furnace/doc/7-systems/genesis.md

# Sega Genesis/Mega Drive

a video game console that showed itself as the first true rival to Nintendo's video game market near-monopoly in the US during the '80's.

this console is powered by two sound chips: the [Yamaha YM2612](ym2612.md) and [a derivative of the SN76489](sms.md).

# effects

- **`10xy`**: set LFO parameters.
  - `x` toggles the LFO.
  - `y` sets its speed.
- **`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 multiplier.
- **`17xx`**: enable PCM channel.
  - this only works on channel 6.
  - **this effect is there for compatibility reasons** - it is otherwise recommended to use Sample type instruments (which automatically enable PCM mode when used).
- **`18xx`**: toggle extended channel 3 mode.
  - 0 disables it and 1 enables it.
  - only in extended channel 3 chip.
- **`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.
- **`20xy`**: set PSG noise mode.
  - `x` controls whether to inherit frequency from PSG channel 3.
    - 0: use one of 3 preset frequencies (C: A-2; C#: A-3; D: A-4).
    - 1: use frequency of PSG channel 3.
  - `y` controls whether to select noise or thin pulse.
    - 0: thin pulse.
    - 1: noise.