If cops want to arrest you, they can always book you for something. It might not stick, but they can arrest you for it. Just like cops must have a reasonable cause to pull someone over, if they suspect them of having something they shouldn't (pot, drugs, etc.), they can pull the "broken headlight" routine.
For this, assault is the non-physical part of "assault-and-battery". But, once again, I don't know the details, but cops can arrest and book someone for basically whatever they want.
The old "disorderly conduct" charge can darn near be anything. Yell, "disrespect to a police officer", cursing, etc. All those can be disorderly conduct for arrest purposes. But, then you have the DA decide if he is going to push it.