Customers want to know the write endurance, given the device has 3 banks of EEPROM. After 50k writes, the next bank of EEPROM is used to store the counter data. But if that same bank was used to continue to store data, you would have the typical EEPROM wear-out condition where a bit or bits would start getting 'burned in' to a particular value and not change. In the DS1682, we know each bank should last for at least 50k writes, so when an internal counter detects that a bank has been written to 50k times, the next write cycle goes to the next bank of EEPROM (transparent to the user) and a 50k counter is started again. Thus with 3 banks, we can guarantee 150k total EEPROM write cycles.