Technical data

LED display of modes Various LEDs on the front panel of the CPU signal the current CPU
mode. The following table shows you the relationship between the
STOP and RUN LED displays and the mode they indicate.
Other LEDs (BASP, ADF, QVZ, ZYK) provide more information.
LED
RUN
LED
STOP
Mode
ON OFF
The CPU is in the RUN mode.
OFF ON
The CPU is in the STOP mode.
After a STOP request at the switch or from the PG, the STOP LED is lit
continuously, because the STOP condition was requested by the user or, in
multiprocessor operation, by another CPU and was not prompted by the CPU
itself.
OFF OFF
The CPU is in the RESTART mode
or
the CPU is in the RESTART/RUN mode, the program test is active and the
program has reached a breakpoint (wait state)
or
the CPU is in the RESTART/RUN mode, the program test is active and a
breakpoint was eliminated again before it was reached (wait state)
OFF flashing
slowly
The CPU is in the STOP mode.
The CPU itself prompted the STOP condition (possibly also of the other CPUs).
Typical causes:
ADF, QVZ, LZF, BCF, CL controller error, interrupt collision, cycle time error,
BSTACK overflow, ISTACK overflow, stop command, end of processing check.
If you switch the mode selector to STOP, the flashing stops and the LED is lit
continuously.
OFF flashing
quickly
The CPU is in the STOP mode.
An overall reset has been requested. This request can be prompted by the CPU
itself or by an operator input.
ON ON
Serious system error
Remedy:
- Overall Reset of CPU;
if error persists,
- Switch off voltage at PLC, remove and re-insert the CPU and
perform Overall Reset;
if error persists,
- Replace CPU or have it repaired.
Table 4-1 Meaning of the LEDs "RUN" and "STOP"
4
Introduction and Overview
CPU 928B Programming Guide
C79000-B8576-C898-01
4 - 5