Seagate SCSI Interface Product 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 reg­istered trademarks of Seagate Technology, Inc. or one of its subsidi arie s. All other trademarks
or registered trademarks are the property of their respective owners.

Seagate reserves the right to change, without notice, product of ferings or specifications. No

part of this publication may be reproduced i n any form without writt en per mission o f Seagate

Te c h n ology, 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, 158­160, 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2

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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 7

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 Initia l izatio n P a ttern Descripto r . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4

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). . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 46

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

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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 (1E h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .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 Diagno stic . . . . . . . . . . . . . . . . . . . . . . . . . . .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 comm and (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 comman d (80h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226

5.58 XPWrite command (51h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228

6.0 Seagate Technology support services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229

Appendix A. SCSI Configured Automatically (SCAM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

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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

SCSI Interface Product Manual, Rev. J 1

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 descr iption of the SCSI interface for those drive
products whose individual drive’s Product Manual, Volume 1, do not contain the details of how the SCS I inter­face is implemented by that drive.

Note.

Individual drive’s Product Manual, Volume 1, have tables that specify w hich 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 des criptions or tables apply to only SCSI-2
or SCSI-3. The combination of this general specification with the detail s in the individual drive’s Product Man­ual, Vol ume 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 Seagat e drives
support. Re ference must be made ba ck to the individual drive’s Product Manual to f ind out which S CSI-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, Vol­ume 1, and this manual. This Volume 2 manual is referenced by other Vol ume 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 st andards

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 S CSI systems model, the functional par titioning of the SCSI-3 stan­dard 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 ac cess.

• 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 fi t within each cat egory. 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 SCS I system standards of opera­tion:

• SCSI-3 Architectural Model-2 (SAM-2), T10/1157-D

• Enclosure Services Command Se t, NCITS 305-199x, T10/1212 -D

• SCSI Primary Commands-2 (S PC-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 Comput er Systems
Interface) as implemented on the Seagate built drives. The interface is compatible with the S CSI Interface
Specifications listed in Section 1.1.1. The dr ives covered by this product manual are class ified 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, sel f-configur ing 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 asynchro­nous or synchronous is g iven in individual dri ve’s Product Manual, Volu me 1. The bus protocol supports multi­ple 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 tha t several
“application clients” from a single initiator may have one or more task s in queue with several “device
servers” in a single target. A drive c ould be a target or it coul d be one of the device servers as par t of
some larger entity. When reading the des cription, 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, t he ter ms in the SCSI architectural m odel as describe d in AN SI specification T10/

SCSI Interface Product Manual, Rev. J 3

1157-D (SAM-3) should be well unde rstood before reading operation descriptions in any SCS I docu­ment. Although a Gl oss ary of term s 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 abor ting 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 t he source of S CSI commands . An object in this sense is no t a ta ngible
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 u nit of work on the client’s behalf (see ANSI SAM-2, T10/
1157-D).

client

—An object that requests a service from a ser ver.

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 comm unicate a command from an

application client to a device server.

completed command

—A command that has ended by returning a st atu s and service response of Task Com-

plete, Linked Command Complete, or Linked Command Complete (with Flag).

completed task

—A task that has ended by return ing 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 ser vice request.

confirmed protocol service

—A ser vice available at the protocol ser vice interface, which requires conf irma-

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 det ecting 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 docum ent , T10/1157D.

device service request

—A request, submitted by an application client, conveying a SCSI command to a

device se rve r.

device service response

—The response returned to an application client by a device server on completion of

a SCSI command.

differential

—A signalling a lternative that em ploys 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 deliv e ry 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 tran sition (DT)

—The latching of data on both the as sertion e dge and the negated edge of the REQ

(ACK) signal.

driver

—The circuitry us ed to control the state of the bus.

enabled (task state)

—The state of a task that m ay complete a t any time. Alternat ively, 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 abor t ed.

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 Ter mi nated 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 respo nse indicating that a task management funct ion 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 requirem ent or feature that is define d in a SCSI-3 standard but whose imp le-

mentation may be specified by the system integrator or vendor.

implementation option

—An option whose actualization within an implement ation is at the discretion of the

implementor.

