09 Assembly Example

7/29/2019 09 Assembly Example

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Assembly Language Example


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Todays Topics

owc ar s

Practice assembly programming


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Flowcharts

ere are o er more sop s ca e me o s o represen ngprograms.

owc arts wor we or so tware wr tten n assem y co elevel.

e w see og ca u ng oc s n owc art ormats a ongwith assembly code templates.


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Flowcharts

Meaning of symbols ere are many more sym o s o er an

these.Start or End

apes may e erent.

In this course, those four symbols areflow

pretty muc a we nee .Decision

Process


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Flowcharts

If-Then-Elsee s or ec s on

Bxx Process A

Process B code

If(PillColor == RED)RealWorld

Color of Pillis RED?

TRUE

MatrixMatrix RealWorld

FALSE

l daa Pi l l Col orcmpa #RED

bne l mat r i xReal Wor l dbr a l ski p

l mat r i x: Mat r i xl ski p: . . .


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Flowcharts

While-Doe s or ec s on

Bxx past BRA

Process code

BRA to Bxx

l daa KnowThi sl l oop: cmpa #YES

KnowThis? StudyMore

TRUE

FALSE

St udyMor el daa KnowThi s

br a l l ool next : Next St ep


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Flowcharts

Repeat-Untilrocess co e

Set CCR bits

Bxx to Process codeDoSomething

Example:l oop: DoSomet hi ng

beq l donebr a l oop

Is the Jobdone?

FALSE

TRUE


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Flowcharts

Bxx to Process 1Set CCR bitsBxx to Process 2

Case

Bxx to Process NDefault Process code

BRA past Process N codeProcess 1 code

nTemp

< 20 TurnOnHeater

TRUE

Process 2 codeBRA past Process N codeProcess N code

FALSE

nTemp< 70

FlashIndicatorTRUE

Example:l daa nTempcmpa #20bhs l 1

FALSE

nTem TRUE

br a l r esl 1: cmpa#70

bhi l 2

Fl ashI ndi cat or

< 100urn n oo er

FALSE

l 2: cmpa #100bhi l 3

TurnOnCool erbr a l r es

Alarm

l r es:


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Flowchart Guidelines

o no re er o reg s ers n e owc ar

Arrows should never cross They will not need to if the flowchart represents a structured

program

e purpose s to remove any quest ons a out ow toprogram and understand the algorithm, and this usuallydetermines when the flowchart contains enough detail.


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Assembly Example

onver an array o - y e g- n an va ues o an array oLittle-Endian values.

et

$1000 hold the address of the array of Big-Endian values,

$1002 hold the address of the array for the Little-Endian values,

$1004 hold the two-byte length of numbers to convert. Write an assembl ro ram to im lement these re uirements.


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Start

1: Point to the first BE item

2: Point to the first LE item

3: Make a copy of the length

4. There are nomore elements

TRUE

5: Copy 1st BE byte to 4th LE byte

6: Co 2nd BE b te to 3rd LE b te

7: Copy 3rd BE byte to 2nd LE byte

9: Point to next elements & dec length

End


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or g $1000Bend ds. w 1LEnd ds. w 1

Start

.

TmpLen ds. w 1or g $2000l dx BEnd


2: Point to the first LE item

l dd Lengt hLoop std TmpLen ; 3

beq Done


,st aa 3, y ; 2l daa 1, x ; 3st aa 2, y ; 2


TRUE

,

st aa 1, y ; 2l daa 3, x ; 3st aa 0, y ; 2


6: Co 2nd BE b te to 3rd LE b te

i nxi nx

i nx


i nyi nyi ny


subd #$0001br a Loop

Done swiEnd


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or g $1000Bend ds. w 1

Start

End s. wLengt h ds . w 1

or 2000


2: Point to the first LE item l dx BEndl dy Lend

l dd Lengt h


oop eq onemovb 0, x, 3, y ; 5movb 1, x, 2, ymovb 2 x 1


TRUE

movb 3, x, 0, yl eax 4, x ; 2l eay 4, y


6: Co 2nd BE b te to 3rd LE b tesu ;br a Loop

Done swi



EndNote:Youcansave10(=3+2x2 +3)cycles.


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Questions?


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Wrap-up

What weve learned owc ar s

Templates will be greatly helpful.

ssem y program examp e


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What to Come

r me c ns ruc ons

Logic instructions

Documents

09 Assembly Example