--
-- Title     : (85) 4-Bit Magnitude Comparator
-- File name : 85.vhd
-- Date      : 2000/12/08  Ver1.0
-- Company   : Future Technology Ltd.
--

--use library
library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.std_logic_unsigned.all;
use IEEE.std_logic_arith.all;

--  entity library --
entity U85 is
    port(
        A   : in    std_logic_vector(3 downto 0);
        B   : in    std_logic_vector(3 downto 0);
        IAB : in    std_logic;
        IEQ : in    std_logic;
        IBA : in    std_logic;
        OAB : out   std_logic;
        OEQ : out   std_logic;
        OBA : out   std_logic
        );
end U85;

-- architecture --
architecture U85 of U85 is

-- signal list --
signal  s_ab    :std_logic;
signal  s_eq    :std_logic;
signal  s_ba    :std_logic;


begin

    s_ab    <=  '1' when (A > B) else '0';
    s_eq    <=  '1' when (A = B) else '0';
    s_ba    <=  '1' when (A < B) else '0';

    OAB     <=  s_ab or (s_eq and ((IAB and not IEQ and not IBA) 
                  or (not IAB and not IEQ and not IBA)));
    OEQ     <=  s_eq and IEQ;
    OBA     <=  s_ba or (s_eq and ((not IAB and not IEQ and IBA) 
                  or (not IAB and not IEQ and not IBA)));

end U85;