Patent Publication Number: US-6907458-B2

Title: Digital multi-room, multi-source entertainment and communications network

Description:
RELATED APPLICATION 
     The present application is related to U.S. patent application Ser. No. 09/849,693 entitled “CONTROL MESSAGING FOR AN ENTERTAINMENT AND COMMUNICATIONS NETWORK” to Tomassetti et al., still pending; U.S. patent application Ser. No. 09/849,698 entitled “DATA STRUCTURE FOR AN ENTERTAINMENT AND COMMUNICATIONS NETWORK” to Tomassetti et al., abandoned; and U.S. patent application Ser. No. 09/849,198 entitled “INITIALIZATION METHOD FOR AN ENTERTAINMENT AND COMMUNICATIONS NETWORK” to Tomassetti et al., all filed on May 4, 2001, coincident herewith and assigned to the assignee of the present invention, still pending. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to peer to peer local area networks (LANs) and, more particularly to a peer to peer network wherein control data and information, especially multimedia information, is provided to stations connected to the network. 
     2. Background 
     A typical audio system has a centralized receiver that includes a tuner and program function selector (where a program source is selected) and one or more sets of speakers, e.g., a local speaker set and remote speaker sets. The centralized receiver controls the volume at all speaker sets, i.e., on both the local speaker set and on the remote speakers. The receiver selects a single program source for play at any and all of the speaker sets. Only one source is selected and available at all of the speaker sets at a time, even though the receiver may have inputs from multiple devices. Input devices may include, for example, a turntable, tape player a compact disc (CD) player, a minidisk (MD) player and other auxiliary devices, such as a digital audio tape (DAT) player, a digital versatile disc (DVD) player, a videocassette recorder (VCR) or television set. 
     Transferring multimedia information over a network is known. e.g., streaming multimedia data over a network such as the internet or a local area network (LAN). The multimedia data may be raw audio or video data such as a wave file, a bitmap or a movie file. However, typically, multimedia files are compressed using, for example, the motion pictures expert group (MPEG) format to reduce the data volume that must be handled. Furthermore, music or songs may be encoded as compressed audio, for example, using the MPEG layer 3 (mp3) standard. This compressed audio may also be made available as an mp3 file for compact storage, transport and handling. Depending upon the complexity of the audio data that is compressed, these audio compression techniques can reduce file size by 90% or more, without losing playback quality, i.e., with CD quality playback. 
     Reduced file size and CD quality sound have made compressed audio files very popular. So, mp3 file libraries are available at numerous internet sites, e.g., mp3.com. Further, various software interfaces are available for playing mp3 files, either directly, as they are downloaded to a personal computer (PC) from the internet or, from a cache of previously downloaded mp3 files, e.g., Winamp and RealPlayer. Software packages are also available to encode uncompressed audio, e.g., encoding a music cut from, for example, a CD into a mp3 file. After encoding (called “ripping”) the condensed file may be stored on a PC either for subsequent playback at the PC or, for transfer to a dedicated mp3 player, such as the Lyra from RCA or the Rio from Diamond Multi-Media. 
     A typical such mp3 player looks like a small (about the size of a cigarette package) personal radio with mini-earphones for private listening. Usually, the mp3 files are stored in non-volatile memory in the mp3 player, which may hold an hour or more of encoded music. These dedicated mp3 players normally serve as personal music players that provide a single individual with music and songs selected for the listener&#39;s taste. 
     Although the personal mp3 players may be attached to a sound system, e.g., as an auxiliary device, usually they are not. So, for example, a musical piece being played on a turntable attached to a sound system is not heard through speakers attached to a computer: and, a streaming audio or mp3 file being played on a computer is passed to a home theater system only with some difficulty. Consequently, a heavy metal music file downloaded by a teenager and being played on a PC in the teen&#39;s room may be disturbing everyone else in the house, while a sound system that is intentionally located in a remote, isolated family room may lie dormant. Light music that is being piped throughout the house from a sound system located in the family room and played at a volume that is barely loud enough to be heard in the crowded family room, may be overly loud in another, nearly empty room. By contrast, the same music set at low volume in a nearly empty family room might not be heard in other rooms where people are standing and chatting. 
     Thus, there is a need for a multimedia system wherein a program source may be located in one zone or room and multimedia data may be streamed to one or more other zones or rooms where it may be independently selected, controlled and played. 
     SUMMARY OF THE INVENTION 
     It is therefore a purpose of the invention to distribute digital audio to different zones within the same structure; 
     It is another purpose of the invention to independently distribute separate audio data streams to different zones within the same structure; 
     It is yet another purpose of the invention to pass digital audio between zones in a structure; 
     It is yet another purpose of the invention to include point to point intercom and audio data in audio data streams distributed to different zones of a structure; 
     It is yet another purpose of the invention to distribute digital audio to different zones within the same structure and provide individual sound quality control of audio distributed and played in individual rooms of a house. 
