bIIII ~6800-S0FTWARE

WARNING - It has been detel-mined that reading this ad may be hazard ou s to your hea lth , if you own
anothN type computer syste m _ We wi ll not b e I-espo nsible fOI- ulcers, heal-t burn , or other
comp li cat io ns if you persist in reading this material.

*
4 K BASIC©
Full floating point math
- 8 K BASIC©
• 1.0E-99 to 9.99999999E+99 numbe l- I-ange
, User programs may be saved and loaded
• Direct mode pwvided for mo st statements
* Wil l run most progl-a ms in 8K bytes of memmy (4K Vel-s ian)
0 1- 12K bytes of memol-y (8K V ersion)
, USER function pw vid ed to ca ll machine language programs
• Str ing variables and trig funct ions-8K BAS IC only

COMMANDS STATEMENTS FUNCTIONS

LIST REM END ABS t VAL t SIN
RUN DIM GOTO' STOP INT t EXT$ t COS
NEW DATA ON . . . GOTO · GOSUB* t LEN $ t TAN
RND
SAV E READ ON_ . _GOSUB' PATCH ' SGN t LEFT$ t EXP
LO AD RE STO RE IF _ . .THEN' RETURN CHR t MID $ t L OG
PATCH LET ' INPUT t DE S USER t R IGHT$ t SQR
FOR PRI NT * t PEEK TAB
'" Direct mode statements NEXT t POKE
t 8K Version only
MATH OPERATORS RELATIONAL OPERATORS
11&
(un ary ) Negate Equal BANKAMERICARD
* Multip li cation () Not Equal -I#MM

•
Di vision ( Less Th an
+ Addition ) Greater Than •• •• • • •
., .,
Subtraction (= Less Than or Equal
t + Expone nt ) = GI-eater Than or Equal

© Copyright 7976 by Southwest Technical Products Corp. 4K and 8K BASIC Version 7.0 program material
and manual may be copied for personal use only. No duplication or modification for commercial use of any
!? ind is au thorized. ____________________________ _____________________________ _
You guys are out of your minds , but who am I to complain. Send -

o 4K BASIC CASSETTE $4.95 o MP-68 Computer

/
o 8K BASIC CASSETTE $9 .95 Kit $395 _00

NAME

ADDRESS

CITY STATE ZIP

Southwest Technical Products Corp_

Bo x 32040, San Antonio , Texas 78284
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ou get more games,

ore fun, more computer uses
with this new joystick
r-----,
8800 I CROMEMCO CO LOR
I OR TV TV
I 8080
DAZZLER SET

,
CROMEMCO
I COMPUTER
_ _ .JI

,
Plugs
~- . into
_. .
C'--l<- computer

(3 I (3
\
\
AND THERE'S AN 8800 or IMSAI 8080. And you'll still STORE/MAIL
have several analog channels left
EASY WAY TO INPUT IT Cromemco wishes you more fun,
over (and one 8-bit output port).
TO YOUR COMPUTER more use from your computer. Get
The D + 7A plugs into the Stand-
You'll get a lot more fun out of this new joystick console and other
ard 100 (S-100) bus of your Altair or
your computer with this new joy- Cromemco peripherals at your com-
IMSAI computer.
stick. puter store or order from the factory.
But note that it is not just an EASY TO DISPLAY
ordinary joystick - it is a console. It Displaying the joystick outputs joystick console kit
has a 2-axis joystick and contains a with the software below is also easy. (Model )5-1 K) .. .. ... ....... .. $ 65
speaker and speaker amplifier. You joystick console assembled
Just use our TV DAZZLER™ board.
(Model jS-1W) .. .... .. ....... $ 95
can have sound with your games or, It also plugs into the S-100 bus. . D+7A I/O kit (Model D+7A-K) .. $145
Gives you
say, warning sounds in D+7A I/ O assembled
other applications. Or
NEW SOFTWARE
sound, too (Model D + 7A-W) ........ . . .. $245
have your computer Here's some new Cromemco soft- TV DAZZLER kit (Model CGI-K) .. . $215

c(]
Four
talk to you.
A third feature you
get is four pushbutton
ware for the joystick (to display, use
DAZZLER interface):
CHASE! (2 persons, 2 joysticks):
TV DAZZLER assembled
(Model CGI-W) . .. . ... . . .. . . . . $350
SOFTWARE
switches. These give the cross chases the circle. The ver- (Punched paper tape
push buttons tical bars move downward to add
you even more pos- with documentation)

[1]m
1 sible uses such as se- more fun to the chase . Score and CHASE! ... . ... ... ... . .. .. .. .. . . $15
[1] lecting various colors remaining time kept automatically. TRACK . .. . . . . . ...... . ........ .. $15
rn on a color graphics TRACK (1 person, 1 joystick):
move the dot to the center of the
DAZZLE DOODLE . . . . .. ....... . .. $15
terminal. PROMPT SHIPMENT
spiral without touching the spiral's
EASY TO COUPLE arms. Mastercharge and BankAmericard accepted with
signed ord er. Pl ease show complete card number
To couple the new joystick to DAZZLE DOODLE (1 person, 1 and expiration date.
your computer, just use our D+7ATt.t joystick): lets you draw pictures in Mail orders shipped prepaid if fully paid with
order. Purchase orders accepted subject to credit
I/O board. It will couple not only 4 colors on your color TV terminal approval.
one but two consoles to your Altair™ using the joystick. California users add 6% sales tax.

Cromemeo
Specialists in computers and peripherals
2432 CHARLESTON RD., MOUNTAIN VIEW, CA 94043 • (415) 964-7400
 In
This page 78 page 32

with a mathematical orientation but Star Trek freaks should turn to Joe
utility for general purpose program- Deres' arti cle to find An Enterprising
min g as we ll. Display. In the artic le you'll find
inform ation on a design for a te le-
How do you do grap hics in a vis ion graphics output which can be
wee kend, without spending a fortune? built from a kit (or your own parts)
In Beer Budget Graphi cs, Peter Nelson for less th an $100.
page 26 tells all : how th e synergistic com bina-
tion of a coup le of di gital to analog Ira Rampil provides Some Graphics
converters and an output la tch or two Background Information, including a
It's More Fun Than Crayons! Read brings th e world of point pl otting to comparison of several displ ay devices
how Mike and Alex Rosner, ages 7 and an osc ill oscope for abo ut $20 in parts. available to individuals.
5, di scove red the joys of co mpu te t· art
and incidentall y proved the need fo r In the July ·1976 BYTE, we ran a Don 't be satisfied with simpl e vi sual
timesharing co mputers in the home. functional specification fo r a grap hics reado uts. Make Your Next Peripheral a
On the cover are super stat·s Mike and interface in answer to reade r Paul Real Eye Opener by impl emen ting a
Alex at work. Hyde J r's letter. Practical ly befo re th e true vector displ ay usin g an XY osc il-
in k had dried on the Jul y press run loscope, circuits and software simil ar
If Isaac Newton were alive today, (fi gure of speech) read er Thomas R to Steve Ciarcia's design. In his article
he'd be immersed in long and co m- Buschbach se nt in this arti cle on how you'll see how to draw a pi cture of a
plicated physics manipulation s, which he made just such a graphics interface moderately high resoluti on Star Sh ip
are ultimately tested using calcu lations for his Digital Group syste m usin g Enterprise.
involving multidimensional matrices ex istin g timing logic of th e telev ision
and matrix operations of linear alge- display unit. Given an ex istin g 8 K Build This Video Display Terminal,
bra. Chances are he might be in ter- memory , processor and television di s- advises Alfred Anderson, who took
acting with a computer, with an inter- pl ay generator, th is hi gh reso luti on C W Gantt Jr's TV interface circuit
preter from th e APL tree of languages. di spl ay can be added to a system for as described in the June 1976 BYTE,
Read Mark Arno ld 's What Is APL? to li ttle as $25 in additional se micon- made a few changes, added a few
find out a bit about APL, a lang uage ductors. goodies, and wrote a few lines of
software. Now he tells you how you
page 106
can do it.

•
What's NOT In This BYTE
... Software Bug of the Month, Book
Reviews, Ask BYTE, a slew of What's
New and BYTE's Bits items we were
dying to print, lots of good letters, and
some dynamite articles. Eve n using
smaller type in places didn't enable us
to include much that we urgentl y
wished to. If you missed it th is month ,
watch for it next.

2
 # 15
NOVEMBER 1976

In I;he Queue staff

- Foreground PUBLISHERS
Virginia Peschke
26 BUI LD THE BEER BUDGET GRAPHICS INTERFACE Manfred Peschke
EDITOR
Graphics System-Nelson
Carl T Helmers, Jr
32 ADD THIS GRAPHICS DISPLAY TO YOUR SYSTEM GENERAL MANAGER
H ardware-Buschbach Manfred Pesch ke
AN ENTERPRISING DISPLAY DEVICE PRODUCTION MANAGER
42
Judith Havey
Hardware-Deres CIRCULATION
78 MAKE YOUR NEXT PERIPHERAL A REAL EYE OPENER Deborah R Luhrs
Graph ics Systems-Ci arci a DEALER CIRCULATION
Deena Zealy
106 BUILD THIS VIDEO DISPLAY TERMINAL PUBLISHERS ASSISTANTS
Systems-Anderson Kimberly Barbour
Debra L Boudrieau
Cheryl Hurd
Background Anne Jackson
Carol Nyland
6 IT'S MORE FUN THAN CRAYONS
Lau rie Stuart
Graphics-Rosner ADVERTISING
20 WHAT IS APL? Elizabeth Alpaugh
Virginia Peschke
Languages-Arnold
TYPOGRAPHY
40 A TIP FOR USING WIRING PENCILS Custom Marketing Resources, Inc
Construction Techniques-Burhans Goodway Graphics
56 SOME GRAPHICS BACKGROUND INFORMATION Mary Lavoie
Taimi Woodward
Graphics Systems-Rampil
PHOTOGRAPHY
Ed Crabtree
Nucleus Custom Marketing Resources, Inc
ART
2 In This BYTE Matthew Arnold
10 A Proposed Standard for Publishing Mary Jane Frohlich
Lynn Malo
Binary Data in Machine Readable Form
Bill Morello
16 The Address Space Saturation Problem PRINTING
16 Outstanding Computer Hobbyist The George Banta Company
Custom Marketing Resources, Inc
54 KilO'Byte
Lennie Cashion
60, 67 BYTE magazine is published Larry Davis
monthly by BYTE Publica-
99, 140 What's New? tions Inc, 70 Main St, Peter- Jeff Pratt
Description: MERLIN Video Interface borough New Hampshire ASSOCIATES
62 03458. Subscription rates are Bob Baker
66 Something for Everyone $12 for one year, $22 for two
years, $30 for three years in Dan Fylstra
68 Letters North America. Elsewhere: Harold A Mauch
$15 one year, $25 two years,
90 BYTE's Bugs $33 three years. Second class Chris Ryland
postage paid at Peterborough SPECIAL PRODUCTS
92 Clubs, Newsletters NH 03458 and at additional
Susan Pearne
mailing offices. Phone
104 Classified Ads 603-924-7217. Entire con- Floyd W Rehling
tents copyright 1976 BYTE
127 BYTE's Bits Publications Inc, Peterborough TECHNICIAN
Description: Astral 2000 NH 03458. Address editorial Melvin G Weir
132 correspondence to Editor, CONSTRUCTION
144 BOMB BYTE, 70 Main St, Peter-
borough NH 03458. , ~ Walter Pence
144 Reader's Service Peter Travisano

3
Photo 7: Alex Rosner, age
5, shown preparing the
graph paper coding sheet
for his picture from a pen-
cil sketch. Once the cor-
relation between picture
locations and commands
was learned, both children
stopped planning layouts
in advance on the coding
sheets. The "snow with
house and mailbox" is
shown in photo 5.

It's More Fun

Now that the home computer is emerging Now, when I wal k in the door after work,
fro m its cry stal rad io stage and now that we the kids corne r me asking which one can use
are becoming more ap pli cations ori ented the computer first.
rather than hardware or iented, we are going The microcomputer system uses aMOS
to find that we have competition for com- Technology 6502 CPU, a TIM (Teletype
puter time right in our homes. While I have Interface Monitor), and 1 kilobyte of pro-
been putting microcomputers using micro- gram mab le memory. The graphics mod ul e
Richard Rosner processors together for alm ost two years, it contains a 2 K by 8 programmable memory
Pocono Rd wasn't until I hooked up the TV to my all owing a 128 by 128 point displ ay. In
Brookfield CT 06804 present system that my fami ly took interest. these pictures the disp lay is configured

Photo 3: "Cage," by Alex Photo 4: Rocket Ship Photo 5: Snow With

Rosner, freehand. With Moon, by Mike House and Mailbox, by
Rosner. Alex Rosner.

6
 Photo 2: Michael Rosner,
age 7, sitting at the Tele-
type entering data for the
image of a rocket ship
with moon (see also photo
4).

Than Crayons
(under software control) as a 32 by 32 array. to then draw a picture by filling in some of
The data for the display is entered seri- the squares. After the drawing is comp lete
ally. The software command s are the paper tape with the program is loaded
R, reset to top line, into the processor and the data is entered
N, go to beginning of next line, with the above five commands using t he
W, enter a white square, drawing as a coding sheet.
K, enter a black sq uare, and Thi s, of course, is not an ideal hardware
H, halt (return to monitor) . or software approach for a video interface.
The procedure is to take a piece of graph The interface was bu il t for another app lica-
paper with a 32 by 32 grid blocked off and tion and the processor was used as a test

-:.
Photo 6: Rocket Ship, by Photo 7: Fun Play (Swing Photo 8: Flower Puzzle,
Mike Rosner. Set, Man, Sun and Mail by Mike Rosner, freehand.
Box), by Alex Rosner.

7
 H 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-
supply produces a true 28 amp memory protect. For the ultimate
cial users. And it looks it. Inside
current, enough to power a full in flexibility, you can design the
and out! The cabinet is attractive,
system. system for low-cost multiprocessor,
heavy-gauge aluminum. The
You can expand to a shared memory capability.
heavy-duty lucite front panel has
powerful system with 64K of Find out more about the
an extra 8 program controlled
memory, plus a floppy disk con- computer you thought didn 't
LED's. It plugs directly into the
troller, with its own on- board exist. Get a complete illustrated
Mother Board without a wire
8080-and a DOS. A floppy disk brochure describing the IMSAI
harness. And rugged commercial
drive, an audio tape cassette input 8080, options, peripherals, soft-
grade paddle switches that are
device, a printer, plus a video ware, prices and speCifications.
backed up by reliable debouncing
terminal and a teleprinter. These Send one dollar to cover handling.
circuits. But higher aesthetics on Call us for the name of the
peripherals will function with an
the outside is only the beginning. IMSAI dealer nearest you.
8-level priority interrupt system.
The guts of the IMSAI 8080 is Dealer inquiries invited.
IMSAI BASIC software is avail-
where its true beauty lies.
able in 4K, that you can get in
The 8080 is optionally
PROM. And a new $139 4K
expandable to a substantial system
RAM board with software
with 22 card slots in a single
printed circuit board. And the IMS Associates, Inc. Dept. 8-11
durable card cage is made of 14860 Wicks Boulevard
San Leandro, CA 94577
commercial-grade anodized (415) 483-2093
aluminum.
The IMSAI 8080 power
 fixture. After testing the display unit, I put a
little "HELLO MOM" and a starship on the
screen and showed it to my wife and two
kids. The children immediately wanted to do
the same thing and we now have a new toy.
The older child, Michael, is seven and
learned to generate a picture and use the
program after about' two hours of instruc-
Photo 9: House, by Alex tion. He is shown in photo 2 as he puts his Photo 72: Mike's first
Rosner. third creation on the screen, a rocket with work, no title.
the moon. Above his right hand can be seen
the drawing he is working from. (The pat-
tern in the lower portion of the TV screen is
the random data in the programmable
memory chips when the power is turned on.)
All his efforts at keypunching have been
saved on paper tape for delayed replay when
Grandma comes to visit.
The younger child, Alex, five, is shown in
photo 1 as he prepares the coding sheet from
a sketch for his third picture - a house with
mailbox and snow. Alex required a consider-
able amount of help with his first two
pictures, but he quickly learned to use the
Photo 70: Illusion Num- graph paper correctly. Photo 73: "Black Cat" by
The cover photo shows the entire setup. Alex Rosner, freehand.
ber 4, by Mike Rosner,
Alex is putting a picture on the TV while
freehand.
Mike is using BRUIN (a language similar to
BASIC). It seems that second graders are
now being taught the rudiments of algebra.
When my calculator batteries went dead I
called up my company's computer to do
some simple calculations. Mike saw me using
the CRT terminal and wanted to try it.
While we can't call this programming, he is
having fun.
The collection of photos from the TV
screen shows some of the work the kids have
been doing along with the titles. The incep-
tion, generation and titling of all th e pictures
Photo 77: Tree Record, by are the kids' own without help from adults. Photo 74: "Illusion Num-
Mike's first three pictures were made using ber 7" by Mike Rosner,
Alex Rosner, freehand.
work sheets as were Alex's first three. The freehand.
rest were made without first making
drawings.
The microcomputer is set up in the family
playroom. I consider myself quite fortunate
in that I have never had to fight with my Editor's Note: Readers
wife for space. From the beginning of this will detect a careful
venture I have had my wife's full support. balance between the
Perhaps this is because (as she has recently amount of photographic
informed me) she plans on using the com- exposure given to Alex
puter to help her in the various business and Mike. Author Richard
courses in which she is enrolling, as well as Rosner reports that the
for household functions such as diet menu realpolitik of family life
planning. requires equal treatment
If you are as lucky as I am, you may find for both children in his
yourself putting up a signup sheet as the article . .. CH
family competes fOl' computer time.-

9
 Walter Banks and Roger Sanderson of the University of Waterloo,
Waterloo, Ontario CANADA, have proposed a method of publishing machine
readable programs in magazines such as BYTE. This proposal was the subect
of some discussion in a . technical session at the Personal Computing 76
show in Atlantic City. I wrote the present report, based upon preliminary
written information provided by Walter and Roger, and telephone discussions
with Walter on August 75 7976. The technical content .of this report, with
the exception of the proposal of format 3 and addition of a frame
identification field to the block format, is supplied by Walter and
Roger.. .. CH

A Proposed Standard for Publishing

Binary Data in Machine Readable Form
by
Walter Banks
and gency manual reading of the data with
Computer Communications Network Group a magnifier is probably more difficult
Carl Helmers due to the need to interpret four
Roger Sanderson
Editor, BYTE magazine states: wide space, wide mark, narrow
Dept of Electrical Engineering
University of Waterloo space, narrow mark. Th is method had
Waterloo, Ontario CANADA been pr'oposed for use in the retail
Purpose trade by Research Inc, Box 24064,
Minneapolis MN 55424, some time
The purpose of this technology is to ago, before the UPC (Universal Pro-
provide a method of encoding binary data in duct Code) scheme was adopted for
the form of printed mar'ks on a magazine, gmcery product checkout use.
book or other published page. These printed • Format 2, ratio recording, has an
marks are to be in a predefined format advantage in certain points of view in
which can be read by a simple and inexpen- its fixed width. Being fixed width, the
sive optical scanning head which drives a amount of data per page is fixed, as is
single bit input port of a personal computer; the amount of data per line of ma-
decoding will be done by means of software chine readable type. However, it is a
in the computer. The goal is to pmvide a lower density form than either format
means of disseminating program information 1 or format 3 below. It can probably
in a machine readable form. be read by eye with greater ease than
format 1 since every bit is present as a
Physical Formats short or long bar which is actually
Figure 1 details three possible physical printed, and only two states need be
formats. These are proposals at the present interpreted.
time. Other formats are possible and should • Format 3, fixed gap bar width modula-
not be excluded from contention; readers tion, is basically a higher density ver-
are invited to make proposals. The for'mats sion of ratio r'ecording. Take the lay-
are described in the captions of figure 1. The out of format 2, and compress the
following comments can be made. gaps between black marks to a fixed
length, and you will' get form at 3.
• Format 1, bar width modulation with Since this format is higher density, it
alternate light and dark, is the most may be preferable to format 2, wh ile
compact method of encoding. Its den- retaining the advantages of having a
sity varies with the detailed content, human readable black mark for every
but for a given minimum light (or bit.
dark) interval measurable by the input
routine and a given binary string of
data, this method will be higher den- Frame Layout and Page Layout
sity than either format 2 or format 3 Figure 2 shows the layout of a single
below. A disadvantage is that emer- frame of information, inter'pr'eted within the

10
Pick a card. Any card.
From the Digital Group.

If you've been considering the purchase of a microcompu- Most of our designs are parallel port driven with their own
ter and looking at the myriad of products on the market, buffers. If you can get eight bits to a Digital Group inter-
chances are you're just a bit confused about which system face, it'll take over and get the job done.
makes sense for you .
Coordinated Cabinets
As you've no doubt discovered by getting further into this
fascinating hobby, if there is one constant it is constant Right down to our new line of cabinets, Digital Group sys-
change. So how do you go about protecting the considerable tems are designed to protect your investment and keep you
investment you are about to make in a microprocessor? at state of the art. Everyone of our unique, custom cabi-
nets is part of a coordinated line, and you can rest assured
The Digital Group offers a safe way to hedge your bets. that each new product will maintain the same unmistakable
Here's how we do it : up·to-the·minute Digital Group image.
CPU-Independent Bus Structure As much as is possible in this fast-growing, ever-changing
field, the D igita I Group offers protection from obsolescence.
Digital Group systems are based on an extensive bus struc- So go ahead and pick a card. Any card from the Digital
ture (the equivalent of 200 lines) that allows you to com- Group is a safe bet.
pletely change your system's architecture by merely ex-
changing CPU cards and reading in a new operating system
tape. It's that simple. One card and a tape to get from 6500
-------------------
~_=_cQJ-=~"__[r[@lJ_
, ___'®=_[J@D!]_O___'W='__~_ _ _)
to 6800 to 8080A to the remarkable new Z-80. Or some-
thing even newer.
L...-C
The Digital Group system design is quite complex but the
result is simple. All CPU dependencies are handled on the P.O. Box 6528 / Denver, Colorado 80206/ (303) 777-7133
CPU card - nothing else in the system changes. Not mem-
0ry' readouts, I/O interfaces or even cabinets. And that re- OK, I'm ready for details on your systems and all the extras.
presents a significant savings for you . Dea l me in .
When many Digital Group system owners wanted to upgrade
to the revolutionary new Z-80 CPU, it cost them a total of Name
$185. Nothing more.
Address
Stand-Alone Design
City/State/Zip
Each component in a Digital Group system is designed to
be as independent from the other components as possible.
-------------------
 Figure 7: Three possible formats. These are proposals at this time, with the appropriate parameters indicated.

L
TO
r-
•••• o tt
TBr- 0 ~
TG
L
o

~
~
TI

+-
TI
L
TB
.L..l...-
TG
1- r-r-
TO
'I
o
tT
TB L
TI
L1-
f-fo- o
o
o
o
t+
TB, 0
TO
I

c ~
FORMAT I o
o
o
o

Figure 7a: Format 7: Bar

o a
width modulation, with al-
ternate dark and light. The
parameters to be specified o Figure lc: Format 3: Fixed gap bar width
in printing are widths TO
and n. A trailing bit com-
a modulation. The parameters to be specified
in printing are the interbar gap width TG,
plementary to the last data Figure 1b: Format 2: Ratio recording. The and the bit length parameters TO and n. In
bit in a string is required. parameters to be specified in printing are the reading this code, the length of the interbit
The leading bit of a string bit length, TB and the TO and n widths for gap gives a calibration for judging the next
will be assumed to be in states of the data. This format has a fixed dark period as a 0 bit (short) or 7 bit (long).
the dark state. In reading length per bit which is independent of the The data density (as in format 1) varies with
this code, time between state of the data. In reading this code, the the statistics of the number of Os and Is in a
transitions falls into two time from one ligh t to dark transition to the given region of the printed data.
categories, long for a 1 bit, nex t light to dark transition is the duration
and short for a 0 bit. of the bit cell, which is compared to the
duration of the dark period to find out
whether a 1 bit (long) or 0 bit (short) was
read.

string as a synchroni za ti on pattern followed character, the decodin g algorithm can pro-
by 8 bit bytes of info rmation. ceed bit by bit wi th the rest of the frame.
The SYNCH pattern is an 8 bit character Th e CHECKSUM field contains an 8 bit
which must occ ur as th e first byte of every check sum of the data in the current frame.
frame, and may be preceded by seve ral This is the primary en'o r detection technique
timing bits to initi ali ze adapti ve software. empl oyed . In manua l sca nning, when an
Once the input string equa ls the SYNCH error occurs, the sensor head can be drawn

_ _ _-L.._ _ _. l -_ _-L._ _ _.l..-_ _ -L.._ _---1_ _ _ ..L---/) I DATA n'l DATA n

Figure 2: Frame Format. The timing bits may not be required, but provide a preliminary leader
before the ASCII SYN character (hexadecimal 16) which leads off the fram e. A ll data is
transmitted most significant bit first. Follo wing the synchronization character is an 8 bit check
sum representing 2's complement modulo 256 summation of all the remaining data on the
record. The FRAMEID field is an 8 bit integer used for relative positioning within an extended
file. Its purpose is to allow manual rescan in the event of errors, so that the so ftware will
recognize the input as the same record. The length field contains a direct integer value for the
number of bytes in the data field. From 1 to 255 bytes can be in the data field,. a length of 0 is
reserved for a special case "end of file" frame. Finally, the remainder of the fram e contains 8
bit bytes of data.

12
 e've got it!
z·ao power for
the Altair bus.
Here it is, TDL's ZPU™ the high-
est point of technology for an
Altair/ IMSAI system. Now,You
can multiply your present cap-
abilities without creating cost-
ly obsolescence. Take advan-
tage of the wide range of exist-
ing hardware backup for your
current system. The ZPU is
compatible and dependable
with many plus features you'll
want to know about.
To further round out your
system we also have available
the fastest and lowest power
static ram boards going (from
4 to 16K with expansion) and
a system monitor board with
a Z-80 monitor, powerful I/O
and audio casette features .
As for software, TDL's user
support program is unmatched
in the micro-processor indus-
try, currently available are the
Z-80 monitor, basic , and the
most sophisticated MACRO-
ASSEMBLER yet developed.
Join the Z-80 revolution -
it's more than just hardware!

ZPU Kit $269.00

Z16K Kit $574.00 Dealer Inquiries Invited.
HOW TO ORDER Just send check o r
money order, o r use your Ban kAm ericard
or Mastercharge, and yo ur o rd ers will be
shi pped to yo u postpaid . COD o rders mu st
be accompanied by a 25% deposit. Yo ur
c redi t ca rd o rder m ust inc lude th e ser ia l
# of the ca rd , expi ration date, and yo ur
TOL TECHNICAL DESIGN LABS, INC.
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dents ad d 5% state sa les tax. Fo r mo re 342 COLUMBUS AVENUE
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 CENTER MARGIN OF MAGAZINE PAGE

Figure 3: Page Layout. A FRAME N START SCAN

H+HHHHHH I#H HHHHHI#H~ ...
-HHHUHHHH 11111111111111 ~--------J
_______
page of data in printed
form [as we would run in
B YTEj would be laid out
FRAME N+ I
4HfHHH HHHIH 1IIIIIIIIIIIIItH III II I#H I#HHHHHHHHHft
...... -----~--------
with the data running par- FRAME N+2
1111111111111 HHHH+HlIIIIIIIII+H 11111 HHHfHlHfHHHHH+Ht- ...
allel to the center margin -------.-------- ~
of the magazine. This al-
lo ws the maximum
FRAMEN+3
1111111111111 HHlIlIlIlIlIIIlIlIf*HHfHHHfffffHHfHfHHfHtt- ...
amount of data in a frame,
-------..--------- ~
thus minimizing the over-
FRAME N+4
-Iff1H+HHH+Hl
_ _ _ _I_ 11111111111111111
_-..- 11111_
ItH_ HHl_
HfH_111111111
__ HIM_I- "'J
head bits of the frame
format.
FRAME N+5
r
\..
-IffH+HHHtHfH IffH+HfHHl~1#H 11111111111111 HHlHft - \
)
II
/

past the data aga in without mov ing the How Is the Data Generated?
straightedge used as a guid e.
Th e sec ret of this whole meth od at the
The FRAMEID field contain s an 8 bit
magaz in e productio n end is usin g modern
id entifi cation of the current frame within an
phototypesetting eq uipment to create the
extended block of data. Thi s identification is im ages of the data which are used in the
requi red in ord er to all ow the user an opt ion
magaz ine maste r layo uts. Wh en (for exa m-
to reload data if a check sum error is
pl e) an article describing an adva nced high
detected .
level langu age interpreter written by a uni-
Th e length of the data is specified by the
versity or base ment lab hac ker is to be
LENGTH field as a byte coun t fro m 1 to
printed, the paper tape or magnetic tape text
255 (actual counts will depend upon data
of the progra m an d its relocatabl e loade r
density, but will most likely be less than 50
would be converted into phototypesett in g
per frame).
co mmand s fo r the typesetting equ ipment,
Fi gure 3 shows the page layo ut to be used
on 9 track tape or paper tape compatible
in a typical magazi ne page size of 7 inches
with the typesetter. Once th e copy is re-
wide by 10 inches hi gh (18 cm by 25 cm) .
ceived from the typesetter, the rest of the
From hi s exper imen tal work, Walter Banks
layo ut is stand ard operating procedure for
re ports t hat a bit density of 50 bits per in ch
any magazine - keep trac k of the ord er of
(20 bits per cm) in the ratio recordi ng
the program pages and add any aux ili ary
method looks quite reasonable. Based on copy needed to id entify pages or segments
this lin ear density, and putting 1/5 inch (0.5 within the progra m. With 2 K bytes per
cm) spaci ng between fr ames in the hori zo n-
page, dissemin ation of an 8 K to 10K
tal direction, the page capac ity of the layo ut
package would onl y require four or five
in figure 3 can be calc ul ated:
pages in the magaz ine, and would be easi ly
Bits per frame = 50 BPI * 10" = 500 accompli shed. We ex pect to perfor m experi -
Bi ts per page = 5 frames per in ch * 7" * ments with thi s sort of di ssemination

l
500 bits per frame = 17,500 technique in future ed itions of BYTE.
Overhead of the fra me format in figure 2,
Will It Work?

•
excludin g timing bits, is 32 bits per fra me, so
the total data ca pac ity is 17,500 - 35 * 32 = The expe riment looks quite reasonable,
16,380 bits. In bytes, this i~ 16,380/8 = but there are numerous possibl e hitch es
2047.5 bytes. Th e actual frame pal·ameters which can be considered . For example, will
- -
--
------
would be ad ju sted to an even number of the data density proj ecte d (50 bits per inch,
----
-
----
- bytes, whatever the format empl oyed. Usin g 20 bits per centimeter) be practical? What
----
- - - - th e fixed format, each page can hold 2 K will be the in cide nce of errors due to ink

~;~~=
(2048 ) bytes with th e density figures re- spl otches and other glitch es? Will the simp le
ported. Shrin king the interbit gaps to the conception of a readi ng head (photo tran-
format 3 fixed size wo uld probably give an sistor, TTL leve l converter and stra igh t edge
improveme nt of 5 to 15 percent depending as a guide) provide the signal needed? Thi s
upon the width parameters chosen and the report is written on the bas is of pre limin ary
A low density test string. statistics of the data being presented in this ex per iments; furth er information on this
form. subj ect will appear in future BYTEs.-

14
 seliDI Here's SCELBI's First Book of
Computer Games for the 8008/8080.
Action-packed. And fun.
, Try to beat the computer at its own game.
" Here's the first complete machine language
computer manual for computer games to
Introducing SCELBAL, include source listings, flow charts,
routines and more. Space Capture - You
the new microcomputer against the computer using "search and
language that's simpler destroy " strategy to shoot down roaming
alien spaceships in outerspace . Hexpawn
than machine language. - a mini-chess game that lets the
computer make mistakes ... but only
once. Hangman - an updated version
of the great kid game. Computer selects
A complete language for words at random from long, expandable
"8008" '''8080'' systems list. Try to beat it in 8 moves or less.
including source listings, .:: ' ......,.... I Illustrated. Fun extras to put your
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more! fun use.
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Techniques . Source Listings. Flow Charts . And more . " 8080" . You must destroy a random
Took several years to develop . Now yours for many years number of allen ships without running
out of stardates, out of fuel, out
to come. First time that intimate deta'ils of higher level of ammunition or out of the galaxy.
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You get 5 Commands: SCR, LIST, RUN, SAVE, LOAD. used for your warp factor? Don 't run
into roaming stars that can damage your
14 Statements: REM, LET, IF ... THEN, GOTO, FOR with ship . Suddenly! Condition Red! Alien In
STEP, END, INPUT, PRINT, NEXT, GOSUB, RETURN and light! How big is he? Fire a phasor or
optional DIM. 7 Functions: INT, SGN , ABS, SQ"R, RND, torpedo! He's damaged or destroyed.
But, you've used valuable fuel. That's
CHR, TAB. And, it runs in SK and more. Here's all the Just the beginning. A new game every
data needed to customize a high level language for your time . Complete program book in machine
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How to ma nipul ate the "8080" program ... plus input / outp ut
st ack. Flow charts and source processing for your basic I / O
listings. General purpose programming through inter-
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 by Carl Helmers
Editorial

The Address Space Saturation Problem

(or, What Happens
After You Use 32 According to an article by Marvin Gold in The designers of the early micro-
the September 6 1976 edition of Electronic processors never conceived of the large scale
16 K Dynamic News , the "16 K dynamic memory chips are integration computer as anything more than
almost ready for volume production, and a controller in dedicated applications (so the
Memory Chips?) grapevine says). The rumor which was
price estimates are quoted. According to Mr
Gold's article, the "1976 ave rage selling price running around some time ago was that one
of 16 K memory chips will be an estimated LSI firm's reaction to the idea of a
$16 each, and when volume production FORTRAN (or other high level language) for
levels are reached in "1977, the average price their microcomplJter was "who'd ever want
at the factory will be $12. Assuming a to do such a silly thing." The history of
personal computing company which has sma ll general purpose computers imple-
moderate volume production purch ases the mented with LSI processors since then
16 K memories at $12, its component cost demonstrates that a lot of people want to do
for a 16 K memory segment is $96, and for a exactly that, and more: APL, SNOBOL,
32 K memory segment is $192 in mid to late LISP, PASCAL, ALGOL, TRACTM etc, etc.
1977. Multiply this by a factor of 3 to 5 to Similarly, the reaction currently might be
take into account packaging, manufacturer "who'd ever want to put more than 64 K
profit margins, and merchant markup ; and it bytes of memory in a personal computing
can be expected that in mid to late 1977 the system?" My claim is that there are plenty
personal computer with 32 K memory will of people who would want to (in order to
have a memory subsystem cost of perhaps
$600 to $1000 at the retail store. Continued on page 65

Personal Computing 76:

Outstanding Computer Hobbyist of the Year Award

by puter Group of New Jersey, seeing it grow

John Dilks from a near handful of people last year to
Cochairman of PC 76 over 400 members with typically 200
attend in g the many meetings. He is a leader
in computer education, where at the Union
At the Personal Computing 76 show, the County Technical Institute he has created a
members of the committee organizing the hands-on training program in microcomputer
show fe lt it would be most appropriate to techno logy and has set up courses which
create an award for a person who has made could easily serve as prototypes for similar
some outstanding contributions to the prog- courses throughout the country. He set up
ress of computing by individuals. We se- and ran the Trenton Computer Festival of
lected the person, then dreamed up the the ACGNJ, one of the first such happenings
award. The person is Sol Libes, president of ever. And, during the past summer, he and
the Amateur Computer Group of New his family travelled throughout the USA,
Jersey. The award consists of a pl aque for meeting with amateur computer clubs and
Sol to keep, and a second plaque with spaces club leaders and manufacturers both to find
for future entries to be engraved. This is how out what's happening and to further the
traditions are started. development of the fie ld. We think these
We had numerous reasons for wanting to reasons more than justify the recognition ,
present this award to Sol. So l is employed as which was a complete surprise to Sol and his
an educator, and is a true amateur interested family at the banquet August 28. We hope
in using the computer. He is one of the to continue this award and tradition at
principal organizers of the Amateur Com- future Personal Computing shows.-
,
16
Meet the Challenger.;"

The Challenger
Self Portrait

The new price and performance champ from OSI.

He's got his act together! our CPU Expander Board, you OSI Challenger Floppy Disk System.
Even our lowest-cost Challenger can always update to any new CPU Fully assembled, for use with OSI
comes fully assembled, complete to be as fast as fast can be . Computers only. $990 Single drive
with a 500 ns 6502A, serial interface, $1490 Dual drive.
And he isn't just good! OSI Audio Cassette Interface.
1 ,024 words of memory and a He 's better! By design. The OSI
UL-approved power supply, all for Comes assembled, but with room
Challenger is the only completely- for you to populate with AID and
$439. Every Challenger comes ready assembled, ultra-high-performance,
for easy expansion with an 8-slot 01 A chips later. (OSI 430 based) $89
fully-e xpandable mainframe computer And all the baseboards and kits of
mother board, backplane expansion that does this much for this little .
capability, and a power supply the powerful OSI 400 System.
Get your hands on one now.
heavy enough to handle a full Send for your Challenger today. OK, OSI, I'm ready to buy!
complement of system boards. Our
4K Challenger comes ready to run You can't beat The Challenger! To order your Challenger System,
BASIC minutes after you unpack it. send the total amount of your
The OSI Challenger 65-1 K. Fully purchase plus $4.00 for shipping and
And there's more . assembled. Features 6502A CPU, insurance (plus sales tax for Ohio
He packs some heavy hardware. serial interface , 1,024 words of orders) by personal money order or
memory . $439. check. Or indicate all numbers
You've never seen memory and
The OSI Challenger 65-4K. Same as on your BankAmericard or Master
interface options like these-not at
65-1 K but with 4,096 words of Charge to charge your order.
our prices, fully assembled! 4K
memory. Will run Tiny BASIC with- Or send a 20% (non-refundable)
RAM memory boards $139! (see
out expansion. $529. deposit to receive your order C.O.D.
below). Single drive OSI Challenger
Floppy Disk $990\ Dual drive The OSI Challenger 65V-4K. NO Delivery is typically 60 days (except
Floppy $1490! Plus 8K PROM NEED for an expensive terminal. when payment is by check, which
boards! A Video Graphics board, Connects to your ASCII keyboard must clear before shipment can be
including alphabetics, graphics, and video monitor through included made). Deliveries are scheduled on
and color! An audio cassette, OSI 440 Video Board. Features a first ordered, first shipped basis.
AID, 01 A and parallel 1/0 board! software utility that simulates a
deluxe CRT terminal. $675. Name _______________________
A backplane extender board!
A prototyping board! And our extra- The OSI Challenger 68-1 K. Based Address, _____________________
ordinary CPU Expander Board-it lets on 6800 CPU. For the casual
you run a Z-80, and 6100 (PDP-8 hobbyist, smaller systems. The City ________ State _____ Zip _____
equivalent) concurrently with The Challenger 68 series comes only in Telephone ___________________
Challenger's 6502, or under its control. serial interface forms and is
compatible with MIKBug software Bank card info Inter Bank # ________
There's nothing soft about through an included OSI software
utilities package. $459. Expiration Date, ________________
his software!
OSI has full software support for our The OSI Challenger 68-4K. With Account #
Challengers. Including extended OSI 4K BASIC on paper tape . $529
BASIC, extended Video Monitor, a SPECIAL! ADDITIONAL 4K MEMORY Check 0 M. O. 0 BAC 0 MC 0
Disk Operating System, some BOARDS . Ordered with your Chal- 20%, bal. C.O.D. 0
very Hollywood real time programs lenger, limit 3 more at this special o Order attached.
for Video Graphics, Animation, Low Price, (total 16K, including 4K o tion
Send additional informa-
on The OSI Challenger.
Sound Processing and so forth, plus already on-board in mainframe). $139
PROM firmware, with more to come. Buy 12K or larger Challenger 65 o tion
Send additional informa-
on OSI 400 Kits.
system and we include Extended
He's fast! BASIC FREE! o $1.00 enclosed
You can order The Challenger with for complete
a 6502C for a 250 ns cycle time, OSI Catalog.
with a standard 6502A for 500 ns
cycle time, or with a 6800 for 1

II
microsecond cycle time. And with

OHIO SCIENTIFIC INSTRUMENT

Dept. B 11679 HAYDEN STREET, HIRAM, OH 44234
 HAVE A MERLIN
The Intelligent Video Interface
If your favorite computerist has an 8080 bus system, what better way to say Merry
Christmas than with a MERLIN Video Interface? MERLIN is not just a superb
character display . .. MERLIN is a whole system
MERLIN is a text display,
a high density graphics display,
a keyboard interface,
a serial 1/0 port,
a regulated power source,
a RAMI ROM memory and
an integrated and expandable software package.
MERLIN is a gift that keeps giving. MERLIN's keyboard and 1/0 connector allows the
MERLIN owner to add a variety of MiniTerm hardware expansion products.
MERLIN's software has been written as an expandable ROM system with many
general purpose subroutines available for use. Give your favorite computerist
(yourself, perhaps?) a MERLIN Christmas!
Order early to insure delivery for Christmas.

FIRMWARE SPECS
MERLIN 'S BASIC INTELLIGENCE (MBI) ROM has

Monitor Functions
• Memory Fill with HEX value
• HE X Memory Dump
• ASCII Te xt Input
• H EX Memory Input or Modify
• Set Display Format
• Examine/Modify CPU registers
• Copy Memory Blocks
• Define Display Memory Area
• Four User Defined Functions
• Execute User Program
• Three Auto-Clear Breakpoints

Editing Functions
• Winking Keyboard Cursor
• Cursor up , down, rt , It, & Home
• Insert and Replace Mode
• Delete Character and Line
• Delete to end of 'Display Memory'
• Four Slave Cursor Functions
Monitor/Debugger Example • Auto or Manual Scroll
• Home/C lear
• Si x User Defined Functions
• Page Up and Page Down
CHRISTMAS ,,,
• • •

HARDWARE SPECS

• Altair / IMSAI Plug - in Compatib le

(Other Computers Soon)
• 40 Character by 20 line ASCII Disp lay Format ~'lERLIN
5 by 7 font , 64 Character Generator ROM
.. ':.
."
'.
• Dual Reso l ution Graphics:
100 V by 80 H or 160 H .. ' .'.
• Mi xe d ASCII / Graph ics Mode
'. ..''.
• Program Control of : .1

'. . . .:-

.' .'
~
'
Cursor: On/Off
Contro l Character: Inverted/Blanked
Carriage Returns: Displayed/B lanked
... ., + " . .~

'.
FIXED or FREE (Memory Saver) Format
Video : Black on White or Reversed (_[!J .', ....
"
'.'

ASCII , Graphics or Mi xed Mode ~, ,

• Plug-in Keyboard Port
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\,-..-.. :'-•.-'.1
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-over 48 K characters per second I .......

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Two 2708 1 K X 8 EPROMs, or
Two 2 K X 8 Mask ROMs, and 160H X 100V Graphics
One 256 X 8 Scratch Pad RA M

MERLIN is just the beginning ... coming soon are . .

• Game control boards that interface via MERLIN's

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• Joysti ck input board for grap h ics drawing , also via
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• Color Graphics and Super Dense Graph ics option board
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• Keyboard and Enclosure to plug into MER LI N's
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------------------------------------- Name ___________________________________________

D MERLIN: assembled and tested including manual
(Does not include Memory) .. . .. . . ...... ....... $349.00 Address _________________________________________
D MERLIN: kit containing PC boards, IC sockets, User
Manual and all parts except memory ........ .. . . $249 .00 City _________________ State ___________ Zi p_____
D MBI MERLIN's Basic Intel li gence: 256 X 8 RAM
Signature ________________________________________
and 2K X 8 mask ROM containing Monitor/ Editor . $ 39.95
D MEl MERLIN 's Expanded Intel l igence: 2K X 8 mask Total $___ MC/BA # _ _ __ _ _ _ _ _ Exp. _ __
ROM with more Monitor/ Editor funct ions and
Graph ics subroutines. . . .. ... . .......... . $ 34.95 All pri ces subject to change without notice. Mass. residents
D MERLIN User Manua l : over 100 pages of detailed please add 5% sales ta x. Master Charge and BankA mericard
hardware and software documentation ... ... . . . . $ 8 .00 accepted .

MlnlTerm ASSOCiates
..
~~
~
Box 268, Bedford, Mass. 01730
 APL is often thought of as heavy mathe-
matical stuff. Terminology used in this
article reflects this background and is sum-
rnatized in tlJe glossary; table 7 should be
referenced when reading the text to identify
operations coded by the special symbols of t
APL. The symbols used in this article are
sometimes approximations of a true "A PL"
ball for a Selectric typewriter. Many of the
symbols are printed on the typical APL
'if\terminal using multiple overstrikes (ie: the
.. character 7, backspace, character

What Is APL?
Mark Arnold APL is the modest name of A Program- have to use a loop which would go aro und
1400 Grand Av ming Language, created by Kenneth Iverson. for each time there was a new score. In APL,
Laramie WY 82070
APL is simpl e to learn , yet in many ways it all you would need (provided the program
is the most powerful language in use today . was set up right) would be a +.
While to the un tra in ed eye APL looks like APL operates as an interpreter; that is, it
the strangest computer language aro und, loo ks at the APL language program and does
with the poss ibl e exception of LI SP, the the operation (perh aps after some inter-
structure of APL is fa irl y close to that of mediate translation). This is different from a
more co mmo n lang uages such as FORTRAN comp il er which translates to machin e lan-
or BASIC. This article will look at some of guage before the program is run . Because of
the features of a large syste m APL. Also, I this, there are two states in whi ch yo u
will explore what feat ures I think a small operate APL. The first is called evalu ated
APL system for a mi crocomp uter could input and the second is called function
have. defi niti on. " Functi on" is the APL name for
Wri ting in FORTRAN is like wri ting how what would be call ed a "program" in other
to go downtown: You don't have to th ink a languages. A workspace is all the functions
lot abo ut what parts of the language yo u and variables that you have created. There
use; you just tell exac tl y what to do. Writing can be more than one fun ction in a work-
in APL is li ke writing poetry: You want to space, an d often you can save the workspace
use the exact part of the language that will on an auxili ary sto rage device.
About the Author:
ex press what yo u want with out any excess. The eva lu ated inpu t mode is as si mpl e as
Mark Arnold is a stu- APL haters critic ize AP L because there are 1+l. Wh en evalu ated input is in control,
dent at the University of so many opera tors fOI' the user to remember, APL prin ts six spaces and req uests input. If
Wyoming, Laramie WY. and the code doesn't always flow out with- you type 1+1, APL will print out the sum of
His experiences to date in- out so me thought, but APL enthu siasts lik e 1 and 1. It would look like this (where the
clude co-authoring the APL because the large number of operators indented part is wh at you type and the
SCELBA L interpreter pro- greatly reduces the size of programs. answe r is printed out starting at the left
gram with Nat Wadsworth. APL is extre mely tim e-effic ient (at least hand margin)
He is currently at work on on large computers) for para ll el opera tio ns,
the definition and imple- such as addi ng two sets of numb ers togeth er. 1+1 USER --+
mentation of an APL sub- Suppose your program was to fig ure out the 2
set interpreter for micro- bowling average of each of the four pl aye rs
processor systems. on your tea m. In most languages you would Notice that no "Print State ment " is neces-

20
sary as it would be in BASIC. Some co mmon Table 7: A PL Operators. This is a complete listing, abstracted from the
operators are +, - , X, 7 . These are the sources in the bibliography of this article, of the A PL operators implemented
normal math symbols for the basic opera- in a typical large scale system such as an IBM/360 or IBM/370. Th e IBM 5700
tions, but not the norma l BASIC and machine is reported to run the full set of APL functions by emulating a
FORTRAN symbols. The original APl used 360/370 architecture in microcode and using close to 200 K bytes of
these and many more strange characters for interpreter ROM. A practical small system APL would necessarily be a subset
its operators, and since the f irst APl systems if the interpreter is to be kept to a small size.
were impl e mented o n I BM j360s, thi s was no
major problem. Changing a character set Monadic Scalar Operators
simply meant changing balls on a Selectric
+ Identity : Returns the right operand as though the operator had not been there.
terminal. Most of the operators have two
meanings (as summarized in table 1 for all Minu s: Returns the negat ive value of the right operand . (Appea rs above normal
APl operators) . The example above of position of minu s sign as in -3.)
adding 1 to 1 is kn o wn as dy adic; that is, the
x Signum : Ret urn s 1 if the right operand is great e r than zero, 0 if it is equal to
addition operator has two operands: the one
ze ro , and -1 if it is less t han zero .
o n the left and the o ne on the right. Th e - is
an example of a mo nadic o perator that has Reciproca l: Return s the reciprocal of the right operand .
only one operand on the right:
* Exponen tial : Return s e ra ised to the right operand.
-3 USER--
Natural Logar ithm : Returns th e LOG base e of the right opera nd .
-APL
L Floor : Return s the greatest integ er less than or equal to the right ope rand .

The -3 calculates the minus of 3. APl

responds with - 3, which is its way of saying r Ce iling : Return s the least intege r greater th an or equal to th e ri ght operand.

"negative three." Note : The - is used only

with numbers, while the - can be used in
I Absolute value: Return s the absolute value of the right operand.

Factorial: R eturn s the factoria l of the right operan d .

any ex press ion.
APL scans an expression from the right to o Pi times: Return s Pi times the right operand.
the left which is opposite the way most
high leve l la nguages do . This means 2- 3-4 Not: Returns a 1 if the right opera nd is 0, 0 if the right operand is 1 ; an error
cond iti o n results if the operand is not logical (1 or 0).
y ield s 3 instead of - 5. (In APL, a raised
hy phen indicates an algebraic negative sign ? Roll : Retu rn s a random number between 1 and the operand.
and an ordinary hyphen is used for subtrac-
tion.] Also unlike most high leve l languages, Monadic Mixed Operators
there is no algebraic hierarchy in APl. So
Rave l: Converts a hi gher dimensioned array into a vector.
2x3+4x5 is 56 and not 26. However, as in
other high level languages, parentheses can Index gen erato r: Retu rn s a vector of consecutive integers between 1 a nd the
be used to override the right to left conve n- righ t ope ra nd .
tion: (2x3) +4x5 is 26.
All the expressions shown up to now have p Shape: Return s the le ngt h of a vector or the dimen sion s of a higher dimensioned
array .
been of scalar va lues, that is, single numbers.
APl also a llows vectors as constants. A Grade up : Return s a vector that wh e n used to inde x the right operand will sort
vector is an ordered set of scalar values, it into ascending o rd er.
something like an array in FORTRAN or
Grade down: Return s a vecto r that when used to inde x the right operand will
BASIC. So to figure the ave rage of the two
sort it into descending orde r .
scores of the four members of your bowling
team : Execute: Returns the va l ue of an expression rep resented by character data as
USER-- thoug h the c haracters value of the right operand had been entered during
.5 x 160 1 09 300 240
eva lu ated input.
+ 203 157 254 165 USER--
Matrix in verse: Return s the inverse of the matri x specifi ed in the right operand.
181.5 133 277 202 . 5
Monadic transpose: Returns a matrix suc h that the rows of t he right operand
where pl ayer one bowled 160 and 203, are t he co lumn s of the ne w matrix .
player two 109 and 157, and so on. The first Reve rsa l: Returns a vector (if the right operand is a vecto r) where the elements
thing APl does is to add the two vectors of the vector a re in the reverse order of the right operand.
(scores) in para llel to get 363 266 554 405.
Then each one of the four sums is mUltiplied Dyadic Scalar Operands
by .5 to produce: 181. 5 133277 202.5, the
average of those two games. All of this was + Addit ion: Retu rn s the sum of the right a nd left operands.
done without an ex pli cit loop or any pro- Subtraction: Ret urn s the d iffe rence of t he right an d left o peran ds.
gra m in the evaluated input mode. {Note: To
do an opera tion, e ither th e size of the two x Multiplication : Ret urn s the prod uct of the right an d left operands.

21
 operands must be the same or one must be a Another type of constant is the character
scalar and the other an array. An operatio n type. 'A' is a character scalar constant and
such as + or x is called a scalar operator 'ABCD' is a character vector. A character
Table 7, continued: because it obeys this rule.) vector in APL is roughly equivalent to the
character string as implemented in languages
like Extended BASIC, PL/1 or XPL.
-.- Division : Returns the quotient of the right and left operands.
Any legal left operand can be subscripted
* Exponentiate: Returns the left operand raised to the right operand. by using the brackets.
Logarithm : Returns the logarithm whose base is the left operand, of the right 33 4 43 34 [1 3 ) USER--
operand.
gives a two element array
L Minimum : Returns the minimum of the two operands.

r Maximum : Returns the ma ximum of the two operands.

33 34 --APL

\ Residue : Returns the remainder resulting from the divi sion of the left operand In this case a three element array is reduced
by the right operand.
to two by choosing elements 1 and 3.
Combinations : Returns the binomial coefficient of the left and right operands. A variable, whose name can be up to 31
characters long, is assigned a value by the
o Circular functions : Returns the function of the right operand where the left assignment arrow.
operand specifies which function:
For example :
Left operand Function of X Function of -X
0 Jl-X2 same
1 Sin X Arcsin X
2 Cos X Arccos X D+- o 0 9 USER--
3 Tan X Arctan X USER _ _
j1+X2 JX2-1 A+- 1 2 3 4
4
5 Sinh X Arcsinh X USER _ _
Cosh X Arccosh X B-<- 5 6 7 4
6
7 Tanh X Arctanh X
C+- A+B USER--
< Less than : Returns 1 if the left operand is less than the right operand, and 0
otherwise . D [1 2 )+- C[3 4 ) USER--

USER _ _
< Less than or equal to: Return s 1 if the left operand is less than or eq ua l to the C
right operand, 0 otherwise. _ _ APL
6 8 10 0
> Greater than : Return s 1 if the left operand is greater than the right operand, 0
otherwise . D USER - - .
_ _ APL
> Greater than or equal to: Returns 1 if the left operand is greater t ha n or equal 10 0 9
to the right operand, 0 otherwise.

Equal to: Return s 1 if the left and right operands are equal, 0 oth e rwi se.

Not equal to: Returns 1 if the right and left operands are not eq ua l, 0 if they Notice that an assignment suppresses lh e
are. printing of a value. In this example D is
given the vector value 0 0 9. A is given the
And : Returns 1 if both left and right operands are 1,0 if e ither or both are O. If vector value 1 234, and B is given the value
one of the operands is not 1 or 0 then an error results.
5 6 7 - 4; C is the sum of these two vectors.
v Or: Returns 1 if either one or both of the operands is 1, 0 if bo t h are O. If Th e first two elements of D are assigned the
operands are not logical (lor 0) an error will result . last two of C. Character data can also be
assigned to a variab le, such as
Nand: Returns 0 if both right and left operands are 1 ,1 if eith e r on e or both are
o. If operands are
not logical an error will result .
MES S+- ' This is a message 'USER - -
Nor: Returns 1 if both right and left operands are 0, 0 if eit her one or both are USER _ _
1. If operands are not logical an error will re sult. ME SS
_ _ APL
Thi s is a message
Dyadic Mixed Operators

? Deal: Generates the number of random numbers specified by the left operand,
between 1 and the right opera nd, such that there is no re pet ition of the Some of the operators listed in table 1 are
numbers. very important to APL programs. One of
these is the monadic iota, known as the
1 Index of: Returns the subsc ript to the left operand where th e fir st occurrence of ind ex generator, which creates a vector of
the right operand can be found. If the right operand is not found in the left
operand then one plus the lengt h of the left operand is re turn ed in stea d.
consecutive integers from 1 to the value of
the operand. This operator can be used to
Catenation: Return s the two operands join ed togeth e r as one vector (or array). eliminate many loops from progra ms. For

22
examp le, if you wanted to calculate the Table 7, continued:
cosine of a number using the Taylor series:
p Reshape: Return s a vector (or array ) created from the elements of the right
operand, such th at the shape of thi s new vector equals the left operand.

1 Decode: Return s the base val ue, where the left operand is a vector of base
weights, and the right operand is a vector of base representation. For example:
10 10 101 2 34 is 234 and 2 2 2 11 0 1 is 5.
(instead of using the 2°X function) this
expression would do it, where N is the
number of terms to be calculated.
T Encode : Returns base representation as a vector, where the left operand is a
vector of base weights, and th e right operand is the base va lue. For example:
10 10 10 T 234 is 2 3 4 and 2 2 2 T5 is 1 0 1,
+/ (-1*-1 +tN) x (X* USER __
2x -1+ tN)~ ! 2x-1+tN USER-- t Take : If the left operand is positive , Nt A returns the first N eleme nts of
A. If th e left operand is negative, (- N)t A returns the last N elements of A.

The sUbexpression 2x-l+tN will generate Drop : If the left operand is positive, N~A returns a vector with the first N
elements of the right ope rand removed. If the left operand is negative (-NHA
N even integers, while this same ex pression return s the last N elements dropped.
is use d to calculate factorials . Th e powers
and the factoria ls are divided in para llel and Membership: For each element of the left operand, members hip returns a 1 if
multiplied by the 1 -1 1 -1 . .. generated the eleme nt is contained in the right operand, 0 otherwise.
by C1*-1+tN) The +/, called a plus reduc-
Matri x divide : Return s th e solut ion of simultaneous linear equations, where the
tion, sums up each one of the elements of left operand is the vector of the constants, and the right operand is the matrix
the vector which contain ed the quotients of of the coeffici ents.
the powers and factoria ls. Another exampl e
of plus red ucti on would be to ave rage the Dyadic transpose : Often used to find the di agonal of a matrix .
vector2345:
Rotation: Returns the right operand rotated the number of elements specified
USER - - by the left operand (to the right if the right operand is negative, to the left if the
(+/2 3 4 5) .- 4
right ope rand is po sitive).
3. 5
/ Compress ion: Return s a vector (or arrav) where the elements of this vector were
Any other dyadic sca ler operator could have se lected from the right operand whe n the corresponding element of the left
operand was 1. If the left operand is not logical an error results. The length of
been used ; for exampl e, instead of the the left operand mu st be equal to the lengt h of the right operand ; but it does
built-in facto rial operator, the factoria l of a not entirely obey the ru le for sca lar operators, since the result will have a length
scalar J could be calculated by: which is equal to the number of 1 s in the left operand .
x/ J USER - -
\ Ex pan sion : Returns a vector (or array ) with zeros inserted in the corresponding
position s of the right operand wherever there is a zero in the left operand.
Two other operators that eliminate loops
are til e grade up and grade down operators, Composite Operators
which fun ction simi larly. They are mon adic (where f and g are any dyadic scalar operator)
only . Th e grade up gives a 'lector of the
subscr ip ts to t he given vector so that if the f/ Reduction : Performs the operation on the elements of a vector (or array ), right
to left.
vector is subscripted by its grade up it wi ll
be sor-kd in ascending orde r. For examp le: f\ Scan: Perform s the operation on the elements of the right operand, left to right ,
and saves the results in a vector, which is what it return s.
A+- 6 4 7 3 5 USER--
f. g Generalized matrix product : A+.xB is normal matrix multiplication.
~ A USER--
o. f Outer product: Can be used to generate multiplication tables, etc.
4 2 5 1 3 --APL
Special Operators and Characters
A [ ~A l USER--
+- Ass ignme nt: Stores the express ion on the right in the variable on the left.
3 4 0; 6 7 --APL
o Quad: Req ue sts an ex press ion for input and return s the value of the ex pression.
Al so used for output .
Suppose the scores of th e players on your
bowling team were in a vector subscripted CJ Quote-qu ad : Reque sts a character value to be input .
by player number (as in previous exa mples) ;
then if you wanted to displ ay the ranking of
pl ayers . best to worst, simpl y do a grade
T T-bar: For information about variable type, and character generation.

down : 'l'A. I I-beam: Returns syste m dependent information .

One of the most interesting operators of !=1 Comment: APL ignores all c haracters to th e right.
APL is th e execute operator, sometimes
represented as 1 or £ which takes a character Del: Used to open a nd c lose fun c tions.
vector and performs operations as if the -+ Bra nch: Cont inues exec ut ion of a funct ion at the lin e whose number is eq ual to
characters had been input during evaluated the va lu e of the expre ss ion on th e right . Branch to empty value branches to next
input. lin e, branch t o 0 stops the function.

23
 For examp le: USER ---+ This function starts at line 1 by initial -
izing the counter N to 0, then it proceeds to
£ '1+1' _APL line 2 where the counter is incremented. At
2 USER ---+
line 4, N is compared to 10, and since they
are not equal a resu lt of 1 is produced,
A-<- ' I' USE R ---+ which all ows the 2 to pass through the com-
pression operator (see tab le 1) . The -'> is
B-<- ' I' USER ---+ the symbo l for branching, so branch to 2
EA, '+',8
in the above examp le takes control back to
-APL
line 2, whe re N is incremented again. Th e
2 loop continues until N=10, in which case
N* 10 returns a va lue of 0. This causes the
The comma is the catenation operator, compression operator to return a null valu e.
which takes the vectors and forms a new Branch ing to a null value is th e sam e as
vector of the old two joined together, so branc hing to the next line in the function,
'+',B forms '+1' and A,'+l' forms "1+1' , This which in this examp le prints out FINISHED.
is then evaluated by the execute operator Since there are no more lines to execute,
which gives the numerical result of 2. execution of the function stops, and APL
Catenation can also be used on numeric pr ints out six spaces like norma l. The output
vectors: of this function wou ld look like thi s:

A-<-l 2 3 USER --+ NEW US ER - -

B+-5 . 5 4 .7 3 USE R __
1
2
A,B USE R ---+
4
1 2 3 5.5 4.7 3 _APL 5
6
7
To create an APL program (function) you 8
9
must leave the executive or eva luated input
10
mode, and enter the function definition FINISHE D
mode . To do this, type the del ( 11) and the
name of the function you wish to create.
Th is program is not a very useful one,
For examp le, to create a function called
since the iota could be used to get essenti ally
NEW type :
the same resu lt, but suppose you wanted to
IlNEW USE R ---+ change this function to output a table of
numbers and their squares. First you would
to which APL wou ld respond : reenter the function defin ition mode, and
type [ 3 ] to say that you wanted to ch ange
[1] li ne three. You wou ld type in:

You wou ld then type the first line of the [ 3 ]N;' '; :-1* 2 JS t-,11 -f'l-

function, and continue until all the function

The semico lon separates things to be prin teJ
is entered, or until you want to leave the
on the same line. You decide you want a
function definition mode, which you can do
header on the output, so you type [1. 5 ] to
by typing another del. Here is a sample
insert a line between 1 and 2. Then you list
function:
the function by typ ing 0 (the box is ca ll ed
a quad, and is also used for input and output
Il NEW US ER - - within an expression).
[1 ] _APL
N+- O US ER - - [1] N-<- O -APL
[2 ] _APL
N+-N+1 USER - - [1. 5 ] 'TABLE OF SQUARES ' _APL
[3] -APL
USER ___
N [ 2 ] W- N+ 1 _APL
[4] _APL
->- (NO O) / 2 USER - - [ 3 ] N;N* 2 _APL
[5 ] _APL
'FINI SHE D ' USER ___ [ 4 ] ->- (NO O) / 2 _APL

To run this function, simply type its Everything looks OK, so you close the
name: NEW. Conti nued o n page 123

24
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 Build the Beer Budget
binary word pairs, we can generate a large
number of dots th at all appear to exist on
the screen at the same time. By repeating the
sequence many times a second, we can
display a steady, nonflickerin g pattern of
dots. Each time we repeat the sequence we
"refresh" the disp lay.
Because the ti me requ ired for the com-
puter to perform a refresh operation will
depend, at least in part, on the number of
dots being displayed, there will certainly be
an upper limit to the total number of dots
that we can displ ay without a noticeab le
flickering of the screen. Th at limi t is deter-
mined by such factors as the speed of the
computer, wh at the computer is doing be-
sides refreshing the disp lay, how the numbers
are obtained (ie : whether they are computed
Photo 7: This image was or read from a buffer in memory), the
inspired by the article 5 persistence of the oscilloscope's ph osphor,
title (or was it the other and what flicker frequency the user con-
way around?). The pro- siders noticeab le. For example, using the
gram of listing 7 was used routine described later in this artic le on an
to draw this picture as well 8080 system with a 1 MH z clock (about half
as the others accom- the speed of an Altair 8800) and using a
panying this article. medium persistence phosphor in the display,
I find that I can disp lay about 512 dots
before flicker begins to appear.
Peter Ne lson In the past, graphics systems avai lable to
68 Seaver St th e experimenter have bee n expensive and The Circu it
Wellesley MA 02181 complicate d or have forced him to settle for The circuit of figure 1 uses components
limited resolution. The simple circuit de- that are all readily available. Most can be
scribed in this artic le will provide resolution bought through the suppliers who adve r'tise
of 128 by 128 dots for under $20 and four in the back pages of BYTE magazine. The
times that resolution for just over $20. It MC1408 digita l to analog converters can be
requires the use of an oscil loscope as the supplied by any Motorola distributor and are
display device, but it need not use an manufactured in severa l different levels of
expensive scope. precision. Th e precision determines th e
We can create im ages on the screen of an exactness with which the output voltage will
oscilloscope by using dots. By placing many correspond to the bin ary input. Th e -L8
dots close together, we can form lines and
sh apes or even letters and numbers. The
location of a dot on the screen is specified to Table 7: Integrated Circuit Power List. This
th e osci lloscope by a pair of vo ltages, one list contains the pin connections for the
vo ltage being applied to the scope's vertical power I/oltages used by figurr:. 7.
input and th e other to its hori zo ntal input.
Integrated +5 V - V
The computer' provides the vo ltage va lues by Circuit Type Power Ground (-7 .1)
outputting two binary words to a pair of
digital to analog converters (known as ICl 74 100 24 7
DACs). The converters produce output volt- IC2 74100 24 7
ages that are prop ortion al to the num eric IC3 MC1408 L7 13 2 3
value of the words. Because an 8 bit word or
MC1408L8
will allow the DAC to produce anyo ne of
IC4 74100 24 7
256 vo ltage values, it shou ld be possibl e,
IC5 MC1408L7 13 2 3
using hi gh precision 8 bit DACs, to position or
a dot anywhere in a 256 by 256 fie ld. MC1408 L8
By prov iding a rapid seq uence of many IC6 7404 14 7

26
Graphics Interface
+5V

RI
1500

14
8 81T 8US
IC I IC2 IC3 +V REF
7 4100

01
LS8
2
3
101 101
5
4
2
3
7 4100
101 101 5
4
12
MCI408
A8 10 4 -®
th TO SCOPE
HOR. INPUT
102 102 102 10 2 A7
~ 02 22 19 22 19 10
103 103 103 103 A6
[ 00 21 20 21 120 9
OUT PUT 03 104 104 104 104 A5
PO RT ::::
4 II 20 1 8 II 8 8
201 2 01 20 1 A4
7
~
05 10 9 10 9
202 202 202 202 A3 -v REF R3
~ 06 15 18 15 18 6 A2 3300
203 203 203 203
07 16 17 16 17 5
2 04 204 2 04 204 AI
MSB CI C2 CI COMP R2
C2
6800
J12 V OUT
23
1 12

!
23
APPROX
CI o TO -4V
+5V
116 P F
r.'7
1500

14
IC4 IC5 +VREF

f-43
74100
101 101
5
4
12
II
MCI408
A8 10 4 -®
th TO SCOPE
VERT. INPUT
'- 102 102 A7
122 103 103
19 10
A6
21 20 9
104 104 A5
II 8 8
201 201 A4
10 9 7 15 R7
202 202 A3 -v REF
15 18 6 3300
203 203 A2
16 17 5 R6
+ 5V 204 204 AI
6800
CI C2 COMP
R4
~12
470 IC6
!
~
C2
v r.?
I 2 1 16 P F

~
XS T ROBE
+ 5V RE S ISTOR.5 -
3 b 4 1/ 4W
R5 VALUES IN OHM S
470 I C6
7404
1.J 6
5 c
YS TROBE

_ ---.--_-------=-l21 II
II OI~F Ir OI~F
IC7

+5V BUS • LM;9A: E t - - - - - - +.....

rl -~-6-~-F----a +7V<+<+35V

'" / rh VOLTAGE DETERMINED

V~n.oo BY VIN .
BYPASS CAPACI TORS (TYPICAL AT SEVERA L
PLACE S ON POWER BU S)

R8
330
1/2W
V EE ------.----------+-----~'I/II'.------a - 8V < -V < -IBV

I
+ C4

~()~~F
DI
7. I V
500 mW

Figure I : Schematic for the Beer Budget Graphics System. This graphics system uses the computer 's main memory as a refresh
source, with a continuously executing program to put the position information out to the X and Y inputs of the oscilloscope.
Both the X and Y outputs change "simultaneously, " limited only by the ampli fier slew rates of the oscilloscope and the Mel408
settling times. Th e driver program enables in terrupts once per scan in order to allow a keyboard controlled drawing mode
commanded by user inputs.

