Connection device, electronic device, and method for controlling electronic device

Abstract

To satisfactorily use a cable that has a specific function such as a register which holds specification data and the like, or a current consumption part of an element and the like for adjusting signal quality.SOLUTION: A cable that is connected between a first electronic apparatus and a second electronic apparatus is provided. A determination section determines whether or not the first electronic apparatus is a corresponding electronic apparatus. A control section performs control to operate in a corresponding mode when the first electronic apparatus is the corresponding electronic apparatus, and to operate in a non-corresponding mode when the first electronic apparatus is not the corresponding electronic apparatus, on the basis of a determination result of the determination section. Moreover, the electronic apparatus that is connected to an external apparatus through the cable is provided. The determination section determines whether or not the cable is a corresponding cable. The control section performs control to operate in the corresponding mode when the cable is the corresponding cable, and to operate in the non-corresponding mode when the cable is not the corresponding cable, on the basis of the determination result of the determination section.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] This technology is , contact Connection device, electronic device, and method for controlling electronic device Regarding do. [Background technology]

[0002] In recent years, HDMI (High Definition Multimedia Interface) and the like have been used as digital interfaces connecting CE (Consumer Electronics) devices. For example, Patent Document 1 describes the HDMI standard. In this HDMI standard, video, audio, and control signals are transmitted as digital signals using three data differential line pairs (TMDS Channel 0 / 1 / 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-111418 A Summary of the Invention [Problem to be solved by the invention]

[0004] For example, when HDMI is used as a digital interface, a source device such as a Blu-ray Disc (BD) player and a sink device such as a TV receiver are connected with an HDMI cable. An HDMI cable is assigned with four high-speed signal lines including a clock line, a +5V power line, a Display Data Channel (DDC) line, a Consumer Electronics Control (CEC) line, a Hot Plug Detect (HPD) line, a utility line, etc. Digital signals such as video, audio, and control are transmitted as TMDS data on the high-speed signal lines. In this case, a current-driven type is used in which the source side draws current from a 50Ω termination resistor connected to 3.3V on the sink side to transmit data "0" and "1". Note that "Blu-ray" is a registered trademark.

[0005] The HDMI standard specifies the sequence for connecting an HDMI cable: when both ends of the cable plug are connected to a source device and a sink device, respectively, a 5V voltage is transmitted from the source device to the sink device via the +5V power line, and when 5V is detected within the sink device, it notifies the source device that the cable is connected correctly by transmitting 5V from the sink device to the source device via the HPD line. When the source device detects 5V on the HPD line, it determines that the cable is connected, and uses the DDC line to read the EDID (Extended Display Identification Data) on the sink side. After that, the source device and sink device start exchanging signals such as HDCP (High-bandwidth Digital Content Protection) using control lines such as the DDC line, and high-speed data signal transmission using TMDS begins.

[0006] To ensure the quality of high-speed transmission, various specifications have been established for cables, and one of the mechanisms for identifying the cable specifications is to have a register inside the cable that holds specification data for identifying the cable specifications. In this case, when a source device accesses a register in the cable via a DDC line, etc., access information is simultaneously sent via the cable to a sink device, which may cause a malfunction in the sink device where the corresponding address is not defined.

[0007] Also, the guaranteed current output from the +5V power line of the source device is a minimum of 55mA, and since a normal HDMI cable consumes almost no power within the cable, 55mA is sufficient. In contrast, in the case of AOC (Active Optical Cable), which communicates using light instead of copper wire, circuits for converting electricity to light and circuits for converting light to electricity are required at both ends of the cable plug, so it is usually difficult to operate at 55mA. In this case, if the cable attempts to draw a current of more than 55mA from a source device that only guarantees 55mA, the source device may not be able to withstand the overcurrent and may break down. Note that ACC (Active Copper Cable), which has a built-in circuit for driving the electrical 50Ω wiring inside the cable, also requires a driving current for the internal circuit.

[0008] An object of the present technology is to enable good use of a cable having specific functions such as a register for storing specification data and the like, and a current consuming section such as an element for adjusting signal quality. [Means for solving the problem]

[0009] The concept of this technology is as follows: A cable connected between a first electronic device and a second electronic device, a determination unit that determines whether the first electronic device is a compatible electronic device; and a control unit that controls the first electronic device to operate in a compatible mode when the first electronic device is a compatible electronic device and to operate in a non-compatible mode when the first electronic device is not a compatible electronic device based on a determination result of the determination unit. It's in the cable.

[0010] In the present technology, the cable is connected between the first electronic device and the second electronic device. For example, the cable can be replaced with a connection device that is generally configured as a wired or wireless connection. The determination unit determines whether the first electronic device is a compatible electronic device. For example, the determination unit may be configured to determine whether the first electronic device is a compatible electronic device based on a voltage monitoring result of a specific line to which a specific voltage is applied via a voltage dividing resistor. In this case, an appropriate determination can be easily made by simply monitoring the voltage of the specific line.

[0011] In this case, for example, a first switch may be connected in series with the voltage dividing resistor, and this first switch may be short-circuited when the determination is made, thereby making it possible to apply a predetermined voltage to a predetermined line via the voltage dividing resistor only when the determination is made.

[0012] In this case, for example, a second switch may be inserted on the second electronic device side from the point where the voltage of the predetermined line is monitored, and the second switch may be set to an open state when the determination is made. This makes it possible to prevent the predetermined voltage applied to the predetermined line from being supplied to the second electronic device and affecting it when the determination is made. This also makes it possible to isolate the point where the voltage of the predetermined line is monitored from the second electronic device when the determination is made, and makes it possible to accurately monitor the voltage of the predetermined line.

[0013] The control unit controls the first electronic device to operate in a compatible mode when the first electronic device is a compatible electronic device based on the determination result of the determination unit, and to operate in a non-compatible mode when the first electronic device is not a compatible electronic device. For example, in the compatible mode, the control unit may change the first switch from a short-circuited state to an open state and then change the second switch from an open state to a short-circuited state when the voltage of the specific line reaches a specific voltage in the voltage monitor. This makes it possible to return the specific line to a usable state without supplying the specific voltage to the second electronic device and affecting it.

[0014] Also, for example, the device may further include a register connected to the communication line, a third switch connected to the communication line on the second electronic device side of the point where the register is connected, and the control unit may change the third switch from an open state to a short state in the corresponding mode after confirming that the register has been accessed by the first electronic device. This makes it possible to prevent register access information from being transmitted to the second electronic device, and to avoid malfunctions in the second electronic device in which the corresponding address is not defined.

[0015] In this case, for example, the control unit may be configured to confirm that the register has been accessed by the first electronic device based on the voltage monitoring result of a predetermined line to which a predetermined voltage is applied via a voltage dividing resistor. In this case, the voltage monitoring unit can also be used to determine whether the first electronic device is compatible with its own cable, making it possible to simplify the cable configuration.

[0016] In this case, for example, a fourth switch may be inserted in the power supply line, and the control unit may change the third switch from an open state to a short-circuit state in the corresponding mode, and then change the fourth switch from an open state to a short-circuit state. This makes it possible to avoid interference with a communication signal sent from the first electronic device to the second electronic device through the communication line after the second electronic device sends a connection detection signal to the first electronic device.

[0017] In this case, for example, the control unit may change the third switch from an open state to a short state in the non-compatible mode without confirming that the register has been accessed by the first electronic device. In this case, the register is not accessed by the first electronic device, and therefore it is possible to quickly return the communication line to a usable state.

[0018] In this case, for example, a fourth switch may be inserted in the power supply line, and the control unit may change the third switch from an open state to a short-circuit state in the non-compatible mode, and then change the fourth switch from an open state to a short-circuit state. This makes it possible to avoid interference with a communication signal sent from the first electronic device to the second electronic device through the communication line after the connection detection signal is sent from the second electronic device to the first electronic device after the third switch is changed from an open state to a short-circuit state.

[0019] Also, for example, the device may further include a current consumption unit connected to the power line, and the control unit may change the current consumption unit from a non-current consumption state to a current consumption state in the corresponding mode after confirming that the first electronic device has determined that its own cable is a corresponding cable. In this case, for example, a fifth switch may be inserted in the power line, and the control unit may change the fifth switch from an open state to a short state in the corresponding mode after confirming that the first electronic device has determined that its own cable is a corresponding cable. This allows the current consumption unit to draw and consume a sufficient current from the first electronic device, enabling appropriate operation. In addition, in this case, since the first electronic device can sufficiently supply the current that can be consumed by the current consumption unit of its own cable, it is also possible to prevent the first electronic device from being unable to withstand an overcurrent and causing a breakdown.

[0020] In this case, for example, the control unit may be configured to confirm that the first electronic device has determined that its own cable is a compatible cable based on the voltage monitoring result of a specific line to which a specific voltage is applied via a voltage dividing resistor. In this case, the voltage monitoring unit for determining whether the first electronic device is a compatible electronic device can also be used, making it possible to simplify the cable configuration.

[0021] In this case, for example, the control unit may change the fifth switch from an open state to a short state in the non-compatible mode without confirming that the first electronic device has determined that its own cable is a compatible cable. In this case, no matter how long you wait, the first electronic device will never be able to confirm that its own cable is a compatible cable, and therefore the power line can be quickly returned to a usable state.

[0022] In this manner, in the present technology, when the first electronic device is a compatible electronic device, the device is controlled to operate in a compatible mode, and when the first electronic device is not a compatible electronic device, the device is controlled to operate in a non-compatible mode. This allows for good use of a cable having specific functions, such as a register for storing specification data, a current consuming section such as an element for adjusting signal quality, etc.

