Hello,
        I am building a PIC network and i pretend to use RS485 chips. I
will use the built in UART to drive them but i need a way to detect
collisions and network idle state, what i think i should do it's when i
send a byte from the UART, or pretend to send it, i monitor the line with
another pin (neither TX or RX) looking for diferent bits. Something link
this:

---
   |       -------          Is this ok or am i forgeting something. I
 Tx|----->|       |--       never used RS485 chips before, they go down
   |      | RS485 |         when more then one drive the line?
 Rx|<--+--|       |--
   |   |   -------
   |<--
   |
---

Antonio Almeida