Patent Publication Number: US-9426006-B2

Title: Low power partial functionality communication link

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of application Ser. No. 11/703,080, filed on Feb. 7, 2007, incorporated herein by reference. This application also claims the benefit of U.S. Provisional Patent Application No. 61/056,410, filed on May 27, 2008, incorporated herein by reference. 
    
    
     BACKGROUND 
     A multimedia system transmitting, for example, video, audio, and controls may enter a standby mode, enabling limited performance, in order to reduced power consumption. In some cases, limited performance refers to transmitting only a subset of the data types that are transmitted in the non-standby mode. For example, a multimedia source in standby mode may still transmit and receive system control data that enable it to read the properties of a sink device, that is also in standby mode, to which it is connected. In other words, there is no need to turn on the source and/or sink devices in order to read their properties. 
     Current video, audio, or multimedia solutions transmit some or all of their standby and/or low power data types over dedicated wires. For example, a High-Definition Multimedia Interface (HDMI™) includes dedicated wires for DDC, HPD, and CEC controls. DisplayPort™ includes two wires for transmitting the auxiliary data. The above solutions implement the standby mode by turning off the transceiver(s) that are not required for transmitting the data types that are supported by the standby mode. For example, in HDMI, only the transceivers that are physically connected to the wires used for transmitting the standby mode data types are operated in standby mode. In other words, standard HDMI systems include dedicated control wires that are connected to dedicated modems, and only these modems operate in standby mode. Moreover, the standby mode bandwidth is much smaller than the regular bandwidth, and allocating dedicated wires for the standby mode increases the total number of required wires because the standby wires are not used for significantly increasing the bandwidth of the regular mode of operation. 
     BRIEF SUMMARY 
     In one embodiment, a transceiver includes a first mode of operation for transmitting data of at least two types, over at least a first subset of conductive wires included in a cable, wherein at least one of the data types is uncompressed high definition digital video and another data type is bidirectional data. The transceiver includes a second low power partial functionality mode of operation for transmitting and receiving data of at least one type over at least a second subset of the conductive wires used by the first mode of operation for transmitting the uncompressed high definition digital video, wherein at least one data type transmitted in the first mode of operation is not transmitted in the second low power partial functionality mode of operation. 
     In one embodiment, a device includes a transmitter for transmitting uncompressed high definition digital video multiplexed with control data over a set of conductive wires, and a receiver for receiving control data over at least a first subset of the conductive wires. The device includes a transceiver for transmitting and receiving bidirectional data over at least a second subset of the conductive wires used by the transmitter, wherein the transmitter and the transceiver do not operate simultaneously and the transmitter transmits at least one data type that is not transmitted by the transceiver. 
     In one embodiment, a communication link includes a first mode of operation for transmitting data of at least two types, over at least a first subset of conductive wires included in a cable, wherein at least one of the data types is uncompressed high definition digital video transmitted from a source device to a sink device and another data type is a first bidirectional data transmitted between the source device and the sink device. The communication link includes a second low power partial functionality mode of operation for transmitting a second bidirectional data between the source device and the sink device over at least a second subset of the conductive wires used by the first mode of operation for transmitting the uncompressed high definition digital video, wherein the first bidirectional data includes at least one data type that is not transmitted in the second bidirectional data. 
     In one embodiment, a device includes a first mode of operation for transmitting and receiving bidirectional data and transmitting uncompressed high definition digital video over at least a first subset of conductive wires included in a cable. The device includes a second low power partial functionality mode of operation for transmitting and receiving bidirectional data over at least a second subset of the conductive wires used by the first mode of operation for transmitting the uncompressed high definition digital video, wherein the ratio between the power consumption of the first mode of operation and the power consumption of the second low power partial functionality mode of operation is at least 3:1. 
     In one embodiment, a transceiver includes a first mode of operation for transmitting a first data stream including a plurality of data types over at least a first subset of conductive wires included in a cable, wherein the throughput of the first data stream is at least 1.1 Gbps. The transceiver includes a second low power partial functionality mode of operation for transmitting a second bidirectional data stream including less data types than the first data stream over at least a second subset of the conductive wires used for transmitting the first data stream, wherein the throughput of the second data stream is less than approximately 1/10 of the throughput of the first data stream. 
     In one embodiment, a device includes a first mode of operation for transmitting, over at least a first subset of conductive wires included in a cable, a first data stream having a throughput of more than approximately 1.1 Gbps including at least two data types, wherein at least one of the data types is transmitted bidirectionally. The device includes a second low power partial functionality mode of operation for transmitting, over a second subset of the conductive wires used by the first mode of operation, a second bidirectional data stream having a throughput of less than approximately 100 Mbps, wherein at least one data type transmitted in the first stream is not transmitted in the second stream. 
     In one embodiment, a system includes a first mode of operation for transmitting, over at least a first subset of conductive wires included in a cable, a first asymmetric data stream including at least two data types. The system includes a second low power partial functionality mode of operation for transmitting, over a second subset of the conductive wires used by the first mode of operation, a second bidirectional data stream, wherein the ratio between the throughput of the first data stream and the throughput of the second data stream is at least approximately 10:1 and wherein at least one data type transmitted in the first mode of operation is not transmitted in the second low power partial functionality mode of operation. 
