为什么这样定义的计数器不能正确功能仿真,好郁闷好几天了,是不是对inout类型不能综 inout, 计数器, 定义, 类型, 功能

yangping010

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity counter is port(
                      clk: in    std_logic;
                    count: inout std_logic_vector(15 downto 0)
            );
end counter;

architecture Behavioral of counter is
  begin
    process(clk)
    begin
     if (clk='1') and (clk'event) then
             count<=count+1; 
     end if;
    end process;
end Behavioral;