Computer Systems Architecture

MemRead ALUSrcA = 0

IorD = 0 IRWrite

ALUSrcB = 01 ALUOp = 00

PCWrite PCSource = 00

ALUSrcA = 0 ALUSrcB = 11 ALUOp = 00

ALUSrcA = 1 ALUSrcB = 00 ALUOp = 10

ALUSrcA = 1 ALUSrcB = 10 ALUOp = 00

MemRead IorD = 1

MemWrite IorD = 1

RegDst = 1 RegWrite

MemtoReg = 0

RegDst = 0 RegWrite

MemtoReg = 1

PCWrite PCSource = 10

ALUSrcA = 1 ALUSrcB = 00 ALUOp = 01

PCWriteCond PCSource = 01

Instruction decode/ register fetch

Instruction fetch

0 1

Start

(Op =

'LW ') o

r (O p =

'SW ')

(O p

= R-

typ e)

(O p

= 'B

E Q

')

(O p

= 'J

')

Jump completion

9862

3

4

5 7

Memory read completon step

R-type completion Memory access

Memory access

Execution Branch

completion Memory address

computation

(Op = 'SW ')

(O p

= 'L

W ')