Yamaha YM3812

The Yamaha YM3812, also known as OPL2 (OPL is an acronym for FM Operator Type -L), is a sound chip manufactured by the Yamaha Corporation or integrated circuit. He found a wide use in sound cards for the IBM PC, such as AdLib and Sound Blaster.

Description

The YM3812 sound chip ( OPL2 ) is backwards compatible with the YM3526 ( OPL1 ) that was used in sound cards for MSX computers. Compared to its predecessor, only three new waveforms have been added. An extended version of the OPL2, the OPL3 aka YMF262, found his use from the Sound Blaster Pro 2 and further dissemination in their successors, such as the Sound Blaster 16 It supports stereo sound and can be used in different modes up to six voices produce with four operators, also were still once four waveforms added. Furthermore, there is the OPL4, it is backward compatible with OPL3 and OPL2, but was expanded to include wavetable synthesis.

The circuit had 244 different registers for writing. You can spend nine -part sound, each voice ( " channel") generated by two oscillators. Each oscillator can produce sine waves, which can be transformed into three other wave forms - the negative portion of the vibration can be muted or inverted and pseudo - sawtooth wave ( sine wave ¼ up with silent regions therebetween ) could be produced. This unusual way to generate waveforms give the YM3812 a characteristic sound. Each of the wave generators has its own ADSR envelope. Its main function to generate tones, the frequency-modulated synthesis - wherein for each channel one of the two oscillators is modulated to the other.

Overview of the registers of a channel

For the entire channel

  • Main frequency (10-bit )
  • Octave (3 bits)
  • Note on / off
  • Synthesis mode (FM or simply additive )
  • Feedback (0-7, wherein the modulator itself modulated)

For each of the two oscillators

  • Frequency factor (which can be set to ½, 1 to 10, 12 or 15)
  • Waveform (sine, half-sine, sine amount or saw - sine )
  • Volume (0-63)
  • Attack, Decay, Sustain, Release ( each 4 bits, logarithmic)
  • Tremolo ( on or off)
  • Vibrato ( on or off)
  • Sustain ( on or off)
  • Envelope scaling per key ( on or off)
  • Volume scaling for each key (0-3)

Parameters for the entire chip

  • Vibrato depth
  • Tremolo depth
  • Percussion mode ( uses three channels to produce five percussion sounds)
  • Composite Speech Mode ( all operators are available simultaneously; provided for speech synthesis, but was hardly ever used and is ( as the only incompatibility ) in OPL3 not included)
Soundchip IBM Personal Computer Ad Lib, Inc. Frequency modulation synthesis
622456
de