Program to multiply two 2-digit BCD numbers in 8085 Microprocessor

Here we will see 8085 Microprocessor program, that will find the multiplication result of two BCD numbers.

Problem Statement −

Write an 8085 Assembly language program to find two BCD number multiplication. The numbers are stored at location 8000H and 8001H.

Discussion −

In this program the data are taken from 8000H and 8001H. The result is stored at location 8050H and 8051H.

As we know that 8085 has no multiply instruction so we have to use repetitive addition method. In this process after each addition we are adjusting the accumulator value to get decimal equivalent. When carry is present, we are incrementing the value of MS-Byte.  We can use INR instruction for incrementing, but here ADI 01H is used. The INR instruction does not affect the CY flag so we need ADI instruction.

Input

first input

Address	Data
…	…
8000	12
8001	20
…	…

second input

Address	Data
…	…
8000	27
8001	03
…	…

 

Flow Diagram

 

 

Program

Address	HEX Codes	Labels	Mnemonics	Comments
F000	21, 00, 80		LXI H,8000H	Load first operand address
F003	46		MOV B,M	Store first operand to B
F004	23		INX H	Increase HL pair
F005	4E		MOV C,M	Store second operand to register C
F006	1E, 00		MVI E, 00H	Clear register E
F008	63		MOV H,E	Clear H register
F009	7B		MOV A,E	Clear A register
F00A	B9		CMP C	Compare C with A
F00B	CA, 23, F0		JZ DONE	When Z = 0, jump to DONE
F00E	80	LOOP	ADD B	Add B with A
F00F	27		DAA	Decimal Adjust
F010	57		MOV D,A	Store A to D
F011	D2, 19, F0		JNC NINC	Jump tp NINC
F014	7C		MOV A,H	Store H to A
F015	C6, 01		ADI 01H	Increase A by 1
F017	27		DAA	Decimal Adjust
F018	67		MOV H,A	Restore H from A
F019	7B	NINC	MOV A,E	Load E to A
F01A	C6, 01		ADI 01H	Increase A by 1
F01C	27		DAA	Decimal adjust
F01D	5F		MOV E,A	Restore E from A
F01E	B9		CMP C	Compare C with A
F01F	7A		MOV A,D	Load D to A
F020	C2, 0E, F0		JNZ LOOP	Jump to LOOP
F023	6F	DONE	MOV L,A	Load A to L
F024	22, 50, 80		SHLD 8050H	Store HL pair at location 8050 and 8051
F027	76		HLT	Terminate the program

Output

first output

Address	Data
…	…
8050	40
8051	02
…	…

second output

Address	Data
…	…
8050	81
8051	00
…	…