The present invention provides a data processing apparatus and method for merging secure and non-secure data. This allows an arrangement of the contact openings to be achieved with optimal space utilization, allowing a narrow structural form. The negative resistance circuit includes a differential amplifying circuit having two transistors emitters of which are connected in common, and a low output impedance circuit such as an emitter follower. The terminal continues the communication of the packet data, while the channel occupying signal is active, determines whether the base station receives the communicated packet data, and ends the process for communicating the packet data if the base station receives the communicated packet data.