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Multiply Two 16-bit Numbers in 8085 Microprocessor

In this tutorial, we will learn how to find the multiplication of two 16-bit numbers in 8085 Microprocessor? By Ayush Sharma Last updated : May 13, 2023

8085 Program to Multiply Two 16-bit Numbers

Given two 16-bit numbers, we have to find their multiplication in 8085 Microprocessor.

Assumption

1. Starting address of program: 2000
2. Input memory location: 2050, 2051, 2052, 2053
3. Output memory location: 2054, 2055, 2056, 2057

Algorithm

1. Load the first data in HL pair.
2. Move content of HL pair to stack pointer.
3. Load the second data in HL pair and move it to DE.
4. Make H register as 00H and L register as 00H.
5. ADD HL pair and stack pointer.
6. Check for carry if carry increment it by 1 else move to next step.
7. Then move E to A and perform OR operation with accumulator and register D.
8. The value of operation is zero, then store the value else goto step 3.

Program

ADDRESS	MNEMONICS	COMMENTS
2000	LHLD 2050	Load H-L pair with address 2050
2003	SPHL	SAVE IT IN STACK POINTER
2004	LHLD 2052	Load H-L pair with address 2052
2007	XCHG	EXCHANGE HL AND DE PAIR CONTENT
2008	LXI H,0000H	H<-00H,L<-00H
200B	LXI B,0000H	B<-00H,C<-00H
200E	DAD SP
200F	JNC 2013	JUMP NOT CARRY
2012	INX B	INCREMENT BC BY 1
2013	DCX D	DECREMENT DE BY 1
2014	MOV A,E	A<-E
2015	ORA D	OR THE CONTENT OF ACCUMULATOR AND D REGISTER
2016	JNZ 200E	JUMP NOT ZERO
2019	SHLD 2054	L<-2053,H<-2054
201C	MOV L,C	L<-C
201D	MOV H,B	B<H
201E	SHLD 2056	L<-2055,H<-2056
2021	HLT	ENDS THE PROGRAM

Explanation

Registers B, C, D, E, H, L and accumulator are used for general purpose.

1. LHLD 2050: load HL pair with address 2050.
2. SPHL: save the content of HL in stack pointer.
3. LHLD 2052: load H-L pair with address 2052.
4. XCHG: exchange the content of HL pair with DE.
5. LXI H, 0000H: make H as 00H and L as 00H.
6. LXI B, 0000H: make B as 00h and C as 00H.
7. DAD SP: ADD HL pair and stack pointer.
8. JNC 2013: jump to address 2013 if there will be no carry.
9. INX B: increments BC register with 1.
10. DCX D: decrements DE register pair by 1.
11. MOV A, E: move the content of register E to accumulator.
12. ORA D: or the content of accumulator and D register.
13. JNZ 200E: jump to address 200E if there will be no zero.
14. SHLD 2054: store the result to memory address 2054 and 2055 from HL pair register.
15. MOV L, C: move the content of register C to L.
16. MOV H, B: move the content of register B to H.
17. SHLD 2056: store the result to memory address 2056 and 2057 from HL pair register.
18. HLT: terminates the program.

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