Metastability in jk flipflop

Thread Starter

imbaine13

Joined Oct 6, 2013
67
Hello everyone,
I long while ago, I asked this same thing but didn't get directions responses. I hope it works out better this time. I'm building a unipolar stepper motor driver with step and direction inputs, using a counter and decoder to drive mosfets which will in turn power the motor coils in sequence.
I'm very aware and actually have bought chips dedicated for these particular purposes, but seeing as their operation can seemingly easily be done using discrete flip flops, I thought I'd give it a shot. Mostly to better understand the underlying concepts. However, as I fiddled around trying to understand the jk flipflop, I wondered what would happen if ALL INPUTS (j, k and clk) were all rising instantaneously. A better way to put it is, what would happen if I used a jk latch instead of a jk flipflop, and kept the enable high, while both the j and k were held high. Would the outputs oscillate?
I also came across this article on Wikipedia which reinforced my curiosity! https://en.m.wikipedia.org/wiki/Metastability_in_electronics
Could this be what would happen?



Appreciate your feedback!
Lovely time!
 

crutschow

Joined Mar 14, 2008
34,285
Normally you don't want to put all inputs high at the same time.
The result may not be "metastable" but it's certainly undefined.
 

Brownout

Joined Jan 10, 2012
2,390
A better way to put it is, what would happen if I used a jk latch instead of a jk flipflop, and kept the enable high, while both the j and k were held high. Would the outputs oscillate?
Lovely time!
That's not a better way to put it. That's a completely different question. The output is very likely to oscillate. At best, the output is indeterminent.
 
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