On Thu, Apr 02, 2015 at 12:50:16AM +1300, IVP wrote:
> > Erasing the device does NOT mean writing zero blocks, or
> > reformatting the filesystem.  All that does is allocate blocks
> > from pages in the flash array
>=20
> So, if you have a directory with file names, pointers to start
> clusters etc, that will reset the FTL's block assignments as
> though the card had been formatted and reloaded ?

I don't understand sorry.

Flash pages are way larger than disk blocks though.  The flash pages
are taken from the list of erased pages, and then blocks are written
into them until the page is full.

The list of erased pages is operated as a FILO queue, so that wear is
levelled across the device.

> If so, that would be practical for a micro to perform, as the
> full format option means that files have to be reloaded, not
> really something you should expect an end user to have to
> do

I don't know any way to do that.  I only suggest it as a diagnostic
tool, not as a permanent method by the micro.

> PS, a question I meant to ask before. How does SDHC Flash
> differ from eg PIC Flash ? For example, if SDHC has an issue
> with read disturb why doesn't a PIC ? Instructions are read
> from Flash billions or even trillions of times

Different types of flash.  The PIC flash is low density and does not
suffer from that problem.  Once you have 4GB on the PIC, you may start
to see problems.  ;-)

--=20
James Cameron
http://quozl.linux.org.au/
--=20
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