Siemens SIMATIC S7-1500 System Manual page 105

Redundancy scenario
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②
③
④
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Figure 5-25 Failure of the backup CPU (using S7-1500R as an example)
Sequence of events
1. The backup CPU of the redundant system fails in the RUN-Redundant system state.
2. The redundant system switches to the RUN-Solo system state. You can find additional
information on the RUN-Solo system state in the section Operating and system states
(Page 263).
3. The primary CPU continues to exchange process data with the IO devices (and standard IO
devices).
4. The redundancy of the system is restricted. The restriction has no impact on the process.
If another system component or another network segment fails, this can result in the
failure of the S7-1500R/H redundant system. You can find additional information in the
section Failure scenarios (Page 124).
S7-1500R/H redundant system
System Manual, 11/2022, A5E41814787-AD
Primary CPU
Backup CPU → failed
PROFINET cable (redundancy connections, PROFINET ring)
IO device ET 200MP
IO device ET 200SP
Application planning
5.4 Redundancy scenarios
105