使用Altera Quartus Ⅱ设计一个具有投币找零功能的简易自动售货机。要求底层的模块采用VHDL文本输入，顶层的电路系统采用原理图输入。 自动售货机可以接受5角和1元硬币，货物价格为1.5元。当投入币值为两元时输出货物并找零5角，投币的钱数通过数码管显示。VHDL代码实现

好的，以下是一个简单的VHDL代码实现：

-- 定义输入输出信号
entity vending_machine is
    port(
        clk : in std_logic;
        reset : in std_logic;
        coin_5 : in std_logic;
        coin_1 : in std_logic;
        item_out : out std_logic;
        change_5 : out std_logic;
        coin_value : out std_logic_vector(3 downto 0);
        seven_seg : out std_logic_vector(7 downto 0)
    );
end entity vending_machine;

-- 实现自动售货机
architecture vending_machine_arch of vending_machine is
    -- 记录投币总数
    signal total_coin : integer range 0 to 15 := 0;
    -- 记录是否可以出货
    signal can_dispense : boolean := false;
    -- 记录是否需要找零
    signal need_change : boolean := false;
    -- 记录是否已找零
    signal change_dispensed : boolean := false;
begin
    -- 用于计算投币总数
    process(clk, reset)
    begin
        if reset = '1' then
            total_coin <= 0;
        elsif rising_edge(clk) then
            if coin_5 = '1' then
                total_coin <= total_coin + 1;
            elsif coin_1 = '1' then
                total_coin <= total_coin + 2;
            end if;
        end if;
    end process;

    -- 判断是否可以出货
    process(total_coin)
    begin
        if total_coin >= 3 then
            can_dispense <= true;
            need_change <= (total_coin = 4);
        else
            can_dispense <= false;
            need_change <= false;
        end if;
    end process;

    -- 判断是否需要找零
    process(clk, reset, can_dispense, change_dispensed)
    begin
        if reset = '1' then
            change_dispensed <= false;
        elsif can_dispense = true and change_dispensed = false then
            if total_coin = 4 then
                change_dispensed <= true;
            end if;
        end if;
    end process;

    -- 控制输出信号
    item_out <= '1' when can_dispense = true else '0';
    change_5 <= '1' when change_dispensed = true else '0';
    coin_value <= std_logic_vector(to_unsigned(total_coin, 4));

    -- 数码管显示投币总数
    process(total_coin)
        variable digit : integer range 0 to 9;
    begin
        digit := total_coin mod 10;
        seven_seg <= "00000000" when total_coin = 0 else
                    "00111111" when digit = 0 else
                    "00000110" when digit = 1 else
                    "01011011" when digit = 2 else
                    "01001111" when digit = 3 else
                    "01100110" when digit = 4 else
                    "01101101" when digit = 5 else
                    "01111101" when digit = 6 else
                    "00000111" when digit = 7 else
                    "01111111" when digit = 8 else
                    "01101111";
    end process;

end architecture vending_machine_arch;

该代码实现了一个自动售货机的基本功能，包括投币、出货、找零和数码管显示。其中，输入信号为时钟信号、复位信号、5角硬币输入信号和1元硬币输入信号；输出信号为货物输出信号、5角零钱输出信号、投币总数显示信号和七段数码管显示信号。