ISSUE NUMBER 14 



$1.50 IN NORTH AMERICA ($2.50 elsewhere) 



OCTOBER 1976 



the small systems 
journal 










PRINTED IN USA 



urzi 



If 

Ul 






Our computer is a bore- 



There is simply no point in trying to 
hide it, everyone is going to find out 
sooner or later anyway. TheSouthwest 
Technical Products 6800 computer is 
a big bore. Discussions with customers 
and dealers have confirmed our worse 
suspicions. 

At first people thought that perhaps 
owners of our system were just a bit 
shy because they were outnumbered at 
local computer club meetings. But then 
as the number of owners rose it be- 
came clear that this was not the pro- 
blem. And it wasn't that they were un- 
sociable or anything like that; they 
were simply just bored because they 
had nothing to talk about. 

Here they were, just sitting there while 
all the other members with other 
brands of computers exchanged data 
on circuit board errors, secret schemes 
of adding extra bypass capacitors to 
make the thing reliable, tricks to keep 
the clock phases from overlapping, cor- 
rections to manual errors and other fun 
subjects. Can you imagine the frustra- 
tion this caused? All our customers 
could do was to sit and be bored. They 
had nothing to talk about. 

Our 6800 has an internal monitor 
ROM that automatically puts the boot- 
strap loader in memory and refers con- 
trol to the terminal, when you power 
up. This feature deprives you of the 
chance to tell sad stories of how many 



times' you had to go back and flip the 
console switches before you got the 
loader program in right. Since you can 
do machine language programs direct- 
ly from your video terminal or teletype 
in hexidecimal form, you will not have 
a chance to exchange horror stories 
with your friends about how you for- 
got the last zero when you entered 
10100110 from the console on your 
374th Byte and messed up the program 
that had just taken you two hours to 
put into memory. It just isn't fair. 

Since we use full buffering on all data, 
address and control lines on all boards 
in our system and since we use low 
power 2102 static memories in our 
system, there are no noise sensitivity 
problems that can lead to hours of fun 
trying to figure out why a program 
"bombed". Dynamic memories that 
some others use can drop bits, fail 
to refresh random cells, cause programs 
to do crazy things by going into 
a refresh cycle at the wrong moment 
and all kinds of interesting things. Our 
poor customers will never have a chance 
to have these interesting experiences. 

Even our documentation and software 
is no help. Not only do we have the 
most complete and thorough set of 
instructions available for any system, 
we are supplying software either 
free, or at crazy low prices. Our big 
documentation notebook for instance 



is just full of information on the sys- 
stem. There are complete sections on 
software with sample programs and 
information on programming. We have 
no assembly instructions in that big 
yellow notebook. They are packed 
with the kits themselves. The note- 
book is completely devoted to instruc- 
tion on using your computer system. 
You are therefore not going to be 
spending day after jolly day trying to 
find out how to put a program into 
your machine; researching all available 
outside literature in an attempt to dis- 
cover just how you write software for 
the beast. Sorry about that folks, we 
didn't mean to spoil all your fun. 

So please, have a heart, when you see 
those poor lonely souls that have pur- 
chased our systems say "hello". All 
they have to keep them interested in 
computers is writing and running pro- 
grams. Our editor, assembler, 4K and 
8K BASIC programs work so well that 
even this is quick and easy. So be kind 
to those poor bored SwTPC-6800 
owners, it's not their fault that they 
have nothing to talk about. 



Computer System 
with serial interface and 2,048 words 
of memory $395.00 




... COMPUTE" 

g-jjli! 6800 s v STeM 



□ I don't like puzzles anyway and have no free time to be bored so 
send information on your 6800 computer system and peripherals. 

LJ Thanks for warning me. Send names of manufacturers of "interest- 
ing" computers. 



ADDRESS. 



CITY . 



.STATE. 



Southwest Technical Products Corp., Box 32040, San Antonio, Texas 78284 



2 or 4 MHz 
switch 



-Z80/4CPU 




The only 

CPU card 

to give you 



4 MHz speed 



2 - 5X MORE THROUGHPUT 

Here is by far the most powerful 
CPU card now available. 

It's Cromemco's new ZPU™ card. 

It uses the slick new Z-80 chip — 
in fact, it uses the even faster Z80/4 
high speed version of the Z-80 — 
and it's the only card that does. The 
Z80/4 is certified by its manufac- 
turer for 4 MHz operation. 

The Z80/4 has all the advantages 
of the 8080 and 6800 — and enor- 
mously more. 

And Cromemco's new ZPU does 
enormously more. 

4 MHz CLOCK RATE 

First, the ZPU lets you choose 
either a 2 or 4 MHz crystal-controlled 
clock rate. Right away that means 
you can have twice the throughput. 
Cuts program running time in half. 
Then the instruction set of the Z80/4 
reduces software even more. 

The 2 or 4 MHz clock rate is 
switch-selectable as shown in the 
above photo. 

POWER-ON MEMORY JUMPS 

Cromemco's ZPU also has some 
neat design innovations of its own. 



For example, you'll like the simpli- 
fied operation you get because upon 
power turn-on the ZPU will jump to 
any desired 4K boundary in mem- 
ory. No switch flipping to go through 
to begin your program. 

SELECTABLE WAIT STATES 

Cromemco engineers have also 
arranged that your present systems 
will always be useful with the new 
ZPU. To do this, the ZPU has been 
designed to have jumper-wire-se- 
lectable wait states on the card. 

These simplify interfacing with 
your present memory or I/O even 
at 4 MHz operation. 

80 ADDITIONAL INSTRUCTIONS 

You've probably heard that the 
Z-80 with its 80 new additional in- 
structions is by far the most power- 
ful chip around. It's true. 

That means with the ZPU you will 
be able to devise much more power- 
ful (as well as faster) software than 
before. 

ALTAIR/IMSAI COMPATIBLE 
WITHOUT MODIFICATION 

Yes, the new ZPU is plug-com- 



patible with the Altair 8800 and 
IMSAI 8080. Just remove the exist- 
ing CPU, plug in the ZPU card, and 
you're up and running. 

Further, the Cromemco ZPU is the 
only card guaranteed to work with 
all present and future Cromemco 
peripherals. (Cromemco manufac- 
tures the popular BYTESAVER'" 
memory, the TV DAZZLER™, the 
D + 7A™ analog interface board, a 
joystick console, and others. 

INCLUDES FREE SOFTWARE 

The ZPU comes with our powerful 
Z-80 monitor, complete documenta- 
tion, source code, and paper tape 
object code. The monitor is also 
available in PROM ($75) for use in 
our BYTESAVER memory board. 

STORE/MAIL 

The new ZPU is available as a kit 
or assembled. Look into it now be- 
cause you can see demand will be 
strong. Present delivery is 30 days. 

ZPU kit (Model ZPU-K) $295 

ZPU assembled 

(Model ZPU-W) $395 

California users add 6% sales tax. 



Q 



Cromemco 

Specialists in computer peripherals 

2432 Charleston Rd., Mountain View, CA 94043 • (415) 964-7400 



About the Cover 



In the Queue is on page 7 this month. 



As a way to highlight the history of 
electronic digital signalling, we dug up 
a picture of one of Joseph Henry's 
original telegraphy keys, circa the 
early 1800s. Robert Tinney then 
placed the key in the frame and wall 
setting you see on the cover, using a 
photo supplied by Brian McCarthy. 



In This EITE 



Once you sit down and Build This 
Mathematical Function Unit as de- 
scribed in part one of R Scott 
Guthrie's two part article, the world of 
high level mathematical functions is 
opened to your microcomputer. In 
part two this month, the software 
needed to interface with the calculator 
is described, as well as several test 
loops used to adjust timing parameters 
with an oscilloscope. As a final illustra- 
tion of the calculator's use, the author 
provides a program called CALCULA 
which enables a Teletype (or other 
ASCII) port to drive the calculator and 
print results, simulating the ordinary 
hand calculator level of operation. 



The problem of decoding arbitrary 
hand generated Morse code is not a 
trivial one. It requires some care and 
thought in the design of adaptive 
algorithms. As one contribution to this 
issue's sub theme of computerized 
Morse code, Lt William A Hickey, 
USN, provides some background infor- 
mation and suggestions on the subject. 



W J Hosking, W7JSW, is an amateur 
radio operator in search of applica- 
tions hardware and software. Read 
about A Ham's Application Dreams 
and find out how to implement one 
aspect of his dream with the Morse 
code input and output conversion 
technology described in detail in the 
balance of this issue .... 



A theme of this October issue is the 
application of microcomputers to the 
decoding of Morse code. One approach 
to the problem is detailed in Robert 
Grappel and Jack Hemenway's article 
on MORSE R ... a program to read 
Morse code, implemented with a 
Motorola 6800 computer. 



Lawrence Krakauer describes a tech- 
nique to store Morse characters as a 
packed table of bit patterns for ma- 
chine generated outputs - or for 
machine decoded inputs. 

If Only Sam Morse Could See Us 
Now. He'd have a fistful of problems 
trying to copy radio transmissions at 
1000 wpm generated by programs 
such as Wayne Sewell's CWBUFFER 
subroutine. But, using one of Wayne's 
set of sundry drivers for CWBUFFER, 
Mr Morse could potentially learn to 
copy — or at least have his computer 
copy — in a code practice mode. 



One application of the Morse code 
problem solvers is documented in 
Bruce Filgate's article on Morse Code 
Station Data Handler. This is an appli- 
cation program which handles direct 
sending of Morse outputs, from 
character text, adaptive interpretation 
of Morse inputs, storing of fixed mes- 
sages (eg: ' CQ CQ CQ DE W1 AW ') in 
a message buffer for later transmission 
or repetitive transmission, etc. Bruce 
has put it all together in the form of a 
comprehensive 1536 byte program for 
an 8008. 



National Semiconductor announced 
the PACE computer some time ago, 
but until recently it has been some- 
what hard to obtain. Now that this 16 
bit minicomputer is beginning to enter 
its volume production stage, we Keep 
PACE With the Times by offering 
Robert Baker's Microprocessor Update 
on this processor. If you missed the 
convenience of your familiar 16 bit 
minicomputer when you started 
reading about and "dry run program- 
ming" for personal computing, then 
the PACE processor might be a logical 
choice for a homebrew or kit system. 



The advent of the personal system 
portends a fundamental change in the 
ways computers are used. In Home- 
brewery vs the Software Priesthood, 
David Fylstra and Mike Wilber make 
some comments about the impact of 
widespread use and knowledge of com- 
puters. 



Looking for ideas for meetings of 
your local computer group? Dr Charles 
F Douds has a few suggestions to make 
in his background article on the 
subject this month. 



KIT-A-MONTH 



The Altair kit-a-month plan allows you to own an Altair mainframe without 
taxing your pocketbook. Mits has made it easy for you to purchase an 8800a, 
8800b or 680b computer in monthly installments where you receive compon- 
ents with each payment. There are no financial charges because we have made 
each monthly shipment a kit in itself. This will give you time to read up on com- 
puters and/or gain knowledge from friends. 

We have set up an Altair kit-a-month payment desk to service your needs. 
When writing or calling the factory for information about your shipment or 
account, just refer to the "kit-a-month payment desk'' 




OWN YOUR 680b IN FIVE EASY PAYMENTS 

1st month 680b Manuals, Main and Display PC Boards, 

and membership in users group 
2nd month 680b Case and Power Supply 
3rd month Parts for 680b Display Board 
4th month Parts for 680b Main Board less Integrated 

Circuits 
5th month 680b Chips 

$93.20 plus $2.00 per month make your payments $95.20 per month and you have your complete 
kit in five easy payments. This plan gives you the full 680b with memory and I/O. The BAUDOT Option is 
still $42.00 extra and may be purchased with Time Payment #4 or #5. Remittance of $95.20 will start you 
on your way to owning your own computer. 

Alaska, Hawaii, APO and FPO customers include $3.00 per month for Air Parcel Post charges instead 
of $2.00 for regular Parcel Post shipment. This would make your payment $96.20 per month. 

Canadian customers include $3.00 per each month for postage and handling fees. 
NOTE: This plan does not apply to foreign sales other than Canada. 



NEW ALTAIR 8800B 

Available on Time Payment Plan 

$105.00 payment per month plus $2.00 postage and handling for each kit makes an easy $107.00 
per month to own the newest of the Altair processors. 

Send in your first $107.00 money order and start receiving your 8800B Kit by August 1, 1976. 

8800B Month #1 Manuals 

#2 EC- 18 

#3 Power Supply Board 8c Parts 

#4 Transformer 

#5 Display Board a Parts 

#6 Case 

#7 Main Chips 

#8 CPU Board a Parts Less 8080A 

Alaska, Hawaii, APO and FPO customers please include $4.00 for shipping charges (making $109 
per month payments) for Air Parcel Post shipment. Otherwise, shipment will come Parcel Post, not insured. 

Canadian customers must accept month #6 Emery Airfreight Collect. All other months must include 
$4.00 postage and handling making monthly payments of $109.00. 



$79.00 / Month 
ALTAIR 8800A TIME PAYMENT PLAN 

8800A Time Payment #1 8800A Manuals and Users Group Membership 

»2 EC-18, PC Board and Hardware 

#3 8800A Power Supply Kit 

#4 8800A case 

#5 CPU PC Board and Bag of Parts less the 

main chip 

#6 Main Processor Chip 

#7 Display Control Board and Parts 

The price of the Altair 8800A mainframe is $539.00. Seven easy payments plus $2.00 per month for 
postage and handling charges make this plan equal $79.00 per month. Upon receipt of your first $79.00 
payment you are on your way to owning your own 8080A basic computer system. A list of available com- 
patible peripherals is enclosed to let you plan your system as you learn about your microprocessor. By 
8800A Time Payment #7 you're ready to go. 

Alaska, Hawaii. APO and FPO customers please include $4.00 for shipping charges (making $81 
per month payments) for Air Parcel Post shipment, otherwise, shipment will come Parcel Post, not insured. 

Canadian customers must accept month #4 Emery Airfreight Collect. All other months must include 
$4.00 postage and handling making monthly payments of $81.00. 



KIT-ArMONTH 

ORDERING INSTRUCTIONS 



In order to smoothly and efficiently expedite your orders, we ask that you 
note the following helpful hints: 

1 . Send all payments other than BankAmericard or Master Charge in the 
form of a cashier's check or money order. Personal checks are acceptable, but 
clearance time will delay your order by 2-3 weeks. 

2. The kit-a-month plan has been set up to proceed in order and we cannot 
deviate from that order. You can help us by noting with your payment what 
month you are on. 

3. When calling or sending in orders, refer to your customer name on 
the original order and also your Mits order number. 

4. If you change your address, keep your name as it is on the original 
order to keep records straight. 

5. Please note special instructions for Alaska, Hawaii, APO, FPO and 
Canadian customers. If these are not followed, it could result in delays in proc- 
essing your order. 

6. The Kit-a-Month desk has been set up to help expedite your orders 
because of the overwhelming response we've had with previous time payment 
plans. Please feel free to use this service whenever you have questions. When 
writing letters to Mits, simply note "Kit-a-Month desk" on the outside of the 
envelope. 



NOTE: Once you start the Kit-a-Month plan you are guaranteed the existing 
price at the time of your first order. You will not be affected by price increases. 



Enclosed is my payment of for the first shipment of my Altair 

kit-a-month. 

Master Charge # or BankAmericard #_ 



Altair 680bQ Altair 8800aD DAItair 8800b 

NAME 

ADDRESS 

CITY STATE & ZIP 



0§ IjuQK§©/2450 Alamo SE/Albuquerque, NM 87106 505-243-7821 



Prices, specifications, and delivery subject to change. 

1 



0J5 IXiOK§©/2450 Alamo SE/Albuquerque, NM 87106 505-243-7821 



In the Queue 



BITE #14 



OCTOBER 1976 



staff 



Foreground 



30 
42 
52 
74 

12 
26 
36 
82 
90 
118 



ADD THIS 6800 MORSER TO YOUR AMATEUR RADIO STATION 

Applications — Grappel-Hemenway 
IF ONLY SAM MORSE COULD SEE US NOW 

Applications — Sewell 
A MORSE CODE STATION DATA HANDLER 

Applications— Filgate 
BUILD THIS MATHEMATICAL FUNCTION UNIT-Part2 

Software — Guthrie 



Background 



THE COMPUTER . . . VERSUS . . . HAND SENT MORSE CODE 

Applications — Hickey 
A HAM'S APPLICATION DREAMS 

Speculation — Hosking 
EFFICIENT STORAGE OF MORSE CHARACTER CODES 

Applications — Krakauer 
KEEP PACE WITH THE TIMES 

Hardware — Baker 
HOMEBREWERY VS THE SOFTWARE PRIESTHOOD 

Philosophy— Fylstra-Wilber 
MEETING ACTIVITIES FOR COMPUTER CLUBS 

Organizations — Douds 



Nucleus 



2 In This BYTE 

9 The Concertina System 

16 Letters 

41 Software Bug of the Month 5 

81 Some Historical Notes 

86, 110, 126 What's New? 

95 BYTE's Bits 

96 Classified Ads 

99 Programming Quickies 

100 Book Reviews 

106 Kil O'Byte 

107 Travelogue 

116 Excerpts from Future History 

130 Clubs, Newsletters 

144 BOMB 

144 Reader Service 



BYTE magazine is published 
monthly by BYTE Publica- 
tions Inc, 70 Main St, Peter- 
borough New Hampshire 
03458. Subscription rates are 
$12 for one year, $22 for two 
years, $30 for three years in 
North America. Elsewhere: 
$15 one year, $25 two years, 
$33 three years. Second class 
postage paid at Peterborough 
NH 03458 and at additional 
mailing offices. Phone 
603—924-7217. Entire con- 
tents copyright 1976 BYTE 
Publications Inc, Peterborough 
NH 03458. Address editorial 
correspondence to Editor, 
BYTE, 70 Main St, Peter- 
borough NH 03458. 



1 



PUBLISHERS 

Virginia Peschke 

Manfred Peschke 

EDITOR 

Carl T Helmers, Jr 

GENERAL MANAGER 

Manfred Peschke 

PRODUCTION MANAGER 

Judith Havey 

CIRCULATION 

Deborah R Luhrs 

DEALER CIRCULATION 

Deena Zealy 

PUBLISHERS ASSISTANTS 

Cheryl Hurd 

Julie Nelson 

Carol Nyland 

Kim Place 

ADVERTISING 

Elizabeth Alpaugh 

Virginia Peschke 

TYPOGRAPHY 

Custom Marketing Resources, Inc 

Goodway Graphics 

Mary Lavoie 

Taimi Woodward 

PHOTOGRAPHY 

Ed Crabtree 

Custom Marketing Resources, Inc 

ART 

Matthew Arnold 

Mary Jane Frohlich 

Lynn Malo 

Bill Morello 

PRINTING 

The George Banta Company 

Custom Marketing Resources, Inc 

ASSOCIATES 

Bob Baker 

Dan Fylstra 

Harold A Mauch 

Chris Ryland 

PRODUCTS COORDINATOR 

Floyd W Rehling 

TECHNICIAN 

Melvin G Weir 

CONSTRUCTION 

Walter Pence 



If you thought a rugged, 
professional yet affordable 
computer didn't exist, 



think 

IMSAI 

8080. 



Sure there are other commercial, 
high-quality computers that can 
perform like the 8080. But their 
prices are 5 times as high. There is 
a rugged, reliable, industrial com- 
puter, with high commercial-type 
performance. The IMSAI 8080. 
Fully assembled, it's $931. 
Unassembled, it's $599. And ours 
is available now. 

In our case, you can tell 
a computer by its cabinet. The 
IMSAI 8080 is made for commer- 
cial users. And it looks it. Inside 
and out! The cabinet is attractive, 
heavy-gauge aluminum. The 
heavy-duty lucite front panel has 
an extra 8 program controlled 
LED's. It plugs directly into the 
Mother Board without a wire 
harness. And rugged commercial 
grade paddle switches that are 
backed up by reliable debouncing 
circuits. But higher aesthetics on 
the outside is only the beginning. 
The guts of the IMSAI 8080 is 
where its true beauty lies. 

The 8080 is optionally 
expandable to a substantial system 
with 22 card slots in a single 
printed circuit board. And the 
durable card cage is made of 
commercial-grade anodized 
aluminum. 

The IMSAI 8080 power 




supply produces a true 28 amp 
current, enough to power a full 
system. 

You can expand to a 
powerful system with 64K of 
memory, plus a floppy disk con- 
troller, with its own on-board 
8080 -and a DOS. A floppy disk 
drive, an audio tape cassette input 
device, a printer, plus a video 
terminal and a teleprinter. These 
peripherals will function with an 
8-level priority interrupt system. 
IMSAI BASIC software is avail- 
able in 4K, that you can get in 
PROM. And a new $139 4K 
RAM board with software 



IMSAI 8080 



iii«— ««« ~ ~ - 



memory protect. For the ultimate 
in flexibility, you can design the 
system for low-cost multiprocessor, 
shared memory capability. 

Find out more about the 
computer you thought didn't 
exist. Get a complete illustrated 
brochure describing the IMSAI 
8080, options, peripherals, soft- 
ware, prices and specifications. 
Send one dollar to cover handling. 

Call us for the name of the 
IMSAI dealer nearest you. 

Dealer inquiries invited. 



wmm 



IMS Associates, Inc. Dept. B-10 
14860 Wicks Boulevard 
San Leandro, CA 94577 
(415) 483-2093 



The Concertina System 



Editorial by 
Carl Helmers 



The often asked question of the personal 
systems cynic is "What on earth do people 
do with home computers?" In many ways 
this question is analogous to what might 
have been asked by automotive skeptics in 
the early part of this century: "What on 
earth do you expect people to do with 
automobiles?" Fifty to 60 years of history 
have answered the latter question in 
numerous concrete demonstrations, and one 
can only expect the coming decades of 
computer evolution to answer the former 
question in numerous ways. 

Of course the simplest reply to the first 
question is "Compute!" and is as empty of 
content as the analogous reply for auto- 
mobiles, "Drive!". Computing without a 
purpose is like driving without a destination, 
an intrinsically enjoyable pastime on 
occasion but hardly touching upon the set of 
possibilities inherent in digital computation 
and control. The key to a broadened per- 
spective on the computer and its place in 
human activities is the concept of the 
application. An application for the computer 
is like a destination for an automotive trip. 
If I set in my mind the goal of driving down 
to Boston for an evening in Symphony Hall 
with Arthur Fiedler, the Boston Pops and 
company, my automobile has now acquired 
an "application." Similarly, if I decide to 
customize my computer system as a vehicle 
for editing and playing music, a very 
ordinary and garden variety Motorola 6800 
plus memory and peripherals has acquired an 
"application" whenever I choose to use it 
for that purpose. (Like an automobile that 
can be driven anywhere without reason, the 
true general purpose computer need not be 
exclusively dedicated to one applications 
goal.) 

The concept of music played using com- 
puters is an excellent focal point to 
demonstrate practical uses for personal 
computers. Here is a specific application of 
the computer technology for very human 
purposes, a concrete argument to throw at 



the skeptic and cynic. The choice of a 
musical application goal, like the decision to 
drive to a concert with an automobile, 
makes the technology come alive with 
human values. 

The traditional concertina is a simple 
pneumatic acoustical instrument similar to 
an accordion. The pneumatic concertina is 
hardly a widely known or used instrument. 
In a hand held package with control buttons, 
it gives the player an ability to create a fairly 
rich timbre similar to a reed organ or a 
harmonica. Like all instruments, it requires 
an element of virtuosity to play at all well, 
but within its limitations it makes an 
interesting vehicle for musical expression. 

The relative obscurity of the original 
concertina instrument, the harmonically rich 
nature of its timbre, noting its use by a 
single (good) artist in creating a polyphonic 
output, and most of all, falling in love with 
the smooth sound and etymological roots of 
its name leads me to propose the name 
"concertina system" for a musical instru- 
ment based on a personal computing system 
integrated with musical software and 
peripherals. The concept of the digitally 
controlled musical instrument is not new, 
but the technology which makes it possible 
at a reasonable price is as new as the whole 
LSI computer technology. For about the 
same price that you or I would pay for a 
virtuoso quality home electronic organ, it is 
possible to add a music playing peripheral to 
a computer system which will allow the 
owner to accomplish musical performance 
feats unheard of on an organ or traditional 
instruments. As of this writing, I know of 
two companies which are in the process of 

preparing products which can simply convert 
an existing computer system into a 
polyphonic synthesizer with the potential 
(with software) of becoming a truly playable 
concertina system. One company is located 
in Arizona and is said to be designing an 
Altair compatible plug-in card with several 
polyphonic channels of digitally controlled 
music output. Another company, ALF 
Products, 2130 Bell Ct, Lakewood CO 
80215, is in the preproduction prototype 
stages of preparation to market a modular 
computer controlled synthesizer which inter- 



faces to any existing computer by using the 
two programmable ports of a single PIA 
chip. (Most existing computers have pro- 
visions for a "PIA card" with one or more 
such "parallel interface adapters" together 
with appropriate plugs.) The ALF design has 
8 fully programmable music channels with 
an option to add 8 less versatile "back- 
ground" channels to achieve the potential 
for a truly orchestral sound. 

There are undoubtedly additional in- 
dividuals and companies working on similar 
systems and products which can simply and 
inexpensively (relative to costs two to three 
years ago) add a minimal concertina system 
capability to the typical home computer 
system. Readers will find more information 
on this subject as the products become 
better defined and reach the marketplace; 
we also expect to publish articles on the 
technology of computer controlled musical 
instruments (experimenters and potential 
authors: take note). 

If you have a computer, you have 75 to 
90% of such a "concertina system" already 
available. All the control and data manage- 
ment power needed to implement a rela- 
tively simple and quite functional 
polyphonic music interpreter is present in a 
microprocessor system using chips such as 
the 8080, Z-80, 6800 or 6502 with several K 
of applications program memory (I use 12 K 
myself for interpreter and text area, but it 
would certainly be possible to program a 
usable system with as little as 4 K memory.) 
The system also requires a video output 



Word Gets Around . . . 

The personal computing field is getting 
some attention as the amount of activity 
creates some micro ripples in the big pond of 
things people do. An article in the July 12 
issue of Business Week featured Paul Terrell's 
Byte Shop computer store in Mountain View 
CA. Paul's shop is one of the largest retail 
outlets among the more than 250 stores 
coast to coast which regularly stock BYTE. 

Also, Ivan Berger, electronics and photog- 
raphy editor of Popular Mechanics magazine, 
reports in phone conversation that he has 
scheduled a short feature article on home 
computers, their present and future 
prospects, in the September Popular 
Mechanics. 

There have of course been several local 
and national newspaper stories lately. As 
products improve and the market expands, 
we should see more and more examples of 
public awareness of computers documented 
in the press and other media, a welcome 
trend indeed." 



display, ASCII text keyboard and a pair of 
audio cassette drives with motor control via 
relays and a data rate of at least 300 baud. 
Obtaining better mass storage peripherals 
such as floppy disks, 3M cartridge drives or 
high speed electronically controlled Philips 
cassette decks is of course highly desirable. 
This use of the computer system, while 
requiring a dedicated peripheral, is com- 
pletely consistent with the concept of the 
general purpose personal system, for when 
the system is not being used for music, 
programs with other purposes can be 
employed. Many typical uses require such a 
peripheral specific to the application; many 
other applications such as record keeping, 
calculation, text processing, mathematical 
and simulation games, and so on merely 
require the general purpose computing sys- 
tem composed of processor, programmable 
memory, text keyboard, video display and 
mass storage on magnetic media. The 
"concertina system" concept is but one of 
innumerable answers to the critic's question 
of "What do you really do with a home 
computer?"" 



Size and Finesse 

Perhaps you've noted a moderate expan- 
sion in the size of your monthly mouthful of 
BYTE_, along with the addition of some 
colorful spices to make each BYTE more 
flavorful. 

Switching metaphors, a magazine such as 
BYTE is in many respects like a very large 
and complicated program design. The first 
concern was and is to fill a high quality 
technical magazine with good useful infor- 
mation and fun, once a month. This is the 
algorithm we have used very successfully and 
continue to use. 

But, like the large program, although the 
basic algorithm design is not subject to 
major changes there are always new features, 
incremental improvements and parameters 
to adjust. Striving for the "best possible 
BYTE" is an ingrained part of our philoso- 
phy, where "best" is defined as serving the 
needs of our customers in this specialized 
field. 

In the area of improving the product, 
recent increases in the size of each BYTE 
reflects a synergistic combination of sub- 
scriber and advertiser support. The added 
spice of color printing on interior pages is 
directly a result of support from advertisers, 
who make such support possible because of 
our readership. We're still experimenting 
with this new possibility of highlighting and 
enhancing technical articles but the presenta- 
tion should continue to improve." 



10 



And now minis too! 
All from a catalog, at discount prices. 



Digital's Direct Sales Catalog — 
the first catalog to offer com- 
puter products by mail with 
off-the-shelf delivery — was 
such a success, we've come out 
with an expanded second edi- 
tion that includes the PDP-8A, 
the newest member of the 
world's most popular mini- 
computer family. 

We've also added the L A180 
line printer and expanded the 
sections on microcomputers, 



logic modules, terminals, cab- 
inets, connectors, accessories, 
and supplies from the first 
edition. 

Of course, you still get our 
5% catalog discount, plus 
another 4% for cash with your 
order. You also get a 10- day 
free trial period, plus our stand- 
ard 90- warranty. (Since we're 
selling by mail, you do have to 
install the equipment yourself.) 

If you were among the thou- 



sands who ordered our original 
catalog, you'll get the new one 
automatically by mail. 

If you weren't, why not sign 
up now? 

For your free copy, call 800- 
225-9480 (Mass. 617-481-7400 
ext. 6608). Or write: 
Components Group, Digital 
Equipment Corp., MR2-2/M59, 
One Iron Way, Marlborough, 
MA 01752. (Catalog sales to 
U.S. only.) 







The Computer... 

Versus... 



Lt William A Hickey USN 
c/o US NSGA Edzell 
FPO New York NY 09518 



Hand Sent 
Morse Code 



INPUT 
FROM 
RECEIVER 



rh 



LEVEL 
5000 



l M F 



T 



^h 



NE567 
PLL 



Rl 

5000 

FREQUENCY 

ADJUST 



6800 < ,-p, ^p 

U-7 M F ]2.2 M F 




.l/iF 



m 



TIMING 

AUDIO BFO OUTPUT 



— MlWIIWr^ — WW^ — 



PLL LOCKUP 

TIME DELAY-» f- 



TTL OUTPUT 



SPACE - 
MARK 



INTERRUPTS REQUIRED 



1 r 



Figure 1 : A suggested circuit to decode the audio output of an amateur radio 
receiver. The receiver produces an audio tone burst corresponding to the 
keyed continuous wave (CW) signal being received. This tone has a frequency 
which depends on the tuning of the receiver. The 567 PLL circuit is a tone 
decoder, which can have its center frequency adjusted by Rl. The receiver 
output frequency and the NE 567 frequency should be the same for the 
desired signals. Noise and garbage (such as other stations nearby) will 
complicate the actual receiver output waveform. 



So you've been reading all about these 
marvelous new microcomputers, and think- 
ing about how nice it would be to have one 
that would translate Morse code for you. 
Well, it certainly sounds reasonable; it really 
depends upon what you expect from your 
computer. If you are expecting error free 
code translation under even the best signal 
conditions, you are in for a rude awakening. 

First of all, a computer (by today's 
standards anyway) cannot beat or even meet 
the standards set by a good human operator 
receiving code. You say you'll concede that 
point? Why should it be so difficult to 
design a translator that would work most of 
the time? That's the purpose of this article! I 
am not trying to discourage all the code 
copying enthusiasts out there; I am trying to 
prepare you for some of the not so obvious 
problems you might expect. 

For the purpose of this article, I will have 
to assume that you have somehow managed 
to translate the audio (code signal plus noise 
plus garbage) into a digital format of 1 's and 
O's. There are many ways to do this, but 
probably the most simple is shown in figure 
1. This is a straightforward tone decoder 
using a 567 integrated circuit. (Remember 
that when a tone is present and decoded, the 
output is a zero.) 

Now that you have this nice (hopefully 
free of noise) digital signal, what do you do 
with it? The answer to this one is sim- 
ple ... . Anything you want to do! In all 
seriousness, I will now branch into a discus- 
sion of hand sent Morse code characteristics. 
Assuming that you all know that a dot is 
assigned a relative time duration of (1.0), it 
follows that you also know that the dash is 
ideally (3.0), the letter space is (3.0) and the 
word space is (7.0). (If you are a ham, you 
do know that, don't you?) At this point I 
can safely say that the problem of transla- 
ting machine sent Morse code is relatively 
trivial. I use the word trivial because it is 
really just one machine talking to another 
machine; the intervals are all fixed and are 
constant, making translation merely a matter 



12 



of a table lookup assuming both machines 
use the same Morse code data rate. 

At this point, it will be convenient to 
illustrate the hand sent Morse translation 
problem. Figure 2 is a histogram of a very 
short message sent with a hand key. 

CQ CQ CQ DE OPERATOR NUMBER ONE 

The largest single distribution in the 
shorter mark group has been assigned the 
relative time value of (1.0). Keeping in mind 
the very small size of this sample, you can 
see that there is a wide variation in mark 
lengths. (This variation will increase pro- 
portionately with an increase in sample size.) 
Space lengths are not as clearly defined, and 
it is very difficult to decide where the 
decision should be made between letter 
spaces and word spaces. This won't be a 
serious problem though, since an extra space 
or the lack of a space between words rarely 
damages the message context. The decision 
problem will become acute when the space 
interval within characters begins to spread 
toward the lower boundary of the space 
interval between characters. This will be one 
of the primary sources for decoding errors. 

This article vvill not and should not 
specifically address such problems as: (1) 
gradual frequency drift from either the 
transmitter or receiver, (2) rapid transmitter 
frequency drift ("chirp"), (3) atmospheric 
fading, (4) noise from natural or human 
made sources, or (5) the presence of many 
other Morse and non-Morse (SSB, RTTY, 
etc) signals in the same receiver passband. 
The reason for this is simple: These factors 
are just too complex to be within the 
correction capability of simple algorithms. 
Remember that these problems are common 
to machine sent and hand sent Morse code 
signals. 

Translating hand sent code really begins 
to get sticky when the sending operator gets 
sloppy. (He or she might send a "special" 

signal like - -- [73, a signoff greeting] 

which tends to give receiving operators 
problems too!) Let's face it, there are a lot 
of really bad "fists" out there. Of course, 
there are some pretty good ones too, but 
frequently the contact you want falls into 
the bad group! 

The reason automatic decoders are usual- 
ly unsuccessful at decoding hand sent Morse 
code is: they are unable to adapt to the time 



AVERAGE = 1.0 



AVERAGE = 3.81 



H 1 I i il i 



I II ' I'flll I 



AVERAGE = 1.13 



varying properties of the statistical Morse 
signal. (This means the signals change charac- 
teristics from time to time .... usually just 
as the machine was ready to adapt to the 
previous change.) These statistical changes 
are reflected only partly in the mark and 
space timing characteristics of different 
operators or those of the same operator over 
an extended time. 

One of the advantages a human has is the 
ability to make contextual analysis on what 
is sent. For example, an operator might hear 
C? Q? 

N N MA 

and understand the signal ["CQ"] ; the 
machine would translate NNMA (just as 
it was sent). Examples of this phenomenon 
are endless and are available on the airwaves 
daily. 

There are three primary approaches to a 
solution of the hand sent Morse translation 
problem: 

1. Macro: You can accumulate statistical 
information on a particular operator 
and use this data to make decoding 
decisions. 

2. Micro: You can make your decisions 
on a mark to mark basis. 

3. Averaging: You can compromise these 
two methods and come up with a 
hybrid algorithm. 

Approach (1) requires a long sample time 
to develop the statistical information, and 
during this time the decoded output would 
probably be unacceptable. Even after the 
statistics become valid, the decoder would 
operate only on operators with similar 



mrrn 



AVERAGE = 4.97 



Figure 2: A histogram of a 
typical hand sent message, 
the text "CQ CQ CQ DE 
OPERATOR NUMBER 
ONE". The terms "mark" 
and "space" refer to the 
low and high TTL levels 
out of the detector of fi- 
gure 1, respectively. 



13 



Data Definitions: 8 bit registers or programmable memory 



X 

AVGDOT 



Duration of the previous input 

state. 

Running average of the previous 

"n" dot times. 



OUTCH Output ASCII character tempo- 

rary buffer. 

MORSREG Morse code pattern input shift 

register. 

PREVSTATE Previous mark or space input 
state. 

STATE Current mark or space input state 



ENTRY 



I 



| FOLLOWING j 

1 INTERRUPT AT ! 
I CHANGE OF ' 

I STATE I 

I J 



/ MORSE \ 

1 DECODER ) 



COMPUTE 
X: - 
(DURATION OF 
PREVIOUS STATE 






SPACE 


« r» AVGDOT 

LTLJT_ 


k — 


— w* 5 * AVGDOT 


morse: 


MARK 


i 


u 


INTERRUPTS 

MORSE 

DECODER 

EXECUTION 




innnni - 

JUUUU1_ 


u 

n 


« u 
nn 

i 


OUTCH KO 


REAL TIME - 




~l_ 


V --END OF CHARACTER 
DETECTED BY 
X> 2 * AVGDOT 



| CONCLUDE: 
I END OF 
L_CHARACTER 



-ThAVE DOT OR | 
I DASH I 

I I 



I CONCLUDE: 1 

'^y°i:. \ 



CLEAR 
MORSREG 



S M 



I FOR AN AVGDOT 
| INCLUDING DASH I 
— 1 AND SPACE READ- I »* 

INGS INSERT CALCU-i 

LATIONS HERE 



SHIFT O 

INTO 

MORSREG 



AVGDOT: > 
(NEW RUNNING 
AVERAGE); 



f RETURN ] 



Note: This routine is intended 
to be executed following an 
interrupt generated by both 
the rising and falling edges of 
the TTL Morse code input 
from a detector. An applica- 
tion routine to receive the 
output of this routine must 
have a wait loop which con- 
tinually tests OUTCH for zero. 
After an interrupt is com- 
pleted, a non zero character 
will be in OUTCH and the 
application routine will leave 
its idling loop and can use the 
character after copying it and 
setting OUTCH back to zero. 



Figure 3: The flow diagram of a relatively unsophisticated Morse decoder program. The adaptive features of this program are 
contained in the calculation of a new running average of the dot length whenever a dot is detected. The speed of the algorithm 's 
response to a change in the keying rate of the Morse input is a function of the number of dots maintained in the running average. 
A more complex algorithm could take into account the nominal dash spacing of three dots as part of the average, as well as the 
spacing between signal elements within characters. 



idiosyncracies. This is a nice idea, and it 
works well for individual operators; but it is 
not very workable for a broad collection of 
operator characteristics. Approach (2) is the 
easiest method — sometimes called the 
"ideal dot" method — but it is very suscep- 
tible to noise pulses and rapid code speed 
changes. (It tends to generate an excessive 
number of errors and is not really that good 
for decoded output.) For now, approach (3) 
seems to offer the best chance of working. 



Many individuals and commercial manu- 
facturers have tried variations on approach 
(3); but they all boil down to: Sample from 
four to eight characters, average the lengths 
of the dots, and use that average to make 
decoding decisions. After the initial average 
is set, you can update the average each time 
a dot is detected; or you can average both 
dot and dash lengths and settle on a median 

Continued on page 106 



14 



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} 



The Digital Group 
P.O. Box 6528 
Denver, Colorado 80206 
(303) 777-7133 



Letters 




MORSE CONVERSION BACKGROUND 
INFORMATION 

A letter from W A Hickey regarding 
Morse translators appeared on pages 92-93 
of your July issue. For the further edifica- 
tion of your readers, perhaps including Mr 
Hickey, I provide the following additional 
references on this topic: 

Althoff, W A, An Automatic Radio- 
telegraph Translator and Transcriber 
for Manually Sent Morse, NTIS 
AD-772 745, Dec 1973. 

Ball, Edison L, Processing of the 
Manual Morse Signal Using Optimal 
Linear Filtering, Smoothing, and 
Decoding, NTIS AD-A019 493, Sept 
1 975. 

Bedzyk, W L, Machine Translation of 
Morse Code Using a Microprocessor, 
NTIS AD-785 130, June 1974. 

Guenther, J A, Machine Recognition 
of Hand-Sent Morse Code Using the 
PDP-12 Computer, NTIS AD-786-492, 
Dec 1973. 

McElwain, D K and M B Evens, "The 
Degarbler — A Program for Correcting 
Machine Read Morse Code," Informa- 
tion and Control, March 1959. 

McNaney, J T, and Richard R Tice, 
System for Converting Telegraphic 
Code into Characters, US Patent 
2,840,637, June 1958. 

Powers, B L, and F R Scalf, The 
Design of a Morse-to-Te/etype Signal 
Converter Using Integrated Micrologic 
Circuitry, NTIS AD-840 255, June 
1968. 



Shenk, E R, and J C Phelps, Auto- 
matic Code Signal Discriminating 
Device, US Patent 2,534,388, Dec 
1950. 

Smith-Vaniz, W R, and E T Barret, 
"Morse to Teleprinter Converter," 
Electronics, July I 1957. 

Tevis, R, Printing Telegraph Receiver, 
US Patent 1,805,1 14, May 1931. 

Thomas L A, Morse Code Printing 
System, US Patent 2,534,387, Dec 
1950. 

Winter, A C, Code-Controlled Appa- 
ratus, US Patent 2,384,513 Sept 1945. 

I doubt that this list is complete; I have 
not been interested enough to do a really 
thorough literature search. 

On a different topic: May I suggest that 
you provide the magazine name, the volume 
number, and the date, at the bottom of each 
page. Despite your predominantly hobbyist 
readership, this small professionalism would 
be useful. 

E Douglas Jensen 

Principal Research Engineer 

Computer Systems Technology Section 

Research Department 

Honeywell Aerospace & Defense Group 

Minneapolis MN 55413 

The current issue of BYTE adds a bit to 
the applications literature. Thanks for 
sending along an excellent list of further 
sources. 



MORE ON MAKING PC BOARDS 

I would like to add a few things to James 
Hogenson's article on making printed circuit 
boards [July 1976 BYTE, page 58]. 

Readers who wish to make their own PC 
boards will find that the spray resists are 
messy and often difficult to use. We have 
found that a dry film resist made by 
Dynachem Corporation, Santa Fe Springs 
CA 90670, works very well and is easy to 
use. The material is called Laminar and 
comes in various thicknesses. The one mil 
thickness is the best for general use. One of 
the nice things about it is that it is developed 
in a water solution of sodium carbonate 
(Arm and Hammer washing soda) made to a 
concentration of 2 to 3%. It is moderately 
sensitive to light and may be used in room 
lighting without difficulty. It is easily ap- 
plied by heating the PC board and rolling it 
on with heating. A hard rubber roller works 
the best. These are available from art supply 



16 



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only $9.95 ppd. 

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ICELBI COIHIIIIED 
CONIULIING INC. 

1322 Rear Boston Post Rd. t Milford, CT 06460 
Telephone: 203/874-1573 





If we credit Charles Bab- 
bage with the first pro- 
grammable digital com- 
puter design, we should 
likewise consider Lady 
Lovelace as the first 
programmer. 



stores. The Laminar also has protective 
plastic coatings on both sides. The soft, 
flexible coating is removed before laminating 
to the clean copper clad. The inflexible 
coating is removed before developing. The E 
I du Pont Company also has a similar type of 
resist material. 

The PC boards must be very clean before 
resist is put down on the copper surface. A 
dip in dilute hydrochloric acid or muriatic 
acid followed by a scrubbing with Ajax or 
steel wool will prepare the surface. Hogen- 
son's photo 9 looks like the result of resist 
put on a dirty board. 

Printed circuit boards shouldn't be drilled 
with regular steel drills. They will wear out 
quickly and will leave ragged holes. Try 
carbide drills made for PC drilling. Most PC 
material houses should stock these. The type 
with an eighth inch shaft will fit in most 
tools. 

Bishop Graphics Inc, 20450 Plummer St, 
Chatsworth CA 91 31 1 , has a wide variety of 
PC layout and tape-up aids. I would suggest 
that readers get a copy of their catalog since 
the last 32 pages are a technical manual on 
PC layout and related techniques. 

I hope this will help your readers to 
improve their PC board technique. 

Jonathan A Titus 

Tychon Inc 

POB 242 

Blacksburg VA 24060 



ON BLANKS, CHARACTERS AND 

WOMEN IN COMPUTING 

I am glad to see BYTE is developing as a 
stable but flexible medium for the computer 
hobbyist. There are, however, three points 
which should be addressed early in your 
history: 

1. Invent a "blank character." Variable 
spacing for uniform column width is 
fine for reading, but poor for showing 
significant blanks. Programmers have 
long used special symbols to represent 
spaces or blanks, much as zeros act as 
placeholders for Arabic numerals. 
Examples are the lower-case b with 
overstruck slash or dash, and a square- 
cornered U. If no special character is 
available, perhaps just a lower-case b 
would do (eg: "LIMb+l" to show a 
blank as necessary) f Only necessary in 
the limited context of character text 
string examples . . . CHl 

2. Publish your character set. Testing the 
character set is often one of the first 
acts performed with a new medium 
(such as a keyboard, video display, or 



printer). It appears that you do not 
have, for example, Greek letters, 
although you have quite a variety of 
fonts and styles. (This suggests using a 
different typeface to spell out symbols 
that may be single characters in the 
original, such as THETA or UP- 
ARROW). Many of us are no longer 
limited to 47 computer symbols, but 
use 128 character ASCII. [Our text 
character set is published by IBM, in 
its literature on Selectric Composer 
balls; for computer graphics we gener- 
ally assume 7 bit ASCII unless noted. ] 
3. While it is awkward in English to avoid 
masculine pronouns (he, him, etc), I 
do think we should try to avoid the 
masculine assumption about readers 
(eg: having a wife). This is a new field, 
which is developing at a time in our 
history when women (and men) are 
outgrowing their traditional roles. I 
think we can expect to see a gradual 
increase in the number of women 
interested in computers, and should 
encourage the trend. 

In this light, it may be relevant that if we 
credit Charles Babbage with the first pro- 
grammable digital computer design, we 
should likewise consider one of his chief 
advocates, the Lady Lovelace, as the first 
programmer. She wrote instructions for set- 
ting up the Analytical Engine to perform 
certain calculations. (This was, of course, 
working in the abstract, as the machine was 
never completed.) 

Zhahai Stewart 

POB 1637 

Boulder CO 80302 

As to the last point, we're all for it. But it 
is a fact that most BYTE readers are male. 
Where is the other 50% of the human race in 
computing? As a rule, we try to keep things 
relatively free of stereotypes in the hopes 
that the other 50% will start finding out 
about the wonderful attractions of com- 
puters and computing. . . . CH 

IDENTITY CRISIS 

This is just a short note to say that I am 
enjoying BYTE and to offer a suggestion in 
the form of a question: 

"What do we call ourselves ? " 

Radio amateurs call themselves hams and 
I am sure other people have other names for 
them. However, in BYTE to date, I find that 
writers are grasping for words to use to 
describe the computer hobby. Perhaps you 



18 



Microcomputers are highly 
complicated devices. When you 
buy one you want to make sure 
the manufacturer has a solid repu- 
tation for reliability and support. You 
want to make sure he'll be in your corner 
a year or two down the road. 
The Altair ,M 8800 from MITS was the first 
general-purpose microcomputer. Today, there are 
more Altair computers up and running than all the 
other general-purpose microcomputers combined. 
Today, Altairs are successfully used for literally hun- 
dreds of personal, business, scientific, and industrial 
applications. 

Because we are so popular, many people have tried 
to copy us. The pages of microcomputer magazines 
are full of advertisements for Altair compatible devices 

and Altair imitation computers. 

Because we are NUMBER ONE, 
we offer a much broader range of 
products and services than any of 
our competitors. One manufacturer 
might be able to copy one of our 
computers. Another might be able 
to produce a working memory card. 
But no one can copy the overall 
Altair concept. 

The Altair concept is a system 
concept aimed at practical, cost 
effective applications. That's why 
we offer three mainframes includ- 
ing the Altair 680b, Altair 8800a, 
and Altair 8800b; ten peripherals 
including a multi-disk system; and 
over 20 plug compatible modules 
including our new, low power 16K 
static memory board. That's why we 
are the only microcomputer manu- 
facturer to go to the extra expense 
of providing our customers with 
quality, higher language software. 
When you buy an Altair, you're 
not just buying a piece of equip- 
ment. You're buying years of reli- 
able, low-cost computing. You're 
buying the support of the NUMBER 
ONE manufacturer in the micro- 
computer field. 



ft 



2450 Alamo SE/ Albuquerque, NM 87106/505-243-7821 



could run a contest of sorts to promote a 
name for those active in the small computer 
hobby. 

Looking through some past BYTEs I find 
words such as microists, kluge, hacker, 
amateur computer, digital, analytical engine, 
cyber(nuts) that may be altered, adapted or 
crossed to coin some new word to describe a 
computer hobbyist. Then we can say: 

"Hi I am a ?????????????????????" 

Do you suppose this will help people under- 
stand what we are up to? 

Bryan Patterson 

Box 1 726 

Port Elgin 

Ontario CANADA NOH2CO 

Well, if we wanted to sound self aggran- 
dizing, we could of course suggest "Byters" 
as a term. Actually, in spite of the negative 
connotations in computer science circles, I 
[CH] tend to prefer the traditional term 
"hacker." At the start of amateur radio, 
"ham" as used previously also had somewhat 
negative connotations. (I make an etymo- 
logical assumption here that the term as used 
in radio circles evolved from the tendency to 
"ham it up" on the air as in the usage of 
"ham actor. ") I like hacker as a term for the 
serious amateur computer nut (who is also 
typically professionally involved as well) 
because it has implications of digging into 
the subject matter and really learning it at 
multiple levels of detail. The "compleat 
modern hacker" is the renaissance man 
(oops . . . person) of computing. 



WHO SAYS THEY AREN'T? 

With respect to BYTE covers, you blew 
it. The phrase "Computers — the world's 
greatest toys" told it like it was and still is. 
Truly, the only difference between men and 
boys is the price of their toys. 

A co-worker commented, "If computers 
are the world's greatest toys, then are 
programmers the world's biggest kids?" How 
can I argue with logic like that? 

Julius T Marinaro 

725 Cricklewood Dr 

State College PA 16801 



VIDEO TAPE AND COMPUTERS? 

I was very pleased to find out about the 
existence of your journal. I have had an 
interest in small system uses for several 
years. At present I am working with video 
tape systems within a school district in Flint 



Michigan. I am interested in finding various 
small computing systems to use in video tape 
editing and special effects for CRT displays. 
Enclosed is my check for a three year 
subscription to BYTE. I am looking forward 
to my subscription. Also I would like to ask 
for your assistance in answering two ques- 
tions. I would like to find out if I could 
obtain back issues of BYTE since it was first 
published, and I would also like to find out 
if you can give me any information on the 
use of small computing systems with video 
tape systems. Any information that you can 
give in these areas would be greatly appre- 
ciated. Thank you for your time and 
trouble. 

William D Wolverton 

10320 Henderson Rd 

Otisville Ml 48463 

September, October and November 1975 
BYTE back issues are sold out at present, as 
is May 1976. Remaining back issues are now 
being serviced at a price of $1 .50 per copy, 
plus 25 £ for postage and handling. Send in 
your requests, but send no money with your 
request. If we have what you 're looking for, 
we'll bill you for what we ship. 

As to the use of computers with video 
tape applications, it sounds like an excellent 
use. However, we have no articles in house 
on the subject . . . . yet. Perhaps you'd like 
to write about your results. 



HELP! 



I have some surplus ICs from our local 
IBM factory and would like to identify 
them. I hope you can help me. I have three 
types: 



2709400 JUQ 

V 721304 
7324FQ 

2709401 
Q Korea 
721304 
7432 FO 

2709170 
JUK 

V 721186 
733180 



Mi 



Mi 



Mi 



They are all ceramic chip with 14 pins 
gold plated in each side and in the top a gold 
square with the numbers and a ground line 
to pin one like in the MOS devices. 

Jose Vincente 
Caiza Postal 764 
13100 Campinas 
S P Brazil 



20 



Jk 



Sir*! 



0$ ""%»', m*L~- S 





%M 



f 



'>■ .'V ■•., 



4 






(it I mi ill 1 1 

Hi Sir lit lit itj 

1i I Milium 

• Wllllllt'lllhi 






Rickey^ tackling the SDK-80 
microcomputer kit for his next science project. 



Rickey likes soccer, lizards, hot 
fudge sundaes, skateboards and 
microscopes. He can't decide if he'd 
rather be Franco Harris, Bobby 
Fischer or Jonas Salk. 

When his Dad brought home 
the Intel SDK-80 microcomputer 
systems kit, Rickey helped him put 
it together. It took only four hours. 
Everything was there. The 8080 
CPU, RAM, PROM, programmable, 
I/O, a printed circuit board with all 
those capacitors and resistors and 
the other things that go with it. The 



best part was the instruction manuals. 
Every step was clearly explained. It was 
easy. The programming part looked 
especially interesting. So simple. Just 
imagine talking to a computer. 

The big thrill came on Saturday 
when they went to his Dad's office to 
use a terminal. When they connected 
the SDK-80 to the teletypewriter 
they got a printout. That was excit- 
ing. Within an hour they were talking 
to the computer, then inventing 
games. They stayed all day. 

Now Rickey is building a micro- 



computer of his own. He may be the 
first kid on his block with his own 
computer. Thanks to a $350 low 
interest loan from his Dad. 

If you're interested in being the 
first on your block to have a micro- 
computer, contact your Intel distri- 
butor: Almac/Stroum, Component 
Specialties, Components Plus, 
Cramer, Elmar, Hamilton/Avnet, 
Industrial Components, Liberty, 
Pioneer, Sheridan, or L. A. Varah. 

Microcomputers. ■■<%!■ I s 
First from the beginning. II I Lol 

3065 Bowers Ave , Santa Clara, California 95051. 



A BIT OF CIRCULATION 

Attention: Circulation 
Dear Ms Luhrs: 

Thank you very kindly for making avail- 
able the lifetime subscription to BYTE 
magazine which I won at the First World 
Altair Convention in New Mexico. Of all the 
door prizes given, I firmly believe I won the 
best. It was generous of your firm to make it 
available. I would appreciate your conveying 
my gratitude to Mr and Mrs Peschke and Mr 
Helmers. 

Since I already have a subscription to 
your fine magazine, I am presently receiving 
two copies. I am passing one along to 
non-subscribers and hopefully it will gen- 
erate additional subscriptions. 

I commend you on the many fine articles 
which have appeared in past issues. Being a 
novice in hardware applications, I parti- 
cularly look forward to tutorial type hard- 
ware articles. 

Gene Straub 

5723 Shasta Cir 

Littleton CO 801 23 



THE IEEE 488 BUS 

Regarding your comments about a stan- 
dard interface for microprocessors, etc, on 
page 96 of the April issue: I imagine you are 
familiar with the IEEE 488 which is being 
used by HP, Tektronix, Fluke and many 
others to interface microprocessors, calcula- 
tors, disks, cassettes, DVMs, counters, etc. 
488 is not as complex as the standards 
document would lead you to believe. It is 
achieving rapid acceptance because it is well 
suited to microprocessor manipulation. For 
various reasons it may not be ideal for 
personal computing, but it seems to be an 
excellent starting point. One drawback is 
that HP has the handshake patented. Their 
license fee is quite reasonable for some 
organizations but perhaps not for hobbyists. 
Other drawbacks include the question of 
common availability of the connector, etc. 
However it would be nice if there could be 
some degree of commonality between 488 
and any hobbyist standard that might 
evolve. 

Bob Huenemann 

4209 Armand Dr 

Concord CA94128 

Yes, 488 might be a good place to start. 
For those unfamiliar with the issue, the full 
name is IEEE Standard Digital Interface for 
Programmable Instrumentation, published 
by the Institute of Electrical and Electronic 



Engineers, Inc, document number IEEE Std 
488-1975. Quoting from the IEEE standards 
document, "The Hewlett-Packard Company 
has assured the IEEE that it is willing to 
grant a license under these patents on 
reasonable and nondiscriminatory terms and 
conditions to anyone wishing to obtain such 
a license. " To obtain a copy of the 80 page 
standards document write IEEE Service Cen- 
ter, 445 Hoes Ln, Piscataway NJ 08854. 



TEXT PROCESSING OUTPUT VIA 
CONVERTED TYPEWRITERS? 

Jim Lang's letter in the August BYTE on 
hard copy and IBM Selectric typewriters 
aroused a responsive chord. I too have been 
interested for some time in using the ubiqui- 
tous Selectric typewriter to obtain high 
quality hard copy. It seems to me that any- 
one familiar with both Selectrics and Tele- 
types would prefer the former — half again 
higher speed, much higher print quality, and 
both upper and lower case. The clincher 
would seem to be that most XYLs would 
look more favorably on the idea of spending 
half a kilobuck or so on something that can 
also be used as a good typewriter instead of 
something that can't. 

As some readers are probably aware, 
there is a commercial firm that markets a 
(rather expensive) applique that attaches to 
a standard Selectric and makes it into a 
terminal. (Tycom Systems Corp, 26 Just Rd, 
Fairfield NJ 07006.) 

In this connection, I'd like to point out 
that the US Patent Office is a veritable gold 
mine of technical information that can be 
obtained for a very modest price. For 
example, the patent documentation covering 
the Tycom system consists of 26 pages of 
diagrams and 50 fine print pages of descrip- 
tive text. An appreciable fraction of this 
consists of a very detailed description of the 
internal workings of the Selectric type- 
writer — it seems to collect details from the 
myriad of IBM patents on the Selectric into 
a single place. 

A copy of the printed version of this (or 
any) US patent can be obtained by speci- 
fying the patent number (#3,453,379 for 
the one mentioned above) and remitting 
50 cents to "Commissioner of Patents, Wash- 
ington DC 20231." 

Obviously one cannot duplicate a 
patented item in making a product for sale. 
Nor, in this case, would one want to, since 
with new ICs and components, the circuitry 
involved is verging on obsolescence. Never- 



Continued on page 136 



22 



altair 8800a 

TECHNICAL INFORMATION 



The Altair 8800a is a parallel 8-bit word/16-bit address 
computer with an instruction cycle time of 2 fis. Its 
central processing unit is the 8080 LSI chip. It can 
accommodate 256 inputs and 256 outputs, all directly 
addressable, and has 78 basic machine instructions. 
It is capable of directly addressing up to 65,000 bytes 
of memory. 




As well as the LSI chip, the CPU board contains 
the two-phase clock, status latch, buffers and 
the various lines going to the bus. (The buffers 
are tri-state devices.) 

The CPU contains six general-purpose registers, 
P counter, arithmetic unit, accumulator, stack 
pointer, instruction decoder, and miscellaneous 
timing and control circuits. The arithmetic unit 
contains the circuitry required to perform 
arithmetic in both decimal and binary forms. The 
stack pointer defines the current address of the 
external stack, which resides in memory. The 
stack is used to service interrupts and provides 
virtually unlimited subroutine nesting. The 
instruction decoder decodes the instructions and 
sets up the various registers, gates, etc., in the 
CPU for proper functioning. 

There are 36 LED status indicators on the front 
panel, 1 6 of which are used for the address bus, 
8 for the system status latches, and 8 for the 
data bus. The four remaining LEDs are used for 
indicating memory-protect, interrupt-enable, 
system-wait and hold status. Address line inputs 
AO through A15, data lines DO through D7, and 
the various status lines originate on the 
CPU board. 

The front panel control board contains the 
circuitry for interfacing between the control 
switches located on the front panel and the CPU. 
In addition to the interconnections to the actual 
processor, this board accepts memory address 
switches AO through A1 5 (also on the front 
panel). The first eight of these switches (DO to 
D7) are used to put data into the CPU. 

The front panel logic permits the following 
functions: STOP — stops the processor 
immediately after it completes the current 
instruction; RUN — starts the processor at the 
current address; EXAMINE — causes the data 
stored at the location (set by the switches) to be 
displayed in binary by LEDs; EXAMINE NEXT— 
steps the P counter once and displays the word 



stored at the next location; DEPOSIT — causes 
the information preset by the switches (A0-A7) 
to be stored in memory; DEPOSIT NEXT— steps 
the P counter and loads the memory; SINGLE 
STEP — steps the program one machine cycle; 
RESET — clears the CPU and sets up a starting 
address of O; PROTECT/UNPROTECT— allows 
selective write protection of blocks of memory. 
When a block of memory is protected, it is 
impossible to write over that block, but its 
contents can be read out. 

With proper adjustments, any memory speed can 
be used in the 8800a computer, although 
memory access time must be 500 nanoseconds 
or less if it is to be run without wait states. In 
addition to semiconductor RAMs, the processor 
will also service ROMs and PROMs. 



NEW FEATURES 
POWER SUPPLY 

The power supply provides three voltages to the 
8800a bus: +8V pre-regulated at 8 amps; 
+ 15V at 500mA; -15V at 500mA. 

FAN 

A fan has been mounted on the back panel of the 
8800a to provide cooler operating temperatures. 

18 SLOT MOTHERBOARD 

The four-slot expander cards in the Altair 8800 
have been replaced with a single-piece 18-slot 
motherboard. The 18-slot motherboard contains 
the 100 solder lands that comprise the 
100 pin bus. 

FRONT PANEL SWITCHES 

The front panel toggle switches have 50% longer 
handles that are flat (instead of round) 
for easier use. 

An assembled Altair 8800a may be ordered with 
six, twelve, or eighteen sets of edge connectors. 
The Altair 880Oa kits include an edge connector 
with every plug-in module purchased. 



•Fan 




-New 18-Slot 
Motherboard 



New Front Panel Switches 



The four boards, along with the power supply, mount 


in an 18" deep x 17" wide x 7 


' high (45.7 x 43.2 x 


17.7-cm) metal cabinet. 




SPECIFICATIONS 


Number of Boards 


Up to 18 


Microprocessor 




Model 


8080A 


Technology 


NMOS 


Data Word Size, Bits 


8 


Instruction Word Size, Bits 


8 


Clock Frequency, 


2MHz 


Add Time, Register to 




Register, Microsec. 




Per Data Word 


2 


Number of Instructions 


78 


Input/Output Control 




I/O Word Size, Bits 


8 


Number of I/O Channels 


256 


Direct Memory Access 


Optional 


Interrupt Capability 


Std. one level 


Vectored Interrupt (8 priority I 


evels) Optional 


Software 




Resident Assembler 


Yes 


Cross Assembler 


No 


Simulator 


No 


Higher-level Language 


BASIC 


Monitor or Executive 


Sys. mon.; text edit. 


Software Separately Priced 


Yes 



(Sddqla^ 



2450 Alamo S.E. Albuquerque, New Mexico 87106 



Consider 
what 




ir ill buy 

in 

M97S: 



or 






5iX7££N 

SLacK&WrtiTe 

PQ5feK5 OF 

cnm.it chan 



xi zooms on 

aN AWUKHE 
FLIGHT 

CrtETZELS £XWQ 



T£N HOUH5 Of 

RWiNS IN 
DOVWoWNJ 

W/15H1NQTON, DC. 





rZ/\ ONE FULL-YEAR 

1 V J MEMBERSHIP IN THE 

IEEE COMPUTER SOCIETY 

and with it, an automatic subscription to 
COMPUTER magazine. 



Special introductory offer: join now and receive FREE the one-volume collection of COMPUTER reprints, 
"Microprocessor Architecture and Applications." 

Fill out and mail the form below. Find out why membership in the IEEE Computer Society is one of the 
wisest investments you'll ever make. (At 24 bucks, can you afford NOT to?) 



25 YEARS OF SERVICE 




IEEE COMPUTER SOCIETY 



Quick — send me everything I need to know about joining the IEEE Computer Society. 
You can send me my free copy of "Microprocessor Architecture and Applications" 
when I join. 

Name 

Address 



MAIL THIS FORM TO: 

IEEE Computer Society • 5855 Naples Plaza • Long Beach, California 90803 



A Ham's 
Application Dreams 



o 



o 

o 






WJ Hosking W7JSW 
8626 E Clarendon 
Scottsdale AZ 85251 



I'm writing this article for a selfish 
motive. I want to build some things and the 
construction articles aren't here yet, parti- 
cularly in state of the art. 

I just finished a television typewriter 
(TVT) which has alphanumeric character 
generation and storage capacity plus capa- 
bility of serial or parallel ASCII (plus con- 
trol) interface. Now that it is finished, I 
want more than a plaything. I would like to 
have the following capabilities: 

a) Keyboard Morse code (CW) transmit 
and receive encoding with CRT dis- 
play. 



b) Keyboard RTTY transmit and CRT 
RTTY read. 

c) Alphanumeric slow scan TV transmit 
and receive. 

d) Computer terminal operation with a 
telephone coupled to a timeshared 
computer system. 

Description 

My envisioned system is shown in figure 
1. Let's tackle that drawing block by block, 
considering the TVT and CRT to already 
exist and applying the constraint of a mini- 
mum hardware (low cost) implementation. 















FAST TO 
SLOW SCAN 
CONVERTER 




















CRT 










ri 






VIDEO 










V 




















i— ► 


CW KEYER 

AND 

CONVERTER 






KEY 
MIC 
RCVR 








1 


i 












r 


>d 




' 






h 


-n 






V 


y 








' 
















TTL i 
DATA 


i 








TVT 




^ 


SMALL 
COMPUTER 
SYSTEM 
WITH 
SOFTWARE 


4— 








PARALLEL 










KEYBOARD 




















i L 


SERI 

V 








DAT 


A 




TRANSCEIVER 




AL 


— ► 


FSK 

KEYER AND 
CONVERTER 








ACOUSTIC 
COUPLER 
























i 
1 






Figure I: An ideal ham 
station configuration, 


•^PH 


UNE 




where "ideal" is defined 
by the author in the ac- 








companying text. 



26 







i 



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SYSTEM WORKS 

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Please enroll me as a member of the Computer Professionals' Book Club 
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MICROPROCESSOR 



216X8 
ROM 



Morse (CW) Transmit and Receive 

Looking back through previously existing 
magazines on electronics and amateur radio, 
I have found several articles on Morse 
keyboards, most using bulky diode matrices. 
The literature on Morse code readers is much 
harder to find, and as this is written I found 
nothing approaching state of the art. 

It would seem that, with the rapidly 
dropping prices of microprocessors and their 
associated memories and peripherals, the 
way to go on this project would be a 
computer using minimum hardware imple- 
mented with an LSI microprocessor. I have 
presented a very basic approach to such a 
system in figure 2. All that would be 
required from the hardware standpoint 
would be the microprocessor, a read only 
memory for permanent program storage, a 
programmable random access memory for 



POWER 
SUPPLY 



256 X 8 

PROGRAMMABLE 

MEMORY 



I/O 
(PIA) 



■T> <S 



8 BIT 
DATA 
AND 
CONTROL 



<^> 







CW OR 

RTTY 

INTF 



Figure 2: For a dedicated 
"black box" ham radio 
data processor, the use of 
a microprocessor system 
with as much as 2 K by 8 
bits of program ROM with 
perhaps 256 bytes of pro- 
grammable memory for 
data buffering. | Exact 
amounts of ROM will 
depend upon the com- 
plexity and features of the 
software loaded; 2 K 
should be reasonable for 
Morse and radioteletype 
support .... CH] 



working storage, and a peripheral interface 
adapter (PIA) for input and output. Some 
other items such as power supplies and 
clocks are also required. I would hope that 
the microprocessor interface unit cost could 
be kept under $100. 

Now for the required design work. This 
black box ! am planning would have to 
accept a seven bit ASCI! code (serial or 
parallel) plus a data present strobe. The box 
would convert the input character to serial 
Morse code and output the code over some 
suitable keying circuit to the station trans- 
mitter. Since we are talking about a small 
computer, the Morse code speed desired 
could be ordered by an appropriate input 
code sequence from the keyboard. The box 
then has to send a character or flag back to 
the TVT to say it is ready for a new 
character. 

The reverse or receive mode is the Morse 
to ASCII conversion. However, here a special 
conversion device will be needed to change 
the audio out of the receiver to some kind of 
signal that the computer can recognize and 
convert. The software which drives the 
converter must also recognize intercharacter 
versus interword spacing and provide space 
characters to the TVT where required in the 
received text. 

The end result would be Morse code sent 
by the keyboard through your transmitter 
and the Morse code heard by your receiver 
being displayed on the TVT CRT. This is a 
job for both hardware and software de- 
signers. [See the articles elsewhere in this 
BYTE for technical details . . . . CH] 

Radioteletype (RTTY) Transmit 
and Receive 

The same basic microprocessor described 
above could be used to provide the radio- 
teletype function instead of or, with more 



Editor's Note 



Here is a short article on a theme of "wouldn't it be nice to have X" v/nere 
X is defined as some automation applications for the amateur radio station. It 
is timely, in the context of this month's Morse code theme, in that one of the 
author's application goals is detailed in several different technical articles In 
this issue. There's still plenty of room for further explorations of computer 
application to amateur radio technology of course .... CH 



28 



ROM, in addition to the Morse code 
function. 

Here, the transmit conversion would be 
from parallel ASCII (or serial) to serial 
Baudot at a transmission speed programmed 
into the computer. The system could easily 
include niceties such as automatic line feed, 
etc. The Baudot output would be serial 
signals sent to an FSK transmit terminal 
unit. When the FCC finally gets around to 
approving ASCII on the air, a simple ROM 
change would reconfigure the hardware to 
reflect this improvement. 

On the receive side, a standard RTTY 
terminal unit would be used to convert the 
received FSK signal to a serial binary signal 
for the microprocessor. This keying signal 
would be routed to the processor which 
would convert it to either serial or parallel 
ASCII, whichever your TVT or terminal 
interface requires. 

This system would work just as a regular 
teleprinter does, except that the received 
copy would be on a CRT instead of hard 
copy on a printer. For those desiring hard 
copy, a printer can easily be interfaced to 
the computer system. The development here 
is mostly software since really good terminal 
unit and keyer designs are readily available. 

