[ECOS] Re: IO_Flash & DataFlash

Savin Zlobec savin@elatec.si
Tue Aug 31 13:02:00 GMT 2004

>Hello, Savin.
>I developed DataFlash driver some time ago,(but it wasn't finished)
>and I had the same issue.
>Simple solution is a ignoring of "unnecessary" bytes in DataFlash
>page. DF Page size is 528 bytes and if we will align that to 512 bytes
>we will losing 16 bytes per page only.
>It can be used internally by DF driver for block regeneration(after
>10.000 writes by Atmels's datasheet).
>As for as I remember Atmels' proprietary filesystem - DFFS using this feature.

This is an possibility if you plan to make use of this 'reserved' bytes, 
if not it sounds like a hack...

I think that using DataFlash through io_flash API is interesting for 
accessing it with RedBoot and
running jffs2 on it. For application use there are a lot of nice 
features that can't be used through io_flash,
for that I'am thinking of making an separate DataFlash API.

About the block regeneration - it is sector limited, if we reserve one 
or two sectors for RedBoot data +
application code it should be OK without any block regeneration, because 
of the nature of writes
(supposing that the RedBoot data doesn't change +10.000 times w/o 
changing the app code).
Jffs2 does wear leveling so the page writes should be distributed - if 
so no regeneration is needed.
As for the app specific usage it is best left to the app itself.


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