[time-nuts] Metastability (was Brooks Shera)
Hal Murray
hmurray at megapathdsl.net
Mon Mar 25 21:55:41 EDT 2013
lists at rtty.us said:
> If the data is changing as the clock fires, the flip flop oscillates rather
> than goes to a single state.
It may not oscillate. Some sit at halfway and then wander off, slowly at
first but with an exponential speedup.
The usual way to describe metastability is how much longer you have to wait
until the data is stable. The clock-to out gets stretched.
Here is an example from the net:
http://www2.tek.com/cmswpt/psdetails.lotr?ct=PS&cs=psu&ci=13298
The first picture, about a page down, shows metastability. You can see the
number of events decaying as you get farther from the normal case.
--
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