Description
CPU Module:
`timescale 1ns / 1ps module PC(
input clk,rst, input [31:0] PCAddress, output reg[31:0] oldPC
);
reg [31:0] newPC; always@(posedge clk) begin
if(rst) begin
newPC = PCAddress; oldPC = newPC;
end else begin newPC = newPC + 4;//PC Adder oldPC = newPC; end end
endmodule
module InstructMem(
input [31:0] if_idin, output [31:0] if_idout
);
reg [31:0] instr_mem[0:127]; initial begin
//initialize the first 10 words of the Data memory with the following HEX values.
instr_mem[100]=32’hA00000AA; instr_mem[104]=32’h10000011; instr_mem[108]=32’h20000022; instr_mem[112]=32’h30000033; instr_mem[116]=32’h40000044; instr_mem[120]=32’h50000055; instr_mem[124]=32’h60000066; instr_mem[128]=32’h70000077; instr_mem[132]=32’h80000088; instr_mem[136]=32’h90000099;
end assign if_idout = instr_mem[if_idin];
endmodule
module IFID(
input clk, input [31:0] do, //output from Instruction memory
//setup R Type output reg [5:0] op, func, //output into Control Unit output reg [4:0] rd, rs, rt, // (rd,rt) into mux. (rs,rt) into regfile output reg [15:0] imm //immediate value going into extender
);
always@(posedge clk) begin op = do[31:26]; // R-Type opcode func = do[5:0]; // R-Type func rs = do[25:21]; // R-Type first source rt = do[20:16]; // R-Type target source rd = do[15:11]; // R-Type destination register imm = do[15:0]; // Address/Immediate Value
end
endmodule
module ControlUnit(
input [5:0] op, input [5:0] func, output reg wreg, output reg m2reg, output reg wmem, output reg aluimm, output reg regrt, output reg [3:0] aluc
);
always@(op,func) begin
case(op) 6’b100011: begin aluimm = 1; aluc = 4’b0010; wreg = 1; m2reg = 1; wmem = 0; regrt = 1; end default: begin aluc = 4’b0000; aluimm = 0; wreg = 0; m2reg = 0; wmem = 0;
regrt = 1; end endcase
end
endmodule
module ControlMux(
input regrt, input [4:0] rd, rt, output [4:0] wn
);
assign wn = regrt?rt:rd; //Multiplexer operation endmodule
module RegFile(
input we, input [4:0] rna, input [4:0] rnb, input [4:0] wn, input [4:0] d, output reg [31:0] qa, output reg [31:0] qb
);
//initialize all registers to 0 reg [31:0] registers [0:127]; initial begin registers[0] = 0; registers[1] = 0; registers[2] = 0; registers[3] = 0; registers[4] = 0; registers[5] = 0; registers[6] = 0; registers[7] = 0; registers[8] = 0; registers[9] = 0; registers[10] = 0; registers[11] = 0; registers[12] = 0; registers[13] = 0; registers[14] = 0; registers[15] = 0; end always@(rna, rnb) begin
qa = registers[rna]; qb = registers[rnb]; end
endmodule
module SignExtend(//input immediate value, extend to 32 bit value input [15:0] imm, output reg [31:0] long //extended value
);
always@(imm) begin
if(imm[15] == 1) begin long[31:16] = 16’hffff; long[15:0] = imm; end else begin long[31:16] = 16’h0000; long[15:0] = imm;
end end
endmodule
module IDEXE( input clk, wreg, m2reg, wmem, aluimm, //input to IDEXE input [3:0] aluc, //output from control unit input [31:0] qa, qb, //output from regfile input [4:0] mux, //output from mux into IDEXE input [31:0] extend, //output from signextender output reg ewreg, em2reg, ewmem, ealuimm, //outputs from control unit output reg [3:0] ealuc, //out from control unit, into ALU output reg [31:0] eqa, eqb, //outputs from regfile output reg [4:0] emux, //output from multiplexor output reg [31:0] eextend //output from sign extender
);
always@(posedge clk) begin
ewreg = wreg; em2reg = m2reg;
ewmem = wmem;
ealuimm = aluimm; emux = mux;
ealuc = aluc; eqa = qa; eqb = qb; eextend = extend; end
endmodule
Testbench Module: `timescale 1ns / 1ps module CPU_Test();
reg clk, rst; reg [31:0] pcin; wire [31:0] pcout; wire [31:0] dowire; wire [5:0] opwire; wire [5:0] funcwire; wire [4:0] rdwire, rtwire, rswire; wire [15:0] immwire; wire wregwire, m2regwire, wmemwire, aluimmwire;
wire regrtwire; wire [3:0] alucwire; reg wewire; wire [4:0] wnwire; wire [4:0] dwire; wire [31:0] qawire, qbwire; wire [4:0] muxwire; wire [31:0] longwire;
wire ewregwire, em2regwire, ewmemwire, ealuimmwire; wire [3:0] ealucwire; wire [31:0] eqbwire, eqawire, Extenderwire; wire [4:0] emuxwire;
PC pc(clk, rst, pcin, pcout);
InstructMem instmem(pcin, dowire);
IFID ifid(clk, dowire, opwire, funcwire, rdwire, rswire, rtwire, immwire);
ControlUnit ctrunit(opwire, funcwire, wregwire, m2regwire, wmemwire, aluimmwire, regrtwire, alucwire);
RegFile regfile(wewire, rswire, rtwire, wnwire, dwire, qawire, qbwire);
ControlMux ctrmux(regrtwire, rdwire, rtwire,muxwire);
SignExtend extender(immwire, longwire);
IDEXE idexe(clk, wregwire, m2regwire, wmemwire, aluimmwire, alucwire,
qawire, qbwire, muxwire, longwire, ewregwire, em2regwire, ewmemwire, ealuimmwire, ealucwire, eqawire, eqbwire, emuxwire, Extenderwire);
initial begin
clk = 1; pcin = 100;
rst = 1; #1 rst = 0; end
always begin #10 clk = !clk; end
endmodule
Waveforms:
