Cyclic program execution
3.3 Time-driven program execution in cyclic interrupts
Cycle and response times
40 Function Manual, 10/2018, A5E03461504-AD
With a cyclic interrupt you have the option of having a specific OB processed in a time
interval. The time interval is independent of the execution time of the cyclic program. A
priority from 2 to 24 can be selected for the cyclic interrupt. This makes the priority of cyclic
interrupts higher than the priority of the cyclic program. A cyclic interrupt increases the
execution time of the cyclic program.
Tip: By shifting program sections to cyclic interrupts, you can reduce the response times or
better adapt them to your requirements.
In STEP 7 the organization blocks OB 30 to OB 38 are intended for processing cyclic
interrupts. You can create additional cyclic interrupts starting with organization block OB 123.
The number of available organization blocks depends on the CPU used.
A cyclic interrupt is an interrupt initiated according to a defined cycle that causes a cyclic
interrupt OB to be processed. A cyclic interrupt OB is assigned to the "Cyclic interrupt" event
class.
The cycle of a cyclic interrupt is defined as the time from the call of a cyclic interrupt OB to
the next call of a cyclic interrupt OB.
The following figure shows an example of the cycle of a cyclic interrupt.
Figure 3-9 Call interval of a cyclic interrupt
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