Keywords: period, global, setup, pad, clock
The Global constraint table does not list PERIOD constraints for BUFR nets (in Virtex-4 and Virtex-5 devices), but these BUFR nets have their Pad to Setup and Clock to Pad fields filled in with "N/A".
BUFRs are capable of driving I/OLOGIC FFs and I/OSERDES, so OFFSET IN/ OUT constraints should be allowed for these clocks.