Section
6
Troubleshooting
This section defines troubleshooting aids that are incorporated in the 545Al548A counter. They are:
Signature analysis
Self diagnostics
Keyboard controlled circuit tests
The procedures and tables are provided for troubleshooting to a functional circuit level.
SIGNATURE ANALYSIS
Signature analysis
is
a technique used to troubleshoot complex logic circuitry.
It
uses data compression
to reduce any data pattern to
a
4 character alpha-numeric word.
The start and stop inputs define the measurement window. Each time
a
transition within the measure-
ment window occurs on the clock input, the probe
is
sampled, and the logic level
is
shifted into the ana-
lyzer. This information
is
used to generate a signature unique to that data string. That signature can then
be compared to a reference signature, taken from
a
known good product, to determine if the data string
is
correct.The counter implements signature analysis in either
a
free running or program controlled manner.
FREE RUNNING
This mode of signature analysis
is
essential for troubleshooting problems that could prevent the program
from running. A CLRB instruction can be forced by breaking the data bus
at
A105 JMPl and grounding
A1 05 TP5, effectively "free running" the microprocessor. "Free running" means forcing a simple in-
struction (such as NOP or CLRB) on the data bus, which the microprocessor sees at every address location.
This causes the microprocessor to continually cycle through its entire address range, accessing everything
on the address bus as
it
does. By strategically placing the start and stop connections the entire bus system
can be probed for bad signatures.
Scans by ArtekMedia © 2007
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