Pragmatics of a polyphonic calculator (chapter 2)

[Garth Wilson]

Quote:Typical row/column decoders do not allow for this so you may have to have one CPU I/O pin for each key if you want no limitations on key press combinations.

So you could go atypical and put a diode in series with each switch in the crosspoint matrix, so you can still scan 64 keys with 8 column output bits and 8 row input bits, and press any number of keys at once, unlike the situation with 2-key rollover. The output bits can also be used for other things between keyboard scans.

The other topic covered the other material.