RS232 and RS485 are electrical specifications, thus no serial communication without MAX(or equivalent) chips can be either.

1) in close proximity, just Rx to Tx
2) in the same box, Tx -> an inverter --- an inverting schmitt trigger -> Rx
3) separate boxes: RS232 or RS485. RS232 if close and only two, else RS485.

Erik

before entering into serial comm, read "Best Serial Comm Appnote site" in links. Especially if you are going 485 read "ten ways to bulltproof"