a master controller for an rram subsystem . an interface communicates with at least one rram controller . a main control unit selects and implements test and repair operations on the rram subsystem through the rram controller . a timer determines a maximum number of test and repair operations that can be implemented within a given time . thus , a master controller is included in the rram subsystem . the master controller has a relatively simple interface , and performs test and repair operations on the rram subsystem . the advantages of using the master controller include an elimination of additional test ports , simplification of the process of preparing the test vectors for rram testing , and the master controller is able to accumulate test results and initiate repairs based on those results . in this manner , the rram subsystem has a self - repair functionality .