AN2540 - Application note

Conclusion

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Conclusion

The external EEPROM can be replaced by an emulated EEPROM using the on-chip Flash

memory of STR91xFxx devices. With the shorter Flash memory write access time, critical

parameters are stored faster into the emulated EEPROM than into an external serial

EEPROM. However, because the Flash memory needs to be erased before being written,

some form of software management is required to store data into the emulated EEPROM.

Two methods are used to implement an emulated EEPROM: both require a minimum of two

Flash memory sectors of identical size, allocated to non-volatile data. One that is initially

erased and can be programmed byte by byte, and the other that is ready to take over when

the first sector needs to be garbage-collected.

The emulated EEPROM can be used in embedded applications where non-volatile data

storage is required, with a byte, half-word or word granularity. The STR91xFxx on-chip Flash

memory allows 16-bit, half-word programming. Data can however be programmed by bytes

or words by using some software techniques.

For write-intensive applications that use more than two sectors (3 or 4) for the emulated

EEPROM, it is recommended to implement a wear-leveling algorithm to monitor and

distribute the number of write cycles among the sectors.