Atari 400 Hardware Manual

SKSTAT (Serial Port-Keyboard Status)(D20F): This address reads the
status register giving information about the serial port and keyboard.
D7
D6
DS D4 D3
D2
D1 l DO I
D7 = 0
Serial Data Input Frame Error
D6
0 = Serial Data Input Over-run
DS 0
Keyboard Over-run
D4 0
Direct from Serial Input Port
D3 0 Shift Key Depressed
D2 0
Last Key is Still Depressed
(Bits are normally true
and provide the following
information when zero.)
Latches
must be
reset = 1
(SKRES)
(DS and D6 are set to
zero when new data
and same bit of IRQST
is zero)
D1 0 = Serial Input Shift Register Busy
DO = 1
Not Used
(Logic True)
SKRES (Reset aboYe Status Register) (D20A): This write address resets
bits 7, 6, and 5 of the Serial Port-Keyboard Status Register to 1.
not used
SERIN (Serial Input Data)(D20D): This address reads the 8 bit parallel
holding register that is loaded when a full byte of serial input data has
been received. This adJress is usually read in response to a serial data in
interrupt (IRQ and bit 5 of IRQST). Also see IRQEN.
D7
D6
DS
D4 D3 D2 D1 DO
Serial I/O Port
Connector
Pinout:
2
4
6
8 10 12
0 0
0 0 0 0
0 0 0
0 0
3
5 7
9
11
1. Clock In
2.
Clock Out
3. Data In to
c.Jmputer
4.
GND
s.
Data Out
of Computer
6.
GND
7.
Command
8.
Motor Control
9. Proceed
1 o.
+5 I
Ready
11.
Audio In
12. +12
13. Interrupt
See
serial port description in OS manual for more details.
III. 18

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)