SCSI Interface Product Manual, Rev. J 5

initiator

—A SCSI device containing application clients which originate device ser vice and task management

requests to be processed by a target SCSI device.

interconnect subsystem

—One or more physical interconnects which appear as a single pa th for the transfer

of information between SCSI devices in a domain.

intersymbol int e rference (IS I)

—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 be gins with the establishment of a nexus. An I/O process normally ends with the B us 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 nexu s

—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 nex us

—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 coll ectively make up
a discrete I/O operation. In such a series, each c ommand has the same ta sk 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 ex ecutes SCSI commands sent by

an application client.

logical unit number

—A 64-bit identifier for a logical unit.

logic a l uni t op ti on

—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 t hrough a p ower

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 bu s without

disrupting the electrical path between the terminat ors.

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 b etween an initiator and a target, logical unit, or queue tag that begins with a n initial
connection and ends with the com pletion of the associated I/O process. This relationship is formed as t he
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 ser vice used by an upper level protocol impleme ntation t o exchang e in for-

mation with its peer.

peer entities

—Entities within the same layer.

pendi ng tas k—

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 l ower 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 re que st

—A call to the lower level protocol service l ayer to begin a prot ocol 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 req uirem ents in an i mpl em entation-indepe ndent

manner.

request

—A transaction invoking a service.

request-response transaction

—An interaction between a pair of dist ributed, cooperating o bjects, 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 an d proced ures that impleme nt or invoke SCSI commands a nd 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 SCS I 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 an d 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 behal f 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.

SCSI Interface Product Manual, Rev. J 7

service delivery por t

—A device-resident interface used by th e application client, device ser ver or tas k man­ager to enter and retrieve requests and respon ses from the ser vice delivery subsystem. Synonymous with
“port.”

service delive ry subsys tem

—That part of a SCSI I/O system which transmits service requests to a logical

unit or target and returns logical unit or target responses to an initiator.

service delivery transaction

—A request or response sent through the service delivery subsystem.

signal—

(n) A detectable asynchronous event possibly accompanied by descriptive data and parameters.

(v) The act of generating such an event.

source device

—The SCSI device from which a service delivery transaction originates.

See

destination device.

subsystem

—An element in a hierarchically par titioned system which interacts directly only with elements in

the next higher division or the next lower division of that system.

suspended information

—Information stored within a logical unit that is not available to any pending tasks.

target

—A SCSI device which receives SCSI commands and directs such commands to one or more logi cal

units for execution.

task

—An object within the logical unit representing the work associated with a c ommand or group of linked
commands. “Work” includes est ablishing an IT nexus, ITL nexus, ITLQ nexus and all of the other processes
associated with the execution of a command by a Logical Unit. Refer to the defini tions of “object” in this glos­sary. See also ANSI SAM-2, T10/1157-D, Section 4.9.

task abort event

—An event or condition indicating that the task h as been abor ted by means of a task m an-

agement function.

task address

—An initiator identifies a task to a target using a Task Address. The Task Address object repre­sents either a Tagged Task Address or an Untagged Task Address without regard for the tagged or untagg ed
nature of the Tas k. A Tagged Task A ddress is composed of a Lo gical Unit Identifier and a Tag. An Untagged
Task Addres s is composed of a Logical Unit Identifier.

task completion event

—An event or condition indicating that the task has ended with a service response of

Task Complete.

task ended event

—An event or condition indicating that the task has completed or aborted.

task management function

—A task manage r servic e which can be invoked by an application client to affect

the execution of one or more tasks.
t

ask manag ement request

—A request submitted by an application client, invoking a task management func-

tion to be executed by a task manager.

task management resp onse

—The response retur ned to an application clien t by a task manager on comple-

tion of a task management request.

task manager

—A server within the target which executes task management functions.

task set

—A group of tasks within a target device, whose interaction is dependent on the queuing and auto

contingent allegiance rules of Section 4.6.1.

task slot

—Resources within the logical unit that may be used to contain a task.

task tags

—A Tag is a field containing up to 64 bits that is a component of a Tagged Task Identifier. An initiator
assigns tag values in each Tagged Task Identifier in a way that ensures that the identifier uniqueness require­ments stated in ANSI SAM-2, T10/1157-D, Section 4.9 are met.

third-party command

—A SCSI command which requires a logica l unit within the target device to assume the

initiator role and send a SCSI command to a target device.

transaction

—A cooperative interaction between two objects, involving the exchange of information or the exe-

cution of some service by one object on behalf of the other.

unconfirm ed protocol s ervice

—A service available at the protocol service interface, which does not result in

a completion confirmation.

