Now implemented.

It's funny, it worked surprisingly-well pretty much off-the-bat. And then... I tried to switch out the 16MHz crystal oscillator with a 22... then a 20... then a whole slew of others, including an 8... Nogo.

Tried *another* 16MHz... nogo.

Tried that first one, again, and it seems OK.

Strange. And I guess lucky that that seems to be the only one I have in my collection that works right, and just happened to be the one I was using at the time.