Interrupt Reaction Time - Siemens SIMATIC S7-400H System Manual

16.8

Interrupt reaction time

Definition of interrupt reaction time
The interrupt reaction time is the time from the first occurrence of an interrupt signal to the
call of the first instruction in the interrupt OB.
General rule: Higher-priority interrupts take precedence. This means the interrupt reaction
time is increased by the program execution time of the higher-priority interrupt OBs, and by
previous interrupt OBs of the same priority which have not yet been processed (queue).
Calculating the interrupt response time
Minimum interrupt reaction time of the CPU
+ minimum interrupt reaction time of the
signal modules
+ DP cycle time on PROFIBUS–DP
= Shortest interrupt reaction time
Maximum interrupt reaction time of the CPU
+ maximum interrupt reaction time of the
signal modules
+ 2 * DP cycle time on PROFIBUS–DP
= Longest interrupt reaction time
Process and diagnostic interrupt reaction times of the CPUs
Table 16-13 Process and interrupt reaction times; maximum interrupt reaction time without
CPU
412-3H stand-alone mode
412-3H redundant
414-4H stand-alone mode
414-4H redundant
417-4H stand-alone mode
417-4H redundant
Increasing the maximum interrupt reaction time with communication
The maximum interrupt reaction time increases when communication functions are active.
The increase is calculated with the following formula:
CPU 41x–4H t
where n = cycle load due to communication
S7-400H
System Manual, 09/2007, A5E00267695-03
communication
Hardware interrupt reaction
times
min.
366 µs
370 µs
231 µs
464 µs
106 µs
234 µs
= 100 µs + 1000 µs × n%, significant extension possible
v
S7-400 cycle and reaction times
16.8 Interrupt reaction time
Diagnostic interrupt reaction
times
max. min.
572 µs 354 µs
1143 µs 620 µs
361 µs 225 µs
726 µs 366 µs
158 µs 104 µs
336 µs 185 µs
max.
563 µs
982 µs
356 µs
592 µs
167 µs
294 µs
281