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furnace/doc/7-systems/ym2608.md

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Yamaha YM2608 (OPNA)

like YM2203, but with twice the FM channels, stereo, an ADPCM channel and built-in drums ("rhythm")!

it was one of the available sound chips for the NEC PC-88VA and PC-98 series of computers.

the YM2610 (OPNB) and YM2610B chips are very similar to this one, but the built-in drums have been replaced with 6 sample channels.

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 multiplier.
  • 18xx: toggle extended channel 3 mode.
    • 0 disables it and 1 enables it.
    • only in extended channel 3 chip.
  • 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.
  • 20xx: set SSG channel mode. xx may be one of the following:
    • 00: square
    • 01: noise
    • 02: square and noise
    • 03: nothing (apparently)
    • 04: envelope and square
    • 05: envelope and noise
    • 06: envelope and square and noise
    • 07: nothing
  • 21xx: set noise frequency. xx is a value between 00 and 1F.
  • 22xy: set envelope mode.
    • x sets the envelope shape, which may be one of the following:
      • 0: \___ decay
      • 4: /___ attack once
      • 8: \\\\ saw
      • 9: \___ decay
      • A: \/\/ inverse obelisco
      • B: \¯¯¯ decay once
      • C: //// inverse saw
      • D: /¯¯¯ attack
      • E: /\/\ obelisco
      • F: /___ attack once
    • if y is 1 then the envelope will affect this channel.
  • 23xx: set envelope period low byte.
  • 24xx: set envelope period high byte.
  • 25xx: slide envelope period up.
  • 26xx: slide envelope period down.
  • 29xy: enable SSG auto-envelope mode.
    • in this mode the envelope period is set to the channel's notes, multiplied by a fraction.
    • x is the numerator.
    • y is the denominator.
    • if x or y are 0 this will disable auto-envelope mode.
  • 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: +0
      • 1: +1
      • 2: +2
      • 3: +3
      • 4: -0
      • 5: -3
      • 6: -2
      • 7: -1
  • 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.