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Re: contributing filesystem and a failsafe update meachanism forFIS from within ecos applications


On Fri, 2005-09-23 at 09:01 -0400, Jon Ringle wrote:
> On Friday 23 September 2005 08:09 am, Neundorf, Alexander wrote:
> > 5. after the image is written, set the valid_flag of the fis directory
> > which will become active to 0xa5a5. In order to do this, the flash block
> > doesn't have to be erased, since the transition from 0xfdfd to 0xa5a5 only
> > sets some bits to 0.
> 
> I didn't know this property of flash. Is this a universal property of NOR 
> flash?

Yes. Erase operations reset all the bits to one.  Programming can
only change a one to a zero.  This can be done on a bit by bit 
basis, thus you can update a block by changing some bits to zeroes
without having to erase it.

-- 
------------------------------------------------------------
Gary Thomas                 |  Consulting for the
MLB Associates              |    Embedded world
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