Slow Scan TV 

This is another area eagerly awaiting new 
developments. The TVT already has fast 
scan composite video as an output and the 
CRT involved accepts composite video. The 
problems and areas for new development are 
mostly in the area of conversion from fast 
scan to slow scan and reverse. It is highly 
likely that the microprocessor box we have 
already discussed can do at least part of this 
job for us. I think this one is really ripe for 
new breakthroughs. 

Computer Terminal Operation 

This is probably the easiest task. There 
are those out there who, had they the 
terminal, could make use of one or another 
timeshared computer system. This use re- 
quires coupling in one way or another to a 
telephone line. The easiest way to do this 
without angering Ma Bell is with an acoustic 
coupler. 

Conclusion 

As I said earlier, this was an idea article 
and now I'm going to sit back and eagerly 
await the neat ideas generated by all you 
experts out there. There's room for much 
development in both hardware and software. 
If you have designed something to do one of 
these jobs, then publish it for the rest of us." 




Meet the new 

OSI400 
Computer System. 

Now more performance and 
more flexibility actually cost you less. 

Ask yourself how much system you need. Or how little. 
Whatever the answer, even if you want to change it later, you 
get more system for less money with the OSI 400. 

Start with the OSI Superboard. Add your choice (!) of a 
6502, 6512 or 6800 microprocessor; eight 2102s for 1024 bytes 
of RAM; and an external front panel. Power it up and you have a 
working CPU. Or populate the board with a processor, system 
clock, 512 bytes of PROM, 1024 of RAM, an ACIA with RS-232 
or 20 ma loop interface, a PIA with 16 I/O lines and full buffer- 
ing to as many as 250 system boards for system expansion. 

Even fully populated, Superboard costs less than $140 with 
a 6502, less than $160 with a 6800. 

But take a look at what you can have for $29. Our special 
offer includes a plated-through-hole G-10 epoxy Superboard, 
bare, plus a 50-page theory of operation and construction 
manual including complete chip documentation in an attrac- 
tive OSI binder. 

And Superboard is just the beginning of the OSI 400 
system. You can expand its memory; interface to many l/Os 

including plotters, cas- 
settes, FSK, ASCII, 
Baudot and more; go 
video, includinggraph- 
ics; even add floppy 
disk. And bare boards 
are just $29each, com- 
plete with in-depth 
manuals. 
But first things first. 

400 me now! SPECIAL —$29 postpaid with this coupon only. 

Name 




Address . 
State 



City _ 

.Phone . 



Enclose check or money order or supply 
Bank Card information below. 



Card No. (include all digits) — 
Interbank No. (Master Charge) 



Good thru . 



Ohio residents, 
please add tax. 



OSI 



Sign your name 

Ohio Scientific Instruments 

11679 Hayden Street 

Hiram, Ohio 44234 Dept. B 



29 



Add This 6800 MORSER 
to Your Amateur Radio Station 



Robert D Grappel 
148 Wood St 
Lexington MA 02173 

Jack Hemenway 
151 Tremont St 
Boston MA 021 11 



A great many amateur radio operators 
find Morse code operation a nuisance. It 
isn't easy to develop proficiency in copying 
code, and it often seems that those stations 
one wants to work are just those whose 
operators send code too fast to readily copy. 
There must be hundreds of Morse coding 
aids developed over the years, ranging from 
mechanical keys and paper tape transmitters 
to fancy code memories and typewriter like 
automatic transmitters. Nearly every ad- 
vance in electronic componentry has 
spawned a new series of Morse code aids. 
Nearly all have been designed to help the 
operator send more effectively; the problem 
of reception has been more difficult to solve. 
Some complex circuits have been devised 
which can copy code, provided that it 
follows strict timing requirements. Truly 
general code followers, circuits which can 



copy code with performance approaching 
that of a skilled human operator, are rare. 
They are very complex, using dozens of 
integrated circuits, large diode matrices, etc. 
The recent advent of inexpensive yet power- 
ful microcomputers can make the dream of a 
relatively simple yet very general code fol- 
lower possible. Why a computer? First of all, 
it allows one to develop and improve an 
algorithm by simply changing program, 
instead of rebuilding complicated circuitry. 
Second, since the computer is not restricted 
to running only the Morse programs, one can 
use the computing power for any number of 
other uses, limited only by the operator's 
creativity. This article describes a code fol- 
lowing computer program as implemented 
on a Motorola 6800 microcomputer. It can 
copy any code speed from 3 to 60 words per 
minute, and can adjust to the irregularities 



Development of MORSER 

The program for MORSER shown in this article was produced by a 
relocating assembler designed and written by Jack Hemenway and described 
somewhat humorously in the August BYTE article "Jack and the Machine 
Talk" /page 52/ by authors Grappel and Hemenway. The relocatability 
feature allows one to put assembled code anywhere in memory without 
reassembly, a feature which is most useful for building large programs. One 
drawback of this is that relocatable addresses (denoted "R" in the listing) are 
always two bytes, so the programmer cannot generally make use of 
Motorola's direct addressing mode, which requires addresses to be in the base 
page, the first 256 bytes of memory address space. Since MORSER was 
programmed so that both data and program code are relocatable, it is not the 
most compact form in which the algorithm could be expressed on a 6800. If 
one rewrote the program to keep all the variables in the first page of memory 
and used direct addressing wherever possible, about 75 bytes of storage could 
be saved. 



30 




Photo I: Author Robert 
Grappel, shown at the con- 
sole of Jack Hemenway's 
computer system with a 
hand held switch used to 
test Morse code inputs to 
MORSER during the de- 
velopment of the program. 



of hand sent code. A minimal amount of 
external hardware is needed, and the 
program only takes about 600 bytes of 
memory. The algorithm can be converted to 
run on almost any 8 bit microprocessor. 
Since you are still reading this, you are 
hooked. Let's begin to dissect the program. 

MORSER consists of five segments: 
initialization, decoding, delay timer, 
sampler, and terminal driver. In the program 
listing, lines 001-068 are initialization, lines 
069-200 are decoding, 200-213 form the 
delay timer, 214-250 form the audio 
sampler, and lines 251-277 drive the output 
terminal. Each segment will be described in 
turn. 

The major function of initialization is to 
define the variables in the program and to 
give them appropriate initial values. The 
operating system of Jack Hemenway's 
machine performs some of the initialization 
automatically at loading time, such as clear- 
ing the peripheral registers and setting the 
stack pointer. If the program is to be run on 
a system without these features, then state- 
ments to perform these functions must be 
added to initialization. The values of DTIME 
and MAXCNT must be set, based on the 
computer running the program. DTIME 
adjusts the program timing to the processor 
cycle time, and MAXCNT adjusts the ter- 
minal driver to the data rate of the terminal 
in use for output. These values are not very 
critical, and the program comments list 
typical values for these. constants. As assem- 
bled, MORSER assumes a 6820 PIA at 
addresses 8040-8043 (hexadecimal). The 
peripheral interface can be relocated to suit 
the particular hardware configuration in use. 



Only one input bit is needed; the rest of the 
PIA may be used for other functions. The 
listing also shows that an external sub- 
routine, OUTCRT, is being used to drive a 
CRT terminal for output. This program is 
part of Jack Hemenway's system. The user 
of MORSER must provide a suitable routine 
for his or her own system. For example, the 
OUTEEE routine in Motorola's MIKBUG 
will work. The idea is that some way must 
be found to take a character from the A 
accumulator and place it appropriately on 
the output device. An automatic carriage 
return and line feed is required, as MORSER 
does not count the characters in a line. 

Initialization also sets up the decoding 
table DECTAB. The ordering of this table is 
the heart of MORSER. The ASCII repre- 
sentation of a character is placed in 
DECTAB at an offset generated as follows: 
Generate a byte with a binary 1 for every 
dot and otherwise; generate another byte 
with a binary 1 for every dash and 
otherwise. For example, the letter A (Morse 
• -) generates 00000010 and 00000001 
respectively. Multiply the dash byte by two 
with a left shift and add the bytes. The 
result is the character offset. Using this 
algorithm, il is seen that A is at an offset of 
4. All other Morse characters are generated 
in the same manner, and the rest of the table 
is filled with blanks. It is the function of the 
remainder of MORSER to convert the 
incoming audio signal into offsets into 
DECTAB, and to transfer the character 
representations found there to the output 
device. 

MORSER decides which inputs are dots, 
dashes or word spaces by sampling the audio 



31 



Listing J: The MORSE R 
program, as assembled for 
the 6800 at location 0000 
hexadecimal using Jack 
Hemenway's assembler. 
The program is written in 
a relocatable fashion, so 
no data references are 
made to page of the 
6800 address space. In 
Jack's assembler, the col- 
umn immediately follow- 
ing the hexadecimal code 
output sometimes has the 
letter "R" in it. This indi- 
cates a reference to a re- 
locatable symbol. 



input at intervals. The delay timer section 
controls the period of the sampling. This 
tiny section of code (only six instructions) 
actually consumes more than 75% of the 
running time of MORSER. In fact, the time 
spent in all other parts of MORSER is 
considered negligible in the design. A rough 
"rule of thumb" states that one word per 
minute of Morse code is equivalent to one 
dot length per second. All other code ele- 
ments have lengths nominally equal to 
integer multiples of the dot length. 
MORSER is designed to sample each dot 
length time unit four times. Since the range 
of code speeds is 3 to 60 words per minute, 
this implies that the sampling period should 



range from 100 to 4 ms. The delay timer is 
adjusted by DTIME to count time in milli- 
second intervals. The variable TIMER de- 
termines how many milliseconds will be 
spent in the delay loops. This time is roughly 
the sampling period, since the longest path 
through the rest of the program is at most 
0.3 ms. TIMER is adjusted in the decoding 
section to suit the speed of the code being 
processed. The formula 250/TIMER gives 
the approximate input code speed in words 
per minute, after the program has been 
running for several characters and has ad- 
justed itself to the code. 

The sampling section repeatedly tests the 
status of the audio input signal against its 



0B5 R RFGIN JMP INI1 



FFtIN INI II ALIZP7IUN 



0002 






0083 


0003 


72F0 


0004 


0003 


8040 


0005 


0003 


8040 


0006 


0003 


8041 


0007 


0003 


8042 


0008 


0003 


8042 


0009 


0003 


8043 


0010 






001 1 


0003 


0020 


0012 






0013 


0023 


00 


001 4 


0024 


FF 


0015 


0025 


42 


0016 






0011 






0018 






0019 






002 


0026 


FF 


002 1 


0027 


FF 


0022 


0028 


0C 


0023 


0029 


09 


002^ 


0020 


14 


002 5 






002 6 






0027 






0028 


002E 


00 


0029 


002C. 


00 


0e30 


0020 


00 


0031 


002F 


0C 


0032 


002F" 


00 


0033 


0030 


00 


0034 


0031 


1 


0035 


0032 


1 4 


0036 


0033 


18 


003 7 


0034 


00 


00 36 






0039 






0040 






004 1 






0042 






0043 






0044 






0045 






0046 






0047 






00 48 






0049 






0050 


0035 


20 


0051 


0036 


45 


0052 


0046 


46 


0053 


0056 


20 


0054 


0066 


2F 


0055 


0076 


20 


005 6 


0079 


04 


0057 


007A 


20 


0058 


007F 


20 


0059 


008F 


20 


0060 


009F 


3F 


0061 


00AF 


20 


0062 






0063 






0064 






006 5 


00P5 


86 04 


0066 


00F7 


P7 8H41 


0067 






0068 






0e69 






007 






007 1 






0072 






007 3 






007 4 






007 5 






007 6 






0077 






0078 






0079 







OUTCRT 


E&U 


S72F0 


SYSTEM CRT HANDLER 


MAI 


E&U 


56 040 


PERIPHERAL LOCATION? 


DDR1 


F.OU 


*8040 




CRRi 


FCU 


«8F41 




M A2 


FGU 


58042 




DDR2 


EhV 


58042 




CRR2 


E6U 


T8 043 




* AUDIO INPUT ON 


SIDE \> PIT 


PUFF1 
COUNT 


RMF 


32 


DECODED OUTPUT PUFFER 


FCB 


H 


OUTPUT 1 [mfr 


DFLAC 


FCF 


TFF 


"DATA-READY" FLA1_ 


DT1MF 


FCF 


66 


DFLAY LOOP TIMER 


* ADJUST DTIMF FOR PROCESSOR CYCLF 1IMF 


* D1IMF=I6S FOR 


1.0 USFC PW0CF550R 


* DTIME = 88 FOK 


£•6 USFC FROCFSSOR 


* DTIMF= 66 FUR 


2.5 USFC PROCESSOR 


LDATA 


FCfc 


*FF 


LAM DATA 


LMARK 


FCF 


TFF 


LAST MARK TYPF 


LMLEN 


FCF 


1? 


LAST MARK LEN(.-IH 


LlftS? 


FCF 


9 


LFTTFR-SRACF L F M t 1 H 


MAXCNT 


FCF 


2 


TERMINAL CONSTANT 


* MAXCNT=40 FOR 


110 PAUU OUTPUT TERMINAL 


* MAACNT=20 FOR 


300 PAUD OUTPUT TERMINAL 


* M£XCNT= 


8 FOR 


FASTER TERMINAL 


MLFN 


FCF 


U 


MARK LFNCTH 


0LPSTA 


FCF 





OLD KARK/SFACF FT AT -US 


OUTXCV 


FCF 





FUFFFF POINTER 


SPL^N 


FCF 


12 


SPATF LFNCTH 


STLDul 


FCF 


i, 


DOT RFCISTFR 


STLDAS 


FCF 





DASH RFC I SI FR 


TCNT'R 


FCF 


1 


1 IMF COUNTFR 


TIMFR 


FCH 


2» 


CLOCK ADJUST VALl'P 


HD5P 


FCF 


24 


WORD-SPAC^" LFNC T -i 


wosxcv 


FCF 


C» 


FUFFFR FOI vT Ffc 



DFC0DING TAFLF GENERATED AS FOLLO'/S: 
TAKF MOR.SF. CODF FUR CHfRACT Fk 

GENERATE 6-EI 1 VALUF. l=OUT> fc=DA5H 
CFNFRATE 6-FIT V/ALUF, 1 = DASH . P = DO T 
SHIFT 5FCGND VALUE LEFT ONE PLACE 

ADD VALUES THE RESULT IS THF OFFSET 

OF THAT CHARACTER IN DEC TAP 

FLANKS OCCUR WHERE THFRE IS NO' VALID 

CHARACTER 

RFF: JO RC EN SON. HAM RADIO, MAY 72 



DECTAF FCC 




• 


FCC 




ET I ANMSURUDKGGHV ' 


FCC 




F LJF EXCYZG 5*' 


FCC 




3 2 16 ' 


FCC 




/ 7 8 90 


FCC 






FCF 




P04 END OF IRAN 


FCC 






FCC 




? • • 


FCC 






FCC 




t < » : ' 


FCC 






* CONFIGURE 


PERIPHERAL INTERF 


I N I T L DA 


A 


• 504 


STA 


A 


Ckhl 



END OF INITIALIZATION SECTION 

DECODING ALGORITHM HAS EI VF RULFS: 

1. IF NEk MARK 15 AT LEAST TWICF 
THE LAS! ONE, 1HFN IT IS A DASH 

2. IF NEW MARK IS LFSS THAN HALF 
THE LAST ONE. THEN II ISA DOT 

3. IE MARK IS MORE THAN HALF. PUT 
LESS THAN TWICF, IT IS SAMF AS 
THE LAS! MARK 

4. IE A SPACE IS MORF THAN 3/4 LIE 

LAST DASH LENGTH, IT IS LFTTER SPACE 
5- IF A SPACF IS MORF THAN TWICE THE 
LAST DASH LFNCTH, IT IS WORD SPACE 



008 2 
008 3 
008 4 
00B5 

008 6 
0087 
0088 
0089 

009 
009 I 
0092 
009 3 
009 4 
009 5 
009 6 
009 7 
009 6 

009 9 
0100 

010 1 

0102 

0103 

0104 
0105 
P106 
0107 
0108 
0109 
ES110 
01 1 1 
01 12 
01 1 3 
01 1 4 
01 15 
01 16 
01 17 
01 18 
01 1 9 
0120 
0121 
PI22 
0123 

012 4 
0125 
B126 
U127 
012b 
0129 
0130 

013 1 
0132 
0133 
0134 
0135 
0136 
01 37 
0138 
0139 
0140 
0)41 
0142 
01 43 
01 44 

ei4s 

0146 
01 47 
0148 
01 49 
0150 
0151 
0152 
01 S3 

01 54 

01 55 
0156 
01 57 
01 58 
0159 
0160 
0161 
0162 



P^F: PETIT, GST. 



00PA 7p 0024 

P0FD 2A 03 

00PE 7F 01C5 

00C2 7D 0026 

0BC5 ?A 03 

00C7 7E 0166 

00CA F6 0028 
00CD 48 

00CE El 002P 

00D1 2F 50 

00D3 E6 0028 

00P6 -57 

00D7 Fl 002P 

00DA 2A 05 

M0DC 7D 0027 

00DE 2P 42 



00 Fl 
00E3 
00F.6 
00F9 
00FC 
00ED 
00FF 
PEFH 
00F2 
00F3 
00F6 
00E9 
00EC 
00.FE 

1 00 

01 03 
0105 
0108 
010F 
010D 
010F 
0111 

0114 

117 

01 19 
01 IF 
01 ID 
0120 



86 01 
B7 0027 
B6 002 F 
E6 0030 
46 

25 6E 
58 

25 6C 
4C 

61 002F 
E7 0030 
E6 002P 
C0 03 
2 0D 
7A 0032 
?F 0F 
7F 0032 
7C 0032 
20 07 
CI 02 
PF 3 
IV. R03? 
E6 0032 
CI 76 
?D pip 
C6 78 
F7 ££32 
7F 0150 



0123 F6 002P 

0126 47 

0127 16 
012B 57 
0129 IP 
012A F7 0f,29 
012D 66 FF 
U12F P7 0C27 
0132 B6 et-2F 
0135 E6 0030 

0138 48 

0139 2 5 2 3 
013B 58 
013C 25 20 
13F 5C 

13F F7 002F 

142 F7 0030 

0145 P6 002F 

0148 48 

0149 2A 02 
014B 8 6 7F 
014D F7 0033 



TST 
FPL 
JMP 
TST 
FPL 
JMF 
LDA 
ASL 
CMP 
PLE 
LDA 
ASR 
CMP 
PPL 
TST 
PMI 



STA 
LDA 
LDA 
ASL 
PCS 
ASL 
E-CS 
INC 
STA 
STA 
LDA 
SUE 
PGF 
DEC 
PCI 
CLR 
INC 
FRA 
CMP 
PLC 
INC 
LDA 
CMF 
PLT 
LDA 



RELOAD STA F 
JMF 



DFLAC 
J 10 
WAI T 
LDATA 

J 1 1 

SFACP 

LMLEN 

ML EN 
DASH 

LMLEN 

MLFN 
DOT 
LMARK 
DASH 



LMARK 
SILIiUT 
STL DAS 



STLDOT 

STLDAS 

ML EN 

#3 

NFAST 

TIMER 

PUT 

TIMFR 

TIMER 

PUT 

#2 

PUT 

TIMFR 

TIMFR 

*\P? 

R EL n A n 

* 120 

TIMER 

STORF 



J AN 19 7 1 
NEW DATA RFADY? 



WAI I FOR DATA 

LAST DATA MARK OR SPACE? 



MLFN .CE. 2*LMLFN? 



MLFN .LT. LHLFN/g? 



LAST DATA MARK OR SPACE? 



R J 12 



LDA 
ASR 
TAP 
ASR 
ABA 
S1A 

Lnr 

STA 
LDA 
LDA 
ASL 
PCS 
ASL 
PCS 
INC 
STA 
STA 
LDA 
ASL 
FFL 
LDA 
STA 



PUT DOT INTO RFCISTFR 



TOO MANY BITS FOR REGISTER 



INSERT POT 



REC-FNFRATF CLOCK RAT F 
PASED ON DOT LFNCTH 
IF LESS THAN 3, CLOCK SLOW 
IF MORF THAN 5, CLOCK FAST 
IF EFTWEEN 3 AND 5, O.K. 



LIMIT T IMFR TU 1- 120 



SET LTRSP=3/4*MLEN 



PUT DASH INTO RFC ISTER 



LTRSF 

*«FF 

LMARK 

STLDOT 

STLDAS 



LENFhR TOO MANY FITS FOR REGISTFR 



STLDOT 
STLDAS 

MLFN 

J 12 

ft 127 
WDSP 



INSERT CASH 



SET WDSP=2*MLEN 



0150 F6 PF2F R STORF LDA A MLFN 

0153 P7 P.VPP, R STA P LMLFN 

0156 86 FF RFSFT LDA A **FF 

0158 P7 0024 R STA A DFLAC- 

01 5E 7E 0IC5 R JMF WAIT 

015F 7F 002E R LENFRR CLR STLDOT 

0161 7F 0030 R CLR STLDAS 

0164 20 E0 BRA RESET 



RFSFT "DAT A-RFAPY" FLAG 



ELIMINATE PAD DATA 
C I VE UP ON CHARACTER 



32 



0163 


01 66 


f'6 


0C.2E 


ft 


SPACE 


LDA 


A 


5PLEN IS SPLEN -CE. LTKSP? 


016-0 


0)69 


PI 


0029 


k 




CM* 


A 


LThSP 


0165 


016C 


2D 


FR 






FLT 




F- F S F T 


0166 


ei6E 


F6 


C030 


i; 




LDA 


P 


STLDAS DECODE L^TT^R FROM F-FCS- 


0167 


0171 


C4 


3F 






AND 


F 


*'3E RESTRICT TO 6 PITS 


0168 


0173 


B6 


002F 


ft 




LDA 


A 


STL DOT 


0169 


0176 


84 


3F 






AND 


A 


* *. 3 F 


0170 


0178 


56 








ASL 


P 




017 1 


01 79 


IP 








AFA 






0172 


01 7A 


84 


7F 






AND 


A 


#<7E ftFSTftlCT TO 7 FITS 


0173 


017C 


CF 


0035 


R 




LDX 




#DFCTAF 


0174 


01 7E 


B7 


0183 


R 




STA 


A 


iwnrx i + i 


0175 


0182 


E6 


00 




IN HEX 1 


LDA 


P 


0»X RETRIEVE ASCII CODF 


0176 


0184 


£6 


00 34 


ft 




LDA 


A 


WDSXCV PUFFER FULL? 


0177 


0187 


81 


a e 






CMP 


A 


#32 


0178 


0189 


2C 


CP 






BGE 




RESET I F SO* P(>NT 


0179 


018B 


BP 


002D 


ft 




ADO 


A 


OUTXCV GENERATE BUFFER POINTER 


0180 


018E 


84 


IF 






AND 


A 


^TlF RESTRICT RANCF 


0161 


0190 


7C 


0034 


R 




INC 




WDSXCV 


0182 


0193 


CE 


0003 


R 




LDX 




#BH3FFI 


01B3 


0196 


F7 


019A 


k 




STA 


A 


1NDEAP+ 1 


0161 


0199 


E7 


00 




IN DFX 2 


STA 


P 


0>X PUT CHAR. IN10 EUFFER 


0185 


019E 


7F 


002F 


ft 




CLft 




STLDOT CLEAR ftECISTERS 


0186 


019E 


7F 


0030 


K 




CLR 




STLDAS 


0187 


01 Al 


E6 


002E 


R 




LDA 


A 


SPLEN IS SPLFN .OP. WDSP? 


0188 


01A4 


PI 


0033 


R 




CMF 


A 


WDSP 


0189 


01A7 


2D 


AD 






BLT 




RESET NOT A WORD SPACF 


0190 


01 A9 


F6 


0034 


R 




LDA 


A 


WDSXCV/ INSFRT PLANK FOR WORD SPACE 


0191 


01AC 


81 


20 






CMP 


A 


#32 IS PUFFFR FULL? 


0192 


eiAF. 


2C 


A6 






POF 




RESET I F SO* PUNT . 


0193 


1F0 


FE> 


002D 


R 




ADD 


A 


OUTXGV GFNFRATF PUFFFR FOI\'TER 


0194 


01E3 


8^ 


IF 






AND 


A 


#«"1F RES1RI CT KA.-.CE 


0195 


01P5 


7C 


0034 


ft 




INC 




WDSXCV 


0196 


01B8 


C6 


20 






LDA 


P 


#S20 ASCII BLANK CHAftACTFF 


0197 


01 PA 


CF 


0003 


ft 




LDX 




#EUFF1 


0198 


01PD 


P7 


01C1 


ft 




STA 


A 


INDFX3+ 1 


0199 


01C0 


F.7 


00 




INDFX3 


STA 


B 


0»X PUT FLANK INTO PUFFER 


0200 


01C2 


7F 


R1 56 


ft 




JMP 




RFSFT 


020 1 










******: 


***** 


>****-*********#******************** 


C202 










* 








0203 










* END OF 


MAIN PROGRAM 


0204 










+ BFG1N DELAY TIMER 


0205 










* C-FNERATE 


"TIMER" MSECS. OF RFLAY 


0206 










* 








0207 










+ *****: 


*** *i 


<**************#******#***#***»*** 


0208 


01C5 


B6 


0032 


ft 


WA1 1 


LDA 


P 


T IMFR 


02 09 


01C8 


F6 


0025 


R 


DLOOP1 


LDA 


F 


D T IMF 


0210 


01CF- 


5A 






DL00P2 


DEC 


P 




021 1 


01CC 


26 


FD 






PNF 




DL00P2 


0212 


01CE 


4A 








DEC 


A 




0213 


01CF 


26 


F7 






ENE 




DL00F1 


02 1 4 










******: 


***** 




.A****************************** 


0215 










* 








0216 










END OF 


:)FLAY TIMFR 


02 17 










* if: 


?T AUDI INPUT HERE 


0218 










* H AN DL F 


01 


JTPUT TO TERMINAL 


0219 










* 








0220 










*********** 


*•■* 


;**************************+*** 


022 1 


1D1 


B6 


6040 






LDA 


A 


MAI LET AODIO INPUT 


(.'222 


eiD-'i 


84 


<m 






AND 


A 


#*0 1 BIT ZERO OF F1A 


0223 


C1D6 


Bl 


002C 


R 




CMP 


A 


OLDSTA PI1=0 I S MARK 


022 4 


01D9 


26 


10 






PNE 




DIFFER 


022 5 


01 DP 


7C 


0031 


K 




INC 




TCNTR 


022 6 


01DF 


7D 


0031 


ft 




TST 




TCNTR OVERFLOW OF TCNTR? 


0227 


01 El 


2C 


05 






PGE 




OKAY 


0228 


01E3 


C6 


78 






LDA 


En 


#120 FIX OV/ERELOW 


0229 


01E5 


F7 


00 3 1 


R 




STA 


E 


TCNTR 


P230 


01E8 


7E 


02 1C 


R 


OKAY 


JMP 




TRANS 


0231 










* 








0232 


P1FP 


C6 


01 




DIFFER 


LDA 


P 


#1 SFT "DATA-READY" FLAC 


02 33 


01FD 


F7 


0024 


ft 




STA 


P 


DFLAC 


0234 


01F0 


F6 


00 3 1 


R 




LDA 


B 


T CN T ft STORE IT FM L EiN C T H 


0235 


01F3 


7D 


002C 


h 




TST 




OLDSTA A MARK Oft SPACE? 


023 6 


01F6 


26 


06 






PNE 




ZERO SPACE 


0237 


01F8 


F7 


002B 


R 




STA 


E 


ML FN 


0238 


01 FP 


7F 


0201 


R 




JMP 




NMARK 


0239 


01 FE 


F7 


002F 


R 


ZERO 


STA 


B 


SPLEN 


02 40 


020.1 


7D 


002C 


R 


NMARK 


TST 




OLDSTA 


0241 


0204 


26 


08 






BNP 




NEWSP 


0242 


0206 


C6 


01 






LDA 


B 


#1 SET LDATA TO OLDSTA 


02 4 3 


0208 


F7 


0026 


R 




STA 


B 


LDA1A -t = SPACF, 1=MARK 


024 4 


020E 


7F 


0213 


H 




JMP 




SKIP4 


0245 


020F 


C6 


FF 




NEWSP 


LDA 


B 


#5FF 


0246 


02 10 


F7 


0026 


R 




STA 


B 


LDATA 


0247 


02 13 


B7 


002C 


ft 


SKI ft 4 


STA 


A 


OLDSTA RESFT OLDSTA 


0248 


0216 


7F 


0031 


ft 




CLK 




TCNTR RFSFT TIME COUNTER 


02 49 


0219 


7C 


0031 


R 




INC 




TCNTR 


02 50 










* 








0251 


02 1C 


P6 


0023 


R 


TRANS 


LDA 


A 


COUNT CHECK FOR TERMINAL PFADY 


0252 


02 IF 


F6 


0032 


R 




Lna 


P 


TIMER 


0253 


0222 


CI 


3C 






CMP 


B 


#60 TRY TO SPEFD 1FRMINAL 


0254 


0224 


2D 


01 






FLT 




SI 


0255 


0226 


48 








ASL 


A 




02 56 


(1227 


El 


0P2 A 


R 


SI 


CMP 


A 


MAXC-NT 


02 57 


022A 


2C 


06 






BGE 




OUTCHK TERMINAL ftEADY 


0258 


022C 


7C 


0023 


R 




INC 




COUNT 


0259 


022F 


7c 


C-PF-^ 


R 




JMP 




START RETURN TO FFCINNINC 


0260 










* 








0261 


0232 


7F 


0023 


R 


OUTCHK 


CLft 




CO UN T 


0262 


0235 


B6 


0034 


R 




LDA 


A 


WDSXCV ANY DATA I i\ PMFFFR? 


02 6 3 


02 38 


26 


03 






BNF 




U DO U T 


0264 


023A 


7F 


00BA 


R 




JtfP 




START I F NOT. R <H UFN 


0265 


02 30 


F6 


002 D 


R 


WDOUT 


LDA 


P 


OUTXCV GENERATE PUFFER POINTEh 


0266 


0240 


CF 


0003 


R 




LDX 




#PUEF ! 


0267 


0243 


F7 


0247 


ft 




STA 


B 


INDEX 4+ 1 


02 66 


0246 


A6 


00 




INDEX4 


LDA 


A 


tt, X OUT PUT CHAR . IN ACCUM A 


02 69 










* USF SYSTEM SUBROUTINE 10 OUTPUT CHAftACT Eft 


027 


0243 


PD 


72Fy 






JS* 




OUTCRT 


027 1 


02 4B 


7A 


10034 


R 




DEC 




WDSXCV 


027 2 


024F 


F6 


002D 


R 




LDA 


B 


OUTXCV 


0273 


0251 


5C 








INC 


B 




027 4 


02 52 


C4 


IF 






AND 


B 


#T1F RF STRICT RANCF 


027 5 


0254 


F7 


002D 


R 




STA 


B 


OUTXCV 


0276 


02 57 


7F 


00FA 


R 




JMP 




START PAGK TO THE BFOINNING 


0277 












END 







previously sampled value. If no change is 
found, the time counter is incremented to 
indicate the increased length of the signal. If 
a change is found, then a series of processes 
are done. The data ready flag is set to tell 
the decoder that a pulse is complete, the 
time counter is stored into the mark length 
or space length variable, the data type (mark 
or space) is recorded, and the time counter is 
reset to one. A few notes are in order about 
sampling. First, the sampler assumes that an 
input level zero (ground) indicates the pres- 
ence of an audio tone (mark), and that a one 
level input (high voltage) indicates no tone 
(space). This setup coincides with the audio 
processing hardware described later; but if 
one wishes to have a one input signify mark 
instead, only two simple program changes 
are necessary. Changing the BNE (branch on 
not equal to zero) instructions on lines 236 
and 241 to BEQ (branch on equal to zero) 
instructions will accomplish the inversion. 
This illustrates the ease of modifying the 
system when it is based on a program instead 
of hardware. One other note: One must 
protect against overflows of the time coun- 
ter. This occurs when long marks or long 
spaces cause the counter value to exceed the 
maximum value representable as a positive 
byte. MORSER checks for such occurrences, 
and resets the time counter to a large 
positive value whenever an overflow is 
detected. 

We come now to the decoding section. 
The section is a software version of algo- 
rithms abstracted from several hardware 
designs. It can be described by a set of five 
decoding rules. The length (time counter 
value) of the last mark received is used to 
determine the type of the present mark. The 
length of the last dash received is used to 
determine the type of space being received. 



RULE 1. If the new mark length is at 
least twice the length of the 
last mark received, then the 
new mark is a dash. 

RULE 2. If the new mark length is less 
than one half of the length of 
the last mark received, then 
the new mark is a dot. 

RULE 3. If the new mark length is 
more than one half but less 
than twice the length of the 
last mark received, then the 
new mark is the same type as 
the old mark was. 

RULE 4. If the new space length is 
more than 3/4 of the last 
dash length received, then the 
new space is a letter space. 

RULE 5. If the new space length is 



33 



longer than twice the last 
dash length received, then the 
new space is a word space. 

Any other space is an element space. These 
rules determine the processing path of each 
data item returned by the sampling section. 
The dots and dashes are stored in memory 
(STLDOT and STLDAS) until a letter space 
is detected. Then the memory contents arc 
converted to an offset in DECTAB, follow- 
ing the process previously described. The 
character code found in DECTAB is then 
transferred to the output buffer. The buffer 
is arranged as a 32 character first in, first out 
store which allows the decoding to get ahead 
of the output device for short periods. The 
detection of a word space causes the latest 
letter to be decoded and an extra blank 
character is inserted into the output buffer 
to provide a space between output words. 

The decoding section also adjusts the 
TIMER value each time a dot is detected. 
Dots are nominally four samples long. If a 
dot is declared shorter than three samples, 
the sampling period is reduced. If a dot is 
declared longer than five samples, the 
sampling period is increased. This mech- 
anism helps MORSER to follow changes 
in code speed during a message or even 
within characters. The flexibility of the 
decoding rules will allow code far from the 
proper timing to be decoded correctly 
during the adjustment process. Most de- 
coding errors will result either in no charac- 
ter at all being output, or a blank being 



substituted for the garbled character. 
MORSER can handle code with wild speed 
variations and weightings from 10% to 90%, 
but it can be fooled by sufficiently erratic 
code. So too, however, can most human 
operators. 

MORSER uses a programming "trick" in 
conjunction with indexed addressing to 
facilitate the decoding and output process. 
This occurs on lines 174, 183, 198, and 267. 
The problem is to retrieve or store data at a 
particular location within a table or buffer. 
The starting address of the area is known, 
and the desired offset is calculated each 
time. MORSER uses the technique of 
modifying itself during execution. Since the 
program is stored in programmable memory, 
it can be changed just as the variables can be 
changed. In Motorola systems, the second 
byte of an instruction using indexed address- 
ing stores an offset to be added to the index 
register contents to generate the final effec- 
tive address for the instruction. MORSER 
loads the index register with the beginning 
of the desired tabic and then writes the 
calculated offset into the second byte of the 
indexed instruction. The processor adds the 
two, making the desired address. This works 
well, as long as the program is stored in 
programmable memory, and one is careful 
where one writes. If this type of trickery is 
to be avoided (for example, if the program is 
to be put into read only memory), the 
process of adding the offset to the base 
address must be done explicitly. The follow- 
ing code will perform the function, where X 
contains the starting address of the table, 
and accumulator A contains the offset: 



AUDIO 
INPUT ai M F 



^ 



.5jiF 



FROM 
RECEIVER 



25 M F 



330il 






IpF 



+ 5V 
A 



<5K 



:z^f 



TO Plfl 
-a INPUT 
PIN 



lOO^F 



NDSAV 


RMB 


2 




Programmable memory area (or 
computation 


NDEX 


STX 




INDSAV 


Starting address 




PSH 


B 




Save contents of B accumulator 




CLR 


B 








ADD 


A 


INDSAV + 1 


Add low order part of address with 
olfset in A 




ADC 


B 


INDSAV 


Add high ordci pan of address with 
carry 




ST A 


A 


INDSAV+1 






STA 


B 


INDSAV 






LDX 




INDSAV 


Put effective address into index register 




PUL 


B 




Restore contents of B accumulator 



m 

Figure I : A suggested audio input processing circuit designed to be used with 
an amateur radio receiver. The tuning adjustment sets the frequency of the 
signal which is to be interpreted as a dot or dash by the program. The receiver 
tuning and BFO should be adjusted so that the desired station will have its 
dots and dashes at the frequency set by R I. 



The output terminal driver makes use of 
the delay timer to prevent the program from 
exceeding the speed capabilities of the out- 
put device. A count is kept of the number of 
delay periods since the last character was 
sent to the terminal. The value of MAXCNT 
is set such that MAXCNT delay periods at a 
60 words per minute Morse code speed are 
roughly equal to the recovery period of the 
terminal in use. If the code speed is less than 
30 words per minute, then one half of 
MAXCNT is used to let the terminal run 
nearer its full speed. This counting ensures 



34 



that the terminal will not receive characters 
faster than it is capable of handling them. 
The output buffer helps absorb speed varia- 
tions. In cases of extreme speed variations 
with a very slow output terminal, a few 
characters may be lost. This would require 
input speeds of over 80 words per minute to 
be maintained for many characters if one 
used a 110 baud terminal. It is not likely 
that the audio processing hardware could 
switch at this rate, so the characters would 
be unreliable anyway. All slower speeds 
could be handled without trouble. The 
system subroutine used to drive the terminal 
is called in this section on line 270. It should 
not use interrupts or any timing loops, since 
these will upset the timing in MORSER. 
Since MORSER already does output timing, 
they are not needed anyway. 

That is all there is to the MORSER 
program. The most critical part of the whole 
system is the audio input hardware. This 
circuit needs rapid response (since switching 
time for 60 words per minute code is about 
13 ms), audio selectivity, immunity to noise, 
and immunity to varying signal levels. No 
optimum circuit is known by the authors. 
The circuit shown is a suggestion which 
shows promise. It uses a 567 phase locked 
loop tone decoder, tuned to a center fre- 
quency of about 1 kHz. The bandwidth is 
set at approximately 10% of the center 
frequency, or about 100 Hz. This circuit 
should switch fast enough for most code 
speeds, and the phase lock design gives noise 
immunity, for the circuit will require 10 or 
more cycles at the correct frequency before 
it will switch. An input level of about 200 
mV seems to give the best immunity from 
interfering signals and noise. The output 
rests at +5 V, dropping to near ground when 
a proper frequency tone is detected. This 
voltage level is read by the sampler program 
through the peripheral interface. This signal 
must be very clean, since variations will 
probably be decoded as extra dots and 
dashes. Lots of 'E's and T's will indicate a 
problem in the audio processing. 

MORSER works surprisingly well, and it 
will be able to decode almost anything that 
its operator can feed it. It does not know 
English or radio terminology, so it cannot 
guess what the characters should be. Il 
simply decodes what it "hears," and may 
not correct some errors that a human would 
recognize. It does decode the input faith- 
fully, and that can be quite a help. Of course 
if you use MORSER to listen to a station 
using automatic code generation technology 
(on a clear channel) you should get perfect 
copy once the speed adaptation is 
complete. ■ 



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any IK group of RAM's. Also 
under software control you can 
check the status of any 4K RAM 
board in IK blocks to determine 
whether it's protected or not. The 
board has LED's that clearly show 
you the memory protect status 
of each IK block and which 
block is active. And there's a 
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This low power board has a 
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35 



Efficient Storage of Morse 
Character 

Since many of BYTE's readers are radio 
amateurs, a number of whom have expressed 
| />/"1/3C an interest in combining computing with 

^j-'V'LJd) their radio hobby, BYTE seems an appro- 

priate place for this short note on a tech- 
nique for storing Morse character codes in a 
minimal amount of memory space. It may 
not be immediately obvious that all of the 
possible Morse characters, up to six elements 
per character, can be stored using a maxi- 
mum of only seven active bits per character 
stored. 

A typical program using such a stored 
representation would be a programmed auto- 
matic keyer. As the user typed at a key- 
board, the computer would receive the 
characters typed in some code (typically 
ASCII code). The computer would then use 
this code to index into a table of Morse 
character codes, retrieving a coded repre- 
sentation of the Morse character to be 
transmitted. With a suitable interface, the 
computer could then directly key the radio 
transmitter. A good program of this type 
would buffer the user's typing, allowing the 



Lawrence Krakauer 
15 Orchard Ln 
Way land MA 01778 



operator to be some large number of char- 
acters ahead of the code actually being 
transmitted. 

Another similar program would be a 
Morse code teaching machine, which could 
use a programmed pseudorandom number 
generator to create arbitrary "code groups." 
Such artificial text is customarily used for 
Morse code training, so that the student does 
not recognize words and thus anticipate the 
next letter to come. The computer in this 
case would key a practice oscillator, and the 
student would attempt to accurately receive 
what it sends. If the student types what he 
receives directly on the computer keyboard, 
the computer could notify him immediately 
of any errors. In addition, the computer 
could adjust its transmission speed for a 
fixed error rate, always sending at the upper 
limit of the student's reception speed, which 
would hopefully produce rapid learning. 

A Morse character is a string of from one 
to six Morse elements, where each element is 
a dot or a dash. Since there are only two 
types of elements, Morse characters seem to 



Table I: Morse Code Patterns and ASCII Equivalents for Selected Graphics. 



Note: The representation 
of Morse characters de- 
scribed in this article is 
also used by Bruce Filgate 
in his extensive Morse 
code applications program 
described on page 52 of 
this issue. The information 
in this table (with some 
minor changes) is found at 
addresses 20/225 to 
20/366 of listing I in 
Bruce 's article. 



Graphic 


ASCII Code 




Morse 


'attern 


Char 


Hex 


Octal 


Hex 


Octal 


Binary 


A 


41 


101 


60 


140 


01100000 


B 


42 


102 


88 


210 


10001000 


C 


43 


103 


A8 


250 


10101000 


D 


44 


104 


90 


220 


10010000 


E 


45 


105 


40 


100 


01000000 


F 


46 


106 


28 


050 


00101000 


G 


47 


107 


DO 


320 


11010000 


H 


48 


110 


08 


010 


00001000 


1 


49 


111 


20 


040 


00100000 


J 


4A 


112 


78 


170 


01111000 


K 


4B 


113 


B0 


260 


10110000 


L 


4C 


114 


48 


110 


01001000 


M 


4D 


115 


E0 


340 


11100000 


N 


4E 


116 


A0 


240 


10100000 





4F 


117 


F0 


360 


1111 0000 


P 


50 


120 


68 


150 


01101000 


Q 


51 


121 


D8 


330 


11011000 


R 


52 


122 


50 


120 


01010000 


S 


53 


123 


10 


020 


00010000 


T 


54 


124 


CO 


300 


11000000 


U 


55 


125 


30 


060 


00110000 


V 


56 


126 


18 


030 


00011000 



aphic 


ASCII Code 




Morse 


3 attern 


liar 


Hex 


Octal 


Hex 


Octal 


Binary 


w 


57 


127 


70 


160 


01110000 


X 


58 


130 


98 


230 


10011000 


Y 


59 


131 


B8 


270 


10111000 


z 


5A 


132 


C8 


310 


11001000 





30 


060 


FC 


374 


11111100 


1 


31 


061 


7C 


174 


01111100 


2 


32 


062 


3C 


074 


00111100 


3 


33 


063 


1C 


034 


00011100 


4 


34 


064 


OC 


014 


00001100 


5 


35 


065 


04 


004 


00000100 


6 


36 


066 


84 


204 


10000100 


7 


37 


067 


C4 


304 


11000100 


8 


38 


070 


E4 


344 


11100100 


9 


39 


071 


F4 


364 


11110100 




2E 


056 


56 


126 


01010110 


, 


2C 


054 


CE 


316 


11001110 


? 


3F 


077 


32 


062 


00110010 


= 


3D 


075 


8C 


214 


10001100 




3A 


072 


E2 


342 


11100010 




3B 


073 


AA 


252 


10101010 


/ 


2F 


057 


94 


224 


10010100 


— 


2D 


055 


86 


206 


10000110 



This table assumes that for machine generated Morse, data is shifted out through the 
most significant bit with shifted into the low order. This process continues until the 
binary pattern 10000000 remains in the working memory location. For input, data is 
shifted in through the LSB. At end of character, a 1 is appended, and the code is left 
justified. 



36 



EXAMPLE 
Sending an L . . . . 

Morse Encoded in binary: 01001000 
Iteration 



/" ^\ I ENTER WITH MORSE BIT 

( SENDCHR 1 1 PATTERN IN TEMPORARY 



Data After 


ASHL 




Morse 


A 


v/ 


CY 


\ 


Out 


10010000 





/ \ 

dot 


00100000 




1 




dash 


01000000 









dot 


10000000 









dot 


00000000 




1 




end char. 



Figure I: Flow chart of the SENDCHR 
routine and the SENDEL routine, used to 
generate Morse code outputs. The key 
element of the method is use of an arith- 
metic left shift operation to interpret the 
code which is presented to the routine. The 
codes are determined by a table lookup prior 
to calling SENDCHR, using an internal table 
equivalent to table 1. An example of the 
operation of the routine on a letter L is 
illustrated. 



be a natural for a binary representation, 
simply letting represent a dot, and 1 
represent a dash. The catch is that all of the 
characters are not the same length, so that 
the number of elements in the character 
must also be included in its representation. 
However, the simple approach of directly 
including a number giving the length requires 
too many bits. Since there are up to six 
elements in a Morse character, we would 
need six bits for the character elements, plus 
three bits to represent the length, for a total 
of nine bits. Since most small computer 
systems are presently oriented around eight 
bit bytes, it would be convenient if all the 
Morse characters could be represented by 
eight, or fewer, bits each. 

Let's try counting. There are two Morse 
characters of length 1 element ( ■ and — ), 

four characters of length 2 (•• • ■ and 

), and so on. So extending this sequence, 

the total number of possible characters of 
length six or less is: 

N = 2 + 4+8 + 16 + 32 + 64 =126 

Since N is less than 2' = 128, we ought to 
be able to represent all the Morse characters 
in seven bits. Perhaps it should be mentioned 
here that this includes all combinations of 
up to six elements, including those which do 
not actually represent legal Morse characters. 
Since we want a representation which will 
make it easy to transmit the character, we 
need a simple form that encodes all arbitrary 
combinations. 

And, indeed, such a simple form exists. 




r 1 

I TEST CARRY 

FLAG I- 
I ARGUMENT I 



( SENDEL J 







YES 




\ ? s' 




x>^ 




NO 








GENERATE 




GENERATE 


DASH 




DOT 


OUTPUT 




OUTPUT 


' 


L 















( RETURN ) 



Listing I: The SENDCHR routine defined as symbolic assembly language for 
the 6800 and 8080 architecture; (a) shows the 6800 code, and (b) shows the 
8080 code. These routines assume that a subroutine called SENDEL (see 
figure I ) is available which sends either a dot or a dash based on the state of 
the carry (CY) flag. Since temporary data is maintained in A, SENDEL must 
not alter the contents of A. 



(a) 


6800 Code: 










Label 


Op 


Operand 


Commentary 




SCHRLOOP 


JSR 


SENDEL 


Send dot or dash; 




SENDCHR 


ASLA 




Entry point and shift left; 






BNE 


SCHRLOOP 


If more data then reiterate, 






RTS 




Else return; 


(b) 


8080 Code: 










Label 


Op 


Operand 


Commentary 




SENDCHR 


ADD 
RZ 


A 


Shift left by adding A to A 
If no data then return; 






CALL 


SENDEL 


Send dot or dash; 






JMP 


SENDCHR 


Reiterate 



37 



( RCVCHR V 



A: - 00000001 



CY: - (received 
dot or dosh )-, 



A:- R0L(A,l); 








CY: . '|'| 




J 


' 




YES 






A: = ROLtA.I); 


< CY:- 


'0' > 



r 1 

I ENTER TO FORMAT 
ONE CHARACTER 

I 

I I 

I 1 

| SETS UP END OF 

I CHARACTER MARKER 

I IN LOW ORDER BIT 

I I 

i ; 1 

| REFERENCES "SET NEXT 

1 ELEMENT" SUBROUTINE 

"J WHICH MAY HAVE ADAPTIVE 
RECOGNITION FEATURES 

| 1 

MORSE | 

ROTATE LEFT: INPUT 

I / I I I I I I I I H D" X I 

I I A CY ) I 

L I 

r 1 

| END OF CHARACTER [ 
J CONDITION IS SET 
\ BY "GET NEXT ELEMENT" 
I SUBROUTINE 
I I 

r 1 

SET UP END 
_! OF CHARACTER MARK : 

I I 

L I 



i LOOP TO LEFT 
) 1 JUSTIFY INPUT PATTERN 



f RETURN J — 



| RETURN WITH 
— I PATTERN IN 



Figure 2: Flow chart of the RCVCHR routine which is used to format 
incoming dots (binary 0) and dashes (binary 1) into an 8 bit code. 
Reference is made to a routine loosely described as "get next element" which 
is used to receive a Morse code element. This "get next element" input 
routine will have adaptive speed interpretation features required if the 
program is to be used with hand sent Morse code. After the end of character 
indication is returned by the input routine, the RCVCHR routine must left 
justify the code so that it is in the same form as found in the code genera- 
tion table (see table I). Control returns with the input code contained in 
register A. 



The Morse character is represented from left 
to right, one bit per element, using for dot 
and 1 for dash. At the end of the character, 
after the last element, a 1 is placed as a stop 
bit. The remaining bits, if any, are filled out 
with zeros. Some examples are: 



Character Morse Code Binary Representation 

E • 0100000 

T - 1100000 

A ■ - 0110000 

L ■ - • ■ 0100100 

• 1100111 

_ _ . . . _ 1000110 

Table 1 is a complete list of alphabetic 
characters, numerals and selected special 
characters shown as hexadecimal and octal 
ASCII along with the equivalent hexa- 
decimal, octal and binary code for the Morse 
pattern. Given the representation, transmis- 
sion of the character is easy. Working from 
left to right, simply transmit each bit as a 
Morse element, until all that remains is a 
single 1 followed by all zeros, at which point 
the character has been completed. This 
operation is easily done using the "rotate" 
or "shift" instructions of the typical micro- 
computer. A flow chart for this procedure is 
given in figure 1. It is so simple that it 
reduces to only a four line subroutine in a 
typical microprocessor. Listing la gives a 
suggested program for the Motorola 6800 
and listing 1b gives a program for the Intel 
8080 (or 8008). These programs use an eight 
bit representation, which can express a code 
of up to seven elements, although no seven 
element characters are actually used in the 
Morse code. 

Note that there are two binary represen- 
tations which represent the null character; 
that is, they result in the subroutine re- 
turning without transmitting anything at all. 
These are the codes 00000000 and 
10000000. If desired, they could be spe- 
cially decoded. For example, one of them 
could be used to represent the special Morse 

character , which is used as a 

delete character. It would have to be trans- 
mitted as a special case, since it contains 
eight elements. If the all zero code were to 
be used for this purpose, it could be tested 
for by a branch-on-zero instruction at the 
subroutine entry point. 

The representation proposed here is also 
easy to build up while receiving Morse code. 
A receive subroutine flow chart is given in 
figure 2. 

The possibilities inherent in the combina- 
tion of small computers and amateur radio 
are enormous. The challenging task of 
machine reception of hand sent code is now 
receiving much more attention due to the 
low cost of microprocessors. The pos- 
sibilities of computer station control, ama- 
teur radio data communications networks, 
and microprocessor control of repeaters have 
barely begun to be explored. The large 
number of radio amateurs who are now 
beginning to experiment with small com- 
puters should produce some rather in- 
teresting results in the near future." 



38 



altair 8800b 

TECHNICAL INFORMATION 



The ALTAIR 8800b computer is a general purpose 
byte-oriented machine (8-bit word). It uses a common 
100-pin bus structure that allows for expansion of 
either standard or custom plug-in modules. It supports 
up to 64K of directly addressable memory and can 
address 256 separate input and output devices. The 
ALTAIR 8800b computer has 78 basic machine 
language instructions and is comprised of a power 
supply board, an interface board, a central processing 
unit (CPU) board, and a display/control board. 

Power Supply Board 

The Power Supply Board provides two output voltages to the 
ALTAIR 8800b computer bus, a positive and negative 18 volts. 
It includes a bridge rectifier circuit and associated filter circuit, 
a 10-pin terminal block connector, and the regulating 
transistors for the positive and negative 18 volt supplies. 

Interface Board 

The Interface Board buffers all signals between the display/ 
control board and the ALTAIR 8800b bus. It also contains eight 
parallel data lines which transfer data to the CPU from the 
Display/Control board- 
CPU Board 

The CPU board controls and processes all instruction data 
within the ALTAIR 8800b computer. It contains the 
model 8080A microprocessor circuit, the master 
timing circuit, eight input and eight output data lines to the 
ALTAIR bus, and control circuits. 

Display/Control Board 

The Display/Control Board conditions all ALTAIR 8800b front 
panel switches and receives information to be displayed on the 
front panel. It contains a programmable read only memory 
(PROM}, switch and display control circuits, and control 
circuits to condition the CPU- 



NEW DESIGN FEATURES 

Several new design features have been incorporated into the 
electronic and mechanical areas of the ALTAIR 8800b 
computer. Some of the new design features include additional 
front panel capabilities, redesigned power supply, and various 
electronic and mechanical design advancements. 

New Front Panel Switches 

Five new front panel switch positions have been added to the 
ALTAIR 8800b computer to expand the front panel capability. 
1 . SLOW position: Permits execution of a program at a rate of 
approximately 2 machine cycles per second or slower. The 
normal machine speed is approximately 500,000 machine 
cycles per second. The ALTAIR 8800b operates in the slow 
mode as long as the SLOW switch is depressed on the 
front panel. 

2. DISPLAY ACCUMULATOR position: Displays the contents of 
the CPU accumulator register on the ALTAIR 880Ob 

front panel. 

3. LOAD ACCUMULATOR position: Loads the information 
present on the lower eight front panel address switches 
into the CPU accumulator register. 

4. INPUT ACCUMULATOR position: Inputs the information 
present at an Input/Output device into the CPU accumulator 
register. The Input/Output device is selected on the upper 
eight front panel address switches. 

5. OUTPUT ACCUMULATOR position: Outputs the contents of 
the CPU accumulator register to a selected input/output 
device. The input/output device is selected on the upper 
eight front panel address switches. 




New Power Supply 



The new power supply in the ALTAIR 8800b contains an 8 
volt, 18 ampere tapped secondary supply which permits the 
addition of up to 16 printed circuit cards, and pre-regulated 
positive and negative 18 volt, 2 ampere supplies. A multiple 
tapped primary transformer provides for 110/220 volt 
operation and a 50/60 Hz operation. 



Electronic Design Advancements 

The electronic design advancements on the ALTAIR 8800b are 

in the CPU and front panel circuit boards. 

1 . CPU. The new CPU circuit board uses the Intel 8224 clock 

generator integrated circuit (IC). The 8224 IC provides a 

specified clock frequency to the ALTAIR 8800b using an 

external crystal and dividing the crystal frequency down to 

2MHz. Therefore, both the clock pulse widths and phasing 

(as well as frequency) are crystal controlled. 

2. Front Panel. All front panel data lines are connected to an 
interface which buffers them from the rest of the ALTAIR 
8800b. The front panel circuits also use a programmable 
read only memory (PROM) which contains programs for the 
following eight functions: 

EXAMINE 

EXAMINE NEXT 

ACCUMULATOR DISPLAY 

ACCUMULATOR LOAD 

DEPOSIT 

DEPOSIT NEXT 

INPUT ACCUMULATOR 

OUTPUT ACCUMULATOR 

The front panel circuits also have a wiring option which 

allows the CPU to perform a complete instruction cycle or a 

single machine cycle during the single step or slow operation. 

Mechanical Design Advancements 

The mechanical design advancements on the ALTAIR 8800b 
are incorporated for ease of assembly and maintenance. 

1 . The wiring harness connection which exists on the front 

panel of the ALTAIR 8800 is replaced with ribbon cables. 
These ribbon cables connect the front panel circuits to the 
interface circuits. 

2 The four slot expander cards in the ALTAIR 8800 have been 
replaced by a single piece 18-slot motherboard. The 18-slot 
motherboard contains 100 solder lands which comprise the 
100 pin bus. 

3. A new multi-color and redesigned dress panel is used in the 
ALTAIR 8800b. The front surface of the dress panel has a 
protective sheet of mylar to insure that the graphics are 
not rubbed or scratched off. 



CPU 








ADDRESS IA0-AI5) 






STATUS 


Memory 
or 
I/O 

Device 


RDY 




(D0-D7I IDI0-D17I 
BI-DATA v^L DATA IN 








ac v 




L <rt 






— ' 1 


.QzL_, 




PDBIN 




< 




h 


^ Data OUT IDOg-c 




t 




. 




Front 
Panel 










/l FDI0- FD17 






T 

BUS CONTROL 




T 


-a=! 












^n 








8800b BLOCK DIAGRAM 



COMPATABILITY 



8800b BLOCK DIAGRAM DESCRIPTION 

The 8800b computer contains four main circuits: a Central 
Processing Unit (CPU), a Memory, an Input/Output (I/O), and a 
Front Panel. The CPU controls the interpretation and execution 
of software instructions, and the Memory stores the software 
information to be used by the CPU. The I/O provides a 
communication link between the CPU and externa! device. The 
Front Panel allows the operator to manually perform various 
operations with the 8800b. The 8800b block diagram 
description explains: A) the communication between the CPU 
and the memory or I/O circuits; and B) the communication 
between the CPU and the front panel. 

CPU to Memory or I/O Operation 



Compatibility 

All of the current 8800 software is compatible with the 8800b, 
and all the current plug-in circuit boards are compatible, with 
the exception of the 8800a CPU Board. 

Memory Cards 

1 . 4K Dynamic RAM Memory Board 

2. 4K Static RAM Memory Board 

3. 16K Static RAM Memory Board 

4. PROM Memory Board 

Interface Cards 

1 . Serial Interface Board 

2. Parallel Interface Board 

3. Audio-cassette Interface Board 

4. Disc Controller Board 



The Memory or I/O operation requires several main signals 
which allow for transfer of data to and from the CPU. The 
ADDRESS (A0-A15) signal consists of sixteen individual lines 
from the CPU to the Memory or I/O device. This signal 
represents a particular memory address location or external 
device number which is needed to establish communications 
with the Memory or I/O Device. Once the ADDRESS (A0-A15) 
data is presented to the Memory or I/O device, the CPU 
generates various STATUS signals. The STATUS signals either 
enable decoding of a memory address, or they condition the 
I/O device card to send or receive data from the CPU. 
Data from the Memory or I/O device is presented on the DATA 
IN (DI0-DI7) lines and applied to eight non-inverting bus 
drivers. The drivers are enabled by a PDBIN signal from the CPU 
and a BC (bus control) signal. The BC signal is LOW when the 
Front Panel is not in operation. The eight non-inverting bus 
drivers, when enabled, present the input data to BI-DATA 
(D0-D7 ) lines which apply the data from the Memory or I/O 
device to the CPU. 

Data to the Memory or I/O device is presented on the DATA 
OUT (DO0-DO7) lines from the BI-DATA (D0-D7) lines from 
the CPU. The RDY (ready) line either forces the CPU to a wait 
state while data is being transferred or allows the CPU to 
process data. 



Front Panel Operation 

The Front Panel Operation is very similar to the Memory or I/O 
operation. The Front Panel gains control of the CPU by 
producing a HIGH BC signal. The BC signal disables the'DATA 
IN (DI0-DI7) lines from a Memory or I/O device and enables 
the FDI0-FDI7 lines. The FDI0-FDI7 lines contain Front Panel 
data which is transferred to the CPU upon the occurrence of the 
PDBIN signal. All data from the CPU to the Front Panel is 
applied to the DATA OUT (DO0-DO7) lines and displayed 
on the Front Panel. 



ALTAIR 8800b 




Spec 


fications 




Number of Boards 




Up to 18 




Microprocessor 








Model 




8080A 




Technology 




NMOS 




Data Word Size, Bits 




8 




Instruction Word Size, Bits 




8 




Clock Frequency 




2M Hz 




Add Time, Register to Register, 






Microsec. Per Data Word 




2 




Number of Instructions 




78 




Input/Output Control 








I/O Word Size, Bits 




8 




Number of I/O Channels 




256 




Direct Memory Access 




Optional 




Interrupt Capability 




Std. 




Vectored Interrupt 








( 8 priority levels ) 




Optional 




Software 








Resident Assembler 




Yes 




Higher-level Language 




BASIC 




Monitor or Executive 




Sys. Mon.; text edit. 


Complete Software Library 








Separately Priced 




Yes 





0§ DDQljS^ 



2450 Alamo S.E./ Albuquerque, New Mexico 87106 



Software Bug 
of the Month 



Private Preston's Folly 

Private Prescott Preston, Proud yet 
Prudent Programmer, is running his first sort 
routine, and it's a mess. See if you can 
straighten him out. 

Private Preston has an array called PR, 
containing 50 elements. He reads in some 
data in unsorted fashion. The idea of the 
sort routine is to test whether two adjacent 
elements are in order. If they're out of 
order, they are interchanged. 

A flag K is kept to tell whether any 
changes have been made in the current pass 
through the array PR (from beginning to 
end). If no changes have been made, we 
are done, because the table is now sorted 
(remember we've gone through the entire 
array). Whenever a change is made, however, 
the flag K is set. If the flag ever gets set, we 
have to make another pass through the 
array, and we keep on doing this until the 
array is sorted. 

The program Private Preston wrote 
looked like this: 

Step 1 : Set K equal to zero. 

Step 2: Set I equal to 1. 

Step 3: If PR(l) is less than or equal to 

PR(I+1), then go to Step 7. 
Step 4: Set K equal to one. 
Step 5: Set PR(I) equal to PR(I+1). 
Step 6: Set PR(I+1) equal to PR(I). 
Step 7: Set I equal to I + 1 . 
Step 8: If I is unequal to 50, go to Step 3. 
Step 9: If K is equal to zero, go to Step 1 . 

I won't even bother telling you what 
language that routine was written in. The 
first few times, of course, it had compilation 
errors. Now it compiles, but it still doesn't 
work. Why not?" 

Solution in Next Month's BYTE 



SOLUTION TO BUG OF THE MONTH 4 

Did you try N = I ? Good for you. One of 
the surest ways a program like this can fail is 
in the low order cases. Unfortunately (for 
you), N = 1 works just fine. We discover that 
1 is not a multiple of 2, and then we quit. So 
I is a prime number. 

Now did you try N = 2? 

You did? I think you saw this one 
somewhere before. 

In fact, for N = 2 - and only for N = 2 - 
this program has a bug. It says that 2 is not 
prime, because 2 is a multiple of 2, when in 
fact it is prime. 

How should the bug be fixed? One simple 
way, of course, is to test N for being less 
than 4; if it is, then it is prime. But this adds 
unnecessary inefficiency in what we shall 
presume arc the bulk of our cases, namely N 
> 4. The real trouble is that we are using a 
"FORTRAN loop" - that must be executed 
at least once - rather than an "ALGOL 
loop" that might be done zero times. Thus, 
when N = 2, the first value of I, namely 2, is 
already larger than the maximum value, 
namely the square root of 2, and so no cases 
should be tested. We can make this into an 
ALGOL loop by putting a statement number 
— say 3 — on the last IF statement, and then 
writing GO TO 3 just before statement 
number 1. 

There is one further acceptable answer. 
Suppose that we called PRIME(L, L). This 
does make sense; we are testing L to sec if it 
is prime, and then, after we test, setting L 
equal to either zero or one. Unfortunately, 
the first thing thai PRIME dors is to set K = 
1, which sets L equal to I (if parameters are 
called by reference). In other words, the 
program is now testing whether 1 is prime, 
not whether L is prime. This can be fixed by 
moving the statement K = 1 (which is 
otherwise perfectly good) down to the end 
of the program, just before the second 
RETURN statement." 



W Douglas Maurer 
University Library Room 634 
George Washington University 
Washington DC 20052 



Only $59.95 

Assembled 

Tested 




f • PerC.nm — 



PerCom 



FINALLY - A CASSETTE INTERFACE THAT WORKS! 
The PerCom Cl-810 

• Easily connected to any computer • An 8-bit parallel interface 

• 'Kansas City' Standard • Load a 1k byte program in 40 seconds 

• Little or no software required • Easily upgraded to 218 byte/sec 

• Operate 2 tape units simultaneously • 18 page Instruction Manual 

PerCom Data Co. 

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(214) 276-1968 

'peripherals for personal computing' 




41 



If Only Sam Morse Could See Us Now 



Wayne Sewell WB5NYC 
9277 LBJ #253 
Dallas TX 75243 



COUNT FIELD 



When dealing with personal computers, it 
is necessary for a person to be familiar with 
his machine from both the hardware and 
software point of view. It has been my 
observation that hardware people often tend 
to stay in hardware and software people in 
software, each faction learning just enough 
about the other side to get along. I am guilty 
of this myself — I never do in hardware what 
could feasibly be done in software. Hope- 
fully, this situation will change as my knowl- 
edge of microcomputing increases, but for 
the time being I am assuming that the 
computer runs because of the little elves 
pushing electrons around in the processor 
and putting most of my effort into 
programming. 

This article is for people with a similar 
bent. There are several electronic Morse code 
keyers on the market, but rather than spend 
precious cash, why not use that little digital 
demon of a small computer that you paid all 
of that money for. You've probably been 



7 




6 


5 


4 


3 


2 


1 





C 


C 


C 


D 


D 


D 


D 


D 


li 


7 


COUNT FIEL 
6 


D 

5 


4 


DATA (l-DASH ,0- 
3 2 


DOT) 
1 





1 


1 


D 





D 


D 


D 


D 



SHIFT 
OUT 



DATA ( I- DASH, 0» DOT ) 



Figure I : Data Formats. The number of ways to represent data within a 
computer can sometimes be equated to the number of programmers there are 
in the world. Here is another way to represent Morse codes internally, which 
differs from several other articles in this issue. The format is supported by 
table 3 which lists the equivalent hexadecimal codes for each Morse code 
graphic. 



trying to find a valid use for it anyway. 
Think of the glory as you transmit a message 
in Morse code several hundred characters 
long at a speed of 1000 wpm. (While there is 
a legal speed limit for radio Teletype, to my 
knowledge Morse Code bandwidth is not 
explicitly mentioned in FCC regulations.) 
Then comes a real challenge: Find someone 
whose computer can receive at that speed. 
Finally, the ultimate goal: Read the response 
sent back to you at the same speed. [See 
articles by Robert Grappel and Jack Hemen- 
way, by Bruce Filgate, and by Lawrence 
Krakauer in this issue. } 

This article describes a software Morse 
code generator. The program listed is for a 
6800 system (specifically the one sold by 
Southwest Technical Products); but a com- 
plete description of the generator is included 
to facilitate conversion to other systems. 

Data Format 

The data format used in my Morse code 
generator makes it possible to pack any of 
the "dot" and "dash" combinations asso- 
ciated with a Morse code character into a 
single byte. The rightmost 5 or 6 bits 
(throughout this article, "rightmost" and 
"least significant" are synonymous) contain 
the pattern of dots and dashes, and the 
upper 2 or 3 bits contain a count which 
informs the program how many of the data 
bits are actually associated with the charac- 
ter. The remaining bits are set to zero 
arbitrarily. Out of all of the characters in 
international Morse code, there are only two 
which will not work in this system: space 
and the error code. It is not surprising that 
the space is a maverick in any data repre- 
sentation, since it is not really data at all, 
but a lack of data. It is simply a lengthening 
of the normal interval between characters to 
form an interval between words, and must 
be handled as a special case. Similarly, the 
error code is not really a character either. 



42 



When an error is made during a Morse 
transmission, due to a spasmodic twitch of 
the operator's hand or similar cause, the 
errant operator sends a string of 8 dots, 
meaning: "Oh I'm sorry I made an error 
please disregard the last character I sent 
please will you huh." Both the space and the 
error code, since they don't fall in the 
normal scheme of things, are treated as 
special cases: Immediately upon detection, 
the program intercepts them, modifies them 
to a compatible format, and inserts them 
back into the main logic flow. 

For all characters five elements long or 
less, the format is absurdly simple, as shown 
in figure 1a. The high order 3 bits contain a 
binary number from 1 to 5 corresponding to 
the number of dots and/or dashes in the 
character. The rightmost 5 bits contain the 
data elements themselves, where is a dot 
and 1 is a dash. They are stored from right 
to left so that when the byte is shifted to the 
right, they are transmitted serially in the 
proper sequence. As an example, the Morse 

code character Q is transmitted as" ■ — ". 

The element count is four, so a binary TOO 
string is stored in the leftmost 3 bits of the 
byte. Using the coding scheme above, the 
equivalent Morse bit pattern for Q (the 
binary string 1 01 1 ) is stored in the rightmost 
4 bits. In this case, bit 4 is not needed so it is 
a "don't-care" bit which is set to zero 
arbitrarily. Therefore, the code for Q stored 
in the table is the binary string 1 0001 01 1 or 
hexadecimal 8B. 

If all Morse code characters contained 
five elements or less, the coding system 
would be much simpler. However, many of 
the special characters, uncooperative cusses 
that they are, contain six elements. At first 
glance, this doesn't seem to be an obstacle, 
since the 3 bit count field can contain a 



binary number up to 7, inclusive. However, 
there are only 5 bits left over within the 
byte, which means that although the count 
can keep track of more than five elements, 
there is no place to store them. The one fact 
that keeps the entire system from collapsing 
into a pile of random logic is that there are 
no characters with seven elements. There arc 
several special codes with six elements, but I 
have been unable to come up with one 
containing seven. Since the difference be- 
tween a count of six, the binary string 110, 
and a count of seven (111) is one bit; and 
since there will never be a count of seven, 
then bit 5 becomes a "don't-care" and can 
be used as a data bit if bits 6 and 7 are both 
1. We simply consider any count greater 
than five (leftmost 2 bits on) to be equal to 
six, shift our wild card bit right with the 
others, and the problem is solved, as seen in 
figure lb. When the count is extracted in 
this case, bit 5 is forced to a zero, making 
the count equal to six. 

