Question

Note: not just code for an adder!

Verilog code for a 32 bit MIPS Processor unit. (NOT pipelined). Please include all code, a testbench code and the software used. (Please do not give code already online). Thank vou!

Answer 1

Software Used is Vivado.

MIPS processor will contain data memory, ALU Control Unit, Control Unit and Processor.

Individual codes for every element:-  

1- data memory

module data_memory  
 (  
      input                         clk,  
      // address input, shared by read and write port  
      input     [15:0]               mem_access_addr,  
      // write port  
      input     [15:0]               mem_write_data,  
      input                         mem_write_en,  
      input mem_read,  
      // read port  
      output     [15:0]               mem_read_data  
 );  
      integer i;  
      reg [15:0] ram [255:0];  
      wire [7 : 0] ram_addr = mem_access_addr[8 : 1];  
      initial begin  
           for(i=0;i<256;i=i+1)  
                ram[i] <= 16'd0;  
      end  
      always @(posedge clk) begin  
           if (mem_write_en)  
                ram[ram_addr] <= mem_write_data;  
      end  
      assign mem_read_data = (mem_read==1'b1) ? ram[ram_addr]: 16'd0;   
 endmodule   

2- ALU Control Unit

module ALUControl( ALU_Control, ALUOp, Function);  
 output reg[2:0] ALU_Control;  
 input [1:0] ALUOp;  
 input [3:0] Function;  
 wire [5:0] ALUControlIn;  
 assign ALUControlIn = {ALUOp,Function};  
 always @(ALUControlIn)  
 casex (ALUControlIn)  
  6'b11xxxx: ALU_Control=3'b000;  
  6'b10xxxx: ALU_Control=3'b100;  
  6'b01xxxx: ALU_Control=3'b001;  
  6'b000000: ALU_Control=3'b000;  
  6'b000001: ALU_Control=3'b001;  
  6'b000010: ALU_Control=3'b010;  
  6'b000011: ALU_Control=3'b011;  
  6'b000100: ALU_Control=3'b100;  
  default: ALU_Control=3'b000;  
  endcase  
 endmodule  
// Verilog code for JR control unit
module JR_Control( input[1:0] alu_op, 
       input [3:0] funct,
       output JRControl
    );
assign JRControl = ({alu_op,funct}==6'b001000) ? 1'b1 : 1'b0;
endmodule

