Siemens Simatic S7-1500R System Manual page 21

System overview
2.1 What is the S7-1500R/H redundant system?
The S7-1500R redundant system consists of:
● Two S7-1500R CPUs
● A PROFINET ring with the Media Redundancy Protocol
● IO devices
● if needed, Switches
All PROFINET IO devices assigned to the S7-1500R system must support system
redundancy S2. These PROFINET IO devices can be located in the PROFINET ring or they
can be separated with a switch.
All PROFINET devices in the PROFINET ring must support media redundancy (MRP). The
H-Sync forwarding function is also recommended. System redundancy S2 is not a
prerequisite. For example, you can use switches and HMI devices without system
redundancy S2.
The redundancy connections in an S7-1500R system are the PROFINET ring with MRP
The two CPUs must be directly connected to each other with a PROFINET cable. All nodes
can still communicate with each other in the event of an interruption in the ring. PROFINET
devices that do not support MRP must be separated from the ring with a switch
One of the two CPUs in the redundant system takes on the role of primary CPU. The other
CPU takes on the role of the following CPU (backup CPU). The role of the CPUs can change
during operation. Synchronization of primary and backup CPU ensures rapid switchover
between CPUs in the event of a failure of the primary CPU. If the primary CPU fails, the
backup CPU takes over control of the process as the new primary CPU.
The redundancy connections use part of the bandwidth on the PROFINET cable for the
synchronization of the R-CPUs. This bandwidth is therefore not available for PROFINET IO
communication.
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S7-1500R/H redundant system
System Manual, 10/2018, A5E41814787-AA
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