The SN76489 Digital Complex Sound Generator (DCSG) is a TTL-compatible programmable sound generator chip from Texas Instruments. It contains:
Its main application was the generation of music and sound effects in game consoles, arcade games and home computers (such as the Texas Instruments TI-99/4A, BBC Micro, ColecoVision, and IBM PCjr), competing with the similar General Instrument AY-3-8910.
The SN76489 was originally designed to be used in the TI-99/4 computer, where it was first called the TMS9919 and later SN94624, and had a 500 kHz max clock input rate. Later, when it was sold outside of TI, it was renamed the SN76489, and a divide-by-8 was added to its clock input, increasing the max input clock rate to 4 MHz, to facilitate sharing a crystal for both NTSC colorburst and clocking the sound chip. A version of the chip without the divide-by-8 input was also sold outside of TI as the SN76494, which has a 500 kHz max clock input rate.
Tone Generators: The frequency of the square waves produced by the tone generators on each channel is derived from two factors:
Each channel's frequency is arrived at by dividing the external clock by 4 (or 32 depending on the chip variant), and then dividing the result by N. Hz to 125 kHz (or typically 108 Hz to 111.6 kHz, with an NTSC Colorburst clock input – a range from roughly A2 (two octaves below middle A) to 5–6 times the generally accepted limits of human audio perception).Thus the overall divider range is from 4 to 4096 (or 32 to 32768). This gives a frequency range at maximum input clock rate of 122
Noise Generator: The pseudorandom noise feedback is generated from an XNOR of bits 12 and 13 for feedback, with bit 13 being the noise output. The pseudorandom generator is cleared to 0s (with the feedback bit set to 1) on writes to chip register 6, the noise mode register.
There are two versions of the SN76489: the SN76489 (Narrow DIP version labeled SN76489N) and the SN76489A (Narrow DIP version labeled SN76489AN). The former was made around 1980–1982 and the latter from 1983 onward. They differ in that the output of the SN76489 is the inverse of the expected waveform (the waveform 'grows' towards 0 V from 2.5 V), while the SN76489A the waveform is not inverted.
The SN76496 seems to be totally identical to the SN76489A in terms of the outputs produced, but features an "AUDIO IN" pin (on pin 9) for integrated audio mixing.
|Chip Variant||Freq (max)||Audio In|
|TMS9919 / SN94624||500 kHz||No|
|SN76489 / SN76489A||4 MHz||No|
|SN76494 / SN76494A||500 kHz||Yes|
|SN76496 / SN76496A||4 MHz||Yes|
Sega used real SN76489AN chips in their SG-1000 game console and SC-3000 computer, but used SN76489A clones in their Master System, Game Gear, and Sega Genesis game consoles. These modified sound chips were incorporated into the system's video display processor. Although basic functionality is almost identical to that of the original SN76489A sound processor, a few small differences existed: the randomness for the noise channel is generated differently, and the Game Gear's version includes an additional flag register that designates which speaker(s) each audio channel are output (left, right, or both). The periodic noise is also 16 stages long on the Sega-made clones rather than 15; this makes a significant difference for music/programs which use periodic noise, as sounds will play at 6.25% lower pitch than on the TI-made chips.
Another clone is the NCR 8496, used in some models of the Tandy 1000 computer. Later Tandy 1000 machines (notably the SL, TL and RL series) integrated the SN76496's functionality into the PSSJ ASIC.
A sound card is an internal expansion card that provides input and output of audio signals to and from a computer under control of computer programs. The term sound card is also applied to external audio interfaces used for professional audio applications.
A signal generator is an electronic device that generates repeating or non-repeating electronic signals in either the analog or the digital domain. These generated signals are used as a stimulus for electronic measurements, typically used in designing, testing, troubleshooting, and repairing electronic or electroacoustic devices, though it often has artistic uses as well.
In electronics and especially synchronous digital circuits, a clock signal oscillates between a high and a low state and is used like a metronome to coordinate actions of digital circuits.
The MOS Technology 6581/8580 SID is the built-in programmable sound generator chip of Commodore's CBM-II, Commodore 64, Commodore 128 and Commodore MAX Machine home computers. It was one of the first sound chips of its kind to be included in a home computer prior to the digital sound revolution.
The Texas Instruments TI-99/4A is a home computer released in June 1981 in the United States. It is an enhanced version of the less successful TI-99/4 which was released in late 1979. The TI-99/4 and TI-99/4A are the first 16-bit home computers, using the Texas Instruments TMS9900 16-bit CPU. Both models include hardware support for sprites, using TI's own chips, and multi-channel sound, making them some of the first home computers to include such custom coprocessors, alongside the Atari 8-bit family also introduced in 1979.
The Yamaha YM3812, also known as the OPL2, is a sound chip created by Yamaha Corporation in 1985 and famous for its wide use in IBM PC-based sound cards such as the AdLib, Sound Blaster and Pro AudioSpectrum (8bit), as well as several arcade games by Nichibutsu, Toaplan and others.