[0023] Also, for example, the control unit may be configured to control the first electronic device to operate in the compatible mode when the first electronic device is a compatible electronic device and there is no relay device separating the power line between the first electronic device and the first electronic device. In this case, for example, the control unit may determine that the first electronic device is a compatible electronic device when the voltage of a specific line to which a specific voltage is applied via a voltage dividing resistor becomes a first voltage, and then determine that there is no relay device between the first electronic device and the first electronic device when the voltage of the specific line changes to a second voltage. As a result, when there is a relay device such as a repeater, the current consumption of a current consumption unit connected to the power line is suppressed, for example, so that it is possible to prevent the relay device from being unable to withstand an overcurrent and causing a breakdown.

[0024] Also, for example, the electronic device may further include an information transmission unit that functions when operating in the corresponding mode and transmits information to the first electronic device. In this case, for example, the information transmission unit may have a variable resistance circuit connected to a predetermined line, and may transmit any information to the first electronic device by changing the resistance value of the variable resistance circuit. In this case, for example, the information transmission unit may receive predetermined information from the first electronic device by monitoring the voltage of the predetermined line with the resistance value of the variable resistance circuit fixed to a predetermined value. This eliminates the need for a register on the communication line, and the access information of the register from the first electronic device is not transmitted to the second electronic device through the communication line, preventing the second electronic device from malfunctioning if the corresponding address is not defined.

[0025] Another concept of the present technology is An electronic device that is connected to an external device via a cable, A determination unit that determines whether the cable is a compatible cable; and a control unit that performs control so that the cable operates in a compatible mode when the cable is a compatible cable and operates in a non-compatible mode when the cable is not a compatible cable based on a determination result of the determination unit. It's in electronic devices.

[0026] The electronic device of the present technology is connected to an external device via a cable. For example, the cable can be replaced with a connection device that is generally configured as a wired or wireless connection. The determination unit determines whether the cable is a compatible cable. For example, the determination unit may determine whether the cable is a compatible cable based on a voltage monitoring result of a specific line to which a specific voltage is applied via a voltage dividing resistor. In this case, an appropriate determination can be easily made by simply monitoring the voltage of the specific line.

[0027] In this case, for example, a first switch may be connected in series with the voltage dividing resistor, and the first switch may be short-circuited when the determination is made, thereby making it possible to apply a predetermined voltage to a predetermined line via the voltage dividing resistor only when the determination is made.

[0028] In this case, a second switch may be inserted on the opposite side of the terminal side of the point where the voltage of the predetermined line is monitored, and the second switch may be set to an open state when the judgment is made. This makes it possible to prevent the predetermined voltage applied to the predetermined line from being supplied to the inside of the electronic device and affecting the electronic device when the judgment is made. This also makes it possible to isolate the point where the voltage of the predetermined line is monitored from the inside of the electronic device when the judgment is made, and makes it possible to accurately monitor the voltage of the predetermined line.

[0029] The control unit controls the device to operate in the compatible mode when the cable is a compatible cable based on the determination result of the determination unit, and to operate in the non-compatible mode when the cable is not a compatible cable. For example, in the compatible mode, the control unit may change the first switch from a short-circuited state to an open state after detecting that the connection detection line has become high level. This makes it possible to detect when the cable is removed while waiting for the connection detection line to become high level, and to take measures such as returning the switch to an initial state to prevent malfunction.

[0030] Also, for example, in the non-compatible mode, the control unit may change the first switch from a short-circuited state to an open state, and further change the second switch from a short-circuited state to an open state. In this case, it is possible to return the predetermined line to a usable state without affecting the inside of the electronic device by supplying a predetermined voltage.

[0031] Also, for example, in the corresponding mode, the control unit may access the register of the cable through the communication line before the first switch is switched from a short-circuited state to an open state. This allows the register of the cable to be accessed before a specific line of the cable is put into use, thus preventing register access information from being transmitted to an external device and avoiding malfunction of an external device in which the corresponding address is not defined.

[0032] Also, for example, in the corresponding mode, the control unit may change the current that can be supplied by the power line from a first current to a second current higher than the first current before the first switch is switched from a short-circuited state to an open state. This allows the cable to be in a state where a sufficient current can be supplied to the current consumption unit of the cable before the current consumption unit is in a current consumption state, in the case where the cable has a current consumption unit. By switching the mode of the current supply amount in this manner, it is possible to reduce the power of the power supply circuit unit.

[0033] Also, for example, the control unit may be configured to control the cable to operate in the compatible mode when the cable is a compatible cable and no relay device is interposed between the cable and the cable to separate the power line. In this case, for example, the control unit may determine that the cable is a compatible cable when the voltage of a specific line to which a specific voltage is applied via a voltage dividing resistor becomes a first voltage, and then determine that no relay device is interposed between the cable and the cable when the voltage of the specific line changes to a second voltage.

[0034] Also, for example, the device may further include an information transmission unit that functions when operating in the corresponding mode and transmits information to and from the cable. In this case, for example, the information transmission unit may have a variable resistance circuit connected to a predetermined line, and may transmit any information to the cable by changing the resistance value of the variable resistance circuit. In this case, for example, the information transmission unit may receive predetermined information from the cable by monitoring the voltage of the predetermined line with the resistance value of the variable resistance circuit fixed to a predetermined value. This eliminates the need for a register on the communication line in the cable, and prevents access information to the register from being transmitted to an external device through the communication line, thereby preventing malfunction in an external device in which the corresponding address is not defined.

[0035] In this way, in the present technology, when the cable is a compatible cable, the cable operates in the compatible mode, and when the cable is not a compatible cable, the cable operates in the non-compatible mode. Therefore, it is possible to effectively use cables having specific functions, such as registers for storing specification data, or current consumption units such as elements for adjusting signal quality. Effect of the Invention

[0036] According to the present technology, it is possible to effectively use a cable having a specific function such as a register for storing specification data, etc., a current consuming section such as an element for adjusting signal quality, etc. Note that the effects described in this specification are merely examples and are not limiting, and additional effects may also be provided. [Brief description of the drawings]

