用sv语言写一个axi-full slave bfm模块

以下是一个简单的AXI-Full Slave BFM模块的SV代码：

module axi_full_slave_bfm (
    input logic                aclk,
    input logic                aresetn,

    // AXI4 signals
    input logic [31:0]         araddr,
    input logic [7:0]          arlen,
    input logic [2:0]          arsize,
    input logic                arvalid,
    output logic               arready,
    input logic [31:0]         rdata,
    input logic [1:0]          rresp,
    input logic                rvalid,
    output logic               rready,

    // Memory interface signals
    input logic [31:0]         mem_addr,
    input logic [31:0]         mem_write_data,
    input logic [31:0]         mem_read_data,
    input logic                mem_write_en,
    input logic                mem_read_en
);

  // AXI4 slave state machine
  enum logic [2:0] axi_state;
  parameter IDLE = 3'h0,
            ADDR = 3'h1,
            DATA = 3'h2,
            RESP = 3'h3;

  // AXI4 slave registers
  logic [31:0] addr_reg;
  logic [31:0] data_reg;
  logic [1:0]  resp_reg;

  // Initialize the AXI4 slave state machine
  initial begin
    axi_state <= IDLE;
  end

  always_ff @(posedge aclk) begin
    if (!aresetn) begin
      // Reset the AXI4 slave state machine
      axi_state <= IDLE;
      addr_reg  <= '0;
      data_reg  <= '0;
      resp_reg  <= '0;
      arready   <= '0;
      rready    <= '0;
    end else begin
      case (axi_state)
        IDLE: begin
          // Wait for a valid AXI4 read request
          if (arvalid) begin
            // Save the read address and move to ADDR state
            addr_reg <= araddr;
            axi_state <= ADDR;
            arready  <= '1;
          end else begin
            arready <= '0;
          end
        end
        ADDR: begin
          // Wait for the address phase to complete
          if (mem_read_en) begin
            // Start the data phase and move to DATA state
            data_reg <= mem_read_data;
            axi_state <= DATA;
          end
        end
        DATA: begin
          // Wait for the data phase to complete
          if (rready && rvalid) begin
            // Save the read data and move to RESP state
            resp_reg <= rresp;
            axi_state <= RESP;
          end else begin
            rready <= '1;
          end
        end
        RESP: begin
          // Wait for the response phase to complete
          if (rready && rvalid) begin
            // Send the read response and move to IDLE state
            rresp    <= resp_reg;
            rdata    <= data_reg;
            axi_state <= IDLE;
          end else begin
            rready <= '1;
          end
        end
      endcase
    end
  end

  // Memory interface
  always_comb begin
    // Write data to memory
    if (mem_write_en) begin
      $mem_write(mem_addr, mem_write_data);
    end

    // Read data from memory
    if (mem_read_en) begin
      mem_read_data <= $mem_read(mem_addr);
    end
  end

endmodule

该模块包含一个AXI4从设备状态机和一个简单的内存接口。当从设备接收到读请求时，它将等待地址阶段完成，然后开始数据阶段，并将读取的数据保存在数据寄存器中。一旦数据阶段完成，从设备将等待响应阶段完成，并将读取的数据和响应发送回主设备。内存接口支持读写操作，并使用了$mem_read和$mem_write系统任务。