Atari 800

SEROUT (Serial Output Data)(D20D): This address writes to the 8 bit
parallel holding register that is transferred to the output serial shift
register when a full byte of serial output data has been transmitted. This
address is usually written in response to a serial data out interrupt (IRQ
and bit 4 of IRQST).
D7
D6 DS
D4
D3 D2 D1 DO
I. CONTROLLER PORTS (front of console)
PORTA (Port A)(D300): This address reads or writes data from Player 0
and
Player 1 controller jacks if bit 2 of PACTL is true. This address
writes to the direction control register if bit 2 of PACTL is zero. I/O for
both ports (A and B) goes through a 6520/6820
Data Register-Addressed if bit 2 of PACTL is 1.
Joystick Operation
I I I I
D7 D6
DS I D4 I D3 I D2 I D1 DO
Right
Left
Back Right Back
Fwd.
Left Fwd.
D7
I
I D7 :
Stick1
(Jack 2)
StickO
(Jack 1)
Paddle Operation
I I I
D6
I DS I D4
I
D3
D2
I D1 I DO
L PTRIG2
I
L PTRIGO
PTRIG3
PTRIG1
K b
ey oar
d c t 11 on ro 0
t'
er Jpera 1on
I I I I
I
I
DO I D6 I DS I D4 I D3 I D2 I
D1
I
I
L._
._____Top
Row
2nd Row
Jack
3rd Row
4th Row
)
Top
2nd
3rd
4rd
2
O=Switch pressed
1=Switch not pressed
O=Switch
1=Switch
Row)
Row
Row
Row
pressed
not pressed
Jack 1
Control Re ister-Addressed if bit 2 of PBCTL is 0
I I I I I I
Each bit corresponds to a jack pin
O=input
1=output
OS SHADOWS: STICKO (hex 278), STICK1 (279), PTRIG0-3 (27C-27F
III.19