CPC-Mousepack 2.0

The mouse that came with the CPC mousepack

A mouse for the Amstrad CPC. The CPC mousepack was manufactured by the German company Reisware.

The mouse/interface includes two buttons (0=pressed), and two signed 8bit motion counters (distance since last access: positive=up/left, negative=right/down). The buttons can be read via the normal BIOS keyboard scanning routines, the motion counters requires custom ASM code that reads & combines four 4bit fragments into two 8bit values (to be done once per frame).

Joystick 1 Read (keyboard row 9):
 Bit0-3  Motion Counter (4bit fragment) (requires four reads to get the two signed 8bit values)
 Bit4    Left Mouse Button  (aka Joystick Fire 2) (0=Pressed)
 Bit5    Right Mouse Button (aka Joystick Fire 1) (0=Pressed)
 Bit6    Unknown/Unused     (aka Joystick Fire 3) (old CPC only, not CPC+)
 Bit7    Keyboard DEL key
Joystick 2 Read (keyboard row 6):
 Bit0-7  Keyboard keys (dummy read from row 6 is done... to request/acknowledge something...?)

The exact mechanism that defines when the hardware does output the next 4bit fragment is unknown. The software does manipulate row 9 & row 6 signals, which does somehow request and/or acknowledge the fragments. Looking at the disassembled software, the hardware seems to work like so (not confirmed):

 switch from row0 to row9 --> invoke reading X counter (after 200 clks: MSB, after another 200 clks: LSB)
 switch from row9 to row6 --> terminate X read
 switch from row6 to row9 --> invoke reading Y counter (after 66 clks: MSB, after another 280 clks: LSB)
 switch from row9 to row6 --> terminate Y read
 switch from row6 to row0 --> terminate all

Whereas, one of the "terminate" actions does apparently reset the motion counter(s) to zero. Instead of "row0" one could use any other non-joystick row (ie. anything else than row6,row9). The "invoke" actions do request the MSB, which is then automatically followed (without another request) by the LSB after some hundred clock cycles.

• CPC Mousepack 2.0
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  The box and contents

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  Back of boxcover

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  Front of boxcover

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  Box open

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  Inside of Interface

The "Mousepack" mouse is sometimes referred to under different names (the names seem to be mainly coming from the software/copyright text on the floppy disks):

 Gerdes Mouse (Gerdes).
 Centaure mouse (Centaur graphics program, included on one of the disks).
 ASS Reis-Mouse (All System Software).
 Reisware-Mouse (Reisware)

• Media:CPC MousePack 2.0.zip - driver disk with sample tools