Method and apparatus for protecting internal memory from external access. A method for protecting a memory space from external access is provided. A plurality of lock bits are stored in a location in memory, each associated with a separate logical portion of the memory space and determinative as to the access thereof for a predetermined operation thereon. a request is then detected for access to a location in the memory space for operating thereon. The requested operation is then compared with the associated lock bit in the associated logical portion and then it is determined if access is allowed for the requested operation. If allowed, the requested operation is performed.