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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. `xx` may be one of the following:
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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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