An electronic control unit has a microcomputer and a backup RAM, which stores its data irrespective of ON/OFF of an engine ignition switch. The backup RAM stores a main data in its storage area, and two checkup data in its storage areas, respectively. The two checkup data are calculated as a two-byte...http://www.google.de/patents/US7181645?utm_source=gb-gplus-sharePatent US7181645 - Method and apparatus for storing main data with two checkup data
