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INTELLON CEBUS

Intellon Corporation is a leading supplier of communication solutions for networking with no new wires. Intellon provides low-cost, high-performance digital, mixed-signal, and radio frequency (RF) based systems on silicon to OEMs worldwide. Intellon's intellectual property, products, technologies, and services are key to a variety of open industry standards and fast-growing markets including telecommunications, networking, transportation, and consumer electronics. Intellon's powerline carrier and radio frequency technologies enable high-speed communication and extend the reach of the Internet to individual products without adding new wires.

Founded in 1989, Intellon is a privately held company based in Ocala, Florida, and operates as a fabless semiconductor company to develop, manufacture, and distribute integrated circuit-based products and modules that are supported by complete reference design information, development, and evaluation tools. The company produces products that conform to the Consumers Electronics Bus (CEBus) standard. The CEBus standard is an open standard that provides separate physical layer specification documents for communication on powerlines and other media. The Intellon technology is oriented toward providing control capabilities to home networks and consists of two fundamental components—a transceiver implementing spread spectrum technology, and a microcontroller to run the protocol. (The next chapter explains spread spectrum technologies in greater detail.) Data packets are transmitted by the transceiver at about 10 Kbps, employing spread spectrum technology. Each packet contains the necessary sender and receiver addresses. The CEBus protocol uses a peer-to-peer communications model so that any node on the network has access to the media at any time. To avoid data collisions, it uses a Carrier Sense Multiple Access/ Collision Detection and Resolution (CSMA/CDCR) protocol. Basically, this Media Access Control (MAC) protocol requires a network node to wait until the line is clear, which means that no other packet is being transmitted before it can send a packet. A CEBus network is comprised of a control channel and potentially multiple data channels on each of the CEBus media. CEBus control channel communication is standardized across all media, with a consistent packet format and signaling rate, and is used exclusively to control devices and resources of the network, including data channel allocations. A control channel signaling rate of 10,000 unit symbols per second is used with a "one" bit taking one unit symbol time (UST) and a "zero" bit taking two UST, resulting in an effective control data rate of approximately 7,000 data bits per second. Data channels typically provide selectable bandwidths that can support high data rates and are used to send data such as audio, video, or computer files over the network. The characteristics of a data channel can vary greatly depending on the medium and connected device requirements. All data channel assignments and functions are managed by CEBus control messages sent via the control channel. CEBus includes a common application language (CAL) that allows devices to communicate commands and status requests between each other using a common command syntax and vocabulary. CAL defines various electronic device functional subunits called contexts. For example, the audio control of a TV, a stereo, a CD Player, or a VCR is a CAL context. Each context is further broken down into objects, which represent various control functions of the context; for example, volume, bass, treble, or mute functions. Finally, objects are defined by a set of instance variables that specify the operation of the function of the object, such as the default or current setting of the volume object. Further details of CAL and CEBus are available in Chapter 15.


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