Nonvolatile memory implementation for electronic devices

摘要

An automobile has an electronic device with a nonvolatile memory implementation. The electronic device includes non-programmable nonvolatile memory (ROM), volatile memory (RAM) and programmable nonvolatile memory (EEPROM). A controller (CPU) is coupled to and controls reads and writes to and from the ROM, RAM, and EEPROM. When the CPU detects a key-off event it calculates an error recovery code (checksum) for a data string stored in the RAM and stores the checksum and data into one of two memory locations in the EEPROM. The CPU will alternate between the two memory locations each cycle. When the CPU detects a key-on event it calculates the checksum for the data string stored in the RAM. If the data string is invalid or if validity of the EEPROM data cannot be confirmed, then the CPU copies a predetermined data string from the ROM to the RAM. If the CPU determines that the calculated KAM checksum does not equal the stored KAM checksum, then the CPU copies the EEPROM data string to the KAM. Otherwise, the RAM data string remains untouched.