void isr_byte_recv(void) __interrupt 7
{
        //the isr toggles led when TF2 overflows.
        if (TF2 == 1) {
                        P1_5 = !P1_5; //P1_5 is connencted to an led.
        }

        TF2 = 0;
        EXF2 = 0;
}