Help!! where is the file allocation table in the SD card ??

[xpratx]

hi,

i want to read the file allocation table inside SD card but i cannot figure out the address where it is??

i know that MBR is at address 0 (logical) but how to find where is FAT??

 

[FvM]

You need to read the MBR partition table to know the partition start sector, then decode the partition's boot sector for the first FAT sector offset.
https://en.wikipedia.org/wiki/Master_boot_record

 

[xpratx]

thanks,

okay now i got partition boot record but it doesn't specify starting address of FAT. how to get to fat from here??

h**p://home.teleport.com/~brainy/fat32.htm
i am assuming the link given has correct partition boot record.

 

[FvM]

You are referring to a lousy commented FAT format description. There are e.g. official MS documents and surely tons of better explaining descriptions. For the FAT table sector offset, refer to the entry BPB_RsvdSecCnt at 0x0E.

MS FAT32 specification tells:

Number of reserved sectors in the Reserved region of the volume starting at the first sector of the volume. This field must not be 0. For FAT12 and FAT16 volumes, this value should never be anything other than 1. For FAT32 volumes, this value is typically 32. There is a lot of FAT code in the world “hard wired” to 1 reserved sector for FAT12 and FAT16 volumes and that doesn’t bother to check this field to make sure it is 1. Microsoft operating systems will properly support any non-zero value in this field.

 

[xpratx]

i don't get much of what is stated there.

but what i have found is i can read number of reserved sector from PBR and add to LBA of partition to get starting address of FAT.
is that right??

---------- Post added at 23:02 ---------- Previous post was at 22:46 ----------

ok i got it..