Whereas I agree that a PC keyboard encoder may be a bit bulky a task, why does it matter how many keys the encoding algorithm can manage? So long as you don't have to do multi-level encoding as the PC does, you can do this quite easily.

If you use an 8x8 (or smaller) matrix encoding technique and use the 805x UART, you can do prettY much whatever you like. If the matrix isn't fully populated, it doesn't matter. It could even save you from having to do table lookups.

Have you read any of the many, Many approaches to keypad encoding on this website? What about the 430,000 hits that GOOGLE produces on a search for "keypad encoding?"

RE