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furnace/doc/7-systems/sid2.md
LTVA1 8f198d3459 SID3 docs, part 1... 
also update SID2/C64 docs with cutoff/suty slide effects
2024-08-17 19:57:33 +03:00

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SID2

a fictional chip created by LTVA. the idea is to fix SID flaws and add more features, but not too much.

unlike SID, it has per-channel volume control, better ADSR envelope which doesn't have bugs, more waveform mixing modes and the ability to play tonal noise waves.

each channel now has its own independent filter. filter cutoff and resonance ranges were extended, as well as the frequency - finally the chip can hit B-7 note with default clock speed!

effects

  • 10xx: change wave. lower 4 bits specify the wave:
    • bit 0: triangle
    • bit 1: saw
    • bit 2: pulse
    • bit 3: noise
  • 11xx: set resonance. xx may be a value between 00 and FF.
  • 12xx: set filter mode. the following values are accepted:
    • 00: filter off
    • 01: low pass
    • 02: band pass
    • 03: low+band pass
    • 04: high pass
    • 05: band reject/stop/notch
    • 06: high+band pass
    • 07: all pass
  • 13xx: disable envelope reset for this channel.
  • 14xy: reset cutoff:
    • if x is not 0: on new note
    • if y is not 0: now
    • this effect is not necessary if the instrument's cutoff macro is absolute.
  • 15xy: reset duty cycle:
    • if x is not 0: on new note
    • if y is not 0: now
    • this effect is not necessary if the instrument's duty macro is absolute.
  • 16xy: change additional parameters.
    • x may be one of the following:
      • 0: attack (y from 0 to F)
      • 1: decay (y from 0 to F)
      • 2: sustain (y from 0 to F)
      • 3: release (y from 0 to F)
      • 4: ring modulation (y is 0 or 1)
      • 5: oscillator sync (y is 0 or 1)
      • 6: filter mode (y is 0 to 7)
      • 7: waveform mix mode (y is 0 to 3)
      • 8: noise mode (y is 0 to 3)
      • 9: phase reset (y is a discarded parameter and does not matter)
      • A: envelope key on/key off (y is 0 (trigger envelope release) or 1 (restart envelope again))
      • B: filter on/off (y is 0 (disable filter) or 1 (enable filter))
  • 17xx: pulse width slide up. xx is speed. 1700 stops the slide.
  • 18xx: pulse width slide down. xx is speed. 1800 stops the slide.
  • 19xx: filter cutoff slide up. xx is speed. 1900 stops the slide.
  • 1Axx: filter cutoff slide down. xx is speed. 1A00 stops the slide.
  • 3xxx: set duty cycle. xxx range is 000 to FFF.
  • 4xxx: set cutoff. xxx range is 000 to FFF.

info

this chip uses the SID2 instrument editor.