A MIPS 32-bit Single- Cycle CPU G r o u p 6 L e M i n h H o a n g L e H o n g T h a n g L u o n g T r a n N h a t T r u n g Instructor: Ho Viet Viet LA: Nguyen Van Hieu - 1 - A MIPS 32-bit Single-Cycle CPU Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung Table of Contents I. ABSTRACT - 3 - II. LAB OBJECTIVES - 3 - III. LAB REQUIREMENTS - 3 - IV. OVERVIEW OF THE IMPLEMENTATION: - 4 - FUNCTION:………………. - 4 - THE INTERGER ARITHMETIC-LOGICAL INSTRUCTIONS: - 4 - THE MEMORY REFERENCE INSTRUCTIONS: - 5 - THE BRANCH AND JUMP INSTRUCTION: - 6 - V. DESIGNING THE MAIN CONTROL UNITS AND A DATAPATH: - 7 - ALU CONTROL AND CONTROL MODULE: - 7 - CONTROL SIGNALS TABLE - 8 - *ENHANCEMENT 1 - 10 - BUILDING A DATA PATH: - 11 - *ENHANCEMENT 2 - 12 - Overall RTL Viewer………… - 13 - VI. DESIGN MODULE - 14 - PC MODULE……………… - 14 - EXTEND MODULE……… - 15 - MUX RegDst MODULE - 16 - SHIFT LEFT 2 MODULE - 18 - CHECK_ZERO MODULE - 20 - MUX 4Addrto1 MODULE - 22 - InstructionMem MODULE - 23 - DATA MEMORY MODULE: - 24 - VII. STIMULATION RESULT OF MIPS SINGLE CYCLE DATA PATH - 25 - ADD INSTRUCTION:…………. - 26 - BRANCH ON NOT EQUAL INSTRUCTION - 27 - JUMP INSTRUCTION:…… - 28 - JUMP REGISTER INSTRUCTION: - 29 - LOAD AND STORE WORD INSTRUCTION: - 30 - - 2 - A MIPS 32-bit Single-Cycle CPU Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung SUB INSTRUCTION:……… - 31 - SET ON LESS THAN INSTRUCTION: - 32 - XORI INSTRUCTION:…… - 33 - VIII. CONCLUSION: - 34 - IX. REFERENCE: - 34 - - 3 - A MIPS 32-bit Single-Cycle CPU Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung **Note: Since this lab contains some work we have done in the two previous labs, we are not going to present them in detail here I. ABSTRACT The purpose of this design problem is building up the data path and constructing a simple version of 32-bit MIPS Single-Cycle CPU. The CPU instructions to be implemented are the memory-reference instruction LW & SW, the arithmetic –logical XORI, ADD, SUB, SLT, and BNE, J, JR function. The system takes PC address as an input and converts it into instruction to implement the functions. The lab report includes the data path single cycle of MIPS overview, the simulation and Verilog code using the Quartus and ModelSim program. II. LAB OBJECTIVES For this lab3 you are to design a simple 32-bit MIPS Single-Cycle CPU. The CPU instructions to be implemented are LW, SW, J, JR, BNE, XORI, ADD, SUB, and SLT. Chapter 4 will give some examples of how architectures are put together, and will be useful as you design your own CPU. For this CPU, you will use your two previous lab projects (the register and the ALU) so you will need to have these fully functional before proceeding to work on your CPU III. LAB REQUIREMENTS 1. Write MIPS 32 -bit Single-Cycle CPU and TestBench on your own. 2. ALL logic must be gate level, structural except that the control logic for CPU can be done behaviorally 3. All gates must have at most 4 input 4. All gates have a delay of 50ps - 4 - A MIPS 32-bit Single-Cycle CPU Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung IV. OVERVIEW OF THE IMPLEMENTATION: FUNCTION: The lab constructs the simple version of the process sufficient to implement an instruction set like MIPS. In the MIPS instruction, there are the integer arithmetic-logical instructions, the memory reference instructions and the branch instructions. THE INTERGER ARITHMETIC-LOGICAL INSTRUCTIONS: In the lab, the arithmetic-logical instructions or R-type include add, sub, slt class. - ADD rd, rs, rt: Reg[rd] = Reg[rs] + Reg[rt]. The instruction will read data in register rs and rt. After that they will be added and written to the register rd. - SUB rd, rs, rt: Reg[rd] = Reg[rs] – Reg[rt]. The instruction will read data from register rs and rt. After that the result from rs sub rt will be written into register rd. - SLT rd, rs, rt: The set on less than instruction which will compare the value in register rs and rt. In the case the value of rs is less than rt‟s one, the value in register rd equal 1, and 0 in the opposite case. As we can see from the data path, the register file will read two indicated register operands. After that, the data will be transferred into the ALU to perform arithmetic or logical operation such as add or sub. The result of ALU will move to the register file again to write output into the chosen register. - 5 - A MIPS 32-bit Single-Cycle CPU Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung THE MEMORY REFERENCE INSTRUCTIONS: In the lab, the memory-reference instructions include load word(lw) and store word(sw). - LW rt, imm16(rs): Reg[rt] = Mem[Reg[rs] + Sign_ext(Imm16)]. The instruction will load word from memory to register rt. - SW rt, imm16(rs): Mem[Reg[rs] + Sign_ext(Imm16)] = Reg[rt]. The instruction will store word from register to memory. As we can see from the data path, the register file will read data then add to the 16bit signed offset field contained in the instruction. If the instruction is a store, the value to be stored must also be read from register file. In the case instruction is a load, the value read from memory must be written into the register file in the specified register. In the data path, there is a data memory, which can read and write data with the control signals. In addition, the sign-extend will be constructed to perform the 16 bit offset to a 32 bit signed value. - 6 - A MIPS 32-bit Single-Cycle CPU Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung THE BRANCH AND JUMP INSTRUCTION: In the lab, the branch and jump instruction include the branch on not equal (bne), jump (j) and jump register (jr). - BNE rs, rt, imm16: if (Reg[rs] != Reg[rt]) PC = PC + 4 + Sign_ext(Imm16)<<2 else PC = PC + 4. The instruction will compare the value in register rs and rt. In the case the value of rs does not equal one in rt, the PC will jump to address of PC +4 Sign_ext(Imm16) after shift left 2. - J target: PC = { PC[31:28], target, 00 }. The jump instruction will take the PC move into the target address. - JR rs: PC = Reg[rs]. The jump register instruction jumps to the address stored in the rs register. As we can see from the data path, there is extra mux2to1 and output jump of control module, which determine PC to jump or not. The addition multiplexor is used to choose between the jump target and either the branch target or the sequential instruction following this one. The instruction need more 1 module shift left 2 to convert the 26bit instruction to 28bit instruction. - 7 - A MIPS 32-bit Single-Cycle CPU Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung V. DESIGNING THE MAIN CONTROL UNITS AND A DATAPATH: ALU CONTROL AND CONTROL MODULE: The ALU control determines the operation of ALU including ADD, SUB, SLT (set on less than), XOR, BNE (branch on not equal). In addition, the Control module will output the control signal for register file, data memory or multiplexors in the system. - 8 - A MIPS 32-bit Single-Cycle CPU Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung CONTROL SIGNALS TABLE Function Format Op code instruction[31-26] Funct instruction[5-0] ALU function ALU ctrl lw I 100011 xxxxxx add 00 sw I 101011 xxxxxx add 00 bne I 000101 xxxxxx sub 10 xori I 001110 xxxxxx xor 01 addi I 001000 xxxxxx add 00 j J 000010 xxxxxx xxx xx jr R 000000 001000 add 00 Add R 000000 100000 add 00 Sub R 000000 100010 sub 10 slt R 000000 101010 slt 11 Function RegDst MemtoReg ALUOp MemWrite ALUSrc RegWrite Zero_Sign Jump JumpReg Branch lw 1 1 00 0 1 1 1 0 0 0 sw 0 0 00 1 1 0 1 0 0 0 bne 1 0 10 0 0 0 1 0 0 1 xori 0 0 01 0 1 1 0 0 0 0 addi 0 0 00 0 1 1 1 0 0 0 j 1 0 xx 0 x 0 1 1 0 0 jr 1 0 00 0 x 0 1 0 1 0 add 1 0 00 0 0 1 1 0 0 0 sub 1 0 10 0 0 1 1 0 0 0 slt 1 0 11 0 0 1 1 0 0 0 The picture below is RTL viewer of Control module in Quartus II. - 9 - A MIPS 32-bit Single-Cycle CPU Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung D ENA PRE CLR Q 0 1 0 0 1 0 D ENA PRE CLR Q 0 1 0 D ENA PRE CLR Q D ENA PRE CLR Q IN[5 0] OUT[63 0] DECODER = A[5 0] B[5 0] EQUAL = A[5 0] B[5 0] EQUAL = A[5 0] B[5 0] EQUAL = A[5 0] B[5 0] EQUAL D ENA PRE CLR Q D ENA PRE CLR Q D ENA PRE CLR Q D ENA PRE CLR Q D ENA PRE CLR Q D ENA PRE CLR Q SEL[3 0] DATA[3 0] OUT SELECTOR SEL[1 0] DATA[1 0] OUT SELECTOR SEL[3 0] DATA[3 0] OUT SELECTOR SEL[3 0] DATA[3 0] OUT SELECTOR SEL[3 0] DATA[3 0] OUT SELECTOR SEL[3 0] DATA[3 0] OUT SELECTOR D ENA PRE CLR Q ALUOp[0]$latch ALUOp[0]~2 ALUOp[0]~3 ALUOp[1]$latch ALUOp[1]~4 ALUOp[1]~5 ALUSrc$latch ALUSrc~0 Branch$latch Decoder0 Equal0 6' h08 Equal1 6' h20 Equal2 6' h22 Equal3 6' h2A Jump$latch JumpReg$latch MemtoReg$latch MemWrite$latch RegDst$latch RegWrite$latch Selector3 3' h1 Selector5 1' h0 Selector11 3' h1 Selector17 3' h1 Selector18 3' h3 Selector19 3' h3 WideOr2 WideOr4 WideOr5 WideOr6 WideOr7 WideOr8 Zero_Sign$latch RegDst MemWrite ALUSrc RegWrite Zero_Sign Jump JumpReg Branch ALUOp[1 0] instr31_26[5 0] instr5_0[5 0] WideOr0 MemtoReg [...]