JP 2009-60204 A 2009.3.19
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`(19) Japan Patent Office (JP)
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`(12) JAPANESE UNEXAMINED PATENT
`APPLICATION PUBLICATION (A)
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`(11) Patent Application
`Publication No.
`JP 2009-60204 A
`(P2009-60204A)
`(43) Publication Date: March 19, 2009 (Heisei 21)
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`FI
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` (51) Int. Cl.
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`(22) Date of Filing
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` Examination Request: Not yet No. of Claims: 17 OL (Total 15 pages)
`(21) Application No.
`JP 2007-223646
`(71) Applicant 000005821
`(P2007-223646)
`Panasonic Corporation
`August 30, 2007
`1006, Kadoma, Kadoma-shi, Osaka-fu
`
`(Heisei 19)
`100072431
`(74) Agent
`Kazuo Ishii, Patent Attorney
`
`100117972
`(74) Agent
`Shin’ichi Kawasaki, Patent Attorney
`
`(72) Inventor Takanori Iwamoto
`
`c/o Matsushita Electric Industrial Co., Ltd.
`1006, Kadoma, Kadoma-shi, Osaka-fu
`F Term (Reference)
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`processing unit
`TMDS signal
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`unit
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`switch processing
`HDMI attribute
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`TMDS input unit
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`TMDS output unit
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`DDC input unit
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`DDC output unit
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`Hot plug output unit
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`Hot plug input unit
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`monitor unit
`TMDS line
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`attribute SW unit
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`TDMS block input/output
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`attribute SW unit
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`DDC block input/output
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`attribute SW unit
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`Hot plug input/output
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`Power supply input unit
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`Power supply output unit
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`output SW unit
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`Power block input/
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`Connector
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`cable
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`(54) [Title of Invention] SOURCE/SINK DUAL-PURPOSE DEVICE
`
`
`(57) [Abstract]
`[Problem] To provide a source/source/sink dual-purpose device
`capable of detecting a function attribute of a HDMI device
`connected to a single connector.
`[Resolution Means] In a source/sink dual-purpose device (100)
`conforming to the HDMI standard, a voltage line monitor unit
`(160) detects a voltage level (VL1) of a connector power supply
`line (111) that connects one of first function means and second
`function means to an external device (20) conforming to the
`HDMI standard, an TDMS line monitor unit (170) detects a
`voltage level (VL2) of a TMDS_CLK line, and an HDMI
`attribute switching unit (180) determines a function (J) of the
`external device (20) on the basis of the detected two voltage
`levels (VL1, VL2).
`[Selected Drawing] FIG. 1
`
`monitor unit
`
`Power supply line
`
`
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`JP 2009-60204 A 2009.3.19
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`[Scope of Patent Claims]
`[Claim 1]
`A source/sink dual-purpose device conforming to the HDMI standard, comprising first function means
`for realizing a function as a source device and a second function means for realizing a function as a sink device,
`the source/sink dual-purpose device further comprising a connector for connecting one of the first
`function means and the second function means to an external device conforming to the HDMI standard,
`first voltage level monitor means for detecting the voltage level of the power line of the connector,
`second voltage level monitor means for detecting the voltage level of a TMDS_CLK line of the
`connector, and
`function determination means for determining a function of the external device on the basis of the
`detected two voltage levels.
`[Claim 2]
`The source/sink dual-purpose device according to claim 1, further comprising operation mode
`determining means for determining an operation of the first function means and the second function means
`based on the determined function.
`[Claim 3]
`The source/sink dual-purpose device according to claim 2, further comprising operation control means
`for controlling the first function means and the second function means based on the determined operation.
`[Claim 4]
`The source/sink dual-purpose device according to any of claims 1, 2, and 3, wherein the first voltage
`level monitor means generate a binary first level signal based on a power source level of the detected power
`source line and
`the second elastic level monitor means generate a binary second level signal based on a voltage level
`of the detected TMDS_CLK line.
