SN76496

Texas Instruments SN76496

Overview

The Texas Instruments SN76496 is a programmable sound generator from the SN76489 family. It became one of the most widely used PSG architectures in 8-bit and 16-bit computer and video-game hardware.

The chip provides three programmable tone channels and one noise channel. Unlike the AY-3-8910, the SN76496 does not use a conventional hardware envelope generator.

Instead, its simple digital architecture provides programmable frequencies, volumes and noise modes that can be rapidly manipulated by software.

Technical characteristics

• Manufacturer: Texas Instruments
• Model: SN76496
• Family: SN76489 / SN76496
• Channels: 3 tone + 1 noise
• Synthesis: PSG
• Tone waveform: Square wave
• Noise: Programmable noise generator
• Volume: 4-bit attenuation control

Three tone channels

Three independent tone generators produce square waves whose frequencies can be programmed by software.

A fourth channel is dedicated to noise generation and can be configured for different noise behaviours.

Noise generator

The noise channel is especially useful for percussion and sound effects. Depending on its configuration, it can generate periodic or pseudo-random noise.

This simple design became extremely effective in video games, where the three tone channels could provide melody and bass while the noise channel handled drums and effects.

Computer and console use

The SN76496 family was used in numerous systems, including the TI-99/4A, Sega SG-1000 and various Sega arcade and home-computer systems.

Compatible and derivative versions also appeared in several other computers and consoles.

Tracker relevance

The SN76496 is an important platform in the history of chiptune music.

Its limited number of channels encouraged composers to use techniques such as rapid arpeggios, pitch manipulation and fast volume changes to create richer musical arrangements.

Historical importance

The SN76496 is one of the classic PSG designs of the early home-computer and video-game era. Its simple architecture, low hardware cost and straightforward programming model helped make it extremely widespread.

Related soundchips

• SN76489 — Closely related member of the same PSG family.
• Toshiba T6W28 — Related PSG architecture used in Sega hardware.
• AY-3-8910 — Alternative three-channel PSG architecture.

Further reading

• Wikipedia — SN76489
• SMS Power! — SN76489 documentation