Atari XL

88
The Atari XL Handbook
12040 READ D:S(CHAN,P+l)=D
12050 NEXT P:RESTORE
12060 NEXT CHAN:P=-2:CHAN=O
12070 DATA 255,14,15:REM MAX DATA
12080 GOSUB OPTION
20000 RETURN
The program creates a display of the current
Frequency, Distortion and Volume parameters for
each of the four tone channels, and allows you to
change them to experiment with the SOUNI)
command.
To select one of the four channels, press the
SELECT key on the function keypad -a> symbol
indicates which channel is selected.
To alter one of the parameters on that channel, use
the OPTION key to make your choice - the heading
of the currently selected column will be
highlighted. Use the < and > keys to increase or
decrease the value displayed. The sound you hear is
changed with the changing parameters, and in this
way you can tailor the four channels to create the
noise you require and make a note of the
parameters. If you make a mess of things, pressing
the START key sets all the parameters back to
zero.
HOW THE PROGRAM WORKS
The program consists of a number of modules,
defined in lines 11000 to 11070.
The display is created by lines 10000 to 10080 and
lines 12000 to 12080 create an array which
contains the parameters for each channel (initially
zero) and the maximum value for each parameter.
The program selects Channel 0 and Frequency
options as a starting point by setting the variables