8 SCSI Interface Product Manual, Rev. J

unlinke d com m and

—A SCSI-3 command having the link bit set to zero in the CDB control byte.

upper level p rotocol

—An application-specific protocol executed through services provided by a lower level

protocol.

1.2.2 Keywords

Several keywords are used to differentiate between different levels of requirements and optionality, as follows:

vendor-specific

—Specification of the referenced item is determined by the device vendor.

protocol-specific

—Implementation of the referenced item is defined by a SCSI-3 protocol standard (see Sec-

tion 1.1.1.)

expected

—A keyword used to describe the behavior of the models specified by this standard.

mandatory

—A keyword indicating items required to be implemented as defined by this standard.

may

—A keyword th at ind i cates flexibility o f ch oic e w it h no imp lied preference .

obsolete

—A keyword indicating items that were defined in prior SCSI standards but have been removed from

this standard.

opti on, opt i onal

—Keywords that describe features which are not required to be implemented by this standard.
However, if any optional feature defined by the standard is implemented, it shall be implemented as defined by
the standard.

reserved

—A key word referring to bits, bytes, words, fields, and code values that are set aside for future stan­dardization. Their use and interpretation may be specified by the future extensions to this or other standards. A
reserved bit, byte, word, or field shall be set to zero, or in accordance with a future extension to this standard.
The recipient shall not check reserved bits, bytes, words, or fields. Receipt of reserved code values in de fined
fields shall be treated as an error.

shall

—A keyword indicating a mandatory requirement. Designers are required t o implement all such manda-

tory requirements to ensure interoperability with other standard conformant products.

should

—A keyword indicating flexibility of choice with a strongly preferred alternative. Equiv alent to the phrase

“it is recommended.”

1.3 Physical interface characteristics

The physical interface characteristics (cables, connectors, electrical descriptions, termination requirements,
etc.) for the drives covered by this Interface Manual are found in each individual drive’s Product Manual, Vol­ume 1, since these features are not the same for all drives.

SCSI Interface Product Manual, Rev. J 9

1.4 Summary of SCSI comm and s and messages

Following is an alphabetical table listing the SCSI commands described in this manual . Details are given in
Section 5.0.

Command name Hex code Device type Page number

Change Definition 40 All 78
Format Unit 04 dir. access 80
Inquiry 12 All 87
Log Select 4C A ll 102

Log Sense 4D A ll 110
Mode Select (6 byte) 15 dir. access 112

Mode Select (10 byte) 55 dir. access 116
Mode Sense (6 byte) 1A dir. access 119
Mode Sense (10 byte) 5A dir. access 149

Persistent Reserve In 5E dir.access 154
Persistent Reserve Out 5F dir. access 159
Prefetch 34 dir. access 161

Read 08 dir. access 162
Read Buffer 3C All 164
Read Capacity 25 dir. access 167
Read Defect Data (10 byte) 37 dir. access 169
Read Defect Data (12 byte) B7 dir. access 171
Read Extended 28 dir. access 173
Read Long 3E dir. access 175
Reassign Blocks 07 dir. access 176
Rebuild 81 dir. access 1 78
Receive Diagnostic Results 1C All 181
Regenerate 82 dir. access 185
Release (6 byte) 17 dir. access 187
Release (10 byte) 57 dir. access 188
Report LUNs A0 dir. access 189
Request Sense 03 All 191
Reserve (6 byte) 16 dir. access 200
Reserve (10 byte) 56 dir. access 202
Rezero Unit 01 dir. access 203

Seek 0B dir. access 204
Seek Extended 2B dir. access 205
Send Diagnostic 1D All 206
Start/Stop Unit 1B dir. access 209
Synchronize Cache 35 dir. access 210

Test Unit Ready 00 All 211
Verify 2F dir. access 212
Write 0A dir. acce ss 213

Write and Verify 2E dir. access 214
Write Buffer 3B All 215
Write Extended 2A dir. access 219
Write Long 3F dir. access 221
Write Same 41 All 222

XD Read 52 dir. access 223
XD Write 50 dir . a ccess 225
XD Write Extended 80 dir. access 226
XP Write 51 dir. access 228

10 SCSI Interface Product Manual, Rev. J

Following is an alphabetical summary of the SCSI messages described in this manual. Details are given in
Section 3.5.

