-- Copyright © 1993 by  McGraw-Hill, Inc. and Zainalabedin Navabi

-- FIGURE 5.1 




-- ENTITY DECLARATION OF BIT COMPARATOR :

ENTITY bit_comparator IS
  PORT (a, b,                -- data inputs
        gt,                  -- previous greater than
        eq,                  -- previous equal
        lt : IN BIT;         -- previous less than
        a_gt_b,              -- greater
        a_eq_b,              -- equal 
        a_lt_b : OUT BIT);   -- less than 
END bit_comparator;
--



-- FUNCTIONAL ARCHITECTURE OF BIT COMPARATOR :

ARCHITECTURE functional OF bit_comparator IS
  FUNCTION fgl (w, x, gl : BIT) RETURN BIT IS
  BEGIN
    RETURN  (w AND gl) OR (NOT x  AND  gl) OR (w  AND  NOT x);
  END fgl;
  FUNCTION feq (w, x, eq : BIT) RETURN BIT IS
  BEGIN
    RETURN  (w AND x AND eq) OR (NOT w  AND  NOT x  AND  eq);
  END feq;
BEGIN 
  a_gt_b <= fgl (a, b, gt) AFTER 12 NS;
  a_eq_b <= feq (a, b, eq) AFTER 12 NS;
  a_lt_b <= fgl (b, a, lt) AFTER 12 NS;
END functional;
--