Difference between revisions of "Unit FATFS"
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Based on information from numerous sources, primarily the document fatgen103.pdf from Microsoft. FAT Disk Blocks are based on reading a group of sectors into a block at once. The BlockNo of each block is therefore the FAT entry no of the first FAT in the block. | Based on information from numerous sources, primarily the document fatgen103.pdf from Microsoft. FAT Disk Blocks are based on reading a group of sectors into a block at once. The BlockNo of each block is therefore the FAT entry no of the first FAT in the block. | ||
Revision as of 05:35, 19 December 2016
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Description
Ultibo FAT12/16/32/exFAT interface unit
Notes:
Based on information from numerous sources, primarily the document fatgen103.pdf from Microsoft. FAT Disk Blocks are based on reading a group of sectors into a block at once. The BlockNo of each block is therefore the FAT entry no of the first FAT in the block.
The use of IsEightDotThree and GenerateShortName(Ex) from the UltiboUtils unit should be replaced by internal routines optimised for maximum performance. All Block and Entry Offsets have been expanded to 32bit to avoid 16bit overflow on 64K clusters.
Constants
FATFS specific constants
fat* fatFAT12 = 0;
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fatFAT16 = 1;
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fatFAT32 = 2;
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fatDotName = '.';
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fatDotDotName = '..';
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fatBlankName= ;
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fatNameCount = 8;
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fatExtCount = 3;
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fatLabelMask = '*';
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fatLabelCount = 11;
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fatOemName = 'MSWIN4.1';
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fatDefaultName = 'NO NAME';
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fatFlagNone = $00;
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fatFlagName = $08;
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fatFlagExt = $10;
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fatFlagBoth = $18;
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lfnMaxName = 2048;
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Buffer size for lfn handling |
lfnMaxAlias = 999999;
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Max number of lfn aliases (ie ~999999) |
lfnMaxNameAlias = 4;
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lfnMaxHashAlias = 999;
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lfnMaxHashShift = 16;
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fatMaxFileSize = 4294967295;
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Max size in bytes of a File (4GB) |
fatMaxDirectorySize = 2097152;
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Max size in bytes of a Directory (2MB = 65536 * 32) |
fatMinClusterSize = 512;
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fatMaxClusterSize = 65536;
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fat12MinClusters = 3;
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fat16MinClusters = 4085;
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Smallest Number of Clusters on a FAT16 volume, is FAT12 if less |
fat32MinClusters = 65525;
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Smallest Number of Clusters on a FAT32 volume, is FAT16 if less |
fat12MinSectors = 6;
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Number of Sectors at which we cannot create a FAT12 (Not possible due to 512 Root entries) |
fat12MinSectors = 798;
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Number of Sectors at which we cannot create a FAT12 |
fat12MaxSectors = 32623;
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Number of Sectors at which we insist on creating FAT16 |
fat16MinSectors = 8400;
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Number of Sectors at which we cannot create a FAT16 |
fat16MaxSectors = 1048576;
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Number of Sectors at which we insist on creating FAT32 |
fat32MinSectors = 66600;
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Number of Sectors at which we cannot create a FAT32 |
fat32MaxSectors = $FFFFFFFF;
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No limit on maximum size of a FAT32 |
| Note: In FAT12 EOC will be >= $0FF0 due to Media ID on Floppy | |
fat12EndOfFile = $0FF0;
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Some Code sets values from $0FF0 - $0FFF as EOF |
fat12EndOfFile = $0FF8;
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Some Code sets values from $0FF8 - $0FFF as EOF |
fat12EndOfCluster = $0FFF;
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EOF Mark, Check for >= $0FF0 - See Above |
fat12FreeCluster = $0000;
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Available for Use |
fat12BadCluster = $0FF7;
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Bad Cluster Mark - Do Not Use |
fat12MediaCluster = $0F00;
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First Cluster - $0F00 + MediaID from BPB Usually $0FF8 |
fat12Reserved0 = $0FF0;
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Reserved Cluster Nos - Do Not Use (Due to Media ID on Floppy) |
fat12Reserved1 = $0FF1;
