV by A I Forsythe, R M Aiken, C E Hughes, and E I Organick. This supplement to Computer Science: A First Course, Second Edition, shows how to turn flowcharts into equivalent FORTRAN programs. Fea- tures include chapters on FORTRAN 10 statements, assignment statements, rounding, formatting, subroutines, practical applications, etc. The advent of FORTRAN software packages for small systems makes this a timely addition to the literature. 210 pp. $5.25. The TTL Data Book for Design Engineers, Second Edition, by Texas Instruments is a > Supplement to I The TTL ^ BITS .( current source of information on the design specifications and characteristics of the Texas Instruments 7400 series of devices. In it you'll find a complete section of 7400 series pinout diagrams at the front, plus the usual detailed descriptive information on the more compli- cated circuits. How do you find out what a 74412 does? Turn to its pinout diagram on page 5-74, then vector to the detail information on page 7-502 where you discover that it's Texas Instruments' version of the Intel 821 2 part. 828 pp. Only $4.95 hardcover. Supplement to the TTL Data Book for Design Engineers, Second Edition, by Texas Instruments. As the name implies, this supplement brings your Texas Instruments TTL Data Book up to date with the latest information about new TTL devices. The 56-page book includes information about synchronous counters, function generators, and many other devices. $1.25. The Microcomputer Bookstore 82 BYTE |ulv 1978 ■^ Last All Year Long BASIC with Business Applications by Richard W Lott focuses on the BASIC language and its application to specific business problems. The book is divided into two sections. Part one introduces the BASIC language and the concept of logical flowcharting. Part two pre- sents problems and possible solutions. Topics include: interest rate calculation, break-even analysis, loan rates, and depreciation. Exercises at the end of each chapter give a greater un- derstanding of BASIC by actual programming. This book is a great aid to the beginner want- ing to learn BASIC without having a technical or scientific background. 284 pp. $10.50. Financial Analysis and Business Decisions on the Pocket Calculator by Jon M Smith is designed to aid the experimenter in performing applied analysis. It gives a variety of numeri- cal techniques, approximations, tables, graphs, and flowcharts for calculations. All methods have been optimized for the pocket calculator, and the book stresses the use of the business- type calculator having the usual complement of business functions. Topics include: calcu- lating present and future values, consumer finances, real estate calculations, business statis- tics, and systems analysis. 317 pp. An invaluable source tool at $14.95 hardcover. Charging for Computer Services by D Bernard, J C Emery, R L Nolan, and R H Scott Business is written for managers who must deal with service charges. This book provides the manager with principles and guidelines for a better understanding of the charge problem. The book provides general design principles along with specific suggestions to deal with specific prob- lem areas. Charging for Computer Services is a necessary book for the manager who must make decisions in this vital area. 120 pp. $10.00 hardcover. A.I. Introduction to Artificial Intelligence by Philip C Jackson Jr surveys the field be- ginning with Turing's test, the mathematical description of phenomena, finite state ma- chines and limits to computational ability, followed by chapters on problem solving, game playing, pattern perception, theorem proving, semantic information processing, parallel processing, evolutionary systems, robots, and a look at the future of the field. This thought- ful and unusual book will make a useful addition to your library. A 50-page bibliography is included. 453 pp. $18.50 hardcover. r Just Out! Howi to Build a Computer-controlled Robot by Tod Loofbourrow. This book combines the dream of robotics— to create an intelligence other than human— with the reality, by pro- viding both hands-on experience with robotics and an application of a microprocessor. You can learn the fundamentals while utilizing the ultimate in current hobby computer technol- ogy. This book details the step-by-step directions for building a robot, named "Mike," con- trolled by a KIM-I microprocessor, with the complete control programs clearly written out. Photographs, diagrams, and tables help to direct you in the construction. $7.95. BITS DIAL YOUR BANK CARD ORDERS ON OUR TOLL-FREE HOT LINE: 1-800-258-5477. Name. The Microcomputer Bookstore 25 Route 101 West Peterborough, NH 03458 [I My check enclosed: Check #: Amount: Address. City -State- .Zip_ Signature. Total Number of books . I I My card #:. Expires:- Postage $.75/book or $1.00 outside U.S. Prices subject to ctiange without notice. Grand Total Dealer Inquiries Invited. You may photocopy this page. 'J Circle 35 on inquiry card. BYTE liriy 1978 83 A Short History of Computing Keith S Reid-Green Director, Software Systems Development Educational Testing Service Princeton NJ 08540 A few weeks ago a master's degree candi- date in computer science confided, with an embarrassed laugh, that he had never seen a computer. His experience with the machines of his chosen vocation had consisted entirely of submitting punched cards through a hole in a wall and later getting printed results the same way. While his opportunities to see equipment are restricted due to his student status, there are also thousands of working programmers and analysts using large scale equipment who have no contact with existing hardware and will never have a chance to see any first or second generation computers in operation. This is in sharp contrast with the way programmers worked in the late 1950s and early 1960s. Before 1964, when multipro- gramming computers were introduced, the typical programmer had opportunities to come in contact with the computer if he or she wanted to do so. Prior to 1960, in fact, most programmers actually operated the machine when debugging their programs. These people learned of the computer as a physical device; the current programmer is more likely to think of it as a vague logical entity at the other end of a terminal. Thus, many large system programmers have the rare distinction of using a tool without knowing how it works or what it looks like. This is in spite of the fact that many im- portant computer developments have Photo 1 : A Chinese abacus. Photo Acknowledgements Photos 1 and 3 courtesy of Bettmann Archive, New York. Photos 2, 4, 5, 6, 7, and 8 courtesy of the IBM Corporation. Photo 9 courtesy of Cray Research Inc. Photo 10 courtesy of the Sperry Rand Corpor- ation. 84 July 1978 © BYTE Publications Inc Photo 2: Pascal's adding machine. Note that the rightmost dial has 12 positions and its neighbor has 20. The machine was in- tended for calculations involving the French currency of the period. occurred within the average programmer's lifetime. However, in the past year or two, dra- matic reductions in the cost of minicom- puter components and the advent of the microcomputer have returned the hands-on computer to respectability in two ways. First, it is now possible to justify hands-on debugging on a small computer, since the hourly rate of the programmer is higher than that of the machine. Second, the decreasing cost of home computing has fostered the birth of a new class of "renais- sance programmers": people who combine programming expertise with hardware know- ledge and aren't afraid to admit it. Renais- sance programmers can learn much from the lessons of computer history; simple and inelegant hardware isn't necessarily best, but it's frequently cheapest. In short, the stored program computer became a necessary tool only recently, even though various mechanical aids to compu- tation have been in existence for centuries. One of the first such aids was the abacus, the invention of which is claimed by the Chinese. It was known in Egypt as early as 460 BC. The Chinese version of the abacus (as shown in photo 1) consists of a frame strung with wires containing seven beads each. Part of the frame separates the top- most two beads from the lower five. The right-hand wire represents units, the next tens, the next hundreds, and so on. The operator slides the beads to perform addi- tion and subtraction and reads the resulting sum from the final position of the beads. The principle of the abacus became known to Roman and early European traders, who adopted it in a form in which stones (called by the Latin calculi, hence the word "calcu- late") are moved around in grooves on a flat board. The use of precision instruments dates back to the Alexandrian astronomers. Like the mathematics of the period, however, the development of scientific instruments died away with the demise of the Alexandrian July 1978 @ BYTE Publicitiom Inc 85 school. The Arabs renewed interest in astronomy in the period between 800 and 1500 AD, and it was during this time that the first specialists in instrument making appeared. The center of instrument making shifted to Nuremberg, beginning about 1400. By the middle of the 16th Century, precise engraving on brass was well advanced due in part to the interest in book printing. Calendrical calculators used for deter- mining the moon's phases and the positions of the planets crop up in all the major periods of scientific thought in the past two thousand years. Parts of a Greek machine about 1800 years old, apparently used to simulate the motions of the planets, were found in 1902 in the remains of a ship off the island of Antikythera. The gears of the machine indicate amazing technical ability and knowledge. Later calendrical calculators, which were usually of the type in which two or more flat disks were rotated about the same axis, came to include a means of telling time at night by visually aligning part of the Big Dipper with the pole star. Trigonometric calculators, working on a graphical principle, were in use in the Arabic period. Such calculators were used mainly to determine triangular relationships in surveying. The popularity of this device was renewed in 14th Century Europe; in fact, calculating aids of all kinds grew rapidly in popularity as well as in scope from this time onward, largely due to the difficulty of the current arithmetic techniques. Napier was continually seeking ways to improve com- putational methods through his inventions. One such invention, "Napier's bones," con- sisted of a number of flat sticks similar to the kind now used in ice cream bars. Each stick was marked off into squares containing numbers. To perform calculations, the user manipulated the sticks up and down in a manner reminiscent of the abacus. Of parti- cular interest is the fact that Napier's inven- tion was used for general calculation at a time when many other devices were used for the specific determination of one measure- ment, such as the volume of liquid in a partly full barrel, or the range of an artillery shot. Pascal invented and built what is often called the first real calculating machine in 1642 (shown in photo 2). The machine consisted of a set of geared wheels arranged so that a complete revolution of any wheel rotated the wheel to its left one tenth of a revolution. Digits were inscribed on the side of each wheel. Additions and subtractions could be performed by the rotation of the wheels; this was done with the aid of a stylus. Pascal's calculator design is still widely seen in the form of inexpensive plastic versions found in variety stores. In 1671 Leibniz invented a machine capable of multiplication and division, but it is said to have been prone to inaccuracies. The work of Pascal, Leibniz, and other pioneers of mechanical calculation was greatly facilitated by the knowledge of gears and escapements gained through advances in the clock. In the 13th Century, a clock was devised for Alfonso X of Spain which used a falling weight to turn a dial. The weight was regulated by a cylindrical container divided into partitions and partly filled with mer- cury. The mercury flowed slowly through small holes in the partitions as the cylinder rotated; this tended to counterbalance the weight. By the 15th Century, the recoil of a spring regulated by an escapement had made its appearance as a source of motive power. Gear trains of increasing complexity and ingenuity were invented. Clocks could now strike on the hours, have minute and second hands (at first on separate dials), and record calendrical and astronomical events. Gears opened the door to wonderful automata and gadgets such as the Strasbourg clock of 1354. This device included a mechanical rooster which flapped its wings, stretched its metal feathers, opened its beak and crowed every day at noon. Later, important improvements in timekeeping included Galileo's invention of the pendulum; and the accurate driving of a clock without weights or pendulum which led to the portable watch. Although mechanical and machine shop techniques still had a long way to go (con- sider the 19th Century machinist's inability to fit a piston tightly into a cylinder), the importance of mechanical inventions as aids to computation was overshadowed by electrical discoveries beginning with the invention of the battery by Volta in 1800. During the 1700s, much experimental work had been done with static electricity. The so-called electrical machine underwent a number of improvements. Other electrical inventions like the Leyden jar appeared, but all were based on static electricity which releases very little energy in a very specta- cular way. In 1820, following Volta's dis- covery. Oersted recognized the principle of electromagnetism that allowed Faraday to complete the work leading to the dynamo, and eventually to the electric motor. It was not until 1873, however, that Gramme demonstrated a commercially practicable direct current motor in Vienna. Alternating current (AC) was shown to be the most feasible type of electric power for distri- bution, and subsequently the AC motor was 86 July 1978 £> BYTE Publications Inc GAMES COMPUTERS Chess Skill in Man and Ma- chine edited by Peter W Frey. This is a most challenging book, concerning itself with the when, how, and why of computer chess. 217 pp. $14.80 hardcover. Game Playing with Com- puters by Donald D Spencer. Read this book for an Introduc- tion to numerous recreational uses of the computer. Topics in- clude mathematical problems, ca- sino games, board games, unusual gambling games, and logic games. Many BASIC language programs and listings are included to show details. 312 pp. $16.95 hardcover. What to do After You Hit Return or PCC's First Book of Computer Games. This is PCC's first book of computer games, a compendium of computer games, including listings of 37 selected BASIC games. 1 70 pp. $8.00. BASIC Computer Games: Microcomputer Edition edited by David H Ahl. Here are 102 classic computer games, every one in standard microcomputer BASIC; every one complete with large leg- ible listing, sample run and des- criptive notes. All the classics are here: Super Star Trek, Football, Blackjack, Lunar Lander, Tic Tac Toe, Nim, Life and Horserace. This revision of 101 BASIC Com- puter Games is a must even if you own the original. 185 pp. $7.50. The Best of Creative Com- puting Volume I. The Best of Creative Com- puting Volume II Culled from the pages of Creative Computing Magazine, these two volumes provide fic- tion, fun, foolishness, and plenty of nuts and bolts commentary and programming information for anyone curious or serious about the wonderful world of personal computing. $8.95 per volume. PLAY Just Arrived*. Chess and Computers by David Levy. If you enjoy playing chess, then you will thoroughly enjoy Chess and Computers. This 145-page book is loaded with chess games played by and with computers. When you settle down with this book, it would be a good idea to set up your chess board and play the games. Half the enjoyment is found in playing along, duplicating the moves, reading the comments by the au- thor and adding your own com- ments. $8.95. Game Playing With BASIC by Donald D Spencer lets you en- joy the challenge of competing with your own computer. Games described include: 3D Tic Tac Toe, Nim, Roulette, Slot Ma- chines, Magic Squares, Keno, Morra, Baccarat, Knight's Magic Tour, and many others. The style is nontechnical, and each section gives complete rules for the game, how it works, illustrative flow- charts, and example outputs for each program. The last chapter contains 26 games for reader solu- tion, including Hexapawn and Poker Dice. 166 pp. $6.95. 57 Practical Programs and Games in BASIC by Ken Tracton is just that: a collection of practi- cal BASIC applications programs for experimenters, students and professionals. In addition to the more conventional programs, there are several unusual ones (Hydrocarbon Combustion, Inter- active Growth Patterns, Vector Cross Product, and Pi-Network Impedance Matching, to name a few). The book includes many flowcharts and diagrams to aug- ment the text and programs. 204 pp. $7.95. BITS Circle 35 on inquiry card. T.M. For your convenience in ordering, please use this page plus the order form on page 83. You may photocopy this page if you wish to keep your BYTE intact. CALL BANK CARD ORDERS TOLL FREE 1-800-258-5477. The Microcomputer Bookstore 25 Route 101 West. Peterborough NH 03458 BYTE July 1978 87 Photo 3: The Jacquard loom, one of the first machines to use holes punched In cards to control Its actions. 88 luly 1978 e BYTE Publications Inc invented in 1 888 by Tesla. The value of elec- tric power for transportation was quictcly recognized and employed in tramways and electric railways. This led to improvements in methods for controlling electricity. Elec- tric lighting methods sprang up like weeds during the latter half of the 19th Century. The most successful were due to the efforts of Swan in England and Edison in the United States. Work on electric lighting, the telegraph and the telephone led to the wonder of the age: radio. In 1895, Marconi transmitted a radio message over a distance of one mile, and six years later from England to Newfoundland. As a consequence of the rapid growth of interest in the radio, much work was done on the vacuum tube. Lee de Forest dis- covered the principle of the triode in 1907. Until the development of the transistor, the vacuum tube was the most important device in computer technology due to its ability to respond to changes in electrical voltage in extremely short periods of time. The cathode ray tube, invented by William Crookes, was used in computers for a few years prior to 1960. It faded temporarily from view but returned in 1964 due to advances in technology that improved its economic feasibility as well as its value as a display tool. In 1948 Bardeen, Brattain and Shockley developed the transistor, which began to replace the vacuum tube in computers in 1959. The transistor has many advantages over the vacuum tube as a com- puter component: it lasts much longer, generates much less heat, and takes up less space. It therefore replaced the vacuum tube, only to fall prey in turn to micro- miniaturization. Of course, the transistor principle didn't go away, but the little flying saucers with three wires coming out of their bases did. Oddly enough, one of the most funda- mental devices in the early history of com- puting predates the electronic computer by more than two hundred years. The punched card was first used to control patterns woven by the automatic loom. Although Jacquard is commonly thought to have originated the use of cards, it was actually done first by Falcon in 1728. Falcon's cards, which were connected together like a roll of postage stamps, were used by Jacquard to control the first fully automatic loom in France, and later appeared in Great Britain about 1810 (see photo 3). At about the same time, Charles Babbage began to devote his thinking to the development of computing machinery. Babbage's first machine, the Difference Engine, shown in photo 4, was completed in 1822 and was used in the computation of tables. His attempts to build a larger Difference Engine were un- successful, even though he spent £23,000 on the project (£6,000 of his own, and £1 7,000 of the government's). In 1833 Babbage began a project that was to be his life's work and his supreme frus- tration: the Analytical Engine. This machine was manifestly similar in theory to modern computers, but in fact was never completed. During the forty years devoted to the project, many excellent engineering drawings were made of parts of the Analytical Engine, and some parts of the machine were actually completed at the expense of Babbage's considerable personal fortune. The machine, which was to derive its motive power from a steam engine, was to use punched cards to direct its activities. The Engine was to include the capability of retaining and dis- playing upon demand any of its 1000 fifty- digit numbers (the first suggestion that a computing machine should have a memory) and was to be capable of changing its course of action depending on calculated results. Unfortunately for Babbage, his theories ■ ^^ ^pBB^^Bi|i|THjn • jHSS rj^iFii ' ' JKujh CE!(-1M ^0 iM k JPI HqB 15 ^ ill ■ imt^" I^ ' f\ t..: f 4 1 t.;.» 8 III j-'i ^HfllB^BfBHfl^KIill^ ..^.J-Bnll . "1 - ft ^-~»^-^^^ ^m « '__ jjji jii* M ■.', m ■ ^» «*^ Photo 4: The Babbage Difference Engine. luly 1978 ® BYTE PuMicitions Inc 89 Photo 5: The first use of punched cards for data processing, Hollerith 's card sorter dramatically re- duced the time required to process data collected in the 1 890 census. were years ahead of existing engineering technology, but he contributed to posterity the idea that punched cards could be used as inputs to computers. Herman Hollerith put punched cards to use in 1890 in his electric accounting machines, which were not computers, but machines designed to sort and collate cards according to the positions of holes punched in the cards (see photo 5). Hollerith's machines were put to effective use in the United States census of 1890. In 1911, the Computing-Tabulating-Re- cording Company was formed, which changed its name to International Business Machines in 1924. In the period between 1932 and 1945 many advances were made in electric accounting machines, culminating in 1946 with IBM's announcement of the IBM 602 and 603 electronic calculators, which were capable of performing arithmetic on data punched onto a card and of punch- ing the result onto the same card. It was Remington Rand, however, who announced the first commercially available electronic data processing machine, the Univac I, the first of which was delivered to the US Census Bureau in 1950. In 1963, just thir- teen years after the beginning of the com- puter business, computer rental costs in the United States exceeded a billion dollars. Univac I was not the first computer, even though it was the first to be offered for sale. Several one of a kind computers were built in the period between 1944 and 1950 partly as a result of the war. In 1939 work was begun by IBM on the Automatic Sequence Controlled Calculator, Mark 1, which was completed in 1944 and used at Harvard University (see photo 6). Relays were used to retain numbers; since relays are electromechanical and have parts that actually move, they are very slow by modern standards. In 1943, Eckert, Mauchly and Goldstine started to build the ENIAC (Electronic Numerical Integrator and Calculator), which became the first electronic computer using vacuum tubes instead of relays (see photo 7). The next year John von Neumann 90 luly 197g©BYTE Publicalions Inc became interested in EN I AC and by 1946 had recognized a fundamental flaw in its design. In "Preliminary Discussion of the Logical Design of an Electronic Computing Instrument," von Neumann pointed out the advantages of using the computer's memory to store not only data but the program itself. Machines without stored program capabilities were limited in scope, since they had to be partly rewired in order to solve a new problem (as was the case with EN I AC). This process sometimes took days during which time the machine could not be used. If rewiring of such machines was to be avoided, instructions had to be entered and executed one at a time, which greatly limited the machine's decision making capa- bilities. Machines with stored program capa- bilities automatically store not only numeric data but also the program (which looks like numbers and can be treated like numbers) in memory. In short, stored program instruc- tions can be used to modify other instruc- tions, a concept that leads to programs which can modify themselves. It is the von Neumann stored program concept which is universally used in modern computers from the smallest microcomputer to the largest number crunchers. The growth of the missile industry in the 1950s greatly stimulated the progress of computers used for scientific work. The nature of missile data handling at that time was such that work loads were very high during the week or so after a firing and virtually nonexistent in between. Computers were too expensive to leave idle, which led managers to look for other work for the machines. Business data processing grew from these roots to its present status, accounting for the lion's share of machine usage today. The latter part of 1959 saw the arrival of the transistorized computer. As a conse- quence of this innovation, air conditioning and power requirements for computers were reduced. Several new computers in that year were announced by IBM, Control Photo 6: IBM's Automatic Sequence Controlled Cal- culator (ASCC), the Mark I, built at Harvard be- tween 1 939 and 1944. ^^?2^^^^; Mi>M - 85 I >— , B4|3>- BJ I ^>— BZ I ^>— I Bo[;[>- Bl [3>- "Dear, when you go downstairs would you turn the printer on for me?" IVly wife Joyce was on her way to the basement with an armload of photographic supplies. "And could you see if I turned the video display off as well?" I was reclining in an overstuffed chair with the keyboard in my lap. Joyce stopped at the doorway and said, "Who was your last servant?" "Please do it for me, honey," I said, chastened. "I have papers all over my lap and you wouldn't want me to spill my mar- tini, would you?" "Hey, kid, I thought computers were sup- posed to make life easier for us poor folk." "They do! It's the peripherals that don't." The next logical question I asked myself was: why shouldn't turning the printer or re- corder on and off be as easy to do as any other computer transaction? A couple of quick solutions came to mind. One is to install an intercom system and station a person next to the computer while the re- mote terminal is in operation. A second and more practical alternative is to put long extensions on the power lines of your peripherals and apply power to them from a remote location, but this means re- wiring your house if the computer is down- stairs and the terminal is upstairs (as in my case). The third and probably best approach is ^ 3 r>s. 4 3 ■^ sr^ 8 6 II ^-^ 10 12 '^ IT' to use some of the unused functions on your keyboard to control peripherals remotely. There are a number of unprinted characters on a keyboard such as: end of transmission, end of text, or device control codes. By at- taching an ASCII decoding circuit to moni- tor the line between the keyboard and the computer, these functions can be isolated and utilized as peripheral device control sig- nals — more about this later. The ASCII Code Most keyboards use ASCII coding, a 7 bit binary code with an eighth bit sometimes added for parity checking. (Here we ignore the proposed extensions to the officially de- fined ASCII code which makes it a true 8 bit code or nine bits with parity.) A complete list of ASCII codes is outlined in "Complete ASCII" by Dave Ciemiewicz (February 1978 BYTE, page 19). When your computer pro- gram is executing and awaiting data from the keyboard, a special keyboard input routine is usually activated in the program. The sub- routine first determines whether a key has been pressed by checking for a key-pressed strobe signal. On systems that do not check parity (and thus use only 7 bit ASCII), the eighth bit of an input port is often set as the strobe bit. The other seven bits are not con- sidered unless thfs strobe bit is "true." When this is the case, the seven bits are compared to a valid entry table within the program to determine what to do with the input. If there is no valid comparison, the input key does nothing. The software read and compare routine is analogous to a hardware address decoder. For a particular ASCII code like CONTROL R hexadecimal 12, a circuit such as that in figure 1 could be used to decode and iden- tify only this particular code. For routine uses such as a hardware reset, this is the way many computer experimenters decode an ASCII code. This basic circuit can be dupli- cated many times to decode other codes. Figure 2 illustrates how this approach can enable a CONTROL R to turn on a device 98 luly 1978 ©BYTE Publicilions Inc Wait No Longer! The new educational programs are here. ■pviscover how to get more out of ■'-' your computer. Magnemedia has produced the innovative line of software pro- ducts you've been waiting for. Designed for use both at home or in the classroom, these programs make learning an exciting ex- perience. This software comes in hand- some two-cassette albums. Each cassette provides voice instruc- tion on one side and a machine readable code on the other. Separate instruction booklets are provided in non-technical language. All software is for APPLE II. Programs available for other micro computers indicated by following key: • RADIO SHACK TRS-80 (Level II) T^ COMMODORE PET ^ HEATH H8 (Extended Basic) Programs Now Available • Quiz Baseball (16K)— An ex- citing game for two teams or players, using your questions. Computer simulates action, total- ing batting averages and scores. • Save-A-SketchTM(8K) — Create a colored picture with your Arizona Personal Computer Place, Mesa (602) 833-8949 Arkansas Datacope. Little Rock (501) 666-8588 California A-Vidd Electronics Co., Long Beacti (213) 598-0444 Byte Stiop, Marina Del Rey (213) 530-3860 Byte Stlop, Tustin (714) 731-1686 Byte Stiop Computer Store, Walnut Creek (415) 933-6253 Byte Sfiop No. 8, Hayward (415) 537-2983 Computerland, El Cerrito (415) 233-5010 Computerland, Lawndale (213) 371-4010 Computerland, Mission Viejo (714) 770-0131 Computerland of West L.A., Inglewood (213) 776-8080 Computers Are Fun, Los Angeles (213) 475-0566 Recreational Computer Ctrs, Sunnyvale (408) 735-7480 Ttie Computer Store, Santa Monica (213) 451-0713 Colorado Ttie Byte Shop. Inc., Englewood (303) 761-6232 Connecticut Computerland, Fairfield (203) 374-2227 Florida Byte Stiop, Miami (305) 264-2983 Georgia Byte Sflop, Atlanta (404) 255-8984 Datamart Inc., Atlanta (404) 266-0336 computer keyboard. Save it for your gallery or use it as an il- lustration in another computer program. • Save-A-StoryTM (16K)— Write or copy a story for practice in typ- ing, speed reading, or for storage in your computer library. • Learning Basic (16K) — A package of two cassettes with multiple programs. Learn pro- gramming the easy way— let the computer teach you. • Mystery WordTM(8K)— De- velop your logic skills by guess- ing the secret word. Computer tells you how many letters are correct in each guess. • Reverse (8K)— A challenging math game that's a real brain teaser. How many times will you have to switch the numbers to get them in proper order? • SupermathTM (16K)-The computer teaches you to add, sub- tract, multiply and divide on your own level— in color! • True/False Quiz (8K)* i^ ^ — Tells you how to enter your own quiz. • Variable Message (8K)tV — You choose message and colors, the computer does the rest. • Matching Quiz (8K) • —Three changeable categories in each pro- gram. Match item on left correct- ly with one on right and they both FAuthorized Distributors! Computerland of Atlanta, Smyrna (404) 953-0406 Illinois Byte Shop, Champagne (217) 352-2323 Computerland, Arlington Heights (312) 255-6488 Imperial Computer Systems, Rockford (815) 226-8200 Kansas Personal Computer Center, Overland Park (913) 649-5942 Louisiana Computer Shoppe, Metairie (504) 454-6600 Maryland Computerland, Rockville (301) 948-7676 Massachusetts The Computer Store, Burlington (617) 272-8770 Michigan Computerland of Grand Rapids, Kentwood (616) 942-2931 New Hampshire Computerland. Nashua (603) 889-5238 New Mexico Interactive Computers, Santa Fe (505) 892-9997 __ Write to: .. Magnemedia 17845 Sky Park Circle, Suite H Irvine, CA 92714 (714) 549-9122 disappear. • Don't FallTM (8K)^-The computer chooses a word— you try to guess the letters without falling off cliff. Then you give the computer a word. • Memory Aide (8K)^— Help memorizing facts, verses, lists. Computer prompts you, asks you to provide missing words, etc. • Study Aide (8K)— The com- puter gives questions in random order. If you miss, it saves the question for a later try. • Keyboard Organ (4K)— Turn your computer into a musical in- strument. Play the keys hke a piano! • Grading Routine (16K) — Takes the drudgery out of finding class curves. Different categories, grading scales, etc. • Drawing (4K)*i5r.^ — Computer picks word at random from list you supply. Here's the best news of all— each package of two pro- grams sells for only $12.00! In- dividual programs are available for $7.50. Magnemedia software is in stock at computer stores everywhere. (Dealers listed below). If not available yet at your store, ask them to order for you. New Jersey Computer Corner, Pompton Lanes (201) 835-7080 The Computer Emporium, Cherry HIM (609) 667-7555 New Vorii Computer Shop of Syracuse, De Witt (315) 446-1284 Computer Tree Inc., Endwell, (607) 748-1223 Computer Micro Systems, Manhasset (516) 627-3640 North Carolina Byte Shop, Raleigh (919) 833-0210 Ohio 21st Century Shop, Cincinnati (513) 651-2111 Oklahoma Microlithics Inc., Oklahoma City (405) 947-5646 Texas Byte Shop, Richardson (214) 234-5955 CompuShop, Dallas (214) 234-3412 Computer Terminal, El Paso (915) 532-1777 Computerland, Austin (512) 452-5701 Computers 'n Things, Austin (512) 453-5970 Interactive Computers, Houston (713) 486-0291 Interactive Computers. Houston (713) 772-5257 Micro Computer Shop, Corpus Christi (512) 865-4516 Washington Ye Olde Computer Shoppe. Richland (509) 946-3330 Ontario, Canada The Computer Mart. Toronto (416) 484-9708 Circle 216 on inquiry card. BYTE July 1978 99 Figure 2: Printer on and off control designed with discrete logic elements. Pressing CONTROL R causes a logic signal to acti- vate an external relay in series with the printer power line. Pressing CONTROL T resets this circuit and turns the printer off KEY-PRESSED STROBE ASCII INPUT FROM KEYBOARD CONTROL R IS PRINTER ON HEXADECIMAL 12 CONTROL T IS PRINTER OFF HEXADECIMAL 14 1 ^ OUTPUT SIGNAL 1 ^ TO RELAY, ETC^ PRINTER ON KEY-PRESSED STROBE ASCII INPUT CONTROL R FROM KEYBOARD 022 OCTAL such as a printer, and a CONTROL T to turn it off. TPie method reaches a point of dimin- ishing returns when more than one device is to be controlled, though. Another disadvantage of this handwired decoding is that it is difficult to change the decoded value. I recently received a letter from a reader who needed a remote reset button. He built a circuit similar to the one in figure 1, and it worked fine for the soft- I702A ALL OTHER OUTPUT BITS REMAIN HIGH HEXADECIMAL 7F STORED AT HEXADECIMAL ADDRESS 92 A7 ADDRESS INPUT DO- D7 DATA OUTPUT Figure 3: 7 702A erasable read only memory used as an 8 bit address decoder. When CONTROL R Is depressed on the keyboard, the output at D7 goes low (or true) for a period equal to that of the key-pressed strobe. This circuit can replace up to eight of the circuits shown In figure /. ware he was using at the time. But when he changed from MaxiBASIC to Zapple BASIC, he found that the control code he had chosen for reset was necessary for use in the BASIC, so out came the soldering iron and in went another integrated circuit. Then came the expansion of more software from other manufacturers, and the circuit had to be changed again. His complaint was con- cerned not with the method of decoding the signal but rather with the difficulty in chang- ing its particular address. I, of course, wanted to have a hardware reset and peripheral device controller. I could build a combination of the circuits in figures 1 and 2 and hope that the next piece of software I get doesn't use one of the con- trol codes I used, but a concept this simple shouldn't require that much wiring or make it that hard to change addresses. Since I like the idea of using the key- board to control the peripheral devices and don't like to solder any more than necessary, the best alternative for me is a program- mable read only memory board control code decoder. Consider how a programmable read only memory works: a binary code is impressed on the address input lines and, in the case of the 1702A, an 8 bit binary word stored at that location appears at the output. By se- 100 July 1978 ©BYTE PuUicallons Inc Control Keyboard Hexadecimal Octal Parity Character Equivalent Alternate Code Names 00 000 EVEN NUL @ NULL.CTRL SHIFT P.TAPE LEADER 01 001 ODD SOH A START OF HEADER.SOM 02 002 ODD STX B START OF TEXT.EOA 03 003 EVEN ETX C END OF TEXT, EOM 04 004 ODD EOT D END OF TRANSMISSION, END 05 005 EVEN ENQ E ENOUIRY,WRU,WHO ARE YOU 06 006 EVEN ACK F ACKNOWLEDGE,RU,ARE YOU 07 007 ODD BEL G BELL 08 010 ODD BS H BACKSPACE,FEO 09 Oil EVEN HT 1 HORIZONTAL TAB.TAB OA 012 EVEN LF J LINE FEED, NEW LINE,NL OB 013 ODD VT K VERTICAL TAB,VTAB QC 014 EVEN FF L FORM FEED.FORM PAGE OD 015 ODD CR M CARRIAGE RETURN, EOL OE 016 ODD SO N SHIFT OUT,RED SHIFT OF 017 EVEN SI SHIFT IN, BLACK SHIFT 10 020 ODD DLE P DATA LINK ESCAPE, DCO 11 021 EVEN DC1 Q XOIM,READER ON 12 022 EVEN DC2 R TAPE, PUNCH ON 13 023 ODD DC3 S XOFF, READER OFF 14 024 EVEN DC4 T TAPE, PUNCH OFF 15 025 ODD NAK U NEGATIVE ACKNOWLEDGE, ERR 16 026 ODD SYN V SYNCHRONOUS IDLE,SYNC 17 027 EVEN ETB w END OF TEXT BUFFER, LEM 18 030 EVEN CAN X CANCEUCANCL 19 031 ODD EM Y END OF MEDIUM 1A 032 ODD SUB z SUBSTITUTE IB 033 EVEN ESC [ ESCAPE,PREFIX 1C 034 ODD FS / FILE SEPARATOR ID 035 EVEN GS ] GROUP SEPARATOR IE 036 EVEN RS A RECORD SEPARATOR IF 037 ODD US - UNIT SEPARATOR Note: To transmit any control code, depress the CTRL key while pressing the character l ■ ► 5v(3> m Notes: RECORDER CONTROL PRINTER CONTROL AUXILIARY CONTROL J V- — 1 r- STROBE 1 ^ '-' CONTROL Y J ^ — I r- STROBE I -^ '-' CONTROL Z 1. The EROM is programmed as per the EROM address and binary value infor- mation listed in table 1. All other address locations should be left fully erased (hexadecimal FF). 2. The signal outputs from integrated circuits 7 and 8 can be connected to solid state relays, which in turn provide on and off control of the designated periph- erals. For an explanation and a design of a solid state relay, see "Tune In and Turn On, Part 2," May 1978 BYTE, page 97. 3. All resistors are 1 /4 W 5% unless otherwise specified. Key Pressed CONTROL Q CONTROL R CONTROLS CONTROL T CONTROL W CONTROL X CONTROL Y CONTROL Z Function Recorder power on Printer power on Recorder power off Printer power off Auxiliary power on Auxiliary power off Bit 1 low true pulse Bit low true pulse 102 July 1978 e BYTE PuMicitJom Inc Table 3: Power wiring tabie for figures 2 and 4. Number Type +5V Gnd IC1 7404 14 IC2 7404 14 IC3 7430 14 IC4 7430 14 IC5 7400 14 IC6 1702A see schematic IC7 7400 14 7 IC8 7400 14 7 Some Final Thoughts I guess I don't have to worry about find- ing someone to be my peripheral "slave" any more. The uses of this remote control sys- tem can be extended beyond the ones I've outlined; my horizons were limited at the time. Once I sit back in that chair with a keyboard in my lap, it takes an earthquake to move me. Do you have any questions, comments or ideas for an article? Write to me; I try to answer every letter. Please enclose a stamped self-addressed envelope. Next month: a touch panel digitizer." o I To further improve service to our customers we have installed a toll-free '\ WATS line in our Peterborough, New Hampshire office.^ If you would i ke to order a subscription to\ BYTE, or if Toll-free \ ^°"'^'^^\ I vril 11^^ ^ question relat-> to a BYTE ' BYTE'S New i Subscriber W.A.T.S. Line ed (800)258-5485 We thank you and look forward to serving you. 3ULaAiLflJUUL8JUA subscription, you are invited^ to call' (800)258-5485 between 8:30 AM and 4:30 PM Eastern Time. ^♦Applies to calls made from within the continental US only. \\^ 9178; A RAM board for only $289? Central Data's got it! Central Data's 16K RAM board comes com- pletely assembled, tested and burned in for only $289. Our competitors find that hard to beat. But, the low price is not all we offer. The Central Data 1 6K RAM board is complete when you buy it from us, but we offer the added feature of expandability to 32K. Someday you'll need more than 16K, and when that day comes, you'll be ready. The cost of adding 16K to your present Central Data 16K RAM board is $200. A 32K RAM board, assembled, tested and burned in, is $475. The invisible refresh feature of our board means that the performance of your system can never be degraded by wait cycles. Our RAM board is S-100 compatible, and it has an access time of 450ns. Each Central Data board comes with a one-year warranty. To order your 16K RAM board or to receive more information, write to us at Central Data today. ^%«i 'iili'silnSM trmi mlml Oafia Ooo^p PO Box 2484, Station A Champaign, IL61820 (217)359-8010 Circle 45 on inquiry card. July l97g@BYTE PuUicitions Inc 103 IDS INTERNATIONAL DATA SYSTEMS, INC. 400 North Washington Street, Suite 200. Falls Church, Virginia 22046 U.S.A. Telephone (703) 536-7373 88-MODEM: A complete serial I/O port and an Originate/Answer MODEM on an SI 00 bus compatible board The 88-MODEM features automatic auto-dialer (not software timed), operates at any software selected baud rate between 66 and 600 baud, has separate 8-pole transmit and receive active filters, and all functions are software selected The 88-MODEM provides communication to -58 dbm and is intended for use with either a CBS (1001 D) or GBT Data Access Arrangement for connection to the telephone system The kit price is S245 00 88-UFC UNIVERSAL FREOUENCY COUNTER: The 88-UFC is an SI 00 compatible frequency and period measurement module. The 88-UFC has four software selected inputs Frequency measurement to above 600MHz and period measurement to 1 /10th microsecond are standard. The counter provides nine digits of readout and is pnced ai $179,00 in kit form 88-SPM CLOCK MODULE: The 88-SPM provides a time of day clock and an inde- pendent realtime clock on one SI 00 compatible module Provisions are included for battery backup so the 88-SPM can maintain the time during power-off conditions $96 00 kit 1001D (Type CBT) Data Access Arrangement $125,00 88-RCB 16 Channel Relay Control Board Kit $179,00 MCTK Morse Code Trainer/Keyer Kit 2900 TSM Temperature Sensing Module Kit 24,00 DAC-8 8-Bit Digital to Analog Converter Kit 1 9,00 88-TCXO Temperature Compensated Crystal Oscillator for 88-UFC 145,00 88-XTAL Crystal Timebase option tor 8B-SPM 25,00 TERMS Payment with order shipped prepaid, added for COD, Master Charge accepted Continued from page 6 sages sent and received would be the follow- ing little loop: var hangup : boolean; hangup := false; repeat look at keyboard, send latest Input"] jnessages to line and display J look at line, send any input] messages to display J until hangup ; (This program fragment is represented in PASCAL with the use of italics enclosed in square brackets [] to denote functions de- scribed verbally but not in detail. Note that "hangup" is a dummy variable within the context of this fragment as shown.) This simple programming model is ap- plied at both ends of the communications line through the phone network. It might in fact be implemented in two totally different computer and software systems, say in as- sembly language on one party's computer and in PASCAL on the other party's com- puter. It also has the unfortunate disadvan- tage of displaying the incoming message from the line mixed with the latest outgoing message from the keyboard. Walking through the process of establish- ing and holding a conversation illustrates some fundamental points which apply to any computer to computer communications method. In this case, much of the work in- volved in setting up the conversation, the protocol, is accomplished manually. Let's look at what a conversation between two parties might be like, using X and Y as suit- able arbitrary names in this script: Phone rings. X picks up the phone. X: "Hello, X here." Y: "Hi, X. Shall we proceed with the communications experiment?" Note the implicit protocol: Y assumes X Is looking for a computer to computer conversation. X: "Sure. I'll load my program. Let me set my modem in the originate mode." Y: "Fine. I'll set my modem in the an- swer mode and load my program." Note the complementary settings of the modem modes. For a full duplex con- versation, one end must be in answer mode, the other end in originate mode. A mode is simply the set of transmis- sion and reception frequencies chosen for use by the modem from two al- ternatives. X: "I'm starting my program. How's yours doing?" 