`[Claim 5]
`The source/sink dual-purpose device according to claim 4, wherein the function determining means
`determine that the external device is not connected when the first level signal is Low and the second level signal
`is Low.
`[Claim 6]
`The source/sink dual-purpose device according to claim 5, wherein the operation mode determining
`means determine to put the first function means and the second function means into a standby mode.
`[Claim 7]
`The source/sink dual-purpose device according to claim 6, wherein the operation control means make
`the first function means and the second function means high impedance.
`[Claim 8]
`The source/sink dual-purpose device according to claim 4, wherein the function determining means
`determine that the external device is abnormal when the first level signal is High and the second level signal is
`High.
`[Claim 9]
`The source/sink dual-purpose device according to claim 8, wherein the operation mode determining
`means determine to put the first function means and the second function means into a shunt mode.
`[Claim 10]
`The source/sink dual-purpose device according to claim 9, wherein the operation control means make
`the first function means and the second function means high impedance.
`[Claim 11]
`The source/sink dual-purpose device according to claim 4, wherein the function determining means
`determine that the external device is a sink when the first level signal is Low and the second level signal is High.
`[Claim 12]
`The source/sink dual-purpose device according to claim 11, wherein the operation mode determining
`means determine to put the first function means and the second function means into a source mode.
`[Claim 13]
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`The source/sink dual-purpose device according to claim 12, wherein the operation control means enable
`the first function means.
`[Claim 14]
`The source/sink dual-purpose device according to claim 4, wherein the function determining means
`determine that the external device is the source when the first level signal is High and the second level signal is
`Low.
`
`[Claim 15]
`The source/sink dual-purpose device according to claim 14, wherein the operation mode determining
`means determine to put the first function means and the second function means into a sink mode.
`[Claim 16]
`The source/sink dual-purpose device according to claim 15, wherein the operation control means enable
`the second function means.
`[Claim 17]
`A source/sink dual-purpose device conforming to the HDMI standard, comprising first function means
`for realizing a function as a source device and second function means for realizing a function as a sink device,
`the source/sink dual-purpose device comprising a connector for connecting one of the first function
`means and the second function means to an external device conforming to the HDMI standard,
`first voltage level monitor means for detecting the voltage level of the power line of the connector,
`second voltage level monitor means for detecting the voltage level of a TMDS_CLK line of the
`connector, and
`operation control means for controlling the first function means and the second function means on the
`basis of the detected two voltage levels.
`[Detailed Description of Invention]
`[Technical Field]
`[0001]
`
`The present invention relates to a source/sink dual-purpose device conforming to the HDMI standard
`and combines attributes of a source device and a sink device.
`[Background Art]
`[0002]
`
`In recent years, AV systems conforming to the HDMI (High Definition Multimedia Interface) standard
`are becoming widespread. HDMI is one of the multimedia interfaces and can transfer video and audio signals
`from an AV playback device to an AV output device without data compression, and therefore, it does not require
`a dedicated chip such as a decoder or software. Furthermore, video signals, audio signals, and control signals
`can be transmitted by a single cable, and thus there are advantages such as being able to simplify the wiring of
`the device and the like (for example, see patent document 1).
`[0003]
`
`An AV system conforming to the HDMI standard is normally configured by connecting a source device
`that supplies AV signals and a sink device that receives the AV signals via a cable conforming to the HDMI
`standard (hereinafter referred to as an “HDMI cable”). A device for supplying a video signal or an audio signal
`such as an STB, a DVD player, or a digital video camera is used as the source device. A device such as a
`television receiver (hereinafter referred to as “television”) or a projector that outputs video or audio is used as
`the sink device. It is conceivable that these constitute a source/sink dual-purpose device having both a function
`of the source device and a function of the sink device, such as a television with a built-in DVD player.
