Reproducibility Of Delay Interrupts And Watchdog Interrupts - Siemens Simatic S7-300 Technical Data Manual

Process interrupt processing
Process interrupt processing begins after process interrupt OB40 is called. Higher-priority
interrupts stop process interrupt processing. Direct I/O access is executed during runtime of
the instruction. After process interrupt processing has terminated, cyclic program execution
continues or further interrupt OBs of equal or lower priority are called and processed.
See also
Overview (Page 5-1)
5.5.2

Reproducibility of delay interrupts and watchdog interrupts

Definition of "Reproducibility"
Delay interrupt:
The period that expires between the call of the first instruction in the interrupt OB and the
programmed time of interrupt.
Watchdog interrupt:
The fluctuation width of the interval between two successive calls, measured between the
respective initial instructions of the interrupt OBs.
Reproducibility
The following times apply for the CPUs described in this manual:
• Delay interrupt: +/- 200 μs
• Watchdog interrupt: +/- 200 μs
These times only apply if the interrupt can actually be executed at this time and if not
interrupted, for example, by higher-priority interrupts or queued interrupts of equal priority.
CPU 31xC and CPU 31x, Technical data
Manual, Edition 08/2004, A5E00105475-05
Cycle and reaction times
5.5 Interrupt response time
5-23