104 luly 1978 e BYTE Pul>licaliom Inc Circle 185 on inquiry card. Y: "Mine is just fine. Do you hear the tones from the modem?" X: "Yes. Okay, let's try the phones." Both parties conclude verbal communica- tions by placing their phone handsets in the acoustic couplers. A computer to computer conversation ensues, using data from the keyboards and sending data to the displays at each end. This is perhaps one of the simplest models of computer to computer communications over a phone line via a modem. But it illustrates a couple of important points which are re- quired in any system which uses the dialup network. First, there must be a protocol tying the two systems together logically. This protocol provides a method of establishing contact. Here, I used the conversation as an example due to the simplicity of the equipment and the model. It could be as complicated as a full network protocol like those of ARPA, PCNET or CIE Net. The protocol must also involve the agreement upon a functional model of the software driving the communi- cations channel. Here the PASCAL program fragment, however it is implemented in de- tail, provides the common functional model for both ends of the line. The actual details of a conversation are independent of the protocol used. Second, the equipment used at both ends must be compatible with respect to modem design. Here, I have tacitly assumed a modem is available which has one outgoing channel and one incoming channel. This could be a Bell 103 style modem which is one of the most commonly available forms on the market, or it could be some haywire kluge with nonstandard frequencies which are shared by the two parties to the conver- sation and nobody else. The choice of "an- swer" or "originate" in the context of this example is arbitrary; when using such a mo- dem with a timesharing computer, the choice is not arbitrary. Third, the protocol can easily be auto- mated to some extent; with proper equip- ment and appropriate systems software running in your system and your network correspondent's system, the entire conversa- tion can take place without human interven- tion from start to finish. But more on that subject a little later. The conversation just described, and its protocol, are not intended as a serious sug- gestion for the use of a typical acoustically coupled modem. It represents if anything just a costly way to bypass the US Postal Service and all its problems and transmission delays; but then the same is true of the tele- 16K RAM Fully Assembled, Tested^ Burned-in .»m\T\ii""'* Fully static ^'"^""'" Using the TMS 4044 250 nsec. chips — $425 Z-80A 4 Mhz. Fast — ^Thls fully assembled and tested 1 6K board was designed to operate without wait states in a 4 Mhz. Z-80A system allowing over-generous time for CPU board buffers. 450 nsec. chips — $375 For 2 Mhz. Systems — Same circuit as above but priced lower because of less expensive memory chips. It is fully assembled, burned-ln, tested and guaranteed. 8K Versions Also Available Both boards available fully assembled with sockets for all 32 MOS chips but supplied with only 8K of chips. 8K— 250 nsec— $265. 4K chip set— $95. 8K-450 nsec. — $235. 4K chip set — $85. Fully Static is Best — Both boards use the state-of- the-art Texas Instruments TMS 4044 which requires no complicated and critical clocks or refresh. The fully static memory chip allows a straight-forward, "clean" design for the board ensuring DMA compatibility. They use a single 8 volt power supply at 1 .7 amps nominal. Fully S-100 Bus Compatible — Each 4K addressable to any 4K slot and separately protected by DIP switches. Commercial Quality Components — First quality factory parts, fully socketed, buffered, board masked on both sides, silk-screened, gold contacts, bus bars for lower noise. Guaranteed — Parts and labor guaranteed for one full year. You may return undamaged board within ten days for a full refund. (Factory orders only — dealer return policy may vary). C/jec/f your local computer store first Factory Orders — You may phone for MC, VISA. Cashier's check, MO. speed shipment for mail orders. Personal check OK. Shipped prepaid with cross country orders sent by air. Shipping — Stock to 72 hours normal. We will confirm order and give expected shipping date for delays beyond this. Washington residents add 5.4% tax. Spec, sheet, schematic, warranty statement sent upon request. V Seattle Computer Products. Inc. ^•r^ 16611 111th S.E., Renton, Washington 98055 (206) 255-0750 Circle 313 on inquiry card. July 1978 3 BYTE Publiuliominc 105 Computers For Everyone! Prices For Everyone! PET 2001-8 by Commodore • 8K user RAM ( expandable to 32K) • 8K BASIC in ROM • Built-in video display • Built-in keyboard with graphic characters • Built-in cassette recorder PET 8001-8 C8k BAM) $795. 1 Blank C-10 casseUe SO. "BASIC BASIC" Book 9. L reg. $824. You pay only $795. Apple II 16K by Apple Computers 16Kuser RAM (expandable to 48K) 6K Integer BASIC In ROM 2K Monitor m ROM Pull ASCII kejfboard 1 6-oolor graphics ( low resolution 40H x 40V) 4-color graphics (high resolution 280H x 192V) Game Paddles Included Includes BASIC software on cassette: • leKStartreck program • Color demonstration programs • 1 OK Floating poixit BASIC • Breakout video game tnterpi^ter Yoiir color TV set reqiilred for display APPLE n C16K BAM) $1195. Merlton cassette recorder 80. M&B BP ModTilator 30. L ^6- $1305. You pay only $1195. Add $1 0-00 per system for shipping and handling. To quali^ for these special package prices, ftill payment must accompany your order. We will refund full amount if you wish to cancel before we ship. Write or Call cemputcf cmcrpri/c/" P.O. Box 71 Fayetteville, N.Y. 13066 Phone C318) 637-6208 Today! Operating Hours: M-W10-8E.S.T. Th-riO-9E.S.T. Closed Sot. & Sun. phone used without a computer. The inter- esting uses are those which tal Don Lancaster's ingenius design provides software controllable options including: • Scrolling • Full performance cursor • Over 2K cm-screen characters with only 3MHz bandwidth • Variety of line/character formats including 16/32, 16/64 ....even 32/64 • User selectable line lengths TELL ME MORE! ( ) send instruction manual for the TVT-6 Kit with full operational details. $1 enclosed, ( ) SEND FREE CATALOG Name; . Address: City: . . Zip: ELECTRONICS. INC. DEPT. 7-B, 1020W.WILSHIREBLVD.. OKLAHOMA CITY. OK 73116 Automatic Communications: A^ computers + N People + Auto Answer + Auto Dial + DAA The protocols appropriate for an acousti- cally coupled modem are heavily biased by the need for manual operations. Just as the audio cassette recorder is the poor second cousin of the floppy disk as a mass storage medium, the acoustically coupled modem works for telecommunications but has many fewer features of merit than the more expensive modem options. The first extension to consider is that of a form of the modem which is wired perma- nently to the phone company's network via an appropriately approved data access arrangement or DAA. Given this extension alone, there would apparently be no great improvement in function relative to the simple acoustic modem. Thus we must consider the second extension, use of an auto answer option through the data access arrangement. Here, with appropriate software, your computer gets a signal from the interface which tells it when someone is calling. The computer can then reply with a signal which "lifts the phone off the hook" by changing appro- priate electrical levels in the interface which simulate that normally manual action. The computer can then proceed to verify that there is indeed a modem on the other end and commence its automated version of that conversation between X and Y given a little earlier. For thorough description of how such protocols work, consult any text book on systems software for timesharing sys- tems: this model is used by your friendly timesharing service to receive calls from its users with ordinary modems at the other end. The third of these three extensions of the basic model is the auto dial function. Here the intent is to allow your computer to place the call automatically, an event which implicitly assumes the number being dialed can receive such calls unless the modem is disconnected after the call is made. This more general function can be had at reasonable prices. The board used by Ward Christensen and Randy Suess costs about $300 assembled and tested, plugging into an S-100 bus slot. Another brand, also assembled and tested, but complete with a Bell approved data access arrangement module, runs about $500 and also plugs into an S-100 bus slot. (The difference between buying your own data access arrangement module or using a phone company version is one of paying monthly installments forever or paying a lump sum of about $100 to $150 once.) 108 |ul> >9;6^BYU rublicitioniinc Circle 298 on inquiry card. Circle 136 on inquiry card. With the economics of the auto dial and auto answer versions and data access arrange- ment settled, what are the possibilities which may be fulfilled? First, there is the matter of regular correspondence with a close friend on the other side of the continent. If you communicate via the simple model of the unautomated link, your prime time for originating a call may be different from the hours of prime functioning as a human being. The phone company rates are much lower in the wee hours of the morning. So, let your automated computer servant sit up late and take advantage of the cheap rates to telephone your correspondent's computer, send the mail you left for him or her and of course receive the mail left for you. More than one correspondent? Simply keep a list of phone numbers associated with the names, and call all of the ones which have been left messages on a disk file or in mem- ory. Don't care to waste phone charges? Well, use the auto answer feature to wait for your correspondent's calls. (This concept of using the auto answer and auto dial features to implement Telemail service is one of the pet projects of Ken Bowles at the University of California at San Diego. We can expect to see a protocol established from that source, written in PASCAL of course, which will be widely available for a nominal charge.) Let's extend the model a bit to the world of games so often frequented by the per- sonal computer user. But now, consider the N party game, a sort of computerized version of Dungeons and Dragons viewed as a prototype of the N player simulation game. Now, the phone network and dialup features can be used to some advantage: instead of one week's long conversation on a party line (the brute force approach), each player node in the game has a computer with a local model of the game plus interaction models which involve dialing up other players in the game for information or to send game messages which affect the other players. To be less than prohibitive in line costs, it would have to be done locally within a "free" dialing zone of your local exchange. It is a challenging problem to even think about defining such a game, let alone playing it. It is a suggestion which is quite within the capabilities of a dedicated group of N enthusiastic participants. Who will be the first to define and implement such a discipline? And then, of course, there is the less esoteric but quite useful concept of the local computer club bulletin board, as prototyped by Ward Christensen and Randy Suess. Here, both the auto answer and the auto dial modes can be used to advantage. The auto answer mode is of course currently being And now... a few well chosen words from EMM 256 words on one chip, to be exact. With TTL compatible inputs and outputs, a 400 ns maximum access time, and needing only a single -)-5V power supply to func- tion. It's a small memory system in one standard 22-pin DIP, with multi-sourced pin-out. And it's available for off-the-shelf delivery. Now. Get the latest word on the EMI^ SEMI 3539 256x8-bit static RAM from any EMM SEMI sales office or distributor. Or call us today. SEMI, INC. A subsidiary of Electronic Memories & Magnetics 3883 N.28th Ave., Phoenix.AZ 85017 (602)263-0202 The Best SELECTRIC II* Printer Going for ANY Computer! SEI,FCTRA-TERM is a liraiid new IBM Selectric II* typewriter which has been fully converted for direct connection to your computer. A special typing ele- ment gives you full ASC^II and upper/lower case alphanumerics. You also have backspace, tab. in- dex and bell— all under computer control. SELECTRA-TERM can also be used as a standard typewriter. It has been approved for computer use and comes with the IBM war- ranty. You may also obtain the yearly service agreement for the typewriter portion. MCD provides *Reg. trademark of IBM Corp. Circle 226 on inquiry card. their own factory warranty on the electronics conversion. Complete electronics package, cable sets and documentation are supplied. Price is $1750 with many options. Ask your dealer for details or contact: micro computer 1^ devices, inc. ■ ' 960 E Orangethorpe, BIdg. F Anaheim, California 92801 Telephone (714) 992-2270 luJy 19786BVIt Publicalions Inc 109 Circle 1 13 on inquiry card. ECHOlab A card guide compatible with the Altain-' motherboard. Speed nuts replace self-tapping screws for ease of installation. These guides also feature extra-rugged black ABS plastic construction. 10 S1.50ea. 25 S1.35ea. 100 S1.20ea. 1000 Sl.OOca. Availability-stock to 30 days. Please en- close check with order. ECHOlab, Inc. 213 Middlesex Turnpike Burlington, MA 01 803 (617)273-1512 employed in the interactive message center concept: users can call in from anywhere and leave messages which are either broad- cast, or specific to particular users. The club can also prepare a file which is sent to every active user upon logging into the system. The concepts of auto dialing and autc answering can also be applied to personal use independent of the use of the modem if provision is made to manually switch from modem data to voice data. The auto answer feature is of course typically used in a standard telephone answering machine, but by having your computer answer the line and listen with one of several voice response boards on the market, you might be able to call up your house and have various options such as lights, radios or sprinklers change state in response to voice command. If the voice recognition method of remote control does not work then consider using a touch tone telephone to send a coded pattern of numbers which are detected by another special demodulator after the phone is answered. Auto dialing coupled with the usual voice mode enables you to build a file of fre- quently called numbers, a "little brown disk" instead of a little black book. These numbers could then have symbolic names like "FIRE," "MOTHER," "SUZY," "JUDY," •SlWii;;.-:! FIND YOURS in The Index of Small Computer Products and Companies' The Computer Data Directory is a new comprehensive index which contains profiles of over 675 small com- puter manufacturers, stores, distributors, publishers, and electronic dealers. AJJ_ addresses are up-to-date and at your finger tips! Products are cross-referenced to their manufacturers. Similar to a telephone directory. Includes reader service card which is "Your DIRECT ory connection" to over 675 firms! Definitely a useful re- ference source. Order yours today — ONLY $4.98 — postage included. D COMPUTER STORES D EASY TO USE a SYSTEMS a PERIPHERALS D ACCESSORIES P WHERE TO WRITE FOR PRODUCT BROCHURES ■^r^ 98 ONLY$"" Postage Included ORDER TODAY Enclose $4.98 each (postage included). Place your order to either: \The Computer Data Directory BITS Inc. \ Box 598 Department B1 25 Route 101 West \ Cleveland, Ohio 441 07 Peterborough, NH 03458 DIAL BANK CARD ORDERS ^^ TOLL FREE 1-800-258-5477. Ohio residents please add tax. 110 |uly 1978 © BYTE PuMicatians Inc Circle 35 on inquiry card. Circle 61 on inquiry card. Circle 101 on inquiry card. etc. When a phone conversation is desired, dialing could be done symbolically by selecting a name with one character referring to a menu list on your display. Of course there are certain things one would not want to do with an auto dial feature, such as create intrusive automatically dialed junk phone calls. Summarizing the State of the Art. . . Computer to computer communications via the dialup phone network are a very real possibility for the personal user. The com- munications can be as simple and inexpen- sive to implement as an acoustic coupler on an ordinary telephone, or slightly more elaborate (but still less than $500 for an S-100 bus computer) with automatic answer- ing and dialing features. However you implement your link to the outside world from a personal computer, the applications of the system expand considerably." How Much Is That Turtle in the Window? As noted with a photograph and some background information on page 6 of the March 1978 BYTE, personal computer users will soon be able to add an abso- lutely fascinating new peripheral: an electromechanical "turtle." Recent word from Cambridge is that the Terrapirr turtle was scheduled for a mid May press conference announcement by Terrapin Inc, 33 Edinborough St, 6th Floor, Boston MA 02111. (This note was written April 24 1978, following a phone conversation with David McClees of Terrapin.) Using simple programming concepts in versions of the LOGO language, it is possible to teach young children many of the concepts of computer science using the mechanism of the turtle to emphasize points. Also quite possible with such a mobile robot appendage are various other applications from delighting friends at an adult or child's party to implementing the world's least expensive plotter output using the tail dragging capability of the turtle's solenoid controlled pen. Sensors on this inexpensive robot are four micro- switches which can determine one of eight possible directions when the unit runs into an object. How much for that "turtle in the window" at your local pet store? While final prices have not yet been set, the kit version is expected to be about $300. To be complete, Terrapin Inc will also sell an assembled version for $500 or so." Retro-Graphics™ FOr y«iMF i^mnra iBrniiiiai:^ jne nerro- Graphics PC card mounts easily in the Lear Siegler ADM-3A to provide you with an affordable graph- ics computer terminal. Features: " "" " ■ Point Plotting Automatic Vector Dot Matrix Generation _..... ^ ... Optional TEKTRONIX Interconnect Software Compatibility Retro-Graphics is available at the regular 100 piece price of only $659 for orders received before August 20th. Write or phone today for complete specifications. DIGITAL RESEARCH & ENGINEERING 5223 Glide Drive . Davis, CA 95616 (916) 756-8055 Z-80 Based 512 by 250 Dot Matrix • Simple Plug-in Interconnect Dumb Terminal is a registered trademarl< of Lear Siegler Inc rlHE INCREDIBLE LEARNING MACHINE I WHAMT, (Wow! rtowd All Thal(*)turfsel InThere?) • She's a Conversational Query System! • She's an Indexing/Filing System! • She's a 'Data Base Manager' for your Microcomputer! "One of the first software products of the New Computer Age ..." -Ted Nelson, author of Computer Lib/Dream Machines Mail to: Information Unlimited (authoriied distributor) P.O. Box 55B, Hsbron. Indian* 46341 n Model NS 3 for North Star BASIC (requires 24K RAM). $75.00 LJ Quantity discount schedule for dealers [J More information (I'm running disc BASIC computer) A CREATION OF '0(OX)(JTGR fCAO(ft)P)RGTM BOX 14694 SAN FRANCISCO 941 14 Circle 73 on inquiry card. July 1978 e BYTE PuWkaliom Inc 111 Lsngusges Fopuff) Pat Fitzgerald Winchmore Irrigation Research Station Private Bag Ashburton NEW ZEALAND BASIC to Assembly Language Linkage Listing 1: PDP-ll assembly language listing of program to output a quo- tation mark. 177564 TPS =177564 177566 TPB =177566 000050 .=50 000050 037426 -WORD SEXF 037426 .=37426 037426 105767 SEXF: TSTB TPS 140132 037432 100375 BPL SEXF 037434 012767 000042 140124 MOV #042, TPB 037442 000167 140404 JMP 52 000052 .END 52 ; teleprinter status ; teleprinter buffer ;link between BASIC and ;external function ; start address of ; external function ; is printer ready? ; if not branch ;move ASCII code for quotation ;mark to buffer and print .•return to BASIC Listing 2: Driver program for the assembly language program in listing 1. 10 PRINT "IN BASIC THE QUOTATION MARK ( " ; 2 LET T = EXF(l) 30 PRINT") IS A DELIMITER" Listing 3: Sample run of the BASIC program of listing 2. This is one simple solution to the problem of printing a quotation mark in a BASIC inter- preter, lacking appropriate escape mechanisms. IN BASIC THE QUOTATION MARK (") IS A DELIMITER Frequently one needs to use a BASIC interpreter to do things it was never designed to do. Getting around the problem can require a great deal of ingenuity. A case in point is David Chapman's article, "All This Just to Print a Quotation Mark?", in May 1977 BYTE. Several versions of BASIC allow assembly language programs to be added to the BASIC interpreter; these programs are linked to BASIC at load time and usually cannot be deleted without reloading BASIC. Using this technique provides a very simple method of getting around the problem described by David Chapman. The assembly language listing is given in listing 1 and the BASIC language program is given in listing 2. A run of the program is in listing 3. It appears that a relatively simple solution to the problem has been found. The version of BASIC I use is single user Digital Equipment Corporation's BASIC V008A for the PDP-ll series of mini- computers. This BASIC allows the user to call the assembly language program by use of an EXF function. Obviously in other ivhy the last mllla§ is the best It has the lates (and prospective Co. computer pro company-control 1 new product info bits about items before the offic by Heath Co. Bu than that--BUSS t news for users on news of compatible hardware & users) of Heath software from other vendors. H8 ducts. It isn't and Hll users may save enough on ed--BUSS can get these products to pay for a BUSS rmation and tid- subscription several times over, being developed And users of the ET-3400 Trainer ial announcement aren't left out either, t BUSS does more The first issue of BUSS came out also lets you in more than a year ago in April of 1977. Every issue goes by first class mail and almost all orders for new subscriptions are filled within two days. Back issues go fast, but most of those for 1978 are still available. BUSS keeps getting better. So send for it: 12 Issues For $ 5.80 The Independent Newsletter of Heath Co, Computers 325 Pennsylvania Avenue, S.E, Washington, DC 20003 112 luly 1978 ® BYTE Publicjtionj Inc Circle 36 on inquiry card. versions of BASIC the calling procedure will be different. The EXF function call can be used as an expression or as an ele- ment of an expression anywhere that an expression is legal in BASIC syntax. The assembly language program is called by use of the EXF function. The argument for the quotation mark program is a dummy one and any number would suffice. However this is a trivial use of the power of the link- ing method. More useful programs can be written to allow BASIC to be used in a variety of applications from real time con- trol of instruments to reading data from cassette transports. It can also be used to add powerful functions to increase the number crunching ability of BASIC. In short the uses of this tool are only limited by the user's imagination. One particular use we can make of the assembly linkage is a program to retain a BASIC program in the machine when the power is turned off. On the PDP-11 series when BASIC is restarted, information necessary to recall the user program is lost from two of the volatile registers (although the main core memory returns its information). However, use of the assembly language program shown in listing 4 allows the contents of these registers to be saved on power down and restored at power up. To use this program when you have temporarily finished with the BASIC pro- Listing 4: A nontrivial use of BASIC to assembly language linkages. This PDP-11 assembly program saves the PDP-11 's registers and restores them so that the program may be used after a restart occurs. 000001 R1 = %1 ;define registers to 000005 R5=%5 ;be saved 000006 SP=%6 ;register 6 to be stack 000050 .=50 037406 .=37406 037406 010146 START .MOV Rl,- (SP) ;save Rl and R5 037410 010546 MOV R5,-(SP) ;on stack 037412 010667 000016 MOV SP,SAVE ;save stack 037416 000000 HALT ;EXIT AND RE-ENTRY POINT 037420 016706 000010 RSTRT :MOV SAVE,SP .-restore stack and 037424 012605 MOV (SP)+,R5 ; registers 1 and 5 037426 012601 MOV (SP) +,R1 037430 000167 140416 J MP 52 ;back to BASIC 037434 000000 SAVE: .WORE 000052 .END 52 i^ wire wrapping center (^k UilREUIRflPPinCKITUiK-S CONTAINS Battery Tool BW-630 Hobby Wrap Tool WSU-30 M PC Edge Conneclor CON-1 DIP/IC Extractor Tool EX-1 DIP/IC Insertion fool INb-1416 PC Card Guides & Brackets TRS-2 Mini-Shear wilh Salety Clip SP-152 14. 16, 24 and 40 DIP Sockets Terminals WWT-1 Tri-Color Wire Dispenser WD-30-TRI Hobby Board H-PCB-1 $J4.9S ADD $1.00 FOR SHIPPING (N. Y. CITY AND STATE RESIDENTS ADD TAX) OK MACHINE & TOOL CORPORATION 3455 Conner St., Bronx, N.Y. 10475 (212) 994-6600 / Telex 125091 Circle 289 on inquiry card. luly 1978 <&J BYTE Publications Inc 113 gram, you type "Print EXF (N)" where N is an arbitrary number. When you wish to reuse the program, you start at address 037420 rather than the conventional 000000 which would destroy the user pro- gram. The machine responds by typing the number N. In this version of BASIC the linkage between the interpreter and the assembly language program is maintained through location 50; this address must contain the start address of the assembler language program. Return to BASIC is achieved by a jump to location 52. Several arguments can be used in the EXF function, but it is the user's responsibility to evaluate each argument after the first. By this tech- nique an assembly program with several entry points can be called up from a BASIC program to do a multitude of tasks not provided for in the BASIC language. Of course this requires that the pro- grammer learn the assembly language. Fortunately for the PDP-1 1 user an excellent introductory manual has been provided by R W Southern (see references). Moral Try using assembly language programs before attempting complex contortions within BASIC." REFERENCES Chapman, David, "All This Just to Print a Quota- tion Mark?", May 1977 BYTE, page 132. Southern, R W, PDP-11 Programming Fur)da- mentals, Algonquinote 12, Algonquin College Bookstore, Ontario CANADA, 1972. Languages Forum is a feature wliich is intended as an interactive dialog about tlie design and implementation of languages for personal com- puting. Statements and opinions submitted to tfiis forum can be on any subject relevant to its purpose of fostering discussion and com- munication among B YTE readers on the subject of lan- guages. We ask that all corres- pondents supply their full names and addresses to be printed with their commen- taries. We also ask that corres- pondents supply their tele- phone numbers, which will be printed unless we are expli- citly asked to omit them. BASIC is BASIC is ... And BASIC does what it should. But if you're ready to step up from Beginner's All-purpose Symbolic /nstruction Code, look at OPUS, the high-level 8080/Z80 language from A.S.I. .. . roots in BASIC, but designed for business applications. OPUS gives you the capabilities you need, like extended precision, string handling, and easy formatting. OPUS/TWO takes up where OPUS/ONE leaves off, allowing subroutines, overlays, and extended disc file management. But we didn't stop there. OPUS programs and data are directly upward-compatible, all the way up through TEMPOS, A.S.I. 's multi-user, multi-tasking operating system. Ask your dealer, or contact A.S.I. We'd like to tell you more. OPUS/ONE $99.00 S.O.S $385.00 OPUS/TWO $195.00 TEMPOS $785.00 □n AD^„N,STRAT,VB SYSTEm. INC. Hnn ^^^ Milwaukee, Suite 102 ij""" ■■■■ ■™J Doni/Qr nrt anonR /-ami q nn Denver, CO 80206 (303) 321-2473 ORDER A MANUAL NOW and we'll apply the price toward your software purchase. OPUS User's Manual $12.50 S.O.S. Manual Set (includes OPUS Manual) $20.00 TEMPOS Manual Set (includes OPUS Manual) . . $20.00 MASTER CHARGE and VISA accepted. Add $1.50 per manual (set) for shipping/handling in U.S. 114 July 1978 ©BYTE PuMicilionsInc Circle 4 on inquiry card. Fooling with the Stack Pointer I think Dr Borrmann ("Relocatability and the Long Branch," page 26, October 1977 BYTE) used the right word when he said he was "fooling with the stack pointer." Using the stack pointer as a general data pointer is bad programming practice; when the system uses NMI interrupts for real time clock main- tenance it is simply intolerable. In this case it is not even particularly necessary: the same two subroutines can be implemented in a stack-safe way for only eight more bytes, as follows: Tom Pittman POB 23189 San Jose CA 95153 Label Op Code Operand Commentary LONGBS STX XSTOR [save X for later] DES make room for copy of return DES TSX point to it in X PSHA save A on stack LDAA 3,X low byte of return address STAA 1,X ADDA #2 point to actual return STAA 3,X LDAA 2,X high byte of return STAA o,x ADCA #0 finish add STAA 2,X BRA BPUSH skip over start of LONGBR LONGBR STX XSTOR PSHA BPUSH PSHB save b on stack TSX point to top of stack in X LDAA 3,X get address of offset . . . LDAB 2,X . . . into A&B LDX 2,X also into X, ADDA 1,X so to add offset ADCB o,x to its address TSX get back to stack STAA 3,X put sum there STAB 2,X PULB restore saved A&B PULA LDX XSTOR [restore old X] RET [go to address] Dr Borrman illustrated a very good idea with a poor program. However, it was a good article, bringing to people's attention the fact that the 6800 alone of all popular processors is capable of self-relocatable code. Something that Dr Borrmann perhaps did not notice is that the subroutine LONGBS (and its chain of BRA stepping stones) is superfluous. At least where the subroutines now sour with CP/M* IN CUSTOMER USE FOR OVER ONE YEAR Full file sort for variable length records, arbitrary length key{s). Ascending or descending order Single-key Multi-key *95 «145 Runs on 16K or larger system. Uses all available memory FILE INDEX Produce cross-index of file names sorted alphabetically across all diskettes in a collection. $45 To order or for more information, write Bothenbera mroBMATKM SVSTEM5, INC. mm 260 Sheridan Avenue Palo Alto, CA 94306 (415) 324-8850 Please provide your CP/M Serial # California purchasers add Sales Tax Pre-paid only. Immediate delivery Dralvr inquinrs invitrii *CP/M IS a trademark of Digital Research Circle 308 on inquiry card. BYTE )uly 1978 115 BSR LINKn BRA EXITn LINKn BSR LONGBR FDB SUBR-* EXITn are to be included in the program, it is probably more economical to do the sub- routine calls this way: [Instead of JSR LONGBS] [jump over linkage] [or JSR if LONGBR Is in monitor] [relative address of subroutine] There is also the technique of using the indexed addressing mode with JMP or JSR when X is not needed in the call itself. Once in the program you compute the address of the first of a dense block of subroutines. Then each time you need one, the following linkage is used (notice that LONGBR is not needed): LDX JSR AFIRST =address of first subroutine SUB-FIRST, X The easiest way to compute the address of FIRST is to jump to a BSR just before it as shown next: BRA INIT (part of initialization) SAVEIT PULA get high byte STAA AFIRST save it in RAIVl PULA now low byte STAA AFIRST+1 (continue with main program) INIT BSR SAVEIT push address onto stack FIRST (first subroutine) If every subroutine knows its stack depth, you can leave the return address generated at INIT on the stack, then use the following calling sequence: TSX LDX JSR depth, X SUBR-FIRST point to stack get saved address of FIRST X Of course these will not work if you need the index register to pass an argument to the subroutine." More On Varistors: A Supplier of Some Note Comments William G Morris General Electric Research and Development POB8 Schenectady NY 12301 I don't know which brand of varistor Stephen Sorger of W N Phillips Inc (Letters, April 1978 BYTE) was using when he experienced "aging," thermal "runaway," and a "fire hazard," but it certainly was not a General Electric GE-MOV"^ varistor. As a typical example, the V130LA10 GE-MOV varistor will run at full rating to 85 °C ambient, which is 15°C greater than Intel specifies as maximum temperature for the 8080. This varistor also exhibits an observed failure rate of less than 0.2% per 1000 hours during accelerated testing at 100 °C ambient. The reader should be reminded that tran- sient suppression is essential to reliable operation of microprocessor systems, par- ticularly in industrial environments, but also in hobby applications. Varistors continue to represent the most cost effective method of achieving transient suppression. The V130LA10 GE-MOV varistor, which can be used directly on 110 VAC lines, is available for $1 to $2 from most industrial electronics suppliers. Additional information is available from General Electric Company, Electronics Park, Syracuse NY 13201." -r^'Wi $95 Stand Alone Video Terminal ♦"tt-4- ^ t. a «. T W « ^"^ ^ » « » • • « fcT- ■''nW<) ++.-./012456739::<=: laWMIgiKfiWl abcdefyhi jklj"inopqrstuyyxyz^i SCT-lOO FEATURES: 64 .X 16 lii.^ ^. Serial ASCII or BAUDOT with multiple Baud rates »$187 Assembled or $157 Kit (Partial Kit $95) \ • Full cursor control with scrolling and paging "■ On board power supply I Many additional features Call or write today. MC/VISA accepted I XITEX CORP. P.O. Box #20887 I Dallas, Texas, 75220 • Phone (214) 386-3859 / Overseas orders and dealer inquiries welcome 116 luly 1978 © BYTE PuUicUMm Inc Circle 400 on inquiry card. Beck fieviews Instant Freeze-Dried Computer Programming in BASIC by Jerald R Brown Dymax, POB310, Menio Park CA 94025 $6.95 How quickly the personal computer owner trades the student's notebook for the teacher's chalk. Says the friend, "Neat, you got a computer. How do you get it to do X or Y?" Or you modestly back yourself into a corner; "Programming isn't hard. I could teach you BASIC in a few hours." In my case it was a deal with my neighbor's recent high school graduate to teach him programming in return for his doing some of my more routine programming chores. But however you got the teaching job. Instant Freeze-Dried Computer Program- ming in BASIC is in my opinion an inter- esting, involving and entertaining text you can use to ease the teaching task. The book resembles a half inch thick collection of BASIC oriented flashes that somehow escaped from the pages of Ripley's Believe It or Not. We see the scene of the keyboard LET fading into the sunset beyond the hills, captioned by "And so, in the name of Efficiency and Ease, the LET was banished forever from Statementland. . . ." Throughout each page the student is ex- horted to either read the explanatory text, or, more often, "do it": the signal for you to actually type out one of the hundreds of brief examples on your waiting terminal. The layout is designed to be both a text and a practical workbook. For example, immediately after you learn to loop with the GOTO statement, half inch type warns you to "WAIT! STOP! HALT! CEASE! DESIST!" before running, so the saving properties of the Control-Ccan be explained to keep you from the terror of the infinite loop. The examples are so clear that not even a computer could complain of ambiguities. The actual keys punched are pictured using the standard key markings of the ASR-33 Teletype. The printed listing for each example explains why you typed this and why the computer typed that. Besides being an excellent teaching text, the book has the two necessities that make it a handy manual to keep forever, plus several bonuses. The necessities are a set of concise summary boxes at appropriate spots throughout the text gaudily surrounded by polka dots; and a good index that not only tells you where the concept is taught, but the precise location of the summary box. The bonuses are the examples cnosen by the author: a broad set of games, pictures, string techniques and useful business pro- grams, all indexed and ready to run. The dialect of the BASIC taught is both a strength and a weakness of the text. Altair 8 K BASIC, revision 3.2 (essentially the same as DEC BASIC Plus), is that ubiquitous version that started so many of us hackers off in BASIC and served us so well. But revision 4.0 is now out, and, especially in its extended version, it far surpasses 3.2 8 K BASIC in flexibility and power. But of course, the further you go from standard BASIC the more machine dependent you become. For the beginner, or those writing for a variety of interpreters. Brown's choice was a wise one. All said. Instant Freeze-Dried Computer Programming in BASIC is the most painless and involving text for that language yet on the market. Jay P Lucas 3409 Saylor PI Alexandria VA 22304 a Address Correction David Clapp, who re- viewed Z-80 Programming Manual by IVIOSTEK (June 1978 BYTE, page 118) has changed his address to: FOB 501, Streetsboro OH 44240.* A SOFTWARE SYSTEMS SPECIALISTS Growth corporation has immediate openings AT ALL LEVELS for candidates with a BS or MS in Engineering/Science and a bacl A (1) 200 J « 1-1 20^ REN BHILE Jk(J) > K 210 IP 1(J) <• R THEB 2'>0 220 * (J*1) ■ I (J) 2J0 J - J - I 235 PER UBTIL J = 21*0 IP J > THEB 20S 250 Jt [J*1) * R 260 BRIT 1 of Computer Programming, Volume 3: Sorting and Searching, by Donald E Knuth. Neal D McBurnett POB 4173 Brown University Providence Rl 02912 WHY NOT JUST USE THE PHONE? I was pleased with Mike Wilber's article on CIE standards ("CIE NET: Part 1, The Beginnings" February 1978 BYTE, page 14) and look forward to seeing more in the same vein. How- ever, I was not equally taken with Jeff Steinwedel's article ("Personal Com- puters in a Communications Network" February 1978 BYTE, page 80) on the ELF 11 by NErmWKS tstiatBfad ia POPIMil ELECTMNKS HOBBYISTS! ENGINEERS! TECHNICIANS! STUDENTS! Write and run machine language programs at liome, display video graphics on your TV set and design microprocessor circuits — the very first night — even if you've never used a computer before! II featuring RCA COSMAC microprocessor/mini r^. u^4.