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Yamaha YM3812
Yamaha YM3812

The Yamaha YM3812 also known as the OPL2 (OPL is an acronym for FM Operator Type-L) is a sound chip (i. Acronyms, initialisms, and alphabetisms are Abbreviations that are formed using the initial components in a phrase or name A sound chip is an Integrated circuit (ie "chip" designed to produce Sound (see Chiptune) 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. Microchipsjpg|right|thumb|200px|Microchips ( EPROM memory with a transparent window showing the integrated circuit inside A sound card (also known as an audio card is a Computer Expansion card that facilitates the input and output of audio signals to/from a computer under This page is about the (now defunct sound card company named Ad Lib — not to be mistaken with the software company Adlib Software or Adlib Information systems. 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

It is backwards compatible with the OPL aka YM3526, to which it is very similar - in fact, it only adds 3 new waveforms. The YM3526, better known as OPL (for "FM Op erator Type L " is a Sound chip that was manufactured by Yamaha. An upgraded version of the OPL2, the OPL3 aka YMF262, was also popular in later sound cards such as the Soundblaster 16. The Yamaha YMF262, also known as the OPL3 (OPL is an Acronym for FM Operator Type-L) is an FM synthesis Sound chip. 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 Another related chip is the YM2413 (OPLL), which is a cut down version. 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. ADSR envelope is a component of many Synthesizers samplers and other Electronic musical instruments. Its main method of synthesis is Frequency modulation synthesis - where one of the channel's oscillators modulates the other. A 220 Hz carrier tone modulated by a 440 Hz modulating tone with

Overview of a channel's registers:

For the whole channel:

For each one of the 2 oscillators:

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

The internal operation of the chip is completely digital. The sound is generated using a form of direct digital synthesis and is sent to an external digital-to-analog converter (DAC), YM3014B, as a stream of floating point numbers at a sampling frequency of approximately 49720 Hz. Direct Digital Synthesis (DDS is an electronic method for digitally creating arbitrary Waveforms and frequencies from a single fixed source Frequency. In Electronics, a digital-to-analog converter ( DAC or D-to-A) is a device for converting a digital (usually binary code to an Analog signal The Yamaha YM3014B is a floating D/A converter with serial input for single channel operation In Computing, floating point describes a system for numerical representation in which a string of digits (or Bits represents a Real number. Scaling the output of an oscillator to a wanted volume would normally be done by multiplication, but the YM3812 avoids multiplications by operating on log-transformed signals, which reduces multiplications into computationally cheaper additions. In Mathematics, the logarithm of a number to a given base is the power or Exponent to which the base must be raised in order to produce A quarter of the log-transformed sine waveform is stored as a sampled approximation in a 256-word read-only memory (ROM) table. In Computing, " word " is a term for the natural unit of data used by a particular computer design The rest of the waveform can be constructed by employing the symmetry properties of the sine. An exponential function stored in another 256-word ROM is used to convert the logarithmic scale signal to linear scale when needed, for example for output. The exponential function is a function in Mathematics. The application of this function to a value x is written as exp( x)

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