Difference between revisions of "PSG"
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[[Category:PSG]] | [[Category:PSG]] | ||
− | + | Various PSGs were used in the Intellivision from the AY-3-891x family, including the AY-3-8914, AY-3-8916 and AY-3-8917. | |
+ | |||
+ | The text below is just a bunch of notes for now, to be organized into something meaningful eventually. | ||
+ | |||
+ | Clock speed is 3579545/16 (223721.5625 Hz) | ||
− | + | ==Registers== | |
+ | |||
+ | |||
+ | ==Channels== | ||
+ | square wave output optionally modified by the envelope generator and/or the noise generator | ||
+ | Volume (0-15) | ||
+ | Period (1-4096) | ||
+ | Tone Enabled | ||
+ | Envelope Enabled | ||
+ | Noise Enabled | ||
+ | |||
+ | 16 volume levels, independent to each channel | ||
+ | |||
+ | if (channel.toneEnabled || channel.noiseEnabled) { | ||
+ | if ( | ||
+ | channel | ||
+ | } | ||
+ | else | ||
+ | channel.output = ; | ||
+ | channel0.output = | ||
+ | (((channel0.toneDisabled | channel0.tone) & | ||
+ | (channel0.noiseDisabled | noise)) | ||
+ | ? (channel0.envelope ? envelopeVolume | ||
+ | : channel0.volume) : 0); | ||
+ | |||
+ | ==Envelope Generator== | ||
+ | Period | ||
+ | Atak, Cont, Hold, Altr | ||
+ | Volume (0-15) | ||
+ | 16-bit period value multiplied by two, from 2 PSG clock cycles to $20000 | ||
+ | |||
+ | |||
+ | ==Noise Generator== | ||
+ | The random noise generator adheres to the following formula once per PSG clock cycle. | ||
+ | |||
+ | noise = (noise >> 1) ^ ((noise & 1) ? 0x14000 : 0); | ||
+ | |||
+ | The lowest bit resulting from this calculation is used to add noise to any channel with noise enabled. |
Revision as of 23:57, 19 January 2005
Various PSGs were used in the Intellivision from the AY-3-891x family, including the AY-3-8914, AY-3-8916 and AY-3-8917.
The text below is just a bunch of notes for now, to be organized into something meaningful eventually.
Clock speed is 3579545/16 (223721.5625 Hz)
Registers
Channels
square wave output optionally modified by the envelope generator and/or the noise generator Volume (0-15) Period (1-4096) Tone Enabled Envelope Enabled Noise Enabled
16 volume levels, independent to each channel
if (channel.toneEnabled || channel.noiseEnabled) { if ( channel } else channel.output = ; channel0.output = (((channel0.toneDisabled | channel0.tone) & (channel0.noiseDisabled | noise)) ? (channel0.envelope ? envelopeVolume : channel0.volume) : 0);
Envelope Generator
Period Atak, Cont, Hold, Altr Volume (0-15) 16-bit period value multiplied by two, from 2 PSG clock cycles to $20000
Noise Generator
The random noise generator adheres to the following formula once per PSG clock cycle.
noise = (noise >> 1) ^ ((noise & 1) ? 0x14000 : 0);
The lowest bit resulting from this calculation is used to add noise to any channel with noise enabled.