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Time-out The detection of a lack of bus activity for some predetermined interval.
Token Packet A type of packet that identifies what transaction is to be performed on the bus.
TPV Third Party Vendor
Transaction The delivery of service to an endpoint; consists of a token packet, optional data packet, and optional
handshake packet. Specific packets are allowed/required based on the transaction type.
Transaction translator A functional component of a USB hub. The Transaction Translator responds to special
high-speed transactions and translates them to full/low-speed transactions with full/low-speed devices attached on
downstream facing ports.
Transfer One or more bus transactions to move information between a software client and its function.
Transfer Type Determines the characteristics of the data flow between a software client and its function. Four
standard transfer types are defined: control, interrupt, bulk, and isochronous.
TS Thermal Shock
Turn-around Time The time a device needs to wait to begin transmitting a packet after a packet has been received
to prevent collisions on the USB. This time is based on the length and propagation delay characteristics of the cable
and the location of the transmitting device in relation to other devices on the USB.
UART Universal Asynchronous Receiver/Transmitter serial port
Universal Serial Bus Driver (USBD) The host resident software entity responsible for providing common services
to clients that are manipulating one or more functions on one or more Host controllers.
Universal Serial Bus Resources Resources provided by the USB, such as bandwidth and power. See also Device
Resources and Host Resources .
Upstream The direction of data flow towards the host. An upstream port is the port on a device electrically closest
to the host that generates upstream data traffic from the hub. Upstream ports receive downstream data traffic.
USBD See Universal Serial Bus Driver .
USB-IF USB Implementers Forum, Inc. is a nonprofit corporation formed to facilitate the development of USB
compliant products and promote the technology.
VBI Vertical Blanking Interval, also known as the "backporch".
Virtual Device A device that is represented by a software interface layer. An example of a virtual device is a hard
disk with its associated device driver and client software that makes it able to reproduce an audio.WAV file.
VLIO Variable Latency Input/Output interface.
YUV A method of characterizing video signals typically used in digital cameras and PAL television specifying
luminance and chrominance.
WAP Wireless Application Protocol. WAP is a set of protocols that lets users of mobile phones and other digital
wireless devices access Internet content, check voice mail and e-mail, receive text of faxes and conduct
transactions. WAP works with multiple standards, including CDMA and GSM. Not all mobile devices support
WAP.
Glossary-13
Intel® PXA27x Processor Family Optimization Guide
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