The document describes a VHDL code for an 8-to-1 multiplexer. The multiplexer has 8 inputs, 3 select lines, and 1 output. The VHDL code uses a case statement to select the appropriate input pin to connect to the output pin based on the value on the select lines.

1. 2:4 Decoder
CODE:
LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
ENTITY MUX8_1 IS
PORT(DIN:IN STD_LOGIC_VECTOR(7 DOWNTO 0);SEL:IN STD_LOGIC_VECTOR(2 DOWNTO
0);DOUT:OUT STD_LOGIC);
END MUX8_1;
ARCHITECTURE BEH123 OF MUX8_1 IS
BEGIN
PROCESS(DIN,SEL)
BEGIN
CASE SEL IS
WHEN"000"=>DOUT<=DIN(0);
WHEN"001"=>DOUT<=DIN(1);
WHEN"010"=>DOUT<=DIN(2);
WHEN"011"=>DOUT<=DIN(3);
WHEN"100"=>DOUT<=DIN(4);
WHEN"101"=>DOUT<=DIN(5);
WHEN"110"=>DOUT<=DIN(6);
WHEN"111"=>DOUT<=DIN(7);
WHEN OTHERS=>DOUT<='Z';
END CASE;
END PROCESS;
END BEH123;

2. OUTPUT:

3. 8:1 Multiplexer
CODE:
LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
ENTITY MUX8_1 IS
PORT(DIN:IN STD_LOGIC_VECTOR(7 DOWNTO 0);SEL:IN STD_LOGIC_VECTOR(2 DOWNTO
0);DOUT:OUT STD_LOGIC);
END MUX8_1;
ARCHITECTURE BEH123 OF MUX8_1 IS
BEGIN
PROCESS(DIN,SEL)
BEGIN
CASE SEL IS
WHEN"000"=>DOUT<=DIN(0);
WHEN"001"=>DOUT<=DIN(1);
WHEN"010"=>DOUT<=DIN(2);
WHEN"011"=>DOUT<=DIN(3);
WHEN"100"=>DOUT<=DIN(4);
WHEN"101"=>DOUT<=DIN(5);
WHEN"110"=>DOUT<=DIN(6);
WHEN"111"=>DOUT<=DIN(7);
WHEN OTHERS=>DOUT<='Z';
END CASE;
END PROCESS;
END BEH123;

4. Output:

5. HARDWARE:
Input switches:
J15=I(0)
L16=I(1)
M13=I(2)
R15=I(3)
R17=I(4)
T18=I(5)
U18=I(6)
R13=I(7)
T18=N.A
Select Lines:
U8=S0
R16=S1
T13=S2
Output LED:
H17