Editing POKEY (section)

===POT7 $D207 Read===
SHADOW: PADDL7 $0277

Paddle Controller 7 Input

{| class="wikitable"
|-
! Bit 7 !! Bit 6 !! Bit 5 !! Bit 4 !! Bit 3 !! Bit 2 !! Bit 1 !! Bit 0
|-
| ? || ? || ? || ? || ? || ? || ? || ? 
|}

Each input has 8-bit timer, counting time when each TV line is being displayed. This had the added advantage of allowing the value read out to be fed directly into screen coordinates of objects being driven by the paddles. The Atari Paddle values range from 0 to 228, though the maximum possible is 244. The Paddle controller reads 0 when turned to its maximum clockwise position, and returns increasing values as it is turned counter-clockwise ending at its maximum value.

The Paddle reading process begins by writing to [[POKEY#POTGO $D20B Write|POTGO]] which resets the POT* values to 0, the [[POKEY#ALLPOT $D208 Read|ALLPOT]] value to $FF, and discharges the potentiometer read capacitors. The POT* values increment as they are being scanned until reaching the resistance value of the potentiometer. When the Paddle reading is complete the corresponding bit in [[POKEY#ALLPOT $D208 Read|ALLPOT]] is reset to 0.

The Paddle scanning process can take the majority of a video frame to complete. The Atari Operating System takes care of Paddle reading automatically. The Paddles are read and paddle scanning initiated during the stage 2 vertical blank. Paddle values are copied to shadow registers. (Note that Paddle triggers are actually joystick direction input read from PIA.)

A faster mode of scanning the Paddles is possible by setting a bit in [[POKEY#SKCTL $D20F Write|SKCTL]]. The reading sequence completes in only a couple scan lines, but the value is less accurate.