For a Xilinx V4, there is an IBUFDS_DIFF buffer that you can use in the I/O pad. However, it appears that there is no differential termination resistor available for this setup. In XAPP861, it shows the buffer and the "optional DIFF_TERM" across the I and IB inputs. When I set the attribute to use the DIFF_TERM, Xilinx tools report that it is an invalid attribute. I assume that the tools are right and that for this particular buffer, there is not termination available. Could anyone give me a definitive answer?
Documentation and/or other info on this primitive is limited at best.
Also, there is a ULVDS standard supported in the I/O's but there isn't much info on that either (ie electrical specs).
Thanks in advance.