DCM usage question

snipped-for-privacy@hotmail.com (Yu Haiwen) wrote in message


Howdy Yu,

   What exactly do you mean by the "clkfx de-skew" portion of your
question?  Considering that there is no fixed phase relationship
between asynchronous clocks (like your 30 MHz and 40 MHz), what good
would the de-skew be?

If you post a more complete description of your application, it would
likely result in multiple responses, possibly each outlining a
different way to meet your requirements.

Good luck,

   Marc

mrand@my-deja.com (Marc Randolph) wrote in message


Thanks for your suggestion.
Let me explain the situation.

When we use the DLL function of DCM. All DCM output clocks are
phase-aligned to CLK0 and, therefore, are also phase-aligned to the
input clock.
There's no problem if I only use one of the clkdv output or clkfx
output.
But now I want to use both the tow output clocks, can they still both
phase-aligned to clkin?

I've read the Xilinx answer record 12582, which sugest to use tow DCMs
in series. Though my application is a little different, and I'm
thinking how about using tow DCMs in parallel. Would there be any
improvement?

40 MHz has a period of 25 ns, and 30 MHz has 33.33333 ns. They meet
every third period of 30 MHz = every fourth period of 25 MHz.
Peter Alfke

Yu Haiwen wrote: