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Assembly Language Programming

2

8051 Microcontroller

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CourseOutline

3

Week Topic

1 Introduction

28051Microcontroller

Architecture

3 Assembly Language

4 Assembly Language Contd.

5, 6

Timers and Counters

Serial Port

Interrupt7 Design and Interface Examples

88086 / 8088 Microprocessor

Introduction and Architecture

9 Midterm Exam

10 Hardware and Design

11 Programming in Assembly

12 PIC 18 F Microcontroller Introduction, Architecture, I/O Pins

13 Programming

14 Timers

15, 16 Peripherals of PIC 18F Microcontrollers

17 Revision

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AssemblyLanguage

Introduction Instruction Set

Software - Keil

AssemblerDirectives

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Programming Languages

Assembly is aLowLevelLanguage High Level

Middle Level

Low Level

5

Assembly

C++

C

FORTRAN

Pascal

COBOL

BASIC

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Assembly LanguageLow Level Language

English-like abbreviations Represent basic operations of computer

Translated to machine language Assemblers convert to machine language

High speed conversion

Easier for human interpretation as comparedlanguage

to Machine

Still tedious and difficultMany instructions for simple tasks

These problems led to High Level languages

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GeneralFormatofAssemblyProgram

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Assembly Language General Format of

Assembly Program

mnemonics operand , [operands]

Sourcedestination,

[label]: mnemonics operand , [operands]Sourcedestination,

Brackets shows that the component is optional

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Assembly Language

General Format ofAssembly Program[label]: mnemonics operand , [operands]

Sourcedestination,

Labels: are used toname

represent addressof a line witha

Labels must end with a colon

Operand: on which the operation is performed

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Assembly Language General Format of

Assembly Program

[label]: mnemonics operand , [operands]

Sourcedestination,

Mnemonics: InstructionExample:

or command

mov A,#67h mov is mnemonic A and #67h are operands

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Assembly Language

Comments Comment begins with a semicolon (;) Assemblerignores the comments

Example:;Thisisacomment

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Instruction Set

8051 Instructions have 8 bit Opcode28 Combinations = = 256 255 are 139

92 24

implemented1

23

Byte

ByteByte

instructions

instructionsinstructions

1 Machine Could take

instruction

cycle = 12 clock cycles1, 2 or 4 Machine Cyclesto execute an

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InstructionSetSummary

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InstructionSet

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Keil for Assembly Programming of 8051

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Keil Vision

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UsingKeilforAssemblyProgramming

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NewProject

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SelectDevice

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NewFile(forcode)

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AddCodetoProject

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Debug Mode

Write Code Save (Ctrl + S)

Build Target File

Debug Mode

(F7)

Ctrl+F5

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DebugMode

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DebugMode

Registers

Accumulator

PSW

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Disassembly(onlyindebugmode)

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Disassembly(onlyindebugmode)

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Disassembly(onlyindebugmode)

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Assembler Directives Change state of assembler

Define Symbols, add informationto the object file etc

Must not be confused withInstructions.Theydonotproduceexecutablecode

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Assembler Directives

Address ControlSymbol Definition

1.

2.

3.

4.

MemoryOthers

Initialization

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Assembler DirectivesAddress Control

ORG, USINGSymbol Definition

Generic Symbols: EQU,

1.

2.SET

Address Symbols: BIT,SFR Symbols: sfr, sbit

Memory Initialization

DBIT, DB, DW

OthersEND

DATA,XDATA

3.

4.

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Address ControlORG Changes location counter of currently active segment

Sets new origin for subsequent statements

Format

ORG expression

where expression must be an absolute address without any forward references

Only absolute addresses and symbols in current segment can be used

When ORG statement is encountered, the assembles calculatesvalue of the expression and changes location counter of current

segment

Examples

ORG 100HORG RESTART

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Address ControlUSING

4 Register Banks USING specifies Format

whichRegister Bank isactive

USING expression

where

expressionvalue fromis the register bank number0 and 3 and itmust be a

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Symbol Definition Symbols and labels can

from the following list:becomposed of31characters

A -Z, a - z,0 - 9, _ and ?

A9

symbolcanstartwithanyoftheseexceptthedigits0-

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Symbol DefinitionEQU and SET Used to create symbols

and addresses Similar to Define in C

that represent registers, numbers

Assign a numeric value / register symbol to the specificsymbol nameDifference between EQU and SET

Symbols defined with EQU may not haven been

previously defined by EQU and can not be redefined

The SET directive allows later redefinition of symbols

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Symbol DefinitionEQU and SET FormatsofSET/ EQU statements are:

symbol EQU expressionsymbol EQU register

symbol

symbol

SET expression

SET register

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Symbol DefinitionEQU and SET symbol is the name of symbol to define

expression specified will be substituted for eachoccurrence of the symbol used in program. expressionnumeric expression which has no forward references

is

register is one of the 8 registers (in the active bank)

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Symbol DefinitionExamples

LIMIT EQU 1200 VALUE EQU LIMIT-200

SERIAL EQU SBUF

VALUE SET 100

COUNTERSET R1COUNTERCOUNTER*VALUE

TEMP TEMP

SETSET

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Symbol Definition - Address Symbols

The BIT, DATA, and XDATA directives assignvalue to the specified symbol

an address

Symbols defined with the BIT, DATAandXDATAdirectivescannotbechangedorredefined

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Symbol Definition - Address SymbolsFormat: BIT, DATA, XDATA

symbol BIT bit_address ; defines a BITsymbol

symbol DATAdata_address ; defines a DATA symbol

symbolXDATAxdata_address ; defines XDATA symbol

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Symbol Definition - Address SymbolsFormat: BIT, DATA, XDATA

Symbol: name of symbol to be defined

Bit_address: is the address of a bit in internalmemory in the area 20h to 2Fh data

Data_address: data memory address

xdata_address is an xdata memory address65535

inrange0 to

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Symbol Definition SFRSymbolssfr, sbitsfr

sfr symbol = address

sbit

sbit symbol = bit-address

Sfr_symbol is the name of symbol to bedefined address is an SFR address with which the symbol

associated bit-address is address of an SFR Bit

is to be

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Memory Initialization

Memory initialization directivesareusedtoinitializecodeor constant space in byteunits

DBIT Used

DB

Used

DW

todefinea bit

todefinebyte 8 bit

UsedtodefineWord 16 bits

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Assembler Directives - OthersEND

Signals the end of assembly module Any text that appears after END is ignored

END directive is required in every assemblymoduleIfmissing,awarningmessageisgenerated byassembler

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Number RepresentationD (or nothing) Decimal

H for Hex

Q for Octal

B for Binary