Originally Posted by HazelNuts39
Thanks for your informed and elaborate reply. I've just one question. As far as I could find in the available documentation, the CPC has only one source for cabin pressure, i.e. its built-in sensor. Am I missing something?
The system diagrams are also quite obscure to me but look at the FCOM note "Control indicators":
Note:
The pilot may notice a variation (up +/- 1000 feet) in CAB ALT indication on the ECAM PRESS page, when the system switches from the cabin pressure control AUTO mode to MAN mode, due to the reduced resolution of the backup pressure sensor. Obviously, the pressure sensors in AUTO and MAN modes are definitively different ones.