I am looking to design a Mockingboard clone. I've built one using legacy parts on a breadboard and connected it to my IIe.
All of the designs I see use an inverter on pin A7 (IIRC). This inverter selects either AY-3-8912 (two of them).
But it looks like the Phasor had FOUR AY chips. But I can't seem to find any schematics on how the Phasor was built.
My idea is to build a soundcard that is Mockingboard compatible but also have support for multiple sound chips. In fact, the microcontroller I plan to use (Propeller by Parallax) has perfect AY-3-8910 emulation (and others). So I'm thinking I could get 4-6 AY chips on one board.
But I'd like to be as compatible with legacy software as possible.
Any information on programming the Phasor schematics, programming it, etc?
Oh, I do have the official Phasor manual but it doesn't help with the design.