When Morse transmission actually starts, 
the data bits are shifted right one at a time. 
If the rightmost bit is a zero, the weight 
factor for a dot is loaded; if the rightmost 
bit is equal to 1, the dash weight factor is 
loaded, normally exactly three times that of 
a dot. The key is turned on, and the timing 
subroutine, controlled by the value stored in 
ELESPEED, generates the proper delay for 
that element. The key is then turned off and 
the timing subroutine is reentered, this time 
to generate the space between elements, 
normally equal to a single dot time. This 
loop is repeated for every element in the 
character, shifting right each time. The space 
between elements is added to the last 
element in the character, also. 

If a string of characters is being trans- 
mitted, rather than a single character, the 



ru 



r 



-A— I— B — I C 1— B — I — A — I — B — I D 1 — A — 4— B — 1 — A — I — B — I D 1 — E — t— B — I D 1 

I F 1 I F 1 I F 1 

I G 1 



Time 
Interval 



Explanation 



A : Dot, key on; basic timing element; duration is number of milliseconds contained in ELESPEED. 

B Space between elements, key off; duration is one dot; also controlled by ELESPEED; generated 

automatically after every dot or dash. 
C : Dash, key on; duration is three times dot in normal weighting. 
D : Character space synchronizer, key off; generated automatically after every character; added to B to 

form total space (F) between characters; duration is twice the dot interval for normal spacing but can 

be increased for greater character separation; controlled by CHRSPEED. 
E Space character (ASCII hexadecimal 20), key off; duration is one dot; added to character space (F) 

before and after to form total space (G) between words. 
F : Space between characters, key off;duration is B + D; if ELESPEED and CHRSPEED are synchronized 

this is equal to three dots; if not, duration is longer. 
G : Space between words, key off; duration = twice F plus one dot; if ELESPEED and CHRSPEED are 

synchronized, this is equal to seven dots; if not, duration is longer. 



Figure 2: Time Relation- 
ships. The Morse charac- 
ters Rl sent in succession, 
followed by a space. The 
intervals identified by 
capital letters are ex- 
plained in the notes below. 



43 



Listing 1: CWBUFFER 
Subroutine. This listing 
gives the complete absolute 
hexadecimal assembled 
code qnd symbolic repre- 
sentation for the 
CWBUFFER routine. Data 
in this listing was prepared 
using the author's SPUCA 
assembler program. 



SOURCE STATEMENT 



0040 






67 


CHRSPEED 


RMB 


2 


0042 






68 

69 


ELESPEED 
* 


RMB 


2 


0044 






70 


INITMASK 


RMB 


1 


0045 






71 


HOLDBYTE 


RMB 


1 


0046 






72 


MASK 


RMB 


1 


0047 






73 


COUNT 


RMB 


1 


0048 






74 


CWPTR 


RMB 


2 


0100 






75 




ORG 


H'100 


0100 






76 


CWBUFFER 


EQU 


* 


0100 


A6 


00 


77 




LDAA 


1,0 


0102 


81 


03 


78 




CMPA 


«3 


0104 


26 


01 


79 




BNE 


CONTINUE 


0106 


39 




80 




RTS 




0107 






81 


CONTINUE 


EQU 


* 


0107 


08 




82 




INX 




0108 


DF 


48 


83 




STX 


CWPTR 


010A 


8D 


08 


84 




BSR 


TRANSMIT 


010C 


DE 


40 


85 




LDX 


CHRSPEED 


010E 


8D 


46 


86 




BSR 


MILDELAY 


0110 


DE 


48 


87 




LDX 


CWPTR 


0112 


20 


EC 


88 




BRA 


CWBUFFER 


0114 






89 


TRANSMIT 


EQU 


* 


0114 


8D 


5C 


90 




BSR 


CliARTOCW 


0116 


4D 




91 




TST 


A 


0117 


26 


06 


92 




BNE 


NOTSPACE 


0119 


C6 


01 


93 




LDAB 


11 


011B 


D7 


47 


94 




STAB 


COUNT 


011D 


20 


25 


95 




BRA 


SPACENT 


011F 






96 


NOTSPACE 


EQU 


* 


011F 


16 




97 




TAB 




0120 






98 




RPT 


4 


0120 


59 




99 




ROL 


n 


0121 


59 




100 




ROL 


B 


0122 


59 




101 




ROL 


B 


0123 


59 




102 




ROL 


B 


0124 


C4 


07 


103 




ANDB 


• 7 


0126 


81 


FF 


104 




CMPA 


IH'FF 


0128 


26 


04 


105 




BNE 


NOTERR 


012A 


4F 




106 




CLR 


A 


012B 


5C 




107 




INC 


B 


012C 


20 


06 


108 




BRA 


COUNTOK 


012E 






109 


NOTERR 


ECU 


* 


012E 


CI 


06 


110 




CMPB 


#6 


0130 


21) 


02 


111 




ELT 


COUNTOK 


0132 


C4 


06 


112 




ANDB 


16 


0134 






113 


COUNTOK 


EQU 


* 


0134 


D7 


47 


114 




STAB 


COUNT 


0136 






115 


BITLOOP 


EQU 


* 


0136 


D6 


44 


116 




LDAD 


INITMASK 


0138 


D7 


46 


117 




STAB 


MASK 


013A 


C6 


01 


118 




LDAB 


tl 


013C 


46 




119 




ROR 


A 


013D 


24 


02 


120 




BCC 


SEND 


013F 


C6 


03 


121 




LDAB 


#3 


0141 






122 


SEND 


EQU 


* 


0141 


73 


00 45 


123 




COM 


HOLDBYTE 


0144 






124 


SPACENT 


EQU 


* 


0144 


8D 


22 


125 




BSR 


ELDELAY 


0146 


7F 


00 46 


126 




CLR 


MASK 


0149 


7F 


00 45 


127 




CLR 


HOLDBYTE 


014C 


C6 


01 


128 
129 


, 


LDAB 


11 


014E 


8D 


18 


130 




BSR 


ELDELAY 


0150 


7A 


00 47 


131 




DEC 


COUNT 


0153 


26 


El 


132 




BNE 


BITLOOP 


0155 


39 




133 




RTS 




0156 






134 


MILDELAY 


ECU 


* 


0156 


D6 


46 


135 




LDAB 


MASK 


0158 


D8 


45 


136 




EORB 


HOLDBYTE 


015A 


D7 


45 


137 




STAB 


HOLDBYTE 


015C 


F7 


80 04 


138 




STAB 


L,H'80O4 


015F 


C6 


8F 


139 




LDAB 


«H'8F 


0161 






140 


LOOP 2 


EQU 


* 


0161 


5A 




141 




DEC 


B 


0162 


26 


FD 


142 




BNE 


LOOP 2 


0164 


09 




143 




DEX 




0165 


26 


EF 


144 




BNE 


MILDELAY 


0167 


39 




145 




RTS 




0168 






146 


ELDELAY 


EQU 


* 


0168 


DE 


42 


147 




LDX 


ELESPEED 


016A 


37 




14 8 




PSHB 




016B 


8D 


E9 


149 




ESR 


MILDELAY 


016D 


33 




150 




PULB 




016E 


5A 




151 




DEC 


B 


016F 


26 


F7 


152 




BNE 


ELDELAY 


0171 


39 




153 




RTS 




0172 






154 


CHARTOCW 


EQU 


* 


0172 


84 


7F 


155 




ANDA 


»H'7F 


0174 


80 


20 


156 




SUBA 


• 32 


0176 


2D 


17 


157 




BLT 


INVALAS 


0178 


81 


40 


158 




CMPA 


•LASTASCW 


017A 


2C 


OD 


159 




BGE 


NOTFNDAS 


017C 






160 


GETENTRY 


EQU 


* 


017C 


5F 




161 




CLR 


B 


017D 


37 




162 




PSHB 




017E 


37 




163 




PSHB 




017F 


30 




164 




TSX 




0180 


A7 


01 


165 




STAA 


1,1 


0182 


EE 


00 


166 




LDX 


1,0 


0184 


A6 


00 


167 




LDAA 


1,0 


0186 


31 




168 




INS 




0187 


31 




169 




INS 




0188 


39 




170 




RTS 




0189 






171 


NOTFNDAS 


EQU 


* 


0189 


80 


20 


172 




SUBA 


• 32 


018B 


81 


20 


173 




CMPA 


• H'20 


018D 


2E 


ED 


174 




BGT 


GETENTRY 


018F 






175 


INVALAS 


EQU 


* 


018F 


4F 




176 




CLR 


A 


0190 


39 




177 




RTS 





I OF MILISECONDS BETWEEN CHARACTERS 
LENGTH OF ELEMENT (DIT) DURATION 

IN MILISECONDS 
OSCILLATOR CONTROL BYTE 



POINTS TO 1ST BYTE IN STRING 



GET CHAR 

IS THIS THE STOP BYTE? 

BE IF NO 

RETURN 

INCRE PTR 

STORE POINTER 

CONVERT THE CHAR TO CW AND TRANSMIT 

LOAD DELAY CONSTANT FOR CHAR SPACING 

DELAY PROPER I OF MILISECONDS 

GET ADDR OF CHAR STRING 

GET NEXT CHAR 

CONVERT CHAR TO CW TRANSMIT CODE 
A = ? 

ER IF NO (VALID NON-BLANK CW CHAR) 
SET NUMBER OF ELEMENTS AT 1, AND 

MAKE THE WEIGHT SAME AS A DIT 
BYPASS KEY-ON INSTRUCTION 

SAVE A IN B 

ROTATE BIT COUNT 

ROTATE BIT COUNT 

ROTATE BIT COUNT 

ROTATE BIT COUNT 

SET COUNT AT < OR = 7 

IS THIS SPECIAL ERROR CODE 7 

BR IF NOT 

SET DATA TO ALL DITS 

INCRE COUNT FROM 7 TO 8 

STORE COUNT 

BIT COUNT = 6 ? 

BR IF NO 

SET COUNT AT 6 

STORE EIT COUNT 

INITIALIZE THE 

OSCILLATOR MASK 
LOAD WEIGHT FACTOR FOR DIT 
ROTATE DATA BIT' INTO CARRY 
BR IF CARRY CLEAR (DIT) 
LOAD WEIGHT FACTOR FOR DAH 

TURN ON KEY 

GENERATE DELAY FOR ELEMENT LENGTH 

CLEAR OSCILLATOR MASK 

TURN OFF KEY 

LOAD WEIGHT FACTOR FOR BREAK 

BETWEEN ELEMENTS 
GENERATE DELAY FOR ELEMENT LENGTH 
LAST ELEMENT IN CHAR 7 
BR IF NO 
RETURN 

HOLD THE KEY OUTPUT CONSTANT 
AND FLIP-FLOP THE 

OSCILLATOR OUTPUT IF 
KEY IS ON 
LOAD MILISECOND LOOP CONSTANT 

COUNT DOWN 

BR IF NOT FINISHED 

DECRE MILISECOND COUNT 

BR IF NOT FINISHED 

RETURN 

LOAD DELAY CONST FOR ELEMENT SPACING 

SAVE I OF INTERVALS 

DELAY PROPER # OF MILISECONDS 

RESTORE # OF INTERVALS 

DECRE t OF INTERVALS 

BR IF NOT FINISHED 



STRIP PARITY BIT 
SUBTRACT OFFSET 
IF INVALID CHAR OR » 
CHARACTER IN TABLE J 
BR IF NO 



BRANCH OUT 



ALLOCATE AND ZERO OUT 

A TEMPORARY 2-BYTE AREA ON 
TOP OF THE STACK 

POINT INDEX REGISTER TO IT 

STORE TABLE OFFSET INTO SECOND BYTE 

LOAD CONSTRUCTED POINTER INTO INDEX 

LOAD CW CODE 

DELETE TEMPORARY HOLD AREA 
i REALIGN STACK 

RETURN 

POINT TO LOWER CASE CHARS 

BETWEEN UPPER (, LOWER CASE 7 

BR IF NO (USE LOWER CASE AS UPPER) 

SET A TO CW NULL 
RETURN 



44 



Figure 3: Output Signals 
from the Morse code 
generation program. This 
program will produce 
either or both of a tone 
burst "oscillating" output 
which can be used to drive 
a speaker for code prac- 
tice, or a steady logic level 
output (during each dot or 
dash) used to control the 
keyer of a typical radio 
frequency transmitter. 



IrnS 

(TOME BURST) 



space between them is generated according 
to the value stored at location CHRSPEED. 
If element and character speeds are syn- 
chronized, the delay caused by CHRSPEED 
is exactly twice the space between elements, 
which has already been generated after the 
last element. Combining the two causes the 
total space between characters to be exactly 
the length of a dash, the established spacing 
between Morse code characters (see figure 

2). 

If a space (in ASCII, hexadecimal 20) is 
detected, it is treated as a phantom character 
consisting of one dot length with the key 
off. When added to the 3 dot interval 
following the previous character, and the 
equal interval following itself, a total interval 
of 7 dot times is generated, the standard 
spacing between words. (ASCII codes with 
no Morse code equivalents are also treated as 
spaces.) 

Speed Control 

There are two separate controls for Morse 
code spacing: element speed and character 
speed. The element speed is the time dura- 
tion of the smallest element of the Morse 
pattern. The time duration of dashes, dots, 
and the breaks in between are based upon it. 
If normal weighting is used, a dot is equal to 
one of these intervals, a dash is equal to 
three of them, and the space between dots 
and dashes within a character is equal to a 
single dot interval. The 2 byte field labelled 
ELESPEED contains a 16 bit binary number 
specifying the element delay as an integer 
number of milliseconds. With normal 
weighting, the duration of a dot will be 
exactly the number of milliseconds con- 
tained in ELESPEED, and the duration of a 
dash will be exactly three times that. 

If you wish the element and character 
speeds synchronized (20 wpm characters 
sent at 20 wpm intervals, etc), the binary 
value stored in CHRSPEED should be exact- 
ly double the binary value stored in ELE- 



SPEED. In this configuration the program 
will generate perfectly synchronized Morse 
code according to the established standard 
(dash duration three times that of dot, 
duration of space between elements equal to 
one dot, duration of space between charac- 
ters equal to that of one dash, and duration 
of space between words seven times that of 
one dot). When you change speeds, change 
the values of ELESPEED and CHRSPEED 
(once again, the value of the latter should be 
twice the value of the former.) 

If you wish to lengthen the interval 
between characters without changing their 
internal speed, simply increase the value of 
CHRSPEED. For instance, if you wish to 
practice copying code, you can set the 
ELESPEED field at the value for 20 wpm 
and the CHRSPEED field to the 5 wpm 
value. This will cause 20 wpm characters to 
be sent at 5 wpm intervals. You can tweak 
either speed to any 1 6 bit value you want 
(except zero), but the value of CHRSPEED 
must never be equal to less than two times 
that of ELESPEED or the spacing will be 
demolished! 

And It Comes Out Here 

The Morse code generator program is 
designed to output the Morse signals through 
a parallel IO port. Two different types of 
output are available simultaneously: logical 
and oscillating. The logical output cor- 
responds to the Morse signal as it is broad- 
cast — the output is high during a dot or 
dash and low in the times between. This 
corresponds to the telegraph key itself and 
may be fed to the transmitter directly or via 
a relay or other driver. The oscillating 
output changes state once every millisecond 
while the logical output is high and is held 
low during the times the logical output is 
low. This output, when connected to a 
speaker, produces a 500 Hz tone and can be 
used as a sidetone or a code practice 
oscillator. Both types of output can be 



45 



produced simultaneously, as seen in figure 3. 

Which of the lines in your parallel port 
are to be used at logical outputs and which 
are oscillators is determined by the control 
byte labelled INITMASK. For every bit in 
INITMASK which is equal to zero, the 
corresponding bit in the parallel port is a 
logical output. Every bit in INITMASK 
which is in an on state causes the corres- 
ponding line in the output port to oscillate. 

I am not a hardware type person; there- 
fore, I am not going to attempt describing 
the interface necessary to take the Morse 
code output of the nonoscillating line and 
transfer it to your ham rig, especially since 
every transmitter has its own keying system. 
In a classic copout I say, "It is up to the 
user to take the logical output of the PI A 
(0=key off, +5 V=key on) and get it onto 
the air without blasting the PIA output 
driver." 

Viva Southwest Tech 

This Morse data generator was written for 
a Southwest Technical Products 6800 sys- 



tem, which uses the Motorola MC6830L7 
ROM (MIKBUG Revision 9). A complete 
cross assembly of CWBUFFER is printed in 
listing 1. The program was written to be 
configuration independent, however, and 
will work for any 6800 system having 
programmable memory at locations hexa- 
decimal 00 to 49, at least 190 bytes of 
programmable memory elsewhere, and one 
PIA. The ASCII to Morse conversion 
subroutine is completely relocatable and 
reentrant, although the main generator 
routines (CWBUFFER and TRANSMIT) are 
not. 

All of the timing loops are calibrated for 
the Southwest Technical Products System, 
which has a 1.797 MHz master oscillator 
crystal. If your clock runs at a different 
speed, you may want to tweak the loop 
constant so that the output of one of the 
oscillating lines is exactly 500 Hz (each 
outer loop of the MILDELAY subroutine is 
supposed to last exactly one millisecond). 
The loop constant is at hexadecimal location 
0160; incrementing or decrementing it by 



Listing 2: Various and 
Sundry Drivers. Three dif- 
ferent driver routines oc- 
cupy the remainder of the 
assembled code prepared 
by the author. These 
drivers are ASDRIVER, 
SINGLECH, and CODE- 
PRAC. ASDRIVER is used 
to load a buffer, then call 
CWBUFFER to transmit 
the data as Morse signals. 
SINGLECH is a simple 
routine to read a character 
from the keyboard then 
call the TRANSMIT sub- 
routine (bypassing 
CWBUFFER) to output 
that character as its Morse 
equivalent. CODEPRAC is 
a routine used to generate 
a random series of Morse 
data for code practice. 
(Note that the instruction 
at 01 D5 should be patched 
to reference a random 
number routine specific to 
your own computer 
system.) 



L0C 


L'OUE 




51M1 


SOUHCt 


SUTtMtNT 




0191 








1 78 


ASDHIVE" 


E»U 


t» 




0191 


7F 


00 


45 


1 79 




Clh 


HOLUBYTE 


CLEAR OUTPUT 


0194 


7F 


80 


04 


180 




ClH 


M'8004 


POKT 


0197 


CE 


01 


F7 


181 




Lux 


WBUFFlH 


LOAD BUFFER ADDRESS 


0194 








182 
1SJ 

184 


LUaULOOH 


l«U 




BRANCH TO A SUBROUTINE »HICH INPUTS 
AN ASCII CHARACTER AND PLACES IT 


019A 


BU 


El 


AC 


185 
188 
187 
188 
189 


a 
H 
o 

s 


jaH 


H'tlAC 


MIKBUG THIS SUBROUTINE IS LOCATED 

AT HEX 'EUC (INEEEI 

NON-MIKBUG SYSTEMS SUBSTITUTE A 
COMPAHABLE ROUTINE 


019D 


A7 


00 




190 




ST* A 


ltO 


STORE INTO BUFFER 


019F 


0B 






191 




J.1X 




INCRE POINTER 


out 


81 


03 




192 




CnP A 


• 3 


IS THIS A CONTROL C (STOP BYTEI 7 


0142 


27 


10 




19J 




Bt.U 


N0NEEU3 


BR IF YES 


01A« 


HI 


0A 




19, 




CMPA 


• Hi 0A 


IS THIS AN ASCII LINE FEED 7 


01A6 


27 


OB 




195 




ULU 


SENU1T 


BR IF YES 


01A8 


HI 


08 




198 




CnP, 


•H' 08" 


IS THIS AN ASCII BACKSPACE COMMAND 7 


0UA 


26 


tt 




197 




B'lE 


LUAULUUP 


BR IF NO 


01AC 


09 






198 




BEX 




BACKSPACE POINTER 2 BYTES 1 FOR 


lilt 


09 






199 




UtX 




DATA BYTE (, 1 FOR BACKSPACE CHAR 


out 


20 


EA 




200 




»ha 


LUADLUOP 


CONTINUE 


01B0 








(01 


SEW IT 


fc-u 


« 




0160 


86 


03 




202 




LUAA 


• 3 


LOAD AND STORE 


0162 


A7 


00 




CUJ 




SUA 


1.0 


DELIMITER (STOP BYTE) INTO BUFF 


o lb- 








CC4 


N0NEEU3 


EUU 


• 




01B- 


CE 


01 


F7 


e05 




LUX 


•BUFFEH 


RELOAD BUFFER ADDRESS INTO INDEX 


01B7 


BU 


01 


00 


cub 




JSM 


LoBUFFth 


CALL C» GENERATOR ROUTINE 


OltIA 


20 


1)9 




eu7 




UHA 


AbUMvtK 


START CYCLE ALL OVER AGAIN 


01CA 








215 


COUEPHAC 


b>u 


<* 




01CA 


7F 


00 


45 


£16 




CLR 


HOLUBYTt 


CLEAR OUTPUT 


OICU 


7F 


80 


04 


217 




CLrt 


H'8004 


PORT 


01D0 


CE 


01 


F7 


ele 




LUX 


•BUFFER 


STORE ADDRESS OF BUFFER 


01D3 


DF 


«B 




Cl9 




SIX 


CWPTK 


INTO START-OF-BUFFER POINTER 


010a 








220 


toENLUUP 


E*U 


• 




01D5 


BL> 


00 


00 


£21 
222 


. 


J5K 


• ~0 


CALL A ROUTINE TO GENERATE A 1-BYTE 
RANDOM NUMBER 


01D8 


3b 






823 




P^HA 




SAVE ORIGINAL ASCII CHAR 


01U9 


BU 


01 


72 


»24 




J8H 


CHAHTuCK 


TEST FOR VALID CX CHARACTER 


01UC 


32 






225 




PULA 




GET ORIGINAL ASCII CHAR 


010D 


27 


F6 




226 




ecu 


GLNLOUP 


BR IF NOT VALID 


01DF 


DE 


48 




227 




LUX 


C«PTH 


LOAD BUFFER POINTER 


01E1 


A7 


00 




228 




SUA 


IiO 


STORE CHARACTER INTO BUFFER 


01 LJ 


0B 






cc* 




Inx 




INCRE POINTER 


01F4 


DF 


48 




H.lli 




six 


C*PTH 


SAVE NEH BUFFER POINTER 


01EG 


ec 


7F 


FF 


2J1 




cPx 


•bUFFENu 


END OF BUFFER OR END OF MEMORY 7 


01E9 


26 


EA 




132 




0h£ 


GENLOOP 


BR IF NOi GET ANOTHER CHARACTER 


01EB 


B6 


03 




233 




LVAA 


• 3 


LOAD AND STORE 


01ED 


A7 


00 




234 




SUA 


ltO 


DELIMITER (STOP BYTE) INTO BUFF 


01EF 


CE 


01 


F7 


235 




LUX 


«BUFFtH 


RELOAD BUFFER ADDRESS INTO INDEX 


01F2 


BD 


01 


00 


<JO 




J&R 


CWBUFFtH 


GENERATE C* FOR ENTIRE BUFFER 


01FS 


20. 


03 




237 




|KA 


COUEPHAC 


CONTINUE 


01F7 








• 38 


guFFEH 


(ag 


« 




7FFF 








• 39 




8Kb" 


H'7FFF 




7FFF 








<40 


BUFFENO 


fc«*U 


• 





Table I: Speed Control Values. CW BUFFER 
uses a 16 bit value, taken from this table, to 
control the basic number of milliseconds 
spent in each dot interval of the generated 
code, and each inter character interval. For 
standard Morse, the values loaded from the 
CHRSPEED column should be double the 
value of the corresponding ELESPEED entry 
of a given code speed. By increasing the 
CHRSPEED values, the spacings between 
characters can be lengthened while pre- 
serving the timing relationships for the data 
rate loaded into ELESPEED. These values 
are calculated assuming the Southwest 
Technical Products 6800 system is being 
used. For other processors with different 
rates for the master oscillator, a new table 
would have to be calculated. 



Morse 






code 


Value Loaded 


Value Loaded 


rate 


into ELESPEED 


into CHRSPEED 


(wpm) 


(hexadecimal) 


(hexadecimal) 


5 


00 D6 


01 AC 


10 


006B 


00D6 


15 


0047 


008E 


20 


0035 


006A 


25 


002B 


0056 


30 


0024 


0048 


35 


001 F 


003E 


40 


001 B 


0036 


50 


0015 


002A 


60 


0012 


0024 


70 


000 F 


001 E 


80 


000 D 


001 A 


90 


OOOC 


0018 


100 


000 B 


0016 


200 


0005 


000A 


500 


0002 


0004 


1000 


0001 


0002 



one will increase or decrease the interval 
which should correspond to a millisecond by 
six machine cycles. If you aren't concerned 
with perfect timing, you can compensate by 
loading different values into ELESPEED and 
CHRSPEED. 

The parallel port address used in the 
program corresponds to the serial control 
interface used by MIKBUG, which is really a 
parallel interface that only simulates a serial 
interface via software. Connect a small 8 
ohm speaker between connections RO and 
GND on the serial control interface. (Your 
computer will probably be unable to talk to 
the TVT or Teletype while the speaker is 
attached, due to loading problems.) In the 
program turn on the rightmost bit in I NIT- 
MASK to produce the oscillating output. 

There is only one output line normally 
available from the PIA on the Southwest 
Technical Products serial control interface, 
although it separates into two output sys- 
tems, RS-232 and 20 mA current loop. 
Another line on the PIA's A side is used for 
MIKBUG input, which leaves six lines com- 
pletely unused. These lines can be used for 
Morse output if you bring them out via 
jumpers from the backside of the PIA. Of 
course, MIKBUG has designated them as 
inputs in the A side data direction register; 
but if you OR a hexadecimal 7E into the 
DDR, you will reset them as outputs and 
leave the normal MIKBUG lines alone. You 
can use any combination of those lines for 
Morse output. 

Sundry Drivers 

The Morse Code generator program is 
designed to be used as a subroutine. It 
simply takes a character or string of charac- 
ters in memory and outputs the Morse code 
equivalents. It is completely up to the user 



as to how this data is input, whether through 
the keyboard, read from tape, generated by 
a random number generator, or conjured up 
by evil spirits. All that is required is that the 
Morse code routine's controls (ELESPEED, 
CHRSPEED, and INITMASK) be set before 
the subroutine is entered, and, if the 
CWBUFFER entry point is used, that the 
index register contains the address of the 
first byte of the string and the stop byte, 
hexadecimal 03, follows immediately after 
the last byte of the string. 

I have included three simple drivers which 
could be used for the 6800: one that 
generates one Morse character at a time from 

Table 2. Special Codes and ASCII Graphics. 
There are several special case codes used in 
radio communications with Morse code. 
These are listed at the left with a short 
explanation. At the right are shown the 
ASCII character graphics and hexadecimal 
codes used by CWBUFFER to represent 
these special case codes. 



To send: 



Keyboard Entry 



SK End of work 

BT Break 

AR End of Message 

KN Invitation to transmit, 
specified station only 

AS Wait 

ERROR CODE (8 dots) 



#' ASCII hexa- 
decimal 23 

&' ASCII hexa- 
decimal 26 

$' ASCII hexa- 
decimal 24 

+' ASCII hexa- 

decimal 2B 

ASCII hexa- 
decimal 3D 

!' ASCII hexa- 

decimal 21 or 

DEL ASCII hexa- 
decimal 7F 



47 



the keyboard; a second that buffers charac- 
ters until a delimiter character (line feed) is 
encountered, after which it sends out the 
characters it has stored in one brilliant blast 
of precision keying; and a third driver which 
fills up a buffer with random characters, 
then sends them out (for code practice). 
These drivers are shown as listing 2. 

The single character driver (SINGLECH) 
lies dormant until a character is entered 
from the keyboard. When the character is 
received, it is passed immediately to 
TRANSMIT and the Morse code is sent out 
the PIA. The driver then goes back to sleep 
until a new character comes in. 

The buffered driver loads incoming 
characters into a buffer in memory until 
either a line feed or ETX (Control C, 
hexadecimal 03) character is encountered. 
When either is received the starting address is 
loaded into the index register, a delimiter 
(ETX) is stored in the buffer after the last 
data byte; and the buffer is passed to 



CWBUFFER, which outputs the CW codes 
in a continuous stream until the end of the 
buffer is reached. Control then returns to 
the driver, which starts loading the buffer all 
over again. When a backspace command 
(Control H, hexadecimal 08) is received, the 
character immediately preceding the com- 
mand is deleted from the buffer. 

CODEPRAC, the code practice program, 
fills a buffer in memory with random charac- 
ters, then passes them to CWBUFFER, 
which sends them out the PIA into your 
speaker (hopefully you have set INITMASK 
so that the line is an oscillating output). The 
speed and spacing are controlled by what- 
ever you have loaded into ELESPEED and 
CHRSPEED. 

This code practice application is where 
the dual speed controls really come into 
play. When a person is first learning code, he 
obviously has to start at an extremely low 
character rate. At this speed, the dots and 
dashes are extremely dragged out and sound 



Table 3: ASCII to Morse 
Conversion Table. This 
table lists the relative off- 
set, data, assembly lan- 
guage text, ASCII equiva- 
lent graphics and ASCII 
hexadecimal codes (H'xx' 
for code xx) for each 
character recognized and 
generated by CWBUFFER. 
To find the Morse encoded 
value of each ASCII graph- 
ic, subtract hexadecimal 
20 from its ASCII hexa- 
decimal value, add the 
difference to the first 
address location of 
ASCWTABL (0 in this 
assembly) and use the 16 
bit result as the address of 
the desired Morse equiv- 
alent. Information in this 
table was prepared using 
the author's "SPUCA " 
cross assembler. 



SOURCE STATEMENT 



0000 




0000 


00 


0001 


FF 


0002 


D2 


0003 


E8 


0004 


AA 


0005 


00 


0006 


Bl 


0007 


DE 


0008 


ED 


0009 


ED 


000A 


00 


000E 


AD 


oooc 


F3 


oooo 


El 


000E 


EA 


000F 


A9 


0010 


BF 


0011 


BE 


0012 


BC 


0013 


B8 


0014 


B0 


0015 


A0 


0016 


Al 


0017 


A3 


0018 


A7 


0019 


AF 


001A 


C7 


001B 


D5 


001C 


00 


001D 


A2 


001E 


00 


001F 


CC 


0020 


00 


0021 


42 


0022 


81 


0023 


85 


0024 


61 


0025 


20 


0026 


84 


0027 


63 


0028 


80 


0029 


40 


002A 


8E 


002B 


65 


002C 


82 


002D 


43 


002E 


41 


002F 


67 


0030 


86 


0031 


8B 


0032 


62 


0033 


60 


0034 


21 


0035 


64 


0036 


88 


0037 


66 


0038 


89 


0039 


8D 


003A 


83 


003B 


ED 


003C 


00 


003D 


ED 


003E 


00 


003F 


FF 


0040 





1 


ASCWTABL EUU 


* 


2 


FCB 


B'00000000 


3 


FCB 


B'llllllll 


4 


FCB 


B'11010010 


5 


FCB 


B'11101000 


6 


FCB 


B'10101010 


7 


FCB 


B'00000000 


8 


FCE 


D'10110001 


9 


FCB 


B'11011110 


10 


FCB 


B'11101101 


11 


FCB 


B'11101101 


12 


FCB 


B'00000000 


13 


FCB 


B'10101101 


14 


FCB 


B'11110011 


15 


FCB 


B'11100001 


16 


FCB 


B'11101010 


17 


FCE 


B'10101001 


18 


FCB 


B'lOllllll 


19 


FCB 


B'lOlllllO 


20 


FCB 


B'lOllllOO 


21 


FCB 


B'10111000 


22 


FCB 


B'10110000 


23 


FCB 


B'10100000 


24 


FCE 


B'10100001 


25 


FCE 


E'10100011 


26 


FCB 


B'10100111 


27 


FCB 


B'10101111 


28 


FCB 


B'11000111 


29 


FCB 


B'11010101 


30 


FCB 


B'00000000 


31 


FCB 


B'10100010 


32 


FCB 


B'00000000 


33 


FCB 


B'11001100 


34 


FCB 


B'00000000 


35 


FCB 


B'01000010 


36 


FCB 


B'10000001 


37 


FCB 


B'10000101 


38 


FCB 


B'01100001 


39 


FCB 


B'00100000 


40 


FCB 


B'10000100 


41 


FCB 


B'OUOOOll 


42 


FCB 


B'10000000 


43 


FCB 


B'01000000 


44 


FCB 


B'10001110 


45 


FCB 


B'01100101 


46 


FCB 


B'10000010 


47 


FCB 


B'01000011 


48 


FCB 


B'01000001 


49 


FCB 


B'01100111 


50 


FCB 


B'10000110 


51 


FCB 


B'10001011 


52 


FCB 


B'01100010 


53 


FCB 


B'01100000 


54 


FCB 


B'00100001 


55 


FCB 


B'01100100 


56 


FCB 


B'10001000 


57 


FCB 


B'01100110 


58 


FCB 


B'10001001 


59 


FCB 


B'10001101 


SO 


FCB 


B'10000011 


61 


FCB 


B'11101101 


62 


FCB 


B'00000000 


63 


FCE 


B'11101101 


64 


FCB 


B'00000000 


65 


FCB 


B'llllllll 


66 


LASTASCW EUU 


*-ASCWTABL 



SPACE 


(ASCII 


11' 20' 






I (ERROR) 


(ASCII 
(ASCII 


H'21' 
H'22' 






1 (SK) 


(ASCII 


h'23' 






S (AR) 


(ASCII 


H 1 24' 






NULL 


(ASCII 


B'25' 






S (BT) 

( 
) 


(ASCII 
(ASCII 
(ASCII 
(ASCII 


H'26' 
H'27' 
H'28' 
H'29' 






NULL 


(ASCII 


Ii'2A' 






+ (KM 


(ASCII 
(ASCII 


H ' 2B ' 
II' 2C 






~ 


(ASCII 
(ASCII 


H'2D' 

H'2E' 






/ 


(ASCII 


K'2F' 









(ASCII 


11' 30' 






1 


(ASCII 


11" 31 ■ 






2 


(ASCII 


H'32 1 






3 


(ASCII 


11' 33' 






4 


(ASCII 


B'34 1 






5 


(ASCII 


H'35' 






6 


(ASCII 


II '36' 






7 


(ASCII 


H'37' 






6 


(ASCII 


H'38' 






9 


(ASCII 
(ASCII 
(ASCII 


H'39' 
H'3A' 
Ii'3B' 






NULL 


(ASCII 


H'3C 






= (AS) 


(ASCII 


H'3D' 






NULL 


(ASCII 


H ' 3E ' 






? 


(ASCII 


II ' 3F ' 






NULL 


(ASCII 


H ' 4 ' 






A 


(ASCII 


H'41' 


OR 


H'61') 


B 


(ASCII 


II"42' 


OR 


H'62' ) 


C 


(ASCII 


Ii'43' 


OR 


H'63') 


D 


(ASCII 


H'44' 


OR 


H'64') 


E 


(ASCII 


II' 45' 


OR 


I1'65') 


F 


(ASCII 


H'46' 


OR 


H'66') 


G 


(ASCII 


H'47' 


OR 


H'67 1 ) 


H 


(ASCII 


11 '48' 


OR 


H'68') 


I 


(ASCII 


H'49' 


OR 


H'69') 


J 


(ASCII 


H'4A' 


OR 


K'6A' ) 


K 


(ASCII 


H'4B' 


OR 


11 ' 6B ' ) 


L 


(ASCII 


H ' 4C ' 


OR 


fI'6C ) 


M 


(ASCII 


H'4D' 


OR 


H'6D') 


N 


(ASCII 


H' 4E' 


OR 


h' 6E' ) 





(ASCII 


H'4F' 


OR 


K'6F' ) 


P 


(ASCII 


H'50' 


OR 


H'70') 


Q 


(ASCII 


H'51' 


OR 


H'71') 


R 


(ASCII 


H'52' 


OR 


H'72') 


S 


(ASCII 


H'53 1 


OR 


H'73') 


T 


(ASCII 


H'54' 


OR 


H'74') 


U 


(ASCII 


H'55' 


OR 


H'75'l 


V 


(ASCII 


I! '56' 


OR 


H'76'l 


K 


(ASCII 


H'57' 


OR 


H'77') 


X 


(ASCII 


H'58' 


OR 


H'78' ) 


Y 


(ASCII 


H'59' 


OR 


H'79') 


2 


(ASCII 


11' 5A' 


OR 


H'7A' ) 


( 


(ASCII 


H'5B' 


OR 


II " 7 B ' ) 


NULL 


(ASCII 


H'5C' 


OR 


H'7C' ) 


) 


(ASCII 


H'5D' 


OR 


K'7D') 


NULL 


(ASCII 


K'5E' 


OR 


11 '7E') 


DEL (ERROR) 


(ASCII 


h'5F' 


OR 


H'7F' ) 



48 



AbC»UbL 


0000 


LAb 1 AjO 


00«0 


CHHbPEEu 


0040 


ELESPEEO 


0042 


INITHASK 


0044 


MOlUBYJE 


004b 


MAbrv 


0046 


COUNT 


0047 


CWPTR 


0048 


CKBUFFER 


0100 


COhIINUE 


0107 


THAiibMI r 


011O 


NOTbPACt 


01U 


NOTERR 


012E 


COUNTOK 


0134 


BITLOOP 


01jh 


bEr^ 


0141 


SPACEN1 


0144 


MILDELAY 


0156 


L00P2 


0161 


ELDELAY 


016B 


CMAKlOC" 


017,! 


6ETENTKY 


017C 


NOTFNDAS 


0189 


INVALAS 


018F 


ASUhl VtH 


0191 


LUADLUOP 


019A 


bENOlT 


OlbO 


NONEED3 


01B4 


SINSLECM 


01BC 


SINOLOUP 


01C2 


CuoephaC 


OKA 


6ENL00P 


010b 


BUFFER 


01F7 


BUFFEND 


7FFF 



Table 4: Label Table. This 
table, also prepared with 
the author's cross as- 
sembler, gives the address 
(hexadecimal) for each 
symbol in CWBUFFER 
and the sundry driver 
programs. 



completely different than they do at higher 
speeds. The Morse code neophyte should 
really learn to recognize the characters by 
listening to the total pattern, not by 
counting dots and dashes. However, speeding 
up the characters also speeds up the charac- 
ter rate if normal element to space ratios are 
maintained and an entire message has gone 
by while the beginner is still trying to 
recognize the first character. Therefore, the 
ideal situation is to retain the sound of the 
high speed characters and yet increase the 
interval between them. This is accomplished 
by leaving the element speed (ELESPEED) 
the same and increasing the duration of time 
between characters (CHRSPEED) to what- 
ever length is desired. 

Anyway, to get back to the code practice 
driver, it will continue to send characters at 
the CHRSPEED rate until the end of the 
buffer is reached, at which time it will 
generate another set of practice characters. 
Unfortunately, the random number genera- 
tion routine itself is missing. The code 
practice driver was a last minute addition, 
and there was not time to develop one. (The 
program was tested using a kluge substitu- 
tion.) However, there are several different 
versions floating around. The one you use 
should generate a one byte random number 
and return it in accumulator A. It should not 
destroy accumulator B or the index register. 
Load the address of the routine in the 
dummy jump to subroutine at hexadecimal 
location 01 D5. The address at location 01 E7 
is the end of buffer address or your maxi- 
mum memory location. Don't forget to leave 
a place for the random number generator 
subroutine. 

The drivers in this article are very primi- 
tive, and are designed simply to get you 
running. If your system is a Southwest 
Tech one, you should be able to load all of 
the programs and the table into your system 
exactly as coded (CODEPRAC too, with the 
addition of a random number routine), 
connect a speaker between RO and ground 
on the control interface, load ELESPEED 
and CHRSPEED according to table 1, turn 
on the rightmost bit of INITMASK, branch 
to the starting address of the driver of your 
choice, and start typing. As you hear the 
speaker sing a 500 Hz aria with perfect 1 to 
3 to 7 spacing, you may reflect that maybe 



programmers aren't such bad guys after all. 
Seriously, the sidetone output is a perfect 
way to ensure that the program is working 
with each of the various drivers before you 
try to tie it into your rig. 

Other 6800 Systems 

For non Southwest Tech 6800 systems, 
the installation of the Morse generator pro- 
gram is not much more difficult. The address 
of the PIA used for the Morse code output 
and that of the input routine are the primary 
concerns. If your system uses MIKBUG, 
which has the single character input routine 
at hexadecimal location E1 AC and the serial 
control interface at hexadecimal 8004, so 
much the better — you shouldn't have to 
modify a single byte. If your configuration is 
different, substitute your own PIA address 
at hexadecimal locations 01 5D, 0195, 01 CO, 
and 01 CE, and your ASCII input routine 
address at locations 01 C3 and 01 9B. 

The programs in this article were not 
assembled on Motorola's assembler. They 
were run on SPUCA (Sewell's Psychedelic 
Universal Cross Assembler), a homemade 
cross assembler which runs on the IBM 370 
and generates code for the 6800 and four 
other microprocessors. Listings 1 and 2, and 
tables 3 and 4 were generated by SPUCA. 

The formats are almost identical, but 
there are some minor differences that should 
be pointed out for the sake of clarity. The 
major difference is in instructions using the 
indexed mode of addressing. Motorola places 
the symbol for the index register (X) after 
the operand with a comma in between, 
where SPUCA looks for an I before the 
operand, again with a comma in between. In 
other words, a Motorola indexed instruction 
looks like this: LDA A OPERAND,X and 
one read in by SPUCA is in this format: 
LDAA l,OPERAND. In addition, the pro- 
grammer must specify explicitly whether 
direct (base page, one byte address) or 
extended (two byte) addressing is to be 
used. If the extended addressing is to be 
used, the operand must be preceded by an L, 
(for Long). Example: LDAA L,OPERAND. 

Most of the rest of the instructions are 
identical to Motorola's except that my as- 
sembler has no FCC (Form Constant Charac- 
ters) directive and no separate column for 
the accumulator ID." 



49 



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A Morse Code Station 
Data Handler 



Bruce Filgate 

Digital Equipment Corporation 

Components Group Engineering 

One Iron Way 

Marlborough MA 01752 



For some time, there has been a need in 
amateur radio for a machine that could both 
decode and generate Morse code; in addi- 
tion, the decoder had to be capable of 
automatically tracking varying received code 
speeds. Although Morse code keyboards 
have been around in the amateur radio field 
for some time, decoders have not been so 
readily available. Since hardwired logic can 
be difficult to modify, I decided to imple- 
ment the coder and decoder in software. 
Since a low price was desirable and high 
performance was not required, I used Digital 
Equipment Corporation's MPS Starter Set. 
This is an Intel 8008-1 based product which 
DEC has been marketing to the commercial 
world. This article describes my implemen- 
tation using MPS. 

Implementation 

The main program consists of a few 
subroutine calls to the main tasks, as shown 



Listing 1: Monitor Entry and Supervisor Main Task. This listing shows the 
symbolic assembly language representation of the outer loop of the Morse 
code program. The detailed assembly is found in listing 2 along with the rest 
of the program. 



RESTRT, 



CAL 


INPEND 


try code input line; 


CAL 


KYBD 


try the keyboard task; 


CAL 


PNTR 


try the printer task; 


LHI 


CMMNDt 


test the mode byte; 


LLI 


CMMND 




XRA 




zero the A reg and figs; 


ADM 




mode byte to A reg and figs; 


JFZ 


CMMNDR 


enter command mode; 


CAL 


IDLE 


non command character feedthrough 


CAL 


OUTPUT 


anything morse to output? 


JMP 


RESTRT 


and loop (?) along; 



in listing 1. As can be seen in the source 
code of the monitor, there are two principal 
routines that provide for Morse input and 
output; these two routines are INPEND and 
OTPUT respectively. The other routines 
within the main modules provide house- 
keeping and data manipulation for these 10 
drivers. 

It should be noted, on consulting the full 
program listing, listing 2, that there are two 
data tables: an ASCII table and a Morse data 
table. The only restrictions on modifying 
these tables are that both tables be the same 
size and in the same sequence. For instance, 
the ASCII table could be changed to reflect 
a non-ASCII code so that the console could 
be other than an ASCII terminal. 

Principle of Code Manipulation 

A search of published literature available 
at the time this program was created showed 
an excellent method of representing Morse 
code in memory, particularly in eight bit 
wide memory. This method, found on page 
13 of the July 1975 QST magazine, was 
adopted here for internal representation of 
Morse code. Binary ones represent dashes, 
binary zeros represent dots and a final 
binary one closes the character. For in- 
stance, the Morse character B(— ■ • •) would 
be represented by the octal number 210 
(binary 10001000). Note that the binary 
strings are left justified with trailing zeros. It 
can be seen that if this representation is to 
be used to generate a Morse character B, the 
bit string should simply be shifted out to the 
left with each bit interpreted as a dash or a 



52 



Figure I : Flow Chart De- 
tail of INPEND, the Morse 
code input service routine. 
This routine, beginning at 
address 24/034 in listing 
2, is responsible for track- 
ing and adapting to the 
variations in speed of 
human generated Morse 
code inputs. This routine 
also detects end of charac- 
ter and end of word gaps 
between Morse inputs. The 
character outputs are 
translated and sent to the 
printer buffer maintained 
by the program. 



dot until a final result in the shift register 
is 200 octal. Thus 200 octal remaining in 
the processor's accumulator is used to sig- 
nify the end of a character. 

To transmit an ASCII keyboard character 
out in Morse code, all that is required is to 
look up the ASCII character in the ASCII 
table and compute its relative location with- 
in the table. Once the relative location is 
calculated, it is necessary to look in the 
Morse table in the same relative location and 
pull the Morse equivalent of the ASCII 
character out of the table. Once this code is 
available, it is loaded into a register and 
shifted out to the left as dashes and dots 
until the register contains octal 200. Con- 
versely, data being received in Morse code 
starts a character by preloading of a register 
with octal 200 and then the shifting in of a 
bit at a time of dash and dot information in 
ones and zeros. When an intercharacter delay 
time is finally recognized, the character is 
considered "closed" and the data that is in 
the register is left justified and looked up in 
the Morse code table. When it is found in the 
Morse code table, the same relative address 
within the ASCII table contains the ASCII 
character equivalent. (See figure 1 for a flow 
chart of the code input service routine.) 

Morse Code Speed Determination 

When code is being transmitted by the 
program, the code output speed is selected 
by a keyboard control sequence. This con- 
trol sequence consists of the escape (ESC) 
key followed by a 'W' and then a second 
character obtained from table 1. Once the 





1 1 

| MOR5E CODE 


f INPEND \ 


1 ROUTINE 

1 LISTING 2 


1 


[ADDRESS 24/034 J 


v/KEY^\ 

^ DOWN p> 


J^2_( RETUR N ) 


Tyes 




INITIALIZE 
■INCHAH" 






UPDATE 
TIMER 




TIMER \ NO 
V SAYS "DOT"JT 

? 



SPEED UP 
CODE RATE 






SLOW DOWN 
CODE RATE 



UPDATE 
TIMER 



PUT SPACE 

INTO 

PRINTER 




LEFT JUSTIFY 

'INCHAR" 

AND TRANSLATE 



PUT INPUT 
INTO 
PRINTER 
FIFO 



( RETURN J 



53 



Table 1: The list of ASCII 
character graphics and 
their equivalent speed set- 
tings when used with the 
speed change command. 
The command sequence is: 
escape character, W, speed 
character. Thus the se- 
quence escape, W, + sets 
the speed to 18 words per 
minute. 



Speed 


Rale 


Character 


(wpm) 


SP 


120 


! 


89 


" 


63 


# 


48 


$ 


44 


0/ 

/o 


37 


' 


27 


) 


22 


+ 


18 


/ 


14 


3 


12 


> 


7.6 


? 


7.2 



Software Availability in Machine Readable Form 

The software for this program in source and 
binary form has been submitted to the DECUS 
library. DECUS is the Digital Equipment Corpora- 
tion User's Society, managed by a board of 
directors composed of DEC equipment users. Free 
membership in the society is open to users of DEC 
equipment. The group periodically publishes 
indices of currently available programs with 
abstracts. 

The documentation for this program is listed 
under the number 8-801. Since it is expected that 
some users will want to modify this program, the 
source in ASCII is available on paper tape from the 
DECUS library. To order copies of the ASCII 
source tape or the binary tape, write to: 

Program Libarian 
DECUS 
146 Main St 
Maynard MA 01754 



as of 
apply: 



the time of writing, the following prices 



8-801 Binary paper tape $2 

8-801 ASCII source paper tape $8 

8-801 DECUS writeup $1 

8-801 Assembly listing $10 



output speed is selected by this method it 
will remain constant until a new value is 
selected. 

Since the DEC M7341 processor card uses 
a variable speed clock, table 1 is calculated 
assuming that the clock be operated at the 
same speed as the clock on the author's 
system. If the clock for the processor on 
which the software is running is operated at 
a different rate, then table 1 must be 
recalculated. 

If it is desired that the user's clock be set 
at the same speed as the clock found in the 
author's processor, a method of calibrating 
the clock is offered here: If the program is 
set up to transmit a sequence of dots, for 
instance the character "five" which is five 
dots sequentially, a string of "fives" will 
generate five dots followed by three dot 
times between characters, five more dots for 
the next "five" and so on. This, in considera- 
tion with the equation: 

Speed (wpm) = dots pe^mjnute = 

2.4 * dots per second 

can be used to compute the effective code 
rate in words per minute. 

The code input speed is never actually 
calculated but instead a rather heuristic 
tracking technique is used to update what 




Photo 1: The Digital 
Equipment Corporation's 
MPS starter set used by 
the author for running the 
Morse code program. Fur- 
ther detail of the central 
processor board is shown 
in photo 2. 



Photo 2: The Digital 
Equipment Corporation 
Ml 341 central processor 
board. The 8008 processor 
is socketed at the lower 
right. This board also in- 
cludes a UART for serial 
interface and the random 
logic needed to buffer and 
drive an 8008. 



Information about the Hardware Used 

This program is designed to generate and 
decode Morse code. Although the program is 
intended to be executed on Digital Equip- 
ment Corporation's MPS M7341, it should 
also execute on almost any Intel 8008-1 
based microprocessor with only slight mod- 
ification. Photos 1 and 2 are supplied by 
Digital Equipment Corporation. 

The following literature is available from: 

Digital Equipment Corporation 
Communications Services 
444 Whitney St 
Northboro MA 01532 

General Interfacing Techniques for the 
M7341 Microprocessor Module 

Interfacing The TU60 to the MPS M7341 
Microprocessor 

M734 1 Processor Module Data Sheet 

M7344-YA, -YB, -YC Read-Write Memory 
Module Data Sheet 

M7345 Programmable Read Only Memory 
Data Sheet 

M7346 External Event Detection Module 
Data Sheet 

M7328 Evoke Decoder Module Data Sheet 

M1501 Bus Input Interface Module Data 
Sheet 

M1502 Bus Output Interface Module Data 
Sheet 

Logic Handbook 

KMP01A Microprocessor Series (MPS) Pre- 
wired Backplane Appl. No te 

MR873 Microprocessor ROM Programmer 
Product Bulletin 

1976 Direct Sales Catalog 



54 



the processor "judges" the current code rate 
to be. Therefore, the processor arbitrarily 
selects the initial code speed to be about 15 
words per minute and, if it deems that the 
input code speed is other than that, a change 
will be made in the appropriate direction 
until the processor is able to synchronize 
against the incoming code speed. At this 
time, small changes in the code rate will be 
made to insure that the code speed remains 
within the tracking range. In addition to 
decoding the dot and dash times, the pro- 
gram must also be able to decode the times 
between characters, between symbols and 
even at the end of sentences. Additionally an 
arbitrary time is selected which is deemed to 
be an end of message; these times are set to 
be a function of a dot time. Thus, as the 
processor works to synchronize the code 



speed, all that is required is to keep track of 
a counter which represents the length of a 
dot. If the dot time is increased, thus 
decreasing the code speed, all the other 
times will be affected in a similar direction. 

Keyboard Monitor 

In general, characters typed on the key- 
board are immediately translated to the 
Morse code bit string and then transmitted 



f CMMNDR J 



GET NEW 
KEY INPUT 





GET NEW 

KEYBOARD 

INPUT 






OPEN 
MESSAGE 


1 

-< 






BUFFER 








/LA 

<^CHAR/ 


S L^\YES 


CLOSE 

MESSAGE 

BUFFER 


J s' 




NO 






PUT NEW 
CHARACTER 
IN MESSAGE 
BUFFER 


NO /deleteV 

-*-— — <CHARACTER !> 


( RETURN J 


I 








YES 




DELETE LAST 
CHARACTER 
OF MESSAGE 
BUFFER 














Figure 2: The command 
interpreter routine, 
CMMNDR, represented as 
a flow chart. The com- 
mand interpreter is de- 
signed to test for the 
several commands possible 
and take appropriate 
actions. The commands in- 
clude exiting the com- 
mand mode, loading the 
message buffer, printing 
the message buffer, send- 
ing the message buffer out 
as Morse code, testing the 
Morse code output by re- 
peatedly sending the mes- 
sage buffer and changing 
the speed of the machine 
generated Morse code out- 
puts. 



COPY MESSAGE 
BUFFER INTO 
OUTPUT 
BUFFER 




ERROR 
MESSAGE 
' ?' 



YES 



COPY MESSAGE 
BUFFER INTO 
PRINT BUFFER 



COPY MESSAGE 
BUFFER INTO 
OUTPUT 
BUFFER 




( RETURN J 



SET NEW 
SPEED FROM 
INPUT 



f RETURN J 



55 



( KYBD ) 



.TlSTING 2 

1 ADDRESS 22/227 



Figure 3: The keyboard 
service routine, K YBD, 
specified as a flow chart. 
This routine is simple: 
Look at the UA R T and see 
if data is available. If so, 
then stuff the data into 
the keyboard input buffer, 
or ring the bell and ignore 
if the buffer was full. 



Figure 4: The printer ser- 
vice routine, PNTR, speci- 
fied as a flow chart. This 
also is very straightfor- 
ward: Look at the UART 
and see if it is ready to 
transmit. If so, then if the 
printer buffer is not empty 
send a character to the 
UART and remove the 
character from the printer 
buffer. 




f RETURN j 



out in Morse code. There are some special 
commands interpreted as shown in figure 2 
to modify this normal mode: 

• <ESC> L is used to reload the 
message buffer until an escape 
(<ESC>). (LOAD command) 

• <ESC> is used to return to normal 
keyboard mode. (EXIT command) 

• <ESC> P causes the message buffer 
contents to be printed. (PRINT com- 
mand) 

• <ESC> S is used to ship the message 



>- 



iTlSTING 2 
"'.ADDRESS 22/316 

["TlART TRANS- 
MITTER BUFFER 
H EMPTY 



< \. 


NO 




Tyes 








/'PRINTER^^ 


fES 


J 


I 


\FIFO EMPTY/ 








\?/- 








Tno 








PRINT A 








CHAR 


!*CTER 








DELETE 


CHAR 








FROM FIFO 














J 


• 













f RETURN ) 



buffer out, translated in Morse code. 
(SEND command) 

• <ESC> T is a test to do <ESC> S 
until an escape is typed. (TEST 
command) 

• <ESC> W loads a new rate constant 
for WPM output. A character obtained 
from table 1 sets the rate, and should 
follow the W. (Speed change 
command) 

• The delete (rub out) can be used in a 
buffer loading mode to remove pre- 
vious characters back to the beginning 
of the buffer. 

Software Buffer 

This program uses overlaid IO to allow 
several operations to be done at the same 
time. First in, first out buffering is imple- 
mented to keep track of data transferred 
from or to the buffer locations. Four effec- 
tive sources or destinations are involved: the 
message holding buffer, the code output 
buffer, the keyboard buffer (see figure 3 for 
the keyboard buffer service routine), and the 
printer buffer (see figure 4 for printer buffer 
service routine). Each buffer uses its first 
location as a byte count of the number of 
locations occupied by valid data. Since this 
is an eight bit machine, and single precision 
arithmetic is used, it is obvious that the 
maximum number of available data locations 
in a buffer can not exceed octal 377; any 
attempt by the user to exceed octal 377 
locations or to exceed the maximum buffer 
size results in an error due to buffer over- 
flow. When the program senses a buffer 
overflow condition, the terminal bell (or bell 
indicator) will be rung and the character that 
would have caused the overflow will be 
ignored. Since the user may choose to 
modify the sizes of these buffers, the fol- 
lowing advice is offered: The message buffer 
should be as large as practically possible, 
followed by the keyboard buffer and then 
the printer buffer in priority. 

Hardware Configuration 

This piece of software has been designed 
and constructed so it can operate without 
modification on DEC Logic Products Starter 
Set 1 (KMP01 based). This starter set con- 
tains adequate memory, hardware, and inter- 
facing to allow the software to execute 
properly. When executed on the starter set, 
the least significant bit of the input byte 
from input device 2 is used as the sense line 
for code input. The entire byte on output 
device 4 is used for code output (any 
particular bit on this output channel may be 

Text continued on page 70 



56 



Listing 2: Complete Assembly of the Morse Code Program for an 8008. This listing was prepared using a cross assembler 
available to the author at Digital Equipment Corporation. The listing is reproduced here in its entirety, with an absolute origin 
picked for the hardware available to the author. The listing is well commented and includes a symbol table found at the end. 



// THIS PROGRAM. CONSISTING OF A PROM SECTION OF 

/SUBROUTINES % MAINLINE TASKS AND A RAM 

/SECTION OF BUFFERS- GENERATES AND DECODES MORSE CODE. 

/THE DECODING SECTION IB DESIGNED TO BE SELF TRACKING 
/AS TO CHANGING SPEEDS. DUE TO THIS SELF TRACKING 
/FEATURE. A FEU ILLEGAL CODES MAY BE DECODED AS THE 
/PROGRAM ATTEMPTS TO LOCK ONTO THE INPUT CODE SPEED. 

/THIS PROGRAM IS DESIGNED TO RUN ON THE INTEL BOOB-l BASED 
/MPS STARTER SET AVAILABLE FROM THE DEC COMPONENTS GROUP. 



/ WRITTEN 1-29-76 BY BRUCE FILGATE OF COMPONENTS 
/APPLICATIONS ENGINEERING AT DIGITAL EQUIPMENT 
/CORPORATION IN MARL .BOUGH MASSACHUSETTS FOR THE 
/LOGIC PRODUCTS MPS PRODUCT LINE 



/WEIGHTING IS 1 DASH W 3 DOTS. 



/JUST A FEU UORDS ABOUT THE STACK STRUCTURE 

/THE STACKS USE THE FIRST LOCATION AS A COUNT OF THE 
/NUMBER OF OTHER USED LOCATIONS IN THE STACK. 

/THE LSB OF THE INPUT BYTE FROM I/O CHANNEL #2 IS RESERVED FOR 
/THE SENSE LINE FOR CODE INPUT. 

/THE BYTE ON I/O CHANNEL *4 IS USED FOR CODE OUTPUT 

/KEY SENSE FOR CODE INPUT AND OUTPUT IS GROUND FOR KEY DOWN 
/CONDITION AND LOGIC HIGH FOR THE KEY UP CONDITION. 



/********** ******************************** 

/ 

/ PROGRAM SHOULD BE STARTED AT STRT 

/ 

/ PROGRAM MAY BE RESTARTED AT RESTRT 

/****************************************** 



/THE TERMINAL BELL WILL BE RUNG WHENEVER A BUFFER 
/OVERFLOW IS CAUSED BY THE USER. THE CHAR 
/THAT WOULU HAVE CAUSED THE OVERFLOW IS TRAPPED 
/AND DELETED. 



/NORMALLY THE KEYBOARD DATA IS TRANSMITTED OUT TRANSLATED 
/BUT ALT MODE (ESC) KEY USED FOR SPECIAL COMMANDS. 
/L=RELOAD THE MESSAGE BUFFER UNTIL ESC 
/ESC=RETURN TO NORMAL MODE 
/P=PRINT THE MESSAGE BUFFER CONTENTS 
/S=SHIP THE MESSAGE BUFFER TRANSLATED 
/T=TE5T BY DOING S UNTIL AN ESC IS TYPED 
/UNLOAD BAUD CONSTANT FOR UPM OUTPUT 
/ SP 120 UPM 



89 

63 



20 124 

20 125 

20 127 

20 131 

20 133 

20 136 

20 140 

20 141 



20 145 
20 146 



20 152 

20 153 



20 157 

20 160 



20 164 
20 166 



20 170 
20 171 



370 
056 
024 
066 
301 
076 
03f 
106 
046 
021 
076 
035 
250 
056 
024 
066 
305 
370 
056 
025 
066 
364 
370 
056 
024 
066 
275 
370 
106 
046 
021 
370 
056 
025 
066 
304 
370 
131 



LMA 




LHI 


BAUD 


LLI 


BAUD 


LMI 


35 


CAL 


INCLI 



8TRTJ . XRA 
LHI 



LMA 
LH.I 



LMA 
LHI 



/SET OUTPUT BAUD AT ABOUT 15 UPM 



INCLH /LIKEWISE WITH INPUT BAUD 



/RESTART FOR "C AND CLEAR THE A REG 
KYFIFO" /CLEAR THE KYBD CHAR COUNT 



OTFIFO" /CLEAR THE OUTPUT BUFFER 
OTFIFO 

CMMND" /INITIALIZE THE MODE BYTE 
CMMND 

INCLH /INIT THE CHAR COUNT 

/SET FOR CRLF INITIALIZATION 

PNFIFO" /INITIALIZE THE PRINTER CHAR CNT 



/ZERO PRINTER CHAR COUNT 
/CLEAR THE TONE AND OTHER BITS 



/MONITOR ENTRY AND SUPERVISOR MAIN TASK 



20 172 106 RESTRT. CAL 

034 

024 
20 175 106 CAL 



20 200 106 

316 

022 

20 203 056 

024 

20 205 066 



275 

20 207 250 

20 210 207 

20 211 110 

150 

021 

20 214 106 

360 

023 

20 217 106 

230 

023 

20 222 104 

172 

020 



LHI 

LLI 

XRA 
ADM 
JFZ 



INPEND /TRY CODE INPUT LINE 

KYBD /TRY THE KEYBOARD TASK 

PNTR /TRY THE PRINTER TASK 

CMMND" /TEST THE MODE BYTE 

CMMND 

/ZERO THE A REG AND FLGS 
/MODE BYTE TO A REG AND FLGS 
CMMNDR /ENTER COMMAND MODE 

IDLE /NON COMMAND CHARACTER FEEDTHROUGH 

OTPUT /ANYTHING MORSE TO OUTPUT? 

RESTRT /AND LOOP (?) ALONG 



7.6 
7.2 



/AND THE DELETE <RUBOUT) KEY IS USED TO EDIT BUFFER AS 
/WELL AS REPRESENT THE ERROR CODE IN THE IMMEDIATE MODE. 



/NEED 
OFDEF 
OPDEF 

OPDEF 
OPDEF 
OPDEF 
/BUFFER SIZE SET UF 
MSGSZ=377 
BUF0UT=60 
BUFSKY=377 
BUFSPN=60 

/TERMINAL DEPENDENT 
UIDTH=110 
CR=15 
LF=12 
W=127 
ERCHAR=7 
ESC=175 
L = U4 
P=120 
5=123 
T = 124 
ESCSYM=44 
QUEST=77 
DELETE=177 
DELSYM=134 
ETX=3 
C = 103 

UPARR0=136 
BLANK=40 



FEW MORE INSTRUCTIONS HERE. 



SENSE? 105f0 
READ 1101 fO 
PRINT* 121 fO 
STATUSJ103! 
OUTPUT* 131 t 



/READ THE SENSE LINE 
/SERIAL INPUT 
/SERIAL OUTPUT 
/SERIAL STATUS 
/ENCODED OUTPUT 



/MESSAGE HOLDING 
/CODE OUTPUT 
/KEYBOARD 
/PRINTER 

CONSTANTS 

/PRINTER WIDTH IN OCTAL 

/CAR RET CHAR (ASCII CR=15 

/LINE FEED CHAR (ASCII LF=12) 

/LOAD NEW SPEED CONSTANT (ASCII U=127) 

/CONSTANT FOR ERROR CHAR (ASCII BEL=7> 

/ENTER COMMAND MODE (ASCII ESC=175) 

/LOAD MESSAGE BUFFER (ASCII L=114) 

/PRINT THE MESSAGE BUFFER (ASCII P=120) 

/TRANSLATE8SEND MESSAGE (ASCII S=123) 

/TEST DO S UNTIL ESC TYPED (ASCII T=124) 

/ECHO A * FOR ESC 

/QUESTION MARK FOR BAD COMMAND 

/CHAR THAT REPRESENTS THE DELETE 

/PRINTABLE CHAR FOR A DELETE 

/CONTROL C EXIT TO STRT 

/REQUIRED TO ECHO ETX. "C 

/REQUIRED TO ECHO ETXi "C 

/ASCII SPACE CONSTANT 



120 056 
026 

122 066 
044 



*20#120 

/START UP TIME HOUSEKEEPING 

LHI MSSGBF" /CLEAR THE MESSAGE BUFFER 



20 225 


101 ASCIABt BLOCt 




102 






103 






104 






105 






106 






107 






110 






111 






112 






113 






114 






115 






116 






117 






120 






121 






122 






123 






124 






125 






126 






127 






130 






131 






132 




20 257 


061 
062 
063 
064 
065 
066 
067 
070 
071 


BLOC) 


20 270 


060 


DATA 


20 271 


055 


DATA 


20 272 


056 


DATA 


20 273 


054 


DATA 


20 274 


077 


DATA 


20 275 


057 


DATA 


20 276 


072 


DATA 


20 277 


050 


DATA 


20 300 


051 


DATA 


20 301 


047 


DATA 


20 302 


042 


DATA 


20 303 


012 


DATA 


20 304 


012 


DATA 


20 303 


073 ASCEND. DATA 



/ASCII TABLE OF DATA 

32.101.1 



/A THROUGH Z 



/l THROUGH 9 



/END OF MESSAGE(CRZLF) 
/END OF UORK(CRZLF) 



57 




AN 
EDUCATIONAL 
EXPERIENCE.. 



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• Execute user's program at any desired starting address. 

• Trap functions display register contents at desired breakpoints inserted in user's program. 

• List programs on your terminal. 

• Look function scans a specified page of memory for a desired value or instruction displaying all memory 
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• Relocator which moves a program from one area of memory to another, changing reference values thus 
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/MORSE TABLE*.l=DASH,0=DOT,WITH A 1 TO END THE CHAR 



20 306 


140 MORTAB, DATA 


140 


/A 


20 307 


21.0 


DATA 


210 


/S 


20 310 


250 


DATA 


250 


/C 


20 311 


220 


DATA 


220 


/Ii 


20 312 


100 


DATA 


100 


/E 


20 313 


050 


DATA 


50 


/F 


20 314 


320 


DATA 


320 


/G 


20 315 


010 


DATA 


10 


/H 


20 316 


040 


DATA 


40 


/I 


20 317 


170 


DATA 


170 


/J 


20 320 


260 


DATA 


260 


/K 


20 321 


110 


DATA 


110 


/L 


20 322 


340 


DATA 


340 


/M 


20 323 


240 


DATA 


240 


/N 


20 324 


360 


DATA 


360 


/O 


20 325 


150 


DATA 


150 


/P 


20 326 


330 


DATA 


330 


/a 


20 327 


120 


DATA 


120 


/R 


20 330 


020 


DATA 


20 


/s 


20 331 


300 


DATA 


300 


n 


20 332 


060 


DATA 


60 


/u 


20 333 


030 


DATA 


30 


/y 


20 334 


160 


DATA 


160 


/w 


20 335 


230 


DATA 


230 


/x 


20 336 


270 


DATA 


270 


tt 


20 337 


310 


DATA 


310 


/z 


20 340 


174 


DATA 


174 


/l 


20 341 


074 


DATA 


74 


/2 


20 342 


034 


DATA 


34 


/3 


20 343 


014 


DATA 


14 


/4 


20 344 


004 


DATA 


4 


/5 


20 345 


204 


DATA 


204 


/6 


20 346 


304 


DATA 


304 


/7 


20 347 


344 


DATA 


344 


/8 


20 350 


364 


DATA 


364 


/9 


20 351 


374 


DATA 


374 


/O 


20 352 


206 


DATA 


206 


/- 


20 353 


126 


DATA 


126 


/. 


'JO 354 


316 


DATA 


316 


/, 


20 355 


062 


DATA 


62 


/? 


20 356 


224 


DATA 


224 


/(SLASH) 


20 357 


342 


DATA 


342 


/: 


20 360 


266 


DATA 


266 


/( 


20 361 


266 


DATA 


266 


/) 


20 362 


172 


DATA 


172 


/' 


20 363 


112 


DATA 


112 


/■ 


20 364 


124 


DATA 


124 


/END DF MESSAGE<CR/LF) 


20 365 


026 


DATA 


26 


/END OF WORK(CRZLF) 


20 366 


252 MOREND, DATA 


252 


/; 



21 056 
21 057 
21 060 



003 
051 
007 



RFC 
DCH 
RET 



/NO BORROW i THEN RETURN 
/FIX THE H AFTER A BORROW 
/DONE 



/SUBROUTINE TO WAIT A UNIT CODE TIHE, DESTROYS A,B,C 



1 061 


056 
02 4 


TICKr 


LHI 


BAUD" 


/POINT AT CONST 


1 063 


066 
30 1 




LLI 


BAUD 




1 065 


026 
050 




LCI 


50 


/MULTIPLIER CONSTANT 


1 067 


317 


UAIT2, 


LBM 




/CONST TO B 


1 070 


01 1 


WAIT1 . 


