Hardware Considerations
Chapter 2
25
PROCESSOR FAULT — Illuminates when the logic circuits controlling
the processor scan fail or if processor error or run-time errors occur
which cause the processor to halt operation.
If the processor fault is a run-time error, the industrial terminal will
display RUN TIME ERROR when the keyswitch is in the PROGRAM
or RUN/PROGRAM position.
RUN — Illuminates when the processor is in the run or run/program
mode. It also indicates that outputs are being controlled by user
program.
DC ON — Illuminates when the 5.1V DC line to the logic circuitry in
the processor memory and I/O modules is satisfactory.
When local I/O racks are powered by 1771-P3, -P4, -P5 or -P7 power
supplies, the processor control module (Cat. No. 1772-LG) may experience
a problem with these racks.
Upon recovery from a power lock (momentary or otherwise), processors in
the RUN or TEST mode attempt to read the local racks before the power
supplies are ready. This leads to a processor fault. The fault may be
identified by the conditions of the indicators:
Indicators
1772LG Module
RUN
PROC FAULT
Series A, Rev. L OFF ON
Series A, Rev. K or earlier OFF OFF
If the problem occurs, put the keyswitch in the program load position, then
return to RUN, or cycle power to the processor.
A switch group assembly is located on the I/O chassis backplane. It is used
to control output behavior when a fault occurs, to identify the I/O rack
number for local systems and to identify the addressing mode for remote
systems.
The switch and its functions, when used in local racks, are shown in
Figure 2.3. In this setup, the PLC-2/30 is communicating with the I/O
chassis through a 1771-AL Local I/O Adapter module.
2.5
PowerUp
Recovery
2.6
Switch Group Assembly
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