     The present invention is a multi-zone entertainment and communications network that includes a digital peer-to-peer network distributing data that is being streamed from multiple sources to multiple independent receivers and/or transceivers. The receivers and transceivers may be located in different zones from each other. The sources may be located in different zones from each other and, may be connected to or part of one of the transceivers. The receivers and transceivers may have independent volume and tone control and are capable of locally manipulating the data stream output. Each source can inject data into the data stream independent of the other sources, which then is streamed on the network and made available to all receivers and transceivers, simultaneously. Each receiver may independently select a source of audio from the data stream. One or more of the sources act as an intercom, providing verbal communication between at least two zones and provide paging to broadcast pages to all the receivers/transceivers on the network. 
     Advantageously, the multi-zone network of the present invention makes streaming digital audio available for use at each zone of a structure. i.e. in different rooms of a house. Further, the multi-zone network includes room stations that can inject audio independently into the data stream and onto the network. Digital data is converted locally to analog audio at each room station and locally amplified for clear CD quality sound. Since the audio is transferred digitally over the preferred multi-zone network, high-cost, low-loss wiring, that otherwise is required to route high quality audio, is unnecessary. Instead, relatively inexpensive CAT 5 wiring may be used to pass digital signals from the hub to the room stations. Further, the room stations independently control and select what is played in the room, selecting from one of several streaming audio data channels, rather than merely playing what is being broadcast from a single audio stream. In addition, each remote station itself can broadcast or receive independent of and simultaneously with other remote stations. Also, each remote station can be programmed for individual specific needs such as, for example, including radio station presets on remote stations equipped with a radio tuner. Alarms or other functional features may be included, such as providing the ability to monitor another remote location using the multi-zone network&#39;s intercom function. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects, aspects and advantages will be better understood from the following detailed preferred embodiment description with reference to the drawings, in which: 
         FIG. 1  is schematic representation of a basic example of a local communication network according to the preferred embodiment of the present invention; 
         FIG. 2  is an of the basic local communication network of  FIG. 1 ; 
         FIG. 3  is a block diagram of the preferred embodiment hub module; 
         FIGS. 4A-B  show a timing diagram and data structure illustrating how messages and data are exchanged between the local nodes and the remote nodes across the backplane; 
         FIG. 5  is an initialization timing diagram; 
         FIG. 6  is a state diagram showing how the preferred local communication network may be initialized; 
         FIGS. 7A-B  show a state diagram and control data structure in an example of how a node may gain access to the control bus; 
         FIG. 8  is an example of a state diagram for message reception control; 
         FIG. 9  is an example of a typical preferred embodiment home communication system; 
         FIG. 10  is an example of the room station; 
         FIG. 11  is a block diagram of a remote station; 
         FIG. 12  is a block diagram of the digital loop filter. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION 
     Referring now to the drawings and more particularly,  FIG. 1  is a block representation of a basic local communication network  100  according to the preferred embodiment of the present invention. In this example, the network  100  includes an expandable hub  102  that may include one or more hub modules  104 , (two in this example) which are attached to and in communication with each other over a back plane  106 . In addition, one or more local feature cards  108  may be locally attached to the back plane  106  for direct communication to the expandable hub  102 . Remote stations  110  and remote feature cards  112  may be located in remote zones (e.g., different rooms) and connected to the hub modules  104  over individual high speed data communications channels  114 , e.g., a pair of Ethernet adapters sending/receiving a high speed (10 Mbit/second) serial data stream over a twisted pair. The hub modules  104  and any optional local feature cards  108  may, be aesthetically encased in a structured wiring cabinet (not shown) to give the appearance of a typical state of the art home entertainment system. For convenience, an expandable arrangement  102  of hub modules  104  and optional feature cards  106  are referred to hereinbelow, generically, as an entertainment hub  102 . 
     Thus, in this example, each hub module  104  includes hub ports  116 ; each local feature card  108  includes a local node  118 ; and, remote nodes  120  are included in each remote station  110  and each remote feature  112 . The hub ports  116  are interfaced to the back plane  106 , each connecting a remote device, i.e., connecting a remote station  110  or feature card  112 , to the network. The local nodes  118  interface the corresponding function of a local feature card  108  to the back plane  106 . The remote nodes  120  interface the multimedia function of the remote stations  110  and the remote feature cards  112  to the hub ports  116 , providing and receiving data in a format suitable for inter unit serial data communication. 
       FIG. 2  is an example of the basic local communication network  100  of  FIG. 1 , which is, essentially, a peer-to-peer network of digital audio devices. Typically, a preferred embodiment system  100  includes a single entertainment hub  102 . However, it is understood that multiple entertainment hubs  102  may be included communicating over connected backplanes  106 , e.g., with a network bridge. Further, the entertainment hub  102  may be located at a convenient location within a structure, such as a home, with the remote stations  110  and the remote feature cards  112  being located throughout the structure in different zones, i.e., in different rooms. In addition, in the basic example of  FIG. 2 , a media/communications face plate is shown as an example of a local feature card  108 . In this example, the face plate includes a stereo audio input  122  (left and right). a stereo audio output  124  (both left and right) and an optional infrared (IR) port  126  for control. As further depicted, the IR interface  126  may include a separate infrared receiver jack  126 I and an infrared emitter jack  126 O or a suitable bidirectional IR port may be substituted. Preferably loud speakers  127  are attached to the room stations  110 ,  120  for playing music, receiving intercom information or, listening to other stations. 
