Atari 400 Field Service Manual

Table
1-2
I/O
Decoder
Select
Line
Enable
Binary
Decode
A12
All
Pin
6
6
S6
4
AIG
3
1
A59
2
AS
1
Active
Pin
Device
Selected
H
L L
L
L
L
YO-15
CTIA
H
L L
L
L
H
U Not
used
H
L
L
L
H
L
Y2-13
POKEY
H
L
L
L
H
H
Y3
-12
PIA
H
L
L
H
L
L 11
Not
Used
H
L
L
H
L
H
Y5-10
9
External
Select
Not
Used
Not
Used
Motherboard
Console
-
800
Read
descriptions
provided
in
Motherboard
Console
-
400, for
items
similar
in
both
the
i^00
and
SOO
Console
Motherboards-
The
following
paragraphs
describe
those
items
unique
to
the 800
Console
Motherboard.
The
800 Console
Motherboard
contains
the POKEY
chip (AiOl),
the PIA
chip (A102),
/^?n'!^f^'^^^
Key-In/Key-Out
analog
multiplexers
(2103
and
2104), the I/O
Decoder
-nn?
'
S^-^i^^c^ional
Data
Buffers
(2105
and
2106), the
controUer
jacks
(JlOl
thru
M.nJ'
5 Jj^n^Jj^^*""^
connector
jack
(3106), the left
and
right
Program
Cartridge
jacks
^ S^^^^^.^l^^L^^*"
^^^
connector
jaci'
(JlOl),
the ROM
Personality
connector
jack
U107J, and
the RAM
Memory
connector
jacks
(3102, J103,
and
JiQi^),
See Fieures 1-1
1
and 1-12.
*
Bi-directional
Data
Buffer
The
Bi-directional
Data
Buffers
(Z105
and Z106)
are
74LS243
quad
transceivers,
commonly
referred
to
as
tri-level
buffers.
Tri-level
refers
to
the
three
levels
that
can
occur
in
the
device;
the
first
level
pin
1
going
high
and pin
13
staying
low,
allows
data
to
tlow
through
the
data
buffer
in the
direction
of
the CPU;
the
second level,
pin 13
going
high
and
pin
1
staying
low,
allows
data to
flow
through
the
data
buffer
in
the
direction
of
the
POKEY
chip,
the
PIA
chip
and the
Personality
PCB;
the
third level,
with
pin
1
and
pin
13 both
staying
low,
creates
a high
impedance
condition
in the
data
buffers
and
allows
other
devices
to transmit
data
on the
Data
Bus
lines.
This
high
impedance
state
also
isolates
the
CPU
and the
RAM PCB
from
noise
generated from
a
device
using
the
Data
Bus
lines.
ATARI
Home
Computers
1-U

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)