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

entity SC_HEX is
    Port ( sc : in std_logic_vector(7 downto 0);
           prs : in std_logic;
           hex : out std_logic_vector(3 downto 0));
end SC_HEX;

architecture behavioral of SC_HEX is

begin

  process(prs, sc)
  begin
    if (prs'event and prs = '1') then
      case sc is
        when X"70" => hex <= "0000"; -- if keypad 0 is pressed (sc = KP 0) then
                                     -- ouptut hex receives 0000
                                     -- You have to do the other cases for keys "KP 1"
                                     -- to "KP 9" and "A" to "F". 
          
        when others => null;         -- invalid key, ignore it
      end case;
    end if;
  end process;


end behavioral;