Introduction to 8051 Assembly Programming

Introduction to 8051 Programming in Assembly Language 8051

This is a low level programming language to code program using mnemonics and all programmer use low level programming language in the development. There are many other high level languages used in development but Assembly language is used popularly all over by embedded programmers. Direct hardware manipulations and memory access and other functions are important.

Important Rules of 8051 Core Assembly Language

  • All code must be written in upper case letters, no lower case.
  • a colon must be followed by label.
  • A letter is mandatory to define labels.
  • Comments use only lower case.
  • END directive is must in the last line.
  • Op-code means MOV, ADD, JMP, are used to perform all important operations.

Op-code: A single instruction code executed by CPU. Here example op-code is Move.

Operands: an op-code is used to execute a single piece of data instruction, Like multiplication etc.

Instruction Set:
The instruction set is the architecture of controller that executes commands to the controller for processing the data. It contains native code, data type, interrupt register, addressing modes, memory architecture and exceptional handling. 8051 core microcontroller used CSIC with Hardvard architecture. There are following instruction sets use to program 8051 using assembly language.


  • Data Transfer Instruction set
  • Sequential Instruction Set
  • Arithmetic Instruction set
  • Branching Instruction set
  • Loop Instrcution Set
  • Conditional Instruction set
  • Unconditional Instruction set
  • Logical Instruction set
  • Boolean Instruction set
  • Arithmetic Instruction Set


ORG 0000h
MOV R0, #03H
MOV A, #05H
Add A, 00H


ORG 0000h
MOV R0, #03H
MOV A, #05H
MUL A, 03H

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