Re: Question about keyboards

[david@uow.edu.au (David Wilson)]

"Ernest" <leucoplast@seanet.NOSPAM.com> writes:
>My question is... what allows one keyboard to work on one system but not
>another? Where is that controlled? I mean, if you can switch different
>keyboards (simple and with numeric pads) between different clones, would you
>be able to switch a IIe and Platinum IIe keyboard between each other? Are
>these old clone keyboards controlled by the character ROM on the
>motherboard, or by a chip on the keyboard circuit board? How does all this
>work?

Different Apple // computers and clones thereof use different keyboard
encoding schemes:

System			Encoder location	keyboard/motherboard interface
------			----------------	------------------------------
Apple ][ & ][+		keyboard PCB		8 bit parallel
Apple //e & //c		motherboard PCB		X/Y matrix
MPF-III (//e clone)	detached keyboard	serial data + clock
//gs			detached keyboard	ADB

The //e keyboard matrix includes a numeric keypad portion (the beige //e
has a numeric keyboard connector). The platinum //e just includes those keys
on the same PCB. They should swap but I have not tried this. Plus, early
//e computers had a different layout for the numeric keypad section - replacing
the //e keyboard ROM would fix this.
--
David Wilson  School of IT & CS, Uni of Wollongong, Australia