furnace/doc/7-systems/ym2612.md

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, that via software mixing, thanks to Z80 sound CPU, can play more than one channel of straight-shot samples at once. as of Furnace 0.6pre5, Furnace offers DualPCM, a Z80 driver that splits channel 6 into two individual PCM channels with variable pitch. using the console's Z80 processor, these are mixed together in software and streamed to channel 6 in PCM mode with a mix rate of 13750 Hz. because this generates a stream of data, exported VGM files will be very large.

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.
• 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 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.
• 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.