Atari 400 Hardware Manual

D. GRAPHICS CONTROL
DMACTL (Direct Memory Access Control)(D400): This address writes data
into the DMA Control Register.
Not
Used
D5 D4 D3
D2 D1
DO
D5 1 Enable instruction fetch DMA
D4 1 1
Line P/M resolution
D4 0 2
line P/H resolution
D3 = 1
Enable Player DMA
D2 = 1
Enable Missile DMA
D1 ,DO = 0
0
No Playfield DMA
= 0
1
Narrow Playfield DMA
(128 Color Clocks)
= 1
0
Standard Playfield
DMA
(160 Color Clocks)
= 1 1
Wide
Playfield DMA
(192 Color Clocks)
See GRACTL. OS
Shadow: SDMCTL (22F) default value hex 22
GRACTL (Graphics Control)(D01D): This address writes data to the
Graphic Control Register.
Not
Used
D2 = 1
D1 = 1
DO = 1
D2 D1 DO
Enable latches on TRIGO - TRIG3 inputs (latches are
cleared and TRIGO - TRIG3 act as normal inputs when this
control bit is zero).
Enable Player DMA to Player Graphics Registers.
Enable Missile DMA to Missile Graphics Registers.
DMA is enabled by setting bits in both DMACTL and GRACTL. Setting
DMACTL only will result in cycles being stolen but no display will be
generated.
III. 4

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)