Data is written to the EEPROM by passing electrons through a tunnel-oxide film. This process places a significant amount of stress on the film, which can lead to erosion and eventual memory bit failures that prevent data from being written to the cells. To avoid this, ROHM utilizes a unique double cell structure that allocates two cells for each bit of data. Consequently, if one cell malfunctions the other will continue to work independently and thus acts as a backup.