Star Tech Journal

11
STAR*TECH JOURNAL/APRIL 1983
tMNUFACTsG
LOGIC BOARD LOCK-UPS
By Frank Becker, Atari, Inc., Somerset, NJ
In the past 5 years that I have worked for Atari, there has always been one question
that is asked by operators and technicians - What do I do when my logic board
locks up? A lock-up, for those of you who are fortunate enough never to have had this
problem, is a term that is used whenever the RESET line on the microprocessor
begins to pulse, thus resetting the MPU. This condition is also known by other
names, one of which is "barking". This name is derived from the watch dog clear
(WDCLR) signal used on most Atari-designed boards; when this signal fails to clear
the counters it indicates a failure has occurred and the "watch dog" is now
"barking" to alert you to the problem (See S*TJ, Dec. '82, Vol. 4, No. 10,
Manufacts).
PRICE
CONVERSION
BREAKTHROUGH!
FOR ROWE
CIGARETTE
1 MACHINES
This month's column shall attempt to answer the above question by providing a
troubleshooting guide that should dissipate the clouds of confusion surround this
mystery.
The first step is always to list the things that can cause a Reset problem, from now
on called a lock-up. Unfortunately, there are almost as many things that can cause a
lock-up as President Reagan has one-liners. But before I discourage you too much,
let's look at the things that can cause a lock-up.
A lock-up occurs when the microprocessor receives invalid information. The
processor becomes confused when it receives this information and forgets to output
a watch dog clear signal, thus causing the game to Reset. The processor receives
invalid information through one of the following problems:
1. Bad ROM - Read Only Memory - Stores permanent game program
2. Bad RAM - Random Access Memory- Temporary memory stores such
items as credits, player scores, first and second player playfields, etc.
3. Open Address Line or Data Line
4. Shorted Address or Data Bus
5. Bad Switch Input Multiplexers
• Will vend up to $1.75 in
increments of 5¢.
• Same mechanical
dependability using your
present totalizer. No
electronic components.
• Accepts any combination of
nickels, dimes and quarters.
6. Bad Address Decoder Circuit
• 4-minute installation on
location OR
7. Bad CPU
8. Bad Address or Data Bus Buffers/f ristates
• Send us your totalizer - we
will convert it ($5.00 service
charge).
9. A Clock Problem
10. Operator-Induced Problem
NOTE: These are the main things that will cause a game to lock up, not all the things
that will cause a lock-up.
*
PRICE
REDUCED
$29. 95 (In Lots of 10)
We will now go over each item and explain how you can best check each item in
the field or on a bench.
1 to 9 Units - $34.95 each
NOTE: Usually, when a game is locked-up, it will not go into self test; nevertheless,
self test should still be tried - you might get lucky and have it tell you what's wrong.
All orders shipped UPS/COD.
TROUBLESHOOTING PROCEDURE
TELEPHONE:
516-928-6868
1. Do the easy things first
2. Check power inputs.
3. If you have socketed ICs, change those first if you have known good
replacements.
4. Check your RO Ms. If you have an Atari C.A. T. Box®, you can do checksums
on the ROMs of most games without taking them out of the board If you can't
do some sort of checksums on the ROMs, you will have to perform step 3.
Continued on page 15.
COIN UP-DATE
INDUSTRIES, INC.
14 Hulse Road
E. Setauket, NY 11733