My design contains multiple OBUFTDS symbols. The design is not yet complete, and I am driving all of these outputs with a single signal. MAP fails and results in multiple driver errors on this net. Why is this happening?
"ERROR:MapLib:22 - Bus isPIN_IBUF/N driven by uIOBUFDS0/OBUFTDS/N/INV and
uIOBUFDS1/OBUFTDS/N/INV has multiple active drivers."
This OBUFTDS symbol is expanded by MAP into a circuit that includes an inverted form of the input signal. The code that does this expansion did not take into account the possibility that multiple OBUFTDSs might be driven by the same signal, and the result is that a separate inverter driver is added for each OBUFTDS load leading to the multiple driver error.
This problem is currently scheduled to be fixed in version ISE 8.1i.
Meanwhile, to work around this issue, provide a unique signal for each OBUFTDS input.