27
 though for most applications AC or DC
coupled inputs can be used. Unless it is
severely limited, bandwidth should not be a
problem: 1 MHz or greater in both channels
should be more than adequate.
In normal operation, the horizontal co-
ordinate is outputted first. The XSTROBE
line is used to load that coordinate into the
first latch of the horizontal channel. Note
that it does not yet appear at the input of
the horizontal digital to analog converter.
Photo 2: An illustration of version should be used if a 256 by 256 The vertical coordinate is then outputted
how different dot bright- resolution is desired. The -L7 version may be and loaded into the vertical latch by the
nesses are achieved by re- used for a 128 by 128 resolution, but YSTROBE line. This strobe signal also loads
peating points. The cursor attempts to use it for higher resolutions will the horizontal coordinate into the second
is a winking point. For result in unevenly spaced dots. For low horizontal latch. Thus, the vertical and
user controlled brightness, resolution applications (64 by 64 or less), horizontal coordinates are both applied to
extra time on a point is the -L6 version provides an economical their respective converters at the same time.
entered by pushing the choice. If you find that the dots seem to vibrate
"deposit key" (ASCII'*,) This circuit is simple enough to bread- or move about on the screen, you are
multiple times using the board using a socketboard array such as I probably picking up 60 Hz hum. Double
program of listing 7. did. Later, I made a permanent board as a check the ground connection to the oscillo-
double layer printed circuit with fake scope and use shielded cable if you are not
"plated through" holes of wire jumpers. It already doing so. Streaked or smeared dots
may also be constructed using wirewrap suggest excessive reactance on the lines
techniques. Leads, especially those associ- going to the oscilloscope or severely limited
ated with the digital to analog converters, bandwidth of the oscilloscope itself. The
should be kept short; and I recommend that direction of the smearing gives you a clue as
the lines going to the oscilloscope be to which channel is being affected. Reducing
shielded. A good ground connection to the the refresh rate may help to control this
oscilloscope is essential. problem if all else fails.
The data bus is assumed to come from an
8 bit parallel output port that can sink 6.4 Some Software Considerations
mA per bit line. I do not recommend driving In many graphics applications such as
this circuit without additional current buf- game programs or interactive graphics, the
fering directly from the system data bus computer is not merely being used to refresh
unless there are relatively few other devices a display but is also called on to perform
on the bus. A dotted line in the drawing other functions, in effect, at the same time.
shows where a 17 line interface to an To allow maximum freedom for the com-
existing latched 10 port might be made, puter to execute these other functions, the
further simplifying the circuit. display refresh routine should be designed to
The strobe lines are active low and the operate quickly rather than, say, to save
entire logic 0 transition should take place memory. Rewriting a dot output routine so
while the data inputs to the latches are as to save a few microseconds may not be a
stable. The inverters provide current buffer- petty exercise if there are 512 dots to be
ing for the 74100 clock inputs as well as the refreshed 20 times a second. Such a savings
appropriate logic 1 load signal. might be obtained by using JUMP i nstruc-
The digital to analog converters in the tions instead of CALLs or, if you are
configuration shown in the schematic pro- outputting from a buffer in memory, de-
duce a negative output voltage. As the fining the limits of that buffer only in terms
numeric value of the binary word becomes of the most significant address byte so you
greater, the output voltage becomes more don't have to perform a time-consuming 16
negative. Note that with the MC1408 DAC bit comparison to find out if you've reached
the A8 input is the least significant bit and the end of the buffer.
A1 is the most significant bit. It is also important to distribute the
Choice of an oscilloscope is not very display refreshes evenly to avoid annoying
critical. I have been using a battle-scarred flicker of the screen. If you decide, for
Heathkit 10-102, which, until they stopped example, to refresh the display 30 times a
producing it, was the bottom of their line. second, it will do no good to perform all 30
The oscilloscope must have both X and Y refresh operations in the first half of that
inputs. If you have direct-coupled inputs, second. This would probably be a good
you may find them preferable at times, application for a programmable interval

28
 timer which would generate an interrupt Listing 7,' An Intel 8080 program to drive the Beer Budget Graphics system.
when it is time to refresh the display. This program uses inputs from an ASCII encoded keyboard to command
Note that it is possibl e to use the soft- various cursor movements and perform the utility functions of clearing the
ware to control dot brightness. By causing a screen and entering data. The cursor is an extremely bright point whose
particular point o n the screen to be coordinates are maintained in the D and E registers. Data is kept in locations
refreshed more often than other points, we 300 to 6FF.
can ge nerate a brighter d ot at that po int. Addr Hex Code Label Op Oper ands Comme ntary
This may be done as simply as storing that 0200 31 FO OF ST ART LXI SP ,F OOF Initialize stack pointer ;
dot in several locatio ns in the buffer. 0203
0206
21
E5
00 03 LX I
PUSH
H,300
H
Ini t ialize nex t new dot pointer
a nd push onto Slack;
The routine detailed in listing 1 was the 0207
020A
21
7E
00 03 REFRESH
MORE
LX I
MOV
H,300
A,M
Set refresh pointer to stan of buffer :
A := @HL [get horizon tal coordinate];
first progra m that I wrote for the graphics 0208
020E
32
23
05 80 ST A
I NX
OUT PUTX
H
X coordinate : = A [memory loca tion is output I ;
HL := HL + 1 Ipoint 10 the vert ical coordinate I ;
circuit. It is written for use with an 8080 020F
0210
7E
32
MOV A,M
OUTPUTY
A : = @HL [get vertica l coord inate J ;
06 80 STA Y coo rdinate : = A {memory location is output];
instruction set and is basically a picture 02 13 23 IN X H HL :'" HL + 1 [poin t to horizontal coordinate] ;
0214 3E 07 MV I A,7 A := buffer page address limit ;
drawing ro utin e. It has a 512 d ot buffer, a 0216 8C CMP H Is HL pai r at end of buffer?
'0217 C2 OA 02 JNZ MORE If no t t h en repeat the display loop ;
winking cursor, and it recogni zes six com- 02 1A OD DCR C C := C - 1 (decrement cursor cou nt er] ;
'0218 CA 77 02 JZ CUR SOR If zero t h en output the cu rsor pattern;
mands: move cursor right; move cursor left ; 021 E AF I NPUT XOR A A· = O'
02 1 F F8 EI E n·able' interrupts from keyboard;
move cursor down; move cursor up; deposit 0220 00 NOP Interrupt window to service keystroke;
022 1 F3 DI Di sab le interru p t s fr om keyboard;
a dot (at the cursor location); a nd, clear 0222 FE 00 CPI o Was there any input ?
'0224 CA 07 02 JZ REFRESH If not then go refresh display again;
display. Because this routine uses a fixed 0 227 E6 7F AN I 7F A := A & 7F [remove mos t signi fi cant b it with mask];
0229 FE 4C CP I 'I.' Was it move cursor left?
buffer size, the clear is perfo rmed by sweep- '0228 CA 4A 02 JZ LEFT If so then go move the cu rsor left;
022E FE S2 CP I 'R' Was it m ove cursor right?
ing all 512 dots into a pile in the lower left '0230 CA 4F 02 JZ RIGHT If so then go move the cursor right;
0233 FE 55 CP I 'u' Was it move cu rsor up?
hand corner of th e display (coordin a te: '0235 CA 54 02 JZ UP If so then go move the cursor up;
0238 FE 44 CP I 'D' Was it move curso r down?
FF,FF). Each co mmand is indicated with a ' 023A CA 59 02 JZ DOWN If so then go move the cu rsor down;
023D FE 2F CP I 'j' Was it a clear command?
si ngle ASCII character inputted from an '023 F CA 5E 02 JZ CLEAR If so then go clear the di sp lay;
0242 FE 2A CPI Was it a deposit dot command?
interrupt driven keyboard. The interrupt '0244 CA 6E 02 JZ DEPOSI T I f so then go deposit a dot ;
'0247 C3 07 02 JMP REFRESH Bad command, so back to re f resh m ents;
serv ice routine merely loads th e accumulator
024A 14 LEF T INR D Move cursor left one space;
from the inpu t port and re turns to where it 0248 14 INR D (Second move, NOP if 8 bit D AC used] :
'024C C3 07 02 JMP REFRESH Ref resh the display;
was called from. Because I use "memory
024F 15 RIGHT DCR D Move cursor right one space;
mapped" 10 (i e: my 10 ports are treated as 0250 15 DCR D [Second move, NOP if 8 b it OAC used]:
'025 1 C3 07 02 JMP REFRESH R ef resh the d isplay;
memory locati ons), I use STA as an output 0254 1D UP DCR E Move curso r up one space;
instruction. Th ose using 8080 10 instruc- 0255
'0256
1D DCR E ISecond move, NOP if 8 bit DAC is used]:
C3 07 02 JMP REFRESH Re fresh the disp lay:
tions will wa nt to substitute OUT instruc- 0259 IC DOWN INR E Move c u rso r down one space;
tions. 025A 1C INR E (Second move, NOP if 8 bit D AC) :
'0258 C3 07 02 JMP REFRESH R efresh the disp lay;
Consider wh at the routine has to keep 025E 21 00 03 CLEAR LXI H, 300 HL := st art ing add ress, refresh bu ffer ;
0261 3E FF AGA IN MV I A, FF A := null coordin ate va lue, lower left ;
track of. When refreshing the display, we 0263 77 MOV M ,A @HL := A (za p a buffer location);
0264 23 I NX HL :'" HL + 1 [point t o nex t locat ion);
have a pointer (HL) that tells us which dot 0265 3E 07 MVI
H
A,07 A := page add ress of buffer limit ;
0267
in the buffer we are refreshing, but when '0268
BC
C2 61 02
CMP
JNZ
H
AGA I N
Is HL at the limit?
I f not then continue zapping memory:
depositing a dot we have to know where in '0268 C3 00 02 JMP ST ART When done, restar t the program;
026E E1 DEPOS IT POP H Pull old buffer location pointer;
the buffer we have space for a "new dot" 026 F 72 MOV M,D @HL := ho ri zon tal cursor position;
0270 23 IN X H HL := H L + 1 Ipoint t o next coo rdin ate i n buffer] ;
(HL on stack). We also have a screen 0271 73 MOV M,E @HL := vert ica l cu rso r position;
0272 23 IN X HL := HL + 1 [point to next coo rdinate] ;
locatio n pointer (DE) for the cursor and a 0273 E5 PUSH
H
H Pu sh cu rr en t buffer loca tion poin ter ;
'0274
counter (C) to determine the cursor's C3 07 02 JMP REFRESH Refresh the display ;
0277 7A CUR SO R MOV A,D A := horizontal position;
wi nking rate. If a routine li ke this is used as 0278 32 OS 80 STA OUTPUTX X coord inate := A:
0278 78 MOV A, E A := vert ica l position;
a subroutine, care should be taken to save 027C 32 06 80 STA OUTPUTY Y coordina te := A;
027F OE 08 MV I C,8
everything o n th e stack before returning t o '0281 C3 1E 02 JMP INPUT
Set c urso r counter to 8;
Go get more inputs;
the main program.
Notes:
Other Ideas All constants are he xa deci mal ;
Can a pa ir o f digital to analog converters @HL in commentary indicates the contents of memory location pointed to bV HL pair;
*nex t to address indicates the in struction contains an address which must be recomputed
connected to a co mputer be used for appli- if the program is relocated ;
cations other than graphics? Absolutely! An 'X' indicates ASCII character X;
obvi o us idea would be waveform ge nerati o n, Note that 16 bit data format for the 8080 stores the low order byte in the lowest
but how abo ut musical instrument syn- address, thus the hexadecimal value 8006 (for example) is seen in the listing as
06 80.
thesis? One converter could be connected to
For 8 bit converters, the increment or decrement instructions at locations 0248,0250,
a wide range voltage to frequency converter 0255, and 025A mu st be replaced by NOP instructions.
such as the Raytheon 4151 and the other
converter could provide envelope informa-
tion . Pass ive components could tailor the. to analog converter. Th e Motorola applica-
output of the 4151 to suit the instrument tion sheet for the MC1408 includes ideas
being synthesized. Just about any con- such as programmable gain a mplifi ers, a
tinuous range phenomenon can be put under programm ab le powe r su pply, a progra m-
the control of the computer using a digital mable constant current source, and others.-

29
There's IMSAI VIDEO DISPLAY

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disc operating system and (415) 483-2093
extend ed BASIC. TWX: 910-366-7287
 Thomas R Buschbach
12310 Purcell Rd
Manassas VA 22110

Since one of the reasons I built a person al

microprocessor was to play video games, I
needed some type of high resolution graph-
ics display capability. After examining the
current unavailability of a low cost commer-
cial product to perform this task, I decided
to build my own unit. Th e main reason,
besides cost, was that I wanted a 256 by 256
dot matrix (as you'll see below, I actually
got 256 by 208). Since my system already
contained a television display generator
board for character information, I decided
to build a graphics display unit which would
utilize ex isting synchronization, blanking,
and timing pulses. For storage of the data to
be displayed, I started with a standard
Photo 7,' With a high resolution display of 256 by 208 pOints, the author's programmable me mory board populated
display system becomes a programmable blacl?board for numerous games and with 8 K eight bit bytes of 500 ns access
visual outputs. A relatively trivial game is the simulated tennis often seen in time 2102 integrated circuits.
bars, restaurants and airport waiting lounges (to say nothing of mass My design goals for this project were to:
produced special purpose home video game sets). The software required is
relatively simple and the display has only three moving objects - the two • Utilize all possible circuitry existing on
paddles and the ball. As in all interactive games, some form of player input is the television display interface board.
required. This can typically be supplied by a variable resistance (as in a • Have the graphics display work in
potentiometer, slide pot or joystick) and an analog to digital converter. parallel with the existing alph an umeric
character display.
• Have the ability to use the graphics
display region of memory for ordinary
programming purposes if the display is

Add This suppressed.

• Use direct memory access techniques
(DMA) so that the graphics display
data appears as ordinary program-
mable random access memory as far as
the computer is concerned.

Graphics was able to meet all these goals for a

total cost of $25 in integrated circuits, above
the cost of the existing display generator and
memory boards of my system. If your
system does not have an 8 K programmable
me mory board available, you will need to

Display purch ase one. Remember, when the graphics

display is not in use, the memory can be
utilized as if it were an ordinary program-
mable memory region; so the investment will
also pay for itsel f in terms of raw memory
power for your non graphics applications.
If your system does not have a television

to Your System display generator board, the synchroniza-

tion, blanking, and timing pulses can easily
be generated using counters. I would suggest
reading Don Lancaster's new book, TV
Typewriter Cookbook. Chapter 4 contains

32
 an explanation and schematics of the circuits
to generate the required pUlses.
The graphics display unit functions as an
interface between the processor, the 8 K
memory board, and the television display
generator, to provide the graphics capability.
A block diagram of this interface is shown in
figure 1. The graphics display unit has two
modes of operation, displ ay mode and up-
date mode. In display mode, the unit
cyclically 'accesses all addre sses of the pro-
grammable memory board using direct
memory access, then converts the output
from parallel to seria l, sending it to the
television display generator to be combi ned
with any alphanumeric information and dis-
pl ayed on the monitor or TV set. Since this Photo 2: With a high resolution display, games need not be kept simple. Here
operation mu st occur in parallel with normal is an example of a much more complex game display on the author's system,
processor functions, the address bus of the again modeled after the commercial games often found in entertainment
memory must be isolated from the pro- centers. To set up such a display typically requires software to create the
cessor's ad dress bus. The output data from background maze, I?eep tracl? of all the movable pieces, and of course
the memory must also be isolated from the program the logic of the game simulation.
system's data buses. In th e update mode, the

PROCESSOR DATA OUTPUT BUS

KEY PROCESSOR
PROCESSOR DATA INPUT BUS
PARALLEL DATA

WRITEI STROBE
SERIAL DATA
GATED WRITE STROBE
J
~ TRI-STATE BUFFERS

PROCESSOR ACCESS GRANT

.. ~
SYSTEM
ADDRESS BUS
I:!
Ii'

~
GRAPHICS
DISPLAY
COUNT ADDRESS
BUS
TV DISPLAY CLOCK GRAPH IC S BK
P'"
GENERATOR VERTICAL BLANK DISPLAY PROGRAMMABLE
UNIT RAM
VIDEO PULSES
MEMORY DATA OUT

Figure 1: System Diagram. The graphics display unit in terfaces to three elements of an existing
system: The processor and its buses, the television display generator, and the 8 K programmable
random access memory. The graphics display unit is normally in the display mode, where it
continually displays data contained in the programmable memory module. If the processor
references a location within the programmable memory's address space, the graphics display
unit enters the update mode either immediately or during the next vertical blanking pulse
depending upon the setting of a switch. In the update mode, the processor commands the
memory and the display looks at random output bits, which are of course ignored during the
blanking period.

33
 processor is given contro l of the memory's shown in figure 2. This design is composed
address bus and all owed to read or write of three functionally distinct areas : the three
data. Th e upd ate mode shou ld onl y be state buffers and their contro l logic, the
entered while the te levision display gener- counters, and the shift registers. The block
ator is send ing a vertical blanking pul se. This diagram and details of this articl e assume
preve nts the upd ate from causin g a sp ul·ious also that the processor has a sp li t "in" and
blip on the screen. However the pen alty for "out" memory data bus as is uti li zed in the
observing this requirement is that the pro- Altair 8800 or Digital Group designs.
cessor may have to wait for nearly a com- The state of the buffers is determined by
pl ete te levision frame time , abo ut 13.5 ms the mode in which the graphics display unit
maximum in the auth or's system. A memory is operatin g. In the disp lay mode, the buffer,
wait this long is impossible for processors block (2) in the figure, all ows signals to pass
such as the 6800 which do not have a while buffers of blocks (1) and (3) must be
memory ready mechanism, in which case an in a high impedance state. This gives the
alternate mechanism such as an input port grap hics display unit's counters control over
bit lin e could be used. the programmable memory's address bus and
A more detail ed block diagram of the blocks the output data from entering the
functions of the graphics disp lay unit is processor's data input bus. In the update

PROCESSOR ADDRESS BUS

AI5 AI3
AI211
1(0
i-l BUFFER
(I)
I AO
CHAR

COUNTERS
f.- CHA R COUNT
FR OM TV
DISP LAY GEN .
f.- CHA R CL EAR
FRO M TV
BUFFER DISP LAY GEN .
BUFFER (2)
STATE
CONTROL -LINE COUNT
LINE FRO M TV
COUNTERS DISP LAY GEN .
VERTICAL BLANKING FRO M
TV DISPLAY GENERATOR
MODE I -[>0---
-LINE CL EAR

WRITE STROBE
FROM PR OC ESS OR
CONTROL
L OGIC
I "''''' ,I 1===
t"'=}"', AI2
FRO M TV
DISP LAY GEN .

BK A ~ PROCESSOR
PROGRAMMABLE RAM DATA OUTPUT

WAIT REOUES T - DATA OUT IN ~ BUS

TO DO
PROCESSOR GATED 07
WRITE
STROBE

07 DO DO DClT11 1

SHIFT
07 Do l III
SHIFT
07

t-.... BUFFER REGISTER REGISTER

(3)
I I I
nr
07 o

~
11111 OUT OUT
CLOCK
FR OM TV
01 SPLAY
TO GEN .
PR OCESSOR
DATA I NPUT BU S LOAD /S HIFT

DATA
VIDEO
SELECTOR OUTPUT
TO TV DISPLAY GEN .

Figure 2: Detail Block Diagram. As in all "top down" system designs, the design progresses by fi!ling in more and more detail.
Here is a block diagram of the actual graphics display unit. This figure shows a detailed functional arrangement of the interface
as constructed by the author. In the display mode, the graphics display unit continually cycles through all addresses in the
programmable memory, outputting serial video levels to the television display generator, for mixing with existing character
graphics in formation. In the update mode, the graphics display unit allo ws the microprocessor to control the programmable
memory unit 's address and data lines for normal access. Th e mode switching is automatic based upon whether or not the address
sent by the processor is within the display's address space.

34
 mode, the buffers (1) and (3) allow signals
to pass while the buffer (2) is in a high
impedance state. This gives the processor
control of the programmable memory's ad-
dress bus and allows memory to be con-
nected to the processor's data input and
address buses. The gated write strobe pulse is
also enabled in this mode. Note that the
processor is the only source of data written
to the memory, so there is no switching of
the processor data output bus which drives
the inputs of the memory banks.
The mode control logic determines the
proper mode of operation at any given time.
It does this by monitoring the three most
significant bits of the processor's address bus
to determine if it is referencing a location in
the programmable memory region assigned
to the graphics display. If it is not refer-
encing graphics memory, then the graphics
display unit will remain in the display mode.
If the processor does reference a location in
the graphics display region of address space,
then the television display generator is
checked to see if it is generating a vertical Photo 3: Not al/ outputs need be game oriented of course. Here is an example
blanking pulse. If it is, and if the graphics of a graphic output which could easily be used for engineering purposes:
display is set (using Sl) to prevent visual plotting the two dimensional behavior for some function. Here the author has
noise ("sparkle") caused by updates, then calculated a sine wave using a BASIC package and appended various character
the display is changed into the update mode graphics captions. The basic X- Y axes and the character graphics can be
and the memory access takes place as if the generated typically by a table lookup with some calculation; the actual points
processor were addressing an ordinary loca- of the curve can be generated directly from the function calculation by
tion. However if the television display gener- calculating integer positions. In either case, to conveniently program the
ator is not in the vertical blanking period, display, a set of bit manipulation subroutines is required to read and write
and the graphics display is set via Sl to avoid individual bits, given the coordinates within the matrix.
arbitrary data during updates, then the
processor is placed in a wait state until the
next vertical blanking pulse is initiated, at board, there are pulses wh ich clear these
which time the update mode is again counters. These pulses should be used to
entered. Note that this feature will only clear the corresponding set of counters in
work with processors incorporating a mem- the graphics display unit. The pulse which
ory ready line for slow response memories; clears the line counters has an added signifi-
an alternate mode of operation in which cance: It also determines how many of the
updating has priority over display must be possible 256 horizontal lines will actually be
used for processors which cannot wait. visible on the screen. Due to overscan on a
The counters control the memory address conventional television screen, the actual
bus during display operations, continually number of lines visible is never 256. A
cycling through all locations with a full cycle typical number of visible lines for a tele-
taking 1/60th of a second (16.67 ms). These vision display generator such as my Digital
counters must be in synchronization with Group product is 208. This means that the
the existing counters in the television display visible display is actually a 256 by 208 dot
generator. Most such television display matrix. Note that this leaves 1536 bytes of
generators contain two sets of counters. One the 8192 bytes in the 8 K byte memory
set counts the character's position on the module free for normal programming pur-
line. Each character is typically 8 bits wide, poses (see figure 4). To determine how many
and there are typically 32 characters per line lines your particular television display gener-
for a total of 256 dots per horizontal line. ator displays, examine the logic which con-
The other set of counters counts the number trols the clearing of the line counters and
of horizontal lines which have been generated determine the value of the counters just
(TV scan lines, not character lines). In a prior to the clearing pulse.
typical television display without interlace The shift registers convert the parallel
there would be a maximum of 256 horizon- data from the programmable memory into a
tal lines. On the television display generator time varying string of video levels in

35
 ICI 8 ~ ::!J
TV DISPLAY VERT. 8 L ANK , I b
• ~~
GEN ERATOR C ~ ~
~

....---. 9 a d 9
_.
6 ..1I C 19 b~
~. ~
.........-, WA IT REO 10 a IC I ge 74 37 5
PROCE SSO R <...J ." 7437 10
IC20
1.. 51 o... ?(>
1(20
----.... 74 0 4 1 0 FF ~. ~
74 0 4
IC20 A ~ ~
7'4 0 4
6
~ ~
L < o (:;.
"""tJ
1(20 s:. -.
NOTE ; 1(20 2 ~ 74 04 ~~
A ,B ,C ARE BOARD ADORE 5S 740 4
1 Ic a
I j IC2 10 12 13 f 12
SELECT JU M PER S . a 741 93 -. ~
L b • ~~
~ ~ .
~ '"t:l':-i
t") ~
! ~ ~
740 4 (HAR _ COUNT c::'I TVT
e CNT UP 5 s·
I 2 CHAR. CLEAR Cl<t::>
'.v- 7437 2 7 00 ( LR 14 n TVT
~
~ '----' CAR BOR - . ...,.
12 13 ~ g:
U ICI8
-.
~
~ ....--
7404
I , 2 ~.g
(? o...
I, Is 1, t 0... 0
ICI
EN- 4 EN-2
IC2
EN·4 EN · 2 5
:=:;, §
8T97 8T97 ( NT CNT
• ~ :
UP OWN ~ ::;-
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, -<r- 2 IC9 ~
2J~A' OA IA , 741 93
..--- AI 5
IB
• OB 5 OB OA
6 7 7 IB •6 ~
I::::' A2 2 DB
&--.a
w 10 IC DC 8' s;
en A' 10 ~~ 9 9 00 ~~ 10 6 DC -. ~
~ A. 12 12 7 00
IE DE " " DE IE 14 G')~
A5 I. OF 13 13 OF
E> IF IF C LR ~ C3 ~
-§ ~
'" ~
~~
~ '"
.... tC;.
1 5
~ ~
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10 EN·4 EN -2 IC . EN· 4 EN-2 ~ ~
e T 97 eT97 o... ~
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7 41 93 tJ n;-
---r>- ~ OA
2
~ A6 2 IA OA ' 3
--<J-
OA IA 2 DB tC;. "~
A7
PROCES SOR 6
4 IB DB 5
7
5 DB
7 IB •6
6 OC ~ -.
.... --
AD DRES S BUS DC DC IC 7 00 ~ ~
10 I C 10
10 00 9 9 00 10 G') '"
LINE CO UNT ~
~ :: AID 12 l E OE II I I OE CNT UP 5 TV T
I E ~- 'o" s:. ~
[ S A il 14 I F OF 13 13 OF e LR I. LI NE CLE AR TVT
IF ~- ( AR BOR
a -§ '"
12 13 .... Cl'
~ '"
~ ~

~. i3
o· ~
~ t")
I, ~ Q26
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EN -4 EN -2 5
IC5 0 1C5b • i3 t")
eT 97 BT 97 CNT ( NT
UP OWN 1( 11 -- ~
r-:: A I2 7 41 93 ~ ~
2 IA ---2.. OA
;::::: AI3 2
<t::>'<::
DB ~ -.
;::::: AI.
4 6 OC
~ ~
:=:: AI5 12 7 00 ~ ~
---c>- IE

OA
, " DE C LR
I. os:.
~
'" t;;-
T -
- -
 ~[;;1
a ,..,
~ ~
:::l '"
Cl --
'-----
Cl
'" :3'"
ICI8 <.c:, '"
'" :::s
:::s .....
6 , 5 WRITE STFii5"BE
' - ' PROCESSOR ~
'" a~
A9 AB A7 A6 A5 A4 A3 A2 AI AO 13 ~
RAM ADD RE SS BUS
~s.
JA 18 Ie

I a
ll. ~
Cl..C)-
'"
a
I 2 I le l2 C)- --
8K RAM 7442 a a
RA'" 2 3 2 1~ 12
ICI9d
BANK 3 4 3 7437 ""~ Cl..~
ENABLE 4 5 4
S 6 5 §:: ~.
RAM DATA OUTPUT
6 7 6 "" ao2l
9 7
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GATED WRITE 7 C)-:3
lSB "'SB
00 01 02 03 STROBE 04 05 06 07 -.
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J L ,..,~~~
g. "-'
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12 ~~r,- iJls 2 ~~
4A 3A 2A IA Ie tl-~ Ie 4A 3A 2A IA ~ a
ICI3 2C ~ ~ 2e IC I4
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74125 74125 ::>,:::l
3e t!£- ~ 3e
4Y 3Y 2Y IY 4eF- ~ 4C 4Y 3Y 2Y IY ~ ~
3 '" ....,
W Cl '"
-.J
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"LlL ~:J~J lCI8 ICIS
'-- 74 04
.- 7404
--/\'"St-
1, 1,5 10 12 13 CLOCK 2'c-
2
." f ~ T VT :::s ....,
EN-4EN-2
"'SB 1C6 el K AJ-:3
eT97 ICl6
07 2 6 74165 + SV
<0- 3 OA IA IH f~
06 5 OB IB 4 9
5 IG OH
05 7 oe Ie 6 4 IF
:::.
St- ,..,Cl
.., .....
9 04 9 00 10 10 ON
3 IE
';:=;'03 II OE IE 12 S2 St-~
141D~ I
02 13 OF 14 13 Ie LOAD J,0FF '"
X IF :3 !:::.
--
12 18
lel7
a M
II I A Cl..t::
~ 74157
ICIB t:: - .
PROCESSOR DATA 3
L2 IB
TO CPU BUS
g 'C2lb\ 6 VIDEO T VT
-- .....
!'>~
Cl
I 4 ~ PULSES
SEl IY :::s
r<ij9
c- ..-1 IA
Cl..
elK
ICl5
I" 74165
EN ' 2 6 IH
1C7 5 IG
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'::=:00 13 OF 3 IE LOAD ;J
14 10
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-<r 12 12 IS
IE
14 :3
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~
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Cl

~.
c;.
 synchronization with the video level infor- to pick the output from the shift register
mation generated by the existing television which is currently shifting data.
display generator. Two shift registers are Figure 3 shows the implementation of
required so that one may be loading data this system for a Digital Group 8080A
whi le the other is shifting data out. To system, using the block diagram of figure 2
insure that the graphics disp lay unit video to guide the detailed design. In my descrip-
information is in synchronization with the tion which fo ll ows, no attempt is made to
video of the television disp lay generator, the explain the schematic in detail . Instead, the
clock pulse for the television display ge ner- various components are related to the func-
ator's shift register should be used fo r the tional blocks of figure 2.
grap hi cs display generator's shift registers. IC1, IC3 and part of IC5 make up the
The load or shift input to the graphics buffer, block (1) in figure 2, which isolates
display unit shift registers is controlled by the processor's address bus from the mem-
the least significant address bit generated by ory in the display mode. IC2, IC4, and part
the graphics displ ay 's counters. This bit of IC5 form the buffer, block (2) of figure 2,
changes state each time that a new byte is which isolates the graphics display unit
accessed in memory. The timing here is counters from the memory in the update
critica l. Th e shift register which was loading mode. IC6 and IC7 form the buffer, bl ock
data must disab le its paral lel inputs before (3) of figure 2, which isolates the processor's
the change in the address lines affects the data input bus from the memory in the
data outp ut from the memory. For the display mode. (The processor' s data outpu t
2102-1 integrated circuits this time is a bus is always connected to the input side of
minimum of 50 ns. This shift register must the memory, since it is the only source of
also change from the load ing state to the data written in the memory.) IC13 and IC14
shifting state pri or to the nex t clock pulse buffer the output from the memory circuits
from the televisi on disp lay ge nerator. This to provide the required output drive current.
may require slightly delaying the clock pul se IC8 and ICg are the character counters.
from the TV displ ay generator. In my Note that the three least significant output
system, it required approximate ly 20 ns de- bits of IC8 are left unconnected . This in
lay in the clock lin e, provided by using a pair effect divides the output by 8. Since each
of inverters in series. A data se lector is used byte from the memory contains 8 bits of

Hex Split Octal Hex Split Octal

>
"'
]-~
2000 040/000--- - - - - - - - - - - - - - - - - 201 F 040/037
0 0
CIl E 2020 040/040--- - - - - - - - - - - - - - - - 203F 040/077
_CIl
:9::!
U)
••
;; •
39EO 071/340-------------- - - - -39FF 071/377

CIl > 39AO 072/000 - - - - - - - -',

;eo I
.!!! E ----'
> CIl /
..:::! \
' - - - - - - - - - - 3FFF 077/377

Table 7: Integrated Circuit Power List.

No Device +5 V GND Programming Note: Addresses even ly divisible by hexadecima l 20 (decimal 32) in this
address space all ocation are the beg innings of a 256 bit (32 byte) raster scan line.
IC1 8T97 16 8 Using SHL(I,J) and SHR(I,J) to indicate the 16 bit left and right shift operations on I,
IC2 8T97 16 8 by J positions, then given 16 bit integer coordinates X (horizontal coordinate from
IC3 8T97 16 8
IC4 upper left) and Y (vertical coordinate from upper left down), the byte address offset of
8T97 16 8
IC5 8T97 16 8 the required bit within the disp layed memory region is:
IC6 8T97 16 8 AB := SHL(Y , 5) + SHR(X,3) ;
IC7 8T97 16 8 Similarly , the rotation factor required to place a mask bit opposite the desired bit of a
IC8 74193 16 8 picture byte is given by:
IC9 74193 16 8 ROTFAC := X & 7;
IC10 74193 16 8 (It is assumed that an 8 bit right rotate is used and the mask starts out with a
IC11 74193 16 8 he xadecimal 80 value.)
IC12 7442 16 8
IC13 74125 14 7
IC14 74125 14 7 Figure 4: MemolY address space allocations for the graphics display. This
IC15 74165 16 8
IC16 74165 16 8
figure charts the specific hexadecimal and split octal address locations for the
IC17 74157 16 8 208 lines and free area in the author's system. Each line is represented by 32
IC18 7404 14 7 eight bit bytes. Each byte specifies 8 col7Secutive dots on the screen, one for
IC19 7437 14 7
IC20 7404 14 7 each bit. Th e zone at the end of the map contains the invisible section of the
IC21 7410 14 7 8 K region devoted to this memolY and display subsystem.

38
 informatio n, a new byte is requ ired on ly waitin g. Thus when loadin g the display
after 8 bits are displayed. This assu mes that mem ory from a cassette tape, th e conflict
a count pulse is received for each bit between the grap hi cs display wait time and
disp layed. IC10 and IC11 are the line coun- the needs of time critical software is resolved
ters. Th ey count the number of sca" lines (at th e ex pense of "sparkle" in the di spl ay
wh ich have been displayed. during the load in g). For processors which
IC15 and IC16 are the two shift registers. ca nn ot wait for slow memory, 51 should be
Note that the clock input to th ese integrated eliminated and the enab le input, IC19 pin 5,
circuits passes through two inverters in should be grounded.
series. Thi s provides the 20 ns delay req uired In makin g the co nn ections from the
to all ow the shift r·egisters to change state gra phi cs display to the te lev isi on displ ay
fro m the load mode to the shi ft enab led ge nerator and memory board, make all wires
mode. Th e output of the shift register which as short as possibl e, certainly not longer than
is shifting out data is selected by IC17 to be 10 to 11 in ches {25 to 28 cm}. Depe nding
sent through a NAND gate to the television upon the ex isti ng loads on the signals you
display ge ner"ator where it is combined with are tapping, buffers may be required to drive
the ex istin g video display signal. Switch 52,
the lin es. The power bus should be heavily
also connected to the NAND gate IC21 b,
bypassed with .01 J.!F capacitors from +5 V
prov id es the capability to blank the vid eo
to gro und.
display from th e screen. If this switch is
omitted and the wire from IC21 pins 3 and 4 In Conclusion
connected to one bit of an outp ut port,
programmab le blanking of the graphi cs can Thi s graphi cs di sp lay ge nerator can be
be ach ieved . built very inexpens ively, taking advantage of
IC12 is a BCD to dec im al conve rter which ex istin g circuitry in the form of memory
is used to select one of the eight progra m- modules and a telev ision display generator.
mable random access memory ban ks on the When you've got it up and runnin g, the
8 K memory card. Thi s in tegrated circuit world of visual im age ry will be avail abl e to
converts the contents of add ress bits A10 to you on your te lev ision outpu t, as is de mon-
A12 in to a ba nk enab le signal which drives strated by the exa mpl es see n in photos 1
the eight 2102s of each 1 K bank within the through 3.-
memory card .
IC18, IC19, IC20 and IC21 provide the ......................................................·····v..
mode contro l logic. Th e board address se lec- ANY WAY YOU WANT IT! ....
tion jumpers are connected to locate the
memory at the desired position in address ....
space. Th e jumpers as shown locate the ....
visible portion of memory in addresses 8192
to 16,383 (hexadecimal 2000 to 3F FF, sp lit ....
octal 0401000 to 0771377). No te that in the ....
case of a television di spl ay ge nerato r with
less than 256 lines visibl e, the upper portion .... ....
.... ·......
of the memory ra nge is avai lab le for program
sto rage. In the 208 lin e case of my syste m,
the 1536 invisibl e bytes are located at .... ··..
hexadec im al add resses 3AOO to 3FFF, sp lit
octal addresses 072/000 to 077/377. Fi gure .... 5 X 7 IMPACT DOT MATRIX • 75 LINES PER MINUTE ==
4 shows the layo ut of memory and its
... 40 COLUMNS. 12 CHARACTERS PER INCH :

.........
6 LINES PER INCH. ORDINARY ROLL PAPER :
relationship to the displayed data. Th e low
addresses in memory define th e to p of the CHOOSE FROM THESE THREE ASSEMBLED AND
TESTED MODELS COMPLETE WITH CASEWORK
···....
image; the hi gh add resses in memory define
the lowe r portion of the im age .
AND POWER SUPPL Y
: • LCP-40 • Parallel IIF without character generator :
·..
Since th e processor is granted access to
the memory onl y during the vertical blank- S• ~~~~~c~al~~:!~:t~/~~~h 64 ~h~r~~ter ..... $329 §
ing pulses in the sc heme just described, : ASC II set ... ............. .. ... . . ... . $425 ::
programs whi ch have criti ca l timing may not : • SSP-40 • Serial RS232 or c urre nt :
work properly. For exam pl e, software fo r a
cassette in te rface has timin g req uirements
..
: loop. TTY co mpatible
: OR SELECT THE "NO FRILLS" KP-40 $179
' .. . .. . .... $499 :

asynchronous to the vid eo display an d ..

: • Mechanism, LCP IIF, PC and co mponents . ... ..
==.

would not work properly if referencin g data

in the display regio n of memory. Switch 51
:
:
SEND FOR FREE LITERA TURE
M,aster Cha rg e Welcome • Utah Residents Add 5% Sa les Tax · ::

in figure 3 is provided to all ow the processor

access to memory at any time, without
: mpl / P.O. BOX 22101/ SALT LAKE CITY / UT / 84122 ..
: 801-566-0201 :
....................................................... ..... ~

39
Photo 7.

A Tip for Using Wiring Pencils

R W Burhans placed on the circuit board after the com-

Avionics Engineering Center mon grounds and positive power buses are
Ohio University
hard wired to the socket pins using bus strips
Athens OH 45701
or heavy gauge wire. Then the task of trying
to see the fine wrap wires becomes much
easier for the remainder of the assembly. An
One of the problems in usi ng the Vec- example showing the underside wiring of an
tor or other brands of "wiring pencils" Omega-VLF receiver interface for use with a
is the poor visibility of the fine #36 wire JOLT microprocessor is shown in photo 1.
viewed against the typical background of [More about the Omega microprocessor in-
Vector Blue circ uit board material. Older terfaces will appear in a future issue of
types of light green epoxy fiberglass boards BYT£.] Small strips of the yellow insul ati ng
give .so mewh at better contrast and the lower tape are cut and pasted to help hold the
quality epoxy paper board is very easy on wires in place for semipermanent prototype
the eyes du e to its light color. Of the various circuits. In general we like to use hard
colors avail ab le, the red wire has the best soldered connect-ions for prototype work
contrast with respect to the newer blue where the microprocessor interface hardware
board materials, but even this is sometimes is used in mobile, marine, or airborne eq uip-
not good enough. The asse mbly of proto- ment. In such app lications, the effects of
type hardware with this technique can be vibration are a major reliability considera-
greatly improved by laying down a layer of tion, hence the need of solder as a "glue" for
yellow insulating tape where the pencil wrap the wiring. A comb ination of top of board
wires are to run. We have used 3M brand jumper wiring and the Vector wire wrap and
yellow coil insul ati ng tape. This is alm ost solder technique results in less eye strain
exactly. like 0.25 inch (0.635 cm) wide tape during asse mbl y when the yellow insul at ing
recorder splicing tape. The yellow tape is tape is used to improve the wire visibility.-

40
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41
Photo 7: Using the data of listing 2 with the program of listing 7, this picture of a famous space craft can be placed on a TV
screen using the Southwest Technical Products GT-6744 display. The actual picture is created from three data table segments
which define the Enterprise, the Earth and the background of "stars. "

An Enterprising Display Device

Joe Deres Unfortunately, the typical high resolution
Southwest Technical Products Corp graphics display norm ally costs thousands of
219 W Rhapsody dollars and is completely beyond the budget
San Antonio TX 78216 of the ave rage person.
The GT-6144 is our answer to this
Many people find games o ne of the most dilemma. By settling for a bit less resolution
interesting applications of a comp uter sys- than is avai lab le in expensive graph ics termi-
tem. These range from simple games such as nals we can generate grap hi c displays on any
Tic Tac Toe, Blackjack and Ping Pong to monitor (or a standard TV set to which a
very complicated games such as Space War. video input has been added).
All of these have one thing in common; they In this design, the display screen is
are much more fun when played using a divided into an array of ce ll s 64 positions
video graph ics display. With such terminals wide by 96 positions high. Each cell is
you can provide in stant response and pro- individu ally addressab le and may be se lec-
vide a pictorial pl ay in g area that ca nn ot be tively turned on or off by programmed
duplicated o n any type printing terminal. com mands from the parallel interface to
Can you imagine attempting to play an you r computer. With a littl e imagin ative
elaborate game on a Teletype machine? programming (and lots of memory) fixed or

42
 Listing 7: A GT-6 744 Demonstration Program. This Motorola 6800 program,
written to illustrate the operation of the GT-6744, contains routines to erase
the screen, to write a pattern using a table of commands, and to select various
options under control of a simple interpreter driven by the terminal
keyboard. The routine is shown in assembly language format, with an origin
at location 0000. This program must be run in programmable memory
without write protection since several data items are located within the
program text. Relocation of the program at arbitrary addresses other than its
present page 0 origin will in general require modifications of symbolic code
and reassembly to eliminate direct addressing at several poin ts. There are
several gaps in the addressing sequence used, reflecting the fact that the
moving images may be disp layed on the program was hand assembled. The data used to generate the picture seen in
screen for added enhancement to game photo 7 is summarized in listing 2.
programs. Photo 1 shows Star Trek's sta r
ship, the " USS Enterprise," ge nerated with Address Hex Code Labe l Op Opera nd Co m ment ary
the GT-6144 by ru nning t he program of .. This program, by Joe Deres, is designed to transfer
listing 1 using data of listing 2 in an SWT PC .. a data table of GT ·6144 commands to the d isplay,
.. Th e main entry pcint;s at locat ion ENTER , address 0016
6800 Computer System. It takes on ly 2 /lS 0000 00 00 START RMB
RMB
2 Pointer to data;
0002 00 00 2
to load a single cell of the disp lay memory; 0004 80 OC PI A3 RMB 2 Pointer to PI A address of GT-6144;
00 05 PI A3L EGU PIA 3+1
much faster than most contemporary per-
• Th e following sub routine sends the co ntents of accu mulat or A
sonal computers can generate the infor- to the GT-6 144 and gene rates th e active low "data ready"
strobe at the peripheral contro l pin of the PI A.
mation. The system features a power up OOOG FE 00 04 OUTGR LDX PIA3
screen blanking circuit which in addition 0009
0008
A7
C6
00
37
STAA
LDAB
O.X
# $37
PIA3(data] := A (send data to GT-6144] ;

may be enab led, or disab led at any time OOOD E7 01 ST AB 1 .X PIA3(control ] := code for low strobe;
OOOF E6 00 LDAB O.X 8 := PIA 3(data] [dummyop for timing I ;
through program commands from the com- 00 11 CG 3F LD AB # $3F
0013 E7 01 STAB 1.X PIA3lcontrol ] := code for high strobe;
puter system or hardwired switches. In 0015 39 RTS
addition, an image reversing feature all ows • The following is the initi alization seq uen ce for the program,
you to se lect betwee n wh ite on black or · and the subroutine ca ll s which invoke the picture generation;
Th e program is entered by ca llin g ENTER with a JSR;
black on white images by a sim ple one word 0016 86 3C ENTER LD AA H$3C
0018 87 80 07 STAA $8007 Disable contro l interface echo option;
command generated by yo ur co mputer's 0018 FE 00 04 LOX PIA3 X := PI A3 add res s pointer;
001 E C6 FF LDAB # SF F
program. The system will operate on either 0020 E7 00 STAB O.X PI A3(direction] := code for output all bits ;
0022 C6 3F LDAB # $3F
50 Hz or 60 Hz power lines with American 0024 E7 01 STAB 1,X PIA3(control) := code for high strobe,
and point to data register;
standard 525 line or Europea n standard 625 0026 BD 00 A2 JSR ERASE clear the sc reen with su broutin e;
line televis ion sets or video monitors. 0029 7E 00 DO JMP SHOW fill screen with U SS Enterprise or other
sui table data table ;
The GT-6144 design incorporates a 6,144 " Th e following su broutine, with entry at PUTGRPHX, is used to run
bit static programmab le memory which .. through a data table stored beginning at the address in START;
0030 FE 00 00 NXTDATA LDX STAR T
elimin ates the requiremen t that it be used 00 33 08 IN X START := STAR T + 1 (16 bits precision] ;
0034 FF 00 00 STX STAR T
with a specific computer system . The termi- 0037 FE 00 00 PUTGRPHX LD X STAR T
003A A6 00 LDAA O,X if@START = FF [leave when data = FF ];
nal will operate with any computer system 003C 81 FF CMPA # $F F
003E 27 l G BEG ENDPUT
whose paralle l TTL level interface outputs 0040 8B 00 DISPl ADDA #0
then go to ENDPUT ;
caut ion: program modifies immedi ate byte!
an 8 bit data word and data ready strobe . 0042
0045
BD 00
FE 00
06
00
NEWXSPOT JSR
LDX
OU TGR
START
The hookup prob lem then reduces to 0048 08 IN X START := START + 1;
0049 FF 00 00 ST X START
mak ing sure that each bit line at the inter- 004C A6 00 LD AA O.X
004 E 81 FE CMPA Ii$ FE if@START = FE then go to NXTDATA
face runs to the correspond ing bit at the 0050 27 DE 8EG NXTDATA {t re at as horizontal position if FE];
0052 88 00 OlSP2 ADDA #0 ca ution ; program modifies immediate byte!
input to the GT-6144. 0054 20 EC 8RA NEWXSPOT
0056 39 ENDPUT RTS return to ca ll er ;
The unit is available as a kit which is
comp lete less the chassis and does not "The fol l owing D ISP LAY routine is used to set up the PUTGRPHX
routine, by modifying two bytes of code and setting up the
include the required video mon itor or mod i- 0057 88 40
initial point er va lue in ST AR T at location 0000 ;
DISPL AY ADDA 4540 I A is defined prior to ent r y J ;
fied television set. Instructions for the 0059 87 00 41 STAA D ISP1+l iD ISP1+11 := #$40 + A;
005C 17 T8A {B is defined prior to entry J ;
addition of a video input jack to a typ ical 005D 88 80 ADDA # $80
005F B7 00 53 ST AA DISP2+1 (DISP2 + 1I := I;S80 + B;
television are included with the kit, and a 0062 FF 00 00 ST X ST AR T STAR T := X {X is defined prior 10 entry];
0065 BD 00 37 JSR PUTGRPHX ca ll graphics put routine;
switch insta ll ed on the back of the TV set 0068 39 RTS return to cal ler;
wil l allow one to select between terminal " DELAY is a routine to generate a delay in processing ,
and normal television operation. You may the parameter (approximately calibrated in seconds) is passed
in the B accumulator; routine uses A and X;
use the same television set or video monitor 0070 86 00 DELAY LDAA #0 A := 0 [outer loop count} ;
0072 CE 00 00 NEWINNER LDX #0 X := a [inner loop count (time ca libration)] ;
used by the CT-1024 term inal system. In 0075 08 DELLOOP IN X X := X + 1;
0076 8C FF FF CPX #$F FFF ifX= FFFF
fact, contro l commands from your computer 0079 27 02 BEG OUT ER then go to OUTER loop check ;
007B 20 F8 BRA OELLOOP else reiterate inn er loop;
all ow you to disp lay grap hic, CT-1 024 alpha- 007D 4C OUTER INCA A := A + 1;
007E 11 CBA if A = B
numeric, or even a comb ination of the two, 007F 27 02 BEG DELAYDON then go to DELAYDON;
all on the same disp lay device . The mi xing of 0081
0083
20
39
EF
DELAYDON
BRA
RTS
NEWINNER else go to NEWINNER Ito start new inne r loop) ;
return to ca ll er;
graphic and alphanumer ic video is engi - .. The ERASE subroutine in locations OOAO to aoee is
neered to work with an SWTPC CT-1024 us ed 10 clear the G T -6144 screen prior to establishing
a new picture; it does thi s by address ing each
termin al. The video from other alpha- disp lay location in turn and setting a null state;

43
Listing 7, continued: numeric terminals will not necessarily work
with the GT-6144 since the unit was
Address Hex Coda Label Op Operand Commentary
specificall y designed to work with the sync
signals of the CT-1024. Power requirements
OOAO 00 HPOS RMB 1 horizontal position data byte;
OOAl 00 VPOS RMB 1 vertical position data byte;
for the terminal are 5.0 VDC @ 1 A,
00A2
00A4
96
81
AO
40
ERASE LOAA
CMPA
HPOS
#$40
[entry point, outer loop for horizontal position] ;
if HPOS = $40 [is it end of outer loop]?
- 12 VDC@20mAand 6 VAC @ 20 mAo
00A6 27 lE BEO OUT then go to OUT {erasure is donel ;
00A8 01 01 NOP (two do nothing NOPs) ;
OOAA BO 00 06 JSR OUTGR define horizontal coordinate; Programming
OOAO 96 Al ERASEV LDAA VPOS (inner loop for vertical position] ;
OOAF 81 60 CMPA #$60 if VPOS = $60 lis it end of inner lOop)?
OOBl 27 OA BEQ SPEC then go to SPEC land restart inner loop) ; The displ ay of the GT-6144 graphics
00B3
00B5
8B
BD
80
00 06
ADDA
JSR
# $80
OUTGR
convert coordinate to venical command;
define vertical coo rd inate and value;
disp lay generator produces a matrix of 6144
00B8
OOBB
7C
20
00
FO
Al INC
BRA
VPOS
ERASEV
VPOS := VPOS + 1;
reiterate inner loop;
small rectangular cells formatted 64 across
OOBD 86 00 SPEC LDAA # $00 and 96 down. Each of these ce ll s can be
OOBF 97 Al ST AA $Al VPOS := 0;
OOCl 7C 00 AO INC HPOS HPOS· := HPOS + 1; turned on or off at will. In order for the
00C4 20 DC BRA ERASE reiterate outer lo op;
00C6 86 00 OUT LDAA # $00 GT-6144 to do a particular function the data
00C8 97 AO STAA HPOS HPOS := 0 ;
OOCA 97 Al ST AA VPOS VPOS := 0 ; fed to it must be formatted correctly. Figure
RTS
OOCC 39 return to caller;
1 summarizes the formatting conventions.
• The SHOW routine is used to define the parameters of DISPLAY,
• pointing to the Enterprise screen location and its data tabl e,
The coordinate of a particular location is
then to call DISPLAY ; since the vertical and horizontal referenced from the top left corner of the
positions are parameters, the picture can be located at arbitrary
places within the display area of the GT·6 144 ; screen with the first square residing at
0000 86 05 SHOW L DAA #$05 locate Enterprise 5 ce ll s across,
0002 C6 00 LOAB # $00 and 13 cells down ; location (0,0), When sending data to the
0004 CE 02 00 LOX #$200 point to Enterprise pattern data;
0007 BD 00 57 JSR DISPLAY call DISPLAY to draw the Enterprise ; GT-6144, the first parallel byte sent to the
OODA
OODC
86
C6
lB
40
LDAA
LDAB
# $1 B
#$40
locate planet Earth 27 cells across,
and 64 cells down ;
terminal must be the horizontal position
OOOE
OOEl
CE
BO
04 00
57
LO X
JSR
#$400
DISPLAY
point to Earth pattern data;
call DISPLAY to flash the Earth ;
coordinate. The actual pOSitIOn is deter-
00
00E4 C6 OA LDAB # $OA set approximatel y 10 second delay parameter ; mined by the binary number in low order
00E6 BD 00 70 JSR DELAY
00E9 86 00 LOAA # $00 locate random "star" data 0 cells across, bits B5 to BO. When bit B6 is 0, a rectangle
OOEB C6 00 LDAB # $00 and 0 cells down ;
OOED CE 05 00 LOX # $500 point to star pattern data; will be removed at the desired coordinates;
OOFO 57 JSR DISPLAY call DISPLAY to draw in the stars;
00F3
BD
7E
00
01 00 JMP OPTFUNC go to OPTFUNC [to perform optional functions] ;
when B6 is 1, a white rectangle will be
4 The OPTFUNC routine is reached afte r the display is set up
generated . Bit 7 must always be 0 for the
• on the screen and is used to interpret several commands display to know that a horizontal position is
from the terminal keyboard in orde r to toggle some of the
options of the display unit; being loaded. A 0 in bit B7 causes the data
0100 BO El AC OPTFUNC JSR INEEE call INEEE IM I KBUG subroutine) to get
a single character of input in A ; holding flip flops in the terminal to store the
4 What follows is a simple series of tests to id entify one of

• eight commands selected by ASC II cha racters '" through '7';

present data.
0103 81 31 CMPA '1' ifA = 'l'
0105 27 lE BEO ONE then go to ONE ; The second byte from the computer
0107 81 32 CMPA '2' if A = '2'
0109 27 1E BEQ TWO then go to TWO;
contains the vertica l coordinate. The loca-
0108
0100
81
27
33
1E
CMPA
BEO
'3'
THREE
if A = '3'
then go to THREE ;
tion is contained in binary in bits B6 to BO
010F
0111
81 34 CMPA
BEQ
'4'
FOUR
if A = '4'
then go to FOUR;
of this second byte while bit 7 must equal
27 1E
0113 81 35 CMPA '5' if A = '5' a 1.
0115 27 lE BEO FI VE then go to FI VE;
0117 81 36 CMPA '6' if A = '6' When programming an image to ap pear
0119 27 1E BEO SI X thengotoS I X;
011 B 81 37 CMPA '7' if A = '7' on the screen there are two ways the
0110 27 lE SEQ SEVEN then go to SEVEN ;
011F 81 38 CMPA ' 8' if A = '8' characters can be loaded. The method used
0121 SEQ EIGHT then go to EI GHT;
0123
27
20
1E
08 BRA OPTFUNC try again, over and over forever;
depends on how your software is organized.
• Each individual command is imp l emented by defining a co nstant
One method is to just send out successive
• in the A accumulato r , then jumping to EXECUTE in order to call coordinates (H1, V1), (H2, V2) etc, until all
• OUTGR and modify the state of the GT·6 144;
0125 86 EO ONE LDAA # $EO ONE : Set nor mal screen mode ; H, V locations are specified. With this
0127 20 lA BRA EXECUTE
0129 86 El TWO LO AA # $El TWO : Enable CT·' 024 ; display; method two bytes must be sent out for each
012B 20 16 BRA EXECUTE
0120 86 E2 THREE LOAA #SE2 THREE : Disable graphics displa y; character.
012F 20 12 BRA EXECUTE
0131 86 E3 FOUR LOAA # $ E3 FOUR: Unu sed bit pattern;
Another method can be used that will
0133
0135
20
86
OE
E4 FIVE
BRA
LO AA
EXECUTE
# $ E4 FIVE : Set inverted scr een mode ;
result in saving time and memory space. In
0137 20 OA SRA EXECUTE this method the horizontal position of a
0139 86 E5 SIX LOAA # $E5 SIX: Disabl e CT· l0 24, display;
013B 20 06 BRA EXECUTE particular column is loaded on ly once into
0130 86 E6 SEVEN LOA A # $ E6 SEVEN : Enabl e graphi cs;
013F 20 02 BRA EXECUTE
0141 86 E7 EIGHT LOAA # $E7 EIGHT: Unused bit pattern;
0143 80 00 06 EXECUTE JSR OUTGR call OUTGR to se le ct option ;
0146 20 B8 BRA OPTFUNC reit erate fore ve r;

0000 START Graphi cs table pointer;

0004 PIA3 8 bit output PIA port; OOAl VPOS ERASE vertical position ;
0006 OUTGR Graphics output routine ; 00A2 ERASE Subroutine to clear the screen;
0016 ENTER Main entry of gra p~ics de mo prog ram; OOAO ERASEV
0030 NXTDATA OOBO SPEC
0037 PUTGRPHX Graphics put rou tine; 00C6 OUT
0040 OISPl 0000 SHOW Routine to sequenc e display of photo 1;
0042 NEWXSPOT 0100 OPTFUNC Options select ion int e rpreter (keyboard dr iven);
0052 D I SP2 0125 ONE
0056 ENOPUT 0129 TWO
0057 DISPLAY Graphic s put routine setup ; 0120 THREE
0070 DELAY Delay rou ti ne (gross calibrat i on in seconds) ; 01 3 1 FOUR
0072 NEWINNER 0135 FIVE
0075 OELLOOP 0139 SIX
0070 OUTER 0130 SEVEN
0083 OEL AYOO N 0141 EIGHT
OOAO HPOS ERASE hori zontal position ; 0143 EX ECUTE

44
the terminal. The vertical coordinate of all decimal) locations giving us 32 extra unde-
other characters that have this same hori- fined locations. These extras can be used as
zontal coordinate can then be loaded by control commands for controlling blanking
themselves since the horizontal position is on and off, reverse screen, etc. The format
latched in the terminal's holding flip flops. for control commands for the GT-6144
This second method is used by the programs display generator is found in figure 2.
accompanying this article. When writing programs care should be
Since there are 96 characters to be taken to optimize them for speed and
accessed in the vertical direction at least memory conservation. All of the above
seven address lines must be used. Seven lines functions can also be under hardware
give the possibility of addressing 27 (128 control by using SPST push button switches.

USS Enterprise data 0200 - 0364 Listing 2: It takes data to

0200 00 0220 08 025A 13 0287 08 0284 FE 02El 24 0300 08 0339 01 produce a picture. Here is
0201 OA 022E 04 0258 08 0288 OC 0285 1 E 02E2 02 030E 15 033A 02
0202 08 022F 05 025C OC 0289 13 0286 02 02E3 08 030F lA 033B 08 a listing of the data which
0203 OC 0230 OF 0250 OF 028A 19 0287 08 02E4 09 0310 FE 033C FE
0204 FF. 0231 .10 025E 17 0288 1F 0288 14 02E5 OA 0311 2A 0330 33 is used by the demonstra-
0205 01 0232 FE 025F 18 028C FE 0289 1 E 02E6 08 0312 02 033E 01
0206 OA 0233 OC 0260 19 0280 19 028A FE 02E7 OC 0313 08 033F 02 tion program of listing 7
0340 08
0207
0208
OC
FE
0234
0235
04
05
0261
0262
lA
18
028E
028F
09
OA
0288 1 F
028C 02
02E8
02E9
00
OE
0314
0315
16
17 0341 FE
to produce the picture of
0209 02 0236 OF 0263
0264
FE
14
0290
0291
08
00
0280 08
028E 14
02EA
02E8
OF
10
0316
0317
18
19
0342
0343
34
01
the USS Enterprise.
020A OA 0237 10
0208 OC 0238 FE 0265 08 0292 13 028F 1 E 02EC 11 0318 lA 0344 02
020C FE 0239 00 0266 OC 0293 19 02CO FE 02EO 12 0319 FE 0345 08
0200 03 023A 05 0267 10 0294 1F 02Cl 20 02EE 13 031A 28 0346 FE
020E 09 0238 OF 0268 16 0295 FE 02C2 02 02EF 14 0318 02 0347 35
020F OC 023C FE 0269 17 0296 lA 02C3 08 02FO 15 031 C 08 0348 01
0210 FE 0230 OE 026A 18 0297 05 02C4 14 02Fl 10 0310 FE 0349 02
0211 04 023E 05 0268 19 0298 OF 02C5 lE 02F2 FE 0 3 1E 2C 034A 08
02 12 09 023F OE 026C lA 0299 13 02C6 FE 02F3 25 031 F 0:2- 0348 08
0213 OC 0240 FE 0260 18 029A lF 02C7 21 02F4 02 0320 08 034C FE
0214 FE 0241 OF 026E lC 0298 FE 02C8 02 02F5 08 0321 FE 0340 36
0215 05 0242 06 026F FE 029C 18 02C9 08 02F6 15 0322 20 034E 01
0216 09 0243 00 0270 15 0290 03 02CA 09 02F7 10 0323 02 034F 02
0217 OC 0244 FE 0271 08 029E 04 02C8 OA 02F8 FE 0324 08 0350 OB
0218 FE 0245 10 0272 OC 029F 06 02CC 08 02F9 26 0325 FE 0351 FE
0219 06 0246 07 0273 11 02AO 07 02CO OC 02FA 02 0326 2E 0352 37
021 A 08 0247 OC 0274 15 02Al 11 02CE 00 02F8 08 0327 02 0353 02
0218 OC 0248 FE 0275 10 02A2 14 02CF OE 02FC 15 0328 08 0354 08
021C FE 0249 11 0276 FE 02A3 19 0200 OF 02FO 18 0329 FE 0355 FE
0210 07 024A 07 0277 16 02A4 1F 0201 10 02FE FE 032A 2F 0356 38
021 E 08 0248 OC 0278 08 02A5 FE 0202 11 02FF 27 0328 02 0357 02
021 F OC 024C 19 0279 OC 02A6 lC 0203 12 0300 02 032C 08 0358 04
0220 FE 0240 FE 027A 12 02A7 02 0204 13 0301 08 0320 FE 0359 05
0221 08 024E 12 0278 14 02A8 08 0205 14 0302 15 032E 30 035A 06
0222 08 024F 08 027C 19 02A9 13 0206 15 030 3 1A 032F 01 0358 07
0223 00 0250 OC 0270 1E 02AA 14 0207 1 E 0304 FE 0330 02 035C FE
0224 FE 0251 00 027E FE 02A8 19 0208 FE 0305 28 0331 08 0350 39
0225 09 0252 16 027F 17 02AC lF 0209 22 0306 02 0332 FE 035E 02
0226 07 0253 17 0280 08 02AO FE 020A 02 0307 08 0333 31 035F 03
0227 OE 0254 18 0281 OC 02AE 10 0208 10 0308 15 0334 01 0360 FE
0228 FE 0255 19 0282 13 02AF 02 020C FE 0 309 lA 0335 02 0361 2A
0229 OA 0256 1A 0283 19 0280 08 020023 030A FE 0336 08 0362 15
022A 05 0257 18 0284 1E 0281 14 020E 02 0308 29 0337 FE 0363 FE
0228 OF 0258 lC 0285 FE 0282 19 020F 10 030C 02 0338 32 0364 FF
022C FE 0259 FE 0286 18 0283 1E 02EO FE

Planet da.. 0400 - 04E F

0400 00 041E 06 043C 09 045A 08 0478 13 0496 17 0484 1C 0402 1F

0401 lA 041 F FE 0430 FE 0458 OC 0479 04 0497 FE 0485 10 0403 FE
0402 10 0420 OA 043E OF 045C 00 047A 05 0498 15 0486 1E 0404 1B
0403 1F 0421 05 043F 02 0450 OE 0478 06 0499 07 0487 1F 0405 OB
0404 FE 0422 06 0440 08 045E OF 047C 08 049A 08 0488 1F 0406 1E
0405 01 0423 07 0441 09 045F 10 0470 OC 049 8 OC 04B9 FE 0407 FE
0406 17 0424 FE 0442 OA 0460 11 047E 00 049C 00 04BA lB 040B lC
0407 FE 0425 08 0443 08 0461 12 047F OE 0490 OE 04BB 05 0409 OA
0408 02 0426 04 0444 OC 0462 13 0480 OF 049E 16 04BC 19 040A FE Notes on Construction
0409 13 0427 05 0445 00 0463 14 0481 10 049F 18 04BO lA 040B 10
040A FE 0428 06 0446 OF 0464 15 0482 11 04AO lC 04BE 1B 040C OB of a GT-6144
0408 03 0429 07 0447 10 0465 FE 0483 12 04 A 1 FE 04BF lC 0400 FE
040C 10 042A 08 0448 FE 0466 12 0484 13 04A 2 16 04CO 10 040E 1E This article contains the
0400 FE 0428 FE 0449 10 0467 02 0485 17 04A 3 03 04Cl 1E 040F 00
042C OC 044A 09 0468 05 0486 FE 04 A 4 18 04C2 lF 04EO FE
complete schematic and
040E 04
040F 00 0420 04 0448 OA 0469 07 0487 14 04A5 19 04C3 lF 04El lF enough details for an indio
0410 FE 042E 05 044C 08 046A 08 0488 02 04A6 lA 04C4 FE 04E2 10
0411 05 042F 06 0440 OC 0468 OC 0489 06 04A7 18 04C5 19 04E3 FE
vidual to wire up a version of
0412 08 0430 07 044E 00 046C 00 048A 07 04A8 1C 04C6 06 04E4 20 the display using parts ob·
0413 FE 0431 OA 044F OE 0460 OE 0488 OA 04A9 10 04C7 lC 04E5 13
0414 06 0432 FE 0450 OF 046E OF 048C 08 04AA 1E 04C8 10 04E6 FE
tained from surplus suppliers
0415 OA 0433 00 0451 10 046F 10 0480 OC 04AB 1F 04C9 lE 04E7 21 and hand wiring techniques
0416 FE 0434 03 0452 11 0470 11 048E 00 04AC 1F 04CA 1F 04E8 17
0435 06 0453 12 0471 12 048F OE 04AO FE 04CB 1F 04E9 FE
such as wirewrap or point to
0417 07
0418 08 0436 09 0454 13 047 2 13 0490 OF 04AE 17 04CC FE 04EA 22 point soldering.
0419 FE 0437 OA 0455 FE 0473 14 0491 10 04AF 04 04CO lA 04E8 lA The GT-6144 graphics dis·
041 A 08 04 38 FE 0456 11 0474 15 0492 11 0480 16 04CE 07 04EC 10
0418 07 04 39 OE 0457 02 0475 16 0493 12 0481 19 04CF 10 04EO 1F play generator is also available
041C FE 04 3A 07 0458 09 0476 17 0494 13 048 2 1A 0400 1E 04EE FE
0477 FE 0495 14 0483 18 0401 lF 04EF FF
from Southwest Technical
0410 09 0438 08 0459 OA
Products Corp, 219 W Rhap·
Star data 0500 - 0534 sody, San Antonio TX 78216,
0500 01 0507 04 050E FE 0515 14 051C 3A 05 23 FE 0529 FE 025F 2A as a complete kit of parts
0501 2C 0508 FE 050F 00 0516 58 0510 FE 0524 31 052A 35 0530 FE including the circuit board.
0502 FE 0509 OA 0510 30 0517 FE 051 E 20 0525 OA 052B lC 0531 3E
050 3 02 050A lE 0511 FE 0518 19 051 F 06 052 6 FE 052C FE 0532 42 The price of this kit is $98.50
0504 58 0508 FE 0512 OF 0519 4C 0520 FE 05 2 7 34 0520 3B 0533 FE postpaid in the United States.
050 5 FE 050C OC 0513 44 051A FE 0521 26 05 28 34 05 2 E 02 0534 FF
0506 05 0500 40 0514 FE 0518 1E 0522 30

45
Photo 2: Here is a picture
of the GT-6744 as . con-
structed using the printed
circuit board and parts
supplied with the South-
west Technical Products
kit. The logic diagrams of
figures 7 to 3 are complete
and based upon the origi-
nal blueprint supplied by
the author. Home brewers
can use the design infor-
mation of this article to
wire up the circuit de-
scribed here, oras a starting
point in designing a cus-
tomized version.

