FLOAT_PKG package declaration

Single-precision (float32) instantiation of FLOAT_GENERIC_PKG.

Use clause: library IEEE;
use IEEE.FLOAT_PKG.all;
Source: ieee/float_pkg.vhdl in the IEEE 1076 OSR, tag 1076-2019
Apache License 2.0, © 2019 IEEE P1076 WG Authors
Length: 55 lines
VHDL revisions: Added in 1076-2008; updated through 1076-2019

Overview

FLOAT_PKG is a single instantiation of FLOAT_GENERIC_PKG at single-precision IEEE-754 (8-bit exponent, 23-bit fraction), with round-nearest rounding, denormals enabled, NaN/overflow processing on, and 3 guard bits. Use it directly for float32 work; instantiate FLOAT_GENERIC_PKG yourself for other precisions (e.g. float64) or different rounding modes.

Per §16.11 of IEEE Std 1076-2019, the instantiation declaration here represents the formal semantics of FLOAT_PKG; the actual operator and conversion bodies live in FLOAT_GENERIC_PKG’s body.

What's defined here

Generic instantiation: float_exponent_width => 8, float_fraction_width => 23, float_round_style => round_nearest, float_denormalize => true, float_check_error => true, float_guard_bits => 3, no_warning => false, fixed_pkg => IEEE.fixed_pkg
Underlying package: FLOAT_GENERIC_PKG - the generic package this is an instantiation of.
Related: FIXED_FLOAT_TYPES (rounding enums), FIXED_PKG (fixed-point peer used internally for some conversions)

VHDL source listing

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File header Comment block (42 lines)

lines 1–42

-- -----------------------------------------------------------------
-- 
-- Copyright 2019 IEEE P1076 WG Authors
-- 
-- See the LICENSE file distributed with this work for copyright and
-- licensing information and the AUTHORS file.
-- 
-- This file to you under the Apache License, Version 2.0 (the "License").
-- You may obtain a copy of the License at
-- 
--     http://www.apache.org/licenses/LICENSE-2.0
-- 
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
-- implied.  See the License for the specific language governing
-- permissions and limitations under the License.
--
--   Title     :  Floating-point package (Instantiated package declaration)
--             :
--   Library   :  This package shall be compiled into a library
--             :  symbolically named IEEE.
--             :
--   Developers:  Accellera VHDL-TC and IEEE P1076 Working Group
--             :
--   Purpose   :  This packages defines basic binary floating point
--             :  arithmetic functions
--             :
--   Note      :  This package may be modified to include additional data
--             :  required by tools, but it must in no way change the
--             :  external interfaces or simulation behavior of the
--             :  description. It is permissible to add comments and/or
--             :  attributes to the package declarations, but not to change
--             :  or delete any original lines of the package declaration.
--             :  The package body may be changed only in accordance with
--             :  the terms of Clause 16 of this standard.
--             :
-- --------------------------------------------------------------------
-- $Revision: 1220 $
-- $Date: 2008-04-10 17:16:09 +0930 (Thu, 10 Apr 2008) $
-- --------------------------------------------------------------------

library ieee;

package float_pkg is new IEEE.float_generic_pkg
  generic map (
    float_exponent_width => 8,    -- float32'high
    float_fraction_width => 23,   -- -float32'low
    float_round_style    => IEEE.fixed_float_types.round_nearest,  -- round nearest algorithm
    float_denormalize    => true,  -- Use IEEE extended floating
    float_check_error    => true,  -- Turn on NAN and overflow processing
    float_guard_bits     => 3,     -- number of guard bits
    no_warning           => false, -- show warnings
    fixed_pkg            => IEEE.fixed_pkg
    );