debouncer.vhd

   1 library ieee;
   2         use ieee.std_logic_1164.all;
   3         use ieee.numeric_std.ALL;
   4         use work.debounce_pkg.ALL;
   5
   6 entity debouncer is
   7
   8         port
   9         (
  10                 clk             : in std_logic;
  11                 rst             : in std_logic;
  12
  13                 pbutton : in std_logic;
  14                 pb_deb  : out std_logic
  15         );
  16
  17 end entity;
  18
  19 architecture rtl of debouncer is
  20
  21         signal cnt_deb           : unsigned(DIV_DEB_W-1 downto 0);
  22         signal clk_en            : std_logic;
  23         signal cnt_threshold : unsigned(DEB_LEN_W-1 downto 0);
  24         signal pb_deb_i          : std_logic;
  25         signal pbutton_s         : std_logic;
  26
  27 begin
  28
  29         -- downcounter for input clock freq. division
  30         process (rst, clk)
  31         begin
  32                 if (rst = '1') then
  33                         cnt_deb <= (others => '0');
  34                         clk_en  <= '0';
  35                 elsif (rising_edge(clk)) then
  36                         if (cnt_deb = 0) then
  37                                 cnt_deb <= to_unsigned(DIV_DEB, cnt_deb'length);
  38                                 clk_en  <= '1';
  39                         else
  40                                 cnt_deb <= cnt_deb-1;
  41                                 clk_en  <= '0';
  42                         end if;
  43                 end if;
  44         end process;
  45
  46         -- sample pushbutton and debounce
  47         process (rst, clk)
  48         begin
  49                 if (rst = '1') then
  50                         cnt_threshold <= (others => '0');
  51                         pbutton_s         <= '0';
  52                         pb_deb_i          <= '0';
  53                 elsif (rising_edge(clk)) then
  54                         pbutton_s         <= pbutton;
  55                         if (pbutton_s = '1' and clk_en = '1') then
  56                                 if (cnt_threshold < (DEB_LEN-1) ) then
  57                                         cnt_threshold <= cnt_threshold + 1;
  58                                 end if;
  59                         end if;
  60                         if (pbutton_s = '0' and clk_en = '1') then
  61                                 if (cnt_threshold > 0 ) then
  62                                         cnt_threshold <= cnt_threshold - 1;
  63                                 end if;
  64                         end if;
  65
  66                         -- Activate output with hysteresis
  67                         if (pb_deb_i = '0' and (cnt_threshold > DEB_THRES_HI)) then
  68                                 pb_deb_i <= '1';
  69                         end if;
  70                         if (pb_deb_i = '1' and (cnt_threshold < DEB_THRES_LO)) then
  71                                 pb_deb_i <= '0';
  72                         end if;
  73
  74                 end if;
  75         end process;
  76
  77         pb_deb <= pb_deb_i;
  78 end rtl;