![](http://datasheet.mmic.net.cn/230000/W722_datasheet_15631126/W722_12.png)
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W722 USB Hub/Compound Device Controller
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10
Oki Semiconductor
GLOSSARY
Term
Explanation
Bandwidth
The amount of data transmitted per unit of time, typically bits per second (bps) or bytes per second (Bps).
Bit
A unit of information used by digital computers. Represents the smallest piece of addressable memory within a
computer. A bit expresses the choice between two possibilities and is typically represented by a logical one (1) or
zero (0).
Bit Stuffing
Insertion of a “0” bit into a data stream to cause an electrical transition on the data wires which allows a PLL to
remain locked.
Bulk Transfer
Nonperiodic, large burst communication typically used for a transfer that can use any available bandwidth and also
be delayed until bandwidth is available.
Control Transfer
One of four Universal Serial Bus Transfer Types. Control transfers support configuration/command/status type
communications between client and function.
CRC
See Cyclic Redundancy Check.
Cyclic Redundancy Check
A check performed on data to see if an error has occurred in transmitting, reading, or writing the data. The result
of a CRC is typically stored or transmitted with the checked data. The stored or transmitted result is compared to
a CRC calculated for the data to determine if an error has occurred.
Device Endpoint
A uniquely identifiable portion of a Universal Serial Bus device that is the source or sink of information in a
communication flow between the host and device.
Endpoint
See Device Endpoint.
Interrupt Transfer
One of four Universal Serial Bus Transfer Types. Interrupt transfers characteristics are small data, nonperiodic, low
frequency, bounded latency, device initiated communication typically used to notify the host of device service
needs.
Isochronous Transfer
One of four Universal Serial Bus Transfer Types. Isochronous transfers are used when working with isochronous
data. Isochronous transfers provide periodic, continuous communication between host and device.
Nonreturn-to-Zero-Invert
A method of encoding serial data in which ones and zeroes are represented by opposite and alternating high and
low voltages where there is no return to zero (reference) voltage between encoded bits. Eliminates the need for
clock pulses.
NRZI
See Nonreturn-to-Zero-Invert.
PLL
Phase-Locked-Loop. A circuit that acts as a phase detector to keep an oscillator in phase with an incoming
frequency.
Protocol
A specific set of rules, procedures, or conventions relating to format and timing of data transmission between two
devices.
Transaction
The delivery of service to an endpoint. Consists of a token packet, optional data packet, and optional handshake
packet. Specific packets are allowed or required based on the transaction type.
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 transfer types are
defined: control, interrupt, bulk, and isochronous.
Universal Serial Bus
A collection of Universal Serial Bus devices and the software and hardware that allow them to connect the
capabilities provided by functions to the host.
Universal Serial Bus Interface
The hardware interface between the Universal Serial Bus cable and a Universal Serial Bus device. This includes the
protocol engine required for all Universal Serial Bus devices to be able to receive and send packets.
USB
See Universal Serial Bus.