TWI_SAVE_CLOCK:

		rcall	START_CONDITION
		cpi	temp0, 0x10	; 0x10 --> Repeat start condition
		brne	DS1307_SAFE_ERROR
		
		; send SLA+W
		rcall	TWI_SLA_W
	
; hier erhalte ich generell 0x20 als status also NACK

		cpi	temp0, 0x18 ; SLA+W is send - ACK is received
		brne	DS1307_SAFE_ERROR

		; send Adress (0x00) for Control register
		ldi	temp0, 0x00   ;0x07 = DS1307 Control register
		rcall	TWI_SEND_DATA
		cpi	temp0, 0x28 ; data byte is send - ACK is received
		brne	DS1307_SAFE_ERROR
				
		; load display memory adress
		ldi	XL, LOW(CLOCK)
		ldi	XH, HIGH(CLOCK)
		adiw	XH:XL, 1
		
		; SECONDS *************
		ld	temp0, X+
		rcall	CODE_DATA
		rcall	TWI_SEND_DATA


		....




;******************************************************************************
;******************************************************************************
WAIT_DS1307:
 	in	temp0, TWCR
	sbrs	temp0, TWINT
	rjmp	WAIT_DS1307
	
	in	temp0, TWSR
	andi	temp0, 0xF8
	ret	

; ***************************************************************
START_CONDITION:
	ldi	temp0, (1<<TWINT)|(1<<TWSTA)|(1<<TWEN)
	out	TWCR, temp0
	rcall	WAIT_DS1307
	ret

; ***************************************************************
STOP_CONDITION:
	ldi	temp0, (1<<TWINT)|(1<<TWSTO)|(1<<TWEN)
	out	TWCR, temp0
	ret

; ***************************************************************	
TWI_SLA_W:	
	ldi	temp0, 0xD0   ; adress DS1307 = 1101000 + W=0
	out	TWDR, temp0
	ldi	temp0, (1<<TWINT)|(1<<TWEN)
	out	TWCR, temp0
	rcall	WAIT_DS1307
	ret