Verilog实现CAN

CAN（Controller Area Network）是一种广泛应用于汽车、工业控制和航空等领域的串行通信协议。CAN使用两根信号线（CANH和CANL）进行通信，支持多个设备在同一总线上进行通信。以下是一个Verilog实现的CAN控制器的示例代码：

module can_controller (
  input clk,
  input rst,
  input tx_req,
  output reg tx_ack,
  input rx_ack,
  output reg [7:0] tx_data,
  input [7:0] rx_data,
  output reg tx_en,
  output reg rx_en
);

  parameter IDLE = 0;
  parameter ARBITRATION = 1;
  parameter TRANSMISSION = 2;
  parameter RECEPTION = 3;

  parameter ACK = 1;
  parameter NACK = 0;

  reg [2:0] state;
  reg [4:0] bit_count;
  reg [7:0] arbitration_id;
  reg [7:0] data;
  reg rtr;
  reg tx_req_int;
  reg rx_ack_int;
  reg tx_err;

  always @(posedge clk) begin
    if (rst) begin
      state <= IDLE;
      bit_count <= 0;
      tx_ack <= 0;
      tx_en <= 0;
      rx_en <= 0;
      tx_data <= 0;
    end else begin
      tx_req_int <= tx_req;
      rx_ack_int <= rx_ack;

      case (state)
        IDLE: begin
          if (tx_req_int) begin
            state <= ARBITRATION;
            tx_en <= 1;
            arbitration_id <= tx_data;
            bit_count <= 4;
            tx_err <= 0;
          end else if (rx_ack_int) begin
            state <= RECEPTION;
            rx_en <= 1;
            bit_count <= 4;
          end
        end
        ARBITRATION: begin
          if (bit_count == 0) begin
            state <= TRANSMISSION;
            bit_count <= 8;
            tx_data <= data;
          end else begin
            arbitration_id <= {arbitration_id[6:0], tx_data};
            bit_count <= bit_count - 1;
          end
        end
        TRANSMISSION: begin
          if (bit_count == 0) begin
            state <= IDLE;
            tx_en <= 0;
            tx_ack <= 1;
            tx_err <= 0;
          end else begin
            tx_data <= {tx_data[6:0], data};
            bit_count <= bit_count - 1;
          end
        end
        RECEPTION: begin
          if (bit_count == 0) begin
            state <= IDLE;
            rx_en <= 0;
            data <= rx_data;
            tx_ack <= 0;
          end else begin
            bit_count <= bit_count - 1;
          end
        end
      endcase
    end
  end

  always @(posedge clk) begin
    if (rst) begin
      rtr <= 0;
    end else if (state == ARBITRATION) begin
      rtr <= tx_data[7];
    end
  end

  always @(posedge clk) begin
    if (rst) begin
      data <= 0;
    end else if (state == TRANSMISSION) begin
      data <= tx_data[bit_count - 1];
    end
  end

  always @(posedge clk) begin
    if (rst) begin
      tx_err <= 0;
    end else if (state == TRANSMISSION && tx_req_int && !rx_ack_int) begin
      tx_err <= 1;
    end else if (state == IDLE) begin
      tx_err <= 0;
    end
  end

endmodule

在这个示例代码中，CAN控制器被实现为一个模块，包括输入端口clk、rst、tx_req、rx_ack和rx_data，以及输出端口tx_ack、tx_data、tx_en和rx_en。模块中包括一个状态机，用于管理CAN控制器的状态。在IDLE状态下，CAN控制器等待发送或接收请求。当CAN控制器接收到发送请求时，它将进入ARBITRATION状态，并发送ID信息进行仲裁。当CAN控制器接收到接收请求时，它将进入RECEPTION状态，并接收数据。在TRANSMISSION状态下，CAN控制器将发送数据。在每个时钟周期中，CAN控制器将根据当前状态和输入信号更新输出信号。可以根据具体的应用进行修改，例如添加过滤器来过滤接收到的消息等。