[0037] [Figure 1] FIG. 1 illustrates an example of the configuration of a transmission system. [Diagram 2] FIG. 1 illustrates an example of the configuration of a transmission system having a register. [Diagram 3] FIG. 11 is a diagram illustrating an example of the configuration of a transmission system in which a switch is arranged in a DDC line to which a register is connected. [Figure 4]FIG. 1 is a diagram showing an example of the configuration of a transmission system when an HDMI cable that is an AOC is used. [Diagram 5] FIG. 1 is a diagram showing an example of the configuration of a transmission system when an HDMI cable is used as an ACC. [Figure 6] 1 is a diagram illustrating an outline of the operation of a source device and an HDMI cable that configure a transmission system according to an embodiment. [Figure 7] FIG. 1 is a diagram showing an example of the configuration of a transmission system having a compatible source device and a compatible HDMI cable (with a register). [Figure 8] FIG. 8 is a diagram for explaining the operation of the transmission system of FIG. [Figure 9] FIG. 8 is a diagram for explaining the operation of the transmission system of FIG. [Figure 10] FIG. 8 is a diagram for explaining the operation of the transmission system of FIG. [Figure 11] FIG. 13 is a diagram showing an example of the configuration of a transmission system (using a utility line) having a non-compliant source device and a compliant HDMI cable (with a register). [Figure 12] FIG. 1 is a diagram showing an example of the configuration of a transmission system (using a utility line) having a compatible source device and a non-compatible HDMI cable. [Figure 13] FIG. 8 is a diagram showing an example of a sequence of a compatible source device in the transmission system of FIG. [Figure 14] 8 is a diagram showing an example of a sequence of a compatible HDMI cable in the transmission system of FIG. 7. [Figure 15] FIG. 1 is a diagram showing an example of the configuration of a transmission system (using a +5V power line) having a compatible source device and a compatible HDMI cable (with a register). [Figure 16] FIG. 16 is a diagram for explaining the operation of the transmission system of FIG. [Figure 17] FIG. 16 is a diagram for explaining the operation of the transmission system of FIG. [Figure 18] FIG. 13 is a diagram showing an example configuration of a transmission system (using a +5V power line) having a non-compliant source device and a compliant HDMI cable (with a register). [Figure 19]FIG. 1 is a diagram showing an example of the configuration of a transmission system (using a +5V power line) having a compatible source device and a non-compatible HDMI cable. [Figure 20] FIG. 20 is a diagram illustrating a configuration example for avoiding the inconvenience of the transmission system of FIG. 19. [Figure 21] FIG. 16 is a diagram showing an example of a sequence of a compatible source device in the transmission system of FIG. [Figure 22] FIG. 16 is a diagram showing an example of a sequence of a compatible HDMI cable in the transmission system of FIG. [Diagram 23] FIG. 1 is a diagram showing an example of the configuration of a transmission system having a compatible source device and a compatible HDMI cable (with a current consumption section). [Figure 24] FIG. 24 is a diagram for explaining the operation of the transmission system of FIG. 23. [Diagram 25] FIG. 24 is a diagram for explaining the operation of the transmission system of FIG. 23. [Figure 26] FIG. 24 is a diagram for explaining the operation of the transmission system of FIG. 23. [Figure 27] FIG. 1 is a diagram showing an example of the configuration of a transmission system (using a utility line) having a non-compliant source device and a compliant HDMI cable (with a current consuming part). [Figure 28] FIG. 1 is a diagram showing an example of the configuration of a transmission system (using a utility line) having a compatible source device and a non-compatible HDMI cable. [Figure 29] FIG. 24 is a diagram showing an example of a sequence of a corresponding source device in the transmission system of FIG. [Diagram 30] FIG. 24 is a diagram showing an example of a sequence of a compatible HDMI cable in the transmission system of FIG. 23. [Diagram 31] FIG. 1 is a diagram showing an example of the configuration of a transmission system (using a +5V power line) having a compatible source device and a compatible HDMI cable (with a current consumption section). [Diagram 32] FIG. 32 is a diagram for explaining the operation of the transmission system of FIG. 31. [Diagram 33] FIG. 32 is a diagram for explaining the operation of the transmission system of FIG. 31. [Diagram 34]FIG. 1 is a diagram showing an example of the configuration of a transmission system (using a +5V power line) having a non-compliant source device and a compliant HDMI cable (with a current consuming part). [Diagram 35] FIG. 1 is a diagram showing an example of the configuration of a transmission system (using a +5V power line) having a compatible source device and a non-compatible HDMI cable. [Diagram 36] FIG. 37 is a diagram showing a configuration example for avoiding the inconvenience of the transmission system of FIG. [Figure 37] FIG. 32 is a diagram showing an example of a sequence of a corresponding source device in the transmission system of FIG. [Figure 38] FIG. 16 is a diagram showing an example of a sequence of a compatible HDMI cable in the transmission system of FIG. [Figure 39] FIG. 1 is a diagram showing an example of the configuration of a transmission system (using a utility line) having a compatible source device and a compatible HDMI cable (with a resistor and a current consumption section). [Diagram 40] FIG. 1 is a diagram showing an example of the configuration of a transmission system (with a repeater) having a compatible source device and a compatible HDMI cable (with a current consuming section). [Diagram 41] 1 is a diagram illustrating an outline of the operation of a source device and an HDMI cable that configure a transmission system according to an embodiment. [Diagram 42] FIG. 1 is a diagram showing an example of the configuration of a transmission system having a compatible source device and a compatible HDMI cable (with a current consumption section) that can be used with a repeater. [Diagram 43] FIG. 43 is a diagram for explaining the operation of the transmission system of FIG. 42. [Diagram 44] FIG. 43 is a diagram for explaining the operation of the transmission system of FIG. 42. [Diagram 45] FIG. 43 is a diagram for explaining the operation of the transmission system of FIG. 42. [Diagram 46] FIG. 43 is a diagram for explaining the operation of the transmission system of FIG. 42. [Figure 47] FIG. 13 is a diagram showing an example of the configuration of a transmission system having a compatible HDMI cable (with a current consumption section) that can accommodate a non-compatible source device and an intermediate repeater. [Figure 48]FIG. 13 is a diagram showing an example of the configuration of a transmission system (with a current consumption unit) having a compatible source device and a non-compatible HDMI cable that can be used with a repeater. [Figure 49] FIG. 13 is a diagram showing an example of the configuration of a transmission system (with repeater) having a compatible source device that is compatible with the repeater and a compatible HDMI cable (with a current consumption section). [Figure 50] FIG. 50 is a diagram for explaining the operation of the transmission system of FIG. 49. [Figure 51] FIG. 50 is a diagram for explaining the operation of the transmission system of FIG. 49. [Figure 52] FIG. 50 is a diagram for explaining the operation of the transmission system of FIG. 49. [Diagram 53] FIG. 50 is a diagram for explaining the operation of the transmission system of FIG. 49. [Figure 54] FIG. 50 is a diagram showing an example of a sequence of a corresponding source device in the transmission system of FIG. 49. [Figure 55] FIG. 50 is a diagram showing an example of a sequence of a compatible HDMI cable in the transmission system of FIG. 49. [Figure 56] FIG. 1 is a diagram showing an example of the configuration of a transmission system having a compatible source device and a compatible HDMI cable (with a register and a current consumption section) that can be used with a repeater. [Figure 57] FIG. 1 is a diagram showing an example of the configuration of a transmission system having a compatible source device equipped with a variable resistance circuit and a compatible HDMI cable. [Figure 58] 11 is a diagram for explaining an example of the operation of the variable resistor circuit when transmitting and receiving information between a source device and an HDMI cable. FIG. [Figure 59] FIG. 13 is a diagram illustrating another configuration example of the variable resistance circuit. [Figure 60] 11 is a diagram showing an example of an information table shared by a source device and an HDMI cable. FIG. [Figure 61] FIG. 58 is a diagram for explaining the operation of the transmission system of FIG. 57. [Figure 62] FIG. 58 is a diagram for explaining the operation of the transmission system of FIG. 57. [Figure 63]FIG. 58 is a diagram for explaining the operation of the transmission system of FIG. 57. [Figure 64] FIG. 1 is a diagram showing an example of the configuration of a transmission system having a non-compliant source device and a compliant HDMI cable equipped with a variable resistance circuit. [Figure 65] FIG. 1 is a diagram showing an example of the configuration of a transmission system having a compatible source device equipped with a variable resistance circuit and a non-compatible HDMI cable. [Figure 66] A diagram showing an example of a sequence of a corresponding source device in the transmission system of Figure 57. [Figure 67] A diagram showing an example of a sequence of a compatible HDMI cable in the transmission system of Figure 57. [Figure 68] FIG. 13 is a diagram showing an example of the configuration of a transmission system having a compatible source device equipped with a variable resistance circuit and a compatible HDMI cable (with a current consumption section) that can accommodate the intermediation of a repeater. [Figure 69] FIG. 69 is a diagram for explaining the operation of the transmission system of FIG. 68. [Figure 70] FIG. 69 is a diagram for explaining the operation of the transmission system of FIG. 68. [Figure 71] FIG. 69 is a diagram for explaining the operation of the transmission system of FIG. 68. [Figure 72] FIG. 69 is a diagram for explaining the operation of the transmission system of FIG. 68. [Figure 73] FIG. 13 is a diagram showing an example of the configuration of a transmission system having a non-compliant source device and a compliant HDMI cable (with a current consumption section) equipped with a variable resistance circuit. [Figure 74] FIG. 1 is a diagram showing an example of the configuration of a transmission system having a compatible source device equipped with a variable resistance circuit and a non-compatible HDMI cable (with a current consumption section). [Figure 75] FIG. 13 is a diagram showing an example of the configuration of a transmission system (with repeater) having a compatible source device that is compatible with the repeater and a compatible HDMI cable (with a current consumption section). [Figure 76] A diagram showing an example of a sequence of a corresponding source device in the transmission system of Figure 68. [Figure 77]A diagram showing an example of a sequence of a compatible HDMI cable in the transmission system of Figure 68. [Figure 78] FIG. 1 is a diagram showing a configuration example of a transmission system in which a cable has an external power supply terminal. [Figure 79] FIG. 13 is a diagram showing an example of an improved configuration of a transmission system in which a cable has an external power supply terminal. [Figure 80] FIG. 1 is a diagram showing an example of the configuration of a transmission system having a compatible source device and a compatible HDMI cable (with a register) that can be used with a repeater. [Figure 81] FIG. 81 is a diagram for explaining the operation of the transmission system of FIG. 80. [Figure 82] FIG. 81 is a diagram for explaining the operation of the transmission system of FIG. 80. [Figure 83] FIG. 81 is a diagram for explaining the operation of the transmission system of FIG. 80. [Figure 84] FIG. 81 is a diagram for explaining the operation of the transmission system of FIG. 80. [Figure 85] FIG. 81 is a diagram for explaining the operation of the transmission system of FIG. 80. [Figure 86] FIG. 81 is a diagram for explaining the operation of the transmission system of FIG. 80. [Figure 87] FIG. 81 is a diagram for explaining the operation of the transmission system of FIG. 80. [Figure 88] FIG. 81 is a diagram for explaining the operation of the transmission system of FIG. 80. [Figure 89] FIG. 81 is a diagram showing an example of a sequence of a corresponding source device in the transmission system of FIG. 80. [Figure 90] FIG. 81 is a diagram showing an example of a sequence of a compatible HDMI cable in the transmission system of FIG. 80. [Figure 91] FIG. 1 is a diagram showing an example of the configuration of a transmission system having a compatible source device and a compatible HDMI cable (with a register and a current consumption section) that can be used with a repeater. [Figure 92] FIG. 1 is a diagram showing an example of the configuration of a transmission system having a compatible source device and a compatible HDMI cable (with a register) that can be used with a repeater. [Figure 93]FIG. 1 is a diagram showing an example of the configuration of a transmission system having a compatible source device and a compatible HDMI cable (with a register and a current consumption section) that can be used with a repeater. [Figure 94] FIG. 1 is a diagram showing an example of the configuration of a transmission system having a compatible source device and a compatible HDMI cable (with a register) that can be used with a repeater. [Figure 95] FIG. 1 is a diagram showing an example of the configuration of a transmission system having a compatible source device and a compatible HDMI cable (with a register and a current consumption section) that can be used with a repeater. [Figure 96] FIG. 1 is a diagram showing an example of the configuration of a transmission system having a compatible source device and a compatible HDMI cable (with a register) that can be used with a repeater. [Figure 97] FIG. 1 is a diagram showing an example of the configuration of a transmission system having a compatible source device and a compatible HDMI cable (with a register and a current consumption section) that can be used with a repeater. [Figure 98] FIG. 1 is a diagram showing pin arrangements for "Display Port" and "Thunderbolt." DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Hereinafter, modes for carrying out the invention (hereinafter, referred to as "embodiments") will be described. The description will be made in the following order. 1. Embodiment 2. Variations

[0039] <1. Preferred embodiment> [Transmission system configuration] 1 shows an example of the configuration of a transmission system 30. This transmission system 30 is an HDMI transmission system that uses HDMI as a digital interface. This transmission system 30 has a source device 310 that is an HDMI transmitter, a sink device 320 that is an HDMI receiver, and an HDMI cable 330 that connects them.

