Chapter 380x86 Instruction, Part 1: Addressing Modes, Flags, Data Transfer, and String Instructions

Objectives:

The style of source files written in 80x86 assembly language

The different addressing modes of the 80x86

The operation and use of the processor flags

Data transfer and string instructions

EE314Microprocessor Systems

Based on "An Introduction to the Intel Family of Microprocessors" by James L. Antonakos

3.2 Assembly language programming

Assembler

...

Linker Library

Object files

Final object file or executable file

Source file(TOTAL.ASM)

List file(TOTAL.LST)

Object file(TOTAL.OBJ)

3.2 Assembly language programmingA Sample Source File

ORG 8000HTOTAL: MOV AX,7000H ;load address of data area;

MOV DS,AX ;init data segment registerMOV AL,0 ;clear resultMOV BL,16 ;init loop counterMOV SI,0 ;init data pointer

ADDUP: ADD AL,[SI] ;add data value to resultINC SI ;increment data pointerDEC BL ;decrement loop counterJNZ ADDUP ;jump if counter not zeroMOV [SI],AL ;save sumRET ;returnEND

1 8000 2 8000 B8 7000 3 8003 8E D8 4 8005 B0 00 5 8007 B3 10 6 8009 BE 0000 7 800C 02 04 8 800E 46 9 800F FE CB10 8011 75 F911 8013 88 0412 8015 CB13

DATA SEGMENT PARA ‘DATA’ORG 7000H

POINTS DB 16 DUP (?)SUM DB (?)DATA ENDS

CODE SEGMENT PARA ‘CODE’ASSUME CS:CODE, DS:DATA

CODE ENDSEND TOTAL

8000 B8 8001 008002 70

LabelEnd Segment

Begin of Data segment

Data name

Begin of Code segment

End Source file Start execution address

3.2 Assembly language programmingA Sample Source File

ORG 8000HTOTAL: MOV AX,7000H ;load address of data area;

MOV DS,AX ;init data segment registerMOV AL,0 ;clear resultMOV BL,16 ;init loop counterMOV SI,0 ;init data pointer

ADDUP: ADD AL,[SI] ;add data value to resultINC SI ;increment data pointerDEC BL ;decrement loop counterJNZ ADDUP ;jump if counter not zeroMOV [SI],AL ;save sumRET ;returnEND TOTAL

1 8000 2 8000 B8 7000 3 8003 8E D8 4 8005 B0 00 5 8007 B3 10 6 8009 BE 0000 7 800C 02 04 8 800E 46 9 800F FE CB10 8011 75 F911 8013 88 0412 8015 CB13

.MODEL SMALL

.DATAORG 7000H

POINTS DB 16 DUP (?)SUM DB (?)

.CODE

3.2 Assembly language programmingPredefined .MODEL types

Memory Model

Data Segments

Copde Segments Special Features

TINY one one .COM files. CS and DS combinedSMALL one one smallest .EXE modelMEDIUM one multipleCOMPACT multiple oneLARGE multiple multipleHUGE multiple multiple Uses normalized addressFLAT one one 32 bit addressing

3.3 Instruction TypesInstruction Types Scope Data size

Data transfer reg<->reg; reg<->mem 8, 16, 32 bitStrings move, scan, compare strings in memory 64KBArithmetic add, sub (signed or no), mul, div, BCD, ASCII 8, 16, 32 bitBit manipulation AND, OR, XOR, NOT, shift, rotate 8, 16, 32 bitLoops and jumps Conditional and unconditional program jumpsSubrutine and interrupt Subrutine (far, near) and interrupt, stack controlProcessor control control flags, enable/disable interrupts,