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 -- Richard Atkinson Software Engineer Tenison Technology EDA Ltd - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail firstname.lastname@example.org.
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