ISO/IEC 14776-251:2014

Information technology — Small computer system interface (SCSI) — Part 251: USB attached SCSI (UAS)

ISO/IEC 14776-251:2014(E) describes a SCSI transport protocol for USB-2 and USB-3 with the following properties: a) mechanism to send commands associated with any SCSI standard to a USB device; b) complies with SCSI Architecture Model - 4 (e.g., autosense and command queuing) and c) other capabilities.

Technologies de l'information — Interface de petit système d'ordinateur (SCSI) — Partie 251: Titre manque

General Information

• Status: Published
• Publication Date: 16-Apr-2014
• ICS: 35.200 - Interface and interconnection equipment
• Technical Committee: ISO/IEC JTC 1/SC 25 - Interconnection of information technology equipment
• Drafting Committee: ISO/IEC JTC 1/SC 25 - Interconnection of information technology equipment
• Current Stage: 6060 - International Standard published
• Start Date: 17-Apr-2014
• Due Date: 09-May-2015
• Completion Date: 09-May-2015

Relations

• Consolidated By: ISO 21487:2012/Amd 2:2015 - Small craft — Permanently installed petrol and diesel fuel tanks — Amendment 2
• Effective Date: 06-Jun-2022

Standards Content (Sample)

ISO/IEC 14776-251
Edition 1.0 2014-04
INTERNATIONAL
STANDARD
colour
inside
Information technology – Small computer system interface (SCSI) –
Part 251: USB Attached SCSI (UAS)

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ISO/IEC 14776-251
Edition 1.0 2014-04
INTERNATIONAL
STANDARD
colour
inside
Information technology – Small computer system interface (SCSI) –

Part 251: USB Attached SCSI (UAS)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
B
ICS 35.200 ISBN 978-2-8322-1507-4

– 2 – ISO/IEC 14776-251:2014 © ISO/IEC 2014
CONTENTS
FOREWORD. 6
INTRODUCTION . 8
SCSI standards family . 8
1 Scope .10
2 Normative references .10
3 Terms, definitions, symbols, abbreviations and conventions .10
3.1 Terms and definitions.10
3.2 Symbols and abbreviations .13
3.3 Keywords.13
3.4 Editorial conventions.14
3.5 Numeric and character conventions .15
3.5.1 Numeric conventions.15
3.5.2 Byte encoded character strings conventions.15
3.6 Sequence figure notation .16
3.7 Notation for procedures and functions.16
4 Model .17
4.1 Overview.17
4.2 Tag handling.18
4.3 Data transfers .18
4.4 UAS domain.19
4.5 Addressing.20
4.6 World wide name .20
4.7 Resets .20
4.8 I_T Nexus loss.21
4.9 Target power loss expected .21
4.10 USB error handling .21
5 USB.22
5.1 Overview.22
5.2 USB resource requirements .22
5.2.1 Overview.22
5.2.2 USB class specific requests .22
5.2.3 USB descriptors .22
6 Transport.27
6.1 Overview.27
6.2 IUs.27
6.2.1 Overview.27
6.2.2 COMMAND IU.28
6.2.3 READ READY IU .29
6.2.4 WRITE READY IU.29
6.2.5 SENSE IU .30
6.2.6 RESPONSE IU.30
6.2.7 TASK MANAGEMENT IU .31
6.3 Information unit sequences .33
6.3.1 Overview.33

6.3.2 Non-data command/sense sequence.34
6.3.3 Non-data command/response sequence .35
6.3.4 Data-out command sequence.36
6.3.5 Data-in command sequence.37
6.3.6 Task management function sequence .37
6.3.7 Bi-directional command sequence.38
6.3.8 Multiple command example .38
6.4 Transport requirements.41
7 SCSI Application Layer transport protocol services.42
7.1 SCSI transport protocol services overview .42
7.2 Send SCSI Command transport protocol service .43
7.3 SCSI Command Received transport protocol service .44
7.4 Send Command Complete transport protocol service.44
7.5 Command Complete Received transport protocol service .45
7.6 Send Data-In transport protocol service .46
7.7 Data-In Delivered transport protocol service .46
7.8 Receive Data-Out transport protocol service.46
7.9 Data-Out Received transport protocol service.47
7.10 Terminate Data Transfer transport protocol service.47
7.11 Data Transfer Terminated transport protocol service.48
7.12 Send Task Management Request transport protocol service.48
7.13 Task Management Request Received transport protocol service .49
7.14 Task Management Function Executed transport protocol service .49
7.15 Received Task Management Function Executed transport protocol service .51
7.16 USB Acknowledgement.52
8 Device server error handling.53

– 4 – ISO/IEC 14776-251:2014 © ISO/IEC 2014
Figure 1 – SCSI document structure.8
Figure 2 – Example Sequence figure .16
Figure 3 – USB Model .17
Figure 4 – Example Simple UAS domain .19
Figure 5 – Example Complex UAS Domain.20
Figure 6 – UAS sequence figure notation .34
Figure 7 – Non-data transfer with Sense.34
Figure 8 – Non-data Transfer with Response.35
Figure 9 – Write Data Transfer .36
Figure 10 – Read Data Transfer .37
Figure 11 – Task management .37
Figure 12 – Bi-directional Data Transfer .38
Figure 13 – Multiple Command example.40

Table 1 – Numbering conventions . 15
Table 2 – Device descriptor . 22
Table 3 – Configuration descriptor. 23
Table 4 – Interface Descriptor. 24
Table 5 – Bulk-in endpoint descriptor.
...