System Redundancy S2 - Siemens SIMATIC ET 200AL System Manual

6.3

System redundancy S2

Introduction
IO devices with S2 system redundancy enable uninterrupted process data exchange with the
S7-1500R/H redundant system in the event of a CPU failure.
An IO device with system redundancy S2 supports system redundancy ARs. The system
redundancy ARs can be present in duplicate (redundantly). Thus, an IO device supports ARs of
2 IO controllers simultaneously (with respect to the same modules).
A system redundancy AR can be either a primary AR or a backup AR. An IO device activates
the data of the primary AR at the outputs. The data of the backup AR is only saved.
In STEP 7, you configure system redundancy S2 for an IO device by assigning the IO device to
both CPUs of the S7-1500R/H redundant system.
Behavior in system state RUN-Redundant
Both CPUs are IO controllers. The PROFINET communication runs simultaneously on both
system redundancy ARs, in each case between one of the CPUs (IO controllers) and the IO
device. If the primary CPU now fails, the backup CPU becomes the primary CPU and, at the
same time, the backup AR changes over to primary AR. The data of this AR becomes active at
the outputs.
Figure 6-2
Behavior in system state RUN-Solo
Only the primary CPU is an IO controller. The PROFINET communication runs on the primary
AR between the primary CPU (IO controller) and the IO device. There is no AR between the
backup CPU and the IO device.
PROFINET with STEP 7
Function Manual, 05/2021, A5E03444486-AL
Primary backup AR
PROFINET with the redundant S7-1500R/H system
6.3 System redundancy S2
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