Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!evax!cs4344af
From: cs4344af@evax.arl.utexas.edu (Fuzzy Fox)
Newsgroups: comp.sys.cbm
Subject: Re: random numbers in ML
Message-ID: <1990Dec3.072647.28822@evax.arl.utexas.edu>
Date: 3 Dec 90 07:26:47 GMT
References: <6389@minyos.xx.rmit.oz.au>
Distribution: comp
Organization: Computer Science Engineering Univ. of Texas at Arlington
Lines: 27

In article <6389@minyos.xx.rmit.oz.au> s887212@minyos.xx.rmit.oz.au (Stephen Riehm [Romulis]) writes:
>According to some books I have it IS POSSIBLE to use the
>oscillator for the third voice...

While I don't have any specific code to show you, you should be able to
generate random numbers with the following setup...

Set the frequency on Voice 3 of the SID to a very high value (like
$FFFF).  Then turn on Voice 3 using the Noise waveform.  If you don't
want to hear the voice, either turn on the "silence voice 3" bit, or set
the volume to zero.  However, the oscillator will still oscillate
randomly, and you should be able to pick up its waveform samplings by
reading the oscillator output at $D41B.

Here's some untested code written from the above:

INIT:	LDA	#$FF
	STA	$D40E
	STA	$D40F
	LDA	#$80
	STA	$D412
	LDA	#$8F	; Volume = 15, but no voice 3 output
	STA	$D418
	RTS

RAND:	LDA	$D41B
	RTS		; Random number returned in A.