module LED3(clk,rst_n,LED);
//programmed by haohaolinux
 input clk,rst_n;
 output [7:0] LED;
 
 reg [7:0] LED;
 reg [23:0] cnt;
 
 //24 bit counter
 always@(posedge clk or negedge rst_n)
  if(!rst_n)
   cnt <= 24'h0;
  else if(cnt == 24'hffffff)
   cnt <= 24'h0;
  else
   cnt <= cnt+1;
   
 always@(posedge clk or negedge rst_n)
  if(!rst_n)
   LED <= 8'hff;
  else if(cnt == 24'hffffff)
   begin
    LED <= {LED[6:0],~LED[7]};
    if(LED == 8'h00)
     LED <= 8'hff;
   end
  else
   LED <= LED;
   
endmodule