附件2-6：BM可引导光盘格式 6.0 New INT 13 Functions Transparent system operation is not always desirable because software installation usually requires the system to be in its "normal"configuration.For this reason 3 new INT 13 functions are provided.These functions allow the system to return to its normal state or to enter the "boot"state a second time after the boot process has already been initiated. 6.1 INT 13 Function 4A-Initiate Disk Emulation This function takes a pointer to the Specification Packet and uses it to make the specified drive letter available,using the Image LBA“"pointer'”in the supplied packet, Registers at call: AH=4A AL=00 DS:SI-Specification Packet as defined in figure 9 Registers on return AX-Return Codes CF-Clear if selected drive is emulating CF-Set if system not in emulation mode 6.2 INT 13 Function 4B-Terminate Disk Emulation This function returns the system to a configuration that matches a normal floppy or hard disk boot.If the CD booted as a floppy,the"A"drive returns and the CD becomes driver addressed.If the CD booted as a hard disk,the drive numbers are all decremented by 1,this returns all hard disks to their standard/normal device numbers. Registers at call: AH=4B AL =00.Return Status and Terminate Emulation AL =01,Return Status only,Do Not Terminate Emulation DL Drive number to terminate,7F =Terminate all DS:SI-Empty Specification Packet,See figure 9 Registers on return: DS:SI-Completed Specification Packet,See Figure 9 AX-Return Codes CF-Clear if system released CF-Set if system not in emulation mode Version 1.0 Copyright1994 Phoenix Technologies and IBM All Rights Reserved. Page 14附件2-6：IBM可引导光盘格式 Version 1.0 Copyright  1994 Phoenix Technologies and IBM All Rights Reserved. Page 14 6.0 6.0 New New INT INT 13 13 Functions Functions Functions Functions Transparent system operation is not always desirable because software installation usually requires the system to be in its “normal” configuration. For this reason 3 new INT 13 functions are provided. These functions allow the system to return to its normal state or to enter the “boot” state a second time after the boot process has already been initiated. 6.1 6.1 INT INT 13 13 Function Function Function Function 4A 4A - - Initiate Initiate Initiate Initiate Disk Disk Emulation Emulation Emulation Emulation This function takes a pointer to the Specification Packet and uses it to make the specified drive letter available, using the Image LBA “pointer” in the supplied packet. Registers at call: AH = 4A AL = 00 DS:SI - Specification Packet as defined in figure 9 Registers on return AX - Return Codes CF - Clear if selected drive is emulating CF - Set if system not in emulation mode 6.2 6.2 INT INT 13 13 Function Function Function Function 4B 4B - - Terminate Terminate Terminate Terminate Disk Disk Emulation Emulation Emulation Emulation This function returns the system to a configuration that matches a normal floppy or hard disk boot. If the CD booted as a floppy, the “A” drive returns and the CD becomes driver addressed. If the CD booted as a hard disk, the drive numbers are all decremented by 1, this returns all hard disks to their standard/normal device numbers. Registers at call: AH = 4B AL = 00, Return Status and Terminate Emulation AL = 01, Return Status only, Do Not Terminate Emulation DL = Drive number to terminate, 7F = Terminate all DS:SI - Empty Specification Packet, See figure 9 Registers on return: DS:SI - Completed Specification Packet, See Figure 9 AX - Return Codes CF - Clear if system released CF - Set if system not in emulation mode