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Format of SFS control data packet

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Offset Size Description

00h

WORD

signature 4330h ('C0')

02h

WORD

function (see #01542)

---function 00h---

04h

WORD

sector size in bytes

06h

BYTE

sectors per cluster

07h

WORD

number of boot sectors

09h

BYTE

number of copies of FAT

0Ah

WORD

size of root directory in entries

0Ch

WORD

number of sectors on disk, 16-bit

0Eh

BYTE

media descriptor byte

0Fh

WORD

sectors per FAT

11h

WORD

sectors per track

13h

WORD

number of heads

15h

DWORD

number of hidden sectors

19h

DWORD

number of sectors on disk, 32-bit

---function 01h---

04h

20 BYTEs

master IV for encrypted disk

18h

64 BYTEs

NDC/SHS keying information

---function 02h---

04h

WORD

read-only state:
00h = read-only
01h = read/write

---function 03h---

04h

WORD

drive number (see #01544)

06h

DWORD

sector offset of logical volume from start of physical volume
0 if logical volume = physical volume

---function 04h---

04h

WORD

mount status
00h = unmounted
01h = mounted

---function 05h---

04h

WORD

hotkey (see #00006)
high byte - shift state
low byte - scan code or 00h
0000h to disable hotkey

---function 06h---

04h

WORD

timeout in minutes before automatic unmount
0000h to disable auto-unmount

Note:

The data for function 00h corresponds to a DOS BPB (see AH=53h).
Functions 00h, 01h, and 03h automatically unmount the encrypted drive.
Unmounting a drive with function 04h also destroys the encryption information in the driver and forces all dirty buffers to be flushed.