<1r: COMPUTER Stii (Bidlni ibBHt GoaiBBtifS u< lat loar iuii n saal ELF II is BR OBtstiBilHi tralRBr iBr nim «ka Raadi te aia a ceaipatar ta aiatlailia bis ar bar parsaaal aHactltaaass. BBt ELF II Isa't iflit a tialaar. Eipaa'ai, It caa bBcaaia tba baart al a paaaifal cbbihI*' sistaai capabia al salilai lapbistlcatad baslaais. laOstrlal. iciaatlllc aa< M'>»al llaaRca iroblaait. ELF II alsa IflclBias tba tn Plila Ciapblcs cblp tbat lati yaa llsplay aajr 251 byta lafaiaat af aaaiary bb a viriaa aiaaltar ar 1Y scraaa. Easy lastractlaai gat yaa staitBl rlfbt a«ay, bibr II yaa'ta aaiar aiai a caapatai batara. EIF II caa ba assaaiblad ia a slafla a>BBlfl| aad yaa'll still baia tlaia ta raa piaiiaaii lacladlai laaias, ijdaa KrapbiGS, ate. balara laiaf ta bad! ri>aiK«->aB SENDTODAY! ■■■■■■■■_ii| NETRONICS R&D LTD., Dept BY-7 (203)354-9375 ' I 333 Litchfield Road. New Milford. CT 06776 I IG YES! I want to run programs at home and have enclosed a M9.9S plus $3 . pth for RCA COSNAC ELF II kit. a »9i for power supply reguireil for ELF II kit I □ S5 00 for RCA 1802 User s Manual ' I G $4.95 for-Short Course on Microprocessor & Computer Programming I G ELF II connects to tlie video input of youi TV set If you preferto connect ELF II to your antenna terminals instead, enclose $8 95 for RF Modulator n $39 95 plus J2 p«tl for ELF GIANT BOARD" kit. _ 4k Static RAM kit. (89 95 ea plus {3 pill G S17.00 plus Jl ptii for Prototype (Klugel Board G $34.95 plus S2 p&h for Expansion Power Supply kit Gold plated 86-pin connectors at $5 70 ea G $64 95 plus $2 pill tor ASCII Keytioard kit a J14 95 for ELF II Tmy BASIC cassette i»— — a I mnt my ELF H wired and tasted witli the power transformer. RCA 1802 User's Manual and Short Course on Microprocessor I Computer Program- mini for tl49.95 plus (3 p&h. Ibtal enclosed (Conn, res add tax) ( D Check here if you are enclosing Sbaaniirltli aptlaaal 4k Maani) Beards. gIwT NARIT" ( KlBia Board. Learning Breakthroughi A Short Course On Microprocessor And Computer Programming Written For Anyone! Minimal Baclrground Needed! Wby speed a small fortaaa aa a parsoRal ceaipBtar ultbaat kaevlai how to usa its advaflcad capabilities? We'll teach yea haw ta aiaka ELF II respaad ta year aaads, witbeat waltlei lar saataaRa to develop the soffvara. Itaa laarn, in BOR-tecbBlcal laaiaaia. aach of ELF ll's 91 iastrBCtions sa you'll andarstaad aieiytblBi EtF II caa da . . . aad boa to (at ELF II to do it. It's year cbaace ta atastar aa adtaacad parsoaal ceaipatar talckly aad paialassly, avea if yaa'va aavsr asad a coaipatar bafore! - SPECIFICATIONS - ELF II feataras aa RCA COSNAC COS/MOS l-bit ailciaprocasser addrassabla ta Mk bytai «ltb BNA, latarrapt. It ta(istars, ALU, 2S( byta RAM, fall bai keyboard, twa dlflt be> eatpat display, 5 slat plB|-ta aipaflsiaa bas (less ceaaactars), stabia crystal clack far tJaiiBi parpasas aad a deabla-slded, platad-tbreagb PC board plas RCA 1111 tidee IC ta display aay SBiataat af aiaaiary or a yidaa ataaltar ar TV scraaa. EXPANSION OPTIONS ELF II GIART BOARD™ with cassatta I/O, RS 232-C/TTr fO, 1-bit P I/O, decoders far 14 separate I/O instractloas and a systeai aieaitar/edltar • 4k Static RAM. Addrassabla ta any 4k page ta i4k • Pratatype (Klafal Beard accapts ap to 39 IC's • Geld plated B6-plB caRRBCtar • Expaasioa Paver Sapply (Kot required aaiass addiai 4k RAMI • All af the abaie PC boards plag directly iota ELF ll's aipaaslaa bas. ELF II TINY BASIC CaaiBiaads iRclada SAf E, LOAO, ± , x . -f , ( ), 2S latiables A-Z. LEI IF/THEK. IRPUl PRIRi; GO TO, GO SBB, RETURN, ERD, REM, CLEAR. LIST, RUR. PLOT, PEER, PORE. CeaiBS tally dacafliaated. (4k Rteaary reqairad.l Money Order or Cashier's Check to expfdite shipment NAME - aODRFSS city ST4TF 7iP ■ ^■MB ^m ^ Dealer 1 nqulries Invltedl aa ^m ■B ^■H Circle 280 on inquiry card. July 1978 e BYTE Publications Inc 121 How to say low-cost data tablet/digitizer in two words. Bit Pad Bit Pad Bit Pad Bit Pad Bit Pad TM TM TM TM BTTP«B 5T'. .,•: ■''- Bit Pad is the low-cost digitizer for small computer systems. Better than a joystick or keyboard for entering graphic information, it converts any point on a page, any distance into its digital equivalents. It's also a menu for data entry. You assign a value or an instruction to any location on the pad. At the touch of a stylus, it's entered into your system. Who can use it? Anyone from the educator and the engineer to the hobbyist and the computer games enthusiast. The data structure is byte oriented for easy compatibility with small computers, so you can add a power supply, stand alone display, cross-hair cursor and many other options. Bit Pad by Summagraphics. The leading manufac- turer of data tablet digitizers. Bit Pad. The only words you need to say when considering digitizers. ■ >Sunmiadu]fihic6 -E-'iF- ^ ' corporation ::!!:?:: 35 Brentwood Ave,, Box 781, Fairfield, CT 06430 ^' """" ^ Phone(203) 384-1344, TELEX 96-4348 use of RF in a data exchange network. His generalities do no justice to tine enormous technical, political and finan- cial complexity of such a system. It is unfortunate that someone who must know quite a bit on this subject would author oversimplifications which could lead less well informed persons to believe that such a system is really a practical option. Anyone who plans to propose that the FCC allocate 1 MHz of precious VHF or UHF spectrum for a short haul, fixed, unattended, personal radio communication service should be pre- pared to be laughed out of Washington. First, just where does Mr Steinwedel suggest that this 1 MHz come from: amateurs, government, broadcasters? Don't count on it! The fact is that there is nothing like a 1 MHz block available below 900 MHz. Second, all services are allocated frequencies on the basis of international standards and demonstrated need. How can anyone demonstrate the need for a frequency hungry radio network to link homes around town so we can all play Star Trek together? How would he reply when asked, "Why not just use the phone?" Third, Mr Steinwedel totally ignores the high cost of such a system. This is probably due to the fact that amateurs don't have to pay first class technicians to maintain their equipment. Why do you think the cost of mobile telephone is so high? Finally, the suggestion that the FCC would authorize this service to employ totally unsupervised trans- mitters exhibits unfamiliarity with one of the prime principles of FCC regu- lation. That is, who is going to pull the plug when the thing gets stuck in trans- mit mode? Every chapter of the FCC Rules and Regulations expounds on this principle at length under the heading of "Operator Requirements." The cases where the FCC has authorized totally unsupervised transmitters are so few as to not be worth noting. In short, why don't you just use the phone? I don't want to give the impression that I am totally against digital radio communications. It is fine by me if amateurs wish to combine hobbies. I personally would love to help set up an intercity tropo or satellite link for CIE use. However, I would not be so bold as to suggest that it would be cheaper than "Ma Bell." Anyone who wishes to explore the possibilities of digital exchange and calling by radio should obtain a copy of the International Telecommunications Union CCIR Study Group 8 Draft Recommendation #493 which proposes some international standards for similar systems. I would also suggest that any- one interested in writing CIE standards should first take a long look at standards accepted by the ITU and other organi- zations so that international compati- bility can be maintained. Donald R Newcomb 819 Bayou Blvd Pensacola PL 32503" 1 22 July 1978 © BYTE Publications Inc Circle 352 on inquiry card. College Sports Report Grinnell Wins Second Midwest Regional Programming Competition Grinnell College of Grinnell lA barely nosed out DePauw University of Green- castle IN in the Second Midwest Re- gional Programming Competition held at Taylor University, Upland IN, April 1 1978. The host team, Taylor, finished third and Wabash College of Crawfords- ville IN was fourth. Grinnell's 2 person team led by Scott Parker of Champaign IL and sponsored by Prof Mark Grundler defeated DePauw's squad by only three points in the 4 person, 4 hour competi- tion using Taylor University's DEC time- sharing system. However Evansville Uni- versity used their IBM 360 over tele- phone lines for the competition. Each team had only one 300 charac- ter per second printing terminal on which to write, test and debug their pro- grams. A team of six judges led by chief judge Bruce Gaff of Plycom Industries (Plymouth IN) and Jere Truex (Upland IN) reviewed the solutions written in BASIC and indicated if the solutions were correct or incorrect. The scoring method included the number of prob- lems, the time required to complete the solution, and the number of judged runs submitted. The four problems posed included writing check amounts in words, screen- ing inaccurate data from an electronic instrument for accuracy, connecting pairs of points in a geometric plane, and retrieving prices from descriptions in a catalog. Although 14 teams from seven mid- western states were expected, schedule changes and other factors caused some teams to miss the competition. In addi- tion to the four teams already men- tioned, others competing were the Uni- versity of Wisconsin/Platteville, Asbury College of Kentucky, plus Grace College and Rose-Hulman Institute from Indiana. Next year the Midwest Region will be held at Rose-Hulman or Taylor Uni- versity. It is hoped that a National BASIC competition between regional champions will be held at a later date. Taylor University had two freshmen on their third place team and other schools had freshmen participating also, so it Is anticipated that next year's competition will be even more strongly contested. Taylor's young team included senior Steve Olsen from Wyckoff NJ, junior Mark Tomlin of West Milton OH, plus freshmen David Woodall of Marengo IL and Stan Rishel of Kalamazoo Ml. The alternate members were freshmen Cory Waller of Franklin Lakes NJ and Mark Collins of Indianapolis, who missed the competition because of illness." DATALYZER ... a 24 channel Logic Analyzer for your SlOO Bus 24 Channel LOGIC ANALYZER, complete with 2 cards and 3 sets of probes. Features — 24 channels with 256 samples each. — Display of disassembled program flow. — Dual mode operation - external mode analyses any external logic system. Internal mode monitors users data and address bus. — Selectable trigger point anywhere in the 256 samples. — 0-16 bit trigger word format or external qualifier. — SIVlHz sample rate — Synchronous clock sample with coincident or delayed clock mode. — User defined reference memory. — Displays and system control through keyboard entry. — TTL Logic level compatible (15 pf and 15 )ja typical input loading.) Displays in Binary Displays in Hex Display of disassembled program flow. The DATALYZER Designed to plug easily into your S-100 Bus, the DATALYZER is a connplete system — for only $595. Display of disassembled program flow is a standard feature, not an extra. And the low price includes 30 logic probes, so you can hook up immediately, without additional expense. The DATALYZER is available in kit form ($595), and as a fully assembled device on two PCB's ($695). Operators' manual $7.50. A substantial warranty, and the Databyte, Inc. commitment to service make the DATALYZER a worthwhile investment. Databyte, Inc. 7433 Hubbard Avenue Middleton, Wisconsin 53562 Tel: (608) 831-7666 Circle 86 on inquiry card. )uly 1978 ©BYTE Publications Inc 123 How to Choose a Microprocessor Lou Frenzel Heath Company Benton Harbor Ml 49022 All personal and hobby computers are microprocessor based. That is, they use a single processor integrated circuit chip. One of the most important decisions you will ever make in purchasing a personal computer is choosing the type of micro- processor. The semiconductor manufacturers have provided computer designers with a wide range of microprocessing units having varying degrees of power and sophistication. As a result, there are at least a half dozen different processors available in hobby computers. This wide variety of products mal ^ ADM-3A 756 00* IN KIT FORM ' 80 CHARACTERS/LINE • 24 LINES/SCREEN ' ADDRESSABLE CURSUR '9, 10, or 11 BIT WORDS Plus Shipping and Handling I I I \ • 75-19,200 BAUD • FULL & HALF DUPLEX • ODD/EVEN/NO PARITY • RS232 INTERFACE OR 20 ma CURRENT LOOP GET COMPLETE DETAILS WITH A DIRECT CALL: 214 258-24ia TWX 910-860-5761 TELEX 73-0022 800 527-3248 capital 930 N. BELTLINE equipment brokers IRVING, TEXAS 75061 I r ^ The KIM to S-100 bus Interface/Motherboard • Combines the power of the 6502 with the flexibility of the S-100 bus • Attaches to any unmodified KIM • Complete interface logic and fully buffered motherboard in one unit • Onboard regulation of power for KIM • Eight slots of S-100 compatibility for additional RAM, Video and I/O boards, PROM Programmers, Speech processors . . . • Includes all parts, sockets for ICs, one 100 pin connector, and full Assembly/Operating documentation ♦ Kit $125, Assembled $165 ♦ All units shipped from stock FORETHOUGHT PRODUCTS P.O. Box 386-F pi^ Coburg, OR 97401 UgJ^j example, most hobbyists use the BASIC language. The speed of the microprocessor will definitely determine the length of time that it takes to execute a program. However, with an interpretive language such as BASIC, an order of magnitude difference in execu- tion speeds is frequently almost unnotice- able to the user. While it may take 200 iis to execute a program on one computer and 20 /is on another, the user is often totally incapable of recognizing the difference. The real value of speed comes when your application requires it. If your applications involve lengthy, complex mathematical operations or highly complex real time functions, speed may be an important con- sideration. Otherwise, speed is one factor which you could practically ignore in the selection of a personal computer. Few per- sonal computer manufacturers know how to specify it, let alone mention it. Computing Power Computing power is a rather nebulous designation that refers to the power of the instruction set and architecture of the com- puter. Computing power also effectively involves speed as discussed above. Yet computing power is far more important than raw speed in determining the capa- bilities of a microprocessor. It is difficult to provide any specific guidelines for determining whether one microprocessor is more powerful than another. However, as a general guideline there are several factors to look for in determining which microprocessor has the greatest power. These factors are: number of instructions in the instruction set, number of working registers, and number and type of addressing modes. Those microprocessors with the greatest numbers of instructions, registers, and addressing modes are essentially the more powerful microprocessors. They can accomplish more complex operations in less time than other microcomputers with lesser characteristics. It is the wide variation in architectures which makes the choice of a microprocessor interesting. In some cases, a superior in- struction set, more flexible register organiza- tion and more addressing modes can offset the superior computing speed of another microprocessor with a simpler architecture. There are never any clear cut answers to the question of which microprocessor is the most powerful since usually the answer lies in a specific application. When a partic- ular application can be defined, the choice of microprocessor can be optimized. How- ever, when choosing a microprocessor-based general purpose computer which must be 1 26 July 197S e BYTE PuUicatisns Inc Circle 140 on inquiry card. Circle 265 on inquiry card. useable in a wide range of applications, the speed and computing power consideration becomes fuzzy at best. Second Sources Another way to assess the value of a microprocessor is to consider the second sources. Second source refers to a manu- facturer other than the original manu- facturer, producing the same device. When a semiconductor manufacturer introduces a new microprocessor, he attempts to capture as much of the marlBYTE Publicdiions Jnc Circle 294 on inquiry card. CANADIANS! Introducing our kit-by-the-month plan available for only $500.00 down and $150.00 per month. (Write for more information) IMSAI 8080 KIT: $897.50 ASSM: $1245.20 Canadian Duty and Federal Tax Included Hobby systems from $999.00 (Kit). Business/engineering systems from $1 1 ,900.00. (Assembled and Installed*). Educational discounts available. We will develop custom application pack- ages. Contact us for further Informa- tion. Send $1.50 for catalogue. VISA • CHARGEX ACCEPTED Rotundra WML Cybernetics flMl Box 1448, Calgary, Alta. T2P 2H9 Phone (403) 283-8076 (Installation outside Western Canada extra}. SAVE $10.00 I AST CHANCE to get the popu- lar OP-80A at the old $74.50 price. Due to increasing costs, there will be a modest price in- crease (our first) in the OP-80A. Effective July 31 the price will be $84.50 Kit - $99.95 A & T. Oliver Advanced Engineering, Inc. 676 W. Wilson Avenue Glendale, Calif. 91203 ATTENTION MOTOROLA MEK6800D2 USERS 4 Slot Card Rack Designed Speicifically for the MEK, MMS68104 MEMORY BOARD, EXORciser, and Micromodule Boards. Kit $64.95 Assembled $79.95 Check, Money Order, VISA or MC add $2.00 shipping, PA. residents add 6% sales tax. DEALER INQUIRY WELCOME PENTEC, INC. P.O. Box 148, Whitehall, PA. 18052 Circle 309 on inquiry card. Circle 292 on inquiry card. Circle 299 on inquiry card. DIABLO TERMINALS ! LIMITED OFFER HYTYPE I TERMINAL $1595.00 30 character per second Daisy wheel printer RS-232 serial interface Also: HyType II NEC Spinwriter Qume Sanders 12/7 Centronics Univac Complete line of microcomputer products MICROCOMPUTERS, PERIPHERALS AND SOFTWARE 101b Navarro San Antonio, TX 78205 512/222 142V Circle 231 on inquiry card. 01 c o o Engineers Hardware/Software Our clients are stepping up their engineering efforti Growth positions in the 15-40K range are available with manufac- turers of sophisticated systems. Di- verse areas include Graphic Arts. Text Handling Systems, Micro-Based Con- trollers, Manufacturing Systems, and Communications. HARDWARE - Design capability in TTLand CMOS Devices, Peripherals, and CPU. SOFTWARE - Real Time Operating Systems, Compilers, and Data Base Design - DOS. Call us at 603-888-5500 (collect) or send us vour resume - in confidence, of course. Touchstone Associates Inc. Engineering/EDP Mgt Consultants 104 D,W. Hwv,, Nashua, N,H. 03060 issC^s DAJEN/TELETEK MIC 3 5502 ' Ctiicago Illinois 60<;80 ' (1121 528 9M5 Circle 386 on inquiry card. BIT BASEMENT BARGAINS . SOROCIQ120 [assbled] ...$869.95/ j LEAR ADM-3A [assbled] ...$859. 95 1 LEAR ADM-IA [assbled] ..$1199.95 ^16K RAM BOARD [assbled] $495.00/ 250nS 180 day warranty f CENTRONICS 779 $1139.95' MICROPOLIS 1042 Mod I . $779.00 BIT BASEMENT P.O. Box 1719 Santa IVIonica. CA 90406 H|(213) 322-9070 Q all items shipped FOB factory Circle 31 on inqyiry card. (a) (b) Digital Equipment Corporation, tine largest minicomputer company, introduced the LSI-i i microprocessor based single board computer to extend its minicomputer line downward into the microcomputer world. This PDP-i 1/03 system (a) is the DEC finished pacliage based on the LSI-I I. The Heath Company offers a version of the LSI-I J (b) which is called the HI J, which is available at lower cost in partial kit form along with extensive documentation aimed at the personal computer kit builder and experimenter. These photos are supplied by Digital Equipment Cor- poration and Heathkit, respectively. grammable and read only memory, as well as Input and output interfaces. The 8048 was designed as a hardwired logic replace- ment and not for general purpose digital computer application. What About 12 and 16 Bit Microprocessors? Without question the trend in micro- processor development is toward larger, more sophisticated designs. While most microprocessor activity is centered around 8 bit devices, there is clear evidence that single chip 16 bit microprocessors will eventually replace the 8 bit units. As semi- conductor technology improves, it will be just as easy to manufacture a 16 bit micro- processor as it is an 8 bit device. When that time comes, the price differential will be minimal. As a result, most purchasers of new equipment will go to the more powerful 16 bit device over the 8 bit device, even though the computing power available is overkill for the application. There are a number of 16 bit micro- computers and one 12 bit device now on the market. In terms of overall microproc- essor usage, their popularity is small. But it is growing rapidly as more devices are developed. As these devices are incorporated in designs, the demand will go up and prices will decline. Some of the manufacturers making a 16 bit microprocessor are given below. National Semiconductor PACE, 8900 General Instrument 1600 Data General microNOVA Digital Equipment Corp LSI-11 Texas Instruments 9900 Fairchild 9440 At present there are few hobby and personal computers based on 16 bit micro- processors. Notably those that are available are the Heathkit H11 which is based on the popular DEC LSI-1 1 and the Technico 9900, based on the TMS-9900 part from Texas Instruments. The reason why 16 bit microprocessors haven't caught on in personal computing is that they have not been widely adopted elsewhere. The price is significantly higher than 8 bit devices and little or no software is available. 16 bit microprocessors are far more powerful and can process data much faster than an 8 bit microprocessor. How- ever, for most personal computing applica- tions such power is not necessary. At this time, the most widely used 16 bit microcomputer is the DEC LSI-11. This particular computer has a wide following among hobbyists because of the great DEC software base. It is an ideal choice for the advanced user. None of the other available 16 bit micro- processors has yet caught on. The first 16 bit microprocessor available was National Semiconductor's PACE. Despite its early lead, PACE never became popular. The newer Texas Instruments 9900 16 bit microprocessor shows promise of becom- ing one of the more popular 16 bit micro- processors. This device may eventually be- come the 8080 of the 16 bit microproc- essors. This device is gaining acceptance in many areas. It is a powerful, general purpose 138 luly 1978 ©BYTE Publicatiominc device. In addition, much of the software available for Texas Instruments minicom- puter line is compatible and could possibly be converted in the future for use on this device. Finally, Texas Instruments is one of the largest and most aggressive semicon- ductor manufacturers. They have the manu- facturing and marketing power to support and promote this device. Watch for it in future designs. The Micro NOVA is another very power- ful 16 bit microprocessor. It can effectively run all of the software available for the popular Data General NOVA line of mini- computers. However, this device like some of the others has not caught on. It is an ex- pensive device and not widely available. While the architecture is straightforward and easy to learn and the Data General software base is tremendous, it is doubtful that Data General will promote this device for the personal computing market or make such software available at competitive prices. (However, Data General is promoting the Micro-NOVA through selected retail stores and electronics distributions. Fairchild's 9440 MPU uses the Data General architec- ture and will run the software. Although it is expensive, someone may eventually use the 9440 in a personal computer. The Intersil 6100 is a 12 bit CMOS micro- processor. Its claim to fame is that it has the architecture and instruction set of the famous DEC PDP-8/E minicomputer. It will also run software written for that machine. This gives the 6100 an excellent software base. But despite the software advantage the 6100 hasn't caught on in personal com- puting. One reason is the high price as- sociated with 6100 based computers. These include Intersil's own Intercept series and a machine made by PCM. For the prices of these machines, a user can buy a used but real DEC PDP-8. In any case, the 6100 is a good chip with much potential. Summary and Conclusion The message in this article is relatively clear. If you are choosing a microcomputer for hobby and personal computer applica- tions, your best choice lies in the 8080, Z-80, 6800 or 6502 based machines. This is the mainstream of personal computing. The 8080/Z-80 combination probably has the edge over all of these. The biggest question is who is going to make the 16 bit micro- processor. Will it be the new Intel 8086? or will Zilog's Z8000 win? We will have to wait and see. Finally, the message here is that "a proc- essor alone does not a computer system Another 16 bit minicomputer architec- ture available In microcomputer form Is the Data General Corporation's MicroNOVA shown here in a picture supplied by Data General. In the foreground is the processor chip standing alone; in back of the inte- grated circuit is a printed circuit board version of the computer Intended for use In dedicated applications. In the background can be seen the MicroNOVA fully inte- grated minicomputer system. These pro- ducts are available at several retail computer stores and at several electronics distributors. make." When it comes right down to it, the type of processor is almost irrelevant to the user who is programming in BASIC or PASCAL or some other high level language. Overall, it is the software that gets the job done. If you base your choice of a personal computer system on the availability of good system and application software, you will not go wrong, whatever low level machine architecture is used." luly 1978 © BYTE Publications Inc 139 »^nt;itr iH3 on inquiry card. A PROFESSIONAL COMPUTER TERMINAL FOR THE NOBBIEST SINGER 7100/7102 New & Reconditioned Terminals with ASCII Code FEATURES: 7100 $650. to $1295. • ASCII CODED witliout tape puncli or reader . 110 to 150 BAUD (11 to 15 CPS adjustable) • Word Processing Quality • RS232 Serial or Current loop Interface • Nationwide Service • Warranty 'Off line use as Typewriter • (Option) Special Interfaces available for Hobby Computers (state which when ordering) 7102 Same features as 7100 plus tape punch & reader TERMS: C.O.D. and Cashier's Check Shipping and Handling $35.00 ea. HK COMPUTER CORPORATION H&K COMPANY 15 East 3 IS' Street Kansas City, Missouri 64108 (816) 561-1776 MOO mi lElOOO MOO mmnpRAfflc imo • NOT A KIT • 8vg;15A. ±16v(&3A power • Rack mountable ^ • 15 slot motherboard iS^ • Card cage ) ' • Fan. line cord, fuse. \ switcti. EMI filter • Desk top version option • 8v(g30A. ±16v(?i10A option • voltage monitor option • 100 pin connectors optional Rack mounted lOdel From S200 Desk top model From 3235 Write or call for a copy of our detailed brochure which includes our application note BUILDING CHEAP COMPUTERS. INFEGI^ND 8474 Ave 296 • Visalia C (209) 733 9288 We accept BankAmericord/Viso and Master Charge Continued from page 46 The integrated circuit manufacturer can sell parts that would otherwise have to be thrown away, and the designer can buy state of the art parts for prices far below those of the equivalent 16 K part. The design task breaks down into the fol- lowing steps: 1. Select the memory chip. For reasons stated earlier, the MK4115 (or equiva- lent) is the clear choice. 2. Decide how to handle refresh. 3. Analyze the timing requirements for the memory and the processor. 4. Merge these two timing diagrams so that they work together. 5. Design the circuitry. 6. Lay out the circuit board. Refreshing Strategy When should you refresh? There are two types of refresh used in a dynamic memory system. Burst refresh suspends all other memory activity and quickly refreshes all the required locations at the top memory speed. This burst occurs once every refresh interval (generally every 2 ms). A preferable approach in a microproces- sor system is to use a distributed refresti approach, in which refresh cycles are inter- spersed with processor access cycles. In this manner the refreshing action is evenly spread over the 2 ms refresh interval. Let's examine some refresh alternatives: 1. Use a 2 ms timer to interrupt the processor and tell it that the memory requires refresh. The processor inter- rupt routine then counts out the proper memory addresses and returns to normal processing. 2. Use a timer with an interval of 2 ms divided by the number of required refresh cycles, and perform item 1 on a distributed basis. 3. Interleave the refresh operation with normal processor timing: For example, notice (as the Z-80 designers did) that the processor address lines serve no useful purpose on the tail end of an instruction fetch cycle. During this time the processor must decode the instruction fetched from memory in anticipation of executing it. Why not put the refresh cycle (which needs the address lines) into this time slot? Items 1 and 2 above require processor overhead (processing time) since the inter- rupt system is used to provide programmed refresh. Of the two, the distributed approach is preferable because it produces less of a timing discontinuity in the background pro- 140 luly 1978 (^ BYTE Publications Inc Circle 1 79 on inquiry card. Circle 120 on inquiry card. gram execution while the interrupt is being serviced. Item 3 is best in all respects, since no direct processor intervention is required to perform refresh. This is the so-called "transparent" or "invisible" refresh. This approach has already been implemented in some small system designs. It does, however, have some drawbacks in Altair (S-100) bus products. In examining the details of this approach, we'll describe an even better method of achieving "Altair (S-100) refresh." This discussion assumes an 8080 or equiva- lent processor. Catching the Bus The only time the processor can guaran- tee that the address bus is not needed is the second half of an instruction fetch cycle. This point in time is signified by the proc- essor control signal called Ml, which means "memory cycle one" of any instruction. Every instruction execution starts with an Ml memory cycle, in which the instruction is brought into the processor from memory. Depending on the instruction, further memory cycles might be required to finish execution of the instruction. During these subsequent cycles, the Ml signal is inactive. For example, the 8080 STA (store A) in- struction operates as follows: 1. Ml: instruction word fetched from memory. 2. M2: first half of the storing location read from memory. 3. M3: second half of the storing loca- tion read from memory. 4. M4: accumulator contents written into memory location specified by data brought in by steps 2 and 3. The STA instruction is a 3 byte instruc- tion, and M2 and M3 are needed to read in the additional two bytes of the instruction. M4 does the actual execution of the instruc- tion, storing the accumulator. In this ex- ample, the Ml control signal is active only for step 1. The actual Ml cycle is divided into five processor cycles, called time states or "T-states." By the end of T3, the proc- essor has received the first byte of the in- struction and now requires two more time states, T4 and T5, to figure out what to do. This is the logical time to force a memory refresh (to be exact, T4 and T5 of Ml ). This is all very nice, but what happens when the processor is halted? During HALT, the signal needed to locate the point in time for refresh. Ml, is not there. In fact, most of the processor signals are not there. This is also true for processor RESET, wait states, and direct memory access cycles. This means 16KRAM FULLY STATIC KIT $350 10 SLOT MAINFRAME TT-10 KIT $325 1 SLOT TABLE TOP MICROCOMPUTERS TT-8080 KITS440 SYSTEM WITH 1 6K & I/O TT-8080-S KIT SI 050 CARD CAGE & MOTHER BOARD ECT-100. KITS100 CCMB-10 K1TS75 WITH CONNECTORS & GUIDES ECT-100-F KITS200 CCMB-10-F. . KIT SI 25 CPU'S, MEMORY MOTHER BOARDS PROTOTYPING BOARDS EXTENDER CARDS POWER SUPPLIES SHIPPING EXTRA DEALER INQUIRIES INVITED ELECTHQI^JC CQf^TRQL TECHI^QLQGV FACTORY ADDRESS: 763 RAMSEY AVENUE HILLSIDE, N. J 07205 MAILING ADDRESS: P O. BOX 6 UNION, N J 07083 1 I I I I I I I I I (201) 686-8080 Kwmimmmpmimmiiimmmmiimmmmgmmmmmammmmmmmmfami^ \ TRS-80 \ SOFTWARE EXCHANGE JOIN INONTHEFUNIII! THE TRS-80 SOFTWARE EXCHANGE CIRCUIT HAS FORMED HOW TO JOIN Send (on cassette) your best general interest program. In return, we send you one of our Circuit Exchange Cassettes (6-10 programs per tape). Programs meeting our standards are considered for retail sales, and you receive commissions on every program sold. MARKETPLACE SUBSCRIBE TO THE TRS-80 SOFTWARE EXCHANGE MARKET BASKET. $3 a year - a catalog of over 100 available software programs, prices starting at $1 . Write TRS-80 SOFTWARE EXCHANGE 17 Briar Cliff Drive Milford, N. H. 03055 Circle 383 on inquiry card. July 1978 ©BYTE Publications Inc 141 Circle 405 on inquiry card. •MC a6XX1C%.%1lgK.%%%%1lliX%1CX.%%%1» 1 6^^ PRAMMER III by xybek The Ultimate EPROM Memory Board For Your S100-Bus Computer * Accommodates from 1 k to 30k of the above EPROMS, in any combination, each addressable on any Ik (2k tor 271 6) boundary within the board's 32k address space. * 1 k of scratch-pad RAM. * On-board programming for all three EPROM types. * Tri-state buffers on all address and data lines. * Empty EPROM sockets do not require address space. * Assembled, tested, ready to run — only $369.50 xybek • P.O. 80x4925 • Stanford, CA 94305 Telephone: (408) 296-8188 16K static RAM S-100 Systems '330 365 Assembled WATCH FOR NEW PRODUCTS • Very Low Power-650MA+5V; 90IVIA+12V; 16MA-5V • Applications Notes-6800 and 6502 Sys. • Low-profile sockets for all chips • Solder mask; silk screen; plated through holes • Each 4K addressable to any 4K boundary • Fully buffered S-100 bus— gold-plated contacts • NEC UPD 410 D memories COD, Master Charge, B of A, Visa Accepted .... Orders shipped prepaid. California residents add 6% sales tax. M ANDENBERG DATA PRODUCTS POBOX2507 SANTA MARIA CAUFORNIA 93454 •05-937-79S1 that the design must do something special for these cases. What is really needed is an approach independent of processor control signals for refresh. The only signals on the Altair (S-100) bus that are present under all cir- cumstances (except power off) are the processor clock signals 01 and 02. Plan Ahead - Backwards Here's the plan: the memory design should contain a self-contained refresh system that uses only 02 for its operation. The control is arranged so that the memory is normally refreshing, and it is the exception cycle that diverts it away from refresh to perform a processor access. This emphasis is "back- wards" from most systems, which treat the refresh operation as the exceptional case. Now the card merrily refreshes itself until called on by the processor. If the processor "goes away," for example, in a prolonged wait state (a method frequently used to im- plement single-step and other front panel operations), the refresh continues. When the processor needs to access the memory card, it must do it on a synchro- nous basis. This means that the processor timing on a memory access into the dynamic memory card is designed to not jeopardize a refresh cycle in progress (it is synch- ronized with the refresh timing). Imagine the processor crashing in on a refresh cycle, and 64 data locations in the memory not being properly refreshed and going to indeterminate states. This is the kind of "soft error" that occurs only when you demonstrate the system ("It worked per- fectly on the bench. . ."), and promptly goes away when you try to fix it. Programmable IVIemory Timing Let's take a detailed look at the dynamic memory integrated circuit itself, and at exactly what signals are required to make it work. The integrated circuit described could be any of the various 16 K parts of the MOSTEK MK4116 type; or, with one small exception, any of the 4 K parts of the MK4027 type. Since 16 K is equal to 2^^, the part re- quires 14 address lines to uniquely select any of its cells. Allowing one line for DATA IN and another for DATA OUT, this adds up to all of the pins of the 16 pin package. That's fine if the chip doesn't require power supplies or read and write control, but un- fortunately, it does. This dilemma is solved by using a multiplexed address approach. Only seven pins are used for address inputs, and the address is loaded in two parts. One 142 luly 1978 % BYTE Publicitions Inc Circle 388 on inquiry card. Circle 95 on inquiry card. of the big benefits of this approach is that, when the technology jumped from 4 K to 16 K, an additional two address lines could be had with only one additional pin. On the 4 K parts, this "unused" pin is a Chip Select input, which is used to select only one bank of parts that share the same output bus. As we'll see, the 16 K part does the chip select function without a chip select pin. Two control pins called RAS and CAS strobe the two 7 bit parts of an address into the memory part. These signals stand for Row Address Strobe and Column Ad- dress Strobe. They are active low signals, which means that they are normally at a high logic level, and are "strobed" by going into the low state momentarily. The sequence of events necessary for a memory cycle is as follows (see figure 3): 1. Set up the low order 7 bit address on the address lines. This requires set- ting the address multiplexer to state 2 (for example). 2. Wait a suitable time for the address lines to settle. There will be a certain delay through the multiplexer, as well as some line settling time. 3. Drop the row address strobe (RAS) to the low state. This latches the low address into the part. Both RAS and the column address strobe (CAS) start out high. 4. Wait the "row address hold time," which specifies for how long after RAS drops the address lines must not change. This requirement is due to the setup time of the on-chip latches. 5. Set up the high order 7 bit address on the address lines. This requires select- ing multiplexer state 3 (for example). 6. Let the lines settle. 7. Drop CAS to the low state. This latches the high address into the part. Don't remove the addresses until after the "column address hold time." When the logic level of the column address strobe drops, the output lines go from a high impedance state to a valid data state after the interval called "CAC" for Column ACess time. This is one way of specifying the access time of the memory part. These seven steps are the same for either a memory read or write cycle, the only dif- ference being the treatment of the RW pin which controls the choice of Read or Write operation. If this pin is held high throughout the cycle, a read operation is performed. To do a write, the RW pin is pulled low some- time after RAS. Exactly when it is pulled low determines whether the outputs become valid for the old data in the selected cell. CP/M™ LOW-COST MICROCOMPUTER SOFTWARE CP/M''' OPERATING SYSTEM: • Includes Editor, Assembler, Debugger and Utilities. • For 8080, Z80, or Intel MDS. • For IBM-compatible floppy discs. • $100-Diskette and Documentation. • S25-Documentation [Set of B manuals) only. MAC™ MACRO ASSEMBLER: • Compatible with new Intel macro standard. • Complete guide to macro applications. • S90-Diskette and Manual. SID™ SYMBOLIC DEBUGGER: • Symbolic memory reference. • Built-in assembler/disassembler. • S75-Diskette and Manual. TEX™ TEXT FORMATTER: • Powerful text formatting capabilities. • Text prepared using CP/M Editor. • S75 Diskette and Manual. d DJGJTflL RESEARCH P.O. Box 579 • Pacific Grove, California 93950 (408) 649-3896 systems, inc. ' ,f : rKt I I I i t I I I I t Boards DO Something CL2400 Real Time Clock S98— Kit $135— Assembled If your system needs to know what time it Is, our CL2400 Is the board for you. The present time in hours, minutes, and seconds is always available for input, and is continuously updated by the highly accurate 60 Hz power line frequency. Need periodic interrupts? The CL2400 can do that, too, at any of 6 rates. Reference manual with BASIC and assembly language software examples included. PC3200 Power Control System PC3232 $299— Kit PC3216 $189— Kit PC3202 $39.50— Kit $360— Assm, $240— Assm. $52— Assm. If your system needs on/off control of lights, motors, appliances, etc., our PC3200 System components are for you. Control boards allow one I/O port to control 32 (PC3232) or 16 (PC3216) external Power Control Units, such as the PC3202 which controls 120 VAC loads to 400 Watts. Optically isolated, low voltage, current-limited control lines are standard in this growing product line. nanaria systems, inc. (formerly comptek) P.O. Box 516 La Canada, CA 91011 (213) 790-7957 Circle 40 on inquiry card. luly 1978©BVTePublicaIianslnc 143 Circle 202 on inquiry card. Pencil Style WIRE WRAPPING GUN For semi automatic machines and test lab use, this new pencil style wire wrapping gun can't be beat! It's light! Operators find it easier to use than heavier old style pistol grip types. With precision made motor, internal gearing and clutch mechanism, it is as quiet and dependable as a swiss made watch. Supplied with wrapping bit, sieeve and unwrapping tooi alitor $58.25 FOBELDON, MO. ForSOAWQWIra OunNumtwr: 830WT-1 For 28 AWG Wire Gun Numlxr: 82SWT-1 Call or write for our catalog on Bread Boards, I C SoclTE Cover Price * plus postage and handling Back Issues for sale llllllllllll = The following issues available: I 76 '77 5 2800 July 600 March j S 100 August 600 May j = 150 October 900 June j = 300 November 900 July | S 375 December 1400 August | s 2450 September : ^ 100 October 1 S 400 November | = 900 December : = * Cover price for all issues thru August 1977 I = is $1.50 plus $.25 postage and handling I = ($3.50 total foreign). September '77 thru j = December '77 issues are $2.00 plus $.50 I S postage and handling ($4.00 total foreign). ■ niiiiiiiiiiiiiiiiiiiitiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiE Send requests to: BYTE Magazine 70 Main St Peterborough NH 03458 Attn: Back Issues 16 lines), and the processor SYNC output. Lines 5 and 6 show the control lines MUX2 and MUX1 to a one-of-four multiplexer, and line 7 shows the state of the multiplexer selected by the two control signals IVIUX2 and MUX1 . Lines 8 and 9 show the principle memory timing signals the row address strobe (RAS) and the column address strobe (CAS); lines 10 and 1 1 show the proc- essor timing requirements for accepting data read out of the programmable memory. The "valid" indication on the waveform of line 10 shows when the eight data lines into the processor must be stable for a success- ful memory read. The DBIN signal (line 11) is a signal issued by the 8080 to notify the input buffers to turn on in preparation for receiving input data. Line 12 shows the write line (WR) from the 8080 which is used to enable the write operation into the memory. Working Together Lines 5 thru 9 of figure 4 constitute the actual memory system design, the result of trading off memory, Altair (S-100) bus and processor parameters, and verifying that all the processor and memory timing con- siderations are met. The ultimate criterion of a good design is that it can pass a "worst case" analysis — every specification for the 8080 and the programmable memory can be the worst specified in the data sheets, and the system will still work. In fact, a good figure of merit for a digital design in- volving complex timing (such as this one) is how far beyond worst case the specifications can be for the system to still function properly. This is known as margin. The better the margin, the better the designer sleeps at night, and the better guarantee that the system will work over a long production run. Notice the similarity between 02 and RAS (lines 2 and 8) of figure 4. RAS is simply 4>2 with certain positive parts missing. Whenever the 8080 starts an instruction fetch cycle (signalled by SYNC), the RAS line must make its negative transition dur- ing MUX state 2 and stay there throughout the memory cycle. If the 02 pulse during T2 were allowed through, the memory tim- ing requirements would not be met. To inhibit this 02 pulse, SYNC is delayed slightly and used to gate off the unwanted part of 02. Notice that this gating signal is MUX1 (line 6). SYNC is delayed very simply by feeding SYNC to the D input of a flip flop and clocking the flip flop with the lead- ing edge of 01 . Before this cycle gets underway with row address strobe line RAS dropping, the address lines to the memory must be set up 146 (uly 1978 6 BYTE Publicitionsinc Circle 318 on inquiry card. to receive the low order part of address lines from the processor. The multiplexer must therefore switch from state (the refresh select state) to state 2 (processor-low address state) prior to the fall of RAS. This is accomplished by the signal IVIUX2, which is turned on by the leading edge of SYNC. This edge gives the address lines more than enough time to settle before they are sampled by RAS. After the row address strobe part of the cycle is satisfied, the multiplexer switches to state 3 (the other half of the processor address lines), and column address strobe is activated. The column address strobe line goes low when three signals are asserted as follows: 1. 02 high. 2. MUX1 high. 3. The bank of programmable memories is selected. The third control, often called "this mem- ory," performs the chip select function by feeding the column address strobe to only one bank of programmable memories at a time. Looking now at lines 9 and 10 of figure 4, we can calculate the access time margin of the memory system. The data out of the programmable memory becomes valid some- time after CAS makes its negative transition. The data into the processor must be stable and valid at the time shown in line 10. Counting the time from CAS-low to the earliest time data must be valid, the pro- grammable memory access time should be 6X55 ns (each division is 55 ns), or 330 ns. In a system, this time is reduced by approxi- mately 50 ns to allow for the delays through the data buffers and line settling time. Let us say that the CAS to data access time (CAC) must be 330-50 or 280 ns. The speci- fication for the slowest IVIK4n5 gives a maximum t^;\c °f ^^^ "5' ^ ^^''y comfort- able margin. (If the margin point seems to be overstressed, its importance will be seen in the section on Altair (S-100) bus compatibility). To complete the cycle, the CAS line must be held low until the processor is definitely through with the data lines. This is indirectly specified in the 8080 data sheet as being the time that DBIN goes high. Since this point is anywhere from 25 to 140 ns after the rising edge of 02 in T3, the CAS line is held low until the falling edge of 02 in T3. Note that the RAS line makes its low- to-high transition well in advance of CAS's going from low to high. This is permitted in the newer dynamic memory parts but would not be acceptable in the older ones, such FORTRAN IV THE MOST EXTENSIVE FORTRAN SYSTEM AVAILABLE, RUNNING ON THE Z-80 * ANSI Standard Fortran IV Compiler — Byte, Word, Real, Double, Complex, and String data types and operations. — Produces efficient and compact code. — Compiles up to 600 statements per minute. — Expressions in Do loops, output lists, etc. * Linking Loader — Merges, links, and locates Fortran and As- sembler modules. — Searches libraries for needed modules. * Runtime Libraries — ANSI standard formatter. — All standard mathematical functions. — Sequential, Random and Blocked disk I/O. — Supports CP/M„ and user-defined devices. 