Do you mean EMP from a nuke device or Microwave EMP from an eBomb?
EMP from nukes will mostly effect electronics connected to long enough conductors to gather sufficient energy. This means anything plugged into a wall outlet, a phone jack or an external antenna. Most battery operated portable electronics will not be effected at all.
eBombs are non-nuke, microwave spectrum energy generating devices using conventional explosives. The energy is generated in the millimeter wavelength range and conductors 1/4 wavelength (one quarter of a milimeter) or longer can collect enough energy to fry microelectronics. eBombs have a city block size effective range and it is very difficult to protect most electronics from them. They are used near hi-value targets such as Radars, Comm centers, Data Centers. Don't be near these areas.