       FIG. 3  is a block diagram of the preferred embodiment hub module  104  according to the present invention. As can be seen, the preferred hub module  104  includes preferably four hub ports  116 . Each hub port  116  can interface up to four unique audio source address locations and one intercom source which shares a common address with the first audio source address. Each hub module  104  includes a serial interface that may be a local area network (LAN) or serial data interface function, in the example an Ethernet physical layer (Ethernet phy)  128 , that connects the serial channel  114  to the hub ports  116 . A hub interface  130  interfaces the hub ports  116  to the backplane  106 . 
     The serial data interface  128  may be readily available Ethernet chip such as, for example, the LU3X31T-64 FASTCAT phy chip interface (phy chip) from Lucent Technologies, the LTX905A Universal 10BASE-T Transceiver from Level One or an equivalent. Preferably, the hub ports  116  and hub interface function  130  are in a single integrated circuit chip such as the Altera 6024, 10K130 or an equivalent. The hub interface function  130  includes a hub port audio channel selector  132  passing digital audio and intercom data between the hub ports  116  and the back plane  106  through an audio/intercom buffer  134 . A back plane controller  136  conducts device address polling/acquisition, selectively passing a unique product serial number for each of the attached devices and, when set as master (as described hereinbelow), the master backplane controller controls other attached hub modules  104  during such operations. The backplane controller  136  either actively drives bus signals at the backplane  106  or passively through the dot OR outputs of drivers  138  which are dot connected to other attached devices. A non-volatile storage interface  140  provides an interface to non-volatile storage  142 . e.g., EEPROM. The non-volatile storage  142  is included in the hub module  104  for maintaining address assignments etc., during power off. In the example of  FIG. 2 , the non-volatile storage  142  is provided for address and configuration data local storage at the hub module. 
     Thus, each remote node  120  is connected to a hub port  116  over a serial channel  114  using a suitable serial communication medium. The serial channel  114  may be a twisted differential pair connected at each end to an appropriate signaling interface, preferably, conforming with the Institute of Electrical and Electronics Engineers (IEEE) 802.3 specification for Ethernet, such as the above mentioned phy chip. Alternatively, an universal serial bus (USB) interface or an IEEE 1394 fire wire interface may be substituted for the Ethernet interface without departing from the scope of the invention. Further, standard category 5 (CAT 5) wire (4 twisted pairs) is preferred for the high speed data communications media in the channel  114  connecting the entertainment hub  102 , i.e., the remote stations  110  and remote feature cards  112  to the hub modules  104 . The serial data interface  128  passes locally synchronized serial data from the high speed serial channels  114  to/from the hub ports  116 . The hub ports  116  convert the serial data from serial data interface  128  to parallel data which is passed to the backplane  106  and vice versa. 
     Pulse Transformers (not shown) in each of the remote nodes  120  and hub ports  116  provide signal isolation. The hub modules  102  provide power to connected channels at a level sufficient to power a 10W Class D amplifier at each station. Channel poster is forty eight volts (48V) DC and is distributed through two pair of conductors of the CAT 5 cabling, passed through to the wiring at the hub port  116  pulse transformers center taps. The current is extracted on the receiving end to power the remote nodes  120 , drawn from the four current carrying CAT 5 conductors and the center taps of the remote node transformers. 
     For additional efficiency, the serial data clock for each channel (remote node  120 —hub port  116  connection) may be embedded into packet data for that channel using, for example, the well known Manchester encoding technique. Thus embedding the serial data clock also balances the data stream, thereby nearly eliminating the exposure to saturation in the pulse transformer. Once embedded in the data stream, the clock may be extracted from the data stream using a phase locked loop (PLL) with the link pulse function indicating the existence of a connection between each hub port  116  and its corresponding remote node  120 . 
     Data is transferred between the hub modules  102  and the remote nodes  120  using a non-Ethernet serial data frame structure at a preferred transfer rate of 10 Mb/s. Preferably, data is transferred in full duplex, each packet being synchronized with the hub backplane. The packet structure is fixed, preferably at 197 bits, and includes a preamble field, a control bus status field, and specific frames for audio (Laudio 1-4 and Raudio 1-4), intercom (Icom), hub control, and for data control. The preamble is a signature bit stream, preferably 24 bits, for synchronizing the physical layer PLL of each channel. The control bus status (CBS) field may be a single bit field that indicates when the control bus is active. The eight audio frames (Laudio 1-4 and Raudio 1-4), two each per channel, each channel having enough bandwidth to pass compressed or uncompressed audio data to/from the remote nodes, preferably two eighteen bit stereo frames for each channel. Since the intercom channel is intended to carry only voice data, the Icom frame need not be as wide the audio frame and, so, is twelve bit mono. Both the hub control frame and the data control frame are a single byte wide. 
