The SN76489 Digital Complex Sound Generator (DCSG) is a TTL-compatible
programmable sound generator chip from Texas Instruments. It
3 square wave tone generators.
A wide range of frequencies.
16 different volume levels.
1 noise generator.
2 types (white noise and periodic).
3 different frequencies.
16 different volume levels.
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, the
BBC Micro and the IBM PCjr), existing
alongside the competing and similar General Instrument AY-3-8910.
2 Product Family
3 Clones and successors
4.1 Arcade games
4.2 Home hardware
5 See also
7 External links
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
Tone Generators: The frequency of the square waves produced by the
tone generators on each channel is derived from two factors:
The speed of the external clock.
A value provided in a control register for that channel (called N).
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. 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 Hz to 125 kHz (or typically 108 Hz to
111.6 kHz, with an NTSC
Colorburst clock input - a range from
roughly A2 (A below middle A) to 5-6 times the generally accepted
limits of human audio perception).
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
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
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.
Texas Instruments SN76489 Product Family Summary
TMS9919 / SN94624
SN76489 / SN76489A
SN76494 / SN76494A
SN76496 / SN76496A
Clones and successors
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 extension for stereo audio output. 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
Tandy 1000 machines (notably the SL, TL and RL series)
integrated the SN76496's functionality into the PSSJ ASIC.
These games shared a common board design by Tehkan that used three of
the functionally identical SN76496.
Baluba-Louk No Densetsu
These games shared a common board design by Universal Entertainment
Lady Bug (used 2)
Mr. Do! (used 2)
Mr. Do's Castle (used 4)
Mr. Do's Wild Ride
Mr. Do's Wild Ride (used 4)
Do! Run Run
Do! Run Run (used 4)
Time Pilot '84
Time Pilot '84 - uses the functionally identical SN76496
Sega System 1
Sega System 2
Sega System E was based on the
Master System and used the clone chip
in its VDP.
ALF's Music Card MC1 - Apple II add-on card, uses three chips for a
total of nine voices
Neo Geo Pocket
Neo Geo Pocket
Neo Geo Pocket Color
Game Gear - used a clone integrated into its VDP; this version has
extensions for stereo audio output.
Master System - used the clone integrated into its VDP.
SG-1000 - uses the SN76489AN
Sharp MZ-800 - uses the SN76489AN
Tandy 1000 - early systems used SN76496 or NCR 8496, later systems
integrated into PSSJ ASIC
Texas Instruments TI-99/4A - uses the original TMS9919
General Instrument AY-3-8910
^ a b c d Engineering staff of
Texas Instruments Semiconductor Group.
"SN 76489 AN" (PDF).
^ "SN76494, SN76494A, SN76496, SN76496A programmable tone/noise
generator" (PDF). Texas Instruments. 1984, 1989. Check date
values in: date= (help)
^ Maxim (April 27, 2005). "SN76489 notes". SMS Power!.
SN76489 Sound Chip Details
PC sound cards
IBM compatible standards
PC speaker (1981)
IBM Music Feature Card
IBM Music Feature Card (1987)
Roland MT-32 (1987)
Roland LAPC-I (1989)
Sound Blaster (1989)
General MIDI (1991)
Roland GS (1991)
Roland Sound Canvas
Roland Sound Canvas (1991)
Roland SC-55 (1991)
Gravis Ultrasound (1992)
Yamaha XG (1994)
General MIDI Level 2 (1999)
Environmental Audio Extensions (2001)
Intel High Definition Audio
Intel High Definition Audio (2004)
Comparison of M