DCB 




/COUNT IT DOWN DELAY 


1 071 


110 
070 
021 




JF2 


WAIT1 




1 074 


021 




DCC 




/MULTIPLY IT 


1 075 


1 1.0 
067 
021 




JFZ 


WAIT2 





316 

022 
007 



024 
066 



104 
067 
021 



1 120 


006 




377 


1 122 


131 


1 123 


104 




137 



DAL KYBD /OVERLAP UITH KEYBOARD INPUT 

CAL PNTR /LIKEWISE WITH THE PRINTER 

RET /DELAY OVER! I I I 

/DELAY, USED FOR 8 SLICE DECODING OF INPUT CODE 

T7CKI, LHI BAUDI" /POINT AT CONSTANT 

LLI BAUDI 

LCI 5 /8 TIMES FASTER THAN TICK 

JMP WAIT2 /FINISH TICKI IN TICK ROUTINE 



OUTPUT /TURN ON THE KEY (DOWN) 

JMP FINDOT /FINISH THE DOT IN THE DASH ROUTINE 



/SUBROUTINE GENERATES DASH ITS POST SPACE, DESTROYS A,B,C-H,L 



20 367 


307 


ENTPAK, 


LAM 


20 370 


021 




DCC 


20 371 


272 




CPC 


20 372 


150 
Oil 
021 




JTZ 


20 375 


004 
001 




ADI 


20 377 


370 




LMA 


21 000 


206 




ADL 


21 001 


360 




LLA 


21 002 


100 
006 
021 




JFC 


21 005 


050 




INH 


21 006 


371 


OK, 


LMB 


21 007 


250 




XRA 


21 010 


007 




RET 


21 Oil 


004 

001 


ERROFL, 


ADI 


21 013 


007 




RET 



/RETURNS WITH A=0 IF NO ERROR, =ERCHAR IF ERROR 
/CHAR COUNT TO A 

/COMPUTE CHARACTER LOCATIONS IN BUFFER 
/DON'T OVERFLOW THE BUFFER 
ERROFL /FULL... 



/BUMP THE COUNT 



/CHAR COUNT UPDATE TO MEM 
/LOW POINTER ADDED TO A 
/GET L VALUE UPDATED TO L REG 
/IF A CARRYf FIX THE H 



/FIX H REG 

/CHAR TO MEMORY 

/CLEAR THE A REG 

/DONE 

/SET A REG NON ZERO ERR RETURN 

/SYSTEM ERROR, SYSTEM MUST FIX! 



21 


014 


307 


21 


015 


024 
001 


21 


017 


370 


21 


020 


104 
036 



21 


023 


106 
046 
021 


21 


026 


327 


21 


027 


106 
052 
021 


21 


032 


372 


21 


033 


301 


21 


034 


024 
001 


21 


036 


053 


21 


037 


310 


21 


040 


106 
046 
021 


21 


043 


104 
023 
021 



21 


046 


060 


21 


047 


013 


21 


050 


050 


21 


051 


007 



21 


052 


306 


21 


053 


024 
001 


21 


055 


360 



/POP subroutine: ENTERED WITH POINTER IN H8L, SIZE IN 
POP, LAM /GET COUNTER TO A REG 

SUI 1 /DECREMENT 



LMA 
JMP 



/RESTORE THE NEW COUNTER 
/GET INTO POPLOP LOOP 



/LOOP FOR POP 

POPLOP, CAL INCLH /POINT AT CHAR TO POP 



/GET CHAR TO C REG 
/POINT TO NEW LOCATION 



LCM 




CAL 


DCRLH 


LMC 




LAB 




SUI 


1 


RTZ 




LBA 




CAL 


INCLH 


JMF 


POPLOP 



/PUT CHAR IN MEMORY 
/B TO A REG 
/SUBTRACT 1 

/DONE? 

/RESTORE B REG 

/RECOVER FROM THE DECREMENT POSITION 



/NEXT PAIR POP 



/SUBROUTINE TO INCREMENT THE H AND L REGS 
INCLH, INL /BUMP THE L 

RFZ /RETURN IF NO CARRY 

INH /BUMP THE H ON A CARRY 

RET /ALL DONE 



/SUBROUTINE TO DECREMENT THE H AND L REGS 
DCRLH, LAL /L TO A 

SUI 1 /DECREMENT THE A 

LLA /RETURN IF NO BORROW 



126 


006 




377 


130 


131 


131 


106 




061 




021 


134 


106 




061 




021 


137 


106 




061 




021 


142 


250 


143 


131 


144 


106 




061 




021 


147 


007 



DASH, LAI 



/SET ALL BITS IN THE A REG 



150 


106 




164 




022 


153 


150 




150 




021 


156 


074 




175 


160 


150 




153 




022 


163 


074 




114 


165 


150 




224 




021 


170 


074 




120 


172 


150 




317 




021 


175 


074 




123 


177 


150 




060 




022 


202 


074 




124 


204 


150 




074 




022 


207 


074 




127 


211 


150 




133 




022 


214 


016 




077 


216 


106 




304 




022 


221 


104 




150 




021 


224 


056 




026 


226 


066 




044 



OUTPUT /KEY DOWN 

CAL TICK /DASH 



FINDOT, CAL 



TICK /ENTERED HERE TO FINISH A DOT 



OUTPUT 

CAL TICK 



/CLEAR THE A REG 
/KEY UP 



/MONITOR TASK SUBROUTINE FOR HANDLING COMMANDS FROM THE KEYBOARD 
CMMNDR, CAL UNPAK /GET CHAR FROM KEYBOARD 



CMMNDR /IF NO CHAR, WAIT... 



CPI 

JTZ 

CPI 
JTZ 

CPI 
JTZ 

CPI 
JTZ 

CPI 
JTZ 

CPI 
JTZ 



ESC /WAS IT ANOTHER ESC? 

CLRMD /EXIT ON ESC 

L /WAS IT A LOAD? 

LDNXT /YES, GO LOAD A MESSAGE 

P /WAS IT A PRINT? 

PRT /YES GO PRINT THE MESSAGE BUFFER 

S /WAS IT A SEND THE BUFFER? 

SNDNX /YES, SHIP OUT THE MESSAGE 

T /WAS IT A TEST? 

TEST /YES, SEND THE BUFFER UNTIL ESC IS TYPED 

W /WAS IT A NEW WPM CONSTANT? 

WPM /YES, LOAD NEXT CHAR AS THE CONST 



/IF HERE A BAD COMMAND 

LBI QUEST /QUESTION MARK 



PPAK /TO THE PRINTER FIFO 



CMMNDR /TRY FDR A VALID COMMAND CHAR 



60 



We've got it! 
■80 power for 
the Altair bus. 




Here it is.TDL's ZPU™ the high- 
est point of technology for an 
Altair/IMSAI system. Now, you 
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in the micro-processor indus- 
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Dealer Inquiries Invited. 



TDL 



(609) 392-7070 



TECHNICAL DESIGN LABS, INC. 
342 COLUMBUS AVENUE 
TRENTON, NEW JERSEY 08629 



076 




LMI 


000 






106 


LDNXTI* 


CAL 


164 







150 
153 
022 
310 
056 
026 
066 
014 
074 
177 
110 
272 



CPI 
JTZ 

LBA 
LHI 

LL] 

CF'l 

JFZ 



/ZERO THE COUNT 

UNFAK /GET KEYBOARD CHAR... 

LDNXTI /WAIT FOR DATA 

ESC /END OF THE INPUT MESSAGE'*' 

CLRMD /EXIT END OF HESSAGE 

/CHAR TO B REG FOR ENTF'AK 

MSSGBF" /POINT AT THE MESSAGE BUFFER 

MSSGBF 

DELETE /DELETE COMMAND? 

LDNXT2 /NO 



016 


106 




304 




022 


021 


104 




035 




022 


024 


056 




025 


026 


066 




364 


030 


026 




060 


032 


106 




367 




020 


035 


150 




341 




021 


040 


'106 




316 



CAL PPAK /PRINT SUBMODE 

JMP PR3 

LHI OTFIFO" /POINT AT OUTPUT BUFFER 

LLI OTFIFO 

LCI BUFDUT /BUFFER SIZE TO C REG 

CAL ENTPAK /XFER TO THE BUFFER 

JTZ PRT1 /LOOP IF NO ERROR 

CAL PNTR /YES* OVERLAY THE I/O 



034 
001 



370 




LMA 


104 




JMP 


232 






021 






026 


LDNXT2 


, LCI 


377 






106 




CAL 


367 






020 







021 
104 
232 



XRA /YES, CLEAR THE A REG AND FLGS 

ADM /GET COUNT TO A AND FLGS 

JTZ LDNXTI /BUFFER EMPTY". A NO NO 



/DECREMENT COUNTER 



/RETURN COUNT TO MEM 
LDNXTI /LOOP 



MSGSZ /BUFFER SIZE SET UP 
ENTPAK /CHAR TO BUFFER 



/TEST FOR BUFFER OVERFLOW 

CFZ WHOOP /TELL USER BUFFER FULL 



LDNXTI /LOOP UNTIL ESC 



/SUBROUTINE FOR USER ERROR IDICATION 



21 


305 


103 


WHOOP, 


STATUS 


21 


306 


044 
020 




NDI 


21 


310 


150 
305 
021 




JTZ 


21 


313 


006 
007 




LAI 


21 


315 


121 




PRINT 


21 


316 


007 




RET 



/YES. GET PRINTER STATUS 
/TBMT MASK 



ERCHAR /SET ERROR INDICATION 



21 


317 


056 

024 


21 


321 


066 
300 


21 


323 


076 
000 


21 


325 


106 
333 

021 


21 


330 


104 
153 
022 



21 


333 


036 
024 


21 


335 


066 

277 


21 


337 


076 
000 


21 


341 


106 
316 



/ROUTINE TO PRINT THE MESSAGE BUFFER 

F'RT. LHI SOH" /SET UP PRINT SUBMODE 

LLI SOH 

LMI 

CAL DMPSUB /PRINT THE MESSAGE BUFFER 



JMF 



CLRMD /EXIT TO THE SUPERVISOR 



/SUBROUTINE TO MOVE THE MESSAGE BUFFER CONTENTS TO LOCATION 

/DEFINED BY THE SOH LOCATION. 0»PR INTER 1=SENDER 

DMPSUB, LHI MSSCNT" /POINT AT TEMP CHAR POINTER 

LLI MSSCNT 

LMI /CLEAR THE POINTER 
PRT1, CAL PNTR /TRY TO FINISH THE PRINTING 





022 


046 


106 




230 




023 


051 


056 




024 


053 


066 




277 


055 


104 




372 




021 



060 


056 




024 


062 


066 




300 


064 


076 




001 


066 


106 




333 




021 


071 


104 




153 




022 



024 

066 
300 
076 
001 
106 
333 



CAL OTPUT 

LHI MSSCNT" /RESET THE H REG FOR ERROR RECOVERY 

LLI MSSCNT 

JMP PR4 /TRY THE CHAR AGAIN 



/ROUTINE TO SHIP OUT THE BUFFER IN CODE 
SNDNX, LHI SOH" /SET UP SEND MODE FOR 



LLI 
LMI 
CAL 



/DMPSUB ROUTINE 



DMPSUB /SEND THE MESSAGE BUFFER 



LHI 


SOH' 


LLI 


SOH 


LMI 


1 


CAL 


BMP! 



/ROUTINE TO TE5T OUTPUT, SHIP UNTIL ESC IS TYPED 
/SET UP FOR SEND MODE 



DMPSUB /SEND THE BUFFER 

UNFAK /CHAR FROM KEYBOARD 

TEST /NOTHING YET, DO IT AGAIN 

ESC /ESC? 

CLRMD /YES. EXIT 

QUEST /ILLEGAL CHAR FOR THIS 

PPAK /NOTIFY THE USER 

TEST1 /IF OVERFLOW. TRY AGAIN 

TEST /AND LOOP 



022 




150 


JTZ 


074 




022 




074 


CPI 


175 




150 


JTZ 


153 




022 




016 TEST1, LBI 


077 




106 


CAL 


304 




022 




110 


JFZ 


120 




022 




104 


JMP 


074 




022 





CAL 



KYBD 







022 


21 


34 7 


106 
230 
023 


21 


352 


056 
026 


21 


354 


066 
044 


21 


356 


250 


21 


357 


207 


21 


360 


053 


21 


361 


056 
024 


21 


363 


066 
277 


21 


365 


277 


21 


366 


053 


21 


367 


317 


21 


370 


010 


21 


371 


371 


21 


372 


006 
044 


21 


374 


207 


21 


375 


360 


21 


376 


056 

026 


22 


000 


100 
004 
022 


22 


003 


050 


22 


004 


317 


22 


005 


250 


22 


006 


056 

024 


22 


010 


066 
300 


22 


012 


207 


22 


013 


110 
024 
022 



LHI 


MSSGBF' 


LLI 


MSSGBF 


XRA 




ADM 




RTZ 




LHI 


MSSCNT' 


LLI 


MSSCNT 


CPM 




RTZ 




LBM 




INB 




LMB 





/TRY TO FINISH THE KEYBOARD INPUT 

/TRY TO FINISH THE TRANSMISSION 

/IS THERE A MESSAGE? 

/FIND CHAR CNTR AND CHECK FOR NON ZERD 

/CLEAR THE A REG 

/ADD IN THE CHAR COUNT 

/NO MESSAGE. EXIT 

/CHECK COUNT ON XFER CHARS 



/BUFFER ALL XFERED? 

/EVERYTHING XFERED, EXIT 

/STILL HERE. BUMP THE CHAR COUNT 



/FETCH THE CHAR FROM THE MESSAGE DUFFER 
LAI MSSGBF /COMPUTE POINTERS 



ADM 
LLA 
LHI 



INH 
LBM 
XRA 
LHI 



ADM 
JFZ 



MSSGBF' 
PR 2 



/ADD IN THE BUFFER OFFSET 
/SET UP THE L, H YET TO GO 
/H SET IF NO CARRY FROM THE L 

/NO CARRY 



/FIX FOR THE L CARRY 
/CHAR TO THE B REG 
/CLEAR THE A REG 
/OET THE SUBMODE 



/SUBMODE IN THE A REG AND FLGS 
S0H1 /SEND SUBMODE 



22 


133 


106 
164 
022 


" 


136 


150 
133 
022 


22 


141 


044 
037 


22 


143 


002 




144 


064 
001 


22 


146 


056 
024 




150 


066 
301 


22 


152 


370 



22 


153 


056 

024 


22 


155 


066 
275 


22 


157 


076 
000 


22 


161 


104 
172 



/CODE TO LOAD A NEW WPM CONSTANT INTO BAUD 

WPM. CAL UNPAK /GET CHAR FROM KEYBOARD 



/WAIT FOR CHAR 



/MASK FOR 5 VALID BITS 



RLC 




/MULTIPLY BY 2 


ORI 


1 


/SET THE LSB 


LHI 


BAUD" 


/POINT AT BAUD 


LLI 


BAUD 





LMA /CONSTANT TO BAUD LOCATION 

/FALL THROUGH TO CLRMD 

/CLEAR THE FLAGS AND EXIT TO SUPERVISOR 
CLRMD, LHI CMMND" /ZERO THE MODE BYTE 

LLI CMMND 

LMI 

JMP RESTRT /TO SUPERVISOR 



/ROUTINE TO GET CHAR FROM KEYBOARD FIFO 

/RETURNS WITH CHAR IN A REG, A REG=0 IF NO CHAR 
106 UNPAK, CAL PNTR /TRY TO FINISH PENDING PRINTING 
316 
022 



62 



r 




You'll Want to Nybble at these 

tEmjr Iv DUUIV5 Where does the editor of a computer magazine turn 

when he must verify some author's hardware design? 
Information on a 75450 interface gate, or a 74147 
priority encoder circuit does not spring forth by magic. 
Checking the information supplied by authors is part of 
BYTE's quality control program. 

When you build a project, you need this same sort of 
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• Understanding Solid State Electronics by Texas Intru- 
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• The Optoelectronics Data Book for Design Engineers by 

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related devices. Order yours at $2.95. 



• The TTL Cookbook by Don Lancaster, published by 
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• The TTL Data Book for Design Engineers, by Texas 
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• The Linear and Interface Circuits Data Book for Design 
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frustration problem occurs again. What kind of gate could that 
be? We won't tell in this ad, but you can find out by reading the 
specifications in The Linear and Interface Circuits Data Book for 
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• The Semiconductor Memory Data Book for Design 
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importance of memories to your systems. Refer to this 272 page 
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random access memories and read only memories. Order your 
personal copy today, only $2.95. 



_TTL Cookbook <s> $8.95 
TTLData Book @ $3.95 
.Supplement to TTL Data Book (s> $1 .95 
.Linear and Interface Circuits @ $3.95 
.Semiconductor Memory Data <s> $2.95 
.Transistor and Diode Data Book (§> $4.95 
.Power Semiconductor Handbook @ $3.95 
.Understanding Solid State Electronics @ $2.95 
.Optoelectronics Data Book <s> $2.95 



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Signature 



J 



22 


167 


106 
227 
022 


22 


172 


106 
230 
023 


22 


175 


056 
024 


22 


177 


066 
305 


22 


201 


250 


22 


202 


207 


22 


203 


053 




204 


106 
046 
021 


22 


207 


347 


22 


210 


106 
052 
021 


22 


213 


106 
014 
021 


22 


216 


204 


22 


217 


007 



LHI 

LLI 

XRA 
ADM 
RTZ 
CAL 



LEM 
CAL 



ADE 
RET 



KYBD /KEYBOARD HAPPY? 

OTPUT /OVERLAY THE CODE OUTPUT 

KYFIFO" /POINT AT KEYBOARD STACK 

KYFIFO 

/CLEAR THE A REG 
/CHAR COUNT TO A REG 
/IF EMPTY. RETURN A REG=0 
INCLH /POINT AT CHAR 



/GET CHAR TO E REG TEMP 
DCRLH /POINT AT KEYBOARD FIFO 



POP /OUT OF FIFO. RETURNS A = 



/CHAR TO A REG AND FLGS 
/RETURN WITH A REG=CHAR 



/SUBROUTINE TO WAIT FOR THE TBMT FLAG 
/GET TBMT FLAG 



22 220 


103 


UAITMTt 


STATU! 




22 221 


044 
020 




NDI 


20 


22 223 


150 
220 
022 




JTZ 


UAITMT 


22 226 


007 




RET 





22 


227 


103 




230 


044 
040 


22 


232 


053 


22 


233 


101 


22 


234 


044 
177 


22 


236 


074 
003 


22 


240 


110 
267 
022 


22 


243 


250 


22 


244 


131 


22 


245 


106 
220 
022 


22 


250 


006 
136 


22 


252 


121 


22 


253 


106 
220 
022 


22 


256 


006 
103 


22 


260 


121 


22 


261 


106 
220 
022 


22 


264 


104 
140 
020 


22 


267 


056 
024 


22 


271 


066 
305 


22 


273 


310 


22 


274 


026 
377 


22 


276 


106 
367 
020 


22 


301 


112 



22 


304 


056 
025 




306 


066 
304 


22 


310 


026 
060 


22 


312 


106 
367 
020 


22 


315 


007 



22 


316 


103 


22 


317 


044 
020 


22 


321 


053 


22 


322 


056 
024 


22 


324 


066 
276 


22 


326 


250 


22 


327 


207 


22 


330 


110 

347 
022 


22 


333 


006 
015 


22 


335 


121 


22 


336 


106 



/OK* HAVE TBMT 



/KEYBOARD HANDLER SUBROUTINE 

STATUS /GET THE SERIAL LINE STATUS 

NDI 40 /MASK 

RTZ /NEXT TASK 

/PUT KEYBOARD CHARACTER IN KYBD FIFO 

READ /GET CHAR FORM KEYBOARD TO A REG 

NDI 177 /GET RID OF ASCII PARITY BIT 



CPI 

JFZ 



ETX /CONTROL C 
NETX /NO 



XRA 

OUTPUT 

CAL UAITMT /SEND OUT 



/YES. CLEAR OUTPUT 



PRINT 

CAL 



LHI 
LLI 



UAITMT /WAIT FOR TBMT 



UAITMT /UAIT FOR TBMT 

STRT1 /GO RESTART FROM ALMOST ZERO 

KYFIFO" /POINT AT KYFIFO 

KYFIFO 

/CHAR TO B REG 

BUFSKY /BUFFER SIZE TO C REG 

ENTPAK /PUT CHAR IN BUFFER 

UHTJOP /IF OVERFLOW. TELL THE USER 



/FALL THROUGH AND RETURN IN NEX1 ROUTINE 



/PUT CHAR IN PRINTER F- IKO FROM B REG 

/RETURNS WITH A REG =0 IF NO ERROR) =ERCHAR IF ERROR 

LHI 

LLI 

LCI 

CAL 



PNFIFO" /POINT AT PNFIFO 

PNFIFO 

BUFSPN /BUFFER SIZE TO C REG 

ENTPAK /PUT CHAR IN FIFO 



/PRINTER HANDLER SUBROUTINE TASK 



STATUS 
NDI 


20 


RTZ 
LHI 


TUIDTH 1 


LLI 


TUIDTH 


XRA 

ADM 

JFZ 


PRT2 



/GET THE PRINTER STATUS 
/MASK FOR TBMT 



/IF BUSY. TRY SOMETHING ELSE 
/FIND PRINT POSITION 



/CLEAR THE A RED 

/COUNT TO FLGS AND A REG 

/NO LINE OVERFLOW 



/LINE OVERFLOU. FIX JT 



22 343 
22 344 



22 346 

22 347 



22 353 
22 354 

22 355 



22 356 

22 361 
22 362 
22 364 
22 366 

22 371 

22 373 

22 375 
22 376 

22 377 

23 000 
23 001 

23 003 

23 006 
23 010 

23 013 
23 015 

23 020 
23 022 



23 027 
23 030 
23 031 

23 033 
23 034 

23 036 
23 037 



006 
012 
121 
076 
110 
007 
056 
025 
066 
304 
250 
207 
053 



106 
046 
021 
347 

066 
304 
056 
025 
106 
014 
021 
056 
024 
066 
276 
317 
Oil 
371 
304 
074 
012 
150 
031 
023 
074 
015 
150 
031 
023 
074 
177 
150 
034 
023 
074 
175 
110 
027 
023 
006 
044 
121 
007 
076 
000 
007 
006 
134 
121 
007 



PRINT 
LMI 



RET 
LHI 



LLI 



WIDTH /RESET PRINT POSITION COUNT 

PNFIFO" /POINT AT CHAR COUNT 

PNFIFO 



XRA 
ADM 

RTZ 



/CLEAR THE A REG 
/CHAR COUNT TO A REG AND FLGS 
/NOTHING TO PRINT. NEXT TASK 
/IF HERE THERE IS PRINTING TO BE HONE!!!!!!! 

/POINT AT CHAR TO PRINT AND PRINT IT 

CAL INCLH 



NXTPNT. LEM /CHAR TO E REG TEMP 

/NOW UPDATE THE CHAR COUNT 
LLI PNFIFO /POINT AT CHAR COUNT 



LHI 

CAL 

LHI 

LLI 

LBM 
DCB 
LMB 
LAE 
CPI 



CPI 
JTZ 

CPI 
JTZ 

CFI 
JFZ 



PNT1. PRINT 

RET 
INCRLF. LMI 

RET 
DEL. LAI 

FRINT 
RET 



PNFIFO" 
POP 



/RIPPLE THE FIFO 



TUIDTH" /UPDATE PRINT POSITION 

TUIDTH 

/COUNT TO B 
/-I 

/BACK TO MEMORY 
/CHAR BACK TO A REG 
LF /IS IT A LF"' 

INCRLF /YES. INSERT A CRLF 

CR /IS IT A CR"? 

INCRLF /YES. INSERT A CRLF 

DELETE /IS IT A DELETE? 

DEL /YES. INSERT A BACKSLASH 



ESC 
PNT1 



/IS IT AN ESC 

/NO 



ESCSYM /YES. SUBSTITUTE A PRINTABLE CHAR 

/PRINT THE CHAR 
/DONE. PRINTED A CHAR 
/SET FOR CRLF NEXT 



DELSYM /SUBSTITUTE A PRINTABLE CHARACTER 
/END TO THE PRINTER TASK 



PRINT 
CAL 



UAITMT /UAIT FOR TBMT 



23 040 


056 
020 


XLATER. LHI 


23 042 


066 
225 


LLI 


23 044 


277 


THISIT. CPM 


23 045 


150 
074 
023 


JTZ 


23 050 


106 
046 
021 


CAL 


23 053 


310 


LBA 


23 054 


006 
020 


LAI 


23 056 


275 


CPH 


23 057 


140 
122 
023 


JTC 


23 062 


006 
305 


LAI 


23 064 


276 


CPL 


23 065 


140 
122 
023 


JTC 
/IF 


23 070 


301 


LAB 


23 071 


104 
044 
023 


JMP 


23 074 


006 
306 


CONVT. LAI 


23 076 


024 
225 


5UI 


23 100 


100 
104 
023 


JFC 


23 103 


051 


DCH 


23 104 


206 


OKI. ADL 


23 105 


100 
HI 
023 


JFC 


23 110 


050 


INH 


23 111 


360 


0K2. LLA 


23 112 


006 
020 


LAI 


23 114 


034 
020 


SBI 


23 116 


205 


ADH 


23 117 


350 


LHA 


23 120 


307 


LAM 


23 121 


007 


RET 


23 122 


006 
200 


NTFUND. LAI 


23 124 


007 


RET 



/THIS SUBROUTINE TRANSLATES A REG TO OUTPUT MODE 
/COMPUTE THE DISPLACEMENT IN ASCTAB 
ASCTAB" /POINT AT ASCTAB 



CONVT 



/IS THIS THE CHAR? 
/GO CONVERT THE CHAR 



INCLH /TRY NEXT CHAR 

/SAVE THE CHAR IN B REG TEMPORARILY 
ASCEND" /GET HIGH LIMIT TO A FOR COMPARE 



NTFUND 



/PAST END OF TABLE"-' 

/PAST END OF TABLE AND NO MATCH 



ASCEND /OET LOU LIMIT TO A FOR COMPARE 



/PAST END OF TABLE? 
NTFUND /PAST END OF TABLE AND NO MATCH 



/IF HERE. STILL IN TABLE. TRY CONTENTS AGAIN. 

/RETURN CHAR TO A REG 
THISIT /LOOP FDR NEXT TABLE ENTRY CHECK 



MORTAB /COMPUTE REL DISPLACEMENT LOU 

ASCTAB 

OKI 



/HANDLE THE BORROW 
/ADD IN THE LOU POINTER 



/HANDLE THE CARRY 

/L IS NOW POINTING IN THE OUTPUT TABLE 

/COMPUTE RELATIVE DISPLACEMENT HIGH 



/ADD IN THE HIGH POINTER 

/H NOU POINTS IN THE OUTPUT TABLE 

/REPLACEMENT CHAR TO A REG 

/CODE IN A REG RETURN 

/CHAR NOT FDUND LOAD OUT A 200 

/ERROR RETURN 



64 



THE POLY 88 
MICROCOMPUTER 

A Complete Microcomputer System with Keyboard Input and Video Output 



The Hardware: The heart of the POLY 88 

microcomputer, the CPU circuit card, features an 
8080A central processor, 512-byte RAM, space for 
3K of PROM, vectored interrupt and real time clock, 
a dual serial port with software-selectable baud rate, 




and single-step logic that allows the processor to 
execute one instruction at a time. 

The POLY 88 also includes our video terminal 
interface circuit card, which is both a video display 
device and an input port for a keyboard. Sixteen lines 
of up to 64 characters may be displayed on a 
standard TV monitor or modified receiver. In addition 
to the 128 ASCII characters which are displayed in an 




ftufnjj* 




easy-to-read 7x9 font, there are 64 graphic characters 
available for plotting on a 48 x 128 contiguous grid. 
These two circuit cards fit into a compact "Altair- 
compatible" chassis with room for up to five cards. A 
6 amp power supply is built right on the mother 
board. The front panel consists of just two switches, 
on/off and reset; the monitor software with video 
screen and keyboard eliminates the need for a 
hardware front panel. As your system grows, you can 
plug chassis together for easy expansion. (The 
expansion connector also eliminates the need for an 
extender card.) Cassette, RS-232, and current loop 
interfaces are available which connect via ribbon 
cable to the CPU board and mount on the backpanel. 



The Software: Supplied with the POLY 88 
microcomputer is a 1024-byte monitor on ROM. The 
program is there when the power is turned on, so you 
don't need to key in a loader. The monitor is designed 
to use a keyboard entry and TV display, with a 
casstte or paper tape as the storage medium. 

With the monitor you can: load data into memory 
in hex, display memory in hex, dump or read data 
from a storage device, and execute program one step 
at a time, displaying the contents of each of the 8080 
registers as well as the values in memory at the 
address of each of the registers. All of these functions 



A r B c 

3BC3 0DF0 
(BC) C3 3B 
(DC) 80 21 
<HL> 00 00 
(SP) 8D 21 
(PC) 00 00 
.C08V 

0C00 00 00 
0C88 78 01 
0C10 47 36 
0C18 A5 C4 
0C20 38 0C 
0C28 IF DA 
0C30 48 0C 
• 



D E H L 
0CFF 0C80 
F0 0D FF 
00 88 75 
00 00 00 
00 88 75 
00 41 00 

00 00 41 

00 20 CD 
08 19 36 
25 0C 3E 
C3 08 0C 
32 0C 01 

01 FE FF 



SP 

0CFF 0C01 
0C 80 BC 
23 7C FE 
00 00 00 
23 7C FE 
06 80 78 

00 06 80 
4D 0C 00 
8E 3E 20 
03 A4 CC 
78 07 3F 
02 00 C3 
C3 48 0C 



are available the instant you turn on the power. 

Future software available with this system will 
include BASIC, an assembler, and games. 

Prices: Basic kit including chassis, CPU and 
video cards — $595, $795 assembled. Cassette option 
— $90 kit and $125 assembled. 8K of RAM — $300 in 
kit form or $375 assembled. We also sell the video 
and other "Altair-compatible" circuit cards separately. 

Dealers: This system sells itself. 

All prices and specifications subject to change 
without notice. Prices are USA only. California 
residents add 6% sales tax. Prepaid orders shipped 
postpaid. BankAmericard and MasterCharge accepted 

| 737 S. Kellogg, Goleta, CA 93017 (805) 967-2351~[ 

□ Please send more information 

□ Order and check enclosed 

I Name 

I Address 



BankAmericard 
Master Charge _ 



L 



.J 



PolyMorphic 
Systems 



23 


125 


074 
377 


23 


127 


022 


23 


130 


100 

127 
023 


23 


133 


074 
000 


23 


135 


110 
143 
023 


23 


140 


006 

134 


23 


142 


007 


23 


143 


056 
020 


23 


145 


066 
306 


23 


147 


277 


23 


150 


150 
177 
023 


23 


153 


106 
046 
021 


23 


156 


310 


23 


157 


006 
020 


23 


161 


275 


23 


162 


140 

023 


23 


165 


006 
366 


23 


167 


276 


23 


170 


140 



/THIS SUBROUTINE TRANSLATES A REG TO PRINT MODE 
XLATt CPI 377 /SET C FLG (GUARD BIT) 



RAL 
JFE 



/ROTATE 

/IF NO LEFT GUARD. LOOP 



/IF A REG CONTAINS A 000. ERROR CHAR WAS SEEN, 
CPI /SET FLGS 



/NOT FRROR. TRANSLATE 



DELSYM /SET UP FOR DELETE SYMBOL 



RET 
LHI 



CPM 
JTZ 



LBA 
LAI 



CPH 

jrc 



/EXIT 
MORTAB" /POINT AT MORTAB 



/IS THIS THE CHAR? 
MCONVT /YES. GO CONVERT I HE CHAR 



INCLH /TRY NEXT CHAR 



/SAVE CHAR IN B REG TEMP 
MOREND" /GET HIGH LIMIT TO A FOR COMPARE 



/PAST END OF TABLE? 
NTFND /YES. UITH NO MATCH 



MOREND /GET LOU LIMIT TO A FOR COMPARE 



CPL /PAST END OF TABLF''' 

JTC NTFND /YES. NO MATCH 









/IF 


HERE. STILI 


23 173 


301 




LAB 




23 174 


104 
147 
023 




JMP 


THIS 


23 177 


006 


MCONVT. 


LAI 


ASCTAB 


23 201 


024 
306 




SUI 


MORTAB 


23 203 


140 
207 
023 




JTC 


MOM 


23 206 


051 




DCH 




23 207 


206 


M0K1. 


ADL 




23 210 


100 
214 
023 




JFC 


H0K2 


23 213 


050 




INH 




23 214 


360 


HQK2. 


LLA 




23 215 


006 
020 




LAI 


ASCTAB' 


23 217 


034 
020 




SBI 


MORTAB' 


23 221 


205 




ADH 




23 222 


350 




LHA 




23 223 


307 




LAM 




23 224 


007 




RET 




23 225 


006 
040 


NTFND. 


LAI 


BLANK 


23 227 


007 




RET 





IN TABLE. TRY CONTFNTS AGAIN 

/RETURN CHAR TO A REG 

/LOOP FOR NEXT TABLE ENTRY CHECK 



/COMPUTE REL DISPLACEMENT LOW 



/HANDLE THE BORROU 
/ADD IN THE LOU POINTER 



/HANDLE THE CARRY 

/L IS NOU POINTING IN OUTPUT TABLE 

/COMPUTE RELATIVE DISPLACEMENT HIGH 



/ADD IN THE HIGH POINTER 
/H NOU POINTS IN THE OUTPUT 
/REPLACEMENT CHAR TO A REG 
/ASCII CODE IN A REG RETURN 
/CHAR NOT FOUND t LOAD OUT A 



23 230 


056 
025 


OTPUT. 


LHI 


23 232 


066 
364 




LLI 


23 234 


250 




XRA 


23 235 


207 




ADH 


23 236 


053 




RTZ 


23 237 


106 
046 
021 




CAL 


23 242 


307 




LAM 


23 243 


074 
177 




CPI 


23 245 


110 
264 
023 




JFZ 


23 250 


036 
007 




LDI 


23 252 


106 
120 
021 


OTERR. 


CAL 


23 255 


031 




DCS 


23 256 


110 
252 
023 




JFZ 


23 261 


104 
342 
023 




JMP 


23 264 


106 
040 
023 


0TPUT1 . 


CAL 


23 267 


330 




LDA 


23 270 


074 
200 




CPI 


23 272 


no 

311 
023 




JFZ 
/IF 


23 275 


036 
006 




LDI 


23 277 


106 
061 
021 


SPACE. 


CAL 


23 302 


031 




DCD 


23 303 


110 
277 
023 




JFZ 


23 306 


104 
342 
023 




JMP 


23 311 


074 
200 


GOOPCH. 


CPI 



/ERROR RETURN 



/SUBROUTINE TASK TO OUTPUT CODE 
OTFIFO- /POINT AT STACK 

OTFIFO 

/CLEAR THE A REG 

/CHAR COUNT TO A AND FLGS 
/NEXT TASK. IF NOTHING TO DO 
INCLH /POINT AT THE DATA 



/CHARACTER TO A REG 
DELETE /ERROR CHARACTER? 

0TPUT1 /NO. GO TRANSLATE 

7 /YES. DO 8 DOTS 
DOT /l DOT 



/-l THE COUNT 
OTERR /NOT DONE.... DO IT AGAIN 



OUTEND /DONE. POP AND EXIT 

XLATER /TRANSLATE 

/SAVE THE CHAR IN D REG 
200 /IS IT A BAD CHAR (OR A SPACE)? 

GQODCH /CHAR OK. SO DO IT UP RIGHT 



/UAIT ONE UNIT 



/DECREMENT THE UNIT COUNTER 
SFACE /LOOP UNTIL DONE 



/IF A=200 THEN DONE 



3 313 


150 
342 

023 


JTZ 


3 316 


100 
327 
023 


JFC 


'3 321 


106 

120 
021 


CAL 


!3 324 


104 

332 
023 


JMP 


!3 327 


106 
126 
021 


DKH. CAL 


13 332 


303 


OTLOOP. LAD 


!3 333 


044 
177 


NDI 


!3 335 


002 


RLC 


'3 336 


330 


LDA 


!3 337 


104 
311 
023 


JMP 


'3 342 


106 
061 
021 


OUTEND. CAL 


'3 345 


106 
061 
021 


CAL 
/SE 


!3 350 


066 

364 


LLI 


!3 352 


056 

025 


LHI 


!3 354 


106 
014 
021 


CAL 


!3 357 


007 


RET 



OUTEND /DONE! 



23 360 

23 362 

23 364 
23 365 
23 366 

23 367 



23 372 
23 373 



24 001 
24 002 



24 007 
24 Oil 



24 013 
24 014 



24 024 
24 025 

24 027 

24 031 

24 033 



/DOT OR DASH? 



/YES A DOTf SO KEY OUT A DOT 



OTLOOP /NEXT SYMBOL 



/MUST BE A DASH, SO KEY A DASH 



/GET THE CHAR BACK TO THE A REG 
177 /THROW OUT THE USED BIT 

/ROTATE IN AN UNUSED BIT 
/SAVE THE NEU IMAGE IN D 
GOODCH /LOOP FOR OTHER SYMBOLS 



/INTER LETTER SPACE 



SET UP TO POP THE STACK 

OTFIFO /POINT AT STACK 



OTFIFO" 

POP /POP THE STACK 



056 
024 
066 
305 



053 
106 
046 
021 
347 
106 
052 
021 
106 
014 
021 
304 
074 
175 
150 
025 
024 
056 
025 
066 
364 
310 
026 
060 
106 
367 
020 
112 
305 
021 
007 
056 
024 
066 
275 
076 
001 
007 



/NEXT TASK 
/END OF THE OUTPUT ENCODED DRIVE TASK SUBROUTINE 



/KEYBOARD DECODER FOR NON COMMAND MODE 

IDLE. LHI KYFIFO" /POINT AT CHAR COUNT 



/CLEAR THE A REG 

/CHAR COUNT TO A REG 

/BUFFER EMPTY. TRY SOMETHING ELSE 

/POINT AT CHAR 



/SAVE CHAR IN E REG TEMP 
/POINT AT START OF BUFFER 



LLI 


KYFIFO 


XRA 




ADM 




RTZ 




CAL 


INCLH 


LEH 




CAL 


DCRLH 



CPI 


ESC 


JTZ 


IDLE1 


LHI 


OTFIFO' 


LLI 


OTFIFO 


LBA 




LCI 


BUFOUT 


CAL 


ENTPAK 



/POP THE CHAR OFF THE BUFFER 



/OUTPUT IN CODE 
/SET UP FOR ENTPAK 



/DATA IN B REG 
/SIZE IN C REG 



/BUFFER FULLf TELL USER 



/DONE 

/SET FOR CDMMAND MODE 



RET 
IDLE1. LHI CMMND" 

LLI CHMND 

LMI 1 
RET 



/SUBROUTINE TO SERVICE MORSE CODE INPUT 

/GET CODE INPUT LINE 
/UE USE THE LSB 



24 034 


105 INPEND. SENSE 


24 035 


044 
001 


NDI 


24 037 


013 


RFZ 


24 040 


056 

024 


LHI 


24 042 


066 
304 


LLI 


24 044 


076 
001 


LMI 


24 046 


056 INTIMEi LHI 




024 




24 050 


066 
303 


LLI 


24 052 


076 
000 


LHI 


24 054 


106 INSENS. CAL 




107 






021 




24 057 


056 
024 


LHI 


24 061 


066 
303 


LLI 


24 063 


317 


LBM 


24 064 


010 


INS 


24 065 


371 


LMB 


24 066 


105 


SENSE 


24 067 


044 
001 


NDI 


24 071 


150 
054 

024 


JTZ 
/IF Hi 


24 074 


046 
000 


LEI 



/NOTHING PENDING. EXIT 
INCHAR" /POINT AT HOLDING REG 



TIMER" 

TIMER 



TIMER- 
TIMER 



/SET UP TO SHIFT IN MORSE 
/POINT AT TIMER REG 



/INITIALIZE FOR TIME=0 

/UAIT FOR PART OF A BAUD (1/B) 



/UPDATE TIMER 



/+1 

/TIMER+1 
/KEY DOWN? 



INSENS /UAIT FOR KEY UP 



66 



MERLIN 

THE INTELLIGENT VIDEO INTERFACE 

HARDWARE SPECS. 

* Altair/IMSAI Plug-in Compatible 

* 40 Character by 20 line ASCI I Display Format 

* 5 by 7 font, 64 Character Generator ROM 
Dual Resolution Graphics: 

100 V by 80 Ho/- 160 H 

* Mixed ASCII/Graphics Mode 

* Program Control of: 
Cursor: On/Off 

Control Characters: Inverted/Blanked 
Carriage Returns: Displayed/Blanked 
FIXED or FREE (Memory Saver) Format 
Video: Black on White or Reversed 
ASCII, Graphics or Mixed Mode 

* Plug-in Keyboard Port 

* DMA makes MERLIN the fastest display available 
— over 48 K characters per second 

* Sockets and Decoding for on-board Memory: 
Two 2708 1 K X 8 EPROMs, or 
Two 2 K X 8 Mask ROMs, and 
One 128 X 8 Scratch Pad RAM 

FIRMWARE SPECS. 

MERLIN'S BASIC INTELLIGENCE (MBI) ROM Contains: 
Monitor Functions Editing Functions 

— Memory Fill with HEX value — Winking Keyboard Cursor 

— HEX Memory Dump — Cursor up, dwn, rt, It, & Home 

— ASCII Text Input — Insert and Replace Modes 

— HEX Memory Input or Modify — Delete Character 

— Set Display Format — Delete to end-of-memory 

— Examine/Modify CPU registers — Four Slave Cursor Functions 

— Copy Memory Blocks — Auto or Manual Scroll 

— Define Display Memory Area — Home/Clear 

— Four User Defined Functions — Six User Defined Functions 

Built-in linkage, through on-board RAM, to user defined routines creates an indefinitely expandable system. 
1 The MBI ROM also includes decoding and direct linkages to our MEI (MERLIN's EXPANDED INTELLIGENCE) ROM 
and to our forthcoming Cassette-Modem Interface on-board ROM. The MEI ROM contains additional Monitor/Editor 
software, plus Graphics subroutines. 

Besides the direct Monitor and Editor commands, the MBI ROM contains many general purpose subroutines including 
general purpose, selectable I/O drivers and KYB and Display drivers. 

PRICING SPECS 

MERLIN: kit containing PC boards, IC sockets, User Manual and all parts except memory $249.00 

MBI: MERLIN'S BASIC INTELLIGENCE - 128 X 8 RAM and 2 K X 8 mask ROM containing Monitor/Editor software . . .$3 4.95 
MEI: MERLIN's EXPANDED INTELLIGENCE - 2 K X 8 mask ROM with more Monitor/Editor functions 

and Graphics subroutines $ 34.95 

MERLIN User Manual: over 100 pages of detailed hardware and software documentation $ 8.00 

Special Offer: All prepaid MERLIN orders received before 1 November 1976 will receive the MBI ROM FREE. 
All prices subject to change without notice. 
Mass. Residents please add 5% sales tax. 
Dealer inquiries invited. 




MimTerm Associates 



Box 268, Bedford, Mass. 01730 



24 


076 


301 


24 


077 


074 
020 


24 


101 


100 
131 
024 


24 


104 


074 
006 


24 


106 


100 
156 
024 


24 


111 


056 

024 


24 


113 


066 

302 


24 


115 


307 


24 


116 


074 



LAB 
CPI 



/TIMER TD A REG (B** OF BAUD) 



INDASH /IF DASH. SERVICE DASH 



/SEE IF CLOCK MUCH TOO SLOW FOR DOT 

CPI 6 /SHOULD BE A 10 IDEAL 

JFC INPOK /CLOCK IS GOOD ENOUGH 

LHI BAUDI" /NOT GOOD ENOUGH. FIX WFH CONSTANT 

LLI BAUDI 

LAM /UPM TD A 

CPI 2 /UPM TOO LOU TO TRACK? 

JTC INPOK /DON'T TRY TO FIX? ALREADY 100 FAST. 



310 

106 
304 
022 
104 
176 
024 



/SET UP FOR PPAK 
PPAK /PRINT THE CHARACTER 



UPTIME /KEEP TIMING THE UP TIME 







024 


24 


123 


034 
001 


24 


125 


370 


24 


126 


104 



24 131 

24 133 



24 135 
24 136 



24 143 
24 144 



24 153 
24 154 

24 156 

24 160 

24 162 
24 163 
24 164 

24 166 
24 167 

24 170 
24 172 
24 174 

24 176 



24 201 
24 202 



24 211 

24 213 
24 214 
24 215 
24 216 
24 217 

24 221 



24 234 

24 235 



24 242 
24 244 

24 247 
24 251 

24 254 

24 256 

24 260 
24 261 



056 
024 
066 
302 
301 
074 
034 
140 
154 
024 
307 
074 
376 
100 
154 
024 
004 
001 
370 
046 
001 
056 
024 
066 
304 
307 
022 
044 
376 
264 
370 



056 
024 
066 
303 
076 
000 
106 
107 
021 
105 
044 
001 
150 
046 
024 
056 
024 
066 
303 
317 
010 
371 
301 
074 
377 
110 
235 
024 
016 
012 
106 
304 
022 
106 
304 
022 
007 
074 
060 
110 
247 
024 
006 
001 
104 
263 
024 
074 
024 
110 
176 
024 
056 
024 
066 
304 
307 
076 
001 
106 
125 
023 



/-l 
/BAUDI-1 



/IF HERE* SYMBOL IS DASH. UPDATE BAUDI FOR TRACKING 
INDASH. LHI BAUDI" /POINT AT INPUT UPM 



LAM /YES 

CPI 376 /TIMER REALLY TOO TOO SLOW? 



INPOK. LHI 

LLI 

LAM 
RAL 
NDI 

ORE 
LMA 



OKDASH /YES. BAIL OUT! 



/BAUDI+1 
1 /SET E=l FDR DASH 

INCHAR" /POINT AT CHAR HOLDING REG 

INCHAR 

/GET PARTIAL CHAR TO A REG 
/SHIFT UP ONE FIT 
376 /JUNK THE OLD CARRY BIT 

/BRING IN NEU SYMBOL FROM E REG 
/NEU PARTIAL CHAR TO INCHAR 



/TIME THE INTERSPACE TO FIND UHAT TYPE IT IS. 
LHI TIMER" /RESET THE TIMER 



LLI TIMER 
LMI 
UPTIME. CAL TICKI 



SENSE 
NDI 



/TIMER RESET 

/DELAY 1/a OF A BAUD TIME 

/GET THE KEY STATUS 



JTZ INTIME /KEY DQUN. GET NEXT SYMBOL 

LHI TIMER" /UPDATE THE TIME 
LLI TIMER 



LBM 
INB 
LMB 

LAB 

CPI 377 



/+1 

/TIMER+1 

/GET TIMER TD A FOR COMPARE 

/END OF MESSAGE? 



JFZ 

LBI 
CAL 



RET 
NOTEOM. CPI 



LAI 
JMF 

ENDLET. CPI 

JFZ 

LHI 
LLI 



NOTEOH /KEEP LOOPING. 



/END OF MESSAGE. CR-LF-CR-LF 



/EXIT TO MAINLINE 
60 /END OF WORD? 

ENDLET /NO. 

1 /YES. OUTPUT A SPACE 
MPAK /DO IT OUT RIGHT. 

24 /END DF LETTER? 

UPTIME /NO. KEEP TIMING THE UP TIME 

INCHAR" /POINT AT HOLDING REG 

INCHAR 

/MORSE FROM HOLDING REG TO A REG 
1 /RESET THE HOLDING REG FOR NEXT CHAR 

XLAT /ASCII TO A EGUIV OF HORSE 



/***ANYTHING BEFORE THIS POINT CAN BE IN PROM*** 
/***EVERYTHING AFTER THIS POINT MUST BE IN RAM*** 



/0=NORMAL MODE. OTHERUISE COMMAND MODE 
/UHEN BYTE IS ZERO. GENERATE A CR/LF 
/TEMP CHARACTER COUNT FOR MESSAGE DUMP 
/BUBMODE FOR DMPSUB 0=PRINT 1=SEND 
/UPM CONSTANT (SEE HEADING ON PROGRAM) 
/INPUT UPM VALUE (GETS MODIFIED) 
/TIME BAUD *FJ (10 OCTAL) COUNTER 
/INPUT CHAR HOLDING REG 



275 


000 


CMMND. 


DATA 


276 


000 


TUIDTH. 


DATA 


277 


000 


MSSCNT. 


DATA 


300 


000 


SOH. 


DATA 


301 


000 


BAUD. 


DATA 


302 


000 


BAUDI . 


DATA 


303 


000 


TIMER. 


DATA 


304 


000 


TNCHAR. 


DATA 



KYFIFD. HLT 



/INPUT BUFFER 



*KYFIFO+BUFSKY 
PNFIPD. HLT /PRINTER BUFFER 



*PNFIFD+BUFSPN 
OTFIFO. HLT /OUTPUT BUFFER FOR CODE 



*OTFIFO+BUFDUT 
MSSGBF. HLT /MESSAGE BUFFER 



ASCEND 


20 


305 


ASCTAB 


20 


225 


BAUD 


24 


301 


BAUDI 


24 


302 


BLANK 


00 


040 


BUFOUT 


00 


060 


BUFSKY 


00 


377 


BUFSPN 


00 


060 


C 


00 


103 


CLRMD 


22 


153 


CMMND 


24 


275 


CHHNDR 


21 


150 


CONVT 


23 


074 


CR 


00 


015 


DASH 


21 


126 


DCRLH 


21 


052 


DEL 


23 


034 


DELETE 


00 


177 


DELSYM 


00 


134 


DMPSUB 


21 


333 


DOT 


21 


120 


DSH 


23 


327 


ENDLET 


24 


247 


ENTPAK 


20 


367 


ERCHAR 


00 


007 


ERROFL 


21 


on 


ESC 


0.0 


173 


ESCSYM 


00 


044 


ETX 


00 


003 


FINDOT 


21 


137 


GOODCH 


23 


311 


IDLE 


23 


360 


IDLE1 


24 


025 


INCHAR 


24 


304 


INCLH 


21 


046 


INCRLF 


23 


031 


INDASH 


24 


131 


INPEND 


24 


034 


INPOK 


24 


156 


INSENS 


24 


054 


INTIME 


24 


046 


KYBD 


22 


227 


KYFIFO 


24 


305 


L 


00 


114 


LDNXT 


21 


224 


LDNXT1 


21 


232 


LDNXT2 


21 


272 


LF 


00 


012 


MCONVT 


23 


177 


M0K1 


23 


207 


M0K2 


23 


214 


MOREND 


20 


366 


HORTAB 


20 


306 


MPAK 


24 


263 


MSQSZ 


00 


377 


MSSCNT 


24 


277 


MSSGBF 


26 


044 


NETX 


22 


267 



NDTEOM 


24 235 


NTFND 


23 225 


NTFUND 


23 122 


NXTPNT 


22 361 


DK 


21 006 


OKDASH 


24 154 


OKI 


23 104 


0K2 


23 111 


OTERR 


23 252 


OTFIFO 


25 364 


OTLOOP 


23 332 


OTPUT 


23 230 


0TPUT1 


23 264 


OUTEND 


23 342 


P 


00 120 


PNFIFO 


25 304 


PNTR 


22 316 


PNT1 


23 027 


POP 


21 014 


POPLOP 


21 023 


POPY 


21 036 


PPAK 


22 304 


PRT 


21 317 


PRT1 


21 341 


PRT2 


22 347 


PR2 


22 004 


PR3 


22 035 


PR4 


21 372 


QUEST 


00 077 


RESTRT 


20 172 


S 


00 123 


SNDNX 


22 060 


SOH 


24 300 


S0H1 


22 024 


SPACE 


23 277 


STRT 


20 120 


STRT1 


20 140 


T 


00 124 


TEST 


22 074 


TEST1 


22 120 


THIS 


23 147 


THISIT 


23 044 


TICK 


21 061 


TICKI 


21 107 


TIMER 


24 303 


TUIDTH 


24 276 


UNPAK 


22 164 


UPARRO 


00 136 


UPTIME 


24 176 


U 


00 127 


UAITMT 


22 220 


UAIT1 


21 070 


UAIT2 


21 067 


UHOOP 


21 305 


UIDTH 


00 110 


UPH 


22 133 


XLAT 


23 125 


XLATER 


23 040 


XLAT1 


23 143 



68 



YourAltair, 

IMSAI, 
or Poly 88 

will love our 
Frugal Floppy! 




It makes program development and loading 100 times faster! 



$1195 plus 
interface card 



iCOM disk drive 




Cable to your Microprocessor 



The affordable floppy 

You've made a big investment in your 
computer. Here's how to make that 
investment really pay off. Order 
iCOM's low cost Frugal Floppy® 
Disk Subsystem. Just $1195 for the 
disk drive, field proven controller and 
cables. And you can order our 
Altair, IMSAI, and Polymorphic bus 
compatible plug-in interface, with 
on-board RAM, in kit form or 
fully assembled. 

What it will do for you 

With our Frugal Floppy,® you can 
load and store programs hundreds of 
times faster than with paper tape, 
cassette, or teletype. Example — 8K 
of memory can be loaded in just 7 
seconds! Plus, you can store up to 
256 programs on a single disk. That's 
why we say our Frugal Floppy will 
turn on your computer. And fast! 

Here's what you get 

The Frugal Floppy includes: 
• Disk drive with daisy chain 
capability 



• Proven IBM compatible controller 

• Interface cable to your computer 

• Controller-to-disk drive cable 

• All required connectors 

If you need a power supply and 
software, we've got that too. 

FDOS-II software 

iCOM's famous FDOS-II software is 
now available for the Altair/IMSAI 
compatible bus. There's nothing 
anywhere to compare with our disk 
based Intel compatible macro 
assembler and string oriented 
text editor. 

With super features, such as named 
variable length files, auto file create, 



MICROPERIPHERALS 




open and close, multiple file merge 
and delete. Use our software either 
in your development system or 
integrate it into your applications 
package. In either case, it's easy 
to do. And low cost too. 

Fast delivery 

See your iCOM dealer today to find 
out how our $1195 Floppy can turn on 
your micro — and fast. If you have 
any questions, or would like the 
name of your local dealer, phone us 
at 213-348-1391. You'll find that when 
it comes to Microperipherals® iCOM 
has the answers. We should. We've 
delivered thousands of systems 
to date. 



6741 Variel Avenue, Canoga Park 
California 91303 • (213) 348-1391 



DEALERS .... FOR COMPLETE 
INFORMA TION ON HANDLING 
OUR LINE OF MICROPERIPHERALS 
PHONE OR WRITE iCOM TODA Y 



Figure 5: The input circuit 
used by the author in de- 
veloping the Morse code 
interpreter. This circuit 
works but is not optimal. 
The operational amplifier 
saturates if any A C signal 
is present on the input to 
the bridge rectifier, so the 
frequency selectivity of 
this circuit is virtually non- 
existent (ie: all stations 
heard in the pass band of 
your receiver will be logi- 
cally "ORed" leading to 
garbled copy if you oper- 
ate in a crowded band). 



3.2 /8fl TO 500J1 




TO 

MI50I 
(COMPUTER 
NPUT) 

7404 POWER 

+ 5V ■ 14 
6ND * 7 



ARCHER 273-1381 
OR EQUIVALENT 



Some Thoughts on Improvements and 
Adaptations 

The Morse code interpreter described here has 
been implemented and used by the author. As in 
any design, there is room for improvement and 
expansions of the capacity of the program. Here 
are some suggestions: 

• Design a good input filter to pick up audio 
and output digital (phase locked loop?). See 
figure 6. 

• Add multiple message buffers. 

• Use multiple precision arithmetic to provide 
a larger message buffer. 

• Modify the program for RTTY (Replace 
Morse table with Baudot table, add single 
byte flag to keep track of FIGS vs LTRS 
modes). 

• Wire 6.3 VAC at 60 Hz into the DEC 
M7346 module and write a real time clock 
routine to keep track of time of day. 

For individuals with 8080 processors, or the new 
Z-80, the source code for this Morse code inter- 
preter (see listing 2) can be translated on a one to 
one basis into code for these newer computers. 
Such code will work without major changes, but 
will not make optimal use of the expanded 
instruction sets. 



INPUT (O 



TO 
<3 SINGLE BIT 
INPUT PORT 




CODE 

(ANALOG TONE BURST) 



m 



Figure 6: A suggested selective input filter for better performance. This 
circuit is adapted from the Signetics Catalog, page 6-97. The design equations 
are shown. The phase lock loop "latches up " when the signal is detected in 
the filter's band, typically after several tens of cycles. C3 determines the time 
taken for the filter to detect this condition. The time taken to unlatch after 
the signal disappears is determined by R2 and C4, with some effects from C3. 



Text continued from page 56 

used since they are all driven in the same 
sequence). In both of the above cases the 
keying sense for input and output is a TTL 
low level for a "key down" condition 
("mark") and a TTL high level for a "key 
up" condition ("space"). 

This program has been tested on a starter 
set and has successfully operated in both 
PROM and programmable memory. When 
used in programmable memory, it should be 
noted that a DEC M7344YB (or an extra 
1 K of programmable memory over the 
starter set M7344YA) is the minimum 
memory requirement. When the program is 
assembled and programmed into PROM, 
approximately 4 1/2 EROMs (1702A) are 
required. 

Experience to Date 

The program has been tested in gene- 
rating Morse code over the speed range of 
7.2 wpm to 120 wpm and appears to 
function properly. The program has been 
tested in receiving Morse code over the speed 
range of 7.2 wpm to 96 wpm: up to about 
63 wpm the decoding function is fairly 
acceptable; at 89 wpm the number of 
erroneous characters is considered to be 
unacceptable by the author in this particular 
test. It is the author's opinion that the error 
rate at the higher code input speeds is 
probably related to the design of a particular 
input processing circuit that was used (see 
figure 5). In general, a phase locked loop, or 
a similar highly selective decoding scheme, 
would be useful, particularly to an amateur 
radio operator working the crowded bands 
of a field day type event. One such circuit is 
illustrated in figure 6. This would provide 
the amateur with a printout of communica- 
tions in both directions from the station 
operating. In fact, with sufficient comment 
being transmitted to and from the stations 
involved, the printout from a hard copy 
terminal would provide a log for the field 
day events." 



70 



Introducing A Remarkable New Microcomputer: 

The Astral 2000 



You're reading this ad, so you're obviously interested in getting a microcomputer. You're probably also a bit confused by the 
number of different microcomputer kits around today. So, think about the things you want in a microcomputer. Ease of assembly, 
quality power supply, well designed cabinet and interconnect scheme, peripheral and memory options for an expanding system. 



Some Kit! 



Although we have called the Astral a "kit", it actually arrives 
over 70% assembled. The power supply, processor board and RAM 
board are fully assembled, burned in and tested before shipment. 

There is no complicated wiring harness. In fact, there is no front 
panel wiring harness at all. The front panel plugs directly into the 
backplane. Additional circuit boards are inserted through the rear 
of the chassis directly into the backplane. 



Complete System 



The Astral 2000 is shipped with power supply, cabinet, front 
panel components, mother board, processor board and one 8K RAM 
board. The processor is 6800-based and operates in serial and in 
parallel. Both RS-232 and 20mA current loop are provided by a ser- 
ial I/O socket on the processor. This processor is shipped with our 
own 16K monitor ROM and has provisions for "cycle-stealing" 
DMA. The memory board contains 8K of low power, 500ns static 
RAM and uses less than 1.5A at 5V. 



Lots Of Options 



A computer isn't much fun if you can't talk to it. But you can 
talk to the Astral with the VID-80 video terminal board for only 
$189.95 unassembled ($245 assembled). The VID-80 has a selectable 
line length of 64, 72 or 80 characters per line. It displays 16 lines 
of upper case characters but gives you the option of installing a 
lower case character ROM as well. 

We also have someplace for you to put your programs. Our 8K 
EPROM board ($59.95) is designed for the 5204 and will allow in- 
system program storage even during power-down. This board is 
assembled with all components except the EPROMs, however 
sockets are provided for the memory chips. 

We've solved program loading, too. The I/O tape interface unit 
($49.95) plugs into the I/O socket on the processor board and allows 
programs to be loaded from any inexpensive, non-digital tape deck. 
But if tape cassette isn't fast or big enough, a floppy disk with an 
Astral bus-compatible controller will be available for under $1,000 
in the last quarter of 1976. 



A New And Powerful BASIC 

A unique and powerful version of BASIC with features never 
seen before in an 8K version has been designed especially for the 
Astral system. Astral BASIC contains all the features of competing 
BASICs and then some; Astral BASIC is also very fast. 

With the User Selectable Floating Point package, the user 
chooses the degree of precision from the four choices of 6, 9, 13 or 
16 digits. Fewer digits use less memory and is faster, however higher 
precisions are useful for scientific and mathematic applications. 

The Astral BASIC'S DO statement is unique; it has never 
appeared in any other version of BASIC. The DO statement is a 
simple and flexible way to subroutine without the restrictions of 
formal subroutines. DOs can be nested, too and —of course — Astral 
BASIC has all the other standard subroutine procedures as well. 

The Trace Mode is another feature rarely found in other 
BASICs. The Trace Mode is used in program debug to list statement 
line numbers as executed. This feature may be programmed to 
Trace On only for routines still needing check-out. Pressing the 
escape key halts the trace and returns control to the terminal. 

The Astral BASIC string facility permits variable length strings 
of unlimited length and includes the ability to search for a substring 
within another larger string, a particlularly useful feature for word 
processing applications. 

Powerful program editing capabilities allow loading, listing and 
saving of programs. Blocks of statements may be deleted or renum- 
bered. The RENUMBER statement may be used to increment all 
specified line numbers and it automatically adjusts the numbering 
of any GO TOs, etc. 

Another feature never seen before in an 8K version is the pop- 
ular PRINT USING statement. PRINT USING permits floating "$", 
"+" and "-" signs as well as floating commas, so numbers such as 
$1,000,000+ can be printed in the standard accounting format. 



m&r enterprises 

P.O. box 61011 . sunn|/rale , California 94088 








«St l 



.---Mi*''***" 



«»^mS? 




The Astral 2000 is $995 partially assembled ($1250 fully assembled) plus $14 for shipping and handling ($18 for Canadian 
orders). Additional 8K RAM boards are $245 each. California residents add 6% sales tax. The Software Package includes Astral 
Basic on magnetic tape cassette or paper tape, the game of Star trek, complete documentation and a free one year subscription to 
the Astral Newsletter, all for $35. For more details, send a self-addressed, 8'A by 11 stamped envelope to M&R Enterprises, P.O. 
Box 61011, Sunnyvale, Ca. 94088. Allow approximately 8 to 12 weeks for delivery. 



Make a Giant of li 



3P+S Input/Output Module 

Our 3P + S is a simple inexpensive answer 
to handling a variety of peripheral devices. 
It has two 8-bit parallel I/O ports, with full 
handshaking logic. Plus, it has a serial I/O 
port, with a data rate range from 05 to 
9600 Baud. Simultaneously handle a paper 
tape reader, a keyboard, a TV terminal, a 
tape punch, and a telephone coupler! 
Available with premium grade low-profile 
IC sockets, $149. Owner's Manual, $4.95.* 

ALS-8 Assembly Language 
Operating System" 

Just turn on the switch, and instantly you 
have the power to write, edit, assemble, 
de-bug, and run your own programs. 
The ALS-8 is the most useful software 
development tool available today Optional 
firmware includes SIM-1, an interpretive 
simulator, that simulates programs without 
running them in real time. Thus, errors 
encountered during testing do not endanger 
your entire system. The TXT-2 firmware adds 
the dimension of text editing. Insert, delete, 
move entire lines or single characters, and 
much more! ALS-8 (assembled only), $425. 
SIM-1, $95.TXT-2, $95. 

VDM1 Video Display Module 

If you're setting up just the system you really 
want, don't fall short by limiting its com- 
municating ability. The VDM-1 is an ultra- 
highspeed video output device. Its 16 display 
lines have 64 characters each, upper and 
lower case. 1 024 bytes of random access 
memory are on the card. It scrolls up or 
down, even to 2000 lines per minute! Any 
combination of the 1024 cursors can be 
displayed as black-on-whife or vice versa. 
Free terminal mode software is included, 
along with premium grade, low-profile 
IC sockets. $199. Owner's Manual, $4.95.* 

8KRA Static Memory Module 

We now offer a low-power static memory 
module, with a full 8192 bytes of memory. 



It has an exclusive KSET™ address selection 
DIP switch, so you can conveniently set 
address boundaries in increments of IK. 
Our low-power RAM's typically require one- 
third less power than those commonly used 
by our competitors. They'll even retain 
memory for 4-5 hours when powered by 
two "D" flashlight cells. On-board recharging 
circuitry and battery connectors make it 
possible to protect your data against sudden 
power loss. Each RAM has its own IC socket, 
too, for easier assembly and repair. $295. 
Owner's Manual, $4.95* 

2KROEPROM Module 

The 2KRO Read Only Memory will accept 
up to eight 1702A or 5203 EPROM's (not 
included), providing 2048 eight-bit words 
of non-volatile storage for monitor, 
executive, loader and other programs. 
Programming services available from your 
dealer or write us for details. $65. 
Owner's Manual, $4.95* 

4KRA Static Memory Module 

The 4KRA (4096 bytes) was our first static 
memory module. It's still very popular, and 
uses the same low-power static RAM's as the 
8KRA. Plus, we've added a DIP switch, and 
every RAM now has its own premium grade, 
low profile IC socket. Onboard recharging 
circuitry (with battery backup) makes if 
possible to retain memory for 8-10 hours 
during power failure. $159. 
Owner's Manual, $4.95.* 

MB-1 MotherBoaid 

Our single piece Mother Board for the Altoir 8800 
gives you 16-cord capacity in one single installation. 
Available with 12 (MB-1 2) or 16 (MB-1) slots. $70. 
(Discontinued; limited to stock on hand.) 

Wire Wrap Board 

Do your own wire wrap prototyping with the WWB 
Wire Wrap Board. Up to 62 16-pin sockets or various 
combinations of 14, 16, 24 and 40-pin sockets. $40. 

EXB Extender Board 

The EXB Extender Board allows accessibility in servicing 
any 8080-compatible module. $35. 

*Fully descriptive Owner's Manual available 
separately. Price refundable with purchase of kit. 



Mir Minicomputer 




Whether your minicomputer system 
is Sol, IMSAl, or Alfair, its reo 
capabilities depend on what 
goes inside. Processor Tech- 
nology Corp. now offers a 
full line of 8080-compat- 
ible components. From 
fine static memories 
to a unique assem- 
bly language 
operating 
system. We 
also have a 
variety of 
useful 
software 
packages, 
available 
for little 
more 
than 
copying 
costs. 

Kit Prices 

are shown, 
and they 
include the 
Owner's Manual. 

Assembled units MB-1 

available at slightly 
higher prices. 



3P + S 



Write Us for further details on all our 
8080-compatible products, and for the 
dealer nearest you. 



[ffitohpolpgyj 

6200-G Hollis Street 
Emeryville, CA 94608 



Build This 

Mathematical Function Unit 



Part 2: Software 



Figure I: Wiring the Mathematical Function Unit to your computer's 10 
structure is accomplished by connecting the data input and output lines to 
appropriate pins of an 8 bit input and an 8 bit output port. For those 
homebrewing an interface, the 16 interface lines could be provided by a single 
dual port integrated circuit such as the Motorola PI A design. The software of 
this article reflects hardware for the input and latched output sides of a single 
Intel 8080 port. 

Processor Output Wiring 
-See Text 



COMPUTER 

OUTPUT 

PORT 



COMPUTER 

INPUT 

PORT 



Making Connections to the Computer 

The connections needed to interface the 
Mathematical Function Unit to an 8 bit 
microprocessor are summarized in figure 1. 
In this interface diagram, only the signal 
wires are shown. A ground connection must 
also be made. If the wiring is done as shown 
here, the READY bit (bit 7) on the Mathe- 
matical Function Unit's output must be 
continually examined to determine comple- 
tion of the calculating or data entering tasks. 
An alternative would be to attach the 
READY line to the computer's interrupt 
structure so the computer could be execut- 
ing code other than the constant examina- 
tion of the READY bit. This would lead to 



X 



Processor Input Wiring 



X 
Y 



► C, 



R 
O 

P 

s 

B 



STROBE 
DIRECTION 



MATHEMATICAL 

FUNCTION 

UNIT 



KEY SELECT 



READY 
OVERFLOW 
DEC. POINT 
SIGN 

BCD DIGIT 



MATHEMATICAL 

FUNCTION 

UNIT 



74 



R Scott Guthrie 
1374 Franchere PI 
Sunnyvale CA 94087 



more efficient usage of the microcomputer 
and overall system, and will only create 
some fairly easy software changes from the 
examples shown in this part of the Mathe- 
matical Function Unit article. In either case, 
software toggling of the X (strobe) line is 
required to initiate operations. 

The operation of the Mathematical Func- 
tion Unit is governed by signals generated in 
the controlling computer system's software. 
The minimum required routines consist of 
an output procedure, an input procedure, 
and a short routine to check the status of 
the ready line, bit 7 of the input interface. 
The Intellec 8 Mod 80 made by Intel and 
belonging to the California Polytechnic State 
University Computer Science Department 
was used for the program development and 
all the controlling programs were written in 
Intel 8080 assembly language code as shown 
in the listings. 

Calculator Entry Routine 

The Mathematical Function Unit load 
procedure, called CAENTR (for CAIculator 
ENTeR) passes the code for the required 
operation to be performed from the micro- 
computer's main memory to the Mathe- 
matical Function Unit. The 8080 assembly 
language symbolic and absolute code for this 
routine is shown in listing 1, hexadecimal 
addresses 01 0D to 011 F. 

