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Interfacing the AY-3-8912 PSG

In a project I and h4xxel worked on a while ago, we used some AY-3-8912 chips as sound generators over MIDI, the Chipster. While doing this, we fell for a few traps, so I thought I might mention them here just in case someone's having issues talking to them.

1 A couple silent traps

As a reference, we used the datasheet linked below. This is the most complete scan of the datasheet I've found so far. If you got a better quality one, feel free to link it in the comments. AY-3-8910/12/13 datasheet

First thing might be obvious for some, but to us it wasn't when we read it. The register numbers are in octal notation. So, for example, r10 is actually register 8 in decimal, or 0x8. This was something that frustrated us a lot. They do actually tell you this in the datasheet, but only in the description, that is very tempting to just skim over.

If you're just setting up a test circuit to make your "hello noise", go for the tone generator. It might be tempting to just flip the "noise" bit, but we discovered that the noise channel by itself doesn't generate any sound. It needs to be modulated with a tone channel to be audible.

Worth mentioning, we had it connected in 2-wire mode (only two of the three control signals used.) This involves pulling BC2 high and only using BDIR and BC1. The datasheet also mentions this.

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