MIPS HW4-Single Cycle CPU II  Solved

1.          Goal
Based on Lab 3 (simple single-cycle CPU), add a memory unit to implement a complete single-cycle CPU which can run R-type, I-type and jump instructions.

 

2.          Demands
A.        Please use iverilog as your HDL simulator.

B.        "Data_Memory.v", and "TestBench.v" are supplied. Please use these modules  and modules in Lab 3 to accomplish the design of your CPU.

Specify in your report if you have any other files in your design.

C.        Submit all *.v source files and report(pdf) on new e3. Other form of file will get -10%.

D.        Refer to Lab 3 for top module’s name and IO ports.

Initialize the stack pointer (i.e., Reg_File[29]) to 128, and other registers to 0

Decoder may add control signals:

Ÿ   Branch_o

Ÿ   Jump_o

Ÿ   MemRead_o

Ÿ   MemWrite_o

Ÿ   MemtoReg_o

3.          Requirement description
A. Basic instruction: 

Lab 3 instruction + lw、sw、beq、bne、j

 

Format:

R-type

Op[31:26]
Rs[25:21]
Rt[20:16]
Rd[15:11]
Shamt[10:6]
Func[5:0]
I-type
 
 
 
Op[31:26]
Rs[25:21]
Rt[20:16]
Immediate[15:0]
Jump
 
 
 
Op[31:26]
 
 
Address[25:0]
 

 

Definition: lw instruction: 

memwrite is 0, memread is 1, regwrite is 1 Reg[rt] ← Mem[rs+imm]

 

sw instruction:

memwrite is 1, memread is 0 Mem[rs+imm] ← Reg[rt]

 

branch instruction: 

branch is 1, and decide branch or not by do AND with the zero signal from ALU beq:

                             if (rs==rt) then PC=PC+4+ (sign_Imm<<2)

bne:

if (rs!=rt) then PC=PC+4+ (sign_Imm<<2)

Jump instruction: 

jump is 1

PC={PC[31:28], address<<2}

Op field:

instruction 
Op[31:26] 
lw
6'b101100
sw
6'b101101
beq
6'b001010
bne
6'b001011
jump
6'b000010
 

Extend ALUOp from 2-bit to 3-bit: (You can modify this if necessary)

instruction 
ALUOp 
R-type
010
addi
100
lui
101
lw、sw
000
beq
001
bne
110
jump
x
 

B.  Advance set 1: 

Jal: jump and link 

In MIPS, 31th register is used to save return address for function call Reg[31] save PC+4 and perform jump

 

Reg[31]=PC+4

PC={PC[31:28], address[25:0]<<2}

 

 

Op[31:26]
Address[25:0]
6'b000011
Address[25:0]
 

 

 

Jr: jump to the address in the register rs PC=reg[rs]

e.g. In MIPS, return could be used by jr r31 to jump to return address from JAL.

 

Op[31:26]
Rs[25:21]
Rt[20:16]
Rd[15:11]
Shamt[10:6]
Func[5:0]
6'b000000
rs
0
0
0
6'b001000
 

C.  Advance set 2: blt (branch on less than): if( rs<rt ) then branch

Op[31:26]
Rs[25:21]
Rt[20:16]
Immediate[15:0]
6'b001110
rs
rt
offset
bnez (branch non equal zero): if( rs!=0) th
en branch (it is same as bne)
Op[31:26]
Rs[25:21]
Rt[20:16]
Immediate[15:0]
6'b001100
rs
000000
offset
 

bgez (branch greater equal zero): if(rs>=0) then branch

Op[31:26]
Rs[25:21]
Rt[20:16]
Immediate[15:0]
6'b001101
rs
000001
offset
 

Example: when CPU executes function call:

 

 

 

 

If you want to execute recursive function, you must use the stack point (REGISTER_BANK [29]). First, store the register to memory and load back after function call has been finished.

4.          Architecture Diagram
 

 

5.          Test
Modify line 139 to 141 of TestBench.v to read different data.

   

CO_P4_test_data1.txt tests the basic instructions.

CO_P4_test_data2.txt tests the advanced set 1.

CO_P4_test_data2_2.txt test the advanced set 2.

 

After the simulation of TestBench, you will get the file CO_P4_result.txt. You can  verify the result with dataX_result.txt.

  

 

 

 

 

 

If your design passes the test data, the following words would show  in the terminal.