用状态机实现循环彩灯控制器(含清零功能)000→001→010→100→010→001→000→111→000→111→（循环）
module led
(
input clk,
input rst_n,
output led_000,
output led_001,
output led_010,
output led_100,
output led_111
);
parameter LED_000 = 5'b00001,
LED_001 = 5'b00010,
LED_010 = 5'b00100,
LED_100 = 5'b01000,
LED_111 = 5'b00010;
reg [4:0] cnt;
reg [4:0] cur_state;
reg [4:0] nxt_state;
always @(posedge clk or negedge rst_n)
begin
if(~rst_n)
cur_state <= LED_000;
else
cur_state <= nxt_state;
end
always @(*)
begin
nxt_state = cur_state;
case(cur_state)
LED_000 : if(cnt==5'h1f)
nxt_state = LED_001;
LED_001 : if(cnt==5'h1f)
nxt_state = LED_010;
LED_010 : if(cnt==5'h1f)
nxt_state = LED_100;
LED_100 : if(cnt==5'h1f)
nxt_state = LED_111;
LED_111 : if(cnt==5'h1f)
nxt_state = LED_000;
endcase
end
always @(posedge clk or negedge rst_n)
begin
if(~rst_n)
cnt <= 5'd0;
else
cnt <= cnt + 1'd1;
end
assign led_000=cur_state[0];
assign led_001=cur_state[1];
assign led_010=cur_state[2];
assign led_100=cur_state[3];
assign led_111=cur_state[4];
endmodule