It is not possible to swap/reverse SERDES XAUI lanes on a LatticeSC/M flexiPCS for the following reasons:
1. The PCS won't be able to support some of the XAUI PCS special functions like section 48.2.4.5 (Link status ) , 48.2.6.4 (Link status reporting)
and Sequence ordered_sets in the IEEE 802.3ae 2002 specification (local fault, remote fault signaling).
2. In the TX PCS direction, the flexiPCS will replace the EOP(0xFD) character, with an IDLE character if the EOP occurs on channel 1, 2 or 3 of the TXD bus.
3. In the RX PCS direction, the flexiPCS will replace the EOP(0xFD) character, with an h07 character if the EOP occurs on channel 1, 2 or 3 of the TXD bus .