Micro 133 Prelim Lecture 2 - Intel Microprocessor Architecture (Real Mode Addressing)

7/24/2019 Micro 133 Prelim Lecture 2 - Intel Microprocessor Architecture (Real Mode Addressing)

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THE MICROPROCESSORAND ITS

ARCHITECTURE( REAL MODE )

Micro 133 Prelim Lecture 2

by: Engr. Ricrey E. Marquez, CpE, MSCS


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In this lecture presents the microprocessoras:

a programmable device by observing atits internal programming model, and

how its addresses can be access in eachmemory space

INTRODUCTION


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MSDOS MEMORY

MAP

MSDOS Memory Map


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Contains 25620-bit addresses

Each address points to a hardware orsoftware interrupt service routine (I!"

#sed by #E!, $I% and &%('&%, $IC"

IVT (INTERRUPT VECTORTABLE)


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#sed by $I% for its temporaryspace)

$I% is !%' based and data cannot bewritten in !%')

Information such as *eyboard +ueue,screen mode and other temporaryvariables are stored here

BIOS DATA


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#sed by &% to store temporaryinformation li*e !rrent "le#na$e,

%iret&r' na$e, etc)

ery similar in operation to the $I%data wor* space

DOS DATA


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bout 5 B &* RAMin total, available for useby a user

Each program has various segments within theuser space (e)g) Code egment (C", &ata egment(&", tac* egment (", and Etra egment (E""

lso includes a 256 +'te area for passingsystem level parameters called rogramegment re3 ("

USER MEMORY SPACE


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#sed by &% programs that is lessfre+uently called

#sually reserved for these programs areformat, print, ch*ds*, scands*, etc)

TRANSIENT DOS


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rimary memory set aside for use by the videodisplay adaptor

ideo !' is physically located on the videoadaptor but is mapped into primary memory

1he full mapping of mono and C4 into !'can be supported

upports E4, 4, 54, or #54 by

swapping bloc*s of memory between the displayada tor and rimar memor

SCREEN (VIDEO) RAM


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#sed for additional hardware devices

rovides space where routines can besupplied to initiali6e and control7!n,n&-n8 hardware (any new device"

E.TENSION ROM SPACE


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pace provided for users to install any!%' programs they may want

USER ROM SPACE


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Early I$' Cs had a $IC boot up

If a &% system was not found on anydrive, this !%' was invo*ed

BASIC ROM SPACE


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It is $asic I9% ystem ($I%" memory space that are:

#se in routines to chec* the system hardware during7+&&t !/8

#se by the programs that load &% system 3les

#se by some routines available to user programs thatperform various functions ($I% service routines"

1hese service routines usually service interrupts, but can

be used to control hardware directly, e)g) screen modes,dis* access, etc)

Installed via !%' chips that contains attachedhardware information and initial drivers

BIOS SPACE


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$efore a program is written or any instructioninvestigated, the internal con3guration of themicroprocessor must be ,n&-n)

rogramming model of the 0; through theCore 2 is considered /r&0ra$ 1ii+le,becauseits registers are used during programming andspeci3ed by the instructions)

!egisters which can not be addressable directlyduring applications programming but may beused indirectly during system programming

INTERNAL MICROPROCESSORARCHITECTURE


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3i0!re 4a 3i0!re 4+illustratesthe programming model of the Intel

0; through the Core 2microprocessor)

ome registers are 0eneral#/!r/&eor $!lti/!r/&e re0iter, whilesome have /eial /!r/&e)

INTERNAL MICROPROCESSORARCHITECTURE


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Re0iter hold various data si6es (bytes,words, or double words" and are used for

almost any purpose as dictated by aprogram)

'ulti-purpose94eneral-purpose

!egisters pecial-purpose !egisters

egment !egisters

REISTERS


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MULTI#PURPOSE REISTERS


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S/eial#/!r/&e Re0iter include !I, !,and !


