Seagate Barracuda 2LP Product Manual

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Barracuda 2LP Disc Drive

○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○

ST31250N/ND, ST31250W/WD,

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ST31250WC/DC, ST32550N/ND,

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ST32550W/WD, ST32550WC/DC

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Product Manual, Volume 1

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Barracuda 2LP Disc Drive

○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○

ST31250N/ND, ST31250W/WD,

○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○

ST31250WC/DC, ST32550N/ND,

○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○

ST32550W/WD, ST32550WC/DC

○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○

Product Manual, Volume 1

○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○

© 1996 Seagate Technology, Inc. All rights reserved
Publication number: 83328930, Rev. D
January 1996

Seagate®, Seagate Technology®, and the Seagate logo are registered
trademarks of Seagate Technology, Inc. Barracuda™ is a trademark of
Seagate Technology, Inc. Other product names are registered trademarks
or trademarks of their owners.

Seagate reserves the right to change, without notice, product offerings or
specifications. No part of this publication may be reproduced in any form
without written permission from Seagate Technology, Inc.

Revision status summary sheet

Sheets

Revision Date Writer/Engineer Affected

A 7/14/94 L. Newman/J. Olson All
B 9/21/94 L. Newman/J. Olson 36, 37, 43, 51, 57, 61,

64, 66

C 3/20/95 L. Newman/J. Olson 1, 9, 12, 14, 24, 25, 26, 27,

28, 29, 33, 34, 35, 36, 39,
41, 42, 47, 48, 50, 52, 55,
57, 58, 59, 60, 61, 62, 63,
64, 66, 68, 69, 70, 71, 73,
80, 82

D 1/9/96 L. Newman/J. Olson 3, 18, 36, 39, 40, 41, 48, 50,

51, 53, 54, 57, 65, 72

Note. Product Manual 83328930 is Volume 1 of a two-volume

document with the SCSI interface information in the

SCSI-2 Interface Product Manual,

Part Number 77738479.

Volume 2

Contents

1.0 Scope .............................................................................................................................. 1

2.0 Applicable standard and reference documentation ...................................................... 3

2.1 Standards ................................................................................................................. 3

2.2 Applicable reference documents............................................................................... 3

3.0 General description.......................................................................................................... 5

4.0 Standard features ............................................................................................................. 7

4.1 Performance ............................................................................................................. 7

4.1.1 Reliability ...................................................................................................... 7

4.2 Unformatted and formatted capacities ...................................................................... 8

4.3 Options ..................................................................................................................... 8

4.4 Installation................................................................................................................. 9

5.0 Performance characteristics ........................................................................................... 11

5.1 Internal drive characteristics ..................................................................................... 11

5.2 SCSI seek performance characteristics .................................................................... 11

5.2.1 Seek time...................................................................................................... 13

5.2.2 Format drive command execution time ......................................................... 13

5.3 General performance characteristics ........................................................................ 14

5.4 Start/stop time........................................................................................................... 15

5.5 Prefetch/multi-segmented cache control ................................................................... 15

5.6 Caching write data .................................................................................................... 16

5.7 Synchronized spindle operation ................................................................................ 17

6.0 Reliability specifications.................................................................................................. 21

6.1 Error rates................................................................................................................. 21

6.1.1 Environmental interference ........................................................................... 21

6.1.2 Write errors................................................................................................... 21

6.1.3 Seek errors ................................................................................................... 22

6.2 Reliability and service ............................................................................................... 22

6.2.1 Mean time between failures (MTBF) ............................................................. 22

6.2.2 Air flow.......................................................................................................... 22

6.2.3 Preventive maintenance ............................................................................... 30

6.2.4 Service life .................................................................................................... 30

6.2.5 Service philosophy........................................................................................ 30

6.2.6 Installation..................................................................................................... 30

6.2.7 Service tools ................................................................................................. 30

6.2.8 Hot plugging Barracuda 2LP disc drives ....................................................... 30

vi Barracuda 2LP Product Manual, Rev. D

7.0 Physical/electrical specifications.................................................................................... 33

7.1 AC power requirements ............................................................................................ 33

7.2 DC power requirements ............................................................................................ 33

7.2.1 Conducted noise immunity............................................................................ 34

7.2.2 Power sequencing ........................................................................................ 34

7.2.3 12V current profile ........................................................................................ 35

7.3 Heat/power dissipation.............................................................................................. 36

7.4 Environmental limits.................................................................................................. 36

7.4.1 Temperature ................................................................................................. 36

7.4.2 Relative humidity .......................................................................................... 36

7.4.3 Effective altitude (sea level) .......................................................................... 37

7.4.4 Shock and vibration ...................................................................................... 37

7.4.5 Air cleanliness............................................................................................... 38

7.4.6 Acoustics ...................................................................................................... 38

7.5 Electromagnetic compatibility.................................................................................... 38

7.6 Mechanical specifications ......................................................................................... 39

7.6.1 Drive orientation............................................................................................ 42

7.6.2 Cooling ......................................................................................................... 42

7.6.3 Drive mounting.............................................................................................. 42

8.0 Media characteristics ....................................................................................................... 43

8.1 Media description...................................................................................................... 43

9.0 Defect and error management......................................................................................... 45

9.1 Defects and errors .................................................................................................... 45

10.0 Option/configuration headers ......................................................................................... 47

10.1 Drive ID/option select headers .................................................................................. 47

10.1.1 ST31250N/ND and ST32550N/ND configuration .......................................... 47

10.1.2 ST31250W/WD and ST32550W/WD configuration ....................................... 50

10.1.3 ST31250WC/DC and ST32550WC/DC configuration.................................... 53

10.2 Synchronized spindles interface ............................................................................... 55

10.2.1 Electrical description ..................................................................................... 55

10.3 Grounding ................................................................................................................. 57

11.0 Interface requirements ..................................................................................................... 59

11.1 General description................................................................................................... 59

11.2 SCSI interface messages supported......................................................................... 59

11.3 SCSI interface commands supported........................................................................ 60

11.3.1 Inquiry data ................................................................................................... 62

11.3.2 Mode sense data .......................................................................................... 63

11.4 SCSI bus conditions and miscellaneous features supported..................................... 66

Barracuda 2LP Product Manual, Rev. D vii

11.5 Synchronous data transfer........................................................................................ 67

11.5.1 Synchronous data transfer periods supported .............................................. 67

11.5.2 REQ/ACK offset............................................................................................ 67

11.6 DC cable and connector ........................................................................................... 68

11.7 SCSI physical interface............................................................................................. 68

11.7.1 Physical characteristics ................................................................................ 70

11.7.2 Connector requirements ............................................................................... 71

11.7.3 Electrical description ..................................................................................... 72

11.8 SCSI non-wide physical interface ............................................................................. 76

11.9 SCSI wide physical interface..................................................................................... 79

11.10 SCSI single-connector attachment (SCA) physical interface..................................... 82

Index .......................................................................................................................................... 87

Figures

Figure 1. Barracuda 2LP disc drive (ST32550N drive shown) .................................................. 1

Figure 2. Barracuda 2LP disc drive (exploded view)................................................................. 5

Figure 3. ASA I OEM thermal calibration ................................................................................. 13

Figure 4. Synchronized drive interconnect diagram .................................................................. 17

Figure 5. Synchronized reference signal characteristics ........................................................... 18

Figure 6. Air flow pattern (ST32550N drive shown) .................................................................. 23

Figure 7. WYGX temperature measurement locations.............................................................. 24

Figure 8. HYHX temperature measurement locations............................................................... 25

Figure 9. JYHX temperature measurement locations ............................................................... 26

Figure 10. KYHX temperature measurement locations............................................................... 27

Figure 11. ZYHX temperature measurement locations ............................................................... 28

Figure 12. PYJX temperature measurement locations................................................................ 29

Figure 13. Temperature measurement location (ST32550N shown)........................................... 29

Figure 14. Barracuda 2LP drives typical +12V current profile ..................................................... 35

Figure 15. ST31250N/ND and ST32550N/ND mounting configuration dimensions..................... 39

Figure 16. ST31250W/WD and ST32550W/WD mounting configuration dimensions.................. 40

Figure 17. ST31250WC/DC and ST32550WC/DC mounting configuration dimensions.............. 41

Figure 18. Recommended mounting........................................................................................... 42

Figure 19. ST31250N/ND and ST32550N/ND jumper connectors .............................................. 47

Figure 20. ST31250W/WD and ST32550W/WD jumper connectors........................................... 50

Figure 21. ST31250WC/DC and ST32550WC/DC jumper connectors ....................................... 53

Figure 22. SCSI reference index signal driver/receiver combination ........................................... 55

Figure 23. ST31250N/ND and ST32550N/ND configuration select header................................. 56

Figure 24. ST31250W/WD and ST32550W/WD configuration select header.............................. 56

viii Barracuda 2LP Product Manual, Rev. D

Figure 25. ST31250WC/DC and ST32550WC/DC configuration select header .......................... 57

Figure 26. ST31250N/ND and ST32550N/ND physical interface................................................ 68

Figure 27. ST31250W/WD and ST32550W/WD physical interface............................................. 69

Figure 28. ST31250WC/DC and ST32550WC/DC physical interface ......................................... 69

Figure 29. Single-ended transmitters and receivers.................................................................... 73

Figure 30. Typical differential I/O line transmitter/receiver and terminators................................. 74

Figure 31. Non-shielded SCSI device connector ........................................................................ 76

Figure 32. Wide SCSI device connector ..................................................................................... 79

Figure 33. Non-shielded, 80-pin I/O and DC power single-connector attachment (SCA) ............ 82

Tables

Table 1. SCSI interface messages supported ......................................................................... 59

Table 2. Supported commands............................................................................................... 60

Table 3. Barracuda 2LP family drive inquiry data–ASA I ......................................................... 62

Table 4. Barracuda 2LP family drive inquiry data–ASA II ........................................................ 62

Table 5. Mode sense data, ST31250 default values–ASA I (SCSI-1 implementation) ............. 63

Table 6. Mode sense data, ST32550 default values–ASA I (SCSI-1 implementation) ............. 63

Table 7. Mode sense data, ST31250 default values–ASA I (SCSI-2 implementation) ............. 64

Table 8. Mode sense data, ST32550 default values–ASA I (SCS-2 implementation) .............. 64

Table 9. Mode sense data, ST31250 default values–ASA II (SCSI-2 implementation) ............ 65

Table 10. Mode sense data, ST32550 default values–ASA II (SCSI-2 implementation) ............ 65

Table 11. SCSI bus conditions and other miscellaneous features ............................................. 66

Table 12. Synchronous data transfer periods............................................................................ 67

Table 13. Mating connector parts .............................................................................................. 68

Table 14. Single-ended cable pin assignments for ST31250N and ST32550N drives ............... 77

Table 15. Differential cable pin assignments for ST31250ND and ST32550ND drives.............. 78

Table 16. Single-ended contact assignments for ST31250W and ST32550W drives ................ 80

Table 17. Differential contact assignments for ST31250WD and ST32550WD drives ............... 81

Table 18. SCA contact assignments for ST31250WC and ST32550WC drives......................... 83

Table 19. SCA contact assignments for ST31250DC and ST32550DC drives .......................... 84

Table 20. Disc drive SCSI timing............................................................................................... 85

Barracuda 2LP Product Manual, Rev. D 1

1.0 Scope

This manual describes Seagate Technology®, Inc. Barracuda™ 2LP (low
profile) disc drives.

Barracuda drives support the small computer system interface-2 (SCSI-2) as
described in the ANSI SCSI and SCSI-2 interface specifications to the extent
described in this manual. The

77738479) describes general SCSI interface characteristics of this and other
families of Seagate drives.

SCSI-2 Interface Product Manual

(part number

Figure 1. Barracuda 2LP disc drive (ST32550N drive shown)

2 Barracuda 2LP Product Manual, Rev. D

Barracuda 2LP Product Manual, Rev. D 3

2.0 Applicable standard and
reference documentation

Seagate takes all reasonable steps to ensure that its products are certifiable
to currently accepted standards. Typical applications of these disc drives
include customer packaging and subsystem design.

Safety agencies conditionally certify component parts, such as the Barra­cuda disc drive, based on their final acceptability in the end-use product. The
subsystem designer is responsible for meeting these conditions of accept­ability in obtaining safety/regulatory agency compliance in their end-use
product and certifying where required by law.

2.1 Standards

The Barracuda disc drive is a UL recognized component per UL1950, CSA
certified to CSA C22.2 No. 950-M89, and VDE certified to VDE 0805 and
EN60950.

If this model has the CE Marking, it complies with the European Union
requirements of the Electromagnetic Compatibility Directive 89/336/EEC of
03 May 1989 as amended by Directive 92/31/EEC of 28 April 1992 and
Directive 93/68/EEC of 22 July 1993.

Seagate uses an independent laboratory to confirm compliance to the above
directives. Drives are tested in representative systems for typical applica­tions. The selected system represents the most popular characteristics for
test platforms. The system configurations include:

• 486, Pentium, and PowerPC Microprocessors

• 3.5-inch floppy disc drive

• Keyboard

• Monitor/display
Although the test system with this Seagate model complies to the directives,

we cannot guarantee that all systems will comply. The computer manufac­turer or system integrator shall confirm EMC compliance and provide CE
Marking for their product.

The Barracuda disc drive is supplied as a component part. It is the
responsibility of the subsystem designer to meet EMC/regulatory require­ments. Engineering test characterizations of radiated emissions are avail­able from the Seagate safety department.

2.2 Applicable reference documents

Barracuda 2LP Installation Guide

Seagate part number: 83328920

SCSI-2 Interface Product Manual (volume 2)

Seagate part number: 77738479

ANSI small computer system interface (SCSI) documents

ANSI X3.131-1986 (SCSI-1)
X3T9.2/86-109 Rev. 10H (SCSI-2)
X3T9.2/91-010 Rev. 10 (SCSI-3) Parallel Interface

4 Barracuda 2LP Product Manual, Rev. D

Barracuda 2LP Product Manual, Rev. D 5

3.0 General description

Barracuda drives are low-cost, high-performance, random-access storage
devices designed to meet the needs of the original equipment manufacturer
(OEM) marketplace.

The Barracuda drive’s interface supports disconnect/reconnect, multiple
initiators, self-configuring host software, and automatic features that relieve
the host from knowing the physical characteristics of the targets (logical
block addressing is used).

The head and disc assembly (HDA) is sealed at the factory. Air circulates
within the HDA through a non-replaceable filter to maintain a contamination­free HDA environment.

Refer to Figure 2 for an exploded view of the drive. This exploded view is for
information only—never disassemble the HDA and do not attempt to service
items in the sealed enclosure (heads, media, actuator, etc.) as this requires
special facilities. The drive contains no replaceable parts. Opening the HDA
voids your warranty.

Figure 2. Barracuda 2LP disc drive (exploded view)

6 Barracuda 2LP Product Manual, Rev. D

Barracuda drives use a dedicated landing zone at the innermost radius of the
media to eliminate the possibility of destroying or degrading data by landing
in the data zone. The drive automatically goes to the landing zone when the
power is removed.

An automatic shipping lock prevents potential damage to the heads and
discs. The shipping lock disengages when power is applied to the drive and
the head load process begins.

Barracuda drives decode track 0 location data from the dedicated servo
surface to eliminate mechanical transducer adjustments and rel ate d reli­ability concerns.

A high-performance actuator assembly with a low-inertia, balanced, pat­ented, straight-arm design provides excellent performance with minimal
power dissipation.

Barracuda 2LP Product Manual, Rev. D 7

4.0 Standard features

Barracuda 2LP drives have the following standard features:

• Integrated SCSI controller

• Single-ended or differential SCSI drivers and receivers

• Asynchronous and synchronous data-transfer protocols

• Firmware downloadable using a SCSI interface

• Selectable sector size from 180 to 4,096 bytes per sector

• Programmable sector-reallocation scheme

• Flawed sector reallocation at format time

• Programmable auto-write and auto-read reallocation

• Reallocation of defects on command (post format)

• 96-bit Reed-Solomon error-correction code

• Sealed head and disc assembly (HDA)

• No preventive maintenance or adjustments required

• Dedicated head-landing zone

• Automatic shipping lock

• Automatic thermal compensation

• Embedded Grey Code track address to eliminate seek errors

• Self-diagnostics performed at power-on

• 1:1 interleave

• Zone bit recording (ZBR)

• Vertical, horizontal, or top-down mounting

• Dynamic spindle brake

• Active IC terminators (N/W models only)

• Synchronous spindle capability

• 512 Kbyte data buffer (see Section 5.5)

• Low audible noise for office environment

• Low power consumption

4.1 Performance

• Programmable multi-segmentable cache buffer

• 7,200 RPM spindle; average latency = 4.17 msec

• Command queuing of up to 64 commands

• Background processing of queue

• Supports start and stop commands

• Provides synchronized spindle capability

• Adaptive seek velocity; improved seek performance

4.1.1 Reliability

• 800,000 hour MTBF

• LSI circuitry

• Balanced low-mass rotary voice-coil actuator

8 Barracuda 2LP Product Manual, Rev. D

4.2 Unformatted and formatted capacities

Standard OEM models are formatted to have 512-byte sectors.
Barracuda 2LP drives have nine (9) spare sectors per cylinder and one (1)

spare cylinder per unit.

Formatted Unformatted

ST31250 1,020.9 Mbytes 1,205.3 Mbytes
ST32550 2,147.4 Mbytes 2,541.3 Mbytes

Users having the necessary equipment may modify the data block size
before issuing a f ormat command to obtain different formatted capacities.
User-available capacity also depends on the spare realloca tion scheme
selected. See the Mode Se lect command and the Forma t command in the

SCSI-2 Inte rfac e P r oduct Manual

(part numbe r 77738479).

4.3 Options

The capacity shown in Section 4.2 is normally provided. Other capacities
can be ord ered depend ing on the spar ing scheme an d sector size re­quested.

The following options are incorporated at the time of production or are
available separately.

• Front panel (green lens), part number 73497151
The standard front panel is black plastic. You may order other colors. Each

panel has a single rectangular green LED indicator lens that, when
glowing, indicates the drive is selected.

•

Barracuda 2LP Installation Guide,

This manual provides basic installation information for persons not
familiar with the product. It also includes information on obta ining techni­cal support and service for the drive.

