Anyone have a Idea about how to use differential pair connector in spartan3an?
I am aware about how to make .ucf file. but i am not able to get how to use TXN_0 and TXP_0 in .ucf as i have only the single bit to transmit. but here two pins for single bit is given.
IBUFDS -- differential input buffer, single bit output
IBUFDS_DIFFOUT -- differential input buffer, both bit and inverse out (used when you need two IDELAY elements)
IOBUFDS -- differential input/output buffer
OBUFDS -- differential output buffer
IBUFGDS -- differential input buffer connected to a global clock network (BUFG or etc...)
As already pointed out, you must have both pins in your top entity, and convert to/from a single ended signal by instantiating one of the buffers mentioned in post #2.
It is a bit different in the Altera world. There you can have a single-ended top port and tell the tools via constraints that it is a differential I/O. It is also possible to manually instantiate the differential buffers.