`[0004]
`
`FIG. 4 illustrates one example of a conceivable source/sink dual-purpose device. The source/sink dual-
`purpose device 10 includes a sink device corresponding block 11, a source device corresponding block 12, a
`connector 13a, and a connector 13b. The sink device corresponding block 11 has a function of a sink device,
`and the source device corresponding block 12 has a function of a source device. The sink device corresponding
`block 11 and the source device corresponding block 12 are respectively connected to a connector 13a and a
`connector 13b conforming to the HDMI standard. When the source/sink dual-purpose device 10 is configured
`as a television with built-in DVD player, the television corresponds to the sink device corresponding block 11
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`JP 2009-60204 A 2009.3.19
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`and the DVD player corresponds to the source device corresponding block 12.
`[0005]
`
`Thus, in the source/sink dual-purpose device 10 configured as the television with built-in DVD player,
`a video signal played back by the DVD player is normally displayed as a video by a television display, and an
`audio signal is output as audio from a speaker of the television. However, there are times when a user would
`like to view the video on a projector without viewing the video on the television display. Furthermore, it may
`be desired that the video and audio captured by the digital video camera be played back by a display and a
`speaker of the source/sink dual-purpose device 10.
`[0006]
`
`In order to respond to such desires, it is required to receive a signal from an external source device to
`the sink device corresponding block 11 provided in the source/sink dual-purpose device 10 and to supply a
`signal from the source device corresponding block 12 to the external sink device. In order to satisfy such a
`request, the connectors 13a and 13b described above are provided.
`[0007]
`
`Next, an AV system configured by connecting an external sink device or an external source device to
`the source/sink dual-purpose device 10 will be described with reference to FIG. 5. FIG. 5(A) illustrates an AV
`system 1a configured by connecting to a source device 20src so that the source/sink dual-purpose device 10 is
`used as a sink, and FIG. 5(B) illustrates an AV system 1b configured by connecting to a sink device 20snk so
`that the source/sink dual-purpose device 10 is used as a source. Connectors 21 and 22 conforming to the HDMI
`standard are also provided at input and output ends of the source device 20src and the sink device 20snk,
`respectively. Note that the source device 20src and the sink device 20snk are collectively referred to as an
`external device 20.
`[0008]
`
`As illustrated in FIG. 5(A), in the AV system 1a in which the source/sink dual-purpose device 10 is
`used as a sink of the source device 20src, such as a digital video camera or a DVD player, the sink device
`corresponding block 11 is connected to the source device 20src via the connector 13a, an HDMI cable 40, and
`a connector 21 conforming to the HDMI standard. In this case, the video signal and the audio signal played back
`by the source device (for example, a digital video camera) 20 are transmitted through the HDMI cable 40 to the
`sink device corresponding block (television) 11 of the source/sink dual-purpose device (for example, a
`television with built-in DVD player) 10, and the video image is displayed on the built-in display or audio is
`output from the speaker.
`[0009]
`
`As illustrated in FIG. 5(B), in the AV system 1b in which a source/sink dual-purpose device 10 serves
`as a source for a sink device such as a projector, the source device corresponding block 12 is connected to the
`sink device 20snk via the connector 13b, the HDMI cable 40, and a connector 22 conforming to the HDMI
`standard. In this case, the video signal and the audio signal played back in the source device corresponding
`block (DVD player) 12 are transmitted to a sink device (for example, a projector) 30 via the HDMI cable 40
`and are projected as impactful video on a large screen.
`[0010]
`
`In an AV system conforming to the HDMI standard, a video signal, an audio signal, and a control signal
`are transmitted between devices via an HDMI cable, and thus a connector conforming to the HDMI standard is
`provided at input and output ends of each device. This principle also holds for the source/sink dual-purpose
`device 10, and the sink device corresponding block 11 and source device corresponding block 12 are
`respectively connected to the external device 20 via the connectors 13a and 13b (and the HDMI cable 40).
