Seagate SCSI Interface User manual

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SCSI Interface
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Product Manual, Volume 2
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SCSI Interface
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Product Manual, Volume 2
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© 1997-1999 Seagate Technology, Inc. All rights reserved
Publication number: 77738479, Rev. J
April 1999
Seagate, Seagate Technology, and the Seagate logo are registered trademarks of Seagate
Technology, Inc. SeaFAX, SeaFONE, SeaBOARD, and SeaTDD are either trademarks or reg-
istered trademarks of Seagate Technology, Inc. or one of its subsidiaries. All other trademarks
or registered trademarks are the property of their respective 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 of Seagate
Technology, Inc.

Revision status summary sheet
Revision Authority Date Signature Sheets Affected
A Issue 12/18/92 D. Ashby/
J. Averyt 1 thru 257.
B PLD:83345 8/18/93 1 thru 4, 4.1, 5 thru 193
deleted shs 194 thru 257.
(Technical changes on pages 5, 9, 10, 78,
93, 94, 104-107, 109, 136, 139-142, 144,
147, 149, 161-164, 166, 167, 181, 185
thru 193.)
C PLD:83534 93 Oct. 19 SS Revised sheets v thru ix, 1 thru 193.
(Technical changes on pages v, vii, 1, 4,
5, 7, 8, 47, 70, 73, 78, 79, 83, 84, 86, 87,
90, 91, 93, 94, 104, 105, 107, 112, 114,
119, 123-131, 136-144, 147-156, 158-
160, 162-170, 176, 178-180, 184, 185,
189, 192, and 193.)
D PLD:85300 5/26/94 SS v thru ix, 1 thru 189. (Technical changes
on pages 1, 8, 12, 26, 29, 34, 35, 70, 71,
77, 79, 80, 84, 85, 86, 95, 101, 104, 125,
150, 125, 150, 151, 160, 162, 163, and
164.)
E PLD:87127 01/24/95 QB v thru ix, 1 thru 187; deleted shs 188 and
189. Renumbered pages 94 thru 187.
(Technical changes on pages vi, vii, ix, 1,
2, 18, 21, 25, 26, 32, 33, 47, 50, 57, 68,
72, 74, 75, 77, 78, 79, 87, 88-90, 94, 105,
110, 114, 122, 124, 126, 127, 133, 135,
136, 139, 140, 143, 150, 152, 154, 158,
160, 162-164, 168-175, 178, 187.
F PLD:86464 06/20/95 QB v thru ix, 1 thru 187. Added pages 188
thru 197.
G PLD:86785 05/02/96 QB v thru ix, 1 thru 197. Added pages 198-
213 and A-1.
H PLD:91095 08/18/97 QB Revised and retraced all sheets, added
214-216. (Technical changes on pages
85, 89, 97, 101, 126, 145, 152, 153, 157,
165, 168-170, 176, 177, 180, 181, 196,
198, 200-203.)
J v thru ix, 1 thru 216. Added pages 217 -
260.

