module key_scanf(clk,reset_n,k1,k2,k3,k4,width,prioed);
input clk;
input reset_n;
input k1,k2,k3,k4;
output[15:0] width,prioed;
reg[3:0] key_rst_n;
always @(posedge clk or negedge reset_n)
 if(!reset_n) key_rst_n<=4'b1111;  //an jianchushiquan1
 else key_rst_n<={k4,k3,k2,k1};
 reg[3:0] key_rst_n_r;
  always @(posedge clk or negedge reset_n)
if(!reset_n) key_rst_n_r<=4'b1111;
else key_rst_n_r<=key_rst_n;  //suo cun liang ji
//jianzhi
wire[3:0] key_an=(~key_rst_n_r)&key_rst_n;  //下降沿產生高電平
reg[19:0] cnt;  //20位計數寄存器
always @(posedge clk or negedge reset_n)
  if(!reset_n) cnt<=20'd0;
  else if(key_an) cnt<=20'd0;  //按鍵按下計數器清零
  else cnt<=cnt+1'b1;
  //*******第一次檢測到的按鍵觸發用於清零計數器，以此用來達到當剛按下20ms后按鍵消抖的目的
  reg[3:0] low_sw;
always @(posedge clk or negedge reset_n)
if(!reset_n) low_sw<=4'b1111;
else if(cnt==20'hfffff)
low_sw<={k1,k2,k3,k4};  //每20ms鎖存當前按鍵值
reg[3:0]low_sw_r;
always @(posedge clk or negedge reset_n)
  if(!reset_n) low_sw_r<=4'b1111;
  else low_sw_r<=low_sw;   //鎖存上個週期按鍵值
   wire[3:0] led_ctrl=(~low_sw_r[3:0])&low_sw[3:0];
 //****第二次檢測按鍵按下用於確認按鍵按下
  reg[15:0] width_r;
 reg[15:0] prioed_r;
always @(posedge clk or negedge reset_n)
 if(!reset_n) begin 
   width_r<=16'b0100000000000000;
  prioed_r<=16'b1000000000100000;
 end
else  begin
  if(led_ctrl[0]) width_r<=width_r+16'b0000100000000000;
  if(led_ctrl[1]) width_r<=width_r-16'b0000100000000000;
  if(led_ctrl[2]) prioed_r<=prioed_r+16'b0000100000000000;
  if(led_ctrl[3]) prioed_r<=prioed_r-16'b0000100000000000;
  end
assign width=width_r;
assign prioed=prioed_r;
endmodule