     Implementations of the disclosed embodiments involve performing or completing selected tasks or steps manually, semi-automatically, fully automatically, and/or a combination thereof. Moreover, depending upon actual instrumentation and/or equipment used for implementing the disclosed embodiments, several embodiments could be achieved by hardware, by software, by firmware, or a combination thereof. In particular, with hardware, embodiments of the invention could exist by variations in the physical structure. Additionally, or alternatively, with software, selected functions of the invention could be performed by a data processor, such as a computing platform, executing a software instructions or protocols using any suitable computer operating system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments of the present invention are herein described, by way of example only, with reference to the accompanying drawings. No attempt is made to show structural details of the embodiments in more detail than is necessary for a fundamental understanding of the embodiments. In the drawings: 
         FIGS. 1A-1B  are schematic diagrams of one embodiment of the invention; 
         FIGS. 2A-2B  are state machines of embodiments of the invention; 
         FIG. 2C  is a schematic diagram of one embodiment of the invention; 
         FIGS. 3-4  illustrate data types in accordance with one embodiment of the invention; 
         FIG. 5  illustrates a MDTCL in accordance with one embodiment of the invention; 
         FIG. 6  illustrates a receiving path in accordance with one embodiment of the invention; 
         FIG. 7  illustrates a transmitting path in accordance with one embodiment of the invention; 
         FIG. 8  is a schematic diagram of one embodiment of the invention; 
         FIG. 9  illustrates a sink side of a MDTCL in accordance with one embodiment of the invention; 
         FIG. 10  illustrates a source side of a MDTCL in accordance with one embodiment of the invention; 
         FIG. 11  illustrates a multimedia system in accordance with one embodiment of the invention; 
         FIG. 12  illustrates one embodiment of a state machine of a MDTCL in accordance with one embodiment of the invention; 
         FIG. 13  illustrates a communication device in accordance with one embodiment of the invention; 
         FIG. 14  illustrates a communication device in accordance with one embodiment of the invention; 
         FIG. 15  illustrates a communication device in accordance with one embodiment of the invention; 
         FIG. 16  is a flow diagram of a modulation based method in accordance with one embodiment of the invention; 
         FIG. 17  is a flow diagram of a symbol rate based method in accordance with one embodiment of the invention; and 
         FIG. 18  is a flow diagram of a throughput based method in accordance with one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth. However, the embodiments of the invention may be practiced without these specific details. In other instances, well-known hardware, software, materials, structures and techniques have not been shown in detail in order not to obscure the understanding of this description. In this description, references to “one embodiment” or “an embodiment” mean that the feature being referred to is included in at least one embodiment of the invention. Moreover, separate references to “one embodiment” in this description do not necessarily refer to the same embodiment. Illustrated embodiments are not mutually exclusive, unless so stated and except as will be readily apparent to those of ordinary skill in the art. Thus, the invention may include any variety of combinations and/or integrations of the embodiments described herein. Also herein, flow diagrams illustrate non-limiting embodiment examples of the methods, and block diagrams illustrate non-limiting embodiment examples of the devices. Some flow diagrams operations are described with reference to the embodiments illustrated by the block diagrams. However, the methods of the flow diagrams could be performed by embodiments of the invention other than those discussed with reference to the block diagrams, and embodiments discussed with reference to the block diagrams could perform operations different from those discussed with reference to the flow diagrams. Moreover, although the flow diagrams may depict serial operations, certain embodiments could perform certain operations in parallel and/or in different orders from those depicted. Moreover, the use of repeated reference numerals and/or letters in the text and/or drawings is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
     The term “different data types” or “data types” or “types of data” as used herein denotes symbols that are used for different purposes and/or feature different characteristics. Examples of different data types include, but are not limited to: video pixel data; audio data; video synchronization control data, such as horizontal and vertical video picture synchronizations; video system controls, such as CEC, HPD and DDC signals; or general data transmissions, such as Ethernet data, USB data, or RS232 data; or infra-red (IR) control data. The data types may also be differentiated by features such as time sensitivity characteristics of the data, the required quality of transmission associated with the data, or the required throughput for each type of data. Examples of such data types include, but are not limited to: (i) time sensitive data, such as video pixel data or audio data, and time insensitive data, such as Ethernet data and video system controls; or (ii) data requiring high transmission quality, such as video synchronization controls or video system controls, and data requiring relatively low transmission quality, such as video pixel data. 
     The term “multi data type communication link” (MDTCL) as used herein denotes a communication link that transfers at least two different data types. The different data types may be multiplexed into one or more data streams that are transmitted over the MDTCL by the same one or more modems. In the embodiments of the present invention, a MDTCL comprises at least one active mode of operation and at least one low-power partial-functionality (LPPF) mode of operation. While in the LPPF mode of operation, the MDTCL: (i) consumes less power than the power consumed in the active mode of operation, (ii) transmits at a lower throughput than the throughput transmitted in the active mode of operation, (iii) transfers only a subset of the data types that are transferred in the active mode of operation, and (iv) optionally transfers one or more low bandwidth data types that are not transferred in the active mode of operation. It is to be understood that the communication channel is not turned off while operating in the LPPF mode of operation. For example, assuming the LPPF mode of operation is utilized for transmitting system control data, there should be no need to establish the communication channel each time a system control datum is to be transmitted. It is also to be understood that the LPPF is a mode of operation and therefore it may transmit data repetitively without changing the mode of operation. In one embodiment, the LPPF mode of operation is non isochronous and non mesochronous. 