Message Name Hex Code Page number

Abort 06 29
Abort Tag 0D 29

Bus Device Reset 0C 29
Clear Queue 0E 30

Command Complete 00 30
Continue I/O Process 12 30

Disconnect 04 30
Extended Message 01 34
Identify 80-FF 31

Ignore Wide Residue 23 39
Initiate Recovery 0F not support ed
Initi a to r Detected Error 05 31

Linked Command Complete 0A 33
Linked Command Complete (with flag) 0B 33

Message Parity Error 09 32
Message Reject 07 32
Modify Data Pointer 01 32, 34 (extended message)

No Operation 08 32
Queue Tag Messages 32

Head of Queue Tag 21 33
Ordered Queue Tag 22 33
Simple Queue Tag 20 33

Release Recovery 10 not supported
Restor e Pointe rs 03 33

Save Data Pointers 02 33
Synchronous Data T ransfer Request 01 33, 34 (extended message)

Target Transfer Disable 1 3 34
Wide Data Transfer Request 01 37 (extended message)

SCSI Interface Product Manual, Rev. J 11

2.0 SCSI bus

This manual discusses only the “logical” and timing characteristics of the SCSI system and interface. The SCSI
bus physical characteristics (voltages, connector configurations, pinouts, etc.) are given in the individual drive’s
Product Manual, Volume 1, in the “Interface requirements” section, which covers all of the inte rface require­ments and SCSI features supported by the drive described in the particula r Product Manual being referenced.

Communication on the SCSI Bus is allowed between only two SCSI devices at a time. Some Seagate dr ives
support systems with a maximum of eight SCSI devices including the host computer(s) connect ed to the SCSI
bus. Some Seagate drives support systems with a maximum of sixteen SCSI devices on the SCS I bus. Each
SCSI device has a SCSI ID Bit assigned as shown in Figu re 3. The SC SI ID is assig ned by installing from 0 t o
3 (8 device systems) jumper plugs or 0-4 (16 device systems) jumper plugs onto a connector in a binary coded
configuration during system configuration. Som e dri ve models have an interface that includes the SCSI bus ID
lines, so that the host can se t the dri ve ID over the interface (see individual dri ve’s Product Manual, Volume 1,
“Option/configuration headers” section). Drives that suppor t SCAM protocol (SCSI Configured Automatically)
can have their drive ID assigned via interface also (see Appendix A).

When two SCSI devices communicate on the SCSI Bus, one acts as an initiator and the other acts as a target.
The initiator (typically a host computer) originates an o peration and the target performs the operation . The
drive always operates as a target, unless specified otherwise (i.e., certain commands are suppor ted) in the
individual drive’s Product Manual, Volume 1.

Figure 3. SCSI ID bits

The Host Adapter/Initiator must be identified by one of the eight SCSI Device Addresses. Make sure that none
of the devices on the SCSI bus have duplicate addresses.

Certain SCSI bus functions are assigned to the initiator and certain SCSI bus functions are assigned to the tar­get. The initiator will select a particular target. The target will request the transfer of Command, Data, Status or
other information on the data bus.

Information transfers on the data bus are interlocked and follow a defined REQ/ACK Handshake protocol. One
byte of information will be transferred with each handshake. Synchronous data transfers do not require a one­for-one interlocking of REQ/ACK signals, but the total number of REQ pulses in a particular data transfer event
must equal the total number of ACK pulses. Synchronous data transfer option is described in Paragraph

3.1.5.2 and 3.5.3.2.
The drive supports single initiator, single target; single initiator , m ul tiple target; multi ple initiator, single target; or

multiple initiator, multiple target bus configurations.

DB(7)

DB(6) DB(5) DB(4) DB(3) DB(2) DB(1) DB(0) DATA B US

SCSI ID = 0

SCSI ID = 1

SCSI ID = 2

SCSI ID = 3

SCSI ID = 4

SCSI ID = 5

SCSI ID = 6

SCSI ID = 7
Additional SCSI ID bits for devices that support 16 devices on the SCSI bus.

