AR# 17925


Synopsys Formality, Verplex Conformal - Verification fails on OBUFTDS when using a simulation netlist generated by the ISE software


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.


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

AR# 17925
Date 05/15/2014
Status Archive
Type General Article
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