     The term “high definition” as used herein denotes at least 720p, 1080i with a total bitrate of more than 1 Gbit per second; wherein the total bitrate equals to the number of lines times the number of columns times the refresh rate times the number of bits per pixel. 
       FIG. 3  illustrates different data types as a function of the required transmission quality and the required bandwidth. As illustrated, video pixel data requires high bandwidth and low transmission quality; general data, audio data, video synchronization control data, and video system control data all require lower bandwidth and require higher transmission quality in increasing order.  FIG. 4  illustrates different data types as a function of the required transmission quality and the required time sensitivity. As illustrated, video pixel data, audio data, and video synchronization control data all require strict timing and require transmission quality in increasing order; general data, such as Ethernet, RS232 data, or USB data, and video system control data are both less time sensitive and require transmission quality in increasing order. It is to be understood that  FIGS. 3 and 4  are just schematic illustrations and should not limit the scope of the disclosed embodiments. 
     In one embodiment, a communication link having at least two modes of operation, operating over the same physical media, connects between a sink device and a source device. As a non limiting example, the sink device may be a display device and the source device may be an HDMI source or an Ethernet source. The link identifies the source and operates according to the type of the source. 
       FIG. 1A  illustrates one embodiment of a MDTCL having two modes of operation. The MDTCL has two transceivers ( 12   a ,  12   b ). A first mode of operation  13 , referred to as the active mode, transmits relatively low throughput bidirectional control signals  17  and relatively high throughput unidirectional data signals  18 , over the four conductive wires ( 11   a ,  11   b    11   c ,  11   d ) of the cable  11 . A second mode of operation  14 , referred to as the low-power partial-functionality (LPPF) mode, transmits relatively low throughput bidirectional control signals  16 , over a subset ( 11   c ,  11   d ) of the conductive wires of the cable  11 . The selector  15  illustrates that the required mode of operation may be set as needed. In one example, the bidirectional control signals  17  are multi media controls and/or HDMI controls; the unidirectional data signals  18  are uncompressed high definition digital video signals; and the bidirectional control signals  16  are standby signals. 
     Optionally, in the active mode of operation  13 , the high throughput data  18  is transmitted over the four conductive wires ( 11   a - 11   d ) of the cable  11  and the control data  17  is multiplexed with the high-throughput data  18 . Alternatively (not shown in the drawings) the high throughput data  18  and the multiplexed controls  17  are transmitted over a first subset of the conductive wires of the cable  11 , and the controls  16  of the LPPF mode of operation  14  are transmitted over a subset of the first subset. Optionally, the cable  11  may be one of the following cables: CAT5, CAT5e, CAT6, CAT6a, CAT7, or coax. 
     In one embodiment, the MDTCL has two or more LPPF modes of operation, featuring different power consumptions, transfer of different data types, and/or different available functionalities. A few examples of LPPF functionalities include: transferring Ethernet without video, transferring the system controls, transferring audio, or a combination thereof. According to another example, the LPPF mode of operation may transfer one or more of the following data types: standby control data, multimedia control data, auto-negotiation data, topology discovery data, network addressing data, general data, or consumer electronic control (CEC) data. Examples of electronic devices which may take advantage of such an LPPF mode of operation include one or more of the following: a display (such as a television, projector, or plasma display), a multimedia source, an audio system, a receiver, a tuner, an amplifier, or an HDMI compatible device. 
       FIG. 5  illustrates one embodiment of a MDTCL having one active mode of operation and two LPPF modes of operation. The different modes of operations are implemented using multi function transceivers denoted in  FIG. 5  by small squares. The multi function transceivers have active, #1 LPPF, and #2 LPPF modes of operations. As illustrated, the DVD  59  transmits uncompressed content to the TV  62 . Therefore, MDTCLs  60  and  61  are in the active mode of operation, i.e. the transceivers are in their active mode. The communication is transmitted through the DLNA compliant audio video (AV) receiver with DLNA client capabilities  56 . The PC DLNA server  51  transmits to the TV  62  CEC communications and a compressed video stream using DLNA over Ethernet. Therefore, MDTCLs  52  and  55  operate in the #2 LPPF mode of operation which supports the required functionalities, e.g. CEC transactions and compressed video over Ethernet. The transceivers implementing the #2 LPPF mode of operation consume less power than the power consumed when operating in the active mode of operation. As illustrated, PC  51  is connected to TV  62  in a Daisy-chain through TV  54 . TV  54  may be in standby mode. In order to save power while supporting the various MDTCL modes of operation, TV  54  may have a plurality of standby modes corresponding to the MDTCL modes of operation. In one embodiment, the standby mode of operation is determined by the MDTCL mode of operation. The STB  57  is in standby mode. Therefore, MDTCL  58  operates in the #1 LPPF mode of operation, which supports only CEC transactions. The TV  62  receives uncompressed video from DVD  59  and compressed video from PC  51  and, as an example, may use the two streams for displaying picture in picture. 
