Commodore Amiga A2000 - Figure 8-4 Typical Paddle Wiring Diagram

LEFT PADDLE RIGHT PADDLE
resistive element resistive element
________ _______ ________ _______
| \/\/\/\/ | \/\/\/\/
| ^ | ^
| /|\ | /|\
| +5 | | +5 |
| |__________ | |__________
| | | |
| | | |
Pin 7 Pin 9 Pin 7 Pin 5
| | | |
|<-----Fire Button----->| |<-----Fire Button----->|
| | | |
Pin 8 Pin 3 Pin 8 Pin 4
Figure 8-4: Typical Paddle Wiring Diagram
In an X-Y proportional joystick, the resistive elements are connected individually to the X
and Y axes of a single controller stick.
READING PROPORTIONAL CONTROLLER BUTTONS
For the paddle controllers, the left and right joystick direction lines serve as the fire
buttons for the left and right paddles.
INTERPRETING PROPORTIONAL CONTROLLER POSITION
Interpreting the position of the proportional controller normally requires some preliminary
work during the vertical blanking interval.
During vertical blanking, you write a value into an address called POTGO. For a standard
X-Y joystick, this value is hex 0001. Writing to this register starts the operation of some
special hardware that reads the potentiometer values and sets the values contained in the
POT registers (described below) to zero.
The read circuitry stays in a reset state for the first seven or eight horizontal video scan
lines. Following the reset interval, the circuit allows a charge to begin building up on a
timing capacitor whose charge rate will be controlled by the position of the external
controller resistance. For each horizontal scan line thereafter, the circuit compares the
charge on the timing capacitor to a preset value. If the charge is below the preset, the
POT counter is incremented. If the charge is above the preset, the counter value will be
held until the next POTGO is issued.
- Interface Hardware 229 -