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一、实验任务

使用开发板上的四个按键控制四个LED灯。按下不同的按键时，四个LED灯显示不同效果。本实验是在EP4CE6F17C8开发板上实现，仿真请用modelsim Altera

二、系统框图

三、代码实现

module key_led (input clk,                      //时钟周期input rst_n,                    //复位信号input [3:0] key ,               //4个按键，提供4个位宽output reg [3:0] key_led        //4个led灯，提供4个位宽
);
reg [1:0] state;                    //两位宽的状态寄存器，存储4个状态
reg [25:0] cnt_1s;                  //存储1s的寄存器parameter MAX_1s = 26'd49_999_999;//1s的时钟周期//1s计数器
always @(negedge rst_n or posedge clk) beginif (!rst_n) begincnt_1s <= 26'd0;endelse if (cnt_1s == MAX_1s) begincnt_1s <= 26'd0;endelse begincnt_1s <= cnt_1s + 26'd1;end
end//状态每隔1s进行跳转
always @(negedge rst_n or posedge clk) beginif (!rst_n) beginstate <= 2'd0;endelse if (cnt_1s == MAX_1s) begin            //每隔1s进入下一个状态state <= state + 2'd1;endelse beginstate <= state;end
end//不同按键不同led灯闪烁方式
always @(negedge rst_n or posedge clk) beginif (!rst_n) beginkey_led <= 4'b0000;endelse if (key[0] == 0) begin            //key0键按下,从右往左流水灯case (state)2'd0: key_led <= 4'b0001;2'd1: key_led <= 4'b0010;2'd2: key_led <= 4'b0100;2'd3: key_led <= 4'b1000;default: key_led <= key_led ;endcaseendelse if (key[1] == 0) begin            //key1键按下，从左往右流水灯case (state)2'd0: key_led <= 4'b1000;2'd1: key_led <= 4'b0100;2'd2: key_led <= 4'b0010;2'd3: key_led <= 4'b0001;default: key_led <= key_led ;endcaseendelse if (key[2] == 0) begin            //key2键按下，led灯闪烁case (state)2'd0: key_led <= 4'b1111;2'd1: key_led <= 4'b0000;2'd2: key_led <= 4'b1111;2'd3: key_led <= 4'b0000;default: key_led <= key_led ;endcaseendelse if (key[3] == 0) begin            //key3键按下，灯常亮case (state)2'd0: key_led <= 4'b1111;2'd1: key_led <= 4'b1111;2'd2: key_led <= 4'b1111;2'd3: key_led <= 4'b1111;default: key_led <= key_led ;endcaseendelse beginstate <= state;end
endendmodule

仿真代码：

`timescale 1ns/1ns
module key_led_tb (
);reg clk;reg rst_n;reg [3:0] key;wire [3:0] key_led;parameter MAX_1s = 9;parameter CYCLE = 20;always #(CYCLE/2) clk <= ~clk;initial beginclk = 1'b0;rst_n = 1'b0;#(CYCLE);rst_n = 1'b1;key = 4'b1111;#(4*(MAX_1s + 1)*CYCLE);  //4个state的时间key = 4'b1110;#(4*(MAX_1s + 1)*CYCLE);  key = 4'b1101;#(4*(MAX_1s + 1)*CYCLE);  key = 4'b1011;#(4*(MAX_1s + 1)*CYCLE);  key = 4'b0111;$stop;endkey_led  #(.MAX_1s(MAX_1s))u_key_led(.clk(clk),.rst_n(rst_n),.key(key),.key_led(key_led));endmodule

四、引脚分配

五、总结

注意：该实验并未进行按键消抖，需一直按着按键才能让该按键所操控的led变化功能实现。