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-------------------------------------------------------------------------------
-- --
-- X X XXXXXX XXXXXX XXXXXX XXXXXX X --
-- XX XX X X X X X X X XX --
-- X X X X X X X X X X X X --
-- X X X X X X X X X X X X --
-- X X X X XXXXXX X X XXXXXX X --
-- X X X X X X X X X --
-- X X X X X X X X X --
-- X X X X X X X X X X --
-- X X XXXXXX XXXXXX XXXXXX XXXXXX X --
-- --
-- --
-- O R E G A N O S Y S T E M S --
-- --
-- Design & Consulting --
-- --
-------------------------------------------------------------------------------
-- --
-- Web: http://www.oregano.at/ --
-- --
-- Contact: mc8051@oregano.at --
-- --
-------------------------------------------------------------------------------
-- --
-- MC8051 - VHDL 8051 Microcontroller IP Core --
-- Copyright (C) 2001 OREGANO SYSTEMS --
-- --
-- This library is free software; you can redistribute it and/or --
-- modify it under the terms of the GNU Lesser General Public --
-- License as published by the Free Software Foundation; either --
-- version 2.1 of the License, or (at your option) any later version. --
-- --
-- This library 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 --
-- Lesser General Public License for more details. --
-- --
-- Full details of the license can be found in the file LGPL.TXT. --
-- --
-- You should have received a copy of the GNU Lesser General Public --
-- License along with this library; if not, write to the Free Software --
-- Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA --
-- --
-------------------------------------------------------------------------------
--
--
-- Author: Roland Hller
--
-- Filename: dcml_adjust_rtl.vhd
--
-- Date of Creation: Mon Aug 9 12:14:48 1999
--
-- Version: $Revision: 1.4 $
--
-- Date of Latest Version: $Date: 2002-01-07 12:17:44 $
--
--
-- Description: Combinational design to calculate the decimal
-- representation (BCD) of a data bus.
--
--
--
--
-------------------------------------------------------------------------------
architecture rtl of dcml_adjust is
begin -- rtl
p_calc_adjst: process (data_i, cy_i)
variable v_cy : std_logic_vector((DWIDTH-1)/4 downto 0);
variable v_nxtcy : std_logic;
variable v_tmpda : unsigned(DWIDTH downto 0);
variable v_tmpda1 : unsigned(4 downto 0);
variable v_compvl : unsigned(3 downto 0);
begin -- process p_calc_adjst
v_tmpda(DWIDTH-1 downto 0) := unsigned(data_i);
v_tmpda(DWIDTH) := '0';
v_cy := cy_i;
v_nxtcy := '0';
for i in 0 to (DWIDTH-1)/4 loop
if DWIDTH-i*4 <= 4 then
-- Calculate the decimal adjustment of the last nibble/rest of bits
v_compvl := conv_unsigned(0,4);
v_compvl(DWIDTH-1-i*4 downto 0) := v_tmpda(DWIDTH-1 downto i*4);
if (v_cy(i) = '1') or (v_compvl > conv_unsigned(9,4)) then
if DWIDTH-i*4 > 2 then
v_tmpda(DWIDTH downto i*4) := v_tmpda(DWIDTH-1 downto i*4) +
conv_unsigned(6,v_tmpda(DWIDTH downto i*4)'LENGTH);
else
v_tmpda(DWIDTH downto i*4) := v_tmpda(DWIDTH-1 downto i*4) +
conv_unsigned(2,v_tmpda(DWIDTH downto i*4)'LENGTH);
end if;
end if;
-- An already set intermediate carry flag must not be lost.
v_cy(i) := v_tmpda(DWIDTH) or v_cy(i);
else
-- Calculate the decimal adjustment of all nibbles, but the last one.
v_compvl := v_tmpda(i*4+3 downto i*4);
v_tmpda1 := conv_unsigned(0,5);
if (v_cy(i) = '1') or (v_compvl > conv_unsigned(9,4)) then
for j in i to (DWIDTH-1)/4 loop
if DWIDTH-1 > j*4+3 then
-- Calculate all subsequent nibbles from the actual position up
-- to the one before the last.
if j=i then
v_tmpda1 := v_tmpda(j*4+3 downto j*4) +
conv_unsigned(6,5);
v_nxtcy := v_tmpda1(4);
v_tmpda(j*4+3 downto j*4) := v_tmpda1(3 downto 0);
else
v_tmpda1 := v_tmpda(j*4+3 downto j*4) +
conv_unsigned(v_nxtcy,5);
v_nxtcy := v_tmpda1(4);
v_tmpda(j*4+3 downto j*4) := v_tmpda1(3 downto 0);
end if;
-- An already set intermediate carry flag must not be lost.
v_cy(j) := v_tmpda1(4) or v_cy(j);
else
-- Calculate the last nibble.
if j=i then
v_tmpda(DWIDTH downto j*4) := v_tmpda(DWIDTH-1 downto j*4) +
conv_unsigned(6,v_tmpda(DWIDTH downto j*4)'LENGTH);
else
v_tmpda(DWIDTH downto j*4) := v_tmpda(DWIDTH-1 downto j*4) +
conv_unsigned(v_nxtcy,v_tmpda(DWIDTH downto j*4)'LENGTH);
end if;
-- An already set intermediate carry flag must not be lost.
v_cy(j) := v_tmpda(DWIDTH) or v_cy(j);
end if;
end loop; -- j
end if;
end if;
end loop; -- i
-- Generate outputs
cy_o <= v_cy(v_cy'HIGH);
data_o <= std_logic_vector(v_tmpda(DWIDTH-1 downto 0));
end process p_calc_adjst;
end rtl;
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