> If I understand correctly, the 4 IOC pins (columns) would be pulled
> up high and the 4 row pins would be driven low. When a button is
> pressed, an IOC is triggered and a timer would delay Xms as a
> debounce, then one would have to drive each of the row pins high
> one at a time to see what row was pressed.

Yes. When the row with the closure on it goes high and therefore
causes the IOC pin to return high, there's your button
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