Re: ADB Ports

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

Paul H Bauer <pbauer@athena.mit.edu> wrote:

>         I bought an ADESSO NUform keyboard for my son's GS Rom1 and when I
> tried it the touch pad worked but none of the keys would send to the GS. I
> tried the keyboard on 2 Mac's and of course it worked fine. I then tried it
> on a Rom 3 GS and it worked just fine on that system. I changed his Rom 1 for
> my Rom3 and he is happy, however I am trying to figure out what the
> difference is in the ADB port between the Rom1 and the rest of the world ie
> Rom3 and Mac.

There is no physical difference between the ADB port on the two versions
of the IIgs motherboard (ROM 00/01 and ROM 3).

There are differences in the firmware contained in the ADB
microcontroller on the IIgs motherboard.  The only obvious ones are that
the ROM 3 ADB micro provides Sticky Keys and Keyboard Mouse, and that it
controls the Caps Lock indicator light on an extended keyboard.

It sounds like it also supports a wider variety of keyboards.

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).

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