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(Multiplexer state selects the refresh counter, the RAS line continuously cycles, and the CAS line remains inactive (high) for the RAS-only refresh operation.) This implements a strategy that maintains refresh on a fail-safe basis. The refresh counter is clocked by a signal which is suppressed during a processor access cycle, so that none of the refresh addresses is skipped. A refinement detail of the de- sign is a flip flop which eliminates some of the redundant refresh cycles to conserve power. This is possible because the latter scheme considerably "over-refreshes" the memory, since a full 128 row refresh is per- formed in much less time than the 2 ms the specification calls for. Refreshing more frequently than the specification requires has no effect on proper memory operation. For a write operation, the 8080's write line (WR) is timed such that it can be fed unmodified to the memory's read or write control (RW) pin. The write operation is RAS £55 RAS/CAS CYCLE LONG RAS/CAS CYCLE RAS ( )NLV CYCLE ' 1 1 ' ^- 1 \ 1 1 1 \ _[_ i + eo + 60 i J _ ^ n - J A. h 1 1 /I j [ l\\ A ' ' ^ I I / k 1 J / / / / / I loo (MA) kw J u ^ Kh J ^ J I \ ^^ J lu H i/ N ^■«_ 1 ; 1 J_ ' 1 tzo (M») ° — 1 !-- 1 1 \ — 1 1 / 1 1 1 V. ^ J L, J^ ^ % ./ ' V H w '" r ^v '^ ./ 1 1 - - % V V An 'SS ien k (M») *'° \ h J 1 \ / w f h \\ A _ / ^ . 1 \ ■V, '\ . / J / ^ 'L \ 50 NANOSECONDS / DIVISON Figure 5: Supply current waveforms for the MOSTEK MK4116 16 K dynamic memory (courtesy MOSTEK). terminated by the WR line going low to high, or the CAS line going low to high, whichever occurs first. Now, the Hard Part You might think that the design is com- plete when the final schematic is drawn. Not so: it is about half complete. As any dynamic memory system designer will tell you, 80 percent of dynamic memory design is printed circuit board iayout. These parts don't just sit there like their static counter- parts, responding with data whenever ad- dressed. The dynamic part is actually a sophisticated analog part inside, aside from being a dense memory array. The circuitry that senses the charge on the storage capaci- tors must resolve millivolt levels in the presence of continuously running 12 V clocks. The power distribution system and power supply noise decoupling are therefore the most critical elements of a good dynamic memory design. This consideration has killed more dynamic designs than any amount of poor circuit design. The dynamic memory has four power pins; 12 V, 5 V, ground and -5 V. The 5 V supply is connected only to the output transistors (to provide TTL compatible outputs), and draws next to nothing in power. The —5 V supply provides high current ptz/jes of very short durations. Since these pulses are bipolar in nature, the actual DC current for the —5 V supply is also very low. It is the 12 V supply and ground system that need special layout consideration. The four power pins are located on the four corners of the dual in line package, which somewhat simplifies a good power distribution layout. The best layout for power is one in which all power pins are fed from a horizontal and a vertical direction. This is known as "gridded" power distribu- tion, since each power pin is placed at the intersection of a grid of power lines that simulates a plane surface. Wherever possible, the power lines should be as wide as the array density will allow. When density con- siderations prohibit wide power buses on all four supplies, the 5 V and —5 V supply buses can be fed with smaller traces (but should still be gridded). The second important consideration is power supply bypassing. The current drawn by the 1V1K4116 is shown in the waveforms of figure 5. Notice that all the current is drawn as a result of RAS and CAS transi- tions. The factor which sets the MOSTEK 4116 apart from all other 16 K devices is that after the RAS and CAS current de- mands, the Iqq (12 V current) drops to nearly 0. The fact that other parts drop to some continuous current (on the order of 148 July 1978 ©BYTE PuWiclIions Inc 20 mA) when the RAS line and CAS line are inactive (high) accounts for the wide dif- ference in power dissipation between the MK4n6 and the others. MOSTEK does it by turning off the sense amplifiers when they are not needed, and the rest of the semiconductor world is presently designing (or redesigning) to duplicate this feature. Looking at the most critical current waveform of figure 5, Iqq, it is seen that the instantaneous current drawn is about 100 mA maximum. TOO mA per device times 32 devices (in a 32 K memory com- prised of 8 K parts) is 3.2 A at 12 V. Before running out to buy a water pump to cool the 12 V regulator, notice that the 100 m A is drawn for only a very brief time. Suppose you connect a capacitor between 12 V and ground, let it charge up during the low cur- rent demand time and supply the instanta- neous current pulses when needed. This is the role of the so-called "bypass" or "de- coupling" capacitors. The value needed for these capacitors can be readily calculated by estimating the area under the curves in figure 5. Using the formula C=(iAt)/Av, the capacitance can be calculated for any allowed drop in the 12 V supply (Av). The MK4116 allows a 10 percent tolerance on all supplies, so a good conservative number to use for the 12 V supply is about 2 percent or 0.24 V. Estimating iAt (the area under one of the current waveforms) from figure 5 to be about 50 ns times 1 00 mA, the formula yields a value for C of approximately 0.02 /jF. (0.1 /iF capacitors should work fine.) The reason for the above exercise is that even though the data sheets may say so, not all dynamic memories are identical. The primary difference between today's dynamic memories is in the current wave- forms, and only two manufacturers (MOS- TEK and Intel) even publish them. For the bypass capacitors to be effective, they must be located as close to the memory power pins as possible, so that the inductance of the printed wire feeding the instanta- neous current to the part does not interfere with this current supply. Note that for exactly the same considerations as the 12 V supply, the —5 V supply should be ade- quately "bypassed" with capacitors. The bypass capacitors should be evenly dis- tributed throughout the memory array. An often neglected detail of dynamic memory layout is that the ground system between the address line drivers and the memory array must be very heavy. As the number of integrated circuits in the memory array increases, the requirements on the address line drivers become more stringent. Each address pin contributes a capacitance of about 4 picofarads, and they are all tied together in the array. If you follow any address line through a printed circuit board memory array, you'll see that it takes a rather long and usually discontinuous path. For this reason, series damping resistors should be placed between the address buffers and the memory array to help damp out the undershoot and overshoot caused by the layout discontinuities. It is quite a trick to achieve optimum power distribution layout on an Altair (S-100) bus format card. The system ground pin comes in at only one corner of the card, and it must be routed in a "web" for a good board level ground distribution. Additionally, the required on board regulators use up a lot of space which, along with the permis- sible heat dissipation, puts an upper limit on the number of chips that can exist on a card. The message here is that a good memory design requires extreme cooperation be- tween the designer and the printed circuit board layout person. Ah, That "Altair (S-100) Compatibility" If you have plowed your way through the timing diagrams and technical discussion of this article, you can now appreciate the fact that the question, "Is it Altair (S-100) bus compatible?" is one that cannot be answered with an unqualified yes or no. The memory system is designed to be Altair (S-100) bus compatible, but when you plug it into a Stromdecker X-3 mainframe, running a Fantastroid Z-SOQ processor card with memory-managed-phantom- indirect-parabolic-vectored-restart imple- mented, it might not work. The design philosophy is to use as few of the Altair (S-lOO) signals as possible, to account for unforeseen variations in various systems. Back to figure 4; the only timing lines the memory counts on being there are (?il, 02, SYNC, DBIN (actually MEMR, memory read) and WR (actually memory write). In the case of the memory write line, any Altair (S-100) design should derive the memory write signal from SOUT and WR, since early designs put the gate to do this on the front panel board, and you therefore cannot guarantee that the signal MEMW will be there in all systems. Some analysis of the interlocked timing of figure 4 reveals that the card will work with any implementation of 01 and 02 that meets the 8080 specifications. The 01 and 02 timing shown in figure 4 is that luly 1978©BYT[ Publications Inc 149 Imagine pulling out four 8 K static memory cards and plugging in a single 32 K card that uses less power than one of the 8 K cards. This can be done with today's dynamic memories. provided by systems using an 8224 clock generator with an 18 MHz crystal; this is the most popular Altair (S-100) implementation. Will it work with Z-80 processor cards? Maybe. The Z-80 requires only a single clock, has no SYNC output, and times its read and write operations slightly differently than the 8080. Designers of Z-80 based Altair (S-100) cards realize that there is a big compatible world out there that they must back into, so they attempt to synthesize 8080-type signals out of the Z-80 system timing. How suc- cessfully they emulate the 8080 (meaning how accurately they reproduce signals such as 01, , > = , < , < =, =, > < . |3 indicates mandatory space. All other spaces are ignored by the interpreter. The only limit to the number of loops that may be nested is the amount of memory space available for storage on the stack. Everything past a semicolon on a line will be ignored as a comment. Each statement must be terminated with a carriage return. 152 July 1978eBYTE Publications Inc Programs also run slower because the code within loops must be reinterpreted on each pass. The language proposed here is suitable for use with both an interpreter and a compiler. If both are available then the time con- suming process of compiling is avoided until permanent machine level code is required; furthermore, the debugging of a developing program may be done quickly and easily with an interpreter in an interactive mode. The purpose of this article is to intro- duce readers to concept interpreters and to present an example of an interpreter for a high level language. The interpreter instruction set is shown in table 1. In addition to evaluating expres- sions, the interpreter can also perform condi- tional branches, loops, subroutine calls with multiple returns, and 10 instructions. These instructions are sufficient to execute very complex tasks. In fact, the language is devised to encourage a top down approach to writing code so that it is easy to under- stand, debug and modify. More complex groupings such as an IF THEN ELSE con- struction might yield slightly shorter pro- grams if included in the language, but the convenience of using such structures does not seem to warrant the considerable effort required for implementation. Good program- ming techniques are essential to useful code. Some other simplifications are made just to simplify this interpreter. No integer vari- ables, arrays, complex variables or double precision variables are included. All numbers are considered to be floating point numbers with a 4 byte mantissa and a 1 byte ex- ponent. Also the subroutine calls do not pass arguments. Since all the variables are global symbols, local variable names within a sub- routine may not duplicate those in another routine. These restrictions are made so that the code for the interpreter would fit on a small machine and so that the main features of the interpreter will not be obscured. The interpreter program is written in terms of a universal set of instructions, MACL1. These macroinstructions can be translated into machine code instructions for a variety of microprocessors if the expan- sions for each macroinstruction are defined for your microprocessor. The translation of the interpreter into machine code is simpli- fied by the use of a program called a macroprocessor. Otherwise it can be done by hand. High Level Language Statements AREA=0 X=1 Y = (Xt2) -^ (2*X)-i-3 DELTX=0.1 IND=11 Notes initialization DO X=IND*0.1 YPLUS=(Xt2)+(2*X)+3 I AREA=AREA+DELTX* (YPLUS+Y)»0.5 / UNTIL IND>=100 IND=IND+1 ENDDO PRINT 1, "The area is", AREA EXIT END loop condition counter is "IND" start of DO loop ; sum areas using trapezoi- dal integration rule UNTIL evaluates loop re- iteration condition ENDDO tests loop reitera- tion condition output message and AREA through channel 1 go back to monitor Listing 1: This example program, written in the high level language of this interpreter, is a trapezoidal integration routine for the function Y=(X\2)+(2*X) 3. P2=3.14159»0.005 READ 2,A IF ASIN(100*P2) PRINT 1,A, "A IS TOO BIG",! EXIT ENDIF LOW=1 Hl = 100 DO UNTIL HI<=LOW+1 IVIID=INT( (HIH-LOW) 12) IF A>SIN(P2*IVIID) Hi=MID ENDIF IF A>SIN(P2*MID) LOW=MID ENDIF ENDDO IF a=sin(p: l*LOW) HI = LOW ENDIF IF A=SIN(P2 !*HI) LOW=HI ENDIF XL0W=SIN(P2*L0W) XHI=SIN(P2 ♦HI) PRINT1,XLOW,XHI,A EXIT END Listing 2: This example program gives the flavor of a longer program with references to various mathematical routines. In- dentation is done to emphasize program structure. luly 1978©BYTE Publicaliom Inc 153 The following sections discuss the im- plementation of each of the five types of instructions and show the function of the instructions in flowchart form. Two exam- ples shown in listings 1 and 2 illustrate the simplicity of the resulting high level language. Interpreter Organization The basic elements of the interpreter and the utilization of memory are shown in figure 1. Besides the source code and the interpreter routines, there are four tables, two stacks and a workspace for control pointers. The workspace is used for pointers to keep track of positions in the various tables, limiting addresses for the tables, scratch area for temporary results, and ad- dresses for 10 channels. The stacks are used for saving subroutine return addresses and for evaluating equations as described in our discussion of the assign- ment operations section. The four tables are for remembering: 1. where previously defined variables are stored. 2. where subroutines are located in the source code. 3. where subroutines are located in the interpreter code. 4. the location of routines to perform the operations (+, — , *, /, t) and functions defined for this language. The tables are searched by a linear search routine which starts with the portion of the table most likely to contain the item. The ASCII byte string in the name list is com- pared with the desired name. The end of a name or symbol in the table is denoted by a CODE TO BE INTERPRETED CONTROL POINTERS INTERPRETER STATEMENT EVALUATION SEMANTIC LOOKUP i TABLE C R F I A ^ V F 1 T A L u R N L TOKEN f f f t POINTER POINTER SEMANTIC • PLOT ^~— • DONE EXPRESSION EVALUATION SYMBOL VALUE TABLE TOKEN POINTER NYSM • X •- >| i 1 p E S P s R T E T A A T C K R R A A C N K D TOKEN POINTER * » ' SIN • -^ Figure 1 : A map detailing ttie utilization of memory by the Interpreter. Part of the memory consists of four tables that are used to look up values of previously used variables, locations of subroutines in source code, locations of machine language subroutines for the interpreter, and locations of routines for symbols and functions defined by the Interpreter. The two stacks are used in the parsing of equations and when a subroutine is called or returned from. The two largest areas of memory contain the source code and actual machine code for the Interpreter. 154 July l97g©BYTEPublicj|iam Inc one in the most significant bit, called a terminator. When a terminator is reached in the name list, the pointer in the cor- responding address table or value table is incremented to the next item. When a name is found, the pointer in the corresponding list points to the location where the value for the symbols table or the address is located. The desired name or symbol is always added to the list to make sure that the search does not run off the end of the table. After the search, the name pointer can be checked to see if the search went beyond the current length of the list. This technique is faster than putting an end check into the search routine. The subroutines in the high level source code are not the same as the routines used by the interpreter for performing operations and functions. The first set of subroutines contain source code and the second set contain machine code for operations exe- cuted by the interpreter. Operation .JSR .JSR .POP .MOV .JSR Operand Igvarad level wdeval (wptr), wdeval Ifinstm Description Get variable address. Use current line pointer to fetch variable name. See if name is in name table. If it is, transfer its address to (wptr). If it is not, add name to table. Transfer symbol address from symbol value pointer to workspace at (wptr). Update the line pointer up to the equal sign. Subroutine EVAL evaluates the right side of the expression and returns the value on the stack. Put result from EVAL call into workspace. Transfer the result from EVAL call to the location specified by the contents of (wptr). Scan the rest of the line of code skipping over the comment field up to the carriage return and update the current line pointer. Table 2: An outline of the EQN routine. The routine first gets the variable address, then evaluates the right side of the expression and puts the value into the workspace. It then skips over the comment field to the carriage return, updates the line pointer, and decodes the next line of code. This outline flows from top to bottom, with the "operations" and "operands" intended to be used with a macroassembler. Interpreter Operation Initialize: The initialize portion of the interpreter has two functions. It loads the source code from a peripheral and it ini- tializes the workspace. As it loads, it also scans the source code looking for subroutine statements. The name of each subroutine is put into the subroutine name table, and the corresponding position in the code is put into the subroutine address lookup table shown in figure 1. The initialize routine is entered from the system monitor, and the initialize routine returns control to the system monitor. Scan: The scan portion of the interpreter receives control from the monitor and scans the code starting from the current contents of the line pointer. Depending upon which of the 12 instructions of table 1 is encoun- tered, this routine jumps to one of the routines as shown in figure 1 in order to execute one line of code. If an end of file (EOF) character or an error is encountered, the scan routine transfers back to the moni- tor for text editing, reloading or further execution. A trace option is included in the scan routine which prints the name and value of all assignment statements as they are exe- cuted. This option is included for debugging and tutorial purposes. Assignments: If the scan routine detects an assignment statement then the interpreter jumps to the EQN routine of figure 2. The EQN routine operation is outlined in table 2 as a list of operations and operands. The EQN routine uses the routine EVAL LI mode: In this mode an operand, unary operator, left parenthesis, or function is expected. If this token type is received Then perform operation operand: stack the operand. If the operator stacked is not a "(", perform the indicated binary operation. Proceed to mode L2. operator: must be unary. Stack operator and stay in mode LI . Push a onto the stack if operator is a minus sign. function: push variable near operand stack. Push $ onto opera- tor stack to indicate a function. Stay in mode LI . right parenthesis: error. left parenthesis: push it onto operator stack. Stay in mode LI . L2 mode: In this mode an operator, right parenthesis, or carriage return is expected. If this token type is received Then perform this operation operator: push operator onto stack. Go go mode LI . operand: error. left parenthesis: error. right parenthesis: pull operator from stack. If it is a "(" unstack it and return to mode L2. If it is a $ perform the function, then return to unstack operation. carriage return: check operator state. Operand stack should have exactly one value. Convert value to floating point. Return to EQN routine. Table 3: The Bauer-Samelson algorithm to determine the order of operation of an expression. The algorithm starts in the LI mode looking for an operand. The execution of the expression starts in the Innermost parenthesis and works from left to right without any consideration for precedence. July 1978 © BYTE Publicitions Inc 1 55 ( EVAL j PUSH - ONTO OPERATOR STACK -® GET NEXT CHARACTER PUSH'( ONTO OPERATOR STACK PUSH '0 ONTO OPERAND STACK PUSH - ONTO OPERATOR STACK OUTPUT ERROR I ( RETURN j CONVERT NUMBER TO BINARY FLOATING POINT GET NEXT CHARACTER PUSH OPERATOR ONTO OPERATOR STACK -hS) PULL NEXT CHARACTER OFF OPERATOR STACK PULL NEXT CHARACTER FROM OPERAND STACK OUTPUT ERROR 5 OUTPUT ERROR 3 ( RETURN ) Explanation of error messages used in this flowchart Error 1 : An operand, "(", or unary operator ex- pected at this point. Error 2: Variable name exceeds six characters. Error 3: An operator, ")", or terminator expected at this point. Error 4: A left parenthesis not found to balance this right parenthesis. Error 5: A carriage return was encountered pre- maturely. Check for missing right parenthesis. OUTPUT ERROR 2 ( RETURN ) CONVERT VARIABLE TO NUMBER ON OPERAND STACK Figure 2: Flowchart of the modified Bauer- Samelson algorithm. The table of error messages summarizes all the errors that may be encountered while an expression is being evaluated. For an algorithmic explanation of the flowchart see table 3. PULL FUNCTION NAME OFF OPERAND STACK DO FUNCTION OUTPUT ERROR 4 ( RETURN ) ( RETURN ) 156 )ulv 1978 ©BYTE Publlcitiom Inc Equation: X = +4.t VAR (CR) Present Character New Operand New Operator Mode Obtained Stack Stack LI +4. 4 = L2 t 4 =,t LI VAR 4,VAR =,t LI (unstack) 4tVAR = L2 CR 4tVAR Equation: X = (+4* -VAR +COS(SIN(- -Y))) (CR) Present Character New Operand New Operator Mode Obtained Stack Stack LI ( =,( LI +4 +4 =,( L2 * 44 = ,(,* LI -VAR 4,0,VAR = ,(,*,- LI (unstack) (4*-VAR) -,( L2 + ( ) =,(,+ LI COS( ( ),COS =,(,+,$ LI SIN( ( ),COS,SIN = ,(,+,$,$ LI -Y ( ),COS,SIN,0,Y = ,(,+,$,$,- LI (unstack) ( ),COS,SIN,(-Y) = ,(,+,$,$ L2 ) ( ),COS,SIN(-Y) =,(,+,$ LI (unstack) (no change) L2 ) ( ),COS,(SlN(-Y) = ,(,+ LI (unstack) ( ) =,( L2 ) ( ) = LI (unstack) no change L2 CR exit Listing 3: Two examples of parsing done by ttie EVAL routine. The first equation is performed sequentially from left to right since there are no parentheses to change the order of execution. The second expression contains parentheses to modify the order of execution. The first opera- tion performed is the sine of — Y. The cosine of that value is then determined. The value of VA R is then subtracted from that value and added to +4. The symbol t /5 used to designate exponentiation. to evaluate the right side of the equation, then the value returned on the operand stack is transferred to the location assigned the variable. The FINSTM routine skips over any comment field up to the carriage return. EVAL: The EVAL routine uses a slightly modified Bauer-Samelson algorithm to deter- mine the order of execution of an expres- sion. [For a thorough discussion of this method see February 1976 BYTE, page 26. J The execution starts in the innermost parentheses and works from left to right without any consideration for precedence. Since many different types of precedence have been used in other languages, confusion is likely. This procedure minimizes the size of the stack and conforms with the conven- tions of APL and most assemblers. Prece- dence is established by parentheses which make the ordering unambiguous. The algorithm is shown in table 3 as an action table with two modes LI and L2. The algorithm starts in the LI mode, expecting an operand, which is a variable or a name. If an operand is found, the algorithm goes to the L2 mode, expecting an operator. After an operand is found, any operators at the top of the operation stack are executed. A flowchart of the algorithm is shown in figure 2. Two examples of parsing by EVAL are shown in listing 3. The t symbol is used for exponentiation. In mode LI, the -•- and — are considered unary operators, but if they are encountered in mode L2 they are considered binary operators. This distinction is the rationale for operating in the two modes. The errors described in the table of figure 2 cause the interpreter to terminate execution, print the line of code up to the error, and print an error message indicating the difficulty. IF: The routine shown in figure 3 first compares the variable with the expression and then the interpreter executes the code up to the corresponding ENDIF statement, but only if the variable meets the conditions specified by the IF statement. This routine uses the EVAL and SEARCH routines. A flowchart of the SEARCH routine is ( '' ) GET VARIABLE AND ITS VALUE SET INEQUALITY FLAG CALL EVAL EVALUATE EXPRESSION /equality\y ssatisfied >■ NO ES CALL SEARCH LOOK FOR END, ENDIF, OR IF 1 CALL FINSTM SKIP THE COMMENT FIELD /^ GO TO A ^^ SCAN J Figure 3: The IF routine evaluates the expression and then checks to see if the inequality has been satisfied. If the inequality is not satisfied it will per- form the operations between the IF statement and the line containing the ENDIF statement If the inequality is satisfied then the interpreter skips over the instructions and goes to the line of code directly after the ENDIF state- ment. luPy 1978IDBYTE Publications Inc 157 shown in figure 4. The SEARCH routine scans the line of code trying to find an ENDIF statement. If another IF statement is encountered the subroutine calls itself to try to first find another ENDIF before it goes back to searching for the first ENDIF. If one ENDIF statement is not found for each IF before an END or ENDDO statement, an error is announced. An IF and its corresponding ENDIF may not straddle an ENDDO. If this were al- lowed, the data stored on the stack by the DO loop might not be unstacked as the DO loop is exited. Search: Each line of code is inspected until an END, ENDIF or IF is encountered. An IF causes the search to initiate another search for an ENDIF, an END causes an error, and an ENDIF causes a return. Figure 4: The SEA RCH routine inspects eacli line of code until an END, ENDIF or IF command is encountered. An I F statement causes the search to initiate another search for an ENDIF. Note that this means that the routine will be calling itself recursively, so care must be taken in allocating and pre- serving local data within SEARCH during recursion. An END statement causes an error and an ENDIF statement causes a return from the SEARCH routine. ( SEARCH ) I IS I EXPRESSION END, ENDIF, GET NEXT EXPRESSION <-^ TE ST^\. MO ENDDO OR IF ! '® EXPRESSION I TEST CALL SEARCH RECURSIVE SEARCH [IS I [EXPRESSION j_ (END OR ENDDO 1. J TEST \YES OUTPUT -^ ? ^ y ERROR 1 NO ( RETURN j Figure 5: The DO routine will perform the operations between the line of code containing the DO statement and the line of code containing the ENDDO statement until the inequality is satisfied. When the inequality is satisfied the interpreter will exit the DO loop and perform the first line of code that follows the ENDDO statement. *- ( - ) PUSH LINE POINTER ONTO STACK CALL FINSTM JUMP OVER COMMENT FIELD CALL SCAN EXECUTE INSTRUCTION PULL OLD LINE POINTER FROM STACK STORE LINE POINTER IN LINE POINTER REGISTER CALL FINSTM JUMP OVER COMMENT FIELD CALL SCAN EXECUTE INSTRUCTION GET VARIABLE NAME VALUE 1 UNTIL ^INSTRUCTION_| 1 SET INEQUALITY FLAG CALL EVAL EVALUATE EQUATION DETERMINE VALUE OF INEQUALITY NO ^Tn-^^ /equalit'n.y e s PULL LINE POINTER OFF STACK riNCREMENT "] ' LINE POINTER ' 1 TO FIRST 1 SEARCH FOR ENDDO 1 LINE AFTER | |_ENDDO J VES 1" \^/ LINE POINTER. 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START OF RETURN ROUTINE CED f END j GET SUBROUTINE NAME FIND SUBROUTINE LOCATION IN LOOKUP TABLE GET VARIABLE VALUE /end ^ V ERROR y JUMP OVER COMMENT FIELD GET VARIABLE VALUE PUSH CURRENT LINE NUMBER ONTO STACK LINE POINTER:- SUBROUTINE LINE NUMBER RESET LINE POINTER OUTPUT ERROR MESSAGE EXECUTE INSTRUCTIONS CLEAR SYMBOL TABLE AND STACKS JUMP OVER COMMENT FIELD SKIP OVER COMMENT FIELD (GO TO \ MONITOR^ PULL OLD LINE POINTER OFF STACK f GO TO ^ V MONITORy JUMP OVER COMMENT FIELD EXECUTE INSTRUCTION Figure 7: The END statement should be the very last statement at the end of a program or subroutine. If during normal operation an END statement is encountered, there has been an error in execution. This END ERROR routine is used before the inter- preter exits to the monitor program. d PULL LOOP ADDRESS OFF STACK -*r SCAN NEXT LINE OF CODE OUTPUT ERROR MESSAGE TURN J Figure 6: Flowchart for the CALL and RETURN routines. The interpreter allows multiple return statements and allows the subroutine to have a return from within a DO loop. Subroutines may be nested with the only limit being the amount of memory space that is available for use by the stack. Figure 8: The EXIT routine transfers control back to the monitor program. The line pointer is reset to the beginning of the program, the stacks are reset to their original values, and the symbol table is cleared. DO: The flowchart of the DO routine is shown in figure 5. The DO loop routine stores the line pointer on the stack. The line pointer will be used later by the ENDDO macroinstruction to determine where to return in the source code. The use of a stack allows nested DO loops. The lack of state- ment labels excludes the possibility of errors caused by not nesting DO loops within each other (which is possible in a language like FORTRAN). The UNTIL instruction provides the means of exit from a DO loop. When the variable satisfies the inequality, the program moves to the code past the next ENDDO statement. For a DO loop of fixed length the variable must be initialized prior to the DO statement and incremented within the loop. Subroutine Call: The CALL routine shown in figure 6 determines the location of the subroutine code in the code list by looking up the location in a table. The table of locations is built for later use during the initialization process before any code is executed. The location of the current posi- tion in the code is saved in the stack. Usually the operand stack is used. The RETURN routine recovers from the subroutine by loading the old line address from the stack into the line pointer. A RETURN from within a DO loop presents a special problem which is resolved by search- ing for any lone ENDDO statements and pulling the loop address off of the stack. END and EXIT: The END routine is shown in figure 7. The END routine denotes the end of the program or subroutine. Its main purpose is to prevent the program execution from proceeding into another routine, causing an error. The EXIT routine shown in figure 8 is responsible for transferring control back to the monitor and mopping up chores such as resetting the line pointer to the beginning, resetting stacks, and clearing the symbol table. It normally would not clear the subroutine table as the code may be rerun later. Conclusion The interpreter is especially adapted to interactive programming. The language 160 |ulv 1978©BYTt Publkalions liic Circle 190 on inquiry card. presented here is tailored to structured programming techniques which can yield clear, precise code. Our implementation of the interpreter is written in a macrolanguage which may be adapted to any microproces- sor by defining each macroinstruction in the assembly language of the microprocessor. A compiler for the same macrolanguage was also written so that a resident machine language version may be made when it is required. The main features of this interpreter are: the structured language, the methods for evaluating expressions, and the methods for handling lO. Much of the detail in handling data is taken over by the interpreter so that only the fundamental considerations must be considered in writing a program." BIBLIOGRAPHY 1. Bloom, A IVI, "The ELSE must go to," Data- mation, pages 123 to 128, IVlay 1975. 2. Maurer, W D, "Processing Algebraic Expres- sions," BYTE, pages 26 to 30, February 1976. 3. Kerninghan and Plauger, The Elements of Programming Style, McGraw Hill, New York, 1974. 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OEM and quantity discounli available ^ #■ ,#^ .\<^* ^^' .^^^ f» ^«:.^^^to6^,y .c/*:.^^'" ^V^-^"' ^>'- Circle 84 on inquiry card. July 1978 © BYTE Publications Inc 161 How To Get Larry Weinstein Objective Design Inc POB 20325 Tallahassee FL 32304 Your Tarbell Going General Theory The function of the Tarbell cassette interface (referred to as the "Tarbell") is to enable a computer system to save the contents of memory on audio tape. The pur- pose of this article is to explain how the Tarbell interface works and to suggest some improvements to its design for readers who have had difficulties with the unit. The Tarbell is intended for use with inexpensive cassette recorders: the inputs and outputs are matched for the typical Aux In, Ext Spkr and Earphone connec- tions. The computer interface to the Tarbell is on a byte level, with the bytes and com- mands passed by 10 instructions on the Altair (S-100) bus. ANALOG SECTION CASSETTE Figure 7 : Block diagram oftfie Tarbeli cassette interface board. The Tarbell converts digital information to an audio form that can be written on magnetic tape. In turn, it recovers the digital data from the audio signal. These are the primary functions; the rest have to do with the "housekeeping" involved with the Altair (S-100) interface. Figure 1 shows a simplified block draw- ing of the Tarbell. A cassette recorder has definite fre- quency limitations. The higher the fre- quency, the less accurate the signal repro- duction will be. On the other hand, speed of operation is critical for the success of a storage medium. The Tarbell makes its compromise at approximately 1500 bps. This is determined by the interface clock. The rate of data flow to the cassette must be known if the data is to be re- covered. At first it might seem that we could use the same clock to move raw data to and from the tape. The problem is that a cumulative error will quickly build up when a long stream of data is read. There are two solutions to this. First, write the data only in small groups (say ten bits) with definite start and stop points in each group. This is called asynchronous recording. Second, write long uninterrupted data streams and include some clock information with the data. This is called synchronous recording. The Tarbell generates synchronous data streams. Some clock information is added to the data by a technique known as phase encoding. To phase encode, one simply performs an exclusive OR operation with the clock and data (see figure 2). The Tarbell block diagram now takes on the form of figure 3. 162 )ulv 1978 e BYTE Publications Inc Note that phase encoding does not mean that the decoding circuitry is free from the tasl< of generating a matching clocl<. This will still be a critical part of the operation. We have simply eliminated the possibility o^ cumulative timing errors. Assembly The Tarbell cassette interface board is plated through but does not use a solder mask or silk screen printing. A 30 page manual is included with all needed parts. The kit does not include sockets for inte- grated circuits. Assembly is not difficult. The original design lacked several pull up resistors and small capacitors, which led to noise prob- lems. Subsequent revisions have incor- porated these parts without any major board changes. Consequently, some of these parts are in unlikely places. A careful ex- amination of the assembly drawing is re- quired. If you have access to a copying machine, I suggest that you copy the parts list, assembly drawing, and two schematic pages to facilitate construction. Repeatedly flipping back and forth in the manual be- comes tiring and one does not feel so bad about checking off items in pencil on a working copy as construction progresses. There is a 50 k potentiometer on the board that is inappropriate. It is of the thumbwheel variety, and is too big: you cannot insert a board in the Altair bus slot directly in front of a Tarbell. There are also electronic problems with this part, which we will get to presently. Operation (Digital Sections) For output, bytes are loaded into a shift register. A timer clocks data out of the register into an exclusive OR gate. The same timing signal goes into the other input of the exclusive OR. The result is that a phase encoded signal is written onto the tape. A status bit informs the computer program that the last bit is being transmitted and the next byte can be loaded. For input, the decoded clock signal feeds the data into a shift register. For startup, the register is examined for a sync byte. When this pattern is detected, a modulo 8 counter CLOCK 1 DATA PHASE ENCODED RESULT Figure 2: Phase encoding. Tine Tarbell interface uses this technique, which involves performing an exclusive OR operation with the clock and the data. is enabled. This counter flags the computer program after eight new bits (byte) are loaded into the shift register. The sync byte pattern (hexadecimal E6, or binary 11100110) is hardwired into the interface. A cassette with a sync stream written on it is supplied. An LED on the Tarbell is supposed to light up when the aforemen- tioned sync code is detected. The setup operation consists of adjusting the cassette volume control and the 50 k pot until the LED remains on with a steady light. Here is where the difficulties begin. CLOCK SHIFT OUT ANALOG SECTION ENCODE -o SHIFT IN BUS INTERFACE ?^ ^Z DATA -<:] CASSETTE BUS INTERFACE Figure 3: A more de- tailed block diagram of the Tarbell cassette inter- face showing the phase encoding and decoding procedures. luly 1978 © BYTE Publications Inc 163 74L86 CLOCK DATA M \ IKA IIKii @ OUTPUT TO CASSETTE AUX INPUT r.luF /77 ft? rh J~U Figure 4: Output section of the Tarbell interface. Tlie circuit contains a simple low pass filter with a cutoff frequency of 1.5 kHz. The filter eliminates the high order harmonics to produce an approximate sine wave, which is then recorded onto the cassette. The presence of a steady sync light is a good indication, but it does not guarantee the ability to read long files. A single missed clock pulse in the sync stream will almost certainly go unnoticed. However, a single missed clock pulse during the reading of a data file will cause the subsequent bits to be read incorrectly. Also, the sync stream does not have a 010 pattern in it, which turns out to be a prime candidate for drop- ping a clock pulse. With some cassette players and Tarbell combinations, the control settings are non- critical. The lack of a good setup indicator isn't important in these cases. On other cassette players the settings are critical; extremely so. Here, the absence of a source of feedback for the setup is sorely missed. Our early experiences with the Tarbell were problematical. As we began to look RECOVERED DATA CASSETTE C6 INPUT .02 *0N SOME MODELS, THIS MAY BE A 2.4K RESISTOR Figure 5: Input circuitry of the Tarbell cassette interface (internal details of the 8T20 circuit have been included for clarity). The incoming sine wave signal is transformed into a digital signal by the comparator circuit inside the 8T20 (see figure 6). 1 64 July 1978 e BYTE Publications Inc more closely at the device, we ran into more questions than answers. For example: A. Why do different Tarbell units have different levels of reliability? B. Why do seemingly equivalent tape decks yield different performances? C. Why will a very cheap cassette machine outperform one costing many times more money? D. Why do some very good cassette tape brands fail to do well with the Tarbell, while others, even less expensive ones, do a fine job? E. Why must (as the manual recommends) the tone control be placed at maxi- mum treble? With the highest fre- quency we wish to have on the tape being 1500 Hz, the results should be better with the tone control on a high bass setting. F. How were the resistance and capaci- tance values in the analog sections chosen? With these questions in mind, we took a closer look at the Tarbell and came up with the following information. The critical part of any tape storage sys- tem is the analog input section. The entire digital data and clock recovery circuit of the Tarbell is constructed from a single IC (the 8T20) and a few passive components. Figure 4 gives the output section. This is really a simple low pass filter with a cutoff frequency of 1.5 kHz. The filter eliminates the high order harmonics of the output digi- tal signal. The result is a sine wave, or nearly so. The input section of the Tarbell is shown in figure 5. We have drawn out the internal 8T20 circuitry. Data on the 8T20 in the early Tarbell manuals was absent. To recover the data, it is first necessary to convert the sine wave recovered from the cassette unit to a digital signal. Assume for the moment that the sine wave is symmetric about V. A comparator with one input grounded (a zero detect circuit) would then produce a digital signal that matches the original one (see figure 6). Once the input signal passes through C6 (a 0.2 juF capacitor in the Tarbell input sec- tion), it loses any DC level. The DC level is then set by the 9 k and 5 k voltage divider resistors inside the 8T20. To convert the signal properly, the positive input of the 8T20 comparator must also be set to this voltage. This is accomplished by the voltage divider formed by Rl and R3. As figure 5 shows, R2 and diode CRT play a part in this circuit by providing hysteresis: When the output of the comparator is high the divider circuit is electrically equivalent to figure 7a. When the output is low, the cir- cuit is roughly equal to that of figure 7b. The effect of this is to eliminate oscillation about the bias point. 1 I I I I ■ > 'I LnLr~L_rL_rL b m Figure 6: Action of ttie comparator inside the 8T20 circuit. T/ie comparator acts as a zero crossover detector to transform the sinusoidal input from the cassette into a stream of digital pulses. (7a) (7b) + 5 +5 : 3K H > 1.9V i lO-i 3K -| > 1.6V ±10% ; I.5K |l.5K I 4.7K rn m ftt Figure 7: Equivalent circuits for the voltage divider input circuit (Rl, R3, R2 and Dl) in figure 5, plus the resulting output waveform. Figure 7a shows the equivalent circuit for the case when the comparator is high, and figure 7b shows the equivalent circuit when the comparator is low. Figure 7c is the output waveform. This hysteresis effect is designed to eliminate oscillation of the comparator if a signal "hovers" about the bias point. July 1978 e BYTE Publications Inc 16S ~L_^ ORIGINAL DATA ~L J \ r ORIGINAL CLOCK M0N0STA8LE TRIGGER ENCODED SIGNAL RECOVERED CLOCK ^ PULSE IS 75% OF CLOCK PERIOD, T^ Figure 8: Recovery of the clock from the encoded signal. The encoded signal Is formed by performing an exclusive OR operation on the data and the clock. To recover the clock, a one shot with a duration of exactly 0. 