How It Works
The entire screen of this video display
HORIZONTAL COMMANO FORMAT:
has been arranged for 96 Iines of 64 charac-
ters per line. In addition to the 96 lines of
INTERFACE BIT ~ 7 6 5 4 3 2 o video data the television or monitor also
o D HORIZONTAL POSITION H requires the terminal to generate vertical and
horizontal sync pulses. The GT-6144 con-

--------------L'-- l 0.; H:63 sists of two major sections. The timing

sections (figure 3) generate the necessary
sync pulses, while the memory section (fig-
DATA BIT:
1 = BRIGHTEN A CELL
ures 4 and 5) takes care of storing the
o
= ERASE A CELL necessary information and recalling it while
a frame is being generated.
'-----FORMAT INDICATOR, VALUE 0
The timebase oscillator as indicated in
the schematic is responsible for initiating the
VERTICAL COMMAND FORMAT:
horizontal sync pulse and for starting the
INTERFACE BIT ~ 7 6 5 4 3 2 o chain of events that will generate one line of
I VERTICAL POSITION V
video data to be displayed. The circuit itself
is a phase locked loop employed as a
---...- ~ ::;;;;
'v'" - frequency multipl ier. A 555, IC1, is used as

L L O ';; V ';; 95

FORMAT INDICATOR, VALUE 1

an astable voltage controlled oscillator. The
2N5139 transistor Q3 and TIS58 field effect
transistor Ql along with capacitor C5 form a
sample and hold circuit which feeds IC1's
Figure 7: Data Formats for the Parallel Interface to the GT-6744. The voltage control input through the TIS58
GT-6744 has two data formats. The horizontal command format is used to field effect transistor Q2. The sample and
set the sense of the data to be written and load a 6 bit integer horizontal hold in this case is being used as a phase
coordinate. Once the horizontal coordinate has been set up, the vertical comparator providing an output voltage pro-
command format is used to pick a vertical line with a 7 bit integer less than portional to the phase difference of the
decimal 95 in value, and write the data value ("on" or "off") selected with 60 Hz power line and the mUltiplied output
the horizontal command. frequency of the 555 oscillator IC1 . The

46
actua l amount of frequency mUltiplication is CONTROL COMMAND FORMAT :
equal to the amount of frequency division INTERFACE BIT-+ 7 6 5 4 3 2 o
between the output of the oscill ator IC1 and
CONTROL
the 60 Hz input reference frequency. As you o o CODE
will see later the value of the frequency

~l ~LIST
divider is 264 and since our reference is
60 Hz so that:
fa = (60 Hz) *(264) = lS,840 Hz BELOW
which is very close to the horizontal osci ll a-
" DON'T CARE" STATES,
tor frequency of a standard television set. SHOWN AS ZEROS
The output of IC I is fed via inverter
IC23c across a jumper to IC17 sections b HIGH ORDER BITS 5 , 6 AND 7 ARE SET
TO ONES TO IDENTIFY COMMAND
and c, where among other things a 4/.1s FORMAT .
hori zontal sync pulse is generated. From
here the pulse is routed to IC1Sb wh ere it is
ORed with the vertical sync pu lse which will Control Hexadecimal
Code Code Meaning
be described in detail later.
The fa lling edge of this sync pulse at the o EO Inverted Screen. After this command is received, the display
output of IC17c triggers IC1 6a, a one shot will show black cells or characters on a white background.

which puts out a positive pulse on pin 4 E1 Normal Screen. After this command is received, the display
adjustable by potentiometer R20 from 10 to w ill show whi t e cells or characters on a black background,
30 f.1S in length. The delay pulse creates a lag 2 E2 Disable Characters . Remove information generated by the
between the start of a line and the beginning CT · 1024 inputs (if any) from the display,
of data, thu s giving an adj ustab le left margin .
3 E3 Enable Characters. Allow information generated by the CT·
Pin 4 of IC16a inhibits dot oscillator IC16b 1024 inputs (if any) to be merged in the displav output.
through ANO-OR-INVERT gate of IC IOa.
4 E4 Enable Graphics. Allow information generated by the GT·
Pin 13 of IC16a resets 7493 counters IC19 6144 display circuitry to be merged into the v ideo display
and IC 13, the 16 bit counters which address output,
one of the horizontal positions on a lin e.
5 E5 Disable Graphics. Remove information generated by the GT·
Since we are just starting a new lin e we must 6144 from the video display output.
first clear the counter to prepare it for
incoming data. At the end of a high to low 6 E6 Unused .

transition of pin 4 of IC16, the 7493 vertical 7 E7 Unused.

position counter IC6 is incremented; and if
there is a ripp le carry, IC7 is incremented as Figure 2: Data Formats for the Control Commands. The unused states of the
well. IC6 and IC7 together keep trac k of the vertical command format described in figure 7 are used to perform control
horizontal scan lin e presently in use. To- operations. The control format and operations are shown here. Note that in
gether these two counters provide a uniqu e the program of listing 7, the contents of bits 3 and 4 are assigned zero value
binary code for each of the 96 * 2 = '192 arbitrarily since they are "don't care" inputs in control commands.
vid eo scan lines generated by the GT-6144.
Now for those of you who are familar
with telev ision circuits, yo u probably know Now let 's get back to the horizontal
that we nee d more like 264 lines and not portion of th e circuit aga in . We left off
192 for a comp lete frame. When a cou nt of earlier by say ing that one shot oscil lator
192 (the 193rd lin e) is reach ed, IC1 Sa sends IC16a provided an adjustab le delay between
out a clock pulse to IC4a and to IC9c which the hori zo ntal sync pulse and the generation
resets the lin e counters. When IC4a is of data to provid e a left margin. We also said
clocked pin 6 goes low, giving a blanking that an astab le osc illator IC16b which is
pulse to prevent any video data from being inhibited during this de lay ph ase via IC10a is
transmitted from the GT-6144. When pin 6 th e dot osc ill ator which actua ll y clocks off
of IC4 is low, pin S is hi gh and enables the dots for each lin e of video which form
decoders IC11 a and IC1 'I b. When the line th e rectangle. To continue the account
counters reach a co unt of 32, IC11 a trigge rs wh ere we left off, potentiometer R19 sets
and remains so for 8 lines until count 40 is the cycl e time for this osci ll ator from O.S to
reached. Th e low output on pin 6 during thi s 1 f.1S whi ch in turn se ts th e hori zo ntal width
time is the vert ica l sync pul se, which goes to of the rec tangles displ aye d. The "dot clock"
IC1Sb as menti oned earlier. At count 72 output, howeve r, is not the output of IC16b
IC11 b triggers clearing flip fl op IC4a which but rath er the output of the ANO-OR-
unbl anks the video and resets line counte rs INVERT gate IC10a. Its output is normally
IC6 and IC7 for the generation of another hi gh, but goes low for about 30 ns each time
line of displayed data. The above circuitry IC16b resets. Th e 30 ns pulse time is set by
gives us a tota l of 192 + 72 = 264 scan lin es. the propagat ion of IC16b and IC10a and is

47
Figure 3: Timing Logic. This figure shows the design of the video timing chain which governs the operation of the GT-6744. The
original diagram of the circuit has been partitioned into three figures for this article, with connections between figures indicated
by symbolic names and references to the connecting figure. Power connections for the integrated circuits in figures 3, 4 and 5
are listed in table 7, and the three jacks used for interconnection are summarized in table 2.

0-<
VI-
o~
;='"
-(5
o
....
rill
-<VI
0'"
:! "
,
g~
'"
",0
N-
II [],
II
00
0'"
"0
...
~a; " :::tIC "'"
giD
"' 0
!:?-<
."
~ ~~o

.
r
r
-<
0
(5 en
III
n '\:....
'"
+
c.D ~ ;;
... '"
" r- 01""
;;;
0:U
0'"
'" :;;)( ;;;
'"
0'"
~g
~
I
.j N
~
,,"" en
~
~
D, '".!.:~zo
",,,, ... "-
t;i 00
CD
....

0
"l-. 0
r
0
"""
)(
0
0'" 0_ -C>0
'" ~r r
-r-=00
" d· 0
:u

en
'" .... 0
......
~Q

)(
'"
...
0
"

en ~-- '" ....

-.. - "
...
0

)? -
... 0
0'"
...
F'N'"

~'"
....-_ _ _-++_--1 o o CD....

CD "
o '"

.... - :u
'" '" '" '"
,..!.» ....... - "~ "0 "-0 "'"0
~» CD-
,,0
-0 0"
",CD '"
0
CD'" '"
'"
f=III 0
J>
0
III
0
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0
III
0
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_"'0 . o
III
0
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C

=
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0
0
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C
;;; CD
'" .---
CD
"'L '" CD '"

~~
C
0
r:> _ ~ ....
-0
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c>0
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Pr
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op
0
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c:;;
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~OU 0 IU O(J
<-
N '-------' '---.--'
:;;
5C> ~
Uo ~

48
very hard if not impossible to see with most No. Device +5V GND -12V Table I: Power Connec-
oscilloscopes. This dot clock is used to
ICl 555 8 1 tions for Integrated Cir-
toggle flip flop IC4b which regulates the IC2 74279 16 8 cuits. This table contains a
transmission data from memory to the video IC3 7451 14 7 complete listing of the
IC4 7474 14 7
output. When IC4b is clocked by the dot power connection pins for
clock, the data input on pin 12 from the IC5 7404 14 7
IC6 7493 5 10 each integrated circuit in
memory is latched until another clock pulse IC7 7493 5 10 figures 3, 4 and 5.
appears. IC8 7408 14 7
The second major portion of the IC9 7432 14 7
IC10 7451 14 7
GT-6144 (figures 4 and 5) consists of the
ICll 7420 14 7
memory and its associated components. IC12 7486 14 7
When no data is being loaded into the IC13 7493 5 10
terminal by a computer, appropriate outputs IC14 7442 16 8
from both the horizontal and vertical coun- IC15 7409 14 7
IC16 74123 16 8
ters are used as address lines for the memo-
IC17 7400 14 7
ries. IC18 and IC37 a long with the necessary IC18 7410 14 7
inverters form the decoders that select the IC19 7493 5 10
appropriate memory integrated circuit (ICs IC20 74157 16 8
27, 28,29,31,32 or 33) depending on the IC21 74157 16 8
IC22 74157 16 8
location being addressed. Note that IC31 to IC23 7404 14 7
IC33 can be enabled when CBO = 0 while IC24 74157 16 8
IC27 to IC29 can be enabled when CBO = 1, IC25 74157 16 8
therefore adjacent rectangles alternate back IC26 74157 16 8
IC27 2102-1 10 9
and forth between the two halves of IC28 2102-1 10 9
me mory. The data outputs of IC27 to IC29 IC29 2102-1 10 9 Table 2: Connector Pin
are "wired OR" as are the outputs of IC31 IC30 7402 14 7 Designations. There are
to IC33. AND-OR-INVERT gate IC10b IC31 2102-1 10 9
IC32 2102-1 10 9 three connectors, labelled
selects which data will be transmitted to the jl, j2 and j3 in the fig-
IC33 2102-1 10 9
video output depending on the state of CBO. IC34 7474 14 7 ures. The following are pin
The desired display for our graphics IC35 7400 14 7 assignments for these
IC36 7404 14 7
terminal is 64 cell positions across and 96 connectors.
cell positions down. This gives a total of IC37 7410 14 7
IC38 7432 14 7
6144 possible character positions which IC39 7410 14 7
means that at least 13 address lines are IC40 7404 14 7 Jl: Power Jack
needed since 212 = 4096 and 2 13 = 8192. IC41 74174 16 8 Pin Assignment
Since some computers are not capable of IC42 7410 14 7
IC43 7408 14 7 1 -12 V
sending out a 16 bit word, the most logical 2 +5 V
thing is to use two 8 bit words with some 3 GND
type of temporary storage in the terminal. 4
5 6 V AC 60 Hz reference
The input control logic of figures 4 and 5 memory currently accessed by the video 6 GND
serves this purpose. The temporary storage timing chain), IC40c will change state
in the GT-6144 is done in flip flops IC34b causing the data selectors IC24 to IC26 to J2 : CT-1024 Connections
and IC41. Since the GT-6144 can accept select the address lines formed by the data
data faster than most small computers can from the computer rather than from the Pin Assignment
send it, only a DATA READY output from counters. IC18 will select and enable the 1 GND
the computer is needed . This DATA correct memory integrated circuit and after 2 CT-1024 Data
READY line should be normally high and go a small time del ay caused by C13, R31 and 3 Reset
4 GND
low only after the data output from the IC15c, a low write pulse will be routed to 5 GND
computer is valid. During the time that the the enabled memory. When the DATA 6 Sync
DATA READY line is low one of two things READY goes back to its high state the write
can happen. If the bit pattern from the pulse will immedi ate ly disappear and after a J3: Parallel Interface
computer is such that it is a horizontal small delay caused by R36, C17 and IC38b,
Pin Assignment
position (bit 7 is 0) 1C30b will trigger, the memory circuit will be disabled and the
causing the data present to be latched into data selectors will return to addresses taken 1 Bit 1
the flip flops. During this time the memory 2 Bit 0
from the terminal's video timing chain. Note
3 Bit 2
is unchanged. If the data present is a vertical that the data is written in one half of the 4 Bit 3
position (bit 7 is 1) IC30b will not change memory while the termin a l reads and out- 5 Bit 7
6 Data Ready
state but IC39a or IC39c will, depending on puts data from the other half. The other half 7 Bit 6
the state of the latc hed low order bit 0 on of memory works exactly as above but has 8
pin 5 of IC41b. If IC41b pin 5 is 0, IC39c BO equal to 1. 9
10 Bit 5
wi ll go low. When the counters come around 11 Bit 4
such that CBO is 1 (the opposite side of the Text continued on page 54 12 GND

49
 BITO A5
2
T4 (FIG~)
D
IC41b
,...! CLK CLR ~
74174
Q

1!1 BO

1 (FIG~) BO
(FIG ~)
BIT I A6
i IN CLK
Til FIG !I)
D ( FIG ~)
IC41d
~ CLK CLR .!....
74174
Q
10
1 AO
(FIG~)

+~v
BIT2 A7
3
TI2
(FIG~) R37
D
IC34b ~
1000

~ CLK CLR
13 h
74174
Q DRDY
9 AI (FIG!I)
1 7402

4~
(FIG !I)

4
BIT 3
T3
A8
(FIG~)
+~V

R38
- 6 , ~

IC40
7404
D 1000
IC41a I
~ CLK CLR
74174
J3 Q

12 10_
A2
~42'
~
\..8
lFIG~) 9 7410
7410
BIT4 A9 T --
II
TI3 (FIG~)

~
D
IC41e
~ I
CLK CLR f-<

~fY-
74174
Q
I 4 7408
11 2 A3
(FIGS)

BIT ~ 1 BI3 ;- r- - ~ D
ICI4
o~
I 2
10 2_
T6 (FIG5) ~ C 2 3
D ~ B 3 4
~3
I 7408

I
IC41,
~ CLK CLR ,.!..... ~ A 4~
74 174 7442 !I,L
Q

17 A4
9
(FIG ~)

~8 10 7408

7
BIT6 I BI4
114 (FIG5)
D
R33
IC41! I 100
.....! CLK CLR I -
74174 1

!
Q

II ~ DATA INP
Ci~
4 (FIG 5)
g39b 6
!I
BIT7 57410

50
 IC23
7404 Figure 4: Input Logic. This figure contains
3 the input control logic used to store the
horizontal command information and de
__________________________~~I C C L K 0~
5 --------,
code the vertical command or control com
mand in formation.
L 4
~ IC34 a
7474
I-PR D

12
0 1-'6=--_ _---,

+ 5V

R3 9
10 0 0

LOGIC I LOGI C I T O IC4a

~ TI 3
( FIG 3 )
10 CLR
PRE
VERTICAL SYNC
IC4b
7474 (F IG 3)
12
XOI
D
CL K
Q ~ t-
( FI G 5 )
X03
DOT CLOCK
(F IG3)
1"
BLANKING
+5V (FIG3)
R4 5
1000 1~6
~!-,=-------------~-----,
+5V
L

\I f02030 PF R24
7 r
~
2
SI IC2 a
52
74279
0 ~
13r-=.-----1 IC5
74 0 4
R2 5

\1 f02060 PF I 111~ I8 13 ~1 2
I~
R 04
7r 10 1 lQ-':"I---I f 15 d II
~7409 2N5129
R44
100 0
K
L--t-...:9:....:I-1LJ IC 3 b I
L ___ _ 24.:.;..J ---- R26
47 JI

R4 7
3
1000 R27
M 100
r,7
C2 1
\II OOOp F 5
Ir R
o~
r-------,
3 2 ,..--
L-----~42~:-~r-~ )~~!~6--~-~I,)~'}O~3~-~I~~~i:3
2
IC2 b
C2 2
74 2 7 9
\I IO OO pF 6 II
S
II

R46
1000
51 J I C3a I
L ___ ~~I..J I ---
N ~ ___________________~
X~0~4~

( FIG 3 )
R4 0
1000
P T H +5V

\1
II
C2 4
1000 pF 11 ,12 S
i G

R4 2
IC2c 9 1000 J 2 - 2 .. ~ DI
C25 742 7 9 0
\ I 1000pF 10 R
JI
NOTE :
R41 UNLESS SPE CIFIED OTHERWISE -
1000
.. Ito D2
RESISTOR VALUES ARE IN OHMS .
0 CAPACITOR VALUES ARE IN /LF.
r, OIODES ARE IN914 / IN4148 .

51
Figure 5: Memory Logic. This figure contains the logic associated with the mem ory of the GT-6144. The 6144 bits of
in formation used for the graphic output are contained in six 2 702 memory integrated circuits.

J3
+5

'fo~
6
~4
.... r...
rh
DATA RO Y
~C46~ 13 7 4 10
ORO Y II e 10 12
'{FIG. 4)
~
IC40
7404 I Rr..Li!°
r-
.-... BO 9 d
L....,.; (FIG. 41 8 91 39C'»L-

IC 40
7404 +5
r--:: IN e L K 13 f 12
~(FIG . 41
V
R30
9 7409 IK
TR 31 100 10 15C') 8
~C13
11000PF DATA INP
(FIG. 'II
4~2

~
10
30c R~~ 100 5 J3eb,)-L
DATA INP
~C17
JIOOOPF

{
I II 12 1 II Id II Id
3 IY 4 8 AO 01 00 AODI DO AO OJ 00
18
(FIG. 'II
""'" AI
kA2 " 6 2B
103B 2Y ~
4
5
AI
A2
AI
A2
AI
A2
~A3 13
4B
IC26 6 A3 IC 3 2 A3 IC31 A3 IC33

r'"
7 A4 2102-1 A42102-1 A4 2102-1
2 IA 74 157
F< CAl 5
2A 3Y .,L.
2 A5 A5 A5
(FIG. 31 F<CA2 II I A6 A6 A6
3A
KCA3
'--'"
144A EL TR
4Y
ILL- 16 A7
15 A8
A7
A8
A7
A8
I I~
~
!th A9eE R/ W A9 EE R/W A9EE R/W

(FIG . 4) { r-... A5
KA6 " 6
IB
2B
Ie 3B
I
IY 4

2Y 7
I~ 13

'1"00
13 3

3 7400
13

II 7400

:
r A7 13 4B IC25
5~
{R~:
IA 74157 170 JI7d
91"'"10 2 I 2
2A 3Y 9
(F I G. 31 kCA6 II 3A +5

1I~7486 j

fW' j~t~
)==:;.CA7 I'
-~
4A iEL 4Y 12
R34
I 12c 1000
II 13 ~
13r-'12

I 15
~ ~
4 (FIG.4 l

~r-.. " ,
IB
I~ 6 8

~'"''
A9 6 74 10 .... 7410
2B
~(I
(FIG . 41 7
ksl3 10 180 Bb 18c
~14 l:l 3B IC 2 4
4B 12 13 3 5 10 II

(FIG. 3 1
{=z,.. ,
-<-CA8

-<"CS13
2

I
IA 74 157
2A
3A
9

= .CBI4 14 4A 12
I 8 I C23 8
7404 "'17486
1 7432

9~
2 90,3 d
9
10

52
 C19, C20
+5V BUS (C28-C33

+ C27 09
100 IN5402
16V
GNO BUS
JI

v·----------------------<D
-12V
12,r!g8
II
TR32 100 13 8 d.J

~
7402 I ....,."....._-., 17432
2 300 R35
100
L'II\~~""""::C~
~
2 380
l'
..J- CI4
1000pF

-b-d4"-
1'1000PF

DATA INP
T
I III 12T III 12T III 121
( r AO 3 1B IY 4 8 AOOI DO B A(} 01 DO B AOOI DO
r::,A I 6 2B 4 AI 4 AI 4 AI
k
U
~ ~ A2
FIG. 4)
A2 10 2Y r - - - - - - - t - - ' 59A2 5 A2

L~_./C"'AA""30"-----'1~97: ~~125~ ~ ~!211~~=1 t---~'i:! 211~~~1 t----~'i~; d~~~,

FIG.3)
D CAI 5 2A 3Y 9 2 A5 2 A5 2 A5
Lr---.._./""CA""2=--....:.I....
1 3A I A6 I A6 I A6
~ CA3 14 4ASEL ST~Y 12 16 A7 16 A7 16 A7

'S
r--~ AB 15 AS 15 A8
I 15 I.. I ~

(, A4 3 IBI
h
15 IY 4
~ A9a R/W

13
A9 ~ R/W

13 ~ 13
9~

3
R/W

.A5 6 2B
(FIG. 4) ~.:::."'A\"'-'6_"""t103B 2Y 7 II 3 6
F<A7 13 IC21 7400 7400 (' 7400
kCA4 2
4B
IA 74157 l5ll 35c ~35b
~CA5 5 2A 3Y 9 12"i3 17 4r;!
(FIG.3) ~ CA6 II 3A
.CA 7 14 4ASEL 4Y 12
\.'
2

~
i7404
IC36 4 IC36 6 IC36
~7404
Lp\
7404
15~
o c
I 5
(~A8 3 IB ly~4~-----~ .--~

(FIG .4)
r--- A9 6 2B
l--'" B I 3 ' - 7
D ~. 3B
L"y8::.:,14..:...----:.1"I3 4 B 1C 2 0
2Yt-!--------...J 8...
~
7410 ~12 ....., 7410 ~L..... 7410
L~y-C"",A"'-8--'2"tIA 74157 37c 70 37b
~ CA9 5 9 II 2 "13 3 5
(FIG.3) L~->_C~BII13---1192A 3Y~9~-------_, .++--------4~---------~
~
,-
I ~CB 14
3A
14 4A 4Y.,.12==-----------,
..
LJ==~;;========~~il~---I~I--:97432
~
o IC 36 B IC 36
7404 404
~7404 10138S»-~B~------+~

I
"II IClob 7451
II
e
4P
~B 13r-----l
~2~4~3~0\.·~3+-~---~ltl-IL-.J I CBO
~ I - iB (FIG.3)XOI
I ~~--------------------------------------~~~~
4 740 B ,--.;;.O~UT.:......:..I_---"9;-;1;.--i-,~ I (FIG. 3)
____________!-~~5}4~:3~b)!6~=T======~10[1~~~
L== ___ .....J I

X02
(FIG.3)

53
Text continued from page 49 transistor 04 to give the required composite
video output.
When the computer sends out data where As shown in figures 3 to 5 the GT-6144
the high order bits B5, Bc and B7 =1 (the unit should work on a video monitor or
control command mode), IC42 pin 8 goes modified televison set. Because of rigid FCC
high so that no changes will be made in requirements, the circuit has been designed
memory. Appropriate data lines from the to be connected directly to the video input
computer are fed to the 7442 decoder IC14. circuit of a television. This typically requires
IC39b disables the decoder in all but the the addition of a jack and if normal tele-
control command mode. Depending on the vision reception is desired as well, a switch
data in low order bits 0, 1 and 2 of the input to select the operating mode.
to the GT-6 144, the proper output of IC14 The data outputs from your computer
is brought low to control the appropriate must be at TTL low state for a logical 0 and
control function. The outputs of IC14 are TTL high state for a logical 1. The DATA
latched in the 74279 circuit IC2. Pin 4 of READY line must stay at logical 1 normally
IC2 controls the screen reversing function. and go to 0 only after the data from the
IC34 prevents the screen from being reversed computer to be loaded into the terminal is
except immediately after a vertical sync guaranteed valid. The DATA READY strobe
pulse. While in the reversed mode the blank- should stay low for at least two micro-
ing pulse is removed, giving a totally white seconds and the data must stay valid during
screen (except for characters). This switch- this time. Cable lengths from the computer
ing is done in IC3b. IC2 pin 7 controls the to the terminal should be as short as
CT-1024 video data. When IC3 pin 4 is high possible.
CT-1024 data is enabled and disabled when If desired the video from a SWTPC
pin 4 is low. Pin 9 of IC2 performs a similar CT-1024 can be mixed with the video from
enabling or disabling function for the the GT-6144 to give an alphanumeric or
graphics video data. Video data from IC3 pin graphic display (or both) on the same TV or
6 is routed to IC15d where it is mixed with video monitor. No extensive modifications
the appropriate blanking pulse. The outputs need be made to the CT-1024 but four wires
of IC15b and d are then mixed in 2N5129 do need to be added through J2.-

54
 OUR FD-8 FLOPPY DISK SYSTEM Interfaces to anybody's
microcomputer system via a single PIA Chip!
If you don 't use PIA 's , then one 8 bit b idirectional data port
and one output only control port Is all that's required - that
simple! If you don't have a bidirectional port then separate input
and output ports will do .
Full sector buffering In 3K of RAM contained on the
controller card itself eliminates any dependence upon
processor speed .
Each drive is contained in its own cabinet with power
supply. Up to 4 drives may be daisy chained together and
selected under software control from a si ngle controller card .
Both single and double density, single or multiple drive
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The PR-1 i nterfaces to any microcomputer system via
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MSI software products including our mini

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For more com pre he n si ve product informat ion. w ri te M S I at t h e address be low. Inc ide nta lly. ou r
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220 W E S T CEDAR. O L AT HE . KA N SAS 6606 1 • P H ONE 9 13 764-3273 • TWX 9 107496403 (MS I OLAT)
 Some Graphics Background
Ira Jay Rampil
University of Wisconsin - Madison
Department of Electrical and Computer Engineering
1425 Johnson Dr
Madison WI 53706
Information
Computer graphics has come a long way screen of a storage tube. The slow speed is a
since its inception as a laboratory curiosity. mixed blessing, actually. These terminals are
It is now a wide ly used tool for human almost always used remote from the com-
information digesters. There is the old say- puter, and use simple asynchronous serial
ing: "One picture is worth one thousand data lines, usually around 300 baud, to talk
words" and thus informati on packed into to the computer, just like a raster scan video
computer generated pictures is now used by display terminal. Using an ordinary tele-
such diverse people as engineers, doctors, ph one lin e for cheap communication, it can
business people, and choreographers. We are take several minutes to draw a reasonably
now at the point where TV compatible complex image at 300 baud. At the very
graphics displays are affo rd able by hobby- least, animation graphics, like Space War or
ists, experimenters, and other randomly as- LI FE, wou ld prove cumbersome, and disap-
sorted computer freaks. pointing due to communications line limita-
Graph ics hardware has also evo lved fal· tions. These terminals are best suited for
from the early dedicated processors and high resolution still lifes such as charts and
point by point plotting osci ll oscopes to schematics. Accessories to produce hard
today's high resolution plasma displays (the copy from the screen are usually available.
so-called flat TV screens), computer ge ne- Storage tube terminals have the advantage of
rated holograms, and intelligent multicolor being quite useful at great distance from the
vector displays. The vast majority of com- processor. They are also comparatively sim-
mercially available graphics, however, is still ple in design and cheap to build. The
based on some kind of single color cathode exception is the price of the storage CRT,
ray tube. Even among the monochrome which can run over $1000 in "onesies" for a
displays there are two different families of large high resolution tube, probably explain-
design, the storage tube design, and the ing why they are not often seen in amateur
continuously refreshed design. The purpose computing circles.
of this articl.e is to present some background
information on the philosophies represented
by these two types of CRT systems, since Continuous Refresh Graphics
they are important differences and have a The continuously refreshed or graphics
large effect on the type of graphics each is processor type of display is like the storage
capable of producing. tube disp lay on ly in the way in which it
draws a line or vector. There the similarity
ends. In thi s system, vectors disappear al-
Storage Tube Graphics
most as fast as they are created. An image
Storage tube techniques can we ll be appears of constant intensity because it is
described as drawing on a paper pad with redrawn or refreshed many times a second.
indelible ink. A line, once drawn, cannot be This illusion, call ed flicker fusion, is the
erased, except by tearing off and throw ing same principle by which the TV and movie
away the entire sheet of paper. In other industry simu late continuous motion. If an
words, once comp leted, individu al sections image flickers fast enough, the brain per-
of a picture (also called subpictures, or ceives it as continuous. Obviously, if there
glyphs) cannot be electl"O nically de leted or are many lines in the image, there has to be a
moved without destroying and then re- very fast lin k betwee n the display and the
drawing the entire picture. Th e need to memory where the image data resides, in
redraw the entire screen might not be so order to refresh the screen in the usu al 1/30
bad, if it were not for the "erase flash," and second (or 1/60 second for TV without
the usually slow speed with which the interlace). Since draw ing a previously
graphics terminal communicates with the created image is just a matter of shipping the
computer. Th e erase flash is a bright wink picture information off to the display, and
that always occurs when you wipe off the therefore requires no great amount of com-

56
Perhaps the most dramatic example of the need for high resolution graphics is demonstrated by these pictures of the famous
"original" lunar lander program written for the Digital Equipment Corporation GT-40 and supplied with that unit as a
demonstrator. These pictures were made by the author using University of Wisconsin facilities, and illustrate a couple of typical
frames from the interactive graphics version of lunar lander.

Photo 7: The lunar mod-

ule is controlled by a light
pen, and is seen initially
high above a lunar plane.

Photo 2: Eventually, if all goes well, the pilot (With his or Photo 3: Of course, if mistakes occur, there is a crash. This
her magic wand control stick) lands the lunar module near picture shows the flying lunar lander above a lunar
the golden arches of a famous fast food chain, orders some mountainside with "rocks" and the remains of previous
food, takes off and leaves. crashes of the module by inept pilots.

With the 256 by 256 graphics capabilities of the newer display output devices for televisions, the personal computer is getting
close to the resolution needed to do the lunar lander simulations shown here, at a far lower price than was previously possible.

57
Table 7: Some graphics display devices listed for comparison.

Professional Systems of interest to individuals

MiniTerm
Tektronix DEC ISC SWTPC Cromemco Assoc
Feature 4006-1 GT-40 Intecolor GT ·6144 TV Dazzler MERLIN Matrox

Design Type Storage tube Refresh vector Raster scan Raster scan Raster scan Raster scan Raster scan
Interface Bit serial DMA DMA Byte parallel DMA DMA DMA
Point Plotting Hardware Hardware Hardware Hardware Hardware Hardware Hardware
Vector Graphics Hardware Hardware Software Software Software Software Software
simulation simul ation simulation simulation simulation
Resolution High High Low Low Lo w Low Medium
1024 x 780 1024 x 768 160 x 100 96 x 64 128 x 128 (BW) 80 x 100 256 x 256
64 x 64 (color) 160 x 100
Drawing Speed Communications 200 IJ.S per Byte tran sfer Programmed 10 Byte transfer Byte transfer Byte transfer
Limitations interface limited vector (fixed) speed for each point speed speed speed
Character Hardware Hardware Hardware Software Software Hardware Software
Generation
Blinking Not possible Hardware Hardwa re Software Software Software Software
Variable No 8 levels No No No No No
Brightness
Remote Yes Yes-contains its Intelligent Yes No No No
Operation own PDP-11/05 terminal use
Altair Bus No No No No Yes Yes No
Plug in?
Multicolor? No No Yes No Yes No No
Is Animation No Yes Yes Yes Yes Yes Yes
Possible?
Hard Copy Yes Yes No No No No No
(Not Photos) (e xtra cost)
Built-in Display? Yes Yes Yes No No No No
ROM Software Not applicable Only a Yes No No Yes No
in System (used with bootstrap System moni tor MERLIN
large systems) monitor
Price Medium High Medium Lo w Low Low Low·Med ium
(Kit price if - $3000 - $14,000 $1,395 (includes $98 .50 $215 $249 + $630
available that computer, dis- $34.95/ ROM
way) play keyboard)
Kit or Assembled Assembled Assembled Kit Kit Kit Kit Assembled
(requires bus
interface)
Design Class High price High price Complete system Low price Integral Integral Medium
High resolution High resolution w ith color Lo w resolution plug in for plug in with resolution
Commercial Commercial graphics Sta nd alone color graphics systems black bo x
d isplay generator software

EDITOR'S NOTES
This table is by no means complete. It is puter, and is a very fl ex ibl e (if now ava il ab le in ki t form at a price within
intended to cover a spectrum of different slightly outdated) syste m widely used the range of a n individual.
systems with different prices and different by graphics hackers at univers ity a nd • The Southwest Te~hnical Produ cts
user orientations. If each column is con- research institutions. The Tektro ni x GT-6144 is a low resolution, low
sidered to be a class of product, then the product and related products are price stand alone product, intended
device shown is a typical member of that within the range of a moderately to be absolutely the least expensive
class. The rationalizations for selection are wealthy private computer hacker, but approach to t he graphics output
roughly as follows : are hardly products for mass con- problem . The intention is quite well
sumption. The 4006-1 is also widely fulfilled. It does require a television
• The DEC GT-40 and the Tektroni x used in the university and rese arch or monitor , ho wever , as do all the
4006·1 are included for comparison communities. amateurs' produ cts except the ISC
purposes only to contrast prices of • The ISC system is an example of a system.
commercial equipment intended for complete system - co mputer , video • The Cromemco TV Dazz ler is the
use with large scale installations. The display (co lor) keyboard, a nd sys- first Altair bus co mpatible product
GT-40 virtually requires a minicom- tems software in ROM - which is avail ab le to a mateurs at a reasonable

58
 puting, we needn't bother the main proces-
sor. Instead, we offer the display direct
access to the memory where the image is
kept. There are two ways to do th is; the first
ALTAIR 8800 OWNERS
is to allow the display to cycle steal, or have
"direct memory access." This is the way
many high performance commercial systems, We recently received the following letter :
like the DEC GT-40, work. This method
does not allow the display to be far removed
from the computer and its memory. In the RUN

AP:=tl L 2611976
GT-40, for example, the input to the display GENTL.EI1EN l

is about six inches from the memory board.

1 J UST \r;AN TEO TO TELL YOU THA T I Tli lt. i; YO UR CLe e K fI X-IT t: l1 I S
The other approach is to give the display REALLY GREA TI I WAS HAVlf\G TRO lia LE RU f\ Nl f>.G BAS I C AN D AF TE?
I NSTALLl r-.;G YOUR KIT F OU R Of "lY NI T S BOAR DS 1 ;;A1 t".I E 2EI~' T RU:', N INJ
its own memory for the image, and its very CAf1E SACK T O LIF E AND t-;O ..- A!1E. HE L?l l>.G ,.j£ TO IWRIT E THIS L EiTER
ON T ilE C Qi1 PUT EP. . E r-. C L QSED 1 5 ANO T HER OReER F O?: A CLOG l!. ;\ 1 T.
own simple processor to keep track of what Tti l S 1 5 Fon THE SECOf\O AL TAi R Ti iA T l ' AI1 r~o\oi 11\ THE: PR.QCi:$S
OF DUILO J :'O.
is going on with the display. The central A3A U ; 1·;';1\'( TH A N KS FG:t St:CH A Flr~£ FilonUC T.

processor then is allowed access to the

S I I\·CE::tE I.. Y
display memory, and need only concern L"' CYC L . 5h ZTX
0 1:
itself with the display when it wants to
change the image. Thus the display can cycle
through its own memory as it pleases, and
the CPU can modify the image at a rate How well does your Altair run?
A Clock Fix Kit is only $15 postpaid.
determined by economy and necessity. This
is the method used by the typical homebrew
or commercial video display used by BYTE
readers. The local memories which have been
used in these devices range from delay lines,
shift registers, and programmable random
PARASITIC ENGINEERING
access core or semiconductor memories for PO BOX 6314 ALBANY CA 94706
alphanumerics, up to dedicated disks for
multicolored high resolution applications
which require vast amounts of storage.
The primary advantage of continuously
refreshed graphics is high speed. This is the about one third that of commercial vector
mode in which anim ation work is most often displays. There is also an additional software
done. Since the images are stored in memory burden on the processor whenever it is
they are very easily manipulated at high desired to simulate vector and character
speed. The resolution can be made equal to hardware.
or better th an storage displ ays. The chart accompanying this article as
The currently popular personal systems table 1 summarizes the characteristics of
displays use the refresh graphics method in se·veral representative graphics display
combination with a video raster scheme. devices. Take this table with a grain of salt,
Instead of directly drawing vectors on a though , because today's specs are tomor-
screen, they can only mark points that lie row's history. I expect that the features of
along the closely spaced parallel horizontal amateur raster scan devices will eventually
lines that make up a normal TV raster. The come close to the commercial continuous-
effect is to limit the maximum resolution to refresh display, except, of course, for price.-

price which could produce color nally intended for the personal sys-
graphics in limited 64 by 64 resolu- tems markets. It is not directly plug
tion. Installation is a simple matter of compatible with any particular com-
plugging it into an unused Altair (or puter, although interfacing to a
equivalent) computer slot. bidirectional microcomputer bus is a
• The MiniTerm MER LI N system is an straightforward matter. It has been
example of a unique combination of promoted in engineering trade maga-
character generator hardware, dual zines as an "OEM" product. Circa
resolution black and white graphics, August 1 1976 it is the oniy com-
direct memory access to main mercially available option for such
memory, and systems software in high resolution at such a low price
ROM form. It uses existing memory (Space War hackers take note). For
of an Altair compatible computer as further information, see "What's
its graphics refresh source. New?" in this issue.
• The Matrox display was not origi-

59
 total of 65,536 dots arranged in a 256 by level of intensity (O .. black, 1 .. white). It
256 dot raster with each dot individually directly connects to a microprocessor data

What's addressed under program control in less than

3.4 us .
The system consists of two modules. A
and address bus and no additional hardware
is necessary.
To a microprocessor an MTX-2S6**2
looks like a write only memory with four 8

New? central timing unit module (CTU) provides

all television synchronization signals and
interface timing signals for any microproces-
sor and for image memory (1M) module. The
bit locations. The locations with addresses 1
and 2 are X and Y coordinates of a given
dot. Cursor (dot address) is loaded by
Graphics Display Memory image memory is a 65,536 bit programmable writing into X and Y address (8 bit each).
memory , and it stores one television frame The intensity (color) is loaded by writing
Matrox Electronic Systems, POB 56, (256 by 256) with one level of intensity. No into location O. Existing cursor address is
Ahuntsic Stn, Montreal, Quebec H3L 3N5 external refresh is required. The image mem- first advanced (moved to the next of 8
CANADA, (514) 481-6838, has introduced ory is continuously scanned to produce a possible directions, specified by 4 MSB bits).
this exciting new peripheral module for use video signal that drives any standard mono- The remaining bits specify the intensity of
in generation of graphics outputs. The chrome or color television monitor directly. the addressed dot. Location 4 is used for
module is the MTX-256**2 graphics display Expandability added intensity or color resolution (up to 24
memory, shown here along with the model Using one CTU and one or more 1M bits for each dot). Clear and present screen
1632 video display memory. modules, various graphic systems can be inputs are also available (minimum screen
The MTX-256**2 graphic displ ay is a designed by simple interconnections. Gray pulse width is 12 ms).
modular low cost graphic system designed Output is a standard composite video
scale, color, image motion, light pen, cursor
for microcomputer applications. It displays a signal (75 ohm, crystal controlled). Both
plot, vector plot, point plot, bar graph plot,
American (60 Hz rate) and European (50
alphanumerics and ROM screen patterns are
Hz) versions are available. Price is $598 in
easily implemented.
The MTX-256**2 provides separate hori - unit quantities for the basic MTX-256**2-1.
Delivery is 2-8 weeks.
zontal and vertical sync outputs which can
be used to drive a slave MTX-1632 SL video
Editor's Note:
programmable memory to obtain fully al-
phanumeric graphic capability, as shown in In conversation with Lome Trottier of
the photo. Matrox, at the Personal Computing 76 show
The si mplest graphic system in A tlantic City, I learned of Matlox's
(MT X-256**2-1) consists of one CTU mod- intention to create a variation of the display
ule and one IM module. The system is also described here which will plug directly into
available as a single 6.5 by 6 inch (16.6 by the Altair/ IMSAI/etc bus [nested note: un-
15.2 cm) printed circuit board, +5 V (400 officially grapevined as the "s 700" bus to
mA); +12 V (120 mAl . This unit will eliminate the kluge of listing all the names of
provide a 256 by 256 dot raster with one all the processors using it ... CHj ... CHj

Introducing The First Professional Quality Modem In Kit Form ...

The Pennywhistle 103

The Pennywhistle 103 Acoustic Coupler is the first professional quality modem available in kit form . The Pennywhistle
may be used either as an acoustic coupler (with the telephone handset) or it may be wired directly into the telephone. In
either case, the Pennywhistle will operate in both the half-duplex (unidirectional) or the full-duplex (bidirectional) modes.
The Pennywhistle 103 is capable of recording data to and from audio tape
without critical speed requirements for the recorder and it is
able to communicate directly with another modem
and terminal for telephone "hamming" and com-
munications for the deaf. In addition, it is free of
critical adjustments and is built with non-precision,
readily available parts.
One of the most significant problems associated
with modems is that there is often difficulty in deter-
mining the difference between a signal of the proper
frequency and one of its harmonics. The Pennywhistle
103, however, employs a three-stage active filter which
prevents noise and harmonics from getting through. for
The Pennywhistle kit includes everything needed for direct wire
the entire unit. All electronic components mount on as" connection, modem-to-
by 9" printed circuit board. The kit also includes all chassis modem communication, tape re-
parts, speakers, speaker grilles, muffs and line cord. corder connection and long distance use.
But just as important, the Pennywhistle is backed up with a
complete documentation manual. This manual describes - in de- The Pennywhistle 103 modem kit is $109.95 (plus
tail - what a modem is and how it works. All theory of operation $2.50 for postage and handling) and is available from
discussions are keyed to a block diagram and schematic. This man- M& R Enterprises, P.O. Box 61011, Sunnyvale, Ca.
ual also contains a thorough set of assembly, test and adjustment 94088. California residents add 6% sales tax. Allow
instructions as well as directions for hooking the Pennywhistle up approximately four weeks for delivery.

60
Introducing A Remarkable New Microcomputer:

The Astral 2000

You're reading this ad, so you're obviously interested in getti ng a mi croco mputer. You 're probably also a bit co nfu sed by th e
numb er of different mi croco mputer kits around tod ay . So, think about th e thin gs you want in a mi crocomputer. Ease of assembly,
quality power supply, well designed cabin et and interconnec t scheme, pe ripheral and memory options for an expan ding system.

Some Kit! A New And Powerful BASIC

Although we have called the Astral a " kit", it actually arrives A unique and powerful version of BASIC with features never
over 70% assembled . The power supply , processor bOal:d and RAM seen before in an 8K version has been design ed especially for th e
board are fully assembled, burn ed in and tested before sh ipm ent. Astral sys tem. Astral BASIC co ntain s all the features of competing
There is no complicated wiring harness. In fa ct, there is no fro nt BASICs and t hen so me; Astral BASIC is also very fast.
pane/ wiring harness at all. The front panel plugs direc tly into the Wi th th e User Se lec table Floating Point pac kage , th e use r
backplane. Additional circuit boards are inserted through the rear chooses the degree of prec ision from the four choices of 6 , 9 , 13 or
of the chassis direc tly into th e backplane. 16 digits. Fewer digits use less memory and is faster , however high er
prec isio ns are useful for sc ientific al1d math ematic applications.
Complete System Th e Astral BASIC 's DO statement is unique ; it h as nev er
appeared in any other version of BASIC. Th e DO statement is a
The Astral 2000 is shipped with power supply , cabinet, front simple and fl ex ibl e way to subroutin e without the restrict ions of
panel components, mother board, processor board and one 8K RAM forma l subro utin es. DOs Cal1 be nested , too and - of course - Astral
board . The processor is 6800-based and operates in serial and in BASIC has all th e other standard subroutine procedures as well.
parallel. Both RS-232 and 20m A current loop are provided by a ser- Th e Trace Mod e is ano th er feature rarely found in o th er
ial I/O socket on the processor. This processor is shipped with our BASICs. The Trace Mode is used in program de bug to list stateme nt
own 16K monitor ROM and has provisions for "cycle-stealing" lin e numbers as exec uted. This feature may be programmed to
DMA. The memory board contains 8K of low power , 500ns static Trace On on ly for routines still need ing chec k-out. Pressing the
RAM and uses less than 1.5A at 5V. esc ape key halts th e trac e and return s contro l to the terminal.
The Astral BASIC string faci lity permits variable length strings
Lots Of Options of unlimited length and includes th e ab ility to search for a substring
with in another larger string, a partic lul arly useful feature for word
A computer isn't much fun if yo u can't talh to it. But yo u can processing applications.
talk to the Astral with the VID-80 video terminal board for only Powerful prog1'am editing c apabilities al low loading , li sting and
$189.95 unassembled ($245 assembled). The VID-80 has a se lectabl e saving of programs . Bloc ks of statements may be dele ted or renum -
line length of 64 , 72 or 80 characters per line. It displays 16 lin es bered . The RENUMBER statem ent may be used to increment all
of upper case characters but gives you the option of installing a specified lin e numbers and it automatically adjusts the numbering
lower case character ROM as well. of any GO TOs, etc.
We also h ave somep lace for you to put your programs. Our 8K Another feature never seen before in an 8K version is th e pop-
EPROM board ($59.95) is designed for the 5204 and w ill allow in- ular PRINT USING statem ent. PRINT USING permits flo ating "$",
system program storage even during power-down. This board is " +" and " - " signs as well as floatin g commas, SO numbers such as
assembled with all components except the EPROMs, however $1,000,000+ can be printed in th e standard accounting format.
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 tap e dec k.
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.

The Astral 2000 is $995 partially assembled ($12 5 0 full y assembled) plus $14 forsilipping and handling ($18 for Canadian
orders). Additional 8K RAM boards are $245 each. California residents add 6% sales tax . Th e Software Pac/wge includes Astral
Basic on magnetic tape cassette or paper tape, the game of Startreh, comple te documentation and a free one year subscriptio n to
the Astral Newsletter, all for $35. For more details, send a self-addressed, 8'/2 by 11 stamped envelope to M&R Enterprises, P.O .
Box 61011, Sunnyvale, Ca. 94088. A llow approx imately 8 to 12 wee/I s for de livery.
Product Description:

The MERLIN Video Interface

Adds a Visual Dimension
to Your Altair or IMSAI

What is mlssmg when you purchase a main frame computer from the MERLIN'S two boards provide far more
catalogues of MITS Inc or IMS Associates? Asking that question has recently than just an ASCII and graphics interface. A
started several companies purveying products to the small systems market. sophisticated DMA controller allows MER-
The identification of gaps in a product line, then independently filling these LIN to display information from any part of
gaps is a highly respected tradition in the computer field, a tradition which the computer memory. Also, since the dis-
has hardly changed as the market widens through microcomputer technology. play starting address is software controlled,
An example of a creative and innovative product idea which augments and the memory segment displayed can be
enhances an existing computer product line is provided by the new MERLIN changed with every screen refresh.
board manufactured by MiniTerm Associates, Bedford MA. The following The number of ways in which the mem-
article is edited from materials supplied by MiniTerm. ory selected can be displayed boggles the
mind. And since the display mode is soft-
ware controlled, it too can be changed with
every refresh. One useful mode option saves
MERLIN (trademark of MiniTerm Asso- memory by beginning a new line whenever a
ciates) is a new concept in peripherals carriage return is detected - eliminating the
modules for mainframe microcomputer need for spaces to the end of a line. This
systems. It is a combined hardware and enables typical text or program source code
software package which provides a keyboard listings to be stored in 30 to 50% savings of
video interface with 20 lines of 40 ASCII memory space depending on the actual text
encoded characters, graphics with a resolu- data involved. Another mode selects white
tion of 100 by 160 points, and read only or black characters. Control cbaracters can
memory software for Monitor and Editor be inverted or blanked - great for storing
programs. The entire price of this unit, $249 "invisible" information on screen for some
plus $34.95 for the ROM software, is well games. Carriage returns are displayed as
within the budget of many small systems boxes or blanks and the cursor winks or
users. In fact it is hard to find a combination remains steady. The dense graphics mode
of the features MERLIN has which even enables 2 K words of memory to be dis-
approaches the cost effectiveness of this two played as 160 dots horizontally by 100 dots
card Altair and IMSAI compatible plug-in vertically, or if memory is in short supply ,
system. Output is an EIA standard video -I K bytes can be used to display as 80 dots
signal to drive a TV monitor or modified horizontally by 100 dots vertically until
television set. your next birthday.

62
 The POLY 88
MicrocODlputer SysteDl
The POLY 88 Microcomputer System brings to the The monitor provides many of the standard driving
user, in one compact package, the capability of routines to greatly simplify the job of programming.
developing programs and hardware as well as The monitor forms the basis of an ever-increasing
enjoying the interaction with computers . The POLY software library available to POLY 88 owners.
88 System uses a video Options from PolyMorphic
monitor for display, a Systems include a board
keyboard for input, and with 8K of additional RAM, a
cassette tape for storage. versatile prototyping board
The system will connect to a ("The Ideaboard"), and an
hard-copy terminal. POLY Analog Interface. Also,
88 hardware consists of many "Altair-compatible"
CPU circuit card with on- products on the market are
board memory and I/O, compatible with this system.
video display circuit card Prices: Basic kit including
with keyboard input port chassis, CPU and video
and graphics capability, and cards - $595, $795 .
mini-cards that connect to assembled. Cassette option
the CPU board via ribbon - $90 kit and $125
cable for cassette or serial assembled. 8K of RAM -
interface. $300 in kiform or $385
Central Processor Card assembled. We also sell the
features 512 bytes of RAM video and other "Altair-
(random access memory), compatible" circuit cards
plus sockets for up to 3K of separately.
2708-type PROM or ROM Dealers: This system sells
(read only memory), itself.
vectored interrrupt, and real All prices and specifications
time clock, as well as an subject to change without
optional serial input-output notice. Prices are USA only.
port featuring software- California residents add 6%
controlled baud rate. sales tax.
The Video Terminal Interface circuit card will Prepaid orders shipped postpaid. BankAmericard
generate 16 lines of 32 or 64 characters or 48 x 128 and Master Charge accepted.
graphics grid on a standard video monitor or slightly
modified TV set. It also includes an 8 bit parallel Io~lease send more informatio~---I
keyboard input port, allowing the board to function
as the complete computer interface .
I 0 Order and check enclosed :
The POLY 88 Chassis and backplane/ motherboard
is Altair compatible,and will provide 6 amps of
I Name I
power to five cards. Only two switches are mounted I Address I
on the front panel- a lighted on/ off switch, and a I City/ State I
push-button, which, in addition to resetting the
system, indicates a halt condition in the processor. I Zip I
The firmware Monitor is integral to the POLY 88
System. This 1024 byte program in ROM allows the
I BankAmericard Expires - I
user to display data on a TV screen, enter data into I Master Charge Expires - I
memory using a keyboard, read and dump data to ~ignatu~ _____________ ~
the cassette interface in a standard format , and
single step through a program while displaying the PolyMorphic Systems (805) 967-2351
contents of each of the 8080's internal registers. 737 South Kellogg Avenue Goleta , CA 93017

PolyMorphic
Systems
 If you are worried abo ut loading all those programs may be executed with up to three
great bytes into your machine with toggle breakpoints. The breakpoints enable the user
switches, don't. MERLIN provides a parallel to return contro l to the Mon itor after
input port to which most keyboards may be executing only part of his code. Once in the
directly tied and sufficient regul ated power Monitor the user may examine or modify
to run them. MERLIN also has a seria l input memory or registers before executing more
port which may be used for binary data of his program.
from tape signa l conditioners, switches, The Editor functions can be invoked by
thermocouples or other arcane hobbit para- keystrokes or called from user programs.
phernalia. The seria l output port is also The functions include :
uncommitted, and the pair can be used to
implement a cassette 10 interface. Control of cursor movement (up,
Best of all , you need not be a software down, right, left, home, two tab sets, and
gen ius to use MERLIN. Monitor and Editor tab).
functions as well as general purpose sub- Either characters or lin es may be
routines, selectable 10 drivers and keyboard in serted, deleted, or replaced.
and display drivers are also stored in MER- Scrolling can be automatic at any lin e
LIN's optional on board MBI ROM. (If you nu mber or under manual or program
are a software genius and have a programmer control. Scrolling may be page up or page
you can substitute up to 2 K of your own down or absolu te.
2708 EROM orl K of 2704 EROM .) Pro- Automatic scroll in g can provide wrap-
vided with the MBI ROM are also 128 words around at the end of the defined display
of scratch pad programmable memory to area (up to 64 K), so th at using the "clear
hold MERLIN's vital statistics and Mon itor disp lay after cursor position" and "copy
stack . Lin kage through this scratch pad to block" functions provides an easily impl e-
user defined routines creates a system which mented "infinite" display area .
can be expanded virtually without bound. Finally, this ROM contains direct
(As though the ten user defined keystroke li nkage to a second optiona l 2 K ROM
executed functions buil t into the mon itor and forthcoming cassette-modem inter-
weren't enough!) face ROM. MERLIN's second ROM con-
Monitor functions provided by the MBI tains extended Monitor/Editor functions
ROM include the abi li ty to fill any portion plus general purpose graphics control
of memory with a given hexa decimal value, su brou ti nes.
the abi lity to sequentially modify me mory
contents, and hexadecimal dumps to the A soon to be announced optional board
display. Processor registers may also be for MERLIN will increase capabilities to
examined or mod ified. ASCII text may be inc lu de color graph ics, and with 320 hori-
input to memory, blocks of memory may be zontal by 200 vertical resolution for black
copied, the beginning and end of the disp lay and white graphics.MiniTerm Associates is
area and di splay format may be set, and user located at Box 268, Bedford MA 01730.-

64
 IF YOU CAN'T FIND IT OFF THE SHELF
TRY THE DATA DOMAIN
We are proud to announce we are now dealers for the Digital Group.

Processor Tech IMS Cromemco CSC Vector OSI

111 S. College Av
Bloomington, Ind. 47401
The DATA DOMAIN Phone(812)33~3607

Continued from page 16 the limitations of 16 bits, the search for

al ternatives is bound to occur. One place
run APL, SNOBOL, LISP, PASCAL, that this can come out is in newer LSI
ALGOL, TRACTM etc), and with the falling processor designs. For examp le, consider the
prices of memory, will do exactly that. I Motorola 6800 as it is presently imple-
know severa l personal computer hackers mented. It resides in a 40 pin pac kage, but
Articles Policy
who have pretty nearly fi ll ed up a 64 K the simplicity of its interfacing requirements
BYTE is continually seek-
memory ad dress space. If a person has a leaves two pins unused at present. In a ing quality manuscripts writ-
choice between a system that costs $1000 hypoth etical "improved" version, the design ten by individuals who are
applying personal systems, or
with 16 K of memory a nd the same system could be modified to support 18 bits of who have knowledge which
with 32 K at an incrementa l cost consistent addressing, or a maximum of 256 K bytes will prove useful to our
readers. Manuscripts should
with the new 16 K chips' estimated costs, (262,144 bytes) with some changes in the have double spaced type-
the extra $300 to $500 at the store may be internal architecture. The simplest internal written texts with wide mar-
gins. Numbering sequences
well worth it ; and as the techno logies change would be to use the uncommitted should be maintained sepa-
rately for figures, tables,
improve, more and more memory will be bits of the status register (bits 7 and 6) as photos and listjngs. Figures
potenti ally possib le for the same dollars. "bank se lection" bits to implement ex- and tables should be provided
on separate sheets of paper.
And there lies the problem. With memory tended external memory by the traditional Photos of technical subjects
getting cheaper and cheaper, we are running "bank switching" trick. Of course, it's should be taken with uniform
lighting, sharp focus and
out of address space in the 8 bit LSI hard ly li kely that this design change will should be supplied in the form
happen, so the extension to memory sizes of clear glossy black and white
processor! The typical 8 bit or 16 bit LSI or color prints (if you do not
processor addresses 65,536 bytes a nd that's above the address range of the mac hines will have access to quality photog-
raphy, items to be photo-
all. For many purposes, such as creating data have to be accomplished by the individuals graphed can be shipped to us
base structures with large buffered data areas designing the computer products which in many cases). Computer
listings should be supplied
internally , it would be extremely convenient employ LSI central processors. using the darkest ribbons pos-
sible on new (not recycled)
to have much larger main memory areas . For Bank switching kluges can be done exter- blank white computer forms
instance, in a super text editing system nally to a processor as well. I n a personal or bond paper. Where possible,
we would like authors to sup-
allowing 50 K bytes for buffer areas limi ts computing system with ROM software of ply a short statement about
one to about 18 standard manuscript pages compilers or interpreters, one way would be their background and experi-
ence.
in memory at any given time (ass uming no to partition a 32 K segment of address space Articles which are accepted
pag ing to expensive electromechanical mag- into two 16 K reg ions along the boundaries are typically acknowledged
with a binder check 4 to 8
netic media). With memory becoming a very of the 16 K chips, with bank switching used weeks after receipt. Honorar-
iums for articles are based
cheap commodity, one would like to have as to al ternate such extended regions of mem- upon the technical quality and
much of it as possible on line for such ory . Again , in a hypothetical case, consider a suitability for BYTE's reader-
ship and are typically $25 to
applications. Simil arly, in setting up infor- 4 bit mapping vector for each 16 K half of $50 per typeset magazine
mation management systems for the home this region of ad dressing. The 4 bit bank page. We recommend that
authors record their name and
user, the more memory the better, since the selection could point to 16 banks of 16 K address information redun-
resource can be used both to speed up bytes or 256 K bytes, with the core of 32 K dantly on materials submitted,
and tha t a return envelope
computation by using table concepts, and to bytes retain ed for system monitor and 10 with postage be supplied in
the event the article is not
minimi ze 10. functions . But these are just conjectures of accepted. -
Given this desire for lots of memory, and ways to acco mplish the extens ion of mem-

65
 ory, given the need for utilizing existing mercial products of the Burroughs Corpora-
machine architecture. tion and experimentally in computer science
and software engineering contexts. This is
Enter the Stack Machine the technology of the high level language
The real reason we need to use more machine, or stack machine. This is a proc-
memory than 64 K is our need to use high essor designed to have a machine language
level language to program sophisticated which is very close to a high level language
information constructs. Traditional LSI consistent with structured programming con -
processor designs to date have merely been cepts. This is the world of the computer
adapted versions of widely used designs to whose instruction set includes control struc-
the constraints of LSI technologies. A 6800 tures like the IF in struction, the THENDO
is si mply an 8 bit approximation of wh at instruction, the ENDELSEDO instruction,
minicomputers have al ways been, and the ENDI F instruction, and data constructs
minicomputers are just miniature versions of appropriate for a high level language. The
the earlier, larger machines. Sure, improve- grapevine currently jingles with rumors that
ments in architecture have been made, such such a machine will soon be on the market,
as use of subroutine linkage stacks with possibly labelled "Z90", and I know of at
built-in pointers, but all the present LSI least one university laboratory version in-
processors are cut of the same mold. If we tended for reduction into LSI masks. High
are running out of room in address space level languages are what make general pur-
with the present designs because of a need to pose computers useful to the larges t number
Authors take note: A
run high level programming languages and of people, so eventua ll y I expect to see stack
tutorial on the architec-
intricate information systems written in machines in LSI form, intended for general
ture of stack machines, the
these languages, why not use the need for purpose computers.
reasons for using such
larger address space as a superficia l spur for a Use of stack machines sure won't cure the
machines, and what it is
high leve l language oriented general purpose address space saturation problem, but if one
like to program such a
processor itself? has to add some extra bits to the memory
machine would be excel-
lent article material for There is a whole technology of machines address bus, why not include a real improve-
oriented towards high level languages, a ment in the processor arch itecture at the
BYTE magazine.-
technology principally seen in the com- same time as the new design is created?-

Publisher's Notes Personal Computing 76 in Atlantic City:

inspired by the show were engaged in con-

Something for Everyone versation until much later.
For those of us who aren't true computer
hackers (I'm a jade carving nut myself) the
choice of Atlantic City as a site was indeed
by Virginia Peschke Personal computing enthusiasts were fortuitous. Though it's somewhat difficult to
treated to a huge, successfu l convention in get to from some parts of the country, once
Atlantic City on August 28 and 29. BYTE there the computer hacker is relieved of the
will have a comp lete pictori al report next usual domestic problem; that is, how to keep
month, but briefly: More than 80 manu- the fami ly entertained. Atlantic City offered
facturers and supp li ers had booths to display so much for the people who didn't wish to
their latest products and exchange ideas with spend much time at the show that the
users; dozens of technical talks and several computer buff was unlikely to hear "We've
seminars provided information on every been here an hour, when can we go?" First,
phase of personal computing; and a huge there was the superb sand beach with a
supp ly of valuable door prizes was dis- warm, gently rolling ocean, the amusement
tributed to many lu cky attendees. park, the boardwalk train, an d the great
The speakers at the Saturday night selection of restaurants and shops. Where
banquet were al l greatly entertaining. As a else could one find, within several blocks of
grand finale, John Whitney showed his tech- each other, dealers in crysta l paperweights,
nically amazing and esthetica ll y beautiful archaic Chinese jade, oriental rugs, British
movies of animated computer graphics with tweeds, Spanish lace, magic tricks, health
musical accompaniment. Though everyone foods, and many o!her things too numerous
had had a full and exhausting day, John's to li st? No, families were not bored and
movies held us all spel lbound until almost hackers were free to spend all the time they
one in the morning, and var iolls persons wanted exchanging information.-

66
 Based on fli ers picked up at the Persona l
TERMINAL SYSTEMS DIVISION-DAYTON
What's Computing 76 show in Atlantic Ci ty,
Augus t 28 and 29:
Edityper Sys tems Corp, subsidiary of
Tycom In c, 26 Ju st Rd , Fairfield NJ
We have a number of new and challenging
opportunities involved with the hardware/soft-
New? 07006, is manufacturing a do it yo ur-
self Selectric typewriter convers io n
kit. This "easy to install " kit for any
I BM Selectric I o r Se lectric II ty pe-
ware design and development of real-time finan-
cial terminals. Immediate needs are at all levels
Miscellaneous
write r " prov ides quality hard copy in the following areas:
o utput for all microprocessor devices."
Th e kit con ta in s fou r modules : a
selection assembly, f un ction group PROGRAMMER/SYSTEMS ANALYSTS
assembly, shift assembly and tab
asse mbl y. It is driven by a 50 pin These positions require knowledge in the areas of
conn ector and req uires user supp li ed microprocessors and minicomputers based on real-time
po wer of 27 V at 1 A peak, and 5 V at operating systems. Responsibilities will be to participate
0.2 A. Th e price is $395 plus shipp ing.
We'd be most interested in pu b li shing in the design of software development and write test
a ' photo article by a reader who ins tall s software for mini and micro based real-time operating
this item in a typewriter and integrates
systems in a distributive network.
it as hard copy outp ut for hi s or her
system .
STM Systems, POB 248, Mont Vernon
An opportunity also exists for participation in the
NH 0305 7, showed off th e new Baby! architectural design of an Automated Health Care
Floppy Dis kette Storage System, This System.
new "mini floppy" drive with power
suppl y and controller will be avai lab le
in the near f uture fo r $750. It uses a Candidat es should have a BS/MS degree in Computer
miniature floppy di sk of about 5 Science or Math and at least 3 years programming
in ches (13 cm) diameter an d stores 90
K bytes (formatted) on 35 tracks with experience. Experience with assembly and COBOL
average latency of 100 ms, 350 ms languages is necessary.
average access time. The dri ve was
shown in prototy pe form at the con-
vention.-
SOFTWARE SYSTEM DESIGN
llIllIlIIlIIllIIllIIlIlIlIllIIllIIlIllIlIllIIlIlIlIIllllllIllIlIlllllllIllllllllllllIl1IIIIIIIIIIIIIIIIIIIIIIIIIIIIIUllI These positions require the ability to provide technical

I baGJGJ S[]fTWfJRE baGJGJ I expertise and leadership in the area of real-time terminal
control and batch operating syst ems. Responsibilities
will be to translate and interpret the state-of-the-art in
operating syste ms to an assigned terminal control project
SPACE VOYAGE
The most comp l e te space s im u lati on game eve r offe r ed to mi c r o use r s. You r
mi ss i on i s to ri d the gala xy o f the en emy us in g your wa r p e ng i nes , phase r s
_
=
=
=
and to select, influence and affect broad t echnical
directions in software. Will be responsible for coordi-
pho t on torpedoe s, s hort an d long ra nge s can ner s , te l cpo rt c r, sh i e l d con tro i
a nd damage co ntr o l. Beware of enemy a ttacks , su pe r no v;:J s , space sto r ms , a nd
o t he r d i s t r ub anccs . To d up l i ca t e t h i s game us i ng BAS IC wou l d requ ire about
20K but your 6800 nee ds on l y 4K to r un t h i s exci tin g program . SIO. OO
=
= nating complex distributed processing operating system
software development which will support applications
FLOATING POINT PACKAGE
Us in g th i s p r ogram yo u can do a rit hmet i c ope rati ons with 9 s i gn i f ic ant d i g-
its and a n expone nt ra nge o f - 99 to +99 . Add ,su bt r act , mu l tip l y and d i v i de
are i mplemented in 5 12 by t es. We incl ude fre e I / O dr i ve r p rog r ; m. 55 . 00
=
=
=
coded in high level languages and run in both microcom-
puter and minicomputer mode environments.
SCIENTIFIC PACKAGE
All t he sc ient i f i c fun ct io ns yo u need - SIN, COS, TAN, AR CS IN, ARCCOS , AR C-
TAN , expo ne n t i a l s, LOGX , LN X, hype r bo li cs, a nd more. Must be used I·lit h the
=
=
= Candidates should have an MS degree in Computer
F lo a t in g Po in t Packa ge above (not i nc l uded) . 5 10 . 00 Science, Systems Engineering, or Math, and 7 to 10
PR ltH, IN PUT , READ ,
MICRO BASIC PLUS
DATA, RE S , GDSUB, GDTD, ON GDSUB , Of' GDTD, RET, LET, =
=
=
years programming experience with at least 5 years in

_
IF, FOR, NEX T, REM,
TAB, SPC , ASS, SGN,
d ur.1p. A 4 K system
EN D, I a nd 2 DIM ar ra ys, RUN , LI ST , SCR, EXT , MON , RNO,
EXP , mu l tip l e s t a t e men t s pe r l i ne , s i mple l oa d and
l eave s a pprox I K for progra ms (SO l i ne s ) . S I S.9S = operating system design and development.

