Atari 400 Hardware Manual

PENH (Light Pen Horizontal Color Clock Position)(D40C): This address
reads the Horizontal Light Pen Register (based on the horizontal color clock
counter in hardware). The values range from 0 to decimal 227. Wraparound
occurs when the pen if near the right edge of a standard-width screen. PENH
and PENV are modified when any of the joystick trigger lines is pulled low.
D7 D6 D5 D4 D3 D2 D1 DO
H7 H6
H5
H4 H3 H2 H1 HO
OS SHADOW: LPENH (hex 234)
PENV (Light Pen Vertical TV Line Position)(D40D): This address reads
the Vertical Light Pen Register (8 most significant bits, same as VCOUNT).
D6
D5
D4
D3
LP8 7
6
5 4
D2
D1
3
2
DO
1 0 LPO not read. Two line
resolution supplied.
OS SHADOW: LPENV (hex 235)
Front Panel (Controller) Jacks as I/O Parts:
PIA (6520/6820)
Out: TTL levels, 1 load
In : TTL levels, 1 load
Port A Circuit (typical):
~-----f
- . ..:.L. • 001
6520
(A) I
Port
220
T
Port B Circuit
6520
.001
"Trigger" Port Circuit (typical):
CTIA Trig 220
1\/V\J.-~---1
l .001
T
III. 23
Jack
Jack
Jack

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)