Philips 170B2M Electronic User's Manual

Also see for 150B2: Technical specifications Technical specifications Electronic user's manual Electronic user's manual Electronic user's manual

Contents

A Universal Serial Bus device that provides additional connections to the Universal Serial Bus.Hubs are a key element in the plug-and-play architecture of USB. The Figure shows a typical hub. Hubsserve to simplify USB connectivity from the user's perspective and provide robustness at low cost andcomplexity.Hubs are wiring concentrators and enable the multiple attachment characteristics of USB. Attachment pointsare referred to as ports. Each hub converts a single attachment point into multiple attachment points. Thearchitecture supports concatenation of multiple hubs.The upstream port of a hub connects the hub towards the host. Each of the other downstream ports of ahub allows connection to another hub or function. Hubs can detect, attach and detach at each downstreamport and enable the distribution of power to downstream devices. Each downstream port can be individuallyenabled and configured at either full or low speed. The hub isolates low speed ports from full speedsignaling.A hub consists of two portions: the Hub Controller and Hub Repeater. The repeater is a protocol-controlledswitch between the upstream port and downstream ports. It also has hardware support for reset andsuspend/resume signaling. The controller provides the interface registers to allow communication to/fromthe host. Hub specific status and control commands permit the host to configure a hub and to monitor andcontrol its ports.DeviceA logical or physical entity that performs a function. The actual entity described depends on the context ofthe reference. At the lowest level, device may refer to a single hardware component, as in a memory device.At a higher level, it may refer to a collection of hardware components that perform a particular function, suchas a Universal Serial Bus interface device. At an even higher level, device may refer to the functionperformed by an entity attached to the Universal Serial Bus; for example, a data/FAX modem device.Devices may be physical, electrical, addressable, and logical.DownstreamThe direction of data flow from the host or away from the host. A downstream port is the port on a hubelectrically farthest from the host that generates downstream data traffic from the hub. Downstream portsreceive upstream data traffic.Glossaryfile:///D|/Grace/K1/english/170b2m/glossary/glossary.htm (3 of 4) [11/22/2001 1:37:40 PM]