=
=
==
PROGRAM OF THE MONTH CLUB
Fo r 52 yo u ge t a one yea r membe r s hi p a nd r ece iv e monthly bu ll e tins de s c ri b-
i ng our newe s t p r og r a ms . Up to 15% d i sc o un t o n the feat ured p r o g r am . No ob -
l igations . You ge t ou r Ran d OTl Numbe r Gene r a t o r fr ee i f you j o i n neM. 52.00
=
=
=
These positions are at NCR's Terminal Systems Division
in Dayton, Ohio. If you qualify and are interested in
CASSETTES these opportunities, submit your resume and salary
=
= =
=
=
==
==
Severa l p r og r ams are now a vail ab l e o n "Kansas Ci ty" s tandard, MI KB UG fo r-
matt ed aud i o casset t es . No in st ructi ons o r I i stin g in c l ud e d, mus t be pur-
c hase d sepa r a t e l y . CT-I SPAC E VOYAGE 58.95, CT- 2 KLi NGON CAPTU RE 56 . 95,
li st in g $ 4 .75 , CT- 3 HA NGMAN a nd ACEY-O UCEY $6. 95 , l ist in gs 5 3. 25 ea ch,
CT -4 MAS TERMIND a nd SWIT CH 56. 95 , li s t ings $ 3.00 and 52 . 00 r esp e c t i ve l y .
=
=
requirements to: Robert L. Opalek, Manager
Employment Department
Terminal Systems Division-Dayton
INFORMATION NCR Corporation
=
=
=
Our source l is t i ngs con ta i n c omme nt s t h r o ugho u t, la be I tab I e, hex c o de d ump
compl e te i ns tr ucti o ns , and samp l e output. Ext e r na l r e ferenc es (to MI KB UG
ro uti ne s) a r e ea s ily roo dified . 'W hen ord e r ing add $ 1 post a ge a nd handlin g
under SID, 5% fo r firs t cl ass ma i l , 4% s ale s ta x ( Ind. r es id e nt s) . Pe r so n-
=
=
=
=
Dayton, Ohio 45479
---
~ a l chec k s wi ll c lear ban k . Ma n y o ther pro grams , f o r i nf o r mati o n s end SASE . S

- TSC Te c i1 :li c al Sys t ems Con s ult a nt s

Box 257 4 W. La f a ye tt e I N !17906 TSC An Equal Opportunity Employer
IJiii 111111111 11111111 III I1111111111111111111111111111111111111111111111111111111111 1111111111 1111 1111111 1111 11111 II ffin
67
 A CASE OF DUPLICITY? HUMANE COMPUTING?

Finally ariving home from work after am working on a survey of the human-
another hard day, see ing my Augu st issue of istic use of computers and would like to get
BYTE in the mai lbox immediately calmed in touch with other people who are inter-
my nerves. I settled into my se mi-auto matic ested in this field. I want to learn about
reading chair, placed my copy in th e scan- what can, and is, being done to make the use
ner, punched up a beer and sausage combo of computers as humanized as possible. More
on the conso le an d prepared to better specifically, I want to know:
myself. Greedily I began. Not wanting to
flounder about, I immed iately flipped to "In • What are the potentially humane
applications of computers?
This BYTE." The highlights leaped at me.
Another fanta stic array of information! (Up • What are the important ingredients in
to thi s point, I had read every issue of BYTE humanized computer systems?
cover to cover and this one promised to • What is cu rrentl y being done in the
ma inta in the trend .) field of humane computing, both in
terms of theory and practice?
I read to th e blurb about the Zilog Z80
and no farther. Expecting to find informa- • Which individuals and groups are
actively doing this work?
tion to del ight and astound me , I started

letters flipping toward the articl e. One page farther • What are their particular goals and
and the ad for the "super ch ip" whet my objectives?
appetite and set me flipping furious ly. My • What are the results so far?
expectations onl y rose as I sk immed for page • What are the major factors deter-
34 and th e "Microprocessor Upd ate: Zilog mining their successes and failures?
Z80". Page 25. (Ju st nine more. ) Fl ip. Flip. I would like to hear from anyone who
ZEROING IN Page 32. Flip. Page SOl!! Fli p back. Page 32. can contribute to answe ring such questions .
Flip. Page 50m They should write to me describing their
I think the point has aga in been mi ssed in I tore my BYTE from the sca nner, and thoughts, fantas ies, plans and experiences
the great 8080/6800 controversy. manually searched for page 34, but nowh ere related to the hu mane use of computers.
Reade r Cochran (August 1976) compares could I find it. It see ms my copy jumps from Besides corresponding with people, I hope to
the 10 structure for what seems to me the page 32 to 49, and agai n from page 80 to 97. actually visit and talk to as many contacts as
milli onth time. Really now, what would it The fact th at there were doubles of pages possible. All the material I co llect in this
take to convert one bus to the other? A 17-32 and 97-112 didn't seem to make up way will go towards the publication of a
couple of AND gates maybe. And who cares for my loss. survey of hum ane computing.
if the 6800 has a few less memory locations I fell back, dejec te d, just as my chair
out of 65536? served me my beer. But the force of me Andrew Clement
The major difference is the purpose be- collapsing backward thrust my beer into the 789 W 18th Av
hind the two in struction sets. While the vibrating unit wh ich promptly shorted out, Vancouver BC Canada V5Z IWI
8080 is super ior at handling structured data, flinging me head long across the room .
the 6800 is better at arithmetic. The former Humanistic needs some precision in
I am now in traction in the county
has an overloaded accumul ator while the hospi tal. I am also very dejected because definition, but it will be interesting to see
latter has an overloaded index regi ster. what you find. Readers interested in
now I have all this time and still can't read
The single accumulator of th e 8080 re- about the Z80. Cou ld you find it somewhere working with Andrew are urged to
quires many transfers to temporary storage. in your heart to fill this emptiness. correspond.
This is most frustrating when doing calcu la-
tion s that involve intermediate results. Un- Depl orab ly yours
MORE COMMENTS ON
fortunately, the arbitrary nature of the W R Macleod COMPUTER TYRANTS
instruction set makes improvement diffi cult. GTE Automatic Electric labs
Zi log's Z-80 is a sli ght improvement, but 4501 W North Av I am a studen t at San Bernardino Valley
only compounds th e inconsiste nci es already Melrose Park I l 60160 Col lege and am majoring in computer en-
present.
Mr MacLeod received the following reply: gineering.- Recently, I was leafing through
Th e 6800's maj or fault is its lack of index
some back issues of BYTE that had been
regi ster capability. However, improvement Dear Mr Mac Leod given to me by a fr iend. I came across an
by add ing in structi ons is easy. Th ere shou ld
Enclosed you will find a complete August article in the February 1976 issu e by Ed
be an instructi on to push the in dex register
issue of BYTE. We hope you enjoy reading Rush entitled "Could a Computer Take
onto the stack and one to pop it off. An
the article "Microprocessor Update: Zilog Over?" /page 76/ .
instruction to compute a 16 bit add ress by
ZSO," during your stay in the county hospi- In his article, Mr Rush points out all the
add ing the acc umul ators to the index reg- specu lation that various sc ience fiction
ister is essential for reentrant programming. tal. If it appears to be an extended stay,
please let us know if we may forlMlrd the writers of today had written into their
Both the 6800 and the 8080 need im- stories about the probabilities of a computer
provement. Because the 6800 has a clea ner September and October issues to you.
The staff at BYTE wishes you a quick taking over so me or all of future society. He
architecture, it has greater potential. So suggested that all those who have any
when Motoro la comes out with a repl ace- recovery.
knowledge of the operatio n of an informa-
ment chip , I'll be first in lin e. l Not if I get tion processi ng system would be the first to
there first . .. CH1 /Any reader who received a similar glitch
should send his/her BYTE back for re- confess this point. Not true.
placement./ I have only been work ing with computers
Stephen Ma for two years, but I have also been an av id
Glenn Fawcett science fiction fan . Th e ide a of th e computer
5170 James Walk COMPUTERPHREAQUENCY as a wor ld dictator makes me think of th e
Vancouver BC CANADA V5W 2K4 naiveity of modern society. Those who do
BYTE No. 13 (September 76), page 12, not want society to progress to an easier
Grapevine, Austin TX, has il that the new letter from Melvo n G Hart , WO IB Z, "Atten· more controlled future have se t the
MC6S09 product (the Motorola answer to tion Hams l . . . " Try 3.865 MH z (LSB) on co mputer lip on a pedesta l as th e ultimate
Z-SO) will have: Two 76 bit true index Thursdays at 2300 GMT. You wi ll find enemy. Sc ience fiction writers have taken
registers, block move, block search, and severa l computer-phreaq ue/ama teurs there. this concern and have written upon it.
perhaps even some 76 bit arithmetic to Carl K Zeltner, W5HFG Th e true enemy is not th e computer. The
enhance pointer manipulations and address 108 Moss Dr sa me people who tend to put down the
calculations at run time. San Antonio TX 78213 computer are precise ly the same people who

68
 Only $59.95
Assembled
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• 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

.- .
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PerCom 'peripherals for personal computing'

can appreciate its power. They are not afraid TREK76 will be one of the best STAR After you make certain th at you are
of th e computer itself, but are afra id of TREK games around . Anyone interested ready to use the terminal safely, you might
those who con trol the co mputer. sho uld contact me (school add ress is: Box consider that elec tro lytics are n't known for
Th e com puter operators and program· 5739, University of Rochester, Rocheste r espec iall y good high frequ ency character-
mers of the future will contro l the world, IF NY 14627 from September to May) . istics. If yo u get a hori zo ntal sm ear in the
world power goes to the computer. I' m a game freak so anyon e with games to display, put a small (0.01 jlF or so) bypass
exc hange just let me know. Also, I'm look- capacitor in parallel with each electrolytic.
Richard G Castle
ing for a li sting of a BASI C game ca ll ed
21951 Vivienda Av Robert F Miles
TREK73.
Colton CA 92324 242 Abingdon Rd
Lenoir NC 2B645
Dave Warker
The neat thing, though, is 50 many
different makes and models of computers SOME THOUGHTS ON Thanks for chipping away at "ignorance. "
doing most of the computing for individuals! " IGNORANCE IS BLISS"
Try to make that situation into a tyranny.
Th e " Ignorance Is Bliss" television dr ive NEEDED : BENCHMARK COMPARISONS
circuit (Jul y 1976 BYTE, page 38) looks li ke
a simple answer to a commo n need. One question whi ch I have had for a long
SUPER STAR TREK: TREK76 However, be sure to check wh ether the tim e concerning microco mputers is through-
televi sion circuitry is isolated from the pow- pu t. I have been using a PDP-8/E now for
BYTE is fantastic and I'm now in the er lin e. If not, use an isolation transformer qui te a while. Many of my programs (such as
process of scrounging up eno ugh money fo r for the television at any time th at it is LI FE) were limi ted by speed. It seems to me
a subsc rip t io n. I n your ) anu ary 1976 issue connected to the te rmin al. Otherwise, plug- tha t the B is consid erab ly faster than many
there was a letter fro m Ri chard Wex ler and ging in th e televis ion th e wrong way will put mi cros; but there are other thin gs whi ch I
he wanted info on STAR TREK programs. I 11 5 volts AC across th e elec trol ytics if the can no t adeq uate ly compare. For in stance,
have almost all th e bugs o ut of an adva nced logi c suppl y is proper ly gro unded, and will th ere seems to be a lot more ways to add ress
ga me called TREK76 which should be just put 115 volts AC on the logic ground if it memory in a B080 (or Z-BO). How do these
wh at he wants. isn't co nn ecte d to an exte rn al gro und. chips compare, in "be nch mark" programs,
TREK76 is written in standard FORT- Also be sure that your tel evisi o n ante nn a to th e mini s? .
RAN so it should run anywhere. Comm and s has a good li gh tnin g arres ter to take care of How fast can the BAS IC soft ware for the
are entered in Engli sh sentences and the the vo ltage surges caused by nea rb y li ghtnin g B080 count in a loop, such as 1=1 to 20000?
ga me is semi-real time; the Klingons attack strikes. Thi s is especial ly importan t because Th e PDP8/ E, under the TSS t im esharing
and have the same armaments as the Fede ra- th e elec trol ytics ca nn ot withstand as much syste m, managed it in abo ut 20 to 40
tion. Once all the bugs are out of it voltage as the small , high voltage capac itors second s. Another co mputer I have used, the
(hopefu ll y ove r the nex t few mo nth s) you could use with an RF mod ulator. HARRIS Sl ash Four, d id 1=1 to 100000 in

I/O I;!oards 1702A * $ 8.50 · 8223 $3 .00

4Kx8 Static Memories
1/0-1 8 bit parallel input & output ports, 2101 $ 4.50 MM5320 $5 .95
MB-l Mk-8 board, 1 usec 2102 or eq.
common addre ss decoding jumper 2111-1 $ 4 .50 8212 $4.00
PC Board . . $22 Kit .. . .. . . $100
selected , Altair 8800 plug compatible. 2111-1 $ 4 .50 8131 $2.80
MB-2 Altair 8800 or IMSAI compatible Kit . . . . . $42 PC Board only . . $25 91 L02A $ 2.55 MM5262 $2 .00
switched address and wait cycles. 1/0-2 I/ O for 8800 , 2 ports committed, 32 ea. $ 2.40 1103 $1.25
PC Board .. $25 Kit (1 usec) $112 pads of 3 more, other pads for EROMs Programming send Hex List $5 .00
Kit (91 L02A or 21 L02-1) . . . . .. $132 UART, etc. AY5-1013 Uart $6.95
MB·4 Imp roved MB-2 designed for 8K Kit . . . $ 47 .50 PC Board only. $25 All kits by Solid State Music
"piggy-back" without cutting traces . Misc. Please send for complete list of products
PC Board . . . .. $ 30 Altair compatible moth er board and ICs .
Kit 4K 0.5 usec . . . . •. $137 15 sockets 11 "xl1 y," . . . $115
Kit 8K 0.5 usec . . .. . . $209 Altair extender board . . . . $ 8 MIKOS
1 00 pin WW sockets .125" 419 Portofino Dr.
MB-3 1702A 's EROMs, Altair 8800 &
centers. . . . . . . . . . . ... . . $5.50 San Carlos, Calif. 94070
Imsa i 8080 compatible switched address
2102's 1 usee 0 .65usee I 0.5usee Check or money order only , calif . res iden ts 6 % tax. All
& wait cycles. 2K may be expanded to
orders postpaid in US. All devi ces tested prior to sal e.
4K.
2K kit . . $145
Kit less Proms . $ 65
4K kit . . . . . $225
ea.
32
$ 1.95
$ 59.00
$ 2.25
$68.00 I $ 1 .65
$50.00
Money back 30 day Guarantee. $10 min . order. Prices
subj ec t to change without notice.

69
about 15 seconds. At the sam e time it was fr om the manufacturer. I would like to make by the additi onal address ing, and th ey
supporting other users. these ava il abl e to interested BYTE readers can get quantity di scounts th at the
Simply counting makes for lousy bench- fo r $12 plu s $1 shippin g. indi vidu al hobby ist cann ot.
mark programs, th ough. I would appreciate En closed is the article fro m E DN and also A sta nd alone dev ice woul d cos t more
an article on the subj ect. an ex pl anati on I received th at differs slightly yet: Th e elec tro nics woul d be more
on how to in stall th e crysta l. Thi s may be compl ex, poss ibl y ju stifyin g a dedi-
James Wiebe
because of the two different versions of ca ted mi croprocessor, and eve n worse ,
208 N Jefferson
HP-45s. I have hoo ked one up for so meo ne you th en need a power suppl y, cab les,
Hillsboro KS 67063
using the HP shee t and it wo rk s fi ne. Th e a box and all the o th er thin gs whi ch so
oth er way may wo rk as we ll . I shall try it rapidl y run up th e cost of a good
The benchmark slot has not been soon. look ing (an d reliabl e) ho meb rew pro-
adequately filled with articles in BYTE, as
ject.
james' letter points out. A uth ors take note: Mark S Egbert
3. I am afraid that th e hobbyist is neve r
A general background article on the theory 1514 S 320 E
going to get not iceab le qu antiti es of true
and validity of benchmarking, applied to Orem UT 84057
state of the art ite ms. Ann oun ce ments in
microprocessor technologies, would be most
PHOBIA magaz ines such as Electronics are at least six
use ful to readers in evaluating processors.
months (if everythin g goes we ll, whi ch it
DOCUMENTATION NEEDED On e of my pet ph obi as is peopl e who usu ally doesn't) ahead of vo lume deli ve ri es.
short out capacitors. In BYTE # 12, page 96, Afte r th at, there is at leas t ano th er six -
fi gure 1, th e key boa rd sw itches directl y month wa it to design an ite m into a hob-
I am searching for a company th at was at
sh ort out the 1 f..LF capacitor and thi s is, no byist ki t, and ge t th at into prod uction. Th e
on e time located in Derry , New Hampshire.
doubt, the cause fo r th e " o il film" refe rred probability approches 1 that one of th ese
The name of the company was/i s Data Inpu t
to in the last paragraph on page 97. Just steps will meet an un fo resee n delay of at
Devices Inc.
imagine th e surge current that flows when a least 90 days, such as the capaci tor shortage
They built a TV typewriter terminal unit
switch is cl osed. Thi s is not good for th e of a fe w yea rs ago.
th at my friend (8800 Altair owner) bought
capacitor and is pos itively damagin g to the Finall y, th e cost of t rul y new ite ms (4 K
at a hamfest.
switch. RAM s, not che aper floppi es) is far more
We are hoping to get schematics from
th an the hobbyist can afford. 1 K RAMs
either the company (if it still ex ists) or fro m
Webb Simmons cost a da rn sight more in thousand quantity
a prime consumer of the unit if we can find
1559 Alcal a PI five yea rs ago th an we are curren tl y pay in g
th at out.
San Diego CA 92111 for one. I wor ked wi th 93410s (256 bits,
Any leads will be much apprecia ted.
50 nsec ) wh en th ey were $20 api ece in
Well, maybe. A capacitor of 7 f..LF, hundreds, and they're now $1.95 in onesies.
T om McMurtrey
charged to 5 vails, holds Q = C * As thi s happen s to 4 Ks we 'll start see ing
WA4FYN
V = 5 * 7a ** - 6 coulombs of charge. If the the m.
244 Roosevelt Av
contact closure produces a spark, which can Anyway, co ngratul at ions on a worthwhil e
Florence AL 35630
be de tected on an AM radio, then it is a sa fe and co ntinu all y improv ing magaz in e.
Can any readers help here? bet to say that the con tact event takes place Frank Richards
in from 7a to 700 microseconds (in order 414 Bradford Way
A QUESTION OF COMPATIBILITY for significant harmonics to be de tected in Norristown PA 19401
the 500 KC to 7500 KC AM radio band).
Is it possible to su ccessfully use the Altair Th us 5 microcoulombs are being discharged AUTHORS, TAKE NOTE
16 K stati c RAM (215 ns) in th e IMSAI at an average rate of 0.5 ampere in the 7a
8080 in li eu of th e IMSAI 4 K RAM and still microsecond case, 50 milliamperes in the Ever sin ce BYTE # 1, I've bee n wa iting
obtain the a) low power, b) memory (1 K 700 microsecond case. Peak values might be fo r more conceptu al articl es like " Write
bl ocks) write protect, c) power fail mem ory considerably higher, possibly pitting the Your Own Assembl er." How about so me
save benefits? con toe 15. This off the cuff analysis does not more arti cles on . ..
How about th e MIKRA-D 16 K RAM in take in to account the effect of the resistance • Rand o m number generators, and th e
the IMSAI 8080? in wires and capacitors, and is conditional on testin g and demonstrati on of ra nd o m-
I am seeking wor kabl e solu tions to co n- these contact conditions being able to ness in vari ous rand om numb er ge nera-
figuring a 64 K processing with out usin g up generate measurable RF fro m a spark ing ti on sch emes.
(16 of 22) all the avail abl e slots while still contact. • Executi ve softwa re stru ctures, what
getting th e advantages offered by th e proces- kind s ex ist, advantages and di sadvan-
sor manufac tures on their sm all er memory KUDOS , GRAPHICS , STATE OF THE ART tages of vari ous meth ods, etc.
boards. • Human enginee rin g fac tors and
Thi s letter of min e is in response to pointers co ncerning co mputer peri-
A B Cl ark several items in your Jul y lette rs column pheral pl ace ment, pane l and console
15425 SW 88th Av (pages 90-94/: des ign, etc.
Miami FL 33157 1. I would also recommend J ames El ec-
tro nics (ICs). Deli very is usua ll y less than a James F Gen try
Has anyone in the B YTE readership tried week.
this particular combination o f modules? We 2. With rega rd to the graphi cs di spl ay NEEDED : USED COMPUTER INFO
have no data with which to give an answer to circuits:
this question. a. For the circuit you asked for I would I am a ch arter subscriber to BYT E. I have
reco mm end that co nsid eratio n be enj oyed every issue fro m # 1 to da te. Your
NEED AN ACCURATE HP-45 TIMER ? give n to maki ng it 256 X 5 '12, all owing publication has ex panded grea tl y my know l-
it to simul ate a standard 16 X 64 edge of so ft ware. Mos tl y I have learned that
I have long been interested in th e timing character te rmin al or disp lay modul e. I have mu ch to learn.
capabilities of the HP-45 and have watc hed b. An y su ch circui t would not be in ex- Like eve ryone who has bee n bitten by th e
for info rmation on it. Last month EDN pensive. It is not clear to me wheth er computer bu g, I wanted very mu ch to have a
published how to add th e crysta l to make an you are aski ng for a plug-i n modul e, or sys tem to pl ay with. I had alm os t decid ed to
accura te timebase , and sa id that HP was a stand alone dev ice to co mmuni ca te embark on the purchase and asse mbl y of
se lling crys tals for $14 pill S $1 for shipping. through an 10 por t. Mr Hyde defi- either a 6800, or an 8080 sys tem kit (w ith
Up on contac ting HP I fo und th ey have nitely wan ts a stand alo ne dev ice. I faint ech os and moa ns from th e wife), wh en
them , but yo u have to know so mebody. doubt that a mod ul e wou ld be not ice- I chanced upon t he purchase of a full bl own
After so me resea rch and a few long dista nce ab ly cheaper th an bu yi ng a Cromemco 16 bit co mputer through a loca l government
ph one call s I was abl e to make so me Dazz ler (TM) . Th e savi ngs du e to surplus outl et. Th e onl y probl em with this
arrangements to obta in a suppl y of crystals givi ng up co lor woul d be eas il y offse t was th at some of the in te rco nnec t cabl es

70
we re mi ssing and there was NO to Mr Legge tt in his pursuit at a personal
Computer
INFORMATION.
The unit I have is a DATA 620 system,
system. Peripherals
VA COMPUTERS NEEDED
housed in two 19 inch wide, 6 foot tall
racks. It cons ists of a CPU, two power
have rece ntl y become aware of the
available from
su pplies, a bootstrap loader pa nel, tape 10
and reader (used to load the progra m, I
world of persona l co mputing and am an-
xious to become part of it. Like many
PolyMorphic
beli eve), a general purpose 10 (purpose
unknown), and two core memory units
others, however, I a m not prepared to lay
out the money for a microp rocessor, 10
Systems
(organized as 2048 words of 16 bits each
devi ce, memory, perm anent sto rage capa-
unit, 4 K total CORE).
bi lity, etc . If th ere were microco mputer kits,
This unit was in use at the Manned as th ere are te lev ision kits, wh ich were part
Sp acecraft Center in Houston (use un- of a Veterans Admini stration approved cor-
known). I bel ieve it was in use c irca 1961. It respon den ce course, th e door wou ld be open
was probably bui lt around th a t time because for thousands more. Could yo u put me in
it uses all discrete logic, no integ rated tou ch with anyo ne hav ing such a course or
circuits. It uses - 10 volt load so urce, +6 volt spread the wo rd to the mi croco mputer kit
logic bias. The machine was made by a industry about this seemingl y untapped,
company ca ll ed Data Machin es I nc, Newport eager pool o f potential customers? Than x .
Beach CA. This company is/was a subs idi ary
of a company called Decision Contro ls In c Steve Packard
(address unknown). As you can see I have 44 S Greenfield Av
more questions than data. Alth o ugh a Hampton, VA 23666
chance investment, I thought it a good buy.
I t is my deep hope that yo u or one of IBM SELECTRIC 10
your readers might be ab le to supp ly me
wi th some information . I have wr itten to Th e lette r from Dr J ames Lang in the
Newport Be ach c/o th e postmaster, but no August BYTE o n t he desirabi li ty of using
such company is in existence out there, and the IBM typewriter for a conso le dev ice hit The Video Terminal Interface circuit
no forwarding address. Any help yo u can clo se to ho me - aft er I design the interface card generates 16 lines of 32 or 64
give me in this matter would be greatly for this Selectric 735 I'm typing on, that's characters (depending on option) on a
apprec iated. what I will have. Pl ease note - this isn't just standard video monitor or slightly
any o ld Selectric, but the one with all the modified TV set. Characters are stored
Godfrey C Leggett solenoids and switches already under it. in a 1/ 2 or 1K RAM on the video board.
185 Marceline Th ese mac hin es are now ava il ab le on the
Beaumont TX 77707
Display capability includes graphics and
text. Text includes all keyboard
We publish this letter in the hope that Continued on page 75 characters including upper and lower
some reader will provide information helpful case, in a clear , highly readable 7 X 9 dot
matrix font. Graphics characters are
made up of 2 x 3 grid in each character
THE BEST IS NOW#I* position, allowing for display of a 48 by
up to 128 contiguous grid on a TV
MFE's 250B Digital Tape Transport screen. The entire screen may be
updated in 20 msec. The Video Terminal
Offers a 32000BPS Data Transfer Rate Interface circuit card also includes an 8
ANSI / ECMA bit parallel keyboard input port, allowing
COMPATI BLE the board to function as the complete
computer interface.
The Video Terminal Interface includes
standard software , allowing scroll and
page modes, insert/delete, and full
cursor control. Literature covers kit-
building, testing, trouble-shooting, and
software.
The PolyMorphic POLY VTI is the onl~1
"Altair-compatible" video terminal
interface with keyboard input port and
OPTIONAL full graphics.
8 BIT PARALLEL
Prices: 32 character line kit - $185
I/ O INTERFACE 64 character line kit - $210
• '15, 000 Hr. MTB F • 1 Year warranty. Two moving par ts Assembled $280
• Reel to ree l • Constant tape tens ion a nd co nsta nt tape Other peripherals available from
spee d - servo controlled. ±5 VDC operation. Guaranteed PolyMorphic Systems includes an 8K
casse tte inte rchangeab ility • Up to 800 BPI. Read after RAM board, a versitile prototyping
write heads • Bi-directional read/write ope ra tion • S ize: board ("The Ideaboard"), and an Analog
4.39 " X 5.46" X 2.42 " • A few $52 5, a hundred $ 325 • Interface.
Call or wr ite Jim Saret
All prices and specifications subject to change without
*Recent survey among leading buyers l1amed M FE number 7. notice. Prices are USA only. California resident s add
Source on request; Over 75, 000 in the field. 6% sales tax. Prepaid orders shipped postpaid .
BankAmericard and Master Charge accepted.

II~ ~ • #jI #1111 ~:~:::~::;:i;,"

. . TWX 710·366 · 1887
PolyMorphic
Systems
lI4FE CORFC>R.A.TION TEL EX 94 -7 477
737 S. Kellogg Avenue, Goleta, Ca . 93017
(805) 967-2351
71
The Irst
computer.
As you thumb through this maga- It's a handsome terminal or
zine, you'll see a lot of ads for small computer that will even look good in your
computers. For $600 you can find a pretty living room or office. Small systems start
good box with a power supply, four slot at just $475.
mother board, CPU module, and all the Full expansion capability
expected lights and switches. The Sol~20 system can be tailored
But you know what? It won't work . to your appl ications usi ng the complete
That's because in order to make the line of peripheral products from Processor
computer go you have to buy memory- Technology. These include the video mon-
normally both read-write (RAM) and read- itor, audio cassette and digital tape sys-
only (PROM), interfaces to the outside tems, dual floppy disc system, memories,
world (parallel, serial, and cassette), and interfaces ... plus all other peripherals
keyboard, video display module, and compatible with the S-100 bus.
software. The Sol-20 greatly simplifies the
Add this all up and it's going to cost computer-buying process . It's a splendid
you at least $1,400 for a complete system. package that wi II excite both present and
Got the picture?
prospective computer owners.
Now I isten to this . The remarkable
Our brochure tells a ll . Write for
new Sol-20 Termi nal Computer wi II give it today.
you all of the above ... pi us more! ... as Processor Technology, 6200 Hollis
standard equipment for just $995, in kit Street, Emeryvi lie, CA 94608.
form. This is because the Sol-20-like no (415) 652-8080 .
other small computer-was designed
from the ground up to be complete .
Here 's what the Sol-20 includes as
standard equipment:
• 8080 microprocessor.
• Video display circuitry. -
..... ...
• 1024 words of static, low-power RAM .
• 512 words of preprogrammed PROM.
• Custom 85-key solid-state keyboard.
• Audio cassette tape interface.
The --. I
• Both parallel and serial interfaces and
connectors .
501-20 expandable
• Power supply.
• A beautiful case with solid walnut sides.
system.
• Software that includes a preprogrammed
PROM personal ity module and a cas-
sette with BASIC-5 language pi us two
sophisticated computer video games .
• Full expansion capability with all S-lOO
bus (Altair/IMSAI/PTC bus) products .
Processor Technology
HARDWARE AND SOFTWARE
Now available from the following dealers
California New York
Applied Computer Audio Design
Technology Electronics
2465 Fourth Street 487 Broadway, Ste. 512
Berkeley, CA 94610 New York, NY 10013
The Byte Shop The Computer Corner
1514 University Ave . 200 Hamilton Ave .
Berkeley, CA 94703 White Plains , NY 10601
The Byte Shop The Computer Mart
2559 South Bascom Ave . of Long Island , Inc.
Campbell , CA 95008 2072 Front Street
The Byte Shop East Meadow, L.I. ,
2227 EI Camino Real NY 11554
Palo Alto, CA 94306 The Computer Mart
The Byte Shop of New York, Inc.
509 Francisco Blvd . 314 Fifth Ave .
New York, NY 10001
San Rafael, CA 94901
The Byte Shop Synchro Sound
2989 North Main St. Enterprises
Walnut Creek , CA 94596 193-25 Jamaica Ave .
Hollis , NY 11423
The Computer Store
of San Francisco Oregon
1093 Mission Street The Rea I Oregon
San Francisco, CA Computer Co .
205 West 10th Ave .
Florida Eugene, OR 97401
Microcomputer
Systems Inc. Rhode Island
144 So. Dale Mabry Hy. Computer Power, Inc.
Tampa, FL 33609 M24 Airport Mall
1800 Post Road
Illinois Warwick, RI 02886
The Chicago
Computer Store Washington
517 Talcott Road The Retail
Park Ridge, IL 60068 Computer Store
itty bitty 410 N .E. 72nd
machine co., inc. Seattle, WA 98115
1316 Chicago Ave .
Evanston, IL 60201 Wisconsin
The Mi Iwaukee
Indiana Com puter Store
The Data Doma i n 6916 West North Ave.
111 South College Ave . Milwaukee, WI 53213
Bloomington , IN 47401

New Jersey
Hoboken Computer
Works
56 Second St. Processor Technology Corp. dealerships are available
Hoboken, NJ 07030 only to qualified retail computer firms.
Continued from page 71 All-new Phi-Deck:
used market for prices ranging from $500 to
$1000, depending on model and condition. precision remote controlled
Thi s machine cos t $1 K, as it was a new
machine bought from one of the used mini cassette transports starting at
houses. I am working on an in terface to
connect thi s gadget to my IMSAI 8080. under $1001
This interface will be comp at ibl e with Featuring :
mos t 8080 software ; that is, the cod e will be Re-engineered precision parts
ASCII·7, with port selection and flag bits New cast frames
jumper-se lectabl e. I also intend to make the 4 motor reliability
interface co mpatibl e with most, if not all, of Remotely controlled
the available opti ons f or the 735 and 73 1. Precise, fast head
(Th e 731 is the narro w version o f the 735, engage/disengage
Quick braking
with an 11 inch writing line in stead of 15
Various speed ranges
inches.) I have heard th at the 735 has been
repl aced in the I BM lineup by something else Ele ctronic packages for control or read /write
- this may be th e reason they are showing For application In : 6. Data duplicating
up in the used computer shops. Whatever the 1. Micro processing 7. Security/automatic warning
reason, it 's nice to be able to get good 2. Data systems
machines at reasonabl e prices. reco rd i ng/Iogg i nglstorage 8. Test applications
3. Programming 9 . Audio visual/education

1IIJ11lfpIeI• --- --
Philip M Spray 4. Instrumentation 10. Hi-Fi

----
3006 N E 26th 5. Industrial Control 11 . Others
Amarillo TX 79107
Avoid mechanical kluges - buy one with
the actuators built in.
A 0;';';0" of The Eco"omy Co I
ARTICLES NEEDED: GETTING SENSOR I 1901 North Walnut P.O . Box 25308 UU
DATA INTO COMPUTERS

I
Oklahoma City, Oklahoma 73125 (405) 521-9000
D I am interested in application no.
D Have Representative call D Send application notes
I
have reall y enj oyed BYTE, espec iall y
art icles such as the Sud ing and Lerse th
Name Title
co ntributi ons in th e Jul y issue, I wonder if
you will be doin g so me articl es on connec- I Company Name
Address ______________________________________ I
I
---------
ti on to th e anal og world. This see ms to be an City ___ __ _ _ State ___________ Zip _____
important regi on that has been shortchanged
in your publicat ion.
I would li ke to see transducer data such
I Phone Number _________________________________

as th ermocoupl es, th ermi sters, and RTD s for

tem perature measurements; strain gauge data
fo r stress, pressure, etc ; opti ca l and /o r
magne tic transducers for vel ocity, etc. I
wo uld also be interes ted in ex pl anati ons
about signal co nditi onin g (bridges, chann el (tKENTUCKY FRIED
CO MPUTERS 0J g
ampli fiers, ze ro set and scaling ampl ifi ers)' A
to D and D t o A techniques and meth ods

~ ~
(such as ramp DAC, successive approx ima-
ti on, an d trac king A to Ds). For a micro, or
any oth er co mputer, to " feel " wh at is going
on in the ph ysica l wo rld, these se nsors that A new retail computer store in Berkeley, California.
co ll ect igniti on pul ses, temperatures, load We sell and service small computers for personal,
pressure data, etc, are ve ry important. educational, and business use, both in kit and
C Southard
assembled form . Many items are at substantial
discounts from manufacturer's list prices . Special
2519 Meadowbrook Dr SE
prices on complete systems . We can help you " put
Cedar Rapids I A 52403 it all together"

TIMMMBBERRR! "IMSAI-Computers, memory, interfaces & peripherals

Processor Technology-Memory, interfaces & software
Encl osed you will find my chec k and
Lear Seigler-ADM3 Terminal kit .
"Polymorphic Systems-Computers, memory & interfaces
sub sc ripti on to BYTE. I've onl y bee n abl e to "Cromemco-TV Dazzler, Bytesaverand A/D-D/A
fin d a few co pi es in thi s area and I found "Apple-Apple-l com puter
eac h of th em ve ry interes ting and infor- "Morrow's Micro Stuff-Cassette interface
mative. Hav in g just go tten our Al ta ir 8800 "Oliver Audio Engineering-Paper tape reader
up n runn ing I th ought you and your readers
might be interested in hearing abou t its "Starred items available by mail order at 10%
uni que appl ication. Presentl y, we are usin g
discount from manufacturer's current list prices .
For prompt delivery, send money order or cashiers
an 8800 at thi s Lumber Mill to monitor our
check plus 2% shipping & handling. Personal
da il y prod ucti on. We have a lumber sor tin g checks require 3 weeks processing. Calif. res , add
machin e that in co rpo rates CMOS tec hn ology sales tax. Minimum order $80.00.
in its co ntrol sys tem. Through th e use of
limi t switches the mac hin e measures eve ry KENTUCKY FRIED COMPUTERS
2465 FOURTH STREET
board as i t sorts it co min g out of the
BERKELEY, CA 94710
sawmil l. I t displ ays the measurement data on
a se t of seven segment LED s bu ilt into th e TELEPHONE: (415) 549-0858
contro l panel. Th at is where we tapped in
our inter face, designed for us by Warren
A COMPUTER IN EVERY POT

75
Stardup, a partner-technician with Micro- of us do not have access to counters or Martin Buchanan's Video Disk article and
Computer Systems Inc, which is based in oscillators. Crystals and common chips are Burt Hashizume 's writeup on the lilog l80
Tampa FL cheap_ were also very interesting. The l80 will most
The interface converts the TTL at the If a 1 MHz crystal oscillator is divided by certainly become the most popul ar micro as
display to serial and relays the data via 32, the result is 31250 Hz. If this is sent to a soon as the price drops to the sa me magn i-
20 mA loop back to the office where the divide by 14, and a divide by 10 chain, then tude of power as the 8080 and 6800_ I really
computer is located _ Currently, we are using the results are 3125 and 2232 Hz. Switch like the maskable and unmaskab le interrupts
a video display with data in memory being between the two with an inverter driven by and arithmetic shifts features of the 6800
dumped on cassette every hour, in case of the data, gate it into an integrator, and one and l80. Does anyone know an easy way to
power failure and 1055 of memory _ A hard gets the triangular wave to drive the tape do an arithmetic shift right usin g the 8080?
copy printer is on order. In the future I plan head. This should eliminate stability prob- But lilog has outdone themselves with the
to scan the logs just before they are cut, lems in the two frequencies and should still bit addressing, block transfer (flush instruc-
compute that versus what comes out at the be within the telephone line frequencies for tion) and search instructions. The mode 2
sorter, thereby giving me a readout of the acoustic couplers for phon e transmission. interrupt is also the way I prefer to do
recovery I get out of each log_ Thought this Man y of us would like to be able to use vectored interrupts, but there are also two
might be of interest to you _ Keep up the cheap cassette recorders if possible_ Suding other ways (modes) if you are fussy .
good work_ Your magazine is refreshing! implies that his filters can be tuned over at John Baird's comments on the informa-
least one octave, and maybe two . If this is tion revolution are beautiful. We all know
Tommy Staten
true, R25 and R26 should be reduced in that BYTE can do what no technical trade
HC Hodges Lumber Co journal can do: Convey practical, down to
value and padded with resistors_
Panama City FL 32401 earth, State of the Art, easy to understand
However, if considerable variation is pos-
sible in frequency, and a long period of each ideas. The techn ical journal s have mostly
THE EMULATION BLUES
tone is put on the tape before the program, become a place for doctorate fellows to
read with interest Don Keek's letter in say 30 seconds each, and a voltmeter were shelter a highly technical snow job just to
the August issue of BYTE concerning the connected to IC37 pin 7, then the filters meet their degree requirements. Decipher
emulation of a PDP-8 instruction set on one could be tuned (max volts out) to the and remove the high level math and the guy
of the popular microcom puters. As the frequencies actually present, and the only usually has littl e informati on to pass on.
author of several emulation programs for requirement on the cassette is that the speed BYTE is the source of innovative design
various computers, I feel obliged to com- be within plus or minus five percent for the ideas (hardware and most certainly
ment on my experiences. I have written two time the program is running. software).
emulators for the PDP-8, one implemented I regret that I do not have the equipment I was a little upset at Dr Suding 's "Why
on the Control Data 6400, a 60 bit scientific to try this syste m, but I am willing to discuss Wait ? Build a Fast Cassette Interface" artic le
computer, the other on the PDP-8 itself. The it with anyone. in the July issue. Hi s artic le would lead you
self emulation has value in a trace-type to believe that frequency sh ift keying (FSK)
debugger for programs and periph eral inter- Cecil H Royce is the only way to fly . Of course any articl e
faces. The CDC 6400 implemented emulator 255 S Marion written by an author writing about a pro-
was used to teach minicomputer program- Oak Park IL 60302 duct he is trying to sell is usually a little
ming techniques to a large number of stu- biased . Dr Suding is obviously an analog man
dents in a batch environment. The point about 3 725 Hz being com- with his filters and tune up notes . Tweek
As Don mentioned in his letter, memory patible with the phone network may be this . .. Tweek that. Sure Manchester em-
and execution time are definite bottlenecks debatable; would any telephone engineers ploys " harmonically related frequencies,"
in emulating one machine on another, parti- care to elaborate? There is a standard set of and frequency discrimin ation techniques just
cularly when the characteristics of the two modem frequencies available, in integrated won't hack it. He has one good point:
machines are different. I would suggest that circuits yet. "Imagine reading 300 baud for 15 minutes
a PDP-8 emulator program written on an 8 A point about standards which should be to discover a noise pulse had des troyed data,
bit micro would be hard put to achieve repeated: The way to approach the subjec tis requiring re-recording." This problem exists
average execution times of less than 20 times to document what is being done by manu- no matte r what recording technique is used .
the execution time on the PDP-8 itself. facturers, with discussions about the virtues The best solution is to use short data
Memory requirements would be about 10 K (or faults) of the systems. This way, the user records; say 64 bytes (also a good format for
bytes for emulation of a 4 K PDP-8. (and other manufacturers) are kepI aware of listin g). Th en if you r cassette has backspace
The higher level langu ages supported on the state of the art as practiced in manufac- capability you si mply back up one record
4 K . PDP-8s are almost all interpreters turable systems. So far, there are two tape and try again instead of a complete rewind.
(FOCAL, BASIC, and 4 K FORTRAN for interface definitions documented in BYTE Using character, record and fil e gaps is a
sure). The further degradation of an inter- for audio use; more will come. worth while consideration for a well man-
pretive language by at least a factor of 20 aged file system. Try to keep th e record size
would be quite noticeable, if not annoying. fixed to whatever corresponds to your single
{Total degradation: 400 times slower.! SOME THOUGHTS ON MISCELLANY
AND TAPE MODULATIONS line li st dev ice, at least the source state-
Quite a few PDP-8 programmers have ments. A fil e is a collection of record s, either
made use of "programmed delays"; that is, a program or subroutin e.
looping a specified number of times to I just finished reading the August issue of
BYTE pretty much cove r to cover and as Back to FSK versus PSK: First of all
achieve a specific time delay, or to deter-
usual found it interesting. I wanted to write Manchester is really phase shift keying (PSK)
mine whether a peripheral has stopped
last month but didn't get around to it and I using squ are waves instead of sinusoids. Both
sending data. Such loops will obviously not
have a few tid Bits (BYTES) of information FSK and PSK require an extra start bit or
emulate faithfully.
and complaints to throw out. sync bit equa l to a one. Even using th e
I recommend that anyone interested in
One minor bug in BYTE is I wish you Suding FSK there is no'physical way to go
writing an emulator acquire the CPU
guys would put the issue date at the bottom from DC (no flux changes at the start of a
diagnostic programs for the machine being
of each page. It makes it rather hard to cassette record) to a 2975 Hz signal , a 0
emulated. This will be an invaluable aid to
reference some of the older artic les that I with out first going through 2125 Hz, a 1. Dr
debugging and benchmarking_
Xeroxed from a fri end's earlier issues. Suding needs to review his Fourier trans-
R A Schottland I thoroughly enjoyed "Jack and the forms if he believes that on ly 2125 and 2975
7040 N Sheridan Rd Machine Jive" by Bob Grappel. It's been a Hz freque ncies ex ist in the FSK waveforms.
Chicago I L 60626 while and I honestly forgot how hashing The PSK (M ancheste r or simil ar) method
works. It was a very interesting and infor- requires the first bit sent to be defined
DIVIDE AND CONQUER (INSTABILITY) mative refresher course. I am presently arbitrarily as a 1. From thereafter one
giving some thought to a "general purpose definition of Manch es ter may be a zero
"Why Wait?" by Suding {july 7976 assembler," one that can be used to assemble phase shi ft meaning no change in th e state of
BYTE, page 46! is very interestin g. Th e code for more than one micro-widget simply the data (ie: a 11) and a 180 degree phase
ratio of his two frequencies is 1 to 1.4. Many by changing the lookup tables. change in the signal mea ns comp lement the

76
 data state lie: 10). Another definition is a domain. They are avai lable to anyone -
low to high transition in the center of a bit including hobbyists - at cost. These pro-
cell is a 1 and a high to low trans ition at the grams include all of the common computer
center of a bit cell is a O. In any case the languages. They obey the instructions of
Manchester code consists of two pulse most terminals. OLDE ENGLISHE
widths: full bit cell and half a bit cell width. There is no need to reinvent the wheel -
A digital demodulator needs then to decrimi- again, and aga in, and aga in. I have been on a crusade over the past
nate a 1/2 bit cell pulse from a 1 bit cell The above programs may be readily trans- few years, trying to discover the true origin
wide pulse. This is usually done with one or lated into 8080, 6800, F-8 6502 micropro- of the word "byte," but my efforts have
more delay elements (one shot or del ay line) cessor instructions. There are no restrictions been unsuccessful. I have begun to think
set at a 3/4 bit cell reference point. The on revising these programs. Th ere are no that the origin is lost, but I have decided on
Manchester or similar codes potentially have restrictions on distributing them. They are in one last attempt.
a faster data rate than FSK. the public domain. Since the name of your magazine happens
For example, say the upper recording Why don't you do yourself, your to be the very same word that has been the
limit on a cassette was 2 kHz. The Man- customers, your subscribers, and thousands source of my frustration, I am hoping that
chester data would be recorded at a of others a grand favor, and write for you can shine some light on the origin of
1000 bits per second rate. The two pulse information from this small word. I have looked in just about
widths of 1 msec (half bit cell) and 2 msec Documents Office every textbook that I can get my hands on.
(full bit cell) would be involved. One bit cell Kiewit Computation Center If you can provide some relief to my
only requires 1/2-1 kHz cycle or 1-2 kHz Dartmouth College plight, it would be most appreciated. Thank
cycle per bit cell. The FSK technique using Hanover NH 03755 you for your trouble.
filters I doubt seriously would be able to Edward L T ottle Thomas P Bishop
respond to a 1-2 kHz cycle pulse. It would PL/C Project Manager
2993 Yorkway
certainly require a bunch of 2 kHz cycles Baltimore MD 21222 Department of Computer Science
(the modulating frequency is obviously got Cornell University
to be less than the carrier). Even if it could Ithaca NY 14853
detect a 2 kHz signal in 4 cycles, say, then HOW TO WIN AN ELECTION
Manchester beats the FSK 4 to 1 in re- I first ran across an etymology of the
cording density (speed). As a professional software engineer (a word BYTE in a book I read on the IBM
Also since there is always at least one flux fancy term for a programmer) , I receive a "Stretch" computer borrowed from an asso-
change per bit cell using Manchester or great many computer related publications ciate of mine at Intermetrics Inc, where I
similar self clocking code, the demodulator each month. I am six months behind in worked prior to founding BYTE. In that
can correct for variations in tape speed by reading Communications of the ACM, two book, which was published in the early 60s,
adjusting its 3/4 cell reference either using a issues behind of Computing Surveys, four a research precursor of the IBM/360 series
phase locked loop (PPL) (see "Improved back of Computer Design ; and I don't even was being described. The "Stretch" com-
Cassette Interface Circuit" by Hal Mauch, want to think of how far of Scientific puter (if I remember correctly) hod a large
page 8, April 1976 BYTE) or a program- American. But every month, as soon as it bit addressable memory, in which the term
mable counter or even a software tracking appears in the mailbox, BYTE gets read byte was an arbitrarily coined word used to
routine. from cover to cover. reference an arbitrary bit string field of
A software routine could count the num- In the free market, there is one sure way length "n". The term at that time was meant
ber of elapsed clocks since the last flux to show one's apprec iation for a product. as a generalized concept of a bit string
change (phase detector) and decide if it was Enclosed is my renewal for three more years subfield. When the 360 come out, all that
a 1/2 cell or full cell change. It could take of BYTE. Keep up the good work. changed, since after System/360, almost all
this number, subtract it from what it was published literature references 8 bit bytes.
Howard L Turetzky
expecting for a 1/2 or full cell clock count, Perhaps a reader can supply a more defin-
HYDRA
then average the error over previous samples itive answer to the question of the term
1575 Ivanhoe St
(low pass filter) and make a correction BYTE's origin, and some of the history of
Denver CO 80220
(prediction actually) to what the next 3/4 the early "supercomputer" work following
cell reference should be. The routine would PS - This letter was typed on an IBM the "second generation" transistorized com-
be realizing what is called a sampled phase Selectric 10 writer driven by an Altair 8800, puters of the late 1950s and early
locked loop. The only read back hardware so blame all the typos on the computer. 1960s . ... CH
need only be a limiter similar to Dr Suding's.
The rest could be software. If a data
transmission is going on, the micro is prob-
ably not doing anything but waiting around FLEXOWRITER FLEXIBILITY
for the character to shift out anyway .

Frank Bennett 4891 SOnGBIRd DR.

COLumBUS, dHIO 43229
Hughes Aircraft Co 31 JULY 1976
Displays Lab
Fullerton CA 92634 DEaR SIRS,
One way around the tape interface
problem is the obvious one, a point raised in I SEE a numBER OF compLaInTS aBOUT THE LaCK OF REasonaBLE
your letter which we emphasize here: With PRICEd Id dEVICES avaILaBLE WHICH WILL pRodUCE HaRd COPY.
the proper general purpose signal condi- THIS LETTER IS BEInG TYpEd on a FRIdEn FLEXWRITER I pURCHaSEd
tioning hardware to convert AC coupled FOR $200 US Ed. THERE aRE many avaILaBLE FOR LESS. As YOU
can SEE IT Has an aTTRaCTIVE TYp FaCE' an BOTH UPPER and
signals into TTL digital levels and vice versa, LOWER caSE" IT Ha s a papER TapE punCH and REadER., BUT a VERY
nearly any modulation method can be gener- pOOR TYpIST. IT Runs aBOUT 10 cps. ALTHOUGH IT IS nOT connECTER
ated and decoded using simple algorithms. TO a comDUTER aT THE DRESEnT IT Has connECTIons FOR daTa InpUT.
Several computers currently being marketed I( RaTHER my SEC) uSES IT FOR a LOT Or REp LETTER WRITInG.
use such generalized hardware backed up by I am SURE somE o nE COULd WORK OUT THE pROBLEms or connECTInG IT up.
software in PROM monitors. These include THE paO ER Ta p E IS a SEVEn TRaCK TapE.
the new Apple computer, BABY by STM
Systems, etc.

~~F~
SOFTWARE

People wa nt softwa re. There are about

1,000 co mpu ter programs in the public Sounds like an excellent hard copy deal. Lawson F. PIERCE
•
77
 Make Your
Next Peripheral
a Real Eye Opener

Steve C iarc ia Some history is in order. About eight

124 Hebron Av years ago, I was at MIT for a conference and
Glastonbury CT 06033 spent some time touring the campus. In the
corner of one room in an otherwise deserted
Photos by Ed Russo computer center was a large, intensely in-
volved and vociferous crowd. Above the
usual crowd noise were heard shouts of
Have you ever gone to a party and been "Shoot your phasers now!", "Watch out for
entertained with some party game which the that meteorite!", and "He's in the space
host introduced to impress his guests and warp!". Because I usually avoid crowds
sa lvage an otherwise boring evening? Ameri- because of something my grandmother once
can life is built upon a succession of gim- said about the corre lation between crowds,
micks. We feel we have to be entertained to fleas, and bubonic plague, I fought off the
exist and cannot just have a good, dull time. urge to investigate further. But, after hear-
An examp le is the success of television as the ing, "His antimatter engines are done - blast
universal babysitter and now all these over ly him out of the sky!", and tumultuous
expensive television games. applause, my curiosity could take no more.
Excuse my "Holier Than Thou" attitude, It took about five minutes of pushing and
but I'm no different than the rest of the shoving to make it through the 15 deep
population, including having one of those crowd to get close enough to see what was
stupid TV games. What I'm trying to lead up go ing on. There were two people sitting in
to is to introduce a microprocessor driven aircraft type chairs holding what appeared to
vector" graph ics display con trol ler wh ich can be small control consoles. They and the
be built for $60 or less. entire crowd were intently watching a 21

78
Figure 7: Raster Scan versus Analog Vec tor Graphics. For a given grid size and a figure co vering a particular area (such as 4 by 4
or 8 by 8), the analog vector graphics method will give a better picture, where better is de fined as a closer approx imation of the
figure desired.

.-
. ~- .I"
. ,,0- 1-..... /'
a. Drawing a circle with a slant line through it is
~
....

". \'
• IDEAL FIGURE I
1 . /" \
t
unrecognizable on a 4 by 4 grid of raster dots, but quite
believable when drawn on a 4 by 4 vector graphics grid. A
.l
"
/
I- .. /" . 7- line drawing of the "ideal" circle with slash overlays the
/

'" 1'.- -r' . " ~ ~ . approximations for reference.

b. Drawing a circle with

a slant line through it is a

· · ;. - r- ..:.. · 1/ · · :--.- 1-- ...: · I'

closer approximation on
an 8 by 8 grid of raster
· #"
· · · · 1\.· X
:/
· /, · · ·, · IX, , splotches, but the 8 by 8
equivalent vector line
./ · · · · ,/
· . ,' · · 7 1\' drawing has a still closer
{ · · · · ./
· ~ f · · · · · \ /
,/
approximation to the

.\\ ·· 1./'· · · · ~'. · · · · / .f

/'
/
~ ~ , )' desired circle and line. A
line drawing of the "ideal"
,/
· · · · .' · · · · ·
/,/
circle with slash overlays
· '" ·...... · .....· .,.· · ",.
· '.x ">, · · !.<· ,,/ · the approximations for
./
· ·
- - = IDEAL
-.-

FIGURE
··· ,/
· -- · · - reference.

· ·, · ,
· · · · · ·
, ,
·· · ·
\ · I · · ·, ·
, ,
· ,
· ·
,
· ·V · · · ,
·
,
· 0
· · 0
T\. o 1/

[\.I 1\11 I'll I'll f\l/ IW

0 0

· · 0 0 0 0
11 ·
0 0 0
· 0 0
IA 1/1\ 1/1\ 1/1\ ~ 11\ 1/1\ l) 0

c. When it comes to detailed graphics, the 0 0

· \· < · '" 1/
· ·
vector method is a real winner. Here is a
· · · 1\' · D- • 1.1' o 0
· · ·
0 0

cartoon figure rendered on a 76 by 76 grid

in both vector and raster scan dot matrix · ··" "'~ L ~ 1/ · ·
\, /
1/
/
· · · · 0

form. The contrast in effective resolution o f · · · ·· 0

· · · 0 0

· , ,
· 1'./· · · · · ·
the two methods is enhanced by the jux ta-
'"'/ 0 0 0 0

position of the two versions in this overlay.

Note that within the same coordinate grid, · ···· · T\. t
the vector graphic version is able to represent
,
·· 0 0
· ~ I- 0 I
some limited alphanumerics, impossible to · 0

··· ·
1,; .... I'.
·
even attempt in the raster graphics version.
· 0
· · 0

")
0

·····
- VECTOR GRAPHICS FIGURE

79
 inch black and white TV screen upon which a confirmed "Space War" freak. I was
there was a scene depicting a star-studded determined to have one of my very own th at
space and two rocket ships. It became I could play until my heart was content.
obvious very soon that they were playing The realization of this dream was, of
"Space War," and the only rules were to course, to be postponed until just recently.
shoot the other guy out of the sky (Do Unto It is now possible for the computer experi-
Others ... J, while not getting wiped out menter to put together a system with capa-
yourself. There were certain limitations on bilities rivaling computers costing many
fuel and armaments which made the game all times more. The LSI microprocessors which
the more interesting. have become increasingly available at modest
I stood and watched this for three hours prices have started a boom in the home
until I jockeyed myself into position to grab computer field with price wars inevitable.
a control console from an exiting player. All The major reason that these small computers
right, you guys, let's play Space War! I have realized so much computer power is
played for what seemed to be an instant on that designers have tailored their designs to
the time continuum; but it was obviously utilize existing hardware which is available
too long in the crowd's opinion because, readily. Consider mass storage, for example.
when some little kid started pulling one of Talk to IBM or any "traditional" computer
my socks down and I let go of the control company about mass storage and your dis-
console to retaliate, I was six deep in the cussion will lead to a $30 K tape drive and
crowd again before I regained control. I did controller with reams of wonderful toler-
eventually get another try, but I was already ances and grandiose specifications. This will
provide an unparalleled mass storage capabil-
ity, but most people would be upset just
considering the electric bill. The alternative
RASTER SCAN GRAPHICS - SUMMARY OF
was, and is, to incorporate the principles
ADVANTAGES AND DISADVANTAGES
that make the "biggies" so good, but make it
Advantages
cheap enough so the average person would
1. No software refresh - computer can load a not go into cardiac arrest over the price.
display once and continue other duties .
American ingenuity had the answer. Develop
2. Fully digital - does not require any analog
conversion or associated "tweeking" of a sophisticated, yet simple modem on a
components. cheap printed circuit board which allows the
3. Requires no special display tube - uses tele- owner to use his kid's cassette tape recorder
vision monitor. to store data. Thus came the invention of
4. Can be color - by using added storage,
color or gray tones can be assigned to each the $100 mass storage system.
element or group of elements. There is a moral to all this. The initi al
5. No limit to total display quantity - since success of the home computer system can, in
storage is provided for all points it is
large part, be directly attributed to inexpen-
irrelevant whether they are shaded or not
and does not affect display refresh time. sive peripherals which utilize readily avail-
6. Inexpensive - in limited forms, raster scan able surplus equipment or home entertain-
uses inexpehsive televisions or monitors. ment devices such as tape recorders and
televisions. The television typewriter, other-
Disadvantages
wise called an alphanumeric CRT display, is
1. Not a pure line display - display is a con- only $150 because it uses an already existing
nection of shaded squares and not line
~egments.
television.
2. Must provide memory for total dis-
'play - for a 256 by 256 point display, 8 K Raster Scan Graphics
bytes of memory must be provided even if
only one element is being displayed. There is an unfortunate lack of sophisti-
3. Must use either an external memory or cated peripheral devices beyond these few,
direct memory access - the composite video and applications using these are limited. The
signal necessary for raster scan requires a
data output rate beyond the capability of Space War game previously mentioned re-
the processor itself. Special controllers must quires a graphics CRT termjnal upon which
be provided to either access standard pro- the players and playing field may be dis-
gram memory directly by DMA or scan an played. The home raster scan television, such
external display buffer which can be peri-
odically changed by the processor to cor-
as that borrowed for an alphanumeric CRT,
respond to changing displays. can be used; but th e display is overly
4. May require fast memory access - in DMA complicated and will appear as a connection
using cycle stealing, memories having access of blocks rather than pure line segments.
speeds of 250 ns or better may be requ ired. There are many raster scan graphics systems
(With a dedicated buffer memory or multi-
port memories, 2 IlS access is typically
now on the market but all exhibit this
required.) "block" phenom enon, which in the simplest
terms is a function of the resolution. A low

80
resolution display will have a limited number ANALOG GRAPHICS - ADVANTAGES
of large blocks and a high resolution display AND DISADVANTAGES
will have a great quantity of small blocks. Advantages
Making various blocks light or dark is what 1. Does not require extensive memory - total
constitutes a picture. Figure 1 illustrates a memory required is whatever is necessary to
circle drawn on a screen with 16 elements store all the beginning and end points of the
line segments to be displayed. Blank areas
(4 by 4) versus one which has 64 (8 by 8) do not require storage.
elements. The lower the resolution of the 2. High resolution and low cost - a simple
display medium, the less recognizable the controller is designed around low cost DACs
display. For true graphics detail necessary in and an analog display does not exhibit
applications such as game boards and pla- "staircase effect" on diagonal lines.
3. Uses available test instrument as display -
yers, high resolution on the order of an inexpensive oscilloscope or other X,Y
256 by 256 is required. This leads to another display may be used as a display medium.,
interesting problem: display storage and 4. Does not require fast memory - any storage
addressing. medium having a byte access time of approx-
imately 100 IlS is adequate. Can use shift
Raster scan graphics is nothing more than registers, delay lines, etc.
a sequential video display of mass memory. 5. Resource conservation - gives the author
The "mass" in mass memory is a function of some reason to use his 8008 system since he
the resolution. If the display has a total of bought an 8080A.
64 elements, 8 bytes (8 bits each) of
Disadvantages
memory are required for storage. If the
display were 64 by 64, there would be 4096 1. Software refresh - the processor must
periodically rewrite data on the screen to
picture elements requiring 512 bytes of keep it from fading. Refresh rate is a
memory. It is important to remember that function of processor speed and the total
the entire 512 bytes is necessary regardless number of line segments in the display.
of the picture being displayed. Within this 2. Uses analog circuitry - all analog circuitry is
subject to drift and to temperature and
display storage, each bit has to have a unique other external influences. These variations
X and Y address: For a 64 bit display X and can be minimized through proper'design and
Y could each be defined with 3 bits; for a construction.
4096 bit display 6 bit X and Y addresses
are necessary.
Most home computers are 8 bit machines
and obviously work most efficiently with The second method which is used most
8 bit manipulations. Taking full advantage of often in the graphics industry is called direct
this and defining 8 bit X and Y display memory access. 8 K of memory is still
addresses results in a very respectable 256 X required for the 64 K element display, but it
by 256 Y display grid containing 65,536 is attached to the computer. It is directly
elements. This corresponds to 8 K 8 bit addressable at all ti mes and not externally
bytes of memory. {See the article by located in the graphics controller, so that
Thomas R Buschbach on page 32 of this when the graphics option is not in use, this
issue for an example of such a design.} 8 K is utilized as any other portion of
Going from the memory to the screen is memory. When using the graphics operation
another problem and requires a special con- this 8 K will contain the bit pattern display
troller to translate the memory into video of the screen and be shared between the
information. Horizontal scanning rate of a processor and the graphics controller. Direct
television is 15.75 kHz wh ich is 63 j.1S. If a memory access means just what it says. The
horizontal line is to be divided up into 256 DMA controller directly addresses and reads
elements, each must be scanned and output memory when the processor is not doing so.
to the TV one every 250 ns. Even if address- In most microprocessors this sharing can be
ing and output were handled 8 bits at a time, done either by suspending the processor
the rate will still be one byte every 2 j.1S. operation with hardware DMA request and
Very few microprocessors are capable of hold logic or by accessing memory on clock
doing this. There are two methods of cycles when the processor is doing some-
acquiring this data. First is to have a thing else. Suspending processor operation is
dedicated 8 K memory in the graphics con- easiest from both a design and component
troller which is synchronously scanned by standpoint but least effective when simul-
the video output generator and asynchro- taneously running large programs. In a raster
nously updated via the output ports of the scan display, the processor would be shut
computer'. This method, though easiest from down and memory read out 30 times a
a design perspective, is the most costly due second to correspond to the non-interlaced
to the extensive memory used only for the update of standard television. The only time
graphics controller. the processor would be allowed to run

81
would be during vertical retrace which is not exist for the home computer enthusiast_
approximately 4 ms out of every 33 ms. Many applications can be more cheaply done
Therefore about 400 instructions {in an with analog. A prime example of this is
8080A} could be run every frame. This is graphics.
quite acceptable for most non-iterative pro- Analog graphics is a method which con-
grams, but it would kill response in inter- verts digital data stored in memory to
active Space War type games which do a fair voltage levels proportional to that value.
amount of number crunching. Modifications Two of these digital to analog converters
to this method can extend processor time would be incorporated to provide two simul-
somewhat but they become involved. DMA taneous outputs which represent physical X
utilizing "stolen" clock cycles or added wait and Y coordinate locations on a display
cycles is the most effective technique since it screen. The display's X and Y full scale
does not significantly reduce processor deflection would be directly proportional to
calculation speed. Not all microprocessors some analog constant times the digital value
are capable of doing this, though; and many in the memory location being accessed. The
more design constraints are involved. An- display medium is an oscilloscope or similar
other method which avoids waiting by the two dimensional proportionally deflected
processor is to use a multiport memory with display.
priority allotted to the processor. This leads As was the case with raster scan graphics,
to some picture breakup during updates but analog graphics has both its advantages and
allows the processor to run at full speed. disadvantages. The most pronounced advan-
Some such form of direct memory access tage is the display method itself. Two bytes
is the much preferred system for high of memory converted to analog X and Y
resolution raster scan graphics but can be positions define the starting point of a line
very expensive when considering the quan- segment and two more set the analog values
tity of memory necessary for display of the end point of that segment. When
storage. triggered by the controller a line will be
drawn between these points. Four bytes
Analog Graphics define the entire line regardless of the length
For those of you that haven't ordered a {within the limits of the screen dimensions
raster scan graphics controller after reading of course}. There is no need to define and
the previous dissertation, I would like to store points along the line, only the begin-
present the other side of the story: analog ning and end point. When using an 8 bit X
graphics. Usually the thought of anything and Y addressing system there are 64 K total
analog associated with a digital computer is locations between which line segments may
abhorrent to the purist. Remember, before be drawn. The path between any two points
there was digital there was analog; and even is direct line and need not coincide with an
though it's hidden, analog's still there. The addressable point location. This results in an
success of digital systems is based upon their extremely high resolution display even
ability to evaluate an action or output a though it is only 256 by 256. This means
value repeatably with no deviation from that in a diagonal line there is absolutely no
previous occasions, given constant input "staircase effect" inherent in a raster scan
data. This is inherent in the machine struc- display. This and relative low cost are the
ture, since it can only exist in either of two chief advantages.
discrete states: 1 or 0, on or off, etc. Analog The major disadvantage of this system is
on the other hand can be influenced by that it requires software I"efresh. When begin-
external conditions such as temperature and ning and end points are sent to the con-
power supply levels, etc, and is repeatable troller a line is drawn - once! It will be seen
only within a more or less closely defined briefly on the screen and quickly fade unless
tolerance band. Industry has been tightening it is refreshed. The computer must do
this tolerance band in recent years to such a whatever it has to do and get back to the
point that analog circuitry becomes too graphics driver program and wl"ite the same
expensive and digital methods are imple- line segment again before it fades. This time
mented. Too often, though, the "band between refreshes is a function of phosphor
wagon syndrome" prevails. Many applica- persistence, a characteristic of the CRT
tions which can be adequately accomplished being used. 25 to 40 ms is usually the
l!sing analog techniques have been converted maximum and if exceeded will result in
to digital. In most cases this unnecessary display flicker. {Storage tubes exist with
conversion to digital can be very costly and longer time constants, but at much higher
requires expensive support equipm,ent. The expense.} The nu mber of lines wh ich can be
tolerance tightening which makes an in- written and refreshed is a function of proces-
dustrial manufacturer use only digital does sor speed. The faster the processor, the

82
sooner it will be able to write a screen, do its IC4 and IC5 are 8 bit digital to analog
own th ing somewhere else, and return to converters. Th eir function is to convert the 8
start writing the screen again. All the dis- bit positi on data into a current which is
plays in this artic le were driven by a slow proporti onal to that value. IC6 and IC12 are
8008 processor (n ot an 8008-1) system and current to voltage converters. The Motorola
abo ut 120 lines could be drawn before any MC 1408-L8 consists of a reference current
flicker was perce ptible. This was using a amplifier, an R-2R ladder, and eight high
worst case programming technique (the one speed current switches. A resistor betwee n a
I'm best at) which I'll explain later. Faster reference voltage and pin 14 is set to
processors would of course increase the produce a reference current of approxi-
number of lines capable of being displayed, mately 2 mAo The R-2R ladder divides the
but would have to have some delay loops in reference amplifier current into binary
the software so as not to overdrive the weighted components which are fed to the
graphics controller. The digital to analog switches. Th e output current from pin 4 will
conversion does take a little time. be proportional to the binary input to the
co nverter. For example, if the binary input
An Analog Graphics Controller were equ ivalent to 128 decimal, then the
output current would be (128/256) *
The circuit for such an analog graphics
2.0 mA which equals 1.0 mAo The current
controller is illustrated in figure 2. Thi s
to voltage conve rter is set to produce - 2.5 V
circuit is based upon a design originally
for a 00 000 000 binary input and +2.5 V
proposed by Hal Chamberlin in the first
for 11 111 111 . Exact ca libratio n procedure
three issues of The Computer Hobbyist.
will be given later.
Modifications and additions have been incor-
porated to allow more ease in calibration. The heart of an analog graph ics con-
The circuit consists of three major sections: troll er is the vector generato r. Th is circu it
digital input latches, digital to analog con- does the actual drawing of the line on the
verters, and vector ge nerators. display. Merely setting a starting location
Since the graphics controller is software and jumping to an end point will not work.
driven, possibly the software side is the The bea m's transiti on between the po ints
easiest starting point. Positioning and draw- would be so fast as to leave only a very weak
ing a line on the display is accomplish ed trace if any at all. A vector generator
through four output commands from the provides a co nsi stent drawing time of ap prox-
processor. The se commands are not some imately 100 /1S , allowin g for a very bright
new processor instructions but rather de- trace.
coded output strobes which transfer 8 bit Actually drawing a line segment is a
position data from the accumulator to the simpl e series of events. First, the processor
controller's input latches ICl to IC3. Th ese outputs sequentially the X and Y starting
four strobe commands are appropriate ly position coordinates with the X-MOVE and
referred to as X-MOVE, V-MOVE, X- V-MOVE co mmands. Th ese values are sto red
STORE, Y-DRAW. In actuality, X-MOVE in IC3 and IC1, respectively, and cause the
and V-MOVE are the two bytes of data digital to analog converters IC5 and IC4
which define the starting location of a lin e to fo llow suit. Within 3/1s, IC6 and IC1 2 have
segment while X-STORE and Y-DRAW is settled out to a voltage representative of
the end point of that lin e segment. There are these coordinates. IC10 and ICll are analog
fo ur separate outputs necessary because we switches which route the raw X and Y
ass ume an 8 bit machine and 16 bits of XY voltages through the vector generator. These
positional data is needed to define a point CMOS switches, equivalent to SPST, are in
on the screen. Obviously, in a 16 bit the off state when their co ntro l terminals are
mach ine, this process could be reduced to at a p~te.nti a l equa l to VDP (- 7.5. V) and on
two output instructions. Extra decoding is when It IS at VSS (+7.5 V). IC19 IS a voltage
often not necessary. Many microprocessor translator which co nverts TTL switching
syste ms lik e the Scelbi series provide extra levels to those necessary for this CMOS
decoding logic on the back pl ane wiring device. An alternate circuit to replace the
whil e not mentioning it. Th e usual clue is to DM8800 is also provided .
check the 10 decoder board in your system In the quiescent state switch es SWl and
and look for an ap propriate decoder chip SW3 are on and switch SW2 is off, as con-
such as a 7442 or 74154. Often only a trolled by signals Tl and T2 . Thi s all ows
couple of output strobes are utili zed on the the output of the vector ge neratol' to be
chip. In the case with the 7442 used in the equa l to the coordi nate position of the
Scelbi, the extra strobes all ow quick unag- beginning of the lin e segment. Th e trace is
gravated hookup to the four necessary for blanked at this time so the dot does not
graph ics. appear on the scree n. Next, X-STORE then

83
 VREF
Y +5.IV
COORDINATE
LATCH Y OAC
RI
ICI IC4 2700
74100 MCI40BL8
2 5
~
07 5 +REF
101 101 AI
~ 06 3 4 6 A2
102 102 Y- CURRENT
5 II 8 7 OUT 4
201 201 A3
8
881T
OUTPUT BUS { 04
03
10
22
202 202
9
19
A4
9 A5
-REF ~
FROM 103 103 R2
PROCESSOR 02 21 20 10 A6 2700
104 104
01 15 18 II A7
DO 16
203 203
17 12
RNG
CNT ~
~ 204 204 A8 m
IG 2G COMP
NOTE :
BUFFERING WILL BE
REOUIREO WHEN USING
~12
~15pF
A TYPICAL PROCE SSOR TCI
OATA BUS -15V
VREF
X X
+5.IV
INPUT COORDINATE
LATCH LATCH X OAC
RI2
IC2 IC3 IC5 2700
74100 74100 MCI408L8
2
.....§ 101 101 5 101 101 5 5 AI +REF ~
3 4 3 102 4 6
102 102 102 A2
~10 201 201 8
9
II
10
201 201 8
9
7
8
A3 OUT
4 X-CURRENT

22
202 202
19 ?2
202 202
19 9
A4 -REF ~
103 103 103 103 A5 RI3
21 20 21 20 10 2700
104 104 104 104 A6
15 18 15 18 II
16
203
204
203
204
17 16
203
204
203
204
17 12
A7
A8
RNG
CNT ~
(;7
IG 2G IG 2G COMP

X-STORE 7404
IC20 L23 112
l..f~_
3 b .4' 2 3 n
-
123 112
-tT 6

15pF
C8
J1. -r' I a
IC21 -15V
X-MOVE n I~ l..f 7437
PROCE SSOR .~ IC20 IC21 .n
IC21 7437
OUTPU T IC20 7404 l..f 7437 J1.
STROB ES Y-MOVE J1. 7404 9
50 6p
~
101 c
-
NOTE:
DATA MUST BE STABLE
Y-ORAW .n 9""

IC~
7404
8 l..f
1 Y- DRAW

DURING HIGH STATE OF

STROBES .
R28
680n
1/2W VREF
+15V,--" +5.IV
~Ol POWER BUS
VOLTAGE
R EFERENCE
GENERATOR
'.4 ,. IN751
5 .IV
400mW
T
+lC18
100I"F
15 VOC

POWER SUPPLY REOUIREMENTS

+5V @ 250mA
+15V @ 100mA
R29
330n -15V @ 100mA
1/2 W
C MOS +15V D- +7. 5V POWER BUS
S WITCH
POWER ... r--~ IN755
02 +lC19
TIOOI"F
15V
S UPPLY

... ~r-- 03
IN755 T
+lC20
100I"F
15V
-15V ~ -7.5V POWER BUS
R30
330n
1/2W
+7.5V

10K

OUTPUT
ALTER NATE CIRCUIT
FOR E ACH DM8800 7404 2N2907
SECTION INPUT
IN914
- 2200
2N2222

- 7.5V

Figure 2: Schematic Diagram of a Vector Graphics Controller. This circuit will produce signals with a range of -2_5 V to +2.5 V
for use in driving a standard XY oscilloscope with bandwidth greater than 700 I?Hz. The power supply wiring of digital

84
VREF
NOTES:
+5,IV
1. Resistors are 1/4 W, ± 5% unless noted
otherwise.
R3 ZERO 2. All variable resistors are trimpots.
5000 AOJ
3. Capacitors are ceramic, 100 V minimum
Y AXIS SLEW CIRCUIT unless noted otherwise.
R4 *Polystyrene or polycarbonate.
4700 SPAN
R6
R5 1000
1800 R9
TI 10K T2
+15V
+15V

R8
10K
6

Y-SLOPE
3 RIO
20K

C5 TI RII
33pF 4700
6 ®YOUTTO
VREF ,), DISPLAY
+5,IV 4 3

RI4 ZERO C6*

5000 ADJ l,OI

X AXIS SLEW CIRCUIT C7

RI5 33pF
4700
SPAN
RI6 RI7
1800 1000 R20
TI 10K
+15V T2
+15V

RI9
6 10K

x- SLOPE
R21
20K

+15V
C9
CI2

t
33pF
33pF
6
X OUT TO
4 3 DISPLAY

+5V +5V

R26
l' C13*
,01
CI4
+5V VECTOR R24 END 1000 33pF
TIMING 10K MATCH
CONTROL ADJ
R23 6 ~ BLANKING
10K R25 TO DISPLAY
+5V 10K
CI5 CI6
4700pF ,01
R22 6 T2
1000

10 3 AI
28

" 2 CLR
ICI6
A2
ICI7
74123 74121
9 10I'SEC 1001' SEC
2A
12 5 B
2Q
R27
1000

;J; CI7
390pF

integrated circuits used in this circuit is summariz ed in table 1. (Analog integrated circuits have their power wiring indicated in
the diagram. These circuits are listed in table 1 but have no power connections indicated.)