     In one embodiment, the LPPF modes of operation and their corresponding standby modes are determined according to one or more of the following: (i) the amount of the transmitted bandwidth, (ii) the type of transmitted data, or (iii) the required functionality of the MDTCL. Examples of three LPPF modes of operation include the following: (i) an LPPF mode for transmitting video system control data, (ii) an LPPF mode for transmitting video system control data and audio data, and (iii) an LPPF mode for transmitting video system control data and general data, such as Ethernet data. The third example may also be considered as a low power mode because the Ethernet transmission consumes less power than uncompressed video transmission. In one embodiment, 100 Mb Ethernet is transmitted over two pairs of wires of a CATx cable, and video system control data is transmitted over the other two pairs of wires of the CATx cable. 
       FIG. 2A  illustrates one embodiment of a state machine for operating a MDTCL over the same physical media (e.g. a copper cable). In this embodiment, the communication link has an Ethernet mode of operation  24  and two MDTCL modes of operation, named LPPF mode of operation  26  and active mode of operation  28 . Optionally, during the Link Partner Detection mode of operation  22 , each side connected to the link performs auto negotiation with the other side, if exists. The Link Partner Detection mode of operation  22  may be entered upon waking up, turning on, or resetting. In one embodiment, one or more interfaces are tested. For example, an Ethernet interface may be tested  22   a ; if the Ethernet interface is established, the state of the communication link changes to Ethernet mode of operation  24 ; otherwise, a MDTCL application, such as HDMI, may be tested  22   b ; if both sides support the MDTCL properties, the state of the communication link changes to LPPF mode of operation  26 . Optionally, if the link is plugged out ( 28   c ,  28   d ) or there is an invalid link response  26   a , the MDTCL switches back to the link partner detection mode  22 . 
     Referring to  FIG. 1B  and  FIG. 2A , optionally, upon entering the LPPF mode of operation  26 , the communication link receives from both sides ( 19   a ,  19   b ) information about their modes of operation. If both sides ( 19   a  and  19   b ) are in active modes of operation, the communication link switches to its active mode of operation  28 . If at least one of the sides ( 19   a  or  19   b ) is in standby mode, the communication link stays in the LPPF mode of operation  26 . 
     While operating in the active mode of operation  28 , if the link is down  28   b  or one of the sides ( 19   a ,  19   b ) changes its mode to #1 LPPF or #2 LPPF ( 28   a ,  28   e ), the communication link enters the LPPF mode of operation  26 . Optionally, during the active mode of operation  28 , one of the following combinations of data types may be transmitted over the communication link: uncompressed high definition digital video data and bidirectional control data, uncompressed high definition digital video and audio data and bidirectional control data, uncompressed high definition digital video and audio data and bidirectional control data and Ethernet general data. 
     Optionally, during the LPPF mode of operation  26 , the communication link is able to transmit control signals needed for the system to determine whether it should change its mode of operation, and/or perform other standby mode activities, such as the standby mode activities defined by DVI™ (Digital Visual Interface), HDMI™, DisplayPort™, or DIVA™ standards. In one embodiment, the LPPF mode of operation  26  may support one or more of the following control signals: (i) control signals needed for nodes in the network to go into and out of standby mode, (ii) control signals supporting network topology changes performed while the devices are in standby mode, (iii) control signals for finding the network topology while some of the network is in standby, or (iv) control signals for assigning identification numbers to the various nodes in the network while the network is in standby mode. In one embodiment, the LPPF mode of operation  26  supports the control signals defined by the HDMI standard. For example, the LPPF mode of operation  26  may support one or more of the following HDMI control signals: EDID DDC transactions, HPD, 5V status signals, or transparent transfer of CEC transactions. 
       FIG. 2B  illustrates one embodiment of a state machine for operating a MDTCL over the same physical media. In this embodiment, the multi function transceivers used by the MDTCL have an active mode of operation  28  and two LPPF modes of operation ( 26   a ,  26   b ). In one example, each mode of the multi function transceiver processes different data type(s) or different combination(s) of data types, such that the different modes of operation ( 26   a ,  26   b ,  28 ) feature different functionalities and optionally different power consumptions. 
     During the link partner detection mode  22 , the system sets the function(s) to be operated by the multi function transceiver. For example, if the devices connected to both sides of the MDTCL are in their active mode of operation, the multi function transceivers are set to be ( 22   c ) in the active mode of operation  28 . If a first device connected to the MDTCL is in the active mode, and a second device connected to the MDTCL is in another mode, a communication takes place between the two devices, optionally resulting in the second device changing its mode to the active mode of operation  28 , or the first device changing its mode to another mode that is accepted by the second device. The MDTCL may also switch between the various LPPF modes of operation ( 27   a ,  27   b ). For example, assuming a first and a second device connected to the MDTCL are in the #1 LPPF mode of operation  26   a , the first device may transmit a message to the second device that may agree to switch mode, resulting in both devices switching  27   a  to the #2 LPPF mode of operation  26   b . Alternatively, assuming the first and the second device connected to the MDTCL are in the #2 LPPF mode of operation  26   b , the first device may notify the second device it switches to the #1 LPPF mode of operation, resulting in both devices switching to the #1 LPPF mode of operation. 
       FIG. 2C  illustrates a configuration supporting the feature of switching between the various LPPF modes of operation using messages. In the illustrated embodiment, the #1 LPPF mode of operation  2 C 1  transmits over pairs of wires  11   c  and  11   d . The #2 LPPF mode of operation  2 C 3 , which transmits over the four pairs of wires ( 11   a - 11   d ), transmits approximately the same data over pairs of wires  11   c  and  11   d  as the #1 LPPF mode of operation and transmits additional data over pairs of wires  11   a  and  11   b . Because the same data transmissions over the same pairs of wires are used by the #1 and the #2 modes of operations, it is possible to switch between the #1 and the #2 modes of operations using messages transmitted over pairs of wires  11   c  and  11   d.    
