Subversion Repositories idea

--Nama file : count2x.fsm

--Deskripsi : counter 2 bit

--Author    : Mas Adit

--Tanggal  : 31 Agustus 2001

entity count2x is

port (

        clk : in bit;

        rst : in bit;

       q : out bit_vector(1 downto 0);

       vdd : in bit;

       vss : in bit

      );

end count2x;

architecture STATE_MACHINE of count2x is

type STATE_TYPE IS (S0, S1, S2, S3);

-- pragma CLOCK clk

-- pragma CURRENT_STATE CURRENT_STATE

-- pragma NEXT_STATE NEXT_STATE

signal CURRENT_STATE, NEXT_STATE: STATE_TYPE;

begin

  process ( CURRENT_STATE, rst )

    begin

      if ( rst = '1' ) then

          NEXT_STATE <= S0;

          q <= "00";

      else

          case CURRENT_STATE IS

             when S0 =>

                q <= "00";

                NEXT_STATE <= S1;

             when S1 =>

                q <= "01";

                NEXT_STATE <= S2;

             when S2 =>

                q <= "10";

                NEXT_STATE <= S3;

             when S3 =>

                q <= "11";

                NEXT_STATE <= S0;

             when OTHERS =>

                assert ( '1' )

                report "Illegal State";

          end case;

      end if;

end process;

process (clk)

  begin

    if ((clk = '1') and not (clk'STABLE)) then

         CURRENT_STATE <= NEXT_STATE;

    end if;

end process;

end STATE_MACHINE;