embed system designing

7/25/2019 embed system designing

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r. Bassel SoudanEmbedded Systems Design 1

Embedded Systems Design

0403334


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Embedded Systems Overview

Computing systems are everywhere

Most of us think of desktop! "omputers# $C%s

# &aptops

# Mainframes

# Servers

'ut there%s another type of "omputing system# (ar more "ommon)))


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Embedded Systems Overview

Embedded "omputing systems*# Computing systems embedded within e+e"troni"

devi"es)

# ,ard to define) -ear+y any "omputing system

other than a desktop "omputer)

# 'i++ions of units produ"ed year+y. versus mi++ions of

desktop units)

# $erhaps /0 per househo+d and per automobi+e)


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Common Chara"teristi"s of Embedded Systems

Sing+efun"tioned# E1e"utes a sing+e program. repeated+y)

2ight+y"onstrained

# &ow "ost. +ow power. sma++. fast. et")

ea"tive and rea+time# Continua++y rea"ts to "hanges in the system%s

environment)

# Must "ompute "ertain resu+ts in rea+time without

de+ay)


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Design Constraints

&imited $ower)# Most embedded systems operate within battery operated

euipment)

&imited Memory)

# 5n embedded system is "onstrained to a finite and sma++amount of memory)

ea+2ime)# Most embedded systems are used in a "ontro+ fun"tion)

# 2hey are e1pe"ted to sense the rea+time status of the

system in whi"h they are housed and produ"e rea+time

responses)


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Definition of Embedded System

5n embedded system is a mi"ropro"essorbasedsystem that is bui+t to "ontro+ a fun"tion or rangeof fun"tions and is not designed to be

programmed by the end user)

# 2he user may make "hoi"es "on"erning the

fun"tiona+ity of the system but "annot "hange the

fun"tiona+ity of the system by adding6rep+a"ing

software)

# Can you program! your refrigerator7

May be sooner than you think)


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5dvantages of Mi"ropro"essorbased

ep+a"ement of dis"rete +ogi"based "ir"uits) $rovide fun"tiona+ upgrades) $rovide easy maintenan"e upgrades) 8mprove me"hani"a+ performan"e)

$rote"tion of inte++e"tua+ property 98$:) ep+a"ement of ana+og "ir"uits)


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E+ements of an Embedded System

$ro"essor Memory

# $rovide storage for the software and data)

$eriphera+s

Software# 8nitia+i;ation and Configuration)

# Operating System)

# 2he app+i"ation software)

# Error hand+ing)

# Debug and maintenan"e support)


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Embedded System Mi"ro"ontro++er

Embedded systems are main+y intended toprovide "ontro+ over the behavior of the systeminto whi"h they are housed)

# 2herefore. it is "ustomary to ta+k about anembedded "ontro++er rather than an embedded

pro"essor)# 8t does pro"ess information but main+y for the

purpose of "ontro+)


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'+o"k Diagram of a Mi"ropro"essor

5 mi"ropro"essor "onsists of an 5&= to performarithmeti" and +ogi" manipu+ations. registers. and a"ontro+ unit)

8n addition.its has someinterfa"es tothe outsidewor+d in theform of busses)


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'+o"k Diagram of a Mi"ro"omputer

2oo mu"h)# (or the +imited app+i"ations intended. this system has too

mu"h of everything) Meaning # too e1pensive)


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,ow do we Define E1pensive7

Money)# 2he system reuires parts that "ost too mu"h money)

Si;e)# 5++ of the additiona+ fun"tiona+ity reuires spa"e)

Chip area or board spa"e)

$ower)# heat)

# Operating inside! another system may not afford us goodheat dissipation)

Effi"ien"y)# 5re we rea++y uti+i;ing a++ of these features and

fun"tiona+ities7


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'+o"k Diagram of a Mi"ro"ontro++er

8t is the spe"ia+i;ed "ir"uitry "ompared to themi"ropro"essor that makes the mi"ro"ontro++ersu"h a uniue devi"e)

2he mi"ro"ontro++eroperates on data thatis fed in through its

seria+ or para++e+ input

ports "ontro++ed bythe software stored

in the on"hip

memory)


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Spe"ia+ (eatures of the Mi"ro"ontro++er

5++ of the additiona+ fun"tions bui+t into the mi"ro"ontro++er

wou+d norma++y reuire additiona+ "ir"uitry e1terna+ to themi"ropro"essor)# 86O $orts)

