Siemens CPU 31 Series Technical Data Manual page 105

Response time
Table 5-12
Shortest response time
-
Now add I/O delay.
The result is the shortest response time.
See also
Longest response time (Page 5-16)
Shortest response time (Page 5-15)
Calculating the cycle time (Page 5-4)
Cycle extension through Component Based Automation (CBA) (Page 5-10)
CPU 31xC and CPU 31x, Technical Data
Manual, 01/2006 Edition, A5E00105475-06
5.4 Calculating method for calculating the cycle/response time
Calculating the response time
Cycle and reaction times
Longest response time
Multiply the physical cycle time by factor 2.
Now add the I/O delay plus the DP cycle times on
PROFIBUS-DP or the PROFINET IO update
times.
The result is the longest response time.
5-19