[Yaffs-archive] Re: yaffs and ecc

[Charles Manning]

> > * YAFFS applies its own ecc, so the mtd level ecc (CONFIG_MTD_ECC or
> > whatever) should be off. I believe this is documented in the
> > yaffs_on_mtd.html doc. If this is not clear enough, I will clarify the
> > doc. * Unlike NOR, you can attempt to write 1's on top of  0's without
> > the operation failing. The result is the logical AND of the two. ie.
> > programming 0xFE on top of 0x07 should yiled 0x06.
>
> That's true and not true. It works this way, but not within the specs of
> NAND chips. The problem of NAND is, that consecutive writes to a page are
> restricted. There are chips around, which allow only _ONE_ write to a page.
> Same applies for oob data.

For my continuing education: Which NANDs only support a single page write? 
All the stuff I've looked at allows at least 3 writes to the page. 

FYI: Yaffs was purpose designed to fit within the limited writes/page. yaffs 
never does more than 2 writes to a page:
- once to write a page (including a write to OOB)
- one to obsolete the page (just writes to OOB to stomp on the tags).

Thanx

-- Charles


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