I honestly don't know the answer to that question--but if you have a design that requires that you are requesting that the remote side stop transmitting after every character I think you need to optimize your implementation or simply decrease your baud rate. There's really no reason to operate at 9600 baud if, with all the RTS activity, you're going to slow things down to 2400 or 1200 baud by pausing after every character. It'd make more sense to just use the lower baud rate.

At the very least establish a small input buffer so you don't have to assert RTS so often.

Regards,
Craig Steiner