Design a Digital Clock Using 8085 Microprocessor

Program to simulate a real-time clock in 8085 Microprocessor

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Here we will see one interesting problem. We will see how to simulate one real-time clock using 8085 microprocessor.

Problem Statement−

Write an 8085 Assembly language program to simulate real-time clock.

Discussion−

In this program we are creating a real time clock using 8085MPU. Here we are generating 1s delay to update seconds. This clock is 24Hrs clock. We are initializing the clock from 00:00:00. To display the values into 7-segment display we have to use some Port ICs and correct configurations. In each 60 seconds the minute field is updated, and in each 60 minutes the hour field is updated. For decimal update, DAA instruction is used in each increment.

We are storing the hour field into 8008H and minute field is stored at 8007H. The second value is stored at location 8009H.

Note: Here for simplicity we are storing the numbers into memory. To show the numbers, we can use 7 – segment display and other display function for showing it into the display.

Input

Here we are not providing any input.

Flow Diagram

Program

Address	HEX Codes	Labels	Mnemonics	Comments
F000	21, 00, 00	BEG	LXI H,0000H	Clear HL with 0000H
F003	22, 07, 80	HR_MIN	SHLD 8007H	Store HL content at 8007H and 8006H
F006	AF		XRA A	Clear A register
F007	32, 09, 80	N_SEC	STA 8009H	Store acc content at 8009H
F00A	CD, 34, F0		CALL DELAY	Delay for 1 second
F00D	3A, 09, 80		LDA 8009H	Load the second value
F010	C6, 01		ADI 01H	Add 01 with Acc
F012	27		DAA	Adjust decimal
F013	FE, 60		CPI 60H	Compare with 60H
F015	C2, 07, F0		JNZ N_SEC	If Z = 0, jump to N_SEC
F018	2A, 07, 80		LHLD 8007H	Load HL from 8007H
F01B	7D		MOV A,L	Load L to A
F01C	C6, 01		ADI 01H	Add 01 with A
F01E	27		DAA	Decimal adjust
F01F	6F		MOV L,A	Load L from A
F020	FE, 60		CPI 60H	Compare A with 60H
F022	C2, 03, F0		JNZ HR_MIN	If Z = 0, jump to HR_MIN
F025	2E, 00		MVI L,00H	Clear L register
F027	7C		MOV A,H	Load H to A
F028	C6, 01		ADI 01H	Add 01 with A
F02A	27		DAA	Decimal adjust
F02B	67		MOV H,A	Send back A to H
F02C	FE, 24		CPI 24H	Compare Hour with 24
F02E	C2, 03, F0		JNZ HR_MIN	Jump to HR_MIN if Z = 0
F031	C3, 00		JMP BEG	Jump to Begin
F034	0E, 02	DELAY	MVI C,02H	Initialize Count to 02H
F036	11, FF, FF	L1	LXI D,FFFFH	Load DE with FFFFH
F039	1B	L2	DCX D	Decrease DE
F03A	7A		MOV A,D	Take D to A
F03B	B3		ORA E	OR A and E
F03C	C2, 16, F0		JNZ L2	If Z = 0, jump to L2
F03F	0D		DCR C	Decrease C by 1
F040	C2, 13, F0		JNZ L1	Jump to L1, if Z = 0
F043	C9		RET	Return from subroutine

Output

                The numbers are storing into memory location 8008H – 8007H and 8009H.

Published on 04-Oct-2019 12:49:24

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Design a Digital Clock Using 8085 Microprocessor

Source: https://www.tutorialspoint.com/program-to-simulate-a-real-time-clock-in-8085-microprocessor

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