As far as i know rs485 specifies a bus common mode voltage of: -7V to +12V
the terminating resistor is 120ohm , using VxV/R , yields high power rating to the resistor , certainly more than 1w . (12x12/120 =1.2w)
However looking at many products and evaluation boards , i see that they use 0805 resistors which are about 0.25w only. They might be pulse withstanding type though.
What am i missing here ? the only explanation i could come up with is that the continuous power rating of this resistor is much lower (so my calculation is wrong), since there is some break between transmitted bytes.
But in this case what happens if transmission is continuous?