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101 lines
3.6 KiB
Markdown
101 lines
3.6 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 stereo, the LFO and DT2 (coarse detune).
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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 NEC PC-88/PC-98 series of computers, the Fujitsu FM-7AV 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 from 1 to 4.
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- `y` is the multiplier.
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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 chip.
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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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- `0`: square
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- `1`: noise
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- `2`: square and noise
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- `3`: nothing (apparently)
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- `4`: envelope and square
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- `5`: envelope and noise
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- `6`: envelope and square and noise
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- `7`: 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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