`[0011]
`
`However, providing dedicated connectors to each of the sink device corresponding block 11 and the
`source device corresponding block 12 leads to increased cost and size of the device. Moreover, it is necessary
`to determine whether the external device 20 connected to the input and output dual-purpose device 10 is the
`source device, which is on the output side, or the sink device, which is on the input side. Furthermore, it is
`necessary to correctly select one of the two, namely the connector 13a (sink side) and the connector 13b (source
`side), to connect the external device 20, which is a troublesome task for the user.
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`[0012]
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`(5)
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`JP 2009-60204 A 2009.3.19
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`Therefore, it is desirable to use a single connector for each block connector. In fact, in the field of AV
`equipment that does not conform to the HDMI standard, technology is widespread (see patent documents 2
`through 4) that uses a single terminal for both the input terminal and the output terminal of video and audio
`signals to automatically switch the connection state according to the input and output state of the video and
`audio signals.
`[Patent Document 1] JP 2007-79176 A
`[Patent Document 2] JP H07-038817 A
`[Patent Document 3] JP 2001-086416 A
`[Patent Document 4] JP H04-368666 A
`[Disclosure of Invention]
`[Problem to Be Solved by Invention]
`[0013]
`
`Applying the switching art proposed in patent documents 2 through 4 described above, it is also
`conceivable that the source/sink dual-purpose device conforming to the HDMI standard is switched to the sink
`or the source according to whether the external device connected to one connector is the sink side or the source
`side. However, the source/sink dual-purpose device that is the subject of the present invention and the device to
`be connected are connected by an HDMI cable.
`[0014]
`
`The video signal and the audio signal transferred on the HDMI cable, as well as the control signal, are
`signals according to the HDMI standard. A device conforming to the HDMI standard does not have a function
`for notifying a connection partner of a function attribute representing whether the device itself is a source or a
`sink. Therefore, in the source/sink dual-purpose device conforming to the HDMI standard, it is not possible to
`obtain information relating to a functional attribute indicating whether the device on the connected side is the
`source or the sink. That is, according to the function attribute of the device connected to one connector, its own
`source/sink function cannot be automatically switched.
`[0015]
`
`Moreover, even were the function attribute of the connected device can be known by some means,
`problems such as impedance mismatches occur when the input (sink) and output (source) of the source/sink
`dual-purpose device are simply switched. Thus, the switching are used in general AV equipment cannot be
`applied to source/sink dual-purpose devices conforming to the HDMI standard.
`[0016]
`
`The present invention has been configured in view of such conventional problems, and an object thereof
`is to provide a source/sink dual-purpose device that can detect a functional attribute of an HDMI device
`connected to a single connector. To provide a source/sink dual-purpose device capable of automatically
`switching its own functions according to the detected function attribute of the device.
`[Means for Solving Problem]
`[0017]
`
`In order to achieve the foregoing object, the source/sink dual-purpose device of the present invention
`
`is
`
`a source/sink dual-purpose device conforming to the HDMI standard, provided with first function
`means for realizing a function as a source device and second function means for realizing a function as a sink
`device,
`
`a source/sink dual-purpose device conforming to the HDMI standard, provided with a second function
`means for realizing, being provided with
`a connector for connecting one of the first function means and the second function means to an external
`device conforming to the HDMI standard,
`first voltage level monitor means for detecting the voltage level of the power line of the connector,
`second voltage level monitor means for detecting the voltage level of a TMDS_CLK line of the
`connector, and
`function determination means for determining a function of the external device on the basis of the
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`detected two voltage levels.
`[0018]
`
`It is preferable that the source/sink dual-purpose device of the present device is further provided with
`operation mode determining means for determining an operation of the first function means and the second
`function means based on the determined function. Furthermore, it is preferable that operation control means for
`controlling the first function means and the second function means based on the determined operation are further
`provided.
`[0019]
`
`Moreover, it is preferable that the first voltage level monitor means generate a binary first level signal
`based on a power source level of the detected power source line and that the second elastic level monitor means
`generate a binary second level signal based on a voltage level of the detected TMDS_CLK line.
