ID:169011 Cannot place I/O pin <name> in pin location <name> -- I/O standard assigned to pin requires VREF value and VREF pin corresponding to pin location not available

CAUSE: You assigned the specified I/O pin to the specified pin location, but, the Fitter cannot place the pin in the location because the I/O standard assigned to the pin requires a VREF value and the VREF pin corresponding to the specified pin location is occupied by a regular I/O pin.

ACTION: Assign the specified I/O pin to a different location that has an available VREF pin corresponding to it.