EEPROM

EEPROM (also E2PROM) stands for electrically erasable programmable read-only memory and is a type of non-volatile memory used in computers, integrated in microcontrollers for smart cards and remote keyless systems, and other electronic devices to store relatively small amounts of data but allowing individual bytes to be erased and reprogrammed. EEPROM (also E2PROM) stands for electrically erasable programmable read-only memory and is a type of non-volatile memory used in computers, integrated in microcontrollers for smart cards and remote keyless systems, and other electronic devices to store relatively small amounts of data but allowing individual bytes to be erased and reprogrammed. EEPROMs are organized as arrays of floating-gate transistors. EEPROMs can be programmed and erased in-circuit, by applying special programming signals. Originally, EEPROMs were limited to single byte operations, which made them slower, but modern EEPROMs allow multi-byte page operations. An EEPROM has a limited life for erasing and reprogramming, now reaching a million operations in modern EEPROMs. In an EEPROM that is frequently reprogrammed while the computer is in use, the life of the EEPROM is an important design consideration. Flash memory is a type of EEPROM designed for high speed and high density, at the expense of large erase blocks (typically 512 bytes or larger) and limited number of write cycles (often 10,000). There is no clear boundary dividing the two, but the term 'EEPROM' is generally used to describe non-volatile memory with small erase blocks (as small as one byte) and a long lifetime (typically 1,000,000 cycles). Many microcontrollers include both: flash memory for the firmware, and a small EEPROM for parameters and history. In early 1970s, some studies, inventions, and development for electrically re-programmable non-volatile memories were performed by various companies and organizations.In 1971, the earliest research report was presented at the 3rd Conference on Solid State Devices, Tokyo in Japan by Yasuo Tarui, Yutaka Hayashi, and Kiyoko Nagai at Electrotechnical Laboratory; a Japanese national research institute.They fabricated an EEPROM device in 1972, and continued this study for more than 10 years.These papers have been repeatedly cited by later papers and patents. One of their research includes MONOS (metal-oxide-nitride-oxide-semiconductor) technology,which is used Renesas Electronics' flash memory integrated in single-chip microcontrollers. In 1972, a type of electrically re-programmable non-volatile memory was invented by Fujio Masuoka at Toshiba, who is also known as the inventor of flash memory.Most of major semiconductor manufactures, such asToshiba,Sanyo (later, ON Semiconductor),IBM,Intel,NEC (later, Renesas Electronics),Philips (later, NXP Semiconductors),Siemens (later, Infineon Technologies),Honeywell (later, Atmel),Texas Instruments,studied, invented, and manufactured some electrically re-programmable non-volatile devices until 1977. The theoretical basis of these devices is Avalanche hot-carrier injection. But in general, programmable memories, including EPROM, of early 1970s had reliability problems such as the data retention periods and the number of erase/write cycle endurance. In 1975, NEC's semiconductor operations unit, later NEC Electronics, currently Renesas Electronics, applied the trademark name EEPROM® to Japan Patent Office.In 1978, this trademark right is granted and registered as No.1,342,184 in Japan, and still survives as of March 2018. In February 1977, Eliyahou Harari at Hughes Aircraft Company invented a new EEPROM technology using Fowler-Nordheim tunnelling through a thin silicon dioxide layer between the floating-gate and the wafer. Hughes went on to produce this new EEPROM devices.But this patentcited NEC's EEPROM® invention.