75 clock cycles fires on every transition of the encoded signal. RESULT OF ALL Is OR ALL Os \ ~L_r~L_r I TO OR TO I TRANSITION IN ORIGINAL DATA J~~LJ L_r^ _l U U \ \ U U U LT \ CLOCK RECOVERY OUT OF SYNC NOW IN SYNC Figure 9: Automatic synchronization of the one shot (monostable) pulses and the signal transitions (see figure 8). As soon as a I to or a to I transition takes place In the data, the recovery one shot is forced to "fall in line." Figure JO: Complete timing diagram for signal processing In the Tarbell interface. HEXADECIMAL 22 E6H-SYNC BYTE OOIOOOIOI I 1001 10 — — A A r f\ / — A i r\ r\ — \ ^ — ^, \ f\ - \ ^. / f\^ (*'i. \j \J 1 — 1 — H y \J \J V y V y J^ J \J V J J \J - — ' — — ORIGINAL DATA TO TARBELL ORIGINAL CLOCK PHASE ENCODED CLOCK AND DATA ANALOG SIGNAL TO AND FROM CASSETTE ASSUMES "PERFECT" REPRODUCTION DIGITAL SIGNAL RECOVERED FROM ANALOG RECOVERED CLOCK - GENERATED BY MONOSTABLE RECOVERED DATA-WHICH IS INVERTED INVERT TO ORIGINAL DATA DATA BECOMES VALID AFTER FIRST TO I TRANSITION ®THIS LOW FREQUENCY WAVE WILL OFTEN BE LOW IN VOLUME AND DISTORTED, RESULTING IN A DROPPED CLOCK AND LOSS OF SYNCHRON IZ ATION 166 lulv 197S ' BYTE Publicalion* In SYMMETRIC SINE WAVE INPUT TO COMPARATOR DC "TRIGGER" LEVELS, WITH HYSTERESIS, INPUT TO COMPARATOR SHOWN INCORRECTLY SET FOR SINE WAVE, TRUE DC LEVEL SINE WAVE DC LEVEL SYMMETRIC RESULT OF MATCHED DC LEVELS INPUTS TO COMPARATOR ASYMMETRIC RESULT OF MISMATCHED DC LEVELS, WITH HYSTERESIS Figure 1 1 : Effect of mis- matched comparator input DC levels. CI 6 reduces any very high frequency noise coming in on the line. C6, besides serving as a coupling capacitor, also forms a filter with the 8T20's internal 5 k resistor. The effect is to reduce the low frequency part of the signal. It is also an effective 60 Hz and "wow" filter. Once the original digital signal has been recovered, we can proceed to reconstruct the clock signal, and from that, the data. On every transition of the digital signal, a monostable is triggered (see figure 8). The timing of the pulse is critical. It should be 75% of the period of the output clock. (You may have to study figure 8 carefully in order to understand how this recovery process works.) Next, examine figure 9. It shows the automatic synchronization process of the monostable pulses and the signal transi- tions. As soon as a 1 to or a to 1 transi- tion occurs in the original data, the recovery monostable is forced to "fall in line." For this reason, some kind of start byte is re- quired ahead of the normal sync byte when using the Tarbell. The entire process is shown in figure 10. The major problem with this circuit is its sensitivity to waveshape and amplitude. The primary cause of this rests in the way the DC levels are set for the comparator. The 8T20 specifications give the reference voltage available at pin 7 as a nominal 1 .4 V, with minimum and maximum values of 0.8 and 2.0 V, respectively. Since the "+" input to the comparator is set by an independent voltage divider, an error of half a volt is possible. Figure 11 shows the effect of mis- matched DC levels. As you can see, the more closely these DC levels are matched, the better off you will be. The timing distortion produced by this effect can be compensated for by the proper setting of the monostable, up to a point. However, the more the timing is off, the more critical the pot setting will be. The monostable pulse time is determined by C7 and R8, a 50 k pot. The timing is defined by the relation: Tw=(C)(R)(ln2) For the given Tarbell output frequency we require a pulse of (.67 ms) (0.75) = 0.5 ms. Therefore, the R/C relation is R= .72/C,with R in kilohms and C in microfarads. For a .033 mF capacitor, R should be 21.85 kf2; for .039 ixV, it should be 18.5 kfi. A large fixed resistor in series with a 5 ki2 trimpot would do a far better job here. The next factor affecting this timing is in the cassette transport itself. Flutter, a high frequency variation in tape speed, will cause the sine waves to vary in period. Figure 1 2a shows the effect of flutter. The shape, symmetry, and amplitude of the wave will also affect this timing. Inexpensive tape machines generally use tone controls that work in tandem with the |uly 1978 ' BVT[ Publications Inc 167 02a) (12b) (12c) (12d) (12e) J" 1 Figure 12: Factors causing timing distortion in Tarbell processed signals. Figure 12a shows tfie effects of flutter, orhigfi frequency variations in tape speed. Figures 12a, 12b and 12c illustrate the effects of shape, symmetry and amplitude, respectively, of the signal waveform on the digitized output. Figure 1 2 shows how changes in signal amplitude caused by the low pass filter in the input circuit (see C6 in figure 5) can affect pulse width. HYSTERESIS PRESENT Figure 13: Effect of the presence of hys- teresis: a sudden unexplained dip in DC level. Figure 14: High amplitude signal with steep sides resulting from a high treble setting on the cassette recorder. volume control. Each will affect the other. The effects of these factors are shown in figures 12b, c, and d. The high pass filter created by C6 in the Tarbell causes the amplitude of the input signal to vary according to frequency. The result is shown in figure 1 2e. This frequency change area is already a sensitive point; the mismatch of amplitudes compounds matters. We noticed one additional effect in a Tarbell unit, for which we have no explana- tion as yet. The input appears as in figure 1 3 whenever the hysteresis circuit is connected. With the hysteresis removed the wave oscillates about a fixed center line. Bearing all of this in mind, we're ready to try for some answers. Tarbell units with the more closely matched DC level inputs to their comparators will be less sensitive to all of the factors that can cause problems. A very slight difference, even 200 mV, is significant. Also, the higher the input signal ampli- 168 July 1978 e BYTE Publicitiominc tude, the less likely any of the waveshape factors are to have any effect. Why do some Tarbell units work in the higher end of their volume range but not at the very top? This is due to the connection between the volume and tone controls. When the volume is at maximum, especially where the treble control is also at an ex- treme, the waveshape is severely distorted. When the tone control is at maximum, the amplitude of the signal is increased and the waveshape is affected. The general out- come is a wave with steep sides about the "zero level" (see figure 14). The amplitude increase and steep sides tend to produce a more accurate digital signal. A high bass setting reduces the amplitude of the wave with a greater effect on the higher frequency section. With some cassette players, a full bass setting can produce up to a 3 dB per octave loss beginning in the area of a few hundred Hz. It is the overall signal loss that makes a high bass tone setting unacceptable. Figure 15: Suggested changes to the Tarbell front end circuitry. CASSETTE INPUT (OR USE LOGIC PROBE HERE) o REMOVING RESISTOR MAY IMPROVE PERFORMANCE 5 OR 10 K POT y^ 1 I.5K -REMOVE HYSTERESIS SUBSTITUTE POT TO ADJUST INPUT DC LEVEL NORTHWEST MICROCOMPUTER _SYSTEMS_ NMS 85/P = 8085 + PASCAL Fully integrated UC5D PA5CAL CP/M* 3 Mhz 8085 CPU Double density DAAA disk controller 1 .2 Megobytes of on-line storage 54 K of static RAM 24x80, 12" CRTdisploy P,5232 Serial communication port R5232 Serial printer port TTL compatible paralleled ports NOW SHIPPING $7495 complete *CP/M is Q trademark of Digital Research V. Options include: Hardware floating point AMD 9511 , 32 bit, Qhthmetic, trig. functions divide approximately 120 us Graphics, bit-mopped dot 5 Mhz 8085 CPU FORTRAN, DASIC-C, COBOL Applications software AAAIN OFFICE: 121 EAST ELEVENTH AVE. • EUGENE, OREGON 97401 • (503) 485-0626 Circle 287 on inquiry card. July 1978 ©BYTE Publications Inc 169 Listing 1: The author's test tape for the Tarbell cassette interface. The presence of even mild dropouts on the cassette tape will also cause problems. A 1 ms loss of a few decibels of output level wouldn't be noticed in audio work, but could mean the fatal dropping of a clock pulse when recording digital information. Thus, some cassette tapes that pass audio tests with flying colors may be unacceptable for digital applications. (We have had ex- cellent results with Scotch low noise, high density C-60 tape.) As for the differences in cassette decks, there are many possible factors: probably the main one is the amplitude of the output signal. However, the amplitude effect is closely tied to the waveshape, and a pure sinewave does not always yield the best results. In other words, high cost and ac- curate reproduction do not guarantee good performance. eeea CASC tl'' 6E.1 00^0 CASE E21I 6FH 0200 * BCeB - * '..'T'lTl OUT STHtAM OF ALTEP.NATING ez0P » SYNC (E6H) EYTE -S ANt; TEST C22H) BYTES e e?0 * 01300 06 22 LOOPV MVI b.. 2 2K 0002 CD 0D 00 CALL fi'b 000? 06 E6 MVI E/L''16H 0007 CD 0D 00 CALL SUB 0e0A C3 00 00 JMP LOOPU 000D « 000D • SI'B VI LL VPITE TO THE TAPbELL ■ • 000D + 000D DB 6E SUB IN CASC » TEST STATUS 0eF E6 20 AN I 2 0H 001 1 C2 0D 00 jn: SUB 001-1 78 MOV A..b 001 E D3 6E OUT CASC * OUTPUT BYTE 0017 C9 RET 0013 * 0018 ♦ TEST PROG PAM = THE TAPE GENEFATED eeis * ABOVE IS PLAY EI ) ".EULE PUNNING THIS 0018 * PPOGP.AM. A SIGNAL CBELLj BEEP. OR 0018 * LIGHT) IMPLI ES AN ERROR DETECTED. e 018 * 0018 3E 10 TEST MVI A- 10H 001A D3 6E OUT CASC « RESET TARBELL 01C « 0010 06 22 LOOPR MVI B/22H 001E CD 32 00 CALL SUBP. « READ BYTE 0021 C2 EC 00 JNZ MISS * NZ--NOT 22H. ERR 024 06 E6 MVI b>0E6H * 22H. CHECK SYNC 026 CD 32 00 CALL SUBR 0029 CA IC 00 JZ LOOPR * SYNC OK- LOOP 02C * 002C * EEH MISSED- GIVE ERPOB SIGNAL. 002C CD 3C 00 HISS CALL SIG * USER SUPPLIED e02F « 002F C3 18 00 JMP TEST * RESET- RESTART 0032 * 0032 DB 6E SUBP. IN CASC 0034 E6 10 AMI IZH « BYTE READY? 036 C2 32 00 JNZ SUBR 0039 DB 6E IN CASD * INPUT BYTE 003B B8 CMP B « COMPARE 003C C9 RET 003D * 03D SIG DS 20D ^ ADD SIGNAL HERE. 0051 * PEADY CASC 006E CASD 006F LOOP. ' 0000 SUB 000D TEST 0018 LOOPP. 001C MISS 002C SUBR 0032 SIG 003D Corrections A few simple changes in the Tarbell input section will significantly improve perform- ance. (Refer to figure 15.) First, remove the hysteresis circuit, either by cutting the trace on the rear of the card that connects R2 to CRT, or by simply removing one of these two com- ponents. If you are a diehard believer in hysteresis, replace R2 with a 47 k or larger resistor. Bear in mind that the 8T20 specs give a ±4 mV input threshold. Next, replace R1 with a 5 k or 10 k pot. This will enable you to set the "-i-" input level to match the signal DC level. Set up the Tarbell with its cassette player. Place a logic probe on pin 1 or 9 of the 8T20 (or add a resistor and LED as in figure 15). With the cassette player off, adjust the R1 replacement pot near the area where the light switches from on to off. Set the tone and volume controls to their halfway points. Use the program in listing 1 to generate a test tape. Note that a special test byte (hexadecimal 22, binary 00100010) alternates with sync. Now play back the tape with the test program running. A signal (light, beep, etc) implies an error. First adjust the 50 k Tarbell pot. You should be able to get a steady sync light with few or no error signals. From there, adjust the volume and tone controls until you can run a long test without a single error signal. As with a well running Tarbell, you should have a large range of acceptable cassette settings. Our experiences with Tarbells with these few changes have been excellent. They are totally reliable. Further, tapes written on other systems, can generally be read without readjusting the various control settings. Conclusions With revision D of the board, the noise prone floating inputs have been tied down (or up). But the input circuit i-j still lacking. The 8T20 internal bias resistors are clearly intended for use with a TTL input, not an analog one. The lack of adjustment on this bias will continue to cause problems, necessi- tating fixes such as the one given. On the plus side, the Tarbell is a con- tinually evolving and improving device. The responsiveness of its manufacturer (Don Tarbell) is unsurpassed in the industry. 1 70 )uly 1978 © BYTE Publications Inc The board is available, has no "exotic" components, and is simple to set up and use. The cassette writing scheme which the Tarbell executes is one of several cassette methodologies now being used in the per- sonal computing field. Several versions of this type of recording method are now available in the hobby market. The 1500 bps speed is acceptable for work with small to medium length data files. For program load- ing, it is excellent. We'll take this opportunity to cast our vote for phase encoding at 800 bits per inch as a cassette standard and recommend it, from whatever manufacturer, for small computer systems." Manufacturer's Reply Thanks for the opportunity to reply to Larry Weinstein 's article. First, to reply to the questions posed: A, B, C, and D are somewhat, related. The main source of reliability problems we have found on the interface is faulty integrated circuits. These are sometimes difficult to isolate, especially when the problem is not occurring all the time. Tape drives vary considerably in their performance charac- teristics. The main requirements for our in- terface are a frequency response to 8000 Hz, and an output amplitude of at least 5 V peak to peak. We haven't found any recorders that have these characteristics that haven't worked with the interface. Some expensive recorders, sadly, don't have the above minimum requirements. As mentioned in question E, the highest frequency the interface works with is ap- parently 1 500 Hz. A certain number of har- monics above this, however, are required to accurately reproduce the phase shifts that this method uses. That's why it's usually better to have the tone set high. To answer question F, the parts values were generally first chosen by a combination of calculation and experience. They were then tuned empirically (ie: diddled on the breadboard) for optimum operation. I don 't think of C6 as a filter capacitor so much as I think of it as a differentiating capacitor. Its main purpose in my mind, in addition to removing the DC component, is to translate the peaks of the Input wave- form into zero crossings. In this way, the circuit becomes less dependent on input amplitude. Although the worst case toler- ances of the components in the input sec tion theoretically could cause a problem, our experience is that they don't. Out of the many units that have been returned for repair, none required adjustment or replace- ment of these components to make them work. On the other hand, it is true that replacement of Rl with a potentiometer could mean the difference between operating or not operating with a marginal recorder. The reason that a pot was not used in the design Is that I felt the fewer pots there were to adjust, the better off the user would be. We don't put a fixed resistor in series with the 50 k pot because we want to allow the user to adapt to much faster or slower speeds, as his requirement dictates. The reason for the hysteresis is to reduce the effects of noise on the input signal. With a sufficient amount of input amplitude, the percentage of distortion introduced by the hysteresis is minimal. IVIany computers have a fairly high level of noise, and so do many recorders. If you have a very clean system, you may not need the hysteresis, and can remove it as he suggests. This will also allow you to work with lower amplitudes, such as are generated by tape decks without amplifiers. In spite of the above comments, I feel that Mr Weinstein 's article is a valuable one, and is accurate, on the whole. His test program, especially, is excellent. I hope, however, that readers will not try the changes suggested in the article unless they actually are having problems. I would also like to take this opportunity to announce that the 90 day, no fault warranty on this product has now been extended to six months, and to encourage customers to send their boards back for a quick repair. Donald E Tarbell Tarbell Electronics 20620 S Leapwood Av, Suite P Carson CA 90746 luly 1978 (S BYTE Publicitions Inc 171 Now, a book for the practicing professional... "This is the best liandbook of data communications system technology that this reviewer has yet oicoiintered." — Arvid G. Larson in ACM Computin g Reviews February 19 78 Digital Press announces the publication of TECHNICAL ASPECTS OF DATA COMMUNI- CATION by John McNamara. Written for the practicing pro- fessional, TECHNICAL ASPECTS OF DATA COMMUNICATION details the nuts-and-bolts prob- lems and solutions in configuring communications systems. It features: • comparison of protocols (DDCMP, BISYNC, SDLC) • exten- sive explanation of interface stand- ards (CCm/V.24, RS232C, RS422, RS423) • six comprehensive appendices (how far/how fast?, modem options, codes, UART, format and speed table for asyn- chronous communication, chan- nel conditioning) • 20 milliampere loop • telephone switching systems • error detection • 382 pages • 125 figures • 70 pages of tables • index • hardcover mma Digital Press Educational Services Digital Equipment Corp. Crosby Drive, Bedford, MA 01730 I would like to order copies of TECHNICAL ASPECTS OF DATA COMMUNICATION at $19.95 per copy, n Check enclosed D Money Order enclosed (Note: Minimum order for Digital Press to process purchase order is $35). Name Address- City _State_ _Zip_ Prices apply in U.S. only. B78 172 (uly I9780BYTE Publications Inc Event Ousus This month we begin a formal Event Queue, a calendar of coming events which we t^now about as of press time. In order to gain optimum coverage of your organization's meetings, computer conferences, seminars, workshops, etc, notice should reach our office at least three months in advance of the date of the event. Entries should be sent to: Event Queue BYTE magazine 70 Main St Peterborough NH 03458 Each month we publish the current contents of the queue for the month of the cover date, and the two following calendar months. Thus a given event may appear as many as three times in this section if it Is sent to us far enough in advance. July 17-19, Data Processing Operations Management, Houston TX. This seminar will offer the senior data processing professional an opportunity to gather the latest management skills. The cur- riculum is designed toward practical, applied data processing management techniques. Contact Philip M Nowlen, Program Chairman, Director, Center for Continuing Education, University of Chicago, 1307 E 60th St, Chicago IL 60637. July 17-21, Coding and Information Theory, UCLA, Los Angeles CA. This course will present the fundamentals of representation, storage and transmission of data. Protection against storage and transmission errors using error detection and error correcting (including ham- ming) codes will be developed. Effi- ciency enhancement through infor- mation compressing codes, predictive run encoding and Markov chains (pro- babilistic finite state machines) will be discussed. Contact Short Course Program Office, 6266 Boelter Hall, UCLA Exten- sion, Los Angeles CA 90024, (213) 825-3344 or 825-1295. July 25-26, Workshop on Use of Com- puters in Teaching Statistics, University of New Hampshire, Durham NH. Work- shop participants will be scheduled for hands-on use of the following packages: Minitab II, IDA, SAS, SPSS and BMDP. Contact Dr Jerry Warren, Director, The Office of Academic Computing, 304 McConnell Hall, University of New Hampshire, Durham NH 03824. July 26, Third Annual Indy Micro- computer Show, Holiday Inn, Indi- anapolis IN. There will be exhibits, demonstrations and technical seminars addressing the engineering, industrial, scientific, business and personal applica- tions of microcomputersystems. Contact Thurman H Gladden, Naval Avionics Center, D-810, 600 E 21st St, Indi- anapolis IN 46218,(317)353-3208. July 31 -August 4, Digital Filters, Uni- versity of Toronto CANADA. This course will provide a practical intro- duction to the subject of digital filters. Topics will include the frequency ap- proach, Fourier series and integrals, non- recursive filter design, theory of recursive filter design, discrete Fourier transforms, fast Fourier transform implementation, estimation of power spectra and non- linear phenomena due to quantizing signals. This course will be of interest to those who use linear combinations of data. The emphasis is on its basic nature and practicability. Contact Nonie Watanabe, Short Courses, 6266 Boelter Hall, UCLA Extension, Los Angeles CA 90024. August 7-9, Third Jerusalem Conference on Information, Jerusalem ISRAEL. The conference will cover a broad range of topics on computing applications, science and technology. Primary empha- sis will be on the role of computers in the transfer of technology between large and small countries. Contact Robert W Rector, Executive Director, AFIPS, 210 Summit Av, Montvale NJ 07645,(201) 391-9810. August 7-9, Laser Beam Information Systems, Minneapolis MN. This sem- inar will cover the growing applica- tion of laser technology in image and data manipulation in the form of scan- ning, transmission, reproduction and control. The principles and practice of laser beam information systems will be covered in preparation for direct appli- cation to such fields as facsimile, com- puter memory and display, target identification, reconnaissance, photo- composition and image manipulation. Contact Philip M Nowlen, Program Chairman, Director, Center for Con- tinuing Education, the University of Chicago, 1307 E 60th St, Chicago IL 60637. August 7-11, Coding and Informa- tion Theory, University of Toronto CANADA. See July 17-21, UCLA, for information. Save 20% on all Dynabyte Save 1 5% on all IMSAI and Cromemco Save at least 1 5% on all TDL and North Star Contact us for savings on Micropolis NORTH STAR HORIZONS ABSOLUTELY BEST PRICES AND BEST DELIVERIES Horizon 1 Kit, List $1599 $ 1349 Assembled and tested, List $1899 . 1599 Horizon-2 (with 2 drives! Kit, List $1999 1699 Assembled and tested. List $2349 . 1939 TDL XITAN ALPHAS — LIMITED TIME SPECIALS — Xitan Alpha 1 , List $993 $ 839.95 Xitan Alpha 1.5, List $1172 964.95 Xitan Alpha 2, List $1601 1309.95 Xitan Alpha 3, List $1541 1278.95 Xitan Alpha 4, List $1970 1599.95 Xitan Alpha 5, List $2041 1703.95 Xitan Alpha 5-Plus, List $2410 2017.95 \ITAN MiniMicroMart ALPHA 1 .95 SPECIAL Similar to TDL Xitan Alpha 2, Kit , $798 TDL Z16K STATIC MEMORY BOARD Assembled and Tested Originally $695 OUR PRICE: $339 We also stock TARBELL, MORROW, SD SALES, XITEX, and others! - SEND FOR FREE CATALOG - MiniMicroMart, Inc. 1618 James Street Syracuse, New York 13203 Phone: (315) 422-4467 Circle 250 on inquiry card. August 21-25, Digital Filters, UCLA. See July 31-August 4, University of Toronto, for information. August 21 -September 2, Courses on Microcomputer Interfacing and Ana- log Signal Conditioning, Virginia Poly- technic Institute and State University, Blacksburg VA 24060. The objective of these programs is to provide an educa- tional experience for scientists, engin- eers, teachers, managers or technicians in the areas of microcomputer data acquisi- tion, instrumentation, and measurement systems ranging from the analog sensor through the analog data channels to the microcomputer. The courses provide a combined lecture/ laboratory experience. Continuing education units are provided for each course. Contact Dr Linda Leffel, Center for Continuing Educa- tion, Virginia Polytechnic Institute and State University, Blacksburg VA 24061, (303) 951-5241. August 24-27, PC '78, Philadelphia Civic Center, Philadelphia PA. The first day of PC 78 (August 24) will be an industry trade show which is open to dealers, the industry and ex- hibitors' guests. For the remaining three days the full Personal Computing Show and Personal Computing College will be running. Over 80 hours of free seminars are planned. Contact John H Dilks III, Rt 1, POB 242 (Warf Rd), Mays Landing NJ 08330. August 29-31, Data Processing Oper- ations Management, New York NY. See July 17-19, Houston TX, for infor- mation. September 6-8, COMPCON Fall '78, Capitol Hilton Hotel, Washington DC. Sponsored by the IEEE Computer Society, this conference will cover computers and communications, inter- faces and interactions. Such topics as microprocessors in communications, multiple computer systems, advances in communications technology and many others will be discussed at this confer- ence. Contact Kenneth H Crandall Jr, COMPCON Fall '78, POB 639, Sil- ver Spring MD 20901. September 11-15, Coding and Informa- tion Theory, Georgia Institute of Tech- nology, Atlanta GA. See July 17-21, UCLA, for information. September 18-22, Digital Filters, Georgia Institute of Technology, Atlanta GA. See July 31-August 4, University of Toronto, for information. September 29-October 1, International Microcomputer Exposition, Dallas Con- vention Center, Dallas TX. This exposi- tion will be directed toward all levels of technology from the professional engin- eer to the beginning computer hobbyist. In addition to the seminars, a panel of experts will be available to answer questions. Contact Beverly Tanner at (214) 271-9311." PROGRA9I >IHl«><<>MI»lTi:i«vS And at an affordable price. The fvlodu-Learn™ home study course from Logical Services, Now you can learn microcomputer programming in ten comprehensible lessons. At home. In your own time. At your own pace. You learn to solve complex problems by breal). However, the dual processor config- uration reduces the window size for two reasons: (1) the delay in processor selection (ie; the data gating signal) incurred by the control logic and, (2) the overlap of the memory request signals from opposing processors that is required to permit full speed operation by the processors. Further, the memory cycle time requirement becomes more stringent, accommodating from more than two clock cycles in a 1 pro- cessor system to less than one clock cycle in this system. 174 |uly 1978 O BYTE Publications Inc SHARED MEMORY ADDRESS BUS MAI5-MA0 NOTE: MAIS IS NOT CONNECTED The clock that drives the processors operates at 2.5 MHz, defining a basic cycle time of 400 ns. With this information it is now possible to calculate the operating char- acteristics required of the shared memory. As stated earlier, the memory access window depends on the control logic switch- ing delay and the request signals overlap. It has been shown (see figure 3) that the smallest window occurs at times of bus request conflicts, and that this window has a length of one clock cycle. The equation, then, for actual window length is: La = *-S"T^-Td where: $ = 400 ns (1 clock cycle) 6 = maximum delay in falling edge of MREQ T = maximum propagation delay of control logic Tj = maximum propagation delay of Figure 4: Block diagram of the shared memory. The memory is arranged in a square array of 64 static programmable memory integrated circuits with 4096 bits per circuit. decoding logic luly 1978 © BYTE Publicilions Inc 1 75 Examining the control logic timing shown in table 2, we observe that the maximum timing delays from either MREQ line going activ e until th e arbiter sets the correspond- ing SELECT line active are as follows: IC In Signal Path Maximum Propagation Delay (ns) 74S04 74S10 74LS126 Total Arbiter Delay: 5 5 +18 28 ns Substituting into the equation for L , we obtain: L = $-5 a Tc-Td = 400-20-28-Tj = 352 -Tj ns The s witching delay of the decoding logic, T^ (SELECT active until the memory receives the signals), further reduces the memory access window. Referring to figures 2b and 4, the signal path Tj is: Tj = 7408 + max [74S1 57 (select), 74S157 (enable)] + 74S1 38 = 19 + max [15, 11] + 12 = 46 ns Finally, L, = 352 -T^ 306 ns This allows plenty of time for a memory access operation; so much time, in fact, that we do not need the faster and more expen- sive bipolar programmable memory. We must also consider the memory cycle timing (L ), reduced by this two processor system to "l> — 6 : L = $-6 = 400-20 = 380 ns It is good design practice to calculate delays in the system using the maximum time figures rather than typical ones, and to adjust the results by including a safety mar- gin. Accordingly, we specify the following requirements for the shared static program- mable memory: • Access time 280 ns or less • Cycle time 350 ns or less Conclusions and Possible Applications The principle advantage of two (or more) parallel processors performing complemen- tary tasks is the cost savings. For example, let us say that we operate a packet switching network in which multiple microprocessors perform the relay functions of each node, such as the TELENET of Telenet Communi- cations Corporation. Our responsibilities include insuring data reliability (eg: using cyclic redundance coding (CRC), checksum, etc), doing format checks, and recognizing the destination of the traffic and routing it to another node in the network. Further, this service must be provided at high speed. Clearly, for one processor to perform these and other nodal functions without some delay, high performance and high cost systems would be required. Conversely, mul- tiple microprocessors could perform all of these tasks in parallel at a significant reduc- tion in cost. For the experimenter, a multiprocessor system doesn't appear to offer much beyond an interesting diversion in design engineering. As mentioned earlier, the benefit from this type of design is increased throughput (by virtue of the reduced per unit cost). This is an idea that has little significance for persons with a dedicated system. One possible application does come to mind, however. Many 8080 system owners are upgrading to the Z-80 for the expanded instruction set, but for some, direct replace- ment of a processor board is not possible. Why not consider adding a Z-80 with your current system acting as a front end? Admittedly, it seems like a bit of overkill, but it is an inexpensive way ($8 for the interface circuitry of this design) to upgrade. Of course, after installing another processor, the owner must write an operating system to accommodate the addition; but that's part of the continuing challenge to be found in the world of microprocessors." REFERENCES Z80-CPU Technical Manual, Zilog, 1 70 State St, Los Altos CA 94022, 1976. 1 76 )uly 1978 © BYTE Publications Inc 85/P =8085 + PASCAL The new 85/P programmer's work- bench from Northwest Microcomputer Systems Inc combines the throughput of the 3 MHz Intel 8085A and the power of PASCAL. Designed for the serious applications programmer, the system features include; 8085A processor, a PASCAL compiler and interpreter, CP/M supporting BASIC, COBOL and FORTRAN, direct memory access, two Shugart floppy disk drives with 1 M bytes of online storage, 54 K bytes of 450 ns user available static programmable memory, a Hall effect keyboard with 103 keys, two serial ports (RS232C), two parallel ports (16 bits), and a 24 by 80 character 12 inch (30.5 cm) video display, all enclosed in a single cabinet. The system provides the full PASCAL environment including a 725 line per minute compiler and interpreter, random and sequential files, a screen oriented editor, interactive source linked debug- ger, plus full documentation and a 90 day warranty. Pricing for the complete system is $7495. A variety of other packages are available, including a screen oriented accounting package and a word processor, from Northwest Microcom- puter Systems Inc, 121 E 11th, Eugene OR 97401." Circle 602 on inquiry card. New 2708 Erasable Read Only Memory Programmer New 6800 Industrial BASIC ?>„ ■■;,.., ill, i?-; 11 .11 tlJK OIHPMT ni-- ■ )if ^w /f ' ^?■ ' '' ^ ^w . , Wintek 4 K BASIC is a 6800 BASIC interpreter optimized for industrial applications. Features of the package include control of interrupts, direct memory read and write, assembly lan- guage subroutine capability and flexible lO. The package is oriented toward proc- ess control and monitoring. 4 K BASIC retains all the advantages of an inter- active high level language, including rapid coding and debugging, easy main- tenance, and advanced control structures. The interpreter may reside in pro- grammable memory or in programmable read only memory for instant power on operation. If the BASIC program is also stored in programmable read only mem- ory, the interpreter will immediately en- ter the RUN mode, allowing unattended operation in dedicated applications. 4 K BASIC is available on cassette at $95 or in programmable read only mem- ory on a Wince read only memory module for $299. The source listing is available for $95. For further information contact Wintek Corp, 902 N Ninth St, Lafayette IN 47904. ■ Circle 603 on inquiry card. A new 2708 erasable read only mem- ory programmer has been announced by Smoke Signal Broadcasting, POB 2017, Hollywood CA 90028. Designated the POP-1, the unit lists for $149 and is de- signed to interface to the company's P-38-1 and P-38-FF erasable read only memory boards, which are SwTPC SS-50 bus compatible products. Complete soft- ware is provided on audio cassette. An adaptive programming technique is used that allows most 2708s to be pro- grammed in 15 seconds. A separate self- contained power supply is used for the programming voltage insuring sufficient current capability to program erasable read only memory from any manufac- turer." Circle 601 on inquiry card. Text Processing System for Microcomputers The Diaspar Text System is said to be a package of four programs which form a commercial text processing system. Text files are stored on diskettes using a named file structure with passwords. Ac- cording to the vendor, hardware needed for this product is an 8080 based micro- computer with 32 K of main memory, a screen terminal, floppy disk and a print- ing terminal. Software required is the CP/M operating system and CBASIC run- time package. The system comes on standard diskettes with a user's manual for $195 from Diaspar Data Systems, POB 888, San Juan Capistrano CA 92675." Circle 604 on inquiry card. July 1978 © BYTE PubNcations Inc 177 Whafs New? Miniature Switching Power Supplies of INTEREST to DESIGNERS Keeping Connected Tlie new 2505 MODCON series is available in double row configurations of 10, 20, 40, 60, 80 and 100. These modu- lar high density receptacle connectors are designed for board to board inter- connect applications. The connectors are easy to mount using box form con- tacts that mate with conventional 0.025 by 0.025 wiring posts on 100 inch center to center spacing. The series operates in temperatures between —55 to -H50° C. Operating voltage is 800 V DC at sea level; insulation resistance is 5000 M n minimum at 500 VDC; current rating is maximum 3 A; and contact resistance is 10 mO at 3 A. Contact Stanford Applied Engineering, 340 Martin Av, Santa Clara CA 95050." Circle 629 on inquiry card. New Probe Extends AQ6800 Microprocessor Analyzer to 6802 Use This buffered probe extends the capabilities of the AQ6800 Microproc- essor Analyzer to 6802 microprocessors. With the PRB68/02 probe, the AQ6800 displays all address, data and status information of any 6802 microcomputer system, and provides direct user inter- action with all memory locations, 10 ports, and internal microprocessor regis- ters. The probe clips directly to the 6802 microprocessor chip in the system being tested. Interactive features include the ability to examine or modify the contents of all 6800 or 6802 internal registers, plus the program counter, manual or breakpoint program halt, single step operation, execution of single byte instructions independent of normal program flow and many other control capabilities. The probe is priced at $295 and the AQ6800/02 system, complete with probe, is $1950. Contact AQ Systems Inc, 1736 Front St, Yorktown Heights NY 10598." Circle 630 on inquiry card. 200 and 400 W Open Frame Switching Regulated Power Supplies The OL-200 is a four output unit which supplies 200 W of continuous power, -^5 V at 25 A (maximum) from one output, -5 V at 4 A, and ±12 V at 4 A each. The OL-400 is a five output unit that is capable of supplying a continuous 400 W, ±5 V at 45 A from one output, ±12 V at 10 A each from two outputs, and -5 V and +24 V at 4 A each from the remaining two out- puts. Each unit is capable under tran- sient conditions of handling three times the rated current. Both units can be adapted to provide voltages specified within ±70 V and up to 4 A per output for the OL-200 and 10 A per output for the OL-400. Input voltages are also user selectable. Both units will operate from either 115 VAC or 230 VAC and are equipped with brownout protection that allows them to operate without performance degradation at line voltages as low as 95 VAC (115 V option) or 190 VAC (230 V option). Both power supplies can provide 16 ms of continu- ous power after full loss of input. Stan- dard features include an input EMI filter, a series thermistor that reduces input line surges at turn on, reverse voltage protection, and protection against system shorts. The OL-200 is priced at $248 and the OL-400 at $395 in quantities of 100. Contact Boschert Associates, 384 Santa Trinita, Sunnyvale CA 94086." Circle 631 on inquiry card. Three 12 V, 15 V and 24 V units, with efficiencies from 75 to 85 percent, have been added to Gould's MMG line of 5 V, 25 W switching power supplies. The new units operate from 1 10 and 120 V or 220 and 240 V ±10%, 50 or 60 Hz, and currents from 1.4 to 2.5 A. Optical coupling is used to provide 4 kV rms insulation (5.7 kV peak) between input and output. Units can be used in series or parallel operation without special interconnections. Remote sensing is available from terminals on the printed circuit board adjacent to the output connections for control of voltage at the load instead of at the power supply. Standard features include overcurrent and overvoltage protection. Gould MMG switching power supplies carry a 5 year warranty. The units cost $135 in quantities of one to nine. Contact Gould's Electronic Components Division, 4601 N Arden Dr, El Monte CA 91731." Circle 632 on inquiry card. It's Late in the Learning Curve for 8080s National Semiconductor Corporation has announced across the board price reductions for its version of 8080A microprocessors. The price of National's plastic package INS8080AN is now listed at $9.98 in quantities of 1 to 24, reduced from a previous listing of $15.50 each. In quantities above 100, the device has been marked down by one third, from $10.80 to $7.10, as quoted in National's latest OEM price list. Contact National Semiconductor Corp, 2900 Semiconduc- tor Dr, Santa Clara CA 9505 1 .■ Circle 633 on mquprv card. 178 luly 1978 ©BYTE Publicalions Inc 5 PLETE SATISFACTION IS OUR GUARANTEE YOUR COMPLETE SATISFACTION IS OUR GUARANTEE YOUR COMPLETE SATISFACTION Huge Discounts! HOBBY WOBLB ELECTBONICS Savings up to 70% on major brand IC parts and computer kits. For complete IC listings write for our catalog. -^KITS WAMECO S-lOO RC. Boards 8K RAM 28.00 8080 CPU 28.00 12-Slot Mother Board 33.00 THACA AUDIO SlOO PC. Boards 8K RAM 28.00 Z-80 CPU 28.00 2708/2716 EPROM $3.75 8224-4 Clk.Gen.&Dvr. 25 @ $8.75ea. 6502 Microprocessor 5 @ $11.00 ea. 410D (200ns) Static Ram 100 @ $8.75ea. MICROCOMPUTER COMPONENTS MICROPROCESSOR-S "'^^^ "^HER COMPONENTS F8 Z8 zaoA CDP1802CD 26S0 AM2901 6S02 6B0O SB02 8008-1 8035 80B0A 8085 TMS9900TL 16.95 12.00 28.00 19.95 24.95 22.95 11.95 18.95 25.00 9.9 5 22.00 11.95 27.00 75.00 8080A SUPPORT DEVICES 8212 3.50 8214 9.00 8216 3.75 8224 3.50 8224-4 9.95 8236 3.95 8228 7.95 823B 7.50 B251 9.95 8253 21.95 8255 21.95 825 7 21.95 8259 21.95 B275 75.00 8279 20.00 FLOPPY DISC CONTROLLER 17718 55.95 1 7 7 1 a-0 1 5 7 .9 5 KEYBOARD CHIPS AYS-2376 13.75 AV5— 3600 13.75 PROM'S 1702A 2704 2708 2716 2716 intl 2758 O3601 D3604 5203 AQ 5204 AQ 6834 6834-t 82S2 3B 82S129B B223B 6800 SUPPORT 6810P 6BB10P 6B20P 6821 P 6828P 6834 P 6850P 6852P e860P 6B62P 6871 P 6875P 6880P 4.00 15.00 12.00 30.00 38.00 26.60 4.50 13.00 5.00 7.50 17.50 14.95 4.00 4.2 5 3,50 4.95 6.00 7.50 J. 50 11.25 16.95 9.75 1 1.75 10.00 14.50 2 8.00 8.75 2.50 Z80 SUPPORT DEVICES 3881 12-95 STATIC RAMS 21L02 1.51 21L02 I 21 Lj02 j 410D 1101 A 2101-1 2102 2111-1 21 12-1 2114-3 2125L 2147 ) 1.7S 1.60 10.75 lO.OO 1.00 .90 2.95 2.75 1.25 I. IS 3.95 3.50 2,95 2.80 1.18 1.25 1.50 9.25 .80 2.60 1,00 3.2 5 2.69 9.25 31 L 3 106 3107 TMS-4 04 4 4200 A TMS-4045 5101 74C89 7489 74S201 PBlOl P8155 P8156 8599 9102BPC 2.35 3.70 3.70 9.00 37.50 2.50 3.9 5 3.95 9.95 12.95 11.00 10.00 8.30 7.40 3,25 3.05 2.25 2.10 4.50 4.00 4.20 3.40 17.00 14.00 21.00 18.00 1.8B 1.7 5 1.6 5 1.4 5 2.00 3.25 3.25 8.95 9.25 7.25 2,85 1.90 3.75 2.B0 CHARACTER GENERATORS 2513 6.75 2513 5v upper 9.75 2513 5v lower 10.95 2516 10.95 MCM6571 10.95 MCM6571 A 10.95 MCM6574 13.25 MCM6575 13.25 WAVEFORM GENERATOR 8038 3.50 MC4 24 2.2 5 566 1.50 DYNAMIC RAMS 4160/4116 32.00 1103 1.00 2104 4.00 2107B 4.25 210 7 8-4 3.9 5 TMS4050 4.00 TMS4060 4.50 TMS4070-2 32.00 4096 4.00 4116/4I6D 32.00 MM52 7 4.50 MCM6605 S.OO USRT S2350 10.75 UART'S AYS 101 3 A AV5-10I4 A TR1602B TMS6 01 I IM6402 < M6 4 3 5. 25 8.25 5.25 S.9S 10.80 lO.BO JADE 8080A KIT $100.00 KIT BAHE BOARD $30.00 N8T20 N8T26 NgT9 5 N8T96 NBT9 7 N8T9 8 8 1 LS9 5 81 LS9 7 1488 1489 D3205 D3207 A D3208A 03 211 63 2 22 B324 2 03 245 C3404 P3408 A P4201 A MM5320 MMS369 TMS5501 OM81 30 OMB131 OMSB3 3 OM8e35 DM8B3 7 MKS0240 MK50250 3.39 2.10 1.35 1.35 1.35 1.35 2.00 2.00 1.75 1.75 4.00 4.55 14.20 10.00 9.75 10.15 5.60 6.75 .2.00 5.20 7.50 1.9 24.9 5 2.9 2.75 2.50 2.50 1.7S 20.0 15.00 2708 (4 50 ns) E— PROM 8 @ $11.00 ea. 4096 Dynamic Ram 100 @ $3.50 ea. E-PROM BOARDS MM 16 I16N uiri 1/ flAWN'ROM IIGK ,1 E I'HOMI S9*»l)0 S99'jO S99 0n SI woo TJ-l Convert T,V. sel to Video Monitor. KIT S8.95 STATIC RAM BOARDS 8K $189,95 $149 75 $169 95 $125 00 2500 2S0ns ASSEMBLED & TESTED 450ni ASSEMBLED 8. TESTED 250ns KIT 450oi KIT BARE BOARD 6800 ADAPTER lo S100 Syttem KIT S12.95 16K 2S0ni ASSEMBLED & TESTED $435.00 4S0ns ASSEMBLED 8. TESTED $380 00 450m KIT $335,00 32 K 2&0nt iiim oi cycle itailing iH)uir«l ■ 8VDC 400MA DC -tSVOC 400MA DC jnd I8VOC SOMA DC EXPANDABLE 8K (375nj| KIT 16K (375ns) KIT 24K I375nil KIT 32K (375nO KIT EXPANDABLE 16K (375ni) KIT 32K (375nil KIT 48K I375nil KIT &4K (375nil KIT $151-00 $259 00 $367.00 $425-00 $281 00 $519.00 $757.00 $995.00 MOTHER BOARD'S - S 100 Style 13 slot - w/front panel ilot BARE BOARD $35.00 KIT $96.00 22 slot $149.95 ASSEMBLED 8i TESTED THE PROM SETTER WRITE S, READ EPROM 1702A - 2708 - 2716 5204 - 6834 - Plugi n.g fs ac<:Ofrtpii\t\ed bv '*^*' Ci*"iijv*i»*f KIT S210.00 ASSEMBLED $376 00 KIM-1 ASSEMBLED & TESTED $245.00 MEMORY PLUS for KIM-1 8K RAM I21L02) 8K EPROM ASSEMBLED & TESTED $245.00 211J02 (250ns) Static Rams 100 @ $1.36 ea. 4200A (200ns) Static Rams 25 S> $10.00 ea. Z— 80A Microprocessor 5 @ $2 5.00 ea. 74LS36 7 Hex Buffer 100 @> .70? jadeZ80„,, -Mth PROVISIONS tor ^\ \ ONBOARD 770B md POWER ON JUMP $135.00 EA.™« $149.95 EA. — BARE BOARD $35.00 Z80 "UPGRADE" KIT Chjnge your JADE 3MHi Z80 lo a 4MHi uersn wiih lhi5 simple kii only $17.95 with trade $49.95 purchase. To trade, you must give ui youf 2MHi 280 chi| and B234 clock dt.ve< The UPGRADE KIT'' mcludei ZSOAchip. 1.8K tesiiior 8224 4 clock dii«er 20 p(. capadtoi 36IV!Hf crystal COMPU.TIME SlOO BUS COMPATIBLE ^ ' lUU TIME & CALENDAR MJcroprocejjors need the power that a leal time cinck can oHet Oaie and time becomes msiantlv available COMPU/TIME does not have lo be mniaiijed eue'v '"^^ the system IS powered up It possesses a crysial connolied time base to obtam superior accurKy and has two seiable coincideriee counters. Time, date, and counterj are set via software. COMPUTATIONAL FUNCTION Microprocessors need to be comp'imenied by hafdwaie arithmetics to free up memory pages dedicated to float ing point routines and mathmaiical software COUPU/ TIME provides a 40 function calculator anay so f'lai algebraic, Inqonometnc, basic aithmetic proMems can be solved wiihotit the need of ripveloping saplnsiicated software. a. COIiAPUTIME CTl( COMPU closure 29 95 Model 710 Numeric Pad 9 95 Model 7S6MF Mig Fr«n^e 8 95 8212 8 Bit I/O Port ?5 @ $3.00 ea. 74LS368 Hex Inverter 100 @ .70^ ea. 4116 (200ns) 16 K Dyn. Ram 16 @ $24.00 ea 2513 (5v) Character Gen. 5 @ $9.00 ea. REAL TIME CLOCK FOR S-IU BUS 1 MHZCrvitai Otcillator Two indepenbeni interrupts One interrupt uiM 16 bBti ill ed wiihaCBTcouplar. FCC regulations when i • All digita' rnodulation and damodulation with on board cyrxal dock and procition dlttr rnean thai NO ADJUSTMENTS ARE REQUIRED • Ball 103 iianda'd fraguartciai • Automated dial (pulsed) and •ntwar • Originata and answer mode • 1 to O' 300 BPS ipee 1 T "! .M.FT ^ lir ■i34 SIMULTANEOUS OUTPUTS AVAILABLE: THE ONLY ONE ON THE MARKET 1. SERIAL TTL LEVEL 2. BUFFERED 8 BIT (TRI-STATE LATCH) PARALLEL OUTPUT WITH VALID DATA SYNC PULSE AND LEVEL 3. 