`[0020]
`
`Here, the function determining means determine that the external device is not connected when the first
`level signal is Low and the second level signal is Low. In this case, the operation mode determining means
`determines to put the first functional means and the second functional means into a standby mode. That is the
`operation control means make the first function means and the second function means high impedance.
`[0021]
`
`Also, the function determining means determine that the external device is abnormal when the first
`level signal is High and the second level signal is High. In this case, the operation mode determining means
`determines to put the first functional means and the second functional means into a shunt mode. That is the
`operation control means make the first function means and the second function means high impedance.
`[0022]
`
`Additionally, the function determining means determine that the external device is a sink when the first
`level signal is Low and the second level signal is High. In this case, the operation mode determining means
`determines to put the first functional means and the second functional means into a source mode. That is, the
`operation control means enables the first function means.
`[0023]
`
`Furthermore, the function determining means determine that the external device is a source when the
`first level signal is High and the second level signal is Low. In this case, the operation mode determining means
`determines to put the first functional means and the second functional means into a sink mode. That is, the
`operation control means enables the second function means.
`[0024]
`
`Moreover, the second source/sink dual-purpose device of the present invention is
`a source/sink dual-purpose device conforming to the HDMI standard, provided with first function
`means for realizing a function as a source device and second function means for realizing a function as a sink
`device,
`
`the source/sink dual-purpose device being provided with a connector for connecting one of the first
`function means and the second function means to an external device conforming to the HDMI standard,
`first voltage level monitor means for detecting the voltage level of the power line of the connector,
`second voltage level monitor means for detecting the voltage level of a TMDS_CLK line of the
`connector, and
`operation control means for controlling the first function means and the second function means on the
`basis of the detected two voltage levels.
`[Effect of Invention]
`[0025]
`
`In the present invention, in a source/sink dual-purpose device connected to an external HDMI device
`via a single connector, the device’s own function can be automatically set according to the function or state of
`the connected HDMI device.
`[Best Mode for Carrying Out Invention]
`[0026]
`
`Before describing embodiments of the present invention in detail, first, main characteristics of the
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`present invention will be described. The source/sink dual-purpose device according to the present invention is
`configured to conform to the HDMI standard and is provided with two monitor units for detecting a state of
`signals flowing through an HDMI cable. When an external device is connected via an HDMI cable to a
`connector shared by both a source and a sink of the source/sink dual-purpose device, a function attribute of
`whether the connected external device conforming to the HDMI standard is the source or the sink is determined
`on the basis of detection results of two monitor units.
`[0027]
`
`The source/sink dual-purpose device switches its own function to the source or the sink according to
`the determined function attribute of the external device. At this time, the source/sink dual-purpose device 1
`adjusts its own impedance so as not to cause an impedance mismatch with the external device. As a result, the
`source/sink dual-purpose device can function as the source device or the sink device according to the attribute
`of the device connected to the shared connector, that is, whether it is the sink device or the source device, without
`a switching operation of the user.
`[0028]
`
`FIG. 1 illustrates a configuration of the source/sink dual-purpose device according to an embodiment
`of the present invention. The source/sink dual-purpose device 100 includes a connector 110, a power supply
`block 120, a hot plug block 130, a DCC block 140, a TDMS block 150, a voltage line monitor 160, a TDMS
`line monitor 170, and an HDMI attribute switching processing unit 180.
`[0029]
`
`The connector 110 conforms to the HDMI standard and is exclusively connected to either one of
`another source device 20src (FIG. 5) and a sink device 20snk (FIG. 5) conforming to the HDMI standard via
`the HDMI cable 200. That is, the connector 110 is shared by the source device 20src and the sink device 20snk.
`The HDMI cable 200 includes a plurality of lines for transmitting signals and data. Typical lines include a CEC
`line, a hot plug line, a DDC line, and an HDMC line.
`[0030]
`
`The CEC line is used for transmission of control data between the source device and the sink device.
