clk_gen.vhd

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--library declaration
library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.std_logic_arith.all;
use IEEE.std_logic_unsigned.all;
--input and output pins declaraction
entity clk_gen is
    port(reset: in std_logic;
         clk:in std_logic;
         ena_scan:out std_logic;
         ena_1Hz:out std_logic;
         flash_1Hz: out std_logic);
end;   

architecture BEHAVIOR of clk_gen is   
CONSTANT scan_bit: positive := 2;
CONSTANT scan_val: positive := 4;
CONSTANT two_Hz_bit: positive := 7;
CONSTANT two_Hz_val: positive := 125;
signal clk_scan_ff:std_logic_vector(scan_bit-1 downto 0); 
signal clk_2Hz_ff:std_logic_vector(two_Hz_bit-1 downto 0); 
signal ena_s,ena_one,ena_two:std_logic;
begin
--to generate 250Hz ena_s via dividing 1KHz clock by 4
   scan:process(reset,clk)
   begin
       if reset='1' then
          clk_scan_ff<="00";
          ena_s<='0';
       elsif (clk'event and clk='1') then
          if clk_scan_ff>=scan_val-1 then
             clk_scan_ff<="00";
             ena_s <= '1';
          else
             clk_scan_ff<=clk_scan_ff+1;  
             ena_s <= '0';
          end if;
       end if;
   end process;  
ena_scan <= ena_s;
--to generate 1Hz ena_1Hz and flash_1Hz via dividing 1KHz clock by
   two_Hz:process(reset,clk,ena_s)
   begin
       if reset='1' then
          ena_one<='0';
          ena_two<='0';
          clk_2Hz_ff<="0000000";
       elsif (clk'event and clk='1') then
          if ena_s='1' then
            if clk_2Hz_ff>=two_Hz_val-1 then
               clk_2Hz_ff<="0000000";
               ena_two <= '1';
               ena_one <= not ena_one;
            else
               clk_2Hz_ff<=clk_2Hz_ff+1;  
               ena_two <= '0';
               ena_one <= ena_one;
            end if;
          end if;
       end if;
   end process; 
ena_1Hz <= ena_one and ena_two and ena_s;
flash_1Hz <= ena_one;
end BEHAVIOR;