This is when a defect occurs by chance in a memory cell during normal operation, resulting in memory corruption. There are limitations on the number of times an EEPROM memory cell can be rewritten. ROHM guarantees the highest number of rewrites: 1 million times. Companies normally do not normally guarantee a chance defect will not occur within a number of times - they only confirm that all bits are normal at shipping. ROHM has developed double-cell construction to reduce the rate of chance defects for greater data reliability.