hi,

RS-232 was never intended for multinode.

Indeed, but UART has possibility to be used for multiprocessor communications (9-bit UART with TB8/RB8 bits). There are derivatives which support individual/broadcast address detection as well.
We have already discussed it somewhere. I can remember two ways:
- ring communication (not usable for original poster);
- one master + slaves. Of course slaves` outputs must have possibility to be disabled (open drain, AND gates, output enable etc).

In one of my projects I have used next scheme: one master (AT89C51) and 8 slaves. All communications were done through 4 MAX232CWE (in sum: 8 transmitters + 8 receivers). For select RS-232 channel I used one 74ALS138 as demultiplexor for transmit line and one 74ALS251 as multiplexor for receive lines. Indeed, with such scheme, only one device may be "online" per time but it was enough to communicate with them all one-by-one.

Regards,
Oleg