• SCSI interface terminating resistors (N/W models only, enabled by jumper)
To enable internal drive termination, install a jumper on J1 pins 5 and 6.

Refer to Section 10.1.

• Single-unit shipping pack kit
The drive is shipped in bulk packaging to provide maximum protection

against transit damage. Units shipped individually require additional
prot ection as provided by the s i ngle-unit shippin g pack.

• Adapter accessory frame kit, part number 75790701
This kit contains a frame, which allows a 3.5-inch drive to be mounted

in a 5.25-inch drive bay. It includes mounting hardware, front panel with
a green lens, an LED with cable that connects to the remote LED
connector, and installation instructions.

part number 83328920

Barracuda 2LP Product Manual, Rev. D 9

4.4 Installation

For option jumper locations and definitions refer to Section 10.1. Drive default
mode parameters are not normally needed for installation. Refer to
Section 11.3.2 for default mode parameters if you need them.

• Ensure that the SCSI ID of the drive is not the same as the host adapter.

• If multiple devices are on the bus, set the drive’s SCSI ID to one that is not
presently used by other devices on the bus.

• If the drive is the only device on the bus, attach it to the end of the SCSI
bus cab le. Inte rnal ter min ati on is availabl e on ST31250N, ST31250W,
ST32550N, and ST32550W drives by enabling this feature with a jumper
(see Section 1 0.1).

External terminators are required for ST31250ND, ST31250WD,
ST31250WC, ST31250DC, ST32550ND, ST32550WD, ST32550WC,
and ST3 2550DC drives. These external terminators must be provided by
the user, systems integ ra t or, or h o s t equipme nt manufacturer.

• If you attach the drive to a bus that contains other devices, and the new
drive is not attached to the end of the bus, remove termination from the new
drive.

• Set all a ppropria te option jumpers prior to appl ying pow er to the d riv e. If
you change j umpers after applying power, recycle the drive’s power to
make th e new se tti ngs effectiv e .

Formatting

• It is not necessary to low-level format this drive. The drive is shipped from
the factory low-level formatted in 512-byte sectors.

• Reformat the drive if:
a. You select a different sector size.

b. You select a different spare-sector allocation scheme.

10 Barracuda 2LP Product Manual, Rev. D

Barracuda 2LP Product Manual, Rev. D 11

5.0 Performance characteristics

This section provides performance-related characteristics and features of
Barracuda 2LP drives.

5.1 Internal drive characteristics

ST31250 ST32550

Drive capacity, Mbytes unformatted 1,205.3 2,541.3
Read/write data heads, 5 11

maximum (physical)
Bytes per track, average bytes 64,160 64,160
Bytes per surface, Mbytes unformatted 232.4 231.03
Cylinders/tracks per surface, 3,711 3,510

user accessible
Tracks per inch 4,048 4,048
Bits per inch 73,820 72,680
Servo heads 1 1
Internal data rate per physical head, 47.5 to 72.0 49.4 to 72.0

Mbits/sec, variable with zone
Disc rotation speed 7,200 ± 0.5% 7,200 ± 0.5%
Average rotational latency, msec 4.17 4.17

5.2 SCSI seek performance characteristics

This section first describes the thermal calibration algorithms used by ASA
I and ASA II download code. Section 5.2.1 provides actual seek times and
section 5.2.2 provides drive format execution times.

Refer to Table 22 in Section 11.10 and to the

Manual

ASA I thermal calibration

All performance characteristics assume that autom atic adaptive thermal
compensation is not in process when the drive rec eives the SCSI command.
Automatic adaptive thermal compensation will not interrupt an active SCSI
command. I f adaptive thermal compensation is in process when a SCSI
command is received, the command is queued until compensation com­pletes. When compensation completes for the head, the first queued SCSI
com mand execu tes, and the drive co ntinues compensation for the remaining
heads.

(part numbe r 77738479 ) f or additional timing deta il s .

SCSI-2 Interface Product

The above procedure continues until compensation for all heads has
completed, or until 10 minutes have elapsed. The drive initiates an automatic
adaptive thermal compensation cycle once on power-up before completing
its initialization sequence, once after 1 minute from the end of initialization,
and then once approximately every 10 minutes. Automatic thermal com­pensation occurs at other times but should be transparent to the user (e.g.,

12 Barracuda 2LP Product Manual, Rev. D

during format, at Re-Zero command, at spindle-up, during read-error recov­ery, and during reassign-block functions) . Y ou can use the Re-Zero com­mand to reset the thermal compensation timer to let the host know when the
interruption for thermal compensation will occur.

ASA II thermal calibration

At power up and following a SCSI reset, the drive calibrates the heads using
the SCSI Rezero Unit command before processing read and write com­mands. The drive then delays a fixed period of time (D) before performing any
additional thermal calibrations. This ensures a specific time interval when no
thermal calibration interruptions will occur.

After the delay interval (D) expires, a single head thermal calibration (t-cal)
is scheduled every N1 seconds. Refer to the equation below.

N1 = (T - D) / (2 * H)
T = 600 seconds (the maximum allowable thermal calibration period for any

single head)
D = 300 seconds (period after the power-up/reset calibration before initiating

subsequent thermal calibrations)
H = Number of heads in the drive
After the drive has cycled once through all of the heads (H) at the N1 time

interval, the scheduling of single head thermal calibrations switches to an N2
time interval. Refer to the equation below.

N2 = T / (2 * H)
When a single head thermal calibration is scheduled, the drive attempts to

find an idle period of 25 to 50 milliseconds prior to performing the thermal
calibration. If the thermal calibration has not been performed after another N1
or N2 seconds elapse (whichever is the current time interval), the drive forces
a thermal calibration to occur at the next command boundary (even during
a read lookahead sequence), and immediately restarts the N2 or N2 second
timer–this guarantees that no head will remain uncalibrated for more than T
seconds and that no thermal calibrations will occur closer together in time
than approximately every N1 or N2 seconds.

Any thermal calibration performed during the standard retry sequence will be
limited to the misaligned head, and will be disabled if the host has selected
a retry count of zero.

Barracuda 2LP Product Manual, Rev. D 13

Start

A

No

No

Write/Read

Miss

command

Has

10 min. TCAL

timer

expired?

Yes

Reset

10 minute

TCAL timer

Is

SCSI

command in

progress?

Yes

Complete
command

Read
ahead

pending?

Yes

Hold

(wait for next 

command)

Independent

10 Minute

Periodic

Abortive Read

Lookahead

Timer

Seek to

TCAL cyl
and select
head zero

No

Read
Sequential
command

All

heads

calibrated?

No

Select

next

head

No

Yes

TCAL

head

Has

target

received a SCSI

command?

Yes

All

heads

calibrated?

Yes

A

No

No

Write/Read

Miss

command

Complete
command

Read

ahead

pending?

Yes

Hold

(wait for next 

command)

Independent

10 Minute

Periodic

Abortive Read

Lookahead

Timer

Has

10 min. TCAL

timer

expired?

No
Seek to

TCAL cyl
and select
next head

Read

Sequential

command

Yes

Figure 3. ASA I OEM thermal calibration

5.2.1 Seek time

Drive including
controller overhead

Drive level (msec) without disconnect (msec)
read write read write

Average typical* 8.0 9.0 9.0 10.0
Single track typical* 0.6 0.9 1.6 1.9
Full stroke typical* 17 19 18.0 20.0

*Typical seek values are measured under nominal conditions of tempera-

ture, voltage, and horizontal orientation on a representative sample of
drives .

5.2.2 Format drive command execution time

≥≥

for

≥ 512-byte sectors

≥≥

ST31250 ST32550

Maximum (with verify) 15 minutes 30 minutes
Maximum (without verify) 10 minutes 20 minutes

14 Barracuda 2LP Product Manual, Rev. D

5.3 General performance characteristics

Minimum sector interleave 1 to 1
Data buffer to/from disc media 512-byte sector
Data transfer rate (≤ 1 sector)

Minimum 5.30 Mbytes/sec*
Maximum 8.94 Mbytes/sec*

Data transfer rate (< 1 track)
Minimum 3.56 Mbytes/sec*

Maximum 7.65 Mbytes/sec*
SCSI interface data

Asynchronous transfer rate * 5.0 Mbytes/sec**
(maximum instantaneous) 10.0 Mbytes/sec***

Synchronous transfer rate fast 2.5 to 10 Mbytes/sec
(ST31250N/ND and ST32550N/ND)

Synchronous transfer rate wide 5.0 to 20 Mbytes/sec
(ST31250W/WD/WC/DC and
ST32550W/WD/WC/DC)

Sector sizes
Default 512-byte data blocks

Variable in even-sector sizes 180 to 4,096 bytes
Read/write consecutive sectors on a track Yes
Flaw reallocation performance impact

Spare sectors per track reallocation Negligible
Spare sectors per cylinder reallocation Negligible
Spare tracks per volume reallocation 35 msec (typical)

Overhead time for head switch 0.7 msec
Overhead time for one-track cylinder switch 1.6 msec (typical)
Average rotational latency 4.17 msec
* Rate measured from the start of the first sector transfer to or from the host.

** Assumes system ability to support 5.0 Mtransfers/sec, 1 byte wide, and

no cable loss.

***Assumes system ability to support 5.0 Mtransfers/sec, 2 bytes wide, and

no cable loss.

Barracuda 2LP Product Manual, Rev. D 15

5.4 Start/stop time

Disabling the Motor Start option causes the motor to start as soon as power
is applied, causing the drive to become ready within 30 seconds after DC
power is applied at nominal voltage. If a recoverable error condition is
detected during the start sequence, the drive executes a recovery procedure
which may cause the drive to become ready in excess of 30 seconds. During
the start sequence the drive responds to some commands over the SCSI
interface. Stop time is less than 30 seconds (maximum) from removal of DC
power.

Enabling the Motor Start option causes the internal controller to accept the
commands listed in the
than 3 seconds after applying DC power. After receiving the Motor Start
command, the drive becomes ready for normal operation within 30 seconds
(excluding the error recovery procedure). The Motor Start command can
also be used to command the drive to stop the spindle (see the Start/Stop
command information in the

There is no power control switch on the drive.

SCSI-2 Interface Product Manual

SCSI-2 Interface Product Manual

(77738479) less

).

5.5 Prefetch/multi-segmented cache control

The drive provides a prefetch/multi-segmented cache algorithm, which in
man y c ase s e nhan ces sys tem perf orma nce . T o sele ct th is f ea ture, the host
sends the Mode Select command with the proper values in the applicable
bytes in page 08h (see the
prefetch and cache operation enabled.

Of the 512 Kbytes physical buffer space, approximately 480 Kbytes can be
used as a cache. The cache can be divided into logical segments from which
data is read and to which data is written.

The drive keeps track of the logical block addresses of the data stored in each
segment of the cache. If the cache is enabled (see RCD bit, Table 5.2.1-27
in the

SCSI-2 Interface Product Manual),

read command is retrieved from the cache before any disc access is initiated.
Data in contiguous logical blocks immediately beyond that requested by the
Read command can be retrieved and stored in the cache for immediate
transfer to the initiator on subsequent read commands. This is referred to as
the prefetch operation. Since data that is prefetched may replace data
already in the cache segment, an initiator can limit the amount of prefetch
data to optimize system performance. The drive never prefetches more
sectors than the number specified in bytes 8 and 9 of Mode page 08h (see
the

SCSI-2 Interface Product Manual

Kbytes of the buffer are used as a circular buffer for read/writes, with no
prefetch operation and no segmented cache operation.

The following is a simplified description of the prefetch/cache operation:

SCSI-2 Interface Product Manual

data requested by the host with a

). If the cache is not enabled, 480

). Default is

Case A. A read command is received and the first logical block is already in
the cache.

1. The drive transfers to the initiator the first logical block requested plus all
subsequent contiguous logical blocks that are already in the cache. This
data may be in multiple segments.

16 Barracuda 2LP Product Manual, Rev. D

2. When a re quest ed logica l block is rea ched that is not in an y s egment,
the d ri ve fetch es it and any remaining requested lo gical block addres ses
from the d isc and p uts them in a se gment of the cach e. The d rive
transfers the remaining requested logical blocks fro m the cac he to the
initiator in accordance with the “buffer-full” ratio specification given in
Mode Select Disconnect/Reconnect parameters, page 02h (see the

SCSI-2 Int erfac e Pr o duct Man ual

3. The drive prefetches additional logical blocks contiguous to those
transferred in step 2 above and stores them in the segment. The drive
stops filling the segment when the maximum prefetch value has been
transferred (s ee the

Case B. A read command is received and the first logical block address
requested is not in any segment of the cache.

1. The drive fetches the requested logical blocks from the disc and
transfers them into a segment, then from there to the initiator in
accordance with the “buffer-full” ratio specification given in Mode Select
Disconnect/Reconnect parameters, page 02h (see the

face Pr oduct Manual

2. The drive prefetches additional logical blocks contiguous to those trans­ferred in Case A, step 2 above and stores them in the segment. The drive
stops filling the segment when the maximum prefetch value has been
transferred.

SCSI-2 Inter fac e Pr oduct Manual

).

).

).

SCSI-2 Inter-

During a prefetch, the drive crosses a cylinder boundary to fetch data only
if the Discontinuity (DISC) bit is set to 1 in bit 4 of byte 2 of the Mode Select
parameters page 8h. Default is zero for bit 4 (see the

Pro duct Manual

Each cache segment is actually a self-contained circular buffer whose
length is a n integer number of sect ors. The drive supports operation with
any integer number of segments 1 to 16. Divide the 491,520 bytes in the
buffer by the number of segments to get the segment size; default is 3
segments (see the
capability of the individual segments greatly enhances the cache’s overall
performance, allowing a wide range of user-selectable configurations
including a pure prefetch strategy.

).

SCSI-2 In t e rface Product Manual

5.6 Caching write data

Write caching is a drive-write operation, which uses a drive’s buffer storage
area where data to be written to the disc is stored while the drive performs
the Write command.

Write caching is enabled along with read caching. Default is cache enabled.
For write caching, the same buffer space and segmentation is used as set
up for read functions. When a write command is issued, the cache is first
checked to see if any logical blocks to be written are already stored in the
cache from a previous read or write command. If there are, the respective
cache segments are cleared. The new data is cached for subsequent read
commands.

SCSI-2 Interface

). The wrap-around

If a 10-byte CDB write command (2Ah) is issued with the data page out (DPO)
bit set to 1, no write data is cached, but the cache segments are still checked

Barracuda 2LP Product Manual, Rev. D 17

and cleared, if needed, for any logical blocks that are being written (see the

SCSI-2 Interface Product Manual

).

If the number of write data logical blocks exceeds the size of the segment
being written into when the end of the segment is reached, data is written
into the beginning of the same cache segment, overwriting data that was
written there at the beginning of the operation. However, the drive does not
overwrite data that has not yet been written to the disc.

5.7 Synchronized spindle operation

The synchronized spindle operation allows several drives operating from the
same host to operate their spindles at the same synchronized rotational rate.
Drives operating in a system in synchronized mode increase the system’s
capacity and transfer rate in a cost-effective manner.

The interface consists of a twisted-pair cable, which connects the drives in
the synchronized system in a daisy-chain configuration as shown below.

Sync Interface

Master Sync

Source

(or other drive)

Host

System

Interface

Spindle
Control

+5V

Drive 1

Spindle
Control

+5V

Drive 2

Spindle
Control

+5V

Drive n

R

T

R

T

R

T

J4 Pin 1 on N/ND drives
J4 Pin 6 on WC/DC drives (+SSREF)
J5 Pin 11 on W/WD drives

J4 Pin 2 on N/ND drives
J5 Pin 12 on W/WD drives

J4 Pin 1 on N/ND drives
J4 Pin 6 on WC/DC drives (+SSREF)
J5 Pin 11 on W/WD drives

J4 Pin 2 on N/ND drives
J5 Pin 12 on W/WD drives

J4 Pin 1 on N/ND drives
J4 Pin 6 on WC/DC drives (+SSREF)
J5 Pin 11 on W/WD drives

J4 Pin 2 on N/ND drives
J5 Pin 12 on W/WD drives

Figure 4. Synchronized drive interconnect diagram

The host can reconfigure the drive any ti me after power-up to be the master
or a slave by using the Mode Select command on the Rigid Di sc Drive
Geometry page. The master provides the reference signal to which all other
drives phase-lock, including the master. There is only one master per
system, and that can be a drive or the hos t computer. All dri ves may be
configured as slaves allowing the host to provide the reference signal.

Each drive also can be configured for the non-synchronized mode in which
it ignores any reference signal that might be present—this is the default mode
as shipped from the factory. Connect t he synchronized ref erence si gnal to
the host only if the host provides the reference signal. If the host does not
provide the reference signal, do not connect the host.

18 Barracuda 2LP Product Manual, Rev. D

1.0 µsec min.

1.37 µsec max.

1.2 µsec ± 0.5

0

1

SSREF +

Rotational position locking
Note. Mode Select page 4, byte 17, bits 1 and 0.
RPL Description

00b Spindle synchronization is disabled (default value)
01b The target operates as a synchronized-spindle slave
10b The target operates as a synchronized-spindle master
11b The target operates as a synchronized-spindle master control

(not supported by the disc drive)

The Pike 2 LSI on the master drive provides the reference signal (SSREF+ ).
The index signal generates a 120 Hz signal. The signal is norm ally
false/negated (nominal 0V) and makes a transition to the true/asserted
(nominal +5V) l evel t o indicate t he refere nce position during the revol ution
period. Master and slave drives use the trailing (falling) edge of the
refere nce signal to phase- lock their spindles. A maximum of 10 seconds
is allo wed for a s la ve to s ynchroni ze with the r eferenc e sig nal. Figur e 5
shows the characteristics of the reference signal.

T = 0.0083 seconds (± 1.0% max)

± 10 microseconds cycle-to-cycle variance
± 20 microseconds phase error while synchronized

Figure 5. Synchronized reference signal characteristics

SCSI interface factors

The Rotational Position Locking (RPL) field in byte 17 (bits 0 a nd 1) of the
Rigid Disc Drive Geometry mode par amete rs page (p age 04h) i s used for
enabling and disabling spindle synchronization mode (see the

Interface P ro duct Manual

). If the target fails to synchroniz e, it creates a unit

SCSI-2

attention condition to all initiators. The sense key is set to Unit Attention and
the addi tion a l sense code is set to Spindle Synchronized (5C01).