[0040] The transmission channels of the transmission system 30 include three TMDS channels that transmit video, audio, and control signals as digital signals using TMDS data, and one TMDS clock channel that transmits a clock signal. Each of the TMDS channels and the TMDS clock channel consists of two differential signal lines. In the illustrated example, only one channel is shown.

[0041] Furthermore, the HDMI system has control signal lanes including a DDC line, a CEC line, an HPD line, a utility line, and a +5V power line. The DDC line is made up of two signal lines, an SDA line and an SCL line, included in the HDMI cable 330. The DDC line is used, for example, by the source device 310 to read out the EDID from the sink device 320. The CEC line is used for bidirectional communication of control data between the source device 310 and the sink device 320.

[0042] The TMDS channel uses a current drive type that transmits data "0" and "1" by drawing a current from a 50 Ω termination resistor connected to the sink device 320 side to the source device 310 side. At this time, the signal is transmitted differentially based on the differential signal of D, D (bar). Note that while the illustrated example shows an example in which a 50 Ω termination resistor is used on the source device 310 side, TMDS can also be driven using only the 50 Ω termination resistor on the sink device side without using this 50 Ω.

[0043] The HDMI standard prescribes a sequence that should be followed when connecting an HDMI cable 330. When both ends of the plug of the HDMI cable 330 are connected to the source device 310 and the sink device 320, respectively, a 5V voltage is transmitted from the source device 310 to the sink device 320 via the +5V power line, and when 5V is detected within the sink device 320, 5V is transmitted from the sink device 320 to the source device 310 via the HPD line, thereby notifying the source device 310 that the cable is connected correctly.

[0044] When the control unit 311 of the source device 310 detects 5V on the HPD line, it determines that the cable is connected, and uses the DDC line to read the EDID from the EDID ROM 321 on the sink device 320 side. After that, the source device 310 and the sink device 320 start exchanging signals such as HDCP (High-bandwidth Digital Content Protection System) using control lines such as the DDC line, and TMDS data starts being transmitted in one direction from the source device 310 to the sink device 320 using the TMDS channel. Note that the source device 310 and the sink device 320 can exchange information by using a register provided in the control unit 322 on the sink device 320 side.

[0045] When a register is provided in the cable 330 and information is to be exchanged between the source device 310 and the cable 330, it is possible to arrange a register 331 in parallel to the DDC line in the cable 330A as shown in the transmission system 30A in Fig. 2. In this case, the information held by the register 331 may include a cable ID, a parameter for adjusting circuit characteristics, the amount of current consumed by the cable, a transmittable data rate, etc. In Fig. 2, the same reference numerals are used for parts corresponding to those in Fig. 1, and detailed explanations thereof will be omitted as appropriate.

[0046] In this configuration, when the source device 310 accesses the new address of the register 331 of the cable 330A, it also accesses the sink device 320. If an unintended address is accessed, the sink device 320 may malfunction.

[0047] To avoid this, as shown in the transmission system 30B in Fig. 3, the simplest method is to insert a switch SW5 on the sink device 320 side from the point where the register 331 of the DDC line is connected in the cable 330B, so that address information is not transmitted to the sink device 320 when the source device 310 accesses the register 331 for read / write. In Fig. 3, the same reference numerals are used for parts corresponding to those in Fig. 2, and detailed explanations thereof will be omitted as appropriate.

[0048] In this case, the cable 330B needs to keep the switch SW5 in an open state initially so that it is ready for access at any time from the source device 310. When the cable 330B detects the end of access to the register 331, it can switch the switch SW5 to a short state and transition to normal operation. However, if the source device 310 is a legacy device, the source device 310 does not access the register 311, so the switch SW5 of the cable 330B remains in an open state, interfering with normal DDC communication.

[0049] Fig. 4 shows a configuration example of a transmission system 30C when using an HDMI cable 330C that is an AOC. In Fig. 4, parts corresponding to those in Fig. 1 are given the same reference numerals, and detailed description thereof will be omitted.

[0050] In the case of this transmission system 30C, a conversion circuit 331A that converts electricity to light is present in the source side plug of the HDMI cable 330C, and a conversion circuit 331B that converts light to electricity is present in the sink side plug. These conversion circuits 331A and 331B are provided with a 3.3V power supply obtained from +5V of a +5V power line by LDO (Low Drop Out) regulators 332A and 332B. The conversion circuits 331A and 331B are elements for adjusting the quality of a signal interposed in a data line (TMDS line) and constitute a current consumption unit.

[0051] In addition, in the source side plug of the HDMI cable 330C, 3.3V obtained by the LDO regulator 332A is applied as a bias voltage to the data line (TMDS line) through a 50Ω termination resistor. Furthermore, in the sink side plug of the HDMI cable 330C, a current driver 333B is provided for differentially transmitting a signal based on the differential signal obtained from the conversion circuit 331B.

[0052] Fig. 5 shows a configuration example of a transmission system 30D in the case where an HDMI cable 330D that is an ACC is used. In Fig. 5, parts corresponding to those in Fig. 4 are given the same reference numerals, and detailed description thereof will be omitted.

[0053] In the case of this transmission system 30D, drive circuits 334A and 334B for driving 50Ω electrical wiring are present in the plugs on both sides of the HDMI cable 330D. These drive circuits 334A and 334B are provided with a 3.3V power supply obtained by LDO regulators 335A and 335B from +5V on the +5V power line. These drive circuits 334A and 334B are elements for adjusting the quality of signals interposed in the data lines (TMDS lines) and constitute current consumption units.

[0054] In addition, in the source side plug of the HDMI cable 330D, 3.3V obtained by the LDO 335A is applied as a bias voltage to the data line (TMDS line) through a 50Ω termination resistor. Furthermore, in the sink side plug of the HDMI cable 330D, a current driver 336B is provided for differentially transmitting a signal based on the differential signal obtained from the conversion circuit 334B.

[0055] The guaranteed value of the current output from the +5V power line in source device 310 is a minimum of 55mA. When using HDMI cable 330C, which is AOC (see FIG. 4), a circuit for converting electricity to light and a circuit for converting light to electricity are required on both ends of the cable plug, and it is usually difficult to operate at 55mA. In this case, if the cable attempts to draw a current of more than 55mA from a source device that only guarantees 55mA, the source device may not be able to withstand the overcurrent and may break down. The same can be said when using HDMI cable 330D, which is ACC (see FIG. 5).

[0056] In this embodiment, as shown in FIG. 6, the source devices and HDMI cables constituting the transmission system each operate differently depending on whether they are compatible or not, and further depending on whether the other device is compatible or not.

[0057] As shown in Fig. 6(a), a compatible source device (compatible source device) operates in a compatible mode when a compatible cable (compatible HDMI cable) is connected, and operates in a non-compatible mode when a non-compatible cable is connected, and a non-compatible source device operates normally whether a compatible cable or a non-compatible cable is connected. Also, as shown in Fig. 6(b), a compatible cable operates in a compatible mode when a compatible source device is connected, and operates in a non-compatible mode when a non-compatible source device is connected, and a non-compatible cable operates normally whether a compatible source device or a non-compatible source device is connected.

[0058] "Embodiment 1" Fig. 7 shows a configuration example of a transmission system 10-1. This transmission system 10-1 is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-1 has a source device 110-1 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-1 connecting them. In Fig. 7, parts corresponding to those in Fig. 1 are given the same reference numerals, and detailed explanations thereof will be omitted as appropriate.

[0059] The HDMI cable 130-1 is a compatible cable having a register 131 in which cable specification data is stored. In addition to the register 131, the HDMI cable 130-1 has a control unit 132, voltage monitor units 133 and 134, switches SW3, SW4, SW5, and SW6, and a resistor R2 for voltage division.

[0060] The resistor 131 is connected to a point P1 of the DDC line. A switch SW5 is inserted on the DDC line closer to the sink device 320 than the point P1. A series circuit of a resistor R2 and a switch SW3 is connected between the point P2 of the utility line and the ground. This allows 0V, which is the ground voltage, to be applied to the point P2 of the utility line via the series circuit of the resistor R2 and the switch SW3. A switch SW4 is inserted on the utility line closer to the sink device 320 than the point P2. A switch SW6 is inserted in the +5V power line.

[0061] Voltage monitor unit 133 monitors the voltage at point P2 of the utility line and sends the monitoring result to control unit 132. Voltage monitor unit 134 monitors the voltage at point P3 on the terminal side of the +5V power line from the insertion position of switch SW6 and sends the monitoring result to control unit 132. Control unit 132 controls the operation of each part of HDMI cable 130-1.

[0062] Source device 110-1 is a compatible source device. In addition to control unit 111 that controls the operation of each unit, source device 110-1 has voltage monitor unit 112, switches SW1 and SW2, and resistor R1 for voltage division. It is desirable that resistor R2 of HDMI cable 130-1 and resistor R1 of source device 110-1 have relatively large values ​​to reduce current consumption. In the following description, R1=100 kΩ and R2=400 kΩ.

[0063] A series circuit of resistor R1 and switch SW1 is connected between the +5V power line and point Q1 of the utility line. As a result, +5V is applied to point Q1 of the utility line via the series circuit of resistor R1 and switch SW1. A switch SW2 is inserted on the opposite side of the utility line from the terminal side of point Q1. A voltage monitor unit 112 monitors the voltage at point Q1 of the utility line and sends the monitoring result to the control unit 111.

[0064] In the transmission system 10-1 shown in Fig. 7, the HDMI cable 130-1 is a compatible cable, and the source device 110-1 is a compatible source device. Therefore, the source device 110-1 determines that the connected HDMI cable is a compatible cable and operates in the compatible mode. Similarly, the HDMI cable 130-1 determines that the connected source device is a compatible source device and operates in the compatible mode.

