code_tran.vhd

VHDL源代码下载

--code_tran.vhd keyboard position to button code transformer
library ieee ;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
entity code_tran is
port(
  scan_cnt : in  std_logic_vector(3 downto 0) ;--keybord scan count
  clk : in std_logic ;--clock
  butt_code : out std_logic_vector(3 downto 0)) ;--button code
end code_tran ;
architecture behavior of code_tran is
begin 
  code_tran:process(clk)
  begin
     if(clk'event and clk='1') then
          case scan_cnt is					--encoding
    	      	when "0000"=>  butt_code <= "0001";--1
        	  	when "0001"=>  butt_code <= "0010";--2
	       		when "0010"=>  butt_code <= "0011";--3
    	      	when "0011"=>  butt_code <= "1100";--c
        	  	when "0100"=>  butt_code <= "0100";--4
	          	when "0101"=>  butt_code <= "0101";--5
    	      	when "0110"=>  butt_code <= "0110";--6
        	  	when "0111"=>  butt_code <= "1101";--d
          		when "1000"=>  butt_code <= "0111";--7
	          	when "1001"=>  butt_code <= "1000";--8
    	      	when "1010"=>  butt_code <= "1001";--9
        	  	when "1011"=>  butt_code <= "1110";--e
	          	when "1100"=>  butt_code <= "1010";--a
    	      	when "1101"=>  butt_code <= "0000";--0
        	  	when "1110"=>  butt_code <= "1011";--b
	          	when others => butt_code <= "1111";--f
   	      end case;
     end if;
  end process;  
end behavior;