[sdiy] Pressing buttons

[harry]

If you use a 4-16 line decoder... hook up the switches to
data inputs Q1-Q4. Then run a high value feedback resistor
from output 1 to Q0, output 2 to Q1, output 4 to Q2, and output
8 to Q3.   Then push a button... the corresponding output goes
high and latches the input because of the feedback....

push another button and the output switches to some 'other'
state with no feedback... then latches the new button.

It can only latch one state. If you have a master reset you could
guarantee
a fixed state at power up.

not my idea, saw it years ago using a 3-8 line decoder in ideas for
design
or some such...

H^) harry

">>>marjan<<<" wrote:

> I'm in need of nice little cct, there are 4 buttons SPST,
> I need 4 outputs, when you press button#1 output#1 goes to
> logic 1 (high) all other outputs to 0, press button#2
> output #2 goes high all others to 0 and so on.
> Also output must stay high until active, not just a pulse.
> And it should be CMOS.
> I'd make it but my mind spits just sorta priority
> codec with f-fs solution, with lotsa gates. There should
> be something more elegant and simple, even inside a cmos
> chip?
>
> I know you know it!
> And no PIC solutions please :)
>
> ThanX!
>
> --
>
> marjan
>
> me    : Marjan Urekar
> e-mail: urekar.m at eunet.yu
> s-diy : http://surf.to/marjansystems
> music : http://go.to/forcemajeure

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