MIPS data path for store word?

Question

Based on this figure, executing the SW instruction would cause these values to be assigned to the signals labeled in blue:

    RegWrite = 0
    ALUSrc = 1
    ALU operation = 0010
    MemRead = 0
    MemWrite = 1
    MemtoReg = X
    PCSrc = 

However, I am a little confused which inputs will be used in the Registers block? Can anyone describe the overall SW procedure in the MIPS datapath?

Answer 1

The execution of sw would follow the following steps in your diagram:

1. Instruction is read and decoded from the PC in the Instruction Memory subcircuit.
2. The register file is read for $rs and $rt (Registers subcircuit)
3. The value of $rs is added to the sign extended immediate (selected by ALUSrc) (ALU subcircuit).
4. The added value and $rt are passed to the Data Memory subcircuit where the value of $rt is written to memory.