DB(15)

DB(14) DB(13) DB(12) DB(11) DB(10) DB (9) DB(8) DATA BUS

SCSI ID = 8

SCSI ID = 9

SCSI ID = 10

SCSI ID = 11

SCSI ID = 12

SCSI ID = 13

SCSI ID = 14

SCSI ID = 15

12 SCSI Interface Product Manual, Rev. J

2.1 SCSI bus signals

There are ten control and eighteen data signals, as listed below:

·

BSY

·

C/D

·

MSG

·

DIFFSNS (Multimode) (may sometimes be designated “DIFFSENS”)

·

SEL

·

I/O

·

REQ

·

DB(7-0, P); DB(15-8,P1)

·

ACK

·

ATN

·

RST

Some drive models have a single 80 pin I/O connector that contains additional interface lines that carry drive
configuration select signals. These are peculiar to certain drives and are not SCSI standard signals. These are
described in the individual drive’s Product Manual, Volume 1, but not here.

The 28 SCSI standard signals are described as follows:

BSY (Busy)

—An “OR-tied” signal to indicate the bus is being used.

SEL (Select)

—A signal used by an initiator to select a target, or by a target to reselect an initiator.

C/D (Control/Data)

—A signal driven by a target to indicate whether Control or Data information is on the Data

Bus. Assertion (see Paragraph 2.1.2) indicates Control.

I/O (Input/Output)

—A signal driven by a target to control the direction of data movement on the Data Bus with
respect to an initiator. Assertion indicates input to the initiator. This signal also distinguishes between Selection
and Reselection phases.

MSG (Message)

—A signal driven by a target during the Message phase.

REQ (Request)

—A signal driven by a target to indicate a request for REQ/ACK data transfer handshake.

ACK (Acknowledge)

—A signal driven by an initiator to indicate an acknowledgment for a REQ/ACK data

transfer handshake.

ATN (Attention)

—A signal driven by an initiator to indicate the Attention condition. It is used to request to send
a message out to the target. See Paragraph 3.2.1. If an initiator asserts ATN while asserting SEL it indicates to
the target that the initiator supports messages other than command comple te.

RST (Reset)

—An “OR-tied” signal that indicates the Reset condition.

DIFFSNS (Differential Sense)

—When the drive has high voltage differential SCSI I/O circuits (HVD), the
DIFFSNS signal disables the drive’s differential driver/receiver circuits if the SCSI I/O cable is plugged in
upside down, or if a single-ended SCSI I/O cable is plugged into a differential I/O drive. Disabling the differen­tial I/O drivers/receivers is necessary to prevent burning them out if a grounde d I /O line is c onnect ed to any of
the differential circuit outputs, which are at a positive voltage (+2 V or +3 V) when not disabled.

Multimode—SE or LVD alternative

—“LW” and “LC” models have I/O circuits that can operate either in single-
ended (SE) or low voltage differential mode (LVD). When the interface “DIFFSNS” line is between 0 V and 0.6
V, the drive interface circuits operate single-ended. When “DIFFSNS” is between +0.7 V and +1 .9 V, the drive
interface circuits operate low voltage differential. This arrangement is not intended to allow dynamically chang­ing transmission modes, but rather to prevent incompatible devices from attempting to interoperate. Drives
must operate only in the mode for which the installation and i nterface cabling is designed. Multimode I/O cir­cuits used by “LC” and “LW” devices do not operate at high voltage differential level s and should never be
exposed to high voltage differential environments unless the comma nd mode voltages in the env ironment are
controlled to safe levels for single-ended and low voltage differential devices (see the ANSI SPI-3 specification,
T10/1302D).

DB(7-0,P) and DB(15-8,P1) (Data Bus)

—Sixteen data bi t signals, plus parity bit signals for m a Data Bus.
DB(7) is the most significant bit and has the highest priority during the Arbitration phase (on both eight and six­teen device systems). Bit number significance, and priority decrease downward to D B(0), and then f rom DB 15
down to DB8 (DB0 is higher than DB15). A data bit is defined as one when the signal is asserted and is defined
as zero when the signal is negated.

Data parity DB(P) and DB(P1) is odd

—The use of par ity is a system option. The dr ive always checks parity
on the data bits, but has the capability to enable/disable parity error repor ting to the host. See configuration
selection in the individual drive’s Product Manual, Volume 1. Parity checking is not valid during the Arbitration
phase.

Greater detail on each of the SCSI Bus signals is found in the following sections.