[0065] The operation of source device 110-1 and HDMI cable 130-1 will be described in detail. In Fig. 7, source device 110-1 and HDMI cable 130-1 are shown in an initial state. In source device 110-1, in the initial state, switch SW1 is shorted and switch SW2 is open. On the other hand, in HDMI cable 130-1, in the initial state, switch SW3 is shorted and switches SW4, SW5, and SW6 are open.

[0066] In this initial state, switches SW1 and SW3 are short-circuited, so that resistors R1 and R2 are connected in series between the +5V power line of source device 110-1 and the ground (0V) of HDMI cable 130-1, and a voltage of 4V is obtained at points Q1 and P2 of the utility line through resistive voltage division.

[0067] Voltage monitor unit 112 of source device 110-1 monitors that the voltage at point Q1 is 4 V, and sends the monitoring result to control unit 111. Based on this monitoring result, control unit 111 determines that the connected HDMI cable is a compatible cable, and controls so as to operate in the compatible mode.

[0068] Similarly, voltage monitor unit 133 of HDMI cable 130-1 monitors that the voltage at point P2 is 4 V, and sends the monitoring result to control unit 132. Based on this monitoring result, control unit 132 determines that the connected source device is a compatible source device, and controls it to operate in the compatible mode.

[0069] Here, in source device 110-1, switch SW2 is open, so the voltage of 4V is not propagated inside source device 110-1 and does not affect the inside of source device 110-1. Similarly, in HDMI cable 130-1, switch SW4 is open, so the voltage of 4V is not propagated to sink device 320 and does not affect sink device 320.

[0070] Since source device 110-1 is controlled to operate in the corresponding mode, control unit 111 accesses (reads / writes) register 131 of HDMI cable 130-1 via the DDC line. In this case, since switch SW5 is in an open state, it is possible to prevent access information of register 131 from being transmitted to sink device 320, and it is possible to avoid malfunction of sink device 320 in which the corresponding address is not defined.

[0071] In source device 110-1, when access to register 131 of HDMI cable 130-1 ends, control unit 111 opens switch SW1 as shown in Fig. 8. Therefore, the voltage at point P2 of the utility line becomes 0V. In HDMI cable 130-1, voltage monitor unit 133 monitors that the voltage at point P2 is 0V, and sends the monitoring result to control unit 132. By monitoring that the voltage at point P2 is 0V in this manner, it is confirmed that register 131 has been accessed from the source device.

[0072] Based on the result of this monitoring, control unit 132 determines that access to register 131 by source device 110-1 has ended, and changes the state of each switch to transition to normal operation as shown in Fig. 9. In this case, in order not to affect sink device 320, first switch SW3 is opened, then switches SW4 and SW5 are shorted, and finally switch SW6 is shorted.

[0073] By shorting switch SW6, a 5V voltage is sent from source device 110-1 to sink device 320 via the +5V power line, and accordingly a 5V voltage (connection detection signal) is sent from sink device 320 to source device 110-1 via the HPD line. This causes control unit 111 of source device 110-1 to recognize that cable preparation is complete, and as shown in Fig. 10, control unit 111 shorts switch SW2 and transitions to normal operation.

[0074] 7, the switch SW5 is kept open until the source device 110-1 finishes accessing the register 131 of the HDMI cable 130-1. Therefore, the access information of the register 131 is not transmitted to the sink device 320 via the DDC line, and it is possible to prevent a malfunction of the sink device 320 in which the corresponding address is not defined.

[0075] 7, the switch SW5 is changed to the short-circuited state after the source device 110-1 finishes accessing the register 131 of the HDMI cable 130-1, and thereafter the switch SW6 is changed to the short-circuited state. This makes it possible to avoid interference with a communication signal transmitted from the source device 110-1 to the sink device 320 via the DDC line after the sink device 320 transmits a connection detection signal to the source device 110-1.

[0076] Fig. 11 shows a configuration example of a transmission system 10-1A. This transmission system 10-1A is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-1A has a source device 310 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-1 connecting them. In Fig. 11, parts corresponding to Figs. 1 and 7 are given the same reference numerals, and detailed explanations thereof will be omitted as appropriate.

[0077] In this transmission system 10-1A, the source device 310 is a non-compliant source device such as a legacy device, and the HDMI cable 130-1 is a compliant cable. In this case, the source device 310 operates normally (see FIG. 6).

[0078] Also, the HDMI cable 130-1 determines that the source device is a non-compatible source device, and operates in the non-compatible mode. In this case, in the initial state, the voltage at point P2 of the Utility line is 0V. The voltage monitor unit 133 of the HDMI cable 130-1 monitors that the voltage at point P2 is 0V, and sends the monitoring result to the control unit 132. The control unit 132 determines that the source device is a non-compatible source device based on this monitoring result and the fact that the +5V power line is at a high level (5V), and controls the device to operate in the non-compatible mode.

[0079] In this case, the control unit 132 changes the state of each switch and transitions to normal operation. In this case, in order not to affect the sink device 320, first the switch SW3 is opened, then the switches SW4 and SW5 are shorted, and finally the switch SW6 is shorted.

[0080] Fig. 12 shows a configuration example of a transmission system 10-1B. This transmission system 10-1B is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-1B has a source device 110-1 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 330 connecting them. In Fig. 12, parts corresponding to Figs. 1 and 7 are given the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0081] In this transmission system 10-1B, the source device 110-1 is a compliant source device, and the HDMI cable 330 is a non-compliant cable such as a legacy cable. In this case, the HDMI cable 330 operates normally (see FIG. 6).

[0082] Source device 110-1 determines that the HDMI cable is a non-compliant cable and operates in the non-compliant mode. In this case, in the initial state, the voltage at point Q1 of the Utility line is 5V. Voltage monitor unit 112 of source device 110-1 monitors that the voltage at point Q1 is 5V, and sends the monitoring result to control unit 111. Based on this monitoring result and the fact that the HPD line is at a high level (5V), control unit 111 determines that the HDMI cable is a non-compliant cable, and controls so as to operate in the non-compliant mode.

[0083] In this case, control unit 111 changes the state of each switch to transition to normal operation. In this case, in order not to affect the inside of source device 110-1, first switch SW1 is opened, and then switch SW2 is shorted.

[0084] 13 shows an example of a sequence of source device 110-1, which is a corresponding source device. In step ST1, for example, when the power switch is turned on and +5V is raised, the sequence starts and proceeds to step ST2. In this step ST2, control unit 111 judges whether voltage monitor unit 112 detects a predetermined bias voltage (4V).

[0085] When a predetermined bias voltage (4V) is detected, in step ST3, the control unit 111 determines that the HDMI cable is a compatible cable. Then, in step ST4, the control unit 111 starts accessing the register of the HDMI cable.

[0086] Next, in step ST5, after access to the register of the HDMI cable is completed, the control unit 111 changes the switch SW1 from the shorted state to the open state. After that, in step ST6, when the control unit 111 detects that the HPD line has become high level (5 V), the control unit 111 changes the switch SW2 from the open state to the shorted state in step ST7. Then, in step ST8, the sequence ends.

[0087] Furthermore, when the predetermined bias voltage (4V) is not detected in step ST2, the control unit 111 determines in step ST9 whether or not a high level (5V) of the HPD line is detected. When a high level (5V) of the HPD line is not detected, the process returns to step ST2. On the other hand, when a high level (5V) of the HPD line is detected, in step ST10, the control unit 111 determines that the HDMI cable is a non-compliant cable.

[0088] Then, in step ST11, the switch SW1 is changed from the short-circuited state to the open-circuited state. Next, in step ST7, the switch SW2 is changed from the open-circuited state to the short-circuited state by the control unit 111. Then, in step ST8, the sequence ends.

[0089] 14 shows an example of a sequence for the HDMI cable 130-1, which is a compatible cable. In step ST21, when the voltage monitor unit 134 detects a voltage of 5V, the sequence starts and proceeds to step ST22. In this step ST22, the control unit 132 determines whether the voltage monitor unit 133 detects a predetermined bias voltage (4V).

[0090] When a predetermined bias voltage (4V) is detected, in step ST23, the control unit 132 determines that the source device is a compatible source device. Then, in step ST24, when the voltage monitor unit 133 detects 0V, in step ST25, the control unit 132 changes the switch SW3 from a short-circuited state to an open state. In this case, the detection of 0V by the voltage monitor unit 133 confirms that the register 131 has been accessed by the source device.

[0091] Next, in step ST26, the control unit 132 changes the switches SW4 and SW5 from the open state to the short state, and then, in step ST27, the control unit 132 changes the switch SW6 from the open state to the short state. Then, in step ST28, the sequence ends.

[0092] Furthermore, when the predetermined bias voltage (4 V) is not detected in step ST22, the control unit 132 determines in step ST29 that the source device is a non-compatible source device. Then, in step ST25, the control unit 132 changes the switch SW3 from the short-circuited state to the open state.

[0093] Next, in step ST26, the control unit 132 changes the switches SW4 and SW5 from the open state to the short state, and then, in step ST27, the control unit 132 changes the switch SW6 from the open state to the short state. Then, in step ST28, the sequence ends.

[0094] Note that switches SW1 and SW2 of source device 110-1 and switches SW3, SW4, SW5, and SW6 of HDMI cable 130-1 are reset to their initial states when the voltage of the +5V power line drops.

[0095] Now, consider a case where the connection between the HDMI cable 130-1 and the source device 110-1 is disconnected in the transmission system 10-1 shown in Fig. 7. In the HDMI cable 130-1, the voltage of the +5V power line is constantly monitored by the voltage monitor unit 134. When the connection is disconnected, the voltage of the +5V power line drops from 5V, so the control unit 132 determines that the connection has been disconnected and resets the state of each switch to the initial state.

