31. Introduction to Addressing Modes
This chapter delves into various addressing modes in CPU programming, elucidating how memory locations are determined and utilized in different instruction formats. It highlights the distinction between immediate, direct, indirect, and displacement addressing modes, while explaining the complexities involved in multiple word instructions and their implications on CPU operations. Through practical examples, the chapter reinforces the concept of memory management as it relates to instruction processing.
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What we have learnt
- Addressing modes are crucial for understanding how data is accessed in a computer's memory.
- Immediate, direct, indirect, and displacement addressing modes each have specific methods for accessing memory.
- Complexity in instructions arises when they cannot fit within a single memory word, necessitating multiple word instructions.
Key Concepts
- -- Addressing Mode
- A method used to access data stored in memory, indicating how an instruction identifies the operands.
- -- Immediate Addressing
- An addressing mode where the operand is specified directly within the instruction, eliminating the need to fetch it from memory.
- -- Direct Addressing
- An addressing mode that specifies the memory address of the operand directly in the instruction.
- -- Indirect Addressing
- An addressing mode where the instruction refers to a memory address that contains the address of the operand.
- -- Displacement Addressing
- An addressing mode that uses an index register along with a displacement value to calculate the effective memory address of the operand.
- -- Multiple Word Instruction
- An instruction that spans multiple memory words due to its size, requiring special handling in the CPU.
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