21-Addressing Modes

21-Addressing Modes - Instruction Sets: Addressing Modes...

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Instruction Sets: Addressing Modes and Formats Presenter Tathagata Bhattacharjee
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Tathagata Bhattacharjee 2 Addressing Modes Usually more than one addressing modes are used Different opcodes use different addressing modes Mode field in instruction indicates addressing mode Common addressing techniques: Immediate Direct Indirect Register Register Indirect Displacement (Indexed) Stack
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Tathagata Bhattacharjee 3 Immediate Addressing Operand is part of instruction Operand = address field e.g. ADD 5 Add 5 to contents of accumulator 5 is operand No memory reference to fetch data Fast Limited range (address field is usually smaller than the word length) Operand Opcode Instruction
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Tathagata Bhattacharjee 4 Direct Addressing Diagram Address A Opcode Instruction Memory Operand
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Tathagata Bhattacharjee 5 Direct Addressing Address field contains address of operand Effective address (EA) = address field (A) e.g. ADD A Add contents of cell A to accumulator Look in memory at address A for operand Single memory reference to access data No additional calculations to work out effective address Limited address space (memory space cannot exceed the length of address field)
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Tathagata Bhattacharjee 6 Indirect Addressing Diagram Address A Opcode Instruction Memory Operand Pointer to operand
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This note was uploaded on 07/15/2011 for the course ECO 2023 taught by Professor Mr.raza during the Summer '10 term at FAU.

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21-Addressing Modes - Instruction Sets: Addressing Modes...

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