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AR# 25449

Virtex-4 IDELAYCTRL - Tap resolution is not what it is specified as in the data sheet when DCM is used for REFCLK


I generate the reference clock for the IDELAYCTRL from a DCM. I then reset the IDELAYCTRL after configuration, and the IDELAY resolution is not 75 ps.

What could cause this?


Before the DCM LOCKs, the output of the DCM is not correct. This can cause the IDELAYCTRL to LOCK to the wrong frequency and, therefore, have the wrong tap resolution. The IDELAYCTRL must be reset after the DCM LOCKs so that it can LOCK to the correct frequency.

AR# 25449
Date Created 09/04/2007
Last Updated 12/15/2012
Status Active
Type General Article