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AR# 67948

Vivado Synthesis - Post-Synthesis DRC Warning PLHOLDVIO #1: A LUT <LUT_cell_name> is driving clock pin of n cells

Description

Vivado Synthesis interprets @(negedge clk) as a LUT-inverter connected to the clock pin of the register.

This causes the following DRC warning if I report DRC in the Synthesized design.

PLHOLDVIO #1
A LUT <LUT_cell_name> is driving clock pin of n cells. This could lead to large hold time violations.
First few involved cells are:
  <FF_cell_name> {FDRE}
  ......

How can I resolve this issue?

Solution

The LUT-inverter on the clock net will be pushed into the register cell to use the local inverter in it during opt_design.

This post-synthesis DRC warning can be ignored.
AR# 67948
Date Created 09/27/2016
Last Updated 10/13/2016
Status Active
Type General Article
Tools
  • Vivado Design Suite