       FIG. 4A  is a timing diagram showing how messages and data are exchanged between the local nodes  118  and the remote nodes  120  (through hub ports  116 ) across the backplane  106  using a data structure, for example, as in FIG.  4 B. The backplane  106  includes a data bus for both audio data and intercom data, an address bus, a control bus and several control lines. For the preferred embodiment, the backplane  106  includes an eight bit Address Bus (A 7 -A 0 ). with addresses being serially cycled. 0-200 in a burst at the 10 MHz backplane clock rate, i.e., one burst in every frame of the 48 KHz clock cycle. Addresses are assigned during initialization as described hereinbelow. Each address corresponds to a possible node in the network  100 . The backplane includes stereo audio on two 18 bit channels, Audio Bus (ADL 17 -ADL 0  and ADR 17 -ADR 0 ), a right and left channel. Intercom data is provided as mono audio on a 12 bit Intercom Bus (I 11 -I 0 ). Bus data is latched on the positive going edge of a Backplane Clock (BPCLK). An eight bit Control Bus (C 7 -C 0 ) provides control data information for controlling communication among devices connected to the backplane  106 . The Control Bus Status bit (CBS) signals hub ports connected to the backplane  106  when the control bus is active. A Frame Clock (FCLK) line is provided for synchronizing the hub ports  116  to the backplane  106 . A Global Reset (Greset) signal initiates a hub wide system reset. A passive pullup Need Initialization (*NEED_INIT) signal is pulled low by any device connected to the backplane that needs initialization. 
     FCLK synchronizes the entire network at the audio data-sampling rate, preferably 48 Khz, although it may be 44.1 Khz. Generally, the network sampling rate determines the number of possible addresses that can be polled at one time, and a different sampling rate may be selected with a corresponding adjustment in the number of addressable features. Since the entire network is synchronized to FCLK, all data sources and sinks (nodes  116 ,  120 ) must operate at the selected sample rate or some sub multiple thereof. i.e., 24 Khz or 12 Khz. 
     FCLK also synchronizes the hub ports  118  to the backplane and to the address bus. Further, the preamble signature synchronizes hub port  118  to remote node  120 . Since the hub ports  118  transmit a packet every FCLK cycle, the preamble provides a precise event which is detectable at the remote nodes  120  for synchronization. Generally, all audio and intercom data conversion processes must be synchronized to the preamble detection to minimize aliasing. Thus, to maintain synchronization, each remote node  120  must initiate a transmission to its corresponding hub port  116  within one frame cycle of receiving a pocket. 
     Sampled audio data is presented to the backplane  106  on a polled address basis, preferably sampled at forty eight thousand samples per second (48 KSPS). Alternately, any suitable sample rate may be selected such as 44.1 KSPS, for example. Thus, the backplane operating at a 10 Mhz BPCLK clock rate can support up to 200 addresses at this 48 KSPS-frame rate. Accordingly, cycling through addresses 0 through 200 at the backplane clock rate in a burst, one burst of 0-200 every frame clock cycle, each value addressing an audio source/sink (either at a local node  118  or at a remote device connected to a hub port  116 ) in the network, each addressed audio source/sink being presented with or providing data in turn. So, when an address is presented on the backplane  106 , the appropriate control bus signals, intercom data and audio data for the selected node are also present on the backplane. For example, a person may be using a remote station  110  to transmit an intercom message, while an audio clip may be provided to a local station  108 . During each address burst, when the address corresponding to the remote station  110  is on the address bus, the intercom data is placed on the backplane intercom bus and, sampled audio is made available when the address of the local station  108  is on the address bus. Other stations remain passive, monitoring the bus for audio or intercom data that may be directed to that particular station or feature. 
       FIG. 5  is a timing diagram for initialization wherein addresses are assigned to attached devices. In each network  100 , a single hub module  104  is assigned as backplane master. Preferably, backplane master hub module assignment is designated for a single unique slot in entertainment hub  102  although any suitable way of assigning a master may be substituted, e.g., jumper pins selecting a backplane master. The single hub module  104  master provides the drive signals for the Frame Clock. Backplane Clock, Address Bus, and Address-in-Use signals. The hub modules are interchangeable and any one may serve as backplane master, provided it is placed in the master slot position in the entertainment hub  102  (or otherwise selected). Thus, the hub interface function  130  includes master control functions that are disabled unless the particular hub module  116  is selected as master. The backplane master hub drives the backplane signals during normal operation and drives initialization signals during the network initialization process. Other devices, i.e., those not the backplane master, accept these signals as inputs. 
     During initialization the C 7 , C 6 , C 5  and C 0  control bus lines are used by the backplane master to provide individual initialization control. The C 7  line is a contention/address acquisition (CONT/*ACQ) signal which is generated by the backplane master to coordinate between a contention cycle and an address acquisition cycle in the period labeled  150 . The C 6  line is a ready for initialization (INIT-RDY) signal that, when high, indicates that a device attached to the backplane is ready to start the initialization process. The C 5  line acts as an address in use (ADD-INT-USE) signal indicating that a device address is already assigned to a node or port. The CO line is a contention (CONT_BIT) signal both during initialization and during normal operation contention. After the last device has been configured in the period labeled  152 , initialization is complete. Normal backplane operation of  FIG. 4  begins in the period labeled  154 . 
