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101 lines
3.4 KiB
Markdown
101 lines
3.4 KiB
Markdown
# Yamaha YM2203 (OPN)
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a cost-reduced version of the YM2151 (OPM).
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it only has 3 FM channels instead of 8 and removes the LFO.
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however it does contain an AY/SSG part which provides 3 channels of square wave with noise and envelope.
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this chip was used in the PC-88/PC-98 series of computers, and in some arcade boards.
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several variants of this chip were released as well, with more features.
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# effects
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- `11xx`: set feedback of channel.
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- `12xx`: set operator 1 level.
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- `13xx`: set operator 2 level.
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- `14xx`: set operator 3 level.
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- `15xx`: set operator 4 level.
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- `16xy`: set multiplier of operator.
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- `x` is the operator (1-4).
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- `y` is the mutliplier.
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- `18xx`: toggle extended channel 3 mode.
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- 0 disables it and 1 enables it.
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- only in extended channel 3 system.
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- `19xx`: set attack of all operators.
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- `1Axx`: set attack of operator 1.
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- `1Bxx`: set attack of operator 2.
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- `1Cxx`: set attack of operator 3.
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- `1Dxx`: set attack of operator 4.
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- `20xx`: set SSG channel mode. `xx` may be one of the following:
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- `00`: square
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- `01`: noise
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- `02`: square and noise
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- `03`: nothing (apparently)
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- `04`: envelope and square
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- `05`: envelope and noise
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- `06`: envelope and square and noise
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- `07`: nothing
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- `21xx`: set noise frequency. `xx` is a value between 00 and 1F.
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- `22xy`: set envelope mode.
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- `x` sets the envelope shape, which may be one of the following:
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- `0: \___` decay
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- `4: /___` attack once
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- `8: \\\\` saw
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- `9: \___` decay
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- `A: \/\/` inverse obelisco
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- `B: \¯¯¯` decay once
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- `C: ////` inverse saw
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- `D: /¯¯¯` attack
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- `E: /\/\` obelisco
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- `F: /___` attack once
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- if `y` is 1 then the envelope will affect this channel.
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- `23xx`: set envelope period low byte.
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- `24xx`: set envelope period high byte.
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- `25xx`: slide envelope period up.
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- `26xx`: slide envelope period down.
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- `29xy`: enable SSG auto-envelope mode.
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- in this mode the envelope period is set to the channel's notes, multiplied by a fraction.
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- `x` is the numerator.
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- `y` is the denominator.
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- if `x` or `y` are 0 this will disable auto-envelope mode.
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- `30xx`: enable envelope hard reset.
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- this works by inserting a quick release and tiny delay before a new note.
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- `50xy`: set AM of operator.
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- `x` is the operator (1-4). a value of 0 means "all operators".
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- `y` determines whether AM is on.
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- `51xy` set SL of operator.
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- `x` is the operator (1-4). a value of 0 means "all operators".
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- `y` is the value.
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- `52xy` set RR of operator.
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- `x` is the operator (1-4). a value of 0 means "all operators".
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- `y` is the value.
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- `53xy` set DT of operator.
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- `x` is the operator (1-4). a value of 0 means "all operators".
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- `y` is the value:
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- 0: +0
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- 1: +1
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- 2: +2
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- 3: +3
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- 4: -0
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- 5: -3
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- 6: -2
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- 7: -1
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- `54xy` set RS of operator.
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- `x` is the operator (1-4). a value of 0 means "all operators".
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- `y` is the value.
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- `55xy` set SSG-EG of operator.
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- `x` is the operator (1-4). a value of 0 means "all operators".
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- `y` is the value (0-8).
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- values between 0 and 7 set SSG-EG.
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- value 8 disables it.
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- `56xx`: set DR of all operators.
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- `57xx`: set DR of operator 1.
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- `58xx`: set DR of operator 2.
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- `59xx`: set DR of operator 3.
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- `5Axx`: set DR of operator 4.
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- `5Bxx`: set D2R/SR of all operators.
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- `5Cxx`: set D2R/SR of operator 1.
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- `5Dxx`: set D2R/SR of operator 2.
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- `5Exx`: set D2R/SR of operator 3.
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- `5Fxx`: set D2R/SR of operator 4.
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