key_scan.vhd

此程序实现的是矩阵式键盘的扫描的电路

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity key_scan is 
  port(clk :in std_logic;
       start:in std_logic;
       kbcol: in std_logic_vector(3 downto 0);--hang
       kbrow: out std_logic_vector(3 downto 0);--lie
       seg7_out:out std_logic_vector(3 downto 0));
end ;

architecture one of key_scan is
  signal cnt:std_logic_vector(1 downto 0); 
  signal sta:std_logic_vector(1 downto 0);
  signal seg7:std_logic_vector(3 downto 0);
  signal dat:std_logic_vector(4 downto 0);
  signal fn:std_logic;
begin
process(clk)
begin
  if clk'event and clk='1' then cnt<=cnt+1;end if;
end process;

process(clk)
begin
  if clk'event and clk='1' then
     case cnt is
          when "00"=>kbrow<="0001"; sta<="00";
          when "01"=>kbrow<="0010"; sta<="01";
          when "10"=>kbrow<="0100"; sta<="10";
          when "11"=>kbrow<="1000"; sta<="11";
    end case;
end if;
end process;


process(clk,start)
begin
  if start='0' then seg7<="0000";
  elsif clk'event and clk='1' then
        case sta is
             when "00"=>
                   case kbcol is
                        when "0001"=> seg7<="0011";dat<="00011";--3
                        when "0010"=> seg7<="0010";dat<="00010";--2
                        when "0100"=> seg7<="0001";dat<="00001";--1
                        when "1000"=> seg7<="0000";dat<="00000";--0
                        when others=> seg7<="0000";dat<="11111";
                   end case;
             when "01"=>
                   case kbcol is
                        when "0001"=> seg7<="0111";dat<="00011";--7
                        when "0010"=> seg7<="0110";dat<="00010";--6
                        when "0100"=> seg7<="0101";dat<="00001";--5
                        when "1000"=> seg7<="0100";dat<="00000";--4
                        when others=> seg7<="0000";dat<="11111";
                   end case;
            when "10"=>
                   case kbcol is
                        when "0001"=> seg7<="1011";dat<="00011";--b
                        when "0010"=> seg7<="1010";dat<="00010";--a
                        when "0100"=> seg7<="1001";dat<="00001";--9
                        when "1000"=> seg7<="1000";dat<="00000";--8
                        when others=> seg7<="0000";dat<="11111";
                   end case;
            when "11"=>
                   case kbcol is
                        when "0001"=> seg7<="1111";dat<="00011";--f
                        when "0010"=> seg7<="1110";dat<="00010";--e
                        when "0100"=> seg7<="1101";dat<="00001";--d
                        when "1000"=> seg7<="1100";dat<="00000";--c
                        when others=> seg7<="0000";dat<="11111";
                   end case;
            when others=> seg7<="0000";
        end case;
 end if;
end process;

fn<=not(dat(0)and dat(2)and dat(3)and dat(1));

 
process(fn)
begin
  if fn'event and fn='1' then
     seg7_out<=seg7;
  end if;
end process;
end;