How does the Airbus ECAM / ND transfer work? On the Airbus A320 a knob on the switching panel says ECAM/ND XFR (Electronic Centralized Aircraft Monitor / Navigation Display Tranfer) and it transfers the either the Engine/Warning Display (E/WD) or the System Display (SD) onto the Navigation Display (ND). The ND gets its information from the Air Data Inertial Reference System (ADIRS) and IT and the ECAM gets its information from the system sensors. 

Both ADIRS, IRS and system sensors information get sent to the Display Management Computers (DMC), and I'm just wondering if im correct but when you switch SD or E/WD the DMC when it is processing the data for, in this example the system sensors, it sends the system sensors data to the ND?

And the other way around when you switch the ND to the ECAM. When the DMC is processing the data, in this example ADIRS and IR data, it will send the ADIRS and IR data to the ECAM? 

So my question is, is it during the processing the data phase that the DMC sends the data to thd correct display?
All this depends on the A320 generation. On early models all computations are done by the SDACs and the DMCs, and the switching corresponds to data switching in the DMCs, so the screen will display what it receives.

On later models all screens receive all data and on request they can display what you ask when you do the ECAM/ND switching.

In fact in latest models of A320 the displays switching possibilities are voluntarily limited just for conformity with earliest A320’s