用vhdl实现ask调制

要使用VHDL实现ASK调制，可以遵循以下步骤：

1. 定义输入和输出端口：输入包括原始数字信号和载波信号，输出为调制后的信号。

entity ask_modulation is
    port (
        clk     : in  std_logic;
        reset   : in  std_logic;
        data_in : in  std_logic;
        car_in  : in  std_logic;
        ask_out : out std_logic
    );
end entity;

2. 在实体中定义信号，包括调制信号和计数器。

architecture rtl of ask_modulation is
    signal car_out : std_logic;
    signal cnt     : integer range 0 to 100;
begin

3. 在architecture中实现调制逻辑。可以使用一个计数器来生成载波信号，当原始数字信号为高电平时，将载波信号和原始数字信号相乘得到调制信号，否则调制信号为低电平。

    process (clk, reset)
    begin
        if reset = '1' then
            cnt <= 0;
            ask_out <= '0';
        elsif rising_edge(clk) then
            if cnt = 100 then
                cnt <= 0;
            else
                cnt <= cnt + 1;
            end if;
            car_out <= '1' when cnt < 50 else '0';
            if data_in = '1' then
                ask_out <= car_out;
            else
                ask_out <= '0';
            end if;
        end if;
    end process;
end architecture;

4. 最后，可以将实体和架构组合在一起，并且进行仿真和综合。

entity top is
end entity;

architecture behavioral of top is
    signal clk     : std_logic := '0';
    signal reset   : std_logic := '0';
    signal data_in : std_logic := '0';
    signal car_in  : std_logic := '0';
    signal ask_out : std_logic;
begin
    dut : entity work.ask_modulation
        port map (
            clk     => clk,
            reset   => reset,
            data_in => data_in,
            car_in  => car_in,
            ask_out => ask_out
        );

    clk_process : process
    begin
        clk <= '0';
        wait for 10 ns;
        clk <= '1';
        wait for 10 ns;
    end process;

    reset_process : process
    begin
        reset <= '1';
        wait for 50 ns;
        reset <= '0';
        wait;
    end process;

    stimulus : process
    begin
        wait for 100 ns;
        data_in <= '1';
        wait for 200 ns;
        data_in <= '0';
        wait for 100 ns;
        data_in <= '1';
        wait for 200 ns;
        data_in <= '0';
        wait;
    end process;
end architecture;

这样就可以在仿真器中进行测试，或者使用VHDL工具进行综合和实现。