Re: Playing samples on both new and old SIDs

From: Richard Atkinson (
Date: 2000-07-27 13:34:18

On Thu, 27 Jul 2000, Marko Mäkelä wrote:

> > I wrote a routine to play samples on the 4 bit volume control with all
> > oscillators off and this worked well (even with the display on because
> > there are no badlines)
> I've done that too.  I played some .wav files from my Linux box that was
> connected to the VIC-20's user port.  And Adam Bergström has written a SID
> emulator for the VIC-20.  But that's nothing new; similar programs have
> been written and used on the C16.

Speaking of which, I haven't looked at the VIC-20's sound output (I
suspect each oscillator produces square waves, except the noise which is
one bit of the polynomial) but I have done some fairly comprehensive
studies of the C16 sound output. The waveform coming out of the SND pin is
digital, pulse-width modulated. I think the width is expressed in master
clock cycles (14.3 or 17.7 MHz) and the period of the cycle depends on
whether both channels are on or just one. The volume bits set the length
of the pulse and if only one channel is on the period is doubled so that
the DC voltage level is halved. I have yet to make a quantitative table of
the mark-space ratios with different register settings but that's
definitely the next thing to do.


Richard Atkinson
Software Engineer
Tenison Technology EDA Ltd

This message was sent through the cbm-hackers mailing list.
To unsubscribe: echo unsubscribe | mail

Archive generated by hypermail 2.1.1.