Assembler Directives of 8086 Microprocessor

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Assembler Directives of 8086 Microprocessor

INTRODUCTION: Constellation phraseologys are low-level phraseologys coercion programming computers, microprocessors, microcontrollers, and other IC. They instrument a partic resemblance of the numeric channel Jurisprudences and other constants needed to program a point CPU edifice. This resemblance is usually mark-outd by the hardware creator, and is established on abbreviations that aid the programmer to recollect indivisible instructions, records. An assembler moral is a assertion to impart coerce to the assembler to consummate function of the constellation arrangement. It coerce the construction if the program and supply needful referableice to the assembler to apprehend the constellation phraseology programs to produce needful channel jurisprudences. They point-out how an operand or a exception of the program is to be arrangemented by the assembler. An assembler supports morals to mark-out postulates, to organise


Galaxy conversations are low-level conversations coercion programming computers, microprocessors, microcontrollers, and other IC. They utensil a classic truthfulness of the numeric deed Jurisprudences and other constants needed to program a point CPU architecture. This truthfulness is usually boundd by the hardware manufacturer, and is fixed on abbreviations that aid the programmer to retain particular instructions, archives. An assembler instructive is a proposition to present coerce to the assembler to effect labor of the galaxy mode.

It coerce the organization if the program and supply compulsory instruction to the assembler to know the galaxy conversation programs to propagate compulsory deed jurisprudences. They mark how an operand or a individuality of the program is to be modeed by the assembler.

An assembler supports instructives to bound facts, to organise limbs to coerce progress, to bound macros. It consists of span models of propositions: instructions and instructives. The instructions are translated to the deed jurisprudence by the assembler since instructives are referable translated to the deed jurisprudences.

Assembler Instructives of the 8086 Microprocessor

(a) The DB instructive

(b) The DW instructive

(c) The DD instructive

(d) The STRUCT (or STRUC) and ENDS instructives (counted as single)

(e)The EQU Instructive

(f)The COMMENT instructive






(l) PROC



Facts statement instructives:

1. DB – The DB instructive is interpretationd to defend a BYTE -2-BYTE inconstant – A BYTE is made up of 8 bits.

Statement examples:

Byte1 DB 10h

Byte2 DB 255 ; 0FFh, the max. likely coercion a BYTE

CRLF DB 0Dh, 0Ah, 24h ;Carriage Return, promiseinator BYTE

2. DW – The DW instructive is interpretationd to defend a WORD model inconstant – A WORD occupies 16 bits or (2 BYTE).

Statement examples:

Promise DW 1234h

Word2 DW 65535; 0FFFFh, (the max. likely coercion a WORD)

3. DD – The DD instructive is interpretationd to defend a DWORD – A DWORD double promise is made up of 32 bits =2 Promise’s or 4 BYTE.

Statement examples:

Dword1 DW 12345678h

Dword2 DW 4294967295 ;0FFFFFFFFh.

4. STRUCT and ENDS instructives to bound a organization template coercion ordering facts individuals.

(1) The STRUCT instructive acquaints the assembler that a interpretationr boundd uninitialized facts organization follows. The uninitialized facts organization consists of a union of the three befriended facts models. DB, DW, and DD. The addresss help as zero-fixed impromptusets into the organization. The primeval part’s impromptuset coercion any organization is 0. A organization part is referenced with the cheap “+” operator precedently the part’s declare.

A Organization ends by using the ENDS instructive aim END of Organization.



Organization_element_declare part_data_type?

. . .

. . .

. . .




Organization_element_declare part_data_type?

. . .

. . .

. . .




Byte1 DB?

Byte2 DB?

Word1 DW?

Word2 DW?


Dword2 DW?


Interpretation OF STRUCT:

The STRUCT instructive enables us to alter the adjust of individuals in the organization when, we better a smooth header and shift the facts. Shift the facts individuals in the smooth header and betterat the posteriority of facts statement in the STRUCT and impromptu you go. No alter in the jurisprudence we transcribe that modees the smooth header is compulsory regular you inoculateed an extra facts part.

(5) The EQU Instructive

The EQU instructive is interpretationd to present declare to some appreciate or class. Each interval the assembler finds the presentn declares in the program, it obtain supply the declare with the appreciate or a class. The appreciate can be in the rank 0 through 65535 and it can be another Equate defendd anywhere overhead or under.

The coercionthcoming operators can so be interpretationd to defend an Equate:




A inconstant – defendd with a DB, DW, or DD instructive – has an discourse and has illimitableness silent at that discourse coercion it in the .COM smooth. But an Equate does referable own an discourse or illimitableness silent coercion it in the .COM smooth.



DB 10

A_ promise EQU THIS WORD

DW 1000

A_ dpromise EQU THIS DWORD

DD 4294967295

Buffer Size EQU 1024

Buffer DB 1024 DUP (0)

Buffed_ ptr EQU $ ; in-fact points to the proximate byte behind the; 1024th byte in buffer.

(6) Extern:

It is interpretationd to acquaint the assembler that the declare or address coercionthcoming the instructive are I some other galaxy module. Coercion example: if you seduce a progress which is in program module assembled at a incongruous interval from that which contains the CALL instructions ,you must acquaint the assembler that the progress is outer the assembler obtain prostrate instruction in the intent jurisprudence smooth so that the linker can converge the span module unitedly.






The GLOBAL instructive can be interpretationd in attribute of PUBLIC instructive .coercion a declare boundd in the present galaxy module; the GLOBAL instructive is interpretationd to produce the class profitable to the other modules. Example:


WORD acquaints the assembler that DIVISOR is a inconstant of model of promise which is in another galaxy module or EXTERN.


It is interpretationd to mark the rointerpretation of a argumentative limb. It is the declare presentn to the the limb. Example: the jurisprudence limb is interpretationd to mark to the assembler the rointerpretation of argumentative limb.


It is interpretationd to establish the rointerpretation of a progress. It follows a declare we present the progress.

Behind the progress the promise NEAR and FAR is interpretationd to particularize the progress Example: SMART-DIVIDE PROC FAR identifies the rointerpretation of progress declared SMART-DIVIDE and acquaints the assembler that the progress is remote.

(10) NAME:

It is interpretationd to present a inequitable declare to each galaxy module when program consists of various modules.

Example: PC-BOARD interpretationd to declare an galaxy module which contains the instructions coercion coerceling a printed circumference consideration.


It is interpretationd to acquaint the assembler to inoculate a fill of spring jurisprudence from the declared smooth into the present spring module. This shortens the spring module. An opinion is interpretation of editor fill charge to cop the smooth into the present spring module.

(12) OFFSET:

It is an operator which acquaints the assembler to indicate the impromptuset or misunderstanding of a declared facts individual from the rointerpretation of the limb which contains it. It is interpretationd to accuse the impromptuset of a inconstant into a record so that inconstant can be accessed with single of the discourseed modes. Example: when the assembler unravel MOV BX.OFFSET PRICES, it obtain indicate the impromptuset of the prices.

(13) GROUP:

It can be interpretationd to acquaint the assembler to order the argumentative limbs declared behind the instructive into single argumentative order. This integralows the discontinuance of integral he limbs to be accessed from the selfselfsame order. Example: SMALL-SYSTEM GROUP CODE, DATA, STACK-SEG.


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