Hitachi Ultrastar 15K73 User manual

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HITACHI3.5 INCH MAGNETIC DISK DRIVE
Reference Manual
For Ultrastar 15K73
SCSI Interface Specification
Document Number : K6602924
SCSI 2/3 SPECIFICATIONS Hitachi, Ltd. Tokyo, Japan

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NOTICE TO USERS
While every effort has been made to ensure that the information provided herein is correct
please feel free to notify us in the event of an error of inconsistency.
Hitachi makes no representations or warranties with respect to the contents hereof and
specifically disclaims any implied warranties or merchantability or fitness for any purpose.
Further, Hitachi reserves the right to revise this publication and to make changes from
time to time in the content hereof without obligation to notify any person of such revisions
or changes.
All Right Reserved, Copyright (C) 2002,2003 Hitachi, Ltd.

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REVISION TABLE
Remarks AD : Addition, CH : Change, CR : Correction, DL : Deletion
REV Date Signature Page Description Remarks
DWN : Shikama
CHK
: Shikama
0’02.10.28
APPD
: Takayasu
All Initial Release.
1’03.03.06 DWN : Shikama 1Change of model name. CH
CHK : Shikama 15 Change of revision number of related CH
APPD
: Takayasu
document.
15 Change of Product Specification
document name. CH
74 Delete the description about the
defect descriptions in the ascending
order of address in case of block
format.
DL
210 Change the description about the
defect descriptions in the ascending
order of address in case of block
format.
CH
263 Addition of description about 2480 AD
REVISION

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REV Date Signature Page Description Remarks
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CONTENTS
1GENERAL DESCRIPTION ..............................................................................................15
1.1 APPLICATION...........................................................................................................15
1.2 RELATED DOCUMENT............................................................................................ 15
1.3 FUNCTION OUTLINE..............................................................................................15
1.4 GLOSSARY.................................................................................................................19
2PRODUCT SPECIFICATION OUTLINE........................................................................21
2.1 ADDRESSING............................................................................................................21
2.2 DISK FORMAT...........................................................................................................21
2.2.1 CYLINDER ALLOCATION ................................................................................21
2.2.2 FORMAT PROCESSING....................................................................................22
2.3 ERROR RETRY ..........................................................................................................26
2.3.1 READ ERROR RETRY .......................................................................................26
2.3.2 WRITE ERROR RETRY .....................................................................................26
2.3.3 VERIFY ERROR RETRY....................................................................................27
2.3.4 SEEK ERROR RETRY........................................................................................27
2.3.5 SPINDLE ERROR RETRY.................................................................................27
2.3.6 ERROR RETRY CONTROL ...............................................................................27
2.4 SUPPORTED SCSI COMMANDS ............................................................................ 28
3SCSI BUS ...........................................................................................................................31
3.1 SCSI BUS FUNCTIONS............................................................................................31
3.1.1 COMMAND RECEPTION..................................................................................31
3.1.2 COMMAND QUEUING......................................................................................31
3.1.3 DISCONNECT / RECONNECT.........................................................................32
3.1.4 UNIT ATTENTION CONDITION......................................................................33
3.1.5 ATTENTION CONDITION................................................................................33
3.1.6 RESET CONDITION..........................................................................................33
3.2 MESSAGES.................................................................................................................34
3.2.1 MESSAGE PROTOCOL .....................................................................................34
3.2.2 MESSAGES.........................................................................................................35
3.2.3 EXTENDED MESSAGE.....................................................................................41
3.3 STATUS.......................................................................................................................49
3.4 SCSI BUS ERROR CONDITIONS............................................................................51
3.4.1 TARGET MODE ERROR CONDITIONS..........................................................51
3.4.2 INITIATOR MODE ERROR CONDITION .......................................................51
3.5 SPI Information Unit .................................................................................................52
3.5.1 SPI Command Information Unit........................................................................52
3.5.2 SPI L_Q Information Unit..................................................................................55
3.5.3 SPI Data Information Unit.................................................................................58
3.5.4 SPI Data Stream Information Unit...................................................................58
3.5.5 SPI Status Information Unit..............................................................................59
4SCSI COMMANDS............................................................................................................62
4.1 COMMAND STRUCTURE........................................................................................ 62
4.1.1 OPERATION CODE............................................................................................64

