furnace/papers/doc/7-systems/ym2151.md
2022-03-22 00:58:07 -05:00

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# Yamaha YM2151
the sound chip powering several arcade boards and the Sharp X1/X68000.
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.
# 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.