The CAENTR routine first saves the 
contents of the A register with a PUSH PSW 
instruction. Then it checks the Mathematical 
Function Unit's ready line, waiting if neces- 
sary for the unit to enter the ready state. 
The waiting is accomplished by a reference 
to the subroutine RDY at address 01 OF. The 
accumulator is then cleared to zero with an 
XRA A instruction, and this state is sent to 
the calculator via the 8080's output port 3, 
symbolically referenced as POUT. Note that 
in the Intellec system used for the proto- 
type, the hardware inverts the state of the 
data. Thus all references to data from or to 
the IO ports have a complement operation 




The purpose of this design project was to develop an 
economical and reliable method of performing simple 
arithmetic, trigonometric and logarithmic functions in 
microcomputer systems. Software routines for floating 
point arithmetic and transcendental functions involve 
extensive algorithms and complex programming on 
contemporary microprocessors (indeed, on any computer). 
A great deal of valuable memory area is often required even 
for some of the simpler mathematical routines. This is 
especially true when using the limited instruction sets of 
the contemporary 8 bit microprocessors. This makes the 
hardware approach a desirable alternative due to the 
powerful software available in some calculator integrated 
circuits on the market today. 

In last month's BYTE [page 26], we provided a 
description of the hardware for a unique Mathematical 
Function Unit built around the MOS Technology 
MPS-7 529-1 03 calculator chip. The parallel I O structure of 
this interface can be used with any system which has 8 bits 
of parallel output and 8 bits of parallel input capability. In 
this month's conclusion to the project, software required to 
control the interface is described, along with a test program 
to emulate a hand calculator by use of a computer's hard 
copy or television display terminal. The software is given as 
developed for an Intellec 8 Mod 80 system, with notes 
concerning hardware idiosyncracies of that computer. 



75 



Listing 1: Standard Input/Output Routines. The standard routines CAENTR, 
CAFTCH, and RDY are presented here in the Intellec 8 Mod 80 assembly 
language format. The hexadecimal address and object code is listed at the left, 
with symbolic assembly code at the right. CAENTR moves a command code 
to the calculator from DIN. CAFTCH reads the current calculator output to 
DOUT. RDY delays return until the calculator ready state is indicated, thus 
syncronizing a fast 8 bit central processor with a slow calculator. Prior to 
using the interface and calculator routines shown in this article, the stack 
pointer must be set to point to some area of programmable memory which is 
not in use. 



-•MATHEMATICAL FUNCTION UNIT 

J STANDARD INPUT/OUTPUT ROUTINES 

-'********************************** 

-"note: all input and output data 
;is complemented by hardware and is 
; re-complemented oy software for 
;this reason. 

*********************************** 









;mfu 


LOAD PROGRAM (CAENTR) 








;PR0GRAM DESCRIPTION: 








-•PROGRAM TRANSMITS DATA AT LOC 'DIN' 








;to 


*FU INPUT 


PORT 








;2 BYTES OF STACK SPACE USED 








;no 


REGISTERS 


AFFECTED BY SUBROUTINE 


0000 






ORG 


010EH 




010D 




DIN 


EQU 


010DH 




0101 




DOUT 


EQU 


0101H 




0003 




PIN 


EQU 


03 


;port IN 


0003 




POUT 


EQU 


03 


;port OUT 


810E 


F5 


CAENTR: 


PUSH 


PSW 


;SAVE REG. A 


010F 


CD5201 




CALL 


RDY 


;test for ready 


01 12 


AF 




XRA 


A 


;ZERO REG. A 


0113 


2F 




CMA 




; *** SEE NOTE *** 


01 14 


D30 3 




OUT 


POUT 


/•TOGGLE MFU 


01 16 


3A0D0 1 




LDA 


DIN 


;get code 


0119 


F6C0 




OR1 


0C0H 


J FORCE ' 1 1XXXXXX' 


01 IB 


2F 




CMA 




; *** see note *** 


01 1C 


D303 




OUT 


POUT 


;send code 


01 IE 


Fl 




POP 


PSW 


; RESTORE KEG . A 


01 IF 


C9 




RET 




; RETURN 



;mfu retrieve program <caftch> 

I 

IPROGRAM DESCRIPTION: 
JDIGITS KLSD) THROUGH 12CMSD) 
SARE LOADED INTO MEMORY STARTING 
SAT LOC 'DOUT'. THE INFORMATION 
ilS OF THE FORM ••ROPSBSBB" WHERE: 

;r=ready bit, p=decimal point 

!0=OVERFLOW- S = SIGN- BBBB=bCD DIGIT. 

i6 BYTES OF STACK USED. 

tNO REGISTERS AFFECTED BY SUBROUTINE. 



0120 


F5 CAFTCH: PUSH 


PSW 


;SAVE A & PSW 


0121 


C5 


PUSH 


B 


;save a « c 


0122 


E5 


PUSH 


H 


-•SAVE H « L 


0123 


60C 


MVI 


B-0CH 


;LOAD 12 IN REG. a 


0125 


210101 


LXI 


H-DOUT 


-•LOAD ADDR. OF SAVE AREA 


0128 


CD520 1 


CALL 


RDY 


;test for ready 


012B 


F3 


Dl 




; DISABLE INTERRUPTS 


012C 


AF 


XRA 


A 


;ZERO REG. A 


012D 


2F 


CMA 




-• *** SEE NOTE *** 


012E 


D303 


OUT 


POUT 


-•TOGGLE MFU 


130 


3ECB 


MVI 


A-0CBH 


-•DISPLAY RESTORE KEY 


0132 


2F 


CMA 




i *** SEE NOTE *** 


3133 


D303 


OUT 


POUT 


-•SEND CODE 


0135 


CD5201 


CALL 


RDY 


-•TEST FOR READY 


0138 


AF LOOP1: XRA 


A 


;ZERO REG. A 


0139 


2F 


CMA 




; *** SEE NOTE *** 


13A 


D303 


OUT 


POUT 


-•TOGGLE MFU 


013C 


3E80 


MVI 


A-080H 


-•SET TOGGLE BIT 



associated with the transfer to compensate 
for the inversion. 

The calculator command code to be sent 
to the Mathematical Function Unit is passed 
to the CAENTR routine in memory location 
DIN. This command code is combined with 
the bit pattern 11000000 using the ORI 
operation at address 0119. This forces both 
the X and Y control bits of the computer 
output port to be in a high state. The X line 
high starts the Mathematical Function Unit 
load sequence, and the Y line in a high state 
indicates that data is to be loaded into the 
calculator from the computer's port. The 
low order bits contain the bit pattern of the 
calculator key selection taken from table 1 
on page 31 of September 1976 BYTE. 
Finally, the CAENTR routine restores the 
saved contents of the A register and returns 
to the calling routine. 

In using the calculator interface, the 
procedure is quite simple: Set up a calcu- 
lator control code from that table in the 
location DIN (hexadecimal 01 0D in this 
case) and then CALL CAENTR. One com- 
mand to the calculator is transferred for 
each such CAENTR call. 

Calculator Fetch Routine 

The Mathematical Function Unit read 
routine, called CAFTCH (for CAIculator 
FeTCH) is responsible for controlling the 
transfer of data from the unit into the 
computer's memory. 

This routine transfers all 12 digit posi- 
tions of the calculator chip's output number 
into 12 sequential locations of the com- 
puter's memory starting at location DOUT, 
shown at location 0101 hexadecimal in 
listing 1. CAFTCH begins by saving the 
processor status. Then the subroutine RDY 
is called to delay until the calculator is ready 
for data transfer. 

When the Mathematical Function Unit is 
ready, return from RDY is followed by 
disabling of interrupts with the Dl instruc- 
tion, so that complete transfer of all 12 
bytes of calculator display output can occur 
without interruption. The calculator's "dis- 
play restore" command [see table 1, page 
31, BYTE September 1976] of 0B hexa- 
decimal is then sent, in the form of the code 
CB (logical sum of 0B and CO). This insures 
that the Mathematical Function Unit output 
will be valid prior to reading the data into 12 
bytes of memory. After another CALL RDY 
wait, the program enters a loop extending 
from address 0138 hexadecimal to 014A. 
This loop transfers 12 output digits in 
sequence into 12 consecutive memory loca- 
tions starting at the location DOUT. (The 
initial address was set up by the LXI H at 



76 



location 0125.) During this loop, the Y 
control line, bit 6 of the computer output 
port, is left at a logic level. The X line, bit 
7 of the computer output port, is toggled by 
the instructions at locations 0138 to 01 3F, 
setting up the next output transfer from the 
calculation. After waiting for the ready 
condition, the data is transferred into the 
computer at location 0144 with an IN PIN 
instruction, addressing the input port of the 
computer. The byte is then saved in memo- 
ry, and the index register provided by the 
HL pair is incremented. A loop counter in 
register B is decremented, and if the loop is 
not completed, reiteration continues. After 
all 12 digits have thus been transferred, the 
interrupts are reenabled and the registers are 
restored prior to return. 

The format of data recovered from the 
calculator in this transfer process was given 
in figure 2a found on page 27 of last 
month's BYTE. The offsets in memory for 
each byte of the data format were given in 
figure 2a. 

Calculator Ready Routine 

The subroutine called RDY is the final 
component of the basic set of interface 
driver software. This program is found at 
addresses 01 52 to 01 5A of listing 1 , and is a 
simple procedure to input from the com- 
puter input port (symbolically PIN, absolute 
value 3 in this case), and test the ready bit, 
bit 7 of the input pattern. If the ready state 
is indicated, the subroutine returns, other- 
wise it keeps reiterating. This routine is used 
by both CAENTR and CAFTCH. 

If the interrupt structure is being imple- 
mented, this routine could return control to 
the operating system, or other programs in 
memory, allowing them to execute until 
being interrupted by the ready state of the 
Mathematical Function Unit. 

Alignment Procedures 

The three variable resistors, R5, R6, and 
R7 adjust the length of the following timing 
pulses: 



Listing 1, continued: 



R5 300 lis 
R6 50 ms 
R7 50 ms 



Set Not-Ready delay 
Key Pressed delay 
Key Released delay 



The use of three short timing loop pro- 
grams, with the aid of an oscilloscope, allow 
these delays to be set. The programs are 
found in listing 2 and assume a 2/us cycle 
time. Adjustments should be made if your 
8080 processor runs at a different speed. 

The 300 /lis pulse can be set by con- 
necting the scope probe to pin 13 of IC 1a 
while executing the 1 ms delay routine, 



013E 


2F 


CMA 




j **» SEE NOTE *** 


913F 


D333 


OUT 


POUT 


;send coul 


0141 


CD520 1 


CALL 


ROY 


;TEST FOR REadY 


144 


DB0 3 


IN 


PIN 


;GET CODE 


0146 


2F 


CMA 




i *** SEE NOTE **» 


147 


77 


MOV 


B,A 


;SAVE DIGIT 


148 


23 


I NX 


H 


; I NCR H « L 


149 


05 


DCR 


a 


; DECREMENT tl 


14A 


C23801 


JNZ 


L00P1 


; CHECK FOR DONE 


014D 


FB 


EI 




; ENABLE INTERRUPTS 


014E 


El 


POP 


H 


;restore h 4 l 


14F 


CI 


POP 


a 


."RESTORE B * C 


1 50 


Fl 


POP 


PSW 


; RESTORE A & PSW 


0151 


C9 


RET 




; RETURN 



.•ready SUBROUTINE 
;THIS SUBROUTINE, WHEN CALLED 
.•RETURNS TO CALLING ROUTINE ONLY 
."WHEN MFU IS IN THE READY STATE. 



152 


DB0 3 


RDY: 


IN 


PIN 


;get MFU INFO 


154 


2F 




CMA 




S *»» SEE NOTE **» 


0155 


E680 




ANI 


080H 


;get ready oit 


157 


CA520 1 




JZ 


RDY 


.•JUMP NOT READY 


15A 


C9 




RET 




J RETURN 


0000 






END 







Listing 2: Alignment of the oneshots in this circuit is accomplished using 
timing loop programs which repeatedly toggle certain aspects of the interface. 
This listing shows three such timing loops, DIMS, D70MS and D140MS. 



-•ALIGNMENT ROUTINES 

tl., 70.. AND 140 MS. DELAY ROUTINES 

■•for computer cycle time of 2 us. 



0000 

0230 CD0B0 4 

0203 067C 

0205 05 

0206 C20502 
3209 C30002 

020C 

3300 CD0B04 

30 3 62 3 

30 5 GDI 604 

0308 C33003 

33B 

0400 CD0B04 

0403 0644 

0405 CD1634 

0408 C30004 



0408 3E7F 

343D 2F 

043E D303 

3410 3EFF 

3412 2F 

04 13 D303 

0415 C9 

3416 3C 
0417 C2I604 
341 A 5 
34 IB C2 1634 
341 E C9 
3330 



Li IMS: 
TL00P: 



U73MS: 



Dl 43MS: 



ORG 

CALL 

MVI 

DCS 

JNZ 

J MP 

ORG 
CALL 
MVI 
CALL 
J MP 

i 

ORG 
CALL 
MVI 
CALL 
J MP 



230H 

OUTPUT 

B.7CH 

a 

TLOOP 

DIMS 

300H 

OUTPUT 
B.35 
DcLAY 
D70MS 

400H 

OUTPUT 

B.68 

DELAY 

U140MS 



OUTPUT: 



,- SUBROUTINES 

A.07FH 



MVI 
CMA 
OUT 
MVI 
CMA 
OUT 
RET 

INS 

JNZ 
DCR 
JNZ 
RET 

END 



33 
A.0FFH 



03 



A 

uELAY 
B 
UELaY 



! STARTING AddRlSS FOR 1 MS 
! OUTPUT STARTING StQ. 
!SET FOR 1 MS. DELAY 



.'STARTING ADDRESS FOR 70 MS 

;SET FOR 7 MS. uELAY 

i RcPEaT 

J STARTING AuDRtSS F Oil 140 MS 

;SET FOR 140 MS. DELAY 

.-REPEAT 



.'SET X LINE LOW 

; INVERT FOR OUTPUT 



J SET X LINc HIGH 
; INVERT FGK OUTPUT 



; RETURN 



»uELAY» 
»L0DP* 



; RETURN 



DIMS. The scope's time base should be set 
at 50 /us per division and R5 adjusted until 
the pulse length is six divisions long. This 
pulse length is not at all critical and does not 
require exact setting. 

The key pressed delay must be approx- 



77 



Listing 3: CALCULA, a Calculator Simulator. CALCULA demonstrates the 
use of the Mathematical Function Unit in an application program. The 
purpose of CALCULA is to drive the calculator interface as a printing 
calculator, interpreting ASCII codes from a keyboard as the key strokes on a 
typical hand calculator. The output of the calculator is displayed after every 
return operation. The original CALCULA was run with a Teletype for input 
and output. 



jmfu-calculator simulator 
;tty keydoard simulates 
;a hand held calculator. 

;note: all input and output data 
;is complemented dy hardware and is 
;re-complementtd dy software for 
;this reason. 



0000 






ORG 


200H 


; STARTING ADDRESS 


010D 




DIN 


EQU 


010DH 




0101 




DOUT 


EQU 


0101H 




0120 




CAFTCH 


EQU 


0120H 




010E 




CAENTR 


EQU 


010EH 




0200 


21B302 




LXI 


H,HEAD 


;H,L -> HEADING 


0203 


061C 




MVI 


B, 28 


.•HEADING COUNT 


0205 


4E 


PHEAD: 


MOV 


CM 


;move char to c 


0206 


CDA702 




CALL 


CO 


iPRINT CHARACTER 


0209 


23 




1 NX 


H 


;iNCR. MEM. PTR. 


020A 


05 




DCR 


a 


J DEC COUNT 


020B 


C20 502 




JNZ 


PHEAD 


;JUMP NOT DONE 


020E 


CD9C02 


LOOP: 


CALL 


CI 


;get INPUT CODE 


021 1 


E67F 




ANI 


7FH 


;REMOVE 8TH dIT 


0213 


FE0D 




CPI 


0DH 


."COMPARE WITH RETURN 


0215 


C27102 




JNZ 


CODEIN 


;JUMP IF NOT RETURN 


0218 


CD2001 




CALL 


CAFTCH 


;get data from mfu 


021B 


4F 




MOV 


CA 


;move return to c 


021C 


CDA702 




CALL 


CO 


; PRINT RETURN 


021F 


0E0A 




MVI 


C0AH 


;move linefeed to c 


0221 


CDA702 




CALL 


CO 


.•PRINT LINEFEED 


0224 


160C 




MVI 


D, 12 


JUIGIT COUNT TO D 


0226 


210101 




LXI 


H,DOUT 


;h,l -> DOUT 


0229 


7E 


DLOOP: 


MOV 


A,M 


;C<H,L) -> REG. A 


022A 


E67F 




ANI 


07 FH 


; FORCE "0XXXXXXX' 


022C 


77 




MOV 


t*»A 


; REPLACE # IN MEMORY 








; CHECK 


FOR OVERFLOW INDICATOR 


022D 


E6BF 




ANI 


0BFH 


;force "xaxxxxxx" 


022F 


BE 




CMP 


M 


;SAME7 


0230 


CA3D02 




JZ 


C0NT1 


;YES = JUMP, ELSE, 


0233 


0E2A 




MVI 


C2AH 


;"»" -> REG. C 


0235 


CDA702 




CALL 


CO 


;print "*" 


0238 


1601 




MVI 


D,01H 


Jl -> D CNO MORE PRINT) 


023A 


C35F02 




J MP 


CONT 


JdACK TO ROUTINE 








; CHECK 


FOR A Nfc 


GATIVE SIGN IN CODr. 


023D 


E6EF 


CONT1 : 


ANI 


■ihlW 


;fohce •XXX0XXXX 1 


023F 


BE 




CMP 


M 


;same? 


02410 


CA4B02 




JZ' 


C0NT2 


;yes ■ jump, llsl. 


0243 


0E2D 




MVI 


C2DH 


;•■-•• -> REG. C 


0245 


CDA702 




CALL 


CO 


;print ■■-•• 


0248 


C35302 




J MP 

;print 


DECPT 
# FOUND 


;go to decimal pt. routine 


024B 


E60F 


C0NT2: 


ANI 


0FH 


; strip off d. p. 


024D 


C630 




ADI 


030H 


-•convert TO ASCII 


024F 


4F 




MOV 


CA 


;cca) -> c 


02 50 


CDA702 




CALL 


CO 


; PRINT NUMdER 


0253 


7E 


DECPT: 


MOV 


A,M 


;c<M) -> a 


0254 


E6DF 




ANI 


0DFH 


;force 'XX0XXXXX 1 


0256 


BE 




CMP 


M 


; same? 


0257 


CASF02 




JZ 


CONT 


,'YES = JUMP, ELSE, 


025A 


0E2E 




MVI 


C , 02 EH 


;••.•■ -> REG. c 


025C 


CDA702 




CALL 


CO 


,-PRINT "." 


025F 


23 


CONT: 


I NX 


H 


,• INCREMENT H,L 


0260 


15 




DCR 


D 


; COUNT DOWN CHAHACTERS 


0261 


C22902 




JNZ 


DLOOP 


CONTINUE DISPLAY 


0264 


0E0D 




MVI 


C0DH 


;RtTURN -> REG. C 


0266 


CDA702 




CALL 


CO 


;PRINT RETURN 


0269 


0E0A 




MVI 


C0AH 


iLINEFEED -> REG. C 


026B 


CDA702 




CALL 


CO 


;PRINT LINEFEED 


026E 


C30E02 




JMP 


LOOP 


;done WITH OUTPUT 


027 1 


210003 


CODEIN: 


LXI 


H, TABLE 


;H,L -> TAdLE 


0274 


1E35 




MVI 


E, 53D 


J 53 = # OF ENTRIES IN TAdLI 


0276 


FE20 




CPI 


20H 


; COMPARE WITH SPACE 



imately 40 ms long for the MPS 7529-103 
Calculator Chip and is set using the 70 ms 
program loop, D70MS. With the scope's 
input connected to pin 5 of IC lb and the 
time base set for 10 ms per division, R6 
should be adjusted for five divisions (50 ms). 
This allows an extra 10 ms from the required 
40 ms minimum for assurance that the data 
will be received in worst case situations. 

The key released delay can be set using 
the 140 ms delay loop, D140MS. Since the 
50 ms key released delay does not start until 
after the 50 ms key pressed delay, the end of 
this pulse should be around 100 msfrom the 
initiation of the sequence. This can be seen 
on pin 13 of IC 19a and set by adjusting R7. 
The scope's external trigger can be con- 
nected to pin 5 on IC 1b and the time base 
set for 10 ms per division for a closer look. 

It is not imperative that all pulse delays 
be exact; however data transmission errors 
may result if the two 50 ms delays are not 
set for at least 40 to 45 ms. 

What's It Good For? 

The application of the Mathematical 
Function Unit is appropriate wherever cal- 
culations must be done. To illustrate a 
specific case, listing 3 provides a very simple 
calculator program which will enable an 
8080 to drive the unit through the routines 
of listing 1 . A sample of the output is shown 
in listing 4. The purpose of the CALCULA 
program is to accept inputs from the normal 
ASCII keyboard of your computer (here 
assumed to be connected to a Teletype using 
input port for data input, input port 1 for 
status, and output port for data output) 
and use these inputs to set up command 
sequences to the calculator. After each "=" 
operation, the current display output of the 
calculator is read and printed. 

The program is set up in a fairly straight- 
forward manner, using a table located at 
hexadecimal location 0300 to store the 
conversion between ASCII input characters 
and calculator control characters. The list of 
ASCII codes and their corresponding calcula- 
tor functions is found in table 1 . 

To use CALCULA, simply load memory 
address space from 0100 to 0334 (hexa- 
decimal) with the content of listings 1 and 3, 
then start the CALCULA program by 
jumping to location 0200. This begins execu- 
tion by printing out the heading MFU 
CALCULATOR SIMULATOR shown at the 
beginning of listing 4, after which an inter- 
active input of various calculator commands 
from table 2 can begin. The sample of listing 
4 shows uses of many of the calculator 
functions. The calculator replies with an 
asterisk (*) if an overflow occurs, as is the 



78 



case with the attempt at 100! (100 facto- 
rial). Display output is normally printed 
following the input of a carriage return. 

CALCULA is of course only the simplest 
of possible uses for this unit. For general 
programming, specialized routines could be 
written to execute sequences of calculator 
keystrokes when needed, using data kept in 
the 12 byte arithmetic format. 

It should be fairly easy to implement a 
simple programmable calculator style inter- 
preter to drive this interface, thus converting 
your personal computer into the equivalent 
of some fairly expensive desk top micro- 
computer packages being sold commercially. 
Ambitious readers will go even further and 
implement a BASIC interpreter or some 
other form of high level language referencing 
this machine both at compile time and in the 
run time software packages. 

Some Parting Comments 

The hardware problems encountered with 
this design were few. The major inelegancy 
of the design is probably the requirement for 
pull down resistors on the calculator chip's 
output lines. These resistors (R10 to R30) 
are required to supply the load normally 
supplied by digit and segment driver circuits, 



Listing 4: CALCULA Program Sample Run. 
This Teletype listing was made using the 
CALCULA program to drive the Mathe- 
matical Function Unit. The command codes 
for operations are listed in table J. A 
carriage return code (hexadecimal OD) is 
used to cue the display of calculator outputs 
after a transfer via CA FTCH. 



MFU CALCULATOR SIMULATOR 

ss 

300000000 .000 

123.456 + 345.678 = 

000469.134030 

S < (3+7 >*<2+I >/10)»4+3 != 

0000000 1 8 .000 

S 987.32IM 

000987 .321000 

SS 10M4H + 26.579M5H = 

0001 .26579-13 

SS 45 S 

00.7071068000 



Listing 3, continued: 



i 


p 


03 


.1415927000 


SS 


16. I 


00000 .062 5000 


$ 


69 1 


01 


71 12244098 


s 


100 1 


SS 


1 E 


02 


7182818000 


S 


10 R 


03 


1622777000 


s$ 


10 Y 2 I = 


03 


1622777000 


SS 


8 Q 


000000064.000 


SS 


F 



0278 


C28202 


JNZ 


AGAIN 


JJUMP IF NOT SPACE 


027B 


4F 


MOV 


CA 


;M0VE SPACE TO REG. C 


027C 


CDA702 


CALL 


CO 


;PR1NT SPACE 


027F 


C30E02 


J MP 


LOOP 


;back to loop 


0282 


BE AGAIN: CMP 


M 


; COMPARE C(A) WITh TAoLE 


0283 


CA8E02 


JZ 


FOUND 


iJUMP IF FOUND 


0286 


ID 


DCR 


E 


; DECREMENT COUNTER 


0287 


CA0E02 


JZ 


LOOP 


;IF NOT FOUND TRY AGAIN 


028A 


23 


I NX 


H 


;iNCR H,L 


028B 


C38202 


J MP 


AGAIN 


;keep trying 


028E 


4F FOUND: MOV 


CA 


;move FOR PRINT 


028F 


CDA702 


CALL 


CO 


; PR I NT 


0292 


7D 


MOV 


A..L 


;move code to a 


0293 


320 D0 1 


STA 


DIN 


; STORE CODE FOR MFU 


0296 


CD0E0 1 


CALL 


CAENTR 


;SEND CODE TO MFU 


0299 


C30E02 


J MP 


LOOP 


JBACK TO ROUTINE 






i CHARACTER INPUT ROUTINE 


029C 


DB0 1 CI: 


IN 


01 


;01 = TTY STATUS PORT 


029E 


E60 1 


AN1 


01 


;01 = MASK FOR DATA AVAI1 


02A0 


C29C02 


JNZ 


CI 


JJUMP IF NO DATA 


02A3 


DB0 


IN 


00 


;READ THE ChARACTtH 


02A5 


2F 


CMA 




;»»* SEE NOTE *** 


02A6 


C9 


RET 




; RETURN TO PROGRAM 






JCHARACTER OUTPUT ROUTINE 


02A7 


DB0 1 CO: 


IN 


01 


;01 = TTY STATUS PORT 


02A9 


E604 


ANI 


04 


.;04 = MASK FOR TTY oUSY 


02AB 


C2A702 


JNZ 


CO 


;L00P UNTIL REaliY 


02AE 


79 


MOV 


A,C 


;move FOR PRINT 


02AF 


2F 


CMA 




;*»» SEE NOTE **» 


02B0 


D300 


OUT 


00 


; OUTPUT CHARACTER 


02B2 


C9 


RET 




J RETURN TO PROGRAM 


02B3 


0D HEAD: DB 


0DH 


; RETURN 


02B4 


0A 


DB 


0AH 


; LINEFEED 


02B5 


4D465520 


DB 


■MFU CALCULATOR SIMULATOR' 


02B9 


43414C43 








02BD 


554C41 54 








02C1 


4F522053 








02C5 


494D554C 








02C9 


41 544F52 








02CD 


3D 


DB 


0DH 


; RETURN 


02CE 


0A 


Lid 


0AH 


."LINEFEED 



02CF 

0300 30313233 TABLE: 

0304 34353637 

0308 38394130 

030C 30303030 

0310 2E2B2D2A 

0314 2F59 3D2 8 

0318 2950485E 

031C 30303030 

0320 5343544C 

0324 47524644 

0328 575A4D24 

032C 30303030 

0330 49515845 

0334 21 

0000 



»*» END OF PROGRAM **» 



ORG 0300H 

DB '01234567b9Ai)' 



•0000 . + -*/Y=< • 



)PH t0000SCTL" 



* GRFDUZMS0k)00" 



; 

END 



1QXE! • 



: END OF TABLE 



000987.321000 
SZ 

0.00000000 .000 
S 53C 

-.0.9182828000 
S Z 

000000000 .000 
S 1000. D 
00000 1000 .000 
S F 

001987.321000 
SS 

000000000 .000 



NOTE: A 10 by 5% inch (25.4 by 13.3 cm) printed 
circuit board with plated through holes is available 
from RSG Electronics, POB 13, Santa Margarita 
CA 93453. The price of this board is $24.95 plus 
$1.23 for postage and handling (California resi- 
dents add 6% sales tax). For questions on obtaining 
the calculator chip or other parts, please write to 
the author. 



79 



Table I: Keyboard Code Assignments for CALCULA. The CALCULA 
program interprets the ASCII keystrokes listed in the "keyboard code" 
column as the corresponding calculator key functions in the "function" 
column. The current content of the output displays is printed whenever an 
ASCII carriage return is input. 



Keyboard 




Keyboard 




Code 


Function 


Code 


Function 








E 


e x 


1 


1 


! 


N! Factorial 


2 


2 


Y 


Y* 


3 


3 


P 


Pi (3.1415927) 


4 


4 


A 


Arc 


5 


5 


S 


Sine 


6 


6 


C 


Cosine 


7 


7 


T 


Tangent 


8 


8 


L 


Natural Log 


9 


9 


G 


Log base 1 




Decimal Point 


Z 


Degree to Radian 


+ 


Plus 




Mode Switch 


— 


Minus 


M 


Store in Memory 


* 


Multiply 


F 


Recall from 


/ 


Divide 




Memory 


= 


Equals 


D 


Add to Memory 


( 


Left Parenthesis 


W 


Swap X with Y 


) 


Right Parenthesis 


$ 


Clear Entry 


t 


Enter Exponent 


ss 


Clear All 


H 


Change Sign 


Carriage 


Output Current 


I 


Inverse l/X 
X 2 


Return 


Contents of Dis- 


Q 




play to Main 


R 


Square Root of X 




Memory and 


X 


10 x 




Output 



BROWN-OUT PROOF 
your ALTAI R 8800 



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power supply kit. A custom engineered power supply for 
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replacement transformer can offer: 

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as low as 90 volts. 
•OVER-VOLTAGE PROTECTION: Less than 2% increase 

for 130 volt input. 
•HIGH OUTPUT: 12 amps @ 8 volts; 2 amps total @ 

± 16 volts. Enough power for an 8800 full of boards. 
•STABLE: Output varies less than 10% for any load. 

Regulators don't overheat, even with just a few 

boards installed. 
•CURRENT LIMITED: Overloads can't damage it. 
•EASY TO INSTALL: All necessary parts included. 



.<*" 



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calif, residents add $4.50 sales tax. 



Don't let power supply problems sabatoge your Altair 8800 

PARASITIC ENGINEERING 



PO BOX 6314 



ALBANY CA 94706 



which are missing due to the use of MOS 
buffers in their place. 

The Mathematical Function Unit has 
been overdesigned in several areas. The ready 
and timing circuitry has been designed for 
easy modification to accommodate some 
different calculator chips in place of the one 
used in this project. The timing pulses can be 
extended or shortened, or even bypassed if, 
for example, the key released delay is not 
needed. All modifications must, however, be 
carefully considered with the chip's specifi- 
cations prior to altering the electronics. 

The Mathematical Function Unit and the 
related software routines provide the micro- 
computer user with a very powerful calcula- 
tion tool where little could easily be done 
before. The programming of this peripheral 
calculator has been found to be very 
straightforward and uncomplicated, re- 
quiring much less memory space (and design 
time) than would be required to perform 
mathematical routines with microcomputer 
software alone. 

After considering the speed versus cal- 
culation ability tradeoffs, as well as the 
points mentioned above, I feel this project 
has been a complete success. I hope the 
microcomputer hobbyist as well as system 
designers will take advantage of this method 
for satisfying their mathematical function 
requirements in cases where high precision 
and low speed prove usable." 

BIBLIOGRAPHY 

1 . Intel Corporation: Intel Data Catalog, 1975, 
pages 6-1 through 6-64. 

2. Intel Corporation: Intellec 8/Mod 80 
Microcomputer Development System Refer- 
ence Manual , 1974. 

3. Intel Corporation: Intellec 8/Mod 80 
Microcomputer System Operator's Manual 
(Preliminary Edition), June 1974. 

4. MOS Technology Inc: "Specifications for 
Single Chip 40 Key Scientific Calculator 
Array MPS 7529-103" Rev 1, July 21 1975. 

5. National Semiconductor Corporation: 
CMOS Integrated Circuits, August 1974. 

6. National Semiconductor Corporation: Digi- 
tal Integrated Circuits, January 1974. 

7. National Semiconductor Corporation: Inter- 
face Integrated Circuits, April 1974. 

8. National Semiconductor Corporation: Lin- 
ear Integrated Circuits, January 1974. 

9. Staken, Patrick H: "Using a Calculator 
Chip to Extend a Microprocessor's Capabili- 
ties," Computer Design September 1975, 
pages 98,99. 

10. Texas Instruments Inc: The TTL Databook 
for Design Engineers, First Edition, 1973. 



80 



SOME HISTORICAL NOTES ON COMMUNICATIONS AND PEOPLE 




SO 

W 



'Jf. 

M 



2! 

OS 

H 

S3 

d 

« 
w 

2! 



Source materials supplied by 
Claude Kagan, Western Elec- 
tric Co. 



Courtesy of Western Electric 
Company from "Catalogue 
No. VII" of 1884. 



The following text is taken exactly from 
a privately circulated English language trans- 
lation of an excerpt (pages 519 to 523) of a 
French work, Traite De Telegraph ie Elec- 
trique by Abbe Moigno, published in Paris in 
1852. 

Telegraph Lines in America 

Electric telegraphy has not spread any- 
where its mysterious network with as much 
speed and success as in the United States of 
North America; nowhere has one either 
conceived as promptly and executed with 
such admirable response the happy thought 
of placing commerce and private enterprise 
in possession of this all powerful means of 
communication. 

The first American telegraph line was 
established in 1844, between Washington 
and Baltimore, on a length of 40 miles. It 
transmitted with such celerity and 
promptness the news relating to the election 
of presidential candidates, that all pro- 
claimed, with a unanimous voice, the excel- 
lence and immense importance of these 
messages prompt as lightning; and one saw 
the formation at once, on all of the territory 
of the Union, private companies with the 
strong intention of making the entire 
country participate in the unexpected bene- 
fit of the electric telegraph. The line from 
Washington to Baltimore was immediately 
extended to Philadelphia and New York, 
over a distance of 250 miles; it reached 
Boston in 1845, and became the great 
Northern line on which two lines branched: 
one, a thousand miles long from Philadelphia 
to Harrisburg, Lancaster, Pittsburgh, Ohio, 
Columbo, Cincinnati, Louis Ville (Ken- 
tucky), and St. Louis (Missouri); the other, 
1,300 miles long, from New York to Albany, 



Troy, Utica, Rochester, Buffalo, Erie, Cleve- 
land (Ohio), Chicaga (Illinois), Milwankie 
(Wisconsin). 

[The text goes on to describe further details 
and give a table totalling the telegraph 
mileage as of July 1849: 10,885 miles. ] 



What Was the Public Response to 
the Telegraphy Revolution? 

[Continuing the excerpt] . . . Here is how 
the work is accomplished: the poles, twenty 
feet long, are cut in the forests and trans- 
ported to the site by the neighboring far- 
mers; one implants them into holes a foot 
and a half deep, one fastens at some distance 
from the top insulators or glass rings, on 
which the conductive wire rests. A few days 
suffice to see the rise, as by enchantment, of 
a long line of poles. The surveillance and 
protection of the poles and of the wire is 
entrusted to these same farmers, all provided 
with the small instruments required by such 
a simple task: a hammer, cutters, a vise, 
pliers, some screws, some rings and some 
nails. 

The telegraph lines usually follow post 
roads, and their maintenance costs ab- 
solutely nothing; there is no instance that 
the wires, delivered to the good public sense, 
were broken through meaness. It is because 
in America all the wishes cooperate in 
concert for the public welfare, and that all 
useful invention is like a family heirloom 
that all wish to safeguard. Each farmer 
participates at the very least by his contribu- 
tion of labor and materials, if not through 
his purse, to all the national undertakings; 
each thus becomes a shareholder and is 
interested in seeing them prosper." 



81 



Microprocessor Update: 



Keep PACE with the Times 



Robert Baker 
15 Windsor Dr 
Atco NJ 08004 



The new National Semiconductor IPC- 
16A/500D microprocessor commonly called 
PACE for Processing And Control Element is 
a single chip 16 bit microprocessor packaged 
in a standard 40 pin dual in line package. As 
a 16 bit general purpose computer it is an 
excellent candidate for personal computing 
applications. 



Table I: PACE Status and Control Flags. These flags are tested to control 
program execution as a result of various conditions. 



Flag Register 
Bit 



7 
8 

9 
10 



Flag Name 



Description 



OVF 
CRY 
LINK 

IEN 
BYTE 



11 


F11 


12 


F12 


13 


F13 


14 


F14 



15 



Always logic 1, not used. 

Flags IE1 to I E5 serve as interrupt enable flags for 5 
of the 6 PACE interrupt levels. These interrupts 
are ignored when IE bit is low. 

Set to the state of the 2's complement arithmetic 
overflow by arithmetic instructions. 

Set to the state of the binary or decimal carry out- 
put of adder by arithmetic instructions. 

Link flag is included in shift and rotate operations as 
specified by instructions. Is unaffected if not 
selected. 

Master interrupt enable. This line simultaneously 
inhibits all five of lowest priority interrupt levels. 

Byte flag selects 8 bit data length when high and 
16 bit when low. 

General purpose control flags. Drive PACE output 
pins to directly control system functions. 

Always 1 , addressing for interrupt exit. 



The Microprocessor Overview 

PACE utilizes 16 bit instruction words to 
operate on software selectable, 8 or 16 bit 
data words for a wide range of applications. 
There are four 16 bit general purpose 
working registers available to the user as well 
as an independent 16 bit status and control 
flag register that automatically and con- 
tinuously preserves system status. Table 1 
lists the various bits of the status and control 
register and gives a brief description of the 
function of each bit. A ten word (16 bit) last 
in, first out, stack automatically saves return 
addresses for subroutine calls and interrupt 
servicing. A stack full or stack empty inter- 
rupt is provided to allow software stack 
expansion when required. A six level, 
vectored priority interrupt system provides 
automatic interrupt identification. More 
than one device may be placed on any given 
priority level using open collector, wired OR 
circuitry external to the processor. An indi- 
vidual interrupt enable is provided in the 
status register for each level and a master 
interrupt enable is provided for all five lower 
priority levels as a group. There are also four 
direct sense inputs and four control flag 
outputs to implement various single bit 
status and control functions. Figure 1 shows 
a functional block diagram of the PACE 
microprocessor while figure 2 shows the 
actual pin connections of the dual in line 
package. 

Instruction Set 

The PACE microprocessor instruction set 
consists of a general purpose mixture of 45 
instruction types in eight classes as shown in 



82 



Table 2: PACE Instruction Set Summary. 
This table lists the mnemonic and a short 
description for all of the PACE instructions. 
For complete functional descriptions and bit 
patterns consult National Semiconductor's 
PACE Technical Description document. 



Mnemonic 



Operation (or meaning) 



Branch Instructions 



Diagrams and information, 
courtesy of National Semi- 
conductor from their PACE 
Technical Description. 



BOC 

JMP 

JMP@ 

JSR 

JSR@ 

RTS 

RTI 

Skip Instructions 

SKNE 

SKG 

SKAZ 

ISZ 

DSZ 

AISZ 



Branch on condition 

Jump 

Jump indirect 

Jump to subroutine 

Jump to subroutine indirect 

Return from subroutine 

Return from interrupt 



Skip if not equal 
Skip if greater 
Skip if And is zero 
increment and skip if zero 
Decrement and skip if zero 
Add immediate, skip if zero 



Memory Data Transfer Instructions 



LD 


Load 


LD@ 


Load indirect 


ST 


Store 


ST@ 


Store indirect 


LSEX 


Load with sign extended 



Memory Data Operate Instructions 



Miscellaneous Instructions 



HALT 


Halt 


SFLG 


Set flag 


PFLG 


Pulse flag 




D15 DI4 D13 D12 Dll D10 D 
[3o] [31 



DOS D07 D06 D05 D04 D03 D02 D01 D00 



rararara^^rararamnmmm 



STFL 

■REQO 

PSIGN 

BITO 

BIT 1 

NREQO 

BIT 2 

CONTIN 

LINK 

IEN 

CARRY 

NSIGN 

OVF 

JC13 



E>* — h- 



AND 


And 




OR 


Or 


JC14 


ADD 


Add 


JC15 


SUBB 


Subtract with borrow 




DECA 


Decimal add 


NADS 


Register 


Data Transfer Instructions 


IDS 


LI 


Load immediate 


ODS 


RCPY 


Register copy 


EXTEND 


RXCH 


Register exchange 




XCHRS 


Exchange register and stack 


BPS 


CFR 


Copy flags into register 


NINIT 


CRF 


Copy register into flags 




PUSH 


Push register onto stack 


NHALT 


PULL 


Pull stack into register 




PUSHF 


Push flags onto stack 




PULLF 


Pull stack into flags 


CLK 
NCLK 


Register Data Operate Instructions 




RADD 


Register add 




RADC 


Register add with carry 




RAND 


Register and 




RXOR 


Register exclusive or 




CAI 


Complement and add immediate 




Shift and Rotate Instructions 




SHL 


Shift left 




SHR 


Shift right 




ROL 


Rotate left 




ROR 


Rotate right 





d E>- 






JUMP 
7 CONDITION 
MULTI- 
PLEXER 



l_. 






INSTRUCTION 
REGISTER 



MICROPROGRAM 

ADDRESS 

GENERATION 



MICROPROGRAM 

ADDRESS 

REGISTER 



MICROPROGRAM 
STORAGE 



CONTROL 
LOGIC 



I/O 

■ DATA 

BUS 



I/O DATA 
BUFFERS 



.J 



TEMP REG 1 
ISCRATCH REGISTERI 



TEMP REG 2 
(SCRATCH REGISTERI 



PROGRAM COUNTER 



10 WORD 
LIFO STACK 




MULTIPHASE 

CLOCK 

GENERATION 



RESULT 
BUS 



STATUS AND CONTROL rLAGS REGISTER 



"1" 

EXIT 
INTO 


F14 


F13 


F12 


F11 


BYTE 


INT 
EN 


LINK 


CRY 


OVF 


IE5 


IE4 


IE3 


IE2 


IE1 


"1" 


J 


0} 

F13 


F12 


{ 


t: 


' \ 


I 




F14 


F11 


INTERRUPT CONTROL 
LOGIC 





OPERAND 
BUS 




I 14| I 161 MSI I 171 - 

NIR5 NIR4 NIR3 NIR2 



Figure I: PACE Microprocessor Functional Block Diagram. This diagram 
shows the major internal sections of the processor, which are reflected in the 
instruction set. The numbered connections refer to the pins of the processor 
package, shown in figure 2. This diagram is reproduced courtesy of National 
Semiconductor from page 2-2 of the PACE Technical Description. 



83 



table 2. Conditional branches are imple- 
mented using the BOC instruction which 
allows testing any one of 16 conditions as 
shown in table 3. Additional testing capa- 
bilities are provided by the skip instructions 
which provide memory and register com- 
parisons without altering data. Memory 



reference instructions use a flexible memory 
addressing scheme which provides three 
floating memory pages and one fixed page of 
256 words (16 bit) each. Figure 3 shows the 
various memory reference instruction for- 
mats used to obtain the four different 
addressing modes. 



Figure 2: PACE Microprocessor Pin Assign- 
ments. Fitting a 16 bit processor's pinout 
into a 40 pin package is a problem: If for 
example separate 16 bit address and data 
lines are used, 32 pins are occupied and only 
8 are left for miscellaneous processor func- 
tions and power. But if only one 16 bit bus 
is used for address and data, with time 
multiplexing of the usage, then a large 
number of pins remain available for miscel- 
laneous uses. National Semiconductor chose 
the latter course of action in the PACE 
design, leaving a large number of externally 
available inputs and outputs including four 
levels of external interrupts, three jump 
condition flags, and control lines. This dia- 
gram is reproduced courtesy of National 
Semiconductor, from page 2-3 of the PACE 
Technical Description. 



Table 3: PACE Branch Conditions. The BOC (branch on condition) 
instruction branches to the effective address if the selected condition is true. 
This table is reproduced courtesy of National Semiconductor, from page B-14 
of the PACE Technical Description. 



Condition Code (cc) 


Mnemonic 


Condition 


0000 


STFL 


Stack Full (contains nine or more words). 


0001 


REQ0 


(AC0) equal to zero (see note 1). 


0010 


PSIGN 


(AC0) has positive sign (see note 2). 


0011 


BIT0 


Bit of AC0 true. 


0100 


BIT1 


Bit 1 of AC0 true. 


0101 


NREQ0 


(AC0) is nonzero (see note 1). 


0110 


BIT2 


Bit 2 of AC0 is true. 


0111 


CONTIN 


CONTIN (continue) Input is true. 


1000 


LINK 


LINK is true. 


1001 


IEN 


IEN is true. 


1010 


CARRY 


CARRY is true. 


1011 


NSIGN 


(AC0) has negative sign (see note 2). 


1100 


OVF 


OVF is true. 


1101 


JC13 


JC13 Input is true 


1110 


JC14 


JC14 Input is true. 


1111 


JC15 


JC15 Input is true. 



DUAL-IN-LINE PACKAGE 



D04 1 


W 


• 


D03 2 






D02 3 






D01 4 






D00 5 






IDS 6 






ODS 7 






NADS 8 






NHALT 9 






CONTIN 10 






JC14 n 






JC15 12 






JC13 13 






NIR5 14 






NIR4 15 






NIR3 16 






NIR2 17 






F11 18 






F12 19 






VSS 20 













40 D05 

39 D06 

38 D07 

37 D08 

36 D09 



35 
34 
33 
32 
31 
30 
29 
28 
27 
26 
25 
24 
23 
22 
21 



D10 

D1 1 

D12 

D13 

D14 

D15 

V GG (-12VI 

BPS 

EXTEND 

NIIMIT 

CLK 

NCLK 

V BB 

F14 

F13 



PIN 



DEFINITION 



CLK, NCLK 



D00 to D15 



True and complemented MOS 
clock input. 

IO MOS data bus lines. 



NOTES: 1. If selected data length is 8 bits, only bits through 7 of AC0 are tested. 
2. Bit 7 is sign bit (instead of bit 15) if selected data length is 8 bits. 



IDS 


Input data strobe, enables exter- 




nal devices to send data to PACE. 


ODS 


Output data strobe, enables exter- 




nal devices to accept data from 




PACE. 


NADS 


Address data strobe, clocks address 




from PACE into ALE. 


EXTEND 


Extended data transfer, increases 




time duration of data IO transfers 




for slow memory or peripherals 




without changing clock frequency. 


N1NIT 


Initialize microprocessor functions. 


CONTIN 


Continue jump condition. 


NHALT 


Control panel halt. 


BPS 


Base page select, selects one of two 




possible base page addressing 




schemes. 


J13to J15 


Jump conditions 1 3 to 15, user 




specified branch condition inputs 




to jump condition multiplexer (see 




table 3). 


F11 to F14 


Flags 11 to 14, status and control 




flag register general purpose control 




flag outputs. 


NIR2-5 


Interrupt requests 2 to 5. 


Vbb 


PACE substrate voltage input. 




derived from Vgg and Vss by STE. 


Vgg 


—12 V supply input. 


Vss 


+5 V supply input. 



84 



Applications 

There is a complete family of support 
chips designed for PACE which are intended 
to interface directly to the microprocessor 
chip. The System Timing Element (STE) 
provides the necessary MOS clock signals 
and V bbo supply voltage for the processor 
chip as well as an optional TTL clock for the 
user's system. Figure 4 shows how the STE 
is connected to the PACE microprocessor 
for a typical application. 

The Bidirectional Transceiver Element 
(BTE) provides single chip, 8 bit input and 
output buffering between the PACE MOS 
input bus lines and TTL devices. Figure 5 
shows how three BTEs are utilized along 
with an STE and PACE chip to assemble a 
system providing a fully multiplexed address 
and data bus with a minimum chip 
configuration. The other two support chips, 
the Address Latch Element (ALE) and the 
Interface Latch Element (ILE), may be 
added for more complex systems as shown 
in the PACE Technical Description available 
from National Semiconductor as publication 
number 4200078A. This book also illus- 
trates a priority encoder, a control panel, 
DMA capabilities, application cards, and 
various applications and features of the 
PACE system along with the information 
contained in this article. 



bits 



15 10 


9 8 


7 


OPERATION CODE 


INDEX (XR) 


DISPLACEMENT (disp) 



Index Field 


Addressing Mode 


Effective Address (EA) 


00 
01 
10 

11 


Base Page 

Program Counter Relative 
AC2 Relative (indexed) 
AC3 Relative (indexed) 


EA = disp 
EA = disp + (PC) 
EA = disp + (AC2) 
EA = disp + (AC3) 


Key: (PC) 
(AC2) 
(AC3) 


= Contents of program counter 
= Contents of AC2 
= Contents of AC3 





Figure 3: Memory Reference Instruction Format. The PACE processor's 
minicomputer-like instruction set has four addressing modes which are 
specified by the index field of an instruction. Addressing can be through an 8 
bit signed or unsigned base page address selection, an 8 bit signed offset 
relative to the program counter, or an 8 bit signed offset relative to registers 
AC2 or AC3. This diagram is reproduced courtesy of National Semicon- 
ductor, from pages 2-1 1 and 2-1 2, PACE Technical Description. 



User Group 

COMPUTE, a National Semiconductor 
sponsored user group for microprocessor 
programmers, users, and technical experts 
publishes a newsletter called The Bit-Bucket. 
They can be contacted at: 

COMPUTE/470 
National Semiconductor Corp 
2900 Semiconductor Dr 
Santa Clara CA 95051 
(408) 732-5000 X7183 

Personal Computing with PACE 

The design of the PACE computer 
is that of a minicomputer. Its instruction 
set presents a conventional minicom- 
puter architecture (with a stack how- 
ever, which was usually unheard of in 
the days of the mini). Looking at the PACE 
architecture is reminiscent of looking at a 
Data General NOVA. For those with a 
strong background in 16 bit minicomputer 
programming, a 16 bit processor like the 
PACE would provide an excellent place to 
take advantage of your present bag of tricks 
to save time while getting oriented. While no 
PACE personal computing kits or finished 
products are presently available (circa June 





EXTERNAL 
+5VDC 
POWER 
SOURCE 














+ 1 






_L 


1 

2 

X1 3 


STE 


24 Q V ss 


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20 
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24 
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PACE 


4.0 1—1 
MHz 1 1 


2§o 

22 V BBO 




T" X2 Q 4 


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20" CLK 


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TTLr ,nr- K( -TTLCLK Q 10 


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FOR USER { TTL CLK* ~11 


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NOTE: — 

V ss , GND, AND V GQ LINES 
SHIELD CLK AND NCLK LINES. 


EXTERNAL 
-12V DC 
POWER 
SOURCE 





Figure 4: The PA CE System Timing Element. In order to make a PA CE work 
without undue engineering inconvenience, National Semiconductor also 
produces the STE chip which is an omnibus multifunction device including 
the master timing source, clock generator and driver, and one of the power 
supplies needed by the chip. The interconnections are shown in this diagram, 
reproduced courtesy of National Semiconductor from page 2-14 of the PACE 
Technical Description. 



85 



SYSTEM 
MEMOHY 



SYSTEM MOS ADDRESS/DATA BUS 



SYSTEM MOS TIMING 
AND CONTROL BUS 



1 — * — t 



A | XI X2 1 



T 



I 



I 



I 



SYSTEM TTL TIMING AND CONTROL BUS 



SYSTEM TTL 
MULTIPLEXED 
ADDRESS/DATA 
BUS 



Figure 5: Minimum Chip Configuration. The minimum configuration for a multiplexed 
addressing and data interface to TTL logic is shown in this block diagram. The blocks labelled 
BTE are "bidirectional transceiver elements, " members of the PACE chip set which are used to 
sense the MOS level outputs of the processor and drive TTL data bus structures, or in the 
opposite direction to convert TTL bus levels into PACE compatible input signals. This diagram 
is reproduced courtesy of National Semiconductor, from page 2-29 of the PACE Technical 
Description. 



1976) for the personal computing market, 
evaluation kits and products like the Pacer 
(see below) will provide a convenient way 



for readers to obtain this 16 bit byte sized 
microprocessor." 



What's 

New? 




So You Want to Keep PACE? 

One way in which to evaluate and use 
PACE is to employ a system known as Pacer, 
which is manufactured by Project Support 
Engineering, 750 N Mary, Sunnyvale CA 
94086. This product, which came our way 
recently for evaluation, is available either in 
kit, semi-kit or assembled versions, with a 
retail price in the $.1000 range, more or less 
depending upon specific options chosen. 
Pacer 1H is totally unassembled, Pacer 2H is 
completely assembled, tested and burned in, 
and Pacer 3H is unassembled except for the 



Photo I ; When assembled, 
Pacer is a neat desk top 
package with a molded 
plastic case and calculator 
style keyboard. The dot 
matrix alphanumeric dis- 
play is here shown as it 
appears when the Pacer is 
initialized by pressing the 
INT button. 



tested and burned in logic cards. The pic- 
tures accompanying this description are of a 
Pacer 3H version which we recently 
assembled. 

The basic unit as it comes (see photos 
1-3) in its simplest version contains a mother- 
board with raw power supply, three main 
logic boards with on board regulators, and a 
control panel assembly. The three boards in 
the configuration shown in the photos are: 

• The Pacer CPU board with the PACE 
processor, buffering elements, address 
decoding for system addresses, and 
clock ogic. This is the board at the 
right in photo 3. 

• Pacer control board which contains 
the Pacer executive ROM, executive 
programmable random access memory 
and initialization logic. This is the 
center board of the three boards 
shown in photo 3. 

• Pacer memory board which contains 
slots for 1 K by 16 of 2112 memory 
chips and 512 by 16 bits of MM5204 
programmable read only memory 
chips. (The unit comes with 256 words 
by 16 bits of programmable memory 
and no user ROMs.) 



Also included is the Pacer control card, 
shown at the top of photo 2 with its ribbon 
cable running down to the motherboard. 
This control card contains the logic and 
switches needed to support the 8 digits of 
alphanumeric display and key board 
functions. 

What Can You Do with Pacer as It Comes? 

In the minimal configuration, you receive 
a powerful 16 bit PACE processor which 
basically resembles a Data General NOVA 
[see Robert Baker's article] . The executive 
features of this minimal configuration allow 
the user to enter and debug machine 
language programs for PACE, using a set of 
commands much more flexible and sophis- 
ticated than the toggle switches of an earlier 
era. These built-in checkout and debugging 
features include: 

Commands to set, modify and examine 
the hexadecimal contents of: 
Program counter 
Accumulators 0, 1 , 2 or 3 
Stack locations through 9 
Flag register 

Any memory location selected 
Any one of several break point ad- 
dresses labelled to 9 
Value and mask fields used for search 
operations 
Extended command functions include: 
Hexadecimal calculator: add, subtract 
display result 

Memory search for value, with op- 
tional mask 

Run, restart, initialize, single step the 
processor. 
For initial checkout of machine language 
programs, this is more than adequate. The 
bus structure is completely documented in 
the manuals, and will prove quite expand- 
able using prototyping boards which are also 
available from the manufacturer. The Pacer 
has 8 slots available on its backplane after 
the minimum three cards are inserted. 

The Number One Expansion 
to Make to Pacer 

One additional board came with our 
Pacer, one which both exhibits its expand- 
ability and will prove quite useful to anyone 
wishing to do software development. This is 
the optional PACE 2 printed circuit card. 
This addition to the system contains a 
parallel Teletype current loop interface, an 
RS-232 interface, and the PACE 2 read only 
memories. 

The read only memories are the key to 
the usefulness of PACE 2. This board has a 
simple assembler (and dissassembler) pro- 



Photo 2: Removing four 
screws and tilting back the 
cover of the assembly 
shows the interior of the 
machine: a motherboard 
with raw power supply 
(unregulated voltages for 
on board regulators) and 
positions for eight boards 
in addition to the three 
boards of the basic Pacer 
kits. The control panel 
board and its ribbon cable 
connector are shown 
mounted on the cover near 
the top of the picture. 



gram and powerful debugging executive, 
which takes over the system instead of the 
original read only memory executive of 
Pacer's minimal configuration. With the 
addition of PACE 2, the original front panel 
is essentially ignored with the exception of 
the restart and initialize buttons. The 
address space locations of the PACE 2 
executive and assembler are contained in an 
8 K block of memory which is completely 
protected by hardware in the standard 
boards as they arrive. (If desired, it is of 
course possible to defeat this feature 
through hardware modifications suggested 
by the logic diagrams supplied.) The hard- 
ware lockout involves write protection and 
automatic return of hexadecimal FFFF 
values when referencing the protected loca- 
tions. In the words of the PACE 2 users 
guide, "As a result PACE 2 will remain 
operable even after a massive failure of the 
user's program . . . . " 

The memory editing commands of PACE 
2 allow the user to display and set memory 
contents from the terminal using ASCII, 
signed decimal, unsigned decimal or hexa- 
decimal conversions. Memory listing com- 
mands allow the user to get an assembly 
language formatted output with symbolic 
references and absolute hexadecimal, sort of 
a built-in "disassembler" program. De- 
bugging features include a sophisticated 
memory snap feature tied to break points, 
snap points or single step execution. This 
feature allows selected contents of registers, 
or memory to be dumped when execution 





Photo 3: This detailed 
view shows the three 
boards of the basic Pacer 
kit product. The processor 
itself is the large chip on 
the rightmost board of the 
three shown. In the Pacer 
shown here, additional 
sockets and card guides 
which came with the kit 
are ready for the PA CE 2 
board and for prototyping 
boards. 



87 



reaches the desired points. As an assembler, 
the PACE 2 module in its "alter" command 
mode allows one to insert symbolic assembly 
language statements to define memory 
content word by word. The symbol table 
capacity built into the system when PACE 2 
arrives is 26 symbols. By adding memory it 
is possible to extend the symbol table to a 
limit of 121 symbols. Each symbol has a 16 
bit address value associated with it. 

By putting the PACE 2 board together 
with the Pacer, the result will be an excellent 
combination of software development tools 
and expandable hardware which will prove 
attractive both to the engineer using PACE 
in systems work, and to an individual who 
wants a prepackaged 16 bit computer with 
good systems software support at a mod- 
erate price. For further information contact 
Project Support Engineering." 



The MOSTEK MK5085N/MK5086N 
Integrated Tone Dialers 

This product provides the electronics 
needed to simply implement remote access 
via telephone to computer using a miniature 
hand held terminal which can be used with 
any telephone. In such a system, the com- 
puter end listens to audio from one of a 
number of Bell approved electronic tape 
answering service devices commercially 
available, and standard touch tone signals are 
sent to the computer after dialing into its 
phone port. This MOSTEK chip, built into a 
tiny case using the circuit described in the 
MOSTEK documentation, and reproduced 
here, is used to drive the remote telephone 
through a speaker you build into the remote 
package. The computer end must have a 



"Figure J" excerpted from MOSTEK's April 1976 data sheet for the 
Integrated Tone Dialer MK5085N/MK5086N. 



DTMF TONE GENERATOR - Fixed Supply Operation 
FIGURE J 




I^ZXTT 



M K 50S5 
MK508G 



3579545 fnhz 




I VOLUME CONTROL 

' L _ _ _ DRiviNGSPEAKER S Z*?1 

TONE OUTPUT TJ 



Rl value is dependent upon impedence and 
^ gain of following stage. Typical values when 
used to drive microphone inputs are 



IK - Carton type mics 

50K - Low impedance dynar 

TOOK - High impedance dyn. 



hardware or software tone decoder and a 
software command interpreter to carry out 
your remote instructions; for reliability, 
such software should be stored in ROM 
against the possibility of power failures. 
Eventually, commercially produced "uni- 
versal signallers" using this technology 
should be available in calculator style 
packages, but until then you'll have to make 
your own. Contact MOSTEK at 1215 W 
Crosby Rd, Carrollton TX 75006." 



SCELBAL, an 8008/8080 High 
Level Language 

In our June 1976 issue [page 82} , we had 
a product description article on the SCEL- 
BAL language, implemented for the 8008 
and 8080 processors by Nat Wadsworth and 
Mark Arnold. Since that time, the language 
design has been published in detail in 
SCELBI Computer Consulting's book of 
documentation, available at $49 postpaid. 

The documentation is very complete, and 
expresses Nat Wadsworth's excellent philos- 
ophy of giving all the information possible 
about the subject at a reasonable price. 
Quoting from the introduction: 

. ... It was known at the start that the 
program could not be developed to 
satisfy every potential user. Nobody 
has a system with that much memory 
available! Care was taken to provide a 
good fundamental selection of syntax 
statements and functions in the lan- 
guage. From that point, backed by the 
descriptions of the program's organiza- 
tion, general flow charts, and highly 
commented listings provided in this 
publication, it is felt that the user will 
be equipped to add extended capa- 
bilities depending on memory avail- 
able, or willingness to sacrifice de- 
scribed functions. 

.... 777e extra measure of providing 
the information so that the user may 
go further if desired is the funda- 
mental premise behind this publication. 

In the words of the sage, "right on!". This 
368 page book contains an overall program 
logic description of the interpreter spread 
over the first 11 chapters, totalling some 162 
pages. Of these pages, 51 alone are spent on 
chapter 6 which describes the statement 
interpretation logic of the program with 
flow charts, symbolic (commented) as- 
sembly language code and verbal descrip- 
tions. In the chapter 12, the detailed as- 
sembly of SCELBAL for an 8008 is given, 



88 



and in chapter 13 the same information is 
repeated for an 8080 assembly. The detailed 
assemblies give absolute code for the pro- 
gram in octal, beginning at origin 01/000 for 
either version. The total memory required is 
the same in either version since the code is 
written for an 8008 and simply reassembled 
for the 8080 version. The actual program 
code covered by the assembly in either case 
is approximately 11.5 K bytes. The listings 
together occupy 164 pages. Chapter 14 
contains operating instructions and chapter 
15 contains "Suggestions for Program 
Tinkerers." The book is concluded with a 
"SCELBAL Labels Reference List" (ie: the 
symbol table of the assemblies), and several 
notes pages for patches. The final sheet of 
the book is a cardboard sheet with a 
personal "SCELBAL Registration Card," a 
change of address card, and a pocket ref- 
erence card. Purchasers of SCELBAL return 
the registration card in order to be placed 
upon the update list for errors and patches 
(several of which are already present on the 
notes pages). 

SCELBI is to be commended for this 
example of complete and thorough docu- 
mentation for a high level language product. 
It will prove a useful volume for any person 
interested in a high level language like 
BASIC which has options for customization 
and extension. ■ 




The Visible Character Buffer Memory is Here 

A firm called Matrox Electronic Systems, 
of Montreal, Quebec, recently came out with 
a unique line of inexpensive video display 
generators in "black box" module form. One 
of the products which will be of immediate 
interest to BYTE readers is the new 
MTX-1632 video display memory, a unit 
which interfaces to a three state bidirec- 
tional processor bus as if it were 512 bytes 
of programmable memory, and continuously 
generates a 16 line by 32 character upper 
and lower case ASCII display in the form of 
a standard video signal output. The unit is 
priced at only $198 in single quantities, and 
has a memory access time of 650 ns. 

The three state bidirectional bus interface 
has specifications compatible with standard 
bus drivers such as the National Semicon- 
ductor DM8833 and similar chips, so with 
the addition of address decoding logic it 
should plug in to most systems with bidirec- 
tional buffered data buses. For readers using 
the Altair, IMSAI, Polymorphics, or Digital 
Group systems, some interfacing logic will 
be required to split the bidirectional bus into 
the "in" and "out" sections required by 
these systems. 



REVOLUTIONARY! 

MTX-1632 
..«* J2SI2 «C R OCOHPUT« 



srartr^iE u „ MftTR 0X- 

» Organized as 512XB R J! efr esh 
» Requires "oe *%£ 7 X9 *ff * 
128 character * D dtsp i a y fiei 
Generates ibXdc supp ly 



LEOTB°H° ME 



The unit comes in one form, a completely 
assembled and tested module with a video 
output drive capability claimed sufficient for 
25 standard television monitors to be wired 
in parallel. Contact Matrox at POB 56, 
Ahuntsic Stn, Montreal, Quebec CANADA 
H3L3N5, (514) 481-6838. ■ 




89 




Homebrewery vs the 



Software Priesthood 



Mike Wilber 
920 Dennis Dr 
Palo Alto CA 94303 

David Fylstra 

PO Box 10051 
Stanford CA 94305 



The movement of com- 
puters into people's homes 
makes it important for us 
personal systems users to 
focus our efforts towards 
having computers do what 
we want them to do rather 
than what someone else 
has blessed for us. 



The movement towards personalized and 
individualized computing is an important 
threat to the aura of mystery that has 
surrounded the computer for its entire his- 
tory. Until now, computers were understood 
by only a select few who were revered 
almost as befitted the status of priesthood. 
The arts of designing and programming 
computers have long been regarded as sacred 
knowledge beyond the reach of the nonspe- 
cialist. Indeed, the journeymen of the trade 
have protected their privileged position by 
keeping their knowledge to themselves. 
These high priests and acolytes of the holy 
alliance of logicians (HAL) have dominated 
the field so far. 

The movement of computers into peo- 
ple's homes makes it important for us 
personal systems users to focus our efforts 
toward having computers do what we want 
them to do rather than what someone else 
has blessed for us. If personal computing 
users freely share their hard-won informa- 
tion and even their programs, then this 
community of users can become quite adept 
at bending their computers to their own 
needs and wants. 

When computers move into people's 
homes, it would be most unfortunate if they 
were merely black boxes whose internal 
workings remained the exclusive province of 
the priests. It is fine to use them as black 
boxes as long as they do what you want, but 



the computer's owner should be able to 
modify its behavior to suit merely personal 
preferences. That is, computer literacy 
should be widespread. Now it is not neces- 
sary that everybody be a programmer, but 
the potential should be there. This under- 
standing must be removed from the private 
reserve of the select few just because com- 
puters will be in the hands of the many. 

Freely available software is perhaps the 
key to the independence of the homebrewer. 

There are several indications that personal 
computing users are likely to be highly 
motivated to generate freely available soft- 
ware. One can be found in the amateur radio 
community: Hams have a long tradition of 
freely sharing their feats of engineering. In 
fact, it is quite natural to be proud of one's 
accomplishments, and that pride finds quite 
natural expression in telling all the details to 
anybody showing the slightest signs of 
interest. Already there are some signs that 
computer hobbyists have similar pride in 
their software achievements. Dr Dobb's 
Journal contains several examples of people 
contributing adaptations and extensions to 
Tiny BASIC. The mode of software develop- 
ment is likely to follow the example of 
program development among the world of 
paid programmers. For a while, people will 
contribute incremental improvements to a 
program (or a concept). During this first half 
of the cycle, the program becomes progres- 
sively more powerful and progressively 
messier until it is quite hard to understand 
or modify. Finally, somebody gives up in 
disgust and rewrites the program in the 
marvelously clear way that had been growing 
increasingly conspicuous by its absence. 
Then another cycle starts, but its starting 
place is far more advanced than the previous 
cycle had reached. 



90 



". . .these are, and of right ought to be, Free 
and Independent. ..." 

— John Hancock, et al 



Personal computing people stand to be 
largely independent of the priesthood be- 
cause they are strikingly sophisticated and 
because they freely share their ideas. A very 
good example of both these traits can be 
found in the nearly spontaneous generation 
of Tiny BASIC through the medium of the 
People's Computer Company and Dr Dobb's 
journal of Computer Calisthenics and Ortho- 
dontia. One issue published some rough 
design notes for a machine independent Tiny 
BASIC, but that was only the beginning. The 
next few issues published refinements on the 
design and later ones included an implemen- 
tation in an interpretive language and then 
both octal and annotated source programs 
realizing the interpreter and the entire sys- 
tem in 3 K of 8080 code. To top it off, the 
whole project was done by far-flung indi- 
viduals in less than a year. 

While Tiny BASIC is a very striking 
example of what amateurs can do when they 
work together, we cannot afford to ignore 
its extreme dependence on good fortune to 
bring it to pass. Your own copy of BYTE 
magazine is another example; it is the result 
of one man's frustration at making his own 
computer work and his desire to let others 
profit by his experience. We've been very 
lucky to have a few people with high ideals 
to point the way for us, but we would be ill 
advised to depend on having these fortunate 
circumstances continue. The time is ripe for 
the community of personal computing 
enthusiasts to start thinking seriously about 
supplying its own steam to back up the 
energies put out by a few people with strong 
motivations to help launch the personal 
computing movement. It's launched now, 
and we have to provide the impetus and 
direction to make sure it develops in a way 
beneficial to the community at large. 

A good example of a means to distribute 
software which divides the effort fairly and 
in a way nobody seems to mind is the 
software exchange of the Homebrew Com- 
puter Club in the San Francisco Bay Area. 
At each meeting (every two weeks) there is a 
table covered with paper tapes of programs 
contributed by all and sundry. Anybody is 
welcome to take any tape at all, subject only 
to the proviso that each copy taken from 
one meeting be replaced by at least one 





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91 




Software exchange is a 
two way street: He or she 
who uses an application or 
system's program from a 
community library is as- 
sumed to be willing and 
able to provide programs 
of equivalent value for 
others to use. 



copy at the next meeting. A few cautions, 
however, must be repeated every few meet- 
ings: that people label the tapes they bring 
back, that they take reasonable steps to 
ensure the accuracy of their copies and that 
they only contribute software with the 
author's consent. Homebrewers have good 
intentions but still need occasional re- 
minders to keep them from getting careless. 

It is most unfortunate that some people 
give free distribution to software against the 
author's wishes. In fact it's usually illegal, 
and anyone caught could face a heavy fine 
because the crime is new enough that many 
think prominent examples should be offered 
to reduce its frequency. Until that lucky 
day, the main people being deterred are the 
people who have contributed the software 
that has immeasurably helped the whole 
hobbyist movement get started. Even though 
we have a tremendous potential for genera- 
ting our own software, we still owe a 
tremendous debt (of gratitude besides the 
money) to those who have brought us Altair 
BASIC and 6800 BASIC, and who may have 
enough faith in us to bring us APL and some 
truly groovy text editors. Freely exchanged 
software should be truly free and untainted 
by ripoffs or by the appearance of ripoffs. 

The extreme ease of software theft could 
present a real barrier to free interchange of 
good software because many valuable people 
could understandably be reluctant to be- 
come very deeply involved in a forum where 
such ripoffs are commonplace. Theft is so 
much easier with software than with hard- 



ware because software has two distinctive 
properties: 

• A buyer cannot evaluate its benefit 
without extensive testing and use. 

