SN76489
From Sonic Retro
Revision as of 14:47, 4 January 2008 by Scarred Sun (talk | contribs)
Revision as of 14:47, 4 January 2008 by Scarred Sun (talk | contribs)
File:SN76489.jpg
SN76489 chip
Features of the SN76489 are:
- Three square wave, programmable tone generators
- One programmable white noise generator
- Programmable attenuation
- Mono audio output
The frequency of the square waves produced at each channel is derived by two factors: the speed of the external clock and a value provided in a control register for that channel (called N). The eventual frequency is arrived at by dividing the external clock by 32 and then dividing the result by N for each channel. The SN76489 is included 'on-chip' in Sega's Video Display Processors (VDP) for their Master System, Game Gear, and Mega Drive game consoles. The Sega VDP is in fact based on the Texas Instruments TMS9918 VDP.