The Macintosh Plus (and earlier) keyboard contains a microcontroller. The microcontroller has on-board mask (factory programmed) ROM.
An interesting project would be to read out the contents of the Macintosh keyboard MC ROM, I think.
It may be possible to figure out what the MC must be doing just by knowing the keyboard communications protocol and the mapping of the keyswitches to the IO ports of the MC, but I think it would be nice to know the exact code in Apple's implementation.
I've seen sources that say the original Macintosh keyboard contains an Intel 8049 or an Intel 8021. They are the same family of MCs, but the 8021 has less on-board ROM and fewer IO lines.
I suspect that the original Mac keyboard contains the 8021 and that the Mac Plus keyboard (with keypad) contains the 8049.
Here's an interesting web page with a hack to read out the contents of the 8049 ROM:
http://www.sbprojects.com/projects/8049spy/index.php
Some chip programmers are capable of reading the contents of the 8049 as well. I don't know if the above project will work on the 8021 but it should, provided that the 8021 has an EA pin.
I'd do this myself, but, ha. The chances of me ever getting to it are near zero.
Oh, and interestingly, Jameco still has stock of the 8049 available at $1.49 each.
An interesting project would be to read out the contents of the Macintosh keyboard MC ROM, I think.
It may be possible to figure out what the MC must be doing just by knowing the keyboard communications protocol and the mapping of the keyswitches to the IO ports of the MC, but I think it would be nice to know the exact code in Apple's implementation.
I've seen sources that say the original Macintosh keyboard contains an Intel 8049 or an Intel 8021. They are the same family of MCs, but the 8021 has less on-board ROM and fewer IO lines.
I suspect that the original Mac keyboard contains the 8021 and that the Mac Plus keyboard (with keypad) contains the 8049.
Here's an interesting web page with a hack to read out the contents of the 8049 ROM:
http://www.sbprojects.com/projects/8049spy/index.php
Some chip programmers are capable of reading the contents of the 8049 as well. I don't know if the above project will work on the 8021 but it should, provided that the 8021 has an EA pin.
I'd do this myself, but, ha. The chances of me ever getting to it are near zero.
Oh, and interestingly, Jameco still has stock of the 8049 available at $1.49 each.