       FIG. 6  is a state diagram showing how the preferred local communication network  100  may be initialized. Network Initialization  160  is an automated process that occurs in the hub modules  104  on first power up  162  or, after a REINIT button (if included) has been pressed to request initialization. The process proceeds through three major phases: remote node scan  164 , contention  166  and address acquisition  168 . Each feature at a hub port  116  or local node  118  requires at least one backplane address for normal operation, which is assigned during initialization. 
     First, on first power up  162  every device asserts the *NEED_INIT line, pulling it low to indicate to the backplane master that attached network devices need initialization. At the initial power up  162 , the hub ports  116  provide power to corresponding connected remote nodes  120  and after a preset delay send a null packet that the remote node  120  uses for synchronization. Each remote node  120  responds returning a null packet that indicates the number of audio channels needed for that particular station or feature. Coincidentally, each remote node  120  also indicates if it needs additional audio channels by placing a non zero value in the left, and right frames of a corresponding returned audio channel. Then, the remote nodes  120  provide the null packet for a selected minimum scan time. If any of a remote node&#39;s audio channels are unused, then the unused frames are driven to all zeros (00000h). Each corresponding hub port  140  requests addressing for each filled (non-zero) audio frame, with every requesting hub module  104  or feature card  108  holding the INIT_RDY line low during the remote scan sequence  164 . 
     Following the remote node scan  164 , every hub port  116  and each feature card  108  configures its backplane-connected audio bus port as a passive high, active low I/O port. Then, the unassigned hub ports  116  and feature cards  108  begin shifting their respective unique serial number (preferably a factory-set 36-bit number) onto the CONT_BIT line synchronized by the frame clock signal, while simultaneously monitoring the CONT_BIT. If for any monitoring device, the value of the CONT_BIT does not match what it shifted out, then another device is also requesting initialization, i.e., devices are in contention; and, each unmatched device discontinues shifting its serial number out and releases the passive pullup CONT_BIT line for the remainder of the contention cycle. Each matching device continues to write their serial numbers to the CONT_BIT until, eventually, only a single device remains actively requesting addresses. The remaining unmatched devices, i.e., those that have placed their respective CONT_BIT output in a high impedance state, wait until the next contention cycle, when the next unassigned device is selected. The matching device proceeds to the address acquisition cycle  168 . 
     For each address acquisition cycle  168 , again synchronized by the FCLK signal, the backplane master sequentially cycles through the all addresses as the matching device monitors the passive pullup *ADD_IN_USE line. Each previously configured device asserts the *ADD_IN_USE line as each of its addresses appears on the address bus. When an available address is identified (i.e., the ADD_IN_USE line is not asserted). the backplane master assigns the identified available address to the requesting internal hub port. Unassigned devices continue monitoring, identifying and requesting addresses until all port address assignment requirements have been fulfilled. As each acquiring device has completed its configuration cycle, it releases the *NEED_INIT line and waits for the initialization process to complete. 
     The contention cycle  166  and address acquisition cycle  168  are repeated until all attached devices have been configured, as indicated by the *NEED_INIT line being released high and then proceeding to Normal Operation  170 . On each subsequent power up  162 , unless a new device has been added, *NEED_INIT will not be pulled low and so, will be high (all assignments having been retained in local or non-volatile storage) and the system proceeds directly to the Normal Operation  170  state. 
     After initialization  160  and upon commencing Normal Operation  170 , additional local nodes  118  or hub modules  116  may be added to the network by powering down the network  100 , attaching the devices to the entertainment hub  102 , another powering up to re-execute the initialization process  160 . On power up the newly-attached device asserts the *NEED_INIT line low. In response, the backplane master then enters the Initialization process  160 , assigning addresses as required. 
     Additional remote nodes  120  may be attached to the network (“hot plugged”) at a configured hub port  116  and so, do not need to be initialized. Further, if remote audio sources/sinks are attached to an existing remote node and the attachment/replacement reduces or does not change the number of sources/sinks at that node, Normal Operation  170  may continue uninterrupted. However, if the number of audio sources/sinks is increased, e.g., a single audio source/sink at a remote node is replaced with a multiple audio sources/sinks, a power down cycle  162  must be initiated to restart the initialization process  160 . Then, when each hub module  104  scans its hub ports  116  through the remote node scan cycle  162 , the added sources/sinks are detected and identified by asserting the *NEED_INIT line. 
     By contrast, removing nodes from the network, typically, does not require reinitialization. Remote nodes may be physically removed from the network  100  for example, by simply disconnecting from the serial stream  114  cable or by turning off the device or remote feature card  112 . The removed device&#39;s hub port retains its address so that the remote node  120  may be re-attached later and it may seamlessly begin to function provided a network re-initialization  160  or a power cycle  162  does not occur before reattachment. However, if the network is re-initialized or power cycled after removal, reattaching the device requires a re-initialization  160 , just as if a new device were being added. Initialized local nodes  118  also can be removed and reattached to the backplane without re-initialization, provided the reattached local node retains its address information. Otherwise, the local device should be reset and, network power cycled to re-initialize the new/replaced local device and node. 
