Re: ADB Ports

[dempson@actrix.gen.nz (David Empson)]

Michael Guitton <webmaster@cardshow.com> wrote:

> In article <19961228134754289879@dempson.actrix.gen.nz>,
> dempson@actrix.gen.nz (David Empson) wrote:
> 
> >At a guess, I'd say that the ROM 00/01 ADB micro doesn't have as much
> >support for extended keyboards, and always sets the operation mode used
> >by the standard IIgs keyboard.  This is probably supported by the Apple
> >extended keyboards and a few third party ones.
> >
> >Other third-party keyboards (such as the ADESSO NUform) may only work if
> >they are told to operate in one of the extended keyboard modes.  There
> >are two modes supported by Apple's keyboards: in the second mode, the
> >left and right modifier keys (command, option, shift, control) can be
> >distinguished by the host.  The ROM 3 ADB micro is probably specifying
> >the first mode (same codes generated by the left and right modifier
> >keys).
> >
> Could somebody disasm the ROM 03 ADB firmware code and write a ROM 01 only
> Init to address this issue? Will this infringes any Copyright?

It is not possible to modify this code (or add functionality to it).
Reading it is a rather clumsy process (but is possible).  The main
complication is that there is no documentation on the inner workings of
the ADB micro, so someone would have to be know exactly which model of
Mitsubishi microcontroller it is, and have documentation on it.

The only way to add support for a keyboard not supported by the ADB
microcontroller is to write a driver (running in the IIgs) which
bypasses the standard keyboard handling, then feeds keystrokes back
through the ADB micro for normal software.  This driver must be
interrupt-driven, and the computer will hang if a program attempts to
read the keyboard with interrupts disabled.  (This is the same problem
that occurs with the Easy Access INIT on a ROM 1 machine.)

I don't think it would be necessary to disassemble the ADB
microcontroller.  There is sufficient documentation on how ADB keyboards
operate (spread over various Macintosh manuals) to be able to write a
driver from the specification.

-- 
David Empson
dempson@actrix.gen.nz
Snail Mail: P.O. Box 27-103, Wellington, New Zealand