Software redundancy: Which CPU coupling types are available?

Hello SIOS Forum Community,

in connection with software redundancy, customers ask us again and again which connection can be used to couple the CPUs.

You can use S7-300 CPUs and S7-400 CPUs for software redundancy.

The following connection types can be used to connect the CPUs for redundancy coupling:

1. MPI via integrated interfaces of the CPU's (observe switch-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 can be found at:

https://support.industry.siemens.com/cs/ww/en/view/42614519

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.

Best regards,

SIMATIC International Technical Support Hub