8085 program to find the sum of a series

Problem – Write a program to find the sum of a series where series starts from 3001 memory address and count of series is at 3000 memory address where starting address of the given program is 2000 store result into 4000 memory address.

Example –

Algorithm –

1. Move 00 to register B immediately for carry
2. Load the data of memory [3000] into H immediately
3. Move value of memory into register C
4. Decrease C by 1
5. Increase H-L pair by 1
6. Move value of memory into accumulator
7. Increase H-L pair by 1
8. Add value of memory with accumulator
9. Jump if no carry to step 11
10. Increase value of register B by one
11. Decrease register C by 1
12. Jump if not zero to step-7
13. Store content of accumulator into memory [4000] (result)
14. Move content of register B into accumulator
15. Store content of accumulator into memory [4001] (carry)
16. Stop

Program –

Memory	Mnemonics	Operands	Comment
2000	MVI	B, 00	[B] <- 00
2002	LXI	H, [3000]	[H-L] <- [3000]
2005	MOV	C, M	[C] <- [M]
2006	DCR	C	[C] <- [C] – 1
2007	INX	H	[H-L] <- [H-L] + 1
2008	MOV	A, M	[A] <- [M]
2009	INX	H	[H-L] <- [H-L] + 1
200A	ADD	M	[A] <- [A] + [M]
200B	JNC	200F	jump if no carry
200E	INR	B	[B] <- [B] + 1
200F	DCR	C	[C] <- [C] – 1
2010	JNZ	2009	jump if not zero
2013	STA	[4000]	result
2016	MOV	A, B	[A] <- [B]
2017	STA	[4001]	carry
201A	HLT		Stop

Explanation – Registers A, B, C, H are used for general purpose.

1. MVI is used to load an 8-bit given register immediately (2 Byte instruction)
2. LXI is used to load register pair immediately using 16-bit address (3 Byte instruction)
3. MOV is used to transfer the data from accumulator to register(any) or register(any) to accumulator (1 Byte)
4. RAR is used to shift ‘A’ right with carry (1 Byte instruction)
5. STA is used to store data from accumulator into memory direct using 16-bit address (3 Byte instruction)
6. INR is used to increase given register by 1 (1 Byte instruction)
7. JNC is used to jump to the given step if their is no carry (3 Byte instruction)
8. JNZ is used to jump to the given step if their is not zero (3 Byte instruction)
9. DCR is used to decrease given register by 1 (1 Byte instruction)
10. INX is used to increase register pair by 1 (1 Byte instruction)
11. ADD is used to add value of accumulator with the given value (1 Byte instruction)
12. HLT is used to halt the program