CDU-541
CD-ROM
DRIVE
SCSI
INTERFACE
MANUAL
If
the
logical
block
address
plus
the
transfer
length
requested
exceeds
that
reported
by
the
READ
CAPACITY
data
a
CHECK
CONDITION
status
will
be
returned.
The
sense
key
is
set
to
ILLEGAL
REQUEST
and
the
additional
sense
code
is
set
to
LOGICAL
BLOCK
ADDRESS
NOT
VALID.
"~/
5 . 2
.16.
READ
BUFFER
Command
==============================================================================
Bit:
7
6
5
4
3
2
1
o
Byte :
=============================================================================-
o I
Operation
Code (3Ch)
-----1-----------------------------------------------------------------------
1 I
Logical
Unit
Number
I
Reserved
I
Mode
-----1-----------------------------------------------------------------------
2 1 Reserved
-----1-----------------------------------------------------------------------,
3 I
(MSB)
I
-----1--- ---I
4 1
Buffer
Offset
I
-----1---
___
I
5 I (LSB)
-----1-----------------------------------------------------------------------
6 1
(MSB)
-----+---
,
,
7
Transfer
Length
-----1---
8 I (LSB)
-----1-----------------------------------------------------------------------
9 I
Control
Byte
==============================================================================
The
READ
BUFFER
command
is
used
in
conjunction
with
the
WRITE
BUFFER
command
as
a
diagnostic
function
for
testing
controller
memory
and
the
bus
integrity.
This
command
will
not
alter
the
medium.
The
function
of
this
command
and
the
meaning
of
fields
within
the
command
descriptor
block
depend on
the
contents
of
the
mode
field.
A
mode
field
value
of
zero
indicates
that
the
buffer
offset
is
zero.
A
mode
field
value
of
one
indicates
that
the
buffer
offset
is
valid
and
the
data
will
be
placed
in
the
buffer
with
that
offset.
The
buffer
offset
is
the
byte
offset
within
the
buffer
where
the
data
will
be
retrieved.
If
the
controller
is
unable
to
accept
the
specified
buffer
offset,
it
will
return
CHECK
CONDITION
status
and
it
will
set
the
sense
key
to
ILLEGAL
REQUEST.
5-30
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