how to use easy68k

8/19/2019 How to Use Easy68k

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Assembly Language


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Introduction

Computers only understand binary code:

Machine language.

Everything is 0’s and 1’s. Instructions.

Data.

Control signals.Hard for humans to understand.


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Try and translate this:

00110000001111000000000000010010


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Try and translate this:

00110000001111000000000000010010

MOVE.W #$12,D0

00 11 000000 111 100 0000 0000 0001 0010

(Data register directaddressing mode, D0)


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Assembly Language

We can represent machine code in AssemblyLanguage:

Easier to understand, program. Simple, low-level programming language.

Using mnemonics (ADD, MOVE, MULU).

Close to human language.

Code generated is machine-specific:

Each µP has own assembly language.


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Assembly Language

Assembler to generate machine code.

Object file (Motorola: S-file).

Contains machine code.

Linker sometimes used for big projects:

Links together multiple S-files.

Creates single S-file from combined files.


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The Assembler

Machine Language:

001100000011110000110010001111000000000000110100

Assembly Language:

MOVE.W #$12,D0

MOVE.W #$34,D1

MULU D1,D0

Assembler


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AssemblyFile #1

AssemblyFile #2

AssemblyFile #3

AssemblyFile #4

ASSEMBLER

ObjectFile #1

ObjectFile #2

ObjectFile #3

ObjectFile #4

LINKER

Final ObjectFile

Listing File


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Source Code (X68)


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Object File (S-File)


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Listing File


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Data Representation

Methods


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Data Sizes

Bit:Most basic representation.Contains either 0 or 1. Can be grouped together to represent more meaning.

Nibble: 4 bits.Can represent 16 values (24). Not recognized in M68k.

Need to write special program to handle. Byte: 8 bits.

Indicated by “.B” notation. Can hold value up to 256 (28).


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Data Sizes

Word: 16 bits.Length of most instructions in M68k.

Can hold value up to 65,535 (216). Indicated by “.W” notation.

Long: 32 bits.

Length of data registers in M68k.Can hold value up to 4,294,967,296 (232).

Indicated by “.L” notation.


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Bit (1)

Nibble (4)

D3 D0

Byte (8)D7 D0

D15 D0

Word (16)

Long (32)

D31 D0

Data Sizes


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Data Representation Method

M68k can accept many types of data:

Binary

Octal

Hexadecimal

Decimal

Character


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Binary

Binary: start with %

Example:

Move binary value 10010101 to D0.

MOVE.B #%10010101,D0

D0 = 0 0 0 0 0 0 9 5

10010101B = 95H


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Octal

Octal: start with @

Example:

Move octal value 45 to D0.

MOVE.B #@45,D0

D0 = 0 0 0 0 0 0 2 5

45O = 25H


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Decimal

Decimal: no need to put any symbols.

Example:

Move decimal value 10 to D0.

MOVE.B #10,D0

D0 = 0 0 0 0 0 0 0 A

10D = 0AH


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ASCII Characters

Characters: Enclose character in singlequotes (‘ ’).

Example:Move ASCII character ‘A’ to D0.

MOVE.B #’A’,D0

D0 = 0 0 0 0 0 0 4 1

A = 41H


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Easy68k


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Easy68k

Designed by Prof. C. Kelly, MonroeCounty Community College.

Freeware.

Installer: http://www.easy68k.com/index.html

Easy68k Quick-Ref:http://www.easy68k.com/QuickStart/LoadPageFrames.htmhttp://www.easy68k.com/files/EASy68KQuickRef.pdf

http://www.easy68k.com/QuickStart/LoadPageFrames.htmhttp://www.easy68k.com/files/EASy68KQuickRef.pdfhttp://www.easy68k.com/files/EASy68KQuickRef.pdfhttp://www.easy68k.com/QuickStart/LoadPageFrames.htm


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Easy68k Interface

LABEL

INSTRUCTION

VARIABLES/PARAMETERS

ANYTHING PAST THIS ISIGNORED, TREATED AS COMMENT.

PROGRAM DESCRIPTION


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Programming in Easy 68k

Easy68k divides program into columns: Label:

Marks memory locations using characters.

Easy reference. Instruction:

What instruction to execute.

Variables/Parameters: Usually specifies source & destination.

May specify parameters as well. Comment:

Used to describe flow of program,


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Simulation Window

Shows status of internalM68k registers.

Memory addresswhere instructionis stored.

Machine code generatedby assembler.

Press here to executeprograms step-by-step.

Press here to restartprogram execution.


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MOVE.B #9,D0 instruction:

Is on line 11 in M68k source file.Is stored in memory address $1000.Its machine code is $103C0009 (00010000001111000000000000001001).


