-- Decode binary input to seven segment

-- Library Declaration
library ieee;
use ieee.std_logic_1164.all;

-- input: A binary number which has the range from "0000" to "1001, 
--	  i.e. 0 to 9.  
-- led: 7-bit output for the 7-bit LED segment.

entity decoder is 
	port (
		input: in std_logic_vector(3 downto 0);
		led: out std_logic_vector(6 downto 0)
	);
end decoder;

architecture behaviour of decoder is

begin

	decode : process(input)
	begin
		if input = "0000" then
			led(6) <= '0';
			led(5) <= '0';
			led(4) <= '0';
			led(3) <= '0';
			led(2) <= '0';
			led(1) <= '0';		
			led(0) <= '1';

		elsif input = "0001" then
			led(6) <= '1';
			led(5) <= '0';
			led(4) <= '0';
			led(3) <= '1';
			led(2) <= '1';
			led(1) <= '1';		
			led(0) <= '1';

		elsif input = "0010" then
			led(6) <= '0';
			led(5) <= '0';
			led(4) <= '1';
			led(3) <= '0';
			led(2) <= '0';
			led(1) <= '1';		
			led(0) <= '0';

		elsif input = "0011" then
			led(6) <= '0';
			led(5) <= '0';
			led(4) <= '0';
			led(3) <= '0';
			led(2) <= '1';
			led(1) <= '1';		
			led(0) <= '0';

		elsif input = "0100" then
			led(6) <= '1';
			led(5) <= '0';
			led(4) <= '0';
			led(3) <= '1';
			led(2) <= '1';
			led(1) <= '0';		
			led(0) <= '0';

		elsif input = "0101" then
			led(6) <= '0';
			led(5) <= '1';
			led(4) <= '0';
			led(3) <= '0';
			led(2) <= '1';
			led(1) <= '0';		
			led(0) <= '0';

		elsif input = "0110" then
			led(6) <= '1';
			led(5) <= '1';
			led(4) <= '0';
			led(3) <= '0';
			led(2) <= '0';
			led(1) <= '0';		
			led(0) <= '0';

		elsif input = "0111" then
			led(6) <= '0';
			led(5) <= '0';
			led(4) <= '0';
			led(3) <= '1';
			led(2) <= '1';
			led(1) <= '1';		
			led(0) <= '1';

		elsif input = "1000" then
			led(6) <= '0';
			led(5) <= '0';
			led(4) <= '0';
			led(3) <= '0';
			led(2) <= '0';
			led(1) <= '0';		
			led(0) <= '0';

		elsif input = "1001" then
			led(6) <= '0';
			led(5) <= '0';
			led(4) <= '0';
			led(3) <= '1';
			led(2) <= '1';
			led(1) <= '0';		
			led(0) <= '0';
		end if;			
	end process decode;
end behaviour;