     On the first initialization of a hub module  104 , each hub port  116  acquires a backplane address. The hub port  116  then signals its address to its connected remote node  120 , which may or may not use or respond to the address. Hub ports  116  do not require a response (ACK or ERR messaging) to their own initiated messages. However, each remote node  120  must signal its corresponding hub port  116  using a hub message to change the listening settings of the hub port  116 . The corresponding hub port  116  responds either with an ACK or an ERR response message within 2 frame clock cycles. The serial data stream may include hub control and data control messaging when initiated by a local node  118  or hub port  116  in addition to audio and intercom data which are transferred continuously. Hub control and data control messages are selectively included in packets and passed in the serial stream, one byte per packet. The hub control message frame designates an audio or intercom channel in remote nodes  120 . Each remote node  120  queries its corresponding hub port  116  for its present sourcing node and its listening channel settings, as well as, setting the listening channels. Automatically, on first hub power up or on re-initialization, each hub port  116  selects the sourcing channel. Each frame cycle includes only one byte of hub messaging in the hub control field. As each hub message is passed, byte by byte, the entire message is re-assembled at the receiving node. i.e., either at the hub module  104  at one end or at the remote station/feature card  110 ,  112  at the other. Preferably, each hub message is four (4) bytes wide and prefaced with an attention byte (e.g., FFh) to notify the intended receiver (either hub module  104  or remote station/feature card  110 ,  112 ) that a hub message is to follow. 
     The attention byte may be followed by a command directing the receiving node regarding how to handle the audio data on the channel. Examples of commands provided in this second command byte are shown in Table 1 below. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
             
            
               
                 NUL 
                 00h 
                 ‘do nothing, idle value 
               
               
                 SET 
                 01h 
                 ‘set the channel to value 
               
               
                 GET 
                 02h 
                 ‘get the channel&#39;s value 
               
               
                 ACK 
                 03h 
                 ‘acknowledge message with channel and value returned 
               
               
                 ERR 
                 04h 
                 ‘error with channel and value returned 
               
               
                   
               
            
           
         
       
     
     The command byte is followed by a channel byte that, preferably, includes two (2) four (4) bit fields. The first 4-bit field indicates whether the receiving device is receiving or sending audio and, so, is a sink or a source. The second field selects an audio field, i.e., intercom, audio  1 , audio  2 , audio  3  and audio  4  for the received/sent audio data. The command byte is followed by an eight bit value ranging from 1 to 200 and indicating the channel address. 
     Local control messaging provides control for peer to peer communication between nodes, primarily for sharing information or controlling either a local feature card  108  or remote feature card  112 . The control message structure may be similar to that of hub messaging wherein one byte in the data control field is passed per packet. However, local control messaging within the communication hub  102  may be quite different. Each local control message contains a multibyte preamble, a destination address, a source address, an indication of the message size, the message and a checksum value for verifying the message validity. Within the communication hub  102 , control information is sent over the control bus (C 7 -C 0 ) which also is an 8 bit aside, contention bus. All hub nodes  116  and local nodes  118  have access to this bus and must contend for control. Preferably, the control bus is passive pull up, active pull down. So, when all connected nodes are idle, the bus is all ones (FFh) indicating that a node is not accessing the bus. 
       FIG. 7A  shows a state diagram  180  of how a node gains access to the control bus. First, before beginning its transmission, in state  182 , nodes requiring access monitor the bus until a quiet time is detected. If two or more nodes attempt to communicate simultaneously, an arbitration process  184  assigns priority based on the control message preamble. For confirmation, the values on the control bus are mirrored back to the remote node via the serial stream data frame, delayed by one frame. Local nodes are directly attached to the contention bus and compensate for the delay to remote nodes during the arbitration process. 
       FIG. 7B  shows an example of the preferred control message structure. The control message preamble, which is preferably 8-10 bytes, is utilized for bus access arbitration. Each preamble byte is one of two possible values, either zero (00h) or one (01h) and sets the contention bit CONT_BIT in the control bus. The 10 byte preamble string represents a pseudo-random 10 bit binary number pattern, with the lowest 10 bit value has the highest bus priority. The preamble is followed by a destination address which is a single byte that contains the network address of the destination node. A single byte source address follows the destination address and contains the network address of the message source node. Two bytes are assigned to designate the Number Of Bytes (NOB) in the control message payload. The payload may be as large as 64K Bytes and is the substance of the control message or data. Finally, the payload is followed by a two byte checksum that is the twos complement of the sum of the entire message less the preamble and the checksum itself. 
     As noted hereinabove, idle nodes monitor the control bus for activity in  182 . When the control bus is quiet and the *CBS bit is one, a node may attempt to begin a transmission by asserting *CBS (pulling it low) in  184  and, begin bus arbitration by sending the preamble. The transmitting node must monitor its message transmission (via the return packet or directly at the control bus) to negotiate for control of the bus, detect a collision with another message, or to detect a serial stream data error. The node attempting to initiate transmission monitors the value of the preamble returned from the bus to confirm whether that node has access to the bus. If the preamble value is returned without error, the node has access to the control bus and continues to transmit in  186 . However, if the node does not have access it releases the *CBS bit, in  188  ceases transmission and waits until the control bus is idle before attempting to transmit again in  184 . 
