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AR# 16152

5.1isp2 Timing Simulation, DCM, Verilog - The DCM does not lock in a verilog timing simulation


Keywords: Timing, Simulation, Verilog, DCM, not, lock, pulse, swallow

Urgency: Standard

General Description:
In a Verilog timing simulation, the DCM may not lock. This could be the result of pulse-swallowing, or the result of simulating without picosecond resolution.


First, ensure that the design is being simulated with picosecond resolution.

If picosecond resolution is being used, the problem is probably the result of pulse-swallowing.

This problem is fixed in the latest 5.1i Service Pack, available at:
The first service pack containing the fix is 5.1i Service Pack 3.

Alternatively, refer to (Xilinx Answer 9872) for a methos of working around this issue.
AR# 16152
Date Created 09/03/2007
Last Updated 11/18/2008
Status Archive
Type General Article