Possible to cionfigure Y-link in S7-300?

Hello CKO

interesting idea to "test" a Y-Link by using a non-redundant DP Master and only connect to one of the IM's.

Certainly haven't tried to do so myself, but am afraid to say that I'm not surprised that it doesn't work.

DP-Slave redundancy means that additional redundancy related Parameters are used at startup and that additional commands can be issued (e.g. DP Master initiated IM changeover). As such the DP Master has to comply with this too and your single S7-300 will unfortunately not be able to do so and I fear thus fail to properly parameterise the single IM of the Y-Link it is connected to.

As said, I haven't tried this myself yet so by any means seek advice from Siemens directly (perhaps there is trick to make this test work, I'd certainly be interested to know).   

And as it turns our dear CKO, it may indeed be possible to use a Y-Link on a non-redundant DP Master, at least if the FAQ Connecting more than 125 DP slaves to a shared DP master system is anything to go by.

Ok, the FAQ is older and refers to usage of the IM157 as the Y-Links IM, but as this has been replaced by the spare part compatible IM153-2 (see HERE for more), it should still work in your setup.

May be worthwhile physically removing one of the IM153-2 from your Y-Link and test it. If that doesn't help, something else may be wrong in your configuration? (let us know either way please).