UCF constraints for DCM outputs?

Jan 24, 2004 1 Replies
K

Hi, all:



I am using a DCM to multiply my clock by 2.5...In the UCF file, do I define a Period constraint for the 2.5X clock or the original input clock?



Thanks for your comments.



Best Regards, Kelvin


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R

define

Kelvin -

You specify the input clock period in the DCM attributes. You can/should also specify the output clock period in a timespec to constrain your logic. Like this:

# for the DCM INST "dcm_inst" CLKIN_PERIOD=25;

# for your logic NET "clk_out" TNM_NET = "clk_out"; TIMESPEC "TS_CLKOUT" = PERIOD "clk_out" 10 ns HIGH 50 %;

Robert

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