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T13/2132-D Revision 3 June 23, 2010
46 Working Draft Enhanced Disk Drive - 4 (EDD-4)
8.18 Lock/Unlock Media (FN 45h)
This function locks or unlocks removable media in a specific device. All removable media devices numbered 80h
and above shall implement this function. If a fixed disk (non-removable device) supports the media locking and
ejecting subset, this function shall return with success (i.e., AH = 00h and CF = 0b). There shall be support for
255 locks per device. A device shall not be unlocked until all locks to that device have been released with unlock
commands. Excess unlock calls shall return with CF = 1b and AH = B0h. If the number of locks supported value
is exceeded on a lock request, this function shall reject the request with CF = 1b and AH = B4h. Locking a
device without media present shall be a valid operation. On return from a lock or unlock request, AL shall contain
the lock state of the media as maintained by the BIOS. This provides for unlock requests when the lock count is
greater than zero. In this case, the media shall remain locked. Any physical locking and unlocking of the media
shall be implementation dependent, but the caller may operate on the assumption that locked media cannot be
removed without an unlock request. After power-on, or a system reset, all devices shall automatically enter an
unlocked state.
Entry
AH 45h
AL
Value Description
00h Lock media in device
01h Unlock media in device
02h Return lock/unlock status
03h-FFh Reserved
DL BIOS device number
Exit
Carry Clear Function completed without error
AH Shall be cleared to zero
AL
Value Description
00h Device is not locked
01h Device is locked
02h-FFh Reserved
Carry Set Function completed with an error
AH Shall be set to the error code