Addressing Modes of 8086 Processor Ammar Anwar Khan Electrical Engineer King Saud University Riyadh Saudi Arabia

Addressing Modes Addressing Modes which are common to 8086 processor. Immediate Addressing Mode. Register Addressing Mode. Direct addressing Mode. Register Indirect Addressing Mode.

Immediate Addressing Mode MOV AL,10h MOV AX,0AC8h MOV AH,4ch MOV DX,1000h

Register Addressing Mode MOV AL,BL MOV AX,BX

Direct addressing Mode MOV DX,[1000H]

Register Indirect Addressing Mode MOV AL,[BX] MOV AX,[BX]

PUSH & POP MOV AX, 30 PUSH AX POP BX SS=FFEE SS=FFEC SS=FFEE

The XCHG Instruction The XCHG InstructionExchange The XCHG (exchange) instruction swaps two values. The general form is: XCHG operand1, operand2 There are four specific forms of this instruction on the 80x86: XCHG reg, mem XCHG reg, reg

The LEA Instruction Load effective address The LEA (Load Effective Address) loads the specified 16 bit general purpose register with the effective address of the specified memory location. LEA takes the form: LEA destinaton, source LEA DX,[BX][SI]+100H DX=effective address= =5600H

The STOSx Instruction Store byte or word string The STOSx (where x: B or W), copies a byte or word from AX, AL to a location pointed by ES:DI and updates DI to point to the next string element. If DF is 0, DI increment otherwise decrements

The LDS Instruction Load Data Segment register Load into destination the contents of two memory locations and segment register the next two memory locations: LDS destinaton, source DS:1200=46 DS:1201:10 DS:1202:38 DS:1202:82 LDS DI,[1200] ; DI=1046 and DS=8238

The MOVSx Instruction Move Byte or word String Moves byte or word from memory location pointed to by DS:SI to the memory location pointed to by ES:DI. SI and DI increment if DF is 0 otherwise decrement: LEA destinaton, source LEA DX,[BX][SI]+100H DX=effective address= =5600H

The XLAT Instruction Translate Replace the contents of AL with the contents of Lookup table pointed by AL, BX contains the starting location of Lookup table.

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