Seagate ST31250N, ST31250ND, ST31250W, ST31250WD, ST31250WC Product Manual

Barracuda 2LP Disc Drive

ST31250N/ND, ST31250W/WD,

ST31250WC/DC, ST32550N/ND,

ST32550W/WD, ST32550WC/DC

Product Manual, Volume 1

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 Volume 2 SCSI-2 Interface Product Manual, Part Number 77738479.

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. TheSCSI-2 Interface Product Manual (part number 77738479) describes general SCSI interface characteristics of this and other families of Seagate drives.

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 Barra-
	cuda disc drive, based on their final acceptability in the end-use product. The
	subsystem designer is responsible for meeting these conditions of accept-
	ability 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 applica-
	tions. 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 manufac-
	turer 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 require-
	ments. Engineering test characterizations of radiated emissions are avail-
	able 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 related 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 format command to obtain different formatted capacities. User-available capacity also depends on the spare reallocation scheme selected. See the Mode Select command and the Format command in the

SCSI-2 Interface Product Manual (part number 77738479).

4.3	Options
	The capacity shown in Section 4.2 is normally provided. Other capacities
	can be ordered depending on the sparing scheme and sector size re-
	quested.
	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, part number 83328920
		This manual provides basic installation information for persons not
		familiar with the product. It also includes information on obtaining techni-
		cal 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
		protection as provided by the single-unit shipping 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.

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 cable. Internal termination is available on ST31250N, ST31250W,
		ST32550N, and ST32550W drives by enabling this featurewith a jumper
		(see Section 10.1).
		External terminators are required for ST31250ND, ST31250WD,
		ST31250WC, ST31250DC, ST32550ND, ST32550WD, ST32550WC,
		and ST32550DC drives.These external terminators must be provided by
		the user, systems integrator, or host equipment 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 appropriate option jumpers prior to applying power to the drive. If you change jumpers after applying power, recycle the drive’s power to make the new settings effective.

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 SCSI-2 Interface Product

Manual (part number 77738479) for additional timing details.

ASA I thermal calibration

All performance characteristics assume that automatic adaptive thermal compensation is not in process when the drive receives the SCSI command. Automatic adaptive thermal compensation will not interrupt an active SCSI command. If 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 command executes, andthe drive continues compensation for the remaining heads.

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). You 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
	Has			TCAL
	10 min. TCAL			head
	timer	No
	expired?
	Yes
	Reset			Has		Complete
	10 minute					command
				target
	TCAL timer
			No	received a SCSI
				command?
	Is					Read
	SCSI			Yes		ahead
No	command in				No	pending?
	progress?
				All
				heads		Yes
	Yes			calibrated?	No
						Hold
		All
	Complete					(wait for next
		heads
						command)
	command	calibrated?	Yes	Yes
		No			Write/Read	Independent		Read
					Miss	10 Minute	Sequential
	Read
					command	Periodic	command
	ahead					Abortive Read
No	pending?					Lookahead
		Select				Timer
				A
	Yes	next
		head
	Hold
						Has
	(wait for next							Yes
	command)					10 min. TCAL
						timer
						expired?
Write/Read	Independent	Read
Miss	10 Minute	Sequential				No
command	Periodic	command
						Seek to
	Abortive Read
	Lookahead					TCAL cyl
	Timer					and select
						next head
	Seek to
	TCAL cyl
	and select
	head zero

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 ³ 512-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 measuredfrom the start of the first sector transfer toor from the host. ** Assumes system ability tosupport 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.

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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 SCSI-2 Interface Product Manual (77738479) less
	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 SCSI-2 Interface Product Manual).
	There is no power control switch on the drive.

5.5 Prefetch/multi-segmented cache control

The drive provides a prefetch/multi-segmented cache algorithm, which in many cases enhances system performance.To select this feature,the host sends the Mode Select command with the proper values in the applicable bytes in page 08h (see the SCSI-2 Interface Product Manual). Default is 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), data requested by the host with a 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 ). If the cache is not enabled, 480 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:

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 requested logical block is reached that is not in any segment,
	the drive fetches it and any remaining requested logical block addresses
	from the disc and puts them in a segment of the cache. The drive
	transfers the remaining requested logical blocks from the cache to the
	initiator in accordance with the “buffer-full” ratio specification given in
	Mode Select Disconnect/Reconnect parameters, page 02h (see the
	SCSI-2 Interface Product Manual).
	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 (see the SCSI-2 Interface Product Manual).
	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 SCSI-2 Inter-
	face Product Manual).
	2. The drive prefetches additional logical blocks contiguous to those trans-
	ferred 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.
	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 SCSI-2 Interface
	Product Manual).
	Each cache segment is actually a self-contained circular buffer whose
	length is an integer number of sectors. 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 SCSI-2 Interface Product Manual ). The wrap-around
	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.
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.

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

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	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	Spindle
Host	Control
(or other drive)	+5V
	RT
	Drive 1
System	Spindle
Interface
	Control
	+5V
	RT
	Drive 2
	Spindle
	Control
	+5V
	RT
	Drive n

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 time after power-up to be the master or a slave by using the Mode Select command on the Rigid Disc 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 host computer. All drives 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 the synchronized reference signal 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.

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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)

ThePike 2 LSI on the master drive provides the reference signal (SSREF+). The index signal generates a 120 Hz signal. The signal is normally false/negated (nominal 0V) and makes a transition to the true/asserted (nominal +5V) level to indicate the reference position during the revolution period. Master and slave drives use the trailing (falling) edge of the reference signal to phase-lock their spindles. A maximum of 10 seconds is allowed for a slave to synchronize with the reference signal. Figure 5 shows the characteristics of the reference signal.

1.2 sec ± 0.5

1

SSREF +

0

1.0 sec min.

1.37 sec max.

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 and 1) of the Rigid Disc Drive Geometry mode parameters page (page 04h) is used for enabling and disabling spindle synchronization mode (see the SCSI-2 Interface Product Manual). If the target fails to synchronize, it creates a unit attention condition to all initiators.The sense key is set to Unit Attention and the additional 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).

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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 Interface Product Manual). The value 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.

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