der Mouse <mouse@Rodents.Montreal.QC.CA> dixit :

> I'm not sure this is actually true; I think I could probably design a
> non-scanned matrix keyboard.  (It would be a bit contrived, but I
> think it would be doable.)

It is definitely doable. Think about a single line of five switches, for
example, connected to ground on one side, the other side being connected
to interrupt lines (negative-edge-triggered) with pull-ups. You don't
have to scan such a "keyboard". A press on any key rises an asynchronous
interrupt. (I omit for clarity's sake the antijitter system)

Vincent