Microprocessor 8085 program to find the Subtraction of two 8-bit numbers

In the third year of the B.Sc. Physics program under TANSCHE, it's really important to learn how microprocessors work. One of the main experiments is with the Microprocessor 8085, which is a popular 8-bit processor. In this experiment, students get to practice basic math operations.

In this blog post, we will talk about the experiment called "Subtraction of Two 8-bit Numbers with the Microprocessor 8085." This hands-on activity helps students understand how the 8085 microprocessor works, including programming and memory tasks. By the end of this experiment, you'll have a good grasp of how the 8085 processes data and performs math operations, giving you a strong base in microprocessor systems.

Microprocessor 8085 program to find the Subtraction of two 8-bit numbers

Aim:

Write an assembly language program to subtract two 8-bit numbers (with and without borrow) using microprocessor 8085.

Apparatus required:

Microprocessor 8085 kit, power supply etc

Program:

Subtraction of two 8-bit numbers; sum 8-bit (without borrow)

Memory address	Machine code	Mnemonics	Operands	Comments
8000	21	LXI	H, 8501H	Address of the LSB of the number
8001	01
8002	85
8003	7E	MOV	A, M	Move the number to the accumulator
8004	23	INX	H	Increment the H-L pair
8005	96	SUB	M	Add the number in the memory with the accumulator
8006	32	STA	8503H	Store the result in the accumulator in the location 8503H
8007	03
8008	85
8009	76	HLT		Stop the program

Example:

Subtraction of two 8-bit numbers; sum 8-bit (without borrow)

First input location 8501H - 23H (In binary form 0001 0010)

Second input location 8502H - 12H (In binary form 0010 0011)

Result location 8503H - 11H (In binary form (0001 0001)

Subtraction of two 8-bit numbers; sum 16-bit (with borrow)

Memory address	Machine code	Labels	Mnemonics	Operands	Comments
8000	21		LXI	H, 8501H	Address of the LSB of the number
8001	01
8002	85
8003	0E		MVI	C, 00H	Store 00H to C register
8004	00
8005	7E		MOV	A, M	Move the number to the accumulator
8006	23		INX	H	Increment the H-L pair
8007	96		SUB	M	Add the number in the memory with the accumulator
8008	D2		JNC	AHEAD	Jump on no carry to AHEAD (800C)
8009	0C
800A	80
800B	0C		INR	C	Increment C register
800C	32	AHEAD	STA	8503H	Store the result in the accumulator in the location 8503H
800D	03
800E	85
800F	79		MOV	A, C	Move the content of C register to accumulator
8010	32		STA	8504H	Store the result in the accumulator in the location 8504H
8011	04
8012	85
8013	76		HLT		Stop the program

Example:

Subtraction of two 8-bit numbers; sum 16-bit (with borrow)

First input location 8501H - 03H (In binary form 0000 0011)

Second input location 8502H - 04H (In binary form 0000 0100)

By adding these two binary numbers the result is, 1 0000 0001

Result location 8503H - 01H (Sum)

Result location 8504H - 01H (borrow)

Procedure:

Result: 

The assembly programmes for microprocessor 8085 for subtraction of two 8-bit numbers were written and executed using the microprocessor 8085 kit.

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