[time-nuts] Can (will) a M12+T generate a negative sawtooth message ?
EWKehren at aol.com
EWKehren at aol.com
Mon May 19 01:43:15 UTC 2014
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,
tvb at 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 <hmurray at 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 at febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
More information about the Time-nuts_lists.febo.com
mailing list