Yamaha YM3812

The Yamaha YM3812 also known as the OPL2 (OPL is an acronym for FM Operator Type-L) is a sound chip (i.e. integrated circuit) created by Yamaha Corporation and famous for its wide use in IBM PC-based sound cards such as the AdLib and Sound Blaster. Image File history File links Download high resolution version (1600x1086, 385 KB) Summary A Yamaha YM3812 sound chip, better known as OPL2 Taken by me on March 21th 2006. ... Image File history File links Download high resolution version (1600x1086, 385 KB) Summary A Yamaha YM3812 sound chip, better known as OPL2 Taken by me on March 21th 2006. ... Acronyms and initialisms are abbreviations formed from the initial letter or letters of words, such as NATO and XHTML, and are pronounced in a way that is distinct from the full pronunciation of what the letters stand for. ... A sound chip is an integrated circuit (i. ... SEM image of an integrated circuit showing defects in the aluminium layer deposition (shown in cyan). ... The Yamaha Corporation (ヤマハ株式会社; TYO: 7951 ) is a Japanese company with a large number of product areas. ... IBM PC (IBM 5150) with keyboard and green screen monochrome monitor (IBM 5151), running MS-DOS 5. ... A Sound Blaster Live! Value card, a typical present-day PCI sound card. ... AdLib, Inc. ... The Sound Blaster family of sound cards was for many years the de facto standard for audio on the IBM PC compatible system platform, before PC audio became commoditized, and backward-compatibility became less of a feature. ...

It is backwards compatible with the OPL aka YM3526, to which it is very similar - in fact, it only adds 3 new waveforms. An upgraded version of the OPL2, the OPL3 aka YMF262, was also popular in later sound cards such as the Soundblaster 16. Another related chip is the YM2413 (OPLL), which is a cut down version. The YM3526, better known as OPL (for FM Operator Type L), is a sound chip that was manufactured by Yamaha. ... The Yamaha YMF262 also known as the OPL3 (OPL is an acronym for FM Operator Type-L), is an improved version of the sound chip Yamaha YM3812 (OPL2). ... The Sound Blaster family of sound cards was for many years the de facto standard for audio on the IBM PC compatible system platform, before audio has been commoditized. ... The YM2413, also called OPLL, is a cost-reduced sound chip manufactured by Yamaha Corporation and based on their YM3812 (OPL2). ...

The circuit has 244 different write-only registers. It can produce 9 channels of sound, each made of two oscillators. Each oscillator can produce sine waves which may also be modified into 3 other waveforms - the negative part of the sine can be muted or inverted, and pseudo sawtooth waves (1/4 sine waves upward only with silent sections in between) can also be produced. This odd way of producing waveforms give the YM3812 a characteristic sound. Each wave generator has its own ADSR envelope generator. Its main method of synthesis is Frequency modulation synthesis - where one of the channel's oscillators modulates the other. In trigonometry, an ideal sine wave is a waveform whose graph is identical to the generalized sine function y = Asin[ω(x − α)] + C, where A is the amplitude, ω is the angular frequency (2π/P where P is the wavelength), α is the phase shift, and C is the... An ADSR envelope is a parameter used in synthesizers, including those that produce sound by subtractive synthesis, to control the sound produced. ... Frequency modulation synthesis (or FM synthesis) is a form of audio synthesis where the timbre of a simple waveform is changed by frequency modulating it with a modulating frequency that is also in the audio range, resulting in a more complex waveform and a different-sounding tone. ...

Here's the overview of a channel's registers:

For the whole channel:

 Main frequency (10 bits) Octave (3 bits) Note on/off Synthesis mode (FM or just additive) Feedback (0-7, the modulator modulating itself) 

For each one of the 2 oscillators:

 Frequency multiply (can be set to 1/2, 1 to 10, 12 or 15) Waveform (Sine, half-sine, absolute-sine, quarter-sine) Volume (0-63, logarithmic) Attack, Decay, Sustain, Release (4 bits each, logarithmic) Tremolo (On or off) Vibrato (On or off) Sustain (On or off) Envelope scaling per key (On or off) Volume scaling per key (0-3) 

There's also a few parameters that can be set for the whole chip:

 Vibrato depth Tremolo depth Percussion mode (uses 3 channels to provide 5 percussion sounds) Composite sine mode (never used and doesn't work on the Opl3) 

External links

• Programming the AdLib/Sound Blaster FM Music Chips
• OPL2 programming information