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Useful data base variables and OS equates
CONSOL
AUDF1
AUDC1
AUDF2
AUDC2
AUDF3
AUDC3
AUDF4
AUDC4
AUDCTL
STIMER
$D01F
$D200
$D201
$D202
$D203
$D204
$D205
$D206
$D207
$D208
$D209
(53279):
(53760):
(53761):
(53762):
(53763):
(53764):
(53765):
(53766):
(53767):
(53768):
(53769):
bit 3 controls console speaker
Audio frequency 1
audio control 1
Audio frequency 2
audio control 2
Audio frequency 3
audio control 3
Audio frequency 4
audio control 4
general audio control
audio timer reset
Go to chapter 16
Go to chapter 18
CHAPTER 18
The joystick ports
The joystick ports are the I/O ports of the PIA chip. This means that they are bidirectional,
capable of output as well as input. The joystick ports are usually set up for input. To read
them, simply read the port registers. PORTA [$D300 (53016)] will read joystick ports 1 and 2.
PORTB [$D301 (54017)] will read joystick ports 3 and 4. Joystick ports 3 and 4 are used for
memory control on the XL/XE models and don’t have external connectors.
Each bit of each port can be configured independently for input or output. To reconfigure a
port, the port control registers, PACTL and PBCTL [$D302 (54018) and $D303 (54019)], are
used. The port control registers also control some lines on the serial I/O connector.
The port control registers
PACTL
or
PBCTL
7 6 5 4 3 2 1 0
−−−−−−−−−−−−−−−−−
|n 0 1 1 n n 0 n|
−−−−−−−−−−−−−−−−−
1 6 3 1 8 4 2 1
2 4 2 6
8
bits
PACTL
93