SCSI Interface Product Manual, Rev. J v
Table of Contents
1.0 Interface requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 How to use this interface manual. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.1 Scope of SCSI-3 standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.2 Applicable standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 General interface description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.1 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.2 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.3 Physical interface characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.4 Summary of SCSI commands and messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.0 SCSI bus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1 SCSI bus signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.1.1 Drive select. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.1.2 Signal values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.1.3 OR-tied signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.1.4 Signal sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2 SCSI bus timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2.1 Arbitration delay (2.4 µs). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.2 Assertion period (90 ns) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.3 Bus clear delay (800 ns). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.4 Bus free delay (800 ns). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.5 Bus set delay (1.8 µs). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.6 Bus settle delay (400 ns) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.7 Cable skew delay (10 ns) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.8 Data release delay (400 ns) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.9 Deskew delay (45 ns). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2.10 Disconnection delay (200 µs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2.11 Hold time (45 ns) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2.12 Negation period (90 ns) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2.13 Reset hold time (25 µs). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2.14 Selection abort time (200 µs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2.15 Selection timeout delay (250 ms recommended) . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2.16 Transfer period (negotiated by Synchronous Data Transfer message) . . . . . . . . . 15
2.3 Fast synchronous transfer option. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3.1 Fast assertion period (30 ns) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3.2 Fast cable skew delay (5 ns) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3.3 Fast deskew delay (20 ns) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3.4 Fast hold time (10 ns). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.3.5 Fast negation period (30 ns). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.0 Logical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.1 SCSI bus phases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.1.1 Bus Free phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.1.2 Arbitration phase. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.1.3 Selection phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.1.3.1 Nonarbitrating system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.1.3.2 Arbitrating systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.1.3.3 All systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.1.3.4 Single initiator option. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.1.3.5 Selection time-out procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.1.3.6 Arbitration and selection under SCAM protocol . . . . . . . . . . . . . . . . . 19
3.1.4 Reselection phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.1.4.1 Reselection procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.1.4.2 Reselection timeout procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.1.5 Information transfer phases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.1.5.1 Asynchronous information transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

vi SCSI Interface Product Manual, Rev. J
3.1.5.2 Synchronous data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
3.1.6 Command phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
3.1.7 Data phase. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
3.1.7.1 Data in phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
3.1.7.2 Data out phase. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
3.1.8 Status phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
3.1.9 Message phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
3.1.9.1 Message in phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
3.1.9.2 Message out phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
3.1.10 Signal restrictions between phases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
3.2 SCSI bus asynchronous conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
3.2.1 Attention condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
3.2.2 Reset condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
3.3 SCSI bus phase sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
3.3.1 Nonarbitrating system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
3.3.2 Arbitrating systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
3.3.3 All systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
3.4 SCSI pointers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
3.4.1 Current pointers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
3.4.2 Saved pointers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
3.5 Message system specification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
3.5.1 General message protocol. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
3.5.2 Messages—General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
3.5.3 Message details. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
3.5.3.1 One and two byte messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
3.5.3.2 Extended Message (01h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
3.6 Message exception conditions handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
3.7 S.M.A.R.T. system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
4.0 SCSI commands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
4.1 Command implementation requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
4.1.1 Reserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
4.2 Command Descriptor Block (CDB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
4.2.1 Operation code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
4.2.2 Logical Unit Number (LUN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
4.2.3 Logical block address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
4.2.4 Relative address bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
4.2.5 Transfer length. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46
4.2.6 Control field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46
4.3 Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47