     Various auto negotiations may be implemented for different devices running different interfaces. The various auto negotiation protocols may differ in the following non-limiting features: (i) using different conductive wires for identification. For example, Ethernet uses the pair of conductive wires A and B, while a MDTCL may use the pair of conductive wires C and D; (ii) using different transmission amplitudes. For example, a MDTCL may utilize amplitude which is below the lower threshold of Ethernet; or (iii) using different pulse shapes. For example, a MDTCL may use a pulse shape that is different from the pulse shape used by Ethernet. 
     US patent application Ser. No. 11/703,080, filed on Feb. 7, 2007, which is incorporated herein by reference in its entirety, discloses methods and systems, which may be used with the discussed embodiments, for transmitting the following data types over the same wires: (i) uncompressed high definition digital video data, (ii) uncompressed audio data, (iii) bidirectional control data, and and/or (iv) general data, such as Ethernet. 
     Power Saving Techniques 
     Since the bandwidth of the LPPF mode of operation is significantly lower than the bandwidth of the active mode of operation, the LPPF mode of operation may utilize one or more of the following techniques for power reduction. 
     The LPPF mode of operation may utilize a simpler modulation scheme than the modulation scheme used in the active mode of operation  28 .  FIG. 16  is a flow diagram illustrating one method comprising the following steps: in step  160 , transmitting in a first mode of operation a first data stream, comprising at least two data types, over conductive wires using a first modulation scheme. And in step  162 , transmitting in a second LPPF mode of operation a second data stream, comprising less data types than the first data stream, over at least a subset of the conductive wires used for transmitting the first data stream, using a second modulation scheme that is simpler than the first modulation scheme. 
     The LPPF mode of operation may utilize a much lower symbol rate than the symbol rate used in the active mode of operation  28 .  FIG. 17  is a flow diagram illustrating one method comprising the following steps: in step  170 , transmitting in a first mode of operation bidirectional data between a source device and a sink device and unidirectional uncompressed high definition digital video from the source device to the sink device over at least a first subset of conductive wires comprised in a cable. And in step  172 , transmitting in a second LPPF mode of operation bidirectional data between the source device and the sink device over at least a second subset of the conductive wires used by the first mode of operation for transmitting the unidirectional uncompressed high definition digital video. Wherein, the bidirectional data transmitted in the second LPPF mode of operation comprises at least one data type that is also transmitted in the bidirectional data of the first mode of operation, and the transmissions in the second LPPF mode of operation are have a much lower symbol rate compared to the transmissions in the first mode of operation. 
     The transmissions in the LPPF mode of operation may utilize a subset of the wires used for the active mode of operation  28 . For example, when operating over a multi twisted pairs cable, such as CAT5e, one pair may be used for transmitting and one pair for receiving. 
     Instead of transmitting full duplex over the same wires, in the LPPF mode of operation, a unidirectional transmission may be transmitted over a first set of wires and a unidirectional transmission may be transmitted to the opposite side over a second set of wires, where the first and second sets of wires are also used by the active mode of operation. Utilizing unidirectional transmissions in the LPPF mode of operation reduces the receiver&#39;s signal analysis workload and as a result reduces the receiver&#39;s power consumption. 
     low amplitude transmissions may be used in the LPPF mode of operation. 
     In the LPPF mode of operation, the link may be activated only when valid data is available for transmissions, instead of activating the link also when there is no data to transmit, usually using idle symbols. 
     In the LPPF mode of operation, the link may be activated on request and may be maintained only when additional transmissions are expected soon. Synchronization and timing problems as a result of turning off the link may be resolved by a self clocking code, such as Manchester II, wherein the clock is embedded within the data. 
     In the LPPF mode of operation, signal acquisition may be performed each time a transaction is to be performed. 
     In the LPPF mode of operation, a modem having at least two modes of operation may be utilized as further discussed below. The plural modes modem may be implemented as one or more modems connected to the same media through the same analog front ends or through different analog front ends. In one embodiment, the first mode of operation is a 10 Gbps Ethernet modem and the second mode of operation is a low power modem utilizing one or more of the above described techniques (lower frequency, fewer conductive wires, low amplitude, partial functionality, maintaining the link, Synchronization, signal acquisition, lower symbol rate, or modem with two modes of operation). 
       FIG. 18  is a flow diagram illustrating one method comprising the following steps: in step  180 , transmitting in a first mode of operation, over a cable comprising conductive wires, a first asymmetric data stream comprising at least two data types. And in step  182 , transmitting in a second LPPF mode of operation, over a subset of the conductive wires used by the first mode of operation, a second bidirectional data stream having a much lower throughput (e.g. at most approximately 1/10 of the throughput) and comprising less data types than the first asymmetric data stream. 
