Hi all,

what is desired method of doing hardwired safety signal exchange for PLd? Intentionally, I'd like to have it hardwired, not exchanged via network (F-Link etc).

Lets determine the conditions:

- 2x S7-1500F CPU

- each CPU connected to its own ET200SP with FDI (6ES7136-6BA01-0CA0) and FDO (6ES7136-6DB00-0CA0) modules

- each ET200SP has E-Stop connected as presented in (https://support.industry.siemens.com/cs/document/21064024/emergency-stop-up-to-sil-3-pl-e-with-a-fail-safe-s7-1500-controller-?dti=0&lc=en-PL) so it's 2x NC channels with 1oo2 evaluation in FDI

FDO manual presents a method to output PLe signal in single channel in Cat.4 .

FDI manual presents how to connect single channel as PLd Cat.3.

We all know that Cat.3 and Cat.4 require dual channel architecture, so I find it a bit dusty.

That's why I doubt about the correct way to exchange E-Stop bit between PLC's. Shall it be 1x FDI - 1x FDO, 2x FDI - 2x FDO or maybe other configuration?

I came across this topic (https://support.industry.siemens.com/forum/pl/en/posts/cat-3-with-single-channel-input/34167) and it makes a little bit sense that 1oo2 evaluation should be done in software when its not done in hardware, but it's just a opinion not statement in the manual.

Does anyone knows the answer ?