Hi Magnus, on our Fury system the phase relationship between the 1PPS (clean OCXO version) and the 10MHz is established during power-on, then held stable (it is generated by the same 10MHz crystal) unless it for some reason drifts more than +/-220ns away from UTC at which point it is reset to UTC, or until it is changed by user-command. We do also have the raw GPS 1PPS available (jumper selection option) which is asynchronous to the 10MHz, and as you mentioned will drift since it is generated by a separate crystal, and clocking system. One could use two or three cascaded FF's two avoid the setup/hold/metastability issues, then set the phase via software command so as to compensate for the FF-induced phase delays. You are right, there are so many ways to cross that river :) bye, Said In a message dated 12/12/2008 15:16:00 Pacific Standard Time, mag...@rubidium.dyndns.org writes:
You really can't sync up some PPSes to the 10 MHz by simple DFFs since the variations may be more than 100 ns during some phases of the training and holdover shifts. The PPS output should always be generated using the 10 MHz such as they have a stable phase-relationship. The generated PPS is then compared to the source PPS and controlled phase adjustments should be done. Cheers, Magnus _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
