Abstract: A controller apparatus for utilizing downgrade memory and method for operating the same are proposed. The controller apparatus uses address assignment to access the downgrade memory, which is classified by accessible address after testing. The controller apparatus is applicable to various applications, including memory interface controller for the accessing of a sub system. The controller apparatus can be integrated into the sub system within single chip. The controller apparatus further comprises at least one recording unit to record the initialization format and address mapping relation of a specific downgrade memory. Therefore, controller apparatus can be adapted to access various kinds of downgrade memory designated by the recording unit.