-- This is an implementation of -*- vhdl -*- ieee.std_logic_1164 based only
-- on the specifications. This file is part of GHDL.
-- Copyright (C) 2015 Tristan Gingold
--
-- This program is free software: you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation, either version 2 of the License, or
-- (at your option) any later version.
--
-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-- GNU General Public License for more details.
--
-- You should have received a copy of the GNU General Public License
-- along with this program. If not, see <gnu.org/licenses>.
package std_logic_1164 is
-- Unresolved logic state.
type std_ulogic is
(
'U', -- Uninitialized, this is also the default value.
'X', -- Unknown / conflict value (forcing level).
'0', -- 0 (forcing level).
'1', -- 1 (forcing level).
'Z', -- High impedance.
'W', -- Unknown / conflict (weak level).
'L', -- 0 (weak level).
'H', -- 1 (weak level).
'-' -- Don't care.
);
-- Vector of logic state.
type std_ulogic_vector is array (natural range <>) of std_ulogic;
-- Resolution function.
-- If S is empty, returns 'Z'.
-- If S has one element, return the element.
-- Otherwise, 'U' is the strongest.
-- then 'X'
-- then '0' and '1'
-- then 'W'
-- then 'H' and 'L'
-- then 'Z'.
function resolved (s : std_ulogic_vector) return std_ulogic;
-- Resolved logic state.
subtype std_logic is resolved std_ulogic;
-- Vector of std_logic.
type std_logic_vector is array (natural range <>) of std_logic;
-- Subtypes of std_ulogic. The names give the values.
subtype X01 is resolved std_ulogic range 'X' to '1';
subtype X01Z is resolved std_ulogic range 'X' to 'Z';
subtype UX01 is resolved std_ulogic range 'U' to '1';
subtype UX01Z is resolved std_ulogic range 'U' to 'Z';
-- Logical operators.
-- For logical operations, the inputs are first normalized to UX01:
-- 0 and L are normalized to 0, 1 and 1 are normalized to 1, U isnt changed,
-- all other states are normalized to X.
-- Then the classical electric rules are followed.
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;
-- Logical operators for vectors.
-- An assertion of severity failure fails if the length of L and R aren't
-- equal. The result range is 1 to L'Length.
function "and" (l, r : std_logic_vector) return std_logic_vector;
function "nand" (l, r : std_logic_vector) return std_logic_vector;
function "or" (l, r : std_logic_vector) return std_logic_vector;
function "nor" (l, r : std_logic_vector) return std_logic_vector;
function "xor" (l, r : std_logic_vector) return std_logic_vector;
function "xnor" (l, r : std_logic_vector) return std_logic_vector;
function "not" (l : std_logic_vector) return std_logic_vector;
function "and" (l, r : std_ulogic_vector) return std_ulogic_vector;
function "nand" (l, r : std_ulogic_vector) return std_ulogic_vector;
function "or" (l, r : std_ulogic_vector) return std_ulogic_vector;
function "nor" (l, r : std_ulogic_vector) return std_ulogic_vector;
function "xor" (l, r : std_ulogic_vector) return std_ulogic_vector;
function "xnor" (l, r : std_ulogic_vector) return std_ulogic_vector;
function "not" (l : std_ulogic_vector) return std_ulogic_vector;
-- Conversion functions.
-- The result range (for vectors) is S'Length - 1 downto 0.
-- XMAP is return for values not in '0', '1', 'L', 'H'.
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;
-- Normalization.
-- The result range (for vectors) is 1 to S'Length.
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.
-- An edge is detected in case of event on s, and X01 normalized value
-- rises from 0 to 1 or falls from 1 to 0.
function rising_edge (signal s : std_ulogic) return boolean;
function falling_edge (signal s : std_ulogic) return boolean;
-- Test for unknown. Only 0, 1, L and H are known values.
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;