Siemens Simatic S7-1500R System Manual page 38

System redundancy S2
An IO device with system redundancy S2 supports system redundancy ARs.
In a redundant system, an IO device with system redundancy S2 has a system redundancy
AR with each of the two CPUs (IO controllers). An IO device thus supports ARs of two IO
controllers simultaneously (for the same modules).
A system redundancy AR can be the primary AR or the backup AR. There must only ever be
one primary AR for one IO device at any given time. The other AR, if there is one, must be
the backup AR. An IO device activates the data of the primary AR at the outputs. The data of
the backup AR is merely saved.
● Behavior in the RUN-Redundant system state:
Both CPUs are IO controllers. PROFINET communication runs on both system
redundancy ARs simultaneously, in each case between one of the CPUs (IO controller)
and the IO device. If the primary CPU then fails, the backup CPU becomes the primary
CPU and also switches the backup AR to primary AR. The data of this AR then becomes
active at the outputs.
● Behavior in the RUN-Solo system state:
Only the primary CPU is the IO controller. 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.
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.
Reference
Additional information on media redundancy and system redundancy S2 can be found in the
PROFINET function manual
(http://support.automation.siemens.com/WW/view/en/49948856).
S7-1500R/H redundant system
System Manual, 10/2018, A5E41814787-AA
System overview
2.3 S7-1500 R/H-CPUs
37