> I've got a system at work with an internal clock oscillator that I want to > get some statistics on, but there's no direct visibility for the > oscillator, nor do I have a convenient test point that I can probe. ...
Fun problem. Thanks for tossing it out. I see two approaches. Are there others? One is to generate something like a PPS pulse and capture timestamps. Then crunch the data and hope you see N buckets so you can ignore anything that isn't in bucket 0. (or correct them by shifting by N ticks) The other approach would be to measure the time between pairs of pulses. You can probably do that much faster than once per second. This should give you 2*N buckets. I can't quite figure out how far apart the pulses should be for best results. (It will probably be simple after I see it.) I expect it will depend on the ADEV of the measuring system and the ADEV of the clock you are trying to measure. I assume you can get a rough ADEV of the clock you want to measure by measuring a similar part on a typical lab setup. It's probably worth sanity checking the divide step to make sure it's dividing by M rather than M-1 or M+1. (Digital geeks are often off by one, especially if nobody has checked carefully.) I'm not sure how to do that. Probably something like divide by 2*M and see if it matches. Or divide by a small M and measure the frequency. ----------- Plan B would be to use an inconvenient test point. (or make one) Years ago, my boss gave a neat talk about how to prototype hardware. Step 0 was hire a good technician. :) -- These are my opinions, not necessarily my employer's. I hate spam. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.