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furnace/papers/doc/7-systems/ym2612.md
freq-mod 4d7c1c9e44
docs update (#519) 
* 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
2022-06-06 16:49:39 +02:00

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Yamaha YM2612

one of two chips that powered the Sega Genesis. It is a six-channel, four-operator FM synthesizer. Channel #6 can be turned into 8-bit PCM player.

For 0.6pre1, Furnace can now support advanced YM2612 features that Fractal sound driver adds: two software-mixed PCM channels (variable pitch, sample offsets, max 13.7 khz rate) and CSM - ch3 special mode feature that can be abused to produce rudimentary speech synthesis.

effects

  • 10xy: set LFO parameters.
    • x toggles the LFO.
    • y sets its speed.
  • 11xx: set feedback of channel.
  • 12xx: set operator 1 level.
  • 13xx: set operator 2 level.
  • 14xx: set operator 3 level.
  • 15xx: set operator 4 level.
  • 16xy: set multiplier of operator.
    • x is the operator (1-4).
    • y is the mutliplier.
  • 17xx: enable PCM channel.
    • this only works on channel 6.
  • 18xx: toggle extended channel 3 mode.
    • 0 disables it and 1 enables it.
    • only in extended channel 3 system.
  • 19xx: set attack of all operators.
  • 1Axx: set attack of operator 1.
  • 1Bxx: set attack of operator 2.
  • 1Cxx: set attack of operator 3.
  • 1Dxx: set attack of operator 4.
  • 30xx: enable envelope hard reset.
    • this works by inserting a quick release and tiny delay before a new note.
  • 50xy: set AM of operator.
    • x is the operator (1-4). a value of 0 means "all operators".
    • y determines whether AM is on.
  • 51xy set SL of operator.
    • x is the operator (1-4). a value of 0 means "all operators".
    • y is the value.
  • 52xy set RR of operator.
    • x is the operator (1-4). a value of 0 means "all operators".
    • y is the value.
  • 53xy set DT of operator.
    • x is the operator (1-4). a value of 0 means "all operators".
    • y is the value:
      • 0: -3
      • 1: -2
      • 2: -1
      • 3: 0
      • 4: 1
      • 5: 2
      • 6: 3
      • 7: -0
  • 54xy set RS of operator.
    • x is the operator (1-4). a value of 0 means "all operators".
    • y is the value.
  • 55xy set SSG-EG of operator.
    • x is the operator (1-4). a value of 0 means "all operators".
    • y is the value (0-8).
      • values between 0 and 7 set SSG-EG.
      • value 8 disables it.
  • 56xx: set DR of all operators.
  • 57xx: set DR of operator 1.
  • 58xx: set DR of operator 2.
  • 59xx: set DR of operator 3.
  • 5Axx: set DR of operator 4.
  • 5Bxx: set D2R/SR of all operators.
  • 5Cxx: set D2R/SR of operator 1.
  • 5Dxx: set D2R/SR of operator 2.
  • 5Exx: set D2R/SR of operator 3.
  • 5Fxx: set D2R/SR of operator 4.