按下列要求设计verilog HDL 代码：（1）电路仅需一个不带锁控制按键；使用三个 LED 作为定时提示灯，分别对应 15 分 钟，30 分钟，45 分钟；另用一个 LED 模拟紫外线消毒灯是否开启；一个蜂鸣器作为语音 提示。 （2）按键用作电源开关及定时时长切换。第一次按下按键时，即可打开电源，同时 15 分钟对应的指示灯亮，如果在 3 秒钟内没有再次按键，系统将进入 30 秒倒计时模式，同 时蜂鸣器发出有不同间隔的报警声，30 秒后，消毒系统开始工作，对应 LED 点亮。如果 在 3 秒内再次按键，将依次切换到 30 分钟定时，45 分钟定时，关闭三种状态，并以此循 环。每种状态需要有对应的 LED 点亮。关闭状态时，三个 LED 定时提示灯全灭。 （3）为了提醒使用者消毒灯即将工作前的倒计时状态，蜂鸣器的报警间隔需不同：倒 数 30-20 秒期间的时间间隔为 1 秒，倒数 20-10 秒期间的时间间隔为 0.5 秒；倒数 10-5 秒期间的时间间隔为 0.3 秒；倒数 5-0 秒期间的时间间隔为 0.1 秒。 （4）系统工作指示灯需要按照所设定的时长点亮，时间结束后自动熄灭。在消毒期间， 可通过设定的时间间隔 3 秒的报警提示用户，系统正处于消毒状态。

以下是一个可行的 Verilog HDL 代码实现，具体实现方式可能会因硬件环境的不同而有所差异，需要根据具体情况进行调整和优化。

module disinfection_system(input clk, input rst, input button, output reg led15, output reg led30, output reg led45, output reg uv_led, output reg buzzer);

    // 定义一些常量和变量，用于控制定时、报警等功能
    parameter COUNT_15_MIN = 90000;
    parameter COUNT_30_MIN = 180000;
    parameter COUNT_45_MIN = 270000;
    parameter COUNT_ALARM_1 = 30000;
    parameter COUNT_ALARM_2 = 20000;
    parameter COUNT_ALARM_3 = 10000;
    parameter COUNT_ALARM_4 = 5000;
    reg [19:0] count;
    reg [1:0] state;
    reg [1:0] alarm_state;
    reg [1:0] led_state;

    // 初始化一些变量
    initial begin
        count = 0;
        state = 0;
        alarm_state = 0;
        led_state = 0;
        led15 = 0;
        led30 = 0;
        led45 = 0;
        uv_led = 0;
        buzzer = 0;
    end

    // 按键检测和状态转换
    always @(posedge clk or posedge rst) begin
        if (rst) begin
            count <= 0;
            state <= 0;
            alarm_state <= 0;
            led_state <= 0;
            led15 <= 0;
            led30 <= 0;
            led45 <= 0;
            uv_led <= 0;
            buzzer <= 0;
        end else begin
            case (state)
                0: begin // 关闭状态
                    if (button == 1) begin
                        state <= 1;
                        led_state <= 1;
                        count <= COUNT_15_MIN;
                        led15 <= 1;
                    end
                end
                1: begin // 15 分钟定时状态
                    if (button == 1) begin
                        if (count <= COUNT_ALARM_1) begin
                            alarm_state <= 1;
                            buzzer <= 1;
                        end else if (count <= COUNT_ALARM_2) begin
                            alarm_state <= 2;
                            buzzer <= 1;
                        end else if (count <= COUNT_ALARM_3) begin
                            alarm_state <= 3;
                            buzzer <= 1;
                        end else if (count <= COUNT_ALARM_4) begin
                            alarm_state <= 4;
                            buzzer <= 1;
                        end else begin
                            uv_led <= 1;
                            led_state <= 2;
                            led30 <= 1;
                            count <= COUNT_30_MIN;
                            state <= 2;
                        end
                    end else if (count == 0) begin
                        uv_led <= 0;
                        led15 <= 0;
                        state <= 0;
                    end else begin
                        count <= count - 1;
                    end
                end
                2: begin // 30 分钟定时状态
                    if (button == 1) begin
                        if (count <= COUNT_ALARM_1) begin
                            alarm_state <= 1;
                            buzzer <= 1;
                        end else if (count <= COUNT_ALARM_2) begin
                            alarm_state <= 2;
                            buzzer <= 1;
                        end else if (count <= COUNT_ALARM_3) begin
                            alarm_state <= 3;
                            buzzer <= 1;
                        end else if (count <= COUNT_ALARM_4) begin
                            alarm_state <= 4;
                            buzzer <= 1;
                        end else begin
                            uv_led <= 1;
                            led_state <= 3;
                            led45 <= 1;
                            count <= COUNT_45_MIN;
                            state <= 3;
                        end
                    end else if (count == 0) begin
                        uv_led <= 0;
                        led30 <= 0;
                        state <= 0;
                    end else begin
                        count <= count - 1;
                    end
                end
                3: begin // 45 分钟定时状态
                    if (button == 1) begin
                        if (count <= COUNT_ALARM_1) begin
                            alarm_state <= 1;
                            buzzer <= 1;
                        end else if (count <= COUNT_ALARM_2) begin
                            alarm_state <= 2;
                            buzzer <= 1;
                        end else if (count <= COUNT_ALARM_3) begin
                            alarm_state <= 3;
                            buzzer <= 1;
                        end else if (count <= COUNT_ALARM_4) begin
                            alarm_state <= 4;
                            buzzer <= 1;
                        end else begin
                            uv_led <= 1;
                            led_state <= 1;
                            led15 <= 1;
                            count <= COUNT_15_MIN;
                            state <= 1;
                        end
                    end else if (count == 0) begin
                        uv_led <= 0;
                        led45 <= 0;
                        state <= 0;
                    end else begin
                        count <= count - 1;
                    end
                end
            endcase
        end
    end

    // 报警控制
    always @(posedge clk) begin
        case (alarm_state)
            0: buzzer <= 0;
            1: if (count % 100000 == 0) buzzer <= ~buzzer;
            2: if (count % 50000 == 0) buzzer <= ~buzzer;
            3: if (count % 30000 == 0) buzzer <= ~buzzer;
            4: if (count % 10000 == 0) buzzer <= ~buzzer;
        endcase
    end

    // LED 控制
    always @(posedge clk) begin
        case (led_state)
            0: begin
                led15 <= 0;
                led30 <= 0;
                led45 <= 0;
            end
            1: begin
                led15 <= 1;
                led30 <= 0;
                led45 <= 0;
            end
            2: begin
                led15 <= 0;
                led30 <= 1;
                led45 <= 0;
            end
            3: begin
                led15 <= 0;
                led30 <= 0;
                led45 <= 1;
            end
        endcase
    end

endmodule