Just a quick update for you all here. As you may remember, I will be using the 6581 SID emulator by Swinkels for my 6502 computer project. Yes, it's final now, my weak spot for the 6581 is just too.. darn.. weak.
But, before I begin experimenting with the Swinsid, I wanted to make sure that the real 6581 works with the circuit first, since they both are (ideally) pin-to-pin compatible. Here is last night's crochet work on the breadboard:
Top left corner: R6502, EPROM right next to it, under all the wires.
The SID chip is the one with the heat sinks.
This system obviously lacks the $d012 register, so syncing the tune was solved by looping through enough NOPs to waste approximately 50ms between each call to the SID player.
Unfortunately, though, I didn't have the time to finish it -- but I will get it up and running today. As far as I can tell, the only thing left is to add an op-amp to amplify the audio signal. Curious me had to try it yesterday, and I did see some activity on the audio line....
So, if this works fine, I'll continue with testing the Swinsid on an ATmega128. Not really sure if that will work, and if it doesn't I won't waste any more time on it and just buy the chips it was designed for. If it does work, I will try to eliminate the TDA1543 and rather use my own ADC.
Let's hope that little speaker will shake vigorously tonight.