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AX = 4402h BX = file handle referencing character device for DRFAT32.SYS driver (e.g. "FAT32XXX" in the default configuration) CX = number of bytes to read DS:DX -> control block (see #04108)
Return:
CF clear if successful AX = number of bytes actually read CF set on error AX = error code (01h,05h,06h,0Dh) (see #01680 at AH=59h/BX=0000h)
Notes: The data returned depends on the first byte of the control block the remainder of the control block is filled by the driver one DRFAT32.SYS device driver supports up to 8 subunits (that is up to 8 FAT32 partitions). By default, DRFAT32.SYS logs in all FAT32 partitions it finds, however, by using command line options /C (CHS), /L (LBA), /H (Hidden) and /P:1..4 (Primary), /E:1..255 (Logical Drive), and /U:min[,max] (Unit 128..255) it can be directed to attach only to one or a specific range of partitions. Multiple DRFAT32.SYS drivers can be loaded in a system when using the /D:name option. To assign them to the redirector, the /D:name option must be repeated for each of the DRFAT32.SYS drivers in the DRFAT32.EXE command line.
See Also: AX=4402h"CD-ROM" - INT 2F/AX=0802h
Format of DRFAT32 control block: Offset Size Description (Table 04108) 00h BYTE data being requested 00h device driver header address 09h media change status 48h address of DRFAT32 geometry table else error ---function 00h--- 01h DWORD device driver header address (see also AH=52h,#01646) ---function 09h--- 01h BYTE media change status 00h don't know 01h media unchanged FFh media has been changed ---DRFAT32 function 48h--- 01h DWORD address of DRFAT32 geometry table (see #04109)
Format of DRFAT32 Geometry Table: Offset Size Description (Table 04109) 00h 8*59 BYTEs eight DRFAT32 partition data tables (see #04110) 1D8h BYTE DRFAT32 access flags (see #04111) 1D9h BYTE DRFAT32 status flags (see #04112)
Note: This is the table layout used by DRFAT32.SYS 1.00 which supports up to 8 sub-units. The layout of this table and its records may change, so the version indicator in the device driver's signature ("FAT320") and the size of the public data structure should be checked first.
See Also: #04108
Format of DRFAT32 partition data table: Offset Size Description (Table 04110) 00h BYTE size of following public data structure (9). --- public data (needed by the DRFAT32.EXE redirector) --- 01h WORD bytes per sector 03h BYTE sectors per cluster 04h WORD reserved sectors 06h DWORD root directory start cluster. --- private data --- 0Ah DWORD sectors per track 0Eh DWORD root directory sector 12h DWORD partition start sector 16h DWORD highest partition sector allowed (only if range checking enabled) 1Ah DWORD absolute cluster start sector (cluster start sector+partition start sector) 1Eh DWORD total sectors per track (number of heads * sectors per track) 22h BYTE drive unit (default 80h)
23h BYTE temp buffer:
CHS sectors to write (if verify enabled) 24h BYTE INT 13h extension version. --- CHS data --- 25h WORD cylinder 27h WORD head 29h WORD sector. --- LBA data --- 2Bh 16 BYTEs disk address packet (see #00272 at INT 13/AH=42h)
See Also: #04109
Bitfields for DRFAT32 access flags: Bit(s) Description (Table 04111) 7 using LBA addressing instead of CHS 6 using INT 13h extensions (see also INT 13/AH=48h) 5 multi-sector access allowed 4 force media change indication on removable drives 3 force verify after every write (/W) 2 more than 1024 cylinders, less than 64 heads (/A) 1 client-side asynchronous buffering allowed (/B), normally =0 0 read-only access (/R)
See Also: #04109 - #04112
Bitfields for DRFAT32 status flags: Bit(s) Description (Table 04112) 7-2 reserved (0) 1 Save Guard enabled (blocks any further writes after a fault) 0 volume may have dirty sectors (set after write operations)
See Also: #04109 - #04111
Category: Uncatagorized - Int 21h - D
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