FlashEEPROM

FlashEEPROM is a technique for providing EEPROM-like nonvolatile storage using flash memory. In many microcontrollers, EEPROM is separate or limited, while flash memory offers larger capacity but requires block erases. FlashEEPROM presents a byte-addressable interface by organizing a portion of flash to store data in a way that emulates conventional EEPROM behavior.

Most implementations reserve a dedicated area of flash and use a write mechanism that resembles a log. A common approach is a two-phase process: append new records containing an address and its data to an active flash page, and when the page fills, consolidate the latest values into a new page and erase the old one. This approach provides wear leveling by distributing writes across flash cells and extending overall life.

Reading data typically involves locating the most recent record for a given address within the active page, possibly supplemented by an in-memory cache for speed. Erase operations are relatively costly, and writes may be interrupted by power loss. To mitigate risk, many designs include features such as redundant records, checksums, or atomic update schemes and recovery routines to restore a consistent state after power failure.

Advantages of FlashEEPROM include providing nonvolatile, configuration-style storage without a dedicated EEPROM, and enabling larger or more flexible storage footprints on devices that lack true EEPROM. Limitations include the complexity of the emulation layer, potential slower write performance, and the need for wear leveling to avoid premature flash wear.

Applications commonly involve storing configuration data, calibration values, and small logs in embedded systems where hardware EEPROM is unavailable or insufficient.