AT90LS4433-4AI datasheet(47/126 Pages) ATMEL

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AT90S/LS4433

1042H–AVR–04/03

Prevent EEPROM

Corruption

During periods of low V

CC, the EEPROM data can be corrupted because the supply volt-

age is too low for the CPU and the EEPROM to operate properly. These issues are the

same as for board-level systems using the EEPROM, and the same design solutions

should be applied.

An EEPROM data corruption can be caused by two situations when the voltage is too

low. First, a regular write sequence to the EEPROM requires a minimum voltage to

operate correctly. Second, the CPU itself can execute instructions incorrectly if the sup-

ply voltage for executing instructions is too low.

EEPROM data corruption can easily be avoided by following these design recommen-

dations (one is sufficient):

Keep the AVR RESET active (low) during periods of insufficient power supply

voltage. This can be done by enabling the internal Brown-out Detector (BOD) if

the operating speed matches the detection level. If not, an external low V

Reset Protection circuit can be applied.

Keep the AVR core in Power-down sleep mode during periods of low V

CC. This

will prevent the CPU from attempting to decode and execute instructions, effec-

tively protecting the EEPROM Registers from unintentional writes.

Store constants in Flash memory if the ability to change memory contents from

software is not required. Flash memory cannot be updated by the CPU and will

not be subject to corruption.

AT90LS4433-4AI Datasheet(PDF) 47 Page - ATMEL Corporation