key.v

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//按键去抖模块：key.v 
 module key(clk,keyin,keyout,keyoutdir,en);
   input clk;
   input [3:0]keyin;
   output [3:0]keyout;
   output keyoutdir,en;
   reg  en;
   reg [3:0]keyout;
   reg [16:0]scan;
   reg [3:0]key;
   reg keyen;
   integer  i=0;
   parameter   FLKxM=10;  //时钟频率MHz
   parameter   LEN=10;    //去抖时间10ms
     assign  keyoutdir=1'b0;
       always@(posedge clk)
         if(keyin!=4'hf)
            if(scan==FLKxM*LEN)//在有键按下10ms以后准备读取键值
                 begin keyen<=1'b0;
                       scan<=scan+1'b0;end 
             else begin keyen<=1'b0;
                       scan<=scan+1'b1;end 
          else  begin
               if(scan!=0) scan<=scan-1'b1;  
                else scan<=scan;
                     keyen<=1'b0;
                end
        always@(posedge clk)
          if(keyen)    //去除抖动后开始读数
                keyout<=~keyin;   
           else     keyout<=4'b0;   
        always@(posedge clk)
          if(keyin!=4'hf)    en=1'b0;
           else    en=1'b1;
  endmodule