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4.1.2 LOGICAL UNIT NUMBER................................................................................65
4.1.3 RELATIVEADDRESS........................................................................................65
4.1.4 LOGICAL BLOCK ADDRESS............................................................................65
4.1.5 TRANSFER LENGTH ........................................................................................66
4.1.6 CONTROL BYTE ................................................................................................67
4.1.7 RESERVED..........................................................................................................67
4.1.8 VENDOR UNIQUE.............................................................................................68
5COMMAND DESCRIPTIONS..........................................................................................69
5.1 FORMAT UNIT:(04H).................................................................................................69
5.2 INQUIRY:(12H)...........................................................................................................78
5.3 LOG SELECT:(4CH)................................................................................................... 89
5.4 LOG SENSE:(4DH)....................................................................................................115
5.5 MODE SELECT:(15H)...............................................................................................117
5.6 MODE SELECT (10):(55H).......................................................................................162
5.7 MODE SENSE:(1AH)................................................................................................ 164
5.8 MODE SENSE (10):(5AH).........................................................................................185
5.9 PERSISTENT RESERVE IN:(5Eh) ........................................................................187
5.10 PERSISTENT RESERVE OUT:(5Fh).....................................................................194
5.11 READ:(08H)................................................................................................................199
5.12 READ (EXTENDED):(28H).......................................................................................200
5.13 READ BUFFER:(3CH).............................................................................................. 202
5.14 READ CAPACITY:(25H)...........................................................................................206
5.15 READ DEFECT DATA:(37H)...................................................................................208
5.16 READ DEFECT DATA(12) :(B7H)...........................................................................211
5.17 READ LONG:(3EH)...................................................................................................213
5.18 REASSIGN BLOCKS:(07H)......................................................................................215
5.19 RECEIVE DIAGNOSTIC RESULTS:(1CH)............................................................ 218
5.20 RELEASE:(17H)........................................................................................................219
5.21 RELEASE(10):(57H)..................................................................................................220
5.22 REPORT LUNS:(A0h).............................................................................................. 221
5.23 REQUEST SENSE:(03H)..........................................................................................223
5.24 RESERVE:(16H)........................................................................................................224
5.25 RESERVE(10):(56H)..................................................................................................226
5.26 REZERO UNIT:(01H)................................................................................................227
5.27 SEEK:(0BH)............................................................................................................... 228
5.28 SEEK (EXTENDED):(2BH)...................................................................................... 229
5.29 SEND DIAGNOSTIC:(1DH).....................................................................................230
5.30 START / STOP UNIT:(1BH)..................................................................................... 239
5.31 SYNCHRONIZED CACHE:(35H).............................................................................240
5.32 TEST UNIT READY:(00H).......................................................................................241
5.33 VERIFY:(2FH)............................................................................................................242
5.34 WRITE:(0AH)............................................................................................................. 244
5.35 WRITE (EXTENDED):(2AH)....................................................................................245
5.36 WRITE AND VERIFY:(2EH).................................................................................... 247
5.37 WRITE BUFFER:(3BH)............................................................................................ 249

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5.38 WRITE LONG:(3FH).................................................................................................252
5.39 WRITE SAME:(41H)..................................................................................................253
6SENSE DATA...................................................................................................................254
6.1 SENSE DATA FORMAT.......................................................................................... 254
6.2 SENSE DATA SET / RESET CONDITIONS .........................................................272
6.2.1 SETTING CONDITIONS .................................................................................272
6.2.2 RESETTING CONDITIONS............................................................................272

