In the last 16 bytes of bank 3 (keyboard mapping):
|0xBFFB||Bit 7 is the middle button status (1=pressed).|
|0xBFFD||Bits b4 to b0 are the low bits of the vertical movement counter.|
Then, plus the addition of the very valuable information showed in the Richard Fairhurst website the low level interface of PCW KeyMouse is:
|0xBFFB||b7: middle button status |
b6 to b0: horizontal movement counter
|0xBFFC||b7 to b6: high bits of vertical movement counter|
|0xBFFD||b4 to b0: low bits of vertical movement counter|
|0xBFFE||b7: left button status |
b6: right button status
For button status: Bit = 1 if button pressed, otherwise = 0.
Values for movement counters: 0 to 127, but when 0 is decreased in 1, 127 is the result, and when 127 is increased in 1, 0 is the result.