85
 Y-DRAW are executed. X-STORE loads the
X coordinate of the endpoint into IC12
where it stays for the moment and does
Table 7,' In tegrated Circuit List. This table nothing. When a Y-DRAW is executed, the
gives each integrated circuit required in whol e unit comes to life. Y-DRAW loads the
figure 2, along with its device type and, in Y endpoint coordinate into IC1 and tra ns-
the case of the CMOS and TTL digital fers the contents of IC2, the X coordinate,
circuits, power wiring pins. into IC3, and both X and Y converters start
to settle toward the endpoint value. Simul-
TTL power CMOS power taneously with this action, switches SW1 and
+5 V GND -7 .5 V +7 .5 V SW3 are turned off by T1, keeping the beam
ICl 74100 24 7
position where it was. After about 10 J.1s,
IC2 74100 24 7 switch SW2 is turned on by T2, the beam is
IC3 74100 24 7 unblan ked and the output of the vecto r
IC4 * MC1408-L8 13 2
IC5 * MC1408 -L8 13 2 generator starts moving toward the endpoint
IC6* LM301A values. Thi s transition or drawing time is
IC7 * LM 30 1A approximately 100 J.1S and is a function of
IC8 * LM 301A
IC9 * LM 301A the endpoint adjustment on IC17 . It shou ld
IC10 CD4016 7 14 be noted th at the movement from the old
ICll CD4016 7 14
IC12 * LM301A
value to the new value is an expone nti al
IC13 * LM 301 A functi on adjusted through the slope con-
IC14 * LM 301A trols, but the lin es between points will be
IC15 * LM301A
IC16 74123 16 8 strai ght since both X and Yare charging in a
IC17 74121 14 7 similar manner, though the velocity (h ence
IC18 7410 14 7 brightness) of the beam does vary a bit from
IC19 DM8800 10 3 7 4
IC20 7404 14 7 beginning to end. At the conclusion of the
IC21 743 7 14 7 draw cycle, the beam is aga in blanked and
* Analog circuit connections are indicated in the controller is ready to draw the next line.
figure 2. {The beam will be positioned wherever it

NOTES ON CALIBRATING THIS volts. Change the input code to 11 111 111
GRAPHICS CONTROLLER (377 octal) and adjust the span pot (R6)
until the output is +2.50 V. Setting an input
Static Calibration
of 00 000 000 (0 octal) should result in
1. With all components except integrated cir- -2.50 V out. The same procedure is used to
cuits inserted a nd mounted, and presuming calibrate IC5 and IC12. (Zero with R14,
th at you have no direct shorts, attach the span adjust is R 17.)
controller to + and -15 V and +5 V and 5. Turn off power. Insert IC16 through IC21 .
turn it on. Temporarily, ground pins 1, 3 and 5 of
2. Using a meter, check to see that the right IC20. Turn power on . Using either a push -
supplV voltages are on the appropriate inte- button or cliplead intermittently ground
grated circuit pins. Check to see that VRef IC20 pin 7 simulating a Y-DRAW strobe. A
is approximatelv 5 to 5.1 V an d that the + scope should be used to determine that
and -7.5 V VDD and VSS supplies are IC16 pulses for about 10 p.s and then
correct. If substituting parts, don't use a triggers IC17 which lasts for abo ut 100 MS .
zener anv higher than 7 .5 V since it could Control lines Tl and T2 should cycle
damage the CD4016s. between +7.5 V and - 7.5 V corresponding
3. Insert only ICl through IC3. Using either to their TTL inputs.
hard wire jumpers, switches or a computer 6. Turn off power. Insert all the rest of the
program to drive the data bus lines BO integrated circuits (be careful of th e CMOS)
through B7, take note that when the bus and temporarily remove IC21. Reapply
inputs are all high, pins 5 through 12 of power and use the method in step 4, but
IC14 a nd IC15 are also high. Grounding all ta ke note that pins 6 on IC9 and IC15 are
data bus inputs should result in low levels equivalent to IC6 and IC12 respectively.
on these pins. It is a good idea to go down Turn off power, reinse rt IC21. This con-
the bus one pin at a time to make very sure cludes static checkout.
that all input lines end at the correct DAC
pins, otherwise the digital to analog conver-
Dynamic Calibration
sion will be incorrect .
4. Turn power off. Insert the DAC IC4 and op 1. Unless you have super fast fingers on
amp IC6. Attach a meter to read the voltage mechanical switches, a computer is neces-
at pin 6 on IC6. Set the bus input switches sary for dynamic checkout (while it is
or prog ra mmed data value to provide a optional in static checkout). It is necessary
binary code of 10 000 000 (200 octal). to write a short program which outputs to
Turn power on and adjust the zero pot (R3) the controller the full sca le coordinates of a
on IC6 until the output at pin 6 reads zero square with two diagonals (see figure 3).

86
was left from the last line segment, so it is to write so me simp le display routines. Any-
possible to reduce software overhead con- one owning a home computer system is
siderab ly on continuous line graphs by just always at a loss to justify it to friends and
issuing a series of new endpoints.) fa mily who continu ally ask what purpose it
Maximum drawing rate can eas ily be serves. By using a littl e psychology and
determined for those who wish to use a realizing that these people identify most
faster processor. Each voltage converter re- often with Mom's apple pie, McDonald's
quires abo ut 3 to 5/.1s to settle out and a and Star Trek, a littl e ingen uity can go a
draw cycle takes 110 /.1s. This means that long way. Graphics goes a long way in
5/.1s at least must be allowed between input impressin g nonbelievers, espe~ i a lly when the
of the beginning and endpoints and 110 /.1S computer is generating a picture of the USS
must lapse before starting the next line Enterprise, shown in photo 1.
segment. With an 8008 such as I used, there Drawing the Enterprise entails a program
is little possibility of driving the contro ll er (see listing 2) which is very similar to that
too fast, but with an 8080A system a delay used for calibration (listing 1) except that
loop may be necessary between segments. the point list is longer so the program is
The next step is to do some cartooning with written to accept variabl e length lists. There
software. al"e many meth ods to program graphics. The
Obviously before we can get too carried easiest from the software point of view, but
away discussing graph ics software you mu st the worst for drawing speed and total
get your co ntroll er calibrated and working. number of lin es, is to treat each line as an
The procedure outlined in "Notes on entity in itself. Four bytes would define the
Calibrating Thi s Graphics Controller" should line segment as in li sting 1 's data table. This
result in the best chance for success. is required wherever it was pl aced on the Figure 3: Vector Graphics
screen, disregarding those displays which Test Pattern. The vector
appear continuous as would be the case of a grap hics generator is
Now How Do I Use It?
square or a triangle. As a specific example, ca librated dynamically
Now that the hardware of vector graphics 12 bytes are required to store the coordi- using a program like the
has been conquered, you should be ready nates of a triangle when the three sides are one in listing 7, to produce
treated as three lin e segments. Only 8 are a 6 segment square with
required if a continuous drawing technique diagonals at the extremes
is incorporated. The problems arise when a of the display grid of 256
This square is all that is necessary to check display is made up of both disjointed and by 256 points. In this fig-
out the remainder of the controller inter- continuous lines. Th e program can be ure, the vectors are identi-
face. (The X, V and blanking outputs of the written to output one list of continuous fied, and octal coordinates
graphics controller have to be connected to
an appropriate display. Any XV oscilloscope of the endpoints are
with a 100 kHz frequency response and a n shown in parentheses.
external horizontal input capability will
suffice. The controller has to be connected
to the output data bus and four decoded
strobe lines.) The software which draws the (000,377) (377,377)
VECTOR NO.3
calibration square is quite simple and con-
sists entirely of outputting a list of co-
ordinates stored in memory. The program of
li st in g 1 was written for an 8008 system but ·
is easily adapted to others.
2. If upon first turning on the display you
V ECTOR NO.6
obtain a perf ect square with the diagonal
meeting in the corners, go have a martini
and relax, you're done (see figure 1c). It is
more likely that the displays will only
vaguely look like a square. If the line
segments are too long or are too short and VECTOR VECTOR
don't meet in the corners, adjust the end NO.4 NO.2
match adjustment, R24, on IC17, until
perimeter segments (disregard the diagonals
at t his point) meet in the corners.
3. Next, fiddle with the slope ad justment pots
(R 10 a nd R21) until the diagonals meet in
the corners. Any problems in acco mplishing
any of this is probably a result of the VECTOR NO.5
following: Frequency response of the op
amps is too low (don't use a nything slower
than a 301 A); the RC time constant of the
slope adjustme nt is in adeq uate; your
CD4016 crapped out; or your program is
outputting incorrect coordinates. (000,000) VECTOR NO. 1 (377,000)

87
 lines and then jump to a li st of separate line
segments. This is the obvious method to
accomp li sh grap hi cs using a slow computer
and lengthy display lists. Some problems
arise when trying to translate such a picture
from one point to another. A way of dealing
with the problem of translation of picture
elements from one location to another was
suggested by Rich ard Lerseth in his artic le,
"A Plot Is Incompl ete Without Characters"
on page 64 of Jul y's BYTE. His technique is
to use picture elements specified as a series
of relative coordinates, to which the X and
Y position coordinates are added at the time
the image is displayed. (His method also
invo lves economizi ng storage by using lin ked
chains, but that is a slightly different issue.)
When using a fast processor such as an
BOBOA or Z-BO, the time required for a
routin e to do simp le B bit additions for X
Photo 7: The author's Sanders 708, a surplus vector graphics display, shown
and Y coordinates should be about the same
portraying the Star Ship Enterprise using data of table 2 and figure 4. The
(order of magnitude, 100 }1s) as the vector
lettering is not included in table 2.
drawing time of the circui t in figure 2. For
those of us who have slower first ge neration
processors, use of separate lin e segme nt li sts
Listing 7: An 8008 Program to Generate the Calibration Pattern. The listing
with abso lute coordi nates calcu lated in ad-
uses original In tel 8008 mnemonics," the data table at the end of the listing
vance may be a requirement if the screen is
contains two bytes of starting coordinate followed by two bytes of ending
to show a complicated picture without
coordinate for each point in the pattern.
Split
Octal
Addr Octal Code Label Op Operand Commentary

001 /000 056 001 ST ART LHI H(TABLE) Page add ress, data table;
001/002 066 040 LLI L(TABLE) Byte address, data tab le;
001/004 307 X FERL OOP LAM A := XMOV E value;
001/005 143 OUT XMOV E Perform XMOVE output;
001/006 060 INL Point to YMOVE value;
001 /007 307 LA M A := YMOVE value;
001 /010 147 O UT YMOVE Perform YMOV E output;
001/011 060 INL Point to XTORE value;
001/012 307 LAM A := XSTORE value;
001/013 145 OUT XSTORE Perform XSTORE output;
001/014 060 INL Point to YDRAW value;
001 /015 307 LAM A := YDRAW va lu e;
001/016 151 OU T YDRAW Perform YDRAW output;
001 /01 7 060 INL Point to next YMOVE va lue;
001/020 306 L AL A := L [check end address
low order] ;
001/021 074 070 CP I L(TABLEND) Is end o f table reached?
001 /02 3 110 004 001 JFZ XFER LOOP If not then continue loop;
001 /026 104 000 001 JMP STAR T Restart pattern when done;

(__- - - - - - octal coordinates - - - - - - - - - . ,

Split r-start~ , - - - end--""l
Octal
Address Label XMOVE YMOVE XSTORE YDRAW Commentary

00 1 040 TABLE 000 000 377 000 Vector # 1;

001 044 377 000 377 377 Vector # 2;
001 050 377 377 000 377 Vector # 3;
00 1 054 000 377 000 000 Vector #4;
001 060 000 000 377 377 Vector # 5;
001 064 377 000 000 377 Vector #6;
001 070 T AB LE ND xxx

Notes :

XMOVE. YMOV E, XSTORE and YDRAW are output port ass ignments of the author's system,
corresponding to the st robe lin es of figure 2.
All constants in th is li stin g are octal.
H(T ABLE) is high order 8 bit field of address of TABLE; L(TABLE) is low order 8 bit field of
address of TAB LE. The two high order b its of H(TABLE) are ignored.

88
flicker. However, a surpnslng number of
lines can be disp layed before flickering
occurs when using the separate line tech-
nique.
To write a stationary disp lay routine, it is
necessary to determine the coordinate points
of the picture's vectors. Graph paper wh ich
has been ruled for 377 by 377 octal squares
(or hexadecimal if that's your preference) is
not easily obta ined, so be ready to count
squares and label ordinary graph paper.
Figure 4 ill ustrates the technique of creating
a display table using graph paper. The
illustration is drawn first, using a ruler or
other straight edge to provide the lines. A
pencil is a must at this stage, since erasure is
a very real requirement when working out
any sketch. Once the drawing has been
final ized, octal coordinates are added to the
basic graph paper pattern. In the case of the Photo 2: A scope trace of the X coordinate output of the circuit in figure 2
Enterprise, I wanted to fill the screen, so I during the display of a typical picture. The trace is 3 V full scale and is
scaled the coordinates to use most of the approximately 75 ms long. The transition time from one voltage to the next
displ ay area in the horizontal (X) direction, is fixed by the hardware at 700 J.1S (approximately 7/7 50th of the horizontal
and used the same scaling in the vertical (Y) width of this picture).
direction. Then, the vector list is created by
going over the drawing line by line and
determining the four coordi nates required . your own processor. (The data of table 2
The small numbers near the line segments in remains the same regard less of the processor
figure 4 identify the octal addresses of these used. )
line segments in the vector tab le, tab le 2. What's Next?
When the data for a picture is all encoded
from the graph paper, it can be loaded into There is a fundamental prob lem with the
your computer's memory. If your processor home computer system or should I say the
is an 8008, then the program of listing 2 can home computer experimenter. The systems
be loaded and executed; otherwise, you'll keep getting bigger and more expensive.
have to create an equivalent program for Contin ued on page 120

Listing 2: An 8008 Program for Drawing Lengthy Pictures. This program is

similar to the program in listing 7 with the addition of a generalized end of
data test. In operation, it will be the sale program active in the 8008,
continuously cycling through the vector table which starts at location
007 /050.
Split
Octal
Addr O ctal Cod e Labe l Op Opera nd Commentary

001 /000 056 001 ST ART LHI H(TABLE) Set up the memory pointer
001 /002 066 050 L LI L (TAB LE ) to the beginning of table;
001/004 307 LAM A := XMOVE value ;
001 /005 143 R FSH L OOP OU T XMOVE Perform XMOVE output;
001 /006 060 I NL Point to YMOVE value;
001/007 307 LAM A := YMOVE value;
001/010 147 OUT YMOVE Perform YMOVE output;
001 /011 060 I NL Point to XSTORE value;
001/012 307 L AM A := XSTORE value;
001/013 145 O UT XSTORE Perform XSTORE output;
001 /014 060 INL Point to YDRAW value;
001 /015 307 LAM A := YDRAW va lue;
001/016 151 OUT YDRAW Perform YDRAW output;
001 /017 060 INL Point to ne xt value;
001 /020 110 024 001 JNZ NOINC H If no overflow then test end of table ;
001 /023 050 INH Else increment high order address ;
001 /024 307 NO INCH L AM A := next value [may be XMOVE or
ENDl ;
001/025 074 377 CP I 377 Is it END of data value?
001 /027 110 005 001 JNZ RFSHLOOP If not then continue inner loop;
001/032 104 000 001 JMP ST ART Else restart the progr'a m;

89
 Conversion Patch Here Are Design Equations

YTE'S Regard ing the September 1976 issue, the In Bruce Fil gate's article, "A Morse Code

BUGS fo ll owing po ints were ph oned in by Bob Van

Valzah, 11 40 Hickory Trail, Downer's Grove
IL.
On page 58, in li sting 4b of James
Brown's article "How To Do A Number of
Conversions," a typographical error occurred
at address 002 1. The correct code and
Station Data Handler, " Octob er 1976, we
omitted the design equ ations for the NE5 67
tone decoder which shoul d have been
printed in figure 6, page 70. To re med y the
situati on, here they are:
Center Frequency:
Band Width:
F ;:" 1 I (Rl * Cl )
BW ;:" 1 070 * SQRT
comment is: (VI I (F * C2))
Here lies documenta- where:
tion of kno wn bugs de- 0021 6F MOV L,A Rl, Cl and C2 are as defined in figure 6,
tected in previous editions page 70 o f October BYTE
of BYTE ... Bob also points out that zero suppression VI is the in p ut voltage to the circuit
works "too well" with the decimal routin e F is the center frequency,.
as designed by auth or Brown: It suppresses a
zero value complete ly. Bob suggests the Refining th e Plot
fo ll ow ing patch I'ep lac in g line 44 (and pu sh- Author Ri chard Lerseth reports that he
ing TENST ABL dow n in relative address received a letter from J C Rucklidge, associ -
space ) : ate professor of geo logy at the University of
Toronto, Ontario CANADA. Prof Ruc kl id ge
MOV A,C get NONZERO flag; used Ri chard's arti cle (" A Plot is In comp lete
ORA A test and set flags;
RZ ori gina l return if some digits With out Characters" in J ulyl976 BYTE) to
pri nted; program charac ter outputs from his system .
MVI A:O' o u tput of an ASC II zero In so doing, he verified the accuracy of the
JMP PUT character and return if a ll
bl a n k so far; printed tab les, but found one min or error in
To use this patch, th e refere nce to equ ations 16 and 17 on page 70. Th ese
TENST ABL will have to be modifi ed at equations shou ld read :
location 000"1.- X = XO + H '. DHX + (V - 5.0)' DVX (1 6 )

Patch of a Patch Y = YO + H * DHY + (V - 5.0) * DVY (17)·

The suggested bi orhythm program patch Caveat Programme

given on page 100 of you r July issue
contains a n error. This patch wi ll, in fact, Past history has show n th at occas ional
initiate all cycles in phase begi nning at one's typesetting or logic bugs occur in programs
printed in BYTE . Readers who f in d such
birt hd ate; but, if used as specified, errol's
bugs are urged to claim a bit of fa me in this
occur in the increme nting of dates on the
chart. By deleting lin es '130 to 470, the loop co lumn by se nding us the ev idence, and
which reads data into the vector T{I) is suggested patches. Two exa mpl es have been
deleted. Data must be read in to th is vector documented here this month.-
in order for the chart dates to increment
properly. I therefore suggest that the fo l- A Bug Way Back
lowi ng patch be added to the prev ious patch.
Boy d S Miner, K4KEP, editor of Bits and
122 FOR 1= 1 TO 12 Dits, the news letter of the Caroli na Com-
124 READ TO)
126 NEXT (I) puter and Radio Amateur Association,
Thi s may save problems fO l' some of yo ur points out an error in the state ment of
readers. amateur radio Teletype mark a nd space
Gary Sleater freq uencies in the September 1975 issue of
302 E EI Cam in ito Dr BYTE, page 32 :
Phoenix AZ 85020 _ Don Lancaster puts out some real good
articles but in "Serial Interface" in BYTE
The Price Is Wrong September 7975, page 32, he states that
Ham radioteletype audio frequ ency shift
Acco rdin g to IMS Assoc iates, the price of I?eying (A FSK) 2725 is marl? and 2925 is the
the IMSA I floppy di sk drive and interface space frequency. This "tain't so. " The marl?
co ntroll er mentioned o n page 83-84 of and space tones are mUltiples of 4 25 Hz. In
BYTE's September 1976 issue is $1919 fact they are the 5th and 7th harmonics.
assemb led, $1 TI9 un asse mbl ed; ad ditional Therefore the marl? is 2725 as stated but the
dr ives with out a cab in et are $1095. The space is 2975, not 2925. A t the time these
prices quoted in "W hat's New ?" are incor- standards came il7to being the FCC required
rect.- 850 Hz shift. -

90
A Note about Borrowing
Routines from EDUCATOR
The EDUCATOR program from the Digi-
tal Group is an extremely effective way to
BABY!
learn what takes place within the processor
when you are learning machine level pro-
gramming.
The EDUCATOR-8080 article in the July
'1976 BYTE (page 22/ appears to contain at
least two errors. I discovered these when
attempting to use some of its text display
rou tines. Complete System
The article neglects to mention that the
user defined subroutine CHRPR (character in a case!
print) has to add 200 (octal) to the code in
the accumulator to get a valid ASCII charac- KEYBOARD: 62 key upper & lower case + Greek;
ter.
The subroutine CHEDT loops indefinitely TAPE INTERFACE: High speed, 1200 Baud! Cas-
on the first string of blanks. The HL register sette, programs included;
needs to be incremented after a string of
VIDEO INTERFACE: E.I.A. Compatible;
blanks is output. I inserted an INX H (043
octal) between the present lines 000/310 MICROPROCESSOR; 6502 based system!
and 000/313 appearing on page 26 of the
July issue. MEMORY: 2K or 4K byte RAM minimum system
Since the listings published are obviously monitor + 3K ROM sockets;
not exactly those used in the Digital Group
software, the readers should be advised that
further debugging may be necessary.
S.T.M. SYSTEMS INC.
Dr Charles F Douds P.O. Box 248
281 Poplar St Mont Vernon, N.H. 03057
Winnetka I L 60093 •
 Ray 0 Lockwood would be interested in

Clubs hearing from you. His address is: 1825

Canal Ct, Merritt Island FL 32952, (305)
452-2159.

and Newsletters The New Orleans Hamfest and

Computer Fest
On October 30-31, the New Orleans
Hamfest and Computer Fest will be held at
Archbishop Rummel High School, 1901
Severn Av, Metairie LA (a New Orleans
suburb). This event is sponsored by the
KIM-1 USER NOTES Jefferson Amateur Radio Club.
At the Midwest Regional Computer Con- The Louisiana Council of Amateur Radio
vention held in Cleveland, a group of KIM-l Clubs, the Louisiana ARRL Convention,
users had the opportunity to meet with Rick MAR and other amateur radio groups are
Simpson of MOS. The group agreed that scheduled to meet. Banquets, noncom-
there was a need for KI M-l owners every- mercial and other exh ibits are being
where to be able to exchange ideas much arranged. Call-in frequencies will be
like other user groups, and that a newsletter 146.34-.94 and 3.95 MHz.
would act as a vehicle for that purpose. Reservations and latest details may be
KIM-l USER NOTES will be published obtained by writing to Dominick "Nick"
every 5-8 weeks. Cost for subscriptions will Tusa, WA5RMC, chairman, New Orleans
be $5 for the next six issues (including first Hamfest, POB 10111, Jefferson LA 70181.
class postage). This rate is for US subscribers
only. Make checks and money orders pay- Byte Back - Ohio
able to: KI M-l c/o Eric Rehnke. No cash Compute, Evaluate, Trade is the name of
please. Write : KIM-l USER NOTES, c/o Eric a new club in Ohio. Meetings are held in
Rehnke, Ap t No. 207, 7656 Broadview Rd, members' homes on the first Saturday of the
Parma OH 44134. month. There are no dues, other than talent
and a desire to exch ange information.
South Florida Computer Group - I/O Business applications are their special
In the August issue 1-4 it was announced interest. Charles E Tyzzer Jr is the contact
that Dr Bruce Camero n will be the new person, and he may be reached at
editor of I/O. Bruce is a research biochemist (513) 268-6551 x587. The mailing address
with Papanicolaou Cancer Research Insti - is : POB 104, Tipp City OH 45371.
tute (PCRI or PAP). All inquiries, news
Southern New England Computer Society
items, articles, etc, should be sent to him at
1155 NW 14th St, Miami FL 33136; or SNECS was formed at a meeting held in
phone (305) 324-5572. New Haven CT in July. Those present came
The group has in the past sent com- from parts of Connecticut bordering on
plimentary issues to interested individu als, Rhode Island as well as Fairfield and the
other clubs, and firms; but the club's mailing Hartford and New Haven areas. They repre-
list has grown to such a point that now it's sented a broad range of hardware, software,
necessary to charge a fee of $2 per year for business, educational, and hobby interest in
12 issues. This will not affect the exchange computers. A newsletter is in the works, and
of newsletters with other clubs. it will be called YANKEE BITS . Anyone
wishing more information on this group
Space Coast Microcomputer Club - Florida should write: SNECS, 267 Willow St, New
This club at present (August) consists of Haven CT 06511 .
about a do ze n individuals who are interested
in microprocessor-based computer systems. Ride the Data Bus - Michigan
A few are employed at the) ohn F Kennedy Data Bus is the official newsletter of the
Space Center, while others are affiliated with Southeastern Michigan Computer Organi za-
Florid a Institute of Technology and Florid a tion. Subscription is only available to
Technological University. Many members persons living more than 50 miles from
also belong to the larger computer clubs Detroit, at $6 per year (unless you're a
such as the Southern California Computer member). Data Bus is also available on a
Society and the Chesapeake Microcomputer newsletter exchange basis to other clubs.
Club . The purpose of this club is to further The editor is Jon Tara (313) 833-2847 . The
the usage of small computer systems through address is SMCO, Data Bus, 665 W Hancock
the mutual sharing of ideas and resources. No. 304, Detroit MI 4820'1.

92
 p-----.--------------------------------.
INTRODUCING THE

COMPUTER
Purdue Has PUNCH
Michael A Troutman, PUNCH presi dent,
informed us of the official existence of the
Purdu e University Computer Hobbyist Club.
Mike says they have a constitution and are
fully recognized as a student organization.
WAREHOUSE
The club meets weekly in the digital lab of
the El ectrical Engineering Building. The STORE
group is also planning lectures by key
speakers for every other month. Their
• BIGGEST COMPUTER
THE STORE
resources (those of EE) include two 6800 IN THE WORLD!
systems (M otoro la and SWTPC), an 8080
system, a KI M-l system, several CRT ter-
SPECIALS
minals, Teletype, high speed paper tape * ALL PURPOSE 12 inch
reader and access to the EE Dept PDP-ll /70 VIDEO DISPLAY $150
timeshare system. Long Persistence Green Phosphor
Membership is limited to students, staff
and faculty; however, for a small activities * 100 PIN ALTAIR / IMSAI HEAVY-DUTY
fee, anyone is welcome to attend meetings. BOARD CONNECTORS - $5
All interested persons may write to PUNCH , * ONE DAY SHIPMENT ON IMSAI 8080,
Room 67, Electrical Engineer ing Building, ADM-3,SwTPC 6800 & TERMINAL KITS
Purdue University, West Lafayette IN
* USED TERMINALS, PRINTERS
47907.
* USED DEC PDP8 & 8S
Charlotte, North Carolina * USED DISK - TAPE DRIVES
•••
A new club has been formed in the * WRITE FOR OUR CATALOG
••
Charlotte NC area. Anyone interested in THOUSANDS OF CABINETS, CASTERS, ELECTRONIC •
making contact with the Char.lotte Micro- PARTS, MOTORS, POWER SUPPLIES, CONNECTORS, etc. ;
computer Society may call Dr Michael Allen DEPT . B, 584 COMMONWEALTH AVE. •

.. _-------------._---------------------,
BOSTON MASS. 02215 •

MODEL CC-7 SPECIFICATIONS: DIGITAL DATA RECORDER $149.95

FOR COMPUTER or TELETYPE USE NEW - 8080 I/O BOARD with ROM.
A. Recording Mode : Tape saturation binary. Permanent Relief from "Bootstrap Chafing"
This is not an FSK or Home type recorder . Any baud rate up to 4800
No voice capability. No Modem_ (NRZ) This is our new "turnkey" board. Tum on
B. Two channels (1) Clock, (2) Data . OR, Two your Altair or Imsai and go (No Bootstrap-
data channels providing four (4) tracks on ping). Controls on e terminal (CRT or TTY)
the cassette. Can also be used for Bi-Phase, and one or two cassettes with all programs
Manchester codes etc. in ROM. Enab)es you to turn on and just
C. Inputs : Two (2), Will accept TTY, TTL or type in what you want done. Loads, Dumps,
RS 232 digital. Examines, Modifies from the keyboard in
D. Outputs : Two (2). Board changeable from He x. Loads Octal. For the cassettes, it is a
RS 232 to TTY or TTL digital .
fully software controlled Load and Dump at
E. Runs at 2400 baud or less. Synchronous or
Asynchronous. Runs at 4BOO baud or less. the touch of a key. Even loads MITS Basic.
Synchronous or Asynchronous . Runs at Ends "Bootstrap Chafe" forever. Uses 512
3 .1 "'sec. Speed regulation ~ .5% bytes of ROM, one UART for the terminal
and one USART for the Cassettes. Our
F. Compatability : Will interface any computer orders are backing up on this one. Nt). 2SI0
or terminal with I serial I/O. (Altair , Sphere,
M6800, PDP8. LS1 11, IMSAI, etc. (R)
G. Other Data : (110-220 VI. (50-60 Hz); 3 Uses the indu st ry standard tape satura-
Kit form $140. - Fully assembled and
Watts total; UL listed 9550; three wire line tion method to beat all FS K systems ten to
one. No modems or FSK decoders required. tested $170.00
cord; on/off switch; audio, meter and light
operation monitors. Remote control of mo- Loads 8K of memory in 17 seco nds . This Send Two Dollars for Cassette Operating
tor optional. Four foot, seven conductor recorder, using high grade a udio cassettes,
e nabl es you to back up your computer by and Maintenance Manual with Schematics
remoting cable provided. Uses high grade
audio cassettes. loading and dumping programs and data fast and Software control data for 8080 and
H. Warrantee: 90 days. All units tested at 300 as you go, thus enabling you to get by with 6800. Includes Manual on
and 2400 baud before shipment. Test cas- less memory. Can be software controlled. I/O board above. Postpaid
sette with 8080 software program inel uded .
This cassette \l\l3S recorded and played back
during quality control. Master Charge & BankAmericard accepted.
Model ee7 ... $149.95
ALSO AVAILABLE: MODEL CC·7A with vari- Model ee7 A ... $169.95 On orders for Reco rders and Kits please add
able speed motor . Uses electronic speed control $ 2.00 for Shipping & Handling.
at 4"/sec. or less . Regulation ~ .2% (N. J . Residents add 5 % Sales Ta x )
Runs at 4800 baud Synchronous or Asynchro·
nous without external circuitry.
Recommended for quantity users who ex-
change tapes . Comes with speed adjusting tape
NATIONAL multiplex 3474 Rand Avenue, Box 288
South Plainfield, New Jersey 07080
to set exact speed. CORPORA TlON (201) 561-3600

93
at (704) 597-2303 days; and Allen Grayson holding a part time job assembling boards
at (704) 366-7879 nights. Allen Grayson is for a local microcomputer distributor. He is
interested in down to earth applications for saving up to buy a 8800 or 6800 based
computers. An example is the one he cited: system while attempting to educate himself
A friend wrote a program creating a robot in computer science. He writes that between
lawn mower. Now his friend sits back with the BASIC he's learning on the PDP 8/E
his favorite beverage under a nice shade tree system, the minimal configuration COSMAC
and watches his "robot" do the work. computer he is building, and as much litera-
ture as he can obtain, along with his "hands-
Northern New Jersey on" hardware experience with his job, he 's
doing OK. You can contact him at the above
The Northern New Jersey Amateur Com-
address.
puter Group opens its membership to any
interested person for an annu al fee of $5.
Meetings will be held from 6:30 to 11 :00 Ottawa - Ontario, Canada
PM the second Friday of each month at
Becton Hall, Fairleigh Dickinso n University, We have received word that a group
Rutherford Campus, Rutherford NJ. For calling itself the Ottawa Computer Club has
further inform ation, contact Murry P formed. At the present time the only in-
Dwight, Dwight Instruments Company, 593 formation we have is that the meeting
New York Av, Lyndhurst NJ 07071. Ph o ne : schedule is posted at Pettazzoli College
(201) 438-3334. Residence, located at Rideau and Ch apel Av,
Ottawa, monthl y. They are looking for new
members, and if you would like to play
TRACE - Ontario, Canada
Sherlock Ohms, we suggest you investigate.
Toronto Region Associ atio n of Computer
Enthusi asts has over 50 members in the
greater Toronto, Hamilton, and Kitch ener, Curriculum Developer Needs Inputs
Ontario areas. They meet once a month, Robert F Tinker has founded Technical
usually on the first or second Fridays. For Education Research Center, located at 575
details concerning the club and newsl etter, Technology Sq, Cambridge MA , phone
write: TRACE, Box 545, Streetsv ille, (617) 547-3890. He is interested in creating
Ontari o CANADA L5M 2C1. curricula in the emerging technologies of low
cost electronics for student use. A news-
Waterloo - Ontario, Canada letter, Hands On.' , is proposed as a quarterly
The Amateur Microprocessor Club of transmission line for practical laboratory
Kitchner-Waterloo, Ontari o, has formed, oriented educational ideas with a bias
with Ch arl es Sooley acting as interim co- toward the uses of electron ics and
ordinator. Th e group has made some quan- computers.
tity purch ases. For further inform ation
Denver Amateur Computer Society
write : Amateur Microprocessor Club of
Kitchener-Waterloo, On tario, Canada, c/o DA CS Newsletter, Volume 2/1, has mu sh-
Reading Room , El ectr ical Engineering, roomed. The July issue was expanded to 44
University of Wate rl oo, Waterloo, Ontar io pages. Some of the changes include longer
CANADA N2L 3G 1. fe atures, new products, users ' reports, tips,
and "Dear Nina," letters from wearied and /
Auckland, New Zealand or wearisome wives to the editor. Th e club is
also holding a contest to come up with a
Info Fil e of Mt Roski ll has formed a name for the publication; the pri ze is a year's
group of N2 users and is aski ng help in free membersh ip. Entries, along with sub-
getting off the ground. They need schema- scription orders ($9) shou ld be se nt to Jim
tics, PC board layo uts, and software. News- Cl ark, DACS Newsletter, POB 6338, Denver
letters would be appreciated. Write: Info CO 80206.
File, POB 27-206-B, Mt Rosk ill, Auckl and
NEW ZEALAND. RPI ACM Chapter (Capital District NY)
Jerry Irving of RPI writes: Th e Rensse lae r
Teen Hobbyist Polytechnic Institute student chapter of the
Jeffrey Rice, 16, of 303 Wilson St, Elkin s ACM is forming a speci al interest group fo r
WV 26241, would like to join or fo rm a peo ple who are interested in mini s and
computer club in his area, if there is any micros. We have had one meeting to see how
interest. much interest there would be and fou nd a
Enterprisin g Jeff, a would-be computer great deal of it. Th e group will be open to
hac ker, is working two paper routes and anyone, not just students . Th ose in the

94
 THE L[]f;1PlJTER R[][]f;1
capital district area of New York should be SMALL COMPUTER SYSTEMS. SOFTWARE. AMATEUR RADIO EQUIPMENT
ju st a short dl-ive from RPI. There al-e many
1455-A So. 1100 E. Sa lt Lake City, Utah 84105 Phone: 801-466-79 11
minicomputers on the RPI campus and a
numbel- of people at the first meeting work
with these, rebuilding, programming or
writing software for them. There al'e people
"WE TAKE THE
in the area who were at the first meeting \\\,~~~\\, OUT OF THE f;1~LR[]"
who are starting to build their own systems.
This gro up is forming in order to supp ly a
pl ace for people to meet to compare their
systems, exchange ideas, and give them the
advantages of being in a nationally recog-
ni zed organization. Once under way we will
have regul ar meetings and try to have
speakers an d demonstrations as often as
possible.
We pl an on having our organizational
meeting to set up the foundation of the
group in eithel" August or September.
One Of The Nations Largest Over 1600 Square Feet Of Sales
Anyone interested in coming or joining Full-Service Computer Stores. And Service Facilities.
shou ld write to the RPI-ACM, Amos Eaton
Hall, RPI, Troy NY 12180, or call either
WHEN YOU WRITE FOR OUR CATALOG AND ENCLOSE $1 TO
Jerry Irving (518) 756-6827 or Will Strang
HELP DEFRAY THE COST OF HANDLING AND MAILING,
(518) 274-8361 for information and direc- HERE'S WHAT YOU GET:
tions.
1. A CERTIFICATE GOOD FOR $2 ON YOUR NEXT
The Computerist - NECS PURCHASE .. . . ...................... . ... . . ... ... ......... .
The Computerist is an extension of the
New Eng land Computer Society. The clu b's 2. THE C[]I';JPlJTER mml':1
EASY TO UNDERSTAND
CATALOG COVERING ....... . ... . ... . ... .... . . " .. ... ... . . .
newslette r is prepared on a text editor, and
is printed by reduced photo offset. In IMSAI
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3. THE COI':1PlJTER ROOI':1 " EASY GUIDE" TO HELP YOU
(step ), key/copy, data in/
data out, and counter up/ PICK THE RIGHT SYSTEM, PERIPHERALS, COMPONENTS,
down. Profile card includes AND SOFTWARE FOR ... ..... .... ... . ........ ........... . . .
high vo ltage pulse regulator,
timing, 8 bit address and 8 THE BEGINNER
bit data drivers/rece ivers. Two 6Y," x 9" stacked ca rds with THE ADVANCED
spacers. A llows programming in 20 minutes - copy ing in
5 minutes. Requ ires +5 , -9, and +80 volts . THE EXPERT
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+ 1 input port) and software . ......... ...... . . . $49 .95
Briefcase unit with power supplies and in terface connectors 5. INFORMATION ON REPAIR SERVICE, LOW COST
(assemb led and tested only) .... _ _ ....... . ... . $599.95
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Our NEW 16K Byte Pseudo·Static, IMSAI /A L TAIR co mpat-
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low power RAM. All memory chips socketed_ Uses all prime, AT THE COI':1PlJTER ROOI':1 YOUR WRITTEN QUESTIONS
f acto ry fresh I Cs. High quality, two-sided, through-hole-
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BANKAMERI CA RD . . . .. . .. .. .. .. .... .. .. . . .... .. .. MASTERCHARGE

95
 Volume 1/1 the goals are set forth: To serve to offer flexible computer services at reason-
all computerist and comp uter clubs in the ab le rates and tailored to the needs of any
New En gland reg ion, report on cl ub meet- business. Some of the se rvices offered to
ings, print a monthly calendar of regi onal busin esses are inventory control, mailing
events. It will also provide up to date reports lists, billing, and purchase orders. They also
on new prod ucts, publi cations, local sup- offer a 24 hour emergency service fo r the
pliers, mail order dealers, and the like. It will deaf, using Teletypewriter, and make avai l-
also in clud e a classified section, and both ab le national and local news stored in a fi le
commercial and individu al advertisements. and accessed by the Tel ety pewriter. If you
The Computerist is an independently pro- would like to learn more, write : Communi-
duced publication, which is the official cation Co-operative, POB 182, W Linn OR
newsletter of the New England Computer 97068.
Society, and is supported in part by dues
and subscription. Subscription rate is $6 per Byte Out of Maple Address
year. Robert Tripp is the contact man; his
address is POB 3, South Chelmsford MA "So meone took a byte (or two) out of
018240 the address for MAPLE, and I don't know
whether all mail is arrivi ng here," writes
Communication Co-operative for the Deaf John Sikorski, president of "Microprocessor
and Hearing Impaired APL Enthusiasts," of the Clubs and Newslet-
Th e Communication Co-operative is a ters item on page 100 of September 1976
nonprofit organization estab li shing a time BYTE. The full address is:
sharing computer system in the Northwest. MAPLE
Its purp ose is to provide data processing Box 574 NUMS
services in order to help support a communi- 303 E Chicago Av
cations system for the deaf. This enables it Chicago IL 60611 •

Have you every be en victimized by is its inspirational data content. Th e

Stamp Out Cybercrud one of a myriad computer based inter- machines we're all busy working o n are
personal putdown s? I n Ted Nelson' s deep personal ex pressions, and not the
book, Computer Lib/ Dream Machines, cold and inhuman mon sters of th e tradi-
you'll find an excellent essay on the tional stereotype. The book def in es

COMPUTER
nature of this "cybercrud." many of th e terms and exp lain s many of
Have you ever wondered wh e re to go the techniques which can be used in the
for a basic starting point in your quest personal computer syste ms we're all
for information about computer appl ica- busy constructing and programming . It
tions and uses? Ted Nel so n's book, performs thi s service in a way w hich
Computer Lib/Dream Machines, is th e adds color and excitement to this newest
place for you to begin . of a rt form s, th e computer application.
Computer Lib/ Dream Machines is for Computer Lib/ Dream Mach ines is
the layman - the person who is intelli- mu st reading for the beginner, and is also
gent and inquisitive about computers. It a refreshing self examination for th e old
is wri tten and se lf published by a hand at programming and systems work.
philosopher who is also a self confessed You can order your copy of Com-
computer fa n and an excellent teacher of puter Lib/ Dream Machines from BYTE 's
basi c concepts. (For those who have not Books for $7 . Send your order today to
yet heard , ivory towers are const ructed BYTE's Books, 70 Main St, Peter-
out of real a nd substant ial white bric ks. ' borough NH 03458. Help stamp out
Th e most important aspect of this book cybercrud.

r--------------------------------
Pl eas e add 50 ce nts for postage and handling. Please allow six weeks for delivery.
Send copies of Computer Lib/Dream Machines to:

Name

Address

Cit y Sla le Zip

• [[ Check enclosed
[[ Bill MC # _ __ _ _ __ Exp. Date _ _ __
fjiijiiiij 0 Bill BA # Exp . Date _ _ __
Signature
PETERBOROUGH, NH 03458

96
 .

POLYPHONIC
WANTED Computer mart
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our complete Altair system_ Processor Tech, Apple, OSI
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all pa rameters of the
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sound at the command EQUIPMENT & SUPPL Y CORP. '
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314 5th Ave
II I I St illman Research S~ste ms
For complete monthly catalog of
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prr ces subject to change wlo notice 5 16- 794-051 0

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10'1 ) ~asic"'::'i .; Problem Solving With
Computer 'Games
[)avidH. Ahl. .An anthology of games
and simulatio~t7fromA;ct!y-Deuc~y . to
So you've got a The Computer
Ted Sage. This text is designed to be used
in 3 onc-semester course in computer
Yahtzee., all in the BASIC language.
Contains a complete listing, sample run,
plus a descriptive write-up of each game.
personal computer. programming. It teaches BASIC in the
context of the traditio nal high school
mathema tics curriculum. There a re 40
carefully graded pro blems dealing with
OUf.. mi)st. popular boo~!J",arge. fonnal,
2>l8PP!·S1.50t6Cl ·""'t .;;. many of the more familiar topics of
algebra and geometry. Probably the
What to Do After
You Hit Return
Now what? most widely adopted computer text. 244
pp. $5.95 [SJ]

Another collection of games a nd A Simplified Guide to

Creative Computing Magazine
simu lations- a ll in BASIC- including
number guessing games, word games,
Fortran Programming
So you've got yo ur own computer. Now what" Creative Computing is chock full
hid e-and-seek games, pattern games, of answers - new computer games with complete listings every issue, TV color Dalliel McCrackell . A thorough first text
board games , busi ness and social scie nce gra phics, simulations, educa tiona l programs, how to catalog your LPs o n in Fortra n. Covers a ll basic statements
simulations and science fiction games. computer. etc. Also compute r stories by Asimov, Pohl, a nd others ; load s of and quickl y gets into case studies ranging
Large format. 15S pp. $6.95 [SA) challenging problems a nd puzzles ; in-dept h equipment reports on kits, terminals, from simple (printing columns) to
and calculators; reviews o f programming and hobby ist books; outrageous challenging (craps games sim ula ti o n) .
cartoons and much more. Creative CompUling is the software and applicatio ns 278 pp. $8.75 [7F]
Fun & Games maga?';ne of perso na l and educational computing. Bi-monthly.
with the Computer I-yea r sub'n $S.OO [I A). 3- yea rs $2 1.00 [ I B], sa mple copy $1.50 [I C]
Understanding Solid
Ted Sage. 'This book is designed as a State Electronics
text for a one-semester course in com- the Best of Creative Problems For
Computing - Vol. 1 An excellent tutorial introduction (0
puter program ming using the BASIC
language. The programs used as il-
Computer Solution transistor . and diode circuitry. Used at
lustrations and exercises are games lJflvid Ahl, ed, 'Staggering diversity of Gruellberger & Ja[[ray. A collection of the T1 Learning Center, this book was
rather than ma thematical algorithms, in articles.. and fiction (Isaac Asimov, .etc.),. 92 prob lems in e ngineering, busi ness, written for the person who needs to
order to make the book appealing and computer ~mes (IS new ones with social scie nce a nd mathematics . The ·understand electronics but can't devote
accessible to more students. The text is complete listings), vivid graprucs, 15 problems are presented in depth and years to the study. 242 pp. $2.95 [9A]
well writte n, with many excellent samp le .pages of "foolishness," and comprehen- cover a wide range of difficult y. Oriented
programs. Highly recommended." - The sive.reviews of over 100 books. The book to Fortran but good for any la nguage . A
Mathematics Teacher 351 pp. $5.95 [SB) consists ' of material which originally' classic. 401 pp . $8.95 [7A] Microprocessors
appeared in the first 6 issues of Creative A collection of articles from Electrollics
Computihg (1975), all of which are now A G magazine. The book is in three par ts:
Game Playing ou.t ofgUnt. 324 pp, $8.95 [6A]
::-,.,. -,;';: :"".f';:,:.;':'" .,":-:::' .
uided Tour of device technology; designing with
With the Computer, L,,;;..,;;;.....;;;.....;;;.....;_ _;;.....;_ _~ Computer Programming microprocessors; a nd a pplications . 160
pp . 1975 $13.50 [9J]
2nd Ed. Computer Libl In Basic
Donald Spencer. Over 70 games, puzzles, Dream Machine Tom Dwyer und Michael Kaufman.
Microprocessors: Tech-
a nd mathe matical recreations for the Ted Nelson. This book is de vo ted t o the "This is a fine book, mainly for young no logy , Architecture
co mputer. Over 25 games in BASIC and
FORTRAN are included complete with
premise tha t everybody should under- people, but of value for eve ryo ne, full of d A I" t" ns
stand computers. In a blithe manner the detail, many exa mples (including an pp Ica 10
descriptions, nowcha rts, and output.
a uthor covers interactive systems, ter- programs for hote l and airline reser- Daniel R. McGIYIln. This introduction
Also includes a fascin a ting account of the
minals, com puter languages, data st ruc- vations systems, a nd payro ll), with much to the microprocessor defines and
history of ga me-playing machines , right
up to today's computer war games. Lots tures , binary patterns, comput er thought having bee n given to the use of describes the related computer structures
a rchitecture, mini-com puters, big com- graphics in teaching. This is the best of and electronic semi-conductor processes.
of " how-to" information for applying
puters, microprocessors, simulation, the introductory texts on BASI C."- Treats both hardware a nd software,
mathematica l concepts to writing your
own games. 320 pp . 1976 $14.95 [SS)
military uses of computers, computer Creati ve Comput ing Large format. 156 giving a n overview of commercially
companies, and much, much more. pp. $4.40 [SL] available microprocesso rs , a nd helps the
Whole earth catalog style a nd size. A ....~_ _~_ _~~~~~==:='I user to determine the best one for
BYTE Magazine
If you are considering a persona l com-
puting system now 'or later, BYTE
provides a wealth of informatio n on how
g~::~;i~::;~r and~:~$~~~~:~it.~l ~~;:1i2:P~~:~:C:ing
to get started at an affordable price. introduction to computer prOgramming Catalogue
Covers theory of computers, practical Joseph Weizenbaum. In this majo r new and IIme-snanng systems. The best tellt Zany 12-page tabloid newspaper !
a pplications, a nd of course, lots of how- book, a distinguished computer scientist on ·BASIC pn almosi"aJl counts·; Raiing;! . cata log lists books, magazines, art prints ,
to build it. Monthly. I-Year sub'n $ 12.00 sounds the warning against the A+"- Creative Computing. 150 pp. $8.50 and T-Shirt s: A conversation piece even
[2A), 3-Y ears $30.00 [2B) dangerous tendenc y to view com puters [7E] •.. . . : if yo u don't order any th ing. Free . [5A]
a nd humans as merely two different
Games & Puzzles
kinds of "thinking machines." Weizen- ~---------------------------------------,
baum explains exactly how the computer CREATIVE COMPUTING, Dept. B
Magazine works and how it is being wrongly
substituted for human choices. 300 pp. P.O. Box 789-M, Morristown, NJ 07960
The only magazine in the world devoted $9.95 [8R]
to games a nd puzzles of every kind - . ~~..._____~_ _ _ _""'_'"
m at hematical , problematic a l , AHI t
crosswo rd s, chess, gomoko, checkers, . ' san: ompu er
'd C
' t ' Please send me the following:
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backgammon, wargames, card games, il,.R~1 aviti; it.d, Presents pers90al
board games, reviews, competitions, and t stat of35 internationally-known
more. Mont/lly. I-Year sub'n$12.00[3A] computer artiSts coupled with overl60
plates in full .fo1o.r and black & White.
Games With The :. §!,lvers y jdeo: a'1, ! opticalphenlJJ!jena,
"'tnatheiniilical : structures, sculpture,
Pocket Calculator weaving/ and 'mqre. 132 pp. $4.95 [60]
Sivasailam Thiagarajan and Harold .. p loth c()ver$10.95 [6E]
Stolovitch. A big step beyond tricks and &;;......-;;;...;;.;--....;.~;;;.----....I
Books Shipping charge $1.00 USA, $2 .00 Foreign
puzzles with the hand calculator, the two Computer Science:
d ozen games of chance and strategy in A F"
this clever new book involve two or more Irst C ourse (2 n d Ed .) NJ Residents add 5% sales tax _ _ __
players in connict and competitiorr. A Forsythe, Keellan, Organick, and
single inexpensive four-banger is all you Stenberg. A new, improved ed ition of
need to play. Large format. 50 pp. $2 .00 this comprehensive survey of the basic o Cash. check, M .O. enclosed TOTAL====
[SH ] components of computer science. There
Card No. _ _ _ _ _ _ _ _ _ _ _ __
has been an updating of important areas o BankAmericard }
Games, Tricks and such as Progra mming, Structured
Programming, Problem Solving, and
Puzzles For A Hand other Computer Science Concepts . The o Master Charge Ex piration date _ _ _ _ _ __ _ _ __
quantity of exercises and problems has
Calculator been increased. S76 pp.$16.95 [70] Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ __ __
Wally Judd. This book is a necessity for
anyone who owns or intends to buy a Mr. Spock Poster Address _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ __
ha nd calcu lator, from the most Dramatic, large (IT' x 23") computer
sophisticated (the HP65, for example) to image of Mr. Spock on heavy poster
the basic "four banger." 110 pp. $2.95 Ci ty _ _ _ _ _ _ _ _ _ _ _ State _ _ _ _ Zip _ __
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[SO] Comes in strong mailing tube. $ 1.50[5B]
----------------------------------------
What's
New?

A Suggestion is Fulfilled
In last month's new products section, a
touch tone frequency generator was sug-
gested as a possible portable product to be
used as a portable data terminal. Well, a
company called Executive Devices has pro-
duced a product which incorporates such a
frequency generator and can be easily used
in the portable terminal mode. This battery
powered hand held device generates the full
16 combinations of tones possible with the
touch tone encoding technique, and inter-
faces with the telephone network through an
acoustic coupler. There are two models
available:
Pocket Data Terminal PDT-700 is $49.95,
postpaid, and is the simple ton e gener-
ator version. (Kit version $39.95.)
Pocket Data Terminal PDT-lOOO is
ALTAIR & IMSAI COMPATIBLE 8K RAM
$89.95 postpaid, and is an extended SPECIFICATIONS:
Access Time: 500 ns max. current requi red < 200 mA/1024
words max.
Memory Chip: low power static RAM processed to mil. std. 883
Voltage suppty: + 5V to + 10V
Address Select: Dip switch accessable from top of board-no
need to remove board to relocate
Power Regulators: 4 ea. 7805
Wait States: NONE! CPU runs at maximum speed
Buffered address and data out lines
Buffer disable line for transparent loader

r·----------------------------
Order your 8K RAM kit for only
CLIP & ORDER TODAY ----------~-,
VECTOR GRAPHIC
$239.00 + 6% Calif. sales tax P.O. BOX 4784
.03% handling. $335.00 assem- THOUSAND OAKS, CA 91359
bled, includes sockets. TEL: (213) 889-9809
o SEND_______ 8KRAMBOARDSTODAY
o CHARGE TO MY CREDIT CARD.
o B of A No. _ _ _ _ _ _ _ _ _ _ _ _ exp. dt. _ _ __

o M.C. No. exp.dt. _ _ __

Signature
Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Address _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
STAN DARD & C U ST OI~ ENCLOSUR ES
City State_ _ _Zip
FOR •.- --------------------------- I NTRODUCTORY OFFER .----------------------------
COMPLETE KEYBOA RD HOUS I NGS, CR T'S & ETC.
--- CAPABILI TIES IN ---
THE COMPUTER CO. OF THE FUTURE
Kydex 100 - Plex ; gla ss - lexa n
PVC ABS

FOR FURT HER I NFO RMATION WRITE OR CALL :

Thermody ne Plastic s . Inc.

11 49 5 Le nexa Driv e
Ola t he , Ka nsa s 66061
91 3-492· 7352

99
 feature model with a nonvo latile user section speaker outputs of a commercia l
programmed mem ory of seven digits ATT approved ph one answe ring device. The
for automatic dialing of a frequently auto answer logic is built into such a phone
used number. (K it ve rsion $69.95.) answering device, so all the computer has to
do is to test th e cassette motor control line
Of course the auto dial product by itse lf and li sten through a bank of tone sensitive
wo n't do much fo r people stuck out in a filters for th e frequ enci es invol ved. Ac-
country te leph one exc hange with re lays and cording to verbal reports, several indi vidu als
stepp er sw itches for di alin g, but any com- are already at work automating such home
puter eq uipped with an auto answe r func- function s as lighting contro l through remote
tio n to a te lephon e por-t can receive and ports accessed in thi s mann er; there ought to
decode the touch tone frequ encies of thi s be a market ni che for the commerc ial
dev ice . For th e home hacker, thi s can be answe ring equipment needed (to plug into
accompli shed by tapp in g into the audio an Altair or other computer main frame).-

Real Time Programming, Anyone? for th e Altair or IMS AI computers. Th e

(or How to Make a Perpetual Audio board contains a conventiona l LSI clock Breadboard Kit Including
Visual Date Book) c hi p, the National Semiconductor Slit-N-Wrap Tool
MM5318N show n in the photograph (the
largest plastic package integrated circuit). Vector Electronic Co, 12460 Gladstone
Th e clock interfaces to the Alta ir in either a Av, Sylmar CA 91342, has introduced this
programmed 10 mode, or an interrupt 10 new modular breadboarding kit containing
mod e of operation. For clock interrupts, the 36 different parts. The li st includes term inals
board ca n be programmed to interrupt 60 sockets, perforated circuit boards, wire,
times per seco nd, once per seco nd , o nce tools and many other items designed for
eve ry I 0 seco nds, once per minute, once custom wrapped wire circuit construction.
eve ry 10 minutes (radio amateurs take note)' The kit is designated 41 X by the company,
once per hour, or twice per day. Also and th e total cost of parts for the' kit is
programmable through the board are the fast lower than the catalog prices when ordered
se tting modes of the clock chip. separately.
Th e microcomputer sys tem treats th e The kit contains the P180 Slit·N-Wrap
cloc k as a periph eral, and re ads the time tool to wrap and strip insulated wire found
COMPTEK, a co mpany lo cated at POB direct ly in a 24 hour HH:MM:SS format, on a spool. Th is tool is a must for wrapping
5 16, La Canada CA 91011, has come up BCD encoded. For the use r wanting to of extended bus structures, since there is no
with ju st the thin g needed to impl ement the impl ement the date book, some software time consuming stripping or measuring to be
application in the subti tle of this new information man agement structures will of performed . (I'm using the P780 to complete
prod ucts story. In order to impl eme nt a rea l cour se have to be created to use it, but the a bus structure of backplane connectors on
ti me process such as an appointment book , hardware of this board is a key element my home brew system which has been par-
so me means of noting tim e and date dig ita ll y which makes such a system possibl e. tially assembled for months due to the
for each hour of the day, every day of the Im ag in e: your computer with its audio and inconvenience of the cutting and stripping
year, is required . video output dev ices nagg in g you to get up, with conventional wire wrap . . . CHj
Th e way to acco mpli sh th is tim e measure- go on vacation, keep th e appointment with In addition, the kit contains ten 16 pin
ment is to use thi s $98 rea l tim e clock board the den tist, etc. - DIP sockets, five types of wrap posts, and
Vectorboard socket cards with and without
printed circuit pads and buses. Also included
are extruded aluminum frames to support
the circuit board as a chassis.
Is This a Programmable Calcu lator
Th e price of this omnibus kit of Vector's
or Computer System?
excellent products is $56.50, and it is
Here is the latest Hew lett-Packard inn ova- available from stock. The 41 X Multi-Conn
tion, the flexib le disk drive for the desk top Kit can be ordered directly from the factory
ca lcul ato r. The disk dri ve plugs into the HP (write to the attention of " Dept X"). Vector
9825 desk top programm abl e ca lculator, to products are frequently found at retail com-
prov id e mass storage capabi li ty far beyond puter stores, and retailers of the Vector line
the bui lt in data ca rtridge drive. The new may find this an exce ll ent "gift" product for
produ ct co mes in two forms. The 9885M the walk-in trade.-
maste r disk drive is pri ced at $39 00, and the
9885S slave (up to three of which may be
E&L Instruments Increases
used with one 9885 M co ntro ll er) is priced at
Memory and Interface Capabilities
$25 00. The 9825 can handl e eight of the
of Their MMD-' Microcomputer with an
9885M units, making it possibl e for the
Accessory Board
extreme case of 32 disk drives run by one
ca lcul ato r. Since each disk hold s 468,480 A new accessory board mod el MMD-1 / MI
bytes of data, in the ext reme, the ca lcul ator with extra RAM memory, Teletype inter-
cou ld have 14,99 1, 360 bytes of on lin e face, and audi o cassette interface has been
rand om access storage - hardl y a mere desk added to the E&L In struments line. The
top ca lculator's worth of mass storage. MMD-1/MI simp ly plugs into the built in
Th e disk opt ion will prove a most useful card edge conn ector on the MMD-1 and
feat ure for thi s ca lculator, which is pro- mounts on top of th e unit as shown in the
gramm ed in a high leve l language command photo.
sys tem. The disk opti on exten ds the software A MM D-1 /M I accesso ry board comp lete ly
of th e ca lcul ator to in clude a direc tory assemb led and tes ted, sells for $200. In kit
feature for up to 320 named fil es on disk. form with all parts for assem bly, th e price is
All operations are done in a write-then ver ify $150. The MMD-1/MI has th e following
mod e to ensure reliability . features:
Hewlett-Pac kard is located at 1501 Page • 2 K byte programmabl e mem ory
Mill Rd, Palo Alto CA 94304.- capabi li ty (1 K supplied) .

