帮我用verilog写一个SRAM的BIST控制器，要求采用主从FSM，流程如下：所有存储单元写5，然后从低地址到高地址读5，然后依次写A，然后依次读A。如果成功，就读A、写5、读5，然后进入第二个部分；如果失败，就回到读5。第二个部分与第一个部分类似，但把数据5换成了0

好的，下面是一个简单的 SRAM BIST 控制器的 Verilog 代码，其中采用了主从 FSM 的设计。

module sram_bist_controller (
  input clk, // 时钟信号
  input reset, // 复位信号
  output reg bist_done // BIST 完成信号
);

// 定义 SRAM 模块的输入输出端口
reg [7:0] sram_data_in, sram_data_out;
reg [7:0] sram_addr;
reg sram_we;

// 定义状态机状态
localparam IDLE = 2'b00;
localparam WRITE_5 = 2'b01;
localparam READ_5 = 2'b10;
localparam WRITE_A = 2'b11;
localparam READ_A = 2'b100;
localparam SUCCESS = 2'b101;
localparam WRITE_0 = 2'b110;
localparam READ_0 = 2'b111;

// 定义主状态机和从状态机的状态寄存器和下一个状态逻辑
reg [2:0] main_state, sub_state;
always @(posedge clk) begin
  if (reset) begin
    main_state <= IDLE;
    sub_state <= IDLE;
  end else begin
    case (main_state)
      IDLE: begin
        bist_done <= 0;
        main_state <= WRITE_5;
      end
      WRITE_5: begin
        sub_state <= WRITE_5;
        sram_data_in <= 8'h55;
        sram_addr <= 8'h00;
        sram_we <= 1'b1;
        main_state <= READ_5;
      end
      READ_5: begin
        sub_state <= READ_5;
        sram_addr <= sram_addr + 1'b1;
        if (sram_addr == 8'hFF) begin
          main_state <= WRITE_A;
        end else begin
          main_state <= READ_5;
        end
      end
      WRITE_A: begin
        sub_state <= WRITE_A;
        if (sram_addr == 8'h00) begin
          sram_data_in <= 8'h41;
        end else begin
          sram_data_in <= sram_addr + 1'b1;
        end
        sram_we <= 1'b1;
        sram_addr <= sram_addr + 1'b1;
        if (sram_addr == 8'hFF) begin
          main_state <= READ_A;
        end else begin
          main_state <= WRITE_A;
        end
      end
      READ_A: begin
        sub_state <= READ_A;
        sram_we <= 1'b0;
        sram_addr <= sram_addr + 1'b1;
        if (sram_addr == 8'hFF) begin
          main_state <= SUCCESS;
        end else begin
          main_state <= READ_A;
        end
      end
      SUCCESS: begin
        sub_state <= SUCCESS;
        sram_we <= 1'b0;
        sram_addr <= 8'h00;
        sram_data_in <= 8'h41;
        main_state <= WRITE_5;
      end
      WRITE_0: begin
        sub_state <= WRITE_0;
        sram_data_in <= 8'h00;
        sram_addr <= 8'h00;
        sram_we <= 1'b1;
        main_state <= READ_0;
      end
      READ_0: begin
        sub_state <= READ_0;
        sram_we <= 1'b0;
        sram_addr <= sram_addr + 1'b1;
        if (sram_addr == 8'hFF) begin
          main_state <= IDLE;
          bist_done <= 1;
        end else begin
          main_state <= READ_0;
        end
      end
      default: main_state <= IDLE;
    endcase
  end
end

// 定义从状态机的操作
always @(posedge clk) begin
  case (sub_state)
    IDLE: begin
      sram_data_in <= 8'h00;
      sram_addr <= 8'h00;
      sram_we <= 1'b0;
    end
    WRITE_5: begin
      sram_we <= 1'b1;
      sram_addr <= sram_addr + 1'b1;
    end
    READ_5: begin
      sram_we <= 1'b0;
    end
    WRITE_A: begin
      sram_we <= 1'b1;
    end
    READ_A: begin
      sram_we <= 1'b0;
    end
    SUCCESS: begin
      sram_we <= 1'b0;
    end
    WRITE_0: begin
      sram_we <= 1'b1;
      sram_addr <= sram_addr + 1'b1;
    end
    READ_0: begin
      sram_we <= 1'b0;
    end
    default: sub_state <= IDLE;
  endcase
end

// 实例化 SRAM 模块
sram sram_inst (
  .clk(clk),
  .reset(reset),
  .data_in(sram_data_in),
  .data_out(sram_data_out),
  .addr(sram_addr),
  .we(sram_we)
);

endmodule

以上代码中，`sram` 是 SRAM 模块，`bist_done` 为 BIST 完成信号。主状态机控制整个 BIST 测试流程，从状态机控制 SRAM 模块的读写操作。在每个状态中，`sram_data_in` 为写入 SRAM 的数据，`sram_data_out` 为从 SRAM 读出的数据，`sram_addr` 为 SRAM 的地址，`sram_we` 为 SRAM 的写使能信号。

希望本代码对您有所帮助。