03_led_horse_run_v1 跑马灯

03_led_horse_run_v1

在Verilog中实现跑马灯通常涉及到使用一个计数器来控制LED灯的亮灭顺序。
跑马灯是一种常见的电子显示方式，它通过控制多个LED灯的顺序点亮，形成一种动态的视觉效果，看起来就像灯在“跑”一样。

更新

使用dip开关控制跑马灯的速度和方向

知识点：

• 循环移位寄存器的使用
• 两种不同的组合逻辑赋值风格(assign, always(*))
• 灵活利用参数设计可复用模块(模块级参数，局部参数)

module led_horse_run #(
    parameter LED_ON  = 1'b0,  //led active low
    parameter CLK_FREQ  = 50*1000*1000 //frequency of input clock
)(
    input  clk,
    input  rst_n,

    input wire [5:0] dip_u6,
   output reg [5:0] led
);

//
//Local parameter, same as const in c/c++
//For 50Mhz clock, 
//one second count to 50*1000*1000 
//one millisecond count to 50*1000 
//

localparam ONE_SECOND = CLK_FREQ;
localparam HALF_SECOND = ONE_SECOND / 2;
localparam ONE_MSECOND = ONE_SECOND / 1000;

//-------------------------------------------
//control the running speed and direction 
//according to the status of dip keys
wire [1:0] speed = dip_u6[1:0];
wire direct = dip_u6[5];

//First style of assignment for combinational logic, (not for sequential logic)
//Note: left value must be wire type, here 'wire [31:0] count_max;'
wire [31:0] count_max;  
assign count_max =  (speed == 0) ? ONE_MSECOND * 2000 :
                    (speed == 1) ? ONE_MSECOND * 1000 :
                    (speed == 2) ? ONE_MSECOND * 500 : ONE_MSECOND * 200;
/*
//another style of assignment of combinational logic
//Note: left value must be reg type, here 'reg [31:0] count_max;'
reg [31:0] count_max;  
always @(*) begin
    count_max =     (speed == 0) ? ONE_MSECOND * 2000 :
                    (speed == 1) ? ONE_MSECOND * 1000 :
                    (speed == 2) ? ONE_MSECOND * 500  : ONE_MSECOND * 200;
end
*/

//---------------------------------------------------------
reg [31:0] count; 
wire time_on = (count == count_max-1);

always @(posedge clk) begin
    if(~rst_n) count <= 0;
    else if(time_on) count <= 0;
    else count <= count + 1;
end

wire [5:0] init_led_status = (LED_ON == 1'b1) ? 6'b000001 : 6'b111110;

always @(posedge clk) begin
    if(~rst_n) led <= init_led_status;
    else if(time_on) begin
        if(direct == 1'b1) led <= {led[4:0], led[5]} ;  //shift left
        else led <= {led[0],led[5:1]} ;                 //shift right
    end
    //else led <= led;
end

endmodule

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扩展思维

适了解流水灯和跑马灯的区别，适当修改上面的跑马灯代码实现流水灯的效果。