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。FPGA的VHDL语言实现

以下是基于VHDL语言实现自动售货机的代码及说明。

首先，需要定义输入输出接口和信号：

entity vending_machine is
    port(
        clk: in std_logic;
        reset: in std_logic;
        nickel_input: in std_logic;
        dime_input: in std_logic;
        output_goods: out std_logic;
        output_change: out std_logic;
        display: out std_logic_vector(3 downto 0)
    );
end vending_machine;

architecture Behavioral of vending_machine is
    -- 定义状态机的状态
    type state_type is (idle, accept_nickel, accept_dime, deliver_goods, dispense_change);
    signal state: state_type;
    -- 定义投币计数器和货币总数计数器
    signal coin_count: integer range 0 to 4;
    signal total_amount: integer range 0 to 30;
begin
    -- 状态机的逻辑实现
    process(clk, reset)
    begin
        if reset = '1' then
            state <= idle;
            coin_count <= 0;
            total_amount <= 0;
        elsif rising_edge(clk) then
            case state is
                when idle =>
                    if nickel_input = '1' then
                        state <= accept_nickel;
                    elsif dime_input = '1' then
                        state <= accept_dime;
                    end if;
                when accept_nickel =>
                    if total_amount + 5 >= 15 then
                        state <= deliver_goods;
                    else
                        state <= idle;
                    end if;
                when accept_dime =>
                    if total_amount + 10 >= 15 then
                        state <= deliver_goods;
                    else
                        state <= idle;
                    end if;
                when deliver_goods =>
                    state <= dispense_change;
                when dispense_change =>
                    state <= idle;
            end case;
        end if;
    end process;
    
    -- 投币计数器的逻辑实现
    process(clk, reset)
    begin
        if reset = '1' then
            coin_count <= 0;
        elsif rising_edge(clk) then
            if state = idle then
                if nickel_input = '1' then
                    coin_count <= coin_count + 1;
                elsif dime_input = '1' then
                    coin_count <= coin_count + 2;
                end if;
            end if;
        end if;
    end process;
    
    -- 货币总数计数器的逻辑实现
    process(clk, reset)
    begin
        if reset = '1' then
            total_amount <= 0;
        elsif rising_edge(clk) then
            if state = idle then
                total_amount <= total_amount + (coin_count * 5);
                coin_count <= 0;
            elsif state = deliver_goods then
                total_amount <= total_amount - 15;
            elsif state = dispense_change then
                total_amount <= total_amount - 5;
            end if;
        end if;
    end process;
    
    -- 输出信号和数码管显示的逻辑实现
    process(clk, reset)
    begin
        if reset = '1' then
            output_goods <= '0';
            output_change <= '0';
            display <= "0000";
        elsif rising_edge(clk) then
            case state is
                when idle =>
                    output_goods <= '0';
                    output_change <= '0';
                when deliver_goods =>
                    output_goods <= '1';
                    output_change <= '0';
                when dispense_change =>
                    output_goods <= '0';
                    output_change <= '1';
            end case;
            display <= std_logic_vector(to_unsigned(total_amount, 4));
        end if;
    end process;
end Behavioral;

上述代码中，状态机的状态包括`idle`（空闲）、`accept_nickel`（接受5角硬币）、`accept_dime`（接受1元硬币）、`deliver_goods`（输出货物）和`dispense_change`（输出找零）。

投币计数器用于计算当前投入的5角和1元硬币数量，货币总数计数器用于计算当前总共投入的金额。

最后，通过输出信号和数码管显示实现自动售货机的功能。

请注意，由于无法进行硬件验证，上述代码仅供参考，可能需要进行调试和修改才能正常工作。