20 MA OPTO-ISOLATED CURRENT LOOP, POLARITY INDEPENDENT 4. EIA RS232C liSINGLE +5 VOLT 300 MA (NOMINAL) POWER SUPPLY (REQUIRED) ^INDUSTRY STANDARD 2 KEY ROLLOVER ENCODER li-ANSI-COMPATIBLE KEY SET; FOR SLIM-LINE "HIDE- AWAY" PACKAGING 5 COMPONENT SALES INC. 77B-A BRANMAN, SAN FRANCISCO. CA 3.41 03 [41B] 861-134S oo ASSEMBLED AND TESTED Plus $3.00 handling charge. California residents add 6'/2% sales tax. ^SEGMENTED SPACE BAR ALLOWS FAST MULTIPLE- SPACING WITHOUT REPEAT KEY irREPEAT KEY REPEATS AT CHARACTER RATE irUSER SELECTABLE UPPER CASE ONLY (KSR/ASR/33 REPLACEMENT) OR UPPER/LOWER CASE liFACTORYSETAT 110 BAUD BUT EASILY ADJUSTED BY USER TO ANY BAUD RATE FROM 110 TO 9600 BAUD ^FLEXIBLE PARITY *LED INDICATOR FOR SHIFT-LOCK KEY ELIMINATES CASE UNCERTAINTY *24 PIN DUAL-INLINE CONNECTOR 6LOW PROFILE CASE (OPTIONAL) $40.00 ^Ml Orders accepted by phone or maU. ■■■■ MASTERCHARGE V VISA J COD* CHECK* MONEY ORDER Circle 60 on inquiry card. BYTE July 1978 183 What's New? PERIPHERALS Centronics Announces Front Feed Option for 700 Series Printers Micromodule Has 16 Keys and IS Displays An optional front feed device has been Introduced by Centronics Data Computer Corp, Hudson NH 03051 . The front feed Is designed for use on eight members of the firm's 700 series of dot matrix printers and permits automatic front Insertion of cut forms and cut multipart form sets. It can be used In any application that requires informa- tion for Immediate utilization, Including invoicing, accounting, banlclngand stock certificates. The price for the front feed option is $700." Circle 639 on inquiry card. Assembled and Kit Plotters Plotter kits and plotters completely assembled are offered by Sylvanhllls Laboratory Inc, POB 646, Pittsburg KS 66762. The kits require the purchaser to mount them on a drawing surface and to do the interconnection between the con- trol printed circuit boards and the com- puter. Plotters require an 8 bit parallel lO port and 5 and 24 V power sources. A basic 8080 software program Is In- cluded In the owner's manual. Applica- tions Include architectural, mechanical, and schematic drawings; printed circuit board artwork; positioning of small ob- jects; computer generated art; games; etc. Sizes available are 11 by 17 inches (30 by 43 cm) at $795 in kit form, 17 by 22 Inches (43 by 56 cm) at $950 In kit form, and 22 by 34 Inches (56 by 86 cm) at $1 300 In kit form." Circle 640 on inquiry card. ■ B B B B B B B B B fl B B B B B This new Wince console lO module provides a versatile but inexpensive means of communication between a hu- man operator and a microprocessor. A 16 key keyboard allows entry of parame- ters such as product codes, gas chro- matograph stream selects, etc, and 15 7 segment displays. It allows output of data such as torque, item counts, etc. Also Included is a real time clock for providing Interrupts and displaying time. For further Information contact WIntek Corp, 902 N 9th St, Lafayette IN 47904.» Circle 641 on inqurry card. Add Some Color •*F «u The RM 9050 series, a new family of raster scan color Imaging and graphic systems, has been announced by the Ramtek Corp, 585 N Mary, Sunnyvale CA 94086. The RM 9150, 9250, 9350 and 9351 are the first members of a compatible family of solid state digital television image generation systems capa- ble of displaying In color, gray scale and black and white. The series was devel- oped to provide a basic Imaging system plus graphics (plots, vectors and bar charts) and alphanumeric capability. The basic system Includes scrolling, character scaling, readback, cursor and interactive capabilities. An assortment of custom video boards are available providing enhancement lookup tables and digital to analog converters which can produce from 256 gray levels to 4096 different colors. Keyboards and cursor controllers are available as add- on options. Pricing for a basic 64 color system is under $6000 with black and white less than $5500." Circle 642 on inquiry card Speed Up DECwrlters The SuperDEC throughput optimizer Is a printed circuit board designed to re- place the existing digital electronics In Digital Equipment's LA361 DECwrlter 11 teleprinter, upgrading It to 1200 bps. Installation of the optimizer takes less than five minutes and Is completely plug compatible with the cables In the DEC- wrlter. Standard features Include auto- matic and manual top of form, full hori- zontal and vertical tabs (addressable and absolute), adjustable right and left mar- gins and an RS-232C Interface. Features not previously offered to DECwrlter users Include a double wide character set, bidirectional printing and 32 user programmable characters. An APL char- acter set, selective addressing and an answer back feature are optional. Price Is $395 with a one year warranty on all parts and workmanship. Contact Inter- tec, 19530 Club House Rd, Gaithers- burgMD 20760," Circle 643 on inquiry card. 184 July 1978 ©BYTE Publicaiions Inc CaIIFoRnIa iNduSTRJAl Post Office Box 3097 B • Torrance, California 90503 WORD PROCESSING PRINTER S255. IBM EXECUTIVE D" This Rubo Goldbergized printer, when properly interfaced to your data processing system, offers the capability of producing error free duplicate personalized letters. A seven bil TTL signal directs one of the 50 solenoid driven fingers to I depi'ess the proper typewriter key. Expandable incremental spacing allows the operator to software control justified copy. The heart of this machine is an Executive "D" serviceable by any IBM repair center. Shipping east of the Mississippi add $20,00; California add $10.00 all other states add $15.00. (Copy above reduced to half size. ) CONNECTORS :r m your c.ioice DB25P male plug & hood or 0B25S female ^395 Qty. fe. male hd. 10 3.45 2.45 1.15 25 3.15 2.25 1.05 100 2.«5 1.90 .95 500 2.25 1.50 .95 IK 1 97 1.37 .73 Edge Connectors 100 PIN IMSAI/ALTAIR S-100 • GOLD PLATED • .125 "CENTERS AHair 140 row. solderlail. . imsai 250 row, sotdeflaiL . . 3 Level Wire Wrap .250 row. SPECIALS W/W same as above without ear5$3.50 3/$10 72 (dual 36) W/W 156" centers . $2.50 3/S6 $5.98 3/$16.50 $4.98 3/$11.95 $4 98 3/$13.00 S-100 Mother Board Quiet 18 slot IMSA HEXADECIMAL KEYBOARD $34.95 Maxl-Stivitcfi hexadecimal keyboards microcompuler syslems Ihat require ■ in standard hen code. Each assemtjiy consists of 16 hermati caliy sealed reed switches and TTL ' shot" debouncB circuitry Reliable low friction acelal resin piungefa are cfedded for the smooth operation and long life ot this premlu keyboard RoQui res single +5 volt supply. :fi ScptcH Diskettes 8inchSoft 14 4015 139 149 4016 69 733H 149 4017 129 320T-12 733N 99 4018 169 739N 1 14 741 N IN 4021 149 4022 125 340K-5 746N ;i9 4023 25 1414N 1/S 1.19 340K-12 1458 (j9 S .25 UART 4028 125 4030 4032 59 49 340T-12 ' •4.98 SPECIAL GENERAL INSTRUMENT ASCII Keyboard Encoder AY 5-3600 Prime but house marked only $4.95 TELETYPE MOraL 43 New from Teletype, ihe Model 43 Is capable of printing 132 ASCII characlera pe' line. Send and receive dataat I0of 30 char, persecond Key- board Qeneralea all 1 23 ASCII code combi tions RS-232 interface, same as the popui Model 33. Data sheet sen! upon request Manufac- turer suggested pr.ce It377 00. • ^ ** ^ *v IMMEDIATE DELIVERY >1219 TTLmodel with NOVATIONbrand Acoustic Modem. n419 TSP MAXI-SWITCH ASCII KEYBOARD Fully ftCS^.97 Assembled •O^*.^' Definitely the best small systtmi keyboard that we have seen. Maxi-Switch has incorporated all the important keyboard features at a reason- able price. Full 128 ASCII funetions, "N" key rollover, automatic repeats, user designated special function keys, escape, control ^ lots of others. Data sheet upon request. FROM ATARI COLOR TELEVISION R.E MODULATOR 1395 HH mfinUfiL CRfiPHiTE DiSPLflV DEnERfiTDR Mprtetn teclinoiogy has P'Q Generator has the capaOilH) kwer case ASCII set Seii-cf the operator lo alimmalB e. Each umi is manutactureo ti QyGlanaaidssel'fiHlhCiy C£ every Ofder }r assembly allows JO Potter &Brumfield REED RELAY 5voltcoil,pulls3.5v. .97 .79 .65 Digital Casseite Drive COMPUTER CONTROLED •V9.50 This precision I/O assembly features remote software controlled searchi capabilities. Two independent capstan drive motors allow the computer to control direction and speed of the transport. The assembly consists of a Raymoncl cassette transport, chassis, mother- board and three edge cards: read/write, capstan drive & control card. Current replacement valued at over $700.00. Schematics and complete documentation included. USED, but in excellent condition. SlOO PROTOTYPE BOARD] OPIOO-Moilmum design ver SQ'illtv along witti stondora oanress decoding and Dut tenng tor SlOO systems Room for 32 uncommiHeO 16 pin ics. 5 bus buffer & de- coding cmps. 1 DIP address select swiicti o 5 volt regu WWIOO-Wire wrap breod- Doora, similar to the GPlOO Allows wire wrap of all sizes of sockets in any sizes of sooieis in any combinotion An extra reguloior position tor muiilDie volioge oopiico- TJujmbwheel switch Ten position BCD '139 «. r^ o;5eo Miniature / Switches A it $.69 Conductor Fl. RIBBON WIRE TWISTED PAIR Transistors ea. 10 SO 100 2N2222A.20 .li .16.15 2N30S5 .69 .65 .59 .55 .79 .75 .69 .65 159 1(I9J391Z9 .15 .11 .09.07 .15 .11 .09.07 odes Ml 3055 2N3772 2N3904 2N3906 Di 10 a 100 1N4002 100«. .08 06.05 tN40a5 600>..10.08.07 lN4148sitnal .07.05.04 ittinb, red ea. 10 25 100 LED'S h5.13.11.09 Power Adapter 6vdc,140mA 51.39 7vdc, 1.4 A. 5.50 9vdc. ISmA. 1.19 10 vAc.300mA. ■a Binding Posts 5-WAY 3.or*1.19 20 100 ».35 .29 SOLDERLESS TERMINAL^ INSULATED 20lor ♦.98 Specify:22-18 16 14 100 soo Ik .213. 679-9001 RELAYS spot miniature 10 25 100 'l.l'ea $115 104 »9 Coil 12 Volt dc. 7 Amp Contacts P. C. Board Mount CAPACITORS ELECTROLrnCS «a. 10 50 80,000/lOv. 355 3.M 2.95 4500/50V.SW9 135 U9 lOOO/lSv 555 49 45 axial your choice t OO 1° 50 100 Ik *-9o s.gg .81.73.66 SPDT Miniature Toggles 7101 C&K ON'NONE-ON I 7107 jM ON.OFF(mnt.ON) 7108 CK ON-(moment.ON> I Rockec IBT . OPOI Rotary 3P-4-POS. Rotary 3P-6-POS. Pu&tiB end Lengths are ovetaM Veiiow. Black. Orange. While Dags Add 25«'length for tubes 2'', in 3 in 3'^ in 100 78 82 86 90 500 2 40 260 280 300 1000 4 30/K 4 7t/K S12/K 5 52/K 5SS0 3e9^K 4 22/K 4 55/K 4 8e'K 4* in 5 in 5'^ in 6 in 94 96 1 02 1 06 3 21 3 42 3 65 3S5 5 93/K 6 34/K 6 75/K 7 16/K 5 21/K 5 52/K 5 86/K 6 19/K 6'^in 7-, in 8 in 1 15 1 20 125 129 4 05 4 25 4 45 4 65 7 57-'K 7 98/K 8 39/K BaO'K 6 52/K 6 85/K 7 18/K 7 53/K 8>j in 9 in gwin 10 in 1 32 136 1 40 1 45 4 85 505 5 25 5 51 9 2t/K 9 62'K 10 03/K 10 44/K 7 84/K ei7/K 8 50/K 8 83/K Addi nches iO 41 82/K 66/ K WIRE KITS £J $6.95 = 2 ?19.W 250 250 100 3- 100 *r 250 2'V 3V 100 5' 500 3- 4" 100 6" 500 3'->' 500 4 Choote Or>e Color or Assonmeni 250 4',. 250 5' 100 5/ 1 250 250 6- 100 6 -■ 100 7 Hon Bulk WIRE WRAP SOCKETS 10-24 25-99 100-249 250-999 1K-5K 18pin- ?0p.r. 22 pin ■ 24 pin 28 pin 40 pin Gold 3-lev*l CloMd Enlry Sockelt d & Side SlBCkaDle All pncM include gold Tin sockeli and 2-ievei sockets available ^ INTERCONNECT CABLES^ bon caDle conneclors 'or connecUng Ironl panels, or board to board Boards lo SINGLE ENDED DOUBLE ENDED I4p,n 16 pin 24p>n 14 pm 16 pin 24 pm 124 1 34 1 33 1 44 152 165 1 91 2 06 205 2 24 263 3 40 2 24 2 33 2 52 291 2 45 3 37 2 55 3 92 2 76 4 31 317 508 WIRE WRAP TOOLS $34.95 With Free Wire Kit (S6 95 Value) HOBBY WRAP Model BW 630 Batteries & Charger $11.00 WSU 30 Hand Wrap-Unwrap Strip Tool 5 95 WSU 30M, for Modified Wrap 6 95 BT 30 Extra Bit 2,95 WIRE WRAP BOARDS 14 5J WW 1024 Connector H-PCB 1 3662 3682 4x4'.', 4x6 4x10 44 44 44 Buses on both sides Blank Buses on one side 4 76 625 10,50 4 50 6,85 10,00 4 00 5,50 9,50 3,00 3,00 300 36822 4066-4 3719-1 4x6 4x6 4x6 44 72 72 Buses on one side Buses on bolh sides Blank 950 13 60 900 900 13,00 8,50 825 12,50 800 3 00 4 00 4 00 3719-4 4350 8800V 4x10 7.9'', 10x5.3 72 80 100 Blank Buses on both sides Buses on bolh sides 11.00 17 50 19,50 1050 16,50 17,96 10,00 16 00 16 96 4 00 700 500 169P84 8v,x 1 7 Blank 626 5.75 5,26 - SOCKET SAI ^' 14 p 16 p 24 p n Gold WVW Socket n Gold WW Socket n Gold WW Socket 30 ,32 ,75 27 pe ,29 pe ,65 pa 400 350 117 44 p n ST Edge Cerd Cddnector 1.75 1 50pe 10 100 pin ST Edge Card Connecior 3. SO 3.00 par 10 lOOpin WW Edge Card Connector 3.50 3,00 par 10 Prices good through 8/1/78 vvhen purchased with Wire Kit —1 or -2 PAGE DIGITAL ELECTRONICS Ordering Information: Orders under S2S and COD'S, add $2 All others, shipped ppd m US via UPS 135 E. Chestnut Street 5 For Blue Label (Air) or 1st Class, add $1 Alt^^w^nln r^nlif^^^',.^ omic weacceptv,Mj,Mas«rch.rg, Monrovia, California 91016 Most orders shipped same day Dealer Inquiries Invited Phone (213) 357-5005 P.O. Box 4430X Santa Clara. CA 95054 For will call only: (408) 988-1640 ^^^^For will call only: (408) 988-1640 ^^^^^^2322 Walsh Ave.^ ^^B^^ ELECTRONICS "^^^ CRYSTALS 1 MHz 4.50 2.0100 MHz 1,95 2 MHz 4.50 2.097152 MHz 4.50 MICROPROCESSOR 2708 14.65 2104A-4 4.95 4 MHz 4.25 2.4576 MHz 4.50 6800 19.50 DH8577 290 2107B 4 95 5 MHz 4.25 3.2766 MHz 4,50 8.95 8223 290 2111-1 4 95 10 MHz 4,25 5,0688 MHz 4.50 m 29.95 2716 28,95 2112-2 3.95 18 MHz 3.90 5.185 MHz 450 8212 2114 8.50 20 MHz 3.90 5.7143 MHz 4.50 8214 8.00 IC SOCKETS MK4116 27 50 32 MHz 3.90 6.5536 MHz 4.50 8216 2.90 2513B 6.30 32768 Hz 4.00 14.31818 MHz 4 25 8224 2,95 PIN 1 UP PIN lUP 21L02-1 1.49 4.50 8228 5.35 MM5262 .40 3.5795 MHzl. 20 22 1164 MHz 4,50 8251 9.25 14 ,18 28 .42 MM5280 3.00 60 Hz Cryital Time Bate Ktl S 4.40 8253 10.00 16 -20 36 .58 MM5320 9,95 30 MHz Fffiquencv Counter Kit S47.7S 18 .27 40 .61 PrHCslv Kit to 350 MHz $19.95 CDP1802CD 19.95 22 30 PD4110-3 4.00 CDP1802D 25,00 PD411D-4 5.00 CDP1861 12.96 P5101 13.95 6620 4200A 12.95 6850 12 95 82S25 290 Extender .Board w/connectot Video Interlace board kit 125.00 PROM 16K EPROM board kit w/o PROMS 74 50 3.95 16K Static RAM board kit 395 00 N82S23 2,95 North Stir Hoppy Dlik Kit >665 00 N82S123 3.50 Additional Drive Kit N82S126 3-75 MOSMEMONT RAM INTERFACE Parstrofllct IMA Logic 8.75 2102AL-4 1,60 8T28 2.75 Model 10 Trigger Expandef Kit ^8^s^37 8.75 21F02 1-85 8T97 1.69 Model 150 Bus Grabber Kit S369.00 New Cosmac Super "ELF" RCA CMOS expandable to 64K microcomputer w/H EX lieypad input and video output for graphics. Just turn on and start loading your program using the resident monitor on ROM. Pushbutton selec- tion of all four CPU modes. LED indicators of current CPU mode and four CPU states. Single step op. for program debug. Built in pwr. supply. 256 Bytes of RAM, audio amp. & spkr. Detailed assy. man. w/PC board & all parts fully socketed. Comp. Kit $106.95. High address display option 8.95; Low address display option 9.95; Custom hardwood cab.; drilled front panel 19.75; Nicad Battery Backup Kit w/all parts 4.95; Fully wireij S, tested in cabinet 151.70; 1802 software club. 10-12 pg. monthly publication 12.00 per yr. Auto Clock Kit $15.95 DC clock with 4. 50' displays Uses National MA-1012 module with alarm option. Includes light dimmer, crystal timebase PC boards. Fully regulated, comp. instructs. Add S3. 95 for beautiful dark gray case. Best value any- where. 4K Ell Expansion Board Kit with Cassette l/F $79.95 Available on board options; 1 K super ROM monitor S19.95. Parallel I/O port $7.95. RS232 l/F $3.50. TTY 20 ma l/F $1.95. S-100 Memory l/F $4.50. Tiny Basic for ANY 1802 System "oltZ Monitor mil ^'"^ E" ™"«'= «*» 30%off. Object code listing or paper tape with manual $5.50 78 IC Update Master Manual 1978 IC Update Master Manual $30.00 Complete IC data selector 2175 pg. Master ref- erence guide. Over 42.000 cross references. Free update service through 1978. Domestic postage $3.50, Foreign $6,00. Final 1977 Master closeout $15.00 Video Modulator Kit $8.95 Convert your TV set Into a high quality monitor without affecting normal usage. Complete kit with full Instructions. RCA CosmacVIP Kit $275.00 Video computer with games and graphics. Sinclair 3V2 Digit Multimeter Batt. oper. ImV and 1NA resolution. Resis- tance to 20 meg. 1% accuracy. Small, portable, completely assem. in case. 1 yr. guarantee. $50.05 FREE; Send for your copy of our NEW 1978 QUEST CATALOG. lericard and e 24« stamp 188 BYTE luly 1978 Circle 307 on inquiry card. ELECTRONIC SYSTEMS Dept. B P.O. Box 21638 San Jose, CA 95151 FOR CATALOG INCLUDING PARTS LISTS AND SCHEMATICS. SEND A SELF ADDRESSED ENVELOPE WITH 2i«r POSTAGE. RS-232/TTL INTERFACE* UART &BAUD RATE GENERATOR* Part no. 101 • Converts serial to parallel and parallel to serial • Low cost on board baud rate generator • Baud rates: 110, 150, 300,600, 1200, and 2400 • Low power drain +5 volts and - 1 2 volts required • TTL compatible • All characters contain a start bit, 5 to 8 data bits, 1 or 2 stop bits, and either odd or even parity. • All connections go to a 44 pin gold plated edge connector • Board only $12.00; with parts $35.00 8K STATIC RAM Part no. 300 • 8K Altair bus memory • Uses 2102 Static memory chips • Memory protect • Cold contacts • Wait states • On board regulator • S-100 bus compatible • Vector input option • TRl state buffered • Board only $22.50; with parts $160.00 , and Part no. 232 • Converts TTL to RS-232, converts RS-232 to TTL • Two separate circuits • Requires 12 and +12 volts • All connections go to a 10 pin gold plated edge connector • Board only $4.50; with parts $7.00 DC POWER SUPPLY* Part no. 6085 • Board supplies a regulated -^5 volts at 3 amps., + 12, - 12, and -5 volts at 1 amp. • Power required is 8 volts AC at 3 amps., and 24 volts AC C.T. at 1.5 amps. • Board only $ 12.50; with parts S42.50 excluding transformers TIDMA' Part no. 112 a^'^f • Tape Interface Direct Memory Access • Record and play programs with- out bootstrap loader (no prom) has FSK encoder/decoder for direct connections to low cost recorder at 1200 baud rate, and direct connections for inputs and outputs to a digital recorder at any baud rale. • S-100 bus compatible • Board only $35.00; with parts $110.00 Part no. Ill TAPE INTERFACE* • Play and record Kansas City Standard tapes • Converts a low cost tape recorder to a digital recorder • Works up to 1200 baud • Digital in and out are TTL-serial • Output of board connects to mic. in of recorder • I^phone of recorder connects to input on board • Requires -^5 volts, low power drain • Board $7.60; with parts $27.50 • No coils Part no. 107 RF MODULATOR* • Converts video to AM modu- lated RF, Channels 2 or 3 • Power required is 1 2 volts AC C.T., or +5 volts DC • Board $7.60; with parts $13.50 Apple II Serial I/O Interface * Part No. 2 • Baud rates up to 30,000 • Plugs into Apple Peripheral connector • Low-current drain • RS-232 Input and Output SOFTWARE • Input and Output routine from monitor or BASIC to teletype or other serial printer. • Program for using an Apple II for a video or an intelligent ter- minal. Board only — $15.00; with parts — $42.00; assembled and tested - $62.00. RS-Z32/TTY* INTERFACE ^ Part no. 600 J^^ • Converts RS-232 to 20mA ^^ current loop, and 20mA current loop to RS-232 • Two separate circuits • Requires +12 and -12 volts • Board only S4.50, with parts «7.00 TELEVISION TYPEWRITER Pari no. 106 • Stand alone TVT • 32 char/line, 16 lines modifi cations for 64 char/line included • Parallel ASCII (TTL) input • Video output • IK on board memory • Output for computer con- trolled curser • Auto scroll • Non-destructive curser • Curser inputs: up, down, left, right, home. EOL, EOS • Scroll up, down • Requires +5 volts at 1.5 amps, and - 12 volts at 30 mA • All 7400, TTL chips • Char. gen. 2513 • Upper case only • Board only 839.00; with parts 8145.00 MODEM Part no. 109 • Type 103 • Full or half duplex • Works up to 300 baud • Originate or Answer • No coils, only low cost com- ponents • TTL input and output-serial • Connect 8 ohm speaker and crystal mic. directly to board • Uses XR FSK demodulator • Requires +5 volts • Board $7.60; with parts $27.50 To Order: Mention part number and description. For parts kits add "A" to part number. Shipping paid for orders accompanied by check, money order, or Master Qiarge, BankAmericard, or VISA number, expiration date and signature. Shipping charges added to C.O.D. orders. California residents add 6.5% for tax. Parts kits include sockets for all ICs, components, and circuit board. Documentation is included with all products. Dealer inquiries invited. 24 Hour Order Line: (408) 226-4064.* Designed by John Bell. Circle 125 on inquiry card. BYTE )ulv 1978 189 What's New? PERIPHERALS Isolated Digital Output Board for Intel Microcomputers A Video Camera Kit This 202 video camera kit may be used for visible or infrared viewing and surveillance with an infrared light source, and is excellent for standard surveillance work because of its light weight (under one pound) and small size {VA by 6V2 inch boards). A 5 V, 1 A power supply is needed. The kit includes all semicon- ductors, boards, data sheets, diagrams, resistors, capacitors, and an 8 mm lens. The kit sells for $349 from Solid State Sales, POB 748, Somerville, MA 021 43.- Circle 61 5 on inquiry card. Video Terminal Offered by Phone 1 The new model PI -11 video terminal features the following: 80 by 24 screen, local editing, upper and lower case dis- play, dual screen intensity, full or half duplex operation, numeric cluster key- board, and 300 bps acoustical modem. The unit sells for $1075 complete and $800 for the terminal alone. Contact Phone 1 Inc, 1330 E State St, Rockford IL61108.- Circle 616 on inquiry card. Module Interfaces Voice and Instruments to Synthesizers PITCH FOtLOWER The Aries AR-333 pitch and envelope follower is an electronic module that in- terfaces external signal sources, such as voice, single note instruments, and tape recorders, to most synthesizers. A one octave change of input signal produces a 1 V change in pitch control output for controlling VC oscillator frequency, fil- ter frequency, etc. Linear and logarith- mic envelope follower outputs allow control of synthesizer functions by the amplitude of the input signal. On the front panel, a trim pot lets you adjust the tracking sensitivity of the pitch con- trol output, and permits use of the mod- ule with different synthesizers without retrimming oscillators. The front panel also provides a tuning control for adjust- ing oscillator frequency which allows tuning to the pitch of other instruments, and a retriggering sensitivity control for picking up accents. A low distortion compressor output is also provided. The module's 36 db, low noise microphone preamp accepts Vi inch phone plugs. It sells for $349 (kit) and $499 (assem- bled). An assembled AR-333 with case and power supply (Model GE-101) sells for $550. Contact Aries Music Inc, Shet- land Industrial Park, POB 3065, Salem MA 01970." Circle 61 8 on inquiry card. Plug compatible 16 or 32 channel iso- lated digital output systems are available for the Intel SBC 80 and Intellec MDS microcomputers. Isolation eliminates ground loop problems and protects the processor from real world transients. Memory mapped MP801 (16 channel) or MP802 (32 channel) systems are con- tained on a single printed circuit board and provide all control and timing circuitry. Channels are implemented by dry reed relays protected by metal oxide varistors and can handle up to 10 W. Re- lays provide low "on-impedance," high output current and isolate output chan- nels from the computer bus (to 600 VDC) and from channel to channel (300 VDC). They are treated as memory by the processor, eight output channels occupying one memory location. Prices of the 16 channel MP801 are $295 and $475 for the 32 channel MP802 in quan- tities of one to nine. Contact Burr- Brown, International Airport Industrial Park, Tucson AZ 85734.» Circle 61 7 on inquiry card. Attention Readers, and Vendors. . . Where Do New Product Items Come From? 77!e information printed in tlie new products pages of BYTE is obtained from "new product" or "press release" copy sent by the promoters of new products. If in our Judgment the neat new whiz- bang gizmo or save the world software package is of interest to the personal computing experi- menters and homebrewers who read BYTE, we print the informa- tion in some form. We openly solicit such information from manufacturers and suppliers to this marketplace. The information is printed more or less as a first in first out queue, subject to oc- casional priority modifications. 190 luly 1978 ©BYTE Publicjtions Inc c^^ri.1 T-W7 n/./^n A "Smart" VIDEO BOARD ^^^^ Ihe tW-2001 KIT At A "Dumb" Price! '^ A VIDEO BOARD + A MEMORY BOARD + AN I/O BOARD - ALL IN ONE! ■ STATE OF THE ART TECHNOLOGY USING DEDICATED MICROPROCESSOR I.C. 4^ 1 QQ O ^ ■ NUMBER OF I.C.s REDUCED BY 50% FOR HIGHER RELIABILITY ■ MASTER PIECE ^fl? J- 3/ 3/« 37 tJ OF ENGINEERING ■ FULLY SOFTWARE CONTROLLED Priced at ONLY Basic Software Included SPECIAL FEATURES: ■ Programmable no. of scan lines OPTIONS: ■ S-100 bus compatible ■ Underline blinking cursor Sockets SI 0.00 ■ Parallel keyboard port ■ Cursor controls: up, down, left, 2K Static Memory ■ On board 4K screen memory right, home, carriage return (with Sockets) $45.00 (optional)* relocatable to main ■ Composite video 4K Static Memory computer memory *Min. 2k required for operation of this board. (with Sockets) S90.00 ■ Text editing capabilities (soft- DISPLAY FEATURES- Complete unit, assembled ware optional) _ .^^ ,. , ., .g^„ . ^ and tested with ' ■ Scrolling- UD and down through " 128 displayable ASCII charact- 4K Memory S335.00 icroumg. up dnu uown uiruugn ers (upper and lower case alpha- „ . , „^.. „^^ ^^ video memory numeric, controls) Basic software on ROM . S20.00 ■ Bhnking characters a 64 ^j. 32 characters per hne Text editor on ROM .... S75.00 ■ Reversed video Oumper selectable) ■ Provision for on board ROM ■ 32 or 16 lines ■ CRT and video controls fully Oumper selectable) programmable (European TV) ■ Screen capacity 2048 or 512 DEALER ' ?rn dot^maTrlx""' INQUIRIES WELCOMED 8080 SUPPORT 8212 S3.00 8214 7.95 8216 3.50 8228 5.95 8251 7.95 8555 8.50 1/4W RESISTOR 10 Ohm- 1.5m $1.75/100 of one value Pole lOPos. ROTARY SWITCH 3 for $1.00 Pole 8 Pos. T05 Miniature Rotary Switch 3 for $1.00 MINIATURE Slide Switch DPDT $.15: 10/$1.00 Push Button Momentary Switch 3 for $ 1 .00 a 080 A CPU $7.75 RAM-2II4 lKx4 450ns $8.00 RIBBON CABLE 32 Conductor 26 AWG - $.60/Foot HEXADECIMAL LABEL KEYBOARD Matrix coded output Interfaces with 74C922 for binary code Zero bounce Est. life: 100 million Remove back to stick on SHIPPING: Keyboard and Video Board: $3.50; others: $1.25 California residents add 6% sales tax ELECTRONICS WAREHOUSE Inc. 1603 AVIATION BLVD. REDONDO BEACH, CA. 90278 TEL. (213)376-8005 WRITE FOR FREE CATALOG Minimum Order: $10 •JfONLY ASCII 3rd GENERATION KEYBOARD KIT *68.00 TTL Logic Circuits Power: +5V 275mA Upper and Lower Case Full ASCII Set (Alpha Numeric, Symbols, Control) 7 or 8 Bits Parallel Data Optional Serial Output Selectable Positive or Negative Strobe, and Strobe Pulse Width 'N' Key Roll-Over Fully Debounced Carriage Return Key Repeat Function Key Shift Lock, 2 Shift Keys 4 User Defineable Keys P.C. Board Size: 17-3/16" x 5" OPTIONS: Metal hnclosure Painted IBM Blue and White) $25.00 18 Pin Edge Con. S2.00 I.C. Sockets $4.00 Serial Output (Shift Register) $2.00 Upper Case Lock Switch for Capital Letters and Numbers $2.00 KIT INCLUDES: Keyboard, P.C. Board, all required com- ponents & assembly manual. NOTE: If you have this 63 Key Teletype Keyboard you can buy the Kit without it for only $44.95. Circle 130 on inquiry card. BYTE July 1978 191 What's New? Full Character Line Printer PERIPHERALS The Writehander: a New Typing Keyboard for One Hand A typing keyboard has been designed that permits typing all 128 characters of the ASCII code with one hand and is particularly useful with computers and terminals that accept ASCII coded parallel input. To use the Writehander, the typist places four fingers on four press switches and the thumb on one of eight press switches. The four finger switches operate as the lower four bits of the 7 bit ASCII code, selecting the group of characters (out of 16 groups) that contains the desired character. The group contains a choice of eight letters, numerals, symbols, etc. The thumb then presses the particular switch that selects the desired character from the choice of eight. A computer is not required to operate the terminal. The Writehander will directly operate terminals such as the Diablo HyType, Teletype ASCII modified Selectric, or a video monitor that accepts parallel 7 bit ASCII signals. Required power is 200 mADC from 5 V regulated or 7 to 25 V unregulated. The unit connects to the terminal through a ribbon cable that has lines for the 7 bit ASCII code, a 1 bit fixed parity, strobe and acknowledge signals and the power and common lines. The price of the Writehander is $98 and it can be ob- tained from the NewO Company, 246 Walter Hays Dr, Palo Alto CA 94303." Circle 646 on inquiry card. Line Printer with Graphic Capabilities IKi mt _ ^^'**^«^_ .f f The Model 160 Malibu Line Printer is a commercial grade dot matrix machine which operates bidirectionally at 165 characters per second and has graphics capabilities. The printer's fea- tures include logic seeking capabilities for fast throughput, reinking rollers (said to increase ribbon life up to 50 million characters), and jumper selectable pri- mary voltage (110 to 220 V, 50 to 60 Hz). Standard software supports the 96 character ASCII set, but the user may easily change the characters to exotic languages, scientific symbols, or what- ever can be printed with a 9 pin head. The tractor operated paper feed allows groups of dots to be placed immediately adjacent to one another either hori- zontally or vertically, giving graphics capabilities at 3000 dot locations per square inch. The Malibu accepts paper from 4 inch (10 cm) to 15 (37.5 cm) inch width and prints up to 132 char- acters per line. Normal line feed is 1/6 inch (0.4 cm), but increments of 1/60 inch (0.04 cm) are possible under software control. All circuitry is de- signed into three circuit boards which plug into the mother board. An optional Altair (S-100) interface card is available, making the printer immediately operable with many popular computers. An RS-232 option with a Z-80 processor on board allows the printer to accept serial input (up to 9600 bps) or parallel ASCII input with handshaking. The Malibu printer is priced at less than $2000 from Malibu Design Group Inc, 21110G Nordhoff St.Chatsworth CA 91311." Circle 653 on inquiry card- The FUTRA Model 10 Line Printer incorporates a belt impact, full character (not dot matrix) 80 column printing mechanism. The unit operates at a mini- mum print rate of 150 lines per minute using the 64 ASCII character set or a minimum of 84 lines per minute using a full 96 ASCII character set and can produce up to four copies including the original. The input is an 8 bit parallel which can be interfaced to a 3P-^S or similar interface card. The unit has a buffer size of one full line (80 char- acters) and a maximum data input rate of 75,000 characters per second. The Model 10 is priced at $2695 and comes with pin feed paper handling mechanism, format control unit (top of form), either 64 or 96 ASCII character set and parallel interface. Options are an off line test print excercisor, $75; and serial interface (RS-232c, 20 mA current loop, TTL direct interface with 1010 byte buffer), $595. Contact FUTRA, 3421 Onyx St, POB 4380, Torrance CA 90510, (213) 371-8138." Circle 583 on inquirv card Fast Cassette Interface The Wince Cassette Interface dumps and loads programs at a data rate of 2400 bps. It also supports the 300 bps Kansas City standard. The unit inter- faces directly to a Motorola 6850 ACIA and includes an RS232 interface at data rates from 150 to 9600 bps. The inter- face board is priced at $139 in single quantities from Wintek Corp, 902 N 9th St, Lafayette IN 47904, (31 7) 742-6802." Circle 584 on inquiry card. 192 July 1978 ©BYTE Publicilioni Inc DIODES/ZENERS SOCKETS/BRIDGES TRANSISTORS, LEDS, etc. 1N914 lOOv 10mA .05 8-pin pcb .20 WW .35 2N2222 NPN (2N2222 Plastic .10) .15 1N4n05 1 N4007 600v lOOOv 1A .08 1A .15 14-pin pcb .20 WW .40 16-pin pcb .20 WW .40 2N2907 2N3906 2N3904 PNP PNP (Plastic - Unmarked) NPN (Plastic - Unmarked) .15 .10 .10 1N4148 75v 10mA .05 18-pin pcb .25 ww .75 2N3054 NPN .35 1N4733 5.1v 1 W Zener .25 22-pin pcb .35 ww .95 2N3055 NPN 15A 60v .50 1N753A 1N758A 6.2v lOv 500mWZener .25 .25 24-pin pcb .35 ww .95 28-pin pcb .45 ww 1.25 T1P125 LED Green, D.L.747 PNP Darlington Red, Clear, Yellow 7 seg 5/8" High com-anode .35 .15 1.95 1N759A 12v .25 40-pin pcb .50 ww 1.25 MAN72 7 seg com-anode (Red) 1.25 IN 5243 1N5244B 1N5245B 13v 14v 15v .25 .25 .25 IVIolex pins .01 To-3 Sockets .25 MAN3610 MAN82A 7 seg com-anode (Grange) 7 seg com-anode (Yellow) 1.25 1.25 2 Amp Bridge 100-prv .95 MAN74A FND359 7 seg com-cathode (Red) 7 seg conrvcathode (Red) 1.50 1.25 25 Amp Bridge 200-prv 1 .95 CMOS - T T L - 4000 .15 7400 .10 7473 .25 74176 .85 74H72 .35 74S133 .40 4001 .15 7401 .15 7474 .30 74180 .55 74H101 .75 74S140 .55 4002 .20 7402 .15 7475 .35 74181 2.25 74H103 .55 74S151 .30 4004 3.95 7403 .15 7476 .40 74182 .75 74H106 .95 74S153 .35 4006 .95 7404 .10 7480 .55 74190 1.25 74S157 .75 4007 .20 7405 .25 7481 .75 74191 .95 74 LOO .25 74S158 .30 4008 .75 7406 .25 7483 .75 74192 .75 74L02 .20 74S194 1.05 4009 .35 7407 .55 7485 .55 74193 .85 74L03 .25 74S257(8123) 1.05 4010 .35 7408 .15 7486 .25 74194 .95 74L04 .30 4011 .20 7409 .15 7489 1.05 74195 .95 74L10 .20 74LS00 .20 4012 .20 7410 .15 7490 .45 74196 .95 74L20 .35 74LS01 .20 4013 .40 7411 .25 7491 .70 74197 .95 74L30 .45 74LS02 .20 4014 .75 7412 .25 7492 .45 74198 1.45 74L47 1.95 74LS04 .20 4015 .75 7413 .25 7493 .35 74221 1.00 74L51 .45 74LS05 .25 4016 .35 7414 .75 7494 .75 74367 .75 74L55 .65 74LS08 .25 4017 .75 7416 .25 7495 .60 74L72 .45 74LS09 .25 4018 .75 7417 .40 7496 .80 751 08A .35 74L73 .40 74LS10 .25 4019 .35 7420 .15 74100 1.15 75491 .50 74L74 .45 74LS11 .25 4020 .85 7426 .25 74107 .25 75492 .50 74L75 .55 74LS20 .20 4021 .75 7427 .25 74121 .35 74L93 .55 74LS21 .25 4022 .75 7430 .15 74122 .55 74L123 .85 74LS22 .25 4023 .20 7432 .20 74123 .35 74H00 .15 74LS32 .25 4024 .75 7437 .20 74125 .45 74H01 .20 74S00 .35 74LS37 .25 4025 .20 7438 .20 74126 .35 74H04 -20 74S02 .35 74LS38 .35 4026 1.95 7440 .20 74132 .75 74H05 .20 74S03 .25 74LS40 .30 4027 .35 7441 1.15 74141 .90 74H08 .35 74S04 .25 74LS42 .65 4028 .75 7442 .45 74150 .85 74H10 .35 74S05 .35 74LS51 .35 4030 .35 7443 .45 74151 .65 74H11 .25 74S08 .35 74LS74 .35 4033 1.50 7444 .45 74153 .75 74H15 .45 74S10 .35 74LS86 .35 4034 2.45 7445 .65 74154 .95 74H20 .25 74811 .35 74LS90 .55 4035 .75 7446 .70 74156 .70 74H21 .25 74S20 .25 74LS93 .55 4040 .75 7447 .70 741 57 .65 74H22 .40 74S40 .20 74LS107 .40 4041 .69 7448 .50 74161 .55 74H30 .20 74S50 .20 74 LSI 23 1.00 4042 .65 7450 .25 74163 .85 74H40 .25 74S51 .25 74LS151 .75 4043 .50 7451 .25 74164 .60 74H50 .25 74S64 .15 74 LSI 53 .75 4044 .65 7453 .20 74165 1.10 74H51 .25 74S74 .35 74LS157 .75 4046 1.25 7454 .25 74166 1.25 74H52 .15 7481 12 .60 74LS164 1.00 4049 .45 7460 .40 74175 .80 74H53J .25 74S114 .65 74 LSI 93 .95 4050 .45 7470 .45 74H55 .20 74LS367 .75 4066 4069/74 C04 .55 .25 7472 .40 74LS368 .65 4071 .25 IVICT2 .95 LINEARS, REGULATORS, etc. 4081 .30 8038 3.95 LIVI320T5 1.65 LM340K15 1.25 LM723 .40 4082 .30 LM201 .75 LIVI320T12 1.65 LM340K18 1.25 LM725N 2.50 MC 14409 14.50 LM301 .45 LM320T15 1.65 LM340K24 1.25 LIVI739 1.50 MC 14419 4.85 LIV1308 (Mini) .95 LM324N 1.25 78L05 .75 LIVI741 (8-141 .25 1 4511 .95 LM309H .65 LM339 .75 78L12 .75 Ll\/1747 1.10 74C1 51 1.90 LM309K(340K-5>85 7805 (340T5) .95 78L15 .75 LM1307 1.25 LIV1310 .85 LM311D(Mrni) .75 LM340T12 .95 LM340T15 .95 78M05 LM373 .75 2.95 LM1458 LM3900 .65 .50 9000 SERIES 9301 .85 95H03 1.10 LM318(Mini) 1.75 LM340T18 .95 LM380(8-i4PiN).95 Ll\/I75451 .65 9309 .35 9601 .20 LM320K5{7905)1.65 LM340T24 .95 LM709(8,i4PiN).25 NE555 .35 9322 .65 9602 .45 LM320K12 1.65 LIVI340K12 1.25 LM711 .45 NE556 NE565 NE566 NE567 .85 .95 1.25 .95 MICRO'S, RAMS. C PU'S, E-PRC 74S188 3.00 1702A 4.50 )MS 8214 8224 8.95 3.25 INTEGRATED CIRCUITS UNLIMIT ED MM5314 3.00 8228 6.00 7889 Clalremont Mesa Boulevard, San Diego, California 92111 MM5316 3.50 2102-1 1.45 8251 8255 8.50 10.60 (714) 278-4394 (Calif. Res.) SPECIAL DISCOUNTS 2102L-1 1.75 8T13 1.50 All orders shipped prepaid No minimum Total Order Deduct 2114 9.50 TR1602B 3.95 8T23 8T24 1.50 2.00 Open accounts invited COD orders accepted $35 -$99 10% TMS4044- 9.95 8T97 1.00 Discounts available at OEM Quantities California Residents add 6% Sales Tax *1^V ' Z.^^ 15% 2107 3-4 4.95 All IC's Prime/Guaranteed. Ail orders shipped same day received. saui - !t>iuuu 20% 8080 8.95 8212 2.95 2708 Z80P 9.50 10 8.50 24 Hour Toll Free Phone 1-800- 854-221 1 American Express / BankAmericard / Visa / MasterCharge Circle 180 on inquiry card. BYTE luly 1978 193 /g aCfipif CT Mates with two rows ot 025" sq. or OUulVCI dia posts on patterns of 100" lilR/IDCDC c^eoters and shielded receptacles JUIVIr tnO Probe access holes in back. Choice Part No. 924003-1 8R 924003 -06R 92400S-18R 924005 -06R 924006-1 8R 924006-06R of 6" or 18" length. No. ot Contacts Lengtl) 26 18" 26 6" 40 18" 40 6" 50 18" 50 6" Price $ 5 38 ea. 4.78 ea. 8.27 ea. 7.33 ea. 10.31 ea. 9.15 ea. HIIIMPFR ^"'"^^ '° ^'' tioards for instant JW"'' f" plug-in access via socket-connector Ijr JinpoQ jurnpers. 025" sq posts Choice nCMUCno of straight or right angie. Part No. 923863-R 923873 -R 923865-R 923875-R 923B66-R 923876 -R No. ot Posts Angle 26 26 40 40 50 50 straight right angle straight right angle straight right angle Price SI .28 ea. 1 52ea 1.94 ea 2.30 ea. 2.36 ea. 2 82ea. DIP JUMPERS Males with stanttard 1C sockets 24" lengtt) • Fully Assembled i Tested PRICE t 1.92 3.02 40 m end sgl end 924106-24 924112-24 924116-24 924122-24 924126-24 924132-24 334 330 S.20 553 Also Available in 12" and 36" lengths 32 CYlft CY1.84 CY2A CV201 CY2 50 CY3.27 CY3.57 CY3A CY491 CY7A CY5.18 CY6.14 CY6.40 CY6.55 CY12A CY14A CY19A CY18 43 CY22A CY30A CRYSTALS I TKESE FREaUENCIE!; ONLY J; FREQUENCY CASE 1 00OMH2 1 8432MH2 2 0OOMH2 2.010I^Hz 2500MH2 3 2768MH2 3579545MH; 4.000MH! 4.916MHz 5.000MHz 5 185MHz 6 144MH2 6400MHz 6 5536MHz 10 000MH2 14 3I818MH; 18.000MHz 18.432MHz 20 000MH2 32 OOOMHz HC33 5 95 HC33 595 HC33 595 HC33 1.95 HC33 4.95 HC33 495 HC33 495 HC18 4 95 HC18 4 95 HC18 4.95 HC18 4 95 HCt8 4 95 HCie 4 95 HC18 4.95 HC18 4.95 HC18 495 HCt8 4.95 HC18 495 HC18 4.95 HC18 4 95 TRIMMERS 10MM size trimmers -.394" Dia. Part No. 1-9 10-24 25-49 100 + TR-11 (valve) 35 .30 25 20 Resisrance values . 10Q. 500 IK ?K. 5K 10K ?0K. 50K. lOOK. ?00k 1 meg TRIMPOTS Single-Turn - 1/2 Walt Square - Top Ailjust - 3/B" Size Pan No. 1-9 10-24 25-49 50-99 63P(value) .99 .89 .80 .70 Resistance Values -50. too 500 IK,2«,5K. 10K.?OK 50K lOOK, 200k, 500K, 1 meg ^j 15-Turn - 3/4 Watt Rectanguiar Side Adjust 3/4" x 1/4" Size Pari No. 1-9 10-24 25-49 50-99 43P(value) 1.35 1.25 1.20 1.15 50. 100.500, IK, ?K,5k, I0K.Z0K,50K, lOOK, 200K, 500K, 1 ™g 1/16 VECTOR BOARD Par! No 64P44 0S2XXXP 169P44 062XXXP 64P'14 D62WE B4P4-1 062Wt 169P44 062WE t69P84 062 WE 169P44 062WEC1 Rsn ?07 fiSO ?m 7 00 hlM 7,00 9 23 Model P180 Includes 2-100' spools #28 AWG wire wrap wire Supplies insul. pingandpreci Model P180 $24.50 REPLACEMENT WRAP BIT forPISOSlit N Wrap No. P180A $12.95 each Replacement wire-wrap wire for P180 #28 AWG (pkg ot 31 $2.75 each W2B-2-A green W28-2-B red W2S-2-C clear W2a-2-D blue INSTRUMENT/ CLOCK CASE IniectJon molded unrt. Complete with red Oe;el $3.49 CPU 8080A CPU MICROPROCESSOR COMPONENTS 8212 8214 8216 8224 8228 8251 8255 8-8it Input/Output Pfionty Interrupt Control Bi -Directional Bus Driver Clock Generator/Driver System Controtler/Bus Driver Prog Comm. Interlace Prog Periph. Interlace $29.95 CDP 1802 CPU 10,95 Z80 CPU 4.95 3650 MPU 7.95 MC6800 MPU 4.95 MC6810API 126 x 8 Static Ram 5.95 MC6820 Penph. Interlace Adapter 5.95 MC6821 Periph, Interface Adapter 9.95 MC6830L8 1024x8 Bit ROM 10-95 MC6850 Asychronous Comm. Adapter S19.95 24.95 26.50 19 95 5.95 7.95 11.50 14.95 14,95 [The Incredible "Pennywhistle 103" 25B 2101 2102 2107/5280 2111 ?112 2114 2)14L 2114-3 21UL-3 7489 aioi 21L02 74200 9342! FUM'S 1 Static X 1 Dynamic 4 Sialic « T Static I 1 Dynamic : 4 Static I 4 Sialic 1 Slatic 450n5 1 Sialic 450ns Low Power 1 Static 300i!s 1 Static 300(15 Low Power 4 Sialic [ 4 Static ( 4 Static 4 static S ! 49 MK4027 (UPD4U) 1 MK4116iUPD416| 1 TMS4044-45NL 4 DYNAMIC 16 PIN DYNAMIC 16 PIN STATIC "STna 2513(2140) 2513(3021) 2516 MM5230N 1802M !80M 2e50M ROMS Characlei Generator (upper case] Cli a racier Generator (lower case) ChariCier Generator 2048 Bil Read Only Memory USER MANUALS CDP1S02 Manual 2S0 Manual 2650 Manual 1702A 5203 B2S23 82S115 B2S123 743287 2708 2716 T.I 2716 Intel 6301-1 6330-1 ;41li6 7418H MM5013N MM5016H MM5017N 2504T :?518 ■^519 2522 2534 2525 2527 2528 2529 2048 X 204B « 32x8 16K PROMS Famous Famous OpenC Bipolar Tristdte Static EPROM EPROM EPflOM Ui Stme Hi(jc)..(; j6 I 1 Onen C Bmnij' 12 > ' ni Ocen CoHecioi 56 1 1 TTL Open Collaaor SHIFT REGISTERS 1024 Bit Accumulator Dynamic 500/512 Bil Dynai-ic Dual 50O,'5l2 eit Uvnamic 1024 Dynamic Hex 32 BiI Sialic net ■lO Bii Static Dual t.i: Bil Siaik' 512 Oynamtf 1024 Dynamic Dual 256 Bit Static Qua' 250 Static Dual 24n Bit SUlic OuaU 80 'in Static 1024 Static Fito" 4X4 Rflgistfi' UARTS 3QK BAUD S 5 95 TELEPHONE KEYBOARD CHIPS Ay-5-9100 $14 95 flY-5-9200 14 95 Ay-5-9500 4 95 Ay-5-2376 14 95 HD0165 7 95 74C922 9.95 SPECIAL REQUESTED ITEMS (CM CHIPS ICM7045 E24.95 ICH7205 19 95 ICM7207 7 50 ICM7208 19.95 ICM7209 6 95 NMOS READ ONLY MEMORIES MCM6571 S13M) MCM6574 13 5(1 MCm57^ 13 50 MISCELLANEOUS MC3061P 'jICUOBI ' "1[;i-lU8L8 PARATRONICS Logic Analyzer Kit Model 100A $229.00/kit pV GAME CHIP SET I AY-3-3500-1 Cliia:intl 2.01D MH2 Crystal $7.9S[ 95H90 s:'-- 00 .'set I I I I I 1111 • «■« 1 Analy/es any type ot digital system Cfi'-'ci'^ data rates in excess o( 8 million words per second I Trouble Stiool TiL. CMOS, OIL. RTL Schonky and MOS tamilies . Displays 1 6 logic states iiplo 8 digits wide I See ones and zeros displayed on your CRT. ocial 01 hrtxadpctmal \o«"'^t ■ Tests circuits unOei acr'jai ope-aling conditions ■ Easy to assemble — comes with step-by-step construction manual which includes 80 pages on logic analyzer operation. (Model 100A Manual ■ $4 951 ,»^r'|^t1HiP""» Some applications are - Troubleshooting microprocessor address, mstruction, and data flow ~ Examine contents ot ROMS - Tracing operation of control logic - Checking counter and shift register operation - Monitoring 1/0 sequences - Veritying proper system operations during testing PARATRONICS TRIGGER EXPANDER - Model 10 Adds 16 additional bits. Provides digilsl delay aid qualilication of input cl and 24-bit trigger word, — Connects direct to Model lOOA for i ntegrated ui I 1G Kit - S229.00 Ba»plate - S9 95 Model 10 Manual - 3Vi-Dlglt Portable DMM • OverloaO Protected • 3 high LED DiSDlay • 8aMerv or AC oppralion • Aiilo 7e;oiny • lin-j IVa I Cfiin ffiSolulrO'i • Ovtiange ifdding • 10 meg input impendence ■ DC Accuracy l-o typical Rang*s; DC Voltage - 0-lOOOV AC Voliage O-lMOV Freq Responw 50-400 h2 DC/AC Current 0-lOOmA ResislacCB 0-Ki meg ohm Size 6 ■: .44 < ? Accessories: AC Adapter BC-28 S9.Q0 Rechargeatile Batteries BP-28 20.00 Carrying Case LC-28 7.50 "95 100 MHz 8-Digit Counter 20 Hz-100 MHz Range , four power souces, i e battenes ' 10 or PZOV witn * charger l?V w tti auio lighter adaqter and eiteinal 7,2-lOV power supply "'x-io" $134.95 • 6' LED Display ■ C rysta I -cpnt rolled timet • Fully Aulomatie ■ Portable — completely self -contained « 5 63' ACCESSORIES FOR MAX 100: MotillB Chargar Eliminator use power Iron) car bahery Model 100 — CLA S3.9S Charger/Eliminator use 1 10 V AC Moilel 1D0 - CAI S9.35 63- Key Unen coded I KEYBOARDS I Hexadecimal Encoder This Is a 63-key, terminal keyboard newly manufactured by a large computer manufac- turer. It is unencoded with SPST keys, unat- tactied to any kind ot PC board. A very solid molded plastic 13x4" base suits most applica- tion. IN STOCK $29.95/each 19-key pad includes 1-10 keys, ABCDEF and 2 optional keys and a shift key. $10.95/each $5.00 IVIinimum Order - U.S. Funds Only California Residents - Add 6% Sales Tax Spec Sheets - Ki I978A Catalog Avallable-Ssnd 3S< stamp J Sameco PHONE ORDERS WELCOME (415) 592-8097 MAIL ORDER ELECTRONICS - WORLDWIDE 1021 HOWARD AVENUE. SAN I:ARL0S. CA 94070 Advertised Prices Good Tliru July $129.95 Kit Only The PennywlHStle 103 is CKRshle ol recorrlmg ^nXi to ana Trom audio laps withDu: nilical soeeil requireinenls lor tue fetonler and il is able lo roinmiiincate liracHv with another modern and teminal lor teleptione tiamimnq snri coimmitiicabon; toi ttie deal In addition , it is free ot critical aHju^lieiits am is tiiiill with non -precision readily availaQle parts Data Transmlnian Method . , Frequency Shitl Keying Itill-ilupiex ihallOuole' selecJaDtei MaKimum Data Rata 300 Baud Dala Format , , Asynctironous Seiial netufn to 'nsrlt level lequnei hetween eacb cbaracteri Receive Channel Freijuencies . .2025 Hz lor space 3?35 Hz lor narK Transmil Ctiaitnel Fteguencies . .Swilcn selectalile Low inornali lQ7fi so^ce 1370 TiatW High 025 spate "i'-'S km fleceivG Sensilivity .46 ilb ti accousiically en..' , i iio-ninal ftiljustsbie I'O i' t ih n Receive Frequency Tolerance Oigital Data Inlerlace to .'ll 'II .Frequency reterence auion^licaiiv .t.i|.isls alio* 'or opeiation belwee'i 1800 h/ rfiti ?.lf)D H .EIA RS-33?C or ?Q ■nA cufiRm iQOi t'Bi'KWi opioisolaled and iion w\fu 120 VAC single Dhasf! 