Atari 400 Field Service Manual

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Figure 1-7.
PIA Pin
Assignments
Key-In
Key-Out
Integrated
Circuits
These two
*051 (ZlOl
and Z102)
integrated
circuits
are used to
scan the Keyboard
for
input
data on
the
'^00
and 800
Computer Consoles.
The *051
integrated
circuits
are
analog
multiplexers
controlled by
the input lines A, B,
C and X.
Memory
Map
Decoder
The
Memory
Map
Decoder integrated
circuit (Z103)
on the 400/800
Motherboard
is
a
one-of-ten
decoder.
Four
input lines
(pins
12, 13, and U,
and 15)
determine which
output line
is
selected.
The 400/800
Computer
Console uses only
three
of the input
lines
(pins
13, 14,
and
15 and pin 12
being
grounded) for
a total of eight
selected
output
lines
(SO -S7),
Refer to Table
l-I for
the line
selected for
each input
combination.
ATARI
Home
Computers
1-12

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)