verilog呼吸灯

上代码：

module led(
	input clk,	// 50MHz 输入时钟
	output reg led // led 输出(低电平有效)
);

//--------------------------------------------------------
// 生成一个延迟，在一段时间内维持led输出一个不变的占空比
`define MAX_DELAY_CNT 500000
reg myclk;
reg [23:0] delay_cnt;
always@(posedge clk)
begin
	if(delay_cnt < `MAX_DELAY_CNT)
		delay_cnt <= delay_cnt + 1'b1;
	else
		begin
			delay_cnt <= 24'd1;
			myclk <= ~myclk;
		end
end
//--------------------------------------------------------
// 占空比分为0~100个级别
// 0的时候，占空比最小，这个时候直接完全输出低电平，led灯最亮
// 100的时候，占空比最大，这个时候直接完全输出高电平，led等熄灭
`define CYCLE_NUMBER 100
reg [7:0] current_cycle;
reg flag;
always@(posedge myclk)
begin
	if(flag == 0)
		begin // 占空比递增
			if(current_cycle < `CYCLE_NUMBER)
				current_cycle <= current_cycle + 1'b1;
			else
				//current_cycle <= 1'b0;
				flag <= ~flag;
		end
	else
		begin // 占空比递减
			if(current_cycle > 0)
				current_cycle <= current_cycle - 1'b1;
			else
				flag <= ~flag;
		end
end
//--------------------------------------------------------
// 轮询 0~100个级别的占空比
reg [7:0] cycle;
always@(posedge clk)
begin
	if(cycle < `CYCLE_NUMBER)
		cycle <= cycle + 1'b1;
	else
		cycle <= 1'b1;
end
//--------------------------------------------------------
// cycle小于current_cycle的时候是高电平
// cycle大于current_cycle并且小于CYCLE_NUMBER的时候是低电平
always@(posedge clk)
begin
	if((cycle == `CYCLE_NUMBER) && (current_cycle != 0))
		led <= 1'b1;
	else if(cycle < current_cycle)
		led <= 1'b1;
	else
		led <= 1'b0;
end
endmodule

仿真时序 效果视频 www.bilibili.com/video/av719…