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SPECIAL#PURPOSEREISTERS


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Se0$ent re0iter are registers used togenerate memory addresses when combinedwith other registers in the microprocessor)

SEMENT REISTERS


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SEMENT REISTERS


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Real M&%eoperation allows the microprocessor to addressonly the "rt 4MB of memory space - even the entiummicroprocessor)

1he 3rst >' byte of memory is called either the REALMEMORY or CONVENTIONAL MEMORY system)

Real M&%e operation allows application software writtenfor the 090;, which contain only 1M byte of

memory, to function in the 02; and above withoutchanging the software)

In all cases, each of these microprocessors begins operationin the real mode by default whenever power is applied orthe microprocessor is RESET)

REAL MODE MEMORY

ADDRESSIN


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Combination of a SEMENT ADDRESS and an O33SETADDRESSaccess a memory location in the real mode)

Se0$ent A%%re (SA) is located within one of thesegment registers, de3nes the beginning address of an'67 B memory segment)

O8et A%%re (OA) selects any location within the 67

Bmemory segment)

SEMENTS AND O33SETS


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2#+it real $&%e a%%re allows one to access the start of asegment at an' 46#+'te +&!n%ar' -it9in t9e "rt 4MB &*$e$&r')

E33ECTIVE:ACTUAL ADDRESS ; SEMENT ADDRESS < 4 =O33SET ADDRESS

ny real mode segments can only begin at a 46#+'te +&!n%ar' inthe memory system and this boundary is often called a /ara0ra/9)

In the 02; (with special eternal circuitry" and the 0?; throughthe entium ro, an e>tra 67 B $in! 46 +'te &* $e$&r' ia%%rea+le when the segment address is 33339, and theHIMEM?SYSdriver is installed in the system)

1his area of memory (33339#433E39" is referred to as 9i09$e$&r' (HIMEM))

SEMENTS AND O33SETS


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'icroprocessors has a et &* r!le that applyto segments whenever memory is addressed

1hese rules, which apply in either the realor/r&tete% $&%e, de3ne the segmentregisterand o@set registercombination usedby certain addressing modes)

1able 2

DE3AULT SEMENT ANDO33SET REISTERS


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C&%e Se0$ent (CS) register de3nes the start ofthe memory space of the code,and the Intr!ti&nP&inter (IP) locates the net instruction within the

code segment)

Sta, %ata are references through the Sta,Se0$ent (SS)at the memory location addressed by

either the Sta, P&inter (SP:ESP) or the BaeP&inter (BP:EBP)

1able ?

DE3AULT SEMENTAND O33SET

REISTERS


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%ne can thin* of segments as windows that canbe moved over any area of memory to accessdata and code

rogram can have a lot of segments, but canonly access *&!r (in 0;-02;" or i> (in0?; and above" segments at a time


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Se0$entand O8etaddressing schemeallows relocation

Rel&ata+le Pr&0ra$ - one that canbe placed into any area of memory andeecuted without change

Rel&ata+le Data - data that can beplaced in any area of memory and usedwithout any change to the program

RELOCATION


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igure 1a. The programming 8-bit Names model of the 8086 through the Core

mi!ropro!essor in!luding the 6"-bit e#tensions$


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%igure &b$ %lat mode 6"-bit a!!ess to numbered registers$


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igure 2 The real mode memory-addressing s!heme' using a segment address plus an

offset$


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Table &$ (#ample segment addresses


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Table $ 8086-80"86 and )entium-)entium ** default &6-bit

segment and offset address !ombinations


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Table +$ 80+86' 80"86' )entium' )entium )ro' and )entium

** default +-bit segment and offset address !ombinations$


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igure ).,n appli!ation program !ontaining a !ode' data' and sta! segment loaded into a DOS system

memory$

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Micro 133 Prelim Lecture 2 - Intel Microprocessor Architecture (Real Mode Addressing)

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