`The hot plug line is used to determine whether an HDMI cable is connected. The DDC line is used for
`transmitting EDID (Extended Display Identification Data) data including video format information. The HDMI
`line is used for transmission of TMDS system video signals and audio signals.
`[0031]
`
`The connector 110 is provided with a power source line 111, a hot plug line 112, a DDC line 113, and
`a TMDS line 114 in forms corresponding to each line of the HDMI cable 200. Of these, a plurality of TMDS
`lines 114 are normally present, but in FIG. 1, only one line is displayed for simplicity.
`[0032]
`
`The power supply block 120 includes a power supply block input/output SW unit 121, a power supply
`output unit 122, and a power supply input unit 123. The hot plug block 130 includes a hot plug input/output
`attribute SW unit 131, a hot plug input unit 132, and a hot plug output unit 133. The DCC block 140 includes a
`DDC block input/output attribute SW unit 141, a DDC output unit 142, and a DDC input unit 143. The TDMS
`block 150 includes a TDMS input/output attribute SW unit 151, a TDMS output unit 152, a TDMS input unit
`153, and a TMDS signal processing unit 154.
`[0033]
`
`The source/sink dual-purpose device 100 can function as a source device conforming to the HDMI
`standard, via a power source output unit 122, a hot plug input unit 132, a DDC output unit 142, a TDMS output
`unit 152, and a TMDS signal processing unit 154. Conversely, the source/sink dual-purpose device 100 can
`function as a sink device conforming to the HDMI standard, via a power input unit 123, a hot plug output unit
`133, a DDC input unit 143, a TDMS input unit 153, and a TMDS signal processing unit 154.
`[0034]
`
`Switching of the source device function and the sink device function in the power supply block 120,
`the hot plug 130, the DDC block 140, and the TDMS block 150 is performed by switching switches in the power
`supply block input/output SW unit 121, the hot plug input/output attribute SW unit 131, the DDC block
`input/output attribute SW unit 141, and the TDMS input/output attribute SW unit 151. Thus, the source device
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`function unit and the sink device function unit in the source/sink dual-purpose device 100 share the connector
`110 for connection with the external device 20.
`[0035]
`
`Next, functions of each block will be described. In the power supply block 120, the power supply output
`unit 122 supplies power to the hot plug input unit 132, the DDC output unit 142, and the TDMS output unit 152
`when the source/sink dual-purpose device 100 realizes a source device function.
`[0036]
`
`In contrast, when the source/sink dual-purpose device 100 realizes a sink device function, the power
`input unit 123 supplies power to the hot plug output unit 133, the DDC input unit 143, and the TDMS input unit
`152. By providing the power output unit 122 and the power input unit 123 separately, backflow of current from
`the sink side to the source side can be prevented.
`[0037]
`
`The hot plug block 130 is used when determining whether the source/sink dual-purpose device 100 is
`connected to the HDMI cable 200. The hot plug input unit 132 is used when the source/sink dual-purpose device
`100 functions as the source, and the hot plug output unit 133 is used when the source/sink dual-purpose device
`100 functions as the sink.
`[0038]
`
`In the DDC block 140, when the source/sink dual-purpose device 100 functions as a source, EDID data
`related to a displayable video format from the sink device 20snk connected to the HDMI cable 200 is transferred
`to a DDC output unit 142 and stored in a memory (not illustrated). The DDC output unit 142 sets a video format
`on the basis of a user instruction from the EDID stored in a memory.
`[0039]
`
`In a memory (not illustrated) of the DDC input unit 143, when the source/sink dual-purpose device 100
`functions as a sink, a displayable video format is stored as the EDID. The EDID stored in the memory is read
`out by access from the source device 20src when the source/sink dual-purpose device 100 is connected to the
`source device 20src.
`[0040]
`
`In the TDMS block 150, when the source/sink dual-purpose device 100 functions as a source, a TDMS
`output unit 152 outputs video data and audio data converted into TDMS system data by the TDMS signal
`processing unit 154 to the sink device 20snk connected to the HDMI cable 200.
