AR# 12054

Description

How do I lock down (constrain) a DCM in a Virtex-II device?

Solution

You can lock the DCM in the User Constraints File (.ucf):

The syntax is as follows:

INST <instancename> LOC = DCM_X[A]Y[B];

where [A] is the X coordinate, starting with 0 at the left-hand bottom corner ([A] increases in value as you move across the device to the right);

and where [B] is the Y coordinate, starting with 0 at the left-hand bottom corner ([B] increases in value as you move up the device).

For example:

INST myinstance LOC = DCM_X0Y0;

NOTE:

- For Virtex/Virtex-E, please refer to (Xilinx Answer 9045).

- For more information about IBUFG-DCM-BUFG/BUFGMUX restrictions, please refer to (Xilinx Answer 11756).