A DS80C320 has two UARTS, so it can talk RS232 and RS485 at the same time. How you handle the 485 protocol is up to you, but we have had a lot of stuff about this recently, so I suggest you check through the archives. We have a nicely working master-slave system running from a PC to slave 8052 systems. A master 8052 -slave '52 would have been a lot easier.

Steve