实验现象：
按键每按下一次，三色LED切换一次状态。
核心源代码：
module key_ctrl( input clk_25m, input rst_n, input key, output fpga_ledr, output fpga_ledg, output fpga_ledb);//--------------------key_in--------------------------------//parameter ms_10 = 250000;reg key_r;reg [17:0]low_cnt;reg [17:0]hig_cnt;always @(posedge clk_25m or negedge rst_n) //按键消抖动，提取按键状态 if (!rst_n) begin key_r <= 1'd0; low_cnt <= 18'd0; hig_cnt <= 18'd0; end else if(key) //检测按键状态为高时，延时10ms，把按键状态提取出来。 begin low_cnt <= 18'd0; if (hig_cnt == ms_10) begin key_r <= key; hig_cnt <= hig_cnt; end else hig_cnt <= hig_cnt + 1'd1; end else //按键状态为低时，延时10ms，把按键状态提取出来。 begin hig_cnt <= 18'd0; if (low_cnt == ms_10) begin key_r <= key; low_cnt <= low_cnt; end else low_cnt <= low_cnt + 1'd1; end wire key_state = key_r;//--------------------led_ctrl-----------------------------//reg [1:0]led_cnt;reg ledr,ledg,ledb;always@(negedge key_state or negedge rst_n) //按键下降沿控制led状态切换 if (!rst_n) begin led_cnt <= 2'd0; end else if (led_cnt == 2'd2) begin led_cnt <= 2'd0; end else led_cnt <= led_cnt + 1'd1;always@(posedge clk_25m or negedge rst_n) //led状态切换的状态机 if (!rst_n) begin ledr <= 1'd1; ledg <= 1'd1; ledb <= 1'd1; end else case(led_cnt) 2'd0: //红灯亮 begin ledr <= 1'd0; ledg <= 1'd1; ledb <= 1'd1; end 2'd1: //绿灯亮 begin ledr <= 1'd1; ledg <= 1'd0; ledb <= 1'd1; end 2'd2: //蓝灯亮 begin ledr <= 1'd1; ledg <= 1'd1; ledb <= 1'd0; end default: //都不亮 begin ledr <= 1'd1; ledg <= 1'd1; ledb <= 1'd1; end endcase assign {fpga_ledr,fpga_ledg,fpga_ledb} = {ledr,ledg,ledb};//--------------------endmodule-----------------------------//endmodule 源代码下载链接：
链接： 密码：u1gd
iCore4链接：