Re: Another simple DCM question

On Mar 30, 3:16 pm, "lecroy7...@xxxxxxxx" <lecroy7...@xxxxxxxx> wrote:
I have a design where I want to have 2 DCMs, each with there own clock
source come up with some known phase. The two clock sources have a
fixed phase relationship. I routed a single reset signal to both
DCMs. If the DCMs are a 1:1 clock ratio, no problem. However, if
they are 2:1 (CLKIN_DIVIDE_BY_2 => TRUE), then often out of reset I
see the phase of the output clocks will change. Even though the reset
is async, I sync'ed it to each of the DCM's input clocks. This seems
to have an effect and does help. The part is a Virtex 4. I have not
tried it on any other device.

Any ideas?


1) Build a circuit to detect the phase relationship and re-reset one
of the DCM's
until they match the phase you want?

2) Don't use the CLKIN_DIVIDE_BY_2.

.

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