Siemens S5-135U/155U System Manual page 199

LEDs for Fault
Indication and
Signaling
QVZ LED
ADF LED
ZYK LED
BASP LED
A detailed description of interrupt and error handling can be found in the
CPU 928 Programming Guide.
System Manual
C79000-G8576-C199-06
CPUs, Memory Cards, Memory Submodules, Interface Submodules
on During direct access or process image update, a module
addressed by the program no longer acknowledges although
either it has acknowledged in single processor operation
upon reset of the CPU 928 in the area of the process
image (IB 0 to 127, QB 0 to 127) and has been entered as
present in the "9th track" (see Programming Guide,
CPU 928),
or it has been entered in DB 1 (address list) in it h b
multiprocessor or single-processor operation and has been
recognized as present during the reset.
Possible causes
Module failure.
Module was pulled out during operation, in the stop state
or in the Off state without a subsequent reset.
on The user program has referenced an I/O address under which
no module is inserted.
on The maximum cycle time has been exceeded.
on Command output is inhibited and the digital outputs will be
directly switched to the safe state.
t d i DB 1 ( dd li t) i
5-59