Cycle and Reaction times
3-14
PLC S7-300, CPU Specifications CPU 312 IFM to CPU 318-2 DP
A5E00111190-01
3.4 Interrupt response time
Interrupt Response Time – A Definition
The interrupt response time is the time that elapses between the first occurrence of
an interrupt signal and the calling of the first instruction in the interrupt OB.
Generally valid is: High-priority interrupts are preferred. This means the interrupt
response time is increased by the program processing time of the higher-priority
interrupt OBs and the interrupt OBs of equal priority that have not yet been
executed.
Calculation
The interrupt response time is calculated as follows:
Shortest interrupt response time =
minimum CPU interrupt response time +
minimum interrupt response time of the signal modules +
PROFIBUS-DPbus cycle time
Longest interrupt response time =
maximum CPU interrupt response time +
maximum interrupt response time of the signal modules +
2 PROFIBUS-DPbus cycle time
Process interrupt response time of the CPUs
Table 3-7 lists the response time of the CPUs to process interrupts (without
communication).
Table 3-7 Response time of the CPUs to process interrupts
CPU Min. Max.
312 IFM 0.6 ms 1.5 ms
313 0.5 ms 1.1 ms
314 0.5 ms 1.1 ms
314 IFM 0.5 ms 1.1 ms
315 0.3 ms 1.1 ms
315-2 DP 0.4 ms 1.1 ms
316-2DP 0.4 ms 1.1 ms
318-2 0.23 ms 0.27 ms
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