void write_EEPROM(unsigned char dato,unsigned char xdata *add){
      if(_POWER_OK==FALSE){
         WMCON=WMCON|EEMWE_; // EEMWE high
	 ET2=FALSE; // stop interrupts
         *add=dato;  // start writing
	 while((WMCON&WDTRST_)==0); // wait WDTRST=1 (2.5ms)
	 ET2=TRUE;  // restart interrupts
	 WMCON=WMCON&(~EEMWE_); // EEMWE low
      }
  }