Dell PowerVault TL4000 SCSI Reference Guide - Page 64

BUFFER, Vendor, Unique

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READ BUFFER (3Ch) The READ BUFFER command is used in conjunction with Write Buffer as a diagnostic function for testing the media changer's data buffer and the SCSI bus integrity. It is also used to read out Vendor Specific settings. Bit 7 Byte 0 1 2 3 (MSB) 4 5 6 (MSB) 7 8 9 6 LUN 5 4 3 2 1 Operation Code (3Ch) Reserved Buffer ID Mode Buffer offset Allocation Length Control 0 (LSB) (LSB) Field descriptions: Mode: The Mode field is used to select the mode of operation. The media changer supports the following values within the field. 0001b 0010b 0011b 1010b 1011b Vendor Unique operation Data Descriptor Echo buffer Echo Descriptor If any non supported value is set, the media changer terminates the command with a Check Condition status and an Illegal Request sense key set. Buffer ID: For all modes only buffer ID zero is supported. Buffer Offset: The Buffer Offset field is not supported and must be set to zero. If the Buffer Offset field specifies an unsupported value, the media changer shall return Check Condition status. The sense key will be set to ILLEGAL REQUEST and the sense data to INVALID FIELD IN CDB. Allocation Length: The Allocation Length specifies the maximum number of bytes that the initiator has allocated for returned data. Vendor Unique Mode A READ BUFFER command with the mode set to Vendor Unique Mode is used to retrieve parameters stored in non volatile Ram. The Buffer ID specifies the requested page. The Buffer Offset field in the CDB is not supported for this mode. Buffer ID 00h Description Variables Setting page Parameter List Length 002Eh 3-50 TL2000 and TL4000 SCSI Reference

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READ
BUFFER
(3Ch)
The
READ
BUFFER
command
is
used
in
conjunction
with
Write
Buffer
as
a
diagnostic
function
for
testing
the
media
changer’s
data
buffer
and
the
SCSI
bus
integrity.
It
is
also
used
to
read
out
Vendor
Specific
settings.
Bit
7
6
5
4
3
2
1
0
Byte
0
Operation
Code
(3Ch)
1
LUN
Reserved
Mode
2
Buffer
ID
3
(MSB)
4
Buffer
offset
5
(LSB)
6
(MSB)
7
Allocation
Length
8
(LSB)
9
Control
Field
descriptions:
Mode:
The
Mode
field
is
used
to
select
the
mode
of
operation.
The
media
changer
supports
the
following
values
within
the
field.
0001b
Vendor
Unique
operation
0010b
Data
0011b
Descriptor
1010b
Echo
buffer
1011b
Echo
Descriptor
If
any
non
supported
value
is
set,
the
media
changer
terminates
the
command
with
a
Check
Condition
status
and
an
Illegal
Request
sense
key
set.
Buffer
ID:
For
all
modes
only
buffer
ID
zero
is
supported.
Buffer
Offset:
The
Buffer
Offset
field
is
not
supported
and
must
be
set
to
zero.
If
the
Buffer
Offset
field
specifies
an
unsupported
value,
the
media
changer
shall
return
Check
Condition
status.
The
sense
key
will
be
set
to
ILLEGAL
REQUEST
and
the
sense
data
to
INVALID
FIELD
IN
CDB.
Allocation
Length:
The
Allocation
Length
specifies
the
maximum
number
of
bytes
that
the
initiator
has
allocated
for
returned
data.
Vendor
Unique
Mode
A
READ
BUFFER
command
with
the
mode
set
to
Vendor
Unique
Mode
is
used
to
retrieve
parameters
stored
in
non
volatile
Ram.
The
Buffer
ID
specifies
the
requested
page.
The
Buffer
Offset
field
in
the
CDB
is
not
supported
for
this
mode.
Buffer
ID
Description
Parameter
List
Length
00h
Variables
Setting
page
002Eh
3-50
TL2000
and
TL4000
SCSI
Reference