     MDTCL Modems 
       FIG. 6  illustrates one example of a receiving path of a receiver used in a MDTCL. The illustrated receiver has (i) an active mode of operation, in which it receives a video stream  66   a , an audio stream  66   b , and a control stream  66   c ; and (ii) an LPPF mode of operation, in which it receives only the control stream  66   c . While the receiver is in its active mode of operation, the video stream  66   a , the audio stream  66   b , and the control stream  66   c  are received from the communication medium through the active mode of operation version of the receiver&#39;s analog front end  69   a , the active mode of operation version of the DSP receiver  69   b , and the active mode of operation version of the link layer data demultiplexer  63 . The optional selector  65  selects the control stream from the active path. In another embodiment, the selector  65  is not required because the control stream received in the active mode of operation is forwarded to a first destination and the control stream received in the LPPF mode of operation is forwarded to a second destination. While the receiver is in its LPPF mode of operation, the control stream  66   c  is received from the communication medium through the LPPF mode of operation version of the receiver&#39;s analog front end  69   a , the LPPF mode of operation version of the DSP receiver  69   c , and the LPPF mode of operation version of the link layer data demultiplexer  64 . As illustrated by  FIG. 6 , in one embodiment, at least some part of the receiver&#39;s analog front end is shared between the active receiving path and the LPPF receiving path because the different data types are received from the same wires. The optional system controller  67  sets the mode of operation of the selector  65  and the receiver&#39;s analog front end  69   a  according to the system controls received from the link layer data demultiplexer  63  the link layer LPPF data demultiplexer  64 . 
       FIG. 7  illustrates one example of a transmitting path of a transmitter used in a MDTCL. The illustrated transmitter has (i) an active mode of operation, in which it transmits a video stream  70 , an audio stream  71 , and a control stream  72 ; and (ii) an LPPF mode of operation, in which it transmits only the control stream  72 . While the transmitter is in its active mode of operation, the video stream  70 , audio stream  71 , and control stream  72  are transmitted to the communication medium through the active mode of operation version of the link layer data multiplexer  73 , the active mode of operation version of the transmit modulator  75 , and the active mode of operation version of the transmitter&#39;s analog front end  103   a . The optional selector  77  selects the video stream  70 , audio stream  71 , and control stream  72  from the active path. In another embodiment, the selector  77  is not required because the streams of the active mode of operation are forwarded to a first analog front end and the control stream of the LPPF mode of operation is forwarded to a second analog front end. While the transmitter is in its LPPF mode of operation, the control stream  72  is transmitted to the communication medium through the LPPF mode of operation version of the link layer LPPF data multiplexer  74 , the LPPF mode of operation version of the transmit modulator  76 , and the LPPF mode of operation version of the transmitter&#39;s analog front end  78 . As illustrated by  FIG. 7 , in one embodiment, at least some part of the transmitter&#39;s analog front end is shared between the active transmitting path and the LPPF transmitting path because the different data types are transmitted over the same wires. The optional system controller  79  sets the mode of operation of the selector  77  and the transmitter&#39;s analog front end  78  using the illustrated “mode” signal, and provides the system controls to the link layer data multiplexer  73  and to the link layer LPPF data multiplexer  74 . 
     MDTCL Transceivers 
       FIG. 8  illustrates an optional configuration, including a source transceiver  81  and a sink transceiver  82 , which is explained in detail by  FIGS. 9 and 10 . In the illustrated example, source transceiver  81  transmits to sink transceiver  82  video data and audio data; and bidirectional control data is transmitted between the source transceiver  81  and the sink transceiver  82 . The video, audio and control data may be transmitted over the same wires. 
       FIG. 9  illustrates one embodiment of the sink side of a MDTCL, wherein the sink is a television, which receives a video stream  90   a , an audio stream  90   b , and a bidirectional control stream  90   c . While the TV is in its active mode of operation, the optional system controller  91   a  sets selectors  91   b  and  91   c  to pass the active path and sets the analog front ends of the transmitted and the receiver ( 93   a ,  93   b ) to operate in their active mode of operation, according to the system controls received from the link layer data demultiplexer  98   a . The system controller  91   a  also provides the system controls to the link layer data multiplexer  94   a . The TV transmits the control stream  90   c  to the bidirectional communication medium through the active mode of operation version of the link layer data multiplexer  94   a , the active mode of operation version of the transmit modulator  95   a , the active mode of operation version of the transmitter&#39;s analog front end  93   a , and the hybrid circuit  92 . The TV receives the video stream  90   a , the audio stream  90   b , and the control stream  90   c  from the bidirectional communication medium through the hybrid circuit  92 , the active mode of operation version of the receiver&#39;s analog front end  93   b , the active mode of operation version of the DSP receiver  97   a , and the active mode of operation version of the link layer data demultiplexer  98   a.    
     While the TV is in its LPPF mode of operation, the optional system controller  91   a  sets selectors  91   b  and  91   c  to pass the LPPF path and sets the analog front ends of the transmitter and the receiver ( 93   a ,  93   b ) to operate in their LPPF mode of operation according to the system controls received from the link layer LPPF data demultiplexer  98   b . The system controller  91   a  also provides the system controls to the link layer LPPF data multiplexer  94   b . The TV transmits the a control stream  90   c  to the bidirectional communication medium through the LPPF mode of operation version of the link layer data multiplexer  94   b , the LPPF mode of operation version of the transmit modulator  95   b , the LPPF mode of operation version of the transmitter&#39;s analog front end  93   a , and the hybrid circuit  92 . The TV receives a control stream  90   c  from the bidirectional communication medium through the hybrid circuit  92 , the LPPF mode of operation version of the receiver&#39;s analog front end  93   b , the LPPF mode of operation version of the DSP receiver  97   b , and the LPPF mode of operation version of the link layer data demultiplexer  98   b.    
