FIGURE 4.16 The effect of each of the seven control signals. Branch – is it a branch instruction? If it is, 1, otherwise 0.
R-format
lw
sw
beq
ALU Op1
1
0
0
0
ALU Op0
0
0
0
1
Complete the output by entering 0,1, or X (don’t care for multiplexors)
Input or output
Input
Output
Signal name (opcode)
Op5
Op1
Op0
RegDst
R-format
(0 = 000000)
0
0
0
lw (35=100011)
1
1
1
sw (43=101011)
1
1
1
beq (4=000100)
0
Op4
Op3
Op2
0
0
0
0
0
0
0
1
0
0
0
1
0
0
ALUSrc
MemtoReg
RegWrite
MemRead
MemWrite
Branch
ALUOp1
ALUOp0