Section 5
SCSI Programming Guidelines
MINIMUM PREFETCH (Byte
4)
- Indicates
to
the
ProDril'e the minimum number
of
logical
blocks to prefetch
on
a cache miss for a
READ
command. The valid range
is
0
to
128;
any
value
outside this range
will
result
in
a
CHECK
CONDITION status with a sense
key
of ILLEGAL
REQUEST. The default value
is
one.
MAXIMUM PREFETCH (Byte 5) - Indicates
to
the
ProDril'e the maximum number of
logical blocks to prefetch
on
a cache miss
for
a
READ
command.
The
valid range
is
0
to
128;
any
value outside this
range
will result
in
a
CHECK
CONDmON status
with
a sense
key
of ILLEGAL
REQUEST. The default
is
16.
5.11. 1 0.7 Quantum UniQue Drive Control parameters. page Code
39J:l
Bit 7
I
6 5
I
4
3
1
I
1
I
0
Byte
0
RESERVED
=0
PAGE
CODE
=
39H
1
PAGE
LENGTH
=
6H
2
DIO
DII
fDB
j
RUEE
FDPE
R::O
I
DUA
1
DRT
3
DDIS
DELDIS
RESERVED=O
SSID
SCSIADR
4-7
RESERVED=O
DIO • DISABLE IDENTIFY OUT (Byte 2, Bit
7)
- Set
to
one indicates that the
ProDrive
will
DQ!
require
an
IDENTIFY message
from
the
initiator
to
be
able
to
disconnect
and
reconnect. A
DIO bit set to zero indicates that the ProDrive
will
require
the
initiator
to
send the IDENTIFY
message
to
be
able
to
disconnect.
The
default
is
zero.
DII • DISABLE IDENTIFY IN (Byte 2, Bit
6)
- Set
to
one indicates that the
ProDrive
will
D.Q!
send
an
IDENTIFY message after reconnecting
to
an
initiator. A
DII
bit set
to
zero indicates
that
the
ProDril'e
will
send
the
IDENTIFY message after reconnecting. The default is zero.
FDB
• FAST DEASSERTION
OF
BUSY
(Byte 2, Bit
5)
- Not used nor required
by
applications using the ProDril'e.
It
is included to maintain software compatibility with Quantum's
Q200 Series
TM
disk drives.
RUEE
• REALLOCATE UNCORRECTABLE ERROR ENABLED (Byte 2, Bit
4)-
Set
to
one indicates that the ProDril't
will
automatically reallocate uncorrectable hard errors if the
ARRE bit in Page 1 of the Error Recovery Parameters
is
set.
The uncorrectable (bad) data
is
written
to a
new
block and a
new
ECC
(one that
is
correct
for
this data)
is
appended. Reading the
new
block
will result
in
a
MEDIUM
(re-allocated uncorrectable data read) error
with
Sense
key
set
to
3, and sense
code set to
AAH.
Any
write to the
new
block
will
clear this condition. A RUEE bit set to zero
indicates that the
ProDril't will
not
attempt automatic reallocation if the hard error encountered
is
determined
to
be
uncorrectable.
In
this case, a
CHECK
CONDmON
with
a sense
key
of
MEDIUM
ERROR - Uncorrectable Data Error
will
result. The default
is
zero.
FOPE -
FILL
DATA PATTERN ENABLED (Byte 2, Bit 3) - Set
to
one indicates that the
ProDril'e
will
write the data pattern specified
in
Byte 2 of the FORMAT
UNIT
command into every
user-accessible sector
of
the drive
when
a
FORMAT
UNIT
command
is
executed. A FDPE bit set
to
zero indicates that the ProDril't
will
ignore the information
in
Byte 2 of the FORMAT UNIT
command. Issuing a FORMAT UNIT command
will
typically cause loss of data, even
if
FDPE
is
set
to
zero;
users should back
up
data prior
to
formatting.
The
default
is
zero.
NOTE: Bit 3
of
byte 2
is
reserved;
it
must
be
set
to
zero.
SCSI Programming Guidelines
5·
51
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