Siemens Simatic S7-1500R System Manual page 229

Commissioning
9.4 Operating and system states
(2) Primary-backup switchover
Figure 9-12 Primary-backup switchover
Table 9- 14 Response to primary CPU error: Backup CPU becomes primary CPU and switches to RUN
No. in CPU 1
diagram
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 oper-
ating state to STOP or POWER
OFF.
Error elimination procedure for redundant operation
1. Eliminate the error.
2. Switch CPU 1 to the RUN operating state.
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 205).
228
System state
RUN-Redundant → RUN-Solo
CPU 2
CPU 2 becomes primary CPU and
switches to the RUN operating state.
The CPU behaves like a standard CPU
and continues to process the user pro-
gram.
S7-1500R/H redundant system
System Manual, 10/2018, A5E41814787-AA