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46 lines
No EOL
1.8 KiB
Markdown
46 lines
No EOL
1.8 KiB
Markdown
# Microchip AY8930
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a backwards-compatible successor to the AY-3-8910, with increased volume resolution, duty cycle control, three envelopes and highly configurable noise generator.
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sadly, this soundchip has only ever observed minimal success, and has remained rather obscure since.
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it is known for being used in the Covox Sound Master, which didn't sell well either.
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while emulation of this chip is mostly complete, the additional noise setup registers are not emulated (yet). whether it ever has been emulated at some point in a now-abandoned tracker with similar goal as Furnace is unknown.
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# effects
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- `12xx`: set channel duty cycle. `xx` is a value between 00 and 08.
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- `20xx`: set channel mode. `xx` may be one of the following:
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- `00`: square
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- `01`: noise
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- `02`: square and noise
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- `03`: envelope
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- `04`: envelope and square
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- `05`: envelope and noise
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- `06`: envelope and square and noise
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- `07`: nothing
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- `21xx`: set noise frequency. `xx` is a value between 00 and FF.
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- `22xy`: set envelope mode.
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- `x` sets the envelope shape, which may be one of the following:
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- `0: \___` decay
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- `4: /___` attack once
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- `8: \\\\` saw
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- `9: \___` decay
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- `A: \/\/` inverse obelisco
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- `B: \¯¯¯` decay once
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- `C: ////` inverse saw
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- `D: /¯¯¯` attack
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- `E: /\/\` obelisco
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- `F: /___` attack once
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- if `y` is 1 then the envelope will affect this channel.
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- `23xx`: set envelope period low byte.
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- `24xx`: set envelope period high byte.
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- `25xx`: slide envelope period up.
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- `26xx`: slide envelope period down.
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- `27xx`: set noise AND mask.
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- `28xx`: set noise OR mask.
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- `29xy`: enable auto-envelope mode.
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- in this mode the envelope period is set to the channel's notes, multiplied by a fraction.
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- `x` is the numerator.
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- `y` is the denominator.
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- if `x` or `y` are 0 this will disable auto-envelope mode. |