Lyle Hazelwood <motoman9@BELLSOUTH.NET> wrote:
> > You could do it with a 4040 and a 4-input AND gate. Take the logic
> > outputs for hA3 = %10100011 (a0,a1,a5,a7) and AND them together,
> > with the output going to the 4040's reset to clear the 4040 back to
> > all zero outputs. A pulse will be produced each time a0&a1&a5&a7
>
> Since the 4040 is Async, wont this method risk false triggering as the
> ripple goes through the stages?

No, and if you think about it a bit, you'll see why.

A ripple counter is made of flip-flops that change state on the high-to-low
transition of the clock. So, because of causality, a given stage has to go
low before the stage that it drives can go high. As a result, you can never
see a count that is "too high", even as a glitch; you'll only see glitch
values that are too low. Therefore, this method of creating a programmable
divider works just fine.

-- Dave Tweed

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