void puerto_serial_event() interrupt 4{
    if(TI==1){          //if transmition occurs
        TI=0;           //clears TI
    }

    if (RI==1){       //if reception occurs
        RI=0;           //clears RI
        if(RB8){
            SM2=0;      //data mode 2
        }
        else{
            if(ind_trama>4){
                ind_trama=0;
            }
            trama[ind_trama]=SBUF;
            ind_trama++;
            SM2=1;      //data mode 1
        }
    }
}