Commodore Plus 4 - Page 402

390 Using Peripheral Devices
3. Send data to the channel with BSOUT ($FFD2).
4. Check the status byte for errors.
5. When all data has been sent, return the input and output channels to default
(keyboard and screen) by calling CLRCH ($FFCC) and close the file, or call
CLALL ($FFE7) to close all the files and reset the input and output channels.
Get
To receive information from the RS232 port, the port must have been opened.
The following outlines the operations required:
1. Load .X with the logical file number of the input file. Designate it as the input
channel by calling CHKIN ($FFC6).
2. Check the status byte for errors.
3. Receive data from the channel with BASIN ($FFCF).
4. Check the status byte for errors.
5. When all data received, return the input and output channels to default
(keyboard and screen) by calling CLRCH ($FFCC) and close the file, or call
CLALL ($FFE7) to close all the files and reset the input and output channels.
The Joystick Ports
The Commodore Plus/4 is equipped with two joystick ports located on the rear of
the computer. The Commodore T-1341 joystick is compatible with the Plus/4.
Older Commodore joysticks are not compatible. The ports are numbered 1 and 2.
Fundamentally, a Commodore joystick consists of five switches, each of which
is assigned to one of the following: up, down, right, left, and fire. In machine
language, the programmer must examine a bit reflecting the status of each switch
to read joystick input. In BASIC, however, the JOY function can be used to
determine the joystick status.
Using Joysticks with BASIC
The JOY function has the following syntax:
JOY (port)
where port is the joystick port to use (either 1 or 2). The function returns a