On 2005-10-26, David Andrews wrote:
I have to expand i/o on a system that now has only 4 inputs and 4 outputs.
I need 12 inputs and 13 outputs.

Anybody got any ideas, i thought this would be easier.
Im familiar with the '249 output latches '151 and input multiplexors
but cant seem to get what i need... ?????

use two of your pins one to clock and one to sense state zero on a counter
that gives you a sequential address scanner...

your 6 remaining lines are inputs and outputs to those addresses.

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Bye.
Jasen