[time-nuts] Can (will) a M12+T generate a negative sawtooth message ?
Tom Van Baak (lab)
tvb at leapsecond.com
Sun May 18 23:51:56 UTC 2014
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.
> 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.
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