SCSI Interface Product Manual, Rev. J 13

2.1.1 Drive select

For SCSI ID selection, install dr ive select jumpers as shown in configuration selection figure i n the individual
drive’s Product Manual, Volume 1. Refer to the “Physical Interface” section of the individual drive’s Product
Manual for the location of the drive select header. The drive using the eight bit data interface can have one of
eight ID bits selected by installing 0 to 3 jumpers in a binary coded configuration on the drive select header.
Drives using the 16 bit data interface can have one of sixteen ID bits selected by installing 0 to 4 jumpers in a
binary coded configuration on the drive select header. Drives that support SCAM protocol (SCSI Con figured
Automatically) can have their drive ID assigned via the SCSI interface (see Appendix A).

2.1.2 Signal values

Signals may assume true or false values. There are two methods of driving thes e signals. In both cases, the
signal shall be actively driven true, or asserted. In the case of OR-tied drivers, the driver does not drive the sig­nal to the false state, rather the bias circuitry of the bus terminators pulls the signal false whenever it is
released by the drivers at every SCS I device. If any driver is asser ted, then the signal is t rue. In the case of
non-OR-tied drivers, the signal may be negated. Negated means that the signal may be actively driven false, or
may be simply released (in which case the bias circuitry pulls it false), at the option of the implementor.

2.1.3 OR-tied signals

The BSY and RST signals shall be OR-tied only. In the ordinary operation of the bus, these signals are simulta­neously driven true by several drivers. No signals other than BS Y, RST, and DB(P) are simultaneously driven
by two or more drivers, and any signal other than BSY and RST m ay employ OR-tied or non-OR-tied d rivers.
DB(P) shall not be driven false during the Arbitration phase. There is no operational problem in mixing OR-tied
and non-OR-tied drivers on signals other than BSY and RST.

2.1.4 Signal sources

Table 1 indicates which type o f SCSI device is allowed to source each signal. All SCSI device drivers that are
not active sources shall be in the pass ive state. Note that th e RS T signal may be sourc ed by any SCS I device
at any time. The drive functions as a target.

2.2 SCSI bus timing

Unless otherwise indicated, the delay time measurements for each SCSI device, defined in Paragraphs 2.2.1
through 2.2.16, shall be calculated from signal conditions existing at that SCSI device’s own SCSI bus connec­tion. Thus, these measurements (except skew delay) can be made without considering delays in the cable.

See Section 2.3 for Fast synchronous transfer option timing.

Table 1: Signal sources

ALL: The signal shall be driven by all actively arbitrating SCSI devices.

Bus phase BSY

Signals
SEL

C/D, I/O,
MSG, REQ ACK/ATN DB(7-0,P) (15-8,P1)

Bus Free None None None None None
Arbitration All Winner None None S CSI ID
Selection I&T Init. None Init. Init.
Reselection I&T Target Target Init. Target

Information transfer phases

Command Target None Target Init. Init.
Data In Target None Target Init. Target
Data Out T arget None Target Init. Init.
Status Target None Target Init. Target
Message In Target None Target Init. Target
Message Out Target None Target Init. Init.

14 SCSI Interface Product Manual, Rev. J

SCSI ID: A unique data bit (the SC SI ID) shall be dr iven by each actively arbitrating SC SI device: the other

seven data bits shall be released (i.e., not driven) by this SCSI device. The parity bit [DB(P), DB(P1)]
may be undriven or dr iven to the true state, but shall never be driven to the false state during this
phase.

I&T: The signal shall be dr iven by the initiator, target, or both, as specified in the Selection phase and

Reselection phase.
Init: If this signal is driven, it shall be driven only by the active initiator.
None: The signal shall be released; that is, not be dr iven by any SCSI device. The bias circuitr y of the bus

terminators pulls the signal to the false state.
Winner: T he signal shall be driven by the one SCSI device that wins arbitration.
Target: If the signal is driven, it shall be driven only by the active target.

2.2.1 Arbitration delay (2.4 µs)

The minimum time a SCSI device shall wait from asserting BSY for arbitration until the Data Bus can be exam­ined to see if arbitration has been won. There is no maximum time.

2.2.2 Assertion period (90 ns)

The minimum time that a target shall assert REQ while using synchronous data transfers. Also, the minimum
time that an initiator shall assert ACK while using synchronous data transfers.

2.2.3 Bus clear delay (800 ns)

The maximum time for a SCSI device to stop driving all bus signals after:

1. The Bus Free phase is detected (BSY and SEL both negated for a bus settle delay).

2. SEL is received from another SCSI device during the Arbitration phase.

3. The transition of RST to assertion.

Note.

