消除了阻止 rs232 中断的 eeprom 问题 #641

	cli(); // Ensure atomic operation for the write operation.
	
       // the folling code waits 3.3ms or 1.8ms for write if previous eeprom was written.
	do {} while( EECR & (1<<EEPE) ); // Wait for completion of previous write.
	#ifndef EEPROM_IGNORE_SELFPROG
	do {} while( SPMCSR & (1<<SELFPRGEN) ); // Wait for completion of SPM.
	#endif
	// this is the end of the problematic code.

	EEAR = addr; // Set EEPROM address register.
	EECR = (1<<EERE); // Start EEPROM read operation.
	old_value = EEDR; // Get old EEPROM value.
	diff_mask = old_value ^ new_value; // Get bit differences.
	
     // insert here cli() instead of above

               // the reason for interrupt disabling is this, the write to EEMPE and the setting of EEPE need
              // to be made quickly after
			EECR = (1<<EEMPE) | // Set Master Write Enable bit...
			       (0<<EEPM1) | (0<<EEPM0); // ...and Erase+Write mode.
			EECR |= (1<<EEPE);  // Start Erase+Write operation.`