After reaching synchronization, if the target detects a change of synchroni­zation and:

1. If the logical unit is not executing an I/O process for the initiator, then the
target creates a unit attention condition. The sense key is set to Unit
Attention and the additional sense code is set to Spindle Synchronized
(5C01) or Spindle Not Synchronized (5C02).

2. If the logical unit is executing an I/O process and no other error occurs,
then the target returns Check Condition status. The sense key is set to
Recovered Error if the target is able to complete the I/O process or to
Hardware Error if the target is unable to complete the I/O process. The
additional sense code is set to Spindle Synchronized (5C01) or Spindle
Not Synchronized (5C02).

Barracuda 2LP Product Manual, Rev. D 19

You may operate the drive with a rotational skew when synchronized. The
rotational skew is applied in the retarded direction (lagging the synchronized­spindle master control). A rotational offset of up to 255/256 of a revolution
lagging may be selected. Select the amount of offset by using the Mode
Select command, Rigid Disc Drive Geometry page (page 04h), byte 18 (see
the

SCSI-2 Inter face Pr o duct Manual

). The v alu e in byte 18 (0–FFh ) is the
numerator of a fractional multiplier that has 256 as the denominator. For
example, 40h selects 40h/FFh or 1/4 of a revolution lagging skew, 80h
selects 1/2 of a revolution lagging skew, etc. Since the drive supports all
offset values from 0 to 255, values sent by the initiator are not rounded off.
The drive’s translation of the digital offset values to physical rotational offsets
results in offset values whose phase error lies within the ± 20 microseconds
phase error with respect to the supplied 120 Hz reference signal.

The drive does not have the capability to adjust the rotational offset value
requested by the initiator to a physical offset in the drive that corresponds
in any way to sector boundaries or changes in ZBR zones. The initiator must
formulate these boundaries or changes, if required, to calculate the value of
offset it sends to the drive.

20 Barracuda 2LP Product Manual, Rev. D

Barracuda 2LP Product Manual, Rev. D 21

6.0 Reliability specifications

The following reliability specifications assume correct host and drive
interface, including all interface timings, power supply voltages, and
environmental requirements.

Seek error rate Less than 10 errors in 108 seeks
Recoverable error rate Less than 10 errors in 1011 bits transferred

(using default settings)
Unrecovered data Less than 1 sector in 1014 bits transferred
Miscorrected data Less than 1 sector in 1021 bits transferred
MTBF 800,000 hours
Service life 5 years
Preventive maintenance None required

6.1 Error rates

The error rates stated in this manual assume the following:

• The driv e is opera ted using DC power as de fined in Section 7.2.

• The drive h as been formatted with S CSI format commands.

• Errors caused by media defects or host system failures are excluded from

error rate computations. Refer to Section 9.0.

6.1.1 Environmental interference

When evaluating system operation under conditions of electromagnetic
interference (EMI), the performance of the drive within the system is
considered acceptable if the drive does not generate an unrecoverable
condition.

An unrecoverable error or condition is defined as one that:

• is not detected and corrected by the drive itself;

• is not capable of being detected from the error or fault status provided

through the drive or SCSI interface; or

• is not capable of being recovered by normal drive or system recovery

procedures without operator intervention.

6.1.2 Write errors

Write errors can occur as a result of media defects, environmental interfer­ence, or component malfunction. Therefore, write errors are not predictable
as a function of the number of bits passed.

If an unrecoverable write error occurs because of a component malfunction
in the drive, the error is classified as a failure affecting MTBF. Unrecoverable
write errors are those that cannot be corrected within two attempts at writing
the record with a read verify after each attempt (excluding media defects).

22 Barracuda 2LP Product Manual, Rev. D

6.1.3 Seek errors

A seek error is defined as a failure of the drive to position the heads at the
addressed track. There must be no more than one recoverable seek error
in 107 physical seek operations. After detecting an initial seek error, the drive
automatically reseeks to the addressed track up to three times. If a reseek
is successful, the extended sense report indicates a Seek-Positioning Error
(15h), No-Seek-Complete Error (02h), or Track-Follow Error (09h), and the
sense key reports a recovered error (1h). If all three reseeks fail, a Seek­Positioning Error (15h) is reported with a Medium (3h) or Hardware Error
(4h) reported in the sense key. This is an unrecoverable seek error.
Unrecoverable seek errors are classified as failures for MTBF calculations.
Refer to Section 5.1.1.2 of the
number 77738479).

SCSI-2 Interface Product Manual

(part

6.2 Reliability and service

You can enhance the reliability of Barracuda 2LP disc drives by ensuring
that the drive receives adequate cooling. This section provides recom­mended air-flow information, temperature measurements, and other infor­mation that may be used to enhance the service life of the drive.

6.2.1 Mean time between failures (MTBF)

The production disc drive achieves an MTBF of 800,000 hours when
operated in an average local disc drive ambient temperature of 95°F (35°C)
or less. Short-term excursions up to the specification limits (122°F, 50°C) of
the operating environment will not affect MTBF performance.

The following expression defines MTBF:

MTBF =

Estimated power-on operating hours means the estimated total power-on
hours for all drives in service.

Drive failure means any stoppage or substandard performance caused by
drive malfunction.

Data is calculated on a rolling-average base for a minimum period of six
months.

6.2.2 Air flow

The rack, cabinet, or drawer environment for the Barracuda 2LP drive must
provide cooling of the electronics and head and disc assembly (HDA). You
should confirm that adequate cooling is provided using the temperature
measurement guidelines described below.

Orient the drive or direct air flow so that the least amount of air-flow
resistance is created while providing air flow to the electronics and HDA.
Also, choose the shortest p ossib le path b etween the air i nlet and exit to
minimize the travel length of air heated by the Barracuda 2LP drive and
other heat sources within t he ra c k, cabinet, or drawer environment.

Possible air-flow patterns are shown in Figure 6. Create the air-flow patterns
by using one or more fans, either forcing or drawing air as shown in the
illustrations. Other air-flow patterns are acceptable as long as the tempera­ture measurement guidelines are met.

Estimated power-on operating hours in the period

Number of drive failures in the period

Barracuda 2LP Product Manual, Rev. D 23

Above unit

Under unit

Note. Air flows in the direction shown (back to front)
or in reverse direction (front to back)

Above unit

Under unit
Note. Air flows in the direction shown or
in reverse direction (side to side)

Figure 6. Air-flow pattern (ST32550N drive shown)

24 Barracuda 2LP Product Manual, Rev. D

To confirm that required cooling for the Barracuda electronics and HDA is
provided, place the drive in its final mechanical configuration, perform
random write/read operations, and after the temperatures stabilize, measure
the case temperature of the components listed below.

Add 15°C to the 800k MTBF case temperatures to obtain the maximum
temperature for each of the reference components. You should not operate
the drive at the maximum case temperature for extended periods of time.
Doing so will reduce product reliability.

Air-flow cooling
ST31250N and ST32550N single-ended drives

MTBF

800k hours

Card Component Reference case temperature (°C)

WYGX ADC 1 49
WYGX Detector 2 60
WYGX Microprocessor 3 55
WYGX Driver 4 57

The air-flow pattern with which the temperature guidelines above were
generated is shown in Figure 6 (opposite direction). Local average air
velocity was 0.61 msec (120 lfpm) and inlet air temperature to the drive was
30°C (86°F), plus a 5°C temperature rise in the test enclosure (35°C ambient
local to the drive).

The maximum allowable HDA case temperature is 60°C (see Figure 13).

3 1

2

Figure 7. WYGX temperature measurement locations

4

Barracuda 2LP Product Manual, Rev. D 25

Air-flow cooling
ST31250ND and ST32550ND differential drives

MTBF

800k hours

Card Component Reference case temperature (°C)

HYHX ADC 1 49
HYHX Detector 2 60
HYHX Microprocessor 3 55
HYHX Driver 4 57

The air-flow pattern with which the temperature guidelines above were
generated is shown in Figure 6 (opposite direction). Local average air
velocity was 0.61 msec (120 lfpm) and inlet air temperature to the drive was
30°C (86°F), plus a 5°C temperature rise in the test enclosure (35°C ambient
local to the drive).

The maximum allowable HDA case temperature is 60°C (see Figure 13).

3

1

2

Figure 8. HYHX temperature measurement locations

4

26 Barracuda 2LP Product Manual, Rev. D

Air-flow cooling
ST31250W and ST32550W wide single-ended drives

MTBF

800k hours

Card Component Reference case temperature (°C)

JYHX ADC 1 49
JYHX Detector 2 60
JYHX Microprocessor 3 55
JYHX Driver 4 57

The air-flow pattern with which the temperature guidelines above were
generated is shown in Figure 6 (opposite direction). Local average air
velocity was 0.61 msec (120 lfpm) and inlet air temperature to the drive was
30°C (86°F), plus a 5°C temperature rise in the test enclosure (35°C ambient
local to the drive).

The maximum allowable HDA case temperature is 60°C (see Figure 13).

3 1

2

Figure 9. JYHX temperature measurement locations

4

Barracuda 2LP Product Manual, Rev. D 27

Air-flow cooling
ST31250WD and ST32550WD wide differential drives

MTBF

800k hours

Card Component Reference case temperature (°C)

KYHX ADC 1 49
KYHX Detector 2 60
KYHX Microprocessor 3 55
KYHX Driver 4 57
The air-flow pattern with which the temperature guidelines above were

generated is shown in Figure 6 (opposite direction). Local average air
velocity was 0.61 msec (120 lfpm) and inlet air temperature to the drive was
30°C (86°F), plus a 5°C temperature rise in the test enclosure (35°C ambient
local to the drive).

The maximum allowable HDA case temperature is 60°C (see Figure 13).

3 1

2

Figure 10. KYHX temperature measurement locations

4

28 Barracuda 2LP Product Manual, Rev. D

Air-flow cooling
ST31250WC and ST32550WC wide single-ended SCA drives

MTBF

800k hours

Card Component Reference case temperature (°C)

ZYHX ADC 1 49
ZYHX Detector 2 60
ZYHX Microprocessor 3 55
ZYHX Driver 4 57

The air-flow pattern with which the temperature guidelines above were
generated is shown in Figure 6 (opposite direction). Local average air
velocity was 0.61 msec (120 lfpm) and inlet air temperature to the drive was
30°C (86°F), plus a 5°C temperature rise in the test enclosure (35°C ambient
local to the drive).

The maximum allowable HDA case temperature is 60°C (see Figure 13).

3 1

2

Figure 11. ZYHX temperature measurement locations

4

Barracuda 2LP Product Manual, Rev. D 29

Air-flow cooling
ST31250DC and ST32550DC wide differential SCA drives

MTBF

800k hours

Card Component Reference case temperature (°C)

PYJX ADC 1 49
PYJX Detector 2 60
PYJX Microprocessor 3 55
PYJX Driver 4 57

The air-flow pattern with which the temperature guidelines above were
generated is shown in Figure 6 (opposite direction). Local average air
velocity was 0.61 msec (120 lfpm) and inlet air temperature to the drive was
30°C (86°F), plus a 5°C temperature rise in the test enclosure (35°C ambient
local to the drive).

The maximum allowable HDA case temperature is 60°C (see Figure 13).

3 1

2

Figure 12. PYJX temperature measurement locations

4

Measure the HDA housing temperature at the location specified in Figure 13.

1.00

.50

Figure 13. Temperature measurement location (ST32550N shown)

30 Barracuda 2LP Product Manual, Rev. D

6.2.3 Preventive maintenance

No preventive maintenance is required.

6.2.4 Service life

The drive has a useful service life of 5 years. Depot repair or replacement
of major parts is permitted during this period.

6.2.5 Service philosophy

Spe ci al e qu ip me nt i s req ui re d t o rep air t h e dr i ve’s HDA . To a c hieve th e
5-year service life, repairs must be performed only at a properly e quipped
and staffed service and repair facil ity. T r oubleshooting and repai r of PCBs
in the field is not recommended because of the extensive diagnostic
equipment require d for effective s ervicing. Also, t here are no spare pa rts
available for this drive. The drive’ s warranty is voided if the HDA is opened.

6.2.6 Installation

The driv e is design ed , ma nufac tur ed, and t este d with a “pl ug in and pla y ”
installation philosophy. This philosophy minimizes the requirements for
hi gh ly t rai ned per so nne l to i nt egr ate t he d ri ve in to t he O EM’ s sy ste m,
whether in a factory or field env ir onment. Refer to S ection 4 .4 a nd t o t he

Barracuda 2LP I nstallation Guide

(8332 892 0 ) f or inst al lation ins truc tion s.

The drive has been low-le vel forma tted a t th e factory and does n ot need
to be reformatted.

6.2.7 Service tools

No special tools are required for site installation or recommended for site
maintenance. Refer to Section 6.2.3. The depot repair philosophy of the
drive precludes the necessity for special tools. Field repair of the drive is not
practical because users cannot purchase individual parts for the drive.

6.2.8 Hot plugging Barracuda 2LP disc drives

Caution. Hot-plug drives are not designed for simultaneous power discon-

nection and physical removal.

During power-up and power-down periods, the hot SCSI connect/disconnect
capability does not produce glitches or any corruptions on an active SCSI
bus. Barracuda 2LP drives conform to the SCSI-3 standard requirements for
glitch-free power-on and power-off. The drive maintains the high-impedance
state of the device connector contacts during a power cycle until the
transceiver is enabled.

Note. The systems integrator must ensure that no temperature, energy, or

voltage hazard is presented during the hot connect/disconnect opera­tion.

Procedure:

1. Configure the drive with no connection between the drive and the
TRMPWR signal on the SCSI bus. To accomplish this, remove all
jumpers from connector J1.

2. Ensure that all SCSI devices on the bus have receivers that conform to
the SCSI-3 standard.

Barracuda 2LP Product Manual, Rev. D 31

3. Eliminate all I/O processes for the drive.

4. Wait until the drive motor and discs have come to a complete stop prior
to changing the plane of operation, ensuring data integrity.

5. Insert or remove the drive after meeting the following conditions:

Caution. Do not hot-plug the first or last device on the SCSI bus (the

SCSI bus termination must be external to the drive you are
inserting or removing).

a. If you are inserting the drive, connect its power ground and logic

ground at least 1 millisecond before coming into contact with the bus
connector. Maintain these ground connections during and after con­necting the device to the bus.

b. If you are removing the device, maintain its power ground and logic

ground connection for at least 1 millisecond after disconnecting the
device from the bus.

c. You may simultaneously switch the power to the electronics and

mechanics of the drive with the bus contacts, if the power distribution
system is able to maintain adequate power stability to other devices
during the transition and if you have met the grounding requirements
given in steps 5a and 5b.

d. Ensure that the drive carrier discharges all static electricity prior to

inserting the drive into the system.

Note. Do not remove or add terminator power or resistance to the SCSI bus

while hot plugging a disc drive.

32 Barracuda 2LP Product Manual, Rev. D

Barracuda 2LP Product Manual, Rev. D 33

7.0 Physical/electrical specifications

This section provides information relating to the physical and electrical
characteristics of Barracuda 2LP drives.

7.1 AC power requirements

None.

7.2 DC power requirements

The voltage and current requirements for a single drive are shown below.
Value s indicated apply at the driv e ’s power connector.

N/W/WC ND/WD/DC

[8]

Voltage 5V
regulation

Max operating current DC 3σ [1] 0.93 0.6 1.17 0.6
Avg idle current

DC X [1] [12] 0.63 0.49 0.70 0.49

Max start current

(peak) DC 3σ [3] [6] 0.93 1.35 1.0 1.35
(peak) AC 3σ [3] – 1.93 – 1.93

Delay motor start (max)

DC 3σ [1] [4] 0.88 0.12 0.92 0.12

Peak operating current

Typical DC X [1] [10] 0.91 0.57 1.13 0.57
Maximum DC 3σ [1] 0.93 0.60 1.17 0.60
Maximum (peak) AC 3σ 1.0 1.56 1.95 1.56

Track following at

OD DC X [1] 0.91 0.5 0.99 0.50
ID DC X [1] 0.88 0.51 0.96 0.51

Read track

OD DC 3σ [1] [14] 0.96 0.53 1.35 0.53
AC 3σ 1.03 0.73 1.95 0.73

Seeking

Typical DC X [1] [13] 0.89 0.78 0.99 0.78
Maximum DC 3σ [1] 0.92 0.82 1.10 0.82
Maximum (peak) AC 3σ 0.95 1.60 1.67 1.60

[5]

Notes

±±

±5%

±±

12V 5V

[2]

±±

±5%

±±

Amps

±±

±5%

±±

[8]

12V

±±

±5%

±±

[2]

Notes:

[1] Measured with average reading DC ammeter. Instantaneous +12V

cur re nt pea k s wil l exceed these va l ues .

[2] A –10% tolerance is permissible during initi al start of the spindl e and

must return to ±5% before 7,200 RPM is reached. Th e ±5% must be
maintain ed after the dri ve signals tha t its power -up sequence has been

completed and that it can accept selection by the host initiator.
[3] See Figure 14.
[4] This condition occurs when the Motor Start Option is enabled and the

drive has not yet received a Start Motor command.

34 Barracuda 2LP Product Manual, Rev. D

[5] See Section 7.2.1 “Conduc t ed nois e immunity . ” Specif ied v ol tage t oler -

ance includes ripple, noise, and transient response.

[6] At power-up, the motor current regulator limits the 12V current to an

average value of less than 1.4A, although instantaneous peaks may
exceed this value. These peaks should measure 5 msec duration or
less.

[7] Minimum current loading for each supply voltage is not less than 4% of

the maximum operating current shown.
[8] The +5V and + 12V supplies use separate ground returns.
[9] Where power is provided to multiple drives from a common supply,

careful consideration for individual drive power requirements should be

noted. Where multiple units are powered on simultaneously, the peak

starting current must be available to each device.
[10] Operating condition is defined as a third-stroke seek at OD and read

one track. A command is issued every 0.075 sec. (0.063 seconds on W/

WD/WC/DC drives)
[11] No terminator power. See Section 11.7.3.4.
[12] All power-saving features enabled--ASA II code only.
[13] Seeking is defined as a third-stroke seek at OD. A command is issued

every 20 msec.
[14] Read track is defined as repeat reads of track 15 with a duty cycle of

78% (N), 32% (W), 48% (WC), 60% (ND), 44% (WD), 44% (DC).