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Figures
Figure 2-1 Track Skew (Skew Factor n)........................................................................24
Figure 2-2 Cylinder Skew ( Skew Factor n ).................................................................24
Figure 2-3 Sector Reallocation.......................................................................................25

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Tables
Table 2.1 Commands Supported ....................................................................................28
Table 2.2 Commands Not Supported.............................................................................30
Table 3.1 Messages..........................................................................................................35
Table 3.2 SYNCHRONOUS DATA TRANSFER REQUEST........................................42
Table 3.3 Transfer period................................................................................................43
Table 3.4 WIDE DATA TRANSFER REQUEST...........................................................44
Table 3.5 TRANSFER WIDTH EXPONENTS..............................................................45
Table 3.6 PARALLEL PROTOCOL REQUEST ............................................................45
Table 3.7 DT Request......................................................................................................47
Table 3.8 Transfer period................................................................................................48
Table 3.9 Status Byte Format ........................................................................................49
Table 3.10 Status Byte Code...........................................................................................49
Table 3.11 SPI Command Information Unit .................................................................52
Table 3.12 Task Attribute...............................................................................................53
Table 3.13 Task Management Flags..............................................................................53
Table 3.14 SPI L_Q Information Unit ...........................................................................55
Table 3.15 TYPE..............................................................................................................56
Table 3.16 BIDI Direction...............................................................................................57
Table 3.17 SPI Data Information Unit..........................................................................58
Table 3.18 SPI Data Stream Information Unit.............................................................59
Table 3.19 SPI Status Information Unit .......................................................................60
Table 3.20 Packetized Failure field................................................................................61
Table 3.21 Packetized Failure Code...............................................................................61
Table 4.1 Standard Command Descriptor Block for 6-byte Commands......................63
Table 4.2 Standard Command Descriptor Block for 10-byte Commands....................63
Table 4.3 Standard Command Descriptor Block for 12-byte Commands....................64
Table 4.4 Operation Code ...............................................................................................64
Table 4.5 Control Byte Format.......................................................................................67
Table 5.1 Format Unit Command Variations................................................................71
Table 5.2 Defect List Header..........................................................................................72
Table 5.3 Defect List --- Block Format......................................................................74
Table 5.4 Defect List --- Byte from Index Format....................................................74
Table 5.5 Defect List --- Physical Sector Format.....................................................75
Table 5.6 Initialization Pattern Descriptor...................................................................75
Table 5.7 IP Modifier.......................................................................................................76
Table 5.8 Standard Inquiry Data...................................................................................79
Table 5.9 Clocking...........................................................................................................82
Table 5.10 Supported Vital Product Data......................................................................83
Table 5.11 Unit Serial Number ......................................................................................84
Table 5.12 Implemented Operating Definition Page....................................................85
Table 5.13 Operating Definition.....................................................................................86
Table 5.14 Device Identification Page............................................................................86
Table 5.15 Jumper Information Page ............................................................................87
Table 5.16 PCR and Parameter List Length Fields......................................................89

