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For example 8x8 small image stored on eeprom will get corrupt over time? I've seen somewhere eeproms losing their data over time like vhs tapes.

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    \$\begingroup\$ Look up their "data retention time." The answer is yes, they lose their data. But for different reasons than VHS tapes. \$\endgroup\$ – jonk Sep 15 at 22:49
  • \$\begingroup\$ even eeprom not used it is going to forget or slowly data inside get garbled like if i write text like test after a time test text will be t4jt? \$\endgroup\$ – TRGamer TR Sep 15 at 22:54
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    \$\begingroup\$ They don't change randomly, the bits eventually all become 1s or 0s depending on the technology. \$\endgroup\$ – Finbarr Sep 15 at 23:07
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    \$\begingroup\$ All data storage systems degrade with time. This is part of thermodynamics (entropy is always increased). Eventually, in billions of years when the universe experiences thermodynamic heat death, there will be no data storage of any kind left intact. But EEPROM is not bad for small amounts of data that must be stored for decades. I think it would be my first choice for high reliability on-board non-volatile memory (in a consumer device). \$\endgroup\$ – mkeith Sep 16 at 2:59
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    \$\begingroup\$ Here is another way to say it. EEPROM will most likely not corrupt data until after you are dead and don't care anymore. But if you are going to expose it to very extreme conditions such as very high temperatures, corrosive atmosphere, etc, then it may fail prematurely. \$\endgroup\$ – mkeith Sep 16 at 3:02
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Yes, they are based on a stupidly tiny charge on a floating gate, so eventually they will lose their memory.

The time is generally pretty long under benign conditions (seldom, if ever, re-written, cool temperatures, no significant ionizing radiation).

enter image description here

If any of those things are not true, the life can be significantly foreshortened. For example, at high temperatures rule of thumb is half for every 10°C (not sure this is 100% valid for EEPROM cells, but let's use it here).. so that 100 years becomes 50 years at 35°C, 25 years at 45°C, 12.5 years at 55°C and so on.. so at the maximum storage temperature of 150°C the retention might be less than a week.

Similarly, a badly written or errant program can quickly exceed the lifetime 10^6 erase/write cycles in a matter of hours.

I believe there is some interaction between the two- many write cycles negatively impact the retention time.

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    \$\begingroup\$ It is good to remember that these 100's of years are an estimate. The technology simply didn't exist for that long yet. \$\endgroup\$ – fraxinus Sep 17 at 10:32
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    \$\begingroup\$ Why 'stupidly'? \$\endgroup\$ – quetzalcoatl Sep 17 at 18:09
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    \$\begingroup\$ @quetzalcoatl It's a figure of speech. The capacitance (fF) number of coulombs (or even electrons) is so small to be far outside of normal experience for non-IC designers. \$\endgroup\$ – Spehro Pefhany Sep 17 at 18:18
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    \$\begingroup\$ @fraxinus Certainly, they were introduced around 1980, not in some dark pre-historic time. Although barely 40 years has passed, I've personally seen a number of EEPROM failures, most of which "bricked" the product. \$\endgroup\$ – Spehro Pefhany Sep 17 at 18:21
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    \$\begingroup\$ Personally, I believe this is a significant threat to digital preservation. EEPROM is a time bomb of the digital (dark) age, the number is only a projected lifetime. How long will today's technology last in the wild is still largely untested. Imagine when a future archeologist wants to download data from a HDD made in 2010, only to find that its firmware and parameters in a EEPROM are gone, permanently bricking the electronics, even when the platters, motors and the head are good. The transition to NAND flash only made the problem worse. \$\endgroup\$ – 比尔盖子 Sep 18 at 21:18
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You can find a datasheet for the EEPROM you want to use. I looked at one for a 24LC64 (from Microchip) and it said data retention was greater than 200 years. So, yes, they don't hold data forever, but may be good enough for your use.

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There are several methods to manufacture an EEPROM, and I mention this only because most of the time when people see "EEPROM", it can be just about anything. Generally speaking, the architecture depends greatly on what they will be used for. For all cases, it's a variation on the floating-gate MOSFET You have a very little amount of charge on NOR and NAND-based storage for SSDs, but you will have larger capacitors for industrial applications where you care about data integrity. Fundamentally, this is a function of the sense amplifier structure and how much charge it takes to flip the bits. I would put my ICs in an oven at 200C to simulate aging and look at charge loss. Generally, we saw no charge loss due to the gates, but possible offsets due to shallow charge trapped in the oxides.

Here's a summary of how you make floating gates:

  • Analog-based that are programmed with injection and tunneling
  • Differential. This uses two different floating gates to store a value, so one is high and one is low. TI uses this to store information on non-FLASH processes.
  • SONOS The charge is trapped in the oxide. This works well for space.
  • NOR/NAND. This has excellent charge density, but is a special manufacturing process.

For all of these, you test them by putting them in an oven and watching the drift over time. The NOR/NAND is the worst because it's driven by density so that there is very little charge. Everything else pretty much will hold charge effectively forever. One needs to also keep in mind that changing the state can be destructive, depending on how you do it.

physics warning: If you are "tunneling", this is a quantum process and this is effectively safe for infinite cycles as you do not have enough energy to move a hole. If you are using hot electron injection, there's a probability that you will eventually have an energy state that high enough to move a hole, and you'll throw an atom into oxide. If you are careful, ie: not in a hurry, you can effectively have infinite programming cycles. The oxides will fill with shallow traps of charge to make a bias, but if you have a large enough capacitor, you'll not have any issues with offsets.

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Other answer have covered the basic risk of corruption on EEPROMs, but this only relates to the hardware. EEPROMs have to be read by software though, and software often has recovery strategies to detect errors in EEPROM data.

If the software provides error recovery, the user may not ever see corruption. If the error is recoverable (and by design this will be the case for most errors), the software will detect the corruption, recover from it, and report the corrected data to the user. The software will typically also rewrite the data on the EEPROM to ensure it remains correct going forwards. The result is that even though corruption is very likely occur sometime over the EEPROM's lifespan, the chances of corruption occurring over the EEPROM's lifespan which cannot be corrected are very, very low.

If the software provides error detection (e.g. a checksum) but not error recovery though, the result may be all or nothing. Corrupted files may be discarded entirely, instead of being made available and showing your "VHS tape" type of errors. In this case, a change to just one bit in the image might result in the entire image being reported as unreadable.

Or of course the software may simply report the data as-is, in which case as previous answers say you may get some small amounts of corruption over time.

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