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USB System Architecture (USB 2.0).pdf
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Chapter 22: Overview of USB Host Software

Command Mechanisms

Command mechanisms allow a client to access and control a USB device. For example, read and write accesses can be made to a device’s data and control endpoints. The command mechanisms provide the following generic types of access/services. The USBDI must provide a mechanism for the following actions:

Interface state control

Pipe may be reset

Pipe may be aborted

Retrieve descriptors

Get current configuration settings

Adding devices (Hub client)

Removing devices (Hub client)

Managing status

Sending class commands

Sending vendor commands

Establishing alternate settings

Establishing a configuration

Establishing the max packet size

Setting descriptors

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USB System Architecture

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