       FIG. 10  illustrates one embodiment of the source side of a MDTCL, wherein the source may be an STB, DVD, Blu-Ray, game console, PC, or any other device that transmits a video stream  100   a , an audio stream  100   b , and a bidirectional control stream  100   c . While the source device is in its active mode of operation, the optional system controller  101  sets selectors  102   a  and  102   b  to pass the active path and sets the analog front ends of the transmitter and the receiver ( 103   a ,  103   b ) to operate in their active mode of operation according to the system controls received from the link layer data demultiplexer  108   a . The system controller  101  also provides the system controls to the link layer data multiplexer  104   a . The source device transmits a video stream  100   a , an audio stream  100   b , and a control stream  100   c  to the bidirectional communication medium through the active mode of operation version of the link layer LPPF data multiplexer  104   a , the active mode of operation version of the transmit modulator  105   a , the active mode of operation version of the transmitter&#39;s analog front end  103   a , and the hybrid circuit  106 . The source device receives a control stream  100   c  from the bidirectional communication medium through the hybrid circuit  106 , the active mode of operation version of the receiver&#39;s analog front end  103   b , the active mode of operation version of the DSP receiver  107   a , and the active mode of operation version of the link layer data demultiplexer  108   a.    
     While the source device is in its LPPF mode of operation, the system controller  101  sets selectors  102   a  and  102   b  to pass the LPPF path and sets the analog front ends of the transmitter and the receiver ( 103   a ,  103   b ) to operate in their LPPF mode of operation according to the system controls received from the link layer LPPF data demultiplexer  108   b . The system controller  101  also provides the system controls to the link layer LPPF data multiplexer  104   b . The source device transmits a control stream  100   c  to the bidirectional communication medium through the LPPF mode of operation version of the link layer data multiplexer  104   b , the LPPF mode of operation version of the transmit modulator  105   b , the LPPF mode of operation version of the transmitter&#39;s analog front end  103   a , and the hybrid circuit  106 . The source device receives a control stream  100   c  from the bidirectional communication medium through the hybrid circuit  106 , the LPPF mode of operation version of the receiver&#39;s analog front end  103   b , the LPPF mode of operation version of the DSP receiver  107   b , and the LPPF mode of operation version of the link layer data demultiplexer  108   b.    
     Ethernet Low Power Partial Functionality Operation Mode 
     In one embodiment, a modified Ethernet interface includes an LPPF mode of operation that transmits only a predefined set of data types. Ethernet with LPPF mode is especially useful when operating with consumer electronic devices, such as, but not limited to, display devices, or source devices such as STBs, DVD players, Video players, Blu-Ray players, game consoles, or multimedia servers. 
     In one example, a consumer electronic source device may use Ethernet for transferring, in its active mode of operation, video, audio, and control data to a display device. While the consumer electronic source device does not transmit video and audio data, for example, when it is in standby mode, the consumer electronic source device may still need to transmit some system controls and/or audio data, which consume much less bandwidth than consumed in the active mode of operation. 
       FIG. 13  illustrates one embodiment of a communication device, also referred to as a modified Ethernet interface, having two types of PHY DSPs. The first PHY DSP is a standard Ethernet PHY DSP  133 , and the second PHY DSP is an LPPF PHY DSP  134 . The LPPF mode of operation may utilize one or more of the power reduction techniques described herein. 
     The data link layer (MAC)  131  of the modified Ethernet interface may operate the standard Ethernet PHY DSP  133  or the LPPF PHY DSP  134 . The optional system controller  130   a  sets selectors  132  and  135  to pass the signals of the required mode of operation. Optionally, the analog front end  136  has also two modes of operation, corresponding to the two PHY modes of operation. In one embodiment, the MAC  131  determines which PHY to operate. In another embodiment, the application layer  130  determines which PHY to operate using the following steps: 
     The MAC  131  on a first side of the communication link receives from the application layer  130  an indication about the required mode of operation of the communication link, for example, active, #1 LPPF, or #2 LPPF modes of operation. 
     The MAC  131  communicates with the device on the other side of the communication link in order to coordinate the operation of the communication link. For example, the first device (connected to the first side of the communication link) may request from the second device (connected to the second side of the communication link) to switch from #1 LPPF mode to active mode; if the second device accepts the request, the communication link switches to active mode; if the second device does not accept the request, the communication link may stay in its current mode of operation, or switch to a predefined mode of operation such as the default mode of operation, or reset the link. In one embodiment, when one device connected to the communication link switches from the active mode to one of the LPPF modes, or from a comprehensive LPPF mode to slimmer LPPF mode, the device on the other side must also change its mode of operation. 
     In one embodiment, the application layer  130  determines which of the available physical layers to operate and which data types are to be transmitted over the communication link. In this case, only frames associated with the allowable data types are forwarded to the MAC  131 ; frames associated with other data types are not forwarded to the MAC  131 . In one embodiment, the application layer  130  determines the type associated with each frame by communicating with the data sources. For example, a video source may be able to identify the data types of the frames it supplies, such as video data, audio data, and AV controls, and to forward that information to the application layer  130 . In one embodiment, the application layer  130  determines the type associated with each frame according to the source of each frame. For example: an Ethernet port supplies a general data type; an HDMI port supplies a video data stream, an audio data stream and control streams; and an audio system provides an audio data stream. 
