Siemens SIMATIC S7-400 Manual page 139

Update Cycle in PN/IO
An overview of the duration of the update cycle depending on the number IO devices
contained in the cycle in the following figure.
Update cycle
Figure 9-8
S7-400 Automation System, CPU Specifications
Manual, 10/2006, 6ES7498-8AA04-8BA0
1 ms
750 ms
500 ms
250 ms
0 8 16
Update cycle
Cycle and Response Times of the S7-400
24 32 40 48
9.5 Reaction Time
56 64
Number of IO devices
in the update cycle
9-13