Commissioning
12.4 Operating and system states
S7-1500R/H redundant system
414 System Manual, 01/2024, A5E41814787-AF
(2) Primary-backup switchover
Figure 12-12 Primary-backup switchover
Table 12- 15 Response to primary CPU error: Backup CPU becomes primary CPU and switches to RUN
No. in
CPU 1 System state CPU 2
Initial situation: The S7-1500R/H redundant system is in the RUN-Redundant system state.
The primary CPU (CPU 1) fails because of a hardware defect.
① Following the failure, CPU 1 switch-
es from the RUN-Redundant operat-
ing state to STOP or POWER OFF.
RUN-Redundant → RUN-Solo
CPU 2 becomes primary CPU and switch-
es to the RUN operating state. The CPU
behaves like a standard CPU and contin-
ues to process the user program.
Error elimination procedure for redundant operation
1. Eliminate the error.
2. Start CPU 1.
CPU 1 becomes the backup CPU and switches from the STOP operating state to the SYNCUP
operating state.
Synchronization starts as detailed in the section SYNCUP system state (Page 388).
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