NAND issue (sorry about the previous post, accidentally hit Send)

Hello everyone,

I'm using a micro controller with ONFi peripheral to control multi-cell (2) NAND. I write the NAND (Micron) from the beginning to the end. I skip bad blocks and use a simple verification system:

1) Write the page, including ECC codes 2) Reading it back and recalculating the ECCs

If ECC fails I write the same data to the next page.

However I seem to experience the following issue with *some* pages:

- During the verification the ECC consistently fails.

- Later, during read-out the same page seems to produce no errors

I keep to all the timing specifications (even far below). The issue does not seem related to the ONFi bus speed. Even at very slow speeds the same issue pops up. I've set the speed to 5 (fastest) and tried various drive strengths. None seem to matter.

a) Could this be related to some analog problem on the NAND it self? b) Has anyone else ever experienced these kind of issues? c) Could it be related to multi-cell? Since it shares bits with another page?

Thanks for any pointers! Vincent van Beveren

Reply to
Vincent van Beveren
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Using single level nand flash at elevated temperatures, I've noticed that reading will often give errors but will come right again when cooled, so the data was clearly written correctly.

I suspect that the read amplifiers/comparators are the temperature sensitive part. If so, I would expect this problem to be much worse for multi-level.

Just one data point.

Cheers

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Syd
Reply to
Syd Rumpo

This is just a nit, and I'm sorry to be raising it when I can't help you with your real problem:

To this hardware-and-software guy, "NAND" means a NAND gate. "NAND Flash" means a chip or assembly that stores an outrageous amount of data (to a guy for whom one MB/pound* was once "huge") in a teeny amount of space.

There. Nitpicking done. You may now return to your normally-scheduled problem solving.

  • I think hard drives are up to or beyond 1TB/pound, and solid state drives are probably higher yet. Oh, how the world changes in 35 years.
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Tim Wescott 
Wescott Design Services 
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Reply to
Tim Wescott

Hi Tim,

I was considering some similar sort of post then I thought we might have to adapt to the language as it changes.... :-). Not that I know what we will call NAND gates - we can (and do) - still buy 7400 (well, HCT, ACT etc.) :D .

Dimiter

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Reply to
Dimiter_Popoff

Hi Syd,

Apparently I will need to cool it then ;). So, maybe if I wait for some time between writing and verification, errors could be reduced. I will see if that is indeed the case. Thanks for your insight.

Regards, Vincent

Syd Rumpo schreef op 25-6-2015 om 18:27:

Reply to
Vincent van Beveren

l
u
a

Lots of acronyms are being reused. My worst one is SDLC. Nowadays it means Software Development Life Cycle, but I cannot help but think of Synchronous Data Link Communications.

ed

Reply to
Ed Prochak

The trouble is with Humpty Dumpty a word means what he wants it to mean, nothing more and nothing less.

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Rick
Reply to
rickman

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