Hi Joseph,
Check out this site. http://www.8052.com/forum/read.phtml?id=66022
I built this MAX038 function generator but never interfaced it to a processor. It would be real easy to do that. This circuit also uses a Phase Lock Loop (PLL).
Phase Lock Loops are really neat. Just do a search on LM4046 and you will get tons of good stuff. Build a couple of simple circuits and you will see why PLL are used so much.
To see the beauty of the world look at analog signals and to see the ugly of the world look at digital.
Regards,
Charles Bannister