7.2.1 Conducted noise immunity

Noise is specified as a periodic and random distribution of frequencies
covering a band from DC to 10 MHz. Maximum allowed noise values given
below are peak-to-peak measurements and apply at the drive’s power
connector.

0 to 100 kHZ 100 kHz to 10 MHz

++

+5V 150 mV 100 mV

++

++

+12V 150 mV 100 mV

++

7.2.2 Power sequencing

The drive does not require power sequencing. The drive protects against
inadvertent writing during power-up and down. Daisy-chain operation re­quires that power be maintained on the terminated device to ensure proper
termination of the peripheral I/O cables.

To automatically delay motor start based on the target ID (SCSI ID), select
the Delay Motor Start option and deselect the Enable Motor Start option. See
Section 10.1 for pin selection information.

To delay the motor until the drive receives a Start Unit command, select the
Enable Motor Start option.

Barracuda 2LP Product Manual, Rev. D 35

0 5 10 15

0.0

0.5

1.0

1.5

Peak AC

Nominal (average) curve

T0 T1 T2 T3T4 T5 T6

Minimum AC

TIME (S)

ST31250

ST32550

+12V CURRENT (A)

0 5 10 15 20 25 30

0.0

0.5

1.0

1.5

2.0

2.5

3.0

2.85

Peak AC

Nominal (average) curve

T0

T1

T2

T3

T4

T5

Minimum AC

TIME (S)

+12V CURRENT (A)

T6

1.9

7.2.3 12V current profile

Figure 14 identifies the drive’s +12V current profile. The current during the
various times is as shown.

Figure 14. Barracuda 2LP drives typical

T0 Power is applied to the drive.
T1 Controller self-tests are performed.
T2 The spindle begins to accelerate under current limiting after performing

T3 The spindle is up to speed and the head-arm restraint is unlocked.
T4 Heads move from the landing zone to the data area.
T5 The adaptive calibration sequence is performed.
T6 Calibration is complete and the drive is ready for reading and writing.

++

+12V current profiles

++

internal diagnostics. See Section 7.2, note 1.

Note. All times and currents are typical. See Section 7.2 for maximum

current requirements.

36 Barracuda 2LP Product Manual, Rev. D

7.3 Heat/power dissipation

The heat and power dissipation values for your drive are listed below.

ST31250 ST31250
N/W/WC ND/WD/DC

Typical seek and read power dissipation* 11W 12W

(35 BTUs/hr) (41 BTUs/hr)

Typical power dissipation under 9W 9W
idle conditions (31 BTU/hr) (31 BTUs/hr)

ST32550 ST32550ND
N/W/WC ND/WD/DC

Typical seek and read power dissipation* 11W 12W

(35 BTUs/hr) (41 BTUs/hr)

Typical power dissipation under 9W 9W
idle conditions (31 BTUs/hr) (31 BTUs/hr)

*DC power average at nominal voltages

7.4 Environmental limits

Temperature and humidity must not cause condensation within the drive.
Altitude and atmospheric pressure specifications are referenced to a
standard day at 58.7°F (14.8°C). Maximum wet bulb temperature is 82°F
(28°C).

7.4.1 Temperature

a. Operating

The MTBF specification for the drive is based on operating at a local
ambient temperature of 95°F (35°C). Occasional excursions to drive
ambient temperatures of 122°F (50°C) may occur without impact to
specified MTBF. The enclosure for the drive should be designed such that
the temperatures at the locations specified in Section 6.2.2 are not
exceeded. Air flow may be needed to achieve these temperatures.
Continual or sustained operation at case temperatures above these
values may degrade MTBF.

The dr iv e m eet s al l specif icat ions w i thin a 41° to 122°F (5° to 50 °C )
drive ambient temperature range with a maximum gradient of
36°F ( 20°C ) per hour.

b. Non-operating

Non-oper ating te mperatur e should rema in betw een –4 0° to 1 5 8°F (–40°
to 70°C) package ambient with a maximum gradient of 36°F (20°C)
per hour. This assumes that t he drive is packaged in the shipping
container designed by Seagate.

7.4.2 Relative humidity

The values below assume that no condensation on the drive occurs.
a. Operating

5% to 95% relative humidity with a maximum gradient of 10% per hour

b. Non-operating

5% to 95% relative humidity

Barracuda 2LP Product Manual, Rev. D 37

7.4.3 Effective altitude (sea level)

a. Operating

–1,000 to +10,000 feet (–305 to +3,048 meters)

b. Non-operating

–1,000 to +40,000 feet (–305 to +12,210 meters)

7.4.4 Shock and vibration

Shock and vibrati on limits are measured directly on the drive’s chassis.
Ensure that you use an encl osure that buffers and restri cts the drive’s
movements to meet the shock and vibration requ irements listed below.

The limits of shock and vibration defined wi thin this manual are specified
with the drive mounted in one of the two methods shown in Figure 18.

7.4.4.1 Shock

a. Operating in a normal environment

The drive as installed for normal operation operates error free while
subjected to intermittent shock not exceeding:

2.0 Gs at a maximum duration of 11 msec (half-sinewave)

Shock may be applied in the X, Y, or Z axis.

b. Operating in an abnormal environment

The drive as installed for normal operation does not incur physical
damage while subjected to intermittent shock not exceeding:

10 Gs at a maximum duration of 11 msec (half-sinewave)

Shock occurring at abnormal levels may degrade operating performance
during the abnormal shock period. Specified operating performance
continues when normal operating shock levels resume.

Shock may be applied in the X, Y, or Z axis. Shock must not be repeated
more than two times per second.

c. Non-operating

The limits of non-operating shock apply to all conditions of handling and
transportation. This includes both isolated drives and integrated drives.

The drive does not cause drive damage or performance degradation
while subjected to non-repetitive shock not exceeding:

50 Gs at a maximum duration of 11 msec (half-sinewave)

Shock may be applied in the X, Y, or Z axis.

d. Packaged

The drive as packaged by Seagate for general freight shipment with ­stands a drop test against a concrete floor or equivalent with specifica­tions n ot e x ce e ding :

20 pounds (8.95 kg) for pack’s gross weight
42 inches (1,070 mm) for distance dropped

Drop test applies to a single- or multiple-drive pack.

38 Barracuda 2LP Product Manual, Rev. D

7.4.4.2 Vibration

a. Operating in a normal environment

The drive as installed for normal operation operates error free while
subjected to continuous vibration not exceeding:

5-400 Hz @ 0.5 G in the X and Y axis
5-375 Hz @ 0.5 G in the Z axis

b. Operating in an abnormal environment

Equipment as installed for normal operation does not incur physical
damage while subjected to periodic vibration not exceeding:

15 minutes of duration at major resonant frequency
5-400 Hz @ 0.75 G

Vibration occurring at these levels may degrade operating performance
during the abnormal vibration period. Specified operating performance
continues when normal operating vibration levels are resumed—this
assumes system recovery routines are available.

Abnormal vibration may be applied in the X, Y or Z axis.

c. Non-operating

The limits of non-operating vibration apply to all conditions of handling
and transportation. This includes both isolated drives and integrated
drives.

The drive does not incur physical damage or degraded performance as
a result of continuous vibration not exceeding:

5-22 Hz @ 0.040 inches (1.02 mm) displacement
22-400 Hz @ 2.00 Gs

Vibration may be applied in the X, Y, or Z axis.

7.4.5 Air cleanliness

The drive is designed to operate in a typical office environment with minimal
environmental control.

7.4.6 Acoustics

Sound power during idle mode (wh en the drive is not seeking, reading, or
writing) is 4.7 bels typical when measured to ISO 7779 specifications.

7.5 Electromagnetic compatibility

As a component assembly, the drive is not required to meet any sus­ceptibility per formance requirements. The system integrator is respon­sible for performing tests to ensure that equipment operating in the same
system as the drive does not adversely affect the performance of the drive.
See Section 7.2 “DC power requirements.”

Barracuda 2LP Product Manual, Rev. D 39

7.6 Mechanical specifications

The following nominal dimensions do not include the decorative front-panel
accessory. Refer to the appropriate figure listed below for your drive’s
mounting configuration dimensions. Maintain a minimum clearance of 0.050
inches from the PWA side of the drive, except in the mounting locations.

Height 1.0 in 25.4 mm
Width 4.00 in 101.6 mm
Depth 5.75 in 146.05 mm
Weight 1.2 lb 545 g

ST31250N/ND and ST32550N/ND drives Figure 15
ST31250W/WD and ST32550W/WD drives Figure 16
ST31250WC/DC and ST32550WC/DC drives Figure 17

N

[1]

R

F

[2]

K

J

[4]

Figure 15. ST31250N/ND and ST32550N/ND mounting configuratio n dimensions

P

D

.050 in. (1.27mm)
minimum clearance

H

A

[3]

C

M

G

L

E

Notes:



[1]

Mounting holes three on each side, 6-32



UNC. Max screw length into side of drive



0.15 in. (3.81 mm). Screw tightening torque



6.0 in-lb (.675 NM) max with minimum



thread engagement of 0.12 in. (3.05 mm).





[2]

Mounting holes four on bottom, 6-32 UNC.

B



Max screw length into bottom of drive 0.15 in.



(3.81 mm). Screw tightening torque 6.0 in-lb



(.675 NM) max with minimum thread



engagement of 0.12 in. (3.05 mm).





[3]

Power and interface connectors can



extend past the “A” dimension by 0.040 in.



(1.02 mm).





[4]

Decorative front panel.

Inches Millimeters

.25

6.35 

4.59 

8.64 

4.83 

0.381

±
±
±





±
±
±
±
±
±
±
±
±
±

max

±
±

.25
.38

.50
.13
.13
.25
.25
.25
.50
.38
.38
.25

.25
.25



±
±

+
–

±
±
±
±
±
±
±
±
±
±

max

±
±

0.010

0.010

0.026

0.010

0.020

0.005

0.005

0.010

0.010

0.010

0.020

0.015

0.015

0.010

0.010

0.010

A

5.750

B

4.000

C

1.000



D

0.625

E

4.000

F

0.250

G

2.375

H

3.750

J

2.370

K

1.750

L

0.181

M

0.340

N

0.190

P

S

0.015

R

1.100

S

4.100

146.05 

101.60 

25.40 

15.87 

101.60 

60.32 

95.25 

60.20 

44.45 



27.94 

104.14









40 Barracuda 2LP Product Manual, Rev. D

N

[1]

R

F

[2]

K

J

[4]

P

D

.050 in. (1.27mm)
minimum clearance

H

A

[3]

C

M

G

L

E

Notes:



[1]

Mounting holes three on each side, 6-32



UNC. Max screw length into side of drive



0.15 in. (3.81 mm). Screw tightening torque



6.0 in-lb (.675 NM) max with minimum



thread engagement of 0.12 in. (3.05 mm).





[2]

Mounting holes four on bottom, 6-32 UNC.



T

Max screw length into bottom of drive 0.15 in.



B

(3.81 mm). Screw tightening torque 6.0 in-lb



(.675 NM) max with minimum thread



engagement of 0.12 in. (3.05 mm).





[3]

Power and interface connectors can



extend past the “A” dimension by 0.040 in.



(1.02 mm).





[4]

Decorative front panel.

Inches Millimeters

.25

6.35 

4.59 

8.64 

4.83 

0.381

6.73

±
±
±





±
±
±
±
±
±
±
±
±
±

max

±
±
±

.25
.25

.50
.13
.13
.25
.25
.25
.50
.38
.38
.25

.25
.25
.50



±
±

+
–

±
±
±
±
±
±
±
±
±
±

max

±
±
±

0.010

0.010

0.026

0.010

0.020

0.005

0.005

0.010

0.010

0.010

0.020

0.015

0.015

0.010

0.010

0.010

0.020

A

5.750

B

4.000

C

1.000



D

0.625

E

4.000

F

0.250

G

2.375

H

3.750

J

2.370

K

1.750

L

0.181

M

0.340

N

0.190

P

0.015

R

S

1.100

S

4.100

T

0.265

146.05 

101.60 

25.40 

15.87 

101.60 

60.32 

95.25 

60.20 

44.45 



27.94 

104.14 





Figure 16. ST31250W/WD and ST32550W/WD mounting configuration dimensions

Barracuda 2LP Product Manual, Rev. D 41

N

[1]

R

F

[2]

P

D

.050 in. (1.27mm)
minimum clearance

A

[3]

C

M

G

L

E

Notes:



[1]

Mounting holes three on each side, 6-32



UNC. Max screw length into side of drive



0.15 in. (3.81 mm). Screw tightening torque



6.0 in-lb (.675 NM) max with minimum



thread engagement of 0.12 in. (3.05 mm).





[2]

Mounting holes four on bottom, 6-32 UNC.

B

[5]



Max screw length into bottom of drive 0.15 in.



(3.81 mm). Screw tightening torque 6.0 in-lb



(.675 NM) max with minimum thread



engagement of 0.12 in. (3.05 mm).





[3]

Power and interface connectors can



extend past the “A” dimension by 0.040 in.



(1.02 mm).





[4]

Decorative front panel.





[5]

Connector is centered on module ±0.020 in.

Inches Millimeters

[4]



±
±

+
–

±
±
±
±
±
±
±
±
±
±

max

±
±

0.010

0.010

0.026

0.010

0.020

0.005

0.005

0.010

0.010

0.010

0.020

0.015

0.015

0.010

0.010

0.010

A

5.750

B

K

4.000

C

1.000



D

0.625

E

4.000

F

0.250

G

J

H

S

2.375

H

3.750

J

2.370

K

1.750

L

0.181

M

0.275

N

0.190

P

0.015

R

1.100

S

4.100

146.05 

101.60 

25.40 

15.87 

101.60 

60.32 

95.25 

60.20 

44.45 



27.94 

104.14



6.35 

4.59 

7.00 

4.83 

0.381

Figure 17. ST31250WC/DC and ST32550WC/DC mounting configuration

dimensions

±
±
±



±
±
±
±
±
±
±
±
±
±

max

±
±

.25
.25
.38


.50
.13
.13
.25
.25
.25
.50
.38
.38
.25


.25
.25

42 Barracuda 2LP Product Manual, Rev. D

7.6.1 Drive orientation

The balanced rotary arm actuator design of the drive allows it to be mounted
in any orientation. All drive performance evaluations have been done with the
drive in horizontal (discs level) and vertical (drive on its side) orientations,
which are the two preferred mounting orientations.

Figure 18. Recommended mounting

7.6.2 Cooling

Ensure tha t the enclo sure y ou use pr ovides adequa te cool ing s o that the
ambient tempera ture immedia tely su rrounding the dri ve does not exce ed
temperat ure conditions specified in S ection 7.4.1 . Ensure that you pr ovide
adequate air circulation a round the printed circuit boards ( PCBs ) to meet
the requir ements of Section 6.2.2.

7.6.3 Drive Mounting

Mount the drive using the bottom or side mounting holes. If you are mounting
the drive using the bottom holes, ensure that you do not physically distort the
drive by attempting to mount it on a stiff, non-flat surface.

The allowable mounting surface stiffness is 80 lb/in (14.0 N/mm). The
following equation and paragraph define the allowable mounting surface
stiffness:

F

k=

where k is the mounting surface stiffness (units in pounds or newton) and x
is the out-of-plane distortion (units in inches or millimeters). The out-of-plane
distortion (x) is determined by defining a plane with three of the four mounting
points fixed and evaluating the out-of-plane defection of the fourth mounting
point when a known force (F) is applied to the fourth point.

=

xin mm

80 lb

or

14.0 N

Barracuda 2LP Product Manual, Rev. D 43

8.0 Media characteristics

This section provides information regarding the media used in Barracuda
2LP disc drives.

8.1 Media description

The media used on the drive has a diameter of approximately 95 mm (3.7
inches). The aluminum substrate is coated with a thin-film magnetic mate­rial, which has a proprietary protective layer for improved durability and
environmental protection.

44 Barracuda 2LP Product Manual, Rev. D

Barracuda 2LP Product Manual, Rev. D 45

9.0 Defect and error management

The drive, as delivered, complies with this product manual. The read error
rates and specified storage capacities are not dependent on using defect­management routines by the host (initiator).

Defect and error management in the SCSI system involves the drive’s
internal defect/error management and SCSI system error considerations
(errors in communications between the initiator and the drive). Tools for
designing a defect/error management plan are briefly outlined in this
section. References to other sections are provided when necessary.

9.1 Defects and errors

Identified defects are recorded on the drive’s defects list (referred to as the
primary or ETF defect list). These known defects are reallocated during the
initial drive format at the factory. (See Format Unit command Section 5.2.1.2
in the

SCSI-2 Interface Product Manual,

correction by ECC recovers data from additional flaws if they occur.
Details of the SCSI commands supported by the drive are described in the

SCSI-2 Interface Product Manual.

Error Recovery philosophy is presented in Section 6 of the

Product Manual.

Also, more information about the drive’s

part number 77738479.) Data

SCSI-2 Interface

46 Barracuda 2LP Product Manual, Rev. D

Barracuda 2LP Product Manual, Rev. D 47

10.0 Option/configuration headers

This section describe s how to co n figure B a rrac uda 2LP drives using the
option headers on the drives. These option headers may be used to
customize many functions of the drives for your particular system.

10.1 Drive ID/option select headers

The headers described in this section en able yo u to configure the drive to
meet specific functionality requirements.

To configure N/ND drives, see Section 10.1.1.
To configure W/WD drives, see Section 10.1.2.
To configure WC/DC drives, refer to Section 10.1.3.

10.1.1 ST31250N/ND and ST32550N/ND configuration

Figure 19 illustrates ST31250N/ND and ST32550N/ND jumper connectors.