100
 8,192 X 8 BIT STATIC MEMORY
ENIGMAS-l
COMPUTER GAMES IN BASIC
PRICE $8.00
TURN ON EXCEPTIONALL Y LOW POWER

WITH COMPTEK
Now your micro can control AC
power outlets with COMPTEK's NEW
ENIGMAS·l IS A BOOK OF COM PUTER GAMES PC3200 Power Control System . KIT $295.00
TA K EN F ROM MY CA T A LOG 'A LTAIR 8800 / IMSA18080 BU S
THE PROGRAMS IN THI S BOOK A RE: • 1 to 32 independently address- COMPATIBLE
GONE FI SHIN G - GO FI SHING TO MAKE
MONEY able control channels ' FAST 2 15 nS- FULL SPEED-FOR
CONCENTR AT I ON - MAT CH THE HIDDE N Z80 ALSO
NUMBERS-TWO CAN PLA Y • Remote power control un its - ' EXC EPTIONALLY LOW POWER -
SLOT·MAC HINE - IT'S E ASY TO LOSE YO UR
MONEY no AC power on logic board LESS HEAT
C RAPS DICE GAME ' LESS THAN OTHER "LOW
WITH DI CE PRINT· OU T - SHOOT CRAPS AND
SEE THE DICE
• Optically isolated, current lim- POWER " MEMORY
TAN K ATTACK - TRY TO DEFEND YOURSELF
ST ARS HIP
ited, low voltage control lines 'BATTERY STAND ·BY
CA PAB ILITY
(ST AR TRE K T Y PE GAME) - SHOOT SOME
K LiNGON S • Accessible through most BASIC's 'A LL SIGNA LS TO MOS DEVI CES
SHERLOCK HOLMES BUFFERED
LOGIC GAME - CHASE PROFESSOR MORI· • ALTAIR and IMSAI compatible
A RTY 'SOCKETS FOR AL L IC 'S
A LL MY PROGRAMS IN BASIC HAV E BEEN
WRITTEN T O RUN IN MOST ANY BAS IC
Write today for more details! PROTOTYPING BOARD
COMP ILER·INTERPRETER WITHOUT ANY LOW PROFI LE IC SOCKETS
CHANGES.
THE Y WILL RUN UNDER A LT A IR 4K OR 8K
BASIC AND MOST ANY OTHER BAS IC COM-
PILER -INTERPRETER PRO V IDED Y OU HAV E
cnrn.ntek.... EDGE CONNECTORS
DB25 CONNECTORS
ENOUGH MEMO RY T O RUN THEM.
SHIPPING EX TRA . ADD $2.00
PRICE S8.00 PPD. SORRY NO COO'S
"Real World Electronics"
NJ RES. ADD 5% SALES TA X
B. ERICKSON
P.O. BOX 11099 P. O. Box 516 ELECTRONIC CONTROL TECHNOLOGY
CHI CAGO. ILL. 60611
La Canada, CA 91011 P.O. Box 6. Un ion. New Jersey 07083

Jr;iJ] DEUB.[JPiDEruT L~~5

P . O. Box
W . Lafayette, IN
2345
47906
HEY, ALTAIR ... NOW!
1/ 4
(317) 463 ·7167

watt carbon film resistors .. .. $0 .03

GOT THE TIME? A Computer Store in
5 per ce nt, 50 per value min . If not, you need COMPTEK's NEW Windsor Locks, CT
CL2400 Real-time Clock.
1/2 watt carbon comp resistors .. $0.02
10 per cent, 50 per value min. • Self-contained hardware clock
Offering the complete line
No -Nik wire strippers .... .. ........ $16 .00
• Can be set and read by BASIC of * Altair mainframes and
10, 12, 14 , 16,1 8,2 1,23.25. 28 .31 • Programmable interrupts peripherals as well as boards
34 ,37 ,44 or 54 thousanths • Top quality board, components,
wire d iameter & boxes, tools &-. instru-
and I.C. sockets ments, books & manuals,
Carbide PC board drills • ALTAIR and IMSAI compatible supplies & media.
w ire size: 55 · 65 ........... $2 .88
66 . 70 ....... .. .......... $2.97 • Uses: 24 hour clock
71 . 75 ......... " ........ $3.06 Software timer
76 . 78 .. . .. .. .$3 .60
Event timer The Computer Store
79 . 80 ............ ....... $3.60
63 S. Main St.
Spec sheets are available . KIT - $98 ASSEMBLED - $135 Windsor Locks, CT 06096
203-871-1783
We w ould be pleased to send you a
' GOODIES' catalog listing all kinds of
cnrn.ntek...
hard to find products including : Molex, " Real World Electronics"
Bishop Graphics, AMP , CDC manuals • Altair is a registered tradename of
MITS, Inc.
and forms. PC drills and mills, elec·
tronics tools, PC board manufacturing
P.O. Box 516
supplies, resistors . and semicon · La Canada, CA 91011
ductor s. For more information
 • Teletype interface (20 mA current Printed Circuit Board
loo p) . Hackers Take Note
• Paper tape reade r control for ASR33 Two new etched circuit board kits from
Tele ty pewri ters.
Vector Electronic Co, 12460 Gladstone Av,
• Audio cassette interface.
Sylmar CA 91342, facilitate rap id produc-
• Sockets to accept up to 1 K PROM or
tion of quality circui t boards without expe n-
ROM.
sive and time consuming processin g with
Th e addition of the MMD-1 / MI board to
cameras and darkrooms. Th e kits , model
the basic MMD-1 Microcompu te r in creases
numbers 32X-l and 32XA-1, con tain posi-
the system memory ca pac ity to 2.5 K pro-
tive res ist coated circuit boards, bare copper
gramm ab le memory and 1.5 K PROM or
clad boards, and all materia ls necessary for
ROM . Th e Telety pe interface and audio
fabric ating circuit boards by the direct art
casse tte interfaces allow easy and in ex pen-
th en etch process, and also by the positive
sive data storage and retrieval. The
photo resist process.
MMD-1 / MI is now avail ab le from E&L
For direct processing, circuit patterns are
In struments and from all E&L Instruments
applied directly on bare copper lam inated
stock ing represe ntat ives. E&L In struments is
circuit boards, using the acid res istant rub
located at 61 First St, Derby CT 06418.-
transfer artwork sheets and oth er art mate-
rials contained in the kits. Th e sheets have
patterns for 40, 24 and 16 pin dual in line
The Briefcase Computer Concept, Revisited packages, flat packs, lines in 5 widths, pads
This neat little package of computing • 5.5 K byte PROM operating syste m in 7 diameters, edge contacts in 2 sizes,
power, the DE68, made by the Digital with mnemoni c translator, tape com- alphabetic and numeric markings, and many
Electronics Corporation, 415 Peterson St, mand s, memory man ipul ation fea- mi sce ll aneous couplin g pad co nfigurat ions.
Oakland CA 94601, is intended for use as a tures, breakpoints, si ngle step ping of Th e rub transfer patte rn s also may be
stand alone computer system in a briefcase. programs, traces, etc. used for making one to one size custom
The syste m is completely self-contained, • 1 K bytes of user programmable positives on th e clear My lar film suppli ed.
with the following characteristics: mem ory stand ard , optio nal expansion This is then used to photo pattern the
to 4 K, 8 K or 32 K. copper clad laminated board s coated with
• 6800 microprocessor.
• alphanumeric keyboard (96 character). Thi s is a co mpletely self-contained micro- photosensitive etch resist. Vector's pos itive
• mini ature electronically controlled computer syste m whi ch could be equall y photo resist elimin ates the need for photo-
digital cassette system with 100 K well used as a person al co mputer, an educa- graphic conversion of master artwork to
byte on line capacity. tional tool orie nted to asse mbl y level pro- negatives. The positive film is placed on the
• 20 co lumn wide alphanumeric di splay. gramming, or custom applicati ons interfaced board, and ex posed to a full or partial
• 20 column alphanumeric printer through its 10 expansion connector (to the ultraviolet li ght source.
(optional). ri ght of th e processor card see n in the Exposure time requires approxi mate ly
ph otograph). Th e DE68 pri ce, completely four minutes with either a GE "sun lamp," a
ready to go as seen in the ph o tograph , is commercial ex posure lamp, or direct su n-
$35 00 (including the printer peripheral light. A six ounce bottle of developer in
opt ion) with delivery 60 days after receipt solution accommodates about 600 square
of ord er.- inch es of sensitized surface.
The exposed and developed board s are
etched in the fe rric chloride so luti on and
Star Trek in BASIC? chemical tray supplied. Th e simpl e devel-
Atlantis Consultants, POB 8493, Sal t oping and etching process takes about 20
Lake City UT 84108, has co me up with two minutes. Foll owing washing, the board is
Star Trek programs, wr itten in BASIC, ready for use.
whi ch are ava il ab le now at $12.50 for the Vector etched circuit kits are useful fo r
se t. Included in the literature acco mp anying both engin ee ring and ex perimental circuit
the program s, according to a letter from Earl board fabrication. Exi sting full sca le artwork
Smith of At lantis, are memory requirements, may be copied directly with the suppli ed
operational in str uctions, and tips and tracing and artwork material s.
patches to help ta il or the programs to any The Vector 32XA-1 kit will make seve n
size sys tem. Th ese prog rams are acco m- printed circ uit boards , an d is priced at $28.
pani ed by a one year warrantee aga in st The 32X-l sa mple kit makes two boards,
programming and typographical errors.- and is priced at $11 .50. _

Need a Fast Microcontroller?

processor with a simpl e two ope rand instru c- graphics application, with an intelli ge nt re-
Signetics Corp, 811 E Arqu es Av, Sunny- tion set and a single in stru ction exec ution fresh command langu age and a commun ica-
vale CA, has introduced a new hi gh speed lim e of about 250 ns (operat in g on 8 bit tions disciplin e for talking (as a peripheral)
microprocessor co mpo nent called th e data). Th e processor is available from stock to your main microprocesso r.
8X300, which is "optimized for co ntrol at distributors for a quantity of 100 price of Take a look at the vertica l micropro-
operations." This is a Schottky bipol ar $86. 75. No sin gle quantity price was quoted, gramming prob lem: emul atin g the instruc-
but based on comparable pricing stra tegies in tion set of a known "nice" processor with
the marke tpl ace, we would ex pect the singl e lots of software. Th e 8 bit data paths of thi s
unit price to a hacke r to be below $25 0. machine, plu s th e hi gh speed and in terna l
Wh at ca n a savvy BYTE reade r do with a scratch pad faci litie s shou ld all ow mi cropro·
chip like this? gramming hackers a very flexibl e alter native
Well, look at the vector grap hics problem, to the bit sli ce ap proach. According to the
an d consider des ign of an ROM programmed press release, it is "possibl e for 8 bit parall el
vector graphics processor. This machine) is data to be rotated or masked, to undergo
fast enough to do both the t iming operat ions arithmetic or logica l ope rations, and then to
of a vector graphics ge ne rato r, and th e be shi fte d and merged into any set of from
storage housekee pin g for refresh. Build a one to eight contiguous bits at the destin a-
cListom machin e for th e 256 by 256 vector tion - all within one 250 ns cyc le." A glance

102
at the block d iagram for the processor in terfaces to utili ze th e capab ili ty of t he portio n covers the mov ing stuff. In a Space
reprod uced here corroborales t hi s state me nt. 619. War ga me, t hi s ter min al would excel since a n
We 'll be look in g forwa rd to so me arti cles Th e sto rage tube of th is dev ice is u sed to intricate background map could be con-
by reade rs o n the use o f t hi s sort o f chip to ach ieve hi gh density grap hics witho ut th e s tru cted using the storage graphi cs tech-
imp lemen t high performance ho mebrew ri gs need for provid ing ex pensive memory d e- no logy of the in strument, wit h t he variab le
in th e near fu t ure, to say no thing of th e vices. But th e b istab le s to rage tube has two grap hics of the space ships, torpedos,
poss ibil ity th a t such a chip could be use d as mod es of operati o n: Th e storage mode players, etc, being pro vided by t he refresh
a key compo ne nt of a tru e " hi gh leve l a ll ows co nve nti o na l storage grap hi cs w hi ch portion. Th e ca paci ties of t he machine in the
language " mach ine imp lemented at low gives high d ensit y fli cke r free picture s bu ilt refresh mode are 3200 in ches of stored
cos l.- up over co nsiderabl e pe ri od s of tim e; a vecto rs a nd 630 inches of refreshed vectors.
second refresh graphics mode all ows a pa r· One ca n expe ct that those lu cky BYTE
Attention , Commercial a nd Industrial tia ll y stored and parti a ll y refreshed disp lay readers who have access to a Tektro ni x 619
Graphics Users to be gene rated . Onl y the fixed porti on of t hro ugh a resea rc h, commercia l o r industria l
the di splay is stored with sto rage graphic s job situ a ti o n will have a field day with this
Here is a state of th e art graphics pro du ct
techn o logy, and a variab le refresh gra ph ics machine for inte ractive games.-
designed for OEM custo mers o nl y, th e
mode l 619 Storage Di spla y Monitor made by
Tek tro ni x In c, Beave rto n OR. OEM only
means th at Tek tro ni x is not inte res ted in
selling to "u nsophi st icated" users in this
If you want a microcomputer
case. But as an exa mpl e o f a high reso lu t io n
vector graphi cs display, all us indi vidu al
with all of these standard features ...
users will be waiting with mouth s wate ring • 8080 MPU (The one • Complete with ca rd
with growing soft- co nn ectors
for the in trod uctio n of smaller sca le but hi gh wa re s upport) • Comprehensive
reso luti o n unit s for perso nal system s. Here is • 1024 Byte ROM User's Manual, plu s
wh at the state o f th e art price of $7125 (W ith m ax im um ca- Inte l 808 0 Use r's
(single quantity OEM) ge ts a system s pacity o f 4K Bytes) Manual
• 1024 Byte RAM • Com pletel y
engineer with graphics in mind these days : ( With maximum factory assemb le d
capac ity of 2 K and tested-n ot
Bytes ) a kit ---:-
• TTY Se ri a l I/ O • O ptional ac-
• EIA Se ria l I/O cessories: Key-
• 3 para ll e l I/O's boa rd /vi d eo
• ASC II/ Baudot display, audio
terminal com - cassette m o d em
patibility with TTY mac hi nes or vid eo units in te rface , powe r s upply, ROM programme r
• Mo nitor hav in g load, dump, d is play, in sert and a tt ractive cabinetry ... p lus more options
a nd go funct ions to fo ll ow. The HAL MCEM-8080. $375

.. . then let us send you our card.

HAL Communi ca tion s Corp. has microcomputer you can buy. For
been a lea der in digital co mmuni - details on the MCEM-8080, write
cations for over half a decad e. today. We'll also include compre-
The MCEM-8080 mi crocomp uter hensive information on the HAL
shows just how far thi s lea dership DS-3000 KSR microprocessor-
ha s taken us .. . and how far it based t erminal, the terminal that
can take you in your applications. gives you multi-code compati-
Th e mode l 619 is a 19 in ch (48cm)
That's why we'd like to se nd bility, flexibility for future
d irect view s torage tube di spl ay whic h is
designed for high dens ity fli c ker free you our card-one PC changes, editing, and a
graphics. The 619 prov ide s stored disp lays of board that we feel is the con venient, large video
combined alph anumer ic and grap hic info r- best-valued, most complete di sp lay format.
mation from anal og so urces and d igital
com puters, with engin eer ing da ta prov id ed HAL Communications Corp.
so that the OEM systems build er has fu ll Box 365, 807 E. Green Street, Urbana, Illinois 61801
con tro l in deve lo ping ana log o r co mpute r Telephone (217) 367-7373

~CGmLPTUU-lI~~ ~rall itCG Cfl~~

without SofTWARE. At last a BASIC SOFTWARE LIBRARY is available!
Volumes I & II available immediately; III & IV in January. * Vol. I - BUSINESS &
RECREATIONAL, source codes, instructions, etc. 300 pg. * * Vol. II - ENGINEERING
STATISTICS & PLOTTING plus BASIC Reference conversions, 250 pg. Each written in
BASIC, immediately executable in ANY computer; micro or mini. SPECIAL CHRISTMAS
_11M OFFER Vol I & II - $39.95; else $24.95 ea. Add $2 ea. for hndl
BmAM£RICARO $4 for ai r mai I, or send SASE for info. TO: SCIENTIFIC RESEARCH
..".,. PO Box 2096; Ashland, VA 23005. * Volume Discounts available *
Daler .lind distribution inqu iries wl!!lcome.

103
•
 Classified Ads for Individuals and Clubs FOR SALE : MDS Technology KIM-1 micro-
computer system . Purchased in March from MOS
FOR SALE : Complete VIATRON System 21, FOR SALE : Limited supply of core memories for $245; completely checked out. $175, including
includes printing robot, camm adaptor, also many from major computer manufacturer with spec 5 V and 12 V power supply . Built to MOS specifi-
tapes. Unit in perfect operating condition. Will sheets. 8 X 64 X 64, $15; 16 X 64 X 64, $30; 17 X cations, and complete documentation. K I M -1 has
consider throwing in the IBM Selectric Model 72 64 X 64, $35; spec sheets, $0.75. Include shipping, hex keyboard, LED display, 1 K RAM. PRDM-
typewriter. Want $500 for all except Selectric. Will excess refunded . Jim Kuiper, 542 Linden Ln, Ann resident executive, TTY , audio tape, and BOS
trade for video display board and memory for Arbor MI 48103 . interfaces. Larry Hill , (6171475-4700 or
IMSAI. or small video terminal. Tom French , c/o (6171 646-6428; 163 Waverly St, Arlington MA
Philips Data Systems, 3320 Holcomb Bridge Rd, 02174.
Norcross GA 30092. FOR SALE: FRIDEN printing terminal 1970,
several available. 12.2 or 14.7 cps - full ASCII FOR SALE OR SWAP : EIS telewriter-keyboard l
FOR SALE: Hewlett-Packard HP-185B oscillo- font - half duplex with breakin - 14 % paper; 140 printer unit, 8-level cod e (ASCIII , 110 baud, full
scope with 187C dual trace plug in. Triggered print positions. Quiet , mechanically simple, cast duplex, TTL level output. Operating condition,
sweep, DC-1000 MHz sampling. Internal DC level, aluminum housing . Size 21" X 23" X 11". Room may need some adjustments. W/so me data $295.
50 MHz sine wave, pulse calibration signals. One for 15 3" X 5" PC cards. Parallel data input and Also some fully ASCII encoded keyboards $50.
knob cracked but scope works good. $300. Mike output. Schematic for electronics to perform shift Money order to : Bill Dumbleton, 1713 Webster St,
Turner, Rt 2, Roberts St, Fletcher NC 28732. decode, repeating and logic interface with UART Omaha NE 68102. (402) 341 -1529 days. 551-0577
(7041 684-2112. included (standard TTL! . Mechanically overhauled, evenings.
excellent operating condition $250 delivered, New
WANTED : I am looking for information on a York-Boston. J Colter, POB 122, Short Beach CT FOR SALE : 16 K words by 9 b it core memory
FREIDEN "5610 Comptyper." (11 Pin outs on the 06405. modules (10" X 12" X 4" 1. Needs only T2L
aux output plugs of this unit. (21 Necessary data to interface and power supplies (+5, -5, and +30
interface this unit with a 8080 system. K9BJN P F voltsl. 1IJs read/write cycle time capability . Com-
Collins, 1611 W Madison St, Kokomo IN 46901. WANTED : ITT Asciscope repair manual and plete documentation available. For additional
(3171 452-0265. schematics. George Ahmuty, 60111 Wendy Ln, information write to Dave Bowman, 5437 W Tierra
Westport CT 06880. (2031 227-8534. Buena Ln, Glendale AZ 85306, (602\ 978-0332.
WANTED: New or used LA36 DECwriter II. I have
written several programs in Altair BASIC. For FOR SALE: Altair 8080, PTC Motherboard, TRADE : Will trade by BYTE collection (issues
information send $0.25 to Timothy G Roscoe, 153 IMSAI cassette interface, 4 K and 1 K RAM, 4 K 1-12, excellent conditonl for a complete set of
Dorman Dr, Elizabeth PA 15037. EROM presently burned with assembler-monitor- aST magazines from January '75·June '7 6 inclu-
editor, MITS quad parallel interface board, TI sive. Jeff Stern, 809 Flanders Dr, Valley Strm NY
WANTED: Need schematics and manuals for ASCII keyboard, PTC VDM -1 with expanded 11581. (5161,791-7471 .
DURA MACH 10, also tech data for ITE L System software and video monitor . Complete system :
3016SQD and/or DURA typewriter models $1600. C G Hullquist, (6151727 -7793 /8437 , Box FOR SALE : FABRITEK core stack, model
8123124 and 133038. I have considerable data H, Mountain City TN 37683. 999-6155-00-B 16 K words by 24 bits, no other
(130 pages I on other models to swap or sell. I wish data. Will include 34 type SN7528 sense amps.
to communicate with other users and parts sources. ENTREPRENEUR seeking creative electronics Best Offer over $200 takes it. Contact : Steve
Ronald Jenkins, 4490 Sirius Av, Apt 4, Lompoc "wizard" as partner in new moonlighting business Marum, 116 Western Hills Dr, Apt 136-J, Howe,
CA 93436. venture to develop computer products for high TX 75059. (3121 532-5292.
potential home and small business markets. Must
FOR SALE: IBM 2315 disk cartridge (S/N 227211 be located in San Francisco area. If interested, PARTNER(SI for microcomputer store wanted in
perfect condition; make offer. Rudy Wrobel , please write R Lum, 20661 Marion Rd, Saratoga Texas, Okla, Colo, or NM. I will finance up to one
12725 W 55 Terrace, Shawnee KS 66216. CA 95070. half interest in store; you must have direc t micro-
computer experience. Dr M E Reed 1417 North-
FOR SALE : MITS 88-4MCD 4 K dynamic memory FOR SALE OR TRADE: Friden Fle xowriter gate Sq B-12, Reston V A 22090. 17031 437 -5992.
card. Fully assembled and tested by MITS $190; Model SFD . Has 8·level printer, paper tape reader,
88PID parallel 10 port with cable and connectors, paper tape punch and keyboard. Excellent con- FOR SALE : Assembled SWTP 6800 CPU board
assembled and tested $60. Complete set of Mark-8 dition. $300 or will trade for TVTI or TVTlI. Call with support information consisting of SWTP 6800
boards with one extra memory board all brand new or write Bill Dawson, 316 21st St, Apt No . 4, User's Manual, Motorola 6800 Programming
plus highly regulated Precision Systems power Virginia Beach VA 23451. (804) 425-4411 (daysl, Manual, and 6800 App lications Handbook . Will sell
supply +5 V /8.5 A -12 V /2.0 A adjustable to (8041 422-5921 evenings. for $260 or best offer. Mark-8 CPU . Addre ss latch.
-9 V, includes Radio Electronics Mark-8 blurb all and Input multiplex boards, includes most TTL
for $110. Steve Caldara, 965 EState St, Ithaca NY SWAP OR SELL: One (1) tape punch machine and resistors and caps, $30 or best offer. 18 slot
14850. (6071 273-9234. with keyboard, 75 cps punch and Burrough dis- ca rd cage used - great condition, with 18, 22 pin
play. $400. Four (41 75 cps punch mechanisms and WW and 17, 100 pin WW Amphenol card edge
FOR SALE: MITS Comter 256 terminal with driver cards. $75 each. Three (31 high performance connectors, $25. Tim Tibbott , 714 N Nottawa,
acoustic telephone coupler, assembled and opera- stepper motor systems (2 motors and power supply Sturgis MI 49091 .
tional. Also, three 4 K dynamic memory boards and control logicl. $300 each. Honeywell 3C
and an 88-ACR cassette interface, all assembled. cards - three (31 each: FC320 and BC320; one (11 FOR SALE : Populated MIL MOD 8 board s: 8-2
Steve Fritts, 2920 Bellevue St, Knoxville TN DK320. Call after 5 PM 16171 369-2075. Albert TTY board $10. 8-3 Con t rol board $10. 8-6. 8-7
37917, (6171 525-5407. Spitzak, 113 Everett St, Concord MA 01742 . 10 boards $10 ea. 8-1 CPU board $18. Unpopu-
lated 8-4 1702 type PROM board $5. C-MOD 8
FOR SALE: I have a supply of new INTEL and TI FOR SALE: I have an HP-65 calculator to sell MOD 8-9 board with .8316 2 K X 8 bit ROM
aOaOA microprocessor chips for $25 each. These before I buy a computer, since having both would containing 800a operating system $30. Plus much
can be used to update your Altair computer, to take too large a byte out of my savings. $700 buys information on the MOD 8 system. All boards built
control intelligent peripherals, or for experimental it. Joseph R Danek, 3945 E Birchwood Av, with PRIME parts. R DeHoff, Smith Hall , Kent OH
circuits. Sockets and specs are available if re- Cudahy WI 53110. Call 14141769-7489 between 9 44242.
quested. G Lorenc, Box 710 LU, Lockport I L and 12 AM CST.
60441, (8151 838-4930. FOR SALE: High speed paper tape punch, Tele-
FOR SALE: Issues 1-12 of BYTE, good condition. type Corp (BRPEI with maintenance manuals and
WANTED: Low cost new or used terminal and/or Best offer above cost of magazine. Robert Camp- parts manual. Eight channels at 110 characters per
acoustic coupler for private use . Write Rob Lufkin, bell, 4324 Walker St NE, Cedar Rapids IA 52402 . second. Very good working condition. Best offer.
Lodge 9, RFD 1, Box 52, Charlottesville VA (3191393 -4191. Ronald Howland, 23 Sumner St, Milford MA
22901. 01757.
FOR SA LE : Altair 8800 co mpu te r, fully assem -
FOR SALE : Zilog Z -80 third generation micro- bled and tested, w ith 1 K static RAM , $500 plus AVAILABLE : Copies 1-9 of BY TE (two cop ies of
processor chips. $95 each including shipping and shipping and handling. R A Stook, Cherry Dr, issue 2), Any offer will be considered but would
handling. We are a club and will purchase these Souderton PA 18964. Telephone : (2151723-4766. prefer to sell all in one transaction . Contact : John
chips from the manufacturer at quantity discount R Kaser, 7500 NW Peavy Arboretum Rd , Corvallis
prices. We need a minimum of 25 orders. For a FOR SALE : MITS VLCT IVery Low Cost Termi - OR 97330. 15031 745-5703 .
description of the Z-80 see the August 1976 nail, complete except for case, $75; 4 K memory
BYTE, page 34. Send orders to Kristopher Kafka, board for Altair 8800, fully assembled and work- FOR SALE: 8008 based operating syst em fea-
166 Marshland Rd, Apalachin NY 13732. ing, $95; tape cartridges for IBM MTST typewriter, turing 11 human-engineered commands, all ows full
(6071625-2972. Sorry, no COOs, no. credit cards. $5 each or swap for ? Used Altair 4 -s lot mother- control of loading /examining memory, octal or hex
board in reason able condition, $10. Jim Einolf, dump, execution initiation, and read / write /control
FOR SALE: SCM computer terminal in perfect 3900 Fox Dr, Lovel and CO 80537. of cassette tape storage. Included are 47 pages of
working order. Complete with cables and well- source code , operating instructions, and schematics
filtered power supply. All in working order. SCM FOR SALE : STELMA Model 2400 data modem . for 256 level hardware pushdown stack. serial-
No. 603601 schematic No. 4391171. Can easily be 1200 and 2400 bps over HF radio (used on parallel interface, PROM interface. $7.50 pos tpaid .
converted to 10 hard copy printer. You pay APOLLO project for long haul data transmission). If 15 orders are not received within 30 days from
shipping and $150. Will trade. Call or write Wallace 2 units, spares, manual $250. Frank Gentges, 3512 publication of this ad , your check will be returned
Hurley , 2753 Parkside Dr, Fremont CA 94536. Orme Dr, Temple Hills MD 20031. uncashed . William E Severance Jr. Center Lovell
(415) 792-8589. (301) 894-2613. ME 04016. 12071 925-2271.

104
 .... COMPUTER Audio Design Electronics PhOtocopy or cut out this sol icitation for
information and send to:

PROGRAMMING Presents A New Concept in

COURSE Mini/Micro Computer 7338 Baltimore Ave., Su ite 200
Free description and outline of Shops College Park, Maryland 20740

Modu-L earn TM Home Study

JOINT VENTURE
Course in m ic r ocomp uter pro-
gramming. Hundreds of pages of
text with examp les, problems, GROUP OEM BUYS
and solu t ion s. Prepared by pro-
fessiona l design engi neers using
The Computer Emporium CHEAP, Inc. was sel up to coord inate joint venture OEM
Group Buys! Depending upon the total quantity of com·
the best software design tech- mitments received. you can expect to pay from 20% to 70% of
niques from stru c tured program - the retail sales price. Now you too can combine your orderi
with others throughout the country to purchase factory new
ming and practical exp erience
electronic components at OEM rales. We witl accept small
wi th microcomputers. Presen t ed Factory and Club commitments as well as individual
in a modula r seque nce of 10 A uthorized Dealers for commitments.
lessons oriented for the new
programmer. Ex tensive ref erence
IMSAI, S.W,T.P.Co, O.A.E. Circle be low the products you may be interested in and
estimate their Quant ity. After we receive this survey. we shan
material you will use lon g after Pro c e ss 0 r T e C h n 0 logy, send. to you. more information. prices and delivery dates.
you become an accomp li shed Memories: 9 1 L02 _ _ , 2102 _ _ , 1702 _ _
m icrocomputer softwa re designer.
D. B.S. and many others. MicroP: zao ___ . 8080A _ _, 6800 _ __
P.C. Boards: Computer Grade double buffered optional parity
Much of the inform ation in t he Come see our showroom memory boards compatible with the Altair 8800 on one
course has been available on ly
throug h cost ly seminars. Now
and see the Difference. edge and the Altair 680 on the opposite edge: 4 :8: 16 K_
Floppy Oisk Orives _ _ . Disk Controller _ _ __
you can purchase this comp lete Support Service Sales Mag. Tape Drives _ _ _ .
TV Monitors _ _ _ _ .
Modems _ _ _ _ __
Oscilloscopc _ _ __ _
hom e study course for u nder Sockets : 14Pin _ _ _ . 16pin. _ __ __ _
$50.00. Send for free descriptive 24pin _ _ • 40pin _ _ , Other _ __ _ __
brochure now. Soflware : Fortran _ _ . PL/1 Subset _ __ __
The Computer Emporium Other :_ _ __ _ _ __ __ __ __ _

LOGICAL
SERVICES INCORPORATED
487 Broadway 510-512 Other: _ __ _ _ _ _ _ _ _ _ _ _ __

EXTRA: We wi ll consider purchasing general purpose P.C.

711 Stier li n Rd, Mountain View, New York, N. Y. 10013 Boards and Kits. etc. Write us about what you may have to
CA 94043 (415) 965-8365 212-226-2038 offer and its OEM prices.

microcomputers
- Computers for People -
NOW!
IMSAI8080 Attention: KIM-1 owners.
A Computer Store in
At Special Introductory Prices
(Prices Effective Unlil De cember 31,1976 On ly)
New York, NY
1·8080 Kit ...... . ....... .......... $506 For Sale: Assembler program com-
1·8080 Kit with 22 Slot Mother .... . $550 patible with MOS Technology assem-
• Add $9 each for shipping and handling
• New Yo rk reside nt s add Sales Tax bler. Uses KIM-1 cassette interface Offering the complete line
• Send check or m oney order for full amount
(A ll ow 3 weeks for personal checks.)
for storage of source and object of * Altair mainframes and
IIIH WE TAKE MASTERCHARGE
OR BANKAMERICARD
!!!!!
~
programs. Also i ncl udes a te xt-editor
program, and both run in 4K of
peripherals as well as boards
FOR MAIL AND PHONE ORDERS
& boxes, tools & instru-
memory. They are distributed on
For orders. informat ion or special prices
ments, books & manuals,
cassette in both source and object
on all lMSAI products
form, in case you wish to improve or
supplies & media.
modify them to suit your ne eds.
Call: (315) 637·6208 Assembler/text-editor •• $19.50 ppd.
Write for details on sale of your
The Computer Store Inc.
programs on a commission basis.
55 West 39th St.
New York, NY 10018
212-221-1404
Micro Software Specialists. Inc.
2024 Wa shington St -Altair Is a
Commerce TX 75428 . MITS. Inc.
P,O . Box 71 • Fayetteville, N .Y. 13066
ASk lor Our Special Price Sheet.
For more information
 Build This
Video Display Terminal
first became interested in micro- It wasn't long until I becam e impatient with
processors about a year ago. After much the slowness of the Tele-Term, its loud
thought, I decided to investigate this rap idly clacking, an d the reams of paper I was go ing
growing field. I did not have any particular through. What did I need? A vid eo terminal,
goal in mind but I did want to learn how of course. There are a number of good kits
they work and what they ca n do. Th erefore, on the market place. My impression was that
I dec id ed not to buy a kit but to build my they are either too expensive for my home-
own fro m scratch. I happened to se lect the brew budget or they are Altair compatible.
Motorola processor for a numb er of reaso ns Now I needed Altair compatibility for my
which I won't consider here. After a few homebrew system like a write only memory.
weeks, I had a small system up and run n in g. It would not have been a trivial task to
Alfred I Anderson I even managed to interface an old "Tele- interface any of the afforda bl e video
721 15th Av SW Term" th at I borrowed from the Mayo modules designed for the Altair to my
Rochester MN 55901 Clinic where I work. Now (I thought) I had homebuilt 6800 system. What could I do?
the cat by the tail (or the byte by the bit?). Th e answer was in th e Jun e 1976 issue of
BYTE. Mr Gantt's article "Build a Television
READ / WRITE
Display" (page 76] provided th e basic infor-
mation I needed on television interfa cing. I
I changed the circuit around a bit, added a
few goodies, incorporated som e memory,
PROCESSOR ADDRESS BUS
RAM ADDRESS BUS
~

) and wrote a few lines of software. I am now

IK X B using a video terminal th at you would like.
PROGRAMMABLE
The following paragraphs should outline
S I MEMORY
Y N K RAM DATA ) everything you need to know to complete
S T one of your own.
E
PROCESSOR DATA BUS T
E
M
R
F
...
K VIDEO ADDRESS Design Specifications
A VIDEO
C GENERATOR FOI' my purposes a video terminal had to
E
have a number of features I deemed to be
PROCESSOR CONTROL BUS VIDEO DATA ~ desirable. First, I wanted imm ediate access
to any character on the screen without
( hav ing to mess aro und moving littl e white
h boxes . This feature all ows me, for examp le,
to keep a real time clock display in the upper
right hand corn er of th e screen. This video
72-300!l RF
TELEVISION
r--... MODULATOR
terminal uses a simpl e mind ed direct
TRANSFORMER

t memory access techniqu e enab lin g a com-

plete screen update in the twinkling of an
eye. I chose a screen configuration of 16
Figure 7: Video Terminal Systems Configuration. This bloC/? diagram shows lin es by 32 characters per lin e. This limited
how the terminal subsystem is organized as a display generator for the amount of data didn't reall y concern me
computer system. since I would also be using sCl"Ol ling. This

106
 ~
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l .----+--I---Q<10c: e 1l1.!..1++-~-
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Ti~ OC~
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7410 CBST 12

SYNp§....
OB~
I~ von=-
I~ C 0 5 ~84-_ _ _.., 6 BlK 14 ..----1Lu_P_ _O.:.;A..J~.
FROM I~ V02 19 g 0 41L<1--~
I~ 3~1- ~TP9 TPIO 7400
SYS-
~~R-'
FACE
I=<.V04
'~V05
E
II I
II N
T
0 2 ~I-
~ I ~ .----+-------+~---+
r.:t:I'3~r--
............ - LL- 0
-...
~NC L-~CTE,.,.......I - 15
CLK INH 14 A
IL>'-""-- Jj I IC65 IC52

~5Tcf63
74165 7492

ClK f!- 7400· J 6

ooiL
B fL---<
OA~

'----IH~I"':."~~,,',j:..:
~ ~ 1J~ ,~;"-
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L--_---l

IC76 B 100g
9 c
+5V
L...----+~~~~\re-'
IC76
7486
6

_
+5V 5 b
~C64
7404 TPI21C64
7404 r-------l R7
Il • .--7486
9 7400 +~~!
IC76 3 ,.-[] +5V b 4 5 C 6 116 680 I 1101

IC 53
8810>"'----'
9 d :><:1--+-<"""" L~ lill~Crj:, I~~ 35IP 23~04 II

~
L..._ _",I0'l C Il7400
r.? IC32
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I 7410
13 IC 42 12
2 0 /'
T PI3
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1000
2

6RI0 II I
hP1480 15

VIDEO
L-----NO-T-E-:-A-ll-R-E-S-IS-T-O-R-V-A-lU-E-S-A-R-E-O-H-M-S-~ ~ 13 R9 4 7 49 10 %T

I
l!E~~
1000
_____ J
B F~6 9\ I

Figure 2: Detail Schematic of the Video Generation Circuitry. This section of the design includes all timing logic and character
generation logic. See table 7 for a complete parts list for figures 2 and 3, and see table 2 for the power wiring list.

107
 BIDIRECTIONAL
DATA BUS
FROM PR OC ESSOR

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15 " OE

~ AO
BO ~
13 OF IF 14

OA ~
AI

I~ IA ~
A2 BI
14
I~ IrB OB f...-
82 EN2

l~ IC OC fz- B3 15
1

EN~ ~6
A-B
DO DI~J2 o ~ < DI!>E 07
READ
V
24.11 25J126J1 34.11 35JI 37.11
27.11 36.11
24.12 ~
1~~2
ADDRESS DATA IN 25 .12
~TPI6
MATCH MEMORY AR RAY 26.12
5 7410 8 21L02 - 1 INTEGRATED CIRCUITS 27. 12 ~
IC24 IC 34 DATA VD4
41IC33Y-- OUT 34.12
IC25 IC35
31 b
- 1~410 WRITE
IC 26
IC 27
IC 36
IC 37
35. 12
36.12
37.12
IY.M
IYJL6.
~D7

I
NOTE : X. 7=ALL IC 'S, PIN 7{TYP.)

E31'';~-,/'''
- II 7410
26.12= PI N 12, IC 26 (T YP')

X. 13
IOIC33 8 CS r-
X. 3 RW
91 C./
A9 A8 A7 A6 A5 A4 A3A2
1lc,14X.15X.l6X.1 X.2 X.7X.~ .5 :.~~ r;
I- PROCE SSOR
O-VIDEO
JJJIJ
.-/ IY 2Y 3Y4Y
ICI4
74157
A9 3 IB
r AS 6
IQ
2B
IA lz
2A 5
VA9_
VAS?
f=S.A7 3B VA7 ,;:-
3A II
i5-A 6 ~ 4B
I
S
4A 14 VA6?
"-
G
4 7 9 12
ADDRESS );5
IY 2Y 3Y 4Y
IC 15
74157
...........,A5 3
IB IA
2 VA5~
ADDRESS BUS
FROM PROCESSOR
~M
.A3
~
10
2B 2A 5
I
VA4>-
VA3r
FROM V IDEO
GENER ATOR
3B 3A
:::SA2 13 4A 4 VA2 .,::-
4B
"-
I S

G 4 7
SELE CTION
J5 IY 2Y
ICI 6
74157
r:: AI VAl Q
r:::
, ........
AO
3 IB
6
2B
IA 2
2A 5 V~CJ,
I
S

G
,);5

Figure 3: Detail schematic of the system in terface and memory for this video terminal design. In this diagram, the processor
interface is at the top and left edge, and the video generator interface to figure 2 is at the right of the drawing.

108
allows the display of any 16 consecutive display generator. The video output is
lines of the 32 lines kept in memory. To be routed through coax to an RF modulator
fancy, I thought it desirable to have both adjusted, in my case, to channel 5. This is
white on black characters and the reverse coupl ed to a nine inch (22.86 cm) GE black
(black on white) for hi ghlighting. The termi- and white portable TV through a six foot
nal shou Id use the standard power supp li es I length of coax and an impedance matching
had avai lab le in my system (+5, +15, transformer. The interface section of the
- 15 V). Since I didn't want to foo l around termina l is quite simp le. Its sole purpose is
modifying my te levision I included an RF to all ow the processor to access the video
modu lator to feed the signal to the TV memory whenever it desires .. I fe lt that an
antenna inputs. My entire system was built occasiona l high pr iority interruptio n to the
on Vector # 3677 and 3682 DI P plugboards. display was preferab le to slowing down the
Th erefo re, this video terminal should also fit processor. After the system was bu ilt, I
on the same type of board. discovered that no interfe rence could be
Finally, and most important, it had to be seen on the term in al wh en the processor was
compatib le with MY system. I shou ld prob- updating the display.
ably add that this terminal ca n of course be This display interface was built on a
adapted for any computer system. It is a lot standard 4W' by 9);1" (11.4 cm by 24.1 cm)
easier to interface Motorola systems to In te l Vector #36 77 plugboard wh ich I highly
systems than vice versa. recommend. The board has two power buses
etched on the reverse side. I have never
experienced any problems with the power
Functional Implementation distribution whi le using these boards. The
Figure 1 shows the relationship between board was wire wrapped with all integrated
various modul es comprising this video termi- circuits in sockets. Iso lated discrete com-
nal. Th e system in corporates a 1 K X 8 ponents were mounted with wire wrappab le
programmable memory to refresh the screen. termi nals. Ana log subsyste ms were mounted
Th e con te nts of the first 512 bytes is on dual in lin e header plugs wh ich, in turn,
constantly being accessed by the vid eo were mounted in wire wrapped integrated

Listing 7: A Memory Test Program for the 6800. This program tests the user memory of the
television interface. If an error is found, the program stores the parameters of the erroneous
location in locations VALUE (th e test pattern to be stored), RSL T (the garbled test pattern
read from the bad location) and A DDR (the address of the bad location). The limits of the test
are arbitrary, being set by the constants at STRTADR and ENDADR. An error condition is
concluded by entry into an endless loop of one instruction in length, thus locking up the
machine until reset by the programmer making the test.

Addr Hex Code Label Op Operand Commentary

0000 DE 22 MTST LDX STRTADR X := STRTADR [define starting address ] ;

0002 86 00 LOO Pl LD AA #0 A := 0 [define first test pattern] ;
0004 A7 00 LOOP2 STAA O,X @X= A [write test pattern] ;
0006 01 NOP Let the memory c irc uits settle
0007 01 NOP down a bit between accesses;
0008 E6 00 LO AB O,X B := @X [read test pattern back] ;
OOOA 11 CBA Do es test pattern read match original?
OOOB 26 09 BNE ERROR If no t then quit with error;
0000 4C INCA A := A + 1 [de fin e next test pattern] ;
OOOE 40 TSTA Is A = O? [have all patterns been used?];
OOOF 26 F3 BNE LOOP 2 If not then continue cycle at current address;
00 11 08 INX X := X + 1 [define next test add ress] ;
0012 9C 24 CPX ENOAOR Is X = last address?
0014 26 EC BNE LOOPl If not then restart t est loops;
0016 97 1E ERROR ST AA VALUE VALUE := A [indicate source va lu e ];
00 18 D7 1F STAB RSLT RSL T := B [indicate resulting value] ;
001A DF 20 STX AOOR AD DR := X [indicate address of problem] ;
001C 20 FE OO PS LOOP BR A OOPSLOOP Han g up in end less loop unti l resta rt ;

Data Required By MTS T: These locations are at absolute addresses in the first
page of memory, and are referenced by direct addressing. I f the program is re-
located, the variables should remain in page zero.

DOlE 00 VA LUE FCB 0 E rro r va lu e;

001 F 00 RS LT FCB 0 E rror resu lt;
0020 00 00 AO OR FOB 0 Error address;
0022 00 00 STRT AOR FOB 0 Starting address of test;
0024 00 00 ENOAOR FDB 0 En ding add ress of test;

109
 circu it sockets, The radio frequency modu la-
tor was located off the board in a shie lded
metal box underneath the computer chassis.
All video and radio frequency signals are
Table 7: Video Terminal Parts List. This listing summarizes the parts routed through 72 ohm RG 59/U coax
identifications sources of supply and approximate cost of this design as built cab le. Needless to say, only good quality
by the author.' The costs for most parts are typical. The only part for which it components were used in the construction
may be difficult to find alternate sources of supply is the Pixe- Verter, a brand of th is system. Ou t of spec ch ips, in my
name product. The names and addresses of the vendors used by the author opinion, are usefu I only for making tie tacs
are listed at the end of the table. [and for stapling notes to bulletin boards].

Approximate
Quan Type IC number Sou rce Cost · Hardware Configuration
Integrated Ci rcu its, TT L Figure 2 is the schematic of the video
1 7400 IC53 James .18 processing subsystem. This circuitry is sub-
2 7404 IC32.IC64 Jame s .32 stantia lly the same as the circuit designed in
2 7410 IC33, IC42 James .40 the article by Mr Gantt. Several component
2 7485 IC ll, IC23 James 1.78
2 7486 IC76, IC77 Jam es .78 valu es have been altered from his original
2 7490 IC31, IC44 James 1.38 design . 74123s were used to reduce the
1 7492 IC52 James .82
2 74123 IC43,IC45 James 2.10
package count with excellent results. The
3 74157 IC14, IC15, IC16 Jam es 3 .90 dot counter clock is not derived from the
1 74165 IC65 James 1 .10 crystal frequency. Instead, a one shot multi-
1 74192 IC46 James 1.50
3 74193 IC47, IC54 , IC55 James 4.30 vibrator is used to give variable character
width . This all ows one to adjust the line
Integrated Circuits, MOS width to the sweep time of the individual
3 8T97B IC12, IC 13, IC17 SD 4.47 TV being used. This frequency can be
8 21 L02-1
IC24, IC25, IC26, IC27,
IC34, IC35, IC36, I C37 SD 12.95 increased to al low 64 characters per line if
2513N IC57 James 11 .00 desired . Although they are clear, I prefer not
MM5320 IC51 Nexus 4 .95 to use a magnifying glass to read the data on
Hardware the nine inch TV sc reen. Exclusive 0 R gates
27 16 pin Wire Wrap Sockets James 11.34 were inserted between the 2513 character
9 14 pin Wire Wrap Sockets James 3.51 generator and the 74165 shift register to
1 24 pin Wire Wrap Socket Jam es 1.05 allow for reverse characters. Note that a
1 14 pin DIP Plug Jam es .64
1 16 pin DIP Plug James .70 cursor is nothing more than a reverse space .
21 Wire Wrap T erm inal s, t ype T-49 Jame s 1.25 Only six data lines are required to specify a
300' # 30 ga Wire Wrap Wire (9.95/1000') Ace 3.5 0
particular 6 bit ASC II subset character code.
Capacitors This all ows the two remaining data lines to
1 22 pF James .05 contai n contro l information. If bit 7 is on
2 47 pF James .10 (the most significant bit), the exc lusive OR
1 100 p F James .05
1 .0047 mF, Mylar James .12 gates act as inverters to produ ce a reverse
1 .01 mF, Mylar James .12 character. If bit 7 is off, they act as buffers,
31 .1 mF, ceramic bypass (3.75/ 50) Jame s 2 .33 passing logica ll y true data for a standard
1 1mF,Tant James .28
2 100 mF, 16 volt, electro lytic James .38 character. Bit 6 is currently unused. This
cou ld be used to enable a blinking gate to
Resistors
make individu al characters flash on and off.
1 47 ohm, Yo watt, 5% carbon James .05
1 100 ohm Jam es
Or it could be used to disab le the character
.05
1 150 ohm James .05 generator and enab le a hand blown PROM
2 330 ohm James .10 array which wou ld allow a certain degree of
1 680 ohm James .05
3 1 k James .15
graphic text capabi li ty. The video combiner
1 18 k (particular value unit dependent) James .05
3 20 k, 10 Turn, Tr impots # 43P203 James 4.05

Semiconductors
lN4742, 12 V Zener Diod e James .29
1 N751 A, 5 V Zener Diode James .25 Vendors' Addresses
2N3904, NPN GP Transistor James .25
SD Sales; POB 28810; Dallas TX 75228 .
Miscellaneous
Burstein-App leb ee; 3199 Mercier St; 'Kansas City
1 10 MHz Crysta l # CY12A Jame s 4.95 MO 64111.
1 Vector #3677 Plugboard B-A 10 .38 Nexus Trading ; Bo x 3357; San Leandro CA 94578 .
1 Vector R644 Plugboard Receptacle B·A 4.32 James Electronics ; 1021 Howard St; San Carlos
1 Pi xe·Ve rter, Model # PXV-2A ATV Rsh 8.50
CA 94070 .
10 ' RG 59 / U Coax Radio Shk .60
1 72 ohm to 300 ohm Transformer Radio Shk 2.95 ATV Re search; 13th and Broadway ; Dakota City
2 RF Connectors Radio Shk .89 NE 68731 .
ACE El ectro nic Parts; 5400 Mitchelldale B-8 ;
Approximate Total Cost $115 .28 Houston T X 77092 .

110
 is different fro m that shown in Mr Gantt's ex per ience in assem bly of electronics.
articl e. The 2N3904 transistor is controlled Photos -I to 17 show waveforms at se lected
by the additi on of the two inputs (co m- test points id ent ified on the schematics.
posite sy nc and video). It prov id es t he These photos illu strate ty pica l wavefor ms of
proper interface to the RF modul ator. Note my com pl eted display board, take n from a
that nea rly every integrated circuit is by- Tektronix 455 osc ill oscope.
passed with a 0.1 mF ceramic capacitor.
This insures a clean power suppl y line with Software Support
littl e or no switching transient noise. I fe lt Th e pr imary disadvantage of th is system
th is to be es peciall y important in view of the as a term inal is the lack of a local mode like
different nonrelated frequencies in the ter- a hard copy printer or trad iti onal displ ay
minal. Notice the small circ led numbers that terminal. All data to be written on the
are alongside of the discrete components in scree n must pass through the processor. Thi s
the crystal tim e base and video combiner is not a serious disadvantage un less one
systems. Th ese refer to t he pin locat ions on desires a stand alone toy TV typewri ter. You
an IC plug which holds the components. may choose to develop yo ur own software
Anyone famili ar with interface boards (you have to if yo ur processor is no t a
will recogn ize the simp licity of the one 6800 !), or, if yo u are running a 68 00
show n in figure 3. The address lines on the system, you mi ght li ke to give mine a try.
left sid e of the schematic are from the Thi s software is a co ll ection of com-
processor's buffered address bus. The data pletely relocatable subr outin es (that is, the
lines at the top are to the bidirectional 8 bit fo ll owing package can resid e anyp lace in
data bu s. The 10 address lines and eigh ( data memory without cha ngin g any subroutine
lin es to the right sid e are interconn ectio ns to add resses ). Th ere are five entry points of
the vid eo te rminal controller. The high order interest. They all ow yo ur progra ms to:
ad dress lin es from the processor along with
the 6800's VMA (Valid Memory Address)
sign al are decoded by the four bit magnitUde Table 2: Power Wiring List This table lists
co mparators IC11 and IC23. Th e memory each integrated circuit of this project and its
address is set by the leve ls on the B si de power supp ly wiring pins. The rest of the
inputs of these 7485s. Th e schematic shows wiring is done according to the schematics of
a setting for a mem ory address of h exa- figures 2 and 3.
dec imal OCOO to OFFF, IC23 pin 6 toggles to
a positive level whenever th e high order No Device +5 V -5 V -12 V GND
ad dress fro m the processor bus match es the
preset address. Within nanoseconds the data IC ll 7485 16 8
IC12 8T 97 16 8
se lectors (74157s, IC14, IC15, IC16) sw itch IC 13 8 T 97 16 8
control of the memory address Iines from IC14 74157 16 8
IC15 74157 16 8
t he displ ay generator to the processor bus. IC16 74157 16 8
Half a microsecond late r, with the address IC17 8T97 16 8
firml y estab lish ed on the memory chips, the IC2 1 A1
IC23 7485 16 8
phase 2 clock goes high enabling the write IC24 2 1 L02-1 10 9
line (if wl-iting data) or the output buffers (if IC25 2 1 L02-1 10 9
reading data). Whil e the memory reference is IC26 2 1 L0 2-1 10 9
IC27 2 1 L02-1 10 9
being made by the processor, the ter min al IC3 1 7490 5 10
hard ware may atte mpt to load a character. IC32 7404 14 7
IC33 7410 14 7
The character it gets is not necessarily the IC 34 2 1 L0 2-1 10 9
one at the add ress it wants but the character IC35 2 1 L 02-1 10 9
that the processor is addressing. This wou Id IC36 21 L02 -1 10 9
IC 37 2 1 L0 2- 1 10 9
see m to cause an impro per character to be IC42 7410 14 7
displayed. Howeve r, since this contenti on IC43 74123 16 8
occurs so infreq uen tly and the refresh is so IC44 7490 5 10
IC45 74 123 16 8
rapid, no visible interference is seen on the IC46 74192 16 8
TV screen in a ty pical situation. Th e pro- IC47 74193 16 8
grammable mem ori es are of the 21 L02-1 IC5 1 MM5320 8
IC52 7492 5 10
variety. Except for the data in and data out IC53 7400 14 7
con nections, the memory integrated circuits IC54 74193 16 8
IC55 74193 16 8
are all wired in para llel. Th ey are perm a- IC57 2513 24 12 10
nently ena bl ed by tying their chip se lect IC61 A2 11 & 13 8
lines to ground . This hard ware is about as IC64 7404 14 7
IC65 74165 16 8
simple as can be expecte d. It should not IC76 7486 14 7
present any prob lems to any one with any IC77 7486 14 7

111
 Waveform Photographs

The oscilloscope photos, 7 to 77, are included for

trouble shooting pU/poses. These were taken on a
Tektronix 4SS oscilloscope using a lOX probe.
Unless otherwise noted, the vertical sensitivity is 7
volt per division. The horizontal sweep speed and
test point location are shown in the caption of
Photo 7: Test point 7, pin each photograph. The ground reference line is one Photo 72: Test point 72,
7 of IC37, SO ns per division below the center line in each photograph. pin 4 of IC64, 200 jJS per
division. division.

Photo 2: Test pOint 2, pin 7 of IC43, Photo 7: Test point 7, pin S of IC43, Photo 73: Test point 73, pin 72 of
200 ns per division. 2 ms per division. le42, SOD jJS per division.

Photo 74: Test point 74,· output,

Photo 3: Test point 3, pin 4 of IC43, Photo 8: Test point 8, pin 72 of IC4S,
O.S V per division vertically, 2 ms per
200 ns per division. SO ns per divisiol1.
division horizontally.
r··,'

~~hhhh
.. I ' I i

; ~ I ~ I I.
Photo 4: Test pOint 4, pin 73 of IC4S, Photo 9: Test point 9, pin 6 of IC42,
20 /1S per division . 700 ns per divisiol1.

Photo S: Test point S, pin 72 of l e44, Photo 70: Test point 70, pin 3 of Photo 76: Test point 76, pin 6 of
S ms per divisiol1. ICS3, 70 /1S per division. I C23, 7 jJS per division.

Photo 6: Test pOint 6, pin 7 of IC44, Photo 77 : Test point 77, pin 2 of Photo 77: Test point 77, pin 6 of
2 ms per division. leS S, 200 /1S per division. le33, SOD ns per division.

112
Photo 78: Video Terminal Board, Component Side. This photograph shows the physical layout
of the board as constructed by the author. The processor connections to and from the terminal
are made by the plug on the left hand side of the photograph. Eight 27 L02-7 memory
integrated circuits are used for the screen's local memory. The three pots at the bottom center
are used (L to R) to control left hand margin, character width, and top of page margin. The
video amplifier is contained in the DIP plug with components, in the lower right hand corner.
Bypass capacitors are sprinkled quite liberally throughout the board.

START JSR ESCRN Erase the ent ire screen;

LOX " TITLE X := address of title string;
1. Display a new lin e of ASCII text. JSR VL INE Write title at top of screen;
LOX " PROMPT X := address of prompting message;
2. Scroll all lines up by one. JSR VlINE Write prompting message on next line;
LDAA II$AO A := ' . + 80 [add hex 80 to b lank giving inverted blank);
3. Erase one character line. JSR VCHAR Write cursor at location of next input;
4. Add one new character to the display.
5. Erase the entire screen. TITLE FCC 'GEN IE OPERATING SYSTEM'
Titl e string;
FC8 4
PROMPT FCC 'WHAT IS YOUR DESIRE. MASTER ?'
Prompting string;
FCB 4
The preambles for each subroutine should
adequately exp lain the calling sequence and Or if yo u I'ea lly have to have a routine
conventions used. These subroutines assume which will all ow you to type data on your
that six words are availabl e in the first page keyboard and look at it on the screen:
(256) of memory (hexadecimal address 0 to LOCAL JSR ESCRN Start by clearing the screen;
FF). These words are used to take advantage LOOP JSR INCH Use normal input routine to define character in A;
JSR VCHAR Transfer input character to screen buffer;
of Motorola's direct add ressing feature. To CMPA 4$04 Is it end of text?
display a character in a preset locati on on BNE LOOP I f not then continue local LOOP;

the screen, initiali ze the words CHAR and

LINE to the desired location, load the 6 bit Return to monitor
ASCII character into the A accum ul ator and
branch to the VCHAR subroutine. Note that scrolling is done automatically
The complete relocatable software is in- for you after you write the 32nd character
cluded as listing 2 with this article. A on the 16th lin e.
symbolic examp le is given here to show the
Construction
use of these routines. Suppose that you
desire to erase the screen, display a title, a Before you can begin building this termi-
prompting message, and place a cursor at the nal, you first must obta in the necessary
next character location. Th is can be accom- compon ents. Refer to the component list in
plished by the fo llowing cod e: tab le 1. I have li sted the vendors from which

113
Photo 79: Video Terminal Board, Wiring Side. This photograph shows the
wire wrapped construction of the circuit's prototype. All integrated circuit I purchased the parts. I selected these peop le
locations were labelled with masking tape containing device location and because I knew I would get quality com-
device type. A II integrated circuit power connections were soldered to the ponents at reasonable prices in a short time.
etched power supply buses which are part of the Vector plugboard used for The prices listed are included as a guide.
the circuit. The orientation of pin 7 is uniformly the upper left corner of the Check the advertisements in this issue to see
integrated circuit, as docum ented by the typical pinout map shown pasted to if they have changed.
the upper righ t side of the board The first step in building this (or any)
board is to determine exactly where the
various components will be located. See
photo 18, ph oto 19 and figure 4 for the
layout I used. Then install all of your bypass
capacitol"s. Th is is easy to do at th is stage.
Solder them directly to the etched lands on
the reverse of the Vector board betwee n the
known locat ions of the wire wrap sockets.
Next (and this is a trick that will rea ll y
reduce the wire wrap errors) cut masking
tape into sections a little smaller than
the size of the integrated circuit top. Write
on the masking tape the integrated circuit
number and the TTL suffix. For example,

Photo 20: A Detail of the Computer System.

This 6800 microcomputer currently consists
of four cards: an 10 card, a processor card, a
4 K byte programmable memolY card, and
the video terminal card described in this
article. One spare location at the left is
awaiting a 76 K dynamic programmable
memory card which is under de velopm ent.
The ribbon connectors in the lo wer right
hand corner are used to interface a control
panel. Each board is supplied from a sepa-
rate 5 V regulator which is mounted on the
chassis for superior heat sinking capability.

114
 o
OL-._ _ _...,..-/

Figure 4: Video Terminal Component Layout. This reduced scale drawing

"IC45-123" identifies the fifth integrated shows the relative position of the parts of the video terminal design as
circuit in the fourth column as a 74123. Pin constructed by the author. See photo 78 for a pictorial version of this layout,
1 is always in the upper left hand corner and see photo 79 for the reverse side of the author's card as wired for his
looking from the wrap side of the board. system.
Pl ace the label on the wrap side of the board
where the socket will go. Next, put a dab of
cement on the bottom of the integrated
circuit socket and insert it on the board. (I Listing 2: Complete Video Support Software for a Motorola 6800 Processor.
used "DUCO" cement. Epoxy or hot melt This package consists of self relocating routines to perform display utility
glue can be used , but are nearly impossible functions. Self relocation is accomplished by exclusively employing branch
to remove once set.) Remember that 16 pin instructions (relative addressing) for program control within the package, and
sockets are a little longer than the 14 pin using the stack as a temporary where necessary. Control variables are assumed
variety and yo u'll be OK. Refer to figure 4 to be in low memory.
for the configuration I used. After the gl ue
has set, wire the power supp ly lines to the The following allocations are loca t ed in page 0 of memo/y, so that the "ideo SlIpport
wire wrap sockets. To do this, wrap half a software can tal?e advantage of the Motorola 6800 direct addressing mode. Relocation
dozen turns around a power pin and solder of these variables should be confined to page 0, in which case the address constants used
the other end to the nearest power bus. for the direct addressing references would be altered to reflect new locations. The main
text of the subroutines Ihemselves is completely position independent, which meall5 reo
Don't " daisy chain" a bunch of circuits
location can be accomplished simply by loading the program code at a different point in
together with one attachment to the power memo/y address space (ln d calculating n ew addresses for the "external references" sum·
bus. The 30 gauge wire can't adequately mari/.ed in a toNe at tlt e end of tltis listing.
handle the required switching current for
Abs
more than a few chips. Insert the wire wrap Addr Hex Code Label Op Operand Commentary
terminals where the discrete components
will be placed. Many of these can be 0020 00 CHAR RMB Cllaracter pos i ti on, 0 (left) 10 3 1 (right):
0021 00 L IN E RMB Line number, 0 (top) to 15 (bottom):
so ldered directly to the power planes. Other- 0022 00 00 CHPSN ROB Memory address pointer to characte r;
wise, they have enough friction to prevent 0023 CH PSN L EOU CHPSN+ 1 Low orde r byte o f memory address pointer;
them from falling out before they are 0024 00 00 SAV EX ROB I ndex regist er save area;

wrapped. It's time for one more trick to 7he l ollo,villlj equat e a.,sigm II value 10 th e address of lite video display melllOlY for
reduce the number of wire wrap errors. Get the purpose., of ,ymholi<' referellce IVilhin this listing. Tlte lIddresses of tlte displayed
a Xerox copy of the schematics (figures 2 portioll of l7IenlOlY ill lite protolYl'e of th i., desigll lire OeOD to OFFF in hexudecimal.
and 3). (BYTE encourages this and gives full
V IDEO EO U "SOCOO
permission for such private use duplication.)
Each time you complete a connection, use a
felt tipped pen to draw over the line on the Listing 2 is continued on the next three pages . ..

