# VHDL 코드 

HDL Coder 을 이용하여 VHDL 코드를 생성한다.

## 생성된 코드


```

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity led_blink is
    port(
        clk  : in  std_logic;
        rst  : in  std_logic;

        key0 : in  std_logic;
        key1 : in  std_logic;
        key2 : in  std_logic;
        key3 : in  std_logic;

        led  : out std_logic
    );
end entity;

architecture rtl of led_blink is

    signal mode      : unsigned(1 downto 0) := "00";
    signal cnt       : unsigned(31 downto 0) := (others=>'0');
    signal period    : unsigned(31 downto 0);
    signal led_state : std_logic := '0';

begin

    ------------------------------------------------------------------
    -- period 결정
    ------------------------------------------------------------------
    process(mode)
    begin

        case mode is

            when "00" =>
                period <= to_unsigned(0,32);

            when "01" =>
                period <= to_unsigned(50000000,32);

            when "10" =>
                period <= to_unsigned(25000000,32);

            when others =>
                period <= to_unsigned(5000000,32);

        end case;

    end process;

    ------------------------------------------------------------------
    -- 메인 상태기계
    ------------------------------------------------------------------
    process(clk,rst)
    begin

        if rst='1' then

            mode      <= "00";
            cnt       <= (others=>'0');
            led_state <= '0';

        elsif rising_edge(clk) then

            ----------------------------------------------------------
            -- mode 저장
            ----------------------------------------------------------
            if key0='1' then
                mode <= "00";

            elsif key1='1' then
                mode <= "01";

            elsif key2='1' then
                mode <= "10";

            elsif key3='1' then
                mode <= "11";
            end if;

            ----------------------------------------------------------
            -- LED 생성
            ----------------------------------------------------------
            if mode = "00" then

                cnt       <= (others=>'0');
                led_state <= '0';

            else

                if cnt >= period then

                    cnt <= (others=>'0');

                    led_state <= not led_state;

                else

                    cnt <= cnt + 1;

                end if;

            end if;

        end if;

    end process;

    led <= led_state;

end architecture;

```

## 핀배치


| 핀 번호 | 신호 |
|---------|------|
| PIN_T2 | clk |
| PIN_E4 | rst |
| PIN_A3 | key0 |
| PIN_A5 | key1 |
| PIN_A6 | key2 |
| PIN_A20 | key3 |
| PIN_B3 | led |



## 테스트 진행

해당 코드를 Quartus 를 이용하여 컴파일 하고, 동작 과정을 실습한다.