Chap#3 80x86 Instructions, Part1:
                Addressing Mode, Flags,
                Data Transfer and String Instructions
Objective :

• Style of source files
• Different addressing mode
• Operation and use of flag
• Data transfer and string instruction

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3.1  Introduction

• Detailed look at the data transfer and string instructions

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3.2  Assembly Language Programming

• Assembler
• Source format : 4 field

    * label
    * opcode
    * operand
    * comment (preceded by semicolon ' ; ')
• Assembler perform 2 pass

    * 1st pass : determine the length of instruction
            & data areas, assign values to all symbols
    * 2nd pass : generating the machine codes
• Assembler directives

ORG, SEGMENT, ENDS, ASSUME, and END
• [.model] type
• Linker

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3.3  Instruction Types
For purpose of discussion divided into 7 groups

• 1)  data transfer
• 2)  strings
• 3)  arithmetic
• 4)  bit manipulation
• 5)  loops & jumps
• 6)  subroutine & interrupt
• 7)  processor control

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3.4  Addressing Mode
@ Effective Address

• instruction fetch : EA = (CS * 16) + (IP)
• data fetch : EA = (DS * 16) + (OFFSET)

@  Initial DS Register
@  Addressing Mode :

• 1) Immediate Addressing
• 2) Register Addressing
• 3) Direct Addressing
• 4) Register Indirect Addressing
• 5) Based Addressing
• 6) Indexed Addressing
• 7) Based Indexed Addressing
• 8) Based Indexed with Displacement Addressing
• 9) String Addressing

        e.g. MOVSB (move byte string )
                detail in section 3.7
• 10) Port Addressing

        e.g.  IN    AL, 40H
               OUT    80H, AL
                IN    AL, DX
               OUT    DX,AL
• 11) Using 32-bit Addressing in real mode

    e.g.  MOV    AX, [EBX] [ECX*4]

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3.5  The Processor Flags (condition code)

• Operation of Zero Flag
• Flag Register
• Zero Generation
• Operation of Carry Flag
• Parity Generation

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3.6  Data Transfer Instructions

• 1)  MOV    Destination, Source (move data)

    e.g.  MOV    AL, 30H  ==>  AL = 30
            MOV    AX, 30H ==>  AX = 0030
    MOV    BYTE PTR [SI], 0 ==> m = 00
    MOV    WORD PTR [SI], 0 ==> m = 0000
    MOV    DWORD PTR [SI], 0 ==> m = 00000000
• 2)  MOVSX    D, S (move with sign extended)

    e.g.  AL = 36H
            BX = C3EEH
        MOVSX    AX,AL  ==> AX = 0036
        MOVSX    EBX,BX ==> EBX = FFFFC3EE
• 3)  MOVZX    D, S (move with zero extended)

    e.g.  AL = 36H
            BX = C3EEH
        MOVZX    AX,AL  ==> AX = 0036
        MOVZX    EBX,BX ==> EBX = 0000C3EE
• 4)  PUSH    Source (push word onto stack)
• 5)  PUSHW/PUSHD Source (push W/DW onto stack)

    PUSHA/PUSHAD(Push all registers/Push all double-registers) (push order)
• 6)  POP    Destination (pop data off stack)
• 7)  POPA/POPAD    Destination (pop all Reg/pop  all double -Reg.) (pop order)
• 8)  IN    Accumulator,Port ( input byte or word from port)
• 9)  INS    Destination,Port (input string from port)
• 10)  OUT    Port,Accumulator ( output byte or word to port)
• 11)  OUTS    DX,Source (output string to port)
• 12)  LEA    D, S (Load Effective Address)
• 13)  PUSHF/PUSHFD (pusf flag(16/32) onto stack)
• 14)  POPF/POPFD (pop flag(16/32) off stack)
• 15)  XCHG    D, S (exchange data)
• 16)  BSWAP    Destination (byte swap)
• 17)  XLAT   Translate-Table (translate byte)
• 18)  LDS    D, S (load pointer using DS)
• 19)  LES/LFS/LGS/LSS    D, S (load pointer using ES/FS/GD/SS)
• 20)  LAHF  (load AH Register from Flags)
• 21)  SAHF  (store AH Register into Flags)

@  Assembler Directives :
        OFFSET, BYTE PTR, WORD PTR, DWORD PTR, FWORD, and SEG

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3.7  String Instructions

• 1)  Initializing the String Pointers

e.g.   MOV    AX, 510H
        MOV    DS, AX
        MOV    SI, 0
        - - -
        MOV    AX, 4A8H
        MOV    ES, AX
        MOV    DI, 0
        - - -
        LDS    SI, StringA
        LES    DI, StringB
        - - -
        CLD
        REP     CMPSB
        - - -
• 2)  REP/REPE/REPZ/REPNE/REPNZ
• 3)  MOVS  D-string, S-string (Move String)
• 4)  MOVSB/MOVSW/MOVSD(Move String)
• 5)  CMPS  D-string, S-string (Compare String)
• 6)  SCAS  D-string (Scan String)
• 7)  LODS  S-string (Load String)
• 8)  STOS  D-string (Store String)
• @  INS/OUTS  (I/O String)

e.g. DS = 0400    ES = 0600    CX = 0003
       SI = 0100    DI = 0200    DX = 03E0
Execute :  REP     INS;        REP    OUTSW

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3.8  Troubleshooting Techniques

• Summary ( page 102 )
• Study  Questions ( #3, #5, #7, #9, #13, #23, #27, #29, #31 )

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