ID:176138 Can't place differential I/O pins and/or associated SERDES transmitters or receivers -- location assignments are illegal

CAUSE: You assigned the differential I/O pins in the design to locations that do not support differential I/O pins and/or do not support their associated SERDES transmitters or receivers. As a result, the Fitter could not place the differential I/O pins.

ACTION: Delete the differential I/O pin assignments, or change the differential I/O pin assignments to locations that support differential I/O pins and support their associated SERDES transmitters or receivers.