写一verilog代码完成交通灯智能控制电路的设计 设计说明：某十字路口带数字显示的智能交通灯控制。能完成定时、倒计时、数字显示及控制红、黄、绿灯亮灭转换等功能。 数码管显示红、黄、绿灯亮的时间倒计时，红灯、黄灯、绿灯顺序点亮，点亮时长：红灯—30s；黄灯—5s；绿灯—30s；

下面是一个简单的Verilog代码，实现交通灯智能控制电路的设计：

module traffic_light(
    input clk,
    output reg red_led,
    output reg yellow_led,
    output reg green_led,
    output reg [3:0] digit1,
    output reg [3:0] digit2,
    output reg [3:0] digit3
);

reg [23:0] tick;
reg [3:0] count;
reg [1:0] state;

always @(posedge clk) begin
    tick <= tick + 1;
    if (tick == 24000000) begin // 1s
        tick <= 0;
        case (state)
            2'b00: begin // Red light
                red_led <= 1;
                yellow_led <= 0;
                green_led <= 0;
                digit1 <= 3'b100; // "3"
                digit2 <= 4'b1111; // "-"
                digit3 <= count;
                count <= count - 1;
                if (count == 0) begin
                    count <= 30;
                    state <= 2'b01;
                end
            end
            2'b01: begin // Yellow light
                red_led <= 0;
                yellow_led <= 1;
                green_led <= 0;
                digit1 <= 3'b011; // "1"
                digit2 <= 4'b1110; // "E"
                digit3 <= count;
                count <= count - 1;
                if (count == 0) begin
                    count <= 5;
                    state <= 2'b10;
                end
            end
            2'b10: begin // Green light
                red_led <= 0;
                yellow_led <= 0;
                green_led <= 1;
                digit1 <= 3'b001; // "0"
                digit2 <= 4'b1100; // "C"
                digit3 <= count;
                count <= count - 1;
                if (count == 0) begin
                    count <= 30;
                    state <= 2'b00;
                end
            end
        endcase
    end
end

initial begin
    tick <= 0;
    count <= 30;
    state <= 2'b00;
end

endmodule

该设计中包含了时钟模块，交通灯控制模块和数码管显示模块。其中，时钟模块通过 `tick` 计数器实现定时功能，交通灯控制模块通过 `state` 状态机控制红、黄、绿灯的转换，数码管显示模块通过 `count` 倒计时计数器实现数字显示功能。最后，每个 `case` 分支中分别控制交通灯和数码管的状态更新。