• The elementary operation in moving 
software is not to transport one copy 
but to generate another copy. 

Another danger threatens free distribution 
of free software, and for some of the same 
reasons, a scarcity of documentation which 
is all too common in software. The tempta- 
tion is strong: Somebody developing it 
understands it well and is concentrating on 
getting it to work at all and usually prefers 
not to be distracted by efforts to make it 
comprehensible to others. On the other 
hand, the task of documentation can easily 
take as much effort as the development 
itself. However, documentation is crucial to 
the value of a piece of software. Un- 
documented software is very hard to use and 
even harder to modify. We have no good 
solutions to either of these problems. The 
only thing to do is to repeatedly urge people 
to be mindful of the problems and to 
broaden their perspectives beyond the gains 
of the short term. 

Telecommunications and the Community 
Information Exchange 

Enthusiasts in this field can share soft- 
ware right now by banding together into 
clubs, but that medium limits sharing to 
small groups of people who live near one 
another. With telecommunications, people 
can share their programs with others living at 
long distances from one another. One vital 
ingredient to such remote communication is 
the ordinary telephone, which works 
wonders at spanning long distances between 
people. Telephones can have the same bene- 
fit for computers, if they are equipped with 
modems, which handle the translation be- 
tween a computer's digital signals and the 
audio signals the telephone can handle. 
Then, one person can call another, and they 
can use that same call to connect their 
computers; one computer can run a special 
program to copy data from a cassette or 
memory to the phone line; and the other can 
run another special program to copy the 
information from the phone line onto its 
own cassette. Of course, the data being 
copied will likely be some program the two 
parties wish to share; and presto, you have 
an instance of software sharing at a long 
distance. 

While that kind of person to person 
exchange is quite effective, it leaves room 
for improvement in several respects. It re- 
quires very close coordination between the 



92 



two parties, and it requires one phone call 
for each interchange of data. However, there 
is another possible mechanism, which can 
permit widely scattered users to com- 
municate far more freely and with much 
looser coordination while improving on the 
economy of phone line usage. That would be 
a sort of "Community Information Ex- 
change," a computer that would be con- 
tinually prepared to automatically answer 
the telephone and would expect a computer 
to be placing the call. It would be located 
where a number of individuals (for example 
members of a local club) could reach it with 
a local call; it would provide bulk storage 
facilities, and it would accept commands in a 
very concise, well understood format from 
the computer which had called it. Then one 
subscriber could leave a program in the bulk 
storage and invite all other subscribers to 
that Community Information Exchange to 
copy it to their own systems at their leisure. 
This is a very powerful means of broad- 
casting software among a local community, 
but it has implicit in it a means of broad- 
casting opinions and news too. It requires a 
means of transmitting plain English text 
between people just so the people will know 
which programs they can or might wish to 
communicate to their computers. Once the 



individual subscribers can communicate 
words among themselves, they can com- 
municate much more than news about the 
latest programs available and how to use 
them. They can also tell one another about 
the problems they are having with some 
program they recently picked up or even 
about problems they are having with some 
hardware they recently bought. The com- 
puter community can find a great deal of 
strength in freely sharing that kind of 
information, in addition to sharing their 
programs. Free communication of informa- 
tion of all types can greatly enhance the 
community's resistance to inferior products, 
and acceptance of superior products. 

The Community Information Exchange is 
not limited to the local communication 
described thus far. In the dead of night, 
when telephone traffic is reduced and the 
transcontinental rates are low, a CIE in one 
locality can call a CIE in another locality. 
Then they can send programs and other data 
back and forth. Of course, they have to 
know just what should be sent where, and 
they could be told by their subscribers. The 
commands they will accept from their sub- 
scribers could direct them to copy a file to 
or from some remote CIE. Nor is it neces- 
sary for a CIE to directly call another to 



Imagine a Community In- 
formation Exchange, com- 
plete with telecommunica- 
tions access ports, mass 
storage and an accounting 
algorithm to keep track of 
operating expenses at- 
tributed to each user's 
activities. 



NOTE: The term "Commu- 
nity Information Exchange" 
was inspired by Michael Ross- 
man. 



MODEL CC-7 SPECIFICATIONS: 

A. Recording Mode: Tape saturation binary. 
This is not an FSK or Home type recorder. 
No voice capability. No Modem. (NRZ) 

B. Two channels (1) Clock, (2) Data. OR, Two 
data channels providing four (4) tracks on 
the cassette. Can also be used for Bi-Phase, 
Manchester codes etc. 

C. Inputs: Two (2). Will accept TTY, TTL or 
RS 232 digital. 

D. Outputs: Two (21. Board changeable from 
RS 232 to TTY or TTL digital. 

E. Runs at 2400 baud or less. Synchronous or 
Asynchronous. Runs at 4800 baud or less. 
Synchronous or Asynchronous. Runs at 
3.1 "/sec. Speed regulation ± .5% 

F. Compatability : Will interface any computer 
or terminal with a serial I/O. (Altair, Sphere, 
M6800, PDP8, LSI 1 1, IMSAI, etc. 

G. Other Data: (110-220 V), (50-60 Hz); 3 
Watts total; UL listed 955D; three wire line 
cord; on/off switch; audio, meter and light 
operation monitors. Remote control of mo- 
tor optional. Four foot, seven conductor 
remoting cable provided. Uses high grade 
audio cassettes. 

H. Warrantee: 90 days. All units tested at 300 
and 2400 baud before shipment. Test cas- 
sette with 8080 software program included. 
This cassette was recorded and played back 
during quality control. 

ALSO AVAILABLE: MODEL CC-7A with vari- 
able speed motor. Uses electronic speed control 
at 4"/sec. or less. Regulation i .2% 
Runs at 4800 baud Synchronous or Asynchro- 
nous without external circuitry. 
Recommended for quantity users who ex- 
change tapes. Comes with speed adjusting tape 
to set exact speed. 



DIGITAL DATA RECORDER $149.95 
FOR COMPUTER or TELETYPE USE 

Any baud rate up to 4800 




Uses the industry standard tape satura- 
tion method to beat all FSK systems ten to 
one. No modems or FSK decoders required. 
Loads 8K of memory in 17 seconds. This 
recorder, using high grade audio cassettes, 
enables you to back up your computer by 
loading and dumping programs and data fast 
as you go, thus enabling you to get by with 
less memory. Can be software controlled. 



Model CC7 . 
Model CC7A . 



.$149.95 
..$169.95 



NATIONAL multiplex 



CORPORATION 



NEW - 8080 I/O BOARD with ROM. 
Permanent Relief from "Bootstrap Chafing" 

This is our new "turnkey" board. Turn on 
your Altair or Imsai and go (No Bootstrap- 
ping). Controls one terminal (CRTorTTY) 
and one or two cassettes with all programs 
in ROM. Enables you to turn on and just 
type in what you want done. Loads, Dumps, 
Examines, Modifies from the keyboard in 
Hex. Loads Octal. For the cassettes, it is a 
fully software controlled Load and Dump at 
the touch of a key. Even loads MITS Basic. 
Ends "Bootstrap Chafe" forever. Uses 512 
bytes of ROM, one UART for the terminal 
and one USART for the Cassettes. Our 
orders are backing upon this one. No. 2SIO 
(R) 

Kit form $140. — Fully assembled and 
tested $170.00 

Send Two Dollars for Cassette Operating 

and Maintenance Manual with Schematics 

and Software control data for 8080 and 

6800. Includes Manual on 

I/O board above. Postpaid 

Master Charge & BankAmericard accepted. 

On orders for Recorders and Kits please add 
$2.00 for Shipping & Handling. 
(N.J. Residents add 5% Sales Tax) 

3474 Rand Avenue, Box 288 
South Plainfield, New Jersey 07080 
(201) 561-3600 



93 




have access to its file storage. Instead, 
commands and data could be relayed from 
one CIE to another until they finally reach 
their destination. Then, many isolated CIEs 
would behave like a vast network capable of 
transmitting software across the country 
overnight. 

We are describing a communication net- 
work which can be very effective and which 
is highly decentralized. In fact, this decen- 
tralization is crucial to its effectiveness in 
promoting free communication between 
individual computer people. For example, 
computer manufacturers now organize their 
customers into user groups in order to 
provide a forum for communication of ideas 
and programs among their users. Most com- 
munication is channeled through publica- 
tions controlled by the manufacturer, how- 
ever; and this all too often results in the 
encouragement of software and viewpoints 
which are consistent with those of the 
manufacturer. On the other hand, it is not 
necessary to use a centralized forum to 
encourage people who need it: most of that 
interaction is on a person to person basis in 
almost any group. 

All well and good, you might say, but just 
how does the personal computing user com- 
pare with the journeyman programmer? 
Well, the computer amateurs live in a world 
in which wholesale copying of programs is 
nearly inevitable. Actually, that represents a 



healthy trend in two ways: the person using 
the copy benefits by its availability; and the 
program's originator benefits by having 
helped spread a good example of the pro- 
grammer's art. Of course, such freely ex- 
changed software may well be worthless at 
best. That does seem a minor penalty, 
though, for all the advantages that stand to 
be gained by ready availability. That is one 
example of the difference between the two 
kinds of programmers. That is, a functioning 
program is required of the professional, 
while it is merely desired by the amateur 
user who figures he or she will have to patch 
and customize anyway. Someone paid to 
write a program has to make it do what the 
client wants; a personal computing user has 
only personal preferences to satisfy. Some- 
body paying for a program has a right to 
expect that it will be reasonably efficient in 
order to conserve the money spent on 
computer time, while your patience is a 
much stronger constraint for you than the 
cost of your computer's time. Somebody 
paying for a program is quite likely to need 
the documentation oriented toward people 
unskilled in the technicalities, while fellow 
enthusiasts won't need to have all the details 
explained to them. Finally, deadlines are 
quite firm in the commercial world but of 
considerably less importance among ama- 
teurs (except for those who fill magazines 
once a month! . . . CH/. 

While the priests who market the old time 
software religion can help the personal sys- 
tems user, such users should be mindful of 
the benefits to be gained from a healthy 
measure of independence. If you can get 
your hands on the symbolic form of freely 
exchanged software, you can revise it to suit 
your own needs. That's considerably easier 
than trying to convince somebody else who 
supplies a high priced package to make your 
favorite changes, especially since the other 
person may differ from you in values, 
priorities and notions of demand. For the 
traditionalist software source, a request from 
a single person could easily seem to repre- 
sent too narrow an interest to motivate a 
change or patch. If program source listings 
are distributed freely and nearly every user 
has the requisite skills to make patches, then 
the person wanting something changed will 
probably be the person making the change. 
Of course, the end result is nearly the best of 
all possible worlds: Your home computer 
will do what you want it to do, and it will 
do it in the way you want it done. It will not 
do what somebody else decided it was 
reasonable for you to want it to do and in a 
way that it was convenient for somebody 
else to have it done." 



94 



Mt~r P- 



J*L. 



■UT- 



./ *L*. « 






THAI'S "HAPPY 6lJ?THDAV" 
IN NORSE CODE! 



ft/*/ ~w*.V~ 



«.*/ 




pv* 



Networking, Anyone? 

Walter Banks of the Computer Communi- 
cations Network Group, University of 
Waterloo, Waterloo, Ontario, CANADA N2L 
3GI, is interested in talking to radio 
amateurs and computer people interested in 
organizing and promoting computer tele- 
communications networks for amateur 
experimental use. The definition of a com- 
munications software discipline modelled 
after existing commercial and academic 
digital networks would be one goal of such 
activity. Such network activity could be 
supported "for free" on the radio bands 
using the OSCAR synchronous satellite 
when it gets launched, or using the dial-up 
capabilities of the phone network at the 
usual Bell rates for long distance calls. Walter 
can be reached by phone at (519) 885-1 21 1 , 
extension 2847." 




What's Coming Up in BYTE 



II 




In the November BYTE, you'll find an article by John Deres of Southwest 
Technical Products Corporation, describing in detail the circuit and operation 
of the new GT-61 graphics display generator product which Southwest 
manufactures. Included in John's article is a 6800 program which is used to 
transfer stored images from the processor's memory to the display generator's 
memory through a parallel data port. One example given in John's article is 
the data needed to produce this display on the screen. Also scheduled for 
November are an article on APL by Mark Arnold, and an article on how to 
homebrew a 256 by 256 point array display interface written by Thomas R 
Buschbach." 



4Kx8 Static Memories 
MB-1 Mk-8 board, 1 usee 2102 or eq. 
PC Board. .322 Kit $100 

MB-2 Altair 8800 or IMSAI compatible 
switched address and wait cycles. 
PC Board. . $25 Kit (1 usee) . . $112 
Kit (91L02Aor21L02-1) $132 

MB-4 Improved MB-2 designed for 8K 
"piggy-back" without cutting traces. 

PC Board $ 30 

Kit 4K 0.5 usee $137 

Kit 8K 0.5 usee $209 

MB-3 1702A's EROMs, Altair 8800 & 
Imsai 8080 compatible switched address 
& wait cycles. 2K may be expanded to 
4K. Kit less Proms . $ 65 
2K kit . . $145 4K kit $225 



I/O Boards 
1/0-1 8 bit parallel input & output ports, 
common address decoding jumper 
selected, Altair 8800 plug compatible. 
Kit $42 PC Board only. .$25 

I/0-2 I/O for 8800, 2 ports committed, 

pads of 3 more, other pads for EROMs 

UART, etc. 

Kit . . . $47.50 PC Board only. . $25 

Misc. 

Altair compatible mother board 

15 sockets 11"x11V4" $40 

Altair extender board $ 8 

100 pin WW sockets .125" 

centers $ 6 

2102's | lusec | 0.65usec 0.5usec 



ea. 
32 



$ 1.95 
$59.00 



$ 2.25 
$68.00 



$ 2.50 
$76.00 



1702A* 


$10.00 


8223 


$3.00 


2101 


$ 4.50 


MM5320 


$5.95 


2111-1 


$ 4.50 


8212 


$5.00 


2111-1 


$ 4.50 


8131 


$2.80 


91 L02A 


$ 2.55 


MM5262 


$2.00 


32 ea. 


$ 2.40 


1103 


$1.25 


Programming send H 


ex List 


$5.00 


AY5-1013 Uart 




$8.00 


All kits by Solid State Music 





Please send for complete list of products 
and ICs. 

MIKOS 

419 Portofino Dr. 
San Carlos, Calif. 94070 

Check or money order only. Calif, residents 6% tax. All 
orders postpaid in US. All devices tested prior to sale. 
Money back 30 day Guarantee. $10 min. order. Prices 
subject to change without notice. 



95 



Classified Ads for Individuals and Clubs 



Headers who have equip- 
ment, software or other items 
to buy, sell or swap should 
send in a clearly typed notice 
to that effect. To be consider- 
ed for publication, an adver- 
tisement should be clearly 
non-commercial, 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 lim- 
ited to 100 words or less. 
Notices can be accepted from 
individuals or bona fide com- 
puter users clubs only. We can 
engage in no correspondence 
on these and your confirma- 
tion of placement is appear- 
ance in an issue of BYTE.* 



HELP! I need schematic & information on 3501 A 
Asciscope S/N 14 by LEAR-SIEGLER. Will give 
almost anything to borrow, reproduce, or even 
glimpse. Emile Alline, 1119 Penn, Slidell LA 
70458. 



FOR SALE: KSR-33s, I have a limited number of 
KSR-33s on stands. We have checked them out on 
an Altair 8800 and they work like champs. S495 
each while they last. Boyd Martin, 5130 Melvin Av, 
Tarzana CA 91356 eves and weekends, (213) 
345-0903. 

FOR SALE: Digital tape cassette transports, WIFE 
model 250, outdated but new. Andruss Peskin 
Corp, POB 268, Natick MA 01760, (617) 
653-3919. 

FOR SALE: Disk controller, asking $800 or best 
offer, worth better than $2,600. IBM 2841 disk 
controller model 1 dual channel, controls up to 8 
drives, power supplies, 4 K RAM, all cables and 
manuals available, maintenance available from 
IBM. Call Pete Arnett at (305) 671-5631 after 5 
PM EST or write 7739 Liverpool, Orlando FL 
32807. 

FOR SALE: TVT-II (SWTP CT-1024), complete 
with SWTP power supply, manual cursor control 
board, parallel interface board, all cables and 
documentation. Includes wiring changes to make 
64 characters per line. All ICs in sockets. Guar- 
anteed working cond, $175. Also have MITS 
expander card (no sockets or card guides) $15. W 
W Crider, 4011 Oak Hill Dr, College Park GA 
30337, (404) 767-6402. 

SWAP: Have first 8 issues of BYTE. Want ham 
radio or electronics magazines. FREE: Schematic 
& service data for almost any radio receiver or TV 
set. Make and model number a must; approx age, # 
of tubes, description helpful. Legal size SASE 
appreciated. Donald Erickson, 6059-K Essex St, 
Riverside CA 92504, (714) 687-5910. 

FOR SALE: FLEXOWRITER Model SFD. Excel- 
lent condition. Has 8 level reader and punch, $300 
or trade for TVT-I or TVT-II. Call or write; 
William Dawson, 316 21st St, Apt 4, VA Beach 
VA 23451, (804) 422-5921. 

WANTED TO BUY: Video terminal (such as 
Sanders model 720 but any type would do) at a 
very reasonable cost. If desired, I would swap for 
my Busicom digital desktop calculator with 14 
digit readout and memory. This is a very early 
digital calculator but is in good operating condi- 
tion. Either way, tell me what you have. Rich 
Nicewonger, 24 Rosewood Rd, Edison NJ 08817. 

FOR SALE: Disk drive, IBM 2311 type, 7.25 
million bytes. Almost new, manuals and documen- 
tation available. Asking $750. P Arnett, 1730 S 
Bumby, Orlando FL 32806. 

CLEANING HOUSE-lf you want a list of items 
for sale, send SASE to Bob Baker, 15 Windsor Dr, 
Atco NJ 08004. 




FOR SALE: Three 4K Altair RAM boards @ 
$180. Assembled, tested, excellent cond; memory 
ICs in sockets, less 100 pin edge connector, 
postpaid. One 1 K static RAM board, also Altair. 
As above $100. John Martin, 808 Day St, Fair- 
mont MN 56031. 

FOR SALE: Paper Tape Splices — prepunched for 
any kind of 8 channel tapes, $3.50 per 100, 
postpaid. H Corbin, 11704 Ibsen Dr, Rockville MD 
20852. 

WANTED: Automatic card reader for demonstra- 
tion project in the New York City Public School 
System. Please call: (212) 852-2957 or write: Alex 
Aderer, 1 66 Bergen St, Brooklyn NY 11217. 

FOR SALE: Altair 8800 system w/ 8 K memory, 
88SIO interface, 8 K BASIC complete and ready to 
run. $950. Also SWTP CT-1024 terminal complete 
with case $300 and Sanyo Monitor $150. Entire 
system with manuals guaranteed $1,400. D Smith, 
(714) 993-9939, Fullerton CA. 

WANTED: MOS KIM-1 or OSI series 400 system, 
also Tl SR-52. Joe Torzewski 51625 Chestnut Rd, 
Granger IN 46530. 

WANTED: Information or documentation for 
SYNER Data total term. If you have same or know 
how to repair, please contact: Paul Massod, 338 N 
Warren Av, Brockton MA 02401, (617) 587-9035. 

FOR SALE: MARK-8 CPU circuit board (as- 
sembled). Needs 8008 chip, some memory, address 
and IO latches to get it going. MARK-8 and Intel's 
8008 manuals included, $20. Also Signetics Data 
Manual (1976) 1200 pages of TTL, ECL, linear, 
interface ICs, MOS memories, and their latest 
microcomps, $8. Frank Canova Jr, 725 Myrtle Av, 
Green Cv Spgs FL 32043, Phone (904) 284-3408. 

WANTED: Software for Altair (BASIC) to keep 
track of club members, print zip code sorted 
mailing labels, and "Membership Directory." Write 
for details. Jack Hardman, 140 Forest Av, Glen 
Ridge NJ 07028, (201 ) 429-8880. 

FOR SALE: DUMP THE MEMORY of your 6502 
system with software system which generates 
BYTE Standard signal for recording onto cassette. 
Documented software listing for only $3. Timing 
variable to match your clock speed. Ideal for 
putting in PROM, with space for other programs. 
Dumps one page or many pages in one run. Don 
Rindsberg, 5958 S Shenandoah Rd, Mobile AL 
36608. 



96 



altair680b 

TECHNICAL INFORMATION 



The ALTAIR 680b microcomputer is an excellent 
compromise between computer power and low cost 
structure, without sacrificing design reliability. The 
system is based on the 6800 microprocessing unit, 
which adapts nicely to a minimum design configuration. 
The ALTAIR 680b measures 11-1/16" wide x 11-1/16" 
deep x 4-11/16" high. The basic system is available in two 
configurations, depending on the intended application. 




Almost all of the 680b circuitry is contained on a single large 
printed circuit board, including memory and a built-in I/O port. 
The full front panel model contains all of the controls necessary 
to program and operate the computer and includes an additional 
printed circuit board, which provides all of the logic circuitry 
necessary to reset, halt or start the processor. Also located on 
this board are switches and associated LED indicator lights for 
each of the sixteen address lines and eight data lines. The front 
panel circuit board mounts directly to the main printed circuit 
board via a 100-contact edge connector. The power switch is 
located on the back panel of the unit for safety purposes.- A 
"turn-key" front panel model, which eliminates all control except 
restarting the processor, is also available. 

The basic ALTAIR 680b computer can be subdivided into five 
functional sections. These are the MPU and clock, the memory, 
an I/O port, control and indication, and the power supply. The 
first three of these sections, along with the power supply 
regulation components, are located on the main printed 
circuit board. 

At the heart of the 680b system is the 6800 Microprocessing 
Unit, which is largely responsible for the overall simplicity of the 
680b design. The 6800 MPU contains three 16-bit registers 
and three 8-bit registers. The program counter is a two byte 
register which keeps track of the current address of the program. 
The stack pointer is also a two byte register which keeps track 
of the current address of the program and contains the next 
address in an external, variable length push-down/pop-up stack. 
The index register is a two byte register used to store data or a 
memory address for indexed addressing operations. There are 
two single byte accumulators used for holding operands and 
results from the arithmetic logic unit (ALU). The 8-bit condition 
code register indicates the results of an ALU operation. In this 
register there are two unused bits, kept at a logic one. The 
remaining six bits are used to indicate the status of the following: 
carry; half carry; overflow; zero; negative; interrupt. 



The 6800 has seven different addressing modes, with the 
particular mode being a function of both the type of instruction 
and the actual coding within the instruction. The seven modes 
include the following: Accumulator Addressing —one byte instruc- 
tions, specifying either of the two accumulators; Immediate 
Addressing —two or three byte instructions, with the MPU 
addressing the location given in the 2nd or 2nd and 3rd bytes 
when the immediate instruction is fetched; Direct Addressing — 
two byte instructions which allow the user to directly address 
the lowest 256 bytes of memory in the machine; Extended 
Addressing — three byte instructions, the second two bytes 
referring to an absolute address in memory for the operation; 
Indexed Addressing —two byte instructions, the second byte 
being added to the 16-bit index register to give the address of 
the operand; Implied Addressing — one byte instructions and 
the instruction itself gives the address; Relative Addressing — 
two byte instructions where the second byte is added to the 
lower 8 bits, allowing the user to address memory + 129 to 
-125 bytes from the location of the present instruction. 
There are several timing and control signals required to 
operate the MPU. Two clock inputs are required, phase 1 and 
phase 2. These must be nonoverlapping and run at the Vcc 
voltage level. In the 680b the clock is a 2-MHz crystal controlled 
oscillator with logic to provide a 500-KHz two phase clock. 
Sixteen active high address outputs are used to specify the 
sections of memory or I/O to be used. These can drive up to 
one standard TTL load and 130 pf. There are also eight 
bi-directional data lines with the same drive capability as 
the address lines. 



NEW MEMORY FEATURES 

MITS is pleased to announce the development of a 16K static 
memory card for the Altair 680b. With an access time of 215 
nanoseconds and low power consumption of 5 watts, we feel 
that this is an excellent addition to the Altair 680b. 
The 680b cabinet has room for up to three 16K static memory 
cards, thereby increasing the memory of the Altair 680b to 49K. 



SPECIAL FEATURES 

PROM monitor. 

1702A PROM monitor chip programmed so that you can 
immediately load and run paper tape object programs such as 
the text editor and assembler {see below). 



Asynchronous Communication Interface Adapter (ACIA 



Allows the machine to transmit and receive a character at a time 
rather than one bit. Minimizes software needed for I/O routines. 
Contains crystal clock for baud rate synchronization. User- 
selectable for RS232, Baudot, TTY, 20ma current loop. Baud 
rates of 50, 75, 110, 134.5, 150, 200, 300, 600, 1200, 
1800, 2400, 4800, and 9600. 

Two Pass Resident Assembler and Text Editor 

A two pass resident assembler and text editor will be available 
for assembly language programming. This software is 
compatible with Motorola's format for assembly language 
programs, text and object files. 8K bytes of memory are required 
to run this package. The assembler produces a full assembly 
listing on the second pass, including the hex codes for the 
location counter and the instruction mnemonics. A symbol table 
listing is also produced. The text editor has full capabilities for 
text editing, including line insertion, printing, deletion and 
modification; as well as commands for changing one string of 
characters to another and for searching the text buffers for a 
particular character string. 

Basic Interpreter 

A BASIC interpreter has been developed which will be 
comparable to the 8800 8K BASIC interpreter. 

Buffered Data Lines 

All data lines are buffered to provide fanout capability of over 20 
standard TTL loads. 





Altair 680b, to 49K. 



Altair 680b 


Specifications 


No. of Boards 


Up to 3 additional 


Microprocessor 




Model 


6800 


Technology 


NMOS 


Data Word Size, Bits 


8 


Instruction Word Size, Bits 


8 


Clock Frequency, 


500K Hz 


Add Time, Register to Register, 




Microsec. Per Data Word 


2 


Number of Instructions 


72 


Input/Output Control 




I/O Word Size, Bits 


8 


Number of I/O channels 


256 Memory Address 




Locations Designated 


Interrupt Capability 


Std. 


Type of Interrupt System 


Maskable (Interrupt Request) 




and Non-maskable Interrupt 


Software 




Resident Assembler and Editor 


Yes 


Higher-level language 


BASIC 


Monitor 


Resident System Monitor 




on PROM 


Complete Software Library 




Separately Priced 


Yes 



The Altair 680b is also available in this Turnkey 
Model which has a power indicator light and 
controls for RESET and RUN/HALT on the front 
panel. The system PROM monitor, when used in 
conjunction with a terminal, eliminates the necessity 
for toggling front panel switches to load bootstraps 
or to examine and change memory contents. 



G£ DuQK% 



2450 Alamo S.E./ Albuquerque, New Mexico 87106 



Programming Quickies: 



The Thompson Lister 

Noel J Thompson, of the Hawaii Institute 
of Geophysics, 2525 Correa Rd, Honolulu 
HW 96822, submits the "Thompson Lister" 
program for the 6800 using Motorola's 
MIKBUG program. This program, shown 
listed at location 0000 in a symbolic assem- 
bly language format, is designed to list 6800 
programs as an address, an operation code 
and an optional one or two byte field 
depending upon the length of the instruc- 
tion. The sample Teletype output shown at 
the bottom of the listing was supplied by 
Noel as part of his listing of the entire 
program. The program figures out complete- 
ly whether the first byte of an instruction 
calls for one, two or three bytes. Quoting 
from Noel's letter accompanying the pro- 
gram, 

"Such a program has two important 
benefits. First, it provides an adequate 



listing for your documentation of pro- 
grams you are working on. You can 
use it over and over while you are de- 
veloping a routine, 

Second it detects the most common 
mistake that I find myself making in 
multi-length-instruction machines — 
the mistake of forgetting to put in the 
right number of bytes. If this lister 
comes up with funny things, probably 
you left out a byte. " 

The program is easily relocated by changing 
constants in the instructions at locations 
0000, 0009 and 005D. The data memory 
used by THMPLSTR is located in the 
MIKBUG programmable memory region 
between locations A000 and A07F. Also, 
the program takes advantage of subroutines 
PDATA1, BADDR, OUT4HS, OUT2HS and 
OUTS which are found in Motorola's 
MIKBUG program. 



Addr Hex Code 



0000 
0003 
0006 
0009 
000C 

000 F 
0012 
0015 
0018 
001A 

001 D 
0020 
0023 
0026 
0027 
002A 
002C 
002E 
0030 
0032 
0034 
0036 
0038 
00 3 A 
003C 
003E 
0040 
0042 
0044 
0046 
0047 
0048 
004B 
004 D 
0050 
0052 
0055 
0057 
005A 
005D 



CE 00 67 
BD E0 7E 
BD E0 47 
CE 00 64 
BD E0 7E 
CE A0 0C 
BD E0 C8 
FE A0 0C 
A6 00 
B7 A0 0B 
BD E0 CA 
FF A0 0C 
BD E0CC 
5F 

B6 A0 0B 
81 8C 
27 18 
81 8E 
27 14 
81 CE 
27 10 
84 F0 
81 20 
27 0B 
81 60 

25 08 
84 30 
81 30 

26 01 
5C 
5C 

F7 A0 0A 

27 10 

7A A0 0A 
27 05 
BD EO C8 
20 03 
BD E0 CA 
FF A0 OC 
7E 00 09 



Constants required: 
Addr Hex Code 



Label 



THMPLSTR 



NEXTBYTE 



0064 
0067 



0D 0A 04 
40 04 



THREE 

TWO 

ONE 



ONLYONE 
SAVEADDR 



Label 

CRLF 
ANATSGN 



Op 

LDX 

JSR 

JSR 

LDX 

JSR 

LDX 

JSR 

LDX 

LDAA 

STAA 

JSR 

STX 

JSR 

CLRB 

LDAA 

CMPA 

BEQ 

CMPA 

BEQ 

CMPA 

BEQ 

ANDA 

CMPA 

BEQ 

CMPA 

BCS 

ANDA 

CMPA 

BNE 

INCB 

INCB 

STAB 

BEQ 

DEC 

BEQ 

JSR 

BRA 

JSR 

STX 

JMP 



Operand 

#ANATSGN 

PDATA1 

BADDR 

#CRLF 

PDATA1 

#XHI 

OUT4HS 

XHI 

o,x 

TEMP 
OUT2HS 
XHI 
OUTS 

TEMP 

#8C 

THREE 

#8E 

THREE 

#CE 

THREE 

#F0 

#20 

TWO 

#60 

#30 
#30 
TWO 



BOX 

NEXTINST 

BOX 

ONLYONE 

OUT4HS 

SAVEADDR 

OUT2HS 

XHI 

NEXTBYTE 



Commentary 

Print an '(3)' sign using 

MIKBUG subroutine PDATA1; 
XHI := (address input) [using MIKBUG] ; 
Print carriage return and line feed 

MIKBUG subroutine PDATA1; 
X := XHI [XHI as defined by MIKBUG] ; 
Print current address as 4 hex characters; 
X := XHI [fetch current address pointer] ; 
A := @X [fetch current data at X] ; 
TEMP := A; 

Print current data then space; 
XHI := X [after OUT2HS has incremented] 
Print an extra space; 
B := 0; 
A := TEMP; 
is op code CPX ? 

if so then go to 3 byte length case; 
is op code LDS? 

if so then go to 3 byte length case; 
is op code LDX? 

if so then go to 3 byte length case; 
A := A & #F0 [mask off low order nybble] , 
is op code a branch? 
if so then go to 2 byte length case; 
is op code less than #60? 
if so then go to 1 byte length case; 
A := A & =?30 [mask to bits 5 and 4 left] ; 
are bits 5 and 4 equal to '1'? 
if not then length TWO is indicated; 
B := B + 1 [here for two increments] ; 
B := B + 1 [here for one increment] ; 
BOX := B; 

if zero in BOX then reiterate; 
BOX := BOX - 1; 

if one in BOX then print only one byte; 
print two bytes of 3 byte instruction; 
go save address for next round; 
print one byte left in 2 byte instruction; 
XHI := X [save pointer to next address] ; 
reiterate program forever till interrupt; 



Sample listing on Teletype: 



Description 

Carriage return, line feed, stop code in PDATA1 format; 
Initialization prompting message in PDATA1 format; 



0018 


A6 


00 


001 A 


B7 


A00B 


00 ID 


BD 


E0CA 


0020 


FF 


A00C 


0023 


BD 


E0CC 


0026 


5F 




002 7 


B6 


A00B 


002A 


SI 


8C 



99 




BOOK REVIEWS 



Computer Resource Book — Algebra by 
Thomas A Dwyer and Margot Critchfield, 
Houghton Mifflin, Boston, 1975; 8-1 14 x 11, 
178 pages. Paperback $4.20. 

This book contains a collection of com- 
puter explorations of algebra that were 
designed to be carried out in any algebra 
course where a computer is available. Since 
the computer programs are written in 
BASIC, the book begins with a 25 page 
"whirlwind tour" of computer programming 
in BASIC. Following this introduction to 
BASIC are 1 sections on things to do with a 
computer while learning algebra. In evalu- 
ating this excellent resource book, one can 
conclude that the authors have taught com- 
puter programming and high school algebra, 
and have taught both subjects well. Dwyer 
and Critchfield have written a book which 
draws the reader into becoming an interested 
and active participant in learning algebra. 
They were able to put themselves in the 
reader's place by asking (and answering) 
some of the questions about algebra and 
computer programming which puzzle stu- 
dents. The book was designed to be read by 
high school students as well as teachers, and 
I suspect that many students will want to 
take it home with them after school. 

As the authors point out in the introduc- 
tion, this resource book is meant to be used 
in an algebra course as a supplement to a 
regular algebra textbook. Access to a time 
sharing system or an on site small computer 
is necessary when using the book. Teachers 
and students may want to integrate these 
computer-related algebra topics in their regu- 
lar algebra courses or select programs from 
the book to use as course projects. Many of 



the BASIC programming skills needed in 
using the book are presented in the prologue 
and the remainder are interspersed through- 
out the algebra topics. 

The "Introduction to BASIC" section 
begins by illustrating the differences among 
system commands, BASIC statements, com- 
puter programs, user input, and computer 
output. The authors put the computer- 
programming novice at ease by taking a 
realistic, relaxed (and at times humorous) 
approach to using computers. For example, 
the reader is given numerous reminders at 
the beginning of the book to press the 
carriage return key after typing a line and is 
told "don't be afraid to make mistakes - 
you won't hurt anything." To avoid mis- 
leading the beginner, each BASIC statement 
is introduced and explained in the context 
of a complete, executable program rather 
than as a non-executable program segment. 
Sufficient margin notes are used to clarify 
lines and sections of program listings and 
sample executions are included with most of 
the program listings. 

The 10 algebra topics included in this 
book are the language of algebra, operations 
with real numbers, linear equations in one 
variable, inequalities, open sentences in two 
variables, systems of linear equations, qua- 
dratic equations and functions, rational 
expressions and polynomial equations, 
polynomial functions and complex numbers, 
and computer-generated animation. Each 
algebra topic begins with a checklist of 
necessary computer programming skills and 
a short quiz on prerequisite knowledge of 
algebra. Next, several coaching and practice 
computer programs are listed and explained, 
followed by a number of application pro- 



100 




Now, you can buy an Altair 8800 or 
Altair 680 computer kit right off the 
shelf. Most all Altair options, software 
and manuals are also available. The 
MITS Dealer List below is just the 
beginning: 



off the shelf 



RETAIL COMPUTER STORE, INC. 
410 N.E. 72nd 
Seattle, WA 98115 
(206)524-4101 

COMPUTER KITS 
1044 University Ave. 
Berkeley, CA 94710 

(415)845-5300 

THE COMPUTER STORE 

(Arrowhead Computer Co.) 

820 Broadway 

Santa Monica, CA 90401 

(213)451-0713 

THE COMPUTER SHACK 
3120 San Mateo NE 
Albuquerque, NM 87110 
(505)883-8282 



GATEWAY ELECTRONICS 
2839 W. 44th Ave. 
Denver, CO 80211 
(303)458-5444 

GATEWAY ELECTRONICS 
8123-25 Page Blvd. 
St. Louis, MO 63130 
(314)427-6116 

BYTE'TRONICS 

Suite 103-1600 Hayes St. 

Nashville, TN 37203 

(615)329-1979 

CHICAGO COMPUTER STORE 
517Talcott Rd. 
Park Ridge, IL 60068 
(312)823-2388 

MARSH DATA SYSTEMS 
5405-B Southern Comfort Blvd. 
Tampa, FL 33614 
(813)886-9890 



MICROSYSTEMS 
6605A Backlick Rd. 
Springfield, VA 22150 
(Washington DC area) 
(703)569-1110 

THE COMPUTER SYSTEMCENTER 
3330 Piedmont Road 
Atlanta, GA 30305 
(404)231-1691 



THE COMPUTER STORE, INC. 
120 Cambridge St. 
Burlington, MA 01803 
(617)272-8700 



COMPUTER PRODUCTS UNLIMITED 
4216 West 12th St. 
Little Rock, AR 72204 
(501)666-2839 

the COMPUTER STORE, INC. 
63 South Main St. 
Windsor Locks, CT 06096 
(203)871-1783 

the COMPUTER STORE of NEW YORK 
55 West 39th St. 
New York, NY 10018 

THE COMPUTER ROOM 
3938 Beau D'Rue Drive 
Eagan, MN 55122 
(612)452-2567 



NOTE: Altair is a trademark of MITS, Inc. 



THE COMPUTER STORE OF ANN ARBOR 
310 East Washington St. 
Ann Arbor, MI 48104 
(313)995-7616 



MITS, Inc. 2450 Alamo S.E. Albuquerque, N.M. 87106 



grams and simulations. Most of the 125 
programs which are listed are interesting 
enough to elicit an "I want to try it out" 
response on the part of students, and many 

of the programs are unavailable in other 
computer supplemented sources. Activities 
such as modifying the given programs to 
make them more efficient, revising programs 
to make them do different things, and 
creating new programs are suggested at the 
end of each algebra topic. 

If you want to liven up your algebra 
classes with computer activities such as 
building an ultramatic root finder, making 
and breaking secret codes, writing robot 
coaching programs, programming Honest Hal 
the simulated used-car salesman, and many 
others, this fascinating book is for you and 
your students. Even if you only want to see 
how computers can be used to enhance 
learning mathematics or find some new ideas 
for mathematical applications of computers, 
the Computer Resource Book — Algebra is 
still appropriate. 

My only complaint about this book is 
that it ends too soon; and where are the 
computer resource books for geometry, 
trigonometry, probability, and statistics? 

Frederick H Bell 

Associate Professor 

School of Education 

University of Pittsburgh 

Pittsburgh PA 15260* 

The Art of Computer Programming by 
Donald E Knuth. Volume I: Fundamental 
Algorithms. Addison-Wesley, Reading MA, 
1975, $20.95. 

There is some doubt in my mind as to 
how to classify this series. It is undeniable 
that we have here a standard, perhaps even 
classic, reference work, which sits handy on 
many a programmer's desk. But it clearly is 
also a text, useful for self instruction and 
used in several university programming 
courses. The exercises, while very instruc- 
tive, could also fall in the realm of recre- 
ational mathematics (another field the 
author has contributed to). It even makes 
entertaining reading at times (no mean feat 
for a text and reference work). I suppose the 
best description, however, would be that this 
is a cookbook of computer algorithms. 

More specifically, it deals with "non- 
numerical analysis." Numbers occur only 
"coincidentally," with more stress given to 
the decision making capabilities of the com- 
puter. The numeric computing which is 
involved consists mainly of addition and 
subtraction (these qualities are among the 
stronger points of inexpensive computers, 



bless 'em). Of course, the techniques pre- 
sented are also of considerable use in nu- 
merical computing, as there is always a 
non-numerical background in programming. 

By numerical computing, I refer to the 
solving of equations, finding of roots, and 
other number oriented calculations (the 
"traditional stuff"). While that aspect of the 
field is little covered by this series, that 
doesn't mean there is no mathematics in- 
volved. Indeed, Mr Knuth is himself a 
professional mathematician. This need not 
scare away those who are not, however, as 
the author kindly presents theory and 
algorithm with the minimum math needed 
to understand and use them, keeping more 
difficult analysis towards the end of each 
section, where only those with more interest 
need tread. (Some knowledge of basic math 
notation would be helpful, though.) Also 
optional are the exercises which conclude 
each section (the answers are included, by 
the way). 

If this series is not just for the mathema- 
tician, who then? Everyone? Not quite. It is 
aimed at the person with more than a casual 
interest in computers, the programmer con- 
cerned not only with how to use some one 
else's subroutines, but with how to use the 
algorithms behind the subroutines to 
improve his own creations. The reader's 
relationship with the computer should be 
beyond the stage of introductions. For 
example, Knuth suggests that the reader 
should have written and debugged at least 
four programs on at least one machine. (The 
programmer who has written scores of pro- 
grams for several machines may get at least 
as much value from the series. As I say, it is 
a reference, too.) It's for you if you're 
getting the hang of your programming units 
(be they hex machine codes or FORTRAN 
statements), and you want to start putting 
them together to do something. 

To connect the units with the application 
in mind, you need algorithms. (Roughly, an 
algorithm is a step by step procedure for 
doing something.) That's what The Art of 
Computer Programming is all about. The 
algorithms are chiefly presented in two 
forms: in a general English-language outline 
form and, when appropriate, in the assembly 
language for a hypothetical computer of the 
author's own concoction, MIX (the "world's 
first polyunsaturated computer"). Knuth has 
several good reasons for getting us involved 
with this mongrel machine (read the book), 
but for our purposes there is the additional 
advantage of easier translation of algorithms, 
ie: from his assembly language to our assem- 
bly language. While many algorithms trans- 
late well to higher level languages like 



102 



BASIC, some things can be better done 
closer to the assembly language level, eg: 
systems programs. 

While it's not necessary to the use of the 
series, I plan to have a MIX simulator 
running on the MOS Technology 6502, and I 
expect there will be simulators for other 
micros as well. This will allow very quick 
checkout and modification of the MIX 
algorithms given in The Art of Computer 
Programming before further translation, and 
make possible the exchange of programs 
with other hobbyists. 

In particular, let's consider Fundamental 
Algorithms, which is the first volume of 
seven in The Art of Computer Programming 
(of which three have been published so far). 
Chapters I and 2 are contained therein. 
Chapter 1 features a concise tutorial of 
much of the math that is particularly useful 
to programming. You may skim this section, 
but don't be surprised if over the years you 
keep referring back to it. Then follows a 
complete presentation of MIX and the MIX 
language, including the description of a MIX 
simulator. In fact a well commented listing 
of the MIX simulator is given and explained 
(written in MIX, of course). This presenta- 
tion will greatly help anyone interested in 
writing their own simulator (which is a very 
useful exercise). 

Chapter 2 is titled "Information Struc- 
tures," and begins the meat of the series. 
Major topics covered include stacks, arrays, 
linked lists, dynamic storage allocation, and 
trees. (These trees have roots and leaves, but 
[generally] aren't green and usually grow 
upside down.) Whether you know all or 
none of the above terms, this chapter should 
leave you with a good understanding of what 
they are and how to use them. No "TKIS" 
I page 42, January BYTE] is complete with- 
out some of these structures. Nor is any 
programmer. 

Zhahai Stewart 
PO Box 1637 
Boulder CO 80302 ■ 



Humanizing Computer Systems by Keith R 
London, McGraw Hill, New York, $15. 

What is the people impact when com- 
puters are placed in a working environment? 
What are associated problems of developing 
and implementing systems to meet the re- 
quirements of an organization and yet 
satisfy the people — the employees? 

This new book, "The people side of 
systems," is a valuable work which puts 
aside the technical aspects of computing and 
looks at the implications for people when a 



computer comes into their every working 
day association. 

The author is Keith R London who has 
produced considerable output related to 
management of computer systems. In this 
new book, he directs attention to how 
computers can cause disruptions in em- 
ployee relationships. 

Keith acknowledges the need and use of 
computers, but he also sees a need to 
reorient project leaders and systems analysts 
away from a pure hardware/software aspect 
to giving some attention to the impact the 
system has on those it comes into contact 
with: workers in a company or group. The 
thrust is to show how to integrate a com- 
puter with people. 

This book is not directly of import to the 
average Byter other than giving some insight 
to better relationship with the rest of the 
family who may think, with some degree of 
justification, that the excessive interest 
hobbyists show towards do it yourself com- 
puters has placed them just this side of the 
funny farm. The book is a must for those 
who have to make computers work in a large 
"people" group. 

Art Brothers 
555 Avenue G 
Boulder City NV 89005 ■ 



ACT- 1 



MICRO-TERM INC. 




$525 complete with high resolution 9" monitor • $400 without 
monitor | NCLUDE d FEATURES: 



Underline Cursor 
RS232C or Current Loop 
All oscillators (horiz., vert., 
baud rate, and dot size) are 
crystal controlled 



• 64 characters by 16 lines 

• Auto Scrolling 

• Data Rates of 110, 300, 600, 
1200, 2400, 4800, and 9600 
baud are jumper selectable 



The ACT-I is a complete teletype replacement compatible with 
any processor which supports a serial I/O port. Completely 
assembled and dynamically tested. 
Prices FOB St. Louis Mastercharge and BankAmericard 



THE AFFORDABLE CRT TERMINAL 



MICRO-TERM INC. P.O. BOX 9387 ST. LOUIS, MO. 63117 
(314) 645-3656 



103 



Interested in Notes about Electronic Music? 

Electronotes is the name of an excellent 
newsletter which will be of interest to 
anyone who is into electronic music 
experimentation. Published by Bernie A 
Hutchins, it is subtitled "Newsletter of the 
Musical Engineering Group." The address is 
203 Snyder Hill Rd, Ithaca NY 
14850 . . . write for information on signing 
up for a subscription. The price of a typical 
subscription is $16 for one year. 

Bernie sent BYTE several copies of the 
newsletter, and a reprint book entitled 
Musical Engineer's Handbook. The news- 
letter has been published by him and his 
associates for several years, and is circulated 
to a select group of electronic music people. 
The beginnings of microprocessor automa- 
tion in traditional electronic music are found 
in the pages of Electronotes where the 
November 1975 issue, EN#59, starts a series 
of tutorials on what a microprocessor can do 
for the electronic musician, written in terms 
familiar to the music person. The author of 
the series, which extends through four issues 
of Electronotes, is Bill Hemsath. The theme 
is continued in the March 1976 issue where 
Douglas Kraul discusses some elementary 



points about "Analog Interfaces for Micro- 
processor Systems." Electronotes is jammed 
full of information on circuitry and equip- 
ment needed to produce electronic music 
sounds, and will provide an excellent and 
specialized forum for those who want to 
find out about progress in this field. 

The Musical Engineer's Handbook is a 
publication in the same vein, as one might 
expect since it is made up of materials 
based upon past issues of Electronotes. 
Its dedication reads: "This book is dedicated 
to musicians everywhere and of all times, 
without whom many of us would have only 
electronics to do." It is a very thick photo 
offset publication (354 pages) in a GBC 
binding, containing fundamental informa- 
tion on the technology of electronics in 
music applications. The book has a combina- 
tion of background theory with numerous 
practical applications circuits. It is an essen- 
tial sourcebook for anyone seriously 
interested in the art and practices of elec- 
tronic music. The book is available from 
Electronotes for $18, in return for which 
you'll get thousands of dollars worth of 
ideas." 



P. C. cards made simple — with COPYDAT! 



1. Prepare the 1X artwork, using an opaque layout aid such as Chartpak, Bishop Graphics, or other 
similar product. 

2. Make a negative: Place the artwork face down, cover with the negative material colored film side 
up (we recommend Scotchcal products), and expose with the Copydat. Typical exposure time is 
1.5 minutes. 

3. Develop the negative in developer provided with negative material. 

4. Attach negative to pre-sensitized face of copper board. Place board and negative face down on 
Copydat. Expose. Typical exposure time: 30 seconds. 

5. Save the negative for reuse, and develop the board in the developer provided. 

6. Etch the board. 

7. As a finishing touch, tin the board to avoid oxidation of the copper and to improve solderability. 
Result: a custom, high quality, single-sided P.C. board. 

With careful alignment, you can make doublesided boards too! 

Alternatively, buy high-quality hardware assemblers from us — and these are predril led as well (and 

feature plated-through holes): 

P.S. The Copydat does a lot more than make high-quality P.C. boards. It makes superior blueline, 
blackline, sepia, and other diazo process copies, and you can make pressure-sensitive labels with it 
and even instrument front panels from pre-sensitized metal plates ! ! 



from $149.95 (B size prints) 



CELDAT Design Assoc. 
P.O. Box 752 
Amherst, N.H. 03031 



104 



Still More 

BYTE's 

Books 





•DESIGNING WITH TTL INTE- 
GRATED CIRCUITS by the Components 
Group, Texas Instruments Inc. Edited by 
Robert L Morris and John R Miller. 

People often ask questions like "Where 
do I get basic information on hardware 
design?" One answer is in "Designing With 
TTL Integrated Circuits." 

This book, published by McGraw Hill in 
1971, is a fundamental starting point for 
any person designing peripherals and custom 
logic employing TTL integrated circuits. 
While its publication date precludes any 
reference to the later additions to the TTL 
7400 series of components found in the 
Data Books, it is nevertheless the source of a 
wealth of ideas on TTL integrated circuits 
and design of logic with this family of 
circuits. 

What is fanout? You may have heard this 
term mentioned at computer club meetings 
or in advertisements for circuitry, or in 
articles in BYTE. You can find out 
background information on the calculation 
of fanouts by reading the chapter on Circuit 
Analysis and Characteristics of Series 54/74. 

Worried about noise, shielding, ground- 
ing, decoupling, cross talk and transmission 
line effect? (Or, more properly, did you 
know you should worry about these effects 
in certain circumstances?) Find out about 
general precautions and background infor- 
mation by reading the chapter on Noise 
Considerations. 

The chapter on Combinatorial Logic 



Design gives 53 pages of background 
information on Boolean algebra and practi- 
cal representations of logic in the form of 
SSI gates. The chapter includes a description 
of Karnaugh mapping techniques and the 
minimization of logic. From combinatorial 
design, the book progresses into Flip Flops, 
including background information on the 
workings of these devices, and fairly 
detailed descriptions of the uses and 
applications of these devices including 
synchronization of asynchronous signals, 
shift registers, flip flop one shots, etc. Then 
the book returns to static combinatorial 
logic with its description of the Decoders 
available in the 7400 line as it stood in 
1970-1971. 

A chapter on Arithmetic Elements gives 
fundamental descriptions of binary arithme- 
tic, diagrams of the basic gate configurations 
for combinatorial logic adders, and a section 
on number representations for use in 
computers. Much of the material in this 
section is dated, due to the fact that the 
later 74181 series of multiple function 
arithmetic units had not yet appeared when 
the book was written. But for a background 
on arithmetic operations implemented with 
the simpler 7483 circuits, this chapter is 
ideal. A chapter on Counters and a chapter 
on Shift Registers complete the detail logic 
sections. The book is closed out by a 
chapter on miscellaneous Other Applica- 
tions including a simple binary multiplier, a 
12 hour digital clock and a modulo-360 
adder. 



BITE 



PETERBOROUGH, NH 03458 



n 



Designing With TTL Integrated Circuits $24 

Microcomputer Design $25 

Send to: Name 



Address 



City 



State 



^ip_ 



Q Check enclosed 

□ Bill MCNo. 

□ Bill BA No. 

Signature 



Exp. Date 
Exp. Date 



L_. 



Please allow six weeks for delivery. 



The most important use of this book is its 
value as an introduction to TTL logic. By 
reading and studying it, you will begin to 
understand the ways in which SSI and MSI 
TTL gates can be utilized in your own 
experimental logic designs. After studying 
this text, you should be able to make much 
more sense out of the technical information 
summaries typically published as specifica- 
tions sheets and data catalogs. 

Order your copy today from BYTE's 
Books, $24 postpaid. 

•MICROCOMPUTER DESIGN by Don- 
ald P Martin, Martin Research. Edited and 
Published by Kerry S Berland, Martin 
Research . 

Purchase your copy of the definitive 
source for circuitry and hardware design 
information on the 8008 and 8080 com- 
puters today. 

Even Intel, the originator of the micro- 
processor revolution, is hard put to compete 
with the wealth of information found in 
Martin Research's new second edition of 
Microcomputer Design. This is the book 
which was originally published as an 
expensive (but quite practical) engineering 
report in loose leaf form, at about the time 
the microprocessor technology was first 
catching on in the form of the 8008. This 
388 page second edition of the manual is 
loaded with detailed information on how to 
build and use computers based on the 8008 
and 8080. 

But even if you do not intend to use the 
8008 or 8080, the practical pointers on 
digital logic design, peripherals and applica- 
tions of hardware techniques will more than 
justify the new low price of $25 for this 
handbook. Microcomputer Design is a must 
for 8008 owners and 8080 owners who 
want to truly understand how their 
processors process. 

Microcomputer Design is complete with 
numerous illustrations, tables and diagrams, 
plus reprints of the specifications sheets for 
the Intel processors. There are numerous 
practical examples of circuitry and many 
complete computer designs ranging from 
"minimal microcomputers" to a full blown 
8080 processor. 

Order your copy today, $25 postpaid 
from BYTE's Books. 



Continued from page 14 



decision boundary. There are innumerable 
ways to vary this technique. 

For those who would like to try their 
luck at hand sent Morse decoding, I have 
included a brief flow chart outlining a 
typical process from approach (3). Success- 
ful models have been constructed by Picker- 
ing Radio Co (to name but one com- 
pany . . . look at Ham Radio, QST, or other 
amateur radio magazines) and a computer 
model has been designed using about 4 K of 
memory on a PDP-12 as described in a 
master's thesis by J A Guenther. For those 
interested in the exact PDP-12 algorithm, 
Guenther's thesis is available for a nominal 
charge from the National Technical Informa- 
tion Service of the US Department of 
Commerce [See bibliography] . 

As you can see, the problem of transla- 
ting hand sent Morse code is not easily 
solved. To further complicate matters, most 
of the really good information is classified, 
or even worse, proprietary to a particular 
company. So, I wish you all the best of luck, 
you'll probably need it. As a final note, just 
remember: When you think you've got the 
problem licked, Chisholm's Law of Human 
Interaction will apply (eg: Some joker — 
radio amateurs call them "lids" — will come 
along with a "fist" that will tear your 
algorithm apart)." 



BIBLIOGRAPHY 

1. Blair, C R, "On Computer Transcription of 
Manual Morse," Journal of the Association for 
Computing Machinery, pages 429-442, vol 6, no 
3, July 1959. 

2. Duda, J S, "Noise Reduction for CW Recep- 
tion," Ham Radio, pages 52-55, September 
1973. 

3. Gold, B, "Machine Recognition of Hand-Sent 
Morse Code," Institute of Radio Engineers 
Transactions on Information Theory, pages 
17-24, March 1959. 

4. Gonzales, C and Vogler, R, "Automatic Radio- 
telegraph Translator and Transcriber," Ham 
Radio, pages 8-23, November 1971. 

5. Guenther, J A, Machine Recognition of Hand 
Sent Morse Code Using the PDP-12 Computer, 
master's thesis, Air Force Institute of Technol- 
ogy, Wright-Patterson Air Force Base, Ohio, 
December 1973. Available as document number 
AD-786-492 for a nominal cost from the Na- 
tional Technical Information Service, US De- 
partment of Commerce, 5285 Port Royal Rd, 
Springfield VA 22151. 

6. McElwain, C K and Evans, M B, "The Degarbler 
— A Program for Correcting Machine Read 
Morse Code," Information and Control, vol 5, 
pages 368-384, May 1962. 



7. Petit, R C, "Morse-a-Verter,' 
January 1971. 



QST, pages 30-35, 



111 

H 
> 
OQ 

O 

2 



INTRODUCING 

KIL O'BYTE, 

VJORLD RENOVINED 

STORY-TELLER, 

ADVENTURER, *& 

HACKER EXTRAORDINAIRE 

THIS EVENING, OUR 

HBO, KIL, 5AT DOWN 

with our micro-Hero 

HI? SON, CHIP, TO TELL 
HIM A STORY AWT 
OUK GREAT- GRANDADDy 
HERO, KILT Q'mi 







106 



Waiting to leave at Logan A irport in Boston, 
Ed Zealy captured this interesting juxtapo- 
sition of transportation technologies. The 
tail of a 707 frames the distant image of a 
727 masked against a sailing vessel leaving 
Boston as a part of "Operation Sail. " 



Travelogue 



. . . Notes by Carl Helmers, Editor 

On July 16, 17 and 18, the American 
Radio Relay League's 1976 National Con- 
vention was held in Denver CO at the Denver 
Hilton hotel. The ARRL is the amateur 
radio operator's main organization and 
representative in matters concerning the 
legal availability of amateur bands in the 
radio spectrum. Without the ARRL, amateur 
radio as it is today and has been practiced 
since early in this century would not exist. 
(For information on amateur radio, contact 
the ARRL at 225 Main St, Newington CT 
06111.) 

As part of the affair, reflecting the 
interest of many radio amateurs in com- 
puting applications to their field, the Denver 
Amateur Computer Society was asked to 
coordinate a series of microprocessor ses- 
sions at the convention, and this in turn 
helped attract a number of personal com- 
puting vendors and spectators to the exhibi- 
tion area. BYTE was present at the con- 





A sign in the lobby of the Denver Hilton 
greets the several thousand visitors to the 
ARRL convention. 




Ideal for 
communicating 

with your 
microprocessor! 

RS-232 interface x 32 characters $400 

TV/TTY kbd./display (16 lines x 64 characters) $500 
Keyboard/CRT Monitor (24 lines x 80 characters) $700 



■ORDER FORM" 



Ship To_ 



Subtotal $_ 
Calif residents add 

sales lax 

Please find a check 
enclosed in the amount 

ol total order $ _ 

Bill my BankAmencard 
Mnstercharge 



My signature as purchaser date 



CO 

MICON 

INDUSTRIES 

Micon Industries 

252 Oak Street 
Oakland, CA 94607 
(415) 763-6033 



107 




Gary Kay (leaning over 
table) and Joe Deres 
(seated) of Southwest 
Technical Products dem- 
onstrate their wares at the 
ARRL convention. The 
table contains an SWTPC 
6800 system, CT-1024 ter- 
minal, GT-6144 graphics 
display unit, and printer. 




Every manufacturer shows off the product in the factory. At MITS, the new 
Altair 880B machine is quite effectively integrated with three floppy disks, a 
Lear-Siegler ADM-3 terminal, and a disk operating system in the display 
room. Here Dave Bunnell and Carl Helmers are engaged in a conversation with 
the demonstration system in the background. 



vention with a booth in the exhibit area 
staffed by Deena and Ed Zealy, Beth 
Alpaugh and me. I also participated in one 
of the microprocessor oriented technical 
sessions by giving an informal talk at which I 
shared the forum with Jack Cox WOKMV. 

After the convention, we all flew to 
Albuquerque where we spent some time 
talking with Ed Roberts and Dave Bunnell of 
MITS, then Beth and I flew to San Antonio 
to pay a visit to Dan Meyer, Gary Kay and 
Joe Deres at Southwest Technical Products. 
Perhaps the highlight of the whole trip (at 
least in my mind) was entirely unplanned. 
While at Southwest, Ron Komatz, the local 
representative for Motorola Semiconductor 
Products in Austin TX, walked in. In 
passing, he suggested something like "How 
would you like to come back with me to 
Austin this afternoon and take a quick lour 
through the Motorola Semiconductor wafer 
fabrication facility?" With an offer like that, 
we could hardly refuse .... 

So, after some hurried reservations 
changes and Ron's call ahead to the people 



The interior of the main 
assembly area at MITS is 
illustrated in this shot 
taken during the tour of 
the facility. 




108 




A candid shot of Ed Roberts, president of 
MITS, during an informal discussion in his 
office in Albuquerque. 



at the Motorola plant, we drove up to Austin 
in Ron's car for a quick tour (total time, less 
than an hour and a half including 45 minutes 
of some informal discussion with several of 
the engineers and software people at 
Motorola). 

It is in places such as the Motorola plant 
in Austin where the space age technology of 
integrated circuits and the technological 
leads of the American semiconductor manu- 
facturers are so much in evidence. The silicon 
wafer fabrication plant is like a science 
fiction image: clean rooms with highly fil- 
tered air, workers dressed in lint- and dust- 
free smocks undergoing cleaning procedures 
prior to entering the fabrication area, exotic 
gases and electricity piped into the work 
areas, intricate optical instruments for the 
microscopic photo reproduction of IC mask 
patterns, air bearing transport slides for the 
disks of silicon being handled by the facility, 
red glowing diffusion ovens maintained at 
carefully controlled temperatures needed to 
dope the silicon chips with precise amounts 
of impurities at each stage of production. 

The result at the end of multiple stages of 
the fabrication process, which we viewed 
through glass partitions, is a three inch wafer 
of silicon with hundreds to thousands 
(depending on the particular IC) of tiny 
circuit patterns, waiting to be ground down 
to less than 10 mils thick, scribed and 
separated into individual pieces which can be 
tested in automatic equipment then shipped 
overseas for assembly. It is the high tech- 
nology of such semiconductor facilities 
which makes possible the personal computer 
as we know it today, and as it will improve 
and evolve in the future." 



ALTAI R 8800 OWNERS 



We recently received the following letter: 



APRIL 26, 1976 



GENTLEMEN: 



I JUST WANTED TC TELL YOU THAT I THINK YOUR CLOCK FIX-IT KIT IS 

REALLY GREAT! I WAS HAVING TROUBLE RUNNING BASIC AND AFTER 
INSTALLING YOUR KIT FOUR OF i-.Y KITS BOARDS THAT WEREN'T RUi.NING 

CAKE BACK TO LIFE AND NOW ARE HELP It. G JiE TC WRITE THIS LETTER 

CN THE COMPUTER. ENCLOSED IS Af.OTHER ORDER FOR A CLOCK KIT- 

THIS IS FOR THE SECOND hLTaIR THAT I 'Ah NOW IN THE PROCESS 
OF BUILDING. 
AGAIN' MANY THANKS i u3. SUCH ft FINE PRuLUCT. 



SINCE3ELY 

-_0Yl. L. 5iilTH 



How well does your Altai r run? 

A Clock Fix Kit is only $15 postpaid. 



PARASITIC ENGINEERING 



PO BOX 6314 



ALBANY CA 94706 



A v 



BABY! 



o. 






^ N ^ 




■J- 



> 



<?, 



& 



% 



O 



Complete System 
in a case! 

KEYBOARD: 62 key upper & lower case + Greek; 

TAPE INTERFACE: High speed, 1200 Baud! Cas- 
sette, programs included; 

VIDEO INTERFACE: E.I.A. Compatible; 

MICROPROCESSOR: 6502 based system! 

MEMORY: 2K or 4K byte RAM minimum system 
monitor + 3I< ROM sockets; 



% 



$■* 



S.T.M. SYSTEMS INC. 

P.O. Box 248 
/lont Vernon, N.H. 03057 



*. 



'* 



109 



What's 

New? 



Mating Game 

What do you use for a plug which will 
mate your computer with the real world 
across a cable? For parallel interconnection, 
one option is this Hirose 20 pin connector 
which according to its distributor has been 
widely used in the video field wherever 
multiple wires must be used with quick 
connect and disconnect. 

These connectors are heavy duty, and will 
handle audio, video and machine control 





signals. They were designed for quick discon- 
nect when the light colored button (see 
photo) is pressed. The contacts are high 
quality brass with silver plating and the cable 
assembly features a heavy duty wire lock. 

Physical ratings are 350 VAC at sea level, 
3 amperes per contact, insulation resistance 
1000 megohm at 500 VDC, contact resis- 
tance 7 milliohms maximum. This press 
release information was provided by the 
Hirose distributor, John Anthony Television, 
Childs Park Rd, Dingmans Ferry PA 18238. 
As a special introductory offer to BYTE 
readers, the price of a combination male 
cable connector and female chassis con- 
nector is $14.95. The same price applies to 
the alternate combination of female cable 
connector and male chassis connector. Nor- 
mal prices are $12.25 for male cable, $12.50 
for female cable, $3.90 for female chassis, 
$4.50 for male chassis. OEM and quantity 
discounts are available as well." 




And Yet Another Dedicated 
Industrial Micro 

Here is an 8080 processor board intended 
by its manufacturer, GNAT Computers, as a 
dedicated computer for industrial applica- 
tions. The MC80 starts at $189 and should 
find its way into communications systems, 
programmable logic for instrumentation and 
machine tools, and other processes where 
dedicated intelligence is required. In the 
experimenter's context, it would make a 
useful foundation for dedicated applications 
such as peripheral controllers, mobile com- 
puters for land, sea and air navigation, smart 
terminals, etc. The basic board has 256 bytes 
of programmable memory, expandable to 
512, and space for up to 2K bytes of 
custom applications programming in pro- 
grammable ROMs. Optionally there is a 
front panel for development and mainte- 
nance checkout. Delivery is quoted as 30 
days after receipt of order, from GNAT 
Computers, 8869-C Balboa Av, San Diego 
CA 92123." 



Building a Homebrew CRT? 

Using a Commercial Digital Display Chassis? 

If your answer is yes, then you'll 
probably want to think about the problem 
of creating an enclosure for your design. 
This new product, the VTE-101 CRT 
Terminal Enclosure, was shown off at the 
Trenton Computer Festival in May, and is 
designed to provide such an enclosure for 
the do-it-yourself person. The enclosure is 
made by a structural foam process which 
uses fire retardant high heat, high impact 
polystyrene. The enclosure is light weight, 
but is said to be rigid and tough. It is 
designed for a complete CRT terminal, and 
consists of a base section 19 inches (48.3 
cm) by 21 inches (53.3 cm) by 4 inches 
(10.2 cm) and a shroud measuring 11.25 
inches high (28.4 cm) featuring a smoke grey 
screen. It is said that the enclosure will take 
a monitor up to 14 inches (35.6 cm) 
diagonal measure. This housing sells for 




110 



$69.95, and less expensive models (without 
monitor shroud) are also available. The 
products are supplied with hardware, and 
additional openings can be cut in the mate- 
rial using ordinary woodworking tools. Con- 
tact Enclosure Dynamics, PO Box 6276, 
Bridgewater NJ 08807." 




Here's an Interesting Combination 
of Peripheral Functions! 

Electronic Product Associates Inc, 1157 
Vega St, San Diego CA 92110, (714) 
276-8911, sent along an announcement of 
this new, low cost audio cassette, Teletype 
or CRT terminal adapter which allows any 
serial TTL or MOS output to simultaneously 
interface a low cost audio cassette recorder 
via frequency shift keying (BYTE Standard) 
up to 300 baud and to a standard RS232 
CRT and a 20 mA current loop Teletype. 
The adapter also simultaneously decodes 
BYTE Standard FSK data from low cost 
audio cassette players and from 20 mA 
current loop Teletype and RS232 CRT. 
Audio cassette information is decoded by a 
proprietary phase locked loop system 
developed by EPA which is said to be the 
most reliable method available for transfer- 
ring digital data to and from low cost audio 
cassette players. The model TCC3 is 4.5 X 
3.25 inches (11.5 cm X 8 cm) and mounts 
piggyback on the EPA Micro-68 develop- 
ment computer. The TCC3 price is $129 in 
singles, completely assembled and tested. 
Delivery is quoted from stock." 



Software New Product 

33 Programs and Projects for the Altai r 
8800 is a new self-published book by 
Jacques Roth, 543 16th Av, San Francisco 
CA 941 1 8. This book is a 51 page collection 
of information printed on loose leaf pages 



^HM ^^^^m *?flW(f ^^^^ UJjjjl^'iP*'* ^Ktw #|BK*s 

mm mm mm mm tmlmm «■ 

^W£ti ^y-*i ^f^^ ^ji.ii ^^U« v L^LU^ f^i^ 



The Tarbell Cassette Interface 

• Plugs directly into your IMS AI 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 

• 25-page manual included 

• Device Code Selectable by DIP-switch 

• Capable of Generating BYTE/LANCASTER 
tapes also. 

• No modification required on audio cassette 
recorder 

• Complete kit $120, Assembled $175, 
Manual $4 

TARBELL ELECTRONICS 

144 Miraleste Drive #106, Miraleste, Calif. 90732 
(213)832-0182 

California residents please add 6% sales tax 



itiiiM:i;siiuri; sysii :a\s 

ITISIaVIS 



i. 4 hj -m« jut 




(TTTrnTfiilll!inmw , ~" ** x -tfrr 



kEM 



m 

EPIC 2K & EPIC 2 

KIT ASSEMBLED 

DISCOVER THE EPIC 2; A COMPLETE ONE-BOARD MICRO-COMPUTER SYSTEM AT AN AFFORDABLE PRICE. 



EPIC 2 features: 



Easy io use teletype sty lu Fully encoded keyboard. 



Programs loaded and stored via yooi Standard audio 
tape recorder. 



Video Interface - displays 16 lines of alpha numei 

characters on your TV set or optional video monitt 



Unified extendable bus. 
2 K RAM memory. 



PTsHS HOd mt . EPIC 2K 1st. End. 

Please und <nc EPIC 7 (si. Enclm 

(Call loi n id ii'iidcnls include 6% sales I 



256 byte PROM bootstrap. 

2 MHz 8080 microcomputer. 

16 general purpose I/O lines. 

Standard programs included: Monitor, Text Edilor. 
Game of Life, Blackjack Game. 

Memory expansion and our optional Vector Graphics 
Software Package allows you to create, display, and 
store graphics. 

