CDU-541
CD-ROM
DRIVE
SCSI
INTERFACE
MANUAL
5 • 2 •
28.
RESERVE
ColDllland
==============================================================================
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
==============================================================================
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superseded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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