Changes
The low-level XA/XB/YA/YB signal must be watched by software (the 300Hz interrupt is probably too slow to sense fast motions, so there's little chance to have the mouse driver running in background).
=== CPC Plus Compatibility ===
The circuit reportedly doesn't work on CPC Plus computers. Probably simply because of the missing Fire3 signal on the joystick port of the CPC Plus (this could be fixed easily, by connecting the missing pin inside of the computer). There are also additional diodes in the CPC Plus, which may drop the voltages a little, but probably do not cause problems in this case.
== Timings ==
XB _____-------------------------------____
In the above case, checking only raising XA would miss the direction change on falling XA (if that happens repeatedly, then the mouse would disappear towards the screen border, eg. if the mouse is in an unstable position, without actually being moved).
== Software supporting the ST-Mouse ==
