PC
Add
Instruction [6-0]
Control
Branch
MemRead
A
MemtoReg
ALUOP
MemWrite
ALUSrc
Read
address
Instruction
[31-0]
Instruction
memory
Add Sum
Shift
left 1
RegWrite
C
Instruction [19-15]
Read
register 1 Read
Instruction [24-20]
data 1
Read
register 2
Instruction [11-7]
Write
Read
register
data 2
Write
Mux1
F
data Registers
0
Mux 1
B
Zero
ALU ALU
result
Address data
Read
1
Write Data
data memory
Muxo
Instruction [31-0]
32
64
Imm
Gen
ALU
control
D
d
E
Instruction [30,14-12]
Single-cycle CPU
For the CPU shown on the previous slide, assume that s1=16, t1=32, and PC=8, and address 8 contains
the instruction: add t2, s1, t1. For each bubble label, determine the stable value (in decimal) of the bus
at the end of the execution cycle of the above instruction. Write that value in the space below and
explain how you obtained it.
Label A (example): 0 The value is O because add is not a branch instruction
Label B:
Label C:
Label D:
Label E:
Label F: