5.2 Error Information
If an error occurs during system start-up or during cyclic processing of
your program, the sources of information described in this section can
help you to find the problem. This includes:
•• LEDs on the front panel of the CPU
•• interrupt stack ISTACK and control bits
•• block stack BSTACK
The following sections explain the ways of evaluating this information
and how to use the information to analyze problems.
LEDs on the front
panel of the CPU
If the CPU goes into the STOP mode when you do not want it to,
check the LEDs on the front panel. They can indicate the cause of the
problem.
LED display Meaning
STOP LED lit continuously The various states of
the STOP LED indicate
specific causes of
interruptions and errors
(see section 4.1).
STOP LED flashes slowly
STOP LED flashes quickly
SYS FAULT LED lit
continuously
ADF LED lit continuously Addressing error
QVZ LED lit continuously Timeout error
ZYK LED lit continuously Cycle time exceeded error
Error Information
CPU 948 Programming Guide
C79000-G8576-C848-04
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