Changes
/* Use with the Amstrad Plus */
When used with the Amstrad plus, the button labelled "I" activates joystick fire 2 (giving 'Z' in BASIC), and the button labelled "II" activates joystick fire 1 (giving 'X' in BASIC), therefore the fire buttons are mapped to the digital joystick 0 fire buttons.
When the sliders are in the middle, the values returned from both axes change rapidly between &1c and &1b, but this changes depending on the exact position of the slider (the fact remains the values change rapidly). The analogue joystick reports X values in &6808 only and Y values in &6809 only.
The range of values reflects the range of motion, with moving half way to the left or up giving a reading of &b.