biosParmBlock Struct Reference

BIOS parameter block. More... #include <FatStructs.h> List of all members. Public Attributes uint16_t  bytesPerSector uint8_t  sectorsPerCluster uint16_t  reservedSectorCount uint8_t  fatCount uint16_t  rootDirEntryCount uint16_t  totalSectors16 uint8_t  mediaType uint16_t  sectorsPerFat16 uint16_t  sectorsPerTrtack uint16_t  headCount uint32_t  hidddenSectors uint32_t  totalSectors32 uint32_t  sectorsPerFat32 uint16_t  fat32Flags uint16_t  fat32Version uint32_t  fat32RootCluster uint16_t  fat32FSInfo uint16_t  fat32BackBootBlock uint8_t  fat32Reserved [12] Detailed Description BIOS parameter block. The BIOS parameter block describes the physical layout of a FAT volume. Member Data Documentation uint16_t biosParmBlock::bytesPerSector Count of bytes per sector. This value may take on only the following values: 512, 1024, 2048 or 4096 uint16_t biosParmBlock::fat32BackBootBlock If non-zero, indicates the sector number in the reserved area of the volume of a copy of the boot record. Usually 6. No value other than 6 is recommended. uint16_t biosParmBlock::fat32Flags This field is only defined for FAT32 media and does not exist on FAT12 and FAT16 media. Bits 0-3 -- Zero-based number of active FAT. Only valid if mirroring is disabled. Bits 4-6 -- Reserved. Bit 7 -- 0 means the FAT is mirrored at runtime into all FATs. -- 1 means only one FAT is active; it is the one referenced in bits 0-3. Bits 8-15 -- Reserved. uint16_t biosParmBlock::fat32FSInfo Sector number of FSINFO structure in the reserved area of the FAT32 volume. Usually 1. uint8_t biosParmBlock::fat32Reserved[12] Reserved for future expansion. Code that formats FAT32 volumes should always set all of the bytes of this field to 0. uint32_t biosParmBlock::fat32RootCluster Cluster number of the first cluster of the root directory for FAT32. This usually 2 but not required to be 2. uint16_t biosParmBlock::fat32Version FAT32 version. High byte is major revision number. Low byte is minor revision number. Only 0.0 define. uint8_t biosParmBlock::fatCount The count of FAT data structures on the volume. This field should always contain the value 2 for any FAT volume of any type. uint16_t biosParmBlock::headCount Number of heads for interrupt 0x13. Not used otherwise. uint32_t biosParmBlock::hidddenSectors Count of hidden sectors preceding the partition that contains this FAT volume. This field is generally only relevant for media visible on interrupt 0x13. uint8_t biosParmBlock::mediaType This dates back to the old MS-DOS 1.x media determination and is no longer usually used for anything. 0xF8 is the standard value for fixed (non-removable) media. For removable media, 0xF0 is frequently used. Legal values are 0xF0 or 0xF8-0xFF. uint16_t biosParmBlock::reservedSectorCount Number of sectors before the first FAT. This value must not be zero. uint16_t biosParmBlock::rootDirEntryCount For FAT12 and FAT16 volumes, this field contains the count of 32-byte directory entries in the root directory. For FAT32 volumes, this field must be set to 0. For FAT12 and FAT16 volumes, this value should always specify a count that when multiplied by 32 results in a multiple of bytesPerSector. FAT16 volumes should use the value 512. uint8_t biosParmBlock::sectorsPerCluster Number of sectors per allocation unit. This value must be a power of 2 that is greater than 0. The legal values are 1, 2, 4, 8, 16, 32, 64, and 128. uint16_t biosParmBlock::sectorsPerFat16 Count of sectors occupied by one FAT on FAT12/FAT16 volumes. On FAT32 volumes this field must be 0, and sectorsPerFat32 contains the FAT size count. uint32_t biosParmBlock::sectorsPerFat32 Count of sectors occupied by one FAT on FAT32 volumes. uint16_t biosParmBlock::sectorsPerTrtack Sectors per track for interrupt 0x13. Not used otherwise. uint16_t biosParmBlock::totalSectors16 This field is the old 16-bit total count of sectors on the volume. This count includes the count of all sectors in all four regions of the volume. This field can be 0; if it is 0, then totalSectors32 must be non-zero. For FAT32 volumes, this field must be 0. For FAT12 and FAT16 volumes, this field contains the sector count, and totalSectors32 is 0 if the total sector count fits (is less than 0x10000). uint32_t biosParmBlock::totalSectors32 This field is the new 32-bit total count of sectors on the volume. This count includes the count of all sectors in all four regions of the volume. This field can be 0; if it is 0, then totalSectors16 must be non-zero. The documentation for this struct was generated from the following file: Arduino/libraries/SdFat/FatStructs.h Generated on Wed Dec 23 08:22:21 2009 for SdFat by  1.6.1