ST31250N and

ST32550N

J1 Connector

Pin 1

Pin 1 End

Pin 1

J2

Pin 1

ST31250ND and
ST32550ND
J1 Connector

J4

ST31250N and
ST32550N

Term. power from
drive (default)

Term. power to 
SCSI bus

Term. power from 
SCSI bus

Term. power to 
SCSI bus and drive

Enable SCSI 
terminator (default)

ST31250ND and
ST32550ND

Term. power to 
SCSI Bus (default)

J1

Pin 1
Pin 2

Pin 1

J1

Pin 2

(front view of J4)

Pin 1

J4

Pin 2
Pin 1

Reserved
Remote 

LED connector
Spindle sync 
cable connector

SCSI ID = 0
(default)

SCSI ID = 1
SCSI ID = 2
SCSI ID = 3
SCSI ID = 4
SCSI ID = 5
SCSI ID = 6
SCSI ID = 7

Ground (cathode)
Positive (anode)

Spindle Sync Reference
Spindle Sync Ground

J2

Pin 2
Pin 1

Reserved
Disable Parity

Write Protect

Enable 
Motor Start
Delay 
Motor Start

Figure 19. ST31250N/ND and ST32550N/ND jumper connectors

48 Barracuda 2LP Product Manual, Rev. D

Block Pins Function

ST31250N and ST32550N J1 1 & 2 Terminator power from the drive (drive

supplies terminator power to its own
terminators).

1 & 3 Terminator power to the SCSI bus (drive

supplies power to an external terminator)

2 & 4 Terminator power from the SCSI bus (drive

receives terminator power from the SCSI
bus–usually the host controller)

1 & 3 & Terminator power to the SCSI bus and drive
2 & 4 (drive supplies termination power to its own

terminators and to the SCSI bus)

5 & 6 Enable SCSI termination. Jumper installed

enables the internal termination on the drive.
Jumper removed disables the drive’s internal
terminators.

ST31250ND and ST32550ND J1 1 & 3 Terminator power to the SCSI bus

ST31250N/ND and J2 1 & 2 Reserved
ST32550N/ND 3 & 4 Reserved

5 & 6 Disable SCSI parity
7 & 8 Write protect
9 & 10 Enable motor start. Jumper installed causes

the drive to wait for the Start Unit command
from the SCSI host. No jumper installed
causes the drive to look at the Delay Motor
Start jumper. Default is no jumper.

11 & 12 Delay motor start. Jumper installed causes a

10-second delay for each SCSI ID number
plus a maximum power-up delay of 3 seconds
before starting the spindle motor automati­cally. Default is no jumper.

Example:

If SCSI ID is equal to three (3)

(3 x 10) +3 = 33

The drive’s spindle motor starts

in 33 seconds.
13 & 14 Reserved
15 & 16 Reserved
17 & 18 Reserved

J4 1 & 2 Reserved

3 & 4 Remote LED connector

Pin 3 = Anode (positive)
Pin 4 = Cathode (negative)

5 & 6 Spindle sync cable connector

Pin 5 = Ground
Pin 6 = Reference

Barracuda 2LP Product Manual, Rev. D 49

7 & 8* SCSI ID bit 0
9 & 10* SCSI ID bit 1
11 & 12*SCSI ID bit 2
13 & 14 Reserved
15 & 16 Reserved
17 & 18 Reserved
19 & 20 Reserved

*See Figure 19 to set the SCSI ID.

50 Barracuda 2LP Product Manual, Rev. D

10.1.2 ST31250W/WD and ST32550W/WD configuration

Figure 20 illustrate s ST31250W/WD and ST32550W/W D option select
jumper connect ors.

ST31250W and
ST32550W
J1 Connector

Pin 1

Pin 1 End

Pin 2

Pin 1

J2

ST31250W and
ST32550W

Term. power to 
SCSI bus

Term. power from 
SCSI bus

Term. power to 
SCSI bus and drive

Enable SCSI 
terminator (default)

ST31250WD and
ST32550WD

J4

Term. power to 
SCSI Bus (default)

ST31250WD and
ST32550WD
J1 Connector

Pin 4

Pin 3

Term. power from
drive (default)

J1

Pin 2
Pin 1

Pin 1
Pin 2Pin 6

J1

Pin 4
Pin 3

SCSI I/O

Connector

DC Power

Connector

Pin 1

Pin 1

J5

(front view of J4)

Pin 2
Pin 1

Pin 1

J2

J5

SCSI ID = 0 (default)
SCSI ID = 1
SCSI ID = 2

SCSI ID = 3
SCSI ID = 4
SCSI ID = 5
SCSI ID = 6
SCSI ID = 7

SCSI ID = 8
SCSI ID = 9
SCSI ID = 10
SCSI ID = 11
SCSI ID = 12

SCSI ID = 13
SCSI ID = 14
SCSI ID = 15

Remote LED Connector
Spindle Sync 

Cable Connector

SSREF

Pin 1

*ST31250W and ST32550W only (internal 
termination is not available on ST31250WD 
and ST32550WD drives).

Cathode (–)
Anode (+)

Pin 2

J4

Pin 1

SCSI ID bit 0
SCSI ID bit 1
SCSI ID bit 2
SCSI ID bit 3
Fault LED pin (–)
Vendor unique

SSREF (+) 
spindle sync

Unit Active
LED pin (–)

Enable SCSI
terminator*

Ground
+5V
No connection
Reserved

Reserved
Disable SCSI Parity

Write Protect
Enable Motor Start
Delay Motor Start

Figure 20. ST31250W/WD and ST32550W/WD jumper connectors

Barracuda 2LP Product Manual, Rev. D 51

Block Pins Function

ST31250W and ST32550W J1 1 & 2 Terminator power from the drive (drive

supplies terminator power to its own
terminators).

1 & 3 Terminator power to the SCSI bus (drive

supplies power to an external terminator)

2 & 4 Terminator power from the SCSI bus (drive

receives terminator power from the SCSI
bus–usually the host controller)

1 & 3 & Terminator power to the SCSI bus and drive
2 & 4 (drive supplies termination power to its own

terminators and to the SCSI bus)

5 & 6 Enable SCSI termination. Jumper installed

enables the internal termination on the drive.
Jumper removed disables the drive’s internal
terminators.

ST31250WD/ST32550WD J1 1 & 3 Terminator power to the SCSI bus

ST31250W/WD and J2 1 & 2 Reserved
ST32550W/WD 3 & 4 Reserved

5 & 6 Disable SCSI parity
7 & 8 Write protect
9 & 10 Enable motor start. Jumper installed causes

the drive to wait for the Start Unit command
from the SCSI host. No jumper installed
causes the drive to look at the Delay Motor
Start jumper. Default is no jumper.

11 & 12 Delay motor start. Jumper installed causes a

10-second delay for each SCSI ID number
plus a maximum power-up delay of 3 seconds
before starting the spindle motor automati­cally. Default is no jumper.

Example:

If SCSI ID is equal to three (3)

(3 x 10) +3 = 33

The drive’s spindle motor starts

in 33 seconds.
13 & 14 Reserved
15 & 16 Reserved
17 & 18 Reserved

J4 1 SCSI ID bit 0; no jumper = 0; yes jumper = 1

2 Fault LED pin (–)
3 SCSI ID bit 1; no jumper = 0; yes jumper = 1
4 Vendor unique
5 SCSI ID bit 2; no jumper = 0; yes jumper = 1
6 SSREF(+) spindle sync
7 SCSI ID bit 3; no jumper = 0; yes jumper = 1

52 Barracuda 2LP Product Manual, Rev. D

8 Unit active LED pin (–)
9 Enable SCSI terminator (ST31250W

and ST32550W drives)
10 Ground
11 (+) 5 volts
12 No connection
13– 20 Reserved

J5 1 & 2 * SCSI ID bit 0

3 & 4* SCSI ID bit 1
5 & 6* SCSI ID bit 2
7 & 8* SCSI ID bit 3
9 & 10 Remote unit active LED connector

Pin 9 = cathode (–), pin 10 = anode (+)
11 & 12 Spindle sync connector

Pin 11 = SSREF (+), pin 12 = ground (–)

*See Figure 20 to set the SCSI ID.

Barracuda 2LP Product Manual, Rev. D 53

10.1.3 ST31250WC/DC and ST32550WC/DC configuration

Figure 21 illustrates ST31250WC/DC and ST32550WC/DC option select
jumper connectors and SCSI ID.

Pin 1

Pin 2

J4

Pin 1

SCSI ID bit 0
SCSI ID bit 1
SCSI ID bit 2
SCSI ID bit 3
Fault LED pin (–)
Vendor unique

SSREF (+) 
spindle sync

Unit Active
LED pin (–)

Ground
+5V
No connection
Reserved

SCSI I/O

Connector

(SCA)

(front view of J4)

Pin 1

Pin 1

J2

Pin 1 End

Reserved
Disable SCSI Parity

Write Protect
Enable 

Motor Start
Delay 
Motor Start

J4

J2

Pin 2
Pin 1

ST31250WC/DC and J2 1 & 2 Reserved
ST32550WC/DC 3 & 4 Reserved

Figure 21. ST31250WC/DC and ST32550WC/DC jumper connectors

Block Pins Function

5 & 6 Disable SCSI parity
7 & 8 Write protect
9 & 10 Enable motor start. Jumper installed causes

the drive to wait for the Start Unit command
from the SCSI host. No jumper installed
causes the drive to look at the Delay Motor
Start jumper. Default is no jumper.

54 Barracuda 2LP Product Manual, Rev. D

11 & 12 Delay motor start. Jumper installed causes a

10-second delay for each SCSI ID number

plus a maximum power-up delay of 3 seconds

before starting the spindle motor automati-

cally. Default is no jumper.

Example:

If SCSI ID is equal to three (3)

(3 x 10) +3 = 33

The drive’s spindle motor starts

in 33 seconds.
13 & 14 Reserved
15 & 16 Reserved
17 & 18 Reserved

J4 1 SCSI ID bit 0; no jumper = 0; yes jumper = 1

2 Fault LED pin (-)
3 SCSI ID bit 1; no jumper = 0; yes jumper = 1
4 Vendor unique
5 SCSI ID bit 2; no jumper = 0; yes jumper = 1
6 SSREF(+) spindle sync
7 SCSI ID bit 3; no jumper = 0; yes jumper = 1
8 Unit active LED pin (-)
9 No connection
10 Ground
11 (+) 5 volts
12 No connection
13–20 Reserved

SCSI ID Bit 3 Bit 2 Bit 1 Bit 0

00000
10001
20010
30011
40100
50101
60110
70111
81000
91001
101010
111011
121100
131101
141110
151111

Default SCSI ID = 0

Barracuda 2LP Product Manual, Rev. D 55

10.2 Synchronized spindles interface

The synchronized spindles interface (SSI) allows several drives operating
from the same host to operate their spindles at a synchronized rotational
rate. Details of the electrical and physical interfaces follow in Section 10.2.1.
The system operation is described in Section 5.7.

10.2.1 Electrical description

The electrical interface consists of one digital TTL reference index signal
and ground. The reference index signal (SSREF+) is an output if the drive
is configured as a master and is an input otherwise. The reference index
signal is connected from drive to drive in a daisy-chain fashion as shown in
Figure 4.

10.2.1.1 Drivers and receivers

Figure 22 shows a diagram of the driver/receiver circuit. The driver circuits
have the following electrical specifications:

Negated (false): 0.V to +0.4V @ I = –24 mA (max)
Asserted (true): +2.24V to +5.25V @ I = +250 µA

Main PWA

Open

Collector

 Driver Receiver

2.21K Ohm

+5V

SSREF +

GND

J4 pin 6 on N/ND/WC/DC drives
J5 pin 11 on W/WD drives

J4 pin 5 on N/ND drives
J5 pin 12 on W/WD drives
J4 pin 10 on WC/DC drives

Figure 22. SCSI reference index signal driver/receiver combination

56 Barracuda 2LP Product Manual, Rev. D

10.2.1.2 Termination

The reference index signal (SSREF+) is terminated with a 2.21K ohm
resistor. Each single-ended drive has a terminator resistor located on the
main PCB. The terminator resistor is not removable and is always in the
circuit. A diode prevents current backfeed.

10.2.1.3 Physical interface
ST31250N/ND and ST32550N/ND drives

Dimensions of the ST31250N/ND and ST32550N/ND J4 connector mounted
on the main PCB to interconnect the drives are shown in Figure 23. It is a 20­pin, 10-position gold 2 mm header type connector. Only pins 5 and 6 are used
for connecting the reference index signal cable, as shown in Figure 19. Pin
6 is SSREF+ and pin 5 is ground.

.787

(19.99 mm)

.079 (2 mm)

.079

(2 mm)

Figure 23. ST31250N/ND and ST32550N/ND configuration select header

J4

.708

(17.983 mm)

ST31250W/WD and ST32550W/WD drives

Dimensions of the ST31250W/WD and ST32550W/WD J5 connector
mounted on the main PCB to interconnect the drives are shown in
Figure 24. It is a 12-pin, 6-position gold 2 mm header type connector. Only
pins 11 and 12 are used for connecting the reference index signal cable,
as shown in Figure 20. Pin 11 is SSREF+ and pin 12 is ground.

.520

.079

(2 mm)

.079

(2 mm)

(13.2 mm)

J5

Pin 1

.185

(4.7 mm)

Figure 24. ST31250W/WD and ST32550W/WD configuration select header

Barracuda 2LP Product Manual, Rev. D 57

ST31250WC/DC and ST32550WC/DC drives

Dimensions of the ST31250WC/DC and ST32550WC/DC J4 connector
mounted on the main PCB to interconnect the drives are shown in Figure 25.
It is a 20-pin, 10-position gold 2 mm header type connector. Only pins 6 and
10 are used for connecting the reference index signal cable, as shown in
Figure 21. Pin 6 is SSREF+ and pin 10 is ground.

.708

(18 mm)

.079 (2 mm)

.079

(2 mm)

Figure 25. ST31250WC/DC and ST32550WC/DC configuration select header

10.3 Grounding

Signal ground (PCB) and HDA ground are connected together in the
Barracuda 2LP family drives— Do not separate this connection. Maximizing
the contact area between HDA ground and system ground may reduce
radiated emissions. If you do not want the system chassis to be connected
to the HDA/PCB ground, you must provide a nonconductive (electrically
isolating) method of mounting the drive in the host equipment. Increased
radiated emissions may result if you do not provide the maximum surface
area ground connection between system ground and drive ground. This is
the system designer’s and integrator’s responsibility.

J4

.629

(16 mm)

58 Barracuda 2LP Product Manual, Rev. D

Barracuda 2LP Product Manual, Rev. D 59

11.0 Interface requirements

This section describes the Barracuda 2LP interface requirements.

11.1 General description

The major portion of the interface requirements/implementation is de­scribed in the

11.2 SCSI interface messages supported

Table 1 lists the messages supported by the Barracuda SCSI-1 and SCSI­2 modes. ASA I is Seagate’s first generation of advanced SCSI architecture
firmware. ASA II is Seagate’s second generation of advanced SCSI archi­tecture firmware.

Table 1. SCSI interface messages supported

Message name code SCSI-1 SCSI-2 SCSI-2

Abort 06h Y Y Y
Abort tag 0Dh Y Y Y

Bus device reset 0Ch Y Y Y
Clear queue 0Eh N Y Y

Command complete 00h Y Y Y
Continue I/O Process 12h N N Y

Disconnect 04h Y Y Y
Extended messages 01h*** Y Y Y
Identify 80h-FFh Y Y Y

Ignore wide residue (two bytes) 23h N N N
Initiate recovery 0Fh N N N
Initiator detected error 05h Y Y Y

Linked command complete 0Ah Y Y Y
Linked command complete with flag 0Bh Y Y Y

Message parity error 09h Y Y Y
Message reject 07h Y Y Y
Modify data pointer *** N N N

No operation 08h Y Y Y
Queue tag messages (two bytes)

Head of queue tag 21h N Y Y
Ordered queue tag 22h N Y Y
Simple queue tag 20h N Y Y

Release recovery 10h N N N
Restore pointers 03h Y Y Y

Save data pointer 02h Y Y Y
Synchronous data transfer request *** Y Y Y

Target transfer disable 13h N N Y
Terminate I/O process 11h N N Y

Wide data transfer request *** N Y Y
*** Extended messages (see the

SCSI-2 Interface Product Manual

Msg ASA I ASA I ASA II

SCSI-2 Interface Product Manual)

(part num b er 7 77 384 79 ).

Supported by

60 Barracuda 2LP Product Manual, Rev. D

11.3 SCSI interface commands supported

Table 2 lists the SCSI interface commands supported in SCSI-1 and SCSI-2
modes. Barracuda 2LP family drives can be changed back and forth
between SCSI-1 and SCSI-2 modes, using the Change Definition com­mand. Standard OEM drives are shipped set to operate in SCSI-2 mode.

Table 2. Supported commands

Supported by

Command ASA I ASA I ASA II

Command name code SCSI-1 SCSI-2 SCSI-2

Change Definition 40h Y Y Y
Compare 39h N N N
Copy 18h N N N
Copy and Verify 3Ah N N N

Format Unit [1] 04h Y Y Y
Inquiry 12h Y Y Y

Date Code Page N Y Y
Firmware Numbers Page N Y Y
Implemented Operating Def. Page N Y Y
Jumper Settings Page N Y Y
Unit Serial Number Page N Y Y
Vital Product Data Page N Y Y

Lock-Unlock Cache 36h N N N
Log Select 4Ch N N N
Log Sense 4Dh N N N

Mode Select 15h Y Y Y
Same pages as Mode Sense command
Mode Select (10) 55h N Y Y
Mode Sense 1Ah Y Y Y

Caching Parameters Page (08h) N Y Y
Control Mode Page (0Ah) N Y Y
Disconnect/Reconnect Control Page (02h) Y Y Y
Error Recovery Page (01h) Y Y Y
Format Page (03h) Y Y Y
Notch and Partition Page (0C) (media zones) N Y Y
Power Condition Page (0D) N N Y
Rigid Disc Drive Geometry Page (04h) Y Y Y
Unit Attention Page (00h) Y Y Y
Verify Error Recovery Page (07h) N Y Y

Mode Sense (10) 5Ah N Y Y
Not used 42–4Bh N N N

Not used 4E–54 N N N
Not used 58–59 N N N
Not used 5B–5F N N N
Not used 60–BFh N N N
Not used C0–DFh N N N
Not used E0–FFh N N N

Prefetch 34h N N N

Barracuda 2LP Product Manual, Rev. D 61

Supported by

Command ASA I ASA I ASA II

Command name code SCSI-1 SCSI-2 SCSI-2

Read 08h Y Y Y
Read Buffer 3Ch Y Y Y
Read Capacity 25h Y Y Y
Read Defect Data 37h Y Y Y
Read Extended 28h Y Y Y
Read Long 3Eh Y Y Y
Reassign Blocks 07h Y Y Y
Receive Diagnostic Results 1Ch Y Y Y

Supported Diagnostics Pages Y Y Y

Translate Page Y Y Y
Release 17h Y Y Y
Release (10) 57h N Y Y
Request Sense 03h Y Y Y

Actual Retry Count Bytes N Y Y

Extended Sense Y Y Y

Field Pointer Bytes Y Y Y
Reserve 16h Y Y Y

Extent Reservation N N N

Third Party Reserve Y Y Y
Reserve (10) 56h N Y Y
Rezero Unit 01h Y Y Y

Search Data Equal 31h N N N
Search Data High 30h N N N
Search Data Low 32h N N N
Seek 0Bh Y Y Y
Seek Extended 2Bh Y Y Y
Send Diagnostics Page 1Dh Y Y Y

Supported Diagnostics Pages Y Y Y

Translate Page Y Y Y
Set Limits 33h N N N
Start Unit/Stop Unit 1Bh Y Y Y
Synchronize Cache 35h N Y Y

Test Unit Ready 00h Y Y Y

Verify 2Fh Y Y Y
Write 0Ah Y Y Y

Write and Verify 2Eh Y Y Y
Write Buffer 3Bh Y Y Y

Firmware Download Option [2] Y Y Y
Write Extended 2Ah Y Y Y
Write Long 3Fh Y Y Y
Write Same 41h N Y Y

[1] Format to any even number of bytes per sector from 180 to 4,096.
[2] Warning: A SCSI Reset or power loss during flash programming can result in

firmware corruption.

