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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
library ieee; use ieee.std_logic_1164.all;
library ieee_proposed; use ieee_proposed.electrical_systems.all;
entity dac_12_bit is
port ( signal bus_in : in std_ulogic_vector (11 downto 0);
terminal analog_out : electrical );
end entity dac_12_bit;
----------------------------------------------------------------
architecture behavioral of dac_12_bit is
constant v_max : real := 3.3;
signal s_out : real := 0.0;
quantity v_out across i_out through analog_out to electrical_ref;
begin
convert : process ( bus_in ) is
variable sum : natural;
begin
sum := 0;
for i in bus_in'range loop
sum := sum * 2 + boolean'pos( bus_in(i) = '1' or bus_in(i) = 'H' );
end loop;
s_out <= v_max * real(sum) / real(2**12 - 1);
end process convert;
v_out == s_out'ramp(1.0E-6);
end architecture behavioral;
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