ps2.vhd

vhdl实现ps2接口的程序,可以接受键盘的输入或者鼠标的输入.

library ieee;
use ieee.std_logic_1164.all;
entity ps2 is
port(sysclk,reset,kbclk,kbdata:in std_logic;
     pdata:out std_logic_vector(7 downto 0);
     parity:out std_logic;
     dtoe :buffer std_logic);
end ps2;
architecture cyclone of ps2 is
signal costate:std_logic_vector(1 downto 0);
signal spdata:std_logic_vector(8 downto 0);
signal start,swto02,recven:std_logic;
signal cnt8:integer range 0 to 15;
begin
str1:  process(reset,kbclk,kbdata,start,costate)
       begin
            if reset = '1' then start <='0';
            elsif kbclk'event and kbclk='0' 
            then if costate = "00" and kbdata = '0' then
                 start<='1';
                 end if;
            end if;
       end process;
str2:  process(reset,kbclk,kbdata,start,costate)
       begin
            if reset = '1' then swto02 <='0';
            elsif kbclk'event and kbclk='1'
            then if costate = "00" and start = '1' and kbdata='0'
                 then swto02<='1';
                 end if;
            end if;
       end process;
chste: process(reset,sysclk,costate,swto02)
       begin 
            if reset = '1' then costate <= "00";
            elsif sysclk'event and sysclk = '1'
            then if swto02 = '1' then costate<="01";
                 elsif cnt8 = 9 then costate <="10";
                 end if;
            end if;
       end process;
recv:  process(reset,kbclk,kbdata,costate)
       begin
           if reset ='1'
           then cnt8 <= 0;
                spdata<="000000000";
           elsif kbclk'event and kbclk = '0'
           then  if costate="01"
                 then if cnt8 /= 9
                      then spdata(7 downto 0) <= spdata(8 downto 1);
                           spdata(8) <= kbdata;
                           cnt8 <= cnt8 +1;
                      end if;
                 end if;
           end if;
       end process;
rxde:  process(reset,kbclk,recven,costate)
       begin 
            if reset = '1' then dtoe <= '0';
            elsif kbclk'event and kbclk ='1'
            then if cnt8 = 9 and costate = "01" then dtoe <= '1';
                 end if;
            end if;
       end process;
parity <= spdata(8);
pdata  <= spdata(7 downto 0);
end;