4.4 Command examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
4.4.1 Single command example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
4.4.2 Disconnect example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
4.5 Timing examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
4.6 Command processing considerations and exception conditions. . . . . . . . . . . . . . . . . . . . . . .66
4.6.1 Auto Contingent Allegiance or Contingent Allegiance . . . . . . . . . . . . . . . . . . . . . . .66
4.6.1.1 Logical Unit response to Auto Contingent Allegiance or
Contingent Allegiance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66
4.6.1.2 Clearing an Auto Contingent Allegiance condition . . . . . . . . . . . . . . . .67
4.6.2 Overlapped commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
4.6.3 Incorrect Logical Unit selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
4.6.4 Sense data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68
4.6.4.1 Asynchronous Event Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68
4.6.4.2 Autosense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69
4.6.5 Unit attention condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69
4.6.6 Target Hard Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70
4.6.7 Logical Unit Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70
4.7 Queued tasks (formerly “Queued I/O Processes”) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71

SCSI Interface Product Manual, Rev. J vii
4.7.1 Untagged task queuing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
4.7.2 Tagged task queuing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
4.8 Parameter rounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.9 Programmable operating definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.10 Incorrect initiator connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
5.0 Command descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
5.1 Change Definition command (40h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
5.2 Compare command (39h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.3 Copy command (18h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.4 Copy and Verify command (3Ah) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.5 Format Unit command (04h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
5.5.1 Format Unit parameter definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
5.5.2 Format Unit parameter list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
5.5.2.1 Defect List header. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
5.5.2.2 Initialization Pattern Descriptor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
5.5.2.3 Defect List formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
5.6 Inquiry command (12h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
5.6.1 Drive Standard Inquiry Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
5.6.2 Vital Product Data pages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5.6.3 Unit Serial Number page (80h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
5.6.4 Implemented Operating Definition page (81h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
5.6.5 Device Identification page (83h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
5.6.6 Firmware Numbers page (C0h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
5.6.7 Date Code page (C1h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
5.6.8 Jumper Settings page (C2h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
5.6.9 Device Behavior page (C3h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
5.7 Lock-unlock Cache command (36h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
5.8 Log Select command (4Ch) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
5.8.1 Write, Read, and Verify Error Counter pages (02h, 03h, and 05h). . . . . . . . . . . . 107
5.8.2 Non-Medium Error page (06h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
5.8.3 Cache Statistics page (37h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
5.8.4 Factory Log page (3Eh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
5.9 Log Sense command (4Dh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
5.10 Mode Select (6) command (15h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
5.10.1 Mode Select parameter list. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
5.10.2 Mode Select page descriptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
5.11 Mode Select (10) command (55h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
5.11.1 Mode Select (10) parameter list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
5.12 Mode Sense (6) command (1Ah). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
5.12.1 Mode Sense page descriptor header . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
5.12.2 Error Recovery page (01h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
5.12.3 Disconnect/Reconnect Control page (02h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
5.12.4 Format Parameters page (03h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
5.12.5 Rigid Drive Geometry Parameters page (04h) . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
5.12.6 Verify Error Recovery page (07h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
5.12.7 Caching Parameters page (08h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
5.12.8 Control Mode page (0Ah) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
5.12.9 Notch page (0Ch) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
5.12.10 Power Condition page (0Dh or 1Ah). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
5.12.11 Xor Control Mode page (10h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
5.12.12 Unit Attention Parameters page (00h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
5.12.13 Informational Exceptions Control page (1Ch). . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
5.13 Mode Sense (10) command (5Ah). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
5.14 Move Medium command (A7h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
5.15 Persistent Reserve In command (5Eh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
5.15.1 Persistent Reserve In parameter data for Read Keys . . . . . . . . . . . . . . . . . . . . . 154
5.15.2 Persistent Reserve In parameter data for Read Reservations . . . . . . . . . . . . . . . 155

viii SCSI Interface Product Manual, Rev. J
5.16 Persistent Reserve Out command (5Fh). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158
5.16.1 Persistent Reserve Out parameter list. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .159
5.17 Prefetch command (34h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .161
5.18 Prevent/Allow Medium Removal command (1Eh). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .161
5.19 Read command (08h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .162
5.20 Read Buffer command (3Ch) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .164
5.20.1 Read Combined Descriptor Header and Data mode (0000b) . . . . . . . . . . . . . . . .165
5.20.2 Read Data mode (0010b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .165
5.20.3 Read Buffer Descriptor mode (0011b). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .165
