FPGA_最基本小实验操作——流水灯

一，概念

        这个很简单，就是移位，数字电路里面要熟悉移位这个操作，就像51单片机一样哈。

二，代码基于verlog

//流水灯操作

module flow_led(

	input            sys_clock,
	input            sys_rst_n,
	output reg [3:0] led

);
//计数0.2S = 1000W-1 =1000_0000-1
reg [23:0]  counter;
always@(posedge sys_clock or negedge sys_rst_n)begin
	if(!sys_rst_n)
		counter <= 24'd0;
	else if(counter < 24'd1000_0000 - 1'b1)//当等于0.2S的时候
		counter <= counter +1'b1;
	else
		counter <= 24'd0;
end

//移位对给LED供电
always@(posedge sys_clock or negedge sys_rst_n)begin
	if(!sys_rst_n)
		led <= 4'b0001;
	else if(counter == 24'd1000_0000 - 1'b1)
		led <= {led[2:0],led[3]};   //位拼接，将最高位换到最低为去，依次
	else
		led <= led;
end 

endmodule