【FPGA/verilog -入门学习13】verilog 1s流水灯实验

//led 1S实验
//使用分屏实验1s计数

`timescale 1ns/1ps

module vlg_design(
    input i_clk,
    input i_rest_n,
    input[7:0] key,
    output reg[7:0] led
    );


`define CNT_1S_DEBUG
`ifndef CNT_1S_DEBUG
parameter CNT_1S_MAX = 1_000_000_000/20 - 1;
`else /*CNT_1S_DEBUG*/
parameter CNT_1S_MAX = 1_000/20 - 1;

`endif


reg [27:0] r_cnt_1s;
reg [3:0] r_i_para;
reg r_cnt1s_flag;
wire [3:0] w_i_para;
always @(posedge i_clk) begin
    if(!i_rest_n) r_cnt_1s <= 'd0;
    else if(r_cnt_1s < CNT_1S_MAX) r_cnt_1s <= r_cnt_1s+1;
    else r_cnt_1s <= 'd0;
end
    
always @(posedge i_clk) begin
    if(!i_rest_n) r_i_para <= 'b0;
    else if(r_i_para == 8) r_i_para <= 'b0;
    else if (r_cnt_1s == CNT_1S_MAX) r_i_para <= r_i_para+1;
    else ;     
end

always @(posedge i_clk) begin
    if(!i_rest_n) r_cnt1s_flag <= 'b0;
    else if (r_cnt_1s == CNT_1S_MAX) r_cnt1s_flag <= 1;
    else r_cnt1s_flag <= 'b0;
end

always @(posedge i_clk) begin
    if(!i_rest_n) led <= 'b0;
    else if (r_cnt1s_flag) led <= (1 << w_i_para-1);
    else ;
end

assign w_i_para = r_cnt1s_flag?r_i_para:w_i_para;

endmodule

另外移位还可以通过以下方式实现if(cnt == MAX_CNT) led <= {led[6:0],led[7]};

    //计数器cnt计数到最大值时，切换点亮的指示灯
always @ (posedge sys_clk_i or negedge ext_rst_n) 
    if(!ext_rst_n) led <= 8'b1111_1110;    //默认只点亮一个指示灯D2
    else if(cnt == MAX_CNT) led <= {led[6:0],led[7]};    //200ms为一个计数周期，执行一次循环移位操作
    else ;                    

`timescale 1ns/1ps

module testbench_top();
    

//参数定义

`define CLK_PERIORD        20        //时钟周期设置为20ns（50MHz）    


//接口申明
reg i_clk;
reg i_rest_n;
reg [7:0]  key;
wire [7:0] led;
    

    
//对被测试的设计进行例化
    
vlg_design        uut_vlg_design(
    .i_clk(i_clk),
    .i_rest_n(i_rest_n),
    .key(key),
    .led(led)
    );    

///

integer i;

initial begin
key <= 8'b11111111;
i_clk <= 0;
i_rest_n <= 0;
#20;
i_rest_n <= 1;

end


always #(`CLK_PERIORD/2) i_clk = ~i_clk;

initial begin

@(posedge i_clk);
@(posedge i_rest_n);




for(i = 0;i < 8;i = i+1) begin
    key <= ~(1<