Changes
Note II: Looking at the photos, it seems that /joystick1 (keyb row 9 select) is wired to the multivibrator, so the mickey timings may be software controlled; accordingly, software would be required to deselect keyboard row 9 between each read.
Confirmed: Software MUST deselect will select keyboard row 9 to read the mouse, but then MUST deselect it to read the mouse correctly.
For example, the loop here doesn't work:
