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# Arcade (Yamaha YM2151/PCM)
this chip combination was used in the Sega OutRun, X and Y arcade boards, and perhaps a few others.
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the actual PCM chip had 16 channels, but the number has been cut to 5 in DefleMask for seemingly arbitrary reasons. a system with all 16 channels may be coming soon.
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# effects
- `10xx` : set noise frequency of channel 8 operator 4. 00 disables noise while 01 to 20 enables it.
- `11xx` : set feedback of channel.
- `12xx` : set operator 1 level.
- `13xx` : set operator 2 level.
- `14xx` : set operator 3 level.
- `15xx` : set operator 4 level.
- `16xy` : set multiplier of operator.
- `x` is the operator (1-4).
- `y` is the mutliplier.
- `17xx` : set LFO speed.
- `18xx` : set LFO waveform. `xx` may be one of the following:
- `00` : saw
- `01` : square
- `02` : triangle
- `03` : noise
- `19xx` : set attack of all operators.
- `1Axx` : set attack of operator 1.
- `1Bxx` : set attack of operator 2.
- `1Cxx` : set attack of operator 3.
- `1Dxx` : set attack of operator 4.
- `20xx` : set PCM frequency.
- only works on the PCM channels.
- `xx` is a 256th fraction of 31250Hz.
