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10進カウンタです。
7セグLEDで表示します。
33MHz / 2^24 Hz ≒ 1.97Hz でカウントします。
非同期リセットも入れてます。*1

-- 10 Counter with AsyncReset
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity Counter10 is
    port(
        CLK      : in std_logic;    -- Osc: 33MHz
        RESET    : in std_logic;
        LED_7SEG : out std_logic_vector(7 downto 0)
    );
end Counter10;

architecture RTL of Counter10 is
signal DIV_COUNTER : std_logic_vector(24 downto 0);
signal DIV_CLK     : std_logic;
signal COUNTER     : std_logic_vector(3 downto 0);

begin
    -- CLK
    process(CLK,RESET)
    begin
        if (RESET = '0') then
            DIV_COUNTER <= (others => '0');
        elsif (CLK'event and CLK = '0') then
            DIV_COUNTER <= DIV_COUNTER + 1;
        end if;
    end process;
    
    DIV_CLK <= not DIV_COUNTER(23);    -- 2Hz:(23)
                                       -- 1Hz:(24) 4Hz:(22) 8Hz:(21)...
    
    -- 10Counter with AsyncReset
    process(DIV_CLK,RESET)
    begin
        if (RESET = '0') then
            COUNTER <= (others => '0');
        elsif (DIV_CLK'event and DIV_CLK='0') then
            if (COUNTER = "1001") then
                COUNTER <= (others => '0');
            else
                COUNTER <= COUNTER + 1;
            end if;
        end if;
    end process;
    
    -- 7seg LED Decoder
    process(COUNTER)
    begin
        case COUNTER is
            when "0000" => LED_7SEG <= "00000011"; -- 0
            when "0001" => LED_7SEG <= "10011111"; -- 1
            when "0010" => LED_7SEG <= "00100101"; -- 2
            when "0011" => LED_7SEG <= "00001101"; -- 3
            when "0100" => LED_7SEG <= "10011001"; -- 4
            when "0101" => LED_7SEG <= "01001001"; -- 5
            when "0110" => LED_7SEG <= "01000001"; -- 6
            when "0111" => LED_7SEG <= "00011111"; -- 7
            when "1000" => LED_7SEG <= "00000001"; -- 8
            when "1001" => LED_7SEG <= "00001001"; -- 9
            when others => LED_7SEG <= "01100001"; -- E
        end case;
    end process;
    -- 7seg LED Decoder end
    
end RTL;

*1：しつこく書いていますが、リセット入力を回路に入れておくのは非常に重要です。