I am working on a circuit with 2 mega324s that talk to each other via rs485. I choose to use two ISL3179E from Intersil, mainly becuase it comes in a MSOP10 package.

http://www.intersil.com/data/fn/fn6365.pdf

I would like to optimize the termination resistance to reduce power consumption, but I am not sure how to do this. I would like to achieve 250 kbps and my cable is high flex 28 guage twisted pair that is about 18 inch long.

From what I have read, have lower termination resistance minimizes reflections. The datasheet lists 52 ohms and 100ohms as two possible options. I would like to use something more like 1k ohms. I am not sure how to caculate the effect of the higher termination resistance.

Any insight into this is appreciated.

-Daniel