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Table 5.17 SP and DS Fields ..........................................................................................90
Table 5.18 Page Control Field (PC)................................................................................90
Table 5.19 Log Page Format...........................................................................................92
Table 5.20 Log Page Codes .............................................................................................92
Table 5.21 Log Parameter...............................................................................................93
Table 5.22 Threshold Met Criteria.................................................................................96
Table 5.23 Supported Log Pages....................................................................................98
Table 5.24 Error Counter Read Page (Page Code = 3H)................................................99
Table 5.25 Parameter Codes for Error Counter Pages...............................................100
Table 5.26 Non-Medium Error Page (Page Code = 6H)...............................................101
Table 5.27 Non-Medium Error Event Parameter Codes............................................102
Table 5.28 Last n Error Events Page(Page Code = 7H)...............................................102
Table 5.29 Temperature Page(Page Code = DH)..........................................................104
Table 5.30 Start-Stop Cycle Counter Page(Page Code = 0EH)...................................105
Table 5.31 Application Client Page(Page Code = 0FH)...............................................107
Table 5.32 General usage application client parameter data....................................108
Table 5.33 Self-Test Results Page(Page Code = 10H)..................................................109
Table 5.34 Self-Test Results Log Parameter Format.................................................. 110
Table 5.35 Self-Test Results Values............................................................................. 111
Table 5.36 Informational Exceptions Page (Page Code = 2FH).................................. 112
Table 5.37 Factory Log Page (Page Code = 3EH)...................................................... 113
Table 5.38 Mode Select Parameter List....................................................................... 119
Table 5.39 Mode Select (Sub_Page Mode) Page Descriptor(s)...................................120
Table 5.40 Read - Write Error Recovery Page (Page Code = 1H)................................123
Table 5.41 Error Control Bit Combinations................................................................126
Table 5.42 Disconnect - Reconnect Page (Page Code = 2H)........................................129
Table 5.43 DTDC (Data Transfer Disconnect Control)............................................131
Table 5.44 Format Device Page (Page Code = 3H).......................................................132
Table 5.45 Rigid Disk Geometry Page (Page Code = 4H)............................................135
Table 5.46 Verify Error Recovery Page (Page Code = 7H)...........................................138
Table 5.47 Caching Page (Page Code = 8H)..................................................................139
Table 5.48 Control Mode Page (Page Code = AH)........................................................142
Table 5.49 Notch and Partition Page (Page Code = CH).............................................145
Table 5.50 Logical Unit Control Page (Page Code = 18H)...........................................147
Table 5.51 Port Control Page (Page Code = 19H)........................................................148
Table 5.52 Margin Control Sub Page (Page Code = 19H, Sub Page Code = 01H)......149
Table 5.53 Saved Training Configuration SubPage
(Page Code = 19H, SubPage Code = 02H).............................................151
Table 5.54 Negotiated Setting Sub Page
(Page Code = 19H, Sub Page Code = 03H)............................................153
Table 5.55 Bus Mode.....................................................................................................154
Table 5.56 Report Transfer Capabilities Sub Page
(Page Code = 19H, Sub Page Code = 04H)..........................................155
Table 5.57 Protocol Options Bits..................................................................................156
Table 5.58 Power Condition Control Page (Page Code = 1AH)...................................157

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Table 5.59 Informational Exceptions Control Page (Page Code = 1CH)....................158
Table 5.60 Method of Reporting Informational Exceptions field...............................160
Table 5.61 MODE SELECT (10) Header.....................................................................163
Table 5.62 Mode Sense Data.........................................................................................166
Table 5.63 Page Descriptor(s) (Sub_Page Mode Page Format)..................................167
Table 5.64 Sense Data Length......................................................................................168
Table 5.65 Mode Page 1HDescriptor Value..................................................................170
Table 5.66 Mode Page 2HDescriptor Value.................................................................171
Table 5.67 Mode Page 3HDescriptor Value.................................................................172
Table 5.68 Mode Page 4HDescriptor Value.................................................................173
Table 5.69 Mode Page 7HDescriptor Value.................................................................174
Table 5.70 Mode Page 8HDescriptor Value.................................................................175
Table 5.71 Mode Page AHDescriptor Value.................................................................176
Table 5.72 Mode Page CHDescriptor Value.................................................................177
Table 5.73 Mode Page 18HDescriptor Value...............................................................178
Table 5.74 Mode Page 19HDescriptor Value...............................................................178
Table 5.75 Mode Page 19H, Sub Page 01HDescriptor Value .....................................179
Table 5.76 Mode Page 19H, Sub Page 02HDescriptor Value .....................................180
Table 5.77 Mode Page 19H, Sub Page 03HDescriptor Value .....................................181
Table 5.78 Mode Page 1AHDescriptor Value...............................................................183
Table 5.79 Mode Page 1CHDescriptor Value...............................................................184
Table 5.80 MODE SENSE (10) Header.......................................................................186
Table 5.81 PERSISTENT RESERVE IN Service Action Code...................................188
Table 5.82 READ KEYS Parameter Data ...................................................................188
Table 5.83 READ RESERVATION Parameter Data...................................................189
Table 5.84 PERSISTENT RESERVE IN reservation descriptor...............................190
Table 5.85 Persistent reservation scope codes ............................................................192
Table 5.86 Persistent Reservation Type Code.............................................................193
Table 5.87 PERSISTENT RESERVE OUT Service Action Code...............................195
Table 5.88 PERSISTENT RESERVATION OUT Parameter List..............................196
Table 5.89 PERSISTENT RESERVE OUT Service Actions and Valid Parameters.198
Table 5.90 Read Buffer Mode.......................................................................................202
Table 5.91 Read Buffer Header....................................................................................204
Table 5.92 Read Buffer Descriptor...............................................................................205
Table 5.93 Echo Buffer Descriptor...............................................................................205
Table 5.94 Read Capacity Data....................................................................................207
Table 5.95 Defect List Format......................................................................................208
Table 5.96 Read Defect Header....................................................................................209
Table 5.97 Read Defect Header....................................................................................212
Table 5.98 Reassign Blocks Defect List.......................................................................216
Table 5.99 REPORT LUNS Parameter List Format..................................................222
Table 5.100 Self-Test Code Field Values......................................................................230
Table 5.101 Diagnostic Page Format...........................................................................233
Table 5.102 Supported Diagnostic Page (Code = 00H)................................................234
Table 5.103 Translate Address Page (Code = 40H)......................................................235