[0096] 7, consider the switch SW2 of the source device 110-1 and the switch SW4 of the HDMI cable 130-1. If there is no problem with bias voltage propagation to the source device 110-1 and the sink device 320, or if the output / input circuits of the utility lines of the source device 110-1 and the sink device 320 do not affect the bias voltage, operation is possible without these switches SW2 and SW4.

[0097] Also, consider the power supply for operating each part of the HDMI cable 130-1 in the transmission system 10-1 shown in Fig. 7. It is possible that the power supply for operating the voltage monitor parts 133 and 134, the register 131, the switches SW3, SW4, SW5, SW6, and the control part 132 is provided from the source device 110-1 via a +5V power line, or from a battery (not shown) in the HDMI cable 130-1, or from an external power supply terminal separate from the HDMI terminal in the cable plug. Note that the idea of ​​the power supply for operating each part of this HDMI cable can be similarly applied to each of the following cables.

[0098] "Embodiment 2" 15 shows a configuration example of a transmission system 10-2. The transmission system 10-2 is an HDMI transmission system that uses HDMI as a digital interface. The transmission system 10-2 includes a source device 110-2 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-2 that connects them.

[0099] In the transmission system 10-1 shown in Fig. 7, the Utility line is used to determine whether the source device and the HDMI cable are compatible, but in this transmission system 10-2, the +5V power line is used to make the determination. In Fig. 15, the same reference numerals are used for parts corresponding to Fig. 1 and Fig. 7, and detailed descriptions thereof will be omitted as appropriate.

[0100] The HDMI cable 130-2 is a compatible cable having a register 131 in which cable specification data is stored. In addition to the register 131, the HDMI cable 130-2 has a control unit 132, a voltage monitor unit 133, switches SW13, SW14, SW15, and a resistor R2 for voltage division. The register 131 is connected to a point P11 of the DDC line. A switch SW14 is inserted on the DDC line closer to the sink device 320 than the point P11.

[0101] Furthermore, a series circuit of resistor R2 and switch SW13 is connected between point P12 of the +5V power line and the ground. As a result, 0V, which is the ground voltage, is applied to point P12 of the +5V power line via the series circuit of resistor R2 and switch SW13. A switch SW15 is inserted on the +5V power line closer to the sink device 320 than point P12. A voltage monitor unit 133 monitors the voltage at point P12 of the +5V power line, and sends the monitoring result to the control unit 132. The control unit 132 controls the operation of each unit of the HDMI cable 130-2.

[0102] Source device 110-2 is a compatible source device. This source device 110-2 has a control unit 111 that controls the operation of each unit, a voltage monitor unit 112, switches SW11 and SW12, and a resistor R1 for voltage division. It is desirable that the resistor R2 of the above-mentioned HDMI cable 130-2 and the resistor R1 of this source device 110-2 each have a relatively large value in order to reduce current consumption. In the following description, R1=100 kΩ and R2=400 kΩ.

[0103] A voltage of 5V is applied to point Q11 of the +5V power line via a series circuit of resistor R1 and switch SW11. A switch SW12 is inserted on the opposite side of the +5V power line from the terminal side of point Q11. A voltage monitor unit 112 monitors the voltage at point Q11 of the +5V power line and sends the monitoring result to the control unit 111.

[0104] In the transmission system 10-2 shown in Fig. 15, the HDMI cable 130-2 is a compatible cable, and the source device 110-2 is a compatible source device. Therefore, the source device 110-2 determines that the connected HDMI cable is a compatible cable and operates in the compatible mode. Similarly, the HDMI cable 130-2 determines that the connected source device is a compatible source device and operates in the compatible mode.

[0105] The operation of source device 110-2 and HDMI cable 130-2 will be described in detail. In Fig. 15, source device 110-2 and HDMI cable 130-2 are shown in an initial state. In source device 110-2, in the initial state, switch SW11 is shorted and switch SW12 is open. On the other hand, in HDMI cable 130-2, in the initial state, switch SW13 is shorted and switches SW14 and SW15 are open.

[0106] In this initial state, switches SW11 and SW13 are shorted, resistors R1 and R2 are connected in series, and a voltage of 4V is obtained through resistive voltage division at points Q11 and P12 on the +5V power line sandwiched between switches SW12 and SW15.

[0107] Voltage monitor unit 112 of source device 110-2 monitors that the voltage at point Q11 is 4 V, and sends the monitoring result to control unit 111. Based on this monitoring result, control unit 111 determines that the connected HDMI cable is a compatible cable, and controls so as to operate in the compatible mode.

[0108] Similarly, voltage monitor unit 133 of HDMI cable 130-2 monitors that the voltage at point P12 is 4 V, and sends the monitoring result to control unit 132. Based on this monitoring result, control unit 132 determines that the connected source device is a compatible source device, and controls it to operate in the compatible mode.

[0109] Since source device 110-2 is controlled to operate in the corresponding mode, control unit 111 accesses (reads / writes) register 131 of HDMI cable 130-2 via the DDC line. In this case, since switch SW14 is in the open state, it is possible to prevent access information of register 131 from being transmitted to sink device 320, and it is possible to avoid malfunction of sink device 320 in which the corresponding address is not defined.

[0110] In source device 110-2, when access to register 131 of HDMI cable 130-2 ends, control unit 111 shorts switch SW12 and opens switch SW11, as shown in Fig. 16. Therefore, the voltage at point P12 of the +5V power line becomes 5V. In HDMI cable 130-2, voltage monitor unit 133 monitors that the voltage at point P12 is 5V, and sends the monitoring result to control unit 132. By monitoring that the voltage at point P12 is 5V in this manner, it is confirmed that register 131 has been accessed from the source device.

[0111] Based on the result of this monitoring, control unit 132 determines that access to register 131 by source device 110-2 has ended, and changes the state of each switch to transition to normal operation as shown in Fig. 17. In this case, first switch SW13 is opened, switch SW14 is shorted, and then switch SW15 is shorted.

[0112] By shorting switch SW15, a 5V voltage is sent from source device 110-2 to sink device 320 via the +5V power line, and accordingly a 5V voltage (connection detection signal) is sent from sink device 320 to source device 110-2 via the HPD line. This causes control unit 111 of source device 110-2 to recognize that cable preparation is complete, and transitions to normal operation.

[0113] 15, the switch SW14 is kept open until the source device 110-2 finishes accessing the register 131 of the HDMI cable 130-2. Therefore, the access information of the register 131 is not transmitted to the sink device 320 via the DDC line, and it is possible to prevent a malfunction of the sink device 320 in which the corresponding address is not defined.

[0114] 15, the switch SW14 is changed to the short-circuited state after the source device 110-2 finishes accessing the register 131 of the HDMI cable 130-2, and thereafter the switch SW15 is changed to the short-circuited state. This makes it possible to avoid interference with a communication signal transmitted from the source device 110-2 to the sink device 320 via the DDC line after the sink device 320 transmits a connection detection signal to the source device 110-2.

[0115] Fig. 18 shows a configuration example of a transmission system 10-2A. This transmission system 10-2A is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-2A has a source device 310 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-2 connecting them. In Fig. 18, parts corresponding to Figs. 1 and 15 are given the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0116] In this transmission system 10-2A, the source device 310 is a non-compliant source device such as a legacy device, and the HDMI cable 130-2 is a compliant cable. In this case, the source device 310 operates normally (see FIG. 6).

[0117] Also, the HDMI cable 130-2 determines that the source device is a non-compatible source device and operates in the non-compatible mode. In this case, in the initial state, the voltage at point P12 of the +5V power line is 5V. The voltage monitor unit 133 of the HDMI cable 130-2 monitors that the voltage at point P12 is 5V, and sends the monitoring result to the control unit 132. The control unit 132 determines that the source device is a non-compatible source device based on this monitoring result, and controls the device to operate in the non-compatible mode.

[0118] In this case, the control unit 132 changes the state of each switch to transition to normal operation. In this case, first, the switch SW13 is opened, the switch SW14 is shorted, and then the switch SW15 is shorted, transitioning to normal operation.

[0119] Fig. 19 shows a configuration example of a transmission system 10-2B. This transmission system 10-2B is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-2B has a source device 110-2 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 330 connecting them. In Fig. 19, parts corresponding to Figs. 1 and 15 are given the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0120] In this transmission system 10-2B, the source device 110-2 is a compliant source device, and the HDMI cable 330 is a non-compliant cable such as a legacy cable. In this case, the HDMI cable 330 operates normally (see FIG. 6).

[0121] Source device 110-2 determines that the HDMI cable is a non-compliant cable and operates in a non-compliant mode. In this case, in the initial state, the voltage at point Q11 of the +5V power line is 5V. Voltage monitor unit 112 of source device 110-2 monitors that the voltage at point Q11 is 5V, and sends the monitoring result to control unit 111. Based on this monitoring result and the fact that the HPD line is at a high level (5V), control unit 111 determines that the HDMI cable is a non-compliant cable and controls to operate in a non-compliant mode. In this case, control unit 111 sets switch SW12 to a short-circuit state, and further sets switch SW11 to an open state, and transitions to normal operation.

[0122] Here, there is a possibility that sink device 320 will start drawing 50 mA when it detects 5 V. If 50 mA is drawn via 100 kΩ resistor R1 in the initial state of Fig. 19, the voltage of the +5V power line from switch SW12 to sink device 320 will drop significantly from 5 V, and it is expected to deviate significantly from the defined specification range.