Many more options to cornel 



Nam 



BURKESHIRE SYSTEMS P. O. Box 512 Mountain View, California 94040 



111 



with three hole punching. Programs range 
from the simple to the devious, and are all 
designed to run in less than 1 K bytes, with 
many taking fewer than 256 bytes. Projects 
include an XY scope plotter using an oscillo- 
scope, two DACs and the Pl/O board, a Pong 
game for the scope interface, a computer 
telephone dialer interface with several phone 
dialing programs, a monitor program, etc. 
Other programming projects include Tic Tac 
Toe, a 1 byte bubble sort program, and a 
package of 4 byte arithmetic functions 
including integer addition, subtraction, nega- 
tion, move, set zero, left shift, right shift and 
multiply. The price of this collection if 
$5.95 postpaid from Mr Roth." 




Attention: Computer Service People 
and Clubs 

One way to check out computer ter- 
minals and other ASCII serial data and 
communications equipment is to utilize an 
ASCII pattern generator such as this new 
product of the Terminal Data Corporation 




Wind Up Your (Paper Tape) Affairs 

Continuous Expression Processor Inc, 12 
Main St, Natick MA 01760, has come out 
with this cordless paper tape winder as an 
accessory for use in paper tape systems. 
(Suppose you have one of the hand powered 
paper tape readers. You can automate your 
input processes by using this paper tape 
winder to pull the tape through the reader.) 
The unit requires two "C" size flashlight 
cells and sells for $29.95 postpaid in the 
continental United States." 



of Maryland, 11878 Coakley Cir, Rockville 
MD 20852. This self contained device comes 
with male and female RS-232 interface 
plugs, utilizes a 0.01% crystal oscillator for 
generation of 110, 300 and 1200 baud data 
rates, and automatically generates ASCII 
serial patterns: one at a time or continu- 
ously, the same character (set by toggle 
switches) or scanning through the character 
set. The Model #900 test set is offered as a 
kit for $249, with a special introductory 
price of $199 good until September 30 
1976. The assembled and tested price is 
$395." 



Another Completely Packaged Computer 

Electronic Tool Co, 4736 W El Segundo 
Blvd, Hawthorne CA 90250, has introduced 
a new microcomputer system, based on the 




MOS Technology 6502 CPU, priced at $675. 
The ETC-1000 comes with a 40 key key- 
board, a programmable 8 digit display, 10 
interfaces, power supply and memory. All 
systems are fully assembled, tested and 
ready to run. According to its manufacturer, 
the ETC-1000 is intended for system 
development, control, and small scale data 
processing applications. As a development 
system, it provides system support for hard- 
ware and software design work. As a control 
system, it offers an inexpensive high speed 
computing capability in a sturdy rack 
mountable package. 

The manufacturer describes the 
ETC-1000 as a "full capability high- 
performance computer system which you 
can have running 10 minutes after you open 
the box." The system needs no external 



112 



ANNOUNCING! 

MICROCOMPUTER 

PRODUCT 

SURVEY 

60 companies manufacture main- 
frames and peripherals for micro- 
computing market. Do you know 
who they are? The MPS does! 
Hardware and software are ex- 
pensive today for small business 
let alone a personal system. Be- 
fore you buy invest in thought- 
ware, shop by comparisonthrough 
MPS. No advertising, we just 
report the electronic parameters, 
software features, price and com- 
pany profile of firms selling in the 
microcomputer market. 

First Issue Nov. 15 

FULL DETAILS $1.00 

SAMPLE ISSUE $3.00 

SUBSCRIPTION $9.00 

SBS 

1800 Wayne #1 
Bellevue Ne 68005 



WANTED 

Microprocessors Kit or Assembled 

ALTAIR • SPHERE • MOTOROLA 
INTEL & OTHERS 

Altairs, immediate delivery. 

Memories, I/O boards, chassis, power 
supplies, modems, peripherals, spe- 
cials, prom programmers, ADCS, 
DACS, GPI0S, RS232 faces, and any 
associated software. Ask about 
our complete Altair system. 
Available now. 

FORWARD INFORMATION AND/OR 
INQUIRIES TO: 

AMERICAN USED MICROPROCESSORS, 

EQUIPMENT & SUPPLY CORP. 

ATTHE CHICAG0LAND AIRPORT 

BOX 515 

PRAIRIEVIEW, ILLINOIS 60069 

TELEPHONE (312) 634-0076 

For complete monthly catalog of 
items available and in stock Enclose 
$10. for six issues. Many new un- 
used items. Amazing values for 
everyone. Tested and guaranteed. 



L^omputer re fan 



in 



¥ jaw UJom ^rnc. 

NOW ON 
LONG ISLAND 



IMSAI, SWTPCo, Digital Group 

Processor Tech, Apple, OSI 

TDL-Z-80, Seals, Cromemco, 

Sphere, Tarbell, Oliver 

Magazines, books, chips, 
sockets, connectors, terminals. 

IT'S ALL HERE WAITING FOR YOU 
FRIENDLY ADVICE TOO 

New York City 
314 5th Ave 
(32nd St) 

Long Island 

2072 Front St 
East Meadow NY 
Phone 



FOR SALE 



13 Altair 880 micropro- 
cessors, all in good physi- 
cal condition, excellent 
working condition. 
$285.00 each 

4K Dynamic memory 
$125.00 

and 

88- ACR Boards 
$100.00 

Call: 

Dr. Dan Nash 

405-524-1 209 

eves, and wknds. 



N. Y.'s Newest Store for 
Micro and Mini Compu- 
ter Hardware and Soft- 
ware. 

We will be featuring a 
large selection of: IMSAI 
(kits and assembled) Pro- 
cessor Technology's full 
line. Also a selection of 
choice modules from 
Cromemco, Solid State 
Music and others. Plus: 
full line of TTL logic, 
discrete components, 
memory and MPU chips. 

Audio Design Electronics 

487 Broadway Suite 512 
New York NY 10013 




Pictured above is the new OP-80A 
High Speed Paper Tape Reader from 
OAE. This unit has no moving parts, 
will read punched tape as fast as you 
can pull it through (0-5,000 c.p.s.), 
and costs only $74.50 KIT, $95.00 
ASSEMBLED & TESTED. It in- 
cludes a precision optical sensor ar- 
ray, high speed data buffers, and all 
required handshake logic to interface 
with any uP parallel I/O port. 

To order, send check or money order 
(include $2.50 shipping/handling) to 
Oliver Audio Engineering, 7330 
Laurel Canyon Blvd., No. Holly- 
wood, CA 91605, or call our 24 hr. 
M/C-B/A order line: (213) 874-6463. 



attachments such as Teletypes, power sup- 
plies, or memory expansions to provide basic 
programming capability and computer 
operation. Many expansion options are avail- 
able, including communications, real-time 
and DMA interfaces, memory expansions, 
and various add-on CPUs. 

A 40 key keyboard for control and data 
entry is mounted on the front of the 
ETC-1000. This keyboard includes a full set 
of hexadecimal keys for data and address 
entry, system function keys such as load, 
reset, examine memory, etc. Eight special 
function keys which may be sensed under 
program control by the user are available for 
assignment to user-specified functions. 

An 8 digit LED panel display is also 
contained in the ETC-1000 control unit to 
display memory contents, system status and 
user programmed information. 

The ETC-1000 contains a direct input 
output system consisting of eight latched 
output lines and eight latching input lines 
which may be used under program control 
to operate external devices. A hardware 
interrupt system with two levels is standard; 
eight additional levels are available. The 
company says one or two independent full 
duplex communications streams at speeds 
between 110 and 1200 bits per second are 



supported by the ETC-1000 basic system 
when appropriate PROMs are included. 
Selection of speed is accomplished auto- 
matically by the hardware. 20 mA DC cur- 
rent loop interfaces are provided as standard, 
with EIA RS-232C capability optional. 

The ETC-1000 CPU consists of a MOS 
Technology 6502 8 bit CPU, plus clocks, 
control logic, interface buffers, 1024 bytes 
of high speed RAM, and 256 bytes of ROM 
containing system control functions. 

Software currently available includes a 
resident assembler, 10 handlers, diagnostics 
and other support tools. The manufacturer 
says that BASIC and PLM support are 
expected to be available during the third 
quarter of 1976. 

Availability of standard configurations is 
30-60 days." 

Attention Analog Interfacers .... 

National Semiconductor Corporation has 
just announced a new building block for 
analog input interfaces. This is the MM5356 
8 bit analog to digital converter. The func- 
tion provided by this chip is converting an 
input voltage of typically to 1 V or —5 to 
+5 V into an 8 bit binary word. In order to 
operate properly, the circuit requires a con- 



Stamp Out Cybercrud 



COMPUTER 




Have you every been victimized by 
one of a myriad computer based inter- 
personal putdowns? In Ted Nelson's 
book, Computer Lib/Dream Machines, 
you'll find an excellent essay on the 
nature of this "cybercrud." 

Have you ever wondered where to go 
for a basic starting point in your quest 
for information about computer applica- 
tions and uses? Ted Nelson's book. 
Computer Lib/Dream Machines, is the 
place for you to begin. 

Computer Lib/Dream Machines is for 
the layman — the person who is intelli- 
gent and inquisitive about computers. It 
is written and self published by a 
philosopher who is also a self confessed 
computer fan and an excellent teacher of 
basic concepts. (For those who have not 
yet heard, ivory towers are constructed 
out of real and substantial white bricks.) 
The most important aspect of this book 



is its inspirational data content. The 
machines we're all busy working on are 
deep personal expressions, and not the 
cold and inhuman monsters of the tradi- 
tional stereotype. The book defines 
many of the terms and explains many of 
the techniques which can be used in the 
personal computer systems we're all 
busy constructing and programming. It 
performs this service in a way which 
adds color and excitement to this newest 
of art forms, the computer application. 

Computer Lib/Dream Machines is 
must reading for the beginner, and is also 
a refreshing self examination for the old 
hand at programming and systems work. 

You can order your copy of Com- 
puter Lib/Dream Machines from BYTE's 
Books for $7. Send your order today to 
BYTE's Books, 70 Main St, Peter- 
borough NH 03458. Help stamp out 
cybercrud. 



PETERBOROUGH, NH 03458 



I Please add 50 cents for postage and handling. Please allow six weeks for delivery. 


Send copies of Computer Lib/Dream Machines to: 


Name 


i Address 


i Cily State Zip 


I > Check enclosed 


! II Rill MC.it Fv n natP 


ll Rill RA # Fv n natP 


i Signature 



114 



version clock of at least 5 kHz and as much 
as 2 MHz. The actual conversion time 
required is specified in the timing diagram of 
its specification as 40 clock periods. Thus if 
the clock rate were 40 kHz, the unit could 
be used to generate a valid digital word 1 
millisecond after the beginning of the "start 
conversion" input command signal. 
Operating at a typical microprocessor clock 
frequency of 1 MHz, the conversion time 
would be 40 /is, corresponding to a maxi- 
mum sample rate of 25,000 measurements 
per second. 

Where would this item prove useful in the 
context of personal systems? Well, consider 
the problem of reading the voltage on a 
thermocouple used to measure temperature. 
After amplification and normalization with 
operational amplifiers, the signal could be 
read by the analog to digital converter and 
used in a program written to implement a 
digital feedback loop used in controlling 
temperature in some way. Consider the 
problem of deriving the coefficients used in 
controlling a digital speech synthesizer: An 
ADC is an essential input to the process of 
analyzing such data. Or simply consider the 
general laboratory problem of using your 
computer as a voltmeter: Put a voltmeter 




analog front end on this converter and have 
your TV display put out the values it reads. 
National Semiconductor is located at 
2900 Semiconductor Dr, Santa Clara CA 
95051. The 100 piece price of this conver- 
sion chip is listed as $7.95, so it certainly 
should be available at a reasonable price 
through distributors and retailers." 



















Photocopy or cu! out tins solicitation foi 
inlormatioii and send to: 

7338 Baltimore Ave., Suite 200 
College Park, Maryland 20740 

JOINT VENTURE 

GROUP OEM BUYS 

CHEAP. Inc. was set up to coordinate joint venture OEM 
Group Buys' Depending upon I tie total quantity ol com 
mitments received, you can expect to pay from 20% (0 70% of 
the retail sales puce. Now you too can combine your orders 
with otheis throughout the country to purchase factory new 
electronic components at OEM rates. We will accept small 
Factory and Club commit merits as well as individual 
commitments. 

Circle below the products you may be interested In and 

estimate then quantity. After we receive this survey, we shall 
send, to you, more information, prices and delivery dates. 




Attention: KIM-1 owners. 

For Sale: Assembler program com- 
patible with MOS Technology assem- 
bler. Uses KIM-1 cassette interface 
for storage of source and object 
programs. Also includes a text-editor 
program, and both run in 4K of 
memory. They are distributed on 
cassette in both source and object 
form, in case you wish to improve or 
modify them to suit your needs. 
Assembler/text-editor . . $1 9.50 ppd. 
Write for details on sale of your 
programs on a commission basis. 

Micro Software Specialists, Inc. 
2024 Washington St 
Commerce TX 75428. 




STANDARDIZE! 
„ II 1 

SPECIAL OFFER. .. 
HIROSE 20 PIN CABLE + 
CHASSIS MOUNT CON- 
NECTOR 

(solder) ONLY $14.95 
REGULARLY $17.00 

Rugged, Reliable, widely 
used in video applications. 
Qty. discount, no C.O.D's, 
Details, Specs: 

JOHN ANTHONY TELEVISION 

DINGMANS FERRY 
A122 PA. 18328 


u.r.nP- 7Bn firiRfifl RRnn 

P.C. Boards: Computet Grade double buffered optional parity 
memory boards compatible with the Aliair 8800 on one 
edge and the Aftair 680 on the opposite edge; 4:8: 16K 

Flnpny nUk nnw( n^k CnnlmUei 








Snftwarf Fortran PI /I Suhsel 




EXTRA: We will consider purchasing general purpose P.C. 
Boards and Kits, etc. Write us about what you may have to 
offer and its OEM prices. 



















115 



Excerpts from Future History 



The following series of passages was compiled by reader John W Burgeson 
in a term paper he wrote for his "history of technology" course in the spring 
term of '25. Note how the attitudes remain the same, but the objects of the 
attitudes evolve with time. 



John W Burgeson 
101 Skyline Rd 
Georgetown TX 78626 



Who Wants an Automobile? 

Toward the end of the last century, 
nobody "wanted" an automobile. Whether 
the invention of the horseless buggy was due 
to accident, play, tinkering or rational 
thinking on the part of people endowed with 
mechanical abilities is immaterial for our 
purposes. Surely the invention did not 
originate with the consumer and was not 
made with an eye to prevailing consumer 
wants. Even when the first cars appeared on 
the road and for many years thereafter, their 
use for mass transportation was envisaged 
neither by producers nor by consumers. But 
today, even small children in America feel 
the need for a car to take them and their 
parents shopping, visiting, and later to 
school. Between the early days of the 
automobile and the present situation there 
was a long period of social learning. The 
learning process was, of course, not spon- 
taneous; first of all, it could not have taken 
place without the original invention; second, 
it was a function of numerous stimuli — 
personal experience, education, and reading, 
as well as propaganda and advertising. Thus 
it may be said that wants for automobiles 
were induced, or to use Galbraith's term, 
"contrived." But are not most of our wants 
contrived in this sense? And are not most of 
our contrived wants, in a certain sense, 
original with the buyer? It can hardly be said 
that such want-creation is artificial. 

George Katona, The Mass Consumption 
Society, New York, McGraw Hill, 1964, page 
55. 

Who Wants a Percom? 

Toward the middle of the 1970s, nobody 
"wanted" a percom. Whether the invention 
of the personal computer was due to acci- 
dent, play, tinkering or rational thinking on 



the part of people endowed with electronic 
abilities is immaterial for our purposes. 
Surely the invention did not originate with 
the consumer and was not made with an eye 
to prevailing consumer wants. Even when 
the first computers appeared in the offices 
of large companies and for many years 
thereafter, their use for mass personal use 
was envisaged neither by producers nor by 
consumers. But today, even small children in 
America feel the need for a percom to help 
them and their parents manage their affairs, 
help them with schoolwork, entertain them 
with electronic games and the like. Between 
the early days of the percom and the present 
situation there was a long period of social 
learning. The learning process was, of course, 
not spontaneous; first of all, it could not 
have taken place without the original inven- 
tion; second, it was a function of numerous 
stimuli — personal experience, education, 
and reading, as well as propaganda and 
advertising. Thus it may be said that wants 
for percoms were induced, or to use Gal- 
braith's term, "contrived." But are not most 
of our wants contrived in this sense? And are 
not most of our contrived wants, in a certain 
sense, original with the buyer? It can hardly 
be said that such want-creation is artificial. 

George Katona Jr, The Mass Consumption 
Society (Second edition), New York, 
McGraw Hill, 1996, page 55. 



Who Wants a Homer? 

Toward the end of the last century, 
nobody "wanted" a homer. Whether the 
invention of the home robot-computer was 
due to accident, play, tinkering or rational 
thinking on the part of people endowed with 
cybernetic abilities is immaterial for our 
purposes. Surely the invention did not 
originate with the consumer and was not 



116 



made with an eye to prevailing consumer 
wants. Even when the first real-time mini- 
computers appeared and for many years 
thereafter, their use for personal home 
management, protection and entertainment 
was envisaged neither by producers nor by 
consumers. But today, even small children in 
America feel the need for a homer to help 
them and their parents to manage their lives, 
protect them, entertain them and the like. 
Between the early days of the homer and the 
present situation there was a long period of 
social learning. The learning process was, of 
course, not spontaneous; first of all, it could 
not have taken place without the original 
invention; second, it was a function of 
numerous stimuli personal experience, 

education, and reading, as well as pro- 
paganda and advertising. Thus it may be said 
that wants for homers were induced, or to 
use Galbraith's term, "contrived." But are 
not most of our wants contrived in this 
sense? And are not most of our contrived 
wants, in a certain sense, original with the 
buyer? It can hardly be said that such 
want-creation is artificial. 

George Katona III, The Mass Consumption 
Society (Third edition), New York, McGraw 
Hill, 2024, page 55. ■ 



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Play aceyducey with (he computet 

Computer constructs a maze 

Computer guesses animals and learns new 

ones Irom you 
Ancienl game ol totaling beans in pits 
Guess a mystery 3 -digit number by logic 
Prints any message on a large bannet 
Baseball gaine 
Basketball game 
Match wits in a battle ol numbers vs 

the computet 
Decode a matrix lo locale enemy 

battleship 
Computer ptmts your card and calls 

the numbers 
BlackiacM very comprehensive!. Las 

Vegas rules 
Blackjack htandardgamel 
Destroy a gunboal Itom yout submarine 
Fly World War II bombing missions 
Plot a bouncing ball 
Bowling at the neigh not hood lanes 
3-i ound Olympic boning match 
Roll dice vs the computer lo draw a bug 
Guess a mystery 5-drgit number « 

the computet 
Throw dw J 

You're the matador in a championship 
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Computet dr awing ol the Playboy bunny 
Compose yout speeches with I he latest 

buz/words 
Calendar lor any year 
DnveaGroup7car in a Can-Am road race 
Computer imitates a cashier 
Game ol checkers 
Dilute kryptocyanrc acid to make tt 
harmless 

Silly arithmetic drill 
Eat a cookie avoiding the poison piece 

)2or more players) 
Fight the Cm) Wat 
Play craps Idicel. Las Vegas style 
Negotiate a 3-D cube avoiding hidden 

landmines 
Prints 1 page diamond patterns 
Summarizes dice rolls 
Computer ines to guess digits you 

select at random 
Penny arcade dog race 
Take obiects Itom a pile- try to end with 

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Same as EVEN -computer improves 

its play 
Solitaire logic game - change a row 

olXstoOs 
Professional football (very comprehensive) 
High School loolball 
Trade lurs wilh the while man 
Goll game - choose your clubs and swing 
Ancieni board game ol logic and slralegy 
Guess a mystery number - computer 

gives you clues 
File a cannon at a stalionary target 
Fue a cannon at a moving target 
Hangman word guessing game 
Computer becomes your friendly 

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Hexapawngame 



Ht-LO 


Try lo hit Ihe mystery uxkpot 




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Try to remove all the pegs Irom a board 


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Govern the ancient city-state ol Sumeria 




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Ice Hockey vs Cornell 


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Find Ihe Hurkle h.ding on a 10 x 10 grid 


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John Conway's Game oIL lie 




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Children's arithmetic drill using 
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Chinese game oINim 


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WORD 


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117 



The formal organizations used for clubs and societies can range from the 
totally informal (one person arranging a regular meeting place) to the setting 
up of all sorts of corporate nonprofit organizational structures, etc. The 
informal versions usually work best for small groups; formal organization 
tends to increase with the size of the group. Whatever the case, the less time 
spent on long drawn out nitpicking at business meetings, the more time there 
is to devote to more interesting matters .... 



Meeting Activities 

for Computer Clubs 



Dr Charles F Douds 
381 Poplar St 
Winnetka IL 60093 



A bunch of you got together and started 
a computer group? Congratulations! That is 
a good thing for this wonderful and fast 
growing hobby. You are meeting once every 
month? Fine, that will help to spread the 
word about the latest products, glitches, and 
cures. New people keep showing up at your 
meetings wondering what it is all about? 
That's the way it went in Chicago, too. And 
lots of other places, I'm sure. But now 
you've gotten to know each other, you're 
beginning to wonder what you should do at 
your meetings. 

That is an important point. The activities 
at meetings can make or break such an 
organization. People don't have to come, 
and they won't if they don't get something 
out of them. They want many different 
kinds of things. They want to learn some- 
thing. They want to share their ideas. They 
want to ask questions. They want to social- 
ize. They want to see things. They want 
help. Of course, not everyone wants all of 
these at the same time and most people 
don't want the same thing all the time. 
Variety and choice are important. If you 
look around you at other successful special 
interest organizations you will find many 
ideas for the kinds of things you might do. 
Here are some that I found. 



Lectures 

This is often the first thing you will think 
of, and quite easy to organize. The lecture 
may be by one of your own members or 
somebody invited in from outside. It could 
be an engineer or analyst from a local firm; a 
college professor; a sales engineer from one 
of the big electronics firms or other com- 
pany utilizing electronics products. The 
bigger firms might even send somebody in. 

Arrangements should be made well in 
advance. Usually you will do this in person 
or by phone and follow it up with a letter. 
Be sure to include detailed instructions on 
how to get to the meeting location. Of 
course, you have to get it set up in time to 
publicize the speaker and his topic. Perhaps 
he can join you for a meal before or after. 
Don't forget to send a letter of thanks 
afterwards. Better yet if you can send it to 
his boss when that is appropriate. 

There are two main problems with 
lectures. One is finding out how good the 
speaker is beforehand. A major problem here 
is that he or she may be good for one kind 
of audience, but not for yours. It is very 
likely that your group will be a very mixed 
bag of hardware types, software types, and 
enthusiastic types that don't know much 



118 



Activities at meetings of computer organizations can 
make or break the group. 



about hardware or software. That poses a 
real problem to a speaker in front of a large 
group. 

The other problem with lectures is having 
too many of them. They are about the 
easiest kind of program to arrange, but 
people get tired of being talked at. Dis- 
cussion with large groups doesn't work too 
well. A couple of poor speakers in a row can 
easily turn off a whole group. Program 
variety and member choice are important 
ingredients to a successful group. 

Clinics 

Clinics are less formal and often involve 
smaller groups than a lecture. More than one 
clinic can go on at the same time. People 
have a choice and different types of topics 
can be handled. A clinic is usually limited, 
for example, to one hour. It may also be a 
lecture, but it can take many different 
forms. The topics covered can be just about 
anything. They might include: design of an 
10 circuit, printed circuit artwork tech- 
niques, debugging procedures, an overview 
of high level languages, etc. The presentation 
may be in the lecture mode, or the author 
might simply talk, work on a blackboard, 
use flip charts, work at his computer key- 
board, or use slides or transparencies. 

Clinics are greatly enhanced if a handout 
is provided. It may be just a list of key 
points or provide details about what is being 
discussed. Sometimes a marketing minded 
manufacturer may be willing to provide 
material to a local member presenting a 
clinic about the manufacturer's equipment. 
For reference purposes handouts should 
include the author's name and address. 

If hardware is used or demonstrated, you 
need to make sure that the group is small so 
that everyone can see. If you are meeting in 
a high school or a college and have a crowd, 
you might be able to use a closed circuit TV 
so that the people in the back of the room 
don't go away saying it was lousy, while the 
ones in the front say it was great. For the 
same reason, consider the use of PA systems 
if you are likely to have a large audience. 



It is very important that the host check 
up well beforehand to find out what the 
author will need and what he or she is going 
to bring. Assume that the speaker will forget 
things like extension cords, chalk, and 
erasers. It is particularly important to check 
on projectors, screens, and electrical outlets. 
Make sure that they actually have power in 
them. Find out where the lighting switches 
are (especially in motels and hotels!) and 
where the background music can be turned 
off. Again, don't forget the thank you 
letters. 

When you gel to the point that on 
occasion several clubs get together for a 
"meet" that might last a weekend, or you 
decide to put on a real bash in just your own 
group, you will probably have several clinics. 
This is great because people can then get 
to the topics that particularly interest them, 
and still not be trapped in a room for 
something they care little about. But many 
people will want to get to all the clinics. This 
can sometimes be worked out by careful 
scheduling and persuading the authors to 
present their clinics twice. This isn't quite as 
bad for the author as it sounds. An hour 
clinic is really only 50 minutes and usually 
at least another 10 minutes should be 
allowed for questions. Besides, the practice 
is good for him or her. (I expect to see a lot 
more women actively involved in this hobby 
than in other comparable ones such as ham 
radio or model railroading.) 

Demonstration ("Hall") Clinics 

If you don't have a lot of rooms for all 
the clinics you would like to provide, or if 
you just have one big room where several 
speakers would interfere with each other, 
"hall" clinics might solve your problem. 
They can literally be set up in the halls; but 
more usually a number of them will be held 
in a large room — the kind that used to be 
called a hall. 

In the demonstration clinics one person 
does his thing for an extended period of 
time. Perhaps he is assembling a kit, laying 
out the artwork for a printed circuit board, 




A lecture, with a good 
speaker on a topic of inter- 
est to the group, is one of 
the easiest types of activ- 
ity to organize. 



NOTE: 

A brief version of this 
article originally appeared in 
the Micro-8 Newsletter, vol 2, 
no 2. 



119 



A panel discussion, with or 
without audience partici- 
pation, can be a good 
round robin affair which 
helps clarify and present 
concepts on a given theme. 



demonstrating his operating system, or what- 
ever. The topics may be similar to the 
regular clinics, but the format is different. 
The author does not lecture. He simply talks 
about what he is doing. He explains and 
answers questions as he goes along. This 
gives people the chance to see all the details 
and exactly how things are done. People are 
free to move from one demonstration to the 
next spending as long as they like at each. 

It is often important that tables or 
railings be set up to keep people a few feet 
back. This makes it possible for a half dozen 
or so people to see, while still being close 
enough to observe the details. It is best 
arranged so that the demonstrator can hand 
things to the viewers if he wishes to. 

Participation Clinics 

These clinics would be called "labs" in a 
school curriculum. The audience gets their 
heads and hands into the topic and learns by 
doing. These are good for such things as 
lessons on programming or introductory 
circuit design. These clinics require very 
careful preparation by the author. He or she 
should fully test out the lesson beforehand. 
Of course, not a whole lot can be accom- 
plished in an hour or two, but the most 
important thing is that it gets people started. 
The author can only do a little bit of 
teaching, followed by a lot of individual 
helping. Often these kinds of clinics are best 
run by two people working together. 

If equipment is going to be used — pin 
boards, voltmeters, etc — it may be neces- 
sary to have people sign up beforehand. 
Sometimes it may be possible to have people 
work in pairs. As long as the room doesn't 
get too crowded, it may be possible to let 
others in as spectators. The host should be 
prepared to shoo out excess people. The 
author will appreciate not having to do this 
for he or she may be busy with the 
instruction. 

Make sure that there will be enough 
materials available for a reasonable number 
of people to participate. Don't call it a 
"participation" clinic if only two or three 
can do so. 

Do It Yourself Clinics 

In these kinds of clinic the audience 
builds something and takes home a working 
device. They are immensely popular if 
adequately publicized, but they often 
require a lot of work to prepare. The item is 
announced beforehand. It might be a logic 
probe or a simple power supply. Participants 
send in their checks for the cost of parts. 
The announcement includes the list of tools 
needed, specified very exactly. (You would 



be amazed at the variety of soldering irons 
and pliers model railroaders will bring to 
build a printed circuit item!) 

At the clinic the author then shows the 
participants how to build the device step by 
step. It is very important that there be 
adequate facilities for checking the devices, 
too. You are trying to provide people with 
their first success in a new (for them) 
endeavor. There is nothing like the feeling of 
going home with a gadget you know for sure 
works. 

Obviously, it is important that the project 
be small enough so that it can be built and 
tested by the neophyte in the available time. 
It is important that this be checked out 
beforehand. If there are more than six or 
eight participants, the author should have 
one or two helpers — people who know a 
capacitor from a resistor, can read the color 
code, and who can recognize a cold-soldered 
joint. 

It might be possible to have "advanced 
level" clinics of this sort. The problem is 
that people who are not adequately ad- 
vanced will still sign up anyway. Not only 
are they likely to go away dissatisfied, but 
the author may get trapped into having to 
rebuild a half dozen units for these people. 
Keep the projects simple and short. With the 
complex chips available today, one still 
might be able to come up with relatively 
sophisticated projects. 

Of course, other variations are possible. If 
it were clearly advertised as such in advance, 
it might be possible to start construction at 
one meeting and complete it at a second 
meeting. The more advanced builders would 
probably complete the project and be able 
to test it themselves, so the second session 
would involve a smaller group. 

The host should make sure that there are 
suitable tables and adequate power outlets 
to accommodate all participants. 

Show and Tell Sessions 

Here we take a page out of the stamp 
collector's and photographer's book. It is a 
lot of fun to simply see each other's equip- 
ment. So much the better if it is up and 
working, but projects under construction 
can be very interesting, too. 

I suppose you could even have prizes for 
the best shaped letters on a TV set — with a 
separate class for monitors. How about one 
for the hardest to read Teletype? Or the 
prettiest set up? Or the worst (or would it be 
"best"?) job of haywiring that actually 
works! The possibilities are endless. Why not 
announce that there will be prizes, but not 
announce the categories. I would expect that 
altogether too soon we will be having too 



120 



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Swap shops and auctions, formal or informal, can be 
a good addition to a meeting which helps to solve 
nagging problems of what to do with surplus junk or 
where to find that critical part or subsystem (which 
is, of course, someone else's surplus junk). 





many committees working on too many 
prizes, although I must admit that contests 
do seem to stir up interest and provide real 
progress among enthusiasts. 

I think that the most important aspect of 
individual displays, apart from the conversa- 
tions that develop, are the many ideas that 
one can acquire in such a short time. These 
may be little details that make life easier or 
they may be whole new vistas that weren't 
really meaningful until seen "in the flesh." 

Workshops 

Workshops can take many forms, cover 
many subjects, and be conducted in many 
ways. An expert might work on debugging 
equipment that participants bring in. Or two 
or three people might design a special 
interface. The area is set up in such a way 
that the audience can watch and listen, but 
they do not participate. It is important, of 
course, that the experts do their thinking 
out loud. Again, a PA system or closed 
circuit TV may be helpful. 

A second type of workshop is essentially 
a "closed door" session, at least once it 
starts. Discussion among all the participants 
is expected. The output of such a workshop 
is often something that is going to benefit 
the whole club or others. For instance, the 
workshop might be devoted to developing a 
chart comparing the characteristics of cer- 
tain types of kits, developing the rules and 
standards for a local computer conferencing 
network, or other such things. The output of 
the workshop might become a regular clinic 
at another meeting. Such workshops require 
minimal facilities on the part of the host, 
but the participants certainly have to come 
adequately prepared and a competent dis- 
cussion leader is needed. 

Panel Discussions 

A good panel discussion can fit into many 
types of programs. The topic area should be 
definite, but not too narrow, ordinarily, for 
a hobby group. Sometimes the usual kind of 



panel discussion, where the discussants speak 
their pieces then argue back and forth, is 
appropriate; but it is probably better for a 
computer group meeting to have a question 
and answer panel. The audience asks 
questions, and one or more panel members 
tell how they handle the problem. Some- 
times members of the audience turn out to 
have good suggestions, too. 

The moderator is the key person in 
setting up a panel. He or she must not hog 
the stage, must be able to summarize long or 
confused questions, and have a facility for 
steering the discussion among the panel 
members. The biggest difficulty is in getting 
the audience participating. It is often wise to 
have several questions planted with a few 
friends in the audience. It is entirely natural 
for people to hesitate to speak up in a crowd 
until they hear one or two questions that 
they recognize as being as simple, or simpler, 
than theirs. A dozen people may have the 
question in mind, but no one wants to be 
first. The other important point is to stop 
the session while the questions are still 
coming. Stop at a high point, not in a valley 
— and everyone will go away thinking how 
great it was. 

Tape Slide Programs 

Many of the activities above can be 
worked up into a prepackaged recorded 
program with accompanying slides. The 
visuals probably should be 35 mm slides 
because projection equipment is always 
available. It might be possible to use cassette 
tapes, but standard reels are probably better. 
The problem is that it may be awkward to 
get adequate sound volume for an ordinary 
size audience from a cassette machine, while 
there is seldom a problem with an ordinary 
home tape recorder. 

Tape slide programs can be made success- 
fully by amateurs, but they do not work out 
by simply recording a live clinic even if it 
uses a lot of slides. A script has to be 
prepared and worked over. The final taping 



122 



A SUPERIOR "301" 
TYPE OP AMP 
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A Summary of 
Meeting Activities 

Lectures 

Clinics 

Demonstration ("Hall") clinics 

Participation clinics 

Do it Yourself clinics 

Show and Tell sessions 

Tape slide programs 

Workshops 

Panel discussions 

Tours 

Swap shops 

Auctions 

Mixer sessions 

Contests 

Business meetings 



should not be done by reading from the 
script unless the person is a professional 
actor or announcer. A clear, distinct cue 
signal, described at the very beginning of the 
tape, must also be provided. It takes a lot of 
work to put together a good tape slide 
program, but the results can be well worth 
it. They provide direct access to top notch 
information, especially for those groups in 
remote locations. 

This is one way that the manufacturers 
might be able to make a name for them- 
selves. Even if a program were purely pro- 
motional, it still would be interesting to 
meet the people at the plant, see their 
facilities, and to watch their products in 
action. Of course, it would be even better if 
they would go into the unique features and 
application possibilities. 

As an example of such materials in a 
specialized field, the National Model Rail- 
road Association has over 30 such programs 
available to its members for a deposit and 
return postage (educational material rate). 
The waiting list is months long. 

Tours 

With a little imagination, some pleading 
and cajoling, and a bit of persistence, you 
may be able to come up with some fas- 
cinating tours. Many of your group may 
never have seen a big computer installation. 
If they have, then they probably haven't 
seen a manufacturing operation. Or how 
about an automated security system? It does 
not matter if there are no electronics manu- 
facturers around; there undoubtedly will be 
many applications nearby. Then there are 
the potential applications . . . quarries, 
turkey farms, mushroom growers, etc. 

But don't forget your own members. 
Maybe some of them would be willing to 
show how they have things set up at home. 
Devise a way to get reasonably small groups 
around to several homes, making sure that 
only those who are wanted stay on until the 
wee hours of the night. 

Swap Shops and Auctions 

Auctions are a lot of fun. If you are 
having a two-day affair, schedule one for 
around 10 in the evening. It may last until 2 
AM, but everyone has a lot of fun — except, 
perhaps, for the auctioneer. It usually takes 
a crew of people to put on a reasonable size 
auction. They need to be adequately pre- 
pared with a good set of forms, display 
tables, and enough space. 

The usual type of swap session, along the 
lines of an amateur radio "hamfest" is well 
known, where everyone selling gets some 
table space and makes his own deals. While 



auctions can easily collect a percentage of 
the sale price (often 10%), swap sessions are 
more easily handled by the host organiza- 
tions collecting a fixed entrance fee from 
sellers, buyers, and lookers. 

As a service to its members, there could 
be a swap session bulletin board at every 
meeting. Just bring a cork board, a bunch of 
3X5 cards, and some thumb tacks. Even if 
the program scheduled flops, you might still 
pick up a bargain. 

Mixer Sessions 

If your club is small, everyone will soon 
get to know what each other's interests are; 
but once it gets over 30 or so people, this 
will no longer be true. There will be the 
devoted core who are doing most of the 
work organizing these programs and doing 
all the other things that need to be done. If 
you are one of them and think you know 
everyone's interests, you will probably dis- 
cover that there are a lot of people showing 
up who don't know. At this point it is time 
for a mixer session. 

Try putting signs up on the walls with 
words indicating topics for discussion. These 
might be the names of manufacturers, types 
of equipment, programming projects, etc. At 
this point a bit of the summer camp 
counselor is needed to get the people to 
assemble in these areas and to discuss the 
topic. Of course, it would be wise to have a 
few people designated to cover each one and 
to handle the initial introductions. 

Once when I attended a regional model 
railroad convention, I wanted to find all the 
people I could who were interested in 
applying electronics to that hobby. I hung a 
piece of cardboard on my back with a few 
key words in large letters, met several 
interesting people, and was given the names 
of several others not at the convention. 
When a speaker has to cancel out at the last 
minute, you might try that idea. Hang a sign 
on everyone's back as they come in the 
door. I bet it will be one of your top-rated 
meetings. 

Contests 

Contests in many special interest and 
hobby groups often seem to wind up taking 
on a life of their own, leaving most of the 
membership out. Most contests can be won 
by the liberal application of not just skill 
and time, but also money. They certainly 
can provide an incentive to improve designs 
and techniques. A major problem is to 
determine what the goals of the contest are 
to be. It seems to me that for a bunch of 
enthusiasts, they should be to encourage 
participation and to have fun. They 



124 



shouldn't get out of hand in terms of skill or 
money demands. When this happens, they 
just become spectator events. In my opinion, 
the major goal of contests should be to 
encourage active participation. We have 
enough TV watchers now; let's apply our 
imaginations and have more keyboard 
button punchers and TVT watchers! 

Business Meetings 

We hate them, but we can't seem to get 
along without them. Every organization has 
to have business meetings. Unfortunately, 
the kind of people who enjoy business 
meetings tend to be the ones who run them. 
Certainly there is little reason why a com- 
puter hobbyists group has to have a business 
meeting involving everyone as a part of every 
meeting. The amount of time spent on 
business meetings should be minimal! 

The work of the organization should be 
done outside the whole group sessions by a 
steering committee. Undoubtedly, you will 
wind up electing officers (although the 
Chicago Area Computer Hobbyists Exchange 
operated for more than a year without 
any). The really important thing is for all to 
know who is making what kind of decisions 
or taking what type of actions. You can have 
officers and still be very confused about this. 
The titles don't make the difference. Some- 
times they just seem to attract people who 
like titles for the sake of having the titles. 

However, it is vital that procedures be 
maintained so that actions by the few can be 
overruled by the whole body, or a clique 
thrown out, when necessary. You are never 
close minded, secretive, or not doing things 
in the best interests of the organization, of 
course. But you can only prove this by 
making it easy for others to do things 
differently than what you think is best. 
Make it easy, and they will probably go 
along with you. 

Do not overorganize! There is very little 
that needs to be "business like" about a 
hobby organization. It is not a business. 
People come voluntarily. They come to 
learn, for relaxation, for fun. The avocation 
is computers. It is not setting up committees 
for everything, or writing rules, regulations, 
and procedures inappropriate for an organi- 
zation of volunteers. 

Do set up committees, but only as needed 
to ensure that things get done, or to keep 
the organizational types out of everyone 
else's hair. 

Keep the business meetings short and to 
the point. Provide a variety of types of 
programs. Don't be afraid to experiment. 
Provide choice and change. You'll have a 
great club." 




r GPeative 
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Creative Computing Magazine 

A bimonthly 88 page magazine for students, hobbyists, and anyone curious 
about computers. Fiction, articles, humor about computers, cybernetics, 
careers, building into,, etc. Emphasis on games, puzzles, and projects. 
Contemporary, nontechnical approach. Subscription: £5.00 (UK), $8.00 (USA), 
$10.00 (Other). 

Games & Puzzles Issue of 
Creative Computing 

88 pages of games and puzzles for pocket calculators, computers, and humans. 
"Beating the Game," "Computer Chess," "Hunting a Wumpus in a Cave," 
building your own computer, reviews of 24 games, books, and much more! £1.00 
(UK), $1.50 (USA), $200 (Other). 

Futures Issue of Creative Computing 

Artificial Intelligence (Bertram Raphael, Herbert Dryfus, etc.), Extraterrestrial 
Intelligence (Isaac Asimov, Martin Harwit, etc.), microprocessors, videodiscs as 
an ultimate computer input device, 4 new games, and more. 88 big pages! £1.00 
(UK), $1.50 (USA). $2.00 (Other). 

Artist and Computer 

A high-quality. 4-color book edited by Ruth Leavitt which displays the work of 35 
internationally-known computer artists. Each artist describes his or her work in 
non-technical terms. 16 illustrations. £3.35 (UK), $5.70 (USA), $6.70 (Other). 

101 BASIC Computer Games 

A collection of 101 games in BASIC, each one with a complete listing, sample run, 
and write-up. Over 30,000 copies sold. 248 pages. £4.75 (UK). $8.25 (USA), 
$9.25 (Other). 

The Best of Creative Computing 

A 328-page book featuring stories by Isaac Asimov and others; articles on 
cybernetics, robots, computer crime, privacy; computer games such as Star 
Trek, Rabbit Chase, Magic Square. Madlib, and 14 more; super computer 
graphics; cartoons: reviews: poetry: and more! £5 50 (UK), $9.70 (USA), 
$10.70 (Other). 

Creative Computing T-Shirt 

Albert Einstein' portrait produced by Blocpix'" process. Scarlet trim, black 
design. Available in adult sizes: S, M. t, XL. £2.50 (UK), $4.00 (USA), $5.00 
(Other). 

Star Trek People Computer Images 

Six 8 1 . x 1 1 computer images on heavy stock of Kirk, Spock, McCoy, Scott, 
Chekov, and T'Prmg. £1.00 (UK), $1.50 (USA). $2.00 (Other). 

Mr. Spock Computer Image 

Big 17x22" computer scanner image. Heavy stock. Comes in strong mailing 
tube. £1.00 (UK). $1.50 (USA), $2.00 (Other). 



Orders m the U K 

Creative Computing 

60 Porchester Road 

Southampton S02 7JD, England 

Orders in the USA and elsewhere 

Creative Computing 

P.0.Box789-M 

Morristown, N.J.07960. U.S.A. 



125 



What's 

New? 



The following item is adapted from a press 
release provided by A P Products, Box 110, 
72 Corwin Dr, Painesville OH 44077. It is 
printed here for its value as background 
information on the use of solderless proto- 
typing jigs to try out experimental circuits 
on a temporary basis. 

Solderless Breadboards 

What is a solderless breadboard? How 
does it work? What advantages does it offer? 
Where can it be used? And how? 

Before the invention of modern solderless 
breadboards, designing and testing any given 
electronic circuit was an aggravating, 




tedious, and time consuming task. First a 
circuit would have to be designed on paper. 
Then the schematic diagram of the circuit 
would have to be translated into a circuit 
board parts layout for either point to point 
or printed circuit wiring. If a printed circuit 
were to be used, as was most often the case, 
the circuit layout would have to be trans- 
ferred to a copper-clad board, the copper 
selectively etched, holes drilled, and com- 
ponents soldered in place. Then, if a com- 
ponent proved the wrong value, it would 
have to be desoldered and a new one 



YTE'S 
UGS 



On page 68 of the August issue, there is a 
typographical error in the box "A Note 
About Construction." The Motorola part 
number referenced at two places in the box 
should be "MCM6571 L" not "MCM6517L" 
as printed." 



soldered in place. If the printed pattern were 
in error, a whole new board would have to 
be designed, etched, drilled, filled and sol- 
dered. 

When A P Products came up with the idea 
of arranging a breadboard with a matrix of 
interconnected holes, the process was simpli- 
fied. The interconnections are made by 
conductive spring clips that grip each com- 
ponent lead firmly to establish a good 
electrical connection without soldering. The 
matrix of holes was placed on a tenth inch 
(.254 cm) spacing pattern to conform with 
standard component lead spacing. 

The interconnection pattern was designed 
to provide ample access to each lead of each 
component, especially with modern transis- 
tor and integrated circuitry in mind. And 
distribution strips were designed to provide 
power and signal lines where needed. 

Circuit design testing now becomes a 
matter of plugging in components and wires. 
Integrated circuits and discrete components 
plug into the solderless breadboard and 
ordinary 22 gauge solid wire jumpers are 
used to interconnect them. 

A given circuit can now be prototyped in 
minutes rather than hours or days. Many 
designers work directly with component 
specification sheets, many with schematic 
diagrams. Changes in parts values are as easy 
as pulling out one part and plugging in 
another. And the geometry of the modern 
solderless breadboard translates into a 
printed circuit layout readily once the 
circuit is ready to commit to hardware. 

In addition, solderless breadboards can 
serve as a basis for semipermanent circuits in 
applications where the need for a given 
circuit requires reliability but does not re- 
quire longevity. 

Applications for modern solderless bread- 
boards are as wide as all of electronics. There 
are professional applications in machine con- 
trol, data processing, test and measurement, 
device testing, prototyping and equipment 
adjunctive aids. There are hobby applica- 
tions ranging from communications to 
photography to automotives to biofeedback 
to music to model railroading and more. 
And, of course, solderless breadboards are 
perfect for educational and instructional 
applications. 

Solderless breadboards and breadboarding 
aids come in many sizes and prices, and have 
been used in designs as simple as a logic 
probe or as complicated as a small computer. 

A P Products has available a free catalog 
of their ACE All Circuit Evaluator solderless 
breadboards, Super Strips™, terminal and 
distribution strips, integrated circuit test 
clips and accessories." 



126 




UNIVERSAL POWER SUPPLY 

A unique plug-in supply by Panasonic. Useful 
for calculators, small radios, charging many & 
various small NiCad batteries. Adjustment 
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to 4V2, 6, 754, or 9 volts DC at 100 MA. Output 
cord with plug, 6 ft long. 

No. SP-143C $4.50 3/$12 



POWER SUPPLY 

LAMBDA 5VDC 74 AMP 

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CLOCK KIT $14.00 

Includes all parts with MM5316 chip, 
etched & drilled PC board, transformer, 
everything except case. 

SP-284 $14.00 each 2/$25.00 







ca&sts 



PARITY DETECTOR 

New packaged, made for RCA, detects even or odd parity, baud rate 110, 150 or 
134.46. Built-in logic supply for the IC's, operates from standard 115 vac. Control 
panel allows manual or automatic reset mode of operation. Aluminum enclosure (not 
shown), covers the electronics. TTY compatible. 

Ship wgt. 10 lbs. $16.50 



COMPUTER DISPLAY TUBE 

New Sylvania 9 inch CRT, 85 degree deflection, with tinted faceplate. Same as used 
in Viatron systems (buy a spare). With complete specs. 

Ship wgt. 5 lbs. $15.00 





LINEAR by RCA, brand new 


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MEMORY SYSTEM $125.00 

New memory system by Honeywell, small . . . 
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a mini-computer. Limited supply on hand. 
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Sends and receives hard copy or audio of touch tone data sent & 
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127 



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Vector Wiring Pencil PI 73 consists ota hand lurid iiMiiurrweiriw (under one ounce) 
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Sialic 
Fast 



3.49 
2.49 

6.95 



$13.95 
14 95 
5.00 



BIPOLAR PROM SPECIAL 

6300-1 (70 NS) 256 x 4 OPEN COLLECTOR BIPOLAR PROM (EQUIVALENT TO 82S126) $2.95 
6301-1 (70 NS) 256 x 4 TRI STATE BIPOLAR PROM (EQUIVALENT TO 82S129) S2.95 



TJfi-t T4i 
T49A Til 

PKG 100 



028 so. 
025 sq 



25 pes 50 pes 

Gold Tin Gold Tin 

1 50 lot 1 00 lot 2 75 lot 1 75 lot 

1.75 lot I 25(01 3.0Qlal 2 25 I nl 

1 25 lot 3 10 lot 2 25 lot 



Terminals S3. 50 C S13 00M 



NIBBLING TOOL DIAGONAL CUTTER 



_J| ..."u'.ivv, V;,,.;;, '71 Vj" Semi-Flush ( 



Vt" Semi-Flush Cul Finn Diagonal 
14 



64 KEY KEYBOARD 



Hits keyboard (natures 64 unerv 
coded SPST keys, unattached to 
any kind ot P C.B A i/cry solid 
molded elastic 13" x 4" base 
suns most ao cheat ions 

$19.95 



HD0165 16 LINE TO FOUR BIT PARALLEL KEYBOARD ENCODER 



w® 



'Special Requested Items* 



Wit 



RC4194 

RC4195 

F9368 

LDII0/11I 

C A3 130 

MC1408L7 

F3341 

MU5641 

AY5-9100 

COP 1802 



Dual Track V Reg 

• 15V Track Reg 

Decoder 

DVM Chip Set 

Super CMOS Op Amp 

D/A 

FIFO 



3.25 
3.95 

25.00 
I 39 
9 95 
6.95 

1800 



NBT97 

4024P 

OM8130 

CD4520 

MCI 401 6 

2525 

2527 

CD4518 

MM5309 



S 2.00 MK5Q.D7 S10 95 MC4044 
2.25 8263 5.95 LM3903 

3.25 8267 2 75 MM5320 

4072AE 
7422 
7497 



74181 



CPj Mi: --processor 39 95 0M813I 



451 1A£ 
XR4136 
4566AE 3.00 B2S90 

ICM 7205 29 95 MCT-2E 



5 FUNCTION ELECTRONIC CALCUUTOR 
RAOOFIN MODEL 8P 



$8.95 



FEATURES: 

• 8 Digit Display 

• 5 FunctinnscaitseEol addition. subtraction. mul- 
tiplication, division, percentage: wilh constant on 
all functions, wild lull Moating decimal point. 

■ Power source is 1 piece 9V DC Batiery OOGP. 
jack lor AC adapter 

• Black superfine grained finish plastic cabinet 




5 FUNCTION ELECTRONIC CALCULATOR WITH 
WALLET-NOTEBOOK AND POCKET CHECKBOOK 
RADOFIN MODEL 1710 

FEATURES: 11)13.90 

• B Digit Display 



i 5 Functions consists ol addition, subtraction, mul- 
tiplication, division, percentage, with constant or 
all (unctions, Willi lull tloating decmal poim. 
■ Power source g 6 AAA cells 9 V DC 
. Wallet rs 2 lone texon; cabinet s black plastic 



0Q 



3 1 / 2 DIGIT DVM KIT 




This 0-2 VDC ,05 pet cent digital voltmeter features the Motorola 3h digit 
DVM chip set. It has a .4" LED display and operates Worn a single +5V 
power supply. The unit is provided complete with an injection molded black 
plastic case complete with Bezel. An optional power supply is available 
which (its into the same case as the 0-2V DVM allowing 1 1 7 VAC operation . 

A. 0-2V DVM with Case $44.95 

B. 5V Power Supply $14.95 



Continental Specialties 



PROTO 



POWER 

FOR THE 

PROFESSIONAL 



POWER! 



Far Ihe economy-minded eipeiimenlsr 




c Proto 

$75 Board 

203 



Proto Board 100 



- ■ 



$17.95 



THE MINI- 

BREADBOARD 
BUDGET KIT 

Piolo Bun! 101 



»*J« 



Prolo Board IM. ( ' " .' ' j if 1'fl OIP tjpjal, I 

HUJH IMIsotolcsi- fi/i -■", f /■ 

!".'i'"!'i ,','■'■ '.*'','•-. i "* '" > / / Pmlo Band 103 

DIPuwW* )>•■ <av § I ? SO soHstrw ix 

■• -79.95 _ J KSg'iS" 

1 ™ I ;4.ucmOic 



29.95 
' 39.95 



g 4 % iV | 




SPECIAL! 



LOGIC MONITOR 

Simultaneously displays Static ant 

dynamic logic slates ol DTL. TTL 

HTL or CMOS DIP IDs. 

Pocket size. SB4.95. 




■K- ... 
■■I 

hoT-12S 

.■■■ana. Ui ' as 
IS Ql-rs 



OT Proto Slrlps 



QT type 

QT-S9S 
OT-59B 
QT-I7S 
OT-47B 
OT-35S 
OT-350 
OT-IBS 
OT-I2S 
QT-BS 
OT-7S 



DIGITAL CLOCK KIT — 3 1 / 2 INCH DIGITS 





JOYSTICK 

These joysticks feature four 
I OOK potentiometers, that vary 
resistance proportional to the 
angle ol the stick. Sturdy metal 
construction with plastics 
components only at the mova- 
ble joint. Perfect for electronic 
games and instrumentation. 

$9.95 ea. 



4 DIGIT KITS49.95 
6 DIGIT KIT S69.95 



4 DIGIT ASSEMBLED S59. 95 
6 DIGIT ASSEMBLED S79.95. 



This clock teatures big 3 1 /?" high digits 
for viewing In oflices, auditoriums, etc. 
Eacti digil Is larmed by 3t bright 0.3" 
LEDs Theclockoperateslrom117VAC. 
has eilhcr 1? or 24 dr. operation. The 6 
digil veision is 2?" x3Vi" x t W. and the 
4 digit is IB" x 3VT x HV. Kits come 
complete with all components, case and 
Iranslormer. 
Speclly 12 Or 24 ilr When Ordering 



Satisfaction Guaranteed. $5.00 Min. Order. U.S. Funds. 

California Residents — Add 6% Sales Tax — Data Sheets 25c each 

Send a 13c Stamp (postage) for a FREE 1976 Catalog 

1021 HOWARD AVE., SAN CARLOS, CA. 94070 
PHONE ORDERS — (415) 592-8097 




115 VAC 



JE700 clock 

The JE7O0 is a low cost digil.il dock, but 
is a very high quality unit The unit lea- 
lures a simulaled walnut case with di- 
mensions nl 6" x 2'j" x 1' . II utilizes a 
MAN72 high brightness readout, and the 
MM531-1 clock chip 

$17.95 



Liquid Crystal Temperature Display I 

Six Digit Light q[_ 33 

Emitting Diode Disp | ay 

Display 

This clock makes an attractive addition to any desk. It has 
an extruded, black anodized aluminum case. It displays 
hours, minutes, and seconds with .11 inch displays, and 
comes complete with a liquid crystal thermometer. It oper- 
ates off 115 VAC at 50 or 60 Hz. CO4 Q5 



1 <? : 4 9 3 ' 



This large digit clock (.6" tiours & 
minotes. .3" seconds) features the 
MM5314 clock chip. It operates 
from 117 VAC, and will operate in 
either a 1 2 or 24 hour mode. The 
dock is complete with a walnut 
grain case, and has last set. slow 
set. and hold time set features. 



KIT - ALL COMPONENTS & CASE S34.95 
WIRED & ASSEMBLED S39.95 



JE803 PROBE 

Ihe Logic Probe is a unit which is lor Hie rmisi pari 
indesnensiUle in trouble slioolinrj logic latnilies 
TTL. DTL. RTL. CMOS It derives the power n- 
needs to operate directly oil ol Ihe circuit under 
lest, drawing a scant 10 mA ma> It uses a MAIV3 
readoul to indicate any ol the tallowing stales Dy 
itiese symbols (H) 1 |LOWl - o tPULSEl - P The 
Prone can detect high lioquency pulses lo 45 MHz 
II can't be used at MOS levels m circuit damage 
will result. 






$9.95 Per Kit 

printed circuit boatd 




PL 5V 1A Supply 

This is a standard TTL power supply using Ihe well known 
LM309K regulator IC to provide a solid 1 AMP ol cuneni at 5 
volts We try lo make Ihings easy lor you by providing 
everything you need in one package, including Ihe hardware 

to,,* sg 95 Per Kit 




exelar 

This watch is manufactured by Na- 
tional Semiconductor. It proviaes 5 
functions; hours, minutes, seconds, 
date, A.M. indicator dot. Accuracy is 
assured to 5 seconds per month by 
precision quartz crystal. If something 
should go wrong with the watch, repair 
is assured within 48 houis after it is 
received. Complete with steel black 
leather band. 

ES4-YS 

3 MICRON GOLD PLATE BEZEL 



$29.95 



DIGITAL ALARM 
CLOCK 

This 4 digit Novus Alarm Clock 
is a very reliable and smartly 
styled unit. It provides such 
teatures as an alarm sellable 
to any minute ol the day, a 7 
minutes snooze alarm, a power 
failure indicator, and even an 
A.M., P.M. indicator. 



Novus 




$17.95 



NOT A KIT 



SOLID STATE 



ANNOUNCES THE 



HILD 



TECHNOLOGY KIT 



• FOR THE EXPERIMENTER WITH TASTE FOR "STATE OF THE ART" PRODUCTS 

• COMPLETE SPECIFICATIONS ARE PRINTED ON THE BACK OF EACH TECHNOLOGY KIT 



FTK0020 



FTK0020 



FTK0011 



PN PTKW2Q 



SOLID STATE 

TECHNOLOGY 



KIT 



SOLID STATE 

TECHNOLOGY 




TEN RED LED LAMPS 

TECHNOLOGY BY 

FAIRCHI 



4001 MIRANDA AVENUE- PALO ALTO, CA 94304 




CARD FRONT 


CARD BACK 




DIGITS 






FTK0001 


0.5" High Common Cathode Digit 


$1.00 


FTK0040 


FTK0002 


0.5" High Common Anode Digit 


1.00 


FTK0041 


FTK0003 


.357" High Common Cathode Digit 


.75 


FTK0042 


FTK0004 


0.8" High Common Cathode Digit 


2.00 




FTK0005 


0.8" High Common Anode Digit 


2.00 


FTK0050 
FTK0051 




0.8" HIGH DISPLAY ARRAYS 




FTK0010 


12 Hour, 3Vi Digit Clock Display 


7.00 




FTK0011 


24 Hour, 4 Digit Clock Display 
LED LAMPS 


8.00 


FTK0400 


FTK0020 


10 Red LED Lamps 


1.00 


FTK0401 


FTK0021 


5 Mixed Colored LED Lamps 


1.00 




FTK0022 


10 LED Mounting Clips 


1.00 


FTK0402 


FTK0023 


5 Three Piece LED Mounting Adapters 


1.00 






PHOTO TRANSISTORS 




FTK0403 


FTK0030 


5 Flat Lens Photo Transistors 


1.00 


FTK0405 


FTK0031 


5 Round Lens Photo Transistors 


1.00 




FTK0032 


3 Flat Lens Photo Darlingtons 


1.00 




FTK0033 


3 Round Lens Photo Darlingtons 


1.00 


FTK0106 




24 HOUR, 0.8" HIGH CLOCK DISPLAY 

TECHNOLOGY BY 

FAIRCHILD 

4001 MIRANDA AVENUE -PALO ALTO, C A 94304 

CARD FRONT 

PHOTO ARRAYS 

9-Element Tape Reader Array 16.00 

12-Element Card Reader Array 24.00 

Reflective Opto Coupler 4.00 

COUPLERS 

3 General Purpose Opto Couplers 1.00 

Darlington Opto Coupler 1.00 

MPS CLOCK CIRCUITS 

Digital Clock/Calendar Circuit 7.00 

(FCM7001) 
Digital Clock/Calendar with BCD 7.00 

Outputs (FCM7002) 
Direct Drive Digital Clock Circuit 5.00 

with AC Output (FCM3817A) 
Direct Drive Digital Clock Circuit 5.00 

with DC Output (FCM3817D) 
Direct Drive Digital Clock/Calendar 6.00 

Circuit (FCM7015) 
KITS 
Automobile Clock Kit 40.00 



i THESE PRODUCTS ARE PACKAGED FOR OUT- 
STANDING WALL DISPLAY APPEARANCE 



.FULL p^JRcmj^ PRODUCT LINE 
TO FOLLOW 



• DEALER'S AND WHOLESALER'S INQUIRIES 
INVITED-PRICE LIST AVAILABLE. 

• BUY WITH PRIDE THE PRODUCTS BUILT BY 



THE INDUSTRY'S LEADER- fairchild 



Satisfaction Guaranteed. $5.00 Min. Order. U.S. Funds. 

California Residents - Add 6% Sales Tax 

Send a 13c Stamp (postage) for a FREE 1976 Catalog. 



<?/47%SS 



1021 HOWARD STREET 

SAN CARLOS, CA 94070 

PHONE ORDERS - (415) 592-8097 




Clubs 

and Newsletters 



LICAof NY 

In issue number 5 of STACK, the news- 
letter of the Long Island Computer Associ- 
ation, is a department heading "LICA, 
Where Goest Thou?", written by Albert L 
deGraffenried. It describes the double-bar- 
reled reward of exchange of information, 
and comradery, which is also found in other 
types of clubs, as well as hidden assets, such 
as the easy crossing of age and credentials 
boundaries. There are group benefits too, 
both given and received, and Al cites what 
radio hams have contributed to the com- 
munity in times of disaster. This leads to 
what a computer club has: "group power" — 
the unique ability to solve numerically large 
problems which may have substantial social 
impact and perhaps dollar returns for the 
club. 

Al may have hit upon a really good idea. 
Maybe your particular community has a 
need that your club or group could fill. This 
could be an area to explore. We'll be looking 
forward to seeing what progress LICA makes 
in this direction, in future issues. 

Morris Balamut is editor of STACK, POB 
864, Jamaica NY 11431. 



AIM RAD Computerfest 

The Amateur Radio Research and Devel- 
opment Corp is sponsoring a Computerfest 
to be held on October 24 1976 at the 
Vienna Community Center, 120 Cherry St, 
Vienna VA, near Exit 1 I S of the Washington 
DC Beltway. The exposition will be almost 
entirely devoted to small computers of the 
type suitable for home use. There will be 
displays of microcomputer systems by 
various manufacturers' reps, as well as tables 
for used or surplus equipment, circuit boards 
and parts. Admission will be $4 at the door, 
$3.50 advance registration by mail. Make 
checks payable to AM RAD. Write: COM- 
PUTERFEST, POB 682, McLean VA 221 01. 

AMRAD is a nonprofit club. The mem- 
bers for the most part have amateur radio 
licenses, although two thirds of their ac- 
tivities are now focused on microcomputer 
subjects. 

Denver Amateur Computer 
Society — DACS 

DACS has informed us of the appoint- 
ment of Jim Clark as the new editor of the 
DACS newsletter. They would like to set up 
an exchange of newsletters with other clubs. 
Send your newsletters to Jim Clark, 538 So 
Swadley St, Denver CO 80228. 

Tektronix 4051 Users Group 

Vic Kley, POB 21 1 7, Berkeley CA 94702, 
is an enthusiastic user of the Tektronix 4051 
scientific computer. This is a machine which 
has a desk top package including keyboard 
and storage tube vector graphics display, as 
well as built-in mass storage and BASIC 
interpreter. Its internal architecture is that 
of a Motorola 6800, and it interfaces for 
scientific use to the IEEE 488 parallel bus 
standard (the Hewlett Packard instrumenta- 
tion bus). 

To date, there has been no organized 
user's group for this machine. Vic Kley 
would like to remedy that situation. Any 
persons interested in the concept of an 
independent 4051 users group should con- 
tact him at the above address. 

CENOACA 

Lee Lilly of the Central Oklahoma 
Amateur Computing Association issues a 
newsletter called NEWSBITS and offers to 
establish a regular exchange of newsletters 
with other clubs. Write: CENOACA, Box 
2213, Norman OK 13069. Anyone in- 
terested in joining the club? They meet on 
the second Saturday of each month at 
10 AM in the Oklahoma City Warr Acres 



130 



S. D. SALES CO. 



P.O. BOX 28810 B 
DALLAS, TEXAS 75228 



4K LOW POWER RAM BOARD KIT 



Imsai and Altair 8080 plug in compatible. Uses low power static 
21L02-1 500 ns. RAM's, which are included. Fully buffered, 
drastically reduced power consumption, on board regulated, all 
sockets and parts included. Premium quality plated thru PC Board. 



THE WHOLE WORKS 



$89.95 



8 Digit LED 
"METRIC MASTER" 

$19.95 

"RAPID MAN - 12" 

$29.95 



$1,000,000 CALCULATOR PURCHASE! 
We bought the entire stock of a major manufacturer. New, guaranteed units. 

Five functions PLUS complete Metric Conversion functions. Re- 
chargeable batteries. Small, hand held size. With AC charger. 

12 Digit - Desk Top Style. Sturdy design. With memory and four 
complete functions. Big, bright display. 



ALARM CLOCK KIT SIX DIGIT LED 

Thousands of hobbyists have bought and built our original clock 
kit and were completely satisfied. But we have received many 
requests for an alarm clock kit with the same value and quality 
that you have come to expect from S. D. So, here it is! 
THE KIT INCLUDES: 

1 Mostek 50252 Alarm Clock Chip 

6 Hewlett Packard .30 in. common cathode readouts 
15 NPN Driver Transistors 

2 Switches for time set 

2 Slide Switches for alarm set and enable 

1 Filter Cap 

4 IN4002 Rectifiers 

1 IN914 Diode 

1 .01 Disc Cap 

15 Resistors 

1 Speaker for alarm PCB — $3.00 

1 LED lamp for PM indicator XFMR — $1.50 



$9.95 



MOTOROLA RTL IC'S 

Brand new, factory prime. Hard to find, but still used in a variety 
of projects. (See the RTL Cookbook by Howard W. Sams.) 
MC724P — 59c MC780P — 89C MC791P— 69c 

IVIC725P — 59c MC785P — 49c MC792P — 59c 

MC764P — 49c MC787P— 89c MC799P— 59c 

MC767P — 69c MC788P — 49c MC970P — 89c 

MC771P— 49c MC789P — 59c MC9709P— 69c 

MC775P — 89c MC790P— 89c MC9760P — 69c 



$5.95 



60 HZ CRYSTAL TIME BASE - 

FOR DIGITAL CLOCKS 
S. D. SALES EXCLUSIVE! 
KIT FEATURES: 

A. 60 hz output with accuracy comparable to a digital watch 

B. Directly interfaces with all MOS Clock chips 

C. Super low power consumption (1.5 Ma 

D. Uses latest MOS 17 stage divider IC 

E. Eliminates forever the problem of AC line glitches 

F. Perfect for cars, boats, campers, or even for portable clocks 
at ham field days. BUY TWO FOR $10.00! 

G. Small size, can be used in existing enclosures. 

KIT INCLUDES CRYSTAL, DIVIDER IC, PC BOARD PLUS ALL 
OTHER NECESSARY PARTS AND SPECS. 



typ.) 



7400 — 19c 
7402 — 19c 
74L04 — 29c 
74S04 — 44c 
7404 — 19c 
7406 — 29c 
7408 — 19c 

7410 — 19c 

7411 — 29c 
7413 — 50c 
7420— 19c 



TTL INTEG 

7430 — 19c 
7432 — 34c 

7437 — 39c 

7438 — 39c 
7440 — 19c 

7447 — 85c 

7448 — 85c 
7451 — 19c 
7453 — 19c 

7473 — 39c 

7474 — 35c 
7575 — 35c 



RATED CI 

7476 — 
7480 — 
7483 — 
7485 — 
7586 — 
7490 — 
7492 — 

7495 — 

7496 — 
74121 - 
74123 - 
74141 - 



RCUITS 

35c 
49c 
95c 
95c 
45c 
65c 
75c 
75c 
89c 

- 38c 

- 65c 

- 75c 



74153 
74154 
74157 
74161 
74164 
74165 
74174 
74181 
74191 
74192 
74193 
74195 



75c 
1.00 

75c 

95c 
1.10 
1.10 

95c 
2.50 
1.25 
1.25 
1.00 

69c 




"CUBO" -DIGITAL ALARM CLOCK CUBE 
A PERFECT GIFT - NOT A KIT! 

The CUBO Alarm Clock mfg. by Corvus, division of 
MOSTEK CORP. Originally sold for $49.95. We bought 
out their entire inventory. All new, individually gjft 
boxed. Mini size (2V2" cube) with maxi performance. 
FEATURES: A - . „,_ 

A. 4 Digit H. P. Bright Display $14.95 

B. "Second Hand" LED Activity Indicator FAPH 

C. 24 Hour Alarm; 12 hour real time format, 

Adjusts to Ambient Light 



% 



1000 MFD FILTER CAPS 

Rated 35 WVDC. Upright style 
with P. C. leads. Most popular 
value for hobbyists. Compare 
at up to $1.19 each from fran- 
chise type electronic parts stores. 
S.D. SPECIAL 4 for $1. 



Auto Display Dimming 
AM/PM Indicator 
Power Failure Indicator 



Uses Famous Mostek MK50250 MOS LSI IC 



MOTOROLA POWER DARLINGTON 
Back in Stock! 

Like MJ3001. NPN 80V. 10A. HFE 
6000 TYP. TO— 3 case. We include a free 
723 C volt reg. with schematic for power 
supply- SPECIAL -$1.99 



FAIRCHILD BIG LED READOUTS 

A big .50 inch easy to read character. Now 
available in either common anode or com- 
mon cathode. Take your pick. Super low 
current drain, only 5 MA per segment typ- 
ical. YOUR CHOICE: 6 for $7.50 
FND-510 Common Anode $1.50 ea. 
FND-503 Common Cathode $1.50 ea. 



WESTERN DIGITAL UART 

No. TR1602B. 40 pin DIP. 

This is a very powerful and popular part. 

NEW - $6.95 with data 

LIMITED QUANTITY 



INTEL 1702A 2K ERASEABLE PROM'S 
$6.95 

We tell it like it is. We could have said these 
were factory new, but here is the straight 
scoop. We bought a load of new computer 
gear that contained a "quantity of 1702A's 
in sockets. We carefully removed the parts 
verified their quality, and are offering them 
on one heck of a deal. First come, first 
served. Satisfaction guaranteed. 
BACK IN STOCK! 



