If Port Is Used As Mouse/Trackball 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 (middle) 6 LBUT* Left button 7 +5V +5V, current limited 8 Ground 9 RBUT* Right mouse button If Port Is Used As 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