... module, it will have Instruction [5-0] as an input also In addition, we put 2 more control signals, which are Zero_Sign and JumpReg Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung - 11 - A MIPS 32-bit Single-Cycle CPU BUILDING A DATA PATH: Below is the datapath in textbook Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung - 12 - A MIPS 32-bit Single-Cycle CPU *ENHANCEMENT 2... with data hazard Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung - 13 - A MIPS 32-bit Single-Cycle CPU Overall RTL Viewer Here is the RTL Viewer of MIPS 32-bit Single-Cycle CPU from Quartus II Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung - 14 - A MIPS 32-bit Single-Cycle CPU VI DESIGN MODULE **Note: There are some modules, which is described in previous labs, such as... Single-Cycle CPU DATA MEMORY MODULE: The module is provided, which has the input : write data, address, and control signal MemWrite, output : ReadData The module will respond for write data into the indicated address through memory Below is its simulation Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung - 25 - A MIPS 32-bit Single-Cycle CPU VII STIMULATION RESULT OF MIPS SINGLE CYCLE DATA PATH... regfile, ALU, and add32bit Thus, in this report we do not explain about them PC MODULE Our PC module is just a 32-bit register (described in lab 1), which take PCin as an input and PCout as a output Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung - 15 - A MIPS 32-bit Single-Cycle CPU EXTEND MODULE We need a unit to sign-extend the 16-bit offset field in the instruction to a 32-bit signed value... use the machine code From the above machine code and simulation result, we can see that our ADD works correctly At PCout = 24 (the instruction at address 32‟d24), $2 is written to, $2 and $3 are read with $2 = 13, and $3 = 8 as you can see in the simulation ALUresult gives the value of 21, meaning the correctness of our ADD in the MIPS 32bits single cycle CPU Group 6 | Le Minh Hoang | Le Hong Thang |... correctly At PC = 48, IMM16 = 7, ReadRegister1= $2, ReadData1=21, and the ALU result = 18, which is written into WriteRegister $3 Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung - 34 - A MIPS 32-bit Single-Cycle CPU VIII CONCLUSION: In conclusion, the MIPS single data path module performs all required instruction correctly The instruction the MIPS can execute: add, sub, set on less than, load,... register, and xori They are the basic and necessary instructions for almost coding program Based on the single cycle data path, the performance of MIPS can be improved to the multiple cycle data path to reduce the time execution IX REFERENCE: 1/ COMPUTER ORGANIZATION AND DESIGN (REVISED) 2/ Fundamentals of Digital Logic with Verilog Design - Stephen Brown and Zvonko Vranesic 3/ http://www.asic-world.com/verilog/... A MIPS 32-bit Single-Cycle CPU *ENHANCEMENT 1 From the knowledge above, we have to design two separate control modules, which costs time, registers and memory Also, from the lab 2, we design the 32-bit ALU, which can only perform 4 operation (add, sub, xor, slt) Therefore, we enhance this situation by combining these two modules into one Specifically, instead of taking only Instruction [31-26] as an... 1 BneAddr 0 0 0 PC4Addr Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung - 23 - A MIPS 32-bit Single-Cycle CPU InstructionMem MODULE The module is given, which has the input: 32-bit address and output: 32-bit instruction The module give us the instruction will be executed Below is its simulation Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung - 24 - A MIPS 32-bit Single-Cycle. .. addr 32'd72: $4 = 1 + 1 = 2 And the testbench like that: module testMIPS(); reg clk, reset; parameter ClockDelay = 10000; SingleCycleMIPS myMIPS(clk, reset); initial begin clk = 0; reset = 1; #100 reset =0; end always #(ClockDelay/2) clk = ~clk; endmodule Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung - 26 - A MIPS 32-bit Single-Cycle CPU ADD INSTRUCTION: The instruction form is: ADD . 0] OUT SELECTOR D ENA PRE CLR Q ALUOp[0]$latch ALUOp[0]~2 ALUOp[0]~3 ALUOp[1]$latch ALUOp[1]~4 ALUOp[1]~5 ALUSrc$latch ALUSrc~0 Branch$latch Decoder0 Equal0 6' h08 Equal1 6' h20 Equal2 6'. A MIPS 32-bit Single-Cycle CPU Group 6 | Le Minh Hoang | Le Hong Thang | Luong Tran Nhat Trung V. DESIGNING THE MAIN CONTROL UNITS AND A DATAPATH: