5.6 Causes of Error and Reactions of the CPU
Specific events can interrupt cyclic, time-controlled, or interrupt-
driven program processing at operation boundaries when the CPU is
in the RUN mode.
During initialization and also in the RESTART mode, interruptions
can stop the start-up program and put the CPU into the STOP mode.
The CPU then changes to the stop mode and calls the organization
block for this particular error. Interruptions during the start-up
program are handled like those in the RUN mode.
The reaction depends on the cause of the interruption:
•• immediate change to the STOP mode, without calling the error OB
(e.g. NAU → hard stop, STUEU → hard stop, PEU → soft stop),
•• before changing to the STOP mode, the system program calls an
error OB which you can program and (depending on the cause of
the error) avoid a change to the stop mode (e.g. QVZ/IB 0 →
OB 28, ADF → OB 25).
If an error occurs, note the entries in the control bits under "Error IDs"
and the entries in the ISTACK under CAUSE OF INTERR.
The following sections explain possible causes of error in greater
detail.
Causes of Error and Reactions of the CPU
CPU 948 Programming Guide
C79000-G8576-C848-04
5 - 23
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