Consider an instruction ADD R1 , R2. ( Add the contents of Register R2 to the contents of Register R1)The following steps are used to execute it over the given path. Assume that PC is incremented appropriately.MAR ← PCR1← R1+R2PC← PC+4MDR ← Mem[MAR]IR← MDRIdentify the correct order of execution of the above steps.
Question
Consider an instruction ADD R1 , R2. ( Add the contents of Register R2 to the contents of Register R1)The following steps are used to execute it over the given path. Assume that PC is incremented appropriately.MAR ← PCR1← R1+R2PC← PC+4MDR ← Mem[MAR]IR← MDRIdentify the correct order of execution of the above steps.
Solution
The correct order of execution of the steps for the instruction ADD R1, R2 would be:
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IR← MDR: The instruction is fetched from memory and loaded into the Instruction Register (IR). This is the instruction decode stage.
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MAR ← PC: The Memory Address Register (MAR) is loaded with the address of the next instruction to be executed, which is contained in the Program Counter (PC).
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MDR ← Mem[MAR]: The Memory Data Register (MDR) is loaded with the instruction at the memory location specified by the MAR. This is the instruction fetch stage.
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R1← R1+R2: The contents of Register R2 are added to the contents of Register R1. This is the execute stage of the instruction.
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PC← PC+4: The Program Counter (PC) is incremented to point to the next instruction. This is the instruction fetch stage.
Please note that the order might vary slightly depending on the specific architecture of the computer system.
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