Thanks Erik - this is an excellent FAQ. In particular it's useful to know exactly when the 80C320 chip sets the RI and TI bits.

One or two more questions though for my full understanding:

1. Does reading SBUF have any effect on the chip? Is receipt of the next byte inhibited until I read SBUF, for example? If I'm not interested in the value of the byte received, or if I don't know whether a byte has been received at all, do I still have to read SBUF to be sure the chip is ready to receive the next byte?
   
2. Does clearing RI have a similar effect? If I don't clear RI, will the chip receive another character? (I know that if I don't clear RI I won't be able to tell when a byte has arrived).
   
3. When receiving another byte, what exactly happens to the value in SBUF, and when? If I continually read SBUF while a character is being received, do I actually see the new character shift through the register, and the old character shift out? Or does the old value of SBUF remain until the new byte has been fully received, and does it then get "instantaneously" transferred into SBUF?
   

Thanks - Rowan