Can AVCCAUXTX/AVCCAUXRX and VTTX/VTRX power filtering networks be shared if the MGT is used as a Transmitter (TX) only or Receiver (RX) only?
Yes. AVCCAUXTX and AVCCAUXRX can share the same power filtering network if the MGT is being used as RX only or TX only.
The same applies for VTTX and VTRX when the link is DC Coupled where VTRX = VTTX = 2.5V.
For an AC Coupled link, this is not possible as VTRX is recommended to be between 1.6V-1.8V and VTTX is 2.5V. Both must have their own filtering networks.
For MGT being used as RX only:
TXINHIBIT must be asserted to drive the TXP/TXN pins to a static value.
For MGT being used as TX only:
The RXP/RXN pins must be driven, that is, RXP = logic High, RXN = logic Low or vice versa.