A data processing apparatus according to the present invention includes: peripheral devices each including a plurality of registers each storing a preset value or data; a processing unit to output access authority information indicative of a first access authority level or a second access authority level, which is an access authority level lower than the first access authority level, according to a program to be executed, and to output an access address to specify a specific register; and a peripheral device protection circuit connected to the processing unit and receiving the access authority information and the access address so as to control access of the processing unit to the peripheral devices. The peripheral device protection circuit controls whether to permit the access to the specific register specified by the access address, based on the access authority level indicated by the access authority information.