For the first condition above, the maximum time for a SCSI device to clear the bus is 1200 ns f rom BSY
and SEL first becoming both negated. If a SCSI device requires more than a bus settle delay to detect
Bus Free phase, it shall clear the bus within a Bus Clear delay minus the excess time.

2.2.4 Bus free delay (800 ns)

The minimum time that a SCSI device shall wait from its detection of the Bus Free phase (BSY and SEL both
negated for a bus settle delay) until its assertion of BSY when going to the Arbitration phase.

2.2.5 Bus set delay (1.8 µs)

The maximum time fo r a SCSI device to assert BSY and its SCSI ID bit on the Data Bus after it detects Bus
Free phase (BSY and SEL both negated for a bus settle delay) for the purpose of entering the Arbitration
phase.

2.2.6 Bus settle delay (400 ns)

The time to wait for the bus to settle after changing cer tain control signals as specified in the protocol d efini­tions.

2.2.7 Cable skew delay (10 ns)

The maximum difference in propagation time allowed between any two SCSI bus signals when measured
between any two SCSI devices.

2.2.8 Data release delay (400 ns)

The maximum time for an initiator to release the Data Bus signals following the transition of the I/O signal from
negation to assertion.

SCSI Interface Product Manual, Rev. J 15

2.2.9 Deskew delay (45 ns)

The minimum time required for deskew of certain signals.

2.2.10 Disconnection delay (200 µs)

The minimum time that a target shall wait after releasing BSY before participating in an Arbitration phase when
honoring a Disconnect message from the initiator.

2.2.11 Hold time (45 ns)

The minimum time added between the asser t ion o f R EQ or ACK and t he ch anging of the dat a lines to provide
hold time in the initiator or target, respectively, while using synchronous dat a transfers.

2.2.12 Negation period (90 ns)

The minimum time that a target shall negate REQ while using synchronous data transfers. Also, the minimum
time that an initiator shall negate ACK while using synchronous data transfers.

2.2.13 Reset hold time (25 µs)

The minimum time for which RST is asserted. There is no maximum time.

2.2.14 Selection abor t time (200 µs)

The maximum time that a target (or in itiator) shall take from its most recent detection of being selected (or
reselected) until asserting a BSY response. This timeout is required to ensure that a target (or initiator) does
not assert B SY after a Selection (or Reselection) phase has bee n aborted. This is not t he selection timeout
period; see Sections 3.1.3.5 and 3.1.4.2 for a complete description.

2.2.15 Selection timeout delay (250 ms recommende d)

The minimum time an initiator (or target) should wait for a BSY response duri ng the S election (or Re se lection)
phase before starting the timeout procedure. The drive implements this 250 ms selection timeout delay.

2.2.16 Transfer period (negotiated by Synchronous Data Transfer message)

The minimum time allowed between the l eading edges of successive REQ pulses and of successive ACK
pulses while using synchronous data transfers. (See Sections 3.1.5.2 and 3.5.3.2)

2.3 Fast synchronous transfer option

When devices negotiate a synchronous dat a transfer period of less t han 200 ns they are said to be using “fast
synchronous data transfers.” Devices which negotiate a synchronous dat a transfer period ≥200 ns use timing
parameters specified in Section 2.2. When a fast synchronous data transfer period is negotiated, those specific
times redefined in this section are used; those not redefined remain the same. The minimum synchronous data
transfer period is 100 ns.

2.3.1 Fast assertion period (30 ns)

This value is the minimum time that a target shal l assert REQ while using fast synchronous data transfers.
Also, the minimum time that an initiator shall assert ACK while using fast synchronous data transfers.

2.3.2 Fast cable skew delay (5 ns)

This value is the maximum difference in propagation time allowed between any two SCSI bus signals mea­sured between any two SCSI devices while using fast synchronous data transfers.

2.3.3 Fast deskew delay (20 ns)

This value is the minimum time required for deskew of certain signals while using fast synchronous data trans­fers.

16 SCSI Interface Product Manual, Rev. J

2.3.4 Fast hold time (10 ns)

This value is the minimum time added between the assertion of REQ or ACK and the changing of the data lines
to provide hold time in the initiator or target respectively, while using fast synchronous data transfers.

2.3.5 Fast negation period (30 ns)

This value is the minimum tim e that a target shall negat e REQ while using fast synchron ous data transfers.
Also, the minimum time that an initiator shall negate ACK while using fast synchronous data transfers.