Vhdl如何重置此信号

1 回答

• 0

  我看到你已经声明了一个枚举类型状态并实例化了一个state状态的信号current_s . 枚举类型包括文字（Start，Space，T，E），但是您可以将文字M，N和A分配给不是状态类型成员的信号current_s . 您的编译器应该抱怨这一点 . 可以？

  代码中包含的fsm有点难以理解，因为状态转换代码与输出信号逻辑混合在一起 . 所以，我重写了它并将其发布在下面 . 我的fsm可能并不完全代表您正在寻找的功能，但是，您可以将其用作模板 . 它说明了如何为点和短划线信号生成一个时钟宽边缘检测器 . 它还说明了如何控制您无法打开和关闭的数据选通信号 .

  输出逻辑没有充分利用继续输出逻辑case语句的默认信号值，因此您可以更轻松地查看发生的情况 . 但是，为了紧凑，可以消除案件中的许多陈述 .

  此外，我还没有编译代码，所以你可能会发现一些语法错误，但模板应该对你有用 .

  -- Note, not all signals are declared here, refer to the posted code for them
  
  Type state_t is (Idle, start_dot, start_dash, E_dot, strobe_3spc_data,
                      wait_1, strobe_7spc_data, wait_2, E_dash);
  
  signal state_snoop : state_t; -- use to monitor state in simulator
  signal dash_ff     : std_logic;
  signal dash_pulse  : std_logic;
  signal dot_ff      : std_logic;
  signal dot_pulse   : std_logic;
  
  fsm: process (clk)
      variable current_s : state_t;
      begin
          if rising_edge(clk) then
              if Reset = '1' then
                  current_s := Idle;
              else
                  case Idle is
                      when Idle =>
                          if dot_pulse = '1' then
                              current_s := start_dot;
                          elsif dash_pulse = '1' then
                              current_s := start_dash;                       
                          end if;
  
                      -- dot related states ----------------------        
                      when start_dot =>
                          current_s := E_dot;
                      when E_dot =>
                          if three_spc = '1' then
                              current_s := strobe_3spc_data;
                          end if;                        
                      when strobe_3spc_data =>
                          if seven_spc = '1' then -- counter strobe from external source
                              current_s := wait_1;
                          end if;
                      when wait_1 =>
                          if seven_spc = '1' then -- counter strobe from external source
                              current_s := strobe_7spc_data;
                          end if;
                      when strobe_7spc_data =>
                          current_s := wait_2;
                      when wait_2 =>
                          current_s := idle;
  
                      -- dash related states ----------------------        
                      when start_dash =>
                          current_s := E_dash;
                      when E_dash =>
                          if three_spc = '1' then
                              current_s := strobe_3spc_data;
                          end if;                        
                  end case;
              end if;
          end if;
          state_snoop <= current_s; -- monitor state in simulator. variables are hard to monitor
  
      --------------   outputs decoded from state variable   -------------------
      -- default signal values
          New_data_s <= '0';
          data_d     <= "0000000";  data_a  <= "00000000";  d_out_d <= "0000000";
          Stop_s     <= '0';        Error_s <= '0';
  
          case current_s is
              when Idle  =>
                  data_d     <= "0000000";
                  data_a     <= "00000000";
                  d_out_d    <= "1100100";
                  Error_s    <= '0';
                  New_data_s <= '0';    
              when start_dot  => 
                  data_d     <= "0000110"; --'ACK'
                  data_a     <= "01000101"; -- ascii dash -> 'E'
                  Error_s    <= '0'; 
                  New_data_s <= '0';
              when E_dot =>
                  data_d <= "1111001";
                  data_a <= "01001001";                
              when strobe_3spc_data =>
                  d_out_d    <= data_d;
                  d_out_a    <= data_a;
                  New_data_s <= '1';                
              when wait_1 => -- switch data strobe off for first data transmission
                  New_data_s <= '0';
              when strobe_7spc_data =>
                  d_out_d    <= data_d;
                  d_out_a    <= "00100000";
                  New_data_s <= '1';
              when wait_2 => -- switch data strobe off for second data transmission
                  New_data_s <= '0';
              -- dash related outputs
              when start_dash  => 
                  data_d <= "1100100";  --'t'
                  data_a <= "01010100"; --'T'
                  Error_s    <= '0'; 
                  New_data_s <= '0';
              when E_dash =>
                  data_d <= "0001000";
                  data_a <= "01000001";
              when others => null;
          end case;
  
  
          -- rising edge detector for dash and dot input.
          if Reset = '1' then
              dash_pulse <= '0'
          else
              dash_ff    << not(Dash);
              dash_pulse << dash_ff and dash;
          end if;
  
          if Reset = '1' then
              dot_pulse <= '0'
          else
              dot_ff    << not(dot);
              dot_pulse << dot_ff and dot;
          end if;
  
  end process fsm
  

  回复于 2024-05-03T03:44:27+08:00