Thanks Jack for the answer; providing me some hints is already a big help and ought (hopefully) to be enough :-) It doesn't seem as straightforward as just connecting the two pins. ISE gives me the following error: Error: branch 'RXD' and branch 'WING_AL0' cannot be joined, because both branches have an I/O marker.Hmmm. Should create a dummy component with TX_IN, RX_IN, TX_OUT, RX_OUT and just assign the INs to the OUTs?