USB 3.0 On-The-Go与嵌入式主机补充规范修订1.1

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本文档是关于USB 3.0规范修订1.1的补充，专注于On-The-Go (OTG) 和嵌入式主机功能。OTG是一种USB技术扩展，它允许设备在没有外部电源的情况下充当主机或从属设备，实现了设备间的双向通信。这份补充主要关注了以下关键知识点： 1. **A3状态机修改**：文档更新了A3状态机，特别是在检测到断开连接时，增加了通用的转换流程，并通过脚注明确了与数据端口(DS)相关的操作。这确保了在不同状态之间的切换更为清晰。 2. **错误处理改进**：对于u1_u2_exit_fail导致的状态迁移，文本和图表进行了调整，明确地展示了从a3/b3_ds_resetting到a3/b3_ds_error，而不是直接从a3/b3_ds_host到a3/b3_ds_error的情况。这样提高了状态转移的精确性和理解性。 3. **新的过渡**：添加了从a3_us_rspto a3_us_disconnected状态的转变条件，当检测到a3_b_wreset_detected和b3_ntf_host_rel时，附有脚注解释了具体行为，以便用户理解设备的行为模式。 4. **设备行为澄清**：将LMPTiebreaker比特的使用规定从强制变为提示，说明OTG设备并不使用这些比特，有助于用户了解OTG设备的设计原则。 5. **恢复超时修正**：文档强调了A3和B3状态机中，当遇到问题时，应统一恢复到*_us_error状态，增强了状态管理的一致性。 6. **图形和文本更新**：最后，文档中的所有图形和文字都经过了校正和更新，以反映这些新规则和改进，确保了规范的准确性和实用性。这份补充文档提供了USB 3.0规范在OTG和嵌入式主机环境下的详细说明，对开发者设计兼容的硬件和软件接口具有重要参考价值，尤其是在处理状态机、错误处理和设备行为一致性方面。

On-The-Go and Embedded Host Supplement to the USB Revision 3.0 Specification Revision 1.1

1 Introduction

1.1 Overview

The Universal Serial Bus (USB), originally designed as an interface between PCs and peripherals, has

become the most successful general-purpose PC interface in the history of computing. The [USB3.0]

specification has added the capability for SuperSpeed communications over USB.

By definition, USB communication occurs between a host and a peripheral. The original intent was to

place the heavier workload on the PC (host) and to allow USB peripherals to be fairly simple.

Accordingly, the USB specification requires that PCs:

• provide power to peripherals (for [USB2.0] 0.5A at ~5V, for [USB3.0] 0.9A at ~5V)

• support all defined speeds (SuperSpeed, Low Speed, Full Speed and High Speed)

• support all defined data flow types (control, bulk, interrupt and isochronous)

As computing resources have become less expensive, the line between PCs and other products has

blurred. Today many devices that are not PCs in the classic sense have a need to connect directly to

peripherals: Printers connect directly with cameras, for example, or mobile phones may need to connect

to USB headsets.

These non-PCs have the computing resources to manage a USB host function, but they need to function

in ways that differ from standard PC hosts. Although they will provide host capability for some devices,

it's unreasonable to require them to support the full range of USB peripherals. For example, connecting a

camera to a printer makes a lot of sense, but the printer manufacturers may not think it is quite as

important for the printer to support a USB GPS dongle.

This specification defines these non-PC hosts as Targeted Hosts. A Targeted Host is a USB host that

supports a specific, targeted set of peripherals. The developer of each Targeted Host product defines

the set of supported peripherals on a Targeted Peripheral List (TPL). A Targeted Host needs to provide

only the power, bus speeds, data flow types, etc., that the peripherals on its TPL require.

There are two categories of Targeted Hosts:

1. Embedded Hosts: An Embedded Host (EH) product provides Targeted Host functionality over one

or more Standard-A or Micro-AB receptacles. Embedded Host products may also offer USB

peripheral capability, delivered separately via one or more Type-B receptacles.

2. On-The-Go: An OTG product is a portable device that uses a single Micro-AB receptacle (and no

other USB receptacles) to operate at times as a USB Targeted Host and at times as a USB

peripheral. OTG devices shall always operate as a standard peripheral when connected to a

standard USB host.

OTG devices can also be attached to each other. This specification enables the underlying driver

components to optionally swap between the role of either USB host or USB peripheral, without needing

to physically turn the cable around.

[OTG&EH2.0] applies to all Universal Serial Bus products. This supplement covers products which have

a SuperSpeed capability (as defined in the [USB3.0] specification) in addition to having capabilities

defined in [OTG&EH2.0]. The following additional configurations are covered by this supplement:

1. SuperSpeed Embedded Host or SS-EH: An Embedded Host which can operate at SuperSpeed

through its one or more Standard-A or Micro-AB receptacles in addition to EH capability defined in

[OTG&EH2.0]

for example support for SRP and ADP.

