Almost OT: Pushbutton switch latching

[dwight elvey]

> From: cclist at sydex.com
>
> How about this?
>
> 8 74xx30's (8 input NAND) with each output feeding one of the inputs
> of the other stages. The remaining input of each gate is connected
> to a pushbutton whose other side is grounded and the gate side pulled
> up to Vcc through an appropriate resistor (say, 2.2K). The circuit
> is self-debouncing and the last button released governs the output.
> Basically an 8-stable flip-flap-floop...-flop. Initial state is
> theoretically random, but probably could be forced with a small
> capacitor across one of the buttons.
>
> If you expand much beyond this, note that fanout issues may rear
> their ugly heads.
>
> Cheers,
> Chuck
>
>

Hi Chuck
 Essencially the same as I described. I think is best meets the
general design criteria. I just used a single throw switch as
the circuit would be more than fast enough to ignore an bounch issues.
 If there was a fan out problem, one could do a ripple ring for clearing
but that might require some timed circuits to keep from racing.
Dwight

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