Yep, Been there, done that. The big problem seems to finding a decent VCL serial comms package. When I get back to work in the morning, I can advise you which one worked in the end. We had enormous problems with internal timings of the VCL component we used. You HAVE to put a couple of nul loops to slow down some bits. The 8052 end was easy...

The other consideration is the RS232-485 interface. We used a MAX 202 and their nice isolating 485 interface chip. The direction signal we drove with the CTS line I think.

Steve