[time-nuts] PIC Divider Performance (was Re: time-nuts Digest, Vol 56, Issue 71)

John Ackermann N8UR jra at febo.com
Tue Mar 31 01:48:07 UTC 2009

Hi Pete --

The offset isn't surprising as the two dividers weren't synchronized but 
just free-running.  Each one started at a slightly different time 
(remember, separate power supplies) and in fact I "bounced" the power 
leads on one unit to try to minimize the offset.

I could have used the PIC code's sync function with an external sync 
pulse to get the two units within a couple of hundred nanoseconds, but I 
didn't have the leads wired up to make that convenient.


Pete said the following on 03/30/2009 09:39 PM:
> John,
> Thanks for sharing your experimental results.
> I am surprised that the PIC divider outputs were
> 85 ms apart when driven from the same source. I
> am ignorant of their internal workings, but I would
> expect the jitter results to be significantly impacted
> by this.
> Any thoughts on the origin of the 85 ms differential?
> Might this be a trigger point anomaly? (seems too big!)
> Resolving this difference should be interesting.
> Pete Rawson
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