用行为语句设计一个8位可变模计数器， 要求：1. 当计数器计到1xx（“xx”为学号后两位）时，自动从零开始重新计数，同时产生一个高电平。 2. 当有加载信号时，装入预置的值（班内序号）。我的学号最后一位93，班内序号3 。写出题目的modelsim测试程序

以下是一个可变模计数器的行为语句设计，满足题目要求：

library ieee;
use ieee.std_logic_1164.all;

entity counter is
    port (
        clk: in std_logic;
        reset: in std_logic;
        load: in std_logic;
        preset: in std_logic_vector(7 downto 0);
        out_count: out std_logic_vector(7 downto 0);
        out_high: out std_logic
    );
end entity counter;

architecture behavior of counter is
    signal count: std_logic_vector(7 downto 0);
begin
    process(clk, reset)
    begin
        if reset = '1' then
            count <= "00000000";
            out_high <= '0';
        elsif rising_edge(clk) then
            if load = '1' then
                count <= preset;
            elsif count = ("1" & "00" & "1001") then
                count <= "00000000";
                out_high <= '1';
            else
                count <= count + 1;
                out_high <= '0';
            end if;
        end if;
    end process;

    out_count <= count;
end architecture behavior;

以下是一个简单的ModelSim测试程序，用于测试可变模计数器的功能：

library ieee;
use ieee.std_logic_1164.all;

entity counter_tb is
end entity counter_tb;

architecture behavior of counter_tb is
    signal clk: std_logic := '0';
    signal reset: std_logic := '0';
    signal load: std_logic := '0';
    signal preset: std_logic_vector(7 downto 0) := "00000011";
    signal out_count: std_logic_vector(7 downto 0);
    signal out_high: std_logic;

    constant PERIOD: time := 10 ns;
begin
    uut: entity work.counter
        port map (
            clk => clk,
            reset => reset,
            load => load,
            preset => preset,
            out_count => out_count,
            out_high => out_high
        );

    clk_process: process
    begin
        while now < 1000 ns loop
            clk <= not clk;
            wait for PERIOD / 2;
        end loop;
        wait;
    end process;

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

    load_process: process
    begin
        wait for 200 ns;
        load <= '1';
        wait for 10 ns;
        load <= '0';
        wait for 200 ns;
        load <= '1';
        wait for 10 ns;
        load <= '0';
        wait;
    end process;

    stimulus: process
    begin
        wait for 100 ns;
        assert out_count = "00000000" and out_high = '0' report "Test failed" severity error;
        wait for 500 ns;
        assert out_count = "00000101" and out_high = '0' report "Test failed" severity error;
        wait for 500 ns;
        assert out_count = "00001010" and out_high = '0' report "Test failed" severity error;
        wait for 500 ns;
        assert out_count = "00001111" and out_high = '0' report "Test failed" severity error;
        wait for 500 ns;
        assert out_count = "00010100" and out_high = '0' report "Test failed" severity error;
        wait for 500 ns;
        assert out_count = "00011001" and out_high = '1' report "Test failed" severity error;
        wait for 500 ns;
        assert out_count = "00000000" and out_high = '1' report "Test failed" severity error;
        wait for 500 ns;
        assert out_count = "00000101" and out_high = '0' report "Test failed" severity error;
        wait;
    end process;
end architecture behavior;

这个测试程序会测试可变模计数器的递增功能、重置功能和装载功能。在测试中，会先重置计数器，等待一段时间后，装载预置值。然后计数器会递增，直到计数器计到193时，会自动从零开始重新计数，同时产生一个高电平。测试程序会检查计数器的输出是否符合预期，如果不符合，则会报告测试失败。