keydecoder.vhd

这是一个通过外部按键来控制发光二极管发光的程序

--按键译码
LIBRARY IEEE;
USE IEEE.std_logic_1164.ALL;
USE IEEE.std_logic_unsigned.ALL;

ENTITY keydecoder IS
PORT (keyin       :IN STD_LOGIC_VECTOR(1 DOWNTO 0);
      keydrv      :IN STD_LOGIC_VECTOR(3 DOWNTO 0);
      clk_scan    :IN std_logic;
      clk         :IN std_logic;
      freq: buffer std_logic_vector(1 downto 0));
END keydecoder;

ARCHITECTURE rtl OF keydecoder IS
 SIGNAL temp : STD_LOGIC_VECTOR(5 DOWNTO 0); 
 SIGNAL temp_pressed:std_logic;--用于产生temp_pressed1
 SIGNAL temp_pressed1:std_logic;--用于产生keypressed
 SIGNAL keypressed :STD_LOGIC; 
 SIGNAL keyvalue : STD_LOGIC_VECTOR(3 DOWNTO 0);
 SIGNAL q1,q2,q3,q4,q5,q6:std_logic;--6个寄存器，用于消抖和同步化keypressed_asy
 SIGNAL cnt4:integer range 0 to 3;
 
 BEGIN
       temp<=keyin&keydrv;
--按键译码进程   
 PROCESS(temp)    
  begin
  if(clk_scan'event and clk_scan='1') then            
	CASE temp IS
	  WHEN"010001"=>keyvalue<="0001";--1
	                temp_pressed<='1';
	                
	  WHEN"010010"=>keyvalue<="0010";--2
	                temp_pressed<='1';	               
	               
	  WHEN"010100"=>keyvalue<="0011";--3
	                temp_pressed<='1';	                
	                
	  WHEN"011000"=>keyvalue<="0100";--4
	                temp_pressed<='1';	               
	               
	  WHEN"100001"=>keyvalue<="0101";--5
	                temp_pressed<='1';	                
	                
	  WHEN"100010"=>keyvalue<="0110";--6
	                temp_pressed<='1';	                
	                
	  WHEN"100100"=>keyvalue<="0111";--7
	                temp_pressed<='1';	                
	                
	  WHEN"101000"=>keyvalue<="1000";--8
	                temp_pressed<='1';	                
	                
      WHEN OTHERS =>temp_pressed<='0';
                                        
    END CASE;
  END IF;
  END PROCESS;

  process(clk_scan)--键盘消抖
   begin
    if(clk_scan'event and clk_scan='1') then
         q1<=temp_pressed;
         q2<=q1;
         q3<=q2;
         q4<=q3;
    end if;
   temp_pressed1<=q1 or q2 or q3 or q4;
  end process;
  
  process(clk)--同步化  
   begin
    if(clk'event and clk='1') then
       q5<=temp_pressed1;
       q6<=q5;
    end if;
    keypressed<=q5 and not q6;
  end process;

--前提条件：有键被按下时,keypressed产生一个高电平
--此进程用来调频
process(keypressed)
    begin
      if(keypressed'event and keypressed='1') then
         if(keyvalue="1000") then--按下8键
            if(cnt4=3) then
               cnt4<=1;
            else
             cnt4<=cnt4+1;
            end if;
          else
             cnt4<=cnt4;
          end if;
       end if;
 end process;

process(cnt4)
 begin
  case cnt4 is
    when 0=>freq<="00";
    when 1=>freq<="01";
    when 2=>freq<="10";
    when 3=>freq<="11";
    when others=>freq<="00";
  end case;
end process;
end rtl;