std_logic_1164 的包头

library std ;
use std.standard.all ;

PACKAGE std_logic_1164 IS

-------------------------------------------------------------------
-- logic state system (unresolved)
-------------------------------------------------------------------
TYPE std_ulogic IS ( 'U', -- Uninitialized
'X', -- Forcing Unknown
'0', -- Forcing 0
'1', -- Forcing 1
'Z', -- High Impedance
'W', -- Weak Unknown
'L', -- Weak 0
'H', -- Weak 1
'-' -- Don't care
);

-------------------------------------------------------------------
-- Directives for synthesis of std_ulogic.
-- Declare the type encoding attribute and set the value for std_ulogic
-- Directives for the resolution function and all other function are
-- in the package body
-------------------------------------------------------------------
ATTRIBUTE logic_type_encoding : string ;
ATTRIBUTE logic_type_encoding of std_ulogic:type is
-- ('U','X','0','1','Z','W','L','H','-')
('X','X','0','1','Z','X','0','1','X') ;

-------------------------------------------------------------------
-- unconstrained array of std_ulogic for use with the resolution function
-------------------------------------------------------------------
TYPE std_ulogic_vector IS ARRAY ( NATURAL RANGE <> ) OF std_ulogic;

-------------------------------------------------------------------
-- resolution function
-------------------------------------------------------------------
FUNCTION resolved ( s : std_ulogic_vector ) RETURN std_ulogic;

-------------------------------------------------------------------
-- *** industry standard logic type ***
-------------------------------------------------------------------
SUBTYPE std_logic IS resolved std_ulogic;

-------------------------------------------------------------------
-- unconstrained array of std_logic for use in declaring signal arrays
-------------------------------------------------------------------
TYPE std_logic_vector IS ARRAY ( NATURAL RANGE <>) OF std_logic;

-------------------------------------------------------------------
-- common subtypes
-------------------------------------------------------------------
SUBTYPE X01 IS resolved std_ulogic RANGE 'X' TO '1'; -- ('X','0','1')
SUBTYPE X01Z IS resolved std_ulogic RANGE 'X' TO 'Z'; -- ('X','0','1','Z')
SUBTYPE UX01 IS resolved std_ulogic RANGE 'U' TO '1'; -- ('U','X','0','1')
SUBTYPE UX01Z IS resolved std_ulogic RANGE 'U' TO 'Z'; -- ('U','X','0','1','Z')

-------------------------------------------------------------------
-- overloaded logical operators
-------------------------------------------------------------------

FUNCTION "and" ( l : std_ulogic; r : std_ulogic ) RETURN UX01;
FUNCTION "nand" ( l : std_ulogic; r : std_ulogic ) RETURN UX01;
FUNCTION "or" ( l : std_ulogic; r : std_ulogic ) RETURN UX01;
FUNCTION "nor" ( l : std_ulogic; r : std_ulogic ) RETURN UX01;
FUNCTION "xor" ( l : std_ulogic; r : std_ulogic ) RETURN UX01;
FUNCTION "xnor" ( l : std_ulogic; r : std_ulogic ) RETURN UX01;
FUNCTION "not" ( l : std_ulogic ) RETURN UX01;

-------------------------------------------------------------------
-- vectorized overloaded logical operators
-------------------------------------------------------------------
FUNCTION "and" ( l, r : std_logic_vector ) RETURN std_logic_vector;
FUNCTION "and" ( l, r : std_ulogic_vector ) RETURN std_ulogic_vector;

FUNCTION "nand" ( l, r : std_logic_vector ) RETURN std_logic_vector;
FUNCTION "nand" ( l, r : std_ulogic_vector ) RETURN std_ulogic_vector;

FUNCTION "or" ( l, r : std_logic_vector ) RETURN std_logic_vector;
FUNCTION "or" ( l, r : std_ulogic_vector ) RETURN std_ulogic_vector;

FUNCTION "nor" ( l, r : std_logic_vector ) RETURN std_logic_vector;
FUNCTION "nor" ( l, r : std_ulogic_vector ) RETURN std_ulogic_vector;

FUNCTION "xor" ( l, r : std_logic_vector ) RETURN std_logic_vector;
FUNCTION "xor" ( l, r : std_ulogic_vector ) RETURN std_ulogic_vector;

-- -----------------------------------------------------------------------
-- Note : The declaration and implementation of the "xnor" function is
-- specifically commented until at which time the VHDL language has been
-- officially adopted as containing such a function. At such a point,
-- the following comments may be removed along with this notice without
-- further "official" ballotting of this std_logic_1164 package. It is
-- the intent of this effort to provide such a function once it becomes
-- available in the VHDL standard.
-- -----------------------------------------------------------------------
FUNCTION "xnor" ( l, r : std_logic_vector ) RETURN std_logic_vector;
FUNCTION "xnor" ( l, r : std_ulogic_vector ) RETURN std_ulogic_vector;

FUNCTION "not" ( l : std_logic_vector ) RETURN std_logic_vector;
FUNCTION "not" ( l : std_ulogic_vector ) RETURN std_ulogic_vector;

-------------------------------------------------------------------
-- conversion functions
-------------------------------------------------------------------
FUNCTION To_bit ( s : std_ulogic; xmap : BIT := '0') RETURN BIT;
FUNCTION To_bitvector ( s : std_logic_vector ; xmap : BIT := '0') RETURN BIT_VECTOR;
FUNCTION To_bitvector ( s : std_ulogic_vector; xmap : BIT := '0') RETURN BIT_VECTOR;

FUNCTION To_StdULogic ( b : BIT ) RETURN std_ulogic;
FUNCTION To_StdLogicVector ( b : BIT_VECTOR ) RETURN std_logic_vector;
FUNCTION To_StdLogicVector ( s : std_ulogic_vector ) RETURN std_logic_vector;
FUNCTION To_StdULogicVector ( b : BIT_VECTOR ) RETURN std_ulogic_vector;
FUNCTION To_StdULogicVector ( s : std_logic_vector ) RETURN std_ulogic_vector;

-------------------------------------------------------------------
-- strength strippers and type convertors
-------------------------------------------------------------------

FUNCTION To_X01 ( s : std_logic_vector ) RETURN std_logic_vector;
FUNCTION To_X01 ( s : std_ulogic_vector ) RETURN std_ulogic_vector;
FUNCTION To_X01 ( s : std_ulogic ) RETURN X01;
FUNCTION To_X01 ( b : BIT_VECTOR ) RETURN std_logic_vector;
FUNCTION To_X01 ( b : BIT_VECTOR ) RETURN std_ulogic_vector;
FUNCTION To_X01 ( b : BIT ) RETURN X01;

FUNCTION To_X01Z ( s : std_logic_vector ) RETURN std_logic_vector;
FUNCTION To_X01Z ( s : std_ulogic_vector ) RETURN std_ulogic_vector;
FUNCTION To_X01Z ( s : std_ulogic ) RETURN X01Z;
FUNCTION To_X01Z ( b : BIT_VECTOR ) RETURN std_logic_vector;
FUNCTION To_X01Z ( b : BIT_VECTOR ) RETURN std_ulogic_vector;
FUNCTION To_X01Z ( b : BIT ) RETURN X01Z;

FUNCTION To_UX01 ( s : std_logic_vector ) RETURN std_logic_vector;
FUNCTION To_UX01 ( s : std_ulogic_vector ) RETURN std_ulogic_vector;
FUNCTION To_UX01 ( s : std_ulogic ) RETURN UX01;
FUNCTION To_UX01 ( b : BIT_VECTOR ) RETURN std_logic_vector;
FUNCTION To_UX01 ( b : BIT_VECTOR ) RETURN std_ulogic_vector;
FUNCTION To_UX01 ( b : BIT ) RETURN UX01;

-------------------------------------------------------------------
-- edge detection
-------------------------------------------------------------------
FUNCTION rising_edge (SIGNAL s : std_ulogic) RETURN BOOLEAN;
FUNCTION falling_edge (SIGNAL s : std_ulogic) RETURN BOOLEAN;

-------------------------------------------------------------------
-- object contains an unknown
-------------------------------------------------------------------
FUNCTION Is_X ( s : std_ulogic_vector ) RETURN BOOLEAN;
FUNCTION Is_X ( s : std_logic_vector ) RETURN BOOLEAN;
FUNCTION Is_X ( s : std_ulogic ) RETURN BOOLEAN;

END std_logic_1164;