Siemens SIMATIC S7-1500 System Manual page 101

System overview
5.3 S7-1500 R/H-CPUs
If the cyclic program exceeds the cycle monitoring time, the time error OB (OB 80) may be
started. Redundancy is lost if the time error OB (OB 80) is not present or the double cycle
monitoring time was exceeded with OB 80. You can find additional information on the
response of the S7-1500R/H redundant system when cycle time is exceeded in the section
Events and OBs.
Note
If failure of the PROFINET cable that directly connects the two CPUs of the redundant S7-
1500R system is unlikely, you can use PROFINET devices without H-Sync forwarding in the
PROFINET ring of the redundant S7-1500R system.
Example: Both CPUs of the redundant S7-1500R/H system are located next to each other
in the control cabinet. In this case, it is unlikely that the PROFINET cable will fail.
System redundancy S2
System redundancy S2 is the connection of an IO device via an interface module that
supports two ARs to the IO controllers in the redundant system.
IO devices with system redundancy S2 enable uninterrupted process data exchange with the
S7-1500R/H redundant system in the event of:
• a CPU fails
• Interruption of the PROFINET ring
• Interruption of the line topology (for S7-1500H as of FW version V3.0)
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 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 are not initially
evaluated.
• 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 fails or is switched to STOP, then the backup CPU becomes the
primary CPU and also switches the backup AR to primary AR. The data of this AR becomes
active at the outputs.
With line topology, only the primary AR can fail. In this case the previous backup AR is
switched over to the primary AR, but the roles of the CPUs remain unchanged.
• Behavior in system state RUN-Solo:
Only the primary CPU is an IO controller. PROFINET communication runs on the primary AR
between the primary CPU and the IO device. There is no AR between the backup CPU and
the IO device.
In STEP 7, assign an IO device with system redundancy S2 to both CPUs of the redundant S7-
1500R/H system.
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S7-1500R/H redundant system
System Manual, 01/2024, A5E41814787-AF