key_scan.vhd

FPGA键盘扫描

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.std_logic_arith.all;
use IEEE.std_logic_unsigned.all;

entity key_scan is
	port ( CLK: in std_logic;
	       RESET: in std_logic;
		   KIN: in std_logic_vector (3 downto 0);
		   SCAN: out std_logic_vector (3 downto 0);
		   output: out std_logic_vector (3 downto 0);
		   EO: out std_logic_vector (5 downto 0);
		   DISPLAY: out std_logic_vector (7 downto 0) 
		);
end key_scan;

architecture key_scan_arch of key_scan is
type STATE_TYPE is (S0, S1, S2, S3);     
signal Sreg: STATE_TYPE;
signal counter: std_logic_vector (3 downto 0);
signal CLK_DIV: std_logic;
signal K: std_logic_vector (15 downto 0);

begin
   	
    process (CLK)             -- 分频
	begin
		if CLK 'event and CLK='1' then       
		    if counter="1111" then           
				counter <= (others=>'0'); 
		    else 
				counter <= counter + 1;      
		    end if;
		end if;
	end process;
	
	CLK_DIV <= not counter(3);     
	
	process (CLK_DIV, RESET)      -- state machine   
	begin
	  if RESET = '0' then Sreg <= S0;
	  elsif CLK_DIV 'event and CLK_DIV='1' then 	 
		case Sreg is                          
	    	when S0 => if    KIN = "0001" then K <= "0000000000000001"; Sreg <= S0;
	                   elsif KIN = "0010" then K <= "0000000000000010"; Sreg <= S0;
	                   elsif KIN = "0100" then K <= "0000000000000100"; Sreg <= S0;
	                   elsif KIN = "1000" then K <= "0000000000001000"; Sreg <= S0;
	                   else  KIN = "0000" then K <= (others=>'0'); Sreg <= S1;
	                   end if;
	   	    when S1 => if    KIN = "0001" then K <= "0000000000010000"; Sreg <= S1;
	                   elsif KIN = "0010" then K <= "0000000000100000"; Sreg <= S1;
	                   elsif KIN = "0100" then K <= "0000000001000000"; Sreg <= S1;
	                   elsif KIN = "1000" then K <= "0000000010000000"; Sreg <= S1;
	                   else  KIN = "0000" then K <= (others=>'0'); Sreg <= S2;
	                   end if;
			when S2 => if    KIN = "0001" then K <= "0000000100000000"; Sreg <= S2;
	                   elsif KIN = "0010" then K <= "0000001000000000"; Sreg <= S2;
	                   elsif KIN = "0100" then K <= "0000010000000000"; Sreg <= S2;
	                   elsif KIN = "1000" then K <= "0000100000000000"; Sreg <= S2;
	                   else  KIN = "0000" then K <= (others=>'0'); Sreg <= S3;
	                   end if;
	        when S3 => if    KIN = "0001" then K <= "0001000000000000"; Sreg <= S3;
	                   elsif KIN = "0010" then K <= "0010000000000000"; Sreg <= S3;
	                   elsif KIN = "0100" then K <= "0100000000000000"; Sreg <= S3;
	                   elsif KIN = "1000" then K <= "1000000000000000"; Sreg <= S3;
	                   else  KIN = "0000" then K <= (others=>'0'); Sreg <= S0;
	                   end if;
			when others => Sreg <= S0; 
		end case;
	  end if;
	end process;

	process (Sreg)         -- output logic
		begin
		case Sreg is
		 	when S0 => SCAN <= "0001"; 
		   	when S1 => SCAN <= "0010"; 
			when S2 => SCAN <= "0100";
			when S3 => SCAN <= "1000"; 
			when others => SCAN <= "0000"; 
		end case;
	end process;

    process (K)    -- seven
    begin
        case K is                          
		    when "0000000000000001" => DISPLAY <= "11111100";   -- 0
			when "0000000000000010" => DISPLAY <= "01100000";   -- 1
			when "0000000000000100" => DISPLAY <= "11011010";   -- 2
			when "0000000000001000" => DISPLAY <= "11110010";   -- 3
			when "0000000000010000" => DISPLAY <= "01100110";   -- 4
			when "0000000000100000" => DISPLAY <= "10110110";   -- 5
			when "0000000001000000" => DISPLAY <= "10111110";   -- 6
			when "0000000010000000" => DISPLAY <= "11100000";   -- 7
			when "0000000100000000" => DISPLAY <= "11111110";   -- 8
			when "0000001000000000" => DISPLAY <= "11110110";   -- 9
		    when "0000010000000000" => DISPLAY <= "11101110";   -- A
			when "0000100000000000" => DISPLAY <= "00111110";   -- B
			when "0001000000000000" => DISPLAY <= "10011100";   -- C
			when "0010000000000000" => DISPLAY <= "01111010";   -- D
			when "0100000000000000" => DISPLAY <= "10011110";   -- E
			when "1000000000000000" => DISPLAY <= "10001110";   -- F
			when others => DISPLAY <= "11111111";               -- no key
		end case;
	end process;

    output <= KIN;	
    EO <= "111110";

end key_scan_arch;