8051 Assembly Code Collection

⚙️ Addition Operation

AIM:
To perform addition
APPARATUS:
PC with Keil software
MOV A, #12h  
MOV R1, #23h  
ADD A, R1  
here: SJMP here
OUTPUT:
A = 35h

➖ Subtraction Operation

AIM:
To perform subtraction
APPARATUS:
PC with Keil software
MOV A, #45h  
MOV R1, #25h  
SUBB A, R1  
here: SJMP here
OUTPUT:
A = 20h

✖️ Multiplication Operation

AIM:
To perform multiplication
APPARATUS:
PC with Keil software
MOV A, #06h  
MOV B, #07h  
MUL AB  
here: SJMP here
OUTPUT:
A = 2Ah (Lower byte of result)
B = 00h (Upper byte of result)

➗ Division Operation

AIM:
To perform division
APPARATUS:
PC with Keil software
MOV A, #1Eh  
MOV B, #05h  
DIV AB  
here: SJMP here
OUTPUT:
A = 06h (Quotient)
B = 00h (Remainder)

📦 Move Block Data

AIM:
To write a program to move a block of data from one location to other
APPARATUS:
PC with Keil software
ORG 00H                     ; Set code starting address

MOV R2, #05H               ; R2 = counter = 5 bytes to move
MOV R0, #50H               ; R0 points to source block
MOV R1, #70H               ; R1 points to destination block

loop: MOV A, @R0           ; Load value from source address into A
      MOV @R1, A           ; Store value from A to destination address

      INC R0               ; Move to next source location
      INC R1               ; Move to next destination location

      DJNZ R2, loop        ; Decrement counter and repeat if not zero

here: SJMP here            ; Infinite loop to end program

END                        ; End of source code
OUTPUT:
Contents of memory from address 50H–54H are copied to 70H–74H

📡 Serial Communication (4800 Baud)

AIM:
To write a program to transmit letter 'N' serially at 4800 baud
APPARATUS:
PC with Keil software
MOV TMOD, #20H             ; Timer1 in Mode2 (8-bit auto-reload)
MOV TH1, #0FAH             ; Load value for 4800 baud (TH1 = -6 = FAH)
MOV SCON, #50H             ; Serial mode1, 8-bit data, 1 stop bit, REN enabled
SETB TR1                   ; Start Timer1

AGAIN: MOV SBUF, #'N'      ; Load letter 'N' into serial buffer

HERE:  JNB TI, HERE         ; Wait until transmission complete
       CLR TI               ; Clear TI flag
       SJMP AGAIN           ; Repeat

💡 Stepper Motor Interface

AIM:
To demonstrate the stepper motor interface
APPARATUS:
8051 microcontroller, PC with Keil software
code segment
assume cs:code

start:  mov ax, 0h         ; Clear AX register
        mov dx, 0ffh       ; Load DX with port address
        out dx, al         ; Clear output port

        mov al, 0aah       ; Load initial stepper pattern
        mov cx, 100        ; Load CX with step count

g1:     mov dx, 0ffh       ; Load DX with port again
        out dx, al         ; Output current pattern to port
        call delay         ; Call delay subroutine
        rol al, 1          ; Rotate left to get next step pattern
        loop g1            ; Loop until 100 steps complete

        mov al, 100        ; Optional stop/cleanup signal

g2:     out dx, al         ; Output to port
        call delay         ; Final delay
        jmp g2             ; Infinite loop to halt

; DELAY SUBROUTINE
delay:  nop                ; No operation (waste time)
        nop                ; No operation (waste time)
        mov w, #ffh        ; Load delay counter

go:     dec bw             ; Decrement delay value
        jnz go             ; If not zero, continue looping
        ret                ; Return to caller

🧠 Logical Operations (AND, OR, XOR, NOT)

AIM:
To perform logical operations AND, OR, XOR, and NOT on 8051
APPARATUS:
PC with Keil software
; main.asm
; 8051 Logical Operations - AND, OR, XOR, NOT
ORG 0000H
MOV A, #0F0H     ; A = 11110000b
MOV R1, #0AAH    ; R1 = 10101010b
ANL A, R1        ; AND → A = A & R1
MOV 30H, A       ; Result → 30H
MOV A, #0F0H
ORL A, R1        ; OR
MOV 31H, A
MOV A, #0F0H
XRL A, R1        ; XOR
MOV 32H, A
MOV A, #0F0H
CPL A            ; NOT (complement)
MOV 33H, A
SJMP $
END
OUTPUT:

                        30H = A0H (AND result: 11110000 & 10101010 = 10100000)

                        31H = FAH (OR result: 11110000 | 10101010 = 11111010)

                        32H = 5AH (XOR result: 11110000 ^ 10101010 = 01011010)

                        33H = 0FH (NOT result: ~11110000 = 00001111)
                    

🔌 DAC Interface - Square Wave Generator

AIM:
To write a program to generate a square wave using dual DAC interface
APPARATUS:
8051 Microcontroller
code segment
assume cs:code

start:  
        mov al, 0FFh        ; Load AL with high value (255)
        mov dx, 0FF0Ch      ; DAC port address
        out dx, al          ; Send high value to DAC

b:      
        mov al, 00h         ; Load AL with low value (0)
        mov dx, 0FF0Ch      ; DAC port address
        out dx, al          ; Send low value to DAC
        call delay          ; Short delay

        mov al, 0FFh        ; Load AL with high value again
        mov dx, 0FF0Ch      ; DAC port address
        out dx, al          ; Send high value to DAC
        call delay          ; Short delay

        jmp b               ; Infinite loop to keep toggling
        int 3               ; Breakpoint (for debugging, optional)

; DELAY SUBROUTINE
delay:  
        mov cx, 64FFh       ; Load delay count (random long value)
d0:     
        nop                 ; No operation (waste 1 cycle)
        loop d0             ; Decrement CX, loop till zero
        ret                 ; Return from subroutine