Date   : Wed, 07 May 1986 09:41:29-EDT
From   : Gern <GUBBINS@RADC-TOPS20.ARPA>
Subject: Re: Commodore 128 Mouse Interface

The C128 'mouse' is not a mouse at all, except it looks like one.   It
is an inverted tracball.  It is simply a digital joystick like interface.
You 'roll-up' (at ANY speed), and it lowers the UP line (pin-1).  Similarly,
for down, left, right (pins 2,3,4 respectively).   The left button is
pin-6, otherwise known as FIRE and the right button is connected in a different
fashion to POT-X (on pin-9).   There is no increments, or timming, or pulse
widths (this is what I consider makes a REAL mouse).   Tracballs work the
same way.   You can use a digital (standard) joystick in place of this
C128 mouse, or a tracball, and the software will not notice (save for no
right button).    This mouse does not even come close to the 'magic' feel
of a real mouse (Microsoft Mouse), but then again it is only $35 instead
of $85 and cheap and marginal is the name of the game in Commodore land.

Cheers,
Gern