Chapter 3

Chapter 3 - MOV Instruction MOV destination,source MOV...

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Unformatted text preview: MOV Instruction MOV destination,source MOV AX,BX MOV SUM,EAX MOV EDX,ARRAY[EBX][ESI] MOV CL,5 MOV DL,[BX] Addressing Modes These are the different ways in which data may be accessed by the microprocessor. Immediate. Register. Memory. Direct. Register indirect. Base plus index. Register relative. Base relative plus index. Scaled indexed. Immediate Directly accessible to the EU. The address is part of the instruction. Useful in initializations. MOV EAX,1111000B MOV CL, 0F1H Register Directly accessible to the EU. Most compact and fastest executing instructions. Operands are encoded in the instruction. MOV EBX,EDX MOV AL,CL Memory When reading or writing to memory the execution unit passes an offset value, the effective address, to the bus interface unit which then computes the physical address. Direct [ ] { } { } [ ] { } operand 16 DS PA operand EA + = = Simplest memory addressing mode. Direct addressing (3 bytes long). MOV EAX,DS:SUM MOV DS:[3000H],AL Displacement addressing (>3 bytes long): MOV DS:[500H],EDX MOV CX,COUNT+5 Register Indirect ( ) ( ) ( ) { } ( ) ( ) ( ) + = = ESI EDI EBX 16 DS PA ESI EDI EBX EA MOV EAX, DS:[EBX] MOV DS:[EDI],EDX Base Plus Index Similar to register indirect. The base registers, (BX, BP), and index registers, (DI, SI), are combined in pairs (base, index) to indirectly access data....
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Chapter 3 - MOV Instruction MOV destination,source MOV...

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