`[0041]
`
`The TDMS input unit 153 receives the video data and the TDMS system audio data transmitted from
`the source device 20src connected to the HDMI cable 200 when the source/sink dual-purpose device 100
`functions as the sink. The video data and the audio data are transferred from the TDMS input unit 153 to the
`TMDS signal processing unit 154 and converted into video data and audio data before TMDS processing is
`performed by the TDMS signal processing unit 154. The problem of impedance mismatch of the TDMS line
`114 can be eliminated by providing the TDMS output unit 152 and the TDMS input unit 153 separately.
`[0042]
`
`Next, two monitoring units 160 and 170 that monitor the connection state between the HDMI cable 200
`and the external device 20 will be described. The power supply line monitor unit 160 repeatedly detects a voltage
`level VL1 of a power supply line 111 among a plurality of lines connected to the connector 110 at predetermined
`time intervals to generate a binary level signal (hereinafter, “power supply line level”) C1.
`[0043]
`
`When the external device 40 to which the connector 110 is connected via the HDMI cable 200 is the
`source device 20src, the voltage level VL1 of the power source line 111 indicates a High level (5 V). In contrast,
`when the connected external device 40 is the sink device 20snk, is not connected, or is not operating due to not
`being energized despite being connected, the voltage level VL1 indicates a low level (0 V). The power supply
`line level C1 has a value of either High or Low corresponding to the level of the voltage level VL1.
`[0044]
`
`The TDMS line monitor unit 170 repeatedly detects a voltage level VL2 of the TDMS line (specifically,
`a TDMS_CLK line) 114 included in the connector 110 at predetermined time intervals to generate a binary level
`
`DELL/HP/LENOVO EXHIBIT 1006
`Page 8
`
`

`

`
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`(9)
`
`JP 2009-60204 A 2009.3.19
`
`signal (hereinafter, “TDMS line level”) C2. When the connector 110 is connected to a sink device via the HDMI
`cable 200, the voltage level VL2 of the TDMS line 114 indicates a High level (3.3 V).
`[0045]
`
`In contrast, when the connector 110 is connected to a source device via the HDMI cable 200 or is not
`connected to another device, the voltage level VL2 indicates a low level (0 V). The TDMS line level C2 has a
`value of either High or Low corresponding to the level of the voltage level VL2.
`[0046]
`
`Operation of the HDMI attribute switching processing unit 180 will be described below with reference
`to FIG. 2. The HDMI attribute switching processing unit 180 determines a function J of the external device
`connected to the connector 110 also used for connection between the source device and the sink device based
`on the power source line level C1 and the TDMS line level C2. Note that “function,” in relation to the external
`device, refers to one of four states of “disconnected,” “abnormal,” “sink,” and “source.”
`[0047]
`
`“Disconnected” refers to a state in which the external device is not connected or is not energized even
`when connected. When both of the power supply line level C1 and the TDMS line level C2 are Low,
`“disconnected” is determined.
`[0048]
`
`“Abnormal” refers to a condition in which an external device is connected but is not normal. When
`both of the power supply line level C1 and the TDMS line level C2 are High, “abnormal” is determined.
`[0049]
`
`“Sink” refers to a sink, that is, a state in which an external device on the input side is connected. Note
`that it goes without saying that the external device is not in an abnormal state and is energized. When the power
`supply line level C1 is low and the TDMS line level C2 is High, “sink” is determined.
`[0050]
`
`“Source” means a source, that is, a state in which an external device on the output side is connected.
`Note that it goes without saying that the external device is not in an abnormal state and is energized. When the
`power supply line level C1 is High and the TDMS line level C2 is Low, “source” is determined.
`[0051]
`
`The HDMI attribute switching processing unit 180 further determines an operation mode M of the
`source/sink dual-purpose device 100 based on the determination result of the externa