On-The-Go and Embedded Host Supplement to the USB Revision 3.0 Specification Revision 1.1

2. SuperSpeed Peripheral Only or SS-PO: A peripheral-only B-device which can operate at

SuperSpeed in addition to having peripheral-only B-device capabilities as described in [OTG&EH2.0].

3. SuperSpeed Peripheral Capable OTG Device or SSPC-OTG: An OTG device compliant with

[OTG&EH2.0] which can also operate as a SuperSpeed peripheral. Products with this configuration are

not able to operate as a SuperSpeed host. When operating as a peripheral, they can operate at either

SuperSpeed or [OTG&EH2.0] speeds. However they may only be able to swap roles when operating at

[OTG&EH2.0] speeds.

4. SuperSpeed OTG Device or SS-OTG: An OTG Device compliant with [OTG&EH2.0] which can also

operate as a SuperSpeed Host or a SuperSpeed Peripheral. Products with this configuration may be

able to dynamically swap host/peripheral roles while operating at SuperSpeed using the mechanisms

defined in this supplement.

Devices which conform to [OTG&EH2.0] are referred to as [USB2.0] devices in this supplement: USB2.0

EH, USB2.0 OTG and USB2.0 PO.

1.2 Related Documents

This is not a stand-alone document. It is a supplement to [USB3.0]. Any aspects of USB which are not

specifically changed by this supplement are governed by [USB3.0].

The following referenced documents can be found on the USB-IF website www.usb.org:

[USB3.0]

Universal Serial Bus Revision 3.0 Specification including ECNs and

errata.

[Micro-USB1.01]

Universal Serial Bus Micro-USB Cables and Connectors Supplement

to the USB 2.0 Specification, revision 1.01.

[USB2.0]

Universal Serial Bus Revision 2.0 Specification including ECNs and

errata.

[OTG&EH2.0]

[USBBattery1.2]

[xHCI]

On-The-Go and Embedded Host Supplement to the Universal Serial

Bus Revision 2.0 Specification including ECNs and errata.

USB Battery Charging Specification, revision 1.2.

eXtensible Host Controller Interface for Universal Serial Bus (xHCI),

revision 1.0

1.3 Terminology

“Shall” is normative and used to indicate mandatory requirements which are to be followed strictly in

order to conform with this standard.

“Should” is normative and used to indicate a recommended option or possibility.

“may” is normative and used to indicate permitted behavior.

“can” is informative and used to indicate behavior which is possible or may be seen

The use of “must” and “will” is deprecated for requirements and shall only be used for statements of fact.

On-The-Go and Embedded Host Supplement to the USB Revision 3.0 Specification Revision 1.1

1.4 Acronyms and Terms

This section lists and defines terms and abbreviations used throughout this specification.

ACA

Accessory Charger Adapter (see [USBBattery1.2]).

A-Device

Device with a Standard-A receptacle or a device with a Micro-A plug attached to

its receptacle. The A-device supplies power to V

BUS and is host at the start of a

session.

A-Host

A-Device operating as a host.

A-Port

Port featuring an A-type receptacle.

A-Peripheral

A-Device operating as a peripheral.

AB-Port

Port featuring an AB-type receptacle.

ADP

Attach Detection Protocol. A protocol which enables an OTG device or EH to

detect when a remote device has been attached or detached (as defined in

[OTG&EH2.0]).

ADP-capable

Device which is able to perform ADP probing and ADP sensing

ADP probing

This enables the local A-device or B-device to probe V

BUS and determine

whether a device is attached.

ADP sensing

This enables the local B-device to detect ADP probing generated by an

attached device. ADP sensing is not a requirement for A-devices.

Application

A generic term referring to any software that is running on a device that can

control the behavior or actions of the USB port(s) on a device.

Attach

This specification makes a distinction betw

een the words “attach” and “connect”.

A downstream device is considered to be attached to an upstream port when

there is a physical cable between the two.

B-Device

Device with:

• a Standard-B receptacle or,

• Mini-B receptacle, or

• Micro-B receptacle, or

• Micro-AB receptacle with either a Micro-B plug or no plug attached to its

receptacle, or

• a captive cable ending in a Standard-A or Micro-A plug.

The B-device is a peripheral at the start of a session.

B-Host

B-Device operating as a host.

B-Port

Port featuring a B-type receptacle.

B-Peripheral

B-Device operating as a peripheral.

Connect

This specification makes a distinction between the words “attach” and “connect”.

A downstream device is considered to be connected to an attached upstream

port when the upstream port has either pulled the D+ or D- data line high

An ADP-capable EH is not required to do ADP sensing since it is not able to operate in the B-device

position.

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