     In another embodiment, the application layer  130  sets the communication link&#39;s mode of operation and notifies the MAC  131  about the data type associated with each frame it receives. According to the selected mode of operation and the data type associated with each frame, the MAC  131  determines which frame will be transmitted over the communication link and selects the PHY that will be used for modulating the signals. For example, and with reference to  FIG. 14 , a DLNA server  140  is able to transmit high definition video and compressed video over Ethernet. In the active mode of operation, the MAC layer  141  transmits all the types of data it receives from the DLNA server  140  through 10 Gbps Ethernet PHY DSP  143 . In the #1 LPPF mode of operation, the MAC layer  141  transmits only audio data and system control data it receives from the DLNA server  140  through #1 LPPF PHY DSP  144 . In the #2 LPPF mode of operation, the MAC layer  141  transmits only system control data it receives from the DLNA server  140  through #2 LPPF PHY DSP  144 . The power consumption of the 10 Gbps Ethernet PHY DSP  143  is significantly higher than the power consumption of the #1 LPPF PHY DSP  144  which is significantly higher than the power consumption of the #2 LPPF PHY DSP  145 . 
     It is to be understood that  FIGS. 13 and 14  may be amended to include designated data link layers for each mode of operation, similar to the structures illustrated in  FIGS. 9 and 10 .  FIG. 15  illustrates a variation of  FIG. 13  including separate MACs for the Ethernet path and the LPPF path. The Ethernet MAC  154  and the LPPF MAC  156  communicate with application layer  130  through selector  152  that is optionally operated by system controller  150 . 
     In one embodiment, the LPPF mode does not change the structure of the Ethernet frame. Maintaining the frame structure enables smooth transitions between network hops. In one embodiment, the LPPF mode and the active mode utilize different frame structures. Utilizing different frame structures may improve the efficiency and reduce overheads. 
     Diva Low Power Partial Functionality Operation Mode 
     It is to be understood that although the name “DIVA” is used herein, the claimed invention should not be limited, in any way, to the Digital Interface for Video and Audio (DIVA) initiated by a working group of some leading Chinese consumer electronics companies, described in http://www.diva-interface.org 
       FIG. 11  illustrates one embodiment of a multimedia system including four pairs of wires. Uncompressed video data and uncompressed audio data, optionally multiplexed with video control data, are transmitted by three transmitters ( 111   a ,  112   a ,  113   a ), over three links ( 111   b ,  112   b ,  113   b ), to three receivers ( 111   c ,  112   c ,  113   c ). Transceivers  114   a  and  114   c  form a bidirectional MDTCL  114   b . In one embodiment, approximately 4.5 Gbps of video and audio are transmitted over three links ( 111   b ,  112   b ,  113   b ), and 4.5 Gbps of data is transmitted, half-duplex, over the fourth link  114   b . Optionally, each of the four communication links ( 111   b ,  112   b ,  113   b , and  114   b ) is made of a pair of copper wires. Optionally, the transmissions are SerDes (Serializer/Deserializer). 
       FIG. 12  illustrates one embodiment of the state machine of MDTCL  114   b  of  FIG. 11  adapted to DIVA. The MDTCL  114   b  may transfer, in its active mode of operation  128 , the following data types over a pair of wires: bidirectional system control data, bidirectional general data, and optional unidirectional audio data from transceiver  114   c  to transceiver  114   a . Optionally, the general data includes Ethernet Data. The MDTCL  114   b  may feature one or more of the following LPPF modes of operation: (i) a first optional LPPF mode of operation  124  for transferring bidirectional system controls; (ii) a second optional LPPF mode of operation  126  for transferring bidirectional system controls and unidirectional audio from transceiver  114   c  to transceiver  114   a ; or (iii) a third optional LPPF mode of operation (not illustrated in the figure) for transferring bidirectional system controls and bidirectional general data in a rate that is lower than the transfer rate of the bidirectional data utilized by the active mode of operation. For example, in its active mode of operation, the system may transmit half duplex general data in a rate of 4.5 Gbps, while in its third LPPF mode of operation, the system may transmit half duplex general data in a rate of 1 Gbps, 100 Mbps, 10 Mbps, or 1 Mbps. 
     The LPPF mode of operation may utilize one or more of the power reduction techniques described herein. For example, operating the MDTCL  114   b  using different rates, using a smaller amplitude, and/or transmitting over the link only when there is a need to transmit data. 
     Although the embodiments have been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. 
     Certain features of the embodiments, which may, for clarity, be described in the context of separate embodiments, may also be provided in various combinations in a single embodiment. Conversely, various features of the embodiments, which may, for brevity, be described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. 
     The embodiments are not limited in their applications to the details of the order or sequence of steps of operation of methods, or to details of implementation of devices, set in the description, drawings, or examples. 
     While the methods disclosed herein have been described and shown with reference to particular steps performed in a particular order, it will be understood that these steps may be combined, sub-divided, or reordered to form an equivalent method without departing from the teachings of the embodiments. Accordingly, unless specifically indicated herein, the order and grouping of the steps is not a limitation of the embodiments. 
     Any citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the embodiments of the present invention. 
     While the embodiments have been described in conjunction with specific examples thereof, it is to be understood that they have been presented by way of example, and not limitation. Moreover, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and scope of the appended claims and their equivalents. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures.