library IEEE;

use IEEE.STD_LOGIC_1164.all;

use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity data_scanC is

 PORT(

       sys_clk : in STD_LOGIC; --系統(tǒng)同步時鐘

       k_data : in STD_LOGIC; --鍵盤數(shù)據(jù)

       k_clock : in STD_LOGIC; --鍵盤時鐘

       reset     : in STD_LOGIC;

       data    : buffer STD_LOGIC_VECTOR(7 DOWNTO 0); --掃描碼輸出

       PA      : buffer STD_LOGIC_VECTOR(7 DOWNTO 0);

       ZHJS    : buffer STD_LOGIC  ; --掃描碼轉(zhuǎn)換結(jié)束信號
       
       ascii   : out STD_LOGIC_VECTOR(7 DOWNTO 0)
       );

end data_scanC;

 architecture behav of data_scanC is

 signal tmp : STD_LOGIC_VECTOR(11 downto 0) :="000000000000";--用來記錄一幀信號

 signal enable : std_logic :='0'; --輸出使能

 signal now_kbclk,pre_kbclk : std_logic;

 

begin

 process(reset,k_clock,sys_clk) --系統(tǒng)時鐘(sys_clk)比鍵盤時鐘(k_clock)快很多

 variable started:STD_LOGIC :='0';

 variable counter :integer range 0 to 11 :=0;

begin

 if reset='0' then ZHJS<='0';counter:=0;

 elsif rising_edge(sys_clk) then --系統(tǒng)時鐘(sys_clk)比鍵盤時鐘(k_clock)快很多

       pre_kbclk <= now_kbclk;

       now_kbclk <= k_clock; 

 

       if(pre_kbclk > now_kbclk) then --由時序圖可知，如果有數(shù)據(jù)發(fā)送則鍵盤時鐘(k_clock)作周期性變化；如果k_clock 一直是高電平，則表示鍵盤正準(zhǔn)備要發(fā)送數(shù)據(jù)。

           tmp(counter)<=k_data;    --鍵盤數(shù)據(jù)存tmp,例如,起始位存tmp[0],8位數(shù)據(jù)存tmp[1]—tmp[8]

            if counter=10 
			then ZHJS<='0'; --ZHJS=’0’表示接收結(jié)束
            else ZHJS<='1';
            end if;

            if counter=11 then 
			  counter:=1;
            else counter:=counter+1; --通過加法器把鍵盤的串行數(shù)據(jù)變成并行數(shù)據(jù),即存tmp[counter]里面,這樣做可以減少占用芯片資源.
            end if;

       end if;

 

 end if;

     if(counter>1 and counter<10) then started:='1'; --started=’1’表示沒有接收完. 

             else started:='0';

     end if;

enable<=started;

end process;

 PA<="00000000" when enable='1' else tmp(8 downto 1); --如果接收完,則將tmp[8..1]存PA

 data<=PA;

 process(PA)
   begin
    case PA is
       when"01000101"=> ascii<="00110000";          --'0'
       when"00010110"=> ascii<="00110001";          --'1'
       when"00011110"=> ascii<="00110010";          --'2'
       when"00100110"=> ascii<="00110011";          --'3'
       when"00100101"=> ascii<="00110100";          --'4'
       when"00101110"=> ascii<="00110101";          --'5'
       when"00110110"=> ascii<="00110110";          --'6'
       when"00111101"=> ascii<="00110111";          --'7'
       when"00111110"=> ascii<="00111000";          --'8'
       when"01000110"=> ascii<="00111001";          --'9'

       when"00011100"=> ascii<="01100001";          --'a'
       when"00110010"=> ascii<="01100010";          --'b'
       when"00100001"=> ascii<="01100011";          --'c'
       when"00100011"=> ascii<="01100100";          --'d'
       when"00100100"=> ascii<="01100101";          --'e'
       when"00101011"=> ascii<="01100110";          --'f'
       when"00110100"=> ascii<="01100111";          --'g'
       when"00110011"=> ascii<="01101000";          --'h'
       when"01000011"=> ascii<="01101001";          --'i'
       when"00111011"=> ascii<="01101010";          --'j'
       when"01000010"=> ascii<="01101011";          --'k'
       when"01001011"=> ascii<="01101100";          --'l'
       when"00111010"=> ascii<="01101101";          --'m'
       when"00110001"=> ascii<="01101110";          --'n'
       when"01000100"=> ascii<="01111111";          --'o'
       when"01001101"=> ascii<="01110000";          --'p'
       when"00010101"=> ascii<="01110001";          --'q'
       when"00101101"=> ascii<="01110010";          --'r'
       when"00011011"=> ascii<="01110011";          --'s'
       when"00101100"=> ascii<="01110100";          --'t'
       when"00111100"=> ascii<="01110101";          --'u'
       when"00101010"=> ascii<="01110110";          --'v'
       when"00011101"=> ascii<="01110111";          --'w'
       when"00100010"=> ascii<="01111000";          --'x'
       when"00110101"=> ascii<="01111001";          --'y'
       when"00011010"=> ascii<="01111010";          --'z'   
       when others=>    ascii<="11111111";         
      end case;
   end process;
end behav;