Atari 400 Hardware Manual

D4 Fifth Player Enable.
D3, D2, D1,
& DO
Higher
Priority
This bit causes all missiles to assume the color of Playfield
Type 3. (COLPF3). This allows missiles to be positioned
together with a common color for use as a fifth player.
Priority Select (Mutually Exclusive).
These bits select one of 4 types of priority. Objects with
higher priority will appear to move in front of objects
with lower priority.
D3=1
D2=1
D1=1 D0=1
I I
I
[PFO
ICPFO
I
PO]
I PO]
PF1
I PF1
I
P1
I P1
PO I PF2
I PFO
I P2
Pl J I PF3 + P5
I PFl
t =~0
P2 I PO]
I PF2
P3 I P1 I PF3 + 5
I PF1
PF2
I P2
I P2 J
I PF2
!;3 + P5 I P3
I P3 I PF3 + 5
BAK 1 BAK
I
BAK
J
BAK
NOTE: The use of Priority bits in a "non-exclusive" mode (more than 1
bit true) will result in objects (whose priorities are in conflict)
turning BLACK in the overlap region.
EXAMPLE: PRIOR code = 1010 This will black PO or P1 if they are over
PFO or PF1. It will also black P2 or P3 if they are over PF2 or
PF3. In the one-color 40 character modes, the luminance of a
pixel in a character is determined by COLPF1, regardless of the
priority. If a higher priority player or missile overlaps the
character then the color is determined by the player's color.
OS SHADOW: GPRIOR (26F)
COLPFO-
COLPF3 (Playfield Color)(D016, D017, D018, D019): These
addresses write data to the Playfield Color-Lum Registers.
D7 D6 D5 D4
D3 D2 D1 DO
(see COLBK for bit assignment)
OS SHADOWS: COLORO - 3 (2C4-2C7)
III.8

Atari 400 Specifications

General

Manufacturer	Atari
Model	400
Type	Home Computer
Release Year	1979
CPU	MOS Technology 6502
CPU Speed	1.79 MHz
ROM	10 KB
Operating System	Atari OS
Keyboard	Membrane keyboard
RAM	8 KB (expandable to 48 KB)
Graphics	ANTIC and GTIA chips
Sound	4 channels
Display	RF output for connection to TV
Storage	Optional cassette tape drive or floppy disk drive
Ports	Cartridge
Display Resolution	320x192 (16 colors)