Atari 800

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