62 Barracuda 2LP Product Manual, Rev. D

11.3.1 Inquiry data

Tables 3 and 4 list the Inquiry command data that the drive should return to
the initiator per the format provided in the

Table 3. Barracuda 2LP family drive inquiry data–ASA I

Bytes Data (hex)

0-15 00 00 ** *** 8F 00 00 [1A] 53 45 41 47 41 54 45 20 Vendor ID
16-31 [53 54 33 32 35 35 30 4E] 20 20 20 20 20 20 20 20 Product ID
32-47 R# R# R# R# S# S# S# S# S# S# S# S# 00 00 00 00
48-63 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
64-79 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
80-95 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

96-111 00 43 6F 70 79 72 69 67 68 74 20 28 63 29 20 31* *Copyright
112-127 39* 39* 35* 20 53 65 61 67 61 74 65 20 41 6C 6C 20 notice
128-143 72 69 67 68 74 73 20 72 65 73 65 72 76 65 64 20
144-147 D# D# D# D#

Table 4. Barracuda 2LP family drive inquiry data–ASA II

Bytes Data (hex)

0 1 2 3 4 5 6 7 8 9 A B C D E F ASCII

0-15 00 00 02 02 8F 00 00 [1E] 53 45 41 47 41 54 45 20 Vendor ID
16-31 [53 54 33 32 35 35 30 4E] 20 20 20 20 20 20 20 20 Product ID
32-47 R# R# R# R# S# S# S# S# S# S# S# S# 00 00 00 00
48-63 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
64-79 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
80-95 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

96-111 00 43 6F 70 79 72 69 67 68 74 20 28 63 29 20 31* *Copyright
112-127 39* 39* 35* 20 53 65 61 67 61 74 65 20 41 6C 6C 20 notice
128-143 72 69 67 68 74 73 20 72 65 73 65 72 76 65 64 20
144-147 41 53 41 32

SCSI-2 Interface Product Manual.

* Copyright year (changes with actual year)
** 01 = SCSI-1 implemented

02 = SCSI-2 implemented (default)
The drive can be changed between these two configurations.

*** 01 = Response data is in SCSI-1 format and has compatibility with Common Command Set data

02 = Response data is in SCSI-2 format (default)

The drive can be changed between these two configurations.
R# Four ASCII digits representing the last four digits of the product firmware release number
S# Eight ASCII digits representing the eight digits of the product serial number
D# Reserved 0000
[1A] Byte 7 is 3A for W/WD/WC/DC drives and 1A for N/ND drives.
[ ] Bytes 16 through 31 reflect the model of the drive (ST32550N/ND drive shown).

ST31250N/ND codes: 53 54 33 31 32 35 30 4E 20 20 20 20 20 20 20 20

ST31250W/WD/WC/DC codes: 53 54 33 31 32 35 30 57 20 20 20 20 20 20 20 20

ST32550W/WD/WC/DC codes: 53 54 33 32 35 35 30 57 20 20 20 20 20 20 20 20 20
Note. Code 20 indicates an empty-character position.

Barracuda 2LP Product Manual, Rev. D 63

11.3.2 Mode sense data

Tables 5, 6, 7, and 8 list the data-byte values the drive returns in response
to the Mode Sense command pages for SCSI-1 and SCSI-2 implementation
(see the

Definitions:
DEF = Default value. Standard drives are shipped configured this way.
CHG = Changeable bits; indicates if default value is changeable.

Table 5. Mode sense data, ST31250 default values–ASA I

Bytes 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Mode
Sense 63 00 10 08
Data 00 1E 6D 35 00 00 02 00

<————————————Mode page headers and parameter data bytes————————————>

Mode
DEF 01 81 06 04 1B 30 00 00 FF
CHG 01 81 06 EF FF 00 00 00 00

DEF 02 82 0A 80 80 00 0A 00 00 00 00 00 00
CHG 02 82 0A FF FF 00 00 00 00 00 00 00 00

DEF 03 83 16 00 05 00 03 00 00 00 05 00 6C 02 00 00 01 00 0A 00 16 40 00 00 00
CHG 03 83 16 FF FF FF FF 00 00 FF FF 00 00 00 00 00 00 00 00 00 00 00 00 00 00

DEF 04 84 12 00 0E 80 05 00 00 00 00 00 00 00 00 00 00 00 00 00 00
CHG 04 84 12 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 03 F F 00

DEF 08 88 12 10 00 FF FF 00 00 00 4F 01 3C 80 03 00 00 00 00 00 00
CHG 08 88 12 BD 00 00 00 FF F F FF FF 00 00 A0 FF 00 00 00 00 00 00

DEF 00 80 02 00 00
CHG 00 80 02 77 00

Page

SCSI-2 Interface Product Manual).

(SCSI-1 implementation)

Table 6. Mode sense data, ST32550 default values–ASA I

(SCSI-1 implementation)

Bytes 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Mode
Sense 63 00 00 08
Data 00 3F FF 0A 00 00 02 00

<————————————Mode page headers and parameter data bytes————————————>

Mode
DEF 01 81 06 04 1B 30 00 00 FF

CHG 01 81 06 EF FF 00 00 00 00
DEF 02 82 0A 80 80 00 0A 00 00 00 00 00 00

CHG 02 82 0A FF FF 00 00 00 00 00 00 00 00
DEF 03 83 16 00 0B 00 09 00 00 00 16 00 6D 02 00 00 01 00 09 00 15 40 00 00 00

CHG 03 83 16 FF FF FF FF 00 00 FF FF 00 00 00 00 00 00 00 00 00 00 00 00 00 00
DEF 04 84 12 00 0D B7 0B 00 00 00 00 00 00 00 00 00 00 00 00 00 00

CHG 04 84 12 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 03 F F 00
DEF 08 88 12 10 00 FF FF 00 00 00 4F 01 3C 80 03 00 00 00 00 00 00

CHG 08 88 12 BD 00 00 00 FF F F FF FF 00 00 A0 FF 00 00 00 00 00 00
DEF 00 80 02 00 00

CHG 00 80 02 77 00

Page

64 Barracuda 2LP Product Manual, Rev. D

Table 7. Mode sense data, ST31250 default values–ASA I

(SCSI-2 implementation)

Bytes 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Mode
Sense 9F 00 10 08
Data 00 1E 6D 35 00 00 02 00

<————————————Mode page headers and parameter data bytes————————————>

Mode

Page

DEF 01 81 0A 04 1B 30 00 00 00 03 00 FF FF
CHG 01 81 0A EF FF 00 00 00 00 FF 00 00 00

DEF 02 82 0E 80 80 00 0A 00 00 00 00 00 00 00 00 00 00
CHG 02 82 0E FF FF 00 00 00 00 00 00 00 00 83 00 00 00

DEF 03 83 16 00 05 00 03 00 00 00 05 00 6C 02 00 00 01 00 0A 00 16 40 00 00 00
CHG 03 83 16 FF FF FF FF 00 00 FF FF 00 00 00 00 00 00 00 00 00 00 00 00 00 00

DEF 04 84 16 00 0E 80 05 00 00 00 00 00 00 00 00 00 00 00 00 00 00 1C 20 00 00
CHG 04 84 16 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 03 F F 00 00 00 00 00

DEF 07 87 0A 00 1B 30 00 00 00 00 00 FF FF
CHG 07 87 0A 0F FF 00 00 00 00 00 00 00 00

DEF 08 88 12 10 00 FF FF 00 00 00 4F 01 3C 80 03 00 00 00 00 00 00
CHG 08 88 12 BD 00 00 00 FF FF FF FF 00 00 A0 FF 00 00 00 00 00 00

DEF 0A 8A 0A 02 10 00 00 00 00 00 00 00 00
CHG 0A 8A 0A 03 01 00 00 00 00 00 00 00 00

DEF 0C 8C 16 80 00 00 1D 00 00 00 00 00 00 00 0E 7F 04 00 00 00 00 00 00 10 00
CHG 0C 8C 16 40 00 00 00 F F FF 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

DEF 00 80 02 00 00
CHG 00 80 02 77 00

Table 8. Mode sense data, ST32550 default values–ASA I

(SCSI-2 implementation)

Bytes 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Mode
Sense 9F 00 10 08
Data 00 3F FF 0A 00 00 02 00

<————————————Mode page headers and parameter data bytes————————————>

Mode

Page
DEF 01 81 0A 04 1B 30 00 00 00 03 00 FF FF
CHG 01 81 0A EF FF 00 00 00 00 FF 00 00 00

DEF 02 82 0E 80 80 00 0A 00 00 00 00 00 00 00 00 00 00
CHG 02 82 0E FF FF 00 00 00 00 00 00 00 00 80 00 00 00

DEF 03 83 16 00 0B 00 09 00 00 00 16 00 6D 02 00 00 01 00 09 00 15 40 00 00 00
CHG 03 83 16 FF FF FF FF 00 00 FF FF 00 00 00 00 00 00 00 00 00 00 00 00 00 00

DEF 04 84 16 00 0D B7 0B 00 00 00 00 00 00 00 00 00 00 00 00 00 00 1C 20 00 00
CHG 04 84 16 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 03 F F 00 00 00 00 00

DEF 07 87 0A 00 1B 30 00 00 00 00 00 FF FF
CHG 07 87 0A 0F FF 00 00 00 00 00 00 00 00

DEF 08 88 12 10 00 FF FF 00 00 00 4F 01 3C 80 03 00 00 00 00 00 00
CHG 08 88 12 BD 00 00 00 FF FF FF FF 00 00 A0 FF 00 00 00 00 00 00

DEF 0A 8A 0A 02 10 00 00 00 00 00 00 00 00
CHG 0A 8A 0A 03 01 00 00 00 00 00 00 00 00

DEF 0C 8C 16 80 00 00 1A 00 00 00 00 00 00 00 0D B6 0 A 00 00 00 00 00 00 10 00
CHG 0C 8C 16 40 00 00 00 F F FF 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

DEF 00 80 02 00 00
CHG 00 80 02 77 00

Barracuda 2LP Product Manual, Rev. D 65

Table 9. Mode sense data, ST31250 default values–ASA II

(SCSI-2 implementation)

Reserved for ST31250 ASA II (SCSI-2 mode sense data)

Table 10. Mode sense data, ST32550 default values–ASA II

(SCSI-2 implementation)

Bytes 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Mode
Sense AB 00 10 08
Data 00 3F FF 0A 00 00 02 00

<—————————Mode page headers and parameter data bytes—————————>

Mode

Page
DEF 01 81 0A 04 21 30 00 00 00 03 00 FF FF
CHG 01 81 0A EF FF 00 00 00 00 FF 00 00 00

DEF 02 82 0E 80 80 00 0A 00 00 00 00 00 00 00 00 00 00
CHG 02 82 0E FF FF 00 00 00 00 00 00 00 00 87 00 00 00

DEF 03 83 16 00 0B 00 09 00 00 00 16 00 6D 02 00 00 01 00 08 00 10 40 00 00 00
CHG 03 83 16 FF FF FF FF 00 00 FF FF 00 00 00 00 00 00 00 00 00 00 00 00 00 00

DEF 04 84 16 00 0D B7 0B 00 00 00 00 00 00 00 00 00 00 00 00 00 00 1C 20 00 00
CHG 04 84 16 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 03 F F 00 00 00 00 00

DEF 07 87 0A 00 21 30 00 00 00 00 00 FF FF
CHG 07 87 0A 0F FF 00 00 00 00 00 00 00 00

DEF 08 88 12 10 00 FF FF 00 00 01 9F 01 C7 80 02 00 00 00 00 00 00
CHG 08 88 12 BD 00 00 00 FF F F FF FF 00 00 A0 FF 00 00 00 00 00 00

DEF 0A 8A 0A 02 10 00 00 00 00 00 00 00 00
CHG 0A 8A 0A 03 F1 00 00 00 00 00 00 00 00

DEF 0C 8C 16 80 00 00 1A 00 00 00 00 00 00 00 0D B6 0A 00 00 00 00 00 00 10 00
CHG 0C 8C 16 40 00 00 00 FF FF 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

DEF 8D 0A 00 02 00 00 00 00 00 00 00 00
CHG 8D 0A 00 02 00 00 00 00 00 00 00 00

DEF 00 80 02 00 00
CHG 00 80 02 77 80

66 Barracuda 2LP Product Manual, Rev. D

11.4 SCSI bus conditions
and miscellaneous features supported

Asynchronous SCSI bus conditions supported by the drive are listed in
Table 11. These conditions cause the SCSI device to perf orm certain
actions and can alter the phase sequen ce. Other miscellaneous operating
features supported are also liste d here.

Table 11. SCSI bus conditions and other miscellaneous features
Condition/feature supported by:

ASA I ASA I ASA II
SCSI-1 SCSI-2 SCSI-2 Conditions or feature

Y Y y Attention condition
Y Y Y Reset condition
N Y Y Contingent allegiance condition
N Y Y Asynchronous event notification
Y Y Y Arbitrating system
Y Y Y Disconnect/reconnect
Y Y Y Asynchronous data transfer
Y Y Y Synchronous data transfer
Y Y Y Synchronized (locked) spindle operation
Y Y Y Differential interface circuits available
Y Y Y Segmented caching
N N N Zero latency read
N Y Y Queue tagging (up to 64 queue tags supported)
N Y Y Deferred error handling
Y Y Y Parameter rounding (controlled by round bit

in Mode Select page 0)

N Y Y Reporting actual retry count in extended sense

bytes 15, 16, and 17
N N N Adaptive caching
Y Y Y SMP = 1 in Mode Select command needed to

save RPL and rotational offset bytes

(in Table 5.2.1-25 of

Manual, Vol. 2)

SCSI-2 Interface Product

ASA I ASA I ASA II
SCSI-1 SCSI-2 SCSI-2 Status supported

Y Y Y Good
Y Y Y Check condition
Y Y Y Condition met/good
Y Y Y Busy
Y Y Y Intermediate/good
Y Y Y Intermediate/condition met/good
Y Y Y Reservation conflict
N Y Y Queue full

Barracuda 2LP Product Manual, Rev. D 67

11.5 Synchronous data transfer

The data transfer period to be used by the drive and the initiator is
established by an exchange of messages during the Message Phase of
operation. See the section on message protocol in the

Product Manual.

11.5.1 Synchronous data transfer periods supported

Table 12 lists the synchronous data transfer periods supported by the
drives.

Table 12. Synchronous data transfer periods

M Transfer period Transfer rate

(decimal) (M times 4 nanoseconds) (mega transfers/second)

25 100 10.0
31 125 8.0
37 150 6.66
50 200 5.0
62 250 4.0
75 300 3.33
87 350 2.86

100 400 2.5

SCSI-2 Interface

11.5.2 REQ/ACK offset

The maximum REQ/ACK offset supported by Barracuda 2LP drives is
15 (0Fh).

68 Barracuda 2LP Product Manual, Rev. D

11.6 DC cable and connector

Note. This section applies only to N/ND/W/WD models. WC and DC models

do not have a 4-pin power connector and do not use DC power cables.

The drive receives DC power through a 4-pin connector mounted at the rear
of the main PCB. Recommended part numbers of the mating connector are
listed below, but equivalent parts may be used.

Table 13. Mating connector parts
Type of cable Connector Contacts (20-14 AWG)

14 AWG AMP 1-480424-0 AMP 60619-4 (loose piece)

AMP 61117-4 (strip)

Note. The output of a power supply must meet SELV (safety extra low

voltage) as defined in IEC 950.

Pins

4

3

1 +12V DC

12

2 +12V DC return
3 +5V DC return
4 +5V DC

11.7 SCSI physical interface

Figures 26, 27, and 28 illustrate the physical interface on Barracuda 2LP
drives. Locations of the DC power connector, the SCSI interface connector,
and the drive select and option select headers are shown.

Details of the physical, electrical, and logical characteristics are given below.
The SCSI operational aspects of Seagate drive interfaces are provided in the

SCSI-2 Interface Product Manual.

DC Power
Connector

SCSI I/O

Connector

ST31250N and
ST32550N
J1 Connector

ST31250ND and
ST32550ND
J1 Connector

J2

J4

Figure 26. ST31250N/ND and ST32550N/ND physical interface

Barracuda 2LP Product Manual, Rev. D 69

ST31250W and
ST32550W

DC Power
Connector

Pin 1

Pin 1

SCSI I/O

Connector

J5

Figure 27. ST31250W/WD and ST32550W/WD physical interface

SCSI I/O

Connector

(SCA)

Pin 1

J1 Connector

ST31250WD and
ST32550WD
J1 Connector

J2

J4

J2

J4

Figure 28. ST31250WC/DC and ST32550WC/DC physical interface

70 Barracuda 2LP Product Manual, Rev. D

11.7.1 Physical characteristics

This section defines the connectors, cables, signals, and terminators
needed to implement the SCSI interface.

