ISO IEC 14776-253-2023 PDF

Full title and description

Information technology — Small Computer System Interface (SCSI) — Part 253: USB attached SCSI - 3 (UAS-3). This international standard specifies how SCSI commands and behavior are transported over USB using the UAS‑3 transport, to ensure interoperable implementations of SCSI over USB devices and hosts.

Abstract

ISO/IEC 14776-253:2023 (UAS‑3) is the first edition defining the UAS‑3 transport for carrying SCSI command sets over USB. The document covers USB device and interface descriptors relevant to UAS, transport and packet structures, mapping of SCSI commands and task management to USB transfer semantics, data transfer mechanisms, error reporting and recovery, and conformance considerations for device and host implementations. It was prepared via INCITS (as INCITS 572-2021) and adopted by ISO/IEC JTC 1.

General information

• Status: Published.
• Publication date: April 2023 (published as International Standard 27 April 2023; edition 1).
• Publisher: ISO / IEC (adopted by ISO/IEC JTC 1; published via the ISO publication process).
• ICS / categories: 35.200 — Interface and interconnection equipment.
• Edition / version: Edition 1 (2023).
• Number of pages: 50.

Key bibliographic and status data above are taken from the ISO record for ISO/IEC 14776-253:2023.

Scope

This part of ISO/IEC 14776 defines the USB transport (UAS‑3) for SCSI: the packet and descriptor structures used over USB, the mapping of SCSI command sets and task management functions to USB transfers, semantics for DATA IN/DATA OUT and streaming/bulk behaviors, error reporting (SCSI sense over USB) and recovery, and behaviours for reset, power and device state transitions to support interoperable host and device implementations. The standard’s scope is to enable consistent implementation, testing and conformance of SCSI over USB devices and host drivers.

Key topics and requirements

• USB device, configuration and interface descriptors for UAS‑3 and required descriptor fields.
• Transport packet formats and sequencing for carrying SCSI commands, data and status over USB.
• Mapping rules for SCSI commands, task management functions and response/sense reporting to USB transfers.
• Data transfer semantics including concurrency, streaming, switching transfers between commands, and bulk/stream behaviour.
• Error conditions, sense reporting, recovery actions and reset/abort behaviour expected from devices and hosts.
• Power management and device state requirements (expected device behaviour after power loss, reset, etc.).
• Conformance and interoperability guidance for testing host and device implementations.

These topics reflect the normative scope and table of contents for the UAS‑3 specification.

Typical use and users

Primary users are storage device and enclosure manufacturers, USB bridge/adapter designers, firmware and device driver engineers, system integrators and OEMs who design or validate SCSI-over-USB products. The standard is used when implementing UAS‑3 in device firmware, host drivers, interoperability test plans and procurement specifications for USB‑attached storage.

Related standards

ISO/IEC 14776-253:2023 is part of the ISO/IEC 14776 family for SCSI protocols. It was prepared from the INCITS UAS‑3 specification (INCITS 572-2021) and the T10 working-group materials that define USB Attached SCSI; related SCSI architecture and command standards (SAM, SPC series) and earlier UAS parts (e.g., INCITS/ISO references for UAS‑1) are also relevant for implementers. Implementers commonly cross‑reference INCITS 572-2021 and T10 publications when working with UAS‑3.

Keywords

USB Attached SCSI, UAS-3, SCSI over USB, SCSI transport, USB storage, device descriptors, SCSI command mapping, interoperability, INCITS 572-2021, ISO/IEC 14776.

FAQ

Q: What is this standard?

A: ISO/IEC 14776-253:2023 is the international standard that specifies the USB Attached SCSI — 3 (UAS‑3) transport, defining how SCSI command sets and behaviors are carried over USB to ensure interoperable host and device implementations.

Q: What does it cover?

A: It covers USB descriptors relevant to UAS devices, transport packet formats, SCSI command and task-management mapping to USB transfers, data-transfer semantics (including switching/switchable transfers), error reporting and recovery, power/reset behaviour and conformance guidance for testing.

Q: Who typically uses it?

A: Device and enclosure manufacturers, firmware and driver developers, system integrators, test labs and procurement teams specifying USB‑attached storage interfaces and interoperability requirements.

Q: Is it current or superseded?

A: As published in April 2023 (first edition), ISO/IEC 14776-253:2023 is the current international standard for UAS‑3. Implementers should monitor the ISO review cycle and T10/INCITS activity for possible future revisions or amendments.

Q: Is it part of a series?

A: Yes — it is Part 253 of the ISO/IEC 14776 series (the SCSI family). It was prepared from the INCITS UAS‑3 work (INCITS 572-2021) and should be considered alongside other SCSI architecture and transport parts for complete system behavior.

Q: What are the key keywords?

A: USB Attached SCSI, UAS‑3, SCSI, USB storage, SCSI command mapping, transport packet, device descriptor, interoperability, INCITS 572.