furnace/papers/doc/7-systems/arcade.md

Arcade (Yamaha YM2151/PCM)

this chip combination was used in the Sega OutRun, X and Y arcade boards, and perhaps a few others. 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.

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.