INT 13H (0x13)
Function 4AH (0x4A or 74) --> Initiate disk Emulation
(Bootable CD-ROM)
Call with: AH = 4AH
AL = 00H
DS:SI = Specification packet (see the Table in comments)
Return: If Function Successful,
Carry Flag = Clear
If Function unsuccessful,
Carry Flag = Set
AX = Status Code
Comments:
This Function is used to initiate the disk emulation. If the function is successful carry flag is clear, else carry flag is set and AX register returns status code and drive will not be in emulation mode.
The Format of Bootable CD-ROM Specification Packet has been given in the following table:
Offset |
Size |
Description |
00H |
BYTE |
Size of packet in bytes (13H) |
01H |
BYTE |
Boot media type |
02H |
BYTE |
Drive Number
Drive Number |
Drive Description |
00H |
Floppy image |
80H |
Bootable hard disk |
81H to FFH |
Non bootable or no Emulation |
|
03H |
BYTE |
CD-ROM controller number |
04H |
DWORD |
Logical Block Address of disk image to Emulate |
08H |
WORD |
Device Specification
Value |
Description |
(IDE) Bit 0 |
Drive is slave instead of master |
(SCSI) Bits 0 to 7 |
LUN (Logical Unit Number) and PUN (Physical Unit Number) |
Bits 8 to 15 |
Bus Number |
|
0AH |
WORD |
Segment of 3Kb buffer for caching CD-ROM reads |
0CH |
WORD |
Load segment for initial boot image (if 0000H, load at segment 07C0H) |
0EH |
WORD |
Number of 512-byte virtual sectors to load (only valid for Function 4CH of INT 13H) |
10H |
BYTE |
Low byte of cylinder count (for Function 08H of INT 13H) |
11H |
BYTE |
Sector count, high bits of cylinder count (for Function 08H of INT 13H) |
12H |
BYTE |
Head count (for Function 08H of INT 13H) |
The Bit fields for Bootable CD-ROM boot media type have been given in the following table:
Bit(s) |
Description |
3-0 |
Media type
Value |
Description |
0000 |
No emulation. |
0001 |
1.2M diskette. |
0010 |
1.44M diskette. |
0011 |
2.88M diskette. |
0100 |
Hard disk (drive C:) |
Other |
Reserved |
|
5-4 |
Reserved (0) |
6 |
Image contains ATAPI driver |
7 |
Image contains SCSI driver(s) |
|
