8085 program to alternate D0 bit with specified delay

Now let us see a program of Intel 8085 Microprocessor. In this program we will see how to alternate the D0 bit and send as output.

Problem Statement

Write 8085 Assembly language program to alternate D0 bit. And send this as output.

Discussion

Alternating D0 bit and sending as output is like generating the square wave. We are adding extra delay in each phase. To generate square wave with 8085, we will rotate 10101010 (AAH) continuously, and send D₀ as output. We will mask the accumulator content by 01H. If this is 0, then output will be 0, if it is 1, output will be 1, thus the pulse will be generated. After sending it, it will wait for some time using delay subroutine.

Input

No input is given in this case

Flow Diagram

Program

Address	HEX Codes	Labels	Mnemonics	Comments
8000	16, AA		MVI D,AAH	Load 10101010 into D
8002	7A	ROTATE	MOV A,D	Load D to A
8003	07		RLC	Rotate A to the left
8004	57		MOV D,A	Store A into D again
8005	E6, 01		ANI 01H	Mask A with 01H
8007	D3, 10		OUT 10H	Send output to port 10
8009	CD, 0F, 80		CALL DELAY	Wait for some time
800C	C3, 02, 80		JMP ROTATE	Jump to ROTATE for next phase
800F	C5	DELAY:	PUSH B	Saving B. This delay subroutine uses 2 single registers A & D and 1 register pair BC
8010	F5		PUSH PSW	Saving PSW
8011	16, 0F		MVI D, 0F H	Loading counter for outer loop
8013	01, 00, 10	ST:	LXI B, 1000 H	Loading counter for inner loop
8016	0B	L:	DCX B	Decrement inner counter
8017	79		MOV A, C	If not exhausted go again for inner loop
8018	B0		ORA B
8019	C2, 27, 80		JNZ L
801C	15		DCR D	Decrement outer counter
801D	C2, 24, 80		JNZ ST	If not exhausted go again for outer loop
8020	F1		POP PSW	Restore PSW
8021	C1		POP B	Restore B
8022	C9		RET	Return to the calling program

Output

Alternating D0 will be reflected as output like square wave.

Chandu yadav

Updated on 07-Oct-2019 13:21:31

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