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RUN Mode
Interruptions
Special features
4 - 36
Owing to the default, the TIMED INTERRUPTS layer has the highest
priority of the basic layers (can be modified in DX 0).
In time-controlled program execution, the execution of
clock-controlled interrupts has the lowest priority. This can therefore
be interrupted by the processing of a delayed interrupt or a cyclic
timed interrupt.
• • A clock-controlled interrupt is only processed in the RUN mode.
Clock-controlled interrupts occurring in the STOP mode, when
there is a power failure or during START-UP are discarded.
• • Once a clock-controlled interrupt has been generated (= OB 151
call has been processed) it is retained in a WARM RESTART and
following POWER DOWN/POWER UP; it is, however, deleted
during a COLD RESTART.
• • If you generate a new clock-controlled interrupt, i.e. call
OB 151 with new time values, a previously set clock-controlled
interrupt is cancelled. A clock-controlled interrupt currently
being processed is continued. This means that only one
clock-controlled interrupt is valid at any one time.
• • If a time-controlled interrupt occurs without the previous one
being completely processed, the clock time-controlled interrupt is
discarded. Clock-controlled interrupts are not checked for
collisions!
• • Note the special functions OB 122 and OB 142 with which you
can disable or delay the servicing of clock-controlled interrupts.
CPU 948 Programming Guide
C79000-G8576-C848-04
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