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8051 Assembly Language8051 Assembly LanguageProgrammingProgramming

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8051 Assembly LanguageProgramming

OutlinesOutlines 8051 programming model

Assembly language syntax

Operation codes and operands

How 8051 interprets binary data

Machine instructions Example of Assembly language program

8051 Instruction Set

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Programming Model

A programmer should; Know the internal structure of the 8051

Understand the Programming modeli.e. how programmers see the 8051

Know how to access the registers and

accumulators with programs

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Binary Data

Unlike human, computers do not know verbalinstructions; they only know 0s and 1s.

Binary data: program in a stream of 0s and 1s

It is also called Machine Language

For convenient purpose, machine languageprograms are usually expressed in hexadecimal(i.e. base-16) format

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8051 Programming Model

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8051 Registers8051 Registers

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8051 Registers8051 Registers

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8051 Program Counter & ROM Space8051 Program Counter & ROM Space

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Assembly Language Syntax Syntax = format/rule

[label:] mnemonic [operands] [;comment] Items in square brackets are optional

Example:

Thus, Machine Code = Operation Code (Opcode) + Operand

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Mnemonic/ Operation Code

(Opcode)

Program = a set of instructionsAll computers work according to the

program

All instructions contain a verb , whichtells the computer what to do

This verb is called mnemonic/operationcode e.g. MOV R0, #12h MOV is theopcode

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Operand Apart from Opcode, an instruction also includes

object to act on. The object is called an operand.

Operand is optional. Instructions can have one,

two or no operands.

e.g.

MOV R0, #12h --- R0 and #12h are two operands ADD R1 --- R1 is the only one operand

NOP --- no operand follows

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Pseudo-Instructions/DirectivesAssembler state controlAssembler state control

ORG (origin)

indicates the beginning of the instructions. The numberthat either hex or decimal.

END Indicates the end of assembly instructions.

EQU (equate)

used to define a constant without occupying a memorylocation. It does not set aside storage for a data itembut associates a constant value with a data label so thatwhen the label appears in the program. Its constant

value will be substituted for the label. Eg. COUNT EQU 25H

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Define Byte (DB) and Data TypesDefine Byte (DB) and Data Types

Used to define 8-bit data and store them inassigned memory locations. Define data can be indecimal, binary, hex, or ASCII formats.

ORG 500HORG 500H

DATA1: DB 28DATA1: DB 28 ;DECIMAL (1C in Hex);DECIMAL (1C in Hex)

DATA2: DB 00110101BDATA2: DB 00110101B ;BINARY (35 in Hex);BINARY (35 in Hex)DATA3: DB 39H ;DATA3: DB 39H ;HEXHEX

ORG 510HORG 510H

DATA4: DBDATA4: DB 25912591 ; ASCII NUMBERS; ASCII NUMBERSORG 518HORG 518H

DATA6: DBDATA6: DB My name isMy name is DeenDeen ;ASCII CHARACTERS;ASCII CHARACTERS

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Opcodes Assembly languageAddress/Program Pointer

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Programming is both a scienceProgramming is both a science

and art !!and art !!

ScienceScience rules of grammar,rules of grammar,punctuation, spelling &punctuation, spelling &

structure.structure.

ArtArt how the words arehow the words arearrangedarranged

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How to tell a lump of sand what to do:How to tell a lump of sand what to do:

1. study common programming techniques

2. analyze example programs

3. write many practice programs

[ Read chapter 4 from Ayala for revision on basic assembly languagRead chapter 4 from Ayala for revision on basic assembly language concepts.e concepts.]

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Program Development

Stop

Create /edit

source codes

Assemble

source codes

Syntax

Errors?

Test / debug

program

Logical

Errors?

Start

Yes

Yes

No

No

Text editor

Debugger

Assembler

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Steps to Create a ProgramSteps to Create a Program

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Assembler/LinkerAssembler/Linker

AssemblerAssembler

Change mnemonic code into machine codeChange mnemonic code into machine code

Label can be used to represent symbolicLabel can be used to represent symbolic

address/dataaddress/data

Directives : like preDirectives : like pre--processing operator (#) in Cprocessing operator (#) in C

language.language.

Linkage EditorLinkage Editor Link objective code into executable fileLink objective code into executable file

(*.(*.objobj *.exe)*.exe)

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List File For Test Program (Assembly)List File For Test Program (Assembly)

Opcodes Assembly language

Address/Program Pointer

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Terima Kasih,

Ceria-ceriaSelalu

&Jumpa

Lagiiiiii!!!