68 lines
3.6 KiB
Markdown
68 lines
3.6 KiB
Markdown
# Yamaha YM2413/OPLL
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the YM2413, otherwise known as OPLL, is a cost-reduced FM synthesis sound chip, based on the Yamaha YM3812 (OPL2). thought OPL was downgraded enough? :p
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OPLL also spawned a few derivative chips, the best known of these is:
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- the famous Konami VRC7. used in the Japan-only video game Lagrange Point, it was **another** cost reduction on top of the OPLL! this time just 6 channels...
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- Yamaha YM2423, same chip as YM2413, just a different patch set
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- Yamaha YMF281, ditto
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# technical specifications
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the YM2413 is equipped with the following features:
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- 9 channels of 2 operator FM synthesis
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- A drum/percussion mode, replacing the last 3 voices with 5 rhythm channels, with drum mode tones hard-defined in the chip itself, like FM instruments. Only pitch might be altered.
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- Drum mode works like following: FM channel 7 is for Kick Drum, which is a normal FM channel but routed through mxier twice for 2x volume, like all drum sounds. FM channel 8 splits to Snare Drum and Hi-Hat. Snare Drum is the carrier and it works with a special 1 bit noise generator combined with a square wave, all possible by overriding phase-generator with some different synthesis method. Hi-Hat is the modulator and it works with the noise generator and also the special synthesis. CH9 splits to Top-Cymbal and Tom-Tom, Top-Cymbal is the carrier and only has the special synthesis, while Tom-Tom is basically a 1op wave.
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- Special syntheis mentioned already is: 5 square waves are gathered from 4x, 64x and 128x the pitch of channel 8 and 16x and 64x the pitch of channel 9 and they go through a process where 2 HH bits OR'd together, then 1 HH and 1 TC bit OR'd, then the two TC bits OR'd together, and those 3 results get XOR'd.
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- 1 user-definable patch (this patch can be changed throughout the course of the song)
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- 15 pre-defined patches which can all be used at the same time
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- Support for ADSR on both the modulator and the carrier
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- Sine and half-sine based FM synthesis
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- 9 octave note control
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- 4096 different frequencies for channels
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- 16 unique volume levels (NOTE: Volume 0 is NOT silent.)
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- Modulator and carrier key scaling
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- Built-in hardware vibrato support
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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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- **`16xy`**: set multiplier of operator.
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- `x` is the operator (1 or 2).
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- `y` is the multiplier.
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- **`18xx`**: toggle drums mode.
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- 0 disables it and 1 enables it.
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- only in drums 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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- **`50xy`**: set AM of operator.
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- `x` is the operator (1-2). 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 (1-2). 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 (1-2). a value of 0 means "all operators".
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- `y` is the value.
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- **`53xy`**: set VIB of operator.
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- `x` is the operator (1-2). a value of 0 means "all operators".
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- `y` determines whether VIB is on.
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- **`54xy`**: set KSL of operator.
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- `x` is the operator (1-2). a value of 0 means "all operators".
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- `y` is the value.
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- **`55xy`**: set EGT of operator.
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- `x` is the operator (1-2). a value of 0 means "all operators".
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- `y` determines whether EGT is on.
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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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- **`5Bxy`**: set KSR of operator.
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- `x` is the operator (1-2). a value of 0 means "all operators".
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- `y` determines whether KSR is on.
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