UP YOUR COMPUTER! 
21 L02-1 IK LOW POWER 500 NS STATIC RAM 

TIME IS OF THE ESSENCE 
And so is power. Not only are our RAM's faster than a speeding bullet but they 
are now very low power. We are pleased to .offer prime new 21L02 — 1 low power 
and super fast RAM's, Allows you to STRETCH your power supply farther and at 
the same time keep the wait light off. 8 FOR $17.50 



SALE ON CUT LEAD SEMICONDUCTORS 

Leads were cut for PCB insertion. Still very 
useable. All new, unused. Some House no 

1N914/In4148 100/$2 

1N4002 1 Amp 100 PIV 40/$l 

1N4745A 16V 1W Zener 20/$l 

EN2222 NPN Transistor 25/$l 

EN2907 PNP Transistor 25/$l 

2N3904 NPN Driver Xstr 25/$l 

2N3392 GE Pre-amp Xstr 25/$l 

C103YSCR. 800MA60V 10/$ 1 



C&K MINI TOGGLE SWITCH 

7103 SUB MINI SPDT Center OFF. 
SPECIAL -99c 



TERMS: , 
Money Back Guarantee. No COD. Texas 
Residents add 5% tax. Add 5% of order for 
postage and handling. Orders under $10. 
add 75c. Foreign orders: US Funds ONLY! 



SLIDE SWITCH ASSORTMENT 

Our best seller. Includes mini- 
ture and standard sizes, single and 
multi-position units. All new, 
first quality, name brand 
Try one package and you'll re- 
order more. SPECIAL - 12/$1. 



RESISTOR ASSORTMENT 

1/4 W 5% and 10%. PC leads 
A good mix of values. 200/$2 



74S200 

256 Bit High Speed RAM 
Same as 82S16 



$3.95 



IK PROM BACK IN STOCK! 

32S129. 256X4. Bipolar, 50 NS. 
FAST. WITH SPECS. 



$3.95 



8T97B 

-lex Tri-State Buffer. Back in stock. 



$1.25 



CALL YOUR BANK AMERICARD OR 
MASTER CHARGE ORDER IN ON OUR 
CONTINENTAL UNITED STATES TOLL 
FREE WATTS: 1 _ 800 _ 5 27. 3 4 6 



Texas Residents Call Collect 

214/271-0022 



S. D. SALES 
P.O. Box 28810- B 
Dallas, Texas 75228 



ORDERS OVER $15. CHOOSE $1. FREE MERCHANDISE 



Branch Library at NW 63rd and MacArthur, 
Oklahoma City. 

Atlanta Bootstrap Volume 

Jim Stratigos of the Atlanta Area Micro- 
computer Hobbyist Club (AAMHC) has sent 
us the first issue of their newsletter. In an 
editorial they say that they will try to print 
items of interest such as software and 
hardware articles, tutorial or instruction 
columns, meeting notices and minutes, club 
activities, and hope to include a swap/buy/ 
sell column in the near future. Anyone 
wishing more information concerning the 
club should write: Jim Stratigos, Editor, Box 
33140, Atlanta GA 30332. 

VCCS — Change of Address 

The Ventura County Computer Society 
has a new address: The VCCS, POB 525, 
Port Hueneme CA 93041 . The society meets 
at the Camarillo Library, Ponderosa Dr, 
Camarillo, the last Saturday of the month. 
Two exceptions are: in November, on the 
20th, and in December on the 18th. 

The Shift Register 

Eric Rehnke, (216) 888-7531, of the 
Cleveland Digital Group sent along a copy of 
the June newsletter, volume 1 :7. It included 
a biorhythm program, impressions of the 
MOS Technology KIM-1, and a number of 
language conversions. The CDG hopes to put 
out a small booklet on the differences 
between systems so users will not have 
problems converting from one basic to the 
next. 

CACHE Register 

In volume 1 :5 of this Chicago area based 
club's newsletter, CACHE reports that they 
have 145 members. In attendance at the May 
meeting were Dr Suding of the Digital 
Group, as was the president, Dick Bemis. 
Besides showing Digital products, Dr Suding 
engaged CACHE members in a discussion of 
the hobbyist field, and of the new Z-80 from 
Zildg. Bill Precht continued his popular 
clinic on programming basics. They say that 
the response to this discussion was so good, 
the steering committee is planning a series of 
talks on the relative merit and drawbacks to 
the major chips. The club's mailing address 
is: POB 36, Vernon Hills I L 60061 . 

Personal Systems of San Diego 

In the June issue of the San Diego 
Computer Society newsletter, a feedback 
sheet was included. These sheets were to be 



mailed back, or turned in at the next 
meeting. It is linked to a column called 
"Interaction" by Ron Eade. The column 
surveys the results of the previous forms, or 
sheets. These sheets are numbered from 
0-60. 1-9 are ways you may assist the club as 
a whole, ie: 

"l will type articles for the newsletter," 

"I will volunteer. . . .," 

"I will help. . . .," 

"I will write. . . ." 

10-45 deals with SIG (special interest 
groups). This is divided into four subgroups, 
hardware, chips and systems; hardware, 
systems support; software, and applications. 
The last section deals with regional organiza- 
tions meetings, ie: Coast, East County, 
South County. By circling the appropriate 
numbers, you are informing the steering 
committee of your willingness to participate 
in club activities, and you will be informed 
as to when and where your SIG will meet. 
This is probably an excellent way to ex- 
change information in large clubs. The club's 
mailing address is: POB 9988, San Diego CA 
92109. 

Homebrew Class 

The Homebrew Computer Club's news- 
letter has a new face. According to Robert 
Reiling and Joel Miller, Laurel Publications 
will be donating typesetting services on their 
computerized typesetting/text editing sys- 
tem as well as providing graphics, layout and 
editorial services. This certainly increases the 
appeal and readability; looks good. Bob will 
continue as chief editor, and Tom Pittman is 
the man to write to regarding the mailing 
list. POB 626, Mountain View CA 94042. 

Triangle of North Carolina 

The Triangle Amateur Computer Club 
meets every fourth Sunday at 2 PM at the 
Dreyfus Auditorium, Research Triangle 
Institute, Research Triangle Park, NC. They 
are currently exploring a club interchange 
standard, have a monthly newsletter, and are 
starting software and hardware club projects. 
For more information on this Raleigh, Dur- 
ham, Chapel Hill area club, contact: Russell 
Lyday Jr at (919) 787-4137 or write Tri- 
angle Amateur Computer Club, POB 17523, 
Raleigh NC 27609. 

A Bit of Ham from Louisiana 

Emil Alline (WA5WUJ) passed a note 
along informing us of the formation of the 
"Crescent City Computer Club." The ad- 
dress is now Box 1097, University of New 
Orleans, New Orleans LA 70122. They meet 
at 8 PM on the second Friday of every 



132 



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the VERAS F8 COMPUTER 

THE SYSTEM DESIGNED WITH THE USER IN MIND 

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THE CPU BOARD FEATURES: 

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I The More Flexible and Expandible 
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• 4K memory boards with connector, buffers and static RAM's are available in kit form for £149.00 

The fully buffered mother board will accept (4, 4K RAM boards for a total of 16K bytes of memory. Individual power ter- 
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^^ Expected delivery time 30 days or less. 



VERAS SYSTEMS 



Warranty: 90 days on pans 
and labor for assembled units. 
90 days on parts for kits. 
Prices, specifications and 

delivery subject to change 
without nol ice. 



> 



•Fai 

n 



bug is a registered trademai k of Fairchild Corp. 

VERAS SYSTEMS 
A Div. of Solid State Sales, Inc. 
Box 74B, Somerville, MA 02143 
(617) 547-1461 

HI Enclosed is check for S 

or PI Master Charge fj 

□ VERAS F-8 Computer Kit 
□4K Ram Board Ouantity 
LlPower Supply Kit 



DAS! 



City, State. 



-Zip. 



INTEL 8080 CPU _ S29.50 

2518 HEX 32 BIT SR S6.00 

2102 1 1024 BT RAM S 2.60 

5280 4 K DYNAMIC RAM $12.50 

5202A UV PROM $12.50 

MM5203 UV PROM $12.50 

1702 A UV PROM S12.50 

5204-4K PROM $24.95 

MINIATURE MULTI-TURN TRIM POTS 
100. 500, 2K 5K 10K 100K. 200K 

S : 75 each. . . -_-_-_- - 3/$2.00 

MULTI TURN TRIM POTS Sim. Im to Bourns 
3010 style 3/16"x5/8"x1 1/4"; 50. 100, 
IK, 10K. 50K ohms 

Sl.SOea 3/S4.00 

LIGHT ACTIVATED SCR's 

TO-18, 200V 1A S 1.75 

TRANSISTOR SPECIALS 

2N3585 NPN Si TO-66 S .95 

2N3772 NPN Si TO-3 S 1 .60 

2N4908 PNP Si TO-3 S 1.00 

7N6055 NPN Si TO-3 Darlington . S 1.30 

2N5086 PNP Si TO-92 4/S 1.00 

2N4898 PNP TO-66 S .60 

2N404 PNP GE TO-5 5/S 1 .00 

2N3919 NPN Si TO-3 RF $1.50 

MPSA 13 NPN Si TO-92 3/$ 1.00 

2N3767 NPN Si TO-66 $ .70 

2N2222 NPN Si TO-18 5/$ 1 .00 

2N3055 NPN Si TO-3 $ .80 

2N3904 NPN Si TO-92 5/$ 1 .00 

2N3906 PNP S. TO-92 5/S 1 .00 

2N5296 NPN S. TO-220 S .50 

'2N6109 PNP S. TO-220 $ .55 

2N3866 NPN Si TO-5 RF S -7b 

2N3638 PNP Si TO-5 5/$ 1 .00 

2N651 7 NPN TO-92 Si 3/S 1 .00 

C/MOS (DIODE CLAMPED) 

74C02- ?5 4016- .50 4035- 1.75 
74C10- .25 401 / 1.30 4042 - 1.60 

4001 25 4018- 1 40 4047 2.60 

4002 .25 4019 GO 4049- .70 
4006- 1 GO 4022-120 4050 .70 
4007 25 4023 25 4055 1.20 

4009 60 4024 1 25 4066- 1 20 

4010 60 4025- ?5 4071 30 

401 1 25 4027 65 4077 .70 
4012- 75 4028-150 4 081 35 
4013 50 4029-1/f, 4076-120 
4015 1.40 4030- 90 

LED READOUTS 

FND 500.5" C.C $1.95 

HP 7740-.3" C.C $1.40 

MAN 7 .3" C.A $1.25 

MS 33-3 dig. array SI .35 

Send 25^ Id our catalog featuring 

Transistors and Rncnf.ers 

145 Hampshire St., Cambridge, Mass. 



is: FOB Cambridge, Mass. 
Send Check or Money Order. 
Include Postage, Minimum 



4 WATT IR LASER DIODE $7.95 



PRINTED CIRCUIT BOARD 



4 1/2" x6 1/2" SINGLE SIDED EPOXY 
BOARD 1/16" thick, unetched 

$.50 ea 5/S2.20 

VECTOR BOARD 1" SPACING 

4.5" x 6" SHEET $1.25 

2N 3820 P FET . . . . $ .45 

2N 5457 N FET S .45 

2N 4891 UJT S 45 

T1S43 UJT S .35 

ER90D TRIGGER DIODES 4 /Si .00 

2N6028 PROG. UJT S .65 

VERIPAX PC BOARD' 
This board is a 1/16" single Sided paper epoxy 
board. 4&"xB%" DRILLED and ETCHED 
which will hold up to 21 single 14 pm iC's 
Oi 8. 16, or LSI DIP IC's with busses toi 

power supply connector . . S4.00 

MV5691 YELLOW-GREEN 

BIPOLAR LED 51 25 

MT 2 PHOTO TRANS S 60 

RED, YELLOW, GREEN OR 

AMBER LARGE LED's . . . ea. S 20 

14 PIN DIP SOCKETS S 25 

16 PIN DIP SOCKETS S .28 

MOLEX PINS 100/Sl.no 

1000/S8D0 

8 PIN MINI DIP SOCKETS $ .25 

10 WATT Z EN ERS 3.9. 4.7, 5 6, 8 2, 12. i 5, 

18, 22, 100. 150 or 200V . . . ea S GO 
1 WATT ZENERS 4.7. 5 6, 10, 12. 15. 

180R 22V ea. S 25 



TANTULUM CAPACITORS 



Full Wave Bridge 



Silicon Power Rectifiers 


PRV 1A 3A 12A ' 50A 


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REGULATED MODULAR 
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< - 15 VDC AT lOOma 

115VAC INPUT S27.95 

5VDC AT 1 A. 1 15VAC INPUT . . . $24.95 

12 VDC AT .5 AMP $24.95 

IN 4148 (1N914) 15/S1 .00 



22UF 35V 5/S1.00 
47UF 35V 6/S1.00 
6BUF 35V 5/S1.00 

1UF 35V 5/S1.00 
3.3UF35V 4/S1.00 
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6.8UF 35V 3/Si.OO 
22UF 35V $ 40 
33UF 35V S 40 
30UT GV 5/S1 00 
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150UF 15V S 40 



M7001 ALARM CLOCK CHIP 



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MM1402 1/5 
MM1403 - 1.75 
MM1404- 1 75 
MM5013- 7.50 
MM5016- 2 50 
MM5017- ? 70 
MM5055- 7 75 
MM5056 2 75 



MM5057 7.75 
MM5058 7 75 
MM5060- 2.75 
MM5061 - 2 50 
MM5555- 4 75 
MM5556- 4.75 
MM5210 1 95 



74 LOO - ,25 

7400 16 

7401- 18 

7402 18 

7403 7? 

7404 .72 

7405 27 

7406 .35 
7407- .33 

7408 .75 

7409 75 

7410- 16 

7411- .25 

7412- 40 

7413- .45 
7414 1.00 
7416 .33 
7417- .33 
7420- .18 

7425 .30 

7426 .35 

7427 78 
7430- .16 
7432- 30 

7437 30 

7438 30 



TTLIC SERIES 

7441 - 

7442 

7445- 

7446- 

744 7 

7448- 

7472- 

7473 

7474- 

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74 76 

7480 

7483 

7485 

7486- 

7489 

7490- 

7491 - 

7492 

7493- 

7494- 

7495 

7496 
74107 
74121 
74 1 23 - 



74126 

74150 

74151 

74153 

74154 

74155 

74157 - 

74161 

74164 

74165 

74173 

74174 

74175 

74177 

74180 

74181 

74190 

74191 ■ 

74192 

74193 

74194 

74195 

74 1 96 

75374- 

75491 

75497- 



1 70 
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1 00 
1 00 
7 40 
1 15 
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7440 18 


74175 


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SW 


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Si 1020 G 20 WATTS $13.95 

Si 1050 G 50 WA TTS S24 95 

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DEVICE $99.00 

CCD 701 100 >; 1 00 CHARGE 

COUP! FD DEVICE . ^ 1 35 00 

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LM 309K 5V 1A REGULATOR 
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560 PHASE LOCK LOOP 

561 PHASE LOCK LOOP 

565 PHASE LOCK LOOP 

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555 2|js 2 HR, TIMER 

553 OUAD TIMER 

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1458 DUAL OP AMP . . 

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LM 382 
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WE SHIP OVER 95% 

OF OUR ORDERS THE 

DAY WE RECEIVE THEM 



month in Room 21 20 of the science building 
of the University. He also notes that the 
FCC and ARRL are taking steps toward 
making it easier than ever before to become 
a ham and with more privileges than ever. 

Chicago Area F-8 Users 

If you live in the Chicago area, Louis 
Burgyan is interested in meeting other F-8 
users. He may be reached at (312) 327-0472, 
evenings. 

The Computer Network of Kansas City 

The KC Thru-Put is the organ of this 
Kansas City group. President Earl Day writes 
a column called "Day Dreams," and Bart 
Schwartz is editor. The group first met in 
May with 12 members and as of the July 
issue, number 2, has increased to 37. At the 
June meeting the possibility of making an 
educational program for the local PBS 
(Public Broadcasting Station) channel was 
discussed, but was deferred until the club is 
more established. Anyone wishing to contact 
this organization may write: KC Thru-Put, 
968 Kansas Av, Kansas City KS 661 05. 

Microcomputer Society of Florida 

In the Marsh Data Systems Newsletter 
number 5, Don Marsh writes that the Micro- 
computer Society of Florida has chapters in 
Vero Beach, Ft Myers, Sarasota, Jackson- 
ville, Gainesville, as well as Tampa. The 
society will soon be publishing a newsletter 
of its own. They suggest that their chapters 
consider getting a free write-up in the local 
papers. Computer groups are newsworthy. In 
Tampa they have had a write-up in each of 
the major papers, and have been on tele- 
vision twice. 

For more information contact: Marsh 
Data Systems, 5405B Southern Comfort 
Blvd, Tampa FL 33614. 

New York Amateur Computer Club 

Elections of club officers have been held, 
but as of the June newsletter, the results 
were not yet complete. Club member David 
Ripps is scheduled to speak on the topic of 
"Systems Monitors and Their Features." 
The newsletter also included a report from 
the technical committee, an article by Alan 
Yorinks, "A Short Course in Digital Logic 



Troubleshooting," and a humorous essay on 
the living room workshop by MCS III. 

The address is: NYACC, c/o R Schwartz, 
1E, 375 Riverside Dr, New York NY 10025. 

ACGNJ News 

In June at the general meeting, Marty 
Nichols, Tom Kirk, and Roger Amidon gave 
a presentation on the "String Language 
Processor." The high level language was 
running on 8080 based systems at the 
meeting. The demonstration was given with 
video monitors which were set up around 
the meeting room. 

The bylaws were also printed, in this, the 
July volume 2:7 issue. A "Life for the 
M6800" reprint, and an article, "Interfacing 
the Original TV Typewriter to a Computer" 
by Monty Shulte, were included. 

The address is: ACGNJ, UCTI, 1776 
Raritan Rd, Scotch Plains NJ 07076. 

Computer Hobbyist Group — North Texas 

In volume 2:6 of the newsletter, they 
state that at the May meeting they were 
honored with the first look at three new 
products by the Southwest Technical Pro- 
ducts Corp (SWTPC). Displayed at the 
meeting were a dual cassette controller/inter- 
face, a graphics controller for input to CRT, 
and a small but quick printer. TCHG-NT's 
address is: 2377 Dalworth 157, Grand 
Prairie TX 75050. 

A Roving Computer Show 
for the Experimenter? 

Well, not quite; but a firm called Mar- 
keting Ventures Inc, 5012 Herzel PI, Belts- 
ville MD 20705, is organizing a show called 
TECHNIHOBBY USA which will be travel- 
ling to four cities in the US this fall. The 
boundaries defined for the show's content 
are not limited to computers alone, but 
encompass amateur radio, radio control 
models, do it yourself electronics, as well. 
The firm is looking for participation by local 
clubs in its exhibitions to be held: 

Boston November 4, 5 and 6 

Washington DC November 12,13 and 14 

Atlanta November 19, 20 and 21 

Los Angeles December 5, 6 and 7 

For further information contact Robert E 
Harar, at (301) 937-71 11 M 



134 




DELTA ELECTRONICS 

POST OFFICE BOX 2, AMESBURY, MASSACHUSETTS 01913 Phone (617) 3884705 



AMP Security System Card Reader 

This card reader was made by AMP for use in SECURITY SYSTEMS. 
A stiff 2 1/8" x 3 3/8" card (credit card size) is inserted, which 
closes a micro-switch. A 115v AC solenoid is then energized, which 
pulls down a set of wipers to read through holes in the card. The 
wipers are arranged in 3 8 bit bytes + 1 bit, for a total of 25 bits. 
By turning the card over, 48 bits are possible. 

This device is ideal for security systems.. .entry can be controlled by 
means of a card with an almost infinite number of combinations, 
rather than using an easily duplicated key. As another example, an entire 
Social Security number, plus an entry code, could be read from a card. 
5" x 5" x 9" deep. Shipping weight 6 lbs. 
STOCK NO. B5353 $19.95 each, 




2 for $35 



B5344 




Wood Cabinets 




B7129 



One of the problems with home-brew projects is finding 
a suitable enclosure, one that will do justice to your 
latest pride & joy. We have 2 wood cabinets that are 
suitable for small projects. B5344 has real teak veneer on all 4 sides 
over a %" particleboard base. Outside dimensions are 13%"W x 5 1/8"H x 6%"D, with a %" deep recess 
in the front. Mounting holes in the bottom. B7129 has a walnut vinyl covering over a 3/8" plywood base. Outside 
dimensions are 8%"W x 4%"H x 10%"D. With small vent and rubber feet on the bottom. 
STOCK NO. B5344 Teak cabinet Shipping weight 6 lbs. $7.95 each, 2/15.00 

STOCK NO. B7129 Walnut cabinet Shipping weight 3 lbs. $5.95 each, 2/10.00 



Switchcraft Push Button Switch Assembly 

Switchcraft series 7000 push button switch assembly, with 6 sections. 5 sections are interlocked 
in a 1-of-5 pattern, and the 6th button is momentary, which releases the others. Sections 4 & 5 
may be depressed together; the others are excluded by means of a lockout bar. The switch comes 
with 12 sets of contacts: 6 SPST, normally open, 3 SPDT, and 3 DPDT, all rated at 3 amps. The 
contacts may be arranged in any order, up to 4 in each section. Buttons are 1 / 2 " square black, on 5/8" centers. Overall size 554" wide x 
3 1 /2" deep x 1%" high. This versatile switch lists for well over $30 I Shipping weight 2 lbs. 
STOCK NO. B6408 $2.50 each, 3 for $6.00 




Lead-Acid Storage Battery 



Lead acid storage batteries are still the cheapest & easiest to work with of all types of 
batteries. Two of these would be ideal for keeping the memory up in your computer 
when the power is off. They are rated at 6 ampere— hours, 6 volts. 2%" x 3%" x 5 1 /2" 
high. The fill holes have screw-in caps and an overflow container is provided, making 
this battery spill proof. We provide charging data, you provide the electrolyte. 3 lbs. 
STOCK NO. B5074 $5.95 each, 2/11.00 




Power Transformers 




B9397.... (shown) A versatile power transformer from a line printer manufacturer. The primary is tapped for 
operation at 1 1 5v or 230v. There are 4 secondaries: 34v centertapped @ 3 amps, 1 7v <s> 4 amps, 1Tv @ 5 amps, 
and 6. 3v @ 1.5 amps. This would make an ideal transformer for a +5 volt and ±1 5 volt power supply. 3%" x 
4'/2" x 4%" high. Shipping weight 10 lbs. 

STOCK NO. B9397 $12.95 each, 2 for $24 

B9940....Dual 1 1 5v primaries, 3 secondaries: 17v center tapped @ 10 amps, 22v center tapped @ 5 amps, and 
25v center tapped @ 1 amps. 3%" x 4%" x 4'/j" high, shipping weight 1 5 lbs. Another good +5v and ±15v 
supply transformer. STOCK NO. B9940 $14.95 each, 2 for $28 



Send for our latest free catalog. Minimum order $5, phone orders welcome. Include sufficient postage (2 lbs min.) , excess will 
be refunded. BANKAMERICARD & MASTERCHARGE welcome, ALL numbers needed for processing. Minimum charge $15. 



Continued from page 22 



theless, amateurs and experimenters may 
find that a perusal of the patent literature 
is quite fruitful. 

Howard L Grams 

2616 N Salisbury St 

W Lafayette IN 47906 

APPLICATIONS DIGEST, 
MATERIALS NEEDED 

I am compiling a "Microcomputer Appli- 
cation Digest" to be published by Howard W 
Sams & Co. The text is arranged by subject 
(Biorhythms, Electronic Music, Speech Anal- 
ysis, RTTY, Terminals, Business Systems, 
Security, Video Art, Video Games, etc). 
Each section will cover several real systems, 
a brief tutorial on the subject, block dia- 
grams, list of components, and names of 
contributing parties. Sources of additional 
information will also be provided. 

At this point, I am seeking inputs from all 
interested persons who wish to share their 
experience to increase the exchange of in- 
formation in their application area. 



First Come First Served 



Back Issues 
of BYTE 

$1.50 



We have very few of some of them and a large supply of others, 
but no more than 2,000 of any one issue. Orders will be filled on 
a first come, first served basis until the supply is exhausted. DO 
NOT SEND MONEY, we will enclose a bill with your order for 
the number of issues we are able to supply plus a 25 cents EACH 
postage and handling charge. 

The back issues listed below are available from BYTE. Circle 
issues desired 

Dec 75 Jan 76 Feb 76 Mar 76 June 76 July 76 




□ Bill me □Bill MC BAC No. 
Name 



Exp. Date 



Address 
City 



State 



Zip_ 



BYTE 70 Main Street Peterborough, NH 03458 



To keep it simple, I would like those who 
want to be in the book to drop me a 
postcard with your name, address, phone 
number, and a brief explanation of your 
application. I will then send you a form to 
fill out which will put the information into a 
standard easy to read format. This will then 
be collated into the book. 

Not all applications need to be up and 
running to qualify for the text. Ideas, well 
thought out, are as valuable as finished 
systems. 

If you wish our field to expand, I urge 
you to take time to drop me a postcard and 
to expound on your efforts with microcom- 
puters-it's by spreading ideas that new ideas 
grow. 

Mitchell Waite 

H S Dakin Co 

3101 Washington St 

San Francisco CA94115 



NEXT OF KIM 

Congratulations on an excellent maga- 
zine! I look forward to its arrival every 
month as each issue contains at least one 
article (and usually 3 or 4) that I can use 
immediately. 

I would also like to publicly thank one of 
your advertisers for their fast delivery times, 
their prompt no-questions-asked warranty 
service, and their excellent newsletters. This 
company is MOS Technology. After months 
of fighting with two other computer manu- 
facturers, I ordered a KIM-1. The KIM-1 is, 
in itself, a fantastic product, but with MOS 
Technology backing it, it is, in my opinion, 
the best buy on the market today! 

There are presently three KIM-1 owners 
who work here at Eastern Washington State 
College. Also, the chemistry department has 
an Altair 8080 and the psychology depart- 
ment has a DEC PDP-8/F. We would like to 
invite anyone in the greater Spokane area (or 
anywhere else) who is interested in building 
a system or learning more about micropro- 
cessors and/or programming techniques to 
contact either myself of Dr R Keefcr. I am a 
technician for the psychology department 
and Dr Keefer is a professor for the mathe- 
matics department. Perhaps we may have 
enough interested people to start a computer 
club or a KIM-1 users group. 

Keep up the good work. 

Tony Kjeldsen K7VNT 

5315 N Allen PI 

Spokane WA 99208 

PS I'm afraid I must agree with B L Donelan 
(June 1976 BYTE) concerning the De- 
cember issue cover. 



136 



Itt all right here 



Prompt service_ 



ELECTRONICS far INDUSTRY 



BRiGAR 
eLecTronics 



In-depth inventories 



LOW, LOW PRICES! 



Offices & Warehouse: 10 Alice Street, Binghan 

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MINIATURE LAM PS a 

CHICAGO MINIATURE LAMPS #387 

SAME AS #327 EXCEPT LONGER LIFE 

28 volts. .04 amps. Bulb Style T-l-3/4 
Mid-Flange Base. BRAND NEW BOXED, 100 
per box. 40,000 pes in stock. 

PRICE SCHEDULE 
1 - 99 .. 400 each 100 - up . . 350 ea 



NIOH INDICATING GLOW LAMPS 



NE-2 neon lamps, with dropping resistor 

to operate directly from 115 VAC. 

Nominal Watts - 1/17. T-2 Clear Bulb, 

wire terminals . 

25,000 pes in stock. Mfd by G.E. Co. 

100 each up to 1000 pes. 

1000 pes & up 70 each. 



llM.,r.?W.l:« «H-hrf.H 



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Ultraminiaturi 
Versatile, low 
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Inst rumen t a tio 
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ndescent Lamps 
zed Series, 100,000 hr.life 
cost indicator lamp. Ideal 
if iers , Mobile Equipment, 
Computer and Display 



ure, T 1-3/4 lamps - Metal 
erminals. Metal base ir.- 
output and protects lamp 



High temper a tur 

Base - Wire Ter 

creases light 

from damage . 

41, 685 pes - 6.3 volts , 75 ma, 8" wire 

leads. 

40,263 pes - 6.3 volts, 200 ma, 13" wire 

leads. 



ISCOUNT SCHEDULE 
- 99 250 ea. 
00-499 200 ea. 
00-999 15C ea. 
000-UP 120 ea. 



bargains s>ias(ga8a®S!& 




BRAND NEW - FINEST QUALITY 



QUAN 

10,686 
3,000 
29,000 
75,000 
35,000 
7000 
3000 
5700 
7900 
7200 
6600 
1800 
1000 



Electra 
Electra 



TOL. 
(%) 

1 

1 

1 



OHMS WATTS PRICE 
Each 



191 

191 

243 

2.43K 

909 

10 

15.4 

28 

53.6 

90.9 

1650 

6190 

2670 



1/8 
1/8 
1/8 
1/8 
1/4 
1/2 
1/2 
1/2 
1/2 
1/8 
1/8 
1/8 

i/e 



.07 
.07 
.07 
.07 
.04 
.04 



Computer Grade Capacitor 



MallorY 



CG (STAN D ARD) 65"C Supplied wilh PVC In sula ting Sleave 

ZELCh 
.75 



Quan. Mfd. Vdc Size 

10000 1100 35 1-25/64 X 2-11/64 

25000 100 350 1-25/64 X 2-11/64 

10000 80 400 1-25/64 X 2-11/64 



.50 
.60 



SUB-MINIATURE 



GENERAL- 
PURPOSE 



POTTER 

& BFIUMFIELD 

RELAYS 

TYPE KH 5505 (Identical to KIIU17D11) 

COIL: 24vdc, 650 ohms. 

CONTACTS: 4PDT, 3amps at 30vdc or 120 vac 

Small rugged DC relay with clear poly- 
carbonate dust cover. Contacts are gold 
flashed silver. 

Mounts by solder terminals or 3-48 stud 
5/16" long. Also mounts as plug-in. 
6500 pc in stock, BRAND NEW, while they 
last at this price. $] __ 25 each 



m 



BRAND NEW PHENOLIC SHEETS 
Grade LE- Natural 
Type - FBE, Mil Spec: 15035, .062" thick 
Needed by all experimenters , amateurs and 
radio men for insulating parts - terminal 
strips - building sets or for research 
& development, etc. 
Stock # 560 - 6" x 6" x .062" 420 each 

# 561 - 6" x 12" x .062 820 each 
jj 563 - 12" x 12" x .062 $1.58 ea 

# 564 - Full sheets 38" x 47" x .062" 
$13.00 each. 

BRAND NEW QUALITY SHEETS 



High-Speed Reset Counter 
Veeder-Root 



4 I-TfiDRE COUNTER MANUAL RES I- I 
HSVOr 115VAC 

VEEDER root meo-i 
115VAC (Rectifier supplied* Basic 
counter is 115VDC, 6 v/Jtts \ figuie, 
black on while background. Push bullon 
resc-t. Dim.: 1-7/8" widlh 1-1/8" high 
x 2-1/2" deep. 



5 12 95 



LIGHTED 



$2.95 Each 



PUSHBUTTON SWITCHES 



Unit can be used on 6 v 
,. or in series for 12 volt 
^SPST, mom, PC board gold 
£. plated pins for wiring o] 
^ easy installation. 

10,000 pes in stock 

Widely used on computers, machine tools, 
office machines, guidance control and a 
wide variety of applications. 




Hfr: Grayhill 

Switch Co. 

2" x 1%" X IV 




Electrolytic Capacitors 



TUBULAR, HIGH RELIABILITY 




QUAN . 

600 

375 

298 

299 

571 

375 

313 

597 

4000 

26,000 

416 

350 

2500 

1161 

2600 

1000 

825 

1099 

6549 

1942 

10,500 

520 

290 

476 

409 

284 

255 

281 

20,000 

339 

400 



MFD 

100 

250 

500 

1000 

1200 

1500 

2000 

100 

50 

200 

1500 

2000 

10 

2000 

10 

500 

100 

150 

250 

300 

60 

80 

300 

40 

100 

200 

5 

10 



VDC 

3 

3 

6 

6 

6 

6 

6 

12 

15 

15 

15 

15 

25 

25 

50 

50 

50 

50 

50 

50 

150 

150 

150 

200 

250 

250 

350 

350 

250 

250 

250 



EACH 

.30 

.35 

SI. 00 

1.00 

1.02 

1.10 

1.11 

.60 

.30 

.30 

1.10 

1.10 

.25 

1.40 

.40 

.80 

.95 

.90 

.98 

1.07 

.70 



1.50 
.90 
.90 
.35 
.70 
.60 



QUAN. 

1055 

246 

967 

400 

529 

453 



MFD. VDC 



30 

40 

4 

10 

15 

20 



350 
350 
450 
450 
450 
450 



EACH 
$1.00 
1.14 
.98 
1.07 
1.07 
1.14 



METALLIZED PAPER FILM 



QUAN 

899 

437 

400 

1360 

820 

4200 

400 

771 

417 

1100 

1100 

1600 

565 

4000 

389 

500 

600 

717 

30,000 

1000 

291 



MFD 

.1 

.33 

1.0 

.22 

.022 

.033 

.1 

1.0 

1.5 

.001 

0022 

.022 

.047 

.022 

.05 

.1 

.2 

.25 

.01 

.047 

.22 



VDC 
100 
100 
100 
150 
200 
200 
200 
200 
200 
400 
400 
400 
400 
600 
600 
600 
600 
600 
100 
100 
400 



.35 
.40 
.45 
.40 
.35 
.35 
.40 
.40 
.40 
.35 
. 40 
.45 
.50 
.25 
.30 
.30 
.30 
. 30 
.15 
.20 
.30 



HIGH POWER DUMMY LOAD 




NEW! 



Computer Grade Capacitors 



PHONE ORDERS 
607 723 3111 



Instant off-the-shelf 
delivery. 









QUfiN. 

350 

494 

1016 

527 

353 

869 

277 

316 

375 

267 

600 

529 



MFD, 

30000 

60000 

25000 

40000 

15000 

15500 

400Q0 

74000 

15000 

14000 

10000 

L2500 



SIZE 

1-3/8 x 4-3/16 

3" x 4-1/2" 

2-1/16" x 4-9/16" 

2" x 5" 

2" x 4-1/8" 

2" x 4-7/16" 

3" x 4-1/2" 

3" x 4-3/4" 

2" x 4-1/2" 

2" x 4-3/8" 

2-1/16" x 4-1/2" 

2" x 4-1/C" 



PRICE EA 
SI. 50 
1.50 
1.50 
1.50 
1.25 
1.25 
1.70 
2.00 
1.25 
1.25 
1.25 
1.25 



QUAN. MFD. 



252 

628 

1014 

10706 

4200 

792 

478 

337 

200 

500 

23436 

11800 



11500 

11000 

8200 

1100 

750 

1500 

450 

400 

500 

750 

100 

80 



100 
100 
150 
200 
350 
400 



SIZE 

2" x 4-1/2" 

2" x 4-1/2" 

1-3/8" x 3-1/8" 
1-25/64" x 2-11/64" 

1" x 3-L/2" 

2" x 4-1/2" 

1-7/1G" x 2-9/16" 

1-7/16" x 2-1/2" 

2-1/16" x 2-3/B" 

1-1/2" x 4" 
1-25/64" x 2-11/64" 
1-25/64" x 2-11/64" 



SI- 25 
1.25 
1.70 
1.00 
.75 
1.30 



1.00 
1.00 



Mfg. Eastern Microwave. #10-1254 ... RF Coaxial Load Re 
sistor utilizing water flow to cool and provide a load 
resistance of 50 ohms for inputs from DC to 4000 MHz. 
Maximum power input is 1 00 watts . Reguires a flow of 

218 GPM min. per 100 watts of input power; 100 psi 
pressure. Compression fittings on water line inlet and 
outlet for copper tubing supply lines. Has a Flange 
type coaxial fitting, friction type, 13/16" I.D. with 
2-1/4" flange. Completely shielded unit of machined 
aluminum. Size: 1-5/8" diameter by 5-3/8" long. 
Shipping weight, 2 lbs. 
5,000 pes in stock, NEW BOXED $14.95 each 



Cherry Electrical Products 




These switches are postage 
stamp sized precision swit- 
ches which feature long op- 
erating life & high electrical capacity for their size 
5 amp, 1/4 IIP, 125-250 vac, SPDT, quick dis-connect 
terminals. 2,000 pes in stock without lever.. 75<= each 
2,400 pes in stock with extended roller lever. 95C ea 



TANTALUM CAPACITORS 



TYPE 109D 

TUBULAR SINTERED- ANODE TANTALEX CAPACITOR 

S109D147X9060T2 

1620 pes - 140 uf ±10% - 60vdc $2.00 ea. 



GENERAL^ ELECTRIC (U „ Al eL « .„...- ^J «»T "«.« 

CLU/U— POLAftlZEO 

3,000 pes CL31BE180KPE, 18' jf - ] 5vdc 65C each 
300 pes CL31BE550MPE, 55uf - 15vdc 85$ each 

non-polarized CL32/33 
900 dcs CL33BL020MME, 2.0uf - 75vdc $1.00 each 



MTP/MTPH ULTRA-MINIATURI TANTALUM CAPACITORS 



10,550 pes MTP685MO20P1D, 6.8uf - 20vdc 55C each 
2,100 pes MTP106MO30P1A, lOuf - 30vdc 754 each 
1,028 pes HTP33GMO10P1A, 33uf - lOvdc 65C each 



ESS'" 5, 



OLID ILECTHOmi TANTALUM CAPACITORS 



4996 pes, 4.7uf- +10%, 6vdc, TAS475K006P1A 35C ea 

394 pes, .47uf i 10%, 6vdc, TAS474K006P1A 384 ea 

1430 pes, 47uf ± 10%, 6vdc, TAS476K006P1C 40C ea 
326 pes, 220uf + 20%, 6vdc, TAS227M006P1G $1.20 ea 

285 pes, 5.6uf J 10%, lOvdc, TAS565K010P1C 404 ea 

4574 pes, lOuf ±10%, lOvdc, TAS106K010P1C 40C ea 

900 pes, 15uf ±20%, lOvdc, TAS156M010P1C 40C ea 

887 pes, .068uf ±10%, 20vdc, TAS633K020PLA 516 ea 

152 pes, 2.2uf ± 20%, 20vdc, Sprague 40? ea 

1457 pes, ,47uf +10%, 35ydc, TAS474K035P1A 51? ea 



GENERAL^ ELEIURIC "*' N '° ,L T * MT * IU '" + 1 " c 

365 pes G.E. 40uf,+20%, 50vdc, 1250c 
Type: 2K105AA6M. $1.75 each 
1168 pes SPRAGUE, 40uf, +20%, 50vdc, 125°C 
Type: 220D005A3M. $1.75 each C 



■Hi 

O A 



m tS 



ATTENTION PDP-8 LOVERS! 

Thought I would drop a line to BYTE 
and say how much I enjoy the magazine. I 
first got into home computing in 1973. A 
friend down in Texas found a used PDP-8 
and called me. We went down on business 
and at the same time stopped over to see the 
machine. We bought it and back home made 
a crate from dimensions in the manual. Next 
trip down we carried the crate knocked 
down on the plane, crated it and shipped it 
back. It went on the air with very little 
trouble and we immediately had a vast 
amount of software from DEC and the users 
group DECUS. We now have six PDP-8s in 
the Washington DC area with one fellow just 
finishing a homebrew machine with the 
Intersil IM6100 chip. Out of this group all 
the fellows are electrical engineers, none of 
which has a computer science background. 
Two of us are interfacing surplus speech 
synthesizers and are interested in using the 
8s for signal processing and speech synthesis. 
One other is interested in motion picture 
photography and is interfacing a high resolu- 
tion CRT system to his 8 and an animation 
camera. The PDP-8s are the straight 8 
version first built about 1966 being im- 
plemented with discrete components 
throughout. We have spare cards and the 



maintenance is done by each person, 
although the more experienced of us give 
help to the others. We are looking forward 
to articles in BYTE on PDP-8 and IM6100 
type systems; no doubt they will start with 
the introduction of the IM6100 kit by PCM. 
We are of course always glad to hear from 
other PDP-8 people. 

Frank Gentges 

3512 Orme Dr 

Temple Hills MD 20031 

(301)894-2613 

A SALUTE TO THE PDP-8 
AND FAREWELL 

This letter is an opinion in response to 
the article in BYTE #9, "Chip Off the Olde 
PDP 8/E" by Robert Nelson [page 60] in 
which he made the incredible statement, 
"The PDP-8 at this point may truly be the 
universal computer" and which concluded 
with the statement that "Many of the 
microprocessor chips available today were 
not designed to be the heart of a general 
purpose minicomputer . . . (but) . . . were 
primarily designed . . . (for industrial control 
applications) . . . . " 

Mr Nelson either overlooks or never knew 
that the PDP-8 was frequently sold not as a 
computer but as a controller. In any case, 



Christmas! 



Can it be that there are still hackers* out there who haven't 
yet subscribed to BYTE? 

From the way new subscriptions are inundating Debby, 
Deena and crew, it seems there are thousands of hackers* 
who are only now discovering what a blessing it is to have 
BYTE come each month whether they remember to go out 
and buy it or not. 



Perhaps you know one or more unfortunate who each 
month runs the risk of missing BYTE. Perhaps you ARE 
one. 

Give him a gift. Give her a gift. Give yourself a gift. 

As our holiday gift to you, each subscription after the first 
at the regular $12 rate (which by the way saves you S3 a 
year over single copy price) will cost only $10 (a vast $5 
saving over single copy price). 

Considering it can take as long as six weeks to process a 
subscription, it's not a bit too early to give the perfect gift 
for the hacker* who hasn't yet subscribed. 



*microists, cybernuts, byters, kluges, etc . . . see letter on pages 18-20 about our identity crisis. 



BYTE GIFT 
70 Main St 

Peterborough NH 03458 
Name 



BYTE GIFT 
70 Main St 

Peterborough NH 03458 
Name 



Address Address 

City State Zip City State 

□ BILL ME □ Check for $12 enclosed □ BILL ME □ Check for $10 enclosed 

□ Bill BankAmericard No DBill BankAmericard No 

□ Bill Master Charge No □ Bill Master Charge No 



Zip. 



NOTE : If you're taking advantage of this offer, please use these coupons instead of the yellow card. If you're sending more than one $10 gift sub 
(Santa Claus incarnate!), photocopy or otherwise copy the coupons. An elf from Mars has been hired to handle gift subscriptions exclusively, and 
the color yellow makes him dangerously bilious. 



138 



HS 7400NT ™ „ 

SN7400N' .16 SN7459A .25 

SN7401N .16 SN7460N 22 SN74154N* 

SN7402N .21 SN7470N 45 SN74155N 

SN7403N .16 SN7472N .39 5N74156N 

SN7404N* .18 SN7473N* .37 SN74157N 

SN7405N 24 SN7474N* 32 SN74160N 

SN7406N .20 SN7475M* 50 SN74161N 

SN7407N 29 SN747GN* .32 SN74163N* 

SN7408N .25 SN7479N* 5 00 SN74T64N 

SN7409N 25 SN7480N 50 SN74165N 

SN7410N* 18 SN7482N 98 SN74166N 

SN7411N .30 SN7483N 70 SN74167N 

SN7412N 33 SN7485N B9 SN74170N 

SN7413N 45 SN7486N 39 SN74172N 

SN7414N 70 SN7488N 3 50 SN74173N 

SN7416N 35 SN74B9N 2.25 SN741 74N 

SN7417N .35 SN7490N* .45 SN74175N 

SN7420N 21 SN7491N 75 SN74176N 

SN7421N 33 SN74g2N 49 SN74177N 

SN7422N* .49 SN7493N' 49 SN74180N 

SN7423N .37 SN7494N 79 SN74181N 

SN7425N .29 SN7495N 79 SN74182N 

SN7426N 29 SN7496JJ 89 SN74184N 

SN7427N .37 SN7497N* 4 00 SN74185N 

SN7429N .42 SN74100N* 1.00 SN741B6N* 

SN7430N 26 SN74107N 39 SN74187N 

SN7432N 31 SN74121N* 39 SN74188N 

SN7437N .27 SN74122N 39 SN74190N 

SN743BN .27 SN74123N* 70 SW74191N 

SN7439N .25 StV74 1 25N .60 SN74 1 92N* 

SN7440N 15 SN74126N 50 SN74193N* 

SN7441N B9 SN74132N 1.09 SN74194N 

SN7-142N 59 5N74I36N 95 SN74195N 

SN7443N 75 SN74141N 1 15 SN74196N 

SN7444N 75 SN74U2N* 4 00 SN74197N 

SN7445N 75 SN74143N* 4.50 SN74198N 

SN7446N 81 SN74144N* 4 50 SN74199N 

SN7447N 69 SN74145N 1.15 SN74200N 

SN7448N 79 SN74147N 2.35 SN74279N* 

SH7450N .26 SN7414BN 2 00 SN74251N 

SN7451N .27 SN74150N 100 SN742B4N 

SN7453N 27 SN74151N 79 SN74285N 

SN7454N 20 SN74 1 53N 89 SN74367N 

MANY OTHERS AVAILABLE ON REQUEST 

20% Discount lor 100 Combined 7400'S 



CD40O0 
CD4001 
CD4002 
CD4006 
CD4O07 
CO4009 
CO401O 
CD4011 
CD4012 
CD4013 
CD4016 
CD4017 
CEM019 
CD4Q20 
CO4022 
CD4023 
CD4024 
CO4025 
CD-1027 
CD4028 
CD4029 
CO4030 

If.Wuou 

LM301H 

LM301CN 

LM302H 

LM304H 

LM3Q5H 

LM307CN 

LM30BH 

LM308CN 

LM309H 

LM309K 

LM310CN 

LM311H 

LM311N 

LM318CN 

LM319N 

LM320K-5 

LM320K-S2 

LM320K-12 

LM320K-15 

LM320T-5' 

LM320T-5 2 

LM32QT-8* 

LM320T-12" 

LM320T-15 

LM320M8* 

LM320T-24 

LM323K-5* 

LM324N 

LM339N 

LM340K-5 

LM340K-6 

LM34QK-B 

LM340K-12 

LM340K-15 

LM340K-1B 

LM340K-24 

LM340T-5 

LM340T-6 

LM340T-B* 

LM340T-12 

LM340T-1S 

LM340T-1B* 

LM340T-24 

LM35QN 

LM351CN 



25 



CMOS 



CD4035 
CD4040 
CO4042 
CO4044 
CD4046 
CD4047 
CD4D49 
CD4050 
CD4051 
CDJ053 
CD4060 
CD4066 
CD4069 
CD4071 



CD4{ 



CD45U 
CD451B 
74C0ON 
7JC02N 



74C04N 

74C10N 

74C20N 

74C3QN 

74C42N 

74C73N 

74C74 

74C90N 

74C95N 

74C107N 

74CT51 

74C154 

74C157 

74C160 

74C161 

74C163 

74C164 

74C173 

74C193 

74C195 

MC4Q44' 

MC14D16" 



LINEAR 

LM370M 1.1 5 

LM373N 3 25 

LM377N 4 00 

LM380N 1.39 

LM390CN 1 05 

LM381N 1 79 

LM382N 1.79 

NE501X 800 

NE510A 6 00 

NE531H 300 

NE536T 6 00 

NE540L 6.00 

NE550N 79 

NE555V* 45 

NE560B* 5.00 

NE561B* 5.00 

NE562B* 5.00 

NES65H' 1 25 

NE565N* 1.75 

UE566CN* 1.25 

NE567H* 1 95 

NE567V* 1 50 

LM703CN .45 

LM709H .29 

LM709N .29 

LM710N 79 

LM711N .39 

LM723H .55 

LM723H 55 

LM733N 1 00 

LH739N 100 

LM741CH .35 

LM741CN 35 

LM74114N 39 

LM747H 79 

LM747N .79 

LM748H 39 

LM748N 39 

LM1303N 90 

LM1304N 1.19 

LM1305N 1 40 

LM1307N 85 



LM1310N 2 

LM1351N 1 

LM1414N 1 

LM1458C 

LM1496N 

LMI556V 1 

LM2111N 1 

LM2901N 2 

LM3065N 

LM3900N 

LM3905N 

LM3909" 1 

LM5556N 1 

MC5558V I 

LM7525N 

LM7535N 1 

8038B* 4 

LM75450 

75451CN 

75452CN 

75453CN 

75454CN 

75491CN 

75492CN 

75494CN 

RCA LINEAR 
CA3013 2 

CA3032 2 

CA3035 2 

CA3039 1 

CA3046 1 

CA3059 3 

CA3060 3 

CA30B0 

CA3081 2 

CA3082 2 

CA3083 1 

CA3086 

CA3089 3 

CA3091 10 

CA3123 2 

CA3130 1 

CA3140 I 

CA360O 1 

RC4194 5 

RC4195 3 



74LSO0 
74LS02 
MLS03 
74LS04 
74LS05 
74LS08 
741S10 
74LS13 
74LS14 
74LS20 
74LS26 
74LS27 
74LS2B 
74L530 
74LS32 
74LS40 
74LS51 



74LS00 TTL 



74LS55 
74LS73 
74LS74 
74LS75 
74LS76 
74LSB3 
74LS8G 
74LS90 
74LS92 
74LS93 
74LS95 
74LS96 
74LS107 
74LS112 
74LS132 
74LS13G 
74 LSI 38 



74LS151 
74LS153 
74LS157 
74LS162 
74 LSI 63 
74LS164 
74LS161 
74 LSI 90 
74LS19T 
74LS192 
74LS193 
74LS194 
74LS195 
74LS257 
74LS260 
74LS279 
74LS670 



5 95 




DATA HANDBOOKS 

7400 Pin-out & Description of 5400/7400 ICS $2.95 

CMOS Pin-out & Description of 4000 Series ICS $2.95 

Bar Pin-out & Functional Description S2.95 
ALL THREE HANDBOOKS S6.95 



100 per strip M0LEX PINS 



Intended for use as an inexpensive subsntule for IC 
sockeis Also perfect lor use as board connectors 
and in subassemblies 
SPECIAL— 100/1.49— 1000/12.00 



CONSUMER ELECTRONICS 



PONG 
SUPER PONG 



SINGLE 
GAME 

4 GAMES 
IN ONE 



$59.95 
$89.95 



PONG 



GAMES INCLUDED IN SUPER PONG ARE: 

• PONG • CATCH 

• SUPER PONG • HANDBALL 

FEATURES OF PONG ANDSUPER PONG 

■ Inaenipmat speed on vollpys increases pxciianeni 

■ Playing lipid adjusts to any see screen 

■ Game appears in color or in black & wtiui». rtepeiianui mi television set. 

■ Unmistakable "PONG " sou ml accompanies each volley 

■ Digital scoring Hashes on [be screen between each point 

■ 2 player challenge or Eolilaire 

■ Hooks up srnoly to any niocli;l television set. me scieen actually Uecoims ihe playing field 

■ English and other techniques can be used to make any member ol the family a Pong champion 

■ Battery operated by -1 size D flashlight Batteries included with the Unit 

AC Adaptor (Eliminates Batteries) $9.95 



Jbfa& 




.125" dia. 

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.13 



"The PDP-8 is an old war- 
horse which should be put 
out to pasture." 



sophistication is where you find it. The 8080 
is far more sophisticated than the PDP-8 so 
if one needs a capable computer, regardless 
of the imputed applications intent of the 
designers, the 8080 is better than the PDP-8 
hands down. 

The PDP-8 was truly a marvel for its time 
and for this DEC deserves great praise. 
However, the PDP-8 is an old warhorse 
which should be put out to pasture. A group 
within DEC's environs realized the PDP-8 
was over the hill so they broke away from 
Data General and made the NOVA which 
was a vast improvement, conceptually, over 
the PDP-8. But now the original NOVA and 
its replacement the SUPERNOVA are both 
also over the hill, eclipsed if you please, by 
later innovations. The DEC people felt the 
hot winds of change blowing on their col- 
lective necks so they developed the PDP-11 
(no doubt partly in reaction to the success 
of the NOVA which is a mighty fine little 
computer except for the possibility it is 
somewhat wasteful in its utilization of 
memory address space). But it is not my 
purpose to discuss the PDP-1 1 . 

It is fantastic that Mr Nelson claims the 
PDP-8 is easy to understand from a software 
standpoint. It is not all that difficult to 
understand, but he must have meant that the 
PDP-8 is easy to understand when compared 
with other computers. The PDP-8 is not a 
"clean" machine — it has some complica- 
tions that are needlessly tedious when com- 
pared with a classic von Neuman computer 
such as the IBM 7090 (the 7090 was 
somewhat larger than the PDP-8). The so- 
called microinstructions are enough to drive 
a beginner right up the wall. The 8080 has 
its little complications; but, if desired, one 
could select a subset of the 8080 instruc- 
tions [Such as Charles Howerton used in his 
July 1976 BYTE article on page 22] which 
if used for comparison with the PDP-8 
would be both simpler and more powerful 
than the PDP-8. Many complications in 
programming have to do with addressing. 
Compared to the pain of addressing on a 
PDP-8, addressing in the 8080 could not be 
easier. Addressing only 4 K on the PDP-8 
requires 24 bits: 12 bits for the instruction 
and another 12 bits for an indirect address 
vector. The poor little 8080 "industrial 
controller" directly addresses 64 K in the 
same 24 bits. 

Mr Nelson says the PDP-8 has a "con- 
venient parallel word length of 12 bits." 
Convenient for what? The only thing I can 
think of is a 12 bit A to D converter or 
reading all 12 levels of a punched datacard. 
One hardly needs 12 bits for an operation 
code (8 bits allows 256 possible operations) 



and 12 bits is a short and limited address 
field. In the "olden" days, before ASCII, the 
12 bit word could hold two characters at 6 
bits each, but that is ancient history. 

The autoindexing locations in octal 0010 
to 0017 are kind of cute. The Data General 
NOVA extended this concept to also allow 
auto decrement locations, but neither the 
auto increment or auto decrement locations 
are used very much these days because no 
program is really quite sure they are not 
used by some other program which leads to 
the consequence that they are not used by 
anyone. In a sense, the NOVA was an 
extension of the PDP-8 in concept, but the 
NOVA people should have looked elsewhere 
for inspiration. 

Now for some fundamental theory. Mr 
Nelson points out that instructions can be 
manipulated and data words can be exe- 
cuted, concerning which he says, "Software 
people will recognize this convenience." 
Convenience my foot — this is a bucket of 
worms. Before the invention of index reg- 
isters and indirect addressing, this was the 
only method available for instruction modi- 
fication. Very few modern programmers 
play such games with instructions because it 
unduly complicates on line debugging and 
prevents a program being written as "pure 
procedure." A program consists of pure 
procedure when it never changes any loca- 
tion that is peculiar to (is assigned to) the 
procedure block itself. Such a program has 
the virtue that it can be placed into read 
only memory (ROM, PROM or EROM) or 
protected programmable memory. A con- 
ventional PDP-8 program cannot be written 
as pure procedure because the return vector 
from a subroutine is always stored into the 
first location of the subroutine. This is the 
classic subroutine linkage and is how it was 
done on most computers for many years. 
Thus, it follows that the PDP-8 and read 
only memory do not get along together. 

The interrupt structure of the PDP-8 (and 
the NOVA) is quite crude when compared 
with most modern computers (maxi, mini, 
and micro). The PDP-11 has a particularly 
nice vectored interrupt structure. 

I think that the article by Mr Nelson is an 
excellent example of the smoke screen that 
is thrown up when discussing a machine that 
is quite deficient in terms of registers. He 
mentions the multiplexer (DX) register and 
the temporary register (TEMP) that are 
absolutely unavailable to you in any sense; 
but, when thrown in with the "real" regis- 
ters, it seems to up the count. He also 
includes features common to all CPUs such 
as the PC, MAR, IR and the ALU which is 
not a register anyway. 



140 



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A virtue of the PDP-8 which must be 
admitted is the large amount of software 
that has been written for it. Considering that 
practically none of it may be placed into 
ROM, this treasure trove is of little value 
unless you have it on disk or other fast mass 
storage device. Now you are beginning to 
talk the kind of bucks that would be better 
spent for a more effective computer. It is 
not nice for me to say it, but this vast store 
of freely available software contains a heck 
of a lot of junk that would be more trouble 
to understand and get working than it is 
worth. You obviously need systems pro- 
grams like an editor, assembler, and a debug 
executive, but beyond these you need little 
more. These should properly be supplied by 
the manufacturer anyway! 

Contrary to Mr Nelson, I say the PDP-8 
or its near equal the IM6100 are not at all 
the "ideal machine for the computer hobby- 
ist." If you could "fall in" and get one for 
nothing, then take it, but for your hard 
earned bucks — no way man. 

Webb Simmons 

1559 AlcalaPI 

San Diego CA 921 11 



There are two sides of every coin, and we 



print your letter to give an example of a 
critique which might be made. Does anyone 
else have some information or opinions to 
contribute on the basis of personal exper- 
ience with PDP-8s? 

Digital Equipment Corporation is the 
source of a whole industry, the minicom- 
puter industry, and the PDP-8 is historically 
the first successfully marketed minicom- 
puter. (Successfully is defined here as widely 
sold and installed.) All present microcom- 
puter work owes its heritage to the earlier 
minicomputer industry and indirectly to 
Digital Equipment Corporation and the 
PDP-8. 

We caution readers that just as Robert 
Nelson may be a bit pro-PDP-8 in his recent 
two part article, the above letter represents 
and emphasizes the other side of the coin. 
An important item to remember in forming 
your own opinion about the matter is that 
virtually any machine with the character- 
istics of programmability can be used in the 
small computer systems context. If you are 
having a race to see who is the fastest, who 
uses the least memory, who has the best 
software development systems, etc, then 
differences in the design and history of a 
computer architecture will enter into the 
decision. ■ 



BYTE T-shirts are here! 




At last! No more wardrobe crises! BYTE T-shirts are here! Now you 
have the perfect garb for computer club meetings, Altair Conven- 
tions, playing Shooting Stars and computer chess. (A pair of 
trousers from your own closet is suggested as an addition to the 
BYTE T-shirt. The Bytique can't do everything for you.) 

BYTE T-shirts are of top quality 100% cotton or cotton-polyester. 
The original design, by artist Judy Lee Rehling, is silk screened in 
red on white shirts with blue trim on collars and sleeves, or on blue 
heather shirts. Each shirt is mailed first class for safe, rapid delivery 
to you. 

The $5 price includes handling and first class postage. 



Send to: 
The Bytique 



In unusual cases, processing may exceed 30 days. 



PO Box 274 

Jaffrey Center NH 03454 

Please send me extra large 

large 

medium 

small 

Total enclosed $ 



Bill MasterCharge No 

Bill BankAmericard No.. 

Name 

Address 

City 



blue heather 

white with blue trim and 

red letters 

T-shirts @ $5 each (includes hand- 
ling and first class postage) 

Exp. Date 

Exp. Date 



Signature 

Other colors, styles I'd like to see_ 



_State^ 



_2ip_ 



142 




TOUCH TONE PARTS KIT 

Basic kit of parts for building 
touch tone generator. Includes 
MC14410P touchtone chip, 12 
key Choroerics keyboard plus 
1 MHz crystal. Comes with a 
set of applications showing 
typical circuits. 

All three components S16.95 



MC14412 UNIVERSAL MODEM CHIP 
MC144I2 contains a complete FSK modulator and de-mod- 
ulator compatible with foreign and USA communications. 
(0-600 BP5) 
FEATURES: 

.On chip crystal oscillator 
• Echo suppressor disable tone generator 
.Originate and answer modes 

.Simplex, half-duplex, and full duplex operation 
.On chip sine wave 
.Modem self test mode 
.Selectable dato rates: 0-200 
0-300 
0-600 
.Single supply 
VDD=4.75 to 15VDC - FL suffix 
VDD=4.75 to 6 VDC - VL suffix 
TYPICAL APPLICATIONS: 

.Stand alone - low speed modems 
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.Remote terminals, accoustic couplers 

MC144I2FL S28.99 

MCI4412VL $21.74 

6 pages of data .60 

Crystal for the above $4.95 

MC1441I BIT RATE GENERATOR. 
Single chip for generating selectable frequencies for equip- 
ment in dato communications such as TTY, printers, CRT s 
or microprocessors. Generates 14 different standard bit 
rates which are multiplied under external control to IX, 
8X, 16X or 64X initial value. Operates from single +5 

volt supply. MC14411 .... $11.98 

4 pages of data 40 

Crystal for the above $4.95 

REMOTE CONTROL TRANSMITTER. MC14422P is a 22 
channel ultra-sonic remote control transmitter I.C. CMOS 
uses little power ond only a few external passive compon- 
ents. Applications include TV receivers, security controls, 
toys, industrial controls and locks. 16 pin DIP plastic pkg 
MC14422P with specs 




.Sll 



BRAND NEW!!! Monsanto 7-segment LED 
readouts ! Common anode, . 27" character 
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MAN-52(green> or MAN-82(yellow)$l .29. 10/S1 1 



4 DIGIT COUNTER. MM74C926 is a 4 digit counter with 
7 segment output. Carry output For cascading ond internal 
display select allows outputting of counter or set of 
internal latches. 3 to 6V operation. Great for clocks, 
event and frequency counters. 
MM74C926 - with spec sheet SI 2 .00 



3 DECADE (BCD) COUNTER CHIP 
MC14553BCP consists of 3 negative edge triggered 
synchronous counters, 3 quad latches and self scan 
multiplexed , TTL compatible outputs. 

MC14553BCP $8.72 

Spec sheets $.60 



TELETYPE CODE CONVERSION CHIP 

MM5220BL converts 5 level Baudot into 8 level ASCII. Use 

this chip ro make your old TTY talk to your new computer. 

MM5220BL $1 8. 00 

Specs for the above .30 

MOS TIME BASE KIT. 

Only 1" X 1.5". Input 5 to 15 VDC, output is 60HZ 
square wave for portable or mobile clocks. PC board is 
drilled ! MTBK-60HZ S5.88 



Says 



PROJECT HEXED??? 
If mailing fees and poor service have got you spooked, 
and looking for those new devices is goblin up your 
project time, and you don't know witch way to turn- 
let the cats at TR1-TEK help !!!!!!!!!!!!!!!!!!!!!!! 



GOLD CHIP 

Linear Integrated Circuits 

Brand new process by RCA in which the aluminum metalizotion 
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uniformity. Plastic parts that meet mil specs! ! 
Tri-Tek is proud to be the first to bring this new level of 
performance to you at SURPLUS PRICES. Why buy regrades?? 

CA301 A. .Improved, general purpose oo-amp,8 pin dip. .59c 

CA307.. .Super 741 op-amp. 8 pin dip 52c 

CA324. . .Compensated quad op-amp, 14 pin dip $1.80 

CA339A.. Low offset quad comparator. 14 pin dip $1.59 

CA74] C. . Famous general purpose op-amp, 8 pin dip.. 45c 
CA747C. .General purpose dual op-amp, 14 pin dip... 82c 

CA748C..Externally compensated 741, 8 pin dip 49c 

CA1458. . General purpose dual op-amp. 8 pin dip 69c 

CA3401..Quad single supply (5-18V) op amp. 14 pin.. 89c 

Another super buy from RCA. CA555 timer. 8 pin dip. 59c 



**&||»i»<rof 




NEW! 



'/' 



ALPHA-NUMERIC KEYBOARD 
Made by Licon for Motorola Dato Systems. Includes full upper cose alpha and numeric with separate 
numeric and cursor control pods. Self scanning with ROM encoder. These beautiful keyboards are 
modern design and recent manufacture. 

Outputs are TTL compatible and have open collector buffers with resistive pull-ups. Encoding is in 
ASCII with some special control codes. Code table is supplied. 
There are only a few of these high quality KB's and at our price they wont last long.... $39.95 



DATA BOOKS BY NATIONAL SEMICONDUCTOR 

DIGITAL . Covers TTL, DTL, Tri-State, etc $3.95 

LINEAR. Covers amplifiers, pre-amps, op-amps, . . $3.95 
Dozens of application notes and 
egulotors, 



LINEAR APPLICATIONS 

technical briefs covering the use of op 

phase locked loops and audio omps $3 . 25 

CMOS Gates, Flip Flops, registers, functional blocks $3 
VOL TAGE REGULATORS. A must for anyone making a 
power supply. Complete theory including transformers, 

filters, heat sinks, regulators, etc $3.00 

MEMORY. Information on MOS and Bipolar memories'' 

RAMS, ROMS, PROMS and decoders/encoders $3.95 

INTERFACE. Covers peripheral drivers, level translators, 
line driver/receivers, memory and clock drivers, sense amps 

display driver and opto-couplers $3.95 

(Outside U.S., add postage for 1.5lbs^ 

SPECIAL FUNCTIONS DATA BOOK contains detailed 
information for specifying and applying special amplifiers, 
buffers, clock drivers, analog switches and D/A-A/D 

converter products $3 . 25 

AUDIO HANDBOOK contains detailed discussions, 
covering many 
examples... $3. 25 



including complete design particular; 
areas of audio with real world design 



NI-CAD BATTERIES. Battery pock of 5 cells. Delivers 
6.25V <i 500mAH. Wire leads. These are brand new 
and fresh!!! NCB-6252 $3.25, 4 pks, $1 2.00 



T.V. CLOCK CHIP SET. MM5318/5841 two chip set forms 
basis for time of doy display on your TV screen. Interesting 
and convenient woy to keep time. 
MM531 8/5841 Set $22.45 Specs $1 .00 



D-A CONVERTER BY ZELTEX 

8 bit precision hybrid circuit for use in controllers, timers, 
volt meters, etc. Molded plastic package with P.C. pins. 
Super buy on this better than usual subsystem. ZELTEX 
model ZD430. DAC-430 $4.95 



PRECISION REFERENCE AMP 

LH0070-1H provides a precise 10.0 volts for use in BCD A 

to D converters or meter calibrators. Typical initial accuracy 

Is .3% ( + - .03V). Comes in TO-5 can. 

LH0070- 1 H with specs S5 . 35 




tRi-tek, inc. 

6522 noRth 43R6 avenue, 
Qlen^ALe, ARizoru 85301 

phone 602 - 931-6949 



We pay shipping on all orders over $10 US, $15 foreign in US funds. Orders 

under $10, please add $1 handling. Please add insurance. Master Charge 
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placed HAM to 5PM daily, Mon thru Fri. Call 602-931-4528. Check reader 
service card or send stamp for our latest flyers packed with new and surplus 
electronic components. 



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BOMB 

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Box 

BOMB Results for July 



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PAGE ARTICLE 

12 Hickey: Computer. . .vs. . .Hand Sent Morse Code 
26 Hosking: A Ham's Application Dreams 
30 Grappel-Hemenway: Add This 6800 Morser. . . 
36 Krakauer: Efficient Storage. . . 
42 Sewell: If Only Sam Morse Could See Us Now 
52 Filgate: Morse Code Station Data Handler 
74 Guthrie: Mathematical Function Unit- Part 2 
82 Baker: Keep PACE with the Times 
90 Fylstra-Wilber: Homebrewery vs Priesthood 
118 Douds: Meeting Activities. . . 



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144 




Compatible with 

Motorola Evaluation Kits SWT Kits Cramer Kits 

With a CRT interface module from Sphere you can communicate 
with your computer . . . PDQ! No fooling around with blinking lights, 
you get up to 32 characters by 16 lines of instant display on your 
television set or video monitor. 

The Sphere CRT module interfaces to your Motorola 6800 product 
with easy to connect flat ribbon cable bus through 16 lines of address bus, 
8 lines of data bus, the VMA, the phase #2 clock and the read/write port. 

Mail this coupon today for your CRT PDQ - OK! 



- 





Measuring just 11" wide x 11" deep x 5" high, and weighing a 
mere 7 pounds, the Altair ™ 680b is a complete, general-purpose 
computer. 

The secret to this revolutionary, small computer is its CPU 
board. This double-sided board fits along the bottom of the Altair 
case and plugs directly into the front panel board. It contains 
the new 6800 microprocessor, 1,024 bytes of RAM memory, a 256 
byte PROM monitor, provisions for 768 bytes of additional PROM 
or ROM, and a single Interface port with a Motorola ACIA serial 
interface adapter which can be configured either RS-232 or TTY 
A five level Baudot interface option is also available. 

The Altair 680b can be programmed from front panel switches, 
or it can be interfaced to a video display terminal, or teletype- 
writer. Three additional circuit boards can be plugged inside the 
Altair 680b for further memory and interface expansion. The first 
of these boards is a 16K static RAM memory board. 

Software already developed includes Altair 680 BASIC with 
all the features of the 8K BASIC previously developed for the 
Altair 8800. These include Boolean operators, the ability to read 
or write a byte from any I/O port or memory location, multiple 
statements per line, and the ability to interrupt program execution 
and then continue after the examination of variable values. This 
software takes only 6.8K bytes of memory space and a copy is 
included free with the purchase of the Altair 680 16K memory 
board. 

Other software includes a resident two pass assembler. The 
Altair 680b is also compatible with Motorola 6800 software. 

The Altair b80h is ideal for hobbyists who want a powerful 
computer system at an economic price. Altair 680b owners qualify 



for membership in the Altair Users Croup, and like other Altair 
owners, they receive a complimentary subscription to Computer 
Notes and complete factory support. 

PRICES: 

Altair 680b kit with complete, easy-to-understand assembly man- 
ual, operator's manual, and programming manual $466 

Assembled Altair 680b $625 

Altair 680b Turnkey model kit 395 

Expander Card 680MB (required to expand 680) $ 24 

Altair 680BSM 16K static RAM board kit with 680 BASIC $685 

Altair 680 BASIC when purchased separately $200 

Baudot option $ 42 

MAIL THIS COUPON TODAY 



D Enclosed is ,i check for $_ 
□ BankAmericard - 



:ir Master Charge 



□ Altair 680b D Kit □ Assembled Q Other (specify) 
enclose $8 for postage and handling 

□ Please send free information package. 



CITY. 



STATE ft ZIP_ 



fl§ GODDSe 



2450 Alamo SE/Albuquerque, NM 87106, 505-243-7821 



NOTE: Altair is a trademark ot MITS, inc. 



Price, specifications subject to change. Please allow up to 60 days for delivery.