LIBRARY ieee;
USE ieee.std_logic_1164.ALL;
ENTITY demux4chan IS
	PORT(
		I, S0, S1, nE		: IN	STD_LOGIC;
		O0, O1, O2, O3		: OUT	STD_LOGIC);
END demux4chan;

ARCHITECTURE a OF demux4chan IS
	SIGNAL input: STD_LOGIC_VECTOR (3 DOWNTO 0);
	SIGNAL output: STD_LOGIC_VECTOR (3 DOWNTO 0);
BEGIN
 --  Concurrent Signal Assignment
 input (3) <= nE;
 input (2) <= I;
 input (1) <= S1;	
 input (0) <= S0;

 --  Selected Signal Assignment
 WITH input SELECT
	output <= 	"0001" WHEN "0100",
				"0010" WHEN "0101",
				"0100" WHEN "0110",
				"1000" WHEN "0111",
				
				"0000" WHEN others;

 O3	<=	output(3);
 O2	<=	output(2);
 O1	<=	output(1);
 O0	<=	output(0);
	
END a;