11.7.1.1 Physical description

You can daisy chain multiple SCSI devices on a common cable if each device
has the same type of drivers and receivers (all single-ended or all differen­tial). Devices having single-ended interface circuits cannot be on the same
daisy chain with devices having a differential interface circuit. Both ends of
the cable must be terminated. All signals are common between SCSI
devices. A maximum of 8 SCSI devices (including the host) may be daisy
chained together when using a non-wide bus and ST31250N/ND or
ST32550N/ND drives. A maximum of 16 SCSI devices (including the host)
may be daisy chained together when using a wide bus and ST31250W/WD/
WC/DC or ST32550W/WD/WC/DC drives.

Terminate both ends of the daisy chain, but do not terminate any interme­diate SCSI device. The single-ended (ST31250N, ST31250W, ST31250WC,
ST32550N, ST32550W, and ST32550WC) drives are equipped with perma­nently mounted IC terminators, which you can turn on or off using the Enable
SCSI Terminator jumper. See Section 10.1 to locate the Enable SCSI
Terminator jumper for each drive model. The differential (ST31250ND,
ST31250WD, ST31250DC, ST32550ND, ST32550WD, and ST32550DC)
drives do not have on-board terminators.

11.7.1.2 Cable requirements

Sections 11.7.1.2.1, 11.7.1.2.2, and 11.7.1.2.3 describe the single-ended,
differential, and general cable requirements for Barracuda 2LP drives.

11.7.1.2.1 Single-ended I/O circuits (ST31250N, ST31250W, ST31250WC,
ST32550N, ST32550W, and ST32550WC drives)

The maximum total cable length for use with drives having single-ended I/
O driver and receiver circuits is 6 meters (19.7 feet) when operating at line
data transfer rates of 5 Mbytes/second or less, and 3 meters (9.85 feet)
when operating at transfer rates greater than 5 Mbytes/second (fast SCSI).
A stub length of no more than 0.1 meter (0.33 feet) is allowed off the mainline
interconnection with any connected equipment. An ideal impedance match
with cable terminators implies a cable characteristic impedance of 132
ohms. Single-ended I/O cable pin assignments for ST31250N and ST32550N
drives are shown in Table 17. Single-ended I/O cable pin assignments for
ST31250W and ST32550W drives are shown in Table 19. Single-ended pin
assignments for ST31250WC and ST32550WC drives are shown in Table

21. ST31250WC and ST32550WC drives do not use I/O cables; they are
designed to plug directly into a back-panel connector.

11.7.1.2.2 Differential I/O circuits (ST31250ND, ST31250WD, ST31250DC,
ST32550ND, ST32550WD, and ST32550DC drives)

The maximum total cable leng th f or us e with drives having differential I/O
drivers and receiver circuits is 25 meters (82 feet). A stub length of no more
than 0.2 meter (0.66 foot) is allowed off the mainline interc onnection with any
connected equipment. An ideal impedance match with cable terminators

Barracuda 2LP Product Manual, Rev. D 71

implies a cable characteristic impedance of 122 ohms. Differential I/O cable
pin assignments for ST31250ND and ST32550ND drives are shown in Table

18. Differential I/O cable p in ass ignments for ST31250WD and ST32550WD
drives are shown in Table 20.

Differential I/O pin assignments for ST31250DC and ST32550DC drives are
shown in Table 19. WC and DC model drives do not require an I/O cable.
They are designed to be connected directly to a back panel .

11.7.1.2.3 General cable characteristics

Note. Use only non-shielded cable connectors with ST31250N/ND and

ST32550N/ND drives. Use a 50-conductor flat cable or 25-conductor
twisted-pair cable. Use a minimum conductor size of 28 AWG to
minimize noise effects. The following non-shielded flat cables (or
equivalents) may be used:

Flat cable 35M-3365-50
Twisted-pair cable Spectra twist in flat 455-248-50

In general, cables having the characteristic impedances given in Sections

11.7.1.2.1 and 11.7.1.2.2 are not available; however, impedances that are
lower are satisfactory. A characteristic impedance of 100 ohm +10% is
recommended for unshielded flat or twisted-pair ribbon cable. To minimize
discontinuities and signal reflections, cables of different impedances should
not be used in the same bus. Your specific setup may require tradeoffs in
shielding effectiveness, cable length, number of loads, transfer rates, and
cost to achieve satisfactory system operation. If shielded and unshielded
cables are mixed within the same SCSI bus, the effect of impedance
mismatch must be carefully considered. Proper impedance matching is
especially important to maintain adequate margin at fast SCSI transfer
rates.

11.7.2 Connector requirements

ST31250N/ND and ST32550N/ND drives

Use a non-shielded 50-conductor cable connector consisting of two rows of
25 female contacts with adjacent centers 100 mils apart.

Recommended mating flat cable connector part numbers:

Closed end 3M-3425-7000 Without strain relief,
(for cable ends) no center key

3M-3425-7050 With strain relief, no center key

Berg-66900-290 With strain relief and center key
Open end 3M-3425-6000 Without strain relief,
(in daisy chain) no center key

3M-3425-6050 With strain relief, no center key

Berg-66900-250 With strain relief and center key

The drive device connector is a non-shielded 50-conductor connector
consisting of two rows of 25 male pins with adjacent pins 100 mils apart. The
connector is keyed (see Figure 31).

Recommended mating panel mount connector part number:

3M-CHE-2050-J01A10-KLE

72 Barracuda 2LP Product Manual, Rev. D

ST31250W/WD and ST32550W/WD drives

Recommended mating wide cable connector part numbers:

AMP 786096-7, female 68-pin
AMP 1-480420-0, power connector 4 circuit housing
BERG 69307-012 (12-position, 2 x 6, 2 mm receptacle housing)

ST31250WC/DC and ST32550WC/DC drives

No cable is required. Recommended mating SCA part numbers:

AMP Vertical (SCA sequence), 80-position

787320-1 with polarization feature
787320-2 without polarization feature

AMP Vertical (Mating blind mate SCA-2), Rcpt Assembly, 80-position

787311-1 3.18 mm tail length, with polarization feature
787331-2 3.18 mm tail length, without polarization feature
787311-3 4.57 mm tail length, with polarization feature
787331-4 4.57 mm tail length, without polarization feature

11.7.3 Electrical description

ST31250N, ST31250W, ST32550N, and ST32550W drives use single­ended interface signals. These signals must be terminated with 110 ohm
active terminator circuits at each end of the total cable. Single-ended circuits
use open collector or three-state drivers. ST31250N, ST31250W, ST32550N
and ST32550W drives can be configured to provide the SCSI termination.

ST31250ND, ST31250WD, ST32550ND and ST32550WD drives use differ­ential interface signals. Each of these signals must be terminated at each end
of the total cable with 330 ohms to +5V and 330 ohms to ground with 150
ohms between each differential pair. All I/O circuits are open collector, three­state drivers. Differential I/O drives are shipped without terminators and have
no provisions for adding terminator sockets on the PCB. You must provide
external termination for these drives.

ST31250WC/DC and ST32550WC/DC drives use the single-connection
attachment (SCA connector). This 80-pin connector plugs directly into a
back panel or plane; no external cables are required. Active terminators on
the back panel must be provided. This connector is not recommended if
cabling is required.

11.7.3.1 Single-ended drivers/receivers

Note. All single-ended terminators must be ANSI SCSI-2 alternative 2

active terminators.

Typical single-ended driver and receiver circuits for the Barracuda 2LP
family are shown in Figure 28. Use terminator circuits only when the disc
drive is first or last on the daisy chain. (See Note 1 following Figure 29.)

Transmitter characteristics

Single-ended drives use an ANSI SCSI compatible open-collector single­ended driver. This driver is capable of sinking a current of 48 mA with a low­level output voltage of 0.4V.

Barracuda 2LP Product Manual, Rev. D 73

Transmitter

(or transceiver)

Line Driver

Flat

Cable

Pair

[3]

[2]

[4]

[1]

+2.85V



110

Ohm

[4]

[1]

+2.85V



110

Ohm

Receiver

Line Receiver

[2]

Receiver characteristics

Single-ended drives use an ANSI SCSI single-ended receiver with hyster­esis gate or equivalent as a line receiver.

Figure 29. Single-ended transmitters and receivers

Notes:

[1] Part of active terminator circuits. Enable drive termination when it is first

or last on the daisy chain.
Interface signal levels and logical sense at the drive I/O connector are

defined as follows:

Logic level Driver output Receiver input

Negated (0) ≥2.5V:≤5.25V ≥2.0V:< 5.25V
Asserted (1) ≤0.4V :≥0.0V ≤0.8V:>0.0V

The difference in the voltages between input and output signals is due to

losses in the cable.
[2] ANSI SCSI compatible circuits.
[3] Total interface cable length should not exceed that specified in Section

11.7.1.2.1.

[4] Source of drive terminator power is VR1 which has an input source

voltage selected by a jumper.

11.7.3.2 Differential drivers/receivers

Typical differential driver and receiver circuits used by ST31250ND,
ST31250WD, ST32550ND and ST32550WD drives are shown in Figure 30.
The differential drives have no provisions for terminator circuits.

Differential signals

All dif ferential in terface sig nals consis t of two lines deno ted +SIGNAL
and –SIGNAL. A signal is true when +SIGNAL is more positive than
–SIGNAL, and a signal is false when –SIGNAL is more positive than
+SIGNAL. Terminate all assigned signals at each end of the cable as
shown in Tables 15, 17 and 19. You must provide external termination for
the differential drives.

74 Barracuda 2LP Product Manual, Rev. D

Output characteristics

Each signal driven by differential interface drives should have the following
output characteristics when measured at the disc drive’s SCSI connector:

Low-level output voltage*

= 2.0V maximum at low-level output current
= 55 milliamps

High-level output voltage*

= 3.0V minimum at high-level output current
= –55 milliamps

Differential voltage

= 1.0V minimum with common-mode voltage ranges

from –7V DC to +12V DC

* Measure these voltages between the output terminal and the SCSI

device’s logic ground reference.

The output characteristics must additionally conform to EIA RS-485-1983.

Input characteristics

Each signal received by differential interface drives should have the following
input characteristics when measured at the disc drive’s SCSI connector:

Input current on either input

= +2.0 milliamps maximum

(includes both receivers and passive drivers)

This requirement is met with the input voltage varying between –7V DC and
+12V DC, with power on or off, and with the hysteresis equaling 35 mV
minimum.

The input characteristics must additionally conform to EIA RS-485-1983.

+5V

+5V

5.6K

Transmit/Receive

Enable [1]

Transmit or
Receive
Signal [2]

DE

LSI

XCVR

RE

R2

1
1

[3]

[4]

Figure 30. Typical differential I/O line transmitter/receiver and terminators

Notes:

[1] Positive logic enables transmitter (+5V = asserted).

Negative logic enables receivers (0V = asserted).

[2] Negative logic signal (0V = asserted).

Barracuda 2LP Product Manual, Rev. D 75

[3] Total interface cable length should not exceed 82.1 feet (25 meters) from

the host to the end of the daisy chain.

[4] You must provide terminators.

11.7.3.3 Terminator requirements
ST31250N, ST31250W, ST32550N and ST32550W drives

Internal disc drive I/O termination consists of active circuits contained in
permanently mounted IC terminator packs on the main PCB. All single
initiator/single target (non-daisy-chain) applications require you to terminate
the initiator and drive.

You must terminate both ends of the SCSI bus with ANSI SCSI-2 standard
alternative 2 (active) termination.

Daisy-chain configurations require you to terminate only the units at each
end of the daisy chain. Do not terminate any other peripheral on the chain.

Note. Remove the Enable SCSI Terminator jumper from J1 pins 5 and 6

when terminators are not required.

ST31250WC/DC and ST32550WC/DC drives

SCA connector drives do not have internal terminators available. Provide
external active terminators when termination is required.

ST31250ND, ST31250WD, ST32550ND and ST32550WD drives

Differential I/O Barracuda drives do not have provisions to add terminator
sockets on the PCB. You must provide external termination.

11.7.3.4 Terminator power
ST31250N, ST31250W, ST32550N and ST32550W drives

You can configure terminator power in four different ways. See Section 10.1
for illustrations that show how to place jumpers enabling each of the following
terminator power configurations:

1. Drive accepts terminator power through SCSI bus pins
ST31250N and ST32550N Pin 26

ST31250W and ST32550W Pins 17, 18, 51, and 52

2. Drive supplies power to the SCSI bus.

3. Drive provides terminator power for optional internal terminator
resistors using the drive’s power connector.

4. Drive provides power to its own terminators and to the SCSI bus
terminator power line.

SCSI devices providing terminator power (TERMPWR) must have the
following characteristics:

• V TERM = 4.50V to 5.25V

• 800 mA minimum source drive capability

• 1.0A maximum

ST31250ND, ST31250WD, ST32550ND and ST32550WD drives

You can configure terminator power only from the drive to the SCSI bus.

76 Barracuda 2LP Product Manual, Rev. D

11.8 SCSI non-wide physical interface

C

L

.100

(2.54)

(4.06)

.051

(1.30)

.16

.037 Ref. Typ.
(.94)

.025

(.64)

Sq. Contact

50 Places

"D" ± .010

.045

(1.14)

"C" ± .010

"B" Ref.

"A" ± .010

.42

(10.67)

Pin 1

.100

(2.54)

Min. Typ. 3

Ref.

Typ.

4

.834 ± .010

(21.18)

.60

(15.24)

3

12

.20

Typ.

(5.08)

.065

x 45° Chamfer Typ.

(1.65)

(6.60)

.335 ± .010

.040

(1.02)

.26

Typ.

(8.50)

+.001

.083

–.002
(2.1)
Trifurcated Pin
(4 places)

Ref.

Dia.

.370 ± .010

(9.398)

No. Pos.



50

"A"



3.767

(95.68)

Figure 31. Non-shielded SCSI device connector

"B"



3.697

(93.90)

"C"



2.720

(69.09)

"D"



2.400

(60.96)

Barracuda 2LP Product Manual, Rev. D 77

Table 14. Single-ended cable pin assignments

(non-shielded connector) for ST31250N
and ST32550N drives

Signal Pin number Signal Pin number

−DB (0) 2 GROUND 28

−DB (1) 4 GROUND 30

−DB (2) 6 −ATN 32

−DB (3) 8 GROUND 34

−DB (4) 10 −BSY 36

−DB (5) 12 −ACK 38

−DB (6) 14 −RST 40

−DB (7) 16 −MSG 42

−DB (P) 18 −SEL 44

GROUND 20 −C/D 46
GROUND 22 −REQ 48
GROUND 24 −I/O 50
TERMPWR 26

Notes:

1. All odd pins except pin 25 are connected to ground. Pin 25 is left open.
Caution. Do not connect pin 25 to ground at the host end or the drive end

of the cable. If you accidentally plug in the I/O connector upside
down, terminator power on pin 26 will be shorted to ground.

2. The minus sign next to a signal indicates asserted state is the low voltage
of the two levels used for logic signals.

78 Barracuda 2LP Product Manual, Rev. D

Table 15. Differential cable pin assignments

(non-shielded connector) for ST31250ND
and ST32550ND drives

++

+Signal name* Pin number

++

−−

−Signal name*

−−

SHIELD GND 1 2 GROUND
DB (0) 3 4 −DB (0)
DB (1) 5 6 −DB (1)
DB (2) 7 8 −DB (2)
DB (3) 9 10 −DB (3)
DB (4) 11 12 −DB (4)
DB (5) 13 14 −DB (5)
DB (6) 15 16 −DB (6)
DB (7) 17 18 −DB (7)
DB (P) 19 20 DB (P)
DIFFSENS 21 22 GROUND
GROUND 23 24 GROUND
TERMPWR 25 26 TERMPWR
GROUND 27 28 GROUND
ATN 29 30 −ATN
GROUND 31 32 GROUND
BSY 33 34 −BSY
ACK 35 36 −ACK
RST 37 38 −RST
MSG 39 40 −MSG
SEL 41 42 −SEL
C/D 43 44 −C/D
REQ 45 46 −REQ
I/O 47 48 −I/O
GROUND 49 50 GROUND

*See Section 11.7.3.2 for detailed electrical characteristics of these

differential signals.

Barracuda 2LP Product Manual, Rev. D 79

11.9 SCSI wide physical interface

Position 1

68 Position SCSI Receptacle
AMPLIMITE .050 Series

.008

Typ

(.20)

1.368

(34.75)

.767

(19.46)

Position 1

.740

(18.8)

12 Position Auxiliary
Shrouded Post Header
AMPMODU 2mm

.010

Typ

(.25)

.300

(7.62)

.870

(22.1)

4 Position Power
Header, Commercial
Mate-N-Lock

.315

(8.00)

Position 1

.403

(10.24)

.033

(.84)

Typ

Figure 32. Wide SCSI device connector

80 Barracuda 2LP Product Manual, Rev. D

Table 16. Single-ended contact assignments (P cable)

for ST31250W and ST32550W drives

Signal Connector Connector Signal
name contact number contact number name

GROUND 1 35 –DB (12)
GROUND 2 36 –DB (13)
GROUND 3 37 –DB (14)
GROUND 4 38 –DB (15)
GROUND 5 39 –DB (P1)
GROUND 6 40 –DB (0)
GROUND 7 41 –DB (1)
GROUND 8 42 –DB (2)
GROUND 9 43 –DB (3)
GROUND 10 44 –DB (4)
GROUND 11 45 –DB (5)
GROUND 12 46 –DB (6)
GROUND 13 47 –DB (7)
GROUND 14 48 –DB (P)
GROUND 15 49 GROUND
GROUND 16 50 GROUND
TERMPWR 17 51 TERMPWR
TERMPWR 18 52 TERMPWR
RESERVED 19 53 RESERVED
GROUND 20 54 GROUND
GROUND 21 55 –ATN
GROUND 22 56 GROUND
GROUND 23 57 –BSY
GROUND 24 58 –ACK
GROUND 25 59 –RST
GROUND 26 60 –MSG
GROUND 27 61 –SEL
GROUND 28 62 –C/D
GROUND 29 63 –REQ
GROUND 30 64 –I/O
GROUND 31 65 –DB (8)
GROUND 32 66 –DB (9)
GROUND 33 67 –DB (10)
GROUND 34 68 –DB (11)

Notes:

1. The hyphen preceding a signal name indicates that signal is active low.

2. Eight-bit devices that connect to the P cable should leave the following
signals open: –DB(8) –DB(9) –DB(10) –DB(11) –DB(12) –DB(13) –DB(14)
–DB(15) –DB(P1). All other signals should be connected as defined.

