Maximum Cycle Time And Time Errors - Siemens Simatic S7-1500 Function Manual

Cycle and response times of the S7-1500R/H redundant system

5.2 Maximum cycle time and time errors

5.2 Maximum cycle time and time errors
Maximum cycle time
As with non-redundant CPUs, you can parameterize a high limit of the cyclic program by
setting the maximum cycle time.
The cycle time of redundant CPUs is usually longer as compared to non-redundant CPUs.
The factor by which the cycle time for redundant CPUs is higher than that for non-redundant
CPUs depends very strongly on your specific automation task.
Note
Maximum cycle time in SYNCUP system state
The length of the parameterized maximum cycle time also affects the SYNCUP system
state.
If the following condition is fulfilled during the SYNCUP, the system initiates a transition to
RUN-Redundant:
The actual cycle time is ≤ 80% of the maximum cycle time over several cycles.
More information on this is available in section Influences on the cycle time in SYNCUP
system state (Page 55).
Maximum cycle time in RUN-Redundant system state
On the failure of one of the two CPUs, the cycle time also contains a dead time of up to
300 ms for R-CPUs and up to 50 ms for the H-CPU. You must schedule this time as cycle
time reserve in case of failure of one of the two CPUs. Therefore, ensure that the longest
cycle time plus this dead time is < 60% of the configured maximum cycle time in RUN-
Redundant system state. By doing so, you prevent the parameterized maximum cycle time
from being exceeded in case of load fluctuations and delays due to synchronization.
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Cycle and response times
Function Manual, 10/2018, A5E03461504-AD