process (dataRX)
    variable overflow1, overflow2 : integer;

    begin
        upper <= conv_integer(unsigned(dataRx(7 downto 4)));
        lower <= conv_integer(unsigned(dataRx(3 downto 0)));

        if lower > 9 then
            lower <= lower - 10;
            overflow1 := 1;
        else
            overflow1 := 0;
        end if;

        if upper > 9 then
            upper <= upper - 10 + overflow1;
            overflow2 := 1;
        else
            upper <= upper + overflow1;
            overflow2 := 0;
        end if;

        digit1 <= conv_std_logic_vector(lower, 4);
        digit2 <= conv_std_logic_vector(upper, 4);
        digit3 <= conv_std_logic_vector(overflow2, 4);
    end process;