Siemens Simatic S7-300 CPU 31xC and CPU 31x S7-300 - Manual (Page 98)

Cycle and reaction times
5.3 Response time
CPU 31xC and CPU 31x, Technical data
5-16
Manual, Edition 08/2004, A5E00105475-05
5.3.2 Shortest response time
Conditions for the shortest response time
The figure below shows the conditions under which the shortest response time is reached.
Delay of inputs
Immediately before reading in the PII, the status of
the monitored input changes. This change of the input
signal is still included in the PII.
The change of the input signal is processed by
the application program.
The response of the user program to the change
of the input signal is issued to the outputs.
Delay of outputs
Response time
CCP (OS)
PIO
PII
User program
CCP (OS)
PIO
Calculation
The (shortest) response time is the sum of:
Table 5-10 Formula: Shortest response time
1 x process image transfer time for the inputs
+ 1 x process image transfer time for the outputs
+ 1 x program processing time
+ 1 × operating system processing time at the SCC
+ I/O delay
= Shortest response time
The result is equivalent to the sum of the cycle time plus the I/O delay times.
See also
Overview (Page 5-14)