GE 90-30 PLC Series Installation And Hardware Manual page 338

Troubleshooting Features of Programming Software
Detailed information about the following items are found in GFK-0467, Series 90-30/20/Micro
PLC CPU Instruction Set Reference Manual, and GFK-0466, Series 90-30/20/Micro Programming
Software User's Manual.
Ladder Screens
Contacts, connections, and coils displayed on the ladder screens that are ON (passing power or
energized) are displayed in enhance brightness, allowing the tracing of signals through the
program. Addresses that refer to physical input (%I and %AI) and output signals (%Q and %AQ)
can be checked against module status lights, voltages, etc. to verify that the hardware is working
properly.
Configuration Screens
Normally, the following information is obtained from the system documentation. However, if they
are not available, the configuration screens can be used to determine:
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Fault Tables
There are two fault tables, the "PLC Fault Table," and the "I/O Fault Table." The fault tables can
be viewed using the PLC programming software. These fault tables will not report such things as a
defective limit switch, but will identify system faults such as:
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System Status References
These discrete references (%S, %SA, %SB, and %SC) can be viewed in the System Reference
(Status) Table, or on-screen if used in the ladder program, for determining the status of various
conditions and faults. For example, the %SC0009 bit turns on if a fault is logged in either fault
table. Another example is that bit %SA0011 will turn on if the CPU memory backup battery is low.
The Series 90-30 PLC CPU Instruction Set Reference Manual, GFK-0467, includes a "System
Status Reference Table."
GFK-0356Q Chapter 13 Maintenance and Troubleshooting
If the software configuration matches the actual hardware. Sometimes, while
troubleshooting, a module is installed in an incorrect slot by mistake. This will create a fault in
one of the two fault tables. The correct configuration can be determined from the
Configuration Screens.
The memory addresses that a particular module is using.
Loss of or Missing Modules, System Configuration Mismatch.
CPU hardware failure, Low Battery
PLC Software Failure, Program Checksum Failure, No User Program, PLC Store Failures.
Maintenance and Troubleshooting
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