Program to compute LCM in 8085 Microprocessor

Now let us see a program of Intel 8085 Microprocessor. This program will find the LCM of two 8-bit numbers.

Problem Statement −

Write 8085 Assembly language program to find LCM of two 8-bit numbers stored at location 8000H and 8001H

Discussion −

In this program we are reading the data from 8000H and 8001H. By loading the number, we are storing it at C register, and clear the B register. The second number is loaded into Accumulator. Set DE as the 2’s complement of BC register. This DE is used to subtract BC from HL pair.

The method is like this: let us say the numbers are 25 and 15. When we divide the first number by second, and then if there is no remainder, then the first number is the LCM. But for this case the remainder is present. Then we will check the next multiple of 25 to check the divisibility. When the remainder becomes 0, the program terminates and the result is stored.

Input

First input

Address	Data
. . .	. . .
8000	03
8001	07
. . .	. . .

Second input

Address	Data
. . .	. . .
8000	23
8001	07
. . .	. . .

Flow Diagram

Program

Address	HEX Codes	Labels	Mnemonics	Comments
F000	21, 00, 80		LXI H, 8000H	Point 8000H to get first number
F003	4E		MOV C,M	Load memory element to C
F004	06, 00		MVI B, 00H	Clear B register
F006	23		INX H	Point to next location
F007	7E		MOV A,M	Load second number to Acc
F008	2F		CMA	Complement Acc
F009	5F		MOV E,A	Load 1's complemented form of A to E
F00A	16, FF		MVI D, FFH	Load 1's complemented form of 00H
F00C	13		INX D	Increase DE register pair
F00D	21, 00, 00		LXI H, 0000H	Load 0000H into HL pair
F010	09	NEXT	DAD B	Add BC with HL
F011	22, 50, 80		SHLD 8050H	Store HL content into 8050H
F014	19	LOOP	DAD D	Add DE with HL
F015	D2, 20, F0		JNC SKIP	When CY = 0, jump to SKIP
F018	7C		MOV A,H	Get H content to A
F019	B5		ORA L	OR L with A
F01A	CA, 26, F0		JZ EXIT	When HL is 0000, jump to EXIT
F01D	C3, 14, F0		JMP LOOP	Jump to Loop
F020	21, 50, 80	SKIP	LHLD 8050H	Load HL from 8050H
F023	C3, 10, F0		JMP NEXT	Jump to NEXT
F026	2A, 50, 80	EXIT	LHLD 8050H	Store HL pair as LCM
F029	76		HLT	Terminate the program