The Atmel? AT24CS01 and AT24CS02 provides 1024/2048 bits of Serial Electrically Erasable and Programmable Read-only Memory （EEPROM） organized as 128/256 words of 8 bits each. The device is optimized for use in many industrial and commercial applications where low-power and low-voltage operation are essential. The AT24CS01/02 is available in space-saving， 8-lead JEDEC SOIC， 8-lead TSSOP， 8-pad UDFN and 5-lead SOT23 packages and is accessed via a 2-wire serial interface. In addition， both devices fully operate from 1.7V to 5.5V VCC. The AT24CS01/02 provides the additional feature of a factory programmed， guaranteed unique 128-bit serial number， while maintaining all of the traditional features available in the 1-Kbit or 2-Kbit Serial EEPROM. The time consuming step of performing and ensuring true serialization of product on a manufacturing line can be removed from the production flow by employing the CS Series Serial EEPROM. The 128-bit serial number is programmed and permanently locked from future writing during the Atmel production process. Further， this 128-bit location does not consume any of the user read/write area of the 1-Kbit or 2-Kbit Serial EEPROM. The uniqueness of the serial number is guaranteed across the entire CS Series of Serial EEPROMs， regardless of the size of the memory array or the type of interface protocol. This means that as an application‘s needs for memory size or interface protocol evolve in future generations， any previously deployed serial number from any Atmel CS Series Serial EEPROM part will remain valid.