VHDL状态机[关闭]

我在VHDL中写了一些代码，期望看到一个旋转开关并反馈给我它的位置 .

当它转动时，它将从转子拨盘读入greycode并将状态切换到相应的greycode状态 .

改变状态的行为告诉我转子被扭转的方式，所以我可以在电路后面的计数器模块上指示上升或下降状态 .

如果状态改变，它应该在 Mag 上触发一个脉冲，并在 up_dwn 上取消1或0 .

当我模拟它时，它不起作用 . 我在 Mag 上得到一个偶然的昙花一现但没有 up_dwn 的变化 .

我怀疑它被困在 START 状态 .

有人想看，告诉我我做错了什么？

[编辑：使用Quartus II版本9]

LIBRARY ieee;
USE ieee.std_logic_1164.ALL;

ENTITY EncoderV2    IS
PORT(
    CH_AB           :   IN  STD_LOGIC_VECTOR (1 downto 0);
    clk             :   IN  STD_LOGIC;
    nReset          :   IN  STD_LOGIC;
    up_dwn, Mag     :   OUT STD_LOGIC);

    END EncoderV2;

ARCHITECTURE a OF EncoderV2 IS  --  
TYPE STATE_TYPE IS ( START, s00, s01, s11, s10);
SIGNAL state:   STATE_TYPE;

BEGIN
PROCESS (clk, nReset)
BEGIN
    IF nReset = '0' THEN                        --    asynch Reset to zero
        state   <=  START;
    ELSIF clk'EVENT AND clk = '1' THEN          --  triggers on PGT
        CASE state IS 
            WHEN START =>
                    IF CH_AB ="00" THEN
                                state   <= s00;
                                Mag <='0';
                    ELSIF CH_AB="01" THEN
                                state   <= s01;
                                Mag <='0';
                    ELSIF CH_AB= "11" THEN
                                state   <= s11;
                                Mag <='0';
                    ELSIF CH_AB= "10" THEN
                                state   <= s10;
                                Mag <='0';
                    ELSE  state <= START;
                    END IF;

            WHEN s00 =>                 --  S10 <- S00 -> S01
                    IF CH_AB= "00" THEN
                                state   <= s00;
                                Mag <='0';
                    ELSIF CH_AB= "10" THEN
                                state   <= s10;
                                up_dwn  <= '0';
                                Mag <='1';
                    ELSIF CH_AB= "01" THEN
                                state   <= s01;
                                up_dwn  <='1';
                                Mag <='1';
                    ELSE  state <= START;
                    END IF;

            WHEN s01 =>                 --  S00 <- S01 -> S11
                    IF CH_AB= "01" THEN
                                state   <= s01;
                                Mag <='0';
                    ELSIF CH_AB= "00" THEN
                                state   <= s00;
                                up_dwn  <= '0';
                                Mag <='1';
                    ELSIF CH_AB= "11" THEN
                                state   <= s11;
                                up_dwn  <='1';
                                Mag <='1';
                    ELSE state <= START;
                    END IF;

            WHEN s11 =>                 --  S01 <- S11 ->S10
                    IF CH_AB= "11" THEN
                                state   <= s11;
                                Mag <='0';
                    ELSIF CH_AB= "01" THEN
                                state   <= s01;
                                up_dwn  <= '0';
                                Mag <='1';
                    ELSIF CH_AB= "10" THEN
                                state   <= s10;
                                up_dwn  <='1';
                                Mag <='1';
                    ELSE state <= START;
                    END IF;

            WHEN s10 =>                 --  S11 <- S10 -> S00
                    IF CH_AB= "10" THEN
                                state   <= s10;
                                Mag <='0';
                    ELSIF CH_AB= "11" THEN
                                state   <= s11;
                                up_dwn  <= '0';
                                Mag <='1';
                    ELSIF CH_AB= "00" THEN
                                state   <= s00;
                                up_dwn  <='1';
                                Mag <='1';
                    ELSE state <= START;
                    END IF;





            END CASE;
        END IF;
    END PROCESS;
END a;