IVP wrote:
> Hi all
>
> Until recently I've been using a couple of unbranded 4GB cards that
> format with a Boot Sector at address 0x000000, directory starting at
> 0x761000 and first file data at 0x762000
>
> Now I've tried a couple of Strontium cards (half the price) and find
> that the Boot Sector is at 0x400000, directory at 0xBAE000, first
> file data at 0xBAF000
>
> 0x000000 to 0x761000 =3D 3b08 sectors, and 8 sectors to first file
> 0x400000 to 0xBAE000 =3D 3d70 sectors, and 8 sectors to first file
>
> Between 0x000000 and 0x4000000 is all zeroes, except for this at
> 0x1c0 (d448)
>
> 03 01 0b 2e ee e7 00 20 00 00 00 d8 7a 00 00 00
>  =20
Looks like your card has a "master boot record" with a partition table=20
and then has the fat filesystem on a partition.

http://en.wikipedia.org/wiki/Master_boot_record

The first partition table entry starts at 0x1be and is 16 bytes long=20
(there are places for three more entries)

So your table entry is

00 00 03 01 0b 2e ee e7 00 20 00 00 00 d8 7a 00

decoding that according to the table at we get

00: non bootable partition
00 03 01: chs start of partition, you can ignore this and use the LBA value=
s
0b: parition type: "fat32 with CHS addressing"
2e ee e7 : chs end of partition again you can ignore this
00 20 00 00: start LBA sector of partition =3D sector 0x2000 =3D byte offse=
t=20
0x400000
00 d8 7a 00: length of partition  =3D 0x7ad800 sectors =3D 0xF5B00000 bytes
> The directory listing of the card in XP looks perfectly normal, but how
> does XP know where to find the Boot Sector ? I've got fatgen.doc and
> see no special mention of location 448. 0x400000 would be the 0x400th
> cluster (@ 512 bytes x 8)
>
> If 0x000000 to 0x3FFFFF is reserved, how is that communicated to
> the PC ? I need to know so I can read any card with a dsPIC
>
> Alternatively, can I force the format to put the Boot Sector at 0x000000 =
?
>
> TIA
>
> Joe
>  =20

--=20
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