------------------------------------------------------------------------------
--
-- This package was developed by CAD Language Systems, Inc. as part of an
-- effort to define a basis for portable VHDL models.  It has been submitted
-- to the VHDL Design Exchange Group (VDEG) to be considered as the basis for
-- a set of industry-wide, portable modeling conventions.
--
-- This package defines a four-valued logic type that can be supported on
-- many subset simulators.
--
-- HISTORY:
--	11-MAY-89 PJM	Updated to reflect May 9-10 VDEG consensus.
--	15-APR-89 WAG	Created.
--
------------------------------------------------------------------------------


library VDEG_Portable;	-- This library is where the package goes
package Types is

 -- Portable multi-valued logic bit:

    type Logic4 is ('X', '0', '1', 'Z');

    subtype LX01 is Logic4 range 'X' to '1';


 -- Portable multi-valued logic bit vector:

    type Vector4 is array (Natural range <>) of Logic4;


 -- Logical operations:

    function "and"  (L, R: Logic4) return Logic4;
    function "nand" (L, R: Logic4) return Logic4;
    function "or"   (L, R: Logic4) return Logic4;
    function "nor"  (L, R: Logic4) return Logic4;
    function "xor"  (L, R: Logic4) return Logic4;
    function "not" (Value: Logic4) return Logic4;

    function "and"  (L, R: Vector4) return Vector4;
    function "nand" (L, R: Vector4) return Vector4;
    function "or"   (L, R: Vector4) return Vector4;
    function "nor"  (L, R: Vector4) return Vector4;
    function "xor"  (L, R: Vector4) return Vector4;
    function "not" (Value: Vector4) return Vector4;


 -- Comparison operations returning Logic4:

    function  "=" (L, R: Logic4) return Logic4;
    function "/=" (L, R: Logic4) return Logic4;

    function  "=" (L, R: Vector4) return Logic4;
    function "/=" (L, R: Vector4) return Logic4;


 -- Resolution functions for wired signals:

    function WiredX   (V: Vector4) return Logic4;
    function WiredAnd (V: Vector4) return Logic4;
    function WiredOr  (V: Vector4) return Logic4;


 -- Definitions for wired scalar signals:

    subtype DotX   is WiredX   Logic4;
    subtype DotAnd is WiredAnd Logic4;
    subtype DotOr  is WiredOr  Logic4;


 -- Definitions for wired vector signals:

    type BusX   is array (Natural range <>) of DotX;
    type BusAnd is array (Natural range <>) of DotAnd;
    type BusOr  is array (Natural range <>) of DotOr;


 -- Definitions for driving various types:

    function Drive (V: Logic4)  return Logic4;
    function Drive (V: Vector4) return Vector4;
    function Drive (V: Vector4) return BusX;
    function Drive (V: Vector4) return BusAnd;
    function Drive (V: Vector4) return BusOr;


 -- Functions for sensing various types:

    function Sense (V: Logic4;  vZ: LX01) return Logic4;
    function Sense (V: Vector4; vZ: LX01) return Vector4;
    function Sense (V: BusX;    vZ: LX01) return Vector4;
    function Sense (V: BusAnd;  vZ: LX01) return Vector4;
    function Sense (V: BusOr;   vZ: LX01) return Vector4;


 -- Portable matrix type for memory:

    type Matrix4 is array (Natural range <>, Natural range <>) of Logic4;

end Types;