Atari 400 Hardware Manual

DLISTL and DLISTH should be changed only during vertical blank or with
DMA disabled. Otherwise, the screen may roll. Bit 7 of NMIEN must be set
in order to receive display list interrupts.
CHBASE (Character Address Base Register)(D409): This address writes
data into the Character Address Base Register. The data specifies the most
significant byte (~SB) of the address of the desired character set (see
section II). Note that the last 1 or 2 bits are assumed to be 0.
40 Character Modes
ID7
\
ID6
IDS~4
jD3
ID2 I
)
*
CHBASE
(1s
ll3]f)ll
110 t9
114
8
I
7
I
6
I
s
4
3
7
l:::J::: I
""""
Base Address Char Name Line Counter
20
Character Modes
!D7
ID6 IDS ID4
-.......r
ID3
ID2
ID1
J *
CHBASE
(1s
114
113
1@1
110
9
ls
I
7
I
6:::S
4 3
:k2
1
X2iJ
Base Address Char Name
Line Counter
OS SHADOW: CHBAS (2F4)
PMBASE (Player-Missile Address Base Register)(D407): This address
writes data into the Player-Missile Address Base Register. The data
specifies the MSB r,f the address of the player and missile DMA data (see
section II).
One Line Resolution
ID7
ID6
IDS ID4
ID3
I
not
used
PMBASE
-
';:1
~s
114
1~112
11c~'"7
6
I
s
I
42::3
I
2
I
1
I
0
]
)
Base Address Player-Missile
Player-Missile Scan
Select
Counters
Two Line Resolution
~D7
ID6
IDS-:84
ID3
ID2
I *
PMBASE
'
Qs
113:::82
110~
}
114
Ill
6 s
I
4
I
3
I
2
I
1
I
0
.........,...
Base Address
Player-Missile Player-Missile Scan
Select
Counter
* Not Used
III. 6

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)