Question

Design in VHDL a 8-1 Multiplexer

Screenshot the simulation and code.

Answer 1

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity multiplexer is
Port (

    din:in STD_LOGIC_VECTOR (7 downto 0);
   sel:in STD_LOGIC_VECTOR (2 downto 0);
   dout : out STD_LOGIC);
end multiplexer;

architecture Behavioral of multiplexer is
begin
    process (din,sel)
    begin
      case sel is
           when "000"=> dout <= din(7);
           when "001"=> dout <= din(6);
           when "010"=> dout <= din(5);
           when "011"=> dout <= din(4);
           when "100"=> dout <= din(3);
           when "101"=> dout <= din(2);
           when "110"=> dout <= din(1);
           when "111"=> dout <= din(0);
           when others=> dout <= din(0);
      end case;
end process;
end Behavioral;

TEST BENCH:

LIBRARY ieee;
USE ieee.std_logic_1164.ALL;
USE ieee.std_logic_unsigned.all;
USE ieee.numeric_std.ALL;

ENTITY tb_multiplexer_vhd IS
END tb_multiplexer_vhd;

ARCHITECTURE behavior OF tb_multiplexer_vhd IS

-- Component Declaration for the Unit Under Test (UUT)
COMPONENT multiplexer
PORT(
din :IN std_logic_vector(7 downto 0);
sel:IN std_logic_vector(2 downto 0);
dout :OUT std_logic
);
END COMPONENT;

--Inputs
SIGNAL din : std_logic_vector(7 downto 0) := (others=>'0');
SIGNAL sel : std_logic_vector(2 downto 0) := (others=>'0');

--Outputs
SIGNAL dout : std_logic;

BEGIN

-- Instantiate the Unit Under Test (UUT)
uut: multiplexer PORT MAP(din => din,
sel => sel,
dout => dout
);

process

         din<= "10100011"; wait for 10ns;

         sel<= "000"; wait for 10ns,

         sel<= "001"; wait for 10ns,

         sel<= "010"; wait for 10ns,

         sel<= "011"; wait for 10ns,

         sel<= "100"; wait for 10ns,

         sel<= "101"; wait for 10ns,

         sel<= "110"; wait for 10ns,

         sel<= "111"; wait for 10ns,

        wait;

end process

END;