//控制led亮灭的状态机
//状态机流程,上电复位后进入空闲状态,并点亮红色led,然后等待按键按下
//当检测到按键的下降沿时,led_cnt加1,加至2时,清零,并依此循环
//依此来实现按键控制三色led状态切换的功能
reg [1:0]led_cnt;//led_cnt三个状态,0、1、2,代表三色led的红、绿、蓝
reg ledr,ledg,ledb;
//状态跳转逻辑设计always块,检测到按键下降沿,切换led_cnt值
always@(negedge key_state or negedge rst_n)
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;
//逻辑输出,根据led_cnt来切换led状态
always@(posedge clk_25m or negedge rst_n)
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