1 ..All c I All c ■ipotie ■myle b R"qiiiie . fl V0^^ Audio Oscillator fieguency Goiintef and O' QscHmscope te the 3 rd Hand $9.95 each 'Leaves two hands 'ree (nr working * Clamps on edge ot bench, lable or work bench ■ Position board on angle or flat position fo' --oldenng or clipping ' Slufrty .-^iii tii'ium consfr^'Ciion tor hobbyist, -nanulacturer or .school rooms DIGITAL STOPWATCH ■ BNgni 6 Digii LEO Display • rtmes 10 S9 minutes 59 59 - • CfVEtai Controlled Time Ba't ■ Tfiree StopwatcWs m One limes Single Event — Split S Tiyii .Sim4 5 t? 15 « 90 i4';ounceii • Uses 3 Penlite Cells Kit - $39.95 Assembled — $49.95 Heavy Duly Carry Case $5.95 Stop Watch Chip Only (7205) (19 95 3y2DIGIT DPM KIT W j^W New Bipolar Unit • Auto Polarity • Auto Zeroing • Low Power . .5" LED • Single IC Unit Model KB500 DPM Kit $49.00 Model KB503 5V Power Kit $17.50 JE700 CLOCK MAN n I] h 1] f "lout diid KIT ONLY $16.95 JE803 PROBE Ifie Lo:|i{, Prnlif .s ,i unit *ni( ri iv fo' tne -tiosi p.ir' indesoenjibte m irouDie ihooliig logic lamiiips ni DH RlL CMOS It de'ivc'; tne oowei n needs to oceiale directly o't ol ine riicuil unoei tesi dia*inija scani 10 mA mai- ituses^MANi readDui to indicate any n' trie toiiowinq slates 3^ tnesesymUois 'Hi i iiOWi mPuLSl' P Tus Probe can dPiect niQ*! ttpauenr-y ouise<. m 45 Mh? II c?r> I tip used ,11 MOS Ipvci-, ii- $9.95 Per Kit printed circuit board VI 5V 1A Supply This IS a standard HL oowf supply uS'ing tbe well knni LM309K regulator ^C to proviOe a soltO 1 AMP o' curreni ai volts We try to make things easy lot yoo by p'Ovidn everyttiing you nepc! in one package including Ihe Itanlwa '" °°' JE225 $9.95 Per Kit PROTO BOARDS PROTO BOARD 6 S15.95 [6 long X 4 wide) wnHnnninmi PROTO CLIPS 14 PIN S4 50 16 PIN 4 75 24 PIN 8 50 40 PIN 13.75> 194 BYTE July 1978 SN7400N SN740m SN7402N SN7403N SN7404N SN7405N SN7406N SN7407N SN7408N SN7409K SN7410N SN74nN SN741;N SN7413N SM7414N SNM16N SN7417N SN7430N SN7421N SN74Z2N SN7423N SN74Z5N SN7426N SN7427N SNM?9N SN7430N 5N7432N SN7437N SN743SN SN7439N St4744(M SN7441N SN7442f( SN7443N SN7444N SNT44SN SN744eN SN7447t, SN7448M SN74S0N SN74S1N SN74S3N SN7454N SN7459A SN7460N Sn;470N CD4000 CD4001 CD4M2 C04006 CIM007 CD4009 CO40I0 C0401 1 CD401? CO4013 CD40)4 CO4015 CD4016 CO4017 CD401B CD4D19 CD4020 CD40J1 C04o;2 C04K3 CO4024 Cn402S CD40?6 74C02 74CM 74C08 7-1C10 74C14 74C20 74C30 74C4! 74048 "IC73 lM3uU»i LM301H IM301CN LM302H I.M304H IM305H LM307CN H LM30eM LM308CN LU309H LM309K LM3tKN LM3ltH LM3nN LM317K LM318CN LM319N LM320K-& LU320K-5 2 LM3raK-12 LM320K-15 LM320K-18 LM320K-24 LM3MT.5 LM3aT-5 2 LM320T-8 LM3!l)T.t2 LM3MT-15 LM320T-ia LM320T-24 LM323K 5 LU324N LM339N LM340K-5 LM340K-6 LM340K-8 LM340K-12 LM340K IS LM340K-1B LM340K 24 LM340T-5 7400 TTL SN7472N SN7473N SN?474N SN7475N' SN7476N SN7479N SN74eON SN74e2K SN7483N SN7485N SN74B6N SN74B9N SN7490N SN7491N SN7492N 5N74g3N SN7494N SN7495N SN7496N SN7497N SN74tOON SN74I07N SN74I09N SN74116N SN74121W SN74122N SN74I23N SN74125N SN74126N SN74132fc SN74136N SN 74 14 IN SN74142N SN74143N SN74144N SN74145N SN74I47N SN74t4aN SN74150N SN7415tN SN74I53N SN74154N SN74155N SN74157N C/MOS CD402e CD4rr?q CD4030 CO4035 CD4040 CD4041 C04042 C04043 C04044 CO4046 CD4047 ca*tm CD4049 C04050 CD4051 CD4053 CD4056 CD4059 CD4060 CD4066 CO4068 CP4069 74C00 74C89 74C90 74C93 74C95 74C107 74Ct51 74C154 74C157 7-1C160 74C161 300 2 15 3 ?5 3^5 LINEAR LM340T 8 ' 25 LM340T 1? 1 25 LM340TI5 1 25 IM340T.16 1 25 LM340T-24 I 25 LM350N 1 00 LM351CN 65 LM370N 1 15 lM3r3N 3 25 LM377N 4 00 LM380N t 25 LU380CN 99 LM381N 1 79 LM382N t 79 NESOIN B 00 NE510A 6 DO NES29A 4 95 NE531H 3 00 W536T em NE540L 6 00 NE55DN 1 30 NESSSV 99 NE556 99 NEseoe 5 00 NE56ie 5 00 NES628 5 00 W565H 1 75 NE£fi5N 1 25 NE566CN 1 75 NE567H 1 25 NE567V 99 NE570 10.50 LMr03CN/H 45 LM709H .29 LM709N 29 LM710N 79 LM71IN 39 LM723H 55 LM723N 55 '^B 3N74160N St474161N SN74162N SN74163N SN74164N SN74165N 5NM166N SN74167N SN74170N SN74172N SM74173N SN74174N SN74176N SN74176N SN74177N SN74179N SH74iaON 5N74181N SN74182N SN74t84N SN74185N SN74iaaN SN741SeN SN74190N SN74i9tN SK74192N SN74193N SN74194N SN74195N SN74196N SN74197N SN74198N SN74199N SN74200N SN74^51N SM74279N SN742B3N SN74284N SN742B5N SN74365N SN74366N SN74367N SN7436BN SN74390N SN74393N C04070 CD407I CO4072 CD4076 CD4081 004082 CO4093 C04098 wet 4409 MC14410 MC144n MCU4t9 MC14433 UC14506 MCI 4507 MCI 4563 MCI 4583 CO4508 CD4510 CD45n CD45I5 CD4518 CD4520 CD456 BUGBOOK® Continuing Education Series S17.00 par tat fits Msigncd to THE S5S nMER APPUCATIONS SOURCEBOOK WITH EXPEWMENTS bf HMirdM. Barlln W3HB jrjpus pho'ogrsDfiV. THIS ifoiurrw Hill intiodura you tD in< tituilous wm c^p — tni inlgpfm Mnntsn diu ttrirunSs dc ind your micocompuU' curiifli loopj. tnil th« RS IIK inlerfKt sbndarii Piniculifly fT05 ■M, Wt4HYJ. MwMui k. IHm Hare IS the tnwli inn puts i all logWu' BesKHs nivmo muctt > (MM ire Dwr imre arc i saxes ol natnmtnis rn lafiy^ tne ruMr comtfatety ItlHOW tna Xidy 10 go BOW cfuo p.n Oy p« and mlroUUMS you 10 ma Miit 60 rmcrocompum arcuils D3fiy un-qua lastt* iniartjcaa syflam It is ^acofimeralafl iha — ■ - — "" "■■ KM BUGROOK III 1e 8UDB0OKS I & II WITi euGBOOK III IHSTRUCTOH'S MANUAL Nacasuiv N>i insirucnO'i ol Bugbooii > and i enpanntants suggesnansloitu'lher tMing p dliilil aiedrDflics * musl lo' sal'-laacning im BUGIDOK V and VI S19.D0 H' nl OP AMP MANUAL by Hmird M. Birlln W3HB tg.QO gugbooK vi loun). at 2S S3.00 t, OnM ~G Urawi, l>IMr H taqr, JMMhta A. tltM J^J']? EipanmanS ui i»||m Bacl'omcs aOSOA micnicomouiar prograip WMA mcrocomuula' inlailidng *n intaijiJtBO iMKoacli lo salt tiasic digital g4«c1ron>cs. Dteaaboiriling 3M 8060* mtarlacmgipFognmrning - —-' - was tfia digital concapW ol BuflboM V into a treMirwni ol nuKr orogiaipming tnfi interfacing Dalai) 9r Utornarv T4Cie5 74Ct64 74C173 74C1 92 74C193 74CI95 74C922 74C923 74C925 74C926 80095 LM733N LM739N LM741CM LM741CN LM74 )4N LM747H LM747N 79 LM748H 39 LM748N 39 LU1303N 90 LM1304N 1 19 IM1305N 1 40 LM1307N 85 LMiSlON 2 95 LM1351N '65 LMI4UN 1 75 l.M145eCN.'M 59 MC1488 1 95 Mcuag t 95 LU1496N 95 LM 1556V 1 75 MC1741SCP 3 00 LM2901N 2 95 LM3053 t 50 LM3065N 69 LM3900N(3401| 49 LM3905N 89 LM3909 1 25 MC5558V 1 00 lM7525N 90 LM7SMN 75 80386 495 LM75450 49 75451 CN 39 75452CN 39 75453CN 39 75454CN 39 75491 CN 79 75492CN 89 75494CN 89 nC415i 5 95 RC4I94 5 95 RC4195 4 49 OBUO BD80 mtgi aisa .03 m^f .05 0047;iF 05 04 03 OVF 05 04 03 022Hf 06 04 03 047,if 06 04 ,035 1«F 12 10Q VOLT MTLAR FILM CAPACITORS 022mt 047mf 10 .07 27 22mt +20% WPPED TANTALUMS (SOLID) CAPACITORS 28 23 17 1 5i3SV 30 26 28 ■>'■. 17 2 2/2SV 31 27 28 23 17 3 3/'25V 31 27 28 ,23 17 4.7/25V .32 28 28 ,23 17 6e/25V .36 31 .28 23 17 10/25V 40 35 28 23 17 15/25V 63 .50 MMIATUflE ALUMINUM ELECTROLmC CAPAaXOftS 47/5CV 1 0/50V 3 3/50V 4 7/25V 10/25V 10/50V 22 '25V 22/50V 47/2 47/50V 100/25V 10D/50V 220/25V 220/50V 470/25V ■ iooo/iev 2200r16V AxiRl LMd Ridlil Lwd 1 0./I6V 1 0/25V 1,0/50V 4 7/1 6V 4 7/25V 4 7/50V 10/16V 10/25V 10/50V 47/50V 100/16V 100/25V 100/50V 220/1 6V 470/25V Circle 200 on inquiry card. BYTE )uly 1978 195 Whsl s Sew? PUBLICATIONS Literature Available for Individuals Interested in Voltage Control Equipment New BITS Catalog Offered The new BITS personal computer publications catalog is now available from BITS, 70 Main St, Peterborough NH 03458. The 13 page illustrated catalog is a comprehensive listing of over TOO personal computing books, all evaluated by the editors of BYTE. The books cover such topics as: funda- mentals for the novice and knowledge- able; reference and resource publi- cations; the art of computer program- ming; programming languages; the computer artist and musician; building your own computer; fun, games and foolishness; and many other areas of interest to the personal computer user. Write for your free catalog." Circle 598 on inquiry card Computer Interconnections From Hewlett-Packard A new application note. Computer Interconnections, describes methods by which Hewlett-Packard HP 1000 com- puter systems and HP 9825 desktop computers can be interconnected to serve together in a wide range of instru- ment control measurement and analysis applications. It is available free of charge from Hewlett-Packard. The appli- cation note, AN 201-6, describes linking the two computers via different com- munications techniques: HP-IB (Hewlett- Packard's implementation of IEEE stan- dard 488-1976), RS 232C and an HP 3070A terminal. Example programs and flowcharts depicting program-to-program communications for ihe different net- works are included. Contact Inquiries Manager, Hewlett-Packard, 1507 Page Mill Rd, Palo Alto CA 94304.* Circle 599 on inquiry card. Electrical Engineering Fundamentals A Programmed Review for Electrical Engineering is a review of electrical engineering fundamentals. Its primary emphasis is on solving the type of prob- lems found on the Professional Engineering Examination. Each problem has been selected to illustrate a specific concept. Background material, in the form of tables, formulas, charts and graphs, provides all the necessary infor- mation to solve the problems. At least one solution is given for each problem. The book covers all the basic principles of electrical engineering. Special con- sideration is given to two significant areas: the field of digital logic and the study of engineering economics. An introductory section includes addresses of state licensing boards and guidelines for exam preparation. An extensive bibliography rounds out the volume. The book is written by James H Bentley and Karen M Hess PhD and is published by Van Nostrand Reinhold, 450 W 33rd St, New York NY 10001. The price is $14.50." Circle 600 on inquiry card. Hand Portable 10 Channel Printing Data Logger Catalog A recently published 12 page bro- chure describing a high resolution printing data logger, Model PDL-10, is available from Datel Systems Inc, 1020 Turnpike St, Canton MA 02021. The PDL-10 offers a simple, low cost ap- proach to measuring, scanning, and logging analog voltages. Ten input channels are provided, along with a 4'/> digit panel meter, a 7 column ther- mal printer for instant hard copy print- out, scan electronics, and a 99 minutes or seconds scan interval clock. Input connections are made through con- venient rear panel terminals. This color brochure details electrical and physical parameters, operating instructions, block diagrams, application notes, and ordering information." Circle 601 on inquiry card. This 60 page powerstat variable trans- former catalog PI 78 consolidates descriptive and technical data on the complete product line. It gives ratings, dimensions, performance curves and schematic connection diagrams in an easy to read format, and includes metric equivalents for universal use and easy reference. For a free copy write to the Superior Electric Company, 383 Middle St, Bristol CT 06010." Circle 602 on inquiry card New Software Buyer's Guide A new publication. Packaged Soft- ware Buyer's Guide, is said to include 44 pages of important software infor- mation and can be helpful to any businessman who is contemplating pur- chasing such a system. The guide is reported to give the prospective software buyer an in depth analysis of the following subjects: how to buy a software package for small business computers; how to buy a general ledger software package; the accounts receivable package; the accounts payable package; the payroll software package; and the inventory control package. Price is $15 from MIC, 140 Barclay Center, Cherry Hill N) 08034." Circle 603 on inquiry card. Computer Accessories Catalog This catalog contains a wide variety of word and data processing supplies and equipment including: magetic tapes, cassettes, cards, cartridges, floppy disks, disk packs, paper tapes, rolls, continuous forms, thermal quiet paper, storage cabinets, containers, racks, reels, vertical format tapes, punches, splicers, auto- matic winders and more. Available from Computer. Accessories Corp, 21 1 New York Av, Huntington NY 11743." Circle 604 on inquiry card. 196 )uly 1978 ©BYTE Publications Inc S-100 32K STATIC MEMORY BOARD features: 1. FULLY STATIC - usable with all DMA devices. 2. BUFFERED - with noise suppressed control inputs. 3. MODULAR - populated in Ik Increments. 4. RELIABLE - single source +5V regulator 5. PROM COMPATIBLE - monitors available on request. AVAILABLE EITHER IN COMPLETE KITS OR ALREADY ASSEMBLED UNITS WHICH HAVE BEEN FULLY TESTED AND BURNED IN. BARE BOARD $38°° KIT ASSEMBLED 8K J270OO $296'» 16K $440«) $465" 24K $580M $6120i> 32K $695»» $740«' niCES QUOTED ARE FOR SOOns MEMORIES KITS MID ASSEMBLED UNITS INCLUDE DOCUMENTATION DEC* LSI-11 16K MEMORY BOARD • QBUS— FULLY "BUFFERED AND STATIC NOISE SUPPRESSED • MODULAR •PROM COMPATIBLE • ADDRESSABLE TO 128K WORDS • MAPPABLE IN 4K INCREMENTS ASSEMBLED, StN $1199'"' COMPLETE "" $110900 LAROeST 4 FASTEST STATIC MEMORY AVAILABLE SlOO EXPANDABLE MOTHER BOARD • 8SL0T EXPANDABLE BACKPUNE— in line male and female connectors enable backplanes to be plugged together, or the female may be used In place of an extender board. QUIET — ground plane decouples all signal lines. RELIABLE— SAE 8100 phenolic body, gold contact connectors. COMPLETE $66 00 ASSEMBLED $8900 UNIVERSAL "U DESIGN" WIRE WRAP BOARDS ALL BOARDS ARE G 10 GLASS EPOXY HAVE Vcc AND GROUND PLANES. PUTED THROUGH HOLES, 4 GOLD PLATED EDGE CONNECTORS No. 1 BEST ON THE MARKET MICRO CPU CARD WITH S ISO 8US. 3 ON BOARD REGULATORS FITS ALL STAN DARD IC SOCKET CONFIGURATIONS 1700+ HOLES SI'E 5 ilO »„„„! $23« No. 2 UNIVERSAL BOARD FITS 86 PIN SOCKET mlH 10' CONTACT SPACING MADE BY LEADING COM PUTER MANUFACTURER AS IN HOUSE' BOARD 1600+ HOLES SIZE 4 7/8 <;S/8' 57'' SlOO EHENDER BOARD wilh connector A MUST for trouble- , 1 1 7 95 shooting your Computer boards * A / BUILD YOUR OWN LOGIC PROBE 24 TO-92, SMALL SIGNAL DARLINGIONS » • qi: AND 24 LEDS.-ALL FUNCTIONAL only ^4' MAXI SWITCH KEYBOARDS UNENCODED MOUNTED ON GIG 6USS EPOXY BOARDSA BUCK METAL FRAME KEEPS KEY SWITCHES SECURELY IN PLACE. No. 1 -53 key main keyboard -10 auxiliary & cursor control keys -11 key numeric pad Bank of 5 auxiliary power and control, rocker arm switches one of them lights up. $3995 WIRE WRAP SOCKET CONNECTOR FOR NO. 1 KEYBOARD $295 BUILD YOUR OWN PAPER TAPE READER l/IO" CENTER STACKABLE PHOTO TRANSISTORS 10/$96o GOLD WIRE WRAP SOCKET STRIPS MAKE UNIVERSAL END AND SIDE STACKABLE WIRE WRAP BOARDS 12 PIN„ 3 LEVEL 48C 14 PIN,„ 2 LEVEl 4gC 3 LEVEL 56c 7 PIN STRIP TOP VIEW No. 2 '53 key keyboard 1 auxiliary power/control DPDT rocker arm switch $29" BEIGE METAL FRAME MOUNT FOR NO. 2 KEYBOARD $995 SOCKET CONNECTOR FOR NO. 2 KEYBOARD $29 TTL COMPATIBLE REED RELAY 400 OHMS $149 7/$975 OUR NEW ASCII KEYBOARD HAS ON BOARD UV PROM, A MAIN KEYBOARD SECTION OF 58 KEYS, A HEX PAD OF 15 KEYS AND 16 MORE PERIPHERAL KEYS. 89 KEYS TOTAL & ASCII ENCODED for only $99" POWER SUPPLY PARTS DIODES EDGE VIEW METER CHARGE DISCHARGE SCALE READS 20.0,40 MOVEMENT -1-60, I20mA «'OAQ 135 OHMS ■^i.*^ 4K STATIC RAMS 2114 650ns TMS40454 450ns HM 472114 300ns 600m« J6.25 300nm SIO 95 200mw $11 95 l.a SOCKETS LOW PROFILE-SOLDERTAIL 8 PIN 14 PIN 16 PIN 22 PIN 24 PIN 28 PIN 40 PIN GOLD INLAID 10/11,59 10/11,89 10/J1,99 5/$l,69 5/$l,89 5/J1-99 4/Jl,99 TIN 10/$1,35 10/11,49 10/11,59 5/Jl,49 5/tl,59 5/H,69 4/$l,69 MINIATURE 16 BUnON PADS 4i4 MATRIX ENCODED «> -I 05 $is lor that pmlessioral loach CARBIDE DMU. Rin For P.C BMIID WORK ASSORTMENT OF SIZES FROM NO, 55 TO NO, 70 5MIX/J7« 10MIX/$12«9 lOOMIX/JSS" IN4001 50V al lA IN4003 200V al lA IN4007 lOOOV al lA IN250 GOV al 20A IN3909 50V al 30A 6c 8c 12c 95c J1,Z5 BRIDGES FAST RECOVERY AVALANCHE BRIDGE IN4436.T 200V al lOA FULL WAVE MINI BRIDGE' WITH TAB PR lOE lOOV al 12A J425 TERMINALS $3 75 5% ZENERS IN4733A 5 1V 1« IN4739A 9 1V 1» IN4744A 15V 1» 39c 39c 39c VOLTAGE REGUUTORS UA723 VARIABLE 2V to 3 7V 78L05 5V at lOOmA TO 92 340T 6 6V at 1 AMP TO 220 PWSIIC 38c MEIAL 69 c 3/98C 2;98c PASS nANSISTORS MIE3055 lOA PLASTIC 2N3055 lOA TO 3 2N5301 30A TO 3 89c 95c Jl 95 PROTECT YOURSELF, INSTALL AN ELECTRONIC CROWBAR CIRCUIT IN YOUR POWER SUPPLY CROWBAR SCR C220O 400V at lOA SI 75 OPTO DEVICES PHOTO TRANSISTORS SIMILAR TO FPT 100 4/98c PHOTO DARUNGTONS MOTOROLA 4/98c ULTRA HIGH SPEED PHOTO DETECTOR 5ns RISE TIME $3's EXIREMELY SENSITIVE IIGHI ACTIVATED SCR t'lggeoble by flashlight at several tiun (Jred yards $2» INFRA RED DETECTOR ULTRA LOW LEVEL PIV 7V I ma $495 HEWLETT-PACKARD JUMBO-RED HIGH EFFICIENCY OH BOARD SUIUS INDICAIOI LED 6/$l»o SOUR CELLS 2ii2cm I30ma $1" ea. 10/$99(i LED LAMP EXTREME WIDE ANGLE VIEWING 3/98C 10/$2«5 GOLD EDGE CARD CONNECTORS No. 1 SAC185/2 2 SINGLE ROW, IS PIN CONNECTOR WITH 156" CON TACT SPACING 99c i No. 2 SAC22S/2 2 SINGLE ROW, 22 PIN CONNECTOR WITH 156 CON TACT SPACING 99c i No. 3 2VH31/ICB6 31 SOLDER LUG CONNECTOR WITH 125- CONTACT SPACING 99c HIGH VOLTAGE DIODES EPOXY 1500V at 1 AMP 10/Jl 99 EG250 2500V at 350mA 95c HV60EL 6KV at 25iiiA $1 95 SUBMINIATURE 20KV at 100mA S2 95 3-1/2 DIGIT LCD.'s LIQUID CRYSTAL DISPLAY No. 1 4' CHARACTER WITH CONI^ECTOR $6 95 No 2 IMIS MiNIAIUFtI I C D IS IDfAl FOB POCKEl SI?EO INSIRIIMIMS $395 WIRE WRAP POST ? LEVEL 10 98c 100 17 40 I000'J64 00 3 LEVEL 10 Jl 25 100 $8 60 !000'$7? 00 HI-REL GOLD WIRE WRAP SOCKET PIN 10/51" 1000/$79«> LIST PRICE 29c OP AMPS SINGLE 709 II 741 1: DUAL MC1458 QUAD LM3900 39c 49c DIODES IN9I IN270 IN914 IN3600 IN4148 15c 12c 15c 15c lOc TMNSISTORS 2N2222 12c 2N3904 12c 2N3906 12c 2N3053 49c D/A CONVERTER SIGNETICS NE5008 $9« SUB MINIAIURE CRYSTAL FILHR 455 KHZ WITH DAIA $295 NO BACK ORDERS FREE DELIVERY BY UPS <"< ^s orders only YOUR PARTS OR IMMEDIATE REFUND OR OY SURFACE MAIL, IF SPECIFIED — CALIF, RES ADD 6% SALES TAX MONEY BACK GUARANTEE (mds and led devices excluded, $20 MINIMUM FOR UNDER 8 HOUR PROCESSING SEND MONEY ORDER, CERTIFIED OR CASHIERS CHECK, SORRY' WE CANNOT ACCEPT PURCHASE ORDERS. CODS, PHONE ORDERS OR CREDIT CARDS FOREIGN ORDERS CANADA PUFRIO RICO U S possessions add us $3 M AIL OTHER ADD U S t' 00 IMMEDIATE SHIPPING ON CHASE MANHATTAN FIRST CITI2ENS CASHIFRS CHECKS S CANADIAN POSTAL MONEY ORDERS LEDS YELLOW. GREEN. OR AMBER (SPECIFY COLOR) 3/88C LOS ANGELES (213) 967 46)1 LMN ELECTRONICS 1042 E GARVEY AV, W COVINA CA (VINCENT & SAN BERDO FWY ) tUE -^ SAT 10 fl - ClOSID SUN i MON DROP INTO ONE OF OUR LOCATIONS PORTLAND 1503) 646 4044 WIZARD OF PARTS 8225 SW CIRRUS Dfi BEAVEfiTON ORE (KOU BUS CNTR WASHINGTON SQUARE) F. Reichert Sales 1110 E. GARVEY AVE. W. COVINA, CA. 91790 DENVER 1303) 573 5214 ELECTRONIC LOLLIPOP 5643 N BROADWAY DENVER, CO il2S & SSIh AVE ) ALL ITtMS SUIIECT TO PRIOR SALE Circle 207 on inquiry card. PRICES SUBJECT TO CHAmE BYTE July 1978 197 Circle 247 on inquiry card. CLjbBrc[m boards MB-1 MK-8 Computer RAM (not S-100), 4KX8 uses 2102 type RAMs. PCBD only $22.00 MB-3 1702A EROM Board, 4KX8, S-100 swilchable address and wait cycles, kit less PROMS $58.00 MB-4 Basic 4KX8 ram, uses 2102 type rams S-100 buss. PC board $24.96 MB-6A Basic 8KX8 ram uses 2102 type rams, S-10Q buss, PCBD $24.95 MB-7 16KX8, Static RAM uses uP410 Protection, fully buffered. KIT $375.00 MB-8A 2708 EROM Board, S-100. 8KX8 or 16KX8 kit without PROMS $75.00 MB-9 4KX8 RAM/PROt^ Board uses 2112 RAMS or 82S129 PROM kit without RAMs or PROMs ,$72.00 10-2 S-100 8 bit parallel I/O port, % of boards is for kludging. Kit $46,00 PCBD $24,95 10-4 Two serial I/O ports with full handshaking 20/60 ma current loop: Two parallel I/O ports. Kit $130. PCBD $24.95 VB-1B 64 X 16 video board, upper lower case Greek, composite and parallel video with software, S-100, Kit $125.00 PCBD $24.95 Altair Compatible Mother Board, 11 x 11 '72 x Vb". Board only . $40.00. With 15 connectors . $90.00 Extended Board full size. Board only $ 9.00 With connector $13.00 SP-1 Synthesizer Board S-100 New Low Price Kit $135.95 82823 $1.50 PRIME DEVICES 823123 1.50 82S126 1.95 8080A $11.50 82S129 1.95 8212 3.75 828130 3.00 8214 6.50 82S131 3.00 8216 3.95 MMI6330 1.50 8224 4.00 4N26 .75 8228 6.95 4N27 .75 8251 9.95 4N2E .75 8255 9.95 LM323 2,96 21L14 8.50 /YfTnC /inc. WAMECO INC. MEM-1 BKXB fully buffered, S-100, uses 2102 type rams, PCBD $24.95 Mather Board 12 slot, terminated, S-100, board only $30.95 CPU-1 8080A Processor board S-100 with 6 level vector interrupt PCBD $24.95 RTC-1 Realtime clock board. Two independent in- terrupts. Software programmable. PCBD ..$23.95 EPM-1 1702A 4K Eprom card PCBD $24.95 EPM-2 2708/2716 16K/32K EPROM CARD PCBD ...$24.95 SHORT MOTHER BOARD Short Version of QM-IA 8 Slots PCBD $25.95 2102AL-2 Prime 260 NSEC $1.70 2102AL-4 Prime 450 NSEC $1,30 2708 Prime (National) $10.00 1702A-6 AMD Prime , $3 50 1702A Intel Not Prime (2US) $2.00 2501 B $1.50 1488N $1.50 2502B 1.50 1489N 1.25 2504 1.50 MC4044 2.25 2507V 1.60 8038 3.90 2510A 1.50 5320 5.95 2517V 1.50 5554 1,90 2518B 1.50 5555 2.50 251 9B 1,50 5556 2,50 2621 1,50 6055 1,25 2522 1,60 5312 4,00 2525 1,50 MH0026 1,50 2527 1.50 MH0026 1.75 2532V 1.50 MH0028 1.90 2529 2.75 5262 .50 2533V 1.95 2101 3.50 m 419 Portofino Drive San Carlos, California 94070 Please send tor IC, Xistor and Computer parts list MIKOS PARTS ASSORTMENTS All piece parts for assembly of Wameco and 8SM PCBD's. All Factory Marketed Parts. Order PCBDs right. Mikos #1 Parts for MEM-1 PCBD with prime 2102AL-4 450 nsec rams. Less PCBD $105,00 Mikos #2 Parts for CPU-1 PCBD with prime 8080A 8212's and 8214, Less PCBD $62.00 Mikos #3 Parts for MEM-1 PCBD with prime 2102AL-2 250 nsec rams. Less PCBD $128.00 Mikos #4 Parts for QM-IA with super low loss gold plated connectors. Less PCBD $52.00 Mikos #5 Parts for RTC-1. Less PCBD $40.00 Mikos #6 Parts for VB-1B less molex connectors and PCBD $65.00 82S06 $1.00 8T26 $2.00 82S07 1.00 8T28 2.00 828 50 1.00 8T34 2.50 82S62 1.00 8T37 250 75324 1,50 8T38 2.50 75325 1.50 8T74 1.50 8T01 2.50 eT80 2.50 8T09 1.25 8T90 2.50 8T10 2.50 8T95 2.30 8T13 2.50 8T96 2.45 8T14 2.50 8T97 1.50 8T20 2.50 8T98 2.00 8T23 3.00 8T110 2,00 8T24 2.50 567 1.50 Check or money order only. If you are not a reg- ular customer and your order is large please send eitlier a cashier's check or a postal mon- ey order, otherwise there will be a delay of two weeks for the check to clear. All items post paid in the U.S. Calif, residents add 6% tax. Money back 30 day guarantee. We cannot accept re- turned IC's that have been soldered to. Prices subject to change without notice. $10 minimum order. $1.00 service charge on orders less than $10. COMMERCIAL GRADE EQUIPMENT- HOBBYIST PRICES!! TAPE DRIVES MODEMS AND PHONE COUPLERS lAMPEX MODEL TMX TAPE DRIVES with built-in NRZl formatter. 806 BPI, 9 track, 12 IPS, 8" reel includes 8 bit CPU controller diagram and 8080 interface instructions. Ideal for microcomputerist who wants back-up mass storage and access to IBM-tvDe svstems via standardized W mag tape. . .3750 •AMCOMP SERIES 2700 TAPE DRIVES: current model, vacuum column control; like new: (2) MODEL 2749 - 45 ips, 800 BPI, 7-Track, 10" reel $1500 (3) MODEL 2769 - 125 ips, 800/1600 BPI, 9-Track, 10" reel. . .$3000 •TAPE DRIVE FORMATTERS, "Pertec Standard Interface": (3) AMCOMP SERIES 2900 NRZl/Phase Encoded, 25-125 ips.. 01500 (1) PICO MODEL 1011, NRZl, 800 BPI FORMATTER/ CONTROLLER for PDP-1 1 $2000 MODEMS, Full-Duplex, Auto Answer circuitry, by VADIC CORP. BELL 103 Type (300 Baud) Circuit Card only $75 BELL 103 Circuit Card, Power Supply, Case, Connectors $125 BELL 202 Type (1200 Baud) with Reverse Channel Transmission from $125 DB-25 MALE CONNECTOR + 2 wire cable to Phone Jack $4 PAPER TAPE READER (ADDMASTER 601-1): 150 cps, LED sensors read 5-8 level tapes, bi-directional stepper njotor, includes TTL serial interface plus 8080 parallel interface instructions. Requires -i-5V & 24V $90 DATATEST PROGRAMMABLE AUTOMATIC CIRCUIT CARD ANALYZER MODEL 4000A S2000 MODEL 4700 $6000 DIABLO SVSTEMS Spare Circuit Cards for HyType Printer, Series 20 h- 40 Disk Drives; complete but defective or below current revision level , $20 ASai ENCODED KEYBOARD from HyType Termmal, never used $60 TELEPHONE ACOUSTIC COUPLER $30 SELECTRIC TERMINALS • SELECTRIC I/O TERMINALS (by GTE/INFORMATION SYSTEMS). In' eludes 8080 interface plus software ASCII translation and I/O driver routines 15" carriage, interchangeable type spheres & carbon/fabric ribbons. Built-in modem optional, MODEL 5541 (IBM Corresoondence Code. 2741-tvDe terminal) $895 MODEL 5550 (Corres. Code w/350 char, line buffer memory + built-in cassette drive for data storage/off-Mne printing/word processing. . '.$1495 MODEL 5560 (ASCII Code, with cassette tape drive) $1495 • IBM SELECTRIC TYPEWRITER with magnets, switches & magnet driver PCB (from GTE/IS Terminal) plus instructions for 8080 printer/driver interface. Typewriter mechanism complete, cleaned & adiusted $325 Aluminum Case & Power Supply (-I-24V, ±12V, +5V («' 5V) S75 • CONVERT IBM OFFICE SELECTRIC to I/O Typewriter; solenoids, switches, wire harness, magnet driver PCB plus instructions + 8080 Interface Diaa. $150 • IBM PIN-FEED PLATENS for 15" SELECTRICS (13 1/8 pin-to-pin) new $50 • IBM SELECTRIC APL TYPE SPHERES (Specify EBCDic or Correspondence Code), new $15 • FORMS TRACTORS, Moore Variable-width "Form-A-Liner" new $50 for 15" Carriage IBM SELECTRICS used $30 ■ DIGITAL CASSETTE DRIVE (from GTE/IS Terminal) 2400 baud, FWD/ REWIND/STOP circuitry, plus tape head, but no read/write electronics. . .$25 ■ INTERDATA 8-BIT MINICOMPUTER (Model One), includes full front panel, 4K core memory (16K addressable), plug-in teletype port; optional serial I/O + Tape Drive Controller PCB's. software $300 ■ RIBBON CABLE 50 Strand X 4' long terminated with 3M edge connector (.10" spacing) + paddle card $3 • AC LINE FILTER 10AMP RFI (110/230V) with Line Relay + Fuses new$15 Call or write for details, quantity discounts, order forms, AH orders shipped from stock — no back orders, no substitutions. All equipment is shipped insured FOB Palo Alto vuithin 7 days after check clears or COD jprder is received. M/C & VISA cards accepted. PACIFIC OFFICE SYSTEMS, IXC. 2600 EL CAAIIXO REAL. SUITE 502 PALO ALTO. CAIJF. 94306 Tel: (415) 321 - 3866 90 day warranty against defects in material or work- manship on all used equipment. Full documentation included PLUS interface instructions where indicated. Availability subject to prior sale. Prices may change without notice. 198 BYTE luly 1978 Circle 296 on inquiry cartd. Close-out Purchase by MiniMicroMart Save up to 50% on the famous TDL SMB System Monitor Board iiu!iua»uiiiiiiiTmTWHmiTmimiii»iiii TWO SERIAL PORTS, PARALLEL PORT, MONITOR ROM, 2K OF RAM, AND CASSETTE INTERFACE ON ONE BOARD. FEATURE ARTICLE IN APRIL BYTE AVAILABLE BARE BOARD, PARTIAL KIT, COMPLETE KIT, OR ASSEMBLED AND TESTED - SMB Bare Board w/const, manual . 05-1002-0 $ 49.95 SMB Board, all IC sockets, addressing and buffering components, ppwer-on jump circuits and FEATURES Does power-on jump to monitor Two fully programmable serial ports (1 10 to 9600 baud RS232or20-milloop) Programmable 8-bit I/O port Provision for 1200-baud audio cassette interface Provision for 1 K or 2K on-board static RAM Provision for 2K ROM (TDL Zapple Monitor or, with minor changes, one 2708 or 2716 EPROM) support circuitry for ROM/RAMs 05-2002-1 99.50 SMB Board, same as above but incl. all components for one parallel/one serial interface05-2002-2 1 1 9.50 SMB Complete Kit, incl. parallel port, two serial ports, audio cassette interface . . 05-3002-0 147.50 SMB Assembled and Tested 05-4002-0 1 97.50 Zapple Monitor ROM for above .... 05-9002-0 29.95 IK RAM (two EMM 4148's) for above 05-6002-0 29.95 Add $2.00 for shipping and insurance. RAMS/EPROMS Prime 2708 EPROMs full spec, 450ns $9.95 each EM M4200 4K Static RAMs $10.95 each T. . 4K Static RAMs 4Kx1 TMS4044's (as usecJ in Heath boarcis) $8.98 each 1Kx4TMS4045's $9.89 each 4Kx1 TMS4027-25's (16-pin) $3.95 each CLOSE-OUT SPECIALS S-100 16K Static RAM Boards for EMM 4200's (bare boards) $24.95 S-100 1702 EPROM board (holds 8 PROMs) complete kit $49.95 S-1 00 4K Static RAM Board Kit(less2102's) $19.95 ASCII Keyboards Used surplus Excellent condition Control functions Upper/lowercase Ready to use $49.95 Teletypes (used) - IMMEDIATE DELIVERY - KSR-33's from $495.00 ASR-33's from $695.00 CONTACT US FOR ADD-ON MEMORY FOR TRS-80 LOTS OF OTHERS Write for close-out and surplus catalog for fantastic prices on TV Typewriter III boards and kits, cursor boards, screen- read boards for above (can also be used with SWTP CT-1024); also, 25 x 40 video boards, UART boards, and Baudot-to-ASCII conversion boards. S-100 Prototype Boards General-Purpose $18.95 Wire-Wrap Version $19.95 IBM 735 I/O Selectrics (used) from $395.00 MiniMicroMart, Inc. Circle 251 on inquiry card. 1618 James Street, Syracuse NY 13203 Phone (315)422-4467 BYTE luly 1978 199 Whafs New? SYSTEMS Microprocessor Card for S-100 Bus INFO 2000 Disk System Upgrades Heatiil Rechargeable batteries and charger I* Measures DC Volts, AC Volts, Ohms and Current I* Automatic polarity, decimal and overload I indication I* No zero oNJjustment and no full-scale ohms adjust • Battery-operated ~ NiCad batteries; also AC line operation. • Large LED display tor easy reading without interpolation ■ Sizs: 1.9'Mk2.7'Wk4"0 Parta & iftbor guwanlvad l yav Tilt ataod option % *.» • Laathwcase S-100 BUS EDGE CONNECTORS Of* M5-15 MINISCOPE ft»cntig—blw Btlfft A Ctingv Unit 15 megahertz bandwidth. External and Internal trigger. Time base — ,1 mlcrosec 10 0.5 Sec/dli sellings •3%. Battery or line operaiion Automaric & line sync modes Power consumclion < 15 watls. Ilinga i 1% 11 PROBE 1« PROBE IC Mith the pufchaseo' SCOPE and the MENTION ol this MAGAZINE > MS-21S Dual Trace Version of MS-1S S39S.00 ^ 3 LEVEL GOLD WIRE WRAP SOCKETS SIOO-WWG 50/100 Cent. 1 26 ctrs 3 LEVEL WIRE WRAP 025' sq posts on 250 spaced rows. GOLD plated 1-4 59 10-24 $4.00 $3.75 $360 S100-STG 50/100 Cont 125 ctrs DIP SOLDER TAIL on 250 spaced rows for VECTOR and IMASI motherboards GOLD plated. 1-4 5-9 1024 $4.00 $3.75 $3.50 RG81G 50/100 Com. ,125 ctrs. DIP SOLDERTAILon 140 spaced rows for ALTAIR motherboards GOLD plated. $6.00 S 1 00 -WWN 50/100 Com 125ctrs 3 LEVEL WIRE WRAP 025' sq posts on 250 spaced rows NASGLO tin nickel plated 14 59 10 24 S3 50 $3 25 S3 00 SIOO-STN 50'100Cont 126 ctrs DIP SOLDER TAIL on 260 spaced rows for VECTOR and trvlASI motherboards NASGLO tin-nickel plated. 14 69 1024 $3 60 $3 25 $300 R681-3 60/100 Com 125 ctrs PIERCED SOLDER EYELET tails GOLD S7 35 Other Popular Edge Connectors R644-3 22/44 Cont WRAP tails GOLD $471 166 ctrs WIRE r^rr special ^^r^^y^^^^AACS2 100 for •14"" - ■ 16CS2 100forM6" 14plnCS2 t0lor'2" 16plnCS2 8lor*2" These low cost DIP sockets mil accept both standard width plugs and chips. Foi use witri chips, the sockets offer a lOw pfoliie height of only 125" above the board. WRAP POST for 042 dia. holes (all boards on this page) T-44pkg 100 S 2.U T-44 pkg 1000 S14.00 A-13 hanflinslallmg tool S Z.BO XX)3] A Woodley A^o Sepulveda CAo 91343 TermS( ViSA. MC. BAC check. Money Order. C D . U S Funds Only LA residents add 6% sales tax Mini- mum orQp $10 00 Orders less than $7b 00 include 10% shipping and hjndlmg. excess refunded. Just in case please'inciude your phone no "Sorry.no over the counter soles" Good thru Aug15. 1978 phone orders welcome (213) 893-8202 oEuanc ir latest brochure. lonal inquiries 3/ $1.00 An / tin nn FREE PROBES FREE PROBES FREE PROBES Circle 304 on inquiry card. BYTE luly 1978 201 Whsfs New? 2708 and 2716 EROM Programmer for KIM-I Light Pen Literature Available A new model LP-316 super high sen- sitivity light pen for long or different focal distances has been introduced by Information Control Corp, 9610 Bellanca Av, Los Angeles CA 90045. The pen features a finder beam to locate the target, and patented touch sense acti- vation to allow the pen to be held back away from the screen for better visi- bility. Luminous sensitivity can be ad- justed down to 0.5 footlamberts. The LP-316 carries a full year warranty. For more information and a complete catalog of ICC light pens, contact the company." Circle 645 on inquiry card. Wide Applications for New 30 MHz Dual Trace Scope The LBO-520 oscilloscope is a 30 MHz dual trace instrument with a fixed delay line. According to the manufac- turer, it has been designed for applica- tions requiring high accuracy signal viewing, single shot trigger, built-in delay and high sensitivity. It is further re- ported that the unit has 5 mV sensitivity to facilitate accurate signal viewing from video cameras and other low level sources. The instrument's 1 shot trigger, on both channels, assures instant capture of transient phenomena without guess- work or double takes. A 20 ns per cm sweep capability combined with a rise time of 1 1.7 ns lets the observer view the fastest signals in typical small computer systems with ease. The 120 ns built-in delay line permits easy viewing of the leading edge of a pulse or pulse train for quick determination of signal character- istics. Contact Leader Instruments Corp, 151 Dupont St, Plainview NY 11803." Circle 646 on inquiry card. Single Sided Wire Wrap Boards in Metric Sizes Single sided integrated circuit plug- gable wire wrap boards are available in metric dimensions from Garry Manufac- turing Company, 1010 Jersey Av, New Brunswick NJ 08902. Both single sizes (series SMP64) and double sizes (series DMP64) are included in the new line. The SMP64 accommodates 20 16 posi- tion integrated circuit chips while the DMP64 size will accept 55 16 position integrated circuit chips. The boards are supplied with either 16 position molded sockets or 16 position patterns of indi- vidual socket/terminals for maximum heat dissipation. They are designed to provide wire wrapping terminals on the component side, allowing the wire wrap boards to be spaced interchangeably with standard printed circuit board rack assemblies. The boards are supplied with or without a 64 position right angle lO connector (Garry P/N MPS64-PD). They are available at prices ranging from $2 to $3 per integrated circuit socket position." Circle 647 on inquiry card. ^m KM tern cai KM KM K3I 1 11 '4 EM trm ■m KM ■M-'--i2m:-^' 3 ^^^B>'to U Optimal Technology Inc, Blue Wood 127, Earlysville VA 22936, announces a programmable read only memory programmer for the KIM-1 microcom- puter with provisions for programming both the 2708 and 2716 (5 V only) EROMs. By using the KIM-1 monitor, any programmable memory starting address may be specified up to 65 K. Additionally, any starting address within the address space of the programmable read only memory may be specified along with the number of bytes to be programmed. The programmer has a verify mode which confirms that all bits have been programmed correctly. Com- pletely assembled and tested, the pro- grammer is packaged on a single printed circuit board and the connector is fur- nished. The program will run on all computers which utilize the MOS Technology 6S0X microcomputer. One and a half lO ports are required. Price is $59.95." Circle 648 on inquiry card. New Soldering Flux The flux is called Spec-Master and is available as a liquid, cored solder, paste solder and soldering paste. It is intended for use where a perfectly clean and safe residue is necessary after only a mild water wash. According to the company, the flux is available in strengths strong enough to solder stainless steel yet safe enough to yield electronically clean sur- faces after water washing. It is said to be nonflammable, nontoxic, nonirritating and nonfuming. For further information write: Nokorode Soldering Products Division, M W Dunton Company, POB 6205, Providence Rl 02940." Circle 649 on inquiry card. 202 luly 19780BYTE Publicilions Inc POLY PAKS PACTS wccrsucp POLY PAKS INTRODUCES THE FIRST MAGAZINE RETAIL STORE FOR THE ELECTRONIC MAIL-ORDER HOBBYIST! ************ ** ********** **** ***** * t "RED** LED READOVrS: t I » low « xoc each t Sli* D«Mriptton Sale * .127" MAN-3" Sfoi Jl.OO f MAN-4* 2 fdi $1.19 1 * Cat. No. ■¥ a 7S1B90 f n TC1503 I a 7tl273 X " 7S3093 Z o 7S3161 X □ 7S3512 ■k Q 7S2949 •{i □ 7S!29S0 id 713483 o 7S2485 f □ 7ft22S6 X 'Common Anodo MAN-1- MAN-72 oquat- MAN-74 equal** FND359*- FND500* FND507* 727-Dual" 727-DuaI* 747- "Common Cathodo $1.00 $1.19 $1.19 $1X»0 $1.50 $1.50 $2.50 $2.50 $1.95 HEXADECIMAL MICROPROCESSOR n LMlircJ::.%:u^Zper^tlA AND CONTROL r\ jttiK rip-^UtTCy roiir^H^*^ KEYBOARD KIT' Cs^ 20keys. 16encoded.4exlernaito «****"«"»"*' •*• * . ^"^ be assigned by user. Output 4 bit "'■■ ^ '"^ binary. Also, an EXCLUSIVE o 4 bit binary/haxadacimal output plus strobe! FEATURE. . . 4 leds dispiav the • Newl Improved design! Saves you time! binary output. TTL/CMOS • Keyboard pre-assemMed onto PC board! compalible. requires +5. - ««. ^- 12VDC. Complete kit! Nothing Cat. No. 7»S009 Hexadecimal Kit $34.95 else to buy! With instructions. Cat. No. 755010 Hexadecimal Wlred$39.9S $ > —— »■■■■ ■•■■•••••••••»••■«[ ********************************** DISCRETE LEO'S 6 for $1.19 ' . Cat. No. Description Similar to Order m multiples o 752 135 Jumbo Red MV50S3 i of « of each type! □ 7S1944 Jumbo Yellow XC556Y D 7S213B Jumbo Green XC5S6G njUMBO .34" h ^ 752785 Medium Red XC22 a MEDIUM .24" ^ JJIlS? ■Medium Green XC22G | Micro Red XC209 a MICRO .21" Q 78 1948 Micro Yellow XC209Y (T0-18> o 7S2140 Micro Green XC290G ■ COMPUTER IT'Vooo \ GRADE D 13.000 ■CAPACITORS^ U:S8S ! Order by C.t. Mo. ' "'JS" ; 7t5U2.ndv.l„.! = JJOJJ WVCD Sale ■ 50 $2.75 a 40 2.25 - 50 2.75 12 1.50 75 3.95 30 2.S0 ■ 30 3.95 ■ li^HIEIIi KETBOARD& EIVCODER KIT Cat. No. 755001 KH $69.95 Cat. No. 7S5O02 Wred $7S.OO Outputs standard 7 bit ASCII; interfaces with most data systems. ■ Uses MOS Encoder ROM! Kejboardpre-asscmbled onto PC board, 2 key rollover, Electronic « 7 led Test Feature! shift lock and carriage return. 4 modes: Normal, control, shift. » ^ ^^^y Iteyboard' ltl'/rV,'^"\'"„';l- Additional. functions can be assigned by user *5 - , Encodes 128 ASCII Characters! 12VDC, 200 ma. Negative or positive logic, jumper selectable ^ |„..rlarP5 with ALTAIR IMSAI, and more! LED's display the ASCII code, e 10 buy! Size: I.T' x 5 1/2 x 1 1/4". S Iba. ■■■>• Vjwxk Poiver ICs J 3a itjf n ii_H_iDa.]i ir inr.iDanciaG I l^^\ BRIDGE rectifiers: § 2 AMP 6 AMP 10 AMP 25 AMP Q PIV («7S1346) (fr7$24S6) (07S2447) (((752273) H □ 50 $ .59 $ J8 $1.05 $1.20 y a 100 .65 .99 1.15 1.25 Q o 200 .69 1.19 1.29 1.95 t: ] a 400 .89 1.40 1.79 2.95 Q □ 600 .99 1.69 1.95 3.95 U i □ 800 1.19 1.95 2.25 4.95 H ] o 1000 1.25 2^5 230 5.50 ^ ] Orer by Cat. No. Amperase and VoHase D OQPnnnaGEXonnnanDiioLDan 5PCCTIIA- TWIST * Twisted pairs of brightly CABLE n Cat. No. 753680 48 cond. 2 ft. $1. a Cat. No. 754081 32 cond. 2 ft. $1.98 O-XXK "ouDnnt jLi k laDLir k j ]DnaDi:iCT[XJOCopD[.]ncoiioc kt RIBBOS CABLE AT THIN PRICES • Ultra-flat! • 28 AWG! • Single color! Indexed! Order by Cat. No. 7S3939 and conductors Cond. Sale o 20 8 ft. $1.98 n 26 6 ft. $1.98 □ 34 5 ft. 51.98 n 40 4 ft. $1.98 u 50 3 ft. $1.98 Order By Cat. No. 7S3667 & Type No. Typo Sale 74LS00 $.33 74LS02 .32 74LS04 .35 74LS06 .32 74LS10 .32 74L511 .32 _ 74LS13 .64 D 74LS20 .32 ~ 74LS21 .32 74LS22 .32 74LS27 .39 74LS30 .32 74LS32 .39 74LS37 .45 74LS3S .45 74L542 1.19 » L 744.547 .99 * C 74LS74 .49 * C 74LS90 .89 J C 74LS92 .89 J C: 74LS93 .89 * n 74LS109 .58 * a 74LS112 .58 I G 74LS113 .58 J a 74LS114 .49 ********** ***** **** * ** ** ****** Type Sale 74LS132 1.19 : 74L5138 1.24 74LS139 : 74LS151 1.25 ' 74LS153 . 74LS15S 1.2s ' 74LS1G0 1.47 : 74LS161 1.47 : 74LS162 1.47 ■ 741.5183 1.47 : 74LS168 1.68 74LS169 1.68 : 74LS173 1.68 ' 74LS174 1.05 - 74LS190 1.77 ' 74LS191 1.75 : 74L5192 1.75 "^ 74LS193 : 74LS195 ' 74LSig7 " 74LS257 1.35 ■ 74LS26e .54 " 74LS366 .66 ■ 74L5368 .69 a 74LS390 HAlirDT COMPUTER IHnLTlTESTER 1000 ohms per volt precision, movement» diode protected against burnout. Measures DC volts 0-15-160-1000: AC volts 0-15-150-1000; DC current 0-150ma:reaistanceX1000. Sensitivity 1000 ohms/volt AC-DC. Uses penlite cell, not included. Sine 2^/b k .IVi X I^'h'*. Wt. 5 ozfi. Cat. No. 7S3921 » 0«00«»» — •■••••••■•••••••••9696»96« I POLT PAKS "CHIPS" AWAY J I IC ASD CRYSTAL PRICES! I I Order by Cat No. 794048 and Type No! t ZType Description *-'- * • □ICM7205 Stopwatch f DAY3-B500-1 6 TV Games • □MMSSSO 4'f2 DIgtt DVM • □8038C Volt Control Osc. sun • al aKR2376-139 BCD Encoder Rom IKR2376-ST ASCII Encoder Rom esOMHz Prescaler 350MHz Prescaler Touch Tone Chip Char Gen. (sIm 2513) Freq Counter pair 3h Digit DVM/DMM 60 Hi TImebase IC Timebase Xtal Touchtone Xtal Stopwatch Xtal 1C90DC a95H90DC OMC14410 □ MK2002P O7207A/7208 a|CM7107 □MMS369 □3.579MHz D LOOM Hz □3.2768MHz — #66 • — 8»*«690 ■6— » >»6 ■•••••• — C-MOS Type CD4000 CD4001 CD4002 CD4006 CD4007 CD4O08 CD4009 CD4010 CD4011 CD4012 „ C04013 Q CD4015 a CD4016 ~ CD4017 CD40ia CD4019 CD4020 CD4021 Sale 5.29 .29 1.29 Order By Cat. No. 752320 & Type No. Type Sale D CD4022 1.19 a CD4023 .29 n CD4024 .79 n CD402S .34 L] CD4027 .69 a CD4028 a CD4029 D CD4030 a CD4033 n CD4035 a CD4040 G CD4041 n CD4042 n CD4046 n CD4049 G CD4066 n CD4071 1.19 .49 1.60 MICROPROCESSORS! memories; SUPPORT! Order by ICG800L G 8080A □ Z80A □ 8008 □ 1101 o 1103 ^ 1702 A rJ 2102-Ll □ 2111 n 2708 11 MK4116 a MK4200P11 n MM5202 n MMS203 n MMS260 □ MMS262 □ 8212 □ 8216 □ 8224 a 8228 □ 8251 a 8255 Cat. No. 7S3459 and type Description 8 bit CPU 8 bit CPU, 2 usee 8 bit CPU CPU 256 X 1 Stat. RAM IK Dyn RAM 256 K 8 EPROM IK X 1 t-o-power RAM 256 X 4 Stat. RAM 8K EPROM 16K Dyn RAM 4K X 1 Dyn RAM, 3S0nsec 2K PROM 2K EPROM IK Dyn RAM 2K X 1 Dyn RAM 8 bit I/O port Bl-dlrect bus driver Clock Gen System cont. Communication Int Periph Inter Sale $19.95 11.95 24.95 9.95 .69 1.29 5.95 1.69 5.95 10.95 29SS 3.95 6.95 8.95 .99 .99 3.9S 3.95 4.95 9.95 11.50 11.95 I SILICON POWER STVD rectifiers; Order by Cat. No. Amperage and vottage. 