5.20.4 Read Data from Echo Buffer mode (1010b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166
5.20.5 Echo Buffer Descriptor mode (1011b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166
5.21 Read Capacity command (25h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .167
5.22 Read Defect Data (10) command (37h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .169
5.23 Read Defect Data (12) command (B7h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .171
5.24 Read Element Status command (B4h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .172
5.25 Read Extended command (28h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .173
5.26 Read Long command (3Eh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .175
5.27 Reassign Blocks command (07h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .176
5.27.1 Reassign Blocks defect list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177
5.28 Rebuild command (81h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .178
5.28.1 Rebuild and Regenerate parameter data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .179
5.29 Receive Diagnostic Results command (1Ch) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .181
5.29.1 Supported Diagnostic Pages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183
5.29.2 Translate Address page (40h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183
5.30 Regenerate command (82h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185
5.31 Release (6) command (17h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .187
5.31.1 Logical Unit Release . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .187
5.31.2 Extent Release. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .187
5.31.3 Third Party Release. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .187
5.32 Release (10) command (57h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188
5.33 Report LUNs command (A0h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .189
5.34 Request Sense command (03h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .191
5.34.1 Extended Sense Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .192
5.34.2 Sense Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .195
5.34.3 Extended Sense, Additional Sense and Additional Sense Qualifier codes . . . . . .196
5.34.3.1 Deferred errors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .199
5.35 Reserve (6) command (16h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .200
5.35.1 Logical Unit Reservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .200
5.35.2 Extent Reservation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .200
5.35.3 Third Party Reservation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .201
5.35.4 Superseding Reservations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .201
5.35.5 Reservations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .201
5.36 Reserve (10) command (56h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .202
5.37 Rezero Unit command (01h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203
5.38 Search Data Equal command (31h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203
5.39 Search Data High command (30h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203
5.40 Search Data Low command (32h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203
5.41 Seek command (0Bh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .204
5.42 Seek Extended command (2Bh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .205
5.43 Send Diagnostic command (1Dh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .206
5.43.1 Supported Diagnostic page—Send Diagnostic . . . . . . . . . . . . . . . . . . . . . . . . . . .207
5.43.2 Translate Address page—Send Diagnostic. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .207
5.44 Set Limits command (33h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .208
5.45 Start/Stop Unit command (1Bh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .209
5.46 Synchronize Cache command (35h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .210
5.47 Test Unit Ready command (00h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .211
5.48 Verify command (2Fh). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .212
5.49 Write command (0Ah) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .213

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5.50 Write and Verify command (2Eh). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
5.51 Write Buffer command (3Bh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
5.51.1 Combined Header and Data mode (0000b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
5.51.2 Write Data Only mode (0010b). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
5.51.3 Download Microcode mode (0100b). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
5.51.4 Download Microcode and Save mode (0101b). . . . . . . . . . . . . . . . . . . . . . . . . . . 216
5.51.4.1 Buffer ID and Buffer Offset fields (CDB bytes 2-5) . . . . . . . . . . . . . . 216
5.51.4.2 Byte Transfer Length (CDB bytes 6, 7, and 8) . . . . . . . . . . . . . . . . . 217
5.51.5 Download Microcode with Offsets (0110b). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
5.51.6 Download Microcode with Offsets and Save mode (0111b). . . . . . . . . . . . . . . . . 217
5.51.7 Write Data to Echo Buffer mode (1010b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
5.52 Write Extended command (2Ah) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
5.53 Write Long command (3Fh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
5.54 Write Same command (41h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
5.55 XDRead command (52h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
5.55.1 Xor commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
5.56 XDWrite command (50h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
5.57 XDWrite Extended command (80h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
5.58 XPWrite command (51h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
6.0 Seagate Technology support services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
Appendix A. SCSI Configured Automatically (SCAM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

SCSI Interface Product Manual, Rev. J xi
List of Figures
Figure 1. Functional scope of SCSI-3 standards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Figure 2. SCSI client-server model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Figure 3. SCSI ID bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Figure 4. Phase sequences with arbitration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Figure 5. Phase sequences without arbitration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Figure 6. Simplified SCSI system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Figure 7. Wide SCSI byte ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Figure 8. Single command example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Figure 9. Disconnect example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

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1.0 Interface requirements
1.1 How to use this interface manual
For information about features not included herein that the newer drives may support, refer to the standards
listed in Section 1.1.1.
