Dell PowerVault TL4000 SCSI Reference Guide - Page 54

Field, descriptions, Length, Block, Descriptor

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Mode Parameter Header The returned data on a Mode Sense (10) command begins with an eight byte Mode Parameter Header. This header has the following structure: Bit 7 6 5 4 3 2 1 0 Byte 0 (MSB) Mode Data Length 1 (LSB) 2 Reserved 3 Reserved 4 Reserved 5 Reserved 6 (MSB) Block Descriptor Length 7 (LSB) Field descriptions: Mode Data Length: This field indicates the number of bytes of parameter information the media changer is returning as a result of this command, excluding the Mode Data Length but including the six additional Mode Parameter Header bytes. If a block descriptor was requested this count is also added to the Mode Data Length. Block Descriptor Length: When the DBD bit is set to zero the media changer may return an eight byte Block Descriptor. When a Block Descriptor is returned the Block Descriptor Length will report 8. When the DBD bit is set the media changer will not return Block Descriptors and the block Descriptor Length will report 0. 3-40 TL2000 and TL4000 SCSI Reference

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Mode
Parameter
Header
The
returned
data
on
a
Mode
Sense
(10)
command
begins
with
an
eight
byte
Mode
Parameter
Header.
This
header
has
the
following
structure:
Bit
7
6
5
4
3
2
1
0
Byte
0
(MSB)
Mode
Data
Length
1
(LSB)
2
Reserved
3
Reserved
4
Reserved
5
Reserved
6
(MSB)
Block
Descriptor
Length
7
(LSB)
Field
descriptions:
Mode
Data
Length:
This
field
indicates
the
number
of
bytes
of
parameter
information
the
media
changer
is
returning
as
a
result
of
this
command,
excluding
the
Mode
Data
Length
but
including
the
six
additional
Mode
Parameter
Header
bytes.
If
a
block
descriptor
was
requested
this
count
is
also
added
to
the
Mode
Data
Length.
Block
Descriptor
Length:
When
the
DBD
bit
is
set
to
zero
the
media
changer
may
return
an
eight
byte
Block
Descriptor.
When
a
Block
Descriptor
is
returned
the
Block
Descriptor
Length
will
report
8.
When
the
DBD
bit
is
set
the
media
changer
will
not
return
Block
Descriptors
and
the
block
Descriptor
Length
will
report
0.
3-40
TL2000
and
TL4000
SCSI
Reference