....
.equ   data = 6
.equ   clk   = 0
.equ   reset = 5



rtc_start: 		nop			; 1us pause
			nop
			nop
			nop
			sbi portd, reset	; Reset Line high
			nop			;1 us Pause
			nop
			nop
			nop
			ret

rtc_stop:		sbi portd, clk
			nop
			nop
			nop
			nop
			cbi portd, reset
			nop
			nop
			nop
			nop
			ret

rtc_read_bit:	
			cbi portd, clk
			nop
			sbis pind, data
			cbr temp1,1<<7
			sbic pind, data
			sbr temp1,1<<7
			sbi portd, clk
			ret

rtc_write:  		cbi portd, clk
			nop
			sbi portd, Data
			sbrs command, 0
			
			cbi portd, data
			nop
			sbi portd, clk
			nop
			ret


rtc_write_byte_init: 			ldi temp, 8
					sbi ddrd, data
rtc_write_byte:			
					
					rcall rtc_write
					lsr command
					dec temp
					brne rtc_write_byte
					ret

rtc_read_byte_init:			ldi temp,8
					ldi temp1, $00
					cbi portd, data
					cbi ddrd, data
rtc_read_byte:				rcall rtc_read_bit
					lsr temp1
					dec temp
					brne rtc_read_byte
					ret

rtc_main1: 	
		cbi portd, reset
		cbi portd, clk
		rcall rtc_start
		ldi command, 0x8E			;Write Protect Bit in Register-
		rcall rtc_write_byte_init		;Control löschen
		ldi command, 0x00
		rcall rtc_write_byte_init
		rcall rtc_stop
		rcall rtc_start
		ldi command, 0xBE			;Schreib-Burst-Modus aktivieren
		rcall rtc_write_byte_init
		ldi command, 0x00			;Sekunden = 00
		rcall rtc_write_byte_init
		rcall rtc_write_byte_init		;Minuten = 00
		ldi command, 0x05		
		rcall rtc_write_byte_init		;Stunden = z.B 5
		rcall rtc_stop				
		ret

rtc_main2: 	
		cbi portd, reset
		cbi portd, clk
		rcall rtc_start
		ldi command, 0xBF			;Lese-Burst-Modus aktivieren
		rcall rtc_write_byte_init
		rcall rtc_read_byte_init		;Sekunden einlesen
		mov rtc_sek, temp1
		rcall rtc_read_byte_init		;Minuten einlesen
		mov rtc_min, temp1
		rcall rtc_read_byte_init		;Stunden einlesen
		mov rtc_std, temp1
		rcall rtc_stop				 
		ret
		
rtc_auswertung:	
			ldi zeit, $0f
			mov temp2, rtc_sek
			and rtc_sek,zeit
			sbr rtc_sek,3<<4
			mov sek_e, rtc_sek
			swap temp2
			sbr temp,3<<4
			mov sek_z, temp2
			mov temp2, rtc_min
			and rtc_min, zeit
			sbr rtc_min, 3<<4
			mov min_e, rtc_min
			swap temp2
			sbr temp2,3<<4
			mov min_z, temp2
			mov temp2, rtc_std
			and rtc_std, zeit
			sbr rtc_std, 3<<4
			mov std_e, rtc_std
			swap temp2
			sbr temp2, 3<<4
			mov std_z, temp2
			ret


.....
rcall rtc_main1  ;initialisieren



loop:
rcall rtc_main2
rcall rtc_auswertung
rcall lcd_write
rjmp loop