Atari 400 Hardware Manual

G. KEYBOARD AND SPEAKER
CONSOL (Console Switch Port)(D01F):
from the console switches and indicators.
code.)
This address reads or writes data
(Set to 8 by OS Vertical Blank
Not Used
(zero forced) D3
D2
D1 DO
Hex 08 should be written to this address before reading the switches.
Ones written will pull down on the switch line.
CONSOL Bit Assignment:
DO
D1
D2
D3
Game Select - 0 means switch pressed.
Game Start )
Option Select
Loudspeaker - should be held at 1
except when writing 0
momentarily. OS writes a
1
during vertical blank.
KBCODE (Keyboard Code)(D209): This address reads the Keyboard Code,
and
is usually read in response to a Keyboard Interrupt (IRQ and bits 6 or 7
of IRQST). See IRQEN for information on enabling keyboard interrupts. See
SKCTL bits 1 and 0 for key scan and debounce enable.
D7
D6
DS D4 D3
D7 Control Key
D6 Shift Key
D2 D1 DO
Read by OS into shadow CH when key is hit. The OS has a get character
function which converts the keycode to ATASCII (Atari ASCII).
III.15

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)