Siemens SIMATIC S7-1500 System Manual page 204

Failure scenario
①
②
③
④
⑤
Figure 6-49
Sequence of events
1. The PROFINET ring is interrupted at one point.
2. The redundant system remains in the RUN-Redundant system state: The primary and backup
CPUs remain in the RUN-Redundant operating state.
3. The PROFINET ring is interrupted at a second point > 1500 ms later.
4. The redundant system switches to the RUN-Solo system state. The primary CPU remains in
the RUN operating state. The backup CPU switches to the STOP operating state.
5. CPU redundancy has failed. The failure has an impact on the process. The RUN-Solo system
state and the cable interruptions mean that not all IO devices in the PROFINET ring can be
accessed.
If the failed inputs and outputs have an important function in the system, their failure can
have a critical impact on the process.
S7-1500R/H redundant system
System Manual, 01/2024, A5E41814787-AF
Primary CPU
Backup CPU
PROFINET ring → interrupted at two points
IO device ET 200MP
IO device ET 200SP
Two cable interruptions in the PROFINET ring (> 1500 ms apart)
Application planning
6.5 Failure scenarios
203