Format of parameter block for functions 40h, 60h

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Offset

Size

Description

00h

BYTE

special functions

bit 0	:	set if function to use current BPB, clear if Device BIOS Parameter Block field contains new default BPB
bit 1	:	set if function to use track layout fields only must be clear if CL=60h
bit 2	:	set if all sectors in track same size (should be set)
bits 3-7	:	reserved (MS-DOS, Novell DOS 7)
bit 5	:	skip head settling time (WinDOS 2.11)
bit 6	:	format access flag (WinDOS 2.11)

01h

BYTE

device type (see #01561)

02h

WORD

device attributes

bit 0	:	set if nonremovable medium
bit 1	:	set if door lock ("changeline") supported
bits 2-15	:	reserved

04h

WORD

number of cylinders

06h

BYTE

media type

for 1.2M drive

00h	=	1.2M disk (default)
01h	=	320K/360K disk

F8h for DUBLDISK.SYS v2.6 expanded drives

always 00h for other drive types

07h

31 BYTEs

device BPB (see #01663 at AH=53h), bytes after BPB offset 1Eh omitted; final six bytes only transferred on function 40h with BYTE 00h bit 0 set for MS-DOS 5.0

---function 40h only---

26h

WORD

number of sectors per track (start of track layout field) (maximum 63)

28h

N WORD

word pairs: number,size of each sector in track

---category code 48h (FAT32), function 40h---

07h

53 BYTEs

extended BPB (see #01664)

3Ch

32 BYTEs

reserved

5Ch

WORD

number of track table entries

5Eh

2N WORDs

sector table (word pairs: number/size of each sector in track)

---category code 48h (FAT32), function 60h---

07h

53 BYTEs

extended BPB (see #01664)

3Ch

32 BYTEs

reserved