Cycle and response times of the S7-1500R/H redundant system
5.3 Influences on the cycle time of the S7-1500R/H redundant system
Cycle and response times
64 Function Manual, 10/2018, A5E03461504-AD
Figure 5-4 Impact of the failure of the primary CPU on the cycle time
The example shows the failure of the primary CPU ② while it is processing the cyclic
program. The primary CPU no longer sends any synchronization telegrams to the backup
CPU. During the period
③, the backup CPU continues operating only on the basis of the
synchronization data transferred before the failure of the primary CPU. At
④, the backup
CPU has reached the point in the program where the primary CPU stopped sending
synchronization telegrams. During the phase
⑤, the backup CPU waits to see whether data
will again be sent from the primary CPU after all. Because the synchronization data is not
transferred even after the monitoring time has expired, the backup CPU becomes the new
primary CPU at point
⑥. The redundant system switches from RUN-Redundant system
state to RUN-Solo system state.
The cycle time
① extends from the time processing of the cyclic program is started in RUN-
Redundant to the time when processing of the cyclic program ends in RUN-Solo.
Because data can no longer be synchronized in the RUN-Solo system state, the cycle
time
⑦ is shorter than the cycle time ①.
the backup CPU. If no synchronization data is received from the primary CPU, the system
automatically performs a system state change after the monitoring time has expired.
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