Siemens SIMATIC S7-400H System Manual page 371

Shortest response time
The figure below shows the conditions under which the shortest response time is achieved.
Figure 19-8
Calculation
The (shortest) response time is calculated as follows:
● 1 x process image transfer time of the inputs +
● 1 x process image transfer time of the outputs +
● 1 x program processing time +
● 1 x operating system processing time at the SCCP +
● Delay of the inputs and outputs
The result is equivalent to the sum of the cycle time plus the I/O delay times.
Note
If the CPU and signal module are not in the central unit, you will have to add twice the delay
time of the DP slave frame (including processing in the DP master).
S7-400H
System Manual, 03/2012, A5E00267695-11
Shortest response time
S7-400 cycle and response times
19.5 Response time
371