Redundancy - Siemens SIMATIC S7-1500 System Manual

5.3.2

Redundancy

Introduction
In the following section you will get an overview how to achieve a higher network and plant
availability in S7-1500R/H redundant systems.
The Media Redundancy Protocol (MRP) enables the connection of IO devices based on ring
topologies.
Despite a network failure (switch failure, line interruption), MRP can ensure communication
via alternative paths throughout the network.
MRP interconnection enables larger quantity structures by redundantly coupling two or
more rings with MRP in PROFINET networks.
The S7-1500R/H redundant system requires media redundancy (MRP) in the PROFINET ring.
As of firmware version V3.0, the H-CPUs no longer have to be part of a PROFINET ring. This
also allows other topologies, such as line topology.
MRP and MRP interconnection can be used independently of the system redundancy of the IO
devices.
You can use the following IO devices on the redundant S7-1500R/H system:
• IO devices with system redundancy S2
• IO devices with system redundancy R1 (only S7-1500H as of FW version V3.0)
• Standard IO devices over the "Switched S1 device" function of the CPU
The System redundancy S2, R1 tolerates errors in the direct IO controller and IO device
communication.
With a switched S1 device, an interruption of the IO controller and IO device communication
is not tolerated. The S1 device fails temporarily and is then resumed if necessary.
Communication relations in S7-1500R/H
For a redundant system S7-1500R/H different IO device types are available. The IO device
types differ with regard to the communication relations AR (Application Relation) they can
establish to the CPUs of the redundant system:
• Standard IO devices as switched S1 devices support an AR
• S2 devices support two ARs
• R1 devices support two ARs (one AR per interface module)
To enable an IO device to exchange data with an IO controller (CPU or R/H system), an AR is
required between the two. If this AR is interrupted or the IO controller fails, no further data
exchange via this AR is then possible. Another AR between the IO device and the second CPU
of the R/H system leads to the redundancy of the connection. This increases the reliability of
the redundant system.
S7-1500R/H redundant system
System Manual, 01/2024, A5E41814787-AF
System overview
5.3 S7-1500 R/H-CPUs
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