       FIG. 8  is an example of a control message reception state diagram  190 . Nodes that are directly connected to the control bus (i.e., hub ports  116  and local nodes  118 ) through the backplane continually monitor the bus and the *CBS bit in  192 . Message transmission begins with the assertion of the *CBS bit in  194  by the transmitting node. Each monitoring node parses the message header, which includes the preamble, destination address, source address and NOB fields in  196  to determine if the node is the message destination. Either the message may be directed to a specific address or it may be broadcast, for example as an intercom message. If the message is addressed to a node in  198 Y, that node continues processing the message. Otherwise, in  198 N, the nodes discard the message and continue to monitor the *CBS bit until it returns to idle in  192 , to receive the next new message. 
     As described above, addresses between 1 and 200 are assigned to each connected node in the initialization process  160 . A remote node  120  sets its address by querying its corresponding hub port for its remote node address(s). Address OOh is reserved for broadcast messages and so, no node is assigned this address. All nodes process broadcast messages. Further, one or more addresses may be reserved for the conference intercom function and only the conference feature node may acquire this reserved address. 
     For synchronization, all backplane address locations must be polled within a FCLK cycle. Further, each serial stream transmission cycle (one upstream and one downstream) cycle completes, preferably, in less than a single frame clock cycle. 
       FIG. 9  is an example of a typical preferred embodiment home communication system  200  with elements identical to the basic system  100  of  FIG. 2  labeled identically. In addition to the entertainment hub  102 , several room stations,  202 ,  204 ,  206 ,  208 ,  210  and  212  are shown that are physically located at different zones or rooms. A video doorbell  214  is locatable at an exterior door. A main communications panel  216  is provided for control from a conveniently selected location. Outside temperature sensors  218  are locatable to provide external temperature information to the system that may be retrieved at any room station  202 - 212  or other connected peripheral. In addition, since the network  200  is a digital one or more computers  220 , printers  222  may be attached, directly, to send or receive communications or entertainment data, the remote node/remote station feature being provided as a hardware feature of the computers  220  or in software executed by the computer  220 . A wireless keyboard  224  may communicate with the system  200  over the computer  220  or directly. e.g. through an IR port  126 . Further access to the Internet may be provided, either through the computer  220  or through a direct connection at the hub port, e.g., through a cable modem or digital subscriber line (DSL) modem. 
     A home theater system  226  may be connected to the network. The home theater system  226  may be capable of playing or displaying multimedia data received from the network or, of sending multimedia data, such as audio files over the home communications system  200  to individual room stations  202 - 212 , for example. A telephone  228  may be included, such that music from the network is played as background music when the telephone  228  is placed on hold and, to provide voice mail that is stored on the system  200 . An entertainment/sound system  230  may be connected to the network and located in a media room. Like the home theater system  226  the sound system  230  can play audio data directly received from the network and may be capable, for example, of placing audio data extracted from an audio cassette onto the network. A television  232 , e.g., digital audio TV or high definition TV (HDTV), can be connected to the network  200 . The television  232 , like the home theater system  226 , and the sound system  230 , can play audio or multimedia data directly from the network and is capable of placing multimedia data or audio data on the network  200 . Also, local, specialized controls may be made available at different zones throughout the network. These local controls  234  can provide, for example, home or away settings to vary the capability of the system. Temperature control  236  for heating and cooling may be connected for independent control at any station  202 - 212 . Also, a programmable logic controller (PLC)  238  may be adapted, if available, allowing independent remote control of lights  239  and other such controlled appliance from enabled stations  202 - 212 . 
       FIG. 10  is an example of the room station.  110 . In this example, the room station includes multiple buttons,  240 ,  242 ,  244 ,  246 ,  248 ,  250 ,  252 ,  254 , for selecting various functions from the room stations. A microphone input  256  is provided for receiving vocal input and a small speaker  258  is included, if loudspeakers are not provided, for intercom function. Jacks  260 ,  262 , are also included for audio input. A digital communication jack  264  in this example, an ethernet connection or category 5 wiring, is also included for connecting the local station  110  to the network. Also, a display  266 , such as a liquid crystal diode (LCD) display, is included, providing a simple local graphical interface. Thus, preferred room stations include the capability to act as an audio source unit, an audio receiver unit and an intercom unit. Sound tone and volume may be set at each individual room station  110  independently of settings at other room stations  110 . Further, a door station does not require the audio source function and, so, a suitable door station results by omitting the audio function from a room station  110 . 
