ATMEL EEPROM endurance?

It means the chip is _guaranteed_ to do 100k cycles and will become flakey some time after that. How long after is anyone's guess. If that is important to you check the Atmel site they will probably have statistical data on longevity.

Mike Harding

Sorry missed a bit: afaik the chip doesn't care about the relative timing of writes so you could do 1 a year for 100,000 years (hmmm) or 10,000 a day for 10 days.

Q: If you write to one single location 100k times is all memory subject to failure after that or just the one location/block?

Mike Harding

In article , Mike Harding writes

Each bit of eeprom is a stand alone memory cell. So you can change the state of each bit from 0 to 1 (or 1 to 0), 100,000 times. After that you might find the bit gets stuck at zero and you can't erase it back to 1.

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Tim Mitchell

I wwas wondering about this recently. I just want to store a couple of parameters every time a control is altered. If the write operation fails, I'll use the next locations. Haven't tried it yet, though.

Leon

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That only works if the next location is not used by another variable.

Rene

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Nice idea. However, there's no guarantee that failure means the write operation fails immediately. It may just fail to store enough charge to last more than a day, a month or a year.

Also the Jedec standard says that if < 5% of parts fail a test at, say

100,000 cycles, then that part has passed the test for 100,000 cycles. Some manufacturers put more stringent requirements on their parts of their own volition. A good intro is

Cheers, Alf Katz

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It means that the eeprom is toast after 100 000 write/erase cycles.

Wumpus

If the write operation fails with a specific byte, then , make shift for all parameters block , providing there is enough free space in EEPROM ( this is usually the case).The remaining thing to do is to use special location in EEPROM which points to the parameters block and update this pointer if shift of the parameters took place.

Yossi

"Leon Heller" wrote

Use an FRAM chip from Ramtron. 10^10 read/writes (read is actualy a read/rewrite). Cycle time 100 ns.

We save data 3 seconds after last user interaction. Never wears out.

Regards, Arie de Muynck

Amazing stuff isn't it? Core memory makes a comeback. ;-D At least some PIC's have a warning about rewriting a location many times (approaching 1,000,000) can corrupt other locations. Therfore they have suggest refreshing everything once in a while.

michael

Not exactly. It means that you should assume that it's toast after

100,000 cycles. ;-) Actually, in normal use you'll get many more cycles than that. The spec assumes worst case conditions for the EEPROM when writes are occuring. This would normally be at the max temp rating. Fortunately, most applications probably wouldn't need to be doing writes at 125C. ;-)

michael

From my reading, the failure is caused by electrons tunnelling only part-way through the insulator around the isolated gate, and being trapped there where they can't be erased they make the cell read as zero (cannot erase back to one). The number of cycles can be a bit misleading - in chips where you control the timing yourself the failure can be caused by a single very long write cycle, of the required total duration. Something to think about if you're writing programming software, because a failure which leaves the programmming voltage applied will fail that cell really quickly.

Clifford.

Not quite - the basic physical mechanism is different.

Core is based on hysteresis of square-loop ferromagnetic material (often called a permanent magnet), and the Ramtron FRAMs are based on the ferroelectric effect (see Ramtron web pages for an explanation).

Been there - used them (both core and FRAM).

Tauno Voipio tauno voipio @ iki fi

What if *that* location breaks down too? I think you can better use some sort of smart search algo on startup (start from the end, searching for the first used block) than a pointer.

Wumpus

If you continue along this line of tought, you'll end at wear-leveling algorithms used in Flash file systems. Not a bad idea at all.

Tauno Voipio tauno voipio @ iki fi

Good spoken. However, a) how do you find out if the write operation has failed? b) when reading the data, how do you find out which locations contain the good copy?