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Flow control for universal serial bus (USB)

A universal serial bus, flow control technology, applied in the field of data communication, can solve problems such as consumption, large USB bandwidth and power

Active Publication Date: 2009-06-03
QUALCOMM INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, NAKed transactions can consume significant USB bandwidth and power

Method used

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  • Flow control for universal serial bus (USB)
  • Flow control for universal serial bus (USB)
  • Flow control for universal serial bus (USB)

Examples

Experimental program
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Embodiment Construction

[0019] The flow control techniques described herein can be used for USB, other buses, poll-based input / output (I / O) systems, and other systems where data is exchanged between entities. For clarity, the techniques described below are specific to USB as covered in the publicly available document "Universal Serial Bus Specification," Revision 2.0, April 27, 2000.

[0020] USB uses the following terms:

Function (Function) - USB device that provides capabilities / tasks to the USB host

• Endpoint - A source or sink in a communication flow between a USB device (or function) and a USB host.

a pipe - a logical channel between a USB host and an endpoint on a USB device, and

• Transaction - a service transfer for an endpoint, consisting of a Token packet, an optional Data packet, and an optional Handshake packet.

[0021] A USB device can have one or more functions, for example a webcam can have one function for video and another function for sound. Each physical USB device is ide...

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PUM

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Abstract

The present invention describes techniques for performing flow control in Universal Serial Bus (USB). In one design, a USB host sends token packets to a USB device to initiate data exchanges with the USB device. The USB device determines that it is incapable of exchanging data with the USB host, e.g., because there is no data to send or because its buffer is full or near full. The USB device then sends a 'flow off' notification to the USB host to suspend data exchanges. The USB host receives the flow off notification and suspends sending token packets to the USB device. Thereafter, the USB device determines that it is capable of exchanging data with the USB host. The USB device then sends a 'flow on' notification to the USB host to resume data exchanges. The USB host receives the flow on notification and resumes sending token packets to the USB device.

Description

[0001] This application claims priority to Provisional U.S. Application No. 60 / 808691, filed May 25, 2006, entitled "Optimized USB FlowControl Mechanism," which is assigned to the assignee of this application and is incorporated by reference In this application. technical field [0002] The present disclosure relates generally to data communications, and more specifically, to techniques for controlling the exchange of data over USB. Background technique [0003] USB is a serial bus widely used to interconnect computers with external devices such as keyboards, mouse devices, printers, scanners, memory sticks, disk drives, digital cameras, web cameras, and the like. USB is also widely used in other electronic devices, such as personal digital assistants (PDAs), game consoles, and the like. [0004] USB utilizes a host-centric architecture to exchange data between a USB host (USB host) and a USB device (USB device) coupled to the USB host. A USB host can reside on a computer,...

Claims

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Application Information

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IPC IPC(8): G06F13/42
Inventor H·郭J·A·戴克
Owner QUALCOMM INC