VHDL为什么当状态S0不应该是活动状态？

Question

我在使用这段代码时遇到了一些麻烦。看起来状态S0总是有效的，即使它不应该是。看起来这个状态的输出是反转的（当它被禁止时是有效的）。有任何想法吗？底部的模拟打印。由于

library IEEE; 
use IEEE.STD_LOGIC_1164.all; 

entity ControlUnit is 
    port(clk   : in std_logic; 
      reset   : in std_logic; 
      validTime  : in std_logic; 
      timeData  : in std_logic_vector(3 downto 0); 
      writeEnable : out std_logic; 
      writeAddress : out std_logic_vector(3 downto 0); 
      averageReady : out std_logic); 
end ControlUnit; 

architecture Behavioral of ControlUnit is 
    type TState is (S0, S1, S2, S3, S4, S5); 
    signal PState, NState: TState; 
begin 

    sync_proc: process(clk, reset) 
    begin 
     if(reset = '1') then 
      PState <= S0; 
     elsif(rising_edge(clk)) then 
      PState <= NState; 
     end if; 
    end process; 

    comb_proc: process(PState, validTime, timeData) 
    begin 
     averageReady <= '0'; 
     writeEnable <= '0'; 
     case PState is 
      when S0 => 
       if(validTime = '1') then 
        writeEnable <= '1'; 
        NState <= S1; 
       else 
        NState <= S0; 
       end if; 
      when S1 => 
       if(validTime = '1') then 
        writeEnable <= '1'; 
        NState <= S2; 
       else 
        NState <= S1; 
       end if; 
      when S2 => 
       if(validTime = '1') then 
        writeEnable <= '1'; 
        NState <= S3; 
       else 
        NState <= S2; 
       end if; 
      when S3 => 
       if(validTime = '1') then 
        writeEnable <= '1'; 
        NState <= S4; 
       else 
        NState <= S3; 
       end if; 
      when S4 => 
       if(validTime = '1') then 
        writeEnable <= '1'; 
        NState <= S5; 
       else 
        NState <= S4; 
       end if; 
      when S5 => 
       averageReady <= '1'; 
       NState <= S0; 
      when others => 
       NState <= S0; 
     end case; 
    end process; 

    with PState select 
     writeAddress <= "0000" when S0, 
          "0001" When S1, 
          "0010" when S2, 
          "0011" when S3, 
          "0100" when S4, 
          "XXXX" when others; 
end Behavioral; 

这里是模拟的打印：

（点击）

Answer 1

一切都确定了你的代码。为什么你认为S0状态总是激活？你不能从波形中说出来，因为你不知道编码方案。另一方面，你不断地写地址信号变化，这意味着你的状态机改变它的状态。