Functional Description
Table 26-25. FAT Boot Sector (continued)
Offset
Length[bytes]
Name
Description
For FAT12/16, number of 32 bytes entries
in the Root Directory (multiple of
0011h
2
BPB_RootEntCnt
BPB_BytsPerSec/32)For FAT32 this value
is 0
Total Count of sectors on the volume. If
the size is bigger than 10000h or for
0013h
2
BPB_TotSec16
FAT32, this field is 0 and BPB_TotSec32
holds the value
Media Type, usually F8h: fixed, non-
0015h
1
BPB_Media
removable
For FAT12/16, size in sectors of one
0016h
2
BPB_FATSz16
FATFor FAT32, holds 0
Number of sectors per track, 63 for
0018h
2
BPB_SecPerTrk
SD/MMC
001Ah
2
BPB_NumHeads
Number of heads, 255 for SD/MMC
Number of sectors preceeding the
001Ch
4
BPB_HiddSec
partition
Total Count of sectors on the volume. If
the size is smaller than 10000h (for
0020h
4
BPB_TotSec32
FAT12/16), this field is 0 and
BPB_TotSec16 is valid
0024h
1
BS_DrvNum
Drive Number
0025h
1
BS_Reserved1
00h
Extended Boot Signature 29h. Indicates
0026h
1
BS_BootSig
that the following 3 fields are present
0027h
4
BS_VolID
Volume Serial Number
FAT12/16
002Bh
11
BS_VolLab
Volume Label
File system Type: “FAT12”, “FAT16”,
“FAT32”.Note: This field is not mandatory
0036h
8
BS_FilSysType
(i.e BS_) therefore it cannot be used to
indentify the partition type.
4137
SPRUH73H – October 2011 – Revised April 2013
Initialization
Copyright © 2011–2013, Texas Instruments Incorporated