[time-nuts] ***SPAM*** Oncore m12+t PPS sawtooth correction board.
phk at phk.freebsd.dk
Wed Dec 3 01:49:54 EST 2014
In message <DECE7BA6-65E7-4C1E-A424-7E258A020E84 at sfr.fr>, Mike Cook writes:
>> I'm using a soekris net4501 that I hacked according to
>> Recenlty I felt the need to add hardware sawtooth correction.
For the net4501 that is probably a bad idea.
When you do the sawtooth correction in software, the hw-component
acts as a jitter to smooth out the net4501's ~120nsec timestamping
Without this jitter, you will have the timestamps sit in the same
window for long periods of a time and then suddenly switch to to
the neighboring window rather rapidly.
With the jitter the switch gets "smeared" out over a longer
period of time, which is a more sensible input to a PLL.
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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