LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.all;
USE  IEEE.STD_LOGIC_ARITH.all;
USE  IEEE.STD_LOGIC_UNSIGNED.all;

-- Hexadecimal to 7 Segment Decoder for LED Display

ENTITY dec_7seg IS
	
	PORT(hex_digit						: IN	STD_LOGIC_VECTOR(3 DOWNTO 0);
		 segment_a, segment_b, segment_c, segment_d, segment_e, 
		 segment_f, segment_g 			: OUT std_logic);

END dec_7seg;

ARCHITECTURE a OF dec_7seg IS
	SIGNAL segment_data : STD_LOGIC_VECTOR(6 DOWNTO 0);

BEGIN
	PROCESS  (Hex_digit)
		-- HEX to 7 Segment Decoder for LED Display
	BEGIN
		-- Hex-digit is the four bit binary value to display in hexadecimal
	  CASE Hex_digit IS
         WHEN "0000" =>
             segment_data <= "1111110";
         WHEN "0001" =>
             segment_data <= "0110000";
         WHEN "0010" =>
             segment_data <= "1101101";
         WHEN "0011" =>
             segment_data <= "1111001";
         WHEN "0100" =>
             segment_data <= "0110011";
       	 WHEN "0101" =>
             segment_data <= "1011011";
       	 WHEN "0110" =>
             segment_data <= "1011111";
    	 WHEN "0111" =>
             segment_data <= "1110000";
 	     WHEN "1000" =>
             segment_data <= "1111111";
     	 WHEN "1001" =>
             segment_data <= "1111011"; 
         WHEN "1010" =>
             segment_data <= "1110111";
       	 WHEN "1011" =>
             segment_data <= "0011111"; 
       	 WHEN "1100" =>
             segment_data <= "1001110"; 
       	 WHEN "1101" =>
       		 segment_data <= "0111101"; 
      	 WHEN "1110" =>
      	     segment_data <= "1001111"; 
      	 WHEN "1111" =>
      	     segment_data <= "1000111"; 
	   	 WHEN OTHERS =>
        	 segment_data <= "0111110";
	  END CASE;

	END PROCESS;

		-- extract segment data bits and invert
		-- LED driver circuit is inverted
	segment_a <= 	NOT segment_data(6);
	segment_b <= 	NOT segment_data(5);
	segment_c <= 	NOT segment_data(4);
	segment_d <= 	NOT segment_data(3);
	segment_e <= 	NOT segment_data(2);
	segment_f <= 	NOT segment_data(1);
	segment_g <= 	NOT segment_data(0);

END a;