module liushui(clk, rst, led); input clk; input rst; output [7 : 0] led; parameter WIDTH =27; parameter COUNT = 99_999_999; reg [WIDTH - 1 : 0] cnt; reg [7 : 0] light; reg flag; always @(posedge clk) begin if (!rst) cnt <= 0; else if (cnt == COUNT) cnt <= 0; else cnt <= cnt + 1; end always @(posedge clk) begin if (light == 8'h01) flag <= 1; //left move else if (light == 8'h80) flag <= 0; //rihgt move else ; end always @(posedge clk) begin if (!rst) light <= 8'h01; else if (cnt == COUNT) begin if (flag) light <= light << 1; else light <= light >> 1; end else ; end assign led = light; endmodule修改代码，使流水灯能够暂停和继续

可以在代码中添加一个控制信号，控制流水灯的暂停和继续。修改后的代码如下：

module liushui(clk, rst, ctrl, led);
    input clk;
    input rst;
    input ctrl;   // 控制信号，为 1 时暂停，为 0 时继续
    output [7 : 0] led;
    parameter WIDTH =27;
    parameter COUNT = 99_999_999;
    reg [WIDTH - 1 : 0] cnt;
    reg [7 : 0] light;
    reg flag;
    
    always @(posedge clk)
    begin
        if (!rst)
            cnt <= 0;
        else if (cnt == COUNT)
            cnt <= 0;
        else if (ctrl)  // 如果控制信号为 1，计数器不增加，实现暂停
            cnt <= cnt;
        else
            cnt <= cnt + 1;
    end
    
    always @(posedge clk)
    begin
        if (light == 8'h01)
            flag <= 1;   //left move
        else if (light == 8'h80)
            flag <= 0;   //right move
        else ;
    end
    
    always @(posedge clk)
    begin
        if (!rst)
            light <= 8'h01;
        else if (cnt == COUNT)
        begin
            if (ctrl)   // 如果控制信号为 1，流水灯不变化
                light <= light;
            else if (flag)
                light <= light << 1;
            else
                light <= light >> 1;
        end
        else ;
    end
    
    assign led = light;
endmodule

修改后的代码中添加了一个名为 `ctrl` 的控制信号，当 `ctrl` 为 1 时，计数器暂停计数，流水灯也不变化；当 `ctrl` 为 0 时，计数器和流水灯继续变化。