按键消抖-----verilog

/********************************Copyright**************************************                           
**----------------------------File information--------------------------
** File name  :key_shake.v  
** CreateDate :2015.03
** Funtions   : 按键的消抖操作：在复位之后的100us内，不响应按键的操作，在之后有按键按下后，有20ms的延迟，之后输出按键输出.
** Operate on :M5C06N3L114C7
** Copyright  :All rights reserved[F]. 
** Version    :V1.0
**---------------------------Modify the file information----------------
** Modified by   :
** Modified data :        
** Modify Content:
*******************************************************************************/
 
 module  key_shake (
           clk,
           rst_n,
           
                     key_in,
                     key_out
             );
 input          clk;            //24Mhz
 input          rst_n;
 
 input          key_in;
 output         key_out;
 
 //--------------------------------------
 //在复位之后的100us内，不响应按键的操作
 localparam    t_100us  = 12‘d2399;
  reg    [11:0]   cnt;
    reg             key_en;         //复位之后允许按键输入标志
 always @(posedge clk or negedge rst_n)
 begin
  if(!rst_n)
   begin
      cnt <= 0;
            key_en <=0;
    end
  else 
    begin
      if(cnt == t_100us)
              begin
                   key_en <= 1;
                 end
             else
                 begin
                        key_en <= 0; 
                        cnt <= cnt + 1;
                 end
    end
  end
 
 //--------------------------------------------------
 wire         HtoL_flag;         //下降沿标志
 wire         LtoH_flag;         //上升沿标志
 reg   [2:0]   key_reg;
 always @(posedge clk or negedge rst_n)
 begin
  if(!rst_n)
   begin
      key_reg <= 3‘b111;            //默认没按下状态为高，按下之后为低.反之则为3‘b000;
    end
  else 
    begin
      key_reg <= {key_reg[1:0],key_in};  
    end
  end
    
 assign HtoL_flag = key_en?(key_reg[2:1] == 2‘b10):0;            //下降沿检测，一个时钟的高电平
 assign LtoH_flag = key_en?(key_reg[2:1] == 2‘b01):0;               //上升沿检测，一个时钟的高电平  
//---------------------------------------------
 reg          cnt_en;                 //计数使能标志
 localparam   t1ms = 16‘d23999;       //定时1ms 
 reg   [15:0]  cnt2; 
 always @(posedge clk or negedge rst_n)
 begin
  if(!rst_n)
   begin
      cnt2 <= 16‘d0;
    end
  else if((cnt_en)&&(cnt2 == t1ms))
    begin
      cnt2 <= 16‘d0;
    end
    else if(cnt_en)
    begin
      cnt2 <= cnt2 + 16‘d1;
    end    
    else 
          cnt2 <= 16‘d0;    
  end
    
 localparam  t_20ms = 5‘d20;
 reg   [4:0]   cnt3; 
 always @(posedge clk or negedge rst_n)
 begin
  if(!rst_n)
   begin
       cnt3 <= 5‘d0;
    end
  else if((cnt_en)&&(cnt2 == t1ms))
    begin
            if(cnt3 == t_20ms )
               cnt3 <= t_20ms;
            else
         cnt3 <= cnt3 + 1;                              
    end
    else if(!cnt_en)
       cnt3 <= 5‘d0;        
  end
    
//----------------------------------
//按键状态机
    reg  [2:0]  i;
    reg      key_down;        //按键按下标志
    reg      key_up;          //按键释放标志  
    always @(posedge clk or negedge rst_n)
     begin
      if(!rst_n)
       begin
                key_down <= 0;
                key_up <= 0;
                i <= 0;
                cnt_en <= 0;
        end
      else 
        begin
          case(i)
                 ‘d0:
                    begin
                             key_down <= 0;
                       key_up <= 0;    
                      if(HtoL_flag) i <= ‘d1;         //检测到按下
                            else if(LtoH_flag) i <= ‘d2;    //检测到释放按键
                            else  i  <= ‘d0;
                     end
                    ‘d1:
                      begin
                            if(cnt3 == t_20ms )
                              begin
                                    if(!key_in)                  //检测到按键依然被按下
                                   begin
                                       key_down <= 1;            //按键按下成功
                                       i <= ‘d3;
                                       cnt_en <= 0;
                                      end
                                    else
                                        begin
                                           key_down <= 0; 
                                         i <= ‘d0;
                                         cnt_en <= 0;        
                                         end
                                 end
                             else
                               cnt_en <= 1;
                            end
                    ‘d2:
                      begin
                            if(cnt3 == t_20ms )
                              begin
                                    if(key_in)                  //检测到按键被释放
                                   begin
                                       key_up <= 1;             //按键释放成功
                                       i <= ‘d3;
                                       cnt_en <= 0;
                                      end
                                    else
                                        begin
                                           key_up <= 0;  
                                         i <= ‘d0;
                                         cnt_en <= 0;        
                                         end
                                 end
                             else
                               cnt_en <= 1;
                            end
                    ‘d3:
                      begin
                             key_up <= 0;  
                             key_down <= 0;            
                             i <= ‘d0;                             
                         end                    
                  default:i <= ‘d0;    
                endcase            
        end
      end
        
 assign      key_out = key_down;         //当按键被按下有效时
// assign   key_out = key_up;         //当按键被释放后才有效时
endmodule

/********************************Copyright**************************************                           
**----------------------------File information--------------------------
** File name  :key_testbench.v  
** CreateDate :2015.03
** Funtions   :按键消抖的测试文件
** Operate on :M5C06N3L114C7
** Copyright  :All rights reserved. 
** Version    :V1.0
**---------------------------Modify the file information----------------
** Modified by   :
** Modified data :        
** Modify Content:
*******************************************************************************/
 
 module  key_testbench;
  
    reg          clk;
    reg          rst_n;
    reg          key_in;
    wire         key_out;
    
 
 key_shake  key_shake_1(
                                     .clk,
                                     .rst_n,
                                     
                                     .key_in,
                                     .key_out
                                         );
                                         

localparam  tck = 24;
localparam  t = 1000/tck;

always  #(t/2)  clk = ~clk;

task key_in_down;
 begin
     #(3*t)       key_in = 1;
     #(3*t)       key_in = 0;     
     #(8*t)       key_in = 1;
     #(8*t)    key_in = 0;
     #(13*t)   key_in = 1;
     #(13*t)     key_in = 0;
  end
 endtask
 
task key_in_up;
 begin
     #(3*t)        key_in = 0;     
     #(3*t)        key_in = 1;     
   #(8*t)        key_in = 0;     
     #(8*t)        key_in = 1;         
     #(13*t)      key_in = 0;     
     #(13*t)      key_in = 1;                   
  end
endtask
    
initial 
  begin
    clk = 0;
        rst_n = 0;
        key_in = 1;
        
        #(100*t)  rst_n = 1;
        
        #(100*t);
      #(10*t)    key_in_down;
      #(100*t);
      #(10*t)    key_in_up;
        
      #(8000*t);         
    #(10*t) repeat(2)     key_in_down;          //按下时抖动
     
      #(640000*t);                             //按下时间
     
      #(10*t) repeat(2)  key_in_up;            //释放时抖动
        
  end
    
endmodule