Given steps: 1. R2r,TEMPr1,ALUadd,TEMPw2 2. R1r,TEMP1w 3. PCr,MARw,MEMr 4. TEMPr2,ROw 5. MDRr,IRW Instruction fetch is first step to be done which is indicated by step 3 and 5
3PcrMARwMEMr,5MDRr,IRw⇒{
MAR←PC
IR←Read(MR)
IR←MDR
Then instruction decoded by cu and then operand fetch should be performed. If is indicated with step 2 and operand fetch and perform operation by step 1 2R1r,TEMPw1,R2r,TEMP4r,ALUadd,TEMPw2⇒{
TEMP1←R1
TEMP2⟵R2
(add)ALU⟵TEMP1
TEMP2.
4. Now, write result operations should be performed. It is indicated by step 4 as result should be in Ro. Step 4:
TEMP 2w,ROw⇒{
TEMP2←ALU(result)
R0←TEMP2
Hence correct order of execution should be, 3, 5, 2, 1, 4