The AT28C040 is a high-performance electrically erasable and programmable readonly memory (EEPROM). Its 4 megabits of memory is organized as 524,288 words by 8 bits. Manufactured with Atmel's advanced nonvolatile CMOS technology, the device offers access times to 200 ns with power dissipation of just 440 mW. The AT28C040 is accessed like a static RAM for the read or write cycle without the need for external components. The device contains a 256-byte page register to allow writing of up to 256 bytes simultaneously. During a write cycle, the address and 1 to 256 bytes of data are internally latched, freeing the address and data bus for other operations. Following the initiation of a write cycle, the device will automatically write the latched data using an internal control timer. The end of a write cycle can be detected by Data Polling of I/O7. Once the end of a write cycle has been detected, a new access for a read or write can begin. Atmel's AT28C040 has additional features to ensure high quality and manufacturability. The device utilizes internal error correction for extended endurance and improved data retention characteristics. An optional software data protection mechanism is available to guard against inadvertent writes. The device also includes an extra 256 bytes of EEPROM for device identification or tracking.