This specification is designed to provide a universal detailed description of the SCSI interface for those drive
products whose individual drive’s Product Manual, Volume 1, do not contain the details of how the SCSI inter-
face is implemented by that drive.
Note. Individual drive’s Product Manual, Volume 1, have tables that specify which SCSI-2/SCSI-3 features
the drive implements, what the default parameters are for the various features they implement and
which parameters are changeable and which are not.
No attempt is made in this universal specification to specify which descriptions or tables apply to only SCSI-2
or SCSI-3. The combination of this general specification with the details in the individual drive’s Product Man-
ual, Volume 1, provides a description of the individual drive implementation of the SCSI interface.
This interface manual is not intended to be stand-alone text on SCSI-2/SCSI-3 features that Seagate drives
support. Reference must be made back to the individual drive’s Product Manual to find out which SCSI-2/
SCSI-3 features a particular drive supports.
This specification is Volume 2 of a set of manuals that is made up of an individual drive’s Product Manual, Vol-
ume 1, and this manual. This Volume 2 manual is referenced by other Volume 1 Product Manuals representing
other drives Seagate produces.
1.1.1 Scope of SCSI-3 standards
Figure 1 uses a representative set of specifications to show the functional partitions and the relationships
among SCSI-3 standards applicable to drives covered by this product manual.
Figure 1. Functional scope of SCSI-3 standards
SCSI-3 Block
Commands (SBC)
SCSI-3 Primary
Commands (SPC)
SCSI-3
Interlocked
Protocol (SIP)
SCSI-3
Parallel
Interface (SPI)
SCSI-3
Fibre Channel
Protocol (FCP)
Fibre Channel
Physical and Signaling
Interface (FC-PH)
SCSI-3 Architecture Model (SAM)
Common Access Method (CAM)
Commands
Protocols
Interconnects

2 SCSI Interface Product Manual, Rev. J
The functional areas define the scope of each standard as follows:
•SCSI Architecture Model: Defines the SCSI systems model, the functional partitioning of the SCSI-3 stan-
dard set and requirements applicable to all SCSI-3 implementations and implementation standards.
•Commands: Implementation standards which define classes including a device model for each class. These
standards specify the required commands and behavior that is common to all devices or unique to a given
class of devices and prescribe the rules to be followed by an initiator when sending commands to a device.
•Common Access Method: Implementation standard which defines a host architecture and set of services for
device access.
•Protocols: Implementation standards which define the rules for exchanging information so that different
SCSI-3 devices can communicate.
•Interconnects: Implementation standards which define the electrical and signaling rules essential for devices
to interoperate over a given physical interconnect.
The diagram of Figure 1 shows how the standards listed below fit within each category. The standards included
in the diagram are meant to serve as examples and may not reflect the full set of standards currently in force.
1.1.2 Applicable standards
The following ANSI standards should be referenced for more details about SCSI system standards of opera-
tion:
•SCSI-3 Architectural Model-2 (SAM-2), T10/1157-D
•Enclosure Services Command Set, NCITS 305-199x, T10/1212-D
•SCSI Primary Commands-2 (SPC-2), T10/1236-D
•SCSI Enhanced Parallel Interface-EPI, T10/1143-D
•SCSI-3 Parallel Interface (SPI-3), T10/1302D
•Profile for Parallel SCSI components used in high availability environments, X3T10/1224-TR
•SCSI-3 Medium Changer Commands (SMC), T10/999-D
•SCSI-3 Controller Command Set-2 (SCC-2), T10/1225-D
1.2 General interface description
This Product Manual describes the Seagate Technology, Inc. subset of the SCSI (Small Computer Systems
Interface) as implemented on the Seagate built drives. The interface is compatible with the SCSI Interface
Specifications listed in Section 1.1.1. The drives covered by this product manual are classified as “Intelligent”
peripherals.
The Seagate SCSI interface described herein consists of a 9 or 18 bit bidirectional bus (8 data + 1 parity or 16
data + 2 parity) plus 9 control signals supporting multiple initiators, disconnect/reconnect, self-configuring host
software, automatic features that relieve the host from the necessity of knowing the physical architecture of the
target (logical block addressing is used), and some other miscellaneous features.
The SCSI physical interface uses either single ended drivers and receivers or differential drivers and receivers
and uses asynchronous or synchronous communication protocols. The bus interface transfer rate for asynchro-
nous or synchronous is given in individual drive’s Product Manual, Volume 1. The bus protocol supports multi-
ple initiators, disconnect/reconnect, additional messages plus 6-byte, 10-byte, and 12-byte Command
Descriptor Blocks.
Unless specified otherwise in the individual drive’s Product Manual, Volume 1, the drive is always a target, and
never an initiator. For certain commands, which may or may not be supported by a particular drive model, the
drive must act as an initiator, but does not otherwise do so. For purposes of this specification, “drive”may be
substituted for the word “target”wherever “target”appears.
Note. In this revision, some new terminology is introduced as taken from the ANSI specifications. In many
instances, the broader scope terms such as “initiator”and “target”are not used, but rather the more
specific terms “Application Client”and “Device Server”appear. In Figure 2, it can be seen that several
“application clients”from a single initiator may have one or more tasks in queue with several “device
servers”in a single target. A drive could be a target or it could be one of the device servers as part of
some larger entity. When reading the description, one needs to be able to put the drive of interest in
the proper context in terms of what is shown in Figure 2. For a proper understanding of the operation of
the SCSI protocol, the terms in the SCSI architectural model as described in ANSI specification T10/

SCSI Interface Product Manual, Rev. J 3
1157-D (SAM-3) should be well understood before reading operation descriptions in any SCSI docu-
ment. Although a Glossary of terms is provided herein, the definitions may not be adequate for some.
The SAM-3 specification gives a more detailed understanding of some of the new SCSI terminology.
Figure 2. SCSI client-server model
1.2.1 Glossary
aborted command—A SCSI command that has been ended by aborting the task created to execute it.
ACA—Auto Contingent Allegiance (see below).
ACA command—A command performed by a task with the ACA attribute (see Section 4.6.1).
application client—An object that is the source of SCSI commands. An object in this sense is not a tangible
piece of hardware, but may be a single numeric parameter, such as a logical unit number, or a complex entity
that performs a set of operations or services on behalf of another object (see ANSI SAM-2, T10/1157-D).
asynchronous event notification—A procedure used by targets to notify initiators of events that occur when
a pending task does not exist for that initiator.
auto contingent allegiance—The condition of a task set following the return of a Check Condition or Com-
mand Terminated status.
blocked (task state)—The state of a task that is prevented from completing due to an ACA condition.
blocking boundary—A task set boundary denoting a set of conditions that inhibit tasks outside the boundary
from entering the Enabled state.
byte—An 8-bit construct.
call—The act of invoking a procedure.
client-server—A relationship established between a pair of distributed objects where one (the client) requests
the other (the server) to perform some operation or unit of work on the client’s behalf (see ANSI SAM-2, T10/
1157-D).
client—An object that requests a service from a server.
command—A request describing a unit of work to be performed by a device server.
command descriptor block—A structure up to 16 bytes in length used to communicate a command from an
application client to a device server.
completed command—A command that has ended by returning a status and service response of Task Com-
plete, Linked Command Complete, or Linked Command Complete (with Flag).
completed task—A task that has ended by returning a status and service response of Task Complete. The
actual events comprising the Task Complete response are protocol specific.
Application
Client
Initiator
Task
Manager
Device
Server
Logical
Unit
Target
Device Service Request
Device Service Response
Task Management Request
Task Management Response

4 SCSI Interface Product Manual, Rev. J
confirmation—A response returned to an object, which signals the completion of a service request.
confirmed protocol service—A service available at the protocol service interface, which requires confirma-
tion of completion.
current task—A task that is in the process of sending messages, sending status, transferring data, or transfer-
ring command data to or from the initiator.
cyclic redundancy check (CRC)—An error detecting code used to detect the validity of data that has been
transferred during the current data phase.
destination device—The SCSI device to which a service delivery transaction is addressed.
See source
device.
device server—An object within the logical unit which executes SCSI tasks according to the rules for task
management described in clause 7 of ANSI SAM-2 document, T10/1157D.
device service request—A request, submitted by an application client, conveying a SCSI command to a
device server.
device service response—The response returned to an application client by a device server on completion of
a SCSI command.
differential—A signalling alternative that employs differential drivers and receivers to improve signal-to-noise
ratios and increase maximum cable lengths.
disconnect—The action that occurs when a SCSI device releases control of the SCSI bus, allowing it to go to
the Bus Free phase.
domain—An I/O system consisting of a set of SCSI devices that interact with one another by means of a ser-
vice delivery subsystem.
dormant (task state)—The state of a task that is prevented from starting execution due to the presence of cer-
tain other tasks in the task set.
double transition (DT)—The latching of data on both the assertion edge and the negated edge of the REQ
(ACK) signal.
driver—The circuitry used to control the state of the bus.
enabled (task state)—The state of a task that may complete at any time. Alternatively, the state of a task that
is waiting to receive the next command in a series of linked commands.
ended command—A command that has completed or aborted.
exception condition—Any event that causes a SCSI device to enter an auto contingent allegiance or contin-
gent allegiance condition.
faulted initiator—The initiator to which a Command Terminated or Check Condition status was returned.
faulted task set—A task set that contained a faulting task.
faulting command—A command that completed with a status of Check Condition or Command Terminated.
faulting task—A task that has completed with a status of Check Condition or Command Terminated.
function complete—A logical unit response indicating that a task management function has finished. The
actual events comprising this response are protocol specific.
hard reset—A target response to a reset event or a Target Reset in which the target performs the operations
described in Section 4.6.6.
implementation—The physical realization of an object.
implementation-specific—A requirement or feature that is defined in a SCSI-3 standard but whose imple-
mentation may be specified by the system integrator or vendor.
implementation option—An option whose actualization within an implementation is at the discretion of the
implementor.

SCSI Interface Product Manual, Rev. J 5
initiator—A SCSI device containing application clients which originate device service and task management
requests to be processed by a target SCSI device.
interconnect subsystem—One or more physical interconnects which appear as a single path for the transfer
of information between SCSI devices in a domain.
intersymbol interference (ISI)—The effect of adjacent symbols on the symbol currently being received.
in transit—Information that has been sent to a remote object but not yet received.
I/O operation—An operation defined by an unlinked SCSI command, a series of linked SCSI commands or a
task management function.
I/O process—An I/O process consists of one initial connection or, if information units are enabled, the
establishment of a nexus, and a zero or more reconnections, all pertaining to a single task or a group of tasks.
An I/O process begins with the establishment of a nexus. An I/O process normally ends with the Bus Free
phase if the quick arbitrate method is disabled. If the quick arbitrate method is enabled, the I/O process
normally ends with a QA Request message.
I T nexus—A nexus that exists between an initiator and a target.
I T L nexus—A nexus that exists between an initiator, a target, and a logical unit. This relationship replaces the
prior I T nexus.
