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AR# 46375

Place & Route- DRC WARNING:PhysDesignRules:372 - Gated clock. Clock net length_​module/​length_​out is sourced by a combinatorial pin

Description

I am receiving the warning below:
 

PhysDesignRules:372 - Gated clock. Clock net length_module/length_out is sourced by a combinatorial pin.

Solution

The warning is being issued because one of the clock net length_module/length_out is sourced by a combinatorial logic, making it a Gated-Clock.

Xilinx highly recommends that you use the CLB clock enable pin instead of gated clocks.

Gated clocks can cause glitches, increased clock delay, clock skew, and other undesirable effects.

Using clock enable saves clock resources, and can improve timing characteristic and analysis of the design.

Refer to page 60 of the user guide: http://www.xilinx.com/support/documentation/sw_manuals/xilinx11/sim.pdf

If you are not finding any issues while generating the bitstream or board test, you can safely ignore this warning.

If you want to use CE instead, refer to the user guide mentioned above.
AR# 46375
Date Created 02/15/2012
Last Updated 03/23/2015
Status Active
Type General Article
Tools
  • ISE Design Suite