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Table 5.104 Translation Format...................................................................................235
Table 5.105 Read Alternate Page (Code = 40H)...........................................................236
Table 5.106 Diagnostic Parameter List.......................................................................237
Table 5.107 Sub Command Codes................................................................................238
Table 5.108 Write Buffer Mode ....................................................................................250
Table 5.109 Write Buffer Header.................................................................................251
Table 6.1 Extended Sense Data Format......................................................................254
Table 6.2 Sense Keys.....................................................................................................256
Table 6.3 Additional Sense Codes & Qualifiers ..........................................................258
Table 6.4 Field Pointer..................................................................................................271
Table 6.5 Actual Retry Count.......................................................................................271
Table 6.6 Progress Indication.......................................................................................272

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Preface
This manual describes the specifications of the Small Computer System Interface (SCSI)
functions supported by the HITACHI 3 1/2 model magnetic disk drives.
1GENERAL DESCRIPTION
1.1 APPLICATION
This manual applies to the SCSI logical interface specification of the magnetic disk
drive.
Refer to the individual Product Specifications for the physical specification of the
product.
1.2 RELATED DOCUMENT
·ANSI SCSI Specification;
ANSI X3.301-1997
X3T10/995D Rev 11a
X3T10/996D Rev 8c
X3T10/1142D Rev 20a
X3T10/1236-D Rev 20
X3T10/1302D Rev 14
X3T10/1416-D Rev 5
X3T10/1365D Rev 10
·Product Specification;
Ultrastar 15K73/36(SCSI Interface) Product Specifications K6602906
1.3 FUNCTION OUTLINE
Interface (SCSI-2).
“Controller or “ ” may be substituted for the disk drive
describes only SCSI interface functions which are implemented by
the SCSI controller in the disk
Its features are listed below.
(1) ANSI STANDARD COMPLIANCE
conform to the ANSI standard listed in article 1.2.