       FIG. 11  is a block diagram of a remote station  110 . Remote station  110 , typically includes a serial data exchange  270 , a programmable digital loop filter  272 , an audio compression/decompression (CODEC)  274 , a microcontroller or microprocessor  276 , a local interface  278  and local storage  280 . The local interface  278  may include a display  282 , such as a LCD display  266 , for displaying status information and time, for example, and individual buttons  284  for manual input, such as providing commands to connected room stations, remotely disabling command input from other stations. Commonly used commands may be maintained in a command menu provided at the display  282 . The local storage  280  may be any suitable storage, in particular random access memory (RAM). Further, the RAM may be static RAM (SRAM), dynamic RAM (DRAM) or non-volatile RAM such as what is typically referred to as Flash memory. As described hereinabove, power  286  is supplied over the high speed serial data channel  114 . 
     The serial data exchange  270  may be a transceiver or, a phy chip as described hereinabove with reference to the hub module  104 . The audio CODEC  274  provides an analog/digital interface between analog audio (provided to the local station  110  from the network or provided by the local station  110 , e.g., from a radio tuner) and digital audio to/from the programmable digital loop filter  272 . The CODEC  274  converts digital audio data from the programmable digital loop filter  272  into analog audio for a local audio performance and converts analog audio received at the local station into digital audio data which is provided to the programmable digital loop filter  272 . Preferably, the audio CODEC  274  is a Crystal CS4227 6-channel 20-bit CODEC chip from Cirrus Logic. The preferred CODEC  274  can support at least one 18-bit stereo/audio channel and one intercom channel. Additional, optional channels may be included. The non-volatile storage  280  locally maintains stored information and program control including a bootstrap program for bootstrap start up of the microcontroller  276 . Preferably, the non-volatile storage is flash memory or EEPROM and may include up to several megabytes of storage. The serial data exchange  270  extracts received serial data from the high-speed serial data channel  114  and, embeds the serial data clock into serial data for transmission across a high-speed serial data channel  114 . 
       FIG. 12  is a block diagram of the programmable digital loop filter  272 . The programmable digital loop filter  272  includes a receive buffer  290 , a transmit buffer  292 , a CODEC interface  292  and a microcontroller interface  296 . The receive buffer  290  is essentially a serial-to-parallel shift register receiving data (RXD) clocked by receiver clock (RXCLK) from the serial data exchange  270  and converts that serial data to parallel data which is provided as audio channel data on lines  298  to CODEC interface  294  and hub control and data on lines  300  to microcontroller control interface  296 . The receive buffer  290  also provides intercom data  302  to the CODEC interface  294  and extracts a hub sync signal  304  from the received data. The transmit buffer  292  receives parallel data from the CODEC interface  294  and microcontroller interface  296  which it converts to serial data (TXD) that is provided to the serial data exchange  270 , clocked by transmission clock (TXCLK). The transmit buffer also provides a transmit enable signal (TXEN) that indicates when the serial data from the station should be transferred through the serial data exchange  270  across the high-speed serial data channel  114 . 
     Parallel data from the CODEC interface  294  includes intercom data on lines  306  and audio channel data on lines  308  as well as hub control and data from the microcontroller interface on lines  310 . The CODEC interface  294  passes received data from the receive buffer to the CODEC  274  and passes data from the CODEC  274  to the transmit buffer  292  for transmission across the high-speed data channel  114 . The microcontroller  296  presents data from the receive buffer  290  to the microcontroller  276  and passes data from the microcontroller  276  back to the transmit buffer  292 . The hub sync signal  304  is generated when the receive buffer  290  senses a preamble in the receive data stream, which initiates a pulse that is the hub sync signal  304 . Additionally, the receive buffer  290  parses serial data from the serial data exchange  270  and identifies audio data for the audio channels  298  and control data and control signals  300  for the microcontroller interface  296 . The hub sync signal  304  synchronizes the remote station to the hub. Although the data may be received at the remote station somewhat delayed from the original transmission, due to transmission channel delays, for example, the extracted signal is a true replica of what the hub transmits. Likewise the hub receives an exact replica of what the remote station transmits. 
     Local feature cards  108  may be formed by directly interfacing the hub function control  130  of the hub module with the CODEC  274 , thereby providing the audio function directly to the hub control function which interfaces the audio digital data to the backplane instead of to hub ports. Local feature cards  108 , may include, for example, a radio tuners providing broadcast radio, e.g., AM, FM and wideband radio such as weather band radio or television broadcast bands. 
     Thus, the multi-zone media network of the present invention provides digital audio available for use at each zone of a structure or different rooms of a house. Further, multi-zone media network includes room stations that can inject audio into the data stream and onto the network. So, at each room station is converted from digital data to analog audio and locally amplified for clear CD quality sound. Since the audio is transferred over the preferred multi-zone media network as digital data, high-cost, low-loss wiring that is required to route high quality audio is unnecessary. Instead, relatively inexpensive CAT 5 wiring may be used to pass data from the hub to the room stations. Further, the room stations independently control and select what is played in the room from one of several audio data channels being streamed, rather than merely play what is being broadcast. In addition, each remote station itself can broadcast or receive independent of and simultaneously with other remote stations. Also, each remote station can be programmed for individual specific needs such as including radio station presets on remote stations equipped with a radio tuner. Alarms or limited functionality may be included, such as to the ability to monitor another remote using the multi-zone media network&#39;s intercom function. 
     While the invention has been described in terms of preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims.