Maybe is a silly question but when using a ctrlX Core (CP-COREX-M) with multiethernet expansion module R911411588 CP-EXT-XC-ET1-21-01-N-NN, all IO modules are attached to this one and every unit is conected (mechanically assembled) via some kind of internal bus building a complete no wired block. In this option no bus coupler (R911406090 XB-EC-12) is needed to connetct IO modules. So my question is, communication between IO modules and ctrlX Core in described case is via this internal bus, I mean, multiethernet expansion module CP-EXT-XC-ET1-21-01-N-NN is not performing the function of XB-EC-12 in the no modular option, is it right?. If I am correct the, multiethernet expansion module R911411588 CP-EXT-XC-ET1-21-01-N-NN is just used a an additional ethernet port to connect to any other external system but not needed to making attached IO modules to work.
Thank you very much in advance.