[time-nuts] NMEA time
Hal Murray
hmurray at megapathdsl.net
Thu Nov 26 18:09:08 UTC 2009
ch at murgatroid.com said:
> These are both problems, but the biggest issue in reducing jitter
> often is minimizing SMM[1]. Some SMI's can suck up 50 us at a go
> though most are less. On some platforms you may see SMI's executing
> at a rate of more than 1 Hz.
I think that's a different issue. That adds jitter to measuring how long
something takes. It doesn't add jitter to what-time-is-it-now, at least if
you are somewhat flexible on what you mean by "now".
How-long jitter can be filtered out or averaged, depending upon what you want.
It's a lot harder to keep accurate time if your basic clock changes
frequency, say due to temperature.
--
These are my opinions, not necessarily my employer's. I hate spam.
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