Siemens SIMATIC S7-1500 System Manual page 212

Failure scenario
①
②
③
④
⑤
⑥
Figure 6-53
Sequence of events
1. The two redundancy connections (fiber-optic cables) are interrupted ≤ 55 ms apart.
2. The redundant system switches to an undefined system state: The primary CPU remains in
the RUN operating state. The backup CPU becomes the primary CPU and remains in RUN
operating state.
S7-1500R/H redundant system
System Manual, 01/2024, A5E41814787-AF
Primary CPU
Backup CPU
Two fiber-optic cables (redundancy connections) → interrupted
IO device ET 200SP
IO device ET 200MP
PROFINET cable (PROFINET ring)
Failure of both redundancy connections
Application planning
6.5 Failure scenarios
211