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RUN Mode
User interfaces
OB 10 to OB 18
Interruptions
4 - 38
When a timed interrupt occurs, the corresponding organization block
is called as the user interface at the next block boundary (or operation
boundary).
For example, you would program the routine to be inserted in cyclic
program execution every 100 ms in OB 10 (default).
The timed interrupt is only processed if the assigned organization
block is loaded. If none of the organization blocks OB 10 to OB 18
are loaded, there is no time-controlled program execution and the
cyclic program is not interrupted.
You can disable the execution of timed interrupts by setting a
parameter in data block DX 0, e.g. for testing your program.
As default, the TIMED INTERRUPTS level has the highest priority of
the basic levels (can be modified in DX 0).
Owing to the distribution of priority within time-controlled program
execution, the following interruptions in the processing of a cyclic
timed interrupt are possible:
• • the processing of a cyclic timed interrupt can be interrupted by the
processing of a delayed interrupt
• • organization blocks with shorter time bases have higher priority
and can interrupt organization blocks with longer time bases (e.g.
OB 12 can interrupt OB 17).
Note
With the three shortest time bases (OB 10 to 12) multiple
processing without interruption is possible. If, for example, while
OB 10 is being processed, a further timed interrupt for OB 10
occurs, the currently active processing of OB 10 is first
completed. Following this, OB 10 is called immediately again. If,
however, there are more than three timed interrupts pending for
one of the time bases, a collision of timed interrupts error occurs.
CPU 948 Programming Guide
C79000-G8576-C848-04
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