[time-nuts] BBB DDMTD - analysis
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Wed Oct 29 20:16:17 UTC 2014
This is the second post related to my attempts to create a BBB DDMTD,
the first post had a load of graphs showing details of what was
happening around glitch periods. This post is about interpreting those
Pretty obvious from only a cursory glance at the graphs are that
transitions are not continuous and are happening at very specific
intervals. I would appreciate some help in understanding how this might
be occuring or how to find out what might be going on as I'm currently
at a loss.
I've tried a few different combinations of oscillators to try and rule
them out and this seems to have no impact. It would seem the effect is
coming from the sampling / BBB bit.
There are 169 clocks/samples between the larger spikes, this corresponds
to ~16.9ms real time or a ~110ps interval at the DUT. The smaller spike
is 94 clocks/samples after the larger spikes (=~9.4ms / ~62ps). The dead
time with no transitions following a smaller spike is 75 clocks/samples
I'm not aware that there is any relation of these intervals to anything
else in the setup.
I'd welcome any thoughts on what might be going on here.
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