Atari 400 Hardware Manual

Serial Mode Control: There are 6 useful modes (of the possible 8)
controlled by bits 4, 5, and 6 of SKCTL. These are described on the next
page.
Note that two tone output (bit 3 of SKCTL) may be used in any of these
modes except for the bottom pair. This is because channel 2 is used to set
the output transmit rate and is therefore not available for one of the two
tones.
Note that the output clock rate is identical to the output data rate.
Serial Mode Control (see also register description SKCTL):
Force Break
ID7ID6 D5ID4ID3ID2ID1IDO I
SKCTL REGISTER
I I I
I I I
Pot scan and keyboard CTRL
I I I
I I I
Two Tone Control
I I I
I I I
Mode
Control Bits
I I I
I I
I I lOut I
ID6 D5ID41Ratel
I I I I I
Out I
Clock I
IO IO IO lext I ext
I I I I I
In
I
Rate!
I
ext
I
I
chan
4
Bi-Dir
Clock
ext
input
ext
input
A=asynchronous
Comments
!Trans. & Receive rates set by
!external clock. Also internal
!clock phase reset to zero.
!Trans. rate set by external
!clock. Receive asynch. (ch. 4)
I(CH3
and CH4)
chan
4
output
!Trans. & Receive rates set by
!Chan. 4. Chan. 4 output on
!Directional clock line.
I
Bi- l
chan
4
ext
input
ext
input
input
!Not Useful
I
!Trans. Rate Set by Chan. 4
!Receive Rate set by External
I Clock.
INot Useful
I
I
Chan Chan Chan !Trans. rate set by chan. 2 I
2 2 4
!Recieve rate set by chan. 4 Chan.l
Chan
2
Chan
4
A
Output 14 out on Bi-Direct. Clock line. I
Input
not
used
!Trans. Rate set by Chan.
lceive async. (chan 3&4)
!Clock not used (Tri-state
ltion)
2. Re-I
Bi-Dir. I
condi- I
I
Two tone (bit3) not useable in these modes
II. 27

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)