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(2) AUTOMATICALTERNATE ASSIGNMENT/ACCESS
By the FORMAT UNIT or REASSIGN BLOCKS command, alternate sectors are
automatically assigned in place of defective sectors. An alternate sector is
allocated next to the defective sector on FORMAT UNIT, so, extra rotational
latency may be avoided. The access to an alternate sector is done automatically on
the read or write operation.
(3) AUTOMATIC ERROR CORRECTION
The automatic error correction scheme with ECC is capable for an error correction
of the medium defect. The On the Fly error correction is also capable for the
medium defect and does not require the extra rotational delay.
Refer to the Product Specifications for details.
(4) AUTOMATIC ERROR RETRY
The error recovery function is automatically initiated in case that an error
occurred during access to the disk drive.
(5) AUTOMATIC POWER-SAVING CONTROL
The automatic power-saving function is supported to reduce the power
consumption and increase the life time of the magnetic heads and the electronic
circuits. This is automatically initiated in an idle condition whenever there are
no pending process by the host command.
(6) AUTOMATIC READ/WRITE REALLOCATION
The automatic read/ write reallocation function is supported. When an error is
detected on reading the data(assuming a data field recoverable error) or writing
the data(assuming a servo field error), this function automatically assigns an
alternate sector in place of the defective sector and stores the data on the
alternated sector prior to sending the completion status.
(7) COMMAND LINK
The command link function transits to next COMMAND phase directly from
current MESSAGE IN phase at the successful command termination.
(8) COMMAND QUEUING
One command per initiator(host computer) is enqueued(Untagged Command
Queuing) and/or maximum 128 commands as total number of commands from all
host computers are enqueued(Tagged Command Queuing).
(9) COMMAND RE-ORDERING
The disk drive executes the multiple tagged commands with the advanced
command re-ordering algorithm. It can optimize the execution time of enqueued
commands and provide the high performance for a random or multi-threading
access environment.
(10) COMPACT DRIVE w/EMBEDDED CONTROLLER
The disk drive with fully embedded SCSI controller has the 3 1/2 inch industrial

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standard form factor.
(11) DEFERRED ERROR REPORTING
The deferred error function reports an error to the subsequent command received
from the host computer if an error occurs after the completion with the GOOD
status returned.
(12) DOWN-LOADABLE SCSI FIRMWARE
The SCSI firmware can be changed by the multi-WRITE BUFFER commands
through the SCSI BUS.
(13) FAST-20/FAST-40/Fast-80(Ultra SCSI/Ultra 2 SCSI/Ultra 3 SCSI)
Fast-20(Ultra SCSI), Fast-40(Ultra 2 LVD SCSI), Fast-80(Ultra 3 LVD SCSI),
Fast-160 Synchronous Data Transfer Mode and other modes are available as
follows.
· Max. 320MB/S (Fast-160 Synchronous w/16-bit bus)
· Max. 160MB/S (Fast-80 Synchronous w/16-bit bus)
·Max. 80MB/S (Fast-40 Synchronous w/16-bit bus)
·Max. 40MB/S (Fast-20 Synchronous w/16-bit bus)
·Max. 20MB/S (Fast-10 Synchronous w/16-bit bus)
·Max. 10MB/S(Synchronous w/16-bit bus)
(14) MULTI-HOST/MULTI-TARGET CONNECTION
The disk drive can be connected to up to sixteen(16) host computers and
targets(including itself) in 16-bit Wide SCSI.
(15) MULTI-SEGMENTED BUFFER
The large capacity data buffer is equipped and this is maintained as a multi-
segmented buffer. A multi-segmented buffer scheme provides a high performance
for a read/write from the host computer which has the multi-tasking feature.
Refer to the Product Specifications for the data buffer size.
(16) READ AHEAD CACHE
The read ahead cache function provides a high performance for a sequential read
access. Reading data which the host computer has not yet requested into data
buffer is done in advance and directly transferring data to the host computer is
done without any latency at sequential access.
(17) SECTOR INTERLEAVE
A 1 : 1 interleave is supported.
(18) SELECTABLE BLOCK LENGTH
A 512 bytes block length is supported as a default and other block length is also
available after the disk re-format.
Refer to the Product Specification for details.
(19) SMART(Self-Monitoring Analysis and Reporting)

