http://www.mentasm.com/~mramiga/files/tech/tech/joymice.htm (Amiga Plus Extra No. 5, 08/1997)Mouse/Joystick Port Pinouts
Mouse Pin Mnemonic Description 1 V Vertical pulses 2 H Horizontal pulses 3 VQ Vertical quadrature pulses 4 HQ Horizontal quadrature pulses 5 UBUT* Unused mouse button 6 LBUT* Left button 7 +5V +5V, current limited 8 Ground 9 RBUT* Right mouse button Joystick Pin Mnemonic Description 1 FORWARD* Forward joystick switch 2 BACK* Back joystick switch 3 LEFT* Left joystick switch 4 RIGHT* Right joystick switch 5 Unused 6 FIRE* Left mouse button 7 +5V 125ma max, 200ma surge 8 Ground 9 Unused