[time-nuts] BBB DDMTD - analysis
hmurray at megapathdsl.net
Thu Oct 30 18:13:34 UTC 2014
subscriptions at burble.com said:
> In an effort to understand which component was responsible for my ~17us
> spikes I decided to go back to basics with just a single DFlop (AC74) on a
> breadboard; no BBB, just a couple of oscillators driving the data and clock
> pins ...
I don't know what the problem is, but metastability won't cause numbers like
With classic metastability, there are 2 parameters. One is the probability
of going metastable. That's the width of the window on setup time where bad
things happen. The other is how long it takes to return to a valid logic
level, the gain-bandwidth around the feedback loop in the FF.
One way of describing metastability is that if you don't meet the setup and
hold times, it won't meet the clock-out time. If you make a histogram of the
measured clock-out times, it decays exponentially - straight line on a log
Metastability scales with the speed of the logic family. If you switch to a
slower part, the histogram should shift to the right.
Also, 17 microseconds is huge. Microseconds. Right?
There are several good scope pictures here:
These are my opinions. I hate spam.
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