Siemens SIMATIC S7-1500 System Manual page 291

(1) Primary CPU switches to the RUN operating state
Figure 11-11 Primary CPU switches to the RUN operating state
Table 11-14 Response to loss of redundancy of CPU: Primary CPU switches to RUN
No. in Primary CPU
diagram
Initial situation: The S7‑1500R/H redundant system is in the RUN-Redundant system state.
The backup CPU fails because of a hardware defect.
The CPU switches from RUN-Redund­
①
ant to RUN. The CPU behaves like a
standard CPU and continues to pro­
cess the user program.
Error elimination procedure for redundant operation
1. Eliminate the error.
2. Start the backup CPU.
The backup CPU switches from the STOP operating state to the SYNCUP operating state.
Synchronization starts as detailed in the section SYNCUP system state (Page 270).
S7-1500R/H redundant system
System Manual, 11/2022, A5E41814787-AD
System state
RUN-Redundant → RUN-Solo
Commissioning
11.4 Operating and system states
Backup CPU
Following the error, the CPU switches from
the RUN-Redundant operating state to
STOP or POWER OFF.
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