A store instruction operates similarly to the load instruction. The main difference would be that
- the memory control would indicate a write rather than a read,
- the second register value read would be used for the data to store, and
- the operation of writing the data memory value to the register file would not occur.
sw, store word, is given as follows.
sw $t1, offset($t2) # mem[[$t2]+offset]=$t1 # mem[ [rs]+offset]= rt |
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ExtOp=“sign”sign-extends the 16-bit immediate to 32 bits.ALUSrc=‘1’selects the extended immediate as the second ALU input.ALUCtrl=“ADD”calculates data memory address as[rs]+sign-extended(imm16).MemWrite=‘1’writes to data memory.RegDst=‘X’means “don’t care” because of no destination register.MemtoReg=‘X’is “don’t care.”RegWrite=‘0’because no register is written by the store instruction.