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Specify Start/End of Program

M68k needs to know where to startexecuting instructions, where to stop.

Specified using ORG (Origin), END (End). Value of ORG loaded into PC, execution

starts there.


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Format: Start/End Program

ORG $1000

END $1000

Program Instructions

PC loaded with $1000,starts executing from here.

END specifies ending of program.


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Format: Start/End Program

START ORG $1000

END START

Program Instructions

PC loaded with $1000,starts executing from here.

END specifies ending of program.


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Use Labels

Any memory location may be given labels.

Easier to refer to specific locations:Useful in for loops, subroutines, branch

commands.


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Using Labels - Example

START ORG $1000

MOVE.B #$2000,A0

MOVE.B #$10, D1CLR.B D0

LABEL1 ADD.B (A0)+, D0SUB.B #1, D1

BNE LABEL1

END START


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Flowchart


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Flowchart

Graphical method to plan flow of ourprograms.

Shows program’s step-by-step operation. Easy to understand and analyze.

Can be used to write organized programs.


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Flowchart Basic shapes:

Terminator.

Process.

Decision.

Input/Output.

Connectors.

A = A + B

D0 = 3?

TRUE FALSE

Input D0


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Basic Shapes – Terminator

Indicates beginning and end of flowchart.

Once at beginning, once at end.

Examples:

START FINISH


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Basic Shapes - Process

Describes actions to be done.

Represented as rectangles.

Short description of process in rectangle.

Example:

A = A + B Reset Ports Clear D0


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Basic Shapes - Decision

Shows alternative program flow based oncondition.

Represented as diamond shape. Should have 2 arrows, representing

TRUE and FALSE program flows.

Can be used in “if…else”, “while”, and “for”situations.


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Basic Shapes - Decision

Examples:

D0 = 3?

TRUE FALSE

Port is active?TRUE

FALSE


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Basic Shapes – Input/Output

Shows the process of inputting oroutputting data.

Represented using rhombus. Examples:

Input D0 Show calculationresults


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Basic Shapes - Connectors

Used to link large process flows together.

Represented using circles, with numbers

inside. Numbers indicate connection.

Examples:

1 3


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Writing the Program

Once flowchart is complete, write code toimplement program.

Follow program flow closely. Check and fix problems if necessary.


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Example: Calculate Area of

RectangleB

L

START

Input L

Input B

1

Area = L xB

1

FINISH


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Translation to Assembly

START

Input D0

Input D1

D0 = D0 x D1

FINISH

ORG $1000

MOVE.W #$12,D0

MOVE.W #$34,D1

MULU D1,D0

END


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Complete Program

START ORG $1000

MOVE.W #$12,D0

MOVE.W #$34,D1

MULU D1,D0

END START


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Example: Add 10 Numbers

Together START

Input numbersinto memory

locations.

D0 = 10

Load startingaddress into A0

Clear D1

FINISH

D0 = 0?

D1 = D1 + (A0)

FALSE

Go to nextmemory location

D0 = D0 - 1

TRUE


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START

Input numbersinto memory

locations.

Load startingaddress into A0

ORG $1000

MOVE.W #$11,$1100MOVE.W #$22,$1102

MOVE.W #$33,$1104MOVE.W #$44,$1106MOVE.W #$55,$1108MOVE.W #$66,$110AMOVE.W #$77,$110CMOVE.W #$88,$110E

MOVE.W #$99,$1110MOVE.W #$11,$1112

MOVEA.L #$1100,A0


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D0 = 10

Clear D1

D0 = 0?

D1 = D1 + (A0)

FALSE

D0 = D0 - 1

MOVE.B #10,D0

CLR.B D1

Go to nextmemory location

LOOP…BNE LOOP, CMP.B #$0,D0

ADD.W (A0),D1

ADDA.L #$2,A0

FINISH

SUB.B #$1,D0

END


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Complete Program

START ORG $1000

MOVE.W #$11,$1100MOVE.W #$22,$1102MOVE.W #$33,$1104MOVE.W #$44,$1106MOVE.W #$55,$1108MOVE.W #$66,$110AMOVE.W #$77,$110CMOVE.W #$88,$110EMOVE.W #$99,$1110MOVE.W #$11,$1112

MOVEA.L #$1100,A0MOVE.B #10,D0

CLR.B D1

LOOP ADD.W (A0),D1ADDA.L #$2,A0SUB.B #$1,D0CMP.B #$0,D0BNE LOOP

END START


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Conclusion


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Conclusion

Assembly language:

Mnemonics instead of binary.

Needs assembler to convert to machine code.

Easy68k organizes code in columns.

Flowcharts simplify program design:

Organize program flow.

Easier to manage and debug.

how to use easy68k

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