Siemens SIMATIC S7-400H System Manual page 165

Calculation of the maximum communication delay
Use the following formula:
Maximum communication delay =
4 x (maximum inhibit time for priority classes > 15)
Decisive factors for determining this time are the process status and the communication load
in your system. This can be understood as the absolute load or as the load relative to the
size of your user program. You may have to adjust this time.
Calculation of the maximum cycle time extension
Use the following formula:
Maximum cycle time extension =
10 x (maximum inhibit time for priority classes > 15)
Decisive factors for determining this time are the process status and the communication load
in your system. This can be understood as the absolute load or as the load relative to the
size of your user program. You may have to adjust this time.
S7-400H
System Manual, 03/2012, A5E00267695-11
Link-up and update
12.4 Time monitoring
165