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CDU-541 CD-ROM DRIVE SCSI INTERFACE MANUAL
5 • 2 • 28. RESERVE
ColDllland
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Bit:
7
6
5
4
3
2
1
o
Byte :
==============================================================================
o
:
Operation Code (16h)
:
-----1-----------------------------------------------------------------------1
1
i
Logical Unit Number
I
3rdPty
I
Third Party Device 10
1
Reserved
1
-----i-----------------------------------------------------------------------:
2
I
Reserved
I
-----1-----------------------------------------------------------------------:
3
I
Reserved
I
-----1-----------------------------------------------------------------------1
4
1
Reserved
:
-----1-----------------------------------------------------------------------1
5
1
Control Byte
1
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The RESERVE command is used to reserve a logical units for the use of the
initiator.
The third-party reservation allows logical units to be reserved
for another specified initiator.
The RESERVE and RELEASE commands provide the
basic mechanism for contention resolution in multiple-initiator systems.
This command will request that the entire logical unit be reserved for the
exclusive use of the initiator until the reservation is superseded by another
valid RESERVE command from the initiator that made the reservation or until
released by a RELEASE command from the same initiator that made the
reservation, by a BUS DEVICE RESET message from any initiator, by a "hard"
RESET condition, or by a power off/on cycle.
A logical unit reservation will
not be granted if the logical unit is reserved by another initiator.
It will
be permiSSible for an initiator to reserve a logical unit that is currently
reserved by that initiator.
If the logical unit, or any extent within the logical unit is reserved for
another initiator, the controller will respond by returning a RESERVATION
CONFLICT status.
If, after honoring the reservation, any other initiator then subsequently
attempts to perform any command on the reserved logical unit other than an
INQUIRY or a REQUEST SENSE command, the command will be rejected with
RESERVATION CONFLICT status.
The third-party reservation for the RESERVE command allows an initiator to
reserve a logical unit for another initiator.
If the third-party (3rdPty) bit is zero, then the third-party reservation
option is not requested.
If the 3rdPty bit is one then the specified logical
unit will be reserved for the initiator specified in the third-party device ID
field.
The controller will preserve the reservation until it is superseded by
another valid RESERVE command from the initiator that made the reservation or
until it is released by the same initiator, by a BUS DEVICE RESET message from
any initiator, or a reset condition.
The controller will ignore any attempt
to Felease the reservation made by any other initiator.
5-54
~~-
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