verilog,用数码管实现流水灯

以下是Verilog代码实现数码管流水灯：

module digit_led(
  input clk,
  output reg [6:0] digit,
  output reg [3:0] seg
  );
  
  reg [25:0] counter;
  reg [2:0] led;
  
  always @ (posedge clk) begin
    counter <= counter + 1;
    if (counter == 500000) begin
      counter <= 0;
      led <= led + 1;
      if (led == 8) begin
        led <= 0;
      end
    end
  end
  
  always @ (led) begin
    case (led)
      0: begin
        digit <= 7'b100_0000;
      end
      1: begin
        digit <= 7'b010_0000;
      end
      2: begin
        digit <= 7'b001_0000;
      end
      3: begin
        digit <= 7'b000_1000;
      end
      4: begin
        digit <= 7'b000_0100;
      end
      5: begin
        digit <= 7'b000_0010;
      end
      6: begin
        digit <= 7'b000_0001;
      end
      7: begin
        digit <= 7'b000_0000;
      end
    endcase
  end
  
  always @ (digit) begin
    case (digit)
      7'b100_0000: begin
        seg <= 4'b0111;
      end
      7'b010_0000: begin
        seg <= 4'b0001;
      end
      7'b001_0000: begin
        seg <= 4'b1011;
      end
      7'b000_1000: begin
        seg <= 4'b0011;
      end
      7'b000_0100: begin
        seg <= 4'b0101;
      end
      7'b000_0010: begin
        seg <= 4'b1100;
      end
      7'b000_0001: begin
        seg <= 4'b1101;
      end
      7'b000_0000: begin
        seg <= 4'b1111;
      end
    endcase
  end
  
endmodule

这里使用了一个计数器 `counter` 和一个变量 `led` 来控制数码管的显示，每当计数器达到一定值时，`led` 加 1，然后根据 `led` 的值来显示相应的数码管和数码的段码。在这个例子中，每个数码管都是由 7 个 LED 组成，因此 `digit` 变量使用了 7 位二进制来控制数码管的 LED 状态，而 `seg` 变量则使用了 4 位二进制来控制数码管的段码。