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The SMART(Self-Monitoring Analysis and Reporting) function is supported. This
function enables to perform an analysis, logging and reporting the error to the host
computer by the disk drive itself .
(20) TRACK/CYLINDER SKEW
In order to avoid a rotational latency for the seek to the adjacent head or cylinder,
Head/ Cylinder Skew function which shifts the sector configuration at the head/
cylinder boundary (between the last sector of the head/ cylinder and the first sector
of the next head/ cylinder) is supported, so that the read write head can be
positioned to the first sector of the next head/ cylinder. Therefore, reading/
writing of contiguous blocks is done without an extra rotational delay, even if an
access is done over the physical track/cylinder boundary.
(21) WRITE CACHE
The write cache function provides a high performance for a sequential write access.
It may return the completion with the GOOD status for a WRITE command after
successfully receiving the data from the host computer and prior to having
successfully stored the data on the disk medium.
(22) ULTRA3 SCSI
The Parallel Protocol Request Message and READ BUFFER/WRITE BUFFER
command(echo buffer mode) is supported for ULTRA3 SCSI.
(23) SCSI Bus Fairness
The SCSI bus fairness function is supported. This function guarantee the
opportunity of an arbitration to all the hosts connected to same SCSI bus, and
target.
(24) Information Unit Transfer(IUS)
The Information Unit Transfer(IUS) function is supported. This function can raise
the performance of the whole system sharply.
Non-data transmission of the status transmitted to a host can be transmitted and
received at synchronization eggplant data transmission speed from the command
transmitted to a controller from a host, and controller.
More I/O processes can be processed, without disconnectting.
(25) QuickArbitration(QAS)
The Quick Arbitration(QAS) is supported. This function can perform an
arbitration through a bus free phase.

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1.4 GLOSSARY
Bit number A number that represents the weighted position of one byte.
Bit n represents a value of 2n.
Command Descriptor Block A command block that is used to communicate requests
from
(CDB) : an initiator to a target.
Connect A function used by an initiator to select a target to initiate
an operation.
Disconnect A function used by a target to release the SCSI bus control,
allowing the SCSI bus to go to the BUS FREE phase.
XXH , XXh A hexadecimal representation of a number (XX with a
subscript H/h represents a hexadecimal number).
Initiator A SCSI device (usually a host computer) that requests
another SCSI device to perform an operation.
INTERMEDIATE status A status code that is sent from a target to an initiator on
completion of a command in a set of linked commands
except the last command in the set.
I/O Process An I/O Process is a command process which is requested by
an initiator to a target. An I/O Process, in general, begins
from an initial selection, through a receiving the CDB and
a disconnecting/ reconnecting from/ to an SCSI BUS, and
ends by a COMMAND COMPLETE or ABORT/Reset. A
set of Linked commands is treated as a single I/O Process.
Logical unit A physical device that is addressable through a target.
Logical unit number (LUN) An encoded 6 - bit identifier for a logical unit.
Nexus A combination on an SCSI interface to perform an I/O
Process.
I_T Nexus A combination of an initiator and a target.
I_T_L Nexus A combination of an initiator, a target and a logical unit.
I_T_L_Q Nexus A combination of an initiator, a target, a logical unit and a
Queue Tag.

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Reconnect A function used by a target to select an initiator to continue
an operation after it has been disconnected.
Reserved (or R) A term used for a bits, bytes, fields, or code values that are
set aside for future standardization.
SCSI address A unique address 0 - 7 (8 - bit SCSI bus) or 0 - 15 (16 - bit
SCSI bus) assigned to an SCSI device. This address is
assigned and set in the SCSI device during system
installation.
SCSI device A host computer (w/ SCSI adapter), peripheral controller,
or intelligent peripheral that can be attached to the SCSI
bus.
SCSI ID The bit significant representation of an SCSI address (this
bit address is associated with a bit number of the data bus).
Status One byte of information sent from a target to an initiator
on completion of each command.
Target An SCSI device (usually a disk drive w/ SCSI controller)
that performs an operation that is requested by an
initiator.
Vendor unique (VU) A bit, byte, field, or code value that can be uniquely
specified by each vendor.