Need advice about coding style

An another comment on coding style - the conv_std_logic_vector and conv_integer functions come from the non-standard std_logic_unsigned and std_logic_arith packages. You shouldnt use them, as they are non-standard. You should use the numeric_std package instead. (and probably use appropriate types to avoid type conversion as much as possible - you can use non-std_logic_vector types in ports - like unsigned or signed type.).