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-- Copyright (C) 2002 Morgan Kaufmann Publishers, Inc
-- This file is part of VESTs (Vhdl tESTs).
-- VESTs 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.
-- VESTs 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 VESTs; if not, write to the Free Software Foundation,
-- Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
package resolved is
type std_ulogic is ('U', 'X', '0', '1', 'Z', 'W', 'L', 'H', '-');
type std_ulogic_vector is array ( natural range <> ) of std_ulogic;
function resolved ( s : std_ulogic_vector ) return std_ulogic;
end package resolved;
package body resolved is
-- code from book
type stdlogic_table is array (std_ulogic, std_ulogic) of std_ulogic;
constant resolution_table : stdlogic_table :=
-- ---------------------------------------------
-- 'U', 'X', '0', '1', 'Z', 'W', 'L', 'H', '-'
-- ---------------------------------------------
( ( 'U', 'U', 'U', 'U', 'U', 'U', 'U', 'U', 'U' ), -- 'U'
( 'U', 'X', 'X', 'X', 'X', 'X', 'X', 'X', 'X' ), -- 'X'
( 'U', 'X', '0', 'X', '0', '0', '0', '0', 'X' ), -- '0'
( 'U', 'X', 'X', '1', '1', '1', '1', '1', 'X' ), -- '1'
( 'U', 'X', '0', '1', 'Z', 'W', 'L', 'H', 'X' ), -- 'Z'
( 'U', 'X', '0', '1', 'W', 'W', 'W', 'W', 'X' ), -- 'W'
( 'U', 'X', '0', '1', 'L', 'W', 'L', 'W', 'X' ), -- 'L'
( 'U', 'X', '0', '1', 'H', 'W', 'W', 'H', 'X' ), -- 'H'
( 'U', 'X', 'X', 'X', 'X', 'X', 'X', 'X', 'X' ) -- '-'
);
function resolved ( s : std_ulogic_vector ) return std_ulogic is
variable result : std_ulogic := 'Z'; -- weakest state default
begin
if s'length = 1 then
return s(s'low);
else
for i in s'range loop
result := resolution_table(result, s(i));
end loop;
end if;
return result;
end function resolved;
-- end code from book
end package body resolved;
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