[0123] As a method of avoiding this, for example, as shown in FIG. 20, an ammeter 113 can be placed between resistor R1 and switch SW11, and when it detects a current increasing from the amount of current I (= 5V / (R1+R2)=5V / 500KΩ=10μA) that flows when both the source device and HDMI cable in FIG. 15 are compatible, switches SW11 and SW12 can be quickly switched so that 50mA can be passed from the source of the +5V power line of source device 110-2 to sink device 320.

[0124] 21 shows an example of a sequence of source device 110-2, which is a corresponding source device. In step ST31, for example, when the power switch is turned on and +5V is raised, the sequence starts and proceeds to step ST32. In this step ST32, control unit 111 judges whether voltage monitor unit 112 detects a predetermined bias voltage (4V).

[0125] When a predetermined bias voltage (4V) is detected, in step ST33, the control unit 111 determines that the HDMI cable is a compatible cable. Then, in step ST34, the control unit 111 starts accessing the register of the HDMI cable.

[0126] Next, in step ST35, after access to the register of the HDMI cable is completed, the control unit 111 changes the switch SW12 from the open state to the short state and changes the switch SW11 from the short state to the open state. Then, in step ST36, the control unit 111 detects that the HPD line has become high level (5 V), and the sequence ends in step ST37.

[0127] Furthermore, when the predetermined bias voltage (4V) is not detected in step ST32, the control unit 111 determines in step ST38 whether or not a high level (5V) of the HPD line is detected. When a high level (5V) of the HPD line is not detected, the process returns to step ST32. On the other hand, when a high level (5V) of the HPD line is detected, in step ST39, the control unit 111 determines that the HDMI cable is a non-compliant cable.

[0128] Then, in step ST40, the switch SW12 is changed from the open state to the short-circuited state, and the switch SW11 is changed from the short-circuited state to the open state by the control section 111. Then, in step ST37, the sequence ends.

[0129] 22 shows an example of a sequence for the HDMI cable 130-2, which is a compatible cable. In step ST51, when the voltage monitor unit 133 detects a voltage of 5V or 4V on the +5V power line, the sequence starts and proceeds to step ST52. In this step ST52, the control unit 132 determines whether the voltage monitor unit 133 detects a predetermined bias voltage (4V).

[0130] When a predetermined bias voltage (4V) is detected, in step ST53, the control unit 132 determines that the source device is a compatible source device. Then, when 5V is detected by the voltage monitor unit 133 in step ST54, in step ST55, the control unit 132 changes the switch SW13 from a short-circuited state to an open state and changes the switch SW14 from an open state to a short-circuited state. In this case, the detection of 5V by the voltage monitor unit 133 confirms that the register 131 has been accessed from the source device. Then, in step ST56, the control unit 132 changes the switch SW15 from an open state to a short-circuited state, and in step ST57, the sequence ends.

[0131] Furthermore, when the predetermined bias voltage (4V) is not detected in step ST52, the control unit 132 determines in step ST58 that the source device is a non-compatible source device. Then, in step ST55, the control unit 132 changes the switch SW13 from a short-circuited state to an open state, and changes the switch SW14 from an open state to a short-circuited state. Then, in step ST56, the control unit 132 changes the switch SW15 from an open state to a short-circuited state, and the sequence ends in step ST57.

[0132] It should be noted that the switches SW11 and SW12 of the source device 110-2 and the switches SW13, SW14, and SW15 of the HDMI cable 130-2 are reset to their initial states when the voltage of the +5V power line drops.

[0133] "Embodiment 3" Fig. 23 shows a configuration example of a transmission system 10-3. This transmission system 10-3 is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-3 has a source device 110-3 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-3 which is an AOC that connects them. In this Fig. 23, parts corresponding to Fig. 4 are given the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0134] The HDMI cable 130-3 includes AOC components such as conversion circuits 331A and 331B, LDO regulators 332A and 332B, and a current driver 333B, as well as a control unit 132, voltage monitors 133 and 134, switches SW23, SW24, and SW26, and a voltage dividing resistor R2.

[0135] A series circuit of resistor R2 and switch SW23 is connected between point P22 of the utility line and the ground. As a result, 0V, which is the ground voltage, is applied to point P22 of the utility line via the series circuit of resistor R2 and switch SW23. A switch SW24 is inserted on the utility line closer to the sink device 320 than point P22. Also, a switch SW26 is inserted in the +5V power line.

[0136] The voltage monitor unit 133 monitors the voltage at point P22 of the utility line and sends the monitoring result to the control unit 132. The voltage monitor unit 134 monitors the voltage at point P23 on the terminal side of the insertion position of the switch SW26 on the +5V power line and sends the monitoring result to the control unit 132. Power is supplied to the LDO regulators 332A and 332B from a point on the sink device 320 side of the insertion position of the switch SW26 on the +5V power line. The control unit 132 controls the operation of each part of the HDMI cable 130-3.

[0137] Source device 110-3 is a compatible source device. This source device 110-3 has a control unit 111 that controls the operation of each unit, a voltage monitor unit 112, switches SW21 and SW22, and a resistor R1 for voltage division. It is desirable that the resistor R2 of the above-mentioned HDMI cable 130-3 and the resistor R1 of this source device 110-3 each have a relatively large value in order to reduce current consumption. In the following description, R1=100 kΩ and R2=400 kΩ.

[0138] A series circuit of resistor R1 and switch SW21 is connected between the +5V power line and point Q21 of the utility line. As a result, +5V is applied to point Q21 of the utility line via the series circuit of resistor R1 and switch SW21. A switch SW22 is inserted on the opposite side of the utility line from the terminal side of point Q21. Voltage monitor unit 112 monitors the voltage at point Q21 of the utility line and sends the monitoring result to control unit 111.

[0139] In the transmission system 10-3 shown in Fig. 23, the HDMI cable 130-3 is a compatible cable, and the source device 110-3 is a compatible source device. Therefore, the source device 110-3 determines that the connected HDMI cable is a compatible cable and operates in the compatible mode. Similarly, the HDMI cable 130-3 determines that the connected source device is a compatible source device and operates in the compatible mode.

[0140] The operation of the source device 110-3 and the HDMI cable 130-3 will be described in detail. In Fig. 23, the source device 110-3 and the HDMI cable 130-3 are shown in an initial state. In the source device 110-3, in the initial state, the switch SW21 is shorted and the switch SW22 is open. On the other hand, in the HDMI cable 130-3, in the initial state, the switch SW23 is shorted and the switches SW24 and SW26 are open.

[0141] In this initial state, SW21 and SW23 are short-circuited, so that resistors R1 and R2 are connected in series between the +5V power line of source device 110-3 and the ground (0V) of HDMI cable 130-3, and a voltage of 4V is obtained at points Q21 and P22 of the utility line through resistive voltage division.

[0142] Voltage monitor unit 112 of source device 110-3 monitors that the voltage at point Q21 is 4 V, and sends the monitoring result to control unit 111. Based on this monitoring result, control unit 111 determines that the connected HDMI cable is a compatible cable, and controls so as to operate in the compatible mode.

[0143] Similarly, voltage monitor unit 133 of HDMI cable 130-3 monitors that the voltage at point P22 is 4 V, and sends the monitoring result to control unit 132. Based on this monitoring result, control unit 132 determines that the connected source device is a compatible source device, and controls it to operate in the compatible mode.

[0144] Here, in source device 110-3, switch SW22 is open, so the voltage of 4V is not propagated inside source device 110-3 and does not affect the inside of source device 110-3. Similarly, in HDMI cable 130-3, switch SW24 is open, so the voltage of 4V is not propagated to sink device 320 and does not affect sink device 320.

[0145] Since source device 110-3 is controlled to operate in the compatible mode, control unit 111 opens switch SW21 as shown in Fig. 24. Therefore, the voltage at point P22 of the utility line becomes 0V. In HDMI cable 130-3, voltage monitor unit 133 monitors that the voltage at point P22 is 0V, and sends the monitoring result to control unit 132. By monitoring that the voltage at point P22 is 0V in this manner, it is confirmed that the source device has determined that its own cable is a compatible cable.

[0146] Based on this monitoring result, the control unit 132 changes the state of each switch as shown in Fig. 25 and transitions to normal operation. In this case, in order not to affect the sink device 320, first the switch SW23 is opened, then the switch SW24 is shorted, and finally the switch SW26 is shorted. After that, the control unit 132 turns on the LDO regulators 332A and 332B to provide a power supply of 3.3V to the conversion circuits 331A and 331B, which are active circuits, and sets these conversion circuits 331A and 331B to an operating state (Enable).

[0147] By shorting switch SW26, a 5V voltage is sent from source equipment 110-3 to sink equipment 320 via the +5V power line, and accordingly a 5V voltage (connection detection signal) is sent from sink equipment 320 to source equipment 110-3 via the HPD line. This causes control unit 111 of source equipment 110-3 to recognize that cable preparation is complete, and as shown in Fig. 26, control unit 111 shorts switch SW22 and transitions to normal operation.

[0148] Although the compatible source device 110-3 may be configured so that the current that can be supplied by the +5V power line is always 55 mA or more and can supply current to the active circuit of the HDMI cable 130-3, which is a compatible cable, the control unit 111 of the source device 110-3 may change the mode to one in which the current that can be supplied by the +5V power line is 55 mA or more when it determines that the connected HDMI cable is a compatible cable. By switching the mode of the current supply amount, the source device 110-3 can reduce the power of the power supply circuit unit. In this case, after determining that the HDMI cable is a compatible cable, the control unit 111 changes the mode to one in which the current that can be supplied is 55 mA or more before opening the switch SW21.

[0149] 23, the HDMI cable 130-3, which is a compatible cable, activates its own active circuit when it determines that the connected source device is a compatible source device that can supply sufficient current to its own active circuit. This allows the active circuit of the HDMI cable 130-3 to operate appropriately, and also prevents the source device from failing due to being unable to withstand the overcurrent.

