Hello Magdy;

The ET 200M can only act as a redundant slave to a S7-400H system, a redundant CPU of another Siemens family (for example a S5-115H), a Software redundancy system with S7-300 CPUs or a PNO redundancy configuration from another manufacturer, as you can see in the screenshot below. Note that FR ans SR, as defined by PNO, is not supported by Siemens PLCs.

The screenshot is taken from the following manual:

https://support.industry.siemens.com/cs/ww/en/view/1142798

In conclusion, you would need a S7-400H configuration to support a redundant ET 200M distributed I/O station.

Hope this helps,

Daniel Chartier