The question is what is the definition on time. Yes it will be always 140 nsec late to what the M12 calls zero. Good for a GPSDO. How ever if you want it to relate to NIST time more hardware is needed unless you can compensate that 140 nsec in antenna delay. A simple solution would be a preset counter that at 10 MHz takes out 9999999 counts and the last 100 nsec are controlled by the DS chip. Using 100 MHz and you can use 10 nsec and 0.1 nsec. resolution. Counter is simple to implement synchronizer on input and output and a PIC in between, or all discrete logic or a 32 cell Altera G/A.In all cases the counter is hard wired and the GPS receiver controls the DS chip. Bert Kehren In a message dated 5/18/2014 7:59:06 P.M. Eastern Daylight Time, t...@leapsecond.com writes:
Hal, Yes, there are negative delays. The goal is that the physical 1PPS output is, on average, exactly on-time. If designed right, that means as many negative offset pulses occur as positive offset pulses. The spread gives you the RMS value. This is exactly what you want for a GPS timing receiver. /tvb (i5s) > On May 18, 2014, at 1:42 PM, Hal Murray <hmur...@megapathdsl.net> wrote: > > > The ref output is the minimal delay through the chip covering the input and > output pad buffers. It will vary slightly with temperature and voltage. > > There are no negative delays in that sort of chip. It's just a bunch of > gates/buffers with a carefully calibrated delay. (For a negative delay, you > would need something like a PLL.) > > If the delay from the M12+T might be negative, set the antenna cable delay to > be a bit short and add on a constant in software. _______________________________________________ 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. _______________________________________________ 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.