ATmega169P datasheet(26/393 Pages) ATMEL

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8018N–AVR–08/09

ATmega169P

7.3.2

EEPROM Write During Power-down Sleep Mode

When entering Power-down sleep mode while an EEPROM write operation is active, the

EEPROM write operation will continue, and will complete before the Write Access time has

passed. However, when the write operation is completed, the clock continues running, and as a

consequence, the device does not enter Power-down entirely. It is therefore recommended to

verify that the EEPROM write operation is completed before entering Power-down.

7.3.3

Preventing EEPROM Corruption

During periods of low V

CC, the EEPROM data can be corrupted because the supply voltage is

too low for the CPU and the EEPROM to operate properly. These issues are the same as for

board level systems using 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. Sec-

ondly, the CPU itself can execute instructions incorrectly, if the supply voltage is too low.

EEPROM data corruption can easily be avoided by following this design recommendation:

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 detection level of the internal

BOD does not match the needed detection level, an external low V

CC reset Protection circuit can

be used. If a reset occurs while a write operation is in progress, the write operation will be com-

pleted provided that the power supply voltage is sufficient.

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