GLM590620 said:
I'm looking for a latch IC or a sutable circuit for use with a 4X4 keypad,
something that will keep only one key on untill another one is pressed.
Thanks
Gavin
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Simple, 16 buttons to ground, each other pole with a guide diode toward
each button. Then pull-ups on the data lines, and pull them down as
needed by wiring the right button to the right bits to encode it in
binary.
Also bring together diodes from each button to one pullup, which
becomes the latch strobe, then use that to latch the value to a
latch, like a 74xx574 or such.
To do two digits, simply debounce the strobe and run it to a 74747
as a divide by two counter, that changes states to enable whichever
of the two digits, back and forth.
You COULD do some clock-driven polled circuit, but this is more elegant
actually. Run the latch outputs to two 7447's and two 7-segment LED
digits.
-Steve