基于VHDL的AD7490驱动代码

以下是一个基于VHDL的AD7490驱动代码的例子，其中包含了模块化设计和状态机控制：

library ieee;
use ieee.std_logic_1164.all;

entity AD7490 is
    port (
        clk         : in std_logic;
        reset       : in std_logic;
        cs          : out std_logic;
        convst      : out std_logic;
        busy        : in std_logic;
        din         : in std_logic_vector(15 downto 0);
        dout        : out std_logic_vector(15 downto 0);
        valid       : out std_logic
    );
end entity AD7490;

architecture Behavioral of AD7490 is

    type state_type is (idle, start_conversion, wait_conversion, read_data);
    signal state : state_type := idle;
    signal data : std_logic_vector(15 downto 0);
    signal counter : unsigned(3 downto 0) := (others => '0');

begin

    cs <= '1';  -- enable chip select

    process(clk, reset)
    begin
        if reset = '1' then
            state <= idle;
            counter <= (others => '0');
            data <= (others => '0');
            valid <= '0';
        elsif rising_edge(clk) then
            case state is
                when idle =>
                    if busy = '0' then
                        state <= start_conversion;
                    end if;
                when start_conversion =>
                    if counter = "0000" then
                        convst <= '1';  -- start conversion
                        state <= wait_conversion;
                    else
                        counter <= counter - 1;
                    end if;
                when wait_conversion =>
                    if busy = '1' then
                        state <= wait_conversion;
                    else
                        cs <= '0';  -- enable data read
                        state <= read_data;
                    end if;
                when read_data =>
                    if counter = "1111" then
                        dout <= data;
                        valid <= '1';
                        cs <= '1';  -- disable data read
                        state <= idle;
                    else
                        data(counter) <= din(counter);
                        counter <= counter + 1;
                    end if;
            end case;
        end if;
    end process;

end architecture Behavioral;

这个代码实现了一个简单的状态机控制器，用于控制AD7490的数据转换和读取。在状态机中，当AD7490处于空闲状态时，它会等待启动转换命令。当AD7490开始转换时，状态机会等待转换完成，然后启动数据读取过程。最后，状态机会将读取的数据输出并返回到空闲状态。