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70 lines
2.6 KiB
Markdown
70 lines
2.6 KiB
Markdown
# Yamaha YM2151
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the sound chip powering several arcade boards, the Sharp X1/X68000 and the Commander X16. eight 4-op FM channels, with overpowered LFO and almost unused noise generator.
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it also was present on several pinball machines and synthesizers of the era, and later surpassed by the YM2414 (OPZ) present in the world-famous TX81Z.
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in most arcade boards the chip was used in combination with a PCM chip, like [SegaPCM](segapcm.md) or [OKI's line of ADPCM chips](oki.md).
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# effects
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- `10xx`: **set noise frequency of channel 8 operator 4.** `00` disables noise while `01` to `20` enables it.
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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 multiplier.
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- `17xx`: **set LFO speed.**
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- `18xx`: **set LFO waveform.**
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- `00`: saw
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- `01`: square
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- `02`: triangle
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- `03`: noise
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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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- `1Exx`: **set LFO AM depth.**
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- `1Fxx`: **set LFO PM depth.**
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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 DT2 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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- `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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