用Verilog HDL设计实现从输入序列“111001011010100110110001”中，检测序列“1001”的序列检测器，并写出仿真文件

以下是Verilog HDL实现“1001”序列检测器的代码：

module sequence_detector(
  input clk,
  input reset,
  input data,
  output reg detect
);

reg [3:0] state;

parameter S0 = 2'b00;
parameter S1 = 2'b01;
parameter S2 = 2'b10;
parameter S3 = 2'b11;

always @(posedge clk, posedge reset) begin
  if (reset) begin
    state <= S0;
    detect <= 0;
  end else begin
    case (state)
      S0: begin
        if (data) begin
          state <= S1;
        end else begin
          state <= S0;
        end
      end
      
      S1: begin
        if (data) begin
          state <= S1;
        end else begin
          state <= S2;
        end
      end
      
      S2: begin
        if (data) begin
          state <= S3;
        end else begin
          state <= S0;
        end
      end
      
      S3: begin
        if (data) begin
          detect <= 1;
          state <= S1;
        end else begin
          state <= S0;
        end
      end
    endcase
  end
end

endmodule

在这个序列检测器中，我们使用一个4位状态机来检测序列“1001”。如果检测到序列，输出信号“detect”将被置为1。

以下是仿真文件的代码：

`timescale 1ns / 1ns

module sequence_detector_tb;

reg clk;
reg reset;
reg data;

wire detect;

sequence_detector dut(
  .clk(clk),
  .reset(reset),
  .data(data),
  .detect(detect)
);

initial begin
  clk = 0;
  reset = 1;
  data = 0;
  #10 reset = 0;
end

always #5 clk = ~clk;

initial begin
  $dumpfile("sequence_detector.vcd");
  $dumpvars(0, sequence_detector_tb);
end

initial begin
  // Test case 1: No sequence detected
  #100 data = 1;
  #20 data = 1;
  #20 data = 0;
  #20 data = 0;
  #20 data = 1;
  #20 data = 0;
  #20 data = 1;
  #20 data = 0;
  #20 data = 1;
  
  // Test case 2: Sequence detected
  #100 data = 1;
  #20 data = 0;
  #20 data = 0;
  #20 data = 1;
  #20 data = 0;
  #20 data = 1;
  #20 data = 0;
  #20 data = 1;
  
  $finish;
end

endmodule

在仿真文件中，我们通过改变输入数据“data”来模拟输入序列。在测试用例1中，我们模拟了没有检测到序列“1001”的情况；在测试用例2中，我们模拟了检测到序列“1001”的情况。我们可以通过查看仿真波形来验证序列检测器的正确性。