Write VHDL code for Full Adder using Structural Modeling

3. VHDL code for full adder using structural modeling



Step1: VHDL code for Half Adder:



library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
entity test_HA is
Port ( a : in STD_LOGIC;
b : in STD_LOGIC;
sum : out STD_LOGIC;
cout : out STD_LOGIC);
end test_HA;
architecture data_flow_test of test_HA is
begin
sum<= a xor b;
cout<= a and b;
end data_flow_test;



Step 2: VHDL code for OR gate:



library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
entity test_or is
Port ( p : in STD_LOGIC;
q : in STD_LOGIC;
r : out STD_LOGIC);
end test_or;
architecture data_flow_test of test_or is
begin
r<= p or q;
end data_flow_test;



Step3VHDL code for full adder using structural modeling:



library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
entity test_Full_Adder is
Port ( x : in STD_LOGIC;
y : in STD_LOGIC;
z : in STD_LOGIC;
sum : out STD_LOGIC;cout : out STD_LOGIC);
end test_Full_Adder;
architecture Structural_test of test_Full_Adder is
component test_HA is
Port ( a : in STD_LOGIC;
b : in STD_LOGIC;
sum : out STD_LOGIC;
cout : out STD_LOGIC);
end component;
component test_or is
Port ( p : in STD_LOGIC;
q : in STD_LOGIC;
r : out STD_LOGIC);
end component;
signal sum1,carry1,carry2:STD_LOGIC;
begin
comp1:test_HA port map(x,y,sum1,carry1);
comp2:test_HA port map(sum1,z,sum,carry2);
comp3:test_or port map(carry1,carry2,cout);
end Structural_test;



Test bench Code for Full Adder:



LIBRARY ieee;
USE ieee.std_logic_1164.ALL;
ENTITY tb_test_fa IS
END tb_test_fa;
ARCHITECTURE behavior OF tb_test_fa IS
COMPONENT test_Full_Adder
PORT(
x : IN std_logic;
y : IN std_logic;
z : IN std_logic;
sum : OUT std_logic;
cout : OUT std_logic
);
END COMPONENT;
--Inputs
signal x : std_logic := '0';
signal y : std_logic := '0';
signal z : std_logic := '0';
--Outputs
signal sum : std_logic;
signal cout : std_logic;
-- No clocks detected in port list. Replace <clock> below with
-- appropriate port name
BEGIN
-- Instantiate the Unit Under Test (UUT)
uut: test_Full_Adder PORT MAP (
x => x,
y => y,
z => z,
sum => sum,
cout => cout
);-- Stimulus process
process
begin
x <= '0';
y <= '0';
z <= '0';
wait for 10 ns;
x <= '0';
y <= '0';
z <= '1';
wait for 10 ns;
x <= '0';
y <= '1';
z <= '0';
wait for 10 ns;
x <= '0';
y <= '1';
z <= '1';
wait for 10 ns;
x <= '1';
y <= '0';
z <= '0';
wait for 10 ns;
x <= '1';
y <= '0';
z <= '1';
wait for 10 ns;
x <= '1';
y <= '1';
z <= '0';
wait for 10 ns;
x <= '1';
y <= '1';
z <= '1';
wait for 10 ns;
end process;
END;