uart带fifo的verilog及其测试代码

以下是一个带有FIFO的UART模块的Verilog代码，同时包含了简单的测试代码：

module uart_with_fifo (
  input clk,
  input resetn,
  input rx,
  output tx,
  input [7:0] data_in,
  input wr_en,
  output reg rd_en,
  output reg [7:0] data_out,
  parameter BAUDRATE = 9600
);

  reg [7:0] tx_reg;
  reg [7:0] rx_fifo [7:0];
  reg [2:0] rx_fifo_wr_ptr;
  reg [2:0] rx_fifo_rd_ptr;
  reg [1:0] bit_count;
  reg [3:0] baud_count;

  // calculate the number of clock cycles required per bit
  parameter CYCLES_PER_BIT = 100000000 / BAUDRATE;

  // baud_count tracks the number of cycles since the start bit
  always @(posedge clk) begin
    if (!resetn) begin
      baud_count <= 0;
      bit_count <= 0;
      rd_en <= 0;
    end else if (baud_count < CYCLES_PER_BIT) begin
      baud_count <= baud_count + 1;
    end else begin
      if (bit_count == 0) begin
        // start bit received, reset FIFO pointers
        rx_fifo_rd_ptr <= 0;
        rx_fifo_wr_ptr <= 0;
        rd_en <= 0;
        bit_count <= bit_count + 1;
      end else if (bit_count < 9) begin
        // data bits received, add to FIFO
        rx_fifo[rx_fifo_wr_ptr] <= rx;
        rx_fifo_wr_ptr <= rx_fifo_wr_ptr + 1;
        bit_count <= bit_count + 1;
      end else if (bit_count == 9) begin
        // stop bit received, enable FIFO read
        rd_en <= 1;
        bit_count <= 0;
      end
      baud_count <= 0;
    end
  end

  // FIFO output logic
  always @(posedge clk) begin
    if (rd_en && (rx_fifo_wr_ptr != rx_fifo_rd_ptr)) begin
      data_out <= rx_fifo[rx_fifo_rd_ptr];
      rx_fifo_rd_ptr <= rx_fifo_rd_ptr + 1;
    end
  end

  // transmit logic
  always @(posedge clk) begin
    if (!resetn) begin
      tx_reg <= 1;
    end else if (bit_count > 0) begin
      if (bit_count < 9) begin
        tx_reg <= data_in[bit_count-1];
      end else if (bit_count == 9) begin
        tx_reg <= 0;
      end else begin
        tx_reg <= 1;
        bit_count <= 0;
      end
      baud_count <= baud_count + 1;
    end else if (wr_en) begin
      tx_reg <= 0;
      bit_count <= 1;
    end
  end

  // output the TX pin
  assign tx = tx_reg;

endmodule

module test_uart_with_fifo;

  reg clk;
  reg resetn;
  reg rx;
  wire tx;
  reg [7:0] data_in;
  reg wr_en;
  wire rd_en;
  wire [7:0] data_out;

  uart_with_fifo uart_inst (
    .clk(clk),
    .resetn(resetn),
    .rx(rx),
    .tx(tx),
    .data_in(data_in),
    .wr_en(wr_en),
    .rd_en(rd_en),
    .data_out(data_out)
  );

  // testbench clock
  always #5 clk = ~clk;

  // reset
  initial begin
    clk = 0;
    resetn = 0;
    rx = 1;
    data_in = 0;
    wr_en = 0;
    #20 resetn = 1;
  end

  // test read from FIFO
  initial begin
    #30;
    rx = 0;
    #10;
    rx = 1;
    #10;
    data_in = 0;
    wr_en = 1;
    #10;
    data_in = 0xAA;
    wr_en = 1;
    #10;
    data_in = 0x55;
    wr_en = 1;
    #10;
    data_in = 0x33;
    wr_en = 1;
    #10;
    data_in = 0xC3;
    wr_en = 1;
    #10;
    data_in = 0x3C;
    wr_en = 1;
    #10;
    data_in = 0x7F;
    wr_en = 1;
    #10;
    data_in = 0x80;
    wr_en = 1;
    #10;
    assert (rd_en == 0);
    #10;
    assert (rd_en == 1);
    assert (data_out == 0xAA);
    #10;
    assert (rd_en == 1);
    assert (data_out == 0x55);
    #10;
    assert (rd_en == 1);
    assert (data_out == 0x33);
    #10;
    assert (rd_en == 1);
    assert (data_out == 0xC3);
    #10;
    assert (rd_en == 1);
    assert (data_out == 0x3C);
    #10;
    assert (rd_en == 1);
    assert (data_out == 0x7F);
    #10;
    assert (rd_en == 1);
    assert (data_out == 0x80);
    #10;
    assert (rd_en == 0);
    #10;
    $display("FIFO test passed");
    $finish;
  end

endmodule

该代码中包含了一个带有FIFO的UART模块，以及一个简单的测试代码。请注意，这只是一个基本的实现，实际上您可能需要根据您的特定要求进行修改。