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fat12Reserved2 = $0FF2;
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fat12Reserved3 = $0FF3;
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fat12Reserved4 = $0FF4;
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fat12Reserved5 = $0FF5;
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fat12Reserved6 = $0FF6;
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fat16EndOfFile = $FFF8;
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Some Code sets values from $FFF8 - $FFFF as EOF |
fat16EndOfCluster = $FFFF;
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EOF Mark, Check for >= $FFF8 - See Above |
fat16FreeCluster = $0000;
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Available for Use |
fat16BadCluster = $FFF7;
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Bad Cluster Mark - Do Not Use |
fat16MediaCluster = $FF00;
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First Cluster - $FF00 + MediaID from BPB Usually $FFF8 |
fat32EndOfFile = $0FFFFFF8;
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Some Code sets values from $0FFFFFF8 - $0FFFFFFF as EOF |
fat32EndOfCluster = $0FFFFFFF;
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EOF Mark, Check for >= $0FFFFFF8 - See Above |
fat32FreeCluster = $00000000;
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Available for Use |
fat32BadCluster = $0FFFFFF7;
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Bad Cluster Mark - Do Not Use |
fat32MediaCluster = $0FFFFF00;
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First Cluster - $0FFFFF00 + MediaID from BPB Usually $0FFFFFF8 |
fat16CleanShutdown = $8000;
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Second Cluster - EndOfCluster + Bits |
fat16HardError = $4000;
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Second Cluster - EndOfCluster + Bits |
fat32CleanShutdown = $08000000;
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Second Cluster - EndOfCluster + Bits |
fat32HardError = $04000000;
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Second Cluster - EndOfCluster + Bits |
fat32ReservedBits = $F0000000;
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Bits 31-29 must be preserved on FAT32 |
fatBootSector = 0;
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fatFreeCluster = 0;
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fatStartCluster = 2;
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Lowest allocatable cluster number |
fatUnevenCluster = $00000001;
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fatUnknownCluster = $FFFFFFFF;
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fatEntryFree = $E5;
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fatEntryFreeAll = $00;
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fatEntrySpecial = $05;
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If real first char is $E5 |
fatEntryPadding = $20;
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Padded with spaces (32) |
fatEntrySize = 32;
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Size of a FAT Directory Entry (or LFNDirectoryEntry) |
lfnEntryMax= $3F;
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Maximum count of an LFN entry |
lfnEntryLast = $40;
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Marker for LFN last entry |
lfnEntryMask = $BF;
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Mask for LFN entry count |
lfnEntryChars = 13;
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Number of characters per LFN entry |
lfnEntryNull = $0000;
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Null terminator on LFN when applicable |
lfnEntryPadding = $FFFF;
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Empty LFN chars padded with (65535) |
lfnAttributeMask = (faReadOnly or faHidden or faSysFile or faVolumeID);
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Not Used - See faLongName |
fat32LeadSignature = $41615252;
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RRaA |
fat32StructSignature = $61417272;
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rrAa |
fat32TrailSignature = $AA550000;
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Standard Boot Sector signature |
fatDotChar:Byte = $2E;
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Checked separately from Invalid chars due to . and .. entries |
fatSpaceChar:Byte = $20;
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fatBaseChars:set of Byte = [$00..$19];
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0..31 (Dont include $20 as that is checked separately) |
fatInvalidChars:set of Byte = [$22,$2A,$2B,$2C,$2F,$3A,$3B,$3C,$3D,$3E,$3F,$5B,$5C,$5D,$7C];
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34,42,43,44,47,58,59,60,61,62,63,91,92,93,124 (Dont include $2E as that is checked separately) |
fatLowercaseChars:set of Byte = [$61..$7A];
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97..122 (These dont account for the code page) |
Type definitions
To be documented
Public variables
To be documented
Function declarations
Initialization functions
procedure FATFSInit;
Description: To be documented
| Note | None documented |
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procedure FATFSQuit;
Description: To be documented
| Note | None documented |
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FATFS helper functions
function FATTypeToString(AType:TFATType):String;
Description: To be documented
| Note | None documented |
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