Hi,

On 29/08/2011 10.27, IVP wrote:
> Hi all,
>
> I've been reading these two pdfs
>
> www.cs.ucr.edu/~amitra/sdcard/ProdManualSDCardv1.9.pdf
>
> www.mikrocontroller.net/attachment/.../SDHC_SDM04G7B7_08G7B7.pdf
>
> The first, SanDisk, says (page 3-24) that there are 20480 sectors
> of 512 bytes in the protected system area. The second, Toshiba,
> says (page 34) that its cards have 65536 * 512 bytes in the protected
> area
I think that "protected system area" is related to the "extended" functio o=
f SD=20
card.
The size is returned in the SD Status data block (512 bit) with command ACM=
D13=20
(CMD55 + CMD13).

>
> I read that the MBR doesn't always start at Sector/Block 0.
FALSE!
>   I'm
> not wanting to use FAT with a particular test card (made by Phison
> AFAICT from the CID response), just straight data storage in an
> embedded environment, so I'd like to know the writable sectors of
> any card I end up using for this product
>
> The card in a reader comes up as I: on my PC, and I tried a
> couple of XP utilities to try and find out which sectors are in
> use after formatting, but nothing was forthcoming
>
> Is there a utility anyone could recommend for finding out what
> sectors FAT is installed in ? I *could* read the whole card a
> sector at a time and log which are not FF but .......
Read sector 0, some card has MBR http://en.wikipedia.org/wiki/Master_boot_r=
ecord=20
and only 1 partition (more not alloved by specs) other has only Boot sector=
=20
http://en.wikipedia.org/wiki/Fat16#Boot_Sector

My datalogger write chunks of 2MB so I wrote a library for FAT16 to find an=
d=20
allocate a contiguous space and to write a file descriptor in the main=20
directory, after this I write directly to the sectors.

If you need to "fill" the card you can just allocate a single file and use =
some=20
"spare" byte in the boot sector to say to firmware: first sector, size (in=
=20
sector or bytes), etc

I'm curious: how many bytes/sec are you able to write?


--=20
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