Description

When I use a OBUFDS in a design, verification might fail when comparing the RTL to a Post-Place&Route netlist. In the back-end netlist, an OBUFDS is converted to an OBUFTDS, allowing the output to be 3-stated. The 3-state enable is then connected to GTS. For equivalency checking, GTS is removed from the netlist. In some cases, this causes the OBUFTDS to have an unconnected 3-state enable, which causes failures during verification. 

NetGen leaves the 3-state net NLW_INST_OBUFDS_LVDS_T_UNCONNECTED unconnected for this design.

Solution

To resolve these errors, set the option in Formality or Conformal to ground unconnected input ports.