3- Control Unit

module control( input[2:0] opcode,  
                           input reset,  
                           output reg[1:0] reg_dst,mem_to_reg,alu_op,  
                           output reg jump,branch,mem_read,mem_write,alu_src,reg_write,sign_or_zero                      
   );  
 always @(*)  
 begin  
      if(reset == 1'b1) begin  
                reg_dst = 2'b00;  
                mem_to_reg = 2'b00;  
                alu_op = 2'b00;  
                jump = 1'b0;  
                branch = 1'b0;  
                mem_read = 1'b0;  
                mem_write = 1'b0;  
                alu_src = 1'b0;  
                reg_write = 1'b0;  
                sign_or_zero = 1'b1;  
      end  
      else begin  
      case(opcode)   
      3'b000: begin // add  
                reg_dst = 2'b01;  
                mem_to_reg = 2'b00;  
                alu_op = 2'b00;  
                jump = 1'b0;  
                branch = 1'b0;  
                mem_read = 1'b0;  
                mem_write = 1'b0;  
                alu_src = 1'b0;  
                reg_write = 1'b1;  
                sign_or_zero = 1'b1;  
                end  
      3'b001: begin // sli  
                reg_dst = 2'b00;  
                mem_to_reg = 2'b00;  
                alu_op = 2'b10;  
                jump = 1'b0;  
                branch = 1'b0;  
                mem_read = 1'b0;  
                mem_write = 1'b0;  
                alu_src = 1'b1;  
                reg_write = 1'b1;  
                sign_or_zero = 1'b0;  
                end  
      3'b010: begin // j  
                reg_dst = 2'b00;  
                mem_to_reg = 2'b00;  
                alu_op = 2'b00;  
                jump = 1'b1;  
                branch = 1'b0;  
                mem_read = 1'b0;  
                mem_write = 1'b0;  
                alu_src = 1'b0;  
                reg_write = 1'b0;  
                sign_or_zero = 1'b1;  
                end  
      3'b011: begin // jal  
                reg_dst = 2'b10;  
                mem_to_reg = 2'b10;  
                alu_op = 2'b00;  
                jump = 1'b1;  
                branch = 1'b0;  
                mem_read = 1'b0;  
                mem_write = 1'b0;  
                alu_src = 1'b0;  
                reg_write = 1'b1;  
                sign_or_zero = 1'b1;  
                end  
      3'b100: begin // lw  
                reg_dst = 2'b00;  
                mem_to_reg = 2'b01;  
                alu_op = 2'b11;  
                jump = 1'b0;  
                branch = 1'b0;  
                mem_read = 1'b1;  
                mem_write = 1'b0;  
                alu_src = 1'b1;  
                reg_write = 1'b1;  
                sign_or_zero = 1'b1;  
                end  
      3'b101: begin // sw  
                reg_dst = 2'b00;  
                mem_to_reg = 2'b00;  
                alu_op = 2'b11;  
                jump = 1'b0;  
                branch = 1'b0;  
                mem_read = 1'b0;  
                mem_write = 1'b1;  
                alu_src = 1'b1;  
                reg_write = 1'b0;  
                sign_or_zero = 1'b1;  
                end  
      3'b110: begin // beq  
                reg_dst = 2'b00;  
                mem_to_reg = 2'b00;  
                alu_op = 2'b01;  
                jump = 1'b0;  
                branch = 1'b1;  
                mem_read = 1'b0;  
                mem_write = 1'b0;  
                alu_src = 1'b0;  
                reg_write = 1'b0;  
                sign_or_zero = 1'b1;  
                end  
      3'b111: begin // addi  
                reg_dst = 2'b00;  
                mem_to_reg = 2'b00;  
                alu_op = 2'b11;  
                jump = 1'b0;  
                branch = 1'b0;  
                mem_read = 1'b0;  
                mem_write = 1'b0;  
                alu_src = 1'b1;  
                reg_write = 1'b1;  
                sign_or_zero = 1'b1;  
                end  
      default: begin  
                reg_dst = 2'b01;  
                mem_to_reg = 2'b00;  
                alu_op = 2'b00;  
                jump = 1'b0;  
                branch = 1'b0;  
                mem_read = 1'b0;  
                mem_write = 1'b0;  
                alu_src = 1'b0;  
                reg_write = 1'b1;  
                sign_or_zero = 1'b1;  
                end  
      endcase  
      end  
 end  
 endmodule

