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------------------------------------------------------------------------------
-- ____ _____________ __ --
-- / __ \/ ____/ ___/\ \/ / _ _ _ --
-- / / / / __/ \__ \ \ / / \ / \ / \ --
-- / /_/ / /___ ___/ / / / = ( M | S | K )= --
-- /_____/_____//____/ /_/ \_/ \_/ \_/ --
-- --
------------------------------------------------------------------------------
--! @copyright Copyright 2020-2022 DESY
--! SPDX-License-Identifier: CERN-OHL-W-2.0
------------------------------------------------------------------------------
--! @date 2020-10-02/2022-04-01
--! @author Lukasz Butkowski <lukasz.butkowski@desy.de>
--! @author Michael Buechler <michael.buechler@desy.de>
------------------------------------------------------------------------------
--! @brief
--! Provides math function/procedures with signed signals
------------------------------------------------------------------------------
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
library work;
use work.math_utils.all;
use work.logic_misc.all;
package math_signed is
--! Saturate *arg* to the maximum or minimum representable value depending on
--! sat
function f_saturate (arg : signed; sat : t_saturation) return signed;
--! Resize with saturation protection
function f_resize_sat (arg : signed; length : positive) return signed;
--! Resize with saturation protection and saturation flag
--! Like the <<f_resize_sat>> function but also sets an overflow bit.
--! To be able to combine this with another preceding operation like shift_right
--! in a process, the argument 'arg' must be a variable instead of a signal.
procedure prd_resize_sat (
signal arg : in signed;
constant length : in positive;
signal result : out signed;
signal sat : out t_saturation
);
end package math_signed;
--******************************************************************************
package body math_signed is
function f_saturate (arg : signed; sat : t_saturation) return signed is
begin
if (sat = ST_SAT_OVERFLOWN) then
return f_max_val_of(arg);
elsif (sat = ST_SAT_UNDERFLOWN) then
return f_min_val_of(arg);
else
return arg;
end if;
end function f_saturate;
function f_resize_sat (arg : signed; length : natural) return signed is
variable var_result : signed(length - 1 downto 0);
begin
prd_resize_sat(arg => arg, length => length, result => var_result);
return var_result;
end function;
procedure prd_resize_sat (
signal arg : in signed;
constant length : in positive;
signal result : out signed;
signal sat : out t_saturation
) is
variable var_sat : t_saturation;
begin
if (length >= arg'length) then
var_sat := ST_SAT_OK;
else
-- check overflow saturation
if (arg(arg'high) = '0' and
f_all_zeroes(arg(arg'high-1 downto length - 1)) = '0') then
var_sat := ST_SAT_OVERFLOWN;
-- check underflow saturation
elsif (arg(arg'high) = '1' and
f_all_ones(arg(arg'high-1 downto length - 1)) = '0') then
var_sat := ST_SAT_UNDERFLOWN;
else
var_sat := ST_SAT_OK;
end if;
result <= f_saturate(resize(arg, length), var_sat);
sat <= var_sat;
end if;
end procedure prd_resize_sat;
end package body math_signed;
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