I T L Q nexus—A nexus between an initiator, a target, a logical unit, and a queue tag following the successful
receipt of one of the queue tag messages. This relationship replaces the prior I T L nexus.
layer—A subdivision of the architecture constituted by subsystems of the same rank.
linked CDB—A CDB with the link bit in the control byte set to one.
linked command—One in a series of SCSI commands executed by a single task, which collectively make up
a discrete I/O operation. In such a series, each command has the same task identifier, and all except the last
have the link bit in the CDB control byte set to one.
logical unit—A target-resident entity which implements a device model and executes SCSI commands sent by
an application client.
logical unit number—A 64-bit identifier for a logical unit.
logical unit option—An option pertaining to a logical unit, whose actualization is at the discretion of the logical
unit implementor.
lower level protocol—A protocol used to carry the information representing upper level protocol transactions.
mandatory—The referenced item is required to claim compliance with a standard.
media information—Information stored within a SCSI device which is non-volatile (retained through a power
cycle) and accessible to an initiator through the execution of SCSI commands.
multidrop—A characteristic of the SCSI bus that allows SCSI devices to be connected to the SCSI bus without
disrupting the electrical path between the terminators.
multimode single-ended (MSE)—A signalling alternative for multimode SCSI devices that employs MSE driv-
ers and receivers to allow multimode SCSI devices to operate when SE SCSI devices are present on the bus.
nexus—A relationship between an initiator and a target, logical unit, or queue tag that begins with an initial
connection and ends with the completion of the associated I/O process. This relationship is formed as the
result of a task.
object—An architectural abstraction or “container”that encapsulates data types, services, or other objects that
are related in some way.
peer-to-peer protocol service—A service used by an upper level protocol implementation to exchange infor-
mation with its peer.
peer entities—Entities within the same layer.
pending task—A task that is not a current task.

6 SCSI Interface Product Manual, Rev. J
physical interconnect—A single physical pathway for the transfer of information between SCSI devices in a
domain.
port—Synonymous with “service delivery port.”A single attachment to a SCSI bus from a SCSI device.
procedure—An operation that can be invoked through an external calling interface.
protocol—The rules governing the content and exchange of information passed between distributed objects
through the service delivery subsystem.
protocol option—An option whose definition within a SCSI-3 protocol standard is discretionary.
protocol service confirmation—A signal from the lower level protocol service layer notifying the upper layer
that a protocol service request has completed.
protocol service indication—A signal from the lower level protocol service layer notifying the upper level that
a protocol transaction has occurred.
protocol service request—A call to the lower level protocol service layer to begin a protocol service transac-
tion.
protocol service response—A reply from the upper level protocol layer in response to a protocol service indi-
cation.
queue—The arrangement of tasks within a task set, usually according to the temporal order in which they were
created.
See task set.
queue tag—The parameter associated with a task that uniquely identifies it from other tagged tasks for a logi-
cal unit from the same initiator.
receiver—A client or server that is the recipient of a service delivery transaction.
reference model—A standard model used to specify system requirements in an implementation-independent
manner.
request—A transaction invoking a service.
request-response transaction—An interaction between a pair of distributed, cooperating objects, consisting
of a request for service submitted to an object followed by a response conveying the result.
request-confirmation transaction—An interaction between a pair of cooperating objects, consisting of a
request for service submitted to an object followed by a response for the object confirming request completion.
reset event—A protocol-specific event which may trigger a hard reset response from a SCSI device as
described in Section 4.6.6.
response—A transaction conveying the result of a request.
SCSI application layer—The protocols and procedures that implement or invoke SCSI commands and task
management functions by using services provided by a SCSI protocol layer.
SCSI device—A device that is connected to a service delivery subsystem and supports a SCSI application
protocol.
SCSI device identifier—An address by which a SCSI device is referenced within a domain.
SCSI I/O system—An I/O system, consisting of two or more SCSI devices, a SCSI interconnect and a SCSI
protocol, which collectively interact to perform SCSI I/O operations.
SCSI protocol layer—The protocol and services used by a SCSI application layer to transport data represent-
ing a SCSI application protocol transaction.
sender—A client or server that originates a service delivery transaction.
server—A SCSI object that performs a service on behalf of a client.
service—Any operation or function performed by a SCSI-3 object, which can be invoked by other SCSI-3
objects.
service delivery failure—Any non-recoverable error causing the corruption or loss of one or more service
delivery transactions while in transit.