Logic and communicating protocols for the RS485
Everything is application dependent.  Specifications like RS-485 and RS-232 are specifications on voltage levels, current levels, bus loading, bus termination, etc.  There is no guidance on using START bits or STOP bits or parity or baud rates.  The specification basically tells you how to make bits and possibly deal with bus contention and such, but otherwise all devices communicating must agree on what the bits mean. 

I know there might be some high-level references on subjects like this but I think in general most people wing it - 8N1 is very popular and most people stick to the 1200,2400,4800 etc sequence of baud rates because those are customary and generally supported. Overall, if you've got a microcontroller on one end of this communication link, you're probably not going to want to deviate outside of the range of:


One START bit
1-2 STOP bits
Even, odd or no parity
1200 baud - 1 Megabaud data rate
7-9 data bits


Maintaining these restrictions generally allows you to put an RS-485 transceiver in front of a generic UART and get simple bus communication.  Of course, you have to add in code to handle changing bus direction from read to write (if you're not using full-duplex communication) and possibly monitor the bus for contention.  Otherwise, it's a wide-open field.