Format of SFS control data packet:
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 (high byte = shift state, low byte = scan code or 00h)
		(see #00006)
		0000h to disable hotkey
---function 06h---
 04h	WORD	timeout in minutes before automatic unmount
		0000h to disable auto-unmount
Notes:	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