On Tue, Jun 25, 2013 at 4:36 AM, ed breya <[email protected]> wrote: > > 4. It seems to me that whenever fd is much higher than fc (fd>>fc), that > fd could be used instead to trigger the second DFF, which would reduce the > metastability of the first DFF somewhat, and also synchronize the output > signal closer to the edges of fd - but with some metastability from that > too. > > Clocking the two FFs of a synchronizer with different clock signals will not work against metastability. When the edges of fd and fc are very close in time, there is a slight chance that the output of the first FF will be in a metastable state for some time. By clocking the second FF with fc you allow for a full (guaranteed) period of fc for that output to stabilize to a solid '0' or '1'. If you clock the two FFs with two different clock signals you don't have that guarantee. There should be a big gain to be had somewhere else to do something like that, but I can't see it. I must say all my experience is with fc very close to fd in frequency, so maybe I am missing something about the fd>>fc case.
Cheers, Javier _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
