Javier,

I put the code in one of my projects, and this was the assembler result:-

...
...
_RXSTAT = 0x00e2
...
...

; heart.c:344: aux=RXSTAT;
; genAssign
    mov    r2,_RXSTAT
; heart.c:345: aux++;
; genPlus
; genPlusIncr
    mov    a,#0x01
; Peephole 236a
    add    a,r2
    mov    _P1,a


Which would indicate that it was functioning correctly. What version of SDCC are you using?

Take the latest nightly build of SDCC from here if you are not using it.

Chris Brooks.