-- M68008 Address Decoder

-- Address decoder for the m68008

-- asbar must be '0' to enable any output

-- csbar(0) : X"00000" to X"01FFF"

-- csbar(1) : X"40000" to X"43FFF"

-- csbar(2) : X"08000" to X"0AFFF"

-- csbar(3) : X"E0000" to X"E01FF"

library ieee;

use ieee.std_logIC_1164.all;

entity addrdec is

        port(

        asbar : in std_logic;

        address : in std_logic_vector(19 downto 0);

        csbar : out std_logic_vector(3 downto 0)

        );

end entity addrdec;

architecture v1 of addrdec is

begin

        csbar(0) <= '0' when

                ((asbar  = '0') and

                ((address >=  X"00000") and (address <=  X"01FFF")))

                else '1';

        csbar(1) <= '0' when

                ((asbar  = '0') and

                ((address >=  X"40000") and (address <=  X"43FFF")))

                else '1';

        csbar(2) <= '0' when

                ((asbar  = '0') and

                ((address >=  X"08000") and (address <=  X"0AFFF")))

                else '1';

        csbar(3) <= '0' when

                ((asbar  = '0') and

                ((address >=  X"E0000") and (address <=  X"E01FF")))

                else '1';                                                                                                                                         

end architecture v1;