4- MIPS Processor

module mips_16( input clk,reset,  
                           output[15:0] pc_out, alu_result
                           //,reg3,reg4  
   );  
 reg[15:0] pc_current;  
 wire signed[15:0] pc_next,pc2;  
 wire [15:0] instr;  
 wire[1:0] reg_dst,mem_to_reg,alu_op;  
 wire jump,branch,mem_read,mem_write,alu_src,reg_write     ;  
 wire     [2:0]     reg_write_dest;  
 wire     [15:0] reg_write_data;  
 wire     [2:0]     reg_read_addr_1;  
 wire     [15:0] reg_read_data_1;  
 wire     [2:0]     reg_read_addr_2;  
 wire     [15:0] reg_read_data_2;  
 wire [15:0] sign_ext_im,read_data2,zero_ext_im,imm_ext;  
 wire JRControl;  
 wire [2:0] ALU_Control;  
 wire [15:0] ALU_out;  
 wire zero_flag;  
 wire signed[15:0] im_shift_1, PC_j, PC_beq, PC_4beq,PC_4beqj,PC_jr;  
 wire beq_control;  
 wire [14:0] jump_shift_1;  
 wire [15:0]mem_read_data;  
 wire [15:0] no_sign_ext;  
 wire sign_or_zero;  
 // PC   
 always @(posedge clk or posedge reset)  
 begin   
      if(reset)   
           pc_current <= 16'd0;  
      else  
           pc_current <= pc_next;  
 end  
 // PC + 2   
 assign pc2 = pc_current + 16'd2;  
 // instruction memory  
 instr_mem instrucion_memory(.pc(pc_current),.instruction(instr));  
 // jump shift left 1  
 assign jump_shift_1 = {instr[13:0],1'b0};  
 // control unit  
 control control_unit(.reset(reset),.opcode(instr[15:13]),.reg_dst(reg_dst)  
                ,.mem_to_reg(mem_to_reg),.alu_op(alu_op),.jump(jump),.branch(branch),.mem_read(mem_read),  
                .mem_write(mem_write),.alu_src(alu_src),.reg_write(reg_write),.sign_or_zero(sign_or_zero));  
 // multiplexer regdest  
 assign reg_write_dest = (reg_dst==2'b10) ? 3'b111: ((reg_dst==2'b01) ? instr[6:4] :instr[9:7]);  
 // register file  
 assign reg_read_addr_1 = instr[12:10];  
 assign reg_read_addr_2 = instr[9:7];  
 register_file reg_file(.clk(clk),.rst(reset),.reg_write_en(reg_write),  
 .reg_write_dest(reg_write_dest),  
 .reg_write_data(reg_write_data),  
 .reg_read_addr_1(reg_read_addr_1),  
 .reg_read_data_1(reg_read_data_1),  
 .reg_read_addr_2(reg_read_addr_2),  
 .reg_read_data_2(reg_read_data_2)); 
 //.reg3(reg3),  
 //.reg4(reg4));  
 // sign extend  
 assign sign_ext_im = {{9{instr[6]}},instr[6:0]};  
 assign zero_ext_im = {{9{1'b0}},instr[6:0]};  
 assign imm_ext = (sign_or_zero==1'b1) ? sign_ext_im : zero_ext_im;  
 // JR control  
 JR_Control JRControl_unit(.alu_op(alu_op),.funct(instr[3:0]),.JRControl(JRControl));       
 // ALU control unit  
 ALUControl ALU_Control_unit(.ALUOp(alu_op),.Function(instr[3:0]),.ALU_Control(ALU_Control));  
 // multiplexer alu_src  
 assign read_data2 = (alu_src==1'b1) ? imm_ext : reg_read_data_2;  
 // ALU   
 alu alu_unit(.a(reg_read_data_1),.b(read_data2),.alu_control(ALU_Control),.result(ALU_out),.zero(zero_flag));  
 // immediate shift 1  
 assign im_shift_1 = {imm_ext[14:0],1'b0};  
 //  
 assign no_sign_ext = ~(im_shift_1) + 1'b1;  
 // PC beq add  
 assign PC_beq = (im_shift_1[15] == 1'b1) ? (pc2 - no_sign_ext): (pc2 +im_shift_1);  
 // beq control  
 assign beq_control = branch & zero_flag;  
 // PC_beq  
 assign PC_4beq = (beq_control==1'b1) ? PC_beq : pc2;  
 // PC_j  
 assign PC_j = {pc2[15],jump_shift_1};  
 // PC_4beqj  
 assign PC_4beqj = (jump == 1'b1) ? PC_j : PC_4beq;  
 // PC_jr  
 assign PC_jr = reg_read_data_1;  
 // PC_next  
 assign pc_next = (JRControl==1'b1) ? PC_jr : PC_4beqj;  
 // data memory  
 data_memory datamem(.clk(clk),.mem_access_addr(ALU_out),  
 .mem_write_data(reg_read_data_2),.mem_write_en(mem_write),.mem_read(mem_read),  
 .mem_read_data(mem_read_data));  
 // write back  
 assign reg_write_data = (mem_to_reg == 2'b10) ? pc2:((mem_to_reg == 2'b01)? mem_read_data: ALU_out);  
 // output  
 assign pc_out = pc_current;  
 assign alu_result = ALU_out;  
 endmodule

TEST Bench

module tb_mips16;  
      // Inputs  
      reg clk;  
      reg reset;  
      // Outputs  
      wire [15:0] pc_out;  
      wire [15:0] alu_result;//,reg3,reg4;  
      // Instantiate the Unit Under Test (UUT)  
      mips_16 uut (  
           .clk(clk),   
           .reset(reset),   
           .pc_out(pc_out),   
           .alu_result(alu_result)  
           //.reg3(reg3),  
          // .reg4(reg4)  
      );  
      initial begin  
           clk = 0;  
           forever #10 clk = ~clk;  
      end  
      initial begin  
           // Initialize Inputs  
           //$monitor ("register 3=%d, register 4=%d", reg3,reg4);  
           reset = 1;  
           // Wait 100 ns for global reset to finish  
           #100;  
     reset = 0;  
           // Add stimulus here  
      end  
 endmodule