CDU-541
CD-ROM
DRIVE
SCSI
INTERFACE
MANUAL
5 . 2 . i
5.
READ
Command
==============================================================================
Bit:
7
6
5
4
3
2
1 o
Byte
:
==============================================================================
o :
Operation
Code (08h) :
-----1-----------------------------------------------------------------------1
1 I
Logical
Unit
Number I
(MSB)
I
-----1------------------------------
---I
2
Logical
Block
Address
:
---I
3 (LSB) I
-----------------------------------------------------------------------1
4
Transfer
Length
I
-----------------------------------------------------------------------:
5
Control
Byte
:
==============================================================================
The
READ
command
requests
that
the
controller
transfer
data
to
the
initiator.
The
data
will
be
transferred
in
whole
blocks
without
delays
occurring
during
a
block
transfer
on
the
bus.
After
completion
of
the
read
operation
the
drive
will
enter
the
hold
track
state
for
the
duration
of
the
inactivity
time.
The
logical
block
address
specifies
the
logical
block
at
which
the
read
operation
will
begin.
The
transfer
length
specifies
the
number
of
contiguous
logical
blocks
of
data
to
be
transferred.
A
transfer
length
of
zero
indicates
that
256
logical
blocks
will
be
transferred.
Any
other
value
indicates
the
number
of
logical
blocks
that
will
be
transferred.
This
command
will
be
terminated
with
a
RESERVATION
CONFLICT
status
if
any
reservation
conflict
exists
and no
data
will
be
read.
This
command
will
be
terminated
with
a
CHECK
CONDITION
status
for
a number
of
reasons.
The
error
recovery
parameters
determine
when and
how
the
data
errors
are
reported.
See
Section
5.3.1.1.
The
data
transfer
will
also
be
terminated
with
a
CHECK
CONDITION
STATUS
if
any
of
the
following
events
occur
while
a
read
operation
is
in
progress.
The
sense
key
will
be
set
to
ILLEGAL
REQUEST
and
the
additional
sense
code
set
to
END
OF
USER
AREA
ENCOUNTERED
ON
THIS
TRACK.
1) A mode
zero
is
detected
(i.e.
post-gap
detected).
2) An
index
equal
to
0
is
detected
(i.e.
pre-gap
detected).
3) A
track
number
change
is
detected
(i.e.
lead-out,
mode
one
(-)
mode
two).
4)
A
change
in
bit
one
of
the
control
field
is
detected.
If
the
logical
block
address
requested
is
not
within
a
data
track
the
command
will
be
terminated
with
a
CHECK
CONDITION
status.
The
sense
key
will
be
set
to
ILLEGAL
REQUEST
and
the
additional
sense
code
set
to
ILLEGAL
MODE
FOR
THIS
TRACK.
5-29
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