Siemens SIMATIC PCS 7 CPU 410-5H System Manual page 306

Supplementary information
15.15 Cycle and response times of the CPU 410-5H
Dependency of the actual cycle time on communication load
The figure below describes the non-linear dependency of the actual cycle time on
communication load. In our example we have chosen a cycle time of 10 ms.
Figure 15-30 Dependency of the cycle time on communication load
Further effects on the actual cycle time
Seen statistically, the extension of cycle times due to communication load leads to more
asynchronous events occurring within an OB 1 cycle, for example interrupts. This further
extends the OB 1 cycle. How much it is extended depends on the number of events per OB
1 cycle and the time required for processing these events.
Remarks
● Change the value of the "communication load" parameter to check the effects on the
cycle time during system runtime.
● Always take the communication load into account when you set the maximum cycle time,
otherwise you risk timeouts.
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CPU 410-5H Process Automation
System Manual, 09/2014, A5E31622160-AB