Monday, January 12, 2009

One by One ... SN76489AN

The SN76489AN is a very basic chip, probably second to the VIC-I. Even though the AY-3-8910 is a tad bit more complex (the envelopes), in many places you will read both the SN and the AY described as "PSG"s or programmable sound generator.
  • Basic 50% duty cycle square
  • "1/15" duty "cyclic noise, (rarely used)
  • 32767 bit long Noise pattern. (different on chip variations)
I was lucky to discover that the 32k-1 bit pattern is different on the SN94624N (used in some TI/99's), and Chip sounds includes both patterns exactly replicated.

That chip was used in way too many computers, consoles and Arcade machines to list, probably due to its simplicity and price... It was however included as a discreet chip on my first video game console, the ColecoVision.
Just a little site to collect my findings and describe my experiments in developing this product.
Already 3 years of work have passed since I started this and first time I actually write about it.
The reason is, well one is always afraid of doing some work for nothing, especially when the concept is pretty bold... to make the Chip Tune VSTi to cover them all.

NAMM 2009 is in two days.
Still things to sort out.... just in the demo.

So its all blips and basic square wavs right? Afraid not!