Barracuda 2LP Product Manual, Rev. D 81

Table 17. Differential contact assignments (P cable)

for ST31250WD and ST32550WD drives

Signal Connector Connector Signal
name contact number contact number name

DB (12) 1 35 –DB (12)
DB (13) 2 36 –DB (13)
DB (14) 3 37 –DB (14)
DB (15) 4 38 –DB (15)
DB (P1) 5 39 –DB (P1)
GROUND 6 40 GROUND
DB (0) 7 41 –DB (0)
DB (1) 8 42 –DB (1)
DB (2) 9 43 –DB (2)
DB (3) 10 44 –DB (3)
DB (4) 11 45 –DB (4)
DB (5) 12 46 –DB (5)
DB (6) 13 47 –DB (6)
DB (7) 14 48 –DB (7)
DB (P) 15 49 –DB (P)
DIFFSENS 16 50 GROUND
TERMPWR 17 51 TERMPWR
TERMPWR 18 52 TERMPWR
RESERVED 19 53 RESERVED
ATN 20 54 –ATN
GROUND 21 55 GROUND
BSY 22 56 –BSY
ACK 23 57 –ACK
RST 24 58 –RST
MSG 25 59 –MSG
SEL 26 60 –SEL
C/D 27 61 –C/D
REQ 28 62 –REQ
I/O 29 63 –I/O
GROUND 30 64 GROUND
DB (8) 31 65 –DB (8)
DB (9) 32 66 –DB (9)
DB (10) 33 67 –DB (10)
DB (11) 34 68 –DB (11)

Notes:

1. The hyphen preceding a signal name indicates that signal is active low.

2. 8-bit devices that connect to the P cable should leave the following signals
open: –DB(12) –DB(13) –DB(14) –DB(15) –DB(P1) –DB(8)
–DB(9) –DB(10) –DB(11) DB(12) DB(13) DB(14) DB(15) DB(P1) DB(8)
DB(9) DB(10) DB(11). All other signals should be connected as defined.

82 Barracuda 2LP Product Manual, Rev. D

11.10 SCSI single-connector attachment
(SCA) physical interface

2.70

(.106)

*

Section X–X

1.32

(.052)

Pin 1

Side View

1.52

(.060)

57.87

(2.278)

*

62.15

(2.447)

Housing

0.15

0.15

0
–0.15
+ .000

[

– .006

MYM

–Y–

± 0.15
(± .005)

MYM

7.00

(.276)

12.70
(.500)

[

Front View

Insert cable

X

connector here

PCB Contacts

Figure 33. Non-shielded, 80-pin I/O and DC power

1.27

(.05)

0.50

(.020)

0.3

MYM

(.012)

Contacts are recessed along the center strip (see side view).

*

Typ

Pin 1

X

C

of Datum Y

L

single-connector attachment (SCA)

Top View

Back View

Barracuda 2LP Product Manual, Rev. D 83

Table 18. SCA contact assignments for ST31250WC/ST32550WC drives

++

+Signal Connector Connector

++

−−

−Signal

−−

name contact contact name

12V 1 41 12V GROUND
12V 2 42 12V GROUND
12V 3 43 12V GROUND
12V 4 44 12V GROUND
RESERVED/NC 5 45 RESERVED/NC
RESERVED/NC 6 46 RESERVED/NC
DB (11) 7 47 GROUND
DB (10) 8 48 GROUND
DB (9) 9 49 GROUND
DB (8) 10 50 GROUND
I/O 11 51 GROUND
REQ 12 52 GROUND
C/D 13 53 GROUND
SEL 14 54 GROUND
MSG 15 55 GROUND
RST 16 56 GROUND
ACK 17 57 GROUND
BSY 18 58 GROUND
ATN 19 59 GROUND
DB(P0) 20 60 GROUND
DB(7) 21 61 GROUND
DB(6) 22 62 GROUND
DB(5) 23 63 GROUND
DB(4) 24 64 GROUND
DB(3) 25 65 GROUND
DB(2) 26 66 GROUND
DB(1) 27 67 GROUND
DB(0) 28 68 GROUND
DB(P1) 29 69 GROUND
DB(15) 30 70 GROUND
DB(14) 31 71 GROUND
DB(13) 32 72 GROUND
DB(12) 33 73 GROUND
5V 34 74 5V GROUND
5V 35 75 5V GROUND
5V 36 76 5V GROUND
SYNC 37 77 ACTIVE LED OUT
RMT_START 38 78 DLYD_START
SCSI ID(0) 39 79 SCSI ID(1)
SCSI ID(2) 40 80 SCSI ID(3)

84 Barracuda 2LP Product Manual, Rev. D

Table 19. SCA contact assignments for ST31250DC /ST32550DC drives

++

+Signal Connector Connector

++

−−

−Signal

−−

name contact contact name

12V 1 41 12V GROUND
12V 2 42 12V GROUND
12V 3 43 12V GROUND
12V 4 44 12V GROUND
RESERVED/NC 5 45 RESERVED/NC
RESERVED/NC 6 46 DIFF SENSE
–DB (11) 7 47 +DB (11)
–DB (10) 8 48 +DB (10)
–DB (9) 9 49 +DB (9)
–DB (8) 10 50 +DB (8)
–I/O 11 51 +I/O
–REQ 12 52 +REQ
–C/D 13 53 +C/D
–SEL 14 54 +SEL
–MSG 15 55 +MSG
–RST 16 56 +RST
–ACK 17 57 +ACK
–BSY 18 58 +BSY
–ATN 19 59 +ATN
–DB(P0) 20 60 +DB (P0)
–DB(7) 21 61 +DB (7)
–DB(6) 22 62 +DB (6)
–DB(5) 23 63 +DB (5)
–DB(4) 24 64 +DB (4)
–DB(3) 25 65 +DB (3)
–DB(2) 26 66 +DB (2)
–DB(1) 27 67 +DB (1)
–DB(0) 28 68 +DB (0)
–DB(P1) 29 69 +DB (P1)
–DB(15) 30 70 +DB (15)
–DB(14) 31 71 +DB (14)
–DB(13) 32 72 +DB (13)
–DB(12) 33 73 +DB (12)
5V 34 74 5V GROUND
5V 35 75 5V GROUND
5V 36 76 5V GROUND
SYNC 37 77 ACTIVE LED OUT
RMT_START 38 78 DLYD_START
SCSI ID(0) 39 79 SCSI ID(1)
SCSI ID(2) 40 80 SCSI ID(3)

Notes:

1. The hyphen preceding a signal name indicates that signal is active low.

2. 8-bit devices that connect to the P cable should leave the following

signals open: –DB(12) –DB(13) –DB(14) –DB(15) –DB(P1) –DB(8)
–DB(9) –DB(10) –DB(11) DB(12) DB(13) DB(14) DB(15) DB(P1) DB(8)
DB(9) DB(10) DB(11). All other signals should be connected as defined.

Barracuda 2LP Product Manual, Rev. D 85

Table 20. Disc drive SCSI timing

Waveform Waveform

Description symbol [1] table [1] Typical Max

Target select time (no arbitration) T00 N/A < 1 µs < 250 µs
Target select time (with arbitration) T01 4.5-1,2 2.31 µs 2.36 µs
Target select to command T02 4.5-1 3.33 µs 3.34 µs
Target select to MSG out T03 4.5-2 1.51 µs 1.54 µs
Identify MSG to command T04 4.5-3 3.34 µs 3.36 µs
Command to status T05 4.5-5 Command dependent
Command to data (para. in) T06 4.5-9 Command dependent
Command to data (para. out) T07 4.5-10 Command dependent
Command to data (write to data buffer) T08 4.5-10 Command dependent
Command to disconnect MSG T09 4.5-6 Command dependent
Disconnect MSG to bus free T10 4.5-6,14 0.64 µs 0.68 µs
Disconnect to arbitration (for re-select) T11 4.5-6 Command dependent

This measures disconnected CMD overhead
Target win arbitration (for re-select) T12 4.5-7 2.8 µs
Arbitration to re-select T13 4.5-7 1.8 µs
Re-select to Identify MSG in T14 4.5-7 1.34 µs
Re-select Identify MSG to status T15 4.5-8 Command dependent
Re-select Identify MSG to data (media) T16 4.5-11 Command dependent
Data to status T17 4.5-15 Command dependent
Status to command complete MSG T18 4.5-5,8,15 1.0 µs
Command complete MSG to bus free T19 4.5-5,8,15 0.75 µs
Data to save data pointer MSG T20 4.5-14 4.5 µs
Save data pointer MSG to disconnect MSG T21 4.5-14 0.75 µs
Command byte transfer T22 4.5-4 0.04
Next command byte access 4.5-4

Next CDB byte access (byte 2 of 6) T23.6.2 4.5-4 0.55 µs 0.56 µs
Next CDB byte access (byte 3 of 6) T23.6.3 4.5-4 0.10 µs 0.10 µs
Next CDB byte access (byte 4 of 6) T23.6.4 4.5-4 0.09 µs 0.10 µs
Next CDB byte access (byte 5 of 6) T23.6.5 4.5-4 0.13 µs 0.14 µs
Next CDB byte access (byte 6 of 6) T23.6.6 4.5-4 0.13 µs 0.14 µs
Next CDB byte access (byte 2 of 10) T23.10.2 4.5-4 0.59 µs 0.60 µs
Next CDB byte access (byte 3 of 10) T23.10.3 4.5-4 0.14 µs 0.14 µs
Next CDB byte access (byte 4 of 10) T23.10.4 4.5-4 0.13 µs 0.14 µs
Next CDB byte access (byte 5 of 10) T23.10.5 4.5-4 0.12 µs 0.12 µs
Next CDB byte access (byte 6 of 10) T23.10.6 4.5-4 0.11 µs 0.12 µs
Next CDB byte access (byte 7 of 10) T23.10.7 4.5-4 0.10 µs 0.10 µs
Next CDB byte access (byte 8 of 10) T23.10.8 4.5-4 0.09 µs 0.10 µs
Next CDB byte access (byte 9 of 10) T23.10.9 4.5-4 0.13 µs 0.14 µs
Next CDB byte access (byte 10 of 10) T23.10.10 4.5-4 0.12 µs 0.12 µs

86 Barracuda 2LP Product Manual, Rev. D

Waveform Waveform

Description symbol [1] table [1] Typical Max

Data in byte transfer (parameter) T24 4.5-12 0.04 µs
Data out byte transfer (parameter) T25 4.5-13 0.04 µs
Next data in byte access (parameter) T26 4.5-12 0.10 µs 0.12 µs
Next data out byte access (parameter) T27 4.5-13 0.10 µs 0.12 µs
Data in byte transfer (media) [2] T28 4.5-12 0.03 µs 0.04 µs
Data out byte transfer (media) [2] T29 4.5-13 0.03 µs 0.04 µs
Next data in byte access (media) [2] T30 4.5-12 0.10 µs 0.12 µs
Next data out byte access (media) [2] T31 4.5-13 0.10 µs 0.12 µs
MSG IN byte transfer T32 4.5-5,7 0.09 µs 0.04 µs

4.5-8,14,15
MSG OUT byte transfer T33 4.5-2 0.04 µs
STATUS byte transfer T34 4.5-5,8 0.04 µs

4.5-15
Synchronous data transfer characteristics:

Request signal transfer period [3] – – various 800 ns

Notes:

[1] See the

SCSI-2 Interface Product Manual

(part number 77738479), Section 4.5.
[2] Maximum SCSI asynchronous interface transfer rate is given in Section 5.3.
[3] Synchronous transfer period is determined by negotiations between an initiator and a drive. The

drive is capable of setting periods as given in Section 11.5 in this manual. See also Sections

3.1.5.2 and 3.5.3.2 of the

SCSI-2 Interface Product Manual

for a description of synchronous

data transfer operation.

General timing diagrams for SCSI interface operation are shown in the

Manual,

Section 4.5.

SCSI-2 Interface Product

Barracuda 2LP Product Manual, Rev. D 87

Index

Symbols

12V current profile 35
96-bit Reed-Solomon error correction code 7

A

AC power requirements 33
acoustics 38
active terminator circuits 72
actuator assembly 6
adapter accessory frame kit 8
air cleanliness requirements 38
air flow 22
altitude, effective limits 37
ambient temperature range 36
ANSI, documents 3
asynchronous

data transfer protocol 7
SCSI bus conditions supported 66

automatic

adaptive thermal compensation 11
shipping lock 6, 7
thermal compensation 7, 11

autowrite and read reallocation 7

B

Barracuda 2LP Installation Guide 8
bits per inch, number of 11
bytes

per sector , allow a ble r ange 7
per surface, n umber of 11
per track, number of 11

C

cable pin assignments

differential 78

single-ended 77
cable requirements 70
cache control 15
caching write data 16
capacities

formatted 8

unformatted 8

conducted noise immunity 34
connector parts, DC power connection 68
contact assignments

differential (P cab le) 81
SCA 84

single-ended (P cable) 80
cooling, mechanical 42
current requirements 33

D

data block size, modifying the 8
data buffer to/from disc media 14
data heads, number of 11
data transfer rate 14
data zone 6
DC

cable and connector 68

power requirements 33
defect and error management 45
defects and errors

ETF defect list 45

primary defect list 45
Delay Motor Start option 48, 51, 54
diameter, media (disc) 43
differential

I/O, cable requirements 70
differential drivers/receiv ers 73

terminating 73
differential I/O

cable requirements 71
digital offset values 19
dimensions

N/ND J4 connector 56

W/WD J5 connector 56

WC J4 connector 57
disc rotation speed 11
drive

failure, defined 22

orientation 42
drivers and receivers 55

E

effective altitude (sea level) 37
electromagnetic

compatibility 38

interference (EMI) 21

88 Barracuda 2LP Product Manual, Rev. D

EMC/regulatory requirements, meeting 3
Enable Motor Start option 48, 51, 53
environmental interference 21
environmental limits

effective altitude 37
shock and vibration 37

temperature 36
error correction code 7
error rates 21

F

fans, positioning for cooling 22
features, listed 7
firmware 7
flaw reallocation performance impact 14
flawed sector reallocation 7
format drive command execution time 13
formatting 9
front panel 8

G

grounding 57

H

head and disc assembly (HDA) 5

cooling 22
head switch, overhead time 14
heat/power dissipation 36
hot plugging Barracuda disc drives 30
humidity 36
HYHX temperature, measuring 25

I

index signal 18
inquiry data 62
installation 30

instructions 9

plug in and play 30

service tools 30
interface

physical 56

requirements 59
interleave 7

minimum sector 14
internal data rate 11

J

J1, jumper connector 48
J2, jumper connector 48, 51, 53
J4, jumper connector 48, 51, 54
J5, jumper connector 52
jumper connectors

explained 48, 51, 53

JYHX temperature, measuring 26

K

KYHX temperature, measuring 27, 29

L

landing zone 6

M

mean time between failures (MTBF) 22
mechanical specifications

depth 39
height 39
weight 39
width 39

media

characteristics 43
description 43

diameter 43
misc. operating features supported 66
miscorrected data transferred 21
Mode Select command 15
Mode Sense data 63
Motor Start command 15
MTBF 21
multiple initiators 5

N

noise

defined 34

maximum allowed 34

O

offset values 19
one track cylinder switch, overhead time 14
operating current 33
option/configuration headers 47

Barracuda 2LP Product Manual, Rev. D 89

P

panel, front 8
performance

general 7, 14
list of characteristics 11

physical

interface 56

rotational offsets 19
physical/electrical specifications 33
power

control switch 15

dissipation 6

requirements, AC and DC 33
prefetch/multi-segmented cache control 15
preventive maintenance 7, 21, 30

R

radiated emissions, characterizations 3
reallocation of defects

on command (post format) 7
recoverable error rate 21
Reed-Solomon error correction code 7
reference documents

Barracuda 2LP Installation Guide 3, 8

SCSI-2 Reference Manual 3
reference index signal 55

termination 56
reference signal 18, 19
relative humidity

non-operating 36

operating 36
reliability

general characteristics 7

service, and 22

specifications 21
REQ/ACK offset 67
rotation speed 11
rotational

latency , a verage 11

position locking 18

skew, operating the drive with 19

S

safety agencies, certification 3
safety/regulatory agency compliance 3

SCA

contact assignments for DC drives 84
contact assignments for WC drives 83
physical interface 82
recommended mating part numbers 72
terminating WC/DC drives 72
wide differential

air-flow and cooling 29

wide single-ended

air-flow and cooling 28

SCSI

bus conditions and misc. features 66
drivers and receivers 7

SCSI interface

cable connector requirements 71
electrical description

differential driv ers/receivers 72

single-ended drivers/receivers 72
messages supported by the 59
physical connections 68
terminator requirements 75
transfer rate 14

SCSI physical interface 68

non-wide 76
wide 79

sector

reallocation scheme 7
size, allowable range 7, 14

seek

error rate 21
errors, defined 22
times, listed 13

seek errors 22
service

life 21, 30
philosophy 30
tools 30

servo heads, number of 11
shock

non-operating 37
operating

abnormal 37

normal 37
packaged 37
vibration, and 37

single-ended

drivers/receivers 72

90 Barracuda 2LP Product Manual, Rev. D

I/O, cable requirements 70
SCSI drivers and receivers 7

single-ended I/O

cable requirements 70
single-unit shipping pack kit 8
spare reallocation scheme 8
spindle

brake 7

enabling and disabling 18

stopping with the Motor Start command 15

synchronization mode 18
start current 33
start/stop time 15
synchronized

drive interconnect diagram 17

spindle operation 17

spindles interface 55

spindles interface, electrical description 55
synchronous

data transfer

periods supported 67
protocol 7

spindle 7

V

vibration

non-operating 38
operating

abnormal 38
normal 38

voltage requirements 33

W

write data, caching 16
write errors 21
WYGX temperature, measuring 24

Z

zone bit recording (ZBR) 7
ZYHX temperature, measuring 28

T

temperature, operating 36
terminating

differential driv ers/receivers 72

SCSI devices 70

single-ended drivers/receivers 72
terminator

power 48, 75

requirements 75
terminator power

options 48
timing 85
tracks

per inch, number of 11

per surface, number of 11

U

UL 3
unit attention 18
unrecoverable

error, defined 21

write errors, defined 21
unrecovered data transferred 21