AMX Mouse

The original mouse with red buttons and a logo

A mouse by the British company Advanced Memory Systems.

The mouse was connected to the joystick port of the CPC.

An additional lead plugged between the 5V power connector coming from the monitor and the 5V-socket of the CPC.

There were three versions in all.

The tape software is : AMX Art.

Technical

The AMX Art software uses the CPC's 300Hz interrupt to read the joystick port (at least it tries to do that, while moving the mouse pointer, the software accidently disables IRQs, and so, misses some interrupts). This is giving it a relative low resolution of max 300 mickeys per second (or actually less, due to the missed IRQs).

The AMX Interface hardware basically converts the incoming mouse signals to joystick signals, issuing LOW pulses (per mickey) on the corresponding direction lines. The protocol is thus very simple (unlike modern RS232 and PS/2 mice, the hardware doesn't contain any motion counters).

 Row9.Bit0 Joy1up    LOW for 1/300s per mickey, when mouse moved up
 Row9.Bit1 Joy1down  LOW for 1/300s per mickey, when mouse moved down
 Row9.Bit2 Joy1left  LOW for 1/300s per mickey, when mouse moved left
 Row9.Bit3 Joy1right LOW for 1/300s per mickey, when mouse moved right
 Row9.Bit5 Joy1fire1 LOW when Right mouse button pressed
 Row9.Bit4 Joy1fire2 LOW when Left mouse button pressed
 Row9.Bit6 Joy1fire3 LOW when Middle mouse button pressed

Note: The exact hardware timings are unknown, the values "1/300s" in the above description assume that the AMX hardware timings were designed to match up with the 300Hz AMX software timings.