VHDL写FPGA数码管静态显示

以下是一个简单的VHDL代码示例，用于在FPGA上实现静态显示数码管：

entity num_display is
    port(
        clk : in std_logic;
        data : in std_logic_vector(3 downto 0);
        seg : out std_logic_vector(6 downto 0);
        anode : out std_logic_vector(3 downto 0)
    );
end entity num_display;

architecture Behavioral of num_display is
    signal counter : integer range 0 to 4999 := 0;
    signal digit : integer range 0 to 3 := 0;
begin
    process(clk)
    begin
        if rising_edge(clk) then
            counter <= counter + 1;
            if counter = 4999 then
                counter <= 0;
                digit <= digit + 1;
                if digit = 4 then
                    digit <= 0;
                end if;
            end if;
        end if;
    end process;

    case digit is
        when 0 =>
            case data is
                when "0000" => seg <= "0000001"; -- 0
                when "0001" => seg <= "1001111"; -- 1
                when "0010" => seg <= "0010010"; -- 2
                when "0011" => seg <= "0000110"; -- 3
                when "0100" => seg <= "1001100"; -- 4
                when "0101" => seg <= "0100100"; -- 5
                when "0110" => seg <= "0100000"; -- 6
                when "0111" => seg <= "0001111"; -- 7
                when "1000" => seg <= "0000000"; -- 8
                when "1001" => seg <= "0000100"; -- 9
                when others => seg <= "1111111"; -- error
            end case;
            anode <= "1110";
        when 1 =>
            -- 程序同上，这里不再赘述
        when 2 =>
            -- 程序同上，这里不再赘述
        when 3 =>
            -- 程序同上，这里不再赘述
    end case;
end architecture Behavioral;

在这个示例中，我们用一个计数器 `counter` 来控制静态显示数码管的刷新频率。每经过 4999 个时钟周期，计数器清零，并将显示的数码管位数 `digit` 加一。在 `case` 语句中，我们为每个位数的数码管设置了对应的 `data` 值与七段数码管的输出 `seg`，并通过 `anode` 控制激活对应的数码管。

当然，这只是一个简单的示例代码，实际应用中可能还需要考虑更多的细节和功能。