7 - Chapter 7 Data Movement Instructions 1 Learning...

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1 Chapter 7 Data Movement Instructions
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2 Learning Outcomes Be able to determine the symbolic opcode, source, destination, and addressing mode for a Hexadecimal machine language instruction. Be able to explain the operation of each data movement instruction with applicable addressing modes. Be able to explain the purpose of directives.
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3 Machine Language Machine language is the native binary code that microprocessor understands and uses as its instructions to control its application. We do not often code in machine language, but an understanding tends to help with learning the instruction set and the form of instructions in the memory.
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4 Machine Language Machine-coded instruction
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5 Machine-code instruction format Register
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6 Instruction Modes Instructions operate in the 16- or 32-bit mode. 16-bit mode instructions are used in DOS and 32-bit mode instructions are used in Windows. A prefix is used to switch between modes for one instruction at a time. The register override prefix is 66H and is a byte that precedes the opcode in the memory, The address override prefix is a 67H.
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7 Window system operates as 16-bit instruction mode, if a 32-bit register is used, then register size prefix (66H) is appended to the front of the machine-code instruction. If 32-bit instruction and 32-bit register is used, register-size prefix is absent. (Windows) MOV EAX,EBX ;reg prefix used Window system operates as 32-bit instruction mode, a 16-bit register is used, then register size prefix is (66H) appended to the front of the machine-code instruction. (Windows) MOV AX,BX ;reg prefix used
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8 The Opcode
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9 Fields of an Instruction The D bit in the first byte of an instruction is the direction of data flow either from or to R/M (Register/Memory) from REG. If D = 0, REG R/M (data flow from register) and if D = 1, R/M REG (data flow to register). The W bit in the first byte of the opcode either
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7 - Chapter 7 Data Movement Instructions 1 Learning...

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