DMA的Verilog模型

以下是一个简单的DMA的Verilog模型，其中包括一个简单的状态机和一个FIFO缓冲区，用于存储传输的数据：

module dma (
  input clk,
  input rst_n,
  input start,
  input [31:0] src_addr,
  input [31:0] dst_addr,
  input [15:0] length,
  output done
);

  // FIFO缓冲区
  reg [31:0] fifo [0:15];
  reg [3:0] wr_ptr;
  reg [3:0] rd_ptr;
  
  // 状态机状态定义
  parameter IDLE = 2'd0;
  parameter READ_SRC = 2'd1;
  parameter WRITE_DST = 2'd2;
  parameter TRANSFER = 2'd3;
  
  // 状态机状态寄存器
  reg [1:0] state;
  
  // 状态机控制信号
  reg read;
  reg write;
  reg [15:0] count;
  
  // 初始化状态机
  always @(posedge clk or negedge rst_n) begin
    if (~rst_n) begin
      state <= IDLE;
      wr_ptr <= 0;
      rd_ptr <= 0;
      count <= 0;
    end else begin
      case (state)
        IDLE:
          if (start) begin
            state <= READ_SRC;
            read <= 1;
            write <= 0;
            count <= length;
          end
        READ_SRC:
          if (count == 0) begin
            state <= IDLE;
            read <= 0;
            write <= 0;
            done <= 1;
          end else begin
            state <= WRITE_DST;
            read <= 0;
            write <= 1;
          end
        WRITE_DST:
          if (wr_ptr == rd_ptr && count == length) begin
            state <= IDLE;
            read <= 0;
            write <= 0;
            done <= 1;
          end else begin
            state <= TRANSFER;
            read <= 0;
            write <= 0;
          end
        TRANSFER:
          if (wr_ptr == rd_ptr) begin
            state <= READ_SRC;
            read <= 1;
            write <= 0;
            count <= count - 16;
          end else begin
            state <= WRITE_DST;
            read <= 0;
            write <= 1;
          end
      endcase
    end
  end
  
  // 数据读写逻辑
  always @(posedge clk) begin
    if (read) begin
      fifo[wr_ptr] <= $readmemh(src_addr + count - 16)[31:0];
      wr_ptr <= wr_ptr + 1;
    end else if (write) begin
      $writememh(dst_addr + count - 16, fifo[rd_ptr]);
      rd_ptr <= rd_ptr + 1;
    end
  end

endmodule

需要注意的是，这只是一个简单的模型，实际使用中可能需要增加更多的控制逻辑和错误检测。