Re: Mice

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

Wayne Stewart <waynes@intergate.bc.ca> wrote:

> Some while back I saw a Mac plus mouse hooked up to a Mac SE via 
> an adaptor.  Unfortunately at the time I was't able to look into 
> that setup. Would anyone know anything about how this adaptor is 
> wired?

It would have to be more than a simple wiring rearrangement.

The Mac Plus (and Lisa, and traditional Apple II) mouse sends raw
signals directly to the host machine: a digital signal indicates whether
the button is pressed, and four more signals are used to indicate mouse
movement.  (Two pins for each direction; a pulse train is generated on
both pins when the mouse moves, and the phase relationship between them
indicates the direction of movement.)

The ADB mouse (SE and most later Macs and the IIgs) is semi-intelligent.
It responds to commands sent over the Apple Desktop Bus and responds
with register values that report the current state of the mouse button
and recent movement along the X and Y axes.

I suspect this adaptor actually contains a small microprocessor which
implements the ADB mouse command set, interpreting the signals from the
mouse to derive the required information.

The same adaptor should work on the IIgs, in theory.

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