Eliahu
How about using a #define to equate rbr
to thr? The mechanism I would use,
though it may not be the best, is to
define a union of the two bytes, for
example:

union {
unsigned char thr;
unsigned char rbr;
} uUARTreg _at_ 0x00;

uUARTreg.thr = outputval;
inputval = uUARTreg.rbr;

Would this work for you?

Chris