(iii) Assuming that the instructions are first fetched to the Instruction Register (IR), the memory operand is brought to the DR register and the result of an operation is stored in the Accumulator register; write and explain the sequence of micro-operations that are required to fetch and execute an addition instruction that adds the contents of the memory and register operands of the instruction. The result is stored in the accumulator register. Make and state suitable assumptions, if any.

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Sequence of Micro-Operations for Addition Instruction Execution:


- The machine follows a Fetch-Decode-Execute cycle.

- Micro-operations are assumed for illustration, and actual micro-operation set may vary based on the specific architecture.

1. Fetch Operation:

   - Micro-Operations:

      - MAR ← PC (Load Program Counter into Memory Address Register)

      - IR ← M[MAR] (Fetch Instruction from Memory to Instruction Register)

      - PC ← PC + 1 (Increment Program Counter)

   - Explanation:

      - The program counter (PC) is loaded into the memory address register (MAR) to fetch the instruction from the specified memory location.

      - The instruction is then fetched from memory and stored in the instruction register (IR).

      - The program counter is incremented to prepare for the next instruction.

2. Decode Operation:

   - Micro-Operations:

      - Decode IR (Determine Operation Code and Operand Fields)

      - Fetch Operand from Memory to Data Register (DR)

      - Fetch Register Operand from Register File to Register Operand Register

   - Explanation:

      - The instruction in the instruction register (IR) is decoded to identify the operation code and operand fields.

      - The memory operand is fetched from the specified memory location to the data register (DR).

      - The register operand is fetched from the register file and stored in a register operand register.

3. Execute Operation (Addition):

   - Micro-Operations:

      - ALU ← Register Operand + Data Register (Perform Addition)

      - Accumulator ← ALU (Store Result in Accumulator)

   - Explanation:

      - The Arithmetic Logic Unit (ALU) performs the addition operation using the register operand and the data in the data register.

      - The result is stored in the accumulator register.

4. Final State:


      - Store Accumulator in Memory or Register File

   - Explanation:

      - The final result in the accumulator can be stored back in memory or the register file, depending on the specific instruction.

This sequence of micro-operations illustrates the execution of an addition instruction, where the contents of the memory and register operands are added, and the result is stored in the accumulator register. The actual micro-operations may vary based on the machine's architecture and instruction set. 

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