[Yaffs] bit error rates

[Claudio Lanconelli]

Hi Charles,
I have a question regarding the condition YAFFS and YAFFS2 mark a block 
as bad.

Charles Manning wrote:

>YAFFS takes a fairly cautious approach to handling bad blocks. If a block 
>fails an ECC test then it's retired at the next garbage collection of that 
>block (ie we suck out the data first).
>  
>
Does this mean that if there is a single bit error corrected by the ECC
algo YAFFS retire the block and mark it as BAD?

If it's the case I think Toshiba suggest a different behavior in the 
document
you linked previously Toshiba NAND Flash Applications design guide on 
page 19.

It says:
"Therefore, blocks should be marked as bad and no
longer accessed if there is either a block erase failure
or a page program failure. This can be determined by
doing a status read after either operation"

and then

"Although random bit errors may occur during use,
this does not necessarily mean that a block is bad.
Generally, a block should be marked as bad only if
there is a program or erase failure"

How YAFFS and YAFFS2 behave?

Thanks,
Claudio Lanconelli