The Pot Keyboard Integrated Circuit (POKEY) is a digital I/O chip designed for the Atari 8-bit family of home computers and found in Atari arcade games of the 1980s. POKEY combines functions for sampling (ADC) potentiometers and scan matrices of switches as well as sound generation. It produces four voices of distinctive square wave sound, either as clear tones or modified with a number of distortion settings. POKEY chips are used for audio in many arcade games including Centipede, Missile Command, Asteroids Deluxe, and Gauntlet. Some of Atari's arcade systems use multi-core versions with 2 or 4 POKEY chips in a single package for more sound voices. The Atari 7800 console allows a game cartridge to contain a POKEY, providing better sound than the system's audio chip. Only two licensed games make use of this: the ports of Ballblazer and Commando.
A voltage-controlled oscillator (VCO) is an electronic oscillator whose oscillation frequency is controlled by a voltage input. The applied input voltage determines the instantaneous oscillation frequency. Consequently, a VCO can be used for frequency modulation (FM) or phase modulation (PM) by applying a modulating signal to the control input. A VCO is also an integral part of a phase-locked loop.
The Yamaha YMF262, also known as the OPL3, is an FM synthesis sound chip released by Yamaha Corporation in the early 1990s. It is an improved version of the Yamaha YM3812 (OPL2). It was used in a number IBM PC soundcards including Sound Blaster 16 and Pro AudioSpectrum (16bit).
The TMS9918 is a Video Display Controller (VDC) manufactured by Texas Instruments, introduced in 1979. The TMS9918 and its variants were used in the ColecoVision and CreatiVision, Memotech MTX, MSX, SG-1000/SC-3000, Spectravideo, Sord M5, Tatung Einstein, Texas Instruments TI-99/4, Casio PV-2000, and Tomy Tutor.
Direct digital synthesis (DDS) is a method employed by frequency synthesizers used for creating arbitrary waveforms from a single, fixed-frequency reference clock. DDS is used in applications such as signal generation, local oscillators in communication systems, function generators, mixers, modulators, sound synthesizers and as part of a digital phase-locked loop.
A function generator is usually a piece of electronic test equipment or software used to generate different types of electrical waveforms over a wide range of frequencies. Some of the most common waveforms produced by the function generator are the sine wave, square wave, triangular wave and sawtooth shapes. These waveforms can be either repetitive or single-shot. Integrated circuits used to generate waveforms may also be described as function generator ICs.
The AY-3-8910 is a 3-voice programmable sound generator (PSG) designed by General Instrument in 1978, initially for use with their 16-bit CP1610 or one of the PIC1650 series of 8-bit microcomputers. The AY-3-8910 and its variants were used in many arcade games—Konami's Gyruss contains five—and pinball machines as well as being the sound chip in the Intellivision and Vectrex video game consoles, and the Amstrad CPC, Oric-1, Colour Genie, Elektor TV Games Computer, MSX, and later ZX Spectrum home computers. It was also used in the Mockingboard and Cricket sound cards for the Apple II and the Speech/Sound Cartridge for the TRS-80 Color Computer.
A video display controller or VDC is an integrated circuit which is the main component in a video signal generator, a device responsible for the production of a TV video signal in a computing or game system. Some VDCs also generate an audio signal, but that is not their main function.
The Korg MS2000 is a virtual analog synthesizer produced by the Japanese electronic musical instrument manufacturer Korg.
The Geneve 9640 is an enhanced TI-99/4A clone. It was sold by the company Myarc as a card to fit into the Texas Instruments TI Peripheral Expansion System. Released in 1987, it is in many ways similar to the earlier TI-99/8, which was in prototype form in early 1983. The Geneve 9640 was designed by Paul Charlton, and the graphical swan on the boot up screen was designed by Mi-Kyung Kim.
A programmable sound generator (PSG) is a sound chip that generates audio signals built from one or more basic waveforms, and often some kind of noise. PSGs use a relatively simple method of creating sound compared to other methods such as frequency modulation synthesis or pulse-code modulation.
SN76477 "complex sound generator" is a sound chip produced by Texas Instruments (TI). The chip came to market in 1978, and TI ceased production of the part. A 100% compatible version, identified as ICS76477, has been listed as 'in stock' by at least one US-based component stockist. The chip is typically used as a sound effects generator in arcade games and toys and for hobby projects. The use of the SN76477 in a musical context is limited by the fact that it was difficult to electronically control the pitch of the produced sound.
Throughout it's lengthy, multi-model lifespan, the Apple II series computers lacked any serious built-in sound capabilities. At the time of its release in 1977 this did not distinguish it from its contemporaries, but by 1982 it shared the market with several sound-equipped competitors such as the Commodore 64, whose SID chip could produce sophisticated multi-timbral music and sound effects.
|Wikimedia Commons has media related to SN76489 .|