[0150] Fig. 27 shows a configuration example of a transmission system 10-3A. This transmission system 10-3A is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-3A has a source device 310 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-3 connecting them. In Fig. 27, parts corresponding to Figs. 4 and 23 are given the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0151] In this transmission system 10-3A, the source device 310 is a non-compliant source device such as a legacy device, and the HDMI cable 130-3 is a compliant cable. In this case, the source device 310 operates normally (see FIG. 6).

[0152] Furthermore, the HDMI cable 130-3 determines that the source device is a non-compatible source device and operates in the non-compatible mode. In this case, in the initial state, the voltage at point P22 of the Utility line is 0V. The voltage monitor unit 133 of the HDMI cable 130-3 monitors that the voltage at point P22 is 0V, and sends the monitoring result to the control unit 132. The control unit 132 determines that the source device is a non-compatible source device based on this monitoring result, and controls the device to operate in the non-compatible mode.

[0153] In this case, the control unit 132 changes the state of each switch and transitions to normal operation. In this case, in order not to affect the sink device 320, first the switch SW23 is opened, then the switch SW24 is shorted, and finally the switch SW26 is shorted. In addition, in this case, the control unit 132 keeps the LDO regulators 332A and 332B off, and keeps the conversion circuits 331A and 331B, which are active circuits, in a non-operating state (Disable). This prevents the HDMI cable 130-3 from drawing a current of 55 mA or more from the source device 310, and prevents the source device 310 from being unable to withstand the overcurrent and causing a breakdown.

[0154] Fig. 28 shows a configuration example of a transmission system 10-3B. This transmission system 10-3B is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-3B has a source device 110-3 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 330C connecting them. In this Fig. 28, parts corresponding to Figs. 4 and 23 are given the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0155] In this transmission system 10-3B, the source device 110-3 is a compliant source device, and the HDMI cable 330C is a non-compliant cable such as a legacy cable. In this case, the HDMI cable 330C operates normally (see FIG. 6).

[0156] Source device 110-3 determines that the HDMI cable is a non-compliant cable and operates in the non-compliant mode. In this case, in the initial state, the voltage at point Q21 of the Utility line is 5V. Voltage monitor unit 112 of source device 110-3 monitors that the voltage at point Q21 is 5V, and sends the monitoring result to control unit 111. Based on this monitoring result and the fact that the HPD line is at a high level (5V), control unit 111 determines that the HDMI cable is a non-compliant cable, and controls so as to operate in the non-compliant mode.

[0157] In this case, control unit 111 changes the state of each switch to transition to normal operation. In this case, in order not to affect the inside of source device 110-3, first switch SW21 is opened, and then switch SW22 is shorted.

[0158] 29 shows an example of a sequence of source device 110-3, which is a corresponding source device. In step ST61, for example, when the power switch is turned on and +5V is raised, the sequence starts and proceeds to step ST62. In this step ST62, control unit 111 judges whether voltage monitor unit 112 detects a predetermined bias voltage (4V).

[0159] When a predetermined bias voltage (4 V) is detected, in step ST63, the control unit 111 determines that the HDMI cable is a compatible cable. Then, in step ST64, the control unit 111 changes the switch SW21 from a shorted state to an open state. After that, in step ST65, when the control unit 111 detects that the HPD line has become high level (5 V), in step ST66, the control unit 111 changes the switch SW22 from an open state to a shorted state. Then, in step ST67, the sequence ends.

[0160] Furthermore, when the predetermined bias voltage (4V) is not detected in step ST62, the control unit 111 determines in step ST68 whether or not a high level (5V) of the HPD line is detected. When a high level (5V) of the HPD line is not detected, the process returns to step ST62. On the other hand, when a high level (5V) of the HPD line is detected, in step ST69, the control unit 111 determines that the HDMI cable is a non-compliant cable.

[0161] Then, in step ST70, the switch SW21 is changed from the short-circuited state to the open-circuited state. Next, in step ST66, the switch SW22 is changed from the open-circuited state to the short-circuited state by the control section 111. Then, in step ST67, the sequence ends.

[0162] 30 shows an example of a sequence for the HDMI cable 130-3, which is a compatible cable. In step ST81, when the voltage monitor unit 134 detects a voltage of 5V, the sequence starts and proceeds to step ST82. In this step ST82, the control unit 132 determines whether the voltage monitor unit 133 detects a predetermined bias voltage (4V).

[0163] When a predetermined bias voltage (4V) is detected, in step ST83, the control unit 132 determines that the source device is a compatible source device. Then, in step ST84, when the voltage monitor unit 133 detects 0V, in step ST85, the control unit 132 changes the switch SW23 from a short-circuited state to an open state. In this case, the detection of 0V by the voltage monitor unit 133 confirms that the source device has determined that its own cable is a compatible cable.

[0164] Next, in step ST86, the control unit 132 changes the switch SW24 from the open state to the short state, and then, in step ST87, the control unit 132 changes the switch SW26 from the open state to the short state. Then, in step ST88, the LDO regulators 332A and 332B are turned on to put the active circuit into an operating state (Enable), and then, in step ST89, the sequence ends.

[0165] Furthermore, when the predetermined bias voltage (4 V) is not detected in step ST82, in step ST90, the control unit 132 determines that the source device is a non-compatible source device. Then, in step ST91, the control unit 132 changes the switch SW23 from the short-circuited state to the open state.

[0166] Next, in step ST92, the control unit 132 changes the switch SW24 from the open state to the short state, and then, in step ST93, the control unit 132 changes the switch SW26 from the open state to the short state. Then, in step ST89, the sequence ends.

[0167] It should be noted that the switches SW21 and SW22 of the source device 110-3 and the switches SW23, SW24, and SW26 of the HDMI cable 130-3 are reset to their initial states when the voltage of the +5V power line drops.

[0168] In the above description, the HDMI cable 130-3, which is a compatible cable, controls the on / off of the LDO regulators 332A and 332B depending on whether the source device is a compatible device or a non-compatible device. However, in this case, if the source device is a non-compatible device, the LDO regulators 332A and 332B are turned off and the active circuit is in an inactive state, making it impossible to transmit data.

[0169] Therefore, when the source device is a non-compliant source device, the HDMI cable 130-3 may guarantee that the current drawn from the source device is 55 mA or less by lowering the data rate, rather than keeping the LDO regulators 332A and 332B in an off state. This allows data transmission even if the source device is a non-compliant source device.

[0170] "Embodiment 4" 31 shows a configuration example of a transmission system 10-4. The transmission system 10-4 is an HDMI transmission system that uses HDMI as a digital interface. The transmission system 10-4 includes a source device 110-4 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-4 that connects them.

[0171] In the transmission system 10-3 shown in Fig. 23 described above, the Utility line is used to determine whether the source device and the HDMI cable are compatible, but in this transmission system 10-4, the +5V power line is used to make the determination. In Fig. 31, parts corresponding to Fig. 4 and Fig. 23 are given the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0172] The HDMI cable 130-4 includes AOC components such as conversion circuits 331A and 331B, LDO regulators 332A and 332B, and a current driver 333B, as well as a control unit 132, a voltage monitor unit 133, switches SW33 and SW35, and a voltage dividing resistor R2.

[0173] A series circuit of resistor R2 and switch SW33 is connected between point P32 of the +5V power line and the ground. As a result, 0V, which is the ground voltage, is applied to point P32 of the +5V power line via the series circuit of resistor R2 and switch SW33. A switch SW35 is inserted on the +5V power line closer to the sink device 320 than point P32. A voltage monitor unit 133 monitors the voltage at point P32 of the +5V power line and sends the monitoring result to the control unit 132. The control unit 132 controls the operation of each unit of the HDMI cable 130-4.

[0174] Source device 110-4 is a compatible source device. This source device 110-4 has a control unit 111 that controls the operation of each unit, a voltage monitor unit 112, switches SW31 and SW32, and a resistor R1 for voltage division. It is desirable that the resistor R2 of the above-mentioned HDMI cable 130-4 and the resistor R1 of this source device 110-4 each have a relatively large value in order to reduce current consumption. In the following description, R1=100 kΩ and R2=400 kΩ.

[0175] A voltage of 5V is applied to point Q31 of the +5V power line via a series circuit of resistor R1 and switch SW31. Switch SW32 is inserted on the opposite side of the +5V power line from the terminal side of point Q31. Voltage monitor unit 112 monitors the voltage at point Q31 of the +5V power line and sends the monitoring result to control unit 111.

[0176] In the transmission system 10-4 shown in Fig. 31, the HDMI cable 130-4 is a compatible cable, and the source device 110-4 is a compatible source device. Therefore, the source device 110-4 determines that the connected HDMI cable is a compatible cable and operates in the compatible mode. Similarly, the HDMI cable 130-4 determines that the connected source device is a compatible source device and operates in the compatible mode.

[0177] The operation of the source device 110-4 and the HDMI cable 130-4 will be described in detail. In Fig. 31, the source device 110-4 and the HDMI cable 130-4 are shown in an initial state. In the source device 110-4, in the initial state, the switch SW31 is shorted and the switch SW32 is open. On the other hand, in the HDMI cable 130-4, in the initial state, the switch SW33 is shorted and the switch SW35 is open.

[0178] In this initial state, switches SW31 and SW33 are shorted, so resistors R1 and R2 are connected in series, and a voltage of 4V is obtained at points Q31 and P32 on the +5V power line sandwiched between switches SW32 and SW35 due to resistive voltage division.

[0179] Voltage monitor unit 112 of source device 110-4 monitors that the voltage at point Q31 is 4 V, and sends the monitoring result to control unit 111. Based on this monitoring result, control unit