The systems and methods disclosed relate to a processor comprising a processing unit and a debugging interface which can be connected to an external emulator for debugging a program executed by the processor, the debugging interface comprising internal resources at least partially accessible to the external emulator. According to one embodiment, the debugging interface comprises a selecting circuit for selecting an internal resource of the debugging interface, according to a reference supplied by the processing unit, and access means for transferring a datum between the resource selected and a data field accessible by the processing unit.