# Memory)

Some of these fun"tions wou+d norma++y be imp+ementedin software)# Counters. timers)


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Memory Considerations


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5dditiona+ $rogramming Considerations

8n a standard "omputer. there is a "omp+i"atedoperating system that hand+es a++ +ow+eve+operations)

# 2hings +ike reading from interfa"ing to the different

devi"es. and a++o"ating memory)

(or an embedded system. the app+i"ation storedin the OM of the mi"ro"ontro++er is the on+y

software that wi++ e1e"ute)

# 2herefore. a++ +ow+eve+ "ode and devi"e interfa"es

ne"essary to e1e"ute the app+i"ation have to be

in"+uded)


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E1amp+e of a $C program

2his "ode simp+y "a++s

the operating systemthat wi++ print the

message stored at the

+o"ation Msg! and

returns e1e"ution to

the operating system)

2o e1e"ute thisprogram in a

mi"ro"ontro++er. this

"ode wou+d be"onsiderab+y +onger)))

MAIN:

mov AH, 9 ; Program start

lds DX, Msg ; Print message

int 0!"

mov AH, 0#$" ; End t"e %rogram

&or A', A' ; (it" a ret)rn *ode

int !" ; o+ 0-

Msg db Hello .orld-, 00D", 00A", 0


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E1amp+e of a mi"ro"ontro++er program

'e"ause the disp+aysubroutine in"+udingits initia+i;ation has

to be written)

2he software hasa+so to know where

the devi"e is

"onne"ted to and to

make sure that the

devi"e is "onne"ted

proper+y)

LCD_INIT proc

setb B_LCDONOFF ; LCD Display On

clr B_LCDCURSOR ; Cursor Off

clr B_LCDBLINK ; No Blinin!

;

call IO_LCD"N_LO ; Clear LCD "nable

call l#p$ ; Sen% Init Byte

call l#p$ ; Sen% Init Byte& '!ain



call LCD_D(OD ; Set Display (o%e

call LCD_CL"'R ; Clear Display

call LCD_)'IT ; )ait For Display To Finis*

+o, a&-.....$$.b ; "ntry (o%e& Increase )it* No S*iftin!

call LCD_IOC ; Strobe Data To Display

+o, D_LCD/OS&-...* ; Set Initial Cursor To .

ret ; Return To Caller

;

l#p$ +o, a&-..$$....b ; Function Set& 0 Bits& $ Line& 1 2 3 Dots

call LCD_IOC ; Strobe Data To LCD Display

+o, r4&-.ff* ; R4 5 ff

+o, r6&-.ff* ; R6 5 ff

l#p6 %7n8 r4&l#p6 ; Loop

%7n8 r6&l#p6 ; )aste (ore T*an 9:$ (s

ret ; Return To Caller

en%proc


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Mi"ro"ontro++er vs) Mi"ropro"essor

Mi"ropro"essor 9$:*# Designed to perform as a C$= in a mi"ro"omputer

system)

# 2he instru"tion set is arranged to a++ow "ode and

+arge amounts of data to be moved between the

$ and the e1terna+ memory and registers)

# Operations on not +ess than four bits)

Mi"ro"ontro++er 9C:*#

Designed to operate with minimum of e1terna+"ir"uitry)

# Simp+e instru"tion set 9?// instru"tions:)

# Operations possib+e on sing+e bits @


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Evo+ution of mi"ro"ontro++ers

Mi"ro"ontro++er evo+ved from a board+eve+ design to a

sing+e "hip in the midB0s) 5s the pro"ess ofminiaturi;ation "ontinued. a++ of the "omponents needed

for a "ontro++er were bui+t right onto one "hip)

8n the midBF0%s embedded systems migrated from thesing+e "hip to mi"ro"ontro++ers embedded into a +arger

5S8C 95pp+i"ation Spe"ifi" 8ntegrated Cir"uit: design)


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5dvantages of using mi"ro"ontro++ers

(ast and effe"tive

# 2he ar"hite"ture "orre+ates "+ose+y with the prob+em beingso+ved 9"ontro+ systems:)

&ow "ost 6 &ow power# ,igh +eve+ of system integration within one "omponent)

# On+y a handfu+ of "omponents needed to "reate a working

system) Compatibi+ity

# Op"odes and binaries are the S5ME for a++ F01/B variants)

Mu+tisour"ed# Over B? manufa"turers. hundreds of varieties)

Constant improvements# 8mprovements in si+i"on6design in"rease speed and power

annua++y)


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