50 AMP (a7S727) 12 AMP PIV (B7S727) D 50 " "" a 100 o 200 G 400 o 600 o SOO % .29 36 AS i .75 1.10 1.35 1.75 2J5 2.75 250 AMP (>I7<6SS) »4.95 6.50 7.50 •.SO 10.50 11.50 DIP SWITCHES Cat. No. G 75 3668 a 75 3669 G 753021 D 75 3670 n 75 3671 D 75 2677 ♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦ □ SN7472 Q SN7473 □ 5N7474 o SN7475 c, SN7476 □ SN7483 ;j 5N7485 □ 5N7486 o SN7490 u SN7492 c SN7493 n SN74107 □ SN74121 □ SN74t23 a 5N74125 □ 5N74132 n 5N74t45 □ SN74151 n SN74153 o SN74154 : SN74157 c SN74161 n SN74164 a SN74174 □ 5N74175 □ SN74181 ^ SN74190 □ SN74191 a SN74192 □ SN74I93 n SN74195 c SN74251 *4444444« : TTL'S « Type J « n SN7400 $C «. □ SN7401 ♦ n SN7402 ♦ n 5N7403 ♦ a SN7404 ♦ o SN7405 ♦ a SN7406 I a SN7407 I □ SN7408 « a SN7410 «. □ SN7411 ♦ n 5N7413 ♦ o 5N7414 ♦ 3 5N7417 ♦ D SN7420 ♦ □ SN7427 ♦ n SN7430 I :: 5N7432 i :: 5N7437 i n SN7440 « Li SN7441 « n SN7442 ♦ G SN7445 ♦ u SN7446 ♦ □ SN7447 « □ SN7448 ♦ Q 5N7450 ♦ n SN7451 ♦ a SN7470 ♦♦♦♦♦♦♦♦♦♦♦♦*« ♦♦♦♦♦♦ .26 .49 ♦ .39 ♦ .83 ♦ .89 ♦ .63 ♦ .63 ♦ .93 .88 1.95 ♦ 1.15 ♦ .99 ♦ .83 ♦ .83 .75 139 ♦«4444 EECO 10-POSITION BCD THUMBWHEEL SWITCH l-a-4-M Ut'D encoding: Positions labeled 0-7. F, L. 3 »Or IF coded for S. L coded for $4. 9 1, While numeriil.f on a black background. Eeco 800 (_] .series. IVa x 1 V4 x V3".• t • e Low profile, solder tail. ♦ ♦ ti 752123 8pl«minidip$ .17 ♦ ♦ n 751308 14 pin dip .19 * * D 751309 16 pin dip JZ2 T □ 783378 18 pin dip _._..^************ —.;•»««»»* * ° /»id7» iBptnoip ^9 ^ .******J{Sr'cTHOL* SKINNYTHIMS" J ; »♦♦ ♦♦♦♦♦«: «Ohiin **^*' ,„.«,lri>.T shi.fl _ ,_, Bt! I jD lO'/. ■'»"Tn\;ii i>""' "'2 '""^ * ♦ MOTHHRBOA te iK::s fSi-^fc -■';U«i*i5'^*:pi.~X«p."t edge_conne^ «n 2»"D lOK' M« TS 3863 25 turn upril***- J-r^ _- « m IMC 'VPEWEE" ,, BOXER FAN Quiet! Oelivera Audible n:s^'-s D S2.50 RD CONNECTOR 106 pins (53 each aide). Use with IMSAI & ALTAIR! 0.J26" pin clrs, goldplated %" wire wrap leads. Open ends, fit wide PC boards. 8 oza.Cal. No. 783987 "MICRO-TONE" 0^88 AUTOPATCH ^^ ENCODER KIT "" Only 2 l.'» s ! .V8 x i,'2", small enough t^) mount in a mike! Snap • Complete action bubble keys contact jn Its own Features output level control. _,_. _^., .. xtal controlled d i K i I a 1 1 y •^"•-*'''W''«*' synthesized tones, on-chip , Family! oscillator. Requires 4.5 to 5.5 ^ Frlanos! VDC. Complete kit! Nothing else to buyl Wt. 12 oz, • Cat. No. 754086 hit $26.88 EmerEency! Cat. No. 754087 wlred$32.9S I □ LM340T-12V X D LM340T-15V « □ LM340K-5V i a LM340K-12V « a LM340K-15V « o LM322N * a LM324N * a LM339N * □ LM377N Z a LM379N 1.19 1.19 1.19 1.19 1.19 1.19 1.19 1.19 1.19 t 1.191 .445 .69* .65 V 1.40 « .39* .22* -29* .42* .29 + .59* .69 X 1A9Z .351 1.19( .69* .75* 1.50« ■-i^^±±*:t****** ** □ LM3S0N a LM381N □ LM5S5V rj LMS5SV a LM565N o LMS67V L: LM703H a LM709H. N n LM710N n LM723N n LM741H,V. N D LM747H, N r: LM 1458V '- LM1800N I LM3900N 1: LM39009V LM7S491 ■; LM75492 ;J PA263 10 AMP POWER TAB SCR'S, piv sale TRIACS. QUADRACSrcatHo o !So ^H SCfl'S 751730 n 200 .88 Order by Cat. No. TRIACS 751448 d 400 1.19 and Voltage QUADRACS 7StS90 g 600 1.59 ■■■■■■■■■■■■■■ TRANSFORMER SALE ^^^^ a^of^i ■■■■«■■■ I ;&*"■">« pots- *>*.5o • Chrome handle and hnoH, **: «> "^ -r?!L!!!!i'*3«08A Cat. No. n 78 3399 D 75 3814 U 7$ 3412 n 75 4029 ri 7S3875 iXOVAC Primaries Output V. Al 500m lA 3 00m Metal encased Open frame Open frame Open frame Isolation Sate Each 51.98 52.49 51.95 $2.49 S1.19 ■■■■■■■■I Noi«e ^Level! Sleeve | bearings rated, for lClyea|8^b^e. XN^WiO Epo%^ Rectifiers For hTfI andComputersJiSVAC^ Cat. No. n 75 2377 □ 7S2378 □ 7S2379 □ 752380 n 75 2381 □ 752382 D 752383 1N4001 1N4002 1N4003 1N4O04 1N4005 1N4006 IN4007 PIV 50 100 200 400 600 SOO 1000 Price 10 lor $.65 10 for .75 10 lor .85 10 for .99 10 for 1.29 10 for 1.39 10 for 1.49 CATALOG WRITE POLY PAKS 1978 FOR FEATURING: • Computer Components! • Over 400 Assortments! • Digital Clocks. DPM's, and Stopwatches! a H(-FI Stereos-Speakers! • Solar Energy! Semi's! • Test Equipment! » Fiber Optics! Plus More n' More! ) COPYRIGHT 1978 - POLY PAKS INC Terms: Add postatre Rated: net 30 Phone : Wakpfifld. Mass. (617) 245-3829 Retail: 16-18 I'el Carmine St.. Wakefield. MINIMUM ORDER — $6.00 POLY PAKS P.O. BOX 942 -S7 C.O.D'i rtn P.O. BOX9az-s>7 c:^ LYNNFIELD, MA. Circle 303 on inquiry card. BYTE July 1978 203 Circle 353 on inquiry card. $199.95 AS IS IBM® Selectric-Based I/O Writers Excellent Hobby Printers $249.95 WORKING & CLEANED Series 72/731 Heavy Duty 8y2" Flatten All Solenoids Original Documentation While Supply Lasts SUPER SALE These terminals are from a large airline reservation system. They are heavy duty and were under continuous maintenance. The units have been in storage. We make every effort to ensure that all essential parts are included. Most work when plugged in. No warranties are given or implied. Conversion Kits. 1 . Conversion instructons, P C board for printer only using soft- ware approach $59.95 2. I/O kit makes the unit into a conversational terminal. Instruc- tions, P C board, components for a parallel or RS232 interface. Will work with any IBM terminal $249.95 3. Completely converted unit and assembled interface for I/O us- ing kit $999.95 Card reader by HP with RS232 interface $299.95 Printec line printers, parallel interface $1 500.00 Honeywell 516 & 316 mini's, make offer, Cables, used 11 conductor, 1 00 ft with connectors $9.99 Electronic parts and circuit boards 1/4 lb bag $4,99 Check, Money Order, Cash. Personal checks require 3 weeks to clear. No COD's. Units shipped UPS or PP collect. Prices Net FOB Tulsa SUPER SURPLUS SALES P.O. BOX 45944 TULSA, OK 74145 1-918-622-1058 4101 STATIC, ni IMHH «l9i>1 N-MOJ UM OENERAL DESCRIPTION P«i1 NumtMr 4«01 ita4KBemicon- ductor random ^ Bccoas memorY ll organizad as 4096 Vbit words. It it fully static and ' a«ds no clock or rafrash pulsas II raquiraa a ringia * 5 volt powar supply and is fully TTL com- patibla on input and output tinas. Tha 4601 ia packaged in a convanient ISpindual-in-lina package. FEATURES ■ Singla ^ 5V Powaf Supply ■ 4KX1 Organization ■ Raolacaa 4 t024xl Sialic RAh4a a Complalaly Static-No Clocks or Rafraah a 18 Pin Package a Access/Cycle Times 600 naac mak ■ 250 mw Typical Operating Power ■ Separata Data In and Data Out a TTL Compatible I/O a Tftree Slate Outputs a Data Bus Compatible I/O Function 4S04 STATIC, HI IN/OUT 1024i4 N-HOS RAM GENERAL DESCRIPTION Part Number 4804 It a 4K semicon- ductor random access memory organiiedas 1024 4-bii words. It is fully sialic and needs no clock or refresh pulses It requires a Single ' 5 voll power supply and is fully TTL com- patible on input and output lines. The 4804 is packaged in a convenient 18 pin dual-m-lme package FEATURES ■ Single • 5V Power Supply ■ 1Kx4 Organization ■ Replaces 4 1024x1 Sialic RAMs « Completely Static-No Clocks or Relresh ■ ISPin Package ■ Access/Cycle Times 600 nsec max • 250 mw Typical Operalir>g Power • Common I/O Bus ■ TTL Compatible I/O ■ Three Slate Outputs \Tr/ tPi-tek, inc. \ >/ 7806 Nwih 27th A«tnue V Phomix, AriionaSSOSI INTEGRATED TONE RECEIVER 7806 Noritt 27tli Atranue Pboania, Aritona 85031 16021 8060362 SigiMHo 2S04TA 1024 bit S.R. nwnary (I404A)... .SO MCM6571PCharacUf GifMrilar 9.^5 MCM6571APCh>ncUfG«Mnlor 9.95 MCI44aai>Tiliphon« Rotary Pulnr tO.S8 MC14419PToud< Pad Convener for 14400 4.2S MC1441 IP Baud Rata Ganaralor 11.88 MC14412VP CMOS Madam Chip ie.86 MU57109NNumbll loiai ntntfllns. Any iMunai wtH M W cMck, n*t en 50< 9.15 9.15 9.15 , 4.98 3.80 13.95 1.50 9.50 .60 •■mpoiclly ou< o> ilock on an Ham, ■n kKk MMr. it ■>• cannot inip In ] ■ notitiM O' 1M aKMCtM >M«plna «ai Fiin I poftae* MM carfl aiiih ■mien l I (fitpplnf onty In USA, CanaOa ar iw»k>9 <(irii cUH, ipacUi naiv«>in«, aic • ■capt CanaM an« Manlco) oMlmaM a' Low Group to High Group i« Row 1 - 697 Ht Row 2 - 770 H> Row 3 - 8S2 Hi Row 4 -941 Hi Column 1 - 1209 Hi Column 3 - 1477 Hi JULY SPECIAL -TIL 31 JULY MK5I02N-5 $33.00 Spec 40 600 :600 C.T. phone transrormer...$1 .50 P. C. BOARD TKMINAL STUIP Motd*d body oncloaAs postivo screw ocfrivotod clomp which will accomodate wire sizes 14-30 AWG. Gvitacts ar>d pins ore solder plated copper. Pins are on .200 in<^ (S.OSmM) for stortdord P. C. mounting. IQAmp rotirig. Compare our prices before you buy. 4pola TS-2S04 .99 8poU TS-2508 1.49 12 polo TS-2512 2.19 0^ 204 July 1978 © BYTE PuMiutions Inc Circle 381 on inquiry card. S.D. COMPUTER PRODUCTS AN EMPIRE IND CO P.O. BOX 28810B DALLAS, TEXAS 75228 EXPANDABLE EPROM BOARD 16K OR 32K EPROM $49 95 W/OUT EPROM Allows You to Use Either 2708s For 16K ot Eprom or 2716's For 32K of Eprom. KIT FEATURES: 1 All Address Lines & Data Buffered 2. Quality Plated through P-C. Board Including Solder Mask and Silk Screen 3. Selectable Unit States 4. On Board Regulation Provided 5. All Sockets Provtded W/Board WE CAN SUPPLY 450As 2708's AT $11.95 WHtN PURCHASED WITH BOARD. EXPANDORAM THE ULTIMATE RAM BOARD 32K FOR $475.00 -HSl.OO . 259.00 367,00 475.00 THE 32K VERSION USES THE MOS 4K LOW POWER RAM KIT The Whole Works - $79.95 Fult Buffered - on board regulated ■ reduced power consumption utilizing low power 21L02-1 500ns RAMS - Sockets provided for all IC's. Quality plated througfi PC board. I^«*!,.;f.^VA^ .'Ifn" J'^n°..r*^.'^L ^i BOARD TO A MAXIMUM OF 65K BOUNDARIES AND PROTECTION UTILIZES DIP SWITCHES P t, BOARD COMES WITH SOCKETS FOR 32K OPERATION SZ81 00 519.00 757.00 995,00 THE 64K VERSION USES THE MOS- TEK MKdlie RAM AND HAS ISK K tirFPI OF FITHFR BK BOUNDARIES AND PROTECTION & nrifiK'.; vnilR nPT%N RV MFRF UTILIZES DIP SWITCHES P. C. ?? purchasing" more' RAM JmPS IPrOPE'RMJoN'"'" '°''"' "" FROM SD COMPUTER PRODUCTS. LOOK AT THE FEATURES WE HAVE BUILT INTO THE EXPANDORAM! • NO WAIT STATES REQUIRED • NO CYCLE STEALING NEEDED • ON BOARD REGULATION • CONTROL, DATA S. ADDRESS INPUTS UTILIZE LOW POWER SCHOTTKY DEVICES • DESIGNED TO WORK WITH Z-80, 8080, 8085. CPU's ADD $50.00 TO ABOVE PRICES FOR FULLY ASSEMBLED AND TESTED BOARDS • MEMORY ACCESS TIME IS 375 ns • MEMORY CYCLE TIME IS 500 n • POWER REQUIREMENTS ARE: 8 VDC 400 MA DC 18 VDC 400 MA DC —18 VDC 30 MA DC • ON BOARD INVISIBLE REFRESH Low Cost Cassette Interface Kit $19.95 Features Play and record K.C. Standard 2400/1200 Hi tapes, 900 Baud. TTl I/O Compatible, Phase Lock Loop, Both 22 Pin ConneetDt and 8 Pin Moie» Connector. Comes parliilly afisembled OsciMalor and phase lock loop pre luned to K C. Standard. Selector switch sends cassette data ot autiliary input data to mi LEO indicates logic 1 level. 8K LOW POWER RAM $159.95 JLLY ASSEMBLED AND TESTED NOT A KIT isai — AHaif — S-100 Buss compalible, uses io* oowet alic 21L02-500ns tutly butlefeU on board regulated, lalily plated Itirough PC Board including solder mask IS dip s*itcfies tor address seiecl ■Add $30.00 for Q 250ns RAM operation Z-80 CPU BOARD KIT Complete Kit $139. :^^jii' '*■ CHECK THE ADVANCED FEATURES OF OUR Z-80 CPU BOARD: Expanded set of 158 instructions, 8080A software capability, operation from a single 5VDC power supply; always stops on an Ml state, true sync generated on card (a real plus feature!), dynamic refresfi and NMI available, either 2MHZ or 4MHZ op- eration, quality double sided plated through PC board; parts plus sockets provided for all IC's. •Add $10. extra for Z-80A chip which allows 4MHZ operation. NEW FROM S.D. "VERSAFLOPPY"' KIT THE VERSATILE FLOPPY DISK CONTROLLER ONLY $149.00 FEATURES: IBM 3740 Soft Sectored Compatible- S-100 BUS Compatible for Z 80 or 8080. Controls up to 4 Drives (smgle or double sided). Directly controls the following drives: 1- Shugarl SA400/4SO Mmi Floppy 2. Shugart SA800/850 Standard Floppy. 3. PERSCI 70 and 277. 4. MFE 700/750. 5. CDC 9404/9406. 34 Pm Connector for Mini Floppy. 50 Pin Connector for Stand- ard Floppy. Operates with modified CP/M operating system and C Basic Compiler. The new "Versaf loppy ■ from S.D. Computer Products provides complete control (or many of the available Floppy Disk Drives, Both Mini and Full S\i«. FDI771B-1 Single Density Controller Chip, Listings for Con- trol Software are included in price, FD 1771B1 CHIP ALONE $39.95 Z80 STARTER KIT LEARN COMPUTERS FROM THE START! SIMPLE, STEP BY STEP LEARNING. CONSTRUCTION, PR0GRAMMi;4G, OPERATION, MEMORIES, INTER- FACING, COMPUTING, AND CONTROLLING WITH AUDIO CASSETTE INTERFACE CAPABILITIES. Complete Kit includes: Key board and Display; Z80 Central Processing Unit; Instructions; Operation Man- ual; Learning Guides- Features: Powerful Z80 CPU with 158 instructions • 1024 Bytes (Expandable to 2048 Bytes ON BOARD) of RAM • 2 BiDirectional Input/Output Ports with Handshaking • Kansas City Standard Audio Cassette Interface for Program Storage • Hexadecimal Keyboard and Display • Wirewrap area for custom circuitry • S-100 Connector on board tor Memory and I/O Expansion • 2716/2758 PROM Programmer • -'Z-BUG" Monitor ROM (Including: Memory, Port and Register Examine and Change Com- mands; Breakpoints; Single Step Capability; Audio Tape Load and Dump; Execute user program Commands.) Many more unique features. The best computer edu- cational kit on the market , . . the complete computer and educational package for only (199.00. (Available June 1978)- INTRODUCING THE SBC-100 (The Z-80 Based. S-100 Single Board Computer) $349.00 FEATURES: • No Front Panel Needed • 2-80 CPU (2 or 4 MHZ) • IK RAM • 4 ROM/PROM Sockets tor 4K/8K of Memory • SYNCHRONOUS/ASYNCHRONOUS Serial I/O w.Ih RS 232 and Curreni Loop Inlerface and Software • Programmable Baud Rate • Parallel Input Port • Parallel Output Port • 4 Channel Timer/Counter • 4 Vectored Interrupts RAMS 8/15 95 14 95 8'S4 CX) MK 4115 -8K 74S 200 ■ 256 CPU'S Z— 80 includes manual Z— 80A includes manual 8080ACPU6BIT 8008 CPU 8 BIT PROMS 1702A ■ IK • l,5ui 3.95 or 10/35. 2708 ■ 8K • 450ns 14.95 5204 ^K 7.95 82S129 — IK 2.50 2708U 8K signatics 650ns . . . .9.95 O. E. M. SPECIAL ASK ABOUT SPECIAL OEM DISCOUNTS ON THE SD COMPATIBLE SET SDC 100 — SINGLE BOARD COMPUTER VERSAFLOPPY' " FLOPPY DISK CONTROLLER EXPANDORAM — 32K RAM EACH KIT IF PURCHASED SEPARATELY TOTAL S973.00 ORDER ALL 3 KITS TOGETHER FOR $899.00 Thi» Powerful Threesome Operates Together to Form A Comolete Computer $349 OO $149 OO $475 OO for Your System. Z-80 Programming Manual IN DEPTH DETAIL OF THE Z-80 CPU MICRO-COMPUTER S. D. SALES SPECIAL $9.95 S.D. NOW HAS SOFTWARE FOR IT'S CUSTOMERS CP/M DISK OPERATING SYSTEM . CP M IS a powerful disk operating system which has become an industry standard disk based FORTRAN and BASICS This package includes a CP/M diskette (mmi oi SBC 100/ VERSAFLOPPY EXPANtXJRAM board set. Complete documentaljon is n islered trademark of Digital Research Corp . Pacific Grove. CA. $99.95 t IS compatible with severa full size) adapted for S D ■ eluded ( I CP/M IS a reg Z-80' DISK BASED ASSEMBLER $69.95 Runs on ANY CP/M based disk system Assembles the official Ziiog-Mostek Mnemonics, Contains ex tensive set of pseudo ops. Available on mini or full size diskette. VERSAFLOPPY' ' CONTROL FIRMWARE . . . $24.95 Provides control for VERSAFLOPPY and boots up CP/M. This runs on Z 80. 8080 or 8085 based computers. Available m 2708 or 2758 prom. SD MONITOR $49.95 Powerful monitor tor SBC 100 smgle board ■com puters Includes all VERSAFLOPPY control firm ware Comes in 2716 prom. Available in 4-6 weeks VERSAFLOPPY DIAGNOSTIC PROGRAM . . $24.95 Provides routines which are hetpful m checking out a disk based system Available m 2708 or 2758 COUNTER CHIPS MK50397 6 Digit tiapsed timer 8 95 MKS02S0 Alirm clocli 4.99 MK50380 Alarm chip 2.95 MK5039S 6 digit up/dn. count. 12.95 MK5002 4 digit counter 8.95 MK5021-Cal. chipsq. root 2.50 * SUPER FLOPPY SPECIAL S. D SALES- VERSAFLOPPY S 100 CONTROLLER BOARD PLUS SHUGART SA 400 FLOPPY DISK DRIVE INCLUDING CABLE FOR ONLY $479.00 * MICROPROCESSOR CHIPS 8212 ■ 1/0 port 8214 — P.I. C 8216 — Non Invert Bus . . . 8224 — Clock Gen 8226 — Invert Bus PIO for Z— 80 . CTC (or Z— 80 8228 Sys. Controller 8251 Prog. comm. interfact. 8255 prog. prep, intertace. . 8820 Dual Line Recr 8830 Dual Line Dr 2513 Char. Gen 8838 Quad Bus. Recvr, . . . 74LS138N— 1/8 decoder 8T97.Hei Tri-State Buffer 1488/1489 RS232 TR 1602B Uart TR 1863 Uart FD 17718-1 .3.50 12.95 495 4.95 3.95 14.95 14.95 8.20 10.95 13.50 1.75 1.75 7.50 2.00 1.25 1.50 3.95 8.50 39 95 CMOS 4001 4002 4011 4013 4016 4017 4020 4022 4024 4027 19 19 19 32 32 95 97 97 75 39 4029 4042 4047 4049 4069 4071 4076 14518 14528 14529 !I9 69 1.50 35 23 19 97 1.10 85 85 CALL IN YOUR BANKAMERICARD (VISA) OR MASTER CHARGE OR- DER IN ON OUR CONTINENTAL TOLL FREE WATTS LlNEr 1-800-527-3460 Texas Residenu Call Collecl: 214/271-0022 DEALER INQUIRIES INVITEDI (All prices subject to ctiange wittiout Dnor notice.) NO CODs. TEXAS RESIDENTS ADD 5% .SALES TAX ADD 5% OF ORDER FOR POSTAGE & HANDLING OR DERS UNDER $10. ADD 75c HAND LINGFOREIGN ORDERS - U. S FUNDS ONLY! Circle 31 5 on inquiry card. BYTE July 1978 205 Unclssaifiei^Ac^B TRADE: BYTE, volume 1, number 2, good condi- tion, for Dr Dobb's Journal of Computer Calisthen- ics and Orthodontia, volume 1, number 1, I need the article on NIBL BAS/C for the SC/MP chip. Joe Price, POB 543, Olton TX 79064. FOR SALE; TRS-80 LEVEL-I BASIC tapes and lists: Star Trek (needs 12 K memory), list $7, tape $9.95: Biorhythm (4 K), list $4.50, tape $7; Lunar Lander (4 K), list $3. tape $5. R Menzies, 7106 Colgate Dr, Alexandria VA 22307. FOR SALE: ASR 32 Teletype with stand, paper tape punch and reader, documentation; excellent condiiion, $325. David Shorthill, RFD #2, Wells ME 04090. (207) 646-5465. TERMINAL: Texas Instruments 725, 30 cps, hard copy, built in modem and coupler, rugged portable case. Very quiet, popular professional terminal, $775 plus shipping. Also memory: Solid State Music, 8 K, static, 500 ns (no waits), assembled, works, $150, Wright, POB 7576, Menio Park CA 94025 (415) 854-5678. FOR SALE: Heathkii computer system. System includes; H8 computer, H9 video terminal, 8 K memory, all standard Heathkit software plus extended BASIC. Completely assembled and tested. Asking $1400. Call or write Paul Randazzo, 37 Maxwell Dr, Wethersfield CT 06109 (203) 529-0530. WANTED; Back issues of CACM, JACM, and JCCs. W Hutchison, Princeton Arms N 191, Cranbury NJ 08512. FOR SALE: Shugart SA400 minifloppy disk drive and ten minifloppy disks, $390, (no controller or power supply). Working video interface per February 1976 BYTE, $100. DECwriter keyboard, $50. Power supply, $35. Case, $42. Parts for 6800 processor board including 6800, 2x6810, 2x6820, 2708, wire wrap sockets and support ICs $150. Everything except disk, $310. James Thomas, POB 26, Sandv Spring MD 20860, (301) 774-7686. FOR SALE: DEC PDP8e modules and peripherals DK8EP, $375. AD8 16 channel A/D $875. DEC- writer $1050. Omnibus expanders, power supplies, KL8Es; lots more. Send for list and tell me if you have anything for trade or sale. I will repair any DEC part or build custom interfaces or modules. J Simpson, POB 632, W Caldwell NJ 07006. FOR SALE: Thinker Toys "Speakeasy" board assembled, RS-232 serial port used, $100. Paul Lamb, 13101 Parson Ln, Fairfax VA 22030. FOR SALE: The Northstar Users group has over 230 outstanding programs including real estate, investment, business, debugging aids and games, t will copy these public domain disks for $5 per disk plus the cost of a disk (or send a disk). About 15 programs on each disk. For a list of programs and details send SASE to J Dvorak, 704 Solano Av. Albany CA 94706, (415) 527-7730. Readers who have eQuipment, software or other items to buy, seft or swap should send in a dearly typed notice to that effect. To be considered for publication, an advertisement should be clearly noncommercial, typed double spaced on plain white paper, and include complete name and address information. These notices are free of charge and will be printed one time only on a space available basis. Insertions should be limited to 100 words or less. Notices can be accepted from individuals or bona fide computer users clubs only. We can engage in no correspondence on these and your confirmation of placement is appearance in an issue of BYTE. Please note that it may take three or four months for an ad to appear in the magazine. ■ FOR SALE Floppy Tape Peripheral complete with 10 board, 8 tapes, new and used. Uses stereo 8 track cartridge. Each cartridge can hold one program per track or 8 per cartridge. Program length limited only by tape length. The used tapes have 5 or 6 programs on each and are included free. They are ready to run and cover Star Trek, Othello, other games and technical programs. Will interface to most microcomputers, schematic included. Will ship UPS. $100, R Mendelson, 27 Somerset PI, Murray Hill NJ 07974. (201) 464 5244. FOR SALE: Teletype model 33ASR, Excellent condition, $600. ALTAIR 8080a, with 8 K mem- ory, TTY and cassette 10 boards. Factory perfect condition, all MITS, $580. Selectric based type- writer with paper tape RDR/PCH. Nice TTY alternative, $480. All for $1500 Andrew Frankford, 2014 Marietta Av, Lancaster PA 17603, (717) 299-2456. TELETYPE FOR SALE; (All 8 level ASCII) Model 33ASR (new), $1000, Model 35KSR (new), $1500. Model 35ASR (used, very good), $1500. Model 35 reperf and reader set, $425. Parts for Model 33 and 35 machines, gears, modems. Model 28 Baudot machines. Send SASE for complete list and prices. Lawrence R Pfleger, 2141 N 52nd St, Milwaukee Wl 53208. PROGRAM EXCHANGE: Programs are now avail- able, in source form, to run on most any home microcomputer. These programs corrte from various sources and are written in BASIC and other languages. In addition, our club needs other pro- grams that you may have developed, making them available to other hobbyists for fun, enjoyment, and practical use. If you can make available such programs we want to hear from you. Please write to us soon. For complete descriptive literature and a list of currently available programs, send $1 to cover copy and mailing costs to: Mikel Home Computing, POB 17105. Irvine CA 92713. FOR SALE: "Elf" microcomputer trainer, $60 complete. Built from Popular Electronics articles. Carefully wire-wrapped on Vector board; all ICs socketed. Full hexadecimal keyboard in out- board module. Hexadecimal display shows 10 byte and memory address. All modifications fully documented. RCA User's Manual, article reprints, much extra data included. Bob Levine, 32 King St. New York NY 10014. FOR SALE: MMD-1 by E&L Instruments, $250, Bug Book V included (6 units). Contact (805) 522-5276, after 6 PM. FOR SALE: BYTE September 75 through December 76 excluding January 76. All in per- fect condition. Make an offer. Fred Henry, 104 Heathercreek Dr, Plainfield IL 60544, (815) 436-6111. FOR SALE: North Star BASIC programs: Corres- pondence Editor: $5, Stock Market Analysis package: $5, Mailing list and random access pack- age: $3, Spacewar game package: $3, plus; Stock Market data on 30 heavily traded companies on North Star disk. Includes: P/E, price, volume, and percent yield, weekly averages for 1977: only $25 for all 30. Send blank disk, or include $5.25 for disk. Write for complete list. Herbert Schildt, 1007 N Division, Urbana IL61801. TRADE: 12 slot ALTAIR 8800A with HD power supply plus 10 slot IMSAI for factory assembled Altair 8800B. Both units fully socketed and fac- tory checkout. Ken Roberts, 10560 Main, fel5, Fairfax VA 22030. (703) 591-6008 or (703) 378-7266. FOR SALE: PORTACOM briefcase ASCII printing terminal w/modem, keyboard, instructions, $595. DEC PDP8es, modules, ASR33s, ham gear, free lists, buy, trade, repair, design also. K2DCY, 1 1 Squire Hill, N Caldwell NJ 07006. FOR SALE: Digital Group Z-80 four board system including CPU, 10, TV cassette and mother board assembled. Two 8 K memory boards, one with ICs, both with sockets, unassembled. Complete assembly plans and documentation. Going to college, must sell. $750. Richard Yero, 12323 Algonquin Rd, Palo Park IL 60464 or call (312) 448-2609 after 4:00 PM or weekends. FOR SALE. Altair 8800a with IMSAI 20A power supply installed in original cabinet. With serial 10 board, Tarbell 1 702A prom board, and 4 to 32 K programmable memory. Everything works 100% and software is included. Tell me what you want and I will quote a price, or make me an offer. For more information call (518) 456-8717 or send SASE to Michael Favitta, 4 Sherwood Forest Rd, Albany NY 12203. FOR SALE. NCR high speed paper tape punches, 110 V, 60 Hz, used but overhauled about 100 cps (according to technical manual), self-contained cabinet, tape spooling mechanism built-tn, eight tracks, weight 40 lbs. Delivery within 5 weeks after your order comes in (ie: 5 weeks till you have it). Price $200 including freight, collective orders from clubs (minimum 5 punches) $150 per punch plus $100 for freight. Order accompanied by crossed checks should be sent to TIME OUT, Siegfried Manfred Rambaum, Rossdoerfer 44, 6100 Darmstadt, GERMANY. FOR SALE: Control Data 200 UT remote batch/ interactive terminal, equipped with a 14 inch CRT, 63 character keyboard, 300 CPM card reader, 300 LPM-136 column line printer and 4800 baud communications capability. Complete original service and operation documentation included. Excellent condition, currently under CDC main- tenance contract. Contact: Bob Levy or Bob Minor (301) 565-9544 8750 Georgia Av, Silver Spring MD 20910. FOR SALE: Motorola MEK6800O2 evaluation kit, 8 K Solid State Music Memory board. Includes 4 slot Altair (S-100) extender board, cabinet, 5 V 6 A power supply, Mik-Bug firmware, 8 K (SwTPC) BASIC, 8 K (SwTPC) Text Editor and Assembler, 4 K Tiny Assembler, PCC's BASIC games, (the evaluation module has an integral Key board /Cassette interface) and COMPLETE SYSTEMS/Family Documentation. Must sell! Asking $350 — will take best offer. Amn Trotz, Psc Box 1 1 16, Wurtsmith AFB Ml 48753. FOR SALE: Lunar Landing simulation program for any Radio Shack TRS-80 computer. On cas- sette, ready to load. Send check or money order for $7.50 to J Quistgaard, 715 S Alder St, Port Angeles WA 98362. FOR SALE: Heathkit H-9 video terminal, expertly assembled, $600. Also, box of ten 8 inch Data Packaging (DPI) floppy disks, never used, $50. I pay shipping, Andy Thornburg, 400 E Jackson St, DeSoto I L 62924. WANTED: Card extender or connector (male and female ELCO PNOO- 701 5-059-000-002) for DATA POINT 3300-101 59 pin. Cecil T Rutledge, 2726 Sandy Ln. Fort Worth TX 761 1 2. FOR SALE: Altair 8800B computer with 32 K 200 ns static programmable memory, two serial ports, one parallel port, PROM board, ACR cassette interface, floppy disk drive and con- troller, panel mounted baud rate switches for fast device change, extended BASIC on cassette, disk extended BASIC, and DOS, along with 30 floppy disks. $5000, Steve Mastrianni, 2952 Mam St, Coventry CT 06238. (203) 742-6727 or (203) 664-2401 . Apple II Software cassette: 16 K Blackjack mutli- color card display, 2 player paddle input, full Las Vegas rules, optional autoplay by computer, sound effects, documentation included, $10. George W Lee, 18803 S Christina Av, Cerritos CA 90701 . FOR SALE: All issues of BYTE from September 1975 to August 1977. All issues completely intact and in mint condition. Best offer over $60 within one month after ad's appearance. Richard Fermoyle, 7597 NW 73rd Ter, Tamarac FL 33319. FOR SALE: One Compucotor 8001 color terminal with BASIC SOOT, background color option 32 K programmable memory (8 K for CRT), floppy tape bulk storage. CPU operating system includes memory manipulation and paper tape 10 sub- routines. One free serial 10 port. In perfect operating condition, $2995. Contact D Brovwi, (803) 771-6087, 1308 Shirley St. Columbia SC 29202. 206 July 1978 © BYTE Publicitions Inc VISIBLE OR INFRA RED USED FOR CHARACTER RECOGNITION FOR COMPUTERS WITH EXTERNAL CIRCUITS MAY BE USED IN A VACUUM, UNDER WATER, HIGH ALTITUDE IN MAGNETIC ENVIRONMENT BECAUSE THERE IS NO HIGH VOLTAGE OR MAGNETIC DEFLECTION MINATURE SOLID STATE 202 VIDEO CAMERA KIT FEATURING A. . . 100 x 100 BIT SELF SCANNING CHARGED COUPLED DEVICE THIS UNIQUE UPDATED CAMERA KIT FEATURES THE FAIRCHILD CCD 202C IMAGE SENSOR ADVANTAGES • IN THE FUTURE WE WILL SUPPLY A COMPUTER VIDEO INTERFACE CARD • All clock voltages operate at 6V reguiring no adjustments • Higher video output signal • We supply the power board, so only a 5V 1 Amp power source is needed • The circuitry has been simplified for easier assembly • Two level TTL output is supplied for interfacing FEATURES • Sensitive to infra red as well as visible light • May be used for IR surveillance with an IR light source • Excellent for standard surveillance work, because of light weight and small size • All components mounted on parallel 33/4"x6V2" single sided boards • Total weight under 1 lb. SURPLUS CENTRONICS PRINTERS 306 '1,150 *900 ^QdQoo ,.„ ^^0^M ^^ IVI I We supply all semiconductors, ... ^ . , _i X i boards, data sheets, diagrams. Add $75. ° to assemble and test resistors and capacitors, and SMM lens. Add $2.00 Postage and Handling sorry we do not supply the case, batteries and 5V supply. UNIVERSAL 4Kx8 MEMORY BOARD KIT $69.95 32-2102-1 fully buffered, 16 address lines, on board decoding for any 4 oi 64 pages, standard 44 pin buss, may be used with F-8 & KIM EXPANDABLE F8 CPU BOARD KIT $99.00 featurint] Fairbug PSU 1 K-ot siaiic ram, RS 232 interface, documentation. 64 BYTE teqis.er 4K BASIC FOR FAIRBUG F8 on naner rai>P $25 00 C/MOS (DIODE CLAMPED) 4001 ■■ IB 4016 - .29 4027 - 37 4053 -• 1.10 4002- ,18 4017 - .90 4028- .80 4055- 1.25 4006- .95 4018- .90 4029- .95 4066- 70 4007 - .18 4019- 37 4030- 33 4071 - .18 4009 • 37 4020 - .90 4036 - .97 4076 - .97 4010- 3? 4021 .90 4042- .65 4518- 1.00 4011 - .18 4022- 90 4046- 1.35 74C10 .22 4012- .18 4023- .T8 4047- 150 74C193 .95 4013- .29 4024- 75 4049- ,34 4015 - .74 4025 ■ 18 4050 - 34 2TO»HK ePROM 1460 nl) $ 9.75 2622 STATIC SHIFT HE6 t 1.95 2513 CHAHACTEH G6N t 6.7B 2B1S HEX 32 BIT SR ..._ ., % 2.20 5203-2K CPROM ^ S 4.60 2102 1 (450ni) S .99 21L02 1 USOnil S 1.26 WM5370 4KXI DYN S 3.4S MK 40O8P ^ S 1.95 2101 1 254 ■ 4 STATIC • 2.46 2111 1-256 X 4 STATIC t 3.45 2112 1 256 M 4 STATIC „ • 2.76 S2B0/21D7e 4K DYNAMIC BAM .„.. t 4.36 TMS 4060L , $ 3.96 5204-4K "ROM _ „ S10.9& 82S23 „ S 1.95 AY 6-1013 UAHT ^ $ 6.96 B703C TELE DYNE 3 STAGE eiNAHY a BIT A/D CONVERTER S13.SD 90eOA . . «H.95 AP SOARD5 USED FOR 50LDERLCSS BREADBOAR Dl NG 264L - 128 FIVE-TIE POINT ,,„ cr, TERMINALS $12.50 212H —POWER BOARD $ 2.50 2248L- 96 FIVE TIE POINT *, „ „„ TERMINALS $10.00 209R - POWER BOARD $ 2.25 IC TEST CLIPS TC-1^~ S4.S0 TC-16 - t4-75 CTS 206-8 ei9hi position dip switch .... $1.90 CTS-206-4 tour position dip swuch . . . .Si.45 LIGHT ACTIVATED SCR'j TO 18. 200V 1A $ 1.10 SILICON SOLAR CELLS 2%" diametef .4V at 500 ma $4.00 FND 359C.C..4"$.50 LED READOUTS FCS8024 4 digit DL-704C.A. .3" $ .85 C.C. 8" airplay $5.95 DL747C.A. ,6- $1.65 FND 503 C.C, ,5" $ .85 FND 800 C.C. ,8" $1.95 FND 510 C.A. .5" $ .85 FND 807 C.A. ,8" $1.95 DL 704 .3" C.C. $ .85 PRINTED CIRCUIT BOARD 7WATTLD 65 LASER DIODE I R $a95 2N 3820 P FET S 45 2N 5457 N FET $ 45 2N2646 UJT $45 ER 900 TRIGGER DIODES 4' SI. 00 2N 6028 PROG UJT S 65 MINIATURE MULTI-TURN TRIM POTS 100, IK, 2K, 5K, 10K. 25K, 50K, TOOK, 200^:. 500K. IMeg, 2Meg, $.75 each 3/$2.Q0 CHARGED COUPLE DEVICES CCD 321 AH2 512 Analog Shiit Register . $95.00 CCD201C 100x100 Image Sensor $95.00 CCD 202C 100x100 Imago Sensor $145.00 VERIPAXPC BOARD $4.00 This board is a 1/16"singla sided paper epoxy board, 4>'j"x6%" DRILLF.D and ETCHED which will hold up to 21 single 14 pin IC's or 8,16 or LSI DIP IC's with busses for power supply connactor, FP 100 PHOTO TRANS . . . S 50 RED, YELLOW. GREEN or AMBER LARGE LED's .2" ... 6/$1 00 TIL-nS OPTO-ISOLATOR $ .75 MOLEX PINS 100/$]. 00 1 ooa/$8 00 10 WATT ZENERS 3.9. 4.7. 5.6. 8.2, 18,22,100,150 or 200V , ea. $ .60 1 WATT ZENERS 4.7, 5.6,10. 12. 15 18 or 22V ea. S .25 MC6860 MODEM CHIP $9.95 MCM6571A 7x 9characiergen ... $10.75 TRANSISTOR SPECIALS 2N6233-NPN SWITCHING POWER $ 1-95 MRF-8(»4a CB RF Transistor NPN $ 1-50 2N3772 NPN Si TO-3 . $ TOO 2N1546 PNP GE TO-3 $ .75 2N4008 PNP yi TO :i S 1 00 2N6056 MPIM Si TO 3 D,iihniHo-i S 1.70 2N5086 PNPSi TO-92 . . . 4/S 1.00 2N3137 NpN Si RF $ .85 2N3919 NPN Si TO 3 RF . --. SI 50 2N1420NPNSiTO54 3/$ 1.00 2N3767 NPN Si TO-66 ... S .70 2N2222 NPN Si T018 . . , 5/S 1 00 2N3055 NPN Si TO 3 ... S .50 2N3904 NPN Si TO-92 . 5/S 1 .00 2N3906 PNP Si T0 92 . . . 5'S 1.00 2N5296 NPN Si TO-220 S .50 2IM6109 PNP Si TO-220. ... S .55 2N3638 PNP Si TO 5 5/S 1.00' ^SESEMS 600 .20 ».oo DIP SOCKETS B PIN .17 24 PIN .35 14 PIN .20 28 PIN .40 16 PIN ,22 40 PIN .60 18 PIN .25 5ANKEN AUDIO POWER AMPS Si 1010 G 10 WATTS. ... $ 7.80 Si 1020 G 20 WATTS ' . . $15.70 Si 1050 G 50 WATTS $28.50 TANTULUM CAPACITORS TTL IC SERIES Silicon Power Rectifiers PRV 1 A 3A 12A 50A 1 ^■fA 241;A 100 06 .14 .30 .80 3 70 s.qq 200 07 .20 .35 1 IS 4.25 6.^0 400 09 25 50 1.40 6.50 9.50 600 11 .30 .70 1 80 8.5Q 12.50 BOO 15 ,35 .90 2.30 10 50 16,50 1000 20 .45 1.10 2 75 12 50 20.00 SAD 1024-B REDICON 1024 stage analog "Bucket B-^iaade" shift regiitar. $16.95 IN 4148 MN914I 15, Si 00 RS232 DB 25P male $2.95 CONNECTORS D6 ^5S female ... $3.50 REGULATORS 309K $ ,95 340K 12,15 723 S .50 Of 24V. .... $ .95 LM 376 .... $ -60 340T 5, 6, 8, 12 320K 5, 12 15.18 or 24V $ .95 or 15V. .. $1-00 78 MG $1.35 '°Ir^2-4V,... $ .95 ^^ MG $1.35 7400- .13 7445- ,65 74151- 7401- .13 7446- .68 74153- 7402- .13 7447- .58 74154- 7403- .13 7448- .68 74155- 7404- .15 7450- .15 74157- 7405- -13 7472- 74161- 7406- -16 7473- .28 74163- 7407- ,20 7474- .28 74164- 7408- .18 7475- .45 74165- 7409- .18 7476- .30 74170- 7410- .13 7480- .31 74173- 7411- IB 7483- .65 74174- 7412- .13 7485- .87 74175- 7413- .36 7486- .28 74176- 7414- .60 7490- ,42 74177- 7416- .22 7491- .58 74180- 7417- .25 7492- .43 74181- 7420- .13 7493- .43 74190- 7425- 25 7494- .67 74191- 7426- .22 7495- .65 74192- 7427- ,19 7496- .65 74193- 7430- .13 74107- ,28 74194- 7432- .22 74121- 75325- 7437- .21 74122- 38 74196- 7438* .21 74123- ,45 74279- 7440- .13 74125- .40 74367- 7441- .70' 74126- 40 75491- 7442- .37 74150- .94 75492- DATA CASSETTES $ 44 Pin Solder Tail .156" Conn. IVIM 5387AA new clock chip which v drive LED's 1 2/24 hrs., 1 supply & al NO. 30 WIRE WRAP WIRE SINGLE STRAND 100' $1.40 22UF 35V 5/Sl.OO 47UF 35V 5/S1 00 68UF 35V 5.S1 00 1UF 35V 5,S1 00 2 2 UF 20V5'S1 00 3 3UF 35V 4 S1 00 4.7UF 15V 5,'$1.00 6 8UF 35V 4.S1 00 lOUF 10V $ .25 22UF 25V S 40 15UF 35V 3/$l,00 30UF 6V 5/$1.00 47UF 20V $ .35 68UF 15V $ .50 LINEAR CIRCUITS" LM30a LM311 LM31S LU319 LM324 LM339 LU 358 LM 370 - 1,26 -2.50 -2-50 ALCO MINIATURE TOGGLE SWITCHES MIA 106 SPOT . .... $ 1.05 MTA 206 DPDT S 1.70 MTA 206 P-DPDT CENTER OFF « i 85 MSD 206 P-DPDT CENTER OFF LEVER SWITCH $ 1.85 Circle 340 on inquiry card. BYTEluly]978 207 Feadep Service To get further information on the products advertised in BYTE, fill out the reader service card with your name and address. Then circle the appropriate numbers for the advertisers you select from the list. Add a 13 cent stamp to the card, then drop it in the mail. Not only do you gain information, but our advertisers are encouraged to use the marketplace provided by BYTE. This helps us bring you a bigger BYTE. Inquiry No. Page No. 4 Administrative Systems 1 14 AJA Software 135 Anderson Jacobson 45 Apple Computer 14 Apple Computer 15 AVR Electronics 159 ATV Research 133 Atwood Enterprises 180 Beckian Enterprises 180 Bit Basement 137 BITS82, 83, 87, 110, 133 Buss 112 BYTE Back Issues 146 BYTE Wats Line 103 California Industrial 185 Canada Systems 143 Capitol Equipment Brokers 126 Carterfone 161 Central Data Corp 103 Component Sales 183 Computer Data Directory 110 Computer Enterprises 106 Computer Headware 1 1 1 Computerland 33 Computer Mart of MA 1 59 Computer Mart of NJ 144 Computer Mart of PA 144 Computer Resources 159 Creative Software 159 Cromemco 1 , 2 T Y Crowell 120 Cybernetic Micro Systems 131 Databyte 123 Digital Equipment Corp 172 Digital Group 19 Digital Research (CA) 143 Digital Research (TX) 187 Digital Research & Engineering 111 Dynabyte 67 ECHOlab Inc 110 Electrolabs 183 Electronic Control Technology 141 Electronic Systems 189 Electronics Warehouse 191 EMM/CMP 118 EMM/Semi Inc 109 Engram Associates Inc 131 Forethought Products 126 Gallaher Research Inc 129 * GFN Industries Inc 79 148 GRT Corporation 22, 23 6 10 14 15 16 17 25 30 31 35 36 39 40 43 84 45 60 61 70 73 75 74 76 76 77 78 80 81 82 90 95 100 101 110 113 115 120 125 130 132 136 137 140 145 Inquiry No. Page No. 149 H & K Computer Corp 140 153 Hamilton Logic Systems 159 155 DC Hayes 119 160 Heath Company CIV, 34 170 Hobby World 1 79 175 IMSAICIII 178 Info 2000 69 73 Information Unlimited 11 1 179 Integrand 140 180 Integrated Circuits Unlimited 193 183 International Data Sciences 129 185 International Data Systems 104 187 International Technical Systems Inc 159 190 Ithaca Audio 161 193 J & E Electronics 133 195 Jade Company 181 200 Jameco Electronics 194, 195 202 Kel-Amlnc144 207 LMN Electronics 197 215 Logical Services 173 216 Magnemedia 99 217 Manchester Equipment 137 219 McGraw Hill Publishing 75 223 Microcompl59 226 Micro Computer Devices 109 231 Micro Mart 137 235 Micropolis96 236 Micropolis97 240 Microware150 247 Mikos 198 250 Mini Micro Mart 173 251 Mini Micro Mart 199 260 Mountain Hardware 5 265 mpi 127 * MVT Microcomputer Systems 147 273 National Digital Diagnostic 133 275 National Multiplex 73 280 Netronicsl21 283 Newman Computer Exchange 146 285 North Star Computer 7, 21 287 Northwest Microcomputing Sys 169 290 Ohio Scientific Instruments 24, 25, 26, 27 289 OK Machines Tool 113 291 Oliver Advanced Engineering 135 292 Oliver Advanced Engineering 137 293 Osborne & Associates 93 294 Pacific Digital 136 296 Pacific Office Systems 198 297 Page Digital 188 298 PAIA Electronics 108 299 Pentech Inc 137 Inquiry No. Page No. 301 PerCom Data 29 302 Personal Computing '78 81, 151 * PolyMorphic Systems 13 303 Poly Paks 203 304 Priority I Electronics 201 305 Processor Technology 8, 9, 10 306 Quantum Science Corp 159 307 Quest Electronics 188 308 Rothenberg Information 115 309 Rotundra Cybernetics 137 311 S-100 108 310 ScelbiSO, 31 322 Scelbi/BYTE Primer 95 * Scientific Research 47, 49 312 Scope Data 133 31 5 SD Computer Products 205 313 Seattle Computer Products 105 314 Sherwood Medical 133 316 Michael Shrayer Software 77 317 Siliconix 59 318 Small Systems Services 147 319 Ed Smith's Software 128 320 Smoke Signal Broadcasting 107 321 Smoke Signal Broadcasting 128 330 Software Records 136 335 Solid State Music 11 340 Solid State Sales 207 350 Southwest Technical Products CM 351 Structured Systems Group 17 352 Summagraphics Inc 122 353 Super Surplus Sales 204 355 Synchro Sound 39 356 Synchro Sound 40, 41 360 Tarbell Electronics 43 370 Technical Systems Consultants 37 372 Technico 65 373 Technicon 117 371 Teletek Enterprises 137 374 Terrapin Inc 71 376 Touchstone Associates 137 377 Transition Enterprises 159 378 TransNet Corp 127 381 Tri Tek 204 383 TRS-80 Software Exchange 141 386 US Robotics 137 388 Vandenberg Data Products 142 393 West Coast Computer Faire 51 395 Worldwide Electronics 133 400 Xitexl16 405 Xybek 142 *Correspond directly with company. mm- BYTE's Cdgcing Moflifon Bex Article No. 1 2 3 4 5 6 7 8 9 10 11 12 13 ARTICLE Baker: KIMER: A KIM-1 Timer Bosen: The Axiom EX800 Printer: A User's Report Hearn: Top-Down Modular Programming Hauck: Who's Afraid of Dynamic Memories? Williams: Antique Mechanical Computers: Early Automata Loewer: The Z-80 in Parallel Libes: The First Ten Years of Amateur Computing Walton: Controlling DC Motors Reid-Green: A Short History of Computing Ciarcia: Build a Keyboard Function Decoder Frenzel: How to Choose a Microprocessor Williams-Conley: A High Level Language for 8 Bit Machines Weinstein: How to Get Your Tarbell Going PAGE 12 28 32 42 48 60 64 72 84 98 124 152 162 Readers Tune In to Ciarcia The winner of the April BOMB is Steve Ciarcia's "Tune In and Turn On: A Com- puterized Wireless AC Control System, Part 1," page 114. Second prize goes to Ernest W Kent's "The Brains of Men and Machines, Part 4: The Machinery of Emotion and Choice," page 66. The authors will receive prizes of $100 and $50, respectively. The BOMB (BYTE's Ongoing Monitor Box) is your way of telling us what you think about the articles in BYTE each month. To cast your votes, see the card on the opposite page." 208 luly 1978 © BYTE Publications Inc icrocomputer System Solution. Announcing thelMSAI VDP'40. Fully integrated video data processor in a single cabinet. T\vin floppies, professional keyboard, S-100 expansion slots. 24 line by 80 char. CRT, insert/delete, programmable font, protected fields, inverse video. Handsome flip-top cabinet for easy access. Serial and parallel I/O ports included. FORTRAN IV, Extended and Com- mercial BASIC. IMDOS (enhanced CP/M*). r rj ISAM. . "f r fft: -ffrr You've decided you want a microcomputer system — but what to buy? The component system? A computer lx)x here, a CRT lx)x there, a keyboard box here, a floppy disk box there . . . Messy! The $695 system? But ... no disk; no way to add enough memory . . . and, if you could, it's not so cheap anymore, and you still wind up with an expensive box collection anyway. Messy! The IMSAI VDP-40, a fully integrated Video Data Processing system that, in one handsome package, combines a profes- sional keyboard, heavy-duty power supply, twin mini-floppies, multi-slotted mother- board and 9-inch CRT at a new low price. System Expansion? The IMSAI VDP-40 was built for you. The extra slots in our S-100 bus motherboard and heavy-duty power supply allow almost unlimited expansion. Need more RAM? Add up to V2 MByte with our Intelligent Memory Manager and 64K RAM boards. Need more disk storage? A controller option of the VDP-40 will allow you to expand to nearly 5 megabytes! Add a line printer, an IBM-compatible tape drive, a MODEM! IMSAI has them all, with the interfaces and software to make it work for you. The standard of excellence IMSAI places at your disposal at a price/ performance no one else has put together allows you to achieve the full potential of your imagination. Check us out. IMSAI has what you want and what you need. Visit your dealer or write us directly. Ask about the IMSAI VDP-40 and the entire IMSAI line. Features and prices subject to change without notice. * CP/M is a trademark of Digital Research Corporation. The Standard of Excellence in Microcomputer Systems IMSAI Manufacturing Corporation, Dept. EWN, 14860 Wicks Boulevard, San Leandro, CA 94577 (415) 483-2093 IMSAI EUROPE Europa Terrassen 8 Rue Jean Engling Dommeldange, Luxembourg 43-67-46 Telex: 1428 See us at the NCC Show, booth 2860 Price/Performance no one else has put together. Circle 175 on inquiry card. This 8-bit machine, by itself, is as versatile as a lot of systems that include peripherals orientation allows you an almost unlimited opportunity for growth. Memory is fully expandable, the 8080A CPU extremely versatile, and with the addition of high speed serial and parallel interfacing you gain the added flexibility of I/O operation with tape, CKT consoles, paper tape reader/punches, and now our new floppy disk systems! The H8 offers superior documen- tation including complete step-by- step assembly and operation manuals, is backed by 54 years of Heath reliability, and comes complete with BASIC, assembler, editor, and debug software - others charge over $60 for! H8, simplicity for the beginner, sophisti- lation for the expert nd at $375* just rigt r you. the H8 is the only machine in its price class that offers full system inte- gration yet, with just 4K of optional mem- ory and using I/O Port Display System Engineered for Personal Computing Be sure to use coupon on page 34 of this magazine to order your FREE Heathkit Catalog! only its "intelligent" front panel for I/O, may be operate completely without peripherals! In addition, by using the features of its built-in Pam-8 ROM panel control program, the H8 actually allows you to dig in and examine machine level circuitry. Responding to simple instructions the "intelligent" panel displays memory and register contents, lets you inspect and alter them even during operation. And for greater understanding, the front panel permits you to execute programs a single instruction at a time. The result is a powerful, flexible learn- ing tool that actually lets you "see" and confirm each detail of H8's inner workings. If you need further evidence, con- sider the fact that H8's system U- Circle 160 on inquiry card.