Siemens Simatic S7-1500 Function Manual page 65

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
Failure of the primary CPU
The figure below shows the impact of the failure of the primary CPU on the cycle time.
①
②
③
④
⑤
⑥
⑦
Figure 5-4
The example shows the failure of the primary CPU
program. The primary CPU no longer sends any synchronization telegrams to the backup
CPU. During the period
synchronization data transferred before the failure of the primary CPU. At
CPU has reached the point in the program where the primary CPU stopped sending
synchronization telegrams. During the phase
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
state to RUN-Solo system state.
The cycle time
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
Note
Monitoring time
The monitoring time is an internal time with fixed duration. You cannot assign parameters for
the internal time. The monitoring time starts as soon as the synchronization data arrives at
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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Cycle time
Failure of the primary CPU
Backup CPU continues processing the program
Backup CPU no longer receives synchronization telegrams
Backup CPU waits for the monitoring time to expire
End of the monitoring time, switchover time and system state transition
Cycle time of the new primary CPU in RUN operating state
Impact of the failure of the primary CPU on the cycle time
③
, the backup CPU continues operating only on the basis of the
⑥
. The redundant system switches from RUN-Redundant system
①
extends from the time processing of the cyclic program is started in RUN-
⑦
is shorter than the cycle time
②
while it is processing the cyclic
⑤
, the backup CPU waits to see whether data
①
.
Function Manual, 10/2018, A5E03461504-AD
④
, the backup
Cycle and response times