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* docs update mentions of fractal, new chips documentation, and other minor stuff * add a link to the Fractal repo as suggested by @breakthetargets * better wording, less typos
59 lines
2.4 KiB
Markdown
59 lines
2.4 KiB
Markdown
# Commodore 64
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a home computer with a synthesizer-grade sound chip of which people took decades to master. Three oscillators with four selectable waveforms, ring modulation, oscillator sync, multimode filter, ADSR envelope...
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very popular in Europe and mostly due to the demoscene, which stretched the machine's limbs to no end.
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Two revisions do exist - 6581 (original chip) and 8580 (improved version with working waveform mixing and somewhat more consistent filter curves)
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# effects
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- `10xx`: change wave. the following values are accepted:
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- `00`: nothing
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- `01`: triangle
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- `02`: saw
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- `03`: triangle and saw
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- `04`: pulse
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- `05`: pulse and triangle
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- `06`: pulse and saw
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- `07`: pulse and triangle and saw
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- `08`: noise
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- `11xx`: set coarse cutoff. `xx` may be a value between 00 to 64.
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- **this effect only exists for compatibility reasons, and its use is discouraged.**
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- use effect `4xxx` instead.
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- `12xx`: set coarse duty cycle. `xx` may be a value between 00 to 64.
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- **this effect only exists for compatibility reasons, and its use is discouraged.**
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- use effect `3xxx` instead.
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- `13xx`: set resonance. `xx` may be a value between 00 and 0F.
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- `14xx`: set filter mode. the following values are accepted:
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- `00`: filter off
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- `01`: low pass
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- `02`: band pass
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- `03`: low+band pass
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- `04`: high pass
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- `05`: band reject/stop/notch
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- `06`: high+band pass
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- `07`: all pass
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- `15xx`: set envelope reset time.
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- this is the amount of ticks the channel turns off before a note occurs in order to reset the envelope safely.
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- if `xx` is 0 or higher than the song speed, the envelope will not reset.
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- `1Axx`: disable envelope reset for this channel.
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- `1Bxy`: reset cutoff:
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- if `x` is not 0: on new note
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- if `y` is not 0: now
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- this effect is not necessary if the instrument's cutoff macro is absolute.
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- `1Cxy`: reset duty cycle:
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- if `x` is not 0: on new note
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- if `y` is not 0: now
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- this effect is not necessary if the instrument's duty macro is absolute.
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- `1Exy`: change additional parameters.
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- `x` may be one of the following:
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- `0`: attack (`y` from 0 to F)
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- `1`: decay (`y` from 0 to F)
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- `2`: sustain (`y` from 0 to F)
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- `3`: release (`y` from 0 to F)
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- `4`: ring modulation (`y` is 0 or 1)
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- `5`: oscillator sync (`y` is 0 or 1)
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- `6`: disable channel 3 (`y` is 0 or 1)
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- `3xxx`: set duty cycle. `xxx` range is 000-FFF
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- `4xxx`: set cutoff. `xxx` range is 000-7FF.
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