Gate2020 cs Q22

22Consider an instruction:R₀ ← R₁ + R₂.The following steps are used to execute it over the given data path. Assume that PC is incremented appropriately. The subscripts r and w indicate read and write operations, respectively.
1. R2_r, TEMP¹_r, ALU_add, TEMP²_w
2. R1_r, TEMP¹_w
3. PC_r, MAR_w, MEM_r
4. TEMP²_r, R0_w
5. MDR_r, IR_w
Which one of the following is the correct order of execution of the above steps ?

Option : A
Explanation :
Given steps:
1. R_2r, TEMP¹_r, ALU_add, TEMP²_W
2. R_1r, TEMP¹_W
3. PC_r, MAR_W, MEM_r
4. TEMP²_r, RO_W
5. MDR_r. IR_W
Instruction fetch is first step to be done which is indicated by step 3 and 5

Then instruction decoded by cu and then operand fetch should be performe
D. If is indicated with step 2 and operand fetch and perform operation by step 1

4. Now, write result operations should be performe
D. It is indicated by step 4, as a result, should be in R0.
Step4:

Hence correct order of execution should be, 3, 5, 2, 1, 4

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