Ok, maybe its not so brainy, but what else am I going to call this part? This is a pretty straightforward schematic, nothing out of the ordinary in the way of circuits here.

The capacitance values on either end of the crystal are best obtained from the crystal manufacturer. On the other hand, if you don't happen to have that data, something in the range as specified on the Microchip data sheets should work.

I chose the 4.9152 MHz crystal for two reasons. First I had plenty of them, and second, they are a nice multiple of the popular RS232 baud rates, which makes the timing loops for the RS232 easy.