53268



                              TRIG3
     (R) Joystick trigger 3 (647). Controller jack four, pin six.

53268          D014           COLPM2
     (W) Color and luminance of player and missile 2 (706).

                              PAL
     (R) Used to determine if the Atari is PAL (European and Israeli
     TV compatible when BITs 1 - 3 equal zero) or NTSC (North
     American compatible when BITs 1 - 3 equal one; 14 decimal, $E).
     European Ataris run 12% slower if tied to the VBLANK cycle (the
     PAL VBLANK cycle is every 50th second rather than every 60th
     second). They use only one CPU clock at three MHZ, so the 6502
     runs at 2.217 MHZ -- 25% faster than North American Ataris.
     Also, their $E000 and $F000 ROMs are different, so there are
     possible incompatibilities with North American Ataris in the
     cassette handling routines. There is a third TV standard called
     SECAM, used in France, the USSR, and parts of Africa. I am
     unaware if there is any Atari support for SECAM standards.

     PAL TV has more scan lines per frame, 312 compared to 262.
     NTSC Ataris compensate by adding extra lines at the beginning
     of the VBLANK routine. Display lists do not have to be altered,
     and colors are the same because of a hardware modification.

53269          D015           COLPM3
     Color and luminance of player and missile 3 (707).

53270          D016           COLPF0
     Color and luminance of playfield zero (708).

53271          D017           COLPF1
     Color and luminance of playfield one (709).

53272          D018           COLPF2
     Color and luminance of playfield two (710).

53273          D019           COLPF3
     Color and luminance of playfield three (711).

53274          D01A           COLBK
     Color and luminance of the background (BAK).(712).

53275          D01B           PRIOR
     (W) Priority selection register. PRIOR establishes which objects
     on the screen (players, missiles, and playfields) will be in front of
     other objects. Values used in this register are also described at
     location 623 ($26F), the shadow register. If you use conflicting
     priorities, objects whose priorities are in conflict will turn black
     in their overlap region.