115
Listing 2, con tinued: copy. You are done when all of the lines are
marked over. Remember to mark the power
supply lines too. I should probably insist
that you recheck all of your connectio ns
VLl NE - This subroutine displays a new line of text on the screen. On entry after you're done ... however, I don't and I
to VL IN£, the index register X has the address of the start of the ASCII text do n't expect that yo u will either. It is eas ier
string to be. displayed. The string is terminated using an ASCI! EaT character, to ve rify your co nn ectio ns as you make
hexadecimal 04, as the last character. them and fi x the ones you missed durin g
checko ut.
Rei Now that your board is wrapped it's time
Addr Hex Code L abel Op O perand Comme n ta ry
to stuff all the circu its in and turn the power
0000 V LlNE EOU Entry point , li ne d isplay routine;
0000 36 PSHA Save A on stac k;
on, right? WRONG. Go slow ly and test your
0001 7F 00 20 CLR CHAR CHA R := 0 [pe rfor m ca rri age re turn ]; work. You may end up savi ng some expen-
0004 7C 00 2 1 INC LINE LINE := LINE + 1 (perform line fe ed );
0007 A600 V LP LO AA O.X A := @X (move next cha racter to AI; sive circuits. First, measure your +5 V power
0009 81 04 CMPA 4 Is it end of text?
OOO B 27 05 BEO V LONE I f so then return to ca ll er; supp ly. If it is not with in 0.25 V of 5 V, find
000 0
OOOF
80 15
08
BSR
INX
VCHAR CA LL VCHA R (d isp lay the cha rac t er) ;
X := X + 1 [po int to next character] ;
out why. Too Iowa vo ltage impedes per-
00 10 20 F 5 BRA VLP Reiterat e until done ; formance . Too high and yo ur chip life is
0012 32 VLONE PULA Restore A from stack;
00 13 39 RTS Return to cal ler ; red uced. Next, install the interface ch ips
(I Cll , IC12, IC 13, IC 14, IC15, IC16, IC17,
IC23 and IC 33). Put a scope on pin 1 of
ESCRN - This subroutine is used to erase the entire screen. It has no input IC16 and verify a pos itive pu Ise each time
parameters. you address this memory space. The address
of the memory space is determined by the 8
Rei
Addr Hex Code L abel Op Operand Commenta ry
side inpu ts to the 7485s. This test can be
done by a front pane l or a software loader.
0014 ESCRN EOU Entry point, erase screen ro utin e;
00 14 36 PSH A Save A on stack; Th is se lect pulse shou ld be about 1.0 ps in
0015 86 OF LOAA ;115 A := 15 [set number of lines to erase) ;
0017 806B ESLOP BSR ELINE CA LL ELINE (erase one linel; duration if you are runni ng with a 1 MHz
0019
001A
4A
2C FB
OE CA
BGE ESLOP
A := A - 1 [decrement lin e count in AI;
if A >= 0 then continue the loop;
clock. Verify the address inputs at the
001C 7F 00 21 CLR LINE LINE := 0 (move cursor to top of screen]; programmab le memory socket locations to
00 1F 7F 00 2 0 CLR CHAR CHAR := a[move cursor to left of line I;
0022 32 PULA R estore A fr om stack ; make sure the 7415 7s are switching cor-
0023 39 RT S Return to calle r ;
rectly. Look at IC33 pin 3 and see a 500 ns
negative pu lse (normall y high, goes low for
abo ut 500 ns, then high again) when you are
VCHAR - This subroutine displays one character on the screen. On entry, writing to the programmable memory.
the A accumulator should contain the ASCI! character code to be displayed. Ver ify that there is no pu lse whe n reading.
VCHAR updates the control variables LINE and CHAR which determine Check for the reverse at IC33 pin 6. Expect
screen location; VCHAR ignores all ASCII control codes except a carriage a negative pu lse whe n reading and just a high
return or line feed. leve l when writing. Turn the power off and
Rei in sert the eight 21 L02-1 memory circu its.
Addr Hex Co de L abel Op Op e rand Com mentary
Each time a circuit is inserted, look to make
0024
0024 8 1 00
VC HAR EOU
CMPA #$00
Entry point of characte r display routine;
Is character a carriage return?
sure all the pin s are in the socket and not
0026 27 09 BEO VCR If so then go juggl e CHAR pointer; bent over. Power up again and run your
0028 81 OA CMPA # $OA Is character a lin e feed?
002A 27 09 BEO V LF I f so then go juggle LI N E pointers ; memory test program. Th is verifies that your
002C 81 20 CMPA
.... ,.
002 ~ 2C 09 BGE VOK
Check for ASCII control character;
I f so then go transfer valid ASC II ;
system can access th is memory and that the
0030 39 RT S Else return with no action; integrated circuits are all good. An examp le
0031 7F 00 20 VC R CLR CHAR C HA R ;= a [perform car ri age return) ;
00 34 39 RT S R et urn to caller; of a simp le memory test program called
0035 7C 00 21 V LF INC LI NE LIN E := LINE + 1 (perform li n e feed I ; MTST is included in this article as listing 1.
0038 39 RT S Return to calle r ;
0039 37 V OK PSHB Save B on s tack ; When you are sure that the processor is
003A 36 PSHA Save A on stack;
003 B 0620 LO AB CH A R B := CHAR; interfaced to memory correctly, insert IC3 2,
0030 C l 1F CMPB #3 1 Is it still on the same line?
003 F 2 F 06 BLE VCOK If so then go test line [do not pass CRLF);
IC31, and IC43. Moun t the DIP plug with
0041
0044
7F 00
7C 00
20 CLR
IN C
CHAR
LI NE
CHAR := 0 Iperform carriage return];
LINE := LINE + 1 !perform nne feed];
the osci ll ator comp onents in the IC21
21 '
004 7 96 2 1 V COK LOAA LINE I s LI NE on socket. Look at IC31 pi n 1 on yo ur scope
0049 80 OF SUBA # 15 the screen?
004B 2 F OB BLE V L OK If so then go to display [do not pass hamel; and check for a 10M Hz "sq uare" wave. See
0040
004 F
80 10
4A
V LNO K BSR
OECA
VSCRO L CALL VSCROL [move all lines up onel;
A := A - 1 [decreme nt scro lling coun t] ;
photo 1 for an example. Photo 2 shows the
0050 26 FB BNE VL NOK if A >= 0 then loop [u n til lin e on scree n l; 2 MHz wave at IC43 pin 1. If all is well so
0052 86 OF L OAA # 15 A := 15 [posi t ion cursor at botto m line I ;
0054 97 2 1 STAA LINE fa r, put your probe on IC43 pin 4. This
0056 80 2C BSR ELINE CAL L E LINE (erase t he bottom li nel ;
0058 96 2 1 V LOK L OAA LIN E Set up LINE parameter for GC HAR ca ll ; shoul d be pretty close to a 2 MHz square
005A
005C
0620
803E
LO AB
BSR
CH AR
GC HAR
Set up C HAR pa ra mete r for GCHAR ca ll ;
CA LL GC H AR [to calcu late CHPSN pointerl ;
wave. Adjust the timing res istor, if neces-
005 E OF 24 ST X SAVEX Save index regist er va lu e; sary, to obtain a 50% duty cycle. Thi s
0060 DE 22 L OX CHPSN X ;= CHPSN [point to c urrent character address I ;
0062 32 PULA A ;= current character; doesn't have to be exact but the 5320 is
0063 A7 00 ST AA O,X @X := A [sto re current character in memory @ xl;
0065 7C 00 20 IN C CHAR CHAR ;= C HAR + 1 [set pointer for next write1; happier with a square wave. Measure pin 1 of
0068
006A
DE 24
33
LO X
PULB
SAV EX restore old index register va lue;
restore B from stack;
IC51 and verify a -12 V (±5%) DC vo ltage.
006B 39 RT S re turn to ca ll er; Wi th power off, insert th is magical inte-

116
grated circuit into its socket. This 5320 Listing 2, continued:
generates all sorts of good signals and saves a
lot of board space. With power on (and pin 1
still at a clean -12 V), scope pins 11, 12, 14,
15, and 16. They will be switching between VSCROL - This subroutine moves all lines on the display up by one pOSition.
+4.5 and - 11 V. Don't be alarm ed by the No input parameters are necessary.
negative output voltage. They will pop up to
Rei
grou nd when a TTL load is hung on them. Addr Hex Code label Op Operand Commentary
With power off again, insert IC45, IC46, 006C VSCROl EOU Entry point of scrolling subroutine ;
IC47, IC64, IC44, and IC42. Adjust the Line 006C
0060
36
OF 24
PSHA Save A on stack;
STX SAVEX Save index register value ;
Delay pot for a 20 J1S positive pulse at IC55 006F CE OC 00 lOX # V IOEO Load pointer for start of move;
0072 A620 VSCRl lOAA 32,X Fetch corresponding character, next line;
pin 14. This adjusts the left hand margin on 0074 A700 STAA O,X Then store it in the current line;
the TV display. It will be trimmed to a final 0076 08 INX X := X + 1 [point to the next character] ;
0077 8C OF E1 CPX # IVIOEO+32 '132-1)+1) [calculated start of the last line in
value at a later time. Adjust the Top of Page 007A
a 1024 byte buffer) ;
26 F6 BNE VSCRl if not at end of buffer, then repeat loop ;
pot for a 3 ms positive pulse at IC44 pin 14 007C 86 OF lOAA # 15 line parameter of erase function;
007E DE 24 lOX SAVEX restore index register
(this will also be trimmed later). Verify 0080 8002 BSR ELINE CALL ELINE [to erase bottom line] ;
pulses at IC57 pins 14, 15, and 16. Set the 0082
0083
32
39
PULA
RTS
Restore A from stack ;
Return to caller;
Character Width pot to midrange (about
6.25 MHz at IC32 pin 12). Refer to the
waveform photographs if problems are en- ELINE - This subroutine is used to erase one line from the display. The line
countered. Insert everything else except for number is specified by the value in accumulator A upon entry.
the character generator (IC57). Check that Rei
the address lines are toggling and that data is Addr Hex Code label Op Operand Commentary

being presented to the character generator 0084 ELINE EQU Entry point of line erase routine;
0084 37 PSHB Save B on stack;
on pins 17 through 22. IC 65 pin 9 shou ld be 0085 36 PSHA Save A on stack;
switch ing erratica ll y. Verify the power 0086 5F CLRB B : = 0 [set local character position to zero] ;
0087 80 13 BSR GCHAR CAll GCHAR [calculate character address ];
supply connections to IC57. The +5, - 5, 0089 OF 24 STX SAVEX Save index register ;
008B DE 22 lOX CHPSN X : = CHPSN [get calculated character address] ;
and - 12 V connections should be within 5% 0080 C6 20 LOAB #32 B : = 32 [the number of characters in a line} ;
#' , A := " [erase means put a blank in each pos.];
and should be clean, that is, without more 008F
0091
86
A7
20
00 EllOP
lOAA
STAA O,X @X : = A [move the blank to current location};
than 100 mV of noise. 0093 08 INX X := X + 1 [point to next location};
0094 5A OECB B := B-1 [decrement loop counter] ;
Turn the power off and remove the 2513 0095 26 FA BNE ElLOP If count remains then reiterate;
0097 DE 24 LOX SAVEX Restore index register ;
from its protective packing. This is the last 0099 32 PULA Restore A from stack ;
device to be added to the board. It is also 009A 33 PUlB
RTS
Restore B from stack ;
Return to caller;
009B 39
the most expensive circuit so don't blow it
With power on, recheck the supp lies and the GCHAR - This subroutine calculates the memory address of a character
ou tpu ts from th is circu it. specified by the current line number, LINE, and the current character
Connect the video output from this ter- position, CHAR. The formula is:
minal module to the video input of an RF CHPSN:= 32 * A + B + BASEADDR ;
modulator. I obtained excellent results using Where A is the line number, passed in accumulator A, B is the character
a Pixe-Verter. The RF output is transmitted position value, passed in accumulator B, and BASEA DDR is a constant giving
by coax to a 72 to 300 ohm transformer. the first address in the character display area of memory. The value of
Disconnect the antenna from the back of BASEADDR in the author's system is hexadeCimal DCDD. Since the low order
your TV and attach the leads from this offset is zero, this constant is only added into the high order at location
transformer. Tune to the channel you DDCD of this listing.
selected when bu ild ing the Pixe- Verter with
the TV's fine tuning set to midrange. With
power on adjust the tuning capacitor on the Rei
Addr Hex Code label Op Operand Commentary
Pixe-Verter for some sort of display on the
009C GCHAR EQU Entry point of the address calculator ;
TV. It will look ridiculous at first You'll 009C 36 PSHA Save A on stack ;
0090 37 PSHB
have to readjust the horizontal and vertical 009E 5F CLR8
Save B on stack ;
Clear the character
hold controls on your TV for a stable 009F
00A1
0722
07 23
STAB CHPSN address variable
STAB CHPSNl prior to calculation;
display. Trim the three pots for a pleasing 00A3 4A GLOP OECA A := A - 1 [decrement line count);
00A4 200A BlT GCDS If A = 0 then multiplication is done;
display on the TV screen. Then you can go 00A6 CB 20 ADDB #32 A ;= A + 32 [multiply is repeated addition) ;
00A8 24 F9 BCC GLOP
to town using the display. OOAA 7C 00 22 INC CHPSN
If no carry then continue inner loop ;
Else increment most significant byte,
The resu Its of my project are shown in OOAO
OOAE
OC ClC clear the carry flag,
20 F3 BRA GLOP and then return to inner loop;
photos 20 and 21. OOBO 07 23 GCOS STAB CHPSNl CHPSN+l : = A [save the low order byte] ;
00B2 33 PUlB Restore the displacement in line from 8 ;
00B3 17 TBA
Trouble Shooting 00B4 9B 23 ADOA CHPSNL
A : = 8 [put it in A for calculation);
A := A + CHPSNL [add low order bytes];
00B6 97 23 STAA CHPSNl CHPSN l : = A [and save result in pointer] ;
Fortunately, this version of a video termi- 00B8 24 04 BCC GOONE If no carry, then calculation is completed;
OOBA 7C 00 24 INC CHPSN Else propagate carry to high order byte ,
nal worked the first time it was tried. This 0080 OC ClC and clear carry ;
OOBE GOONE
means I don't have any suggestions for OOCO
96 22
8B OC
LOAA
AOOA
CHPSN
# H(VIOEO)
A := CHPSN [fetch high order byte];
A := A + high order of VIDEO address;
locating failures based on experience. If you OOC2 97 22 STAA CHPSN CHPSN := A [save final high order byte] ;
00C4 32 PULA Restore A;
run into trouble, compare your waveforms OOC5 39 RTS Return to caller ;

117
 with those shown in the photos 1 to 17. The
most likely cause of probl ems are defective
integrated circuits and incorrect wiring.
Listing 2, continued:
Future Additions
Notation conventions :
If you want to displ ay more ch aracters on
RMB = "reserve memory byte" wit h or without labe l, uninit ia liz ed. the TV screen, try disconnecting th e wire
ROB =: "reserve double byte" with or without label, uninitiali zed.
EQU = "equate". Assign an address value to a label. from IC55 pin 2 to IC64 pin 11 . Repl ace
=" indicator for imme diat e address ing o n Motoro la 6800 . with a wire from IC55 pin 6 to IC64 pin 11) .
Sonn = he xadecima l value nnn .
nnn = decimal va lue nnn. Wire IC55 pin 2 to th e 9th address bit at
= the current location counter as in an assembly. IC14 pin 2. Readjust the Character Width
'X' = notation for ASCII character X.
Hl v IDEO ) = notatio n for high order by te of address V I DEO . pot to squeeze all those characters on a
@X = data at location X (used in co mm ent ary). single line. The software will have to be
adjusted to handle the new memory con-
External Symbol Ta ble: figuration of 16 by 64.
Like to try graphic text? Functiona ll y
The following symbols and their relative addresses are (he en(IY points to the "ideo display replace the 2513 with your own PROM. Bit
support software. To calculate the absolute addresses needed to reference these entries, add the
6 cou ld be used to perfo rm this selection
starting address at which you load the paclwge to each of these offsets, giving the absolute
address to reference in a jump to subroutine instruction. electronically. Th is PROM cou ld be used to
define various line segm ents within a charac-
Relative Address Label Op eration ter field depending upon the 6 (or 7) bit
0000 V LlNE Line display code supplied.
0014 ESCRN Erase sc reen
0024 VC HAR Display one character
Th e very nicest thing about a home buil t
006C VSC ROL Scro ll up one line project is that after it is working, you're not
0084 ELINE Erase one line
009C GCHAR Ca lculate address given line, position afraid to modify it! Happy Wrapping.-

Photo 27: A Microcomputer Development Workshop? The processor is off in the left hand corner of the table, with a cassette
tape recorder to its right. A keyboard with ASCII encoding is connected to the 10 card for control of the processor. Th e video
display's television set output is to the left of the oscilloscope at the right side of the picture. Th e parts cabinets, wire wrap gun,
soda pop and ash tray were essential to the development of this system.

118
 '~ ~
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listing. : J
Continued from page 89 Many peop le have done as I have, wh ich is to program and refresh vector table would be
put aside their 8008 and replace it with an contained withi n the 8008 as well as a very
8080A or newer generation equ ipment. This simp le commu nications driver which all ows
8008 unit which is kicking around can solve it to ta lk with your new 8080, Z-80, 6800 or
the chief disadvantage of vector graphics - what have you. Communication would be
software refresh. The 8008 is more than between a couple of parallel input and output
adequate to drive the controller with fixed ports. The 8080 system cou ld contain all the
data tab les: Why not take advantage of it? A number crunchi ng routines and large pro-
very reasonab le so lution is to dedicate your grams such as Space War while the 8008
Scelbi, Mark 8, or what-have-you-kluge to drew and refreshed the playing field or
run and refresh the display. The graphics hyper space. Vector table updates would be
sent from the main game processor to the
8008 display processor periodically as the
Table 2: Refresh Vector Table for Drawing the Star Ship Enterprise. This game progressed. This system would be
table contains the information needed (in octal) to generate the Enterprise on fa ntastic.
a vector display. The addresses are relative to page 007, starting at location
50, for use with the program of listing 2. The end of the display string is Bigger Displays
indicated by the octal code 377 found stored at location 330. If you were to
Whi le 5 inch scopes are quite adequate,
put some extra imaging information in the picture, the additional vectors
fu ll apprec iation of vector graphics is re-
would begin at location 330 instead of the end code. The fine print numbers
alized on ly on large screen displays. Com-
in figure 4 near each line segment are the addresses of the appropriate vector
merciall y sold large screen XY disp lays start
specification in this table.
at about $600. Hal Chamberlin, in his
Computer Hobbyist articles mentioned
Vector r::- start - : t r:;-end-::l
earlier, describes how such a display can be
Add ress X Y X Y co mmentary bu il t (w ith some difficulty) using television
050 004 104 014 070 Begin Enterprise's bridge
sty le disp lay mechanisms. His work was an
054 014 070 110 070 invaluable help to me in getting my disp lay
060 030 070 054 060 going; the circuits you see in this article are
064 054 060 074 070
070 110 070 120 104 my adaptations of some of the circuits Ha l
074 120 104 004 104 pub li shed in his exce ll ent pub lication in
100 014 104 040 110
104 040 110 120 104
connection with his vector display design .
110 040 110 042 114 The Computer Hobbyist is located at Box
114 042 114 064 114 295, Cary NC 27511. At last report, back
120 064 114 070 116
124 046 114 050 120 issues were avai lable.
130 050 120 060 120 Another possible source of big screen
134 060 120 062 114
disp lays is auctions of electronic equipment
140 074 070 104 034 Bridge connecting strut line {often attended by dealers in surp lus}. For
examp le, Electronic News often publishes
144 104 034 064 030 Main body out line
150 064 030 064 010
154 064 010 104 004
160 104 004 140 004
164 140 004 210 014 RE F ER ENCES
170 2 10 0 14 204 024
174 204 024 170 027
Worth noting are two articles which contain in-
200 154 032 140 034
204 140 034 104 034 formation on vector graphics experimentation be-
yond t hat contained in this issue of BYTE:
210 140 034 114 076 Bridge connecting strut line Concerning the conversion of the Sanders 708 see:
214 074 032 074 006 Phaser weapons ban k Ciarcia, Steve and Robertson, Carl L :
220 064 020 054 030 "Simple Graphics Termi nal Using Inexpen-
224 054 030 054 010 sive Surplus Equipment," 73 Magazine,
230 054 010 064 020 September 1976, pages 116-123. (The cir-
234 054 020 050 020 cuits shown in figure 2 of the present article
240 134 104 134 are rev ised versions of some of the circuits
130 Engine pod outline
244 134 130 320 130 in author Ciarcia 's earlier published work
250 320 130 304 104 cited here.)
254 304 104 304 130 Concerning the generation of character graphics for
260 304 104 134 104
264 170 104 a vector display see:
170 024
270
274
300
170
154
140
024
024
104
154
154
140
024
104
} Engine pod support strut Lerseth, Richard J: "A Plot Is Incomp lete
Without Characters," BYTE, Ju ly 1976,
130 pages 64-72.
304 134 130 130 124
310 130 124 126 120 Concerning experimentation with a magnetic de-
314 126 120 126 114 flection CR T display buil t from scratch, see :
320 126 114 130 110
324 130 110 134 104 A series of graphics articles by Hal Cham-
berlin in Volume 1, issues 1, 2 and 3 of The
330 377 End of picture code Computer Hobbyist.

120
 .,-r-
- -
I I I I

II
2 4
pO 17
13 319' 2 4
1"1 14 I 2~( In II
II I 0 3,1a-.
f- 2 0
~ IV 1/
IV: Ole; I)
1\
k
00 1--- Vo 4 1\
••
h.
I\
14
20
\
2E4

f\
1\
h, \ 0 1\
b3 j l- t-
7( I-- J
f! 3 15 1m II
1~ V \
V 6 f-f- 7
16 I- \
I I.
J J
{ IT
I
'- ...... _'-v
- '-- ~ ....-'- - '- --,,-V '- '-
_ L.....

" -- L-
11
_D

Figure 4: Th e Star Ship En terprise, drawn on a graphing grid. One way to prepare data for a display such as this is to plot it out
ahead of time on a coordinate grid, such as graph paper. This figure was constructed using the data of table 2; but in the normal
procedure the figure would be dra wn first, and then one would prepare the table of vector speci fications.

auction ann oun ce ments when th ey are held ; pl ete with guns and flag on th e screen. Photo 3: Using the graph-
and for th ose of us in th e New England area, Graphi cs opens a new dime nsion fo r th e ics display for engineering
the Boston Globe auctions section has adver- home compu ter ex perimenter and it need ou tputs. This is a con-
tise ments of elec tronic co mpani es' publi c not be prohi bitive ly ex pensive. Usin g hi gh cocted display to illustrate
aucti ons fro m time to t ime. performance peripherals such as this se rves to XY plotting situations.
In my own case, I purchased a surplu s compl ement a well des igned co mpu te r sys- Wh atever "output" is, it
Sand ers Assoc iates 708 CRT termin al fr om a te m, and prov id e uses fo r osc ill oscopes wh en varies with "time" in a
local surplu s house. Thi s terminal, sold every thing is working right wi th your ragged sawtooth defined
through the 1960s and earl y 70s, is an all hardware.- by several vectors.
solid sta te vid eo termin al which was used fo r
alph anumeric displ ay, typi call y in medical
info rmation systems. Th e terminal used a
starburst ge nerato r for alph anumerics. Thi s
fact alone is enough fo r one to reali ze th at it
is in fact an analog vector scope. Th e 708
CRT has a 12 in ch scree n and a P31 hi gh
persistence ph osph or whi ch makes fo r so me
tre mendo us graphics. I got mine fo r less th an
$200, and I fo und that it was readil y
co nverted to a 12 in ch XY vector scope fo r
thi s purpose.
Wh atever you choose as a di spl ay me-
dium, whether it is a 5 inch osc ill oscope or a
12 in ch XY displ ay tube, you wil l find
vector gra phics both chall enging and
fasc in ating. Pr in ting out a message describin g
a battleship on an alph anumeri c CRT is
inte resting, but it ca nn ot hold a candle to a
syst-em whi ch ca n draw a battl eship com-

121
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 Continued from page 24 it has no argu ments. Here is an exa mple of a
niladic function which returns a result:
function with a del and atte mpt to execute
it: llRESULT+-THISFUN

- APL [1] X+-A+8

NEW _ APL

J
_ APL [2 ] RE SULT+-pX
TABLE OF SQUARES
_ APL II
1 1
- APL The function could be called inside an
TABLE OF SQUARES expression and used wherever a variable
- APL could be used. For exa mpl e:
2 4

A+-1 -USER
Something is wrong, so you reenter the
function definition mode and list your 8+-1234
function:
USER __ 3+THI SF UN -USER
IINEW
7 - APL
[6]

USER __
[0]
THISFUN calcul ates the sum of A and B
IINEW then finds the length of the sum and returns
it as the value of THISFUN . In the function
[1 J N+-O

[2] ' TABLE OF SQUARES' Proposed Micro APl Specifications

[3 ] N+-N+1 _ APL
Operators:

[4 J N; N*2 All monadic and dyadic scalar operators wil l be

imp lemented (except for the exponential, logarith-
[ 5 ] "" (N~10) / 2 mic and circu lar if space does not permit).
The following monadic mi xed operators will be
implemented: ravel, inde x generator, shape . The
Th e line which used to be 2 is now 3, since fo llowing will probab ly be implemented: grade up,
APL renumbers all lines to integers when grade down, execute, an d reversal. Catenation ,
inde x of, reshape, and compression will be the
you close the function . You could change dyadic mi xed operators implemented, probably
the 2 to a 3 in th e fifth line; however, there along with: take, drop, element of, rotate, and
is a better way. If you have to insert or perhaps encode a nd decod e if space permits.
delete lines from your function again , all The only co mposite operator impl e mented will
be reduction.
places where there is a branch arrow may
also have to be changed. If APL did not Data Structures:
provide a way around this prob lem, the Numeric and characte r data will be allowed, but
language would not be as popul ar as it is. In all numbers will be stored in IBM 360/370 single
a function you can specify a variable to prec ision floating point format. Character data will
become a label by putting it at the beginning be stored one character every four bytes to
conform with floating point format . The space
of a line and following it by a colon. allocated for character and numeric data wil l be 1
Whenever you execute th at function the to 2 K, so the ma ximum number of elements in all
labels in it are automatically assigned the variables and internal variables created by evalua-
value of the lines where they are located. tion of an expression must be less than 256 to 512.
The function wh en corrected using a label Vector wi ll be the only type of array allowed.
would look like this : Functions:
IINEW Up to eight functions may be defined in
workspace. T he tota l memory for fun ct ion storage
[1] N-<-O will be around 1 to 2 K. Although the functions
are stored in essen tially the sa me fo rmat in which
[2 J ' TABLE OF SQUARES ' they are defined, a number of pointers also have to
- APL be stored in thi s area. Recursive function s and local
[3] LOOPLABEL: N+-N+1 variables mayor may not be allowed depending on
the amo unt of memory ava il able.
[4J N; N* 2
Total Memory Requirement :
[5 J ""(N~10) / LOOPLABEL 12K 8008 system . An 8080 or 6800 version
The function NEW above is a niladic func- could probably ru n in 8 K by reducing the amount
of memory allocated to the workspace.
tion, which returns no result. Nil adic means

123
the va lue that will be returned is assigned to A dyadic or monadic function need not
the dummy variable specified in the function return a result such as this function:
header (in th is case, RESULT). 17M SUM BB _ APL
A function cou ld also be mon adic, as this
function which finds the cosine of a num- [1] 'THE SUM IS'; M+BB
ber:

l ~APL
_ APL
I7e+COS x 3 SUM 4
USER -
[1] C+-20X
THE SUM IS 7

However, it is illegal to use a function which

does not ret urn a result inside an expression.
A monadic function which returns a result,
The previous discussion has shown what
such as COS, cou ld be used anywhere a
the typical APL functions are like. In addi-
monadic operator is legal. (See table 1 for
tion, there are usually several system com-
the meaning of symbols used.) Thus APL
mands assoc iated with an APL interpreter.
allows the programmer to effectively create
Table 2 gives a short listing of several typical
new APL operators, which sometimes adds
system commands. These refer to the means
the readabi lity of a program. An examp le of
of load ing, clearing and saving the APL
the use of this particular function is:
workspace, catalogs of what is in the work-
(COS 02 ) + (COS 03 ) space, etc.
Th is should give you a good idea of the
Th is is certain ly more readab le than
power of APL on a large system, but how
2002 + 3003 usefu l would APL be on your small system
byte banger? Obviously many of the opera-
which wou ld calculate cos (21T) + cos (31T). A
dyadic function which returns a result cou ld tors wou ld take a good deal of the memory
be used anywhere a dyadic operator is legal, of an average small system to imp lement
so the function ADD cou ld replace +: (matrix divide, for examp le). Another prob-
lem is that since AP L is so generalized in its
I7AB+-A ADD B operations, it is somewhat memory ineffi-
cient. For examp le, to add two vectors, A
[1 ] AB+-A+B - APL and B, together, all you have to type is:
17 1 A+B USER _

34 2 ADD 4 6 USER -
but, in order to calcu late the sum, APL has
38 4 - APL to make a copy of each of the vectors first;
so if the length of A and B is 64 (256 bytes
at 4 bytes per floating point number), then
1 K would be in use during this operation.
Table 2: Typical APL System Commands. Using a comparable program in BAS IC
These are the global instructions used to wou ld require 516 bytes, since the sum
control the interpreter program. A small could be ca lculated one element at a time,
system APL would use versions of these print ing each sum out as it was calcu lated.
commands. There is also an 10 problem, since most
people have ASC II encoded terminals (or the
)CLEAR Clears a ll functions, variables, etc. equivalent), terminals which do not have the
entire APL character set on them .
)LOAD Loads a new workspace from an
aux il iary storage device . The only way I see that APL could be
practical for a memory and 10 limited
)SAVE Saves a workspace on an auxi liary personal processor is if the features were
storage device. limited (on ly vectors, for instance, instead of
)FNS Lists a ll functions in the current
up to 63 dimensions for arrays), and if the
workspace. number of operators were kept to a work-
able minimum. Al l the sca lar operators are
)VARS Lists all varia b les in the current performed in a similar manner, so they could
workspace.
be easi ly implemented. But on ly the most
)SI Displays the state indicator (interna l powerfu l of the mixed operators shou ld be
information about where execution imp lemented, for example:
stopped, and where errors have
occurred ). p / t

)S I CLEAR Clears the state ind icator. E ?

124
 Of the composite operations, reduction is would waste memory in the workspace
the most used, and easiest to implement. proper, it would greatly reduce the size of
Whether or not character data would be the interpreter, and in a small system this is
allowed depends on what size system was where most of the memory is used. On large
available. An easy way to handle character systems, logical (1 and 0) data is stored as
data would be to store one character every bit level data for memory efficiency, but on
four bytes, so the routines used for numbers a small system the major programming prob-
would not have to take care of the special lem of unpacking bits would probably not
case of character data. Although this method be worth the small savings it would provide.

GLOSSARY level program and performs operations as the

meaning of the program is being translated.

Array: An array is a group of numbers (or Mixed operator: In APL a mixed operator is one
characters) which in APL can be subscripted or that allows or requires the operand(s) not to obey
treated as a single object. Vectors are the only type the rule for the size and shape that scalar operators
of arrays discussed in this article; however, a full do require .
implementation of APL allows matrices and up to
63 dimensions for arrays. Monadic: A function or operator which has only
one operand to the right of the operator.
Character: As an AP L data type, character is the
kind of operand which is allowed for most mixed Niladic: A function which has no operands.
operators, but not for scalar operators other
than = and oF . Operator: An operator is a built-in function which
performs some common task such as addition, and
Command: An APL system command causes some is represented by a single, reserved, character.
operation to occur, such as destroying the current
workspace, or loading a new workspace from an Quad: The quad is used in expressions to perform
external device. A command begins with a right input and output, and in the function definition
parenthesis and has an English keyword, such as mode to list the function. To the right of an
) CLEAR or) SAVE. A command is normally legal assignment arrow quad will request an expression,
in either execute or function definition mode. which will be evaluated, and the result used in
place of the quad in the expression. To the left of
Compiler: A program which translates a high level an assignment arrow, quad prints out the value
source program into machine language object code assigned to it. Quote-Quad is for input of character
is called a compiler. string data only.

Composite operator: A generalized operator which Rank: This is the shape of the shape of an array; in
takes a built-in operator(s) and performs it (them) other words the number of dimensions of the
in a special way. An example is reduction, which array.
takes a scalar operator and performs it upon all the
elements of the operand, right to left. Scalar: A single value, such as 8 or -23.4. Scalars
can be used with dyadic scalar operators to operate
Dyadic: A mathematical term meaning having two on all the elements of the other operand.
operands. An AP L function or operator wh ich is
dyadic must have an operand on both sides of it. Scalar operator: An operator which obeys this
rule: If the size of the two operands (for the
Execute mode: This is the APL system mode dyadic operation) is the same, do the operation on
where an expression such as 1 +1 will print the the values in parallel. If one or the other is scalar,
result. The del is used to leave the execute mode do the operation between the scalar and all the
for the function definition mode. elements of the other operand.

Function: This is the name of an APL program. Shape: In a full implementation of APL, this is a
Since a workspace may have more than one vector which represents the dimension of an array.
function and a function can be niladic, monadic, or
dyadic, and mayor may not return a result, Subscript: This points to which elements of an
functions can be used as main programs, sub- array are to be used. APL allows subscripts to be
routines, or functions. vectors, a feature most other languages do not
allow.
Function definition mode: This is the mode in
which APL functions are created. The del is used Variable: A symbolic name given to a value, such
to go back and forth between the execute and as 3, or -4. A local variable (dummy) is one which
function definition modes. will be destroyed after the function in which it is
in finishes executing.
Function header: This is the first line of a
function, before the actual program starts. It gives Vector: A one dimensional array , the only type of
information to the interpreter about the function: array which can be represented as a constant in
Does the function return a result? What, if any, APL.
local variables are used in the function?
Workspace: The APL name for all the functions,
Interpreter: APL is implemented as an interpreter, variables, and internal state indication data which
a program which takes a source listing of the high the user has created.

125
 Figure 7: Two examples of
alternate dot matrices for
APL characters. The char-
acter at the left is the
Greek character rho,
shown in an approxima-
tion which distinguishes it
from a Roman P. The
character at the right is a
Greek iota.

The storage problem of A+B could easily In APL the programmer has the advan-
be avo ided by writing a program similar to tage of being able to choose whether or not
the one in BASIC: he or she wants to use the built-in vector
operator or progra m it, which is something
'VNOPROBLEM
that the programmer of most smal l system
BASICs does not have.
(1) N-<-O As far as th e character set problem is
concerned, a translation table could be built
( 2 ) LOOP: N<-N+l
to translate ASCII input like $ R (control R)
- - APL
(3) A[N )+ B[N)
into the internal code for P , or $1 into the
intern al code for l . Once translated, the
(4) ~ (N~p N)/LOOP computer would not care if the 1 came from
an APL terminal or even a Baudot Tel etype.
Or, an ASCII keyboard could be used when
the internal codes for the APL character set
BIBLIOGRAPHY were chosen so that the positi ons of the
characters on the ASCII keyboard simulated
John Coake and J T Schwart z, Programming whe re the same key was on the APL key-
Languages and Their Compilers, Courand In stitute board. An upper case I would be \ while i
of Mathematical Science , New York, 1970, pages
601-642. Thi s book describes th e methods of would be translated into I. Th e same transla-
writing a compiler for various languages, including tion would occur with Rand p; rand R.
an involved chapter on APL. On such a system a TV displ ay cou ld be
converted to show a 5 by 7 representation of
Leonard Gillman and Allen J Rose , APL 360: An
Interactive Approach, Wiley and Sons, New York,
the character, as shown in fi gure 1.
1974. Of course, software would have to handl e
the transl ation from the internal codes to
Kenneth Iverson, A Programming Language, the graphics codes, and software would have
Queens University, Kingston, Ontario, 1968. This
is a fairly mat hematical type book, and does not
to take care of the cursor; so that if the APL
repre se nt APL as it was implemented, although progra mmer backspaced to create a lega l
I verson is the creator of AP L. overstrike, such as ' over. to form ~, or 0
over I to for m ~, the rotate o perator, it
Harry Katzan, APL Programming and Computer would appear as if the overstrike actuall y
Techniques , Van Nostra nd Reinhold, New York,
1970. occurred. (On most CRTs, it would not
have; but rather it would have been repl aced
Harry Katzan, APL User Guide, V an Nostrand by a new code, created by the software as
Reinhold, New York, 1971 . soon as the backspace and corresponding
overstrike were entered.)
Sandra Pakin, APL/360, Sci ence Resea rch A sso-
ciates, Chicago, 1972. Thi s i s a manual for the IBM Some people love APL and some peo pl e
360 implementation of APL. hate it. I think it is one of the best
interpreters around, next to BASIC. I hope
Sandra Pakin, APL: A Short Course, Prentice Hall, to be abl e to implement a subset of APL on
Englewood Cliffs NJ, 1973.
my computer in my spare time so that it will
William Prager, Introduc tion to APL , Allyn and speak more than one language. I'm not sure
Bacon, Boston, 1971. how powerful a small system APL would be,
but I will report my success or failure in a
Xerox APL Reference Manual, Xerox Corp, EI
Segundo CA 1973. Thi s is where I got the idea of
later article. In the mea ntime, I'd like to
mnemonic representation of APL characte rs using hear from anybody who is interested in or
the $. knowledgeabl e about small systems APL.-

126
 B YTE'S
ITS
Hot Off the Grapevine
BROWN -OUT PROOF
your ALTAIR 8800
With the unique Parasitic Engineering constant voltage
power supply kit. A custom engineered power supply for
your Altair. It has the performance features that no simple
Texas Instruments has announced (in replacement transformer can offer:
marke ting literature of somewh at limi ted
circulati on) a new single chip video co n-
· BROWN -OUT PROOF : Full output with the line voltage
troll er integra ted circuit whi ch is envi sioned
as low as 90 volts _
as part of th e 9900 fa mil y line. Thi s is a
· OVER-VOLTAGE PROTECTION : Less than 2% increase
single chip generator for all th e timing and
for 130 volt input.
contro l inform ation needed to run a ras ter
sca n display interfaced to an LSI processor 's · HIGH OUTPUT: 12 amps @ 8 volts; 2 amps total @
bus. Th e grapevine says that it is being ± 16 volts . Enough power for an 8800 full of boards.
sa mpled at the present time, and wi ll be on · STABLE: Output varies less than 10 % for any load .
di stribu to r shelves nex t spring. Th e sa me Regulato rs don't overheat, even with just a few
grapevine iden ti f ies a second , similar con- boards ins talled .
troll er chi p announced by anoth er co mpany · CURRENT LIMITED: Overloads can't damage it.
as we ll . Either item would make exce llent ·EASYTO INSTALL: All necessary part s included .
materi al for a tu tori al review article in BYTE
since these chips have obvious uses in per-
sonal computing systems.- only $75 postpaid in the USA.
calif. residents add $4.50 sales tax.
Editor's Pet Peeve : All you wo nderf ul users
of the Engl ish language, engineering subset, Don 't let power supply problems sabatoge your Altair 8800
take note: A "baud rate" is a redundant
abomination. Th e concept is data rate, so me-
times measured in units of baud whi ch we PARASITIC ENG IN EERING
take to signi fy bits per second . (Th e original
defi nition of a rate measured in baud is a PO BOX 6314 ALBANY CA 94706
little more compl ex .) .

Not juSt a prellV face:

Morrow's .presents a front panel with brains--- $249.95
Comllination.f"!lJt
CPU board "Speeds
Rep l aces and up g rades ALTAIR/
UISAI front panel and CPU
boards, or forms the nucleus
of a custom system.
This isn ' t a toy . . . or a con -
ver sation piece ... but a tool
for serious pro gram develop -
ment, riva ll in g the soph i sti -
cat ion of man y minicomputer
systems. Granted no system
can make bugs go away: b u t We ve made some st r on g c l a ims
this one, finally, makes them The " Slmv S te p" mode a l lows in this ad --- and g i ven t h e
manageable. you to run through a pro gram way some compan i es advert i se,
at a variable rat e from 1 to yo u have a r i ght to be skep -
1\.0 exc l usive operating modes
65,000 steps per minute . The t i ca l . In order to di s p e l a n y
giv e yo u contro l over rea l
time, allowing you to work on display indicates the program dou bts, we ' ve put toget h er a
a program while it' s running_ counter and a processor regis - complete document at i on packet
ter of your choice. (sc h ematic, l ayo ut , sof t wa r e,
The "Contro l Ha l t " mode ref - assembly inst ruct i ons ), ava il-
uses to l et the SOSOA CPU go Unambi g uous readouts rep l ace
blinkin g LEDs; a 12 pad key - a bl e for $5_00 p os t pa id. You
dormant upon execut i ng a HALT may b e s ur pr i sed t o fi nd o u t
instruction; instead, specia l board rep l aces time-consumin g
toggle switches. And because we ' ve un d e rsta t e d
pur po se har dwa r e fo r ces a NO
OP in struct i on then passes the front pane l /CPU is Al tair
contro l to the front pane l buss compatible, you can bui l d
progr am , wh ere you can exam - a custom system around this
ine and al t e r p rocessor reg i s - board using Al ta ir compat i b l e
ters ... memory l ocations ... and periphera l s. Also compatib l e
I/O port s directly from t h e with an y soft,.are written for
front anel. an Al tair type buss.

127
 WHO DARED TO CHALLENGE THE 8080 & 6800 SYSTEMS?
WE DID!
VERAS SYSTEMS
"F-8"
A COMPLETE SYSTEM
$459 00
FOR ONLY
• KIT FORM

7" x 16" x 14 ·3/4" $709.00 ASSEMBLED and TESTED

COMPARE STANDARD FEATURES ON BASIC SYSTEMS
YOU'LL SEE WHY THE VERAS F·8 SYSTEM WINS HANDS DOWN! ' Registered T rad ema rks of Fai rchi ld and Motoro la

8080 & 8080A 6800

STA ND AR D FEAT URE S VERAS F8
SYSTEMS . SYST EM
Parallel I/ O Ports (3) 8 Bit Bidirectiona l Brought Out To Rear Panel Conn's. None None
Seria l I/ O Port RS-232 or TTY Brought Out To Rear Panel Term . Strip. None RS- 232 or TT Y
I nterva l Timers (2) Programmab le Interva l Timers None None
-- --
a) Vectored Interrupt To Location 0090 Hex . a) 2 .~on Vedo red
b) Vectored Interrupt Programmable Location I nt erru pts on P I A
Interrupts c) T w o Vectored Interrupts Associated With Interval Non e b) 2 V ect ored S W I ~
Timers NM I
d) Tota l of (4) Interrupts In A User Defined Prior ity c) Tota l of 4 Non Pri-
I nterrupt Structure o·r itized I nte rru pts
Bu ilt In M ini Operat ing System
ill ROM For T ermin al A nd FA I RB UG * None M I KB UG'
Memory Debug
Manual Console A utomat ic I nternal
Loader Prog ram Automatic Internal ROM
Sw itches ROM
Stati c RA M Memory 1024 BYTES None 2048 BY TE S
Rugged Alum . Self Contained Card Rack/ Plastic Self
Ca rd Rack Card Supports None
Aligning Card Guides
A ux iliary DC Power T o +5V, -5V, +12V, - 12V @ 1 Amp . Ea . Regulated At
None None
Power Peri pherals Rear Panel Terminal Strip
$539 .00, $599 .00 or
Basic K it Price $459 .00 $8 40 .00 Depend ing $395 .00
On Syst em

OUR 4K STATIC RAM BOARD FEATURES: (OPTIONAL) The More Flexible and Expandable
• On board decoding for any fo u r of 6 4 p ages. • Address a nd d a ta li ne s a re fully buffered . Computer at a Comparative Pri ce.
• No o nb oa rd reg ul a tors to ca use hea t prob lem s. (C hass is m o unted )
• 4K m emory boards w ith c on nec to r, buff ers, stat ic RA M' s & soc kets arc ava ilab le in k it f orm
$149 00
VERAS SYSTEMS
The VERAS Syste m ca n be made into a
17K processor b y m er ely ad di ng fo u r o f o u r TH E VERAS SYSTEM Warranty : 9 0 da y s o n p art s a nd la bor f or
optio nal mem or y boa rds. T h e kit in c l udes
eve r y t il i ng you need to b uild th e VE R AS F·B Co m p ut er as d escribed. A ll boa rds. co nn ec tor s, assembled unit s. 90 day s o n pa rts for ki ts .
sw itc hes, d isc rete co mpo nen ts, power su pply a nd cabi net are su pp lied , Prog ramming ma n ua l, Prices, spec if ica ti o ns, a nd deli ve ry su b jec t
dat a book a nd sim plified support docu ment at io n su pp lied, 8K Assemb ler a nd Edit o r !paper to c hange w ith out no tice .
tape or K.C. std . cassette) avai lab le o n request w i t h m i ni mum order o f 8K R AM .

• T wo 110 pari S each o n th e C PU and ROM ch ip make 32 b id ir ecl la nai TTl lines.
• T h e FCl lriJ ug ' p ro grammc cl s to rage Uillt p ro vide s th e prog ra mmer w ith all
r V ERASS YSTEMS- - - - - - - -
THE CPU 1/ 0 subro utIn es, al lows th e Ilr o ~ramm e r to alter o r d Isp lay m em o ry , and
re g Ister it s co n te n ts vra t e let ype .
I A Div. of Solid State Sales, Inc.
Bo x 74B, Som ervill e, MA 02143
BOARD
• Progr<l mmab le in te rn <J1 t i m er is hu il t in t o t he ROM ch Ip.
• Bu i lt in cloc k g e ne r ~tor and p o wer o n rese t Me b u i l t In to t he C PU c h ip . I (617) 547-1461

FEATURES:
• Th ere i s a local In ter rupt wi th au to m allc add ress vec t or .
• I t is e xp andab le to 65K by t es o f memor y .
• 20 m i l loo p <l nd / or RS 232 In t erlace Inc lu ded .
I o Enclosed is check for S ______________
o r 0 Master Ch a rg e # ____________________
• 1 K a l a n boa r d 2 102 R A M .
• S e ri a l in t e rf a ce bu ill i nl O PS U c h ip . Io V ER AS F-B Co mputer Ki t 0 Asse mbl ed
• Fai rbug i s a registered lf adem ark o f Fai rc h ild Co r p .
Io 4K RAM Boa rd Quantity _ _ _ _ __

TINY 2 K BASIC (AVAILABLE) OCT. 15, 1976 $25.00 I Name ________________________

FULL BASIC (AVAILABLE) DEC. 15, 1976 $50.00 I

Addr ess --------------------------------
Cit y. State __________________ Zip _ _
Compute r deal ers and hobbyist club inquiries are invited . E x pect ed d eli very t i me 3 0 day s o r less .
I
 SOLID STATE SALES
PO BOX 748
SOMERVILLE , MASS. 02143

WE ARE LEADING THE WAY IN CUS-

TOMER SERVICE AND DELIVERY
TIME FOR THE COST CONSCIOUS
SEMI -CONDUCTOR USER, LARGE OR
SMALL.

DIODES

.TRANSISTORS TRIACS
II ~. .
.,.
1. l,' Po f ..

.",,',-;:' ':' :'. INTEGRATED CIRCUITS

, .

INTEL 8080 CPU

251 B ·HEX 32 BIT SA
. 524.50
$6.00 4· 1/ 1"x6· 1/2" SINGLE SI DED EPOXY
: .... .22UF 35V 5/$1.00
. .
6.8UF 35V 3/$1.00
PRV 2A ___6i\ _ __
2Q!L _-__ ....:..9 5 _ _ _1._2 5_ _ _2.00
~A

21U2 · ' 1024 6T RAM S 1.80 BOA RD 1/ 16" thil:k, UIl!'1t:hcd

5280·4K DYNAM I C RAM . . $12.50 .47UF 35V 5/$1.00 22UF 35V $.40
5.50 Cil . 5 / $2.20 400 1.15 1.50
3.00

....
.68UF 35V 5/$1.00 33UF 35V $.40
5202A UV PROM .. $12.50 VECTOR BOARD 1 'SPAC I NG .600 - ~.35 - - - 1~5 - - - -4 .00
lUF35V 5/ $1.00 :WUF 6V 5/$ 1.00
MM5203 UV PROM. . . $12.50 4 .5" x 6" SHEET $1.25
1702 A UV PROM 512.50
3.3uF 35V 4 /$1.00 100UF 35V S.50 SANKEN AUDIO POWER AMPS
4 . 7UF 35V -1 / $ 1.00 150UF 15V $ .40 Si 1010 G 10 WATTS. . . . . . $ 6 .90
5204·4K PROM .. . . . . . . . . . . $24.95
MIN IA TURE MUl TI·TURN TRIM POT S Si 1020 G 20 WATTS. . . .. $13 .95
M700 1 ALARM CLOCK CH I P. . $6.00
100, 500, 2K. 5K, 10K , lOOK, 200K 2N 3820 P FET S .45 Si 1050G50WATTS. .. $24.95
S.75 each . . . . . .. . . . . . .. .. 3/52.00 2N 5457 N FET . S .45 NATIONAL MOS DEVICES CCD 110 LINEAR 256 XI BI T SELF
MUlTI ·TUHN TR IM POTS S imilar to Bourns 2N 4891 UJT. $ .4 5 I'I.'M I40 2- 1. 7!) MM5057 - 2.25 SCANNlfI,iG CHARGED COUPLED
3010 style 3/ 16"x5/8"xl · 1/4"; 50,100, TI$ 43 UJT $ .35 MM 1403 - 1.7f) MM5058- 2.75 DEVICE . $99 .00
I K, 10K, SDK ohms ER 900 TRI GGER D IODES. . 4 /$ 1.00 MM1 404 - 1.75 MM5060 - 2.75 CCD 201 100 x 100 CHARGE
$1.50 ea . . . . . . . . . . . . . . .. . 3/54.00 2N 6028 PROG . UJT 5 .65 MM50 13 - 2.50 MM506 1- 2.50 COUPLED DEVICE . S 135.00
LIGHT ACTIVATED seA's MM50 16 - 2.50 MM5555 - 4.75
TO -IB, 20QV IA . . . . . . S 1.75 VER I PAX PC BOARD ' MM50 17 - 2.70 MM5556 - .1. 75 LINEAR CIRCUITS
T his bO<:ird is iI 1/16" single sided papel ep oxy LM 309K 5V l A REGULATOR $1.15
MMS055- 2.25 MM52 10- 1.95 S .50
TRANSISTOR SPECIALS board, 4 \1, " x6 '1/ ' DRILLED and ETCHED 723 - 40 + 40VV REGULATOR
MM5056 - 2.25 S .3 1
2N3585 NPN 5i TO-66 . . .. S .95 which wi ll hold up to 2 1 sil1gle 14 Pili IC's 301/748 ·Hi Pcr. OP. Amp.
2N3772 ~JPN Si TO·3 .. . . . . . . S 1.60 or 8, 16, or LSI DIP IC's with busses for 3201' 5, 12,15, OR 24V
2N490B PNP S, TO ·3 . S 1.00 power suppl y connector . . . .. . . . 54 .00
TIL IC SERIES NEGAT I VE REG. $1.50
74LOO - .25 7441 - .85 74126- .60 709C Op. AnI\). .3 .3 1
2NG055 NPN 51 TO ·3 Dartin!lton S 1.30 MV 5691 YELLOW·GRE EN 74150 - 1.00
7400 - . 16 7442 .55 741Aor74 I COPAMP. S .31
2NS086 PNP Si TO ·92 . . . . . . . 4 / $ 1.00 B I PO L AR LED 51.25 7415 1- .80
2N4898 PNP T O·66 . . .. $ .60 7401 - . 18 7445 - .75 710 COMPAR A T OR. $ .35
MT·2 PHOTO TRANS . . .. . .. . $ .60 74153 - .79
2N404 PNP G E TO ·S 5/$ , .00 REO, YELLOW. GREEN OR 7402 . IR 7446- .80 CA 3047 Hi Pef. Op. Amp.. . .. $ .95
7403 - .22 7447 -- .69 74 154 - 1.05
2N3919 flJPN SI TO ·3 RF . . $ 1.50 AMBER LARG E LE D's 5 20 74 155 - 1.00 340T 5, 6,8,12.15,18. 24V pOS
MPSA 13 NPN SI TO ·92 3/$ 1.00 14 PIN DIP SOCKETS . $ 25 7404 - .22 7448- .77 REG. TO·220 $1.50
7405 - .22 7472 - .40 74157 - .75
2N3767 {lJPN Si TO ·6 6 . S .70 16 PIN DIP SOCKETS. . .. 5 .28 74161 - 1.00 101 OPER. AMP. HI PERFORM. S 75
2N2222 NPN Si TO · 18 .5/$ 1.00 7406 - .35 7473- .40 L M 308 OPCI . Amp., Low Power $ .95
MOLEX PINS 100 /5 1.00 74164 - 1.05
2N3055 NPN Si TO·3 .. $ .80 1000 /57.50 7407 - .33 74 74 - .40 747 - DUAL 741 S .65
7408- .25 7475 - .50 74165- 1.05
2N3904 NPN Si TO ·92 . . . . . . . 5/ 5 1.00 8 PI N M I N I D I P SOCKETS . . . . . . 5 .25 74173 · .9!; 556 - DUAL T I MER $ 1.00
2N3906 PNP Si TO·92 SIS 1.00 7409 - . 25 7476 - 040 537 - PRECISION OP. AMP . . . $1 70
10 WATT ZENERS 3.9, 4 .7,5.6.8 .2, 12, '. 5, 7410 - . 16 74 80 - .48 74174 · 1.20
2N5296 NPN Si TO·220 . S .50 18.22. 100,150 01 200V . . Cil . $ .60 74175 · .95 L M 3900 - QUAD OP. AMP $ .49
'2N6109 PNP Si T O·220. . . . .. . $ .55 7411 - .25 7483 - .80 L M 324 - OUAD 74 1 . . . . $ 1.50
I WATT ZENERS 4 .7, 5.6, 10,12.15, 74 12- 040 7485 - .88 74177 - 1.00
2N3638 PNP 51 TO ·5 . . . . . 5/$ 1.00 7 41 80- 1.00 560 - PHASE L OCK L OOP $2.00
180R 22V .ea . 5 .25 74 13 - .45 7486 - .45
2N651 7 NPN TO ·92 Si . 3/5 1.00 74181 - 2.40 561 - PHASE L OCK LOOP 52.00
7414 - 1.00 7489 - 2. 00
CIMOS (DIODE CLAMPED) Silicon Power Rectifiers 7416 - .33 7490 - .48 741 90- 1.1!; 565 - PHASE L OCK L OOP . $1.25
74191- 1. 10 566 FUNCT ION GEN. $1.65
74C02- .25 4016 - .50 403q- 1.75 7417 - .33 7491 - .75 567 - TO NE DECODER
74192 - .80 51.50
74Cl0 - .25 40 1 / - 1.30 4042 - 1. 60 7420 - . I B 7492 - 049 LM 1310N FM STEREO DEMOO .
74193 - .90 $2.75
4001 .25 40 18 - 1.40 4047 - 2.60 7425 .30 7493 - .49 8038 IC VOL TAGE CONT . OSC. $3.90
4002 ~ .25 4019 - .GO 4049 - .7 0 7426 .35 749-1 - .80 7 41 9 4- 1.25
74195 - ."/ 4 LM 370 - AGC SOUELCH AMP. $ 1.15
4006- 1.60 4022 - 1.20 ~050 - .70 7427 - .28 7495 - .80 555 - 2~s - 2 HR. TIMER.
74196- 1.1 0 5 .45
4007 - .25 4023 - .25 4055- 1.20 7430 - . 16 749G - .73 553 OUAD T I MER ..
75324- 1.75 52.50
4009 - .60 4024 - 1.25 4066- 1.20 7432 ~ .30 74 107 - .40
75491 - .60 FCD 8 10 OPTO· ISOLATOR 5 .80
4010 - .60 4025 - .25 4071 - .30 7437 - .30 74121 - .39 1458 DUAL OP AMP.
75492- .60 5 .60
401 1- .25 4027 - .65 4077- . 70 7438- .30 74 123 - . 75 LM 380 ~ 2W AUDIO AMP. $ .95
401 2- .25 4028 - 1. 50 4081 - .35 7440 - . 18 74 '125 - .60
4013 - .50 4029 - 1.75 4076-1.20 SILICON SOLAR CELLS L M 377 - 2W StCICO Audio Amp. $2.50
M I NIATURE D IP SW I TCHES LM 38 1 - STEREO PREAMP. $1.50
4015- 1.40 4030 - .90 2%" diameter LM 382 - DUAL AUDIO PREAMP $1.50
C1'S · 20G·4 Four SPST swi lches LM 3 11 - H I PER. COMPARATOR $ .90
LED READOUTS .5V at 500 rna .... . $5.00 ea., 6/$27.50 in one minidip j)ilck;l!IC. $ 1.50
FND 500·.5" C.C. $ 1.95 LM 319 - Dllal Hi Speed Co mpo $ 1.25
HP 7740·.3" C.C. $ 1.4L CTS·206 ·8 Eig ll1 SpST sw ilches i ll [l 16 LM 339 - QUAD COMPARATOR $ 1. 50
MAN ·7·.3" C.A . 51.25 REGULATED MODULAR pin DIP packa!lc . S2.55
NS 33·3 dl!l. array 51.35 POWER SUPPLIES
DL 747 .. . .. 52 .75 /I. Y ·5· 10 13·A30K SI~1 ./par., par .Ise.r., uni· ~R,! ...!~~ 25A ....!..5A 6A 3§.A
, - 15 VDC AT 100ma
versa l UART . $6.95 100 _ ~9_ ,lQ 1.30 .40 .50 1.20
115VAC I NPUT. . . . . . 527.95
Scnd 25t fOl OUI cata log fe.Jlur ing 5VDCAT IA. 1 15VAC INPUT .. . 524.95 200 _ . .J.Q--1 ,J..Q 1-:75- .G~01.60

6$'
A. LCO M I N IAT URE TOGGLE SW ITCHES
Tr,msistolS and Rect if lcrs 12 VDC A T .!:i AMP. . . 524.95 MTA 106 SPOT, .. $ 1. 20 400 1 .10 1.60 2.60 1.00- ~:io
145 Hampshire St ., Cambridge, Mass. IN 4148 ON914 J 15/5 1 00 MT A 206 DPDT $1 70 600 1 70 230 360 150 300

T.nn.: FOBC.mbrldg.,M....
SendCh.ckorMon.~Ord.r.
SOLID STATE SALES
PO BOX 74B
WE SHIP OVER 95%
OFOURORDERSTHE
~~~~:t.:.~,~~:Io"' SOMERVILLE, MASS. 02143 TEL. (617) 547.4005 DAY WE RECEIVE THEM
You'll Want to Nybble at these
Byte Books 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
information . All you find in the advertisements for parts
are mysterious numbers identifying the little beasties ...
hardly the sort of information which can be used to
design a custom logic circuit. You can find out about
many of the numbers by using the information found in
these books. No laboratory bench is complete without
• The TTL Cookbook by Don Lancaster, published by an accompanying library shelf filled with references -
Howard W Sams, Indianapolis, Indiana. Start your quest for data
here with Don's tutorial explanations of what makes a TTL logic and this set of Texas Instruments engineering manuals
design tick. 335 pages, $8 .95. plus Don Lancaster's TTL Cookbook will provide an
• The TTL Data Book for Design Engineers, by Te xa s excellent starting point or addition to your personal
Instruments Incorporated . How does an engineer find out about library .
the TTL circuits? He reads the manufacturer's literature. This
640 page beauty covers the detailed specs of most of the 7400 • The Transistor and Diode Data Book for Design Engi·
series TTL logic devices. No experimenter working with TTL has neers, by Texas Instruments Incorporated . You 'd expect a big
a complete library without The TTL Data Book for Design fat data book and a wide line of diodes and transistors from a
Engineers. Order yours today, only $3.95 . company which has been around from the start of semicon·
ductors. Well, it's available in the form of this 1248 page manual
• The Supplement to The TTL Data Book for Design from TI which describes the characteristics of over 800 types of
Engineers, by Texas Instruments Incorporated. What happens
transistors and over 500 types of silicon diodes. This book covers
when you can't find a 7400 series device listed in The Data Book
the TI line of low power semiconductors (1 Watt or less). You
for Design Engineers? Before you start screaming and tearing
won't find every type of transistor or diode in existence here,
your hair out in frustrat ion, turn to the Supplement . The
but you ' ll find most of the numbers used in switching and
Supplement has 400 pages of additional information including a
amplifying circuits. Order your copy today, only $4.95.
comprehensive index to both TTL Data Book volumes. To be
complete (and keep your hair in place and vocal cords intact) • The Power Semiconductor Handbook for Design Engi-
you'd best order the supplement at $1 .95 to accompany the neers by Texas Instruments Incorporated. To complement
main volume. the low power transistor handbook, TI supplies this 800 page
tome on high power transistors and related switching devices.
• The Linear and Interface Circuits Data Book for Design
Here is where you find data on the brute force monsters which
Engineers, by Texas Instruments Incorporated . When you run
are used to control many Watts electronically . Fill out your
across one of those weird numbers like 75365 the immediate
library with this book, available for only $3.95 .
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 • Understanding Solid State Electronics by Texas Intru -
specifications in The Linear and Interface Circuits Data Book for ments Incorporated. This is an excellent tutorial introduc-
Design Engineers. You can interface your brain to the 72 x xx tion to the subject of transistor and diode circuitry. The book
(Jjnear) and 75xxx (interface) series of functions by ordering was created for the reader who wants or needs to understand
your copy of this 688 page manual at only $3.95. electronics, but can't devote years to the study. This 242 page
softbound book is a must addition to the beginner's library at
• The Semiconductor Memory Data Book for Design
only $2.95.
Engineers, by Texas Instruments Incorporated . Don't forget the
importance of memories to your systems. Refer to this 272 page • The Optoelectronics Data Book for Design Engineers by
manual to find out about the TI versions of many of the popul ar Texas Instruments Incorporated. Th is 366 page book is a
random access memories and read only memories. Order your compendium of information on TI phototransistors, LEDs and
personal copy today, only $2.95. related devices. Order yours at $2.95.
_ _TTL Cookbook@$8.95 Pl ease add 25 cents for each book for postage and handling, Please allow six weeks for delivery.
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 _1"_a_I_Ir-.:ig~h_t_h_e_re______ Prompt servic.=...e_ __ Electrolytic Capacitors

BR I
@GAR-In-depthinventories
~.S
e. ELECTRONICS (or INDUSTRY
LOW, LOW PRICES!

eleCTrOniCS ~~~~2~~~:
Oflicrs & Warehouse: 10 Alitl Slrerl, 8inghamlon, New York 13904· Tel.: 607-723·3111
QUAN. MFO VDC EACH QUA.'I. MFD. VDC EACH
SAVE SAVE 600 100 3 . 30 1 055 30 350 $1. 00
375 250 3 . 35 246 40 350 1.1 4
298 500 6 $ 1. 00 967 4 450 .98

:~I=ra.Cilorll (fi
299 1 000 6 1. 00 400 10 450 1. 07
MINIATURE LAMPS 571
375
1200
1500
6
6
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529
453
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20
450
450
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INCANDESCENT LAMPS 597 100 12 . 60 METALLIZED PAPER FILM
4000 50 15 . 30
CHICAGO MINI.4TURE LAMPS #387 CG (STANDARD) 85°C Supplied wi th PVC Insulatmg Sleeve
26,000 200 15 . 30 QUAN MFD VDC EACH
SAME AS 1327 EXCEPT LONGER LI FE 41 6 1500 15 1.10 899 .1 1 00 $ . 35
Quan . Hfd. Vdc Size Each 350 2000 15 1.10 437 .33
28 volts . • 04 amps. Bu l b Sty l e T- 1 - 3/4 100 .40
10000 1100 35 1- 25/64 x 2-11/64 S.75 2500 10 25 .25 400 1.0 100 .45
r.1id - Flanqe Base . BRAND NEW BOXED, 1 00 25000 100 350 1-25/64 x 2-11/64 . 50
pe r box . 40,000 pcs in stoc k. 1161 2000 25 1. 40 1360 . 22 150 .40
10000 80 400 1- 25/64 x 2-11/64 . 60 2600 10 50 .40 820 .022 200 .35
PRICE SCHEDULE 10 0 0 500 50 .80 4200 .033 200 .35
- 99 . . 40¢ each 100 - up .. 35¢ ea. SUB-MiNIATURE 825 100 50 . 95 400 .1 200 .40
POTTER 1 099 150 50 .90 771 1.0 200 .40
"'OM '"DIC A1IHO GLOW LAM"S 6349 250 50 .98 417 1. 5 200 .40
& BRUMFIELO GENERAL-
1942 3 00 50 1. 07 1100 . 00 1 400 .35
rm - 2 neon lamps, with droppi n g resistor
to operate d irectly from 115 VAC.
RE LAYS PURPOSE
10,500
520
60
80
150
150
.70
. 90
1100
1600
. 0022
.022
400
400
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.45
Nominal Watts - 1/1 7. T - 2 Clear Bu l b , 290 300 150 1. 00 565 .047 400 .50
wire terminals. TYPE KH 5505 (Identical to KI IU170 1 l) 476 40 200 1. 00 4000 .022 600 .25
COIL: 24vdc, 650 ohms . 409 100 250 1. 39 389 .05 600 .30
25,000 pcs in stock. Mfd by G.E. Co. CONTACTS : 4PDT, 3amps at JOvdc or 1 20 284 200 250 1. 50 500 .1 600 .30
10¢ each u!> to 1000 pcs. 255 5 350 . 90 600 .2 600 . 30
Small rugg ed DC relay with clear poly-

J_
1000 pcs & up 7¢ each. carbonate dust cover . Co nt clcts are gold 281 10 350 .90 717 .25 600 . 30
flashed silver. 20,000 4 250 .35 30,000 .0 1 1 00 .15
Mou nts by solder terminals Ot:" 3- 4 8 stud 339 8 250 . 70 1000 .047 100 . 20
291 .22
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6500 pc in s t ock. BRAND NEI·I. while they
400 16 250 .60 400 .30

last at this price . $ 1 .2 5 each

IIITI GLO INCANOUCINT LA Mrs ~
LAMINATED PHENOLIC
PLASTIC PANELS
BRITE- GLO :ncandescent Lamps . '"
HIG H POWER OUMMY lOAO
Ult ramini atu rized Series. lDO . OOO hr. life BRAND NEW PHENOLIC SHEETS
Versatile, l ow cost indicator lamp. Id ea l Mfg . Easter n r.ticrowave. #1 0 - 1254 .• . RF Coaxial Loa d Re -
for Ster o Amplifiers, !"obile Equipment, Grade LE- Natural sistor uti l izing water flow to cool and provide a load
Ins trumentation , Computer and Displ ay Type - FBE. I'hl Spec : 1503 5 • . 062" thick r e sistance of 50 ohms for inputs from DC to 4000 MHz.
Pane ls. Etc. t.Jeeded by all e xperi menters. am.J. t~urs and Maximum power input is 1000 watts. Requires a flow of
. 21B GP M min. per 100 watt s of input power ; 100 psi
High tempe rature. T 1- 3/4 lamps - Meta l radio :nen for insulating parts - terminal
Base - lV irc Term inal s . I'-letal base in- strips - bu ild ing sets" or for research pressure. Compression fittings on water line inl et and
crease s light ou t pu t and protects l amp & developr:tent . etc . o utl et for copper tubing supp l y lines. Has a F l ange
f rom damage. type coaxia l f i t ting, friction type, 13/16 " 1.0. with
Stock; 560 - 6 " x 6" x . 062" 42¢ each
" # 561 - 6 " x 12" x .062 82C each 2- 1/4" flange. Completely shielded unit of machine d
41, 685 !,CS - 6.3 volts. 75 rna, 8 " wire aluminum . Size: 1-5/B" diameter by 5- 3/B" long.
lead s. # 563 - 12" x 12" x .062 $1 . 58 ea
# 564 - Full sheet s 3a" x 47 " x .062" Shipping weight, 2 Ibs.
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leads .
BRAND NEW QUALI TY SHEETS
DIS CO UNT SCHEDULE
1 - 99 25¢ ea .
SALE 100-499
500 - 999
20¢ ea .
IS¢ ea.
SALE High-Speed Reset Counter
lOOO - uP 12¢ ea .
Veeder-Root
.. FI(;ti RE ('O tJ :o.:TI~ 1I \I.\., n·\!. It ESET
I t ~V n C / 11 5\'AC'

lI SVAC (Rl.'ctlfH~1 s uppllcdr. BaSIC

counter is 11 5VDC. 6 ....·aus ·1 figult".
blilck on ..... hLII' b3ckground. Pu sh hutton roller lever. 95¢ ea
reset. Dim.: 1· 718" ..... Idth 1· 1/8" high
~ 2· 1/2" deep.

TANTALUM CAPACITORS x
o ro
o ~"
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QUAN HFR TOL. OHI·lS i'lATTS PRICE V> ~ ~
-0'-<
TYPE 1090 < -
(%) Each 1-1 • ..-1 It!
10,686
3 ,0 00
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Electra
191
191
1/8
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PUSHBUTTON SWITCHES TUBULAR SINTERi::D- ANODE TANTl\LEX CAPACITOR
~
-0
H
~
~
"'-0
~

29,000 I R C 243 1/8 . 04

o -0
1 /8 .04 Unit can be used on 6 v
n09D147X9060T2 E ~ ro
75 . 000 T.1. 2.43K 1620 pes - 140 uf ±lO% - 60vdc $2 . 00 e d. ~ ro ~
35 , 000 [.I. 909 1/4 . 06 I/. or in series for 12 volt ~ 4J U}
7000 T . I. 10 1/2 . 07 ~ SPST , mom, PC board gold .r{ Ul ItS

3000 El ec tra 15.4 1/2 .07 /"/~ .a:. plated pins for wiring or GENE RAl ~ ElE CT RIC 1 ~,l.AI;L:lo~~.~:.~,~~uc::~o~· ~;,' :l.cn C
•..-1 )-1..-1
~

5700 £!ectra 28 1/2 .07 ! ~ :(':r ~ easy installation.

.... ' ... 4a . C",111 • • "',I.r.' .... )
C l IO / II_'OL .. ltlZ[O
:;: z 0.

7900 IRe 53.6 1/2 .07 . 10 , 000 pes in stoc k 3,000 pc:s CL31BE180t-"iPE. l8'Jf - J5vdc 65C each
7200
6600
1800
IRe
IRe
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90 .9
1650
6190
~~~
1 /8
:g:
.04 ,
MEr : Grayhill Widely used on computer s, m achine tools,
Swi tch Co. office machines, guida nce control and a
300 pes CL31BE550t>1PE, 55uf - 15vdc
non-(X>larized 0...32/33
S5C each

1000 IRe 267C l i E . 04 2" X l~" x 1.," wide variety of applications. 900 DeS C.'L33BL020!otlE, 2. 0uE - 75vdc S1.00 each
1--------------...;...-------l\..:..--..:.......:.:....:.:.:....--------t&\-----lI~lfc1lul ;;. MTP / MTPH ULU .... MINI::,U:,I,,:ANT ... lU~U
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2.100 p::s ,·n'PI06r·[)30PlA. lOuE - 30vdc
l ,028 pes Hl'P336j·[)10PL\ . 33uf - lOvdc

Ifjffil'iil'i\*,'A' 'au. 'LlmOLm 'A.,ALUM ,,,A,,,OlS

55< each
75C each
65C each

4996 pes, 4.7uE- ±lO% . 6vdc, TAS475K006PLA 35¢ ea

394 pes •. 47uE ± 10%. 6vdc . TAS474K006PlA 38C ea
QUAN. MFD. VO LTS SIZE PRICE EA QUAN . MFD. VOLTS SI:lE PRI C E: EA 1430 pes. 47uf ± 10% . 6vdc , TAS476K006Plc 40C ea
326 pes, 220uf ± 20%. 6vdc , TAS227l-1006PIG S1. 20 ea
350 )0000 1-3/8 x 4-3/16 $1.50 252 11500 18 2" x 4-1/2" $1.25 285 pcS, 5.6uf ± 10% , 10vdc , TASS6SKOIOPlC 40¢ ea
49 4 60000 3" x 4 -1 /2" 1. 50 628 11000 19 2 " x 4-1 /2" 1.25 4574 pes . lOuE !lO'! . 10vdc. TAS106KOIOPlC 40¢ ea
1016 25000 2-1/16 " x 4 - 9/16" 1. 50 1014 8200 25 1-3/8" x 3- l/8" 1 . 70 900 pes. 15uf ±20%, l Ovdc , TAS156~1010PlC 40¢ ea
527 4 0000 2" x 5" 1. 50 10706 1100 )5 1- 25/64 " x 2-11/64" 1. 00 a87 pes , .068uf !l0%. 20vdc , TAS6B31<020PlA SlC ea
353 15000 10 2 " x 4-1/8" 1. 25 4200 750 60 1" x 3-1/2" .75 152 pes . 2. 2uf ± 20%. 20vdc. Sprague 40¢ ea
869 15500 10 2" x 4- 7/16" 1. 25 792 1500 80 2 " x 4-1 /2" 1.30 1457 pes • . 47uf !lO%. 3Sydc. TAS474K035PLA SI C e::l
277 40000 10 3" x 4 - 1/2" 1. 70 478 450 100 1-7/16" x 2- 9/16 " 1.00
31 . 74000 10 3" x 4-3 / 4" 2 . 00 337 400 100 1-7/ 16" x 2-1 /2" 1 . 00 GEN ERAl ~ ElEC.TRIC ,u.,,.. 'OIL JA,,"AlUMS +1 U
O
C

375 15 000 12 2" x 4-1/2" 1. 25 200 500 150 2 -1 /16 " x 2- 3/8" 1. 00
365 pcs G.E. 40uf,±20% , SOvdc . l25 0 C
267 14 000 13 2 " x 4- 3/8" 1. 25 500 750 200 1-1/2" x 4" 1. 00 Type : 2KI05AA6M. $1.75 each
600 10000 15 2- 1/16" x 4-1/2" 1. 25 2343.6 100 350 1-25/64 " x 2-11/6 4" .75
1168 pes SPRAGUE. 40uf , ±20% . 5Dvdc. 12SOC
529 12 500 16 2" x 4-1/0" 1. 25 11800 80 '00 1- 25/6 4" x 2 - 11/64" .7 5 7ype: 220D005A3M. S1.7S eacH C
Production Description: signed offset for branches, jumps and
subroutine calls, with extended 16 bit
addresses or addresses indexed by 8 bit
offset, and inherent operands for mis-
cellaneous processor control instruc-
tions).
Data control manipulations include the
usual and expected operations of a good
••• general purpose instruction set in the second
generation of microprocessors. Also worth
noting are a decimal adjust instruction to
handle packed decimal data and push and
pull operations for the accumulators uti-
li zing the stack as temporary data storage.
The processor has a software interrupt, a
reset sequence, a maskable interrupt line,
Photo 7. and a nonmaskable interrupt line ; all of
these except the reset completely save the
processor state prior to the beginning of the
new instruction sequence. These interrupt-

The Astral 2000 li ke operations are vectored to a new pro-

gram location via 4 pointers located in the
last 8 bytes of address space (locations F F F8
to FFFF.) For more complete description of
Editor's Note The Astral 2000 system is based upon the the 6800 architecture see the Motorola 6800
Motorola 6800 central processor design. The literature.
This descriptive sum- use of anyone of the many microprocessors As implemented in an Astral 2000 sys-
mary is based upon materi- is subject to numerous design choices in the tem, the first 56 K bytes of a total 64 K
als supplied by M&R En- detai ls of how the chip will be buffered and bytes in the 6800 memory address space are
terprises, as well as first interact with the rest of the computer world. left open for ordinary programmable memo-
hand inspection of proto- The designer of the Astral 2000 computer ry, the single most va luable resource of any
type hardware during a chose to take a route which seems inherent genera l purpose processor's central proces-
trip to California in April in th e design simp li city of the second genera- sing unit. What th is means is that the user
of this year. The market- tion microprocessors such as the 6800. The can insert cards in increments of 8 K to the
ing and development of Astral 2000 bus is a minimum comp lexity, point where some level less than or equal to
the Astral 2000 is, to say minimum pinout design which in essence 56 K has been acquired . (This assumes that
the least, cautious and si mply buffers the processor pins of the there are enough card slots in the backplane
painstaking. It has been 6800. As a result, it fits into th e stand ard 44 to accommodate such an expansion.) M& R
essentially kept under contact (dual 22 pin) edge connectors which Enterprises presently has avai lab le both an 8
wraps until the BASIC fa- are widely availab le at moderate cost. (This K programmable memory board and an 8 K
cility was sufficiently de- choice of a minimum pinout backp lane EROM board (using the 5204 UV erasab le
veloped to allow release. configuration also makes it possibl e for this chips) with wh ich to take advantage of
The system has been computer to use standard Vector Electronic memory address space. The standard pack-
shown off in bits and Co cards as the basis for home brew peripher- age of the Astral 2000 includes one of the 8
pieces throughout the de- al interfaces.) This simplicity of the back- K programmable memory boards. The upper
sign process by people plane bus and use of standard connectors is 8 K of a Motorola 6800's address space is
from M&R who attend the one of the most elegant features of the reserved for the system monitor and periph-
sessions of the Homebrew Astral 2000. erals of the Astral 2000 design.
Computer Club in Palo Without indulging in a major rev iew, here
Alto CA. Now that M&R in summary is what the 6800 processo r The Monitor and 10
Enterprises is finally to the chosen for the Astral 2000 wi ll give the
point of delivering the programmer in machine assembly language: The basic concept of the Astral 2000 is
systems in initial produc- 1 index register (16 bits) , that of a "turn key" system, even when the
tion quantities it leaves the 1 stack pointer register (16 bits), unit is purchased in kit form. An aspect of
rumor stage and becomes a 2 accumulators (8 bits), th is is the preasse mbled and tested processo r
full fledged contender in 1 flag register (6 bits active), board and memory board. Another aspect of
the marketplace.... CH 5 address in g modes for data operations this is in the physical configuration seen in
(direct 8 bit, extended 16 bit, immedi- the photographs. The front panel may seem
ate, indexe d with 8 bit offset, and at first sight to be an unimaginative repeat of
inh erent operands), the traditional front panel seen in computers
4 addressing modes fo r processor co n- from time immemorial. But it is not essen-
trol operations (relative with 8 bit tial, and is put in the design apparently for

132
FAIRCHILC ANNOUNCES THE FAIRCHILC

SOLID STATE 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 FTK0106

•
PN FTKOO20
SOLID STATE

TECHNOLOGY
Th"

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SOUl) STNn :

TECHNOLOGY KIT
automobile clock
• ~'~'U "." "" .• "'~ '" ',"" ...
KIT • ' . ' " - . " ~I" .... '"
• "'I.M~ " .'" C ... .. ' .. . ·.I
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TEN RED L ro l.4Mf'S

TECHNOLOGY BY

FAIRCHIL.O
4001 MIRANDA AVEN UE · PALO ALTO. CA 94304

CARD FRONT CARD BACK CARD FRONT

DIGITS PHOTO ARRAYS

FTKOOOl OS' High Common Cathode Digit $1.00 FTK0040 9-E lement Tape Reader Array 16.00
FTKOO02 OS' High Common Anode Digit 1.00 FTK0041 12-Element Card Reader Array 24.00
FTKOO03 .357" High Common Cathode Digit .75 FTK0042 Reflective Opto Coupler 4.00
FT KOO04 0.8" High Common Cathode Digit 2.00 COUPLERS
FTKOO05 0.8" High Common Anode Digit 2.00
FTK0050 3 General Purpo se Opto Couplers 1.00
0.8" HIGH DISPLAY ARRAYS FTK0051 Darlington Opto Coupler 1.00
FTK0010 12 Hour, 3% Digit Clock Display 7.00 MOS CLOCK CIRCUITS
FTKOOll 24 Hour, 4 Digit Clock Display 8.00
FTK0400 Digital Clock / Calendar Circuit 7.00
LED LAMPS (FCM7001)
FTK0020 10 Red LED Lamps 1.00 FTK0401 Digital Clock / Cal endar with BCD 7.00
FTK0021 5 Mixed Colored LED Lamps 1.00 Outputs (FCM7002)
FTK0022 10 LED Mounting Clip s 1.00 FTK0402 Direct Drive Digital Clock Circuit 5.00
FTK0023 5 Three Piece LED Mounting Adapters 1.00 with AC Output (FCM3817 A)
FTK0403 Direct Drive Digital Clock Circuit 5.00
PHOTO TRANSISTORS
with DC Output (FCM3817D)
FTK0030 5 Fl at Lens Photo Tran sistors 1.00 FTK0405 Direct Drive Digital Clock / Calendar 6.00
FTK0031 5 Round Len s Photo Transistors 1.00 Circuit (FCM7015)
FTK0032 3 Fl at Lens Photo Darlingtons 1.00
KITS
FTK0033 3 Round Lens Photo Darlingtons 1.00
FTK0106 Automobile Clock Kit 40.00

eTHESE PRODUCTS ARE PACKAGED FOR OUT- e DEALER'S AND WHOLESALER'S INQUIRIES
STANDING WALL DISPLAY APPEARANCE INVITED-PRICE LIST AVAILABLE.

eFULL FAIRCHILO PRODUCT LINE eBUY WITH PRIDE THE PRODUCTS BUILT BY
TO FOLLOW THE INDUSTRY'S LEADER - FAIRCHILO

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PHONE ORDERS - (415) 592-8097
 level language hacker. These debugging facili-
ties include patching and displaying memory
contents, insertion of break points, stepping
through break points, etc. The Astral 2000
monitor also has larger scale data manipUla-
tion facilities which include memory check
sum calculation, "block insert" for tempora-
ry program patches, a command which can
be used to calculate relative branch offsets,
and patch points for the software interrupt,
nonmaskable interrupt or maskable interrupt
requirements of applications systems and
programs.

High Level Language Facilities

A major concern of most users is the need
for high level language facility. In the Astral
2000 case, one of the strong points in the
Photo 2: The Astral 2000 computer is $995 partially assembled or $ 7250 descriptive literature is its 8 K extended
fully assembled and tested. Additional fully assembled 8 K RAM boards BASIC implementation. This is part of a
are $245 each and the 8 K EROM board is $59.95. The V/D-80 video ter- standard $35 software package which is
minal is $ 789.95 in kit form or $245 fully assembled and tested. 10 tape available to the purchaser of the system. The
interface units are $49.95 each. The software package includes Astral BASIC descriptive literature of Astral BASIC im-
on magnetic tape cassette or paper tape (specify), complete documen tation plies that it will prove quite useful, whether
and a free one year subscription to the Astral Newsletter, all for $35. The the application is business processing, games
Astral 2000 is available from M&R Enterprises, POB 6707 7, Sunnyvale hacking, or a host of other small computer
CA 94088. uses. Here is a summary list of the points
found in the Astral BASIC which supple-
ment the usual features of any good ex-
purposes of imagery and showing off a tended BASIC.
classical "computer. II The toggle switches
and lamps don't really control a thing • Floating point arithmetic with user
directly, since they lead directly to a group selectable precisions of 6, 9, 13 or 16
of PIA ports, as do the other "front panel II
decimal digits. (Trade execution time
features such as the system's real time clock. off against precision of calculation.)
The "turn key" effect is achieved by two • A unique 00 statement references
groups of statements by number to
subsystems of the central processor board
provide a simple form of subroutine
design and an optional VI 0-80 video display
call not usually found in BASIC.
terminal board. The processor board con-
• Full statement trace facility.
tains the key to turn key operation, a 2 K
• Variable length character strings of
byte ROM monitor. This monitor program
unlimited (ie: 2**16) length.
can be used in one of two modes : It can
• Substring search function for charac-
drive the V10-80 terminal interface board,
ter strings.
or a standard serial Iine interface with both • Complete line oriented editing facili-
20 mA current loop (Teletype compatible) ty including a renumbering facility
and EIA RS-232C compatible drivers for which alters all GO TOs.
typical commercial terminals. The serial ter- • Formatted output with PRINT US-
minal interface also includes control lines for ING, an essential for practical applica-
auxiliary functions such as reader and punch tions programming.
control.
The logical features of the Astral 2000's
monitor program will prove quite useful. Miscellaneous
The input of the monitor is buffered so that
commands can be repeated simply byenter- Rounding out the details of the Astral
ing an ASCII space code from the keyboard. 2000, the standard version includes an audio
In the context of a command Ii ke the one interface for magnetic tape recording, a real
wh ich dumps "n" bytes, th is can be a saver time clock based upon a standard 24 hour
of keystrokes: once "TYPE 8" has been clock chip accessed through PIAs and level
entered, additional 8 byte groups of data can shifters, and a centralized power supply with
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space. The monitor also includes machine component modules are printed in the cap-
language debugging facilities to aid the low tion for photo 2.-

134
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BYTE's
Books

-DESIGNING WITH TTL INTE- Design gives 53 pages of background The most important use of this book is its
GRATED CIRCUITS by the Components information on Boolean algebra and practi- value as an introduction to TTL logic. By
Group , Texas Instruments Inc. Edited by cal representations of logic in the form of reading and studying it, you will. begin to
Robert L Morris and John R Miller. SSI gates. The chapter includes a description understand the ways in which SSI and MSI
of Karnaugh mapping techniques and the TTL gates can be utilized in your own
People often ask questions Ii ke "Where minimization of logic. From combinatorial experimental logic designs. After s·tudying
do I get basic information on hardware design , the book progresses into Flip Flops, this text, you should be able to mll ke much
design?" One answer is in "Designing With including background information on the more sense out of the technical information
TTL Integrated Circuits." workings of these devices, and fairly summaries typically published as specifica-
This book, published by McGraw Hill in detailed descriptions of the uses and tions sheets and data catalogs.
1971, is a fundamental starting point for applications of these devices incl uding Order your copy today from BYTE 's
any person designing peripherals and custom synchronization of asynchronous signals, Books, $24.
logic employing TTL integrated circuits. shift registers, flip flop one shots, etc. Then
While its publication date precludes any the book returns to static combinatorial
-MICROCOMPUTER DESIGN by Don-
reference to the later additions to the TTL logic with its description of the Decoders
ald P Martin, Martin Research . Edited and
74 00 series of components found in the available in the 7400 line as it stood in
Published by Kerry S Berland, Martin
Data Books, it is nevertheless the source of a 1970-1971.
Research.
wealth of ideas on TTL integrated circuits A chapter on Arithmetic Elements gives
and design of logic with this family of Purchase your copy of the definitive
fundamental descriptions of binary arithme-
circuits. source for circuitry and hardware design
tic, diagrams of the basic gate configurations
What is fanout? You may have heard this information on the 8008 and 8080 com-
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term mentioned at computer club meetings on number representations for use in
puters today.
or in advertisements for circuitry, or in computers. Much of the material in this
Even Intel, the originator of the micro-
articles in BYTE. You can find out section is dated, due to the fact that the
processor revol ution, is hard put to compete
background information on the calculation later 74181 series of multiple function
with th e wealth of information found in
of fanouts by reading the chapter on Circuit arithmetic units had not yet appeared when
Martin Research's new second edition of
Analysis and Characteristics of Series 54/74. the book was written. But for a background
Microcomputer Design. This is the book
Worried about noise, shielding, ground- on arithmetic operations implemented with
which was originally published as an
ing, decoupling, cross tal k and transmission the simpler 7483 circuits, this chapter is
expensive (but quite practical) engineering
line effect? (Or, more properly, did you ideal. A chapter on Counters and a chapter
report in loose leaf form, at about the t ime
know you should worry about these effects on Shift Register.; complete the detail logic
the. microprocessor technology was first
in certain circumstances?) Find out about sections. The book is closed out by a
catching on in the form of th e 8008: This
general precautions and background infor- chapter on miscellaneous Other Applica-
388 page second edition of the manual is
mation by reading the chapter on Noise tions including a simple binary multiplier, a
loaded with detailed information on how to
Considerations. 12 hour digital clock and a modu10-360
build and use computers based on the 8008
The chapter on Combinatorial Lo~r. adder. 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-
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__ Designing With TTL Integrated Circuits $24 handbook. Microcomputer Design is a must
_ _ Microcomputer Design $25 for 8008 owners and 8080 owners who
Send to: ~N~a~m~e~_ _ _ _ _ __ __ _ __ _ __ __ __ _ ____ vwnt to truly understand how their
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City State Zip
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SllN30" .26 SN14107N 39 SNl4 Ia7N 600
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XC209 0rango I1 / S1 XC 111 0rn nge 4 / S 1

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StH4~IN .89 SIIW3211 1.09 S N 7419~N 1 25
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SN7~I96N
5t17443N
SNN~4tl
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.15
SN74141N
5N74142N*
1.1 5
4.00 SN74197N
1.25
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SN7>t45N .75 SN74143N* 4.50 SN74 198N 1.75 SA01' • O•••'I ... I'I.,~ (....." ' . 40
SRB B . BI.nlo.S",ly t• ..,hl 40
SNN46N .81 SN74 144N* 4.50 SN74199N 1 75 ,200" dia. .185" dia. .200 " dia . .085" di a. SIlItIl_ It.III:IOC1 ¥ lu<M 40
5tmml"" .69 SN74145N liS SII74200li 5.59
SIj744811 .79 StlNI47N 2.35 SN74279N* .90 XC22 Red 10 $1 XC526Red 1 0 / S1 XC556Reci 10 / 5 1 MV50
SIm50t/ .26 SN74\48N 2.00 SN74251N 1.79 XC22 G reen 4 /$ 1 XC5 26Grcen ·1151 XC556G reeil 7/$ 1
7/1' .085" diil. Micro DIP SWITCH
~~~~6~~'r~~~ ~~~ ~ ~§~~g6~~'~g~ ~~~ ~
SN745HI .27 SN74150N 1.00 SN74284N 600 XC556Yc ii ow
XC5560rilnDO 7/ 1 red LED f hese SlVl tf,tICS lealUlI!SCVCn SPS I shlleswltches III J
SN7453N .27 SN74151 N .79 SN74285N 6.00 SSL ·22AT ';'51 XC526C lear .1 SI XC556C lea r 71 1 6/5 1 molded 0111 T~cy a!c locally SUltt.'C1 lO! nucroprOCCSS01
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MANY OTHERS AVAILABLE ON REQUEST
DISPLAY LEOS
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20% Discount for 100 Combined 7400's

gg!: ~~ eM 0 S i~~~~~ .~~ Dl707

Dl747
CLlPLITE !! 4/$1.00
CO·1002
C04006
CO~OO7
C04009
C04010
25
250
25
59
59
C04035
C040~ 0
CO~o.:2
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C04046
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245
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o f the Panel in 0 .250 hole on 3 / 8 "
NEW LED
m~u~~ ~,!!~,~c ~;;'~;EM
centeno Palle l th ick ness from 1/ 16" to 1 / 8".
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C04011 25 C04().l7 275 74C90N 300 __ • _ C Ll PLITE equoli zcs ilnd i ncreilsos lho brightness of
~g~~:~ ~~ gg~~~ ~~ ;:~g~~~N ~~ TYPE POLARITY HT TYPE POLARITY lI300
T common ly used wi de beam LEOS.
_ CLIPLITE is to b e used wi th XC5 56 LEOS.
C040 16 .56 CO ~ 051 295 7<1C 151 2.90 MAN 1 Common Ano~c 270 2 95 ~.IAII 3620 Common Anone·oran(jc I 75
_ Spoclfy c olo rs - red , groen, ;}mt)er. or yellow w h on
CCOO',"0',7, ' .3,5, C04053 2,95 74CI54 4 00 i~~~ ~ ~O~I:II~~I~~~~~~c 3~~ .) ~; :'i~~ 36·10 Common C.II~olle·orJngc 300 1 75 ordcring. - - -- --
C04060 325 74C I57 2.15 MAN .I Common CartJOde :87 95 O' 4710 Common AnOllti·Rcd ~oo 195
gg:g~ ~ ;~ ~g~~~~ I ~~ j;g;~ i' ~~ MAN 7 CommOIl Ano~e 300 : 25 ot~~~ ~:::~~~ ~~~~:.!ed : : ~ 'ZENERS-DIODES-RECTIFIERS
C04023 25 CO~071 45 7':C163 300 r.1AU 7G Common Anode-green 300 I !IS OL 728 Common C.ltIlOlle 500 295 TYPE VOLTS W PRICE TYPE VOLTS W PRICE
C04024 1 50 C04081 ~5 74CH).; 325 MtlN I Y COffi'non :'node·yenow 300 I 95 OL i':7 Common ;',nOlle 600 225 1N746 33 ':OOfil 4 1 00 1t/400S- 600 PIV 1 AMP 10 I 00

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LMJ05H
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LMJ09H 1 10 lM381N 1.79 LM390or~ 55 22 pm 37 36 35 SOLDERTAll STANDARD (TIN) INJOO3 Z1)O PIV l ;\MP 12100 ItwB6 200 PIV 35 AMP 180
LM309K .99 LI.l38211 1.79 W 3905N 60 IN':OO': ':00 PIV I AMP 12 I 00 H11l88':00 PIV 35 AMP 300
LM310Ctl 115 tlE501K 8.00 l M3909* 1 25 1·1 pm S27 28 pin , 99 90
LM311H
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.90
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NE510A
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35 "
311
36prn
4[J pm
!.J9
1.59 '"
1.<1 5
"
'IS
1.30 C360
SCR AND FW BRIDGE RECTIFIERS
15A @ 400V scn S195
lM318CtI
LM319N
I ,SO
1.30
IIE536T
IlE5-l0L
6,00
6.00
LM7525N
l M7535tl
.90
1 25
2~ pin
." .t2
SOLDERTAIL STANDARD IGQLD)
C38M 35A @200V scn
SCR
<9,
LM320K ·5
lM320K·5.2
LM320K·12
1.35
135
1.35
NE550N
IIE555V·
NE5608*
.79
.45
5.00
80386*
LM 75450
7545 1CN
495
49
39 8 pin 530 27 S 70 63 .57
2N2328
MOA980·1
MDA980'3
16A @2ooV
25A @ 50V
2 ~.o'@ 200V
FW BRIDGE REC
FW BRIDGE REC
"
<9,
<9,
LM320K-15 1.35 NE5616* 5.00 7S452CN .39 14 PIli 35 J2 "29 _ 28prn
24 pm 110 '00 <JO
161)1n <7,
LM320T-5*
LM320T·5.2
LM320r-S*
1 75
1 75
1.75
NE5628*
NE565H*
IlE565t"
500
1.25
1 75
75453CN
75454CN
7549 1cr1
39
39
79
18 pm "
51
35

"
32
43
WIRE WRAP SOCKETS (GOLD) LEVEL # 3
JfiPII"I
400111 'IS
I ~O
<5, 1.26
'"
Bl 00
SS I OO
3 $100
TRANSISTORS
PIIJ5iii 35100
1'N~?~9
Ptl~ ?!>O
:':t.I~OO
4 Sl 00
~ SI 00
~ SI 00
1'113568 ~ Sl 00 m·I~OI ~ 51 00
LM320T-12* 1.75 NE566CN* 1.25 75-192CN 89 .151 00
P113569 !51 00 t:tH1 0] .ISloo
lM320T'15 1 75 NE567H* 1,95 75<1!l4CN .89 10 Pi!! 5 45 ." 37 24 Pill S105 95 5 51 00 , 00
~::~~~ H)~ ~
.65 W~.wJ ~S!
5 51 00
LM320l-18*
LM320T·24
1.75
1.75
NE567V*
LM703CN
1.50
.45
ACALINEAR
CA3013 2 15
1·1 Pi!!
16pm
39 36
.,.
37 28 p"l
361l1n
140
159
1 25
145
1.10 ~ 5HlO
1I1~.\09
~t. ~Mi
5 51 00
~Sl 00
LM323K·5* 995 l1.l709H 29 CAJ032 256
43
" <30 5 5100 2!1l1Oi 5 5100 7·.~; 451 00
It.I324/1
LI.I339N
1.60
1 70
l1.l709tl
LM710N
.29
79
CAJ035
CAJ039
2 48
1 35
18pII"I 75
" " 40 pm 175 155 1.:0 ~ 51 00
~ 51 00
5 $100
lImll
m Jn~
5 5100
S &5
2'.
~'. )08g
15 100
! 51 00

LM340K-5
lM340K'5
1.95
1.95
lM711N
lM723H
.39
.55
CAl046
CAJ059
1 30
3,25
50 PCS, RESISTOR ASSORTMENTS $1.75 PER ASST. ~ SI 00
251 00
S 89
2:13725
2113903
2tI J90~
2/013905
51 00
5 5100
~ 51 00
!SI OO
;>t. ~ l a
21151:}S
?!15139
n lS209
~ Sl 00
~ Sl 00
5:$ 1 00
5 51 00
LM340K-8 1.95 lM723H .55 CAlOGO 3,25 10 OHM 12 OHM 15 OHM 18 OHM 22 OHlll SI OO 2N39()f; ~ $1 00 2 1. :'~1 55100
LM.)40K·12 1.95 LM733N 1.00 CAJOaO .85 ASST. 1 5 ea. 27 OHI.\ 33 OHM 39 OHM .j 7 OHM 55 OHM 1/4 WATT 5~. 50PCS. 5125 CIOiiBISCR Hl oo
lt1!OI3 3 51 00
lM340K ·1 5 1.95 LM739U 100 CAJ081 200 5 5100
2t/! QI! 35100 ]'.,.:31 QOO
LM.)40K-18 1.95 U.174 1CH 35 CAJOB2 200 680W.I 82 OHM tOO OHM 120 OHM 150 OHM 5S1oo 2H4t23 IO~1 00 473 l. 75ca.
LM340K ·24 1 95 LM741Ctl 35 CAJ083 1.60 ASST. 2 5 ea. 1800UM 220 OHM 270 OHM 330011111 390 OHM 114 WATT 5~. 50 PCS.
LMJ40T·5 1.75 lM74 114N .39 CAJ086 85
LM340T -6 1.75 LM747H .79 CAJ089 3.75
4700lIM S60 OHM 680 OHM 820 OHM lK CAPACITOR 50 VOLT CERAMIC CORNER
LM340T-8* 1.75 LM7471j 79 CAJ09 1 1020 ASST. 3 Sea. 12K 1 5K 1 8K 2 2K 2iK 1/ 4 WATT 5 ~. 50 pcs . DlSCCAPAC1TDRS
LM340T ·12 1.75 l M748H 39 CAJ123 2.15 33< 39K .1 7K S(iK 66K 1·9
10'':950·100 1-9 IO·~9 50·100
l M340T-15
LM.)40T·18*
1.75
1.75
lM74811
LMI303N
39
90
CAJI30
CA3140
1 39
1.25
ASST. 4 Sea .82K
22'
' OK
271( '"
33<
' 5K
39K
,"
"K
114 WAn 5~. 50 PCS. 10pi
22 pl
47 p!
0·1
04
.04
05
.05
.05
.03
03
.03
001,..F
0047,..F
.011,F
05
05
.05
OJ
. O~
.04
035
035
035
LM340T'24 1.75 lM1304N 1.19 CAJ600 1.75
ASST . 5 S ea. 56K 114 WATT 5~. 50PCS.
~~~~~!j I :~ ~~~;~~~ 1.!~ ~~ :~ ; ~~ 1501<
Sea . J9l) K
'"
180K
.~ iOK
'"
220K
lOOK
2iOK
120K
330K
114 WAn 50PCS.
100 pi
220 pi
~70 pi
04
04
04
.05
.05
05
.03
03
.035
022,..F
OJ7,..F
II,f
06
06
12
05
05
09
'"
'"
075
ASST. 6 '60K 680K 820K 5~.

;:~~:'i
74lS03
;: 74LSOO
39 74lS74
TTL ;:,';~~
65 7·1lS15J
\~
1 69 ASST. 7
1M
5 ea . 2.7 M
\ 2M
33 M
15M
39M
I BM
.\ 7M
22M
5.6M 114 WATT 5% 50 PCS .
OO lrnt
0022
.12
.12
\00 VDLT MYLAR FILM CAPACITORS
.10
10
.07
07
022ml
047ml
13
.21
II
17
DB
\3
~~t~~~ :~ ;~t~~~ ~~ ;~~~~ ~~ ~ ~~ 0047ml .12 10 .07 1m! .27 23

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ASST. SR All Sevcn Resisto r Assortment $ 10.95 ea. .Olml .12 10 07 22ml 33 27
~~ ~~ ~: 7:4C1~; ~.!: ~~t~:~; ~~; t-....' .25.....P:;jC;i,S_::i
05~'I.
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0.~
49~'=PC'!:S~~03=='='=-"iiiiOO...9.9:'"
' """'02~"l...;'.::.'_.. +2~. DIPPED TANTAlUMS !SOLID) CAPACITORS
.28 .23 . 17 1.51l5V 30 .26
74LS<3 79 7'LS66 65 74LSI75 1.95 SINGLE TURN ¥o" CERMET POTENTIOMETER
1135V
.15/35V .28 23 . 17 2.2125V 31 27 ""
l4l SI,1
74LS20
74lS26
2. 19
39
49
74L590
74tS92
74lS93
1.25
125
125
74lS181
74lS190
74lS19t
369
2 65
285
•
•
Resista nce To terance :!: 20%
H' I P
Igl ower - .
0 5 Wat! at 70°C $ 89 22135V
.33/35V
.47135V
28
,28
28
.23
23
23
.17
.17
17
3.3/25V
4.7/25V
6.8/25V
31
32
36
.27
.28
.31
"
23
25
741527 .15 7~ l595 2 19 7~lS192 2 85 • Wide Dperaling Temp . Range - 55°C to + 125°C • 68/35V 28 23 .17 IOl25V olD .35 .29
7~lS28 49 i':lS96 189 7;llS 193 285 STAND ARD RES ISTANCE VALUES 1.0135V 28 .23 .17 15125V 63 50 -'0
74LS3O 39 7'lSl07 65 7,:LSI" '25 50n loon 500n IK 2K 5K 10K 20K 50K 100K 200K 500K 1 MEG MINIATURE ALUMINUM ELECTROLYTIC CAPACITORS
~:t~~ ~~ ;:~:~ .~; ;~t~;~~ ~.~~ t-.;;;;;;.;....;,;;;;;.;...;;;=":'A~II~A":'dv.;;;en~i~se;;;d~p:-ri~ce;;,;s-:G~O;;;Od~Fo;;,;r;:Th-:i..;
S ~M;;.on..;lh~on;;;I,;.Y--;;';N~o~v-em';'b';;e";r;;"'---1 AlIalLead
47150V IS . 13 .10 .47/25V
AlidlalLead
15 13 .'0
74LS51 39 7J lSI32 155 7JlS260 55 I O,5OV .16 1~ .11 47/50V 16 I~
7olLS55 _39 7~lS136 65 7.:tS279 i9 Salislaction Guarantee d . S5.00 Min . Order. U.S. Fund s.
Calilornia Residents _ Add 6% Sates Tax _ Data Sheets 25c each
3 3 SOV .15 13 .10 10116V 15 .13 "
10
741Si3 65 74lS138
DATA HANDBOOKS
189 7JlS6iO 595
Send a 24 ~ Stamp (poslagejlor a Free 1977 Catalog
4 1125Y .16
10!25V
10/SOV
15
.16
14
13
14
12
.10
.12
10/25V
1.0150V
4.7I1 6V
16
.16
. 15
1~
.14
.\3
",.
.10
7400 Pin ·out & Descript ion 0 1 5 1100/74 00 ICS $2.95

~~~~~?1t&S
CMOS Pin·oul & Descript ion o f 4 000 Series ICS $2.95 22125V .17 15 12 4.7/25V . 15 . 13 10
22/50V . 2~ 20 18 U I50V 16 . 14
Linear Pi n-oul & Functional Descript ion
ALL THREE HANDBOOKS $6.95
S2.95
J7J25V
47150V
19
.25
17
21
15
19
IO/16V
1012SV
14
15
12
13
"
09
10
100 PER STRIP MOLEX PINS lool25V . 2~
.35
20
.30
. 18
.28
IOl50V
47/5fJV
16
24
. 14
21
12

Inlcndedfor useasan rnexpcns1VCsubslrllJle lor Ie

l00/50V
220125V
220/50V
32
.45
28
41
.25
38
lool1 6V
l oo/2SV
. 19
24
.15
20
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"""
~1..H1U!
sockets. Also perlect lor useas board conlicClors
andrnsubassernblies .
1021 HOWARD AVE., SAN CARLOS, CA. 94070 ~ 70 /25V ,33 29 .27 100/50V 35 30
10001lGV .55 50 .45 220116V 23 . 17
SPECIAL - 100/1.49 - 1000/12.00 PHONE OROERS WELCOME - (415) 592-8097 2200l lGV .70 62 .55 470/25V .31 28 .26
 ROPROCESSOR COMPONE .'-
.1
CRYSTALS CBRADIO
rtI!ri~
- - •_ _ =--.; THE SE FREQUE NCIES ONLY
Pa r1: # Frequ ll ncy Case/Slyle BOBO SUPPORT DEVICES'
CV1A
CV2A
1.000 MHz
2.000 MHz
HC33/U
HC33/U
8 BIT INPUT/OUTPUT PORT FOR 8080 S 5.95 8080 $99.95
NON INTERRUPT BI-OIRECTIONAL BUS ORIVER 7.95
CY3A
CY7A
4.000 MHz
5.000 MHz
HC18fU
HC1S/U
CLOCK GENERATOR ANO OR IVER FOR 8080 12.95 NEW 101 ICB-630
CV12A 10.000 MHz HC1B/U SYSTEM CONTROLLER AND BUS DRIVER FOR 8080 12 .95 23 -Channel Synthesized CB Transceiver
CPU'S RAM 'S
CY14A 14.31818 MHz HC18U 8BITCPU SIZE: 6% (W) x 2" (H) x 8 /,
51995 1101 256xl Sialic S 225
CV19A lB .OOO MHz HC1BIU Super B008 2~ 95 1103 1024xl DynamiC 21011 .00 '
POWER IN PUT: 5 Watls/12-Volt Max.
CV22A 20 .000 MHz HC1BIU SuperSOiJ8 3~ . 95 2101 256xl Slatlc 5.95
CY30B 32.000 MHz HC1BIU SR 'S 2102 102411 SI~hc 1.75 POWER OUTPUT: 4 Watls RMS
1024 0ynamit 59,00 2107 4096 x I DynamiC 9,95
CLOCK CHIPS - CALCULATOR CHIPS Hex 32 BIT
Hex ~O 3ll
700
~ 00
2111
iOl0
256 l ~
1024 x I
Slatrc
MN05
6,95
29 .95
MOBILE CB ANTENNA $24.95
MM5309 601gn, BCD Outputs. Ami PIN 512 Dynamic 2_49 7~89 16x4 Stallc 2.49 BASE LOAD - FIBERGLASS WHIP KA-2401
MMS311 6 DiOl!. BCD Outputs. 12 0124 Haul 1024 DynamiC 6,00 8101 256x4 SIaliC 6.95
1.11.15312 4 Digl\. BCD Outputs . 1 PPS Output Dual 256 BiT 395 8111 256 1 ~ StatiC 6.95
Mounts on Hood or Tru nk Li d
MM5JH 601011. 12 or 2~ Hour. 50 or 60 Hz DualSI2 BIT HO 8599 10''; StaliC 3"
MI.'.531 6
1.11,\5315
: Digit. Alarm, lPPSOulpul
'M fOCloc](CIlIP. ForUseWlthMI.l5!!J l
Ouaa 80 BIT
1024 SIaliC
395
7 95
91L02
i J200
1024 ~ I
256 ~ 1
51atlc
SIaliC
2.25
695
AMTEX 8 TRACK AM/FM STEREO
Fllo 695 93421 256xl SIaliC
cnool 60lQII. CalanOer . Alarm, 1, or 24 Hour
CALCULATOR CHIPS
1 6xJR~
UART'S
395 MM 5262 2Kxl Dynarnlc
PROMS
2.95
.99 FEATURES
• 8 tracksteroo player
$69.95
1.1/.15725 50lga Feu/Function Less Ow mal 30K Bau~ 55.95 l i 02:' 20·:9 Famos SlU5 • AM /FM rnp~ radio
l.tMsna S D'gl!. 5 r unC1l0n ... "' . x -, ~o RUM 'S 5203 2048 Famos • Advanced ICconslructioli
1·1 95
MM5739 8 DIOIt. ! Function fIOa!ln~ Dwmal Chaf Gen 59.95 82523 32 xB Open C 5CO • Oial 011 door and slide·bar switch Iypc
CT5030 '2 D I~It. 4 Functoan and ~ b CMI Gen 10.95 825123 32 ~ 8 TnSlate • Compact - only 1-25132" (45mm) high. 4·13/16 ' (122rnm) deep . 6·11/16
5.00
102-l·Blt ProgfJmmable 195 745287 102~ Stai lC 795 (170mm) wide and 5 posilion adiustabte sha!t distance
MISC. MOS 3601 256 ~ 4 Fasl 3.!!5
/;\1.15320 TV Camera Sync. Generator • Cornplete in-dash type design .
MM51jO 4'IJ Dlgi! DVM Chip • Easily adjustable anlcnna trimmer !or bcst performance
MM5369 50 Hz Timebase Cifelli! From 3.58 MHz BIPOLAR PROM SPECIAL
MM58:1
M C 1 ~ O :H 7
'{ideo Generator !or MM5319
7 BII Digital to Analog Convener
1900
995
6300 -1 (70 NS) 256 X4 OPEN COLLECTOR BIPOLAR PROM (EQUIVALENT TO 825126) $2.95 KRACO CAR SPEAKER
MK5()Oi 4 Oeca~e Counter with Latches 10 95 6301-1 (70 NS) 256 X 4 TRI STATE BIPOLAR PROM (EQUIVALENT TO 825129) $2.95 Ffush Mount 10 Oz. Mag./8 ohm
toilO toi 11 J l, Dlgl! DVM Chip Se! 2500
!l5H90 100 MHz ..;. 10 Counter For Plescalers 1395 5 FUNCTION ELECTRONIC CALCULATOR
RADOFIN MODEL BP
DIGIT DVM KIT
FEATURES: $8.95
• 8 Oigit DISplay
• 5 FunctlonsconSISJSol a~~ltlon . subtra(tion . fT1u l ·
lipllcat ion. division . pPlcMta!l~ . withcDnslanton
alilunctlOns, with fu ll floaringdrcimal point
• PowprsourCflS I PlfCf9V DCSat1tryOOGP.
lae~ lor AC adaPtfl

l!J
ThiS 0-2 VQC .05 per cenl dig ital voltmeter teatures the Motorola 3111 digit • B l ac~ supri1 lnr GramM fmlSh plastiC cablnrt
DVM chip set. It h~s a .4" LED display and operates from a single + 5V
power supply . The unit is provided complete with an injectionmo Idedblack 5 FUNCTION ELECTRONIC CALCULATOR WITH
plastic case complele with Bezel. An oplional power supp:y is available
which fits into the same case as the 0-2V DVM allowing I 17VAC operation.
WALLET ·NOTEBOOK ANO POCKET CHECKBOOK
OESIGN MATE I RADOFIN MOOEL 1710
A. 0-2V DVM with Case $49.95
. ", .::,~:~~:.~:
. ·" "'I.·,,':"'«It'·''' ~IW'''(O''' '''
CIRCl.ItrO ( SIG ~I A ..... , .· ~"tJ<~ •• ~ .. """" I,,, ••
B. 5V Power Supply $14.95 ' 0. " ..·11'·· .· "!HI Il os' C~ ,~".
<,,," ,~ ... ~"t · IO""~ (O .t~'·':::'f. 1
IJ., t"'W"" (t"Cu·l SD'>;1 . n A', ••
'0" l .... • 11-;" 'CI~
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Cc"l>l>O"'" " f"U.rc"
10 ~~ ~~ . '
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Sus ,~ . ", "" ' .,~ , . no .,, ~ , PI", Of
••1'I<l ..' .. ""..
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FEATURES
• BDigil DlSptay
$19.95
SIr,""'M!O'il l .OMH YJ">!o~ I "OU
VECTOR WIRING PENCIL ro ~ .' ,,,.?I , ~ .." ~ I ~ \'OC ~:~; 7~G'~": ~~;: - 5 FunctrOflSconSlStsoladdllron sublraCllOn rnul .. ..

'!IIII!!!!!!.' ~~i~;f.$~:~~~·~ ~II~I:~~~~~~ v~:~n!U~r:~~\~~Pd;CI!~~lo~tl~~lon ~

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•
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---" .-.~
~~:I ~ :~o.I~;"'t.<'H~ • Wallfl IS 2 tonf (rx(}n cahtnfl IS bl~ck :llastlc
'; .
, O" .. .,".J"I;,.l)Ile' .!l M '''' ...... \1 M."O;.<l
. ,'<... ".. ,. --;-. :;.~:'.I~'~~<:).~"~~::~~ :;~~~,';, Prolo Board 6 S15.95
~D~IG~IT~A-L-AL-A~RM~---N-o-v-u--S~
;'....:, .,.- ~ .
'..... -"""

,--_W/
~ lOGIC MONITOR
Vector Wiring PenCil Pli3 CO II ~IS I~ ot.1 h~lld tlet(j leatMrl'lCI!ltlt (under olle OUllcet
10o lw IIICfl ISuSC!l:CIjUl(le a n!l l'l l" IJmSlll at e~ wII C led oUa selt·cont.llled rcpl.lceaole
MbnlO onto COl11llDnentlea:ts or terminals Installed on nre·llunchtd P Polte rn
) ;.
5imulla neously displays s talic ann
dynamic logic states 01 OTl. TTL
HTL or CMOS DIP ICs
Pocket size 584.95.
CLOCK
This 4 digit Novus Alarm Clock
is a very reliable and smartly
VeclorOordare made
tcrt!1lnals Conn{ClI0nsoel
by soldering I!i~ mJOOC~
. . . eenComplete I'Ilth .....
250 Ire nanaotCOIllPonent
Icd WIIC leads parIs or $7.95 ft-:~~=::~~-;;;-~--liif::--~::-"::~::-l
aT P.oto Sr.tps
styled unil.lfprovides such
fea tures as an alarm sellable
10 any minute 01 the day. a 7
OTrYPII _ hol es prtce
OT·595 minutes snooze alarm. ·a power
REP LACEMEN T WIRE - BOB8 1NS FOR WIRING PENCIL ''''
~· · OT·59B
!)I.!l!!I.:
!lIMI: 01 -12S QT ·59B tJUS5!rIP "'"
250 failureindicalor. and even an
W36-3-A-Pkg . 3 250 II 36 AWG GREEN $1.95
:==:~: O: ·~7S OT·475
'" A.M .. P.M. indicator.
W36·3·B-Pkg , 3 250 It. 36 AWG REO $1.95
t; r'W~ '
OT-478
OT·355
busstnp

''''
,,,,
225
$17.95 NOT A KIT
W36·3·C-Pkg . 3
W36·3·lHkll 3
250 tt . 36
250 It 36
AWG
AWG
CLEAR
BLUE
SI .95
$1 .95
· ",,, "~~" ·"' · O I ·': iB
:riG 01 ·85 QT·358 OUSSIfIP zoo
OT·18S '"0 ~ 75

01 ·75
OT'125
OT·85
OT·7S
'"
60 '"
'"
300
JE700 CLOCK
" The JE700 IS a low eosl dlglt~1 clock. ~ut
IS avery hfgh quahl)' untl. The Ufllt lea·
'u les a srrnulaled walnut case v,lth ~l·
pH[ r.OlIC b :f':: Or-;It . • p l ElU 6.,0 1;2 1 5:
DIGITAL WATCHES menslonsoI6··x2'1·' X I _Itutlhzesa
rf,gp.;: O" ~ '. ' P I ~o riUL! ]G' 1:1;) <§; MAN7211i911 blightne5S readout. an~ the
fPf) · ,
(ill,55
, :p·: : I)&l
S :D:~ OO?
I·)np~_: O(i?
: 50
: :'0
::,c
1150
8"
I'Dli
207
2 ~!:i
'i0.:
'66
? 11
: Jj
Lad ies Watch
• 6 Function
EXELAR Mens Watch
• 5 Function MM5J$"f l.95

-
loQFr. : O.,7 - 00 g ~} 11 5 VAC
H!lli • Quartz Crystal
"" r • Bracelet Styling

II •
[PfJ~V GLASS 169P :·: Oti2cr \ ',0 1,·00 li 80 6"
• Black Leather Band i
COI'P[~ CL.\O • 1 Year Guarantee minules . . 3· · seconds)leatureslhe
• Model 900 • Manufacturer Guarantee
MM5314 clock chip . II operates
HEAT SINKS • Specify Gold • Specify Gold
or Chrome
Irom 117 VAG. and will operate in
or Chrome either a 120r 24 hour mode . The
205-CB Bcrvlhu<n COllP~' ffU! 5111<Willi Blac, r "sl1fo r 10 ·5 .25
$69 .95 $29.95 clock is complete with a walnut
29 1-.36H /lllIInlll um Heal 511lk tor TO·220 TranSistors to Reg ulators .25 grain case. and has (asl sel. slow
680- .75A BI,I{\1: A n od lle~ ,\llltnlllum Heal Srnk tOf 10·3 1.60 sel. and hold timesct leaturcs .
KIT - ALL COMPONENTS & CASE S34. 95

11 •.· ···
NIBBLING TOOL DIAGONAL CUTTER WIREO & ASSEMBLED S39 .95
il,'·
I,
S~mi·Flush CUi Flnr OJagonal
JE803 PROBE ~~
/ - ------- --1-
~. t--.-!- -
I

$9.95 Per Kit

63 KEY KEYBOARD printed circuit
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..
......--...
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~ ., ~ ,~
,~,

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 Updates to the 9900 Line should show up in personal computing end
products in the next half year or so, is as
Texas In struments has announced add i-
follows :

What's tions to the TMS9900 microcomputer prod-

uct fam ily in a release dated July 20. A
short summ ary of the ad ditions, which
• TMS9980: Thi s is a new MOS version
of the TMS9900, packaged as a stan-
dard 40 pin dual in line package with a

New? (11.4 cm by 15.2 cm) with a standard

double sid ed 22 pin edge connector. The
physical description similar to most 8
bit microprocessors: 8 bit data bus, 16
bit address bus, etc. But there is a
difference. If readers will recall Robert
term "complete" has the following seman-
Baker's article on the TMS9900 chip
ti cs acco rdin g to the Pronet ics Corp press
in the April 1976 BYTE, the internal
release:
architecture of a 9900 is that of a 16
• F8 Microprocessor with 2 I1S instru c- bit minicomputer with hardware
A World's Smallest Microcomputer tion time. multiply and divide, 16 general pur-
System? • 1 K byte programmable memory. pose register like work areas, etc. The
Th e manu facturer of this card, the Model • 1 K bytes programmable memory. same instruction set is executed by the
710A, claims that this F8 computer card is • 32 bidirectional latc hed single bit 10 9980 with a slight drop in speed of
"the wor ld' s sma ll est co mpl ete 8 bit micro- ports. execution due to the fact that byte
computer." The card co mes fully assemb led • 2 independent external in terrupt addressing is now done in the external
and tested and measures 4.5 by 6.5 in ches inputs. world with an 8 bit wide memory and
• 2 ind epe nd ent programmable interval peripherals data path instead of a 16
tim ers. bit data path . Thi s product is to be
• Flexible terminal inte rface. sa mpled late in 1976, and we expect at
• Physical size fits standard card cage least one manufacturer to pu t this on
products. an Altair compatible plug in board for
the personal computing market. The
At $159, comp lete ly asse mbl ed and
hard ware of the 9980 featu res an
tested, the F8 Mode l 710A looks like a fair
fulfillment of the adject ive " co mpl ete." onchip oscillator and clock generator,
so the breadboarding and productio n
Indi vid uals look ing for a dedicated firmware
of hardware with this chip should
controller, a star tin g point for an F8 general
prove convenient.
purpose syste m, or a com pu ter for use in
educatio nal or laborato ry programs should • TMS9904 is a 4 phase clock generator
find thi s board to be a useful option. The and driver for use with the TMS9900
manufacturer is Pronetics Corp, 643 1 computer circuit, using a crystal con-
Preston Crest, Dallas TX 75230, (214) trolled input.
270-8626.- • TMS9901 is a programmable systems

It's Almost Too Late • • •

. . . to snap up bicentennial memorabilia before you have
to hunt through the nostalgia shops and pay 100 times
the original price- if you're lucky enough to find a
bargain-for an item as anachronistic and otherwise
remarkable as Robert Tinney's Computing 1776 picture.

A same-size (16 by 20 inches, 41 by 51 cm) reproduc-

tion of Tinney's original oil painting, this poster makes
an off-beat gift.

Don't wait for the nostalgia shops to get the last of these
posters; get yours now for only $2.95. (Do you know
what your old Amazing Science Fiction magazines and
Superman comics that Mom threw out are worth now?)

BYTE Posters Allow 6 - 8 weeks for processing.

PO Box 274
Jaffrey Center NH 03454
603-924-721 7 ___ Posters $2.95 each

Name ___________________________________________

Address _________________________________________

City __________________--"'State ________-<..7i p _______

oBil1 BankAmericard oCheck Enclosed

oBil1 Master Charge $-----------
No. Exp. Date _ _ __

140
 S. D. SALES Co. P.O . BOX 28810- 8 • DALLAS, TEXAS 75228

4K LOW POWER RAM BOARD KIT

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$1 ,000,000 CALCU LATOR PURCHASE !

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8 D i g it LED
We bought the entire stock of a major manufacturer. New, guaranteed units.
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Five functions PLUS complete Metric Conversion functions. Re-
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" RAPID MAN - 12" 12 Digit - Desk Top St yle. St urdy design . Wit h memory and four
complete functions. Big, br ight d isplay .
$29.95
ALARM CLOCK KIT SIX DIGIT LED 6 0 H Z CRYSTAL TIME B ASE -
Tho u sa n ds of hobbyi st s have bo u ght a n d bui l t our orig in a l c lock
kit and were comp letely satisfied. B ut we have received many
re q uests for an ala r m c lock kit with t he same value and qua l ity K I T FEATURES:
FOR D I G ITA L C L OCKS
S. D . SA L ES EXCLUSIVE! $5.95
that you have come to expect fro m S. D. So. h ere it is! A . 60 hz output with accuracy comparab le to a dig ita l watch
TH E K IT I NCLUD E S : B. Directly interfaces with all MOS Clock ch i ps
1 Mostek 50252 A l arm C lock Chip C. Super low power consumption (1.5 Ma typ. )
6 Hewl ett Packard .30 in . common cat h ode readouts D . Uses latest MOS 17 stage divider I C
15 NPN Driver Transistors E. Elim i nates f o rever the problem of AC li ne g li tches
2 Switc h es for time set F. Perfect for ca rs, boats, campers, or even for portable ClOCkS
2 Slide Sw itches for al arm se t and enable at ham field days. BUY TWO F O R $ 10.00!
1 F il ter Cap
4 I N4002 Rectifiers
1 IN9 1 4 D iode
$9 .95 G. Sma ll size, can be used i n ex i sting enclosu res.
K I T I NCLUD E S CRYSTAL, D I VIDER IC, PC BOARD PLUS AL L
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1 . 0 1 Disc Cap
15 Resistors
1 Speaker for alarm PCB - $3.00 TTL I NT EGR A TED CIRCUITS
LED l amp for PM i n d icator X FMR - $ 1.50 7400 - 19c 7430 - 19c 7476 - 35c 74153 - 75c
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MOT OROLA RTL IC ' S 74S04 - 44c 7438 - 39c 7485 - 95c 74161 - 95c
Bra n d new, factory p r i me. Hard to f i nd , but sti ll used in a variety 7404 - 19c 7440-19c 7586-45c 74164 - 1.10
of p roj ects. (See t h e R TL Cookbook by H oward W. Sams.) 7 40 6 - 29c 7447 - 85c 7490 - 65c 74165 - 1.10
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"CUBO" -DIGITAL ALARM CLOCK CUBE Rated 3 5 WVDC. Upright sty le

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The C U BO A l arm Clock mfg. by Corvus, division of value for hobbyists. Compare
MOSTEK COR P. Or igina ll y so ld for $49.95 . We bought

Ii
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out their ent i re inventory. Al l new, individu a ll y gift c hise type e lectronic parts stores.
boxed . Mini size (2 1/z " cube) w ith ma xi perf or man ce . S.D . SPECIAL 4 fo r $1 .
FEATUR E S :
A. 4 Digit H.P. Bright Displa y $ 14.95 SLIDE SWITCH ASSORTMENT
B. "Second Hand" L ED Activ itY .1nd icator EACH Our b est se ll er. Inc l udes mini·
c. 16
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E. Auto Display Dimming - Adjusts to Ambient Light first quality, name brand
F . AM / PM I nd i cator Try one package and you'll reo
G. Power Fai lu re I ndicator order more. SPECIAL - 12/$1.
Uses Famous Mostek MK50250 MOS LSI I C
RESISTOR ASSORTMENT ~
MOTOROLA POWER DARLINGTON WESTERN DIG I T A L UA RT 1/4 W 5% a n d 10%. PC lea ds .
No. TR 1602 B . 4 0 p i n DIP. A good mix o f values. 200 /$2 .
B ack in St ock!
Like MJ300 1. N PN 80V. lOA . HFE This i s a very po werful an d popu lar p a rt.
6000 TYP. TO-3 case. We include a free NEW - $6.9 5 wit h d ata 7 4 S2 00
723 C volt reg . wit h schemat ic for power LI M ITED QUANTITY 256 Bit High Speed RAM
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MICROPROCESSORS & THINGS $3.95
A b ig .50 i n c h easy to read character. Now By AMD
ava il ab le In either "common anode or com · 1 K PROM BACK IN STOCK!
mon ca t hode. T ake yo u r pick . Super low 8080A Better than (nte ( $24.00 82S129. 256X4. Bipolar, 50 NS .
current drain, only 5 MA per segment ty po FAST. W ITH SPECS .
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YOUR CHOICE : 6 f o r $ 7 .50
8212 I/ O Port 3.50
$3.95
FND - 510 Com'mon Anod e $1 .50 ea.
F ND - 503 C o mmon Cathode $ 1.50 ea . 8224 Clock Generator 4.95 8 T97B
He x Tri·State Buffer . Back in stock.
2513 Ch aracter Generat or 10.00
$1.25
UP YOUR COMPUTER!
21 L02 - 1 1K LOW POWER 5 00 NS STAT IC RAM
:r I ME IS OF THE ESSENCE CALL YOUR BANK AM E RICARD OR
A n d so is power. Not on ly are ou r RAM ' s faster than a speeding bullet but they MASTER CHARGE ORDER IN ON OUR
are now very low power. We are pl eased to offer prime new 2 1L02 - 1 low powe r
a n d super fast R A M·s. Allows you to STRETCH yo ur power supply farther and at CON T INENTAL UNITED STATES TOLL
t h e same time keep t he wait lig h t off. 8 FOR $1 7 .5 0 FREE WA TTS: 1-800- 527-3460
SALE ON CUT LEAD SEMICONDUCTORS C & K MINI TOG GLE SWITCH T exas R esid e n ts C a ll Coll e ct
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usea"bl e. A ll new, u n used. Some H ouse no. SPEC I AL - 9 9 c 214/271 -0022
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IN4002 1 Amp 100 P I V . · .
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EN2222 N PN Transistor . . .
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ORDERS OVER $15. CHOOSE $ 1. FREE MERCHANDISE
 interface for the TMS9900 or • TMS9903 is the sy nchronous co m- Would You Like to Find Out About
TMS9980, which in terfaces directly to muni ca tion s port for the 9980 and Hardware for Diagnosing and Testing
the processo r's CRU port for interrupt 9900 co mputers. Thi s is simil ar to Microprocessor Designs?
priority, 10 contro l and interval what is sometime s ca ll ed a "USART" Hewlett- Packard makes a b road line of
timing. It provides 15 individually and features a wid e vari ety of optio ns. test equ ipme nt intended for industri al and
maskable in te rrupt request li nes or up It wi ll ha ndl e most synchro nous data commercial design an d ma inte nance ap pli ca·
to 16 programmabl e 10 ports, and can t ran smi ss io n protocols, in cluding the
tions. A new appl ica tions note , AN 167·13,
be programmed as an interval timer BiSync and IBM's new Sy nchronous
is now ava il abl e, written by Bruce G Far ly of
with reso lut io n fro m 21 f.l S to 699 ms. Data Link Contro l discip li ne, at data
Hewlett-Packard's Co lorado Springs facility,
• TMS9902 is the 9900 fami ly 's ve rsion rates from DC to 250,000 bits per
describing some of the uses and ap pli cations
of a UART. This circuit is custo mi zed second.
of so phi sticated testin g eq uipme nt such as
to the TI CRU (Communications logic state ana lyzers and data generators.
Samples have not yet been de li vered on
Register Unit) 10 addressing scheme, This 6 page applications no te, e n t itl ed "The
these items, an d pricing is to be announced
a nd features data rates from 5 to
when samp les are ava ilabl e. In quiries from Role of Logic State Analyzers in Microproc·
76,800 bits per second, character
OEMs should be directed to T exa s Instru· essor Based Designs" is avai lab le fo r t he
lengths from 5 to 8 bits, an d 1, 1.5 or
me nts Inc, POB 5012, MS/84, Dallas TX asking by writing to: In quiries Ma nager,
2 sto p bits per character with or Hewlett-Pac kard Co, 1501 Page Mill Rd,
75222 , attention "9900 Family".-
without parity.
Palo Alto CA 94304.-

A New Graphics Option for OSI

Shown off at th e Perso nal Co mputing 76
show in Atlantic City was th e interface
which produces these pictures. The manu -
fac turer of the "Super Vide o Board" which
generates 128 by 128 raster grap hics is Ohio
Scientific In struments, 1167 9 Hayde n St,
Hiram OH 44234. Thi s board, which plugs
into th e OS I Model 400 system, can be used,
as in photo 1, to draw pictures with low to
moderate reso lution, and to display the
output of a software " logic sta te analy ze r"
progra m, as in photo 2.-

Photo 1. Photo 2.

BYTE T-shirts
The Perfect Gift: If you can't afford to give that special person in your life a new
microcomputer, consider the BYTE T-shirt. A gift in exquisite taste,
that says you really care, that suggests, ever so SUbt ly, that NEXT
Christmas, when things are a little better, you might give h im or her
a new microcomputer.

Or~dare to be se lfish! Buy yourself a BYTE T -s hirt. Avail able in

blue heather with blue trim and red letters, or in white with blue
trim and red letters. Only $5, including postage and handling.

rSe~~---In7n~~~~~~m~~~eed30da~-
The Bytique
PO Box 274
Jaffrey Center NH 03454
Please send me _~extra large _~ blue heather
_~ Iarge _~white with blue trim and
_~medium red letters

_~small T-shirts @ $5 each (includes

Total enclosed $, _ _ _ _ __ postage and handling)

Bill MasterCharge No. _ _ _ __ Exp.Date _ _ _ __ _ _ __

Bill BankAmericard No. _ _ _ __ Exp. Date' _ _ _ _ _ _ __
Name' _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Addressi _ _ _ __ _ __ _ _ _ _ _ _ _ _ __ _ _ _ _ __
CitY _ _ _ _ _ _ _ _ _ _ _ _--"'State'_ _ _ _ _ _LZip _ _ __
Signature _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _~
Other colors, styles I'd like to see' _ _ _ _ _ _ _ _ _ _ __ _ __

142
 UNIVERSAL POWER SUPPLY
A unique pi ug-in supply by Panasonic. Useful
for calculators, small radios, charging many &
various small NiCad batteries. Adjustment
screw plug on the side changes output voltage
to 4%, 6, 7%, or 9 volts DC at 100 MA. Output
cord with plug, 6 ft long.
No. SP-143C $4.50 3/$12
PARITY DETECTOR
New packaged, made for RCA, detects even or odd parity, baud rate 110, 150 or
POWER SUPPLY 134.46. Built-in logic supply for the IC's, operates from standard 115 vac. Control
LAMBDA 5VDC 74 AMP panel allows manual or automatic reset mode of operation. Aluminum enclosure (not
shown), cover.; the electronics. TTY compatible.
LV-EE-5-0V $125.00 Ship wgt. 10 Ibs. $16.50

COMPUTER DISPLAY TUBE

NJE 5/0UP-D5
5 VDC 32 AMP New Sylvania 9 inch CRT, 85 degree deflection, with tinted faceplate_ Same as used
$75.00 in Viatron systems (buy a spare). With complete specs .
Ship wgt. 5lbs. $15.00
----------------------------------
LINEAR by RCA, brand new, gold bond process
CLOCK KIT $14.00 301 $ 060 747 $ .82 MM5314 $3.00
Includes all parts with MM5316 chip, 307 .52 748 .50 MM5316 3.00
etched & drilled PC board, transformer, 324 1.80 1458 .96 7001 8.00
everything except case_ 339A 1.60 3401 .80
SP-284 $14.00 each 2/$25.00 741 .50 555 timer .60

.A

MEMORY SYSTEM $125.00

New memory system by Honeywell, small _ ..
measures only 9x4xl inches. 1024 core memory,
1024 words with 8,9,10 bits/word. Random access,
with all logic, register, timing, control, core select and
sense functions in one package. New, booklet of
schematics and data. Looks like a good beginning for
a mini-computer. Limited supply on hand.
Ship wgt 3 Ibs. # SP-79 ......... $125.00

COMPUTER GRADE LOGIC SUPPLY CAPS, BRAND NEW

47,000 Uf 25V $2.00 ST 1,000 50 .90 AL

3 Power supplies, transistorized & regulated.
Made by TRANSISTOR DEVICES 32,000 25 1.75 ST 3,300 35 1.25 AL
15 volts DC 5 amps . .. ............. $25.00 160,000 10 2.00 ST 1,600 20 .60 AL
30 volts DC 2 amps ....... ........ . 25.00 66,000 10 2.00 ST 16 1.25 AL
15 volts DC 4.5 amps ... ........... 25.00 8,000
1,000 60 .90 AL 500 6 .35 AL
2,000 55 1.00 AL "ST" screw-top .... "AL" axial

Please add shipping cost on above.

PHON E 617-595-2275 FREE CATALOG SP-8 NOW READY

MESHNA PO Bx 62 E. Lynn Mass. 01904

 To get further information on the products advertised in BYTE , fill out the reader
service card with your name and address. Then circle the appropriate numbers for the
advertisers you select from this list. Add a 9 cent stamp to the card, then drop it in the
mail. Not only do you gain information, but our advertisers are encouraged to use the
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reader Computer Store (NY) 105 A 90 Logical Services 105

service
A104
A140 Computer Talk 97 A 18 Meshna 143
A138 Compute r Warehou se Store 93 A145 MFE 71
A 6 Continental Specialties 25 A 71 MPI39
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A 70 American Microprocessors 97 A 41 Cromemco 1 A119 Midwestern Scientific I nst. 55
A 142 A ss ociated Electronics 95 A 97 Data Domain 65 A 57 Mikos 69
A107 Audio Design Electronics 105 A 7 Delta 137 A112 MiniTerm 18, 19
A 111 Brigar 131 A 78 Digital Group 11 MITS CIV, 4, 5
BYTE' s Books 96 , 130,136 A 79 Economy Co. 75 A 62 Morrow 127
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BYTE's T-Shirts 142 A102 Eltron 135 A 22 National MUltiplex 93
A126 Cheap , Inc. 105 A135 Erickso n 101 A146 NCR 67
A 127 Comptek 101 A 9 Godbout 119 A 40 Oh io Scientific I nst. 17
A 143 Computer Enterprises 105 HAL Communication s 103 A147 OK Tool 91
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Subscribers, please bear with us. If you have not received a response to a A 30 Sphere CIII
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A 99 STM 91
advertisers. We have quite fran!?/y been inundated with requests since putting A 96 Synchro-Sound 41
reader service on reply cards, and recently got a bit behind in processing. A 82 Techn ical Design Labs 13
Each card must be keypunched and run through a (somewhat traditional) A136 Technical Systems Con. 67
data processing operation currently implemented on an IBM/360 Model 25 A144 Thermodyne Plastics 99
A 32 Tri Tek 122
with 76 K bytes of memory, 23 77 dis/? drives and an archaic tape operating A137 Vector Graphics 99
system. As this note is written (September 70) the current reader service
requests total 24,000 individual cards with multiple requests per card, and are *Reader service inquiries not solicited.
being mailed to advertisers as mailing label printouts.- Correspond directly with company.

Feedback is what keeps a linear amplifier in line. Like a linear amplifier, BYTE can use a bit
of feedback. The BOMB analysis is done once a month to provide encouragement to authors
and some formal feedback on how readers appreciate articles. BYTE pays the winning author a
$50 bonus, so you can encourage the authors you like by voting your preferences. Remember
that with few exceptions BYTE authors are just readers who have sat down at their typewriters
to tel! a story about what they've done or what they know about some aspect of this
technology.
BOMB Bonus to Burt
BOMB: BYTE's Ongoing Monitor Box
The winner of the August BOMB survey
LIKED and a $50 bonus was Burt Hashi zume, who
PAGE ARTICLE LEAST BEST wrote "Microprocessor Update: lilog l80."
6 Rosner : It's More Fun Than Crayons o1 2 3 4 5 6 7 8 9 10
The runners-up for August were Robert
Suding for his article on the Digital Group
20 Arnold : What Is APL? o1 2 3 4 5 6 7 8 9 10
TV readout device, and Terry Steeden who
26 Nelson : Beer Budget Graphics Interface o1 2 3 4 5 6 7 8 9 10
wrote "What's an 12L (I squared L)."
32 Buschbach: Add This Graphics Display . .. o1 2 3 4 5 6 7 8 9 10
Remem ber that your preferences count
40 Burhans : A Tip for Using Wiring Pencils o1 2 3 4 5 6 7 8 9 10 in t he BOMB evaluation. It is a way of giv ing
42 Deres: An Enterprising Display Device o1 2 3 4 5 6 7 8 9 10 direct feedback to authors about the content
56 Rampil: Some Graphics Background ... o1 2 3 4 5 6 7 8 9 10 of their articles, an d it gives us a real world
78 Ciarcia : A Real Eye Opener 0 1 2 3 4 5 6 7 8 9 10 basis for judgment of which artic les to push
106 Anderson : Video Display Terminal o1 2 3 4 5 6 7 8 9 10 into print the fastest.-

144
 SPHERE OFFERS:
A Programmable Microprocessor
Controller!
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The Sphere TPu/l micro computer on a expandable to 32k and you can control tele-
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En.g ineering. TPU is an expandable CPU on a module.
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the Motorola 6800 microprocessor a 6820 tually any device which needs to be intelli-
parallel interface 256 or 512 bytes ofEPROM gently monitored or controlled. Whether
2048 bits of static RAM, and a crystal con- need a personal computer to handle your
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You can program the read only memory with This is not a toy! It was designed for use
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