Step 7 - Siemens S5-155U System Manual

Step 7

Possible faults
System Manual
C79000-B8576-C199-03
Executing a RESET at all CPUs:
Action
Execute a RESET at each
individual CPU:
1)
Hold the MC mode switch at
the RESET setting;
simultaneously set the mode
switch from STOP to RUN.
1)
MC: Momentary-contact
Symptom 1:
The STOP LED of one CPU flashes slowly. When the control bits of
this CPU are read out with the programmer, "DB 1 error" is marked in
addition to the usual information. There is no output of an ISTACK.
Remedy:
Check whether data block DB1 in the CPU was correctly loaded and
programmed.
Symptom 2:
After execution of a RESET:
Undefined states or faults occur at the CPUs (e.g. after a RESTART at
CPU 922, it goes to the RUN state although the other CPUs are still at
STOP).
Remedy:
Verify the following points:
• • Is the coordinator inserted?
• • Are all modules correctly inserted (engaged)?
• • Are all modules at the correct slots?
Starting the Multiprocessor Operation
Reaction
The red STOP LED on each CPU
is continuously lit; each CPU
emits the output inhibit signal.
The CPUs are in the wait state.
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