Siemens S5-135U/155U System Manual page 163

LEDs for Fault
Given in the following overview are the causes for LEDs lighting up:
Indication and
Signaling
QVZ LED
ADF LED
ZYK LED
BASP LED
INIT LED
A detailed description of interrupt and error handling can be found in the
CPU 948 Programming Guide.
System Manual
C79000-G8576-C199-06
CPUs, Memory Cards, Memory Submodules, Interface Submodules
on A module addressed by the program no longer acknowledges
although/because
it either acknowledged in single-processor operation upon
restart of the CPU 948 in the area of the process image
(IB0 to 127, QB0 to 127) and has been entered as present
in the so-called 9th track;
or it has been entered in multi or single-processor
operation in DB 1 (address list) and has been recognized
as present during the restart;
or it was addressed in direct access by operations LPY,
LPW, TPY, TPW, LOY, LOW, TOY, TOW;
or the data handling blocks cannot access the module.
Possible causes:
Module failure
Module removed during operation, in the STOP state or in
the Off state without subsequent restart.
A timeout occurred during access to the user memory.
on The user program has referred to an address in the process
image under which no module was inserted in the I/Os or was
not entered in DB 1 during the last restart.
on The preset cycle time monitor has responded and cyclic
program processing is interrupted.
on Command output is inhibited and the digital outputs will be
directly switched to the safe state (0).
on This LED is continuously lit for a short time during
initialization after power ON and during operation in the
event of system faults.
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