EEPROM data corruption by power cut off

[Gaku]

I use M24C64-R eeprom. If power is cut off during its write cycle, the data in writing address will become corrupted. In the other hands, will the data out of writing address be kept or become corrupted too?

[Peter BENSCH]

Welcome @Gaku, to the community!

Yes, if the voltage fails during writing to an EEPROM address, the content of this memory address is no longer defined and must be regarded as invalid. For this reason, the capacitance at the VDD of the EEPROM should be dimensioned sufficiently large in the circuit design so that the write process is terminated cleanly. Parallel to this, it makes sense to have a voltage monitor that continuously checks the VDD of the EEPROM and only allows write operations if the buffer capacity guarantees a successful write.

Do you mean by your question whether the read data is corrupted when reading at an address and simultaneous power failure?
Well, this is actually irrelevant, because in the event of a power failure, the reading MCU or CPU can also no longer work. A power failure has no effect on the data of the EEPROM itself. Once they are successfully written, they remain until they are erased or overwritten.

I hope I have answered your question?

Regards /Peter

[Gaku]

Thank you very much for your replying!  I understood well the content of an address is corrupted during the writing process but it is not during the reading process. 

My question is the corruption in the writing process.

 When there are an address  "A" and another address "B", if I write into the address "A", is the content in the address "B" corrupted too or not with a power failure?

[Peter BENSCH]

Well, on the one hand, typically only the value on the respective address to be written can be damaged in case of a power failure, other addresses should not be affected.

On the other hand, however, it is strongly recommended to take measures against such an interruption of the writing process, e.g. monitoring the power supply and sufficiently large capacitors on it that are designed for the maximum writing time and buffer the voltage for that long.

Regards
/Peter