设计MOORE型和MEALY型的可重叠101序列检测器

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1.  未收到一个有效位（0）：S0
2.  收到一个有效位（1）：S1
3.  连续收到两个有效位（10）：S2
4.  连续收到三个有效位（101）：S3
5.  状态转移表如下

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    `timescale 1ns / 1ps
    //
    // Company: 
    // Engineer: 
    // 
    // Create Date: 2018/05/13 16:50:14
    // Design Name: 
    // Module Name: Checker
    // Project Name: 
    // Target Devices: 
    // Tool Versions: 
    // Description: 
    // 
    // Dependencies: 
    // 
    // Revision:
    // Revision 0.01 - File Created
    // Additional Comments:
    // 
    //


module Checker(
    input x, clk, rst,
    output y
    );
    reg y;
    //register to store the state and nextstate 
    reg [1:0] currentstate, nextstate;
    //the code for states, can be changed
    parameter S0 = 2'b00;
    parameter S1 = 2'b01;
    parameter S2 = 2'b10;
    parameter S3 = 2'b11;
    //the D_trigger to set the currentstate
    always@(posedge clk or negedge rst)
    begin
        if(!rst)
            currentstate <= S0;
        else
            currentstate <= nextstate;
    end
    //the nextstate
    always@(currentstate or x or rst)
    begin
        if(!rst)
            nextstate = S0;
        else
        begin
            case(currentstate)
                S0:nextstate = (x==1)?S1:S0;
                S1:nextstate = (x==0)?S2:S0;
                S2:nextstate = (x==1)?S3:S0;
                S3:nextstate = (x==1)?S1:S0;
                default:nextstate = S0;
            endcase
        end
    end
    //the output
    always@(rst or currentstate)
    begin
        if(!rst)
            y = 0;
        else
        case(currentstate)
            S0:y = 0;
            S1:y = 0;
            S2:y = 0;
            S3:y = 1;
            default:y = 0;
        endcase
    end
endmodule

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        `timescale 1ns / 1ps
        `//
        // Company: 
        // Engineer: 
        // 
        // Create Date: 2018/05/13 17:19:43
        // Design Name: 
        // Module Name: Checker_testbench
        // Project Name: 
        // Target Devices: 
        // Tool Versions: 
        // Description: 
        // 
        // Dependencies: 
        // 
        // Revision:
        // Revision 0.01 - File Created
        // Additional Comments:
        // 
        //

module Checker_testbench(

   );
    reg clk,rst;
    reg x;
    wire y;
    Checker ch(.clk(clk),.rst(rst),.x(x),.y(y));
    initial begin
        clk = 0;
        rst = 1;
        #5 rst = 0;
        #3 rst = 1;
        #40 x = 1;
        #40 x = 1;
        #40 x = 0;
        #40 x = 1;
        #40 x = 1;
        #40 x = 0;
        #40 x = 0;
        #40 x = 1;
        #40 x = 0;
        #40 x = 1;
        #40 x = 0;
        #40 x = 0;
        #40 x = 1;
        #40 x = 0;
        #40 x = 0;
        #40 x = 1;
        #40 x = 0;
        #40 x = 1;
        #40 x = 0;
    end
    always #50 clk = ~clk;
    endmodule

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`timescale 1ns / 1ps
/
// Company: 
// Engineer: 
// 
// Create Date: 2018/05/13 22:26:33
// Design Name: 
// Module Name: Mealy
// Project Name: 
// Target Devices: 
// Tool Versions: 
// Description: 
// 
// Dependencies: 
// 
// Revision:
// Revision 0.01 - File Created
// Additional Comments:
// 
/


module Mealy(
    input clk, rst, x,
    output y
    );

    //make the output y to be a register
    reg y;

    /*temp_y: to store the temp value of y, becaouse the output y is decided
    the state and the input*/
    //currentstate and nextstae: the present state and the next state
    reg temp_y;
    reg[1:0] currentstate, nextstate;

    //the state parameter 
    parameter S0 = 2'b00;
    parameter S1 = 2'b01;
    parameter S2 = 2'b10;

    //the D_trigger to modify the state
    //if reset, set the currentstate to S0
    //else, set the currentstate to nextstate
    always@(posedge clk or negedge rst)
    begin
        if(!rst)
            currentstate <= S0;
        else
            currentstate <= nextstate;
    end

    //the modifier of state
    always@(currentstate or x or rst)
    begin
        if(!rst)
            nextstate <= S0;
        else
            begin
                case(currentstate)
                    S0: nextstate = (x==1)?S1:S0;
                    S1: nextstate = (x==0)?S2:S0;
                    S2: nextstate = (x==1)?S1:S0;
                    default: nextstate = S0;
                endcase
            end
    end

    //the temp output
    always@(rst or currentstate or x)
    begin
        if(!rst)
            temp_y = 0;
        else
            case(currentstate)
                S0: temp_y = 0;
                S1: temp_y = 0;
                S2: temp_y = (x==1)?1:0;
                default: temp_y = 0;
            endcase
    end

    //the real output
    always@(posedge clk or negedge rst)
    begin
        //reset
        if(!rst)
            y <= 0;
        else
            begin
                //
                if((temp_y == 1)&&(nextstate == S1))
                    y <= 1;
                else
                    y <= 0;
            end
    end
endmodule

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`timescale 1ns / 1ps
//
// Company: 
// Engineer: 
// 
// Create Date: 2018/05/13 22:59:56
// Design Name: 
// Module Name: Mealy_testbench
// Project Name: 
// Target Devices: 
// Tool Versions: 
// Description: 
// 
// Dependencies: 
// 
// Revision:
// Revision 0.01 - File Created
// Additional Comments:
// 
//

    module Mealy_testbench(

    );
    reg x, clk, rst;
    wire y;
    Mealy meal(.x(x),.clk(clk),.rst(rst),.y(y));
    initial begin
        clk = 0;
        rst = 1;
        #5 rst = 0;
        #3 rst = 1;
        #40 x = 1;
        #40 x = 1;
        #40 x = 0;
        #40 x = 0;
        #40 x = 1;
        #40 x = 0;
        #40 x = 0;
        #40 x = 1;
        #40 x = 0;
        #40 x = 0;
        #40 x = 0;
        #40 x = 0;
        #40 x = 1;
        #40 x = 0;
        #40 x = 0;
        #40 x = 1;
        #40 x = 0;
        #40 x = 1;
        #40 x = 0;
    end
    always #50 clk = ~clk;
endmodule