Software redundancy: Which CPU coupling types are available?

Hello SIOS forum community,

in connection with Software Redundancy the customers ask us again and again, over which connection one can couple the CPUs.

You can use S7-300 CPU's and S7-400 CPU's for software redundancy.

To connect the CPU's for the redundancy coupling, you can use the following connection types:

1. MPI via integrated interfaces of the CPU's (consider change-over times).
2. Profibus via integrated interfaces of the CPU's or also via CP 342-5
3. Ethernet via integrated interfaces of the CPU's or also via CP343-1lean

A complete release list may be found at:

Which modules can you use when implementing software redundancy?

Due to the switching speed we would always recommend an Ethernet coupling.

This shortens the time during which the outputs remain quasi frozen when switching over.

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