Control system with improved protective ability for external program code

摘要

PURPOSE: A control system for protecting an external program code is provided to offer a suitable MCU(Micro Controller Unit) to protect the data of an external ROM installed to the outside. CONSTITUTION: The system includes the MCU(20) and the external ROM(21) encrypting and storing the program code of the MCU(20). A non-encryption part(20c) converts the encrypted program code transmitted from the external ROM(21) into the code of the MCU(20). The encrypted program code includes the code reordering the program code of the MCU(20) by a byte, a word, or a double word unit. The non-encryption part(20c) includes a bit-reorder logic converting the reordered code into the original program code. An external ROM interface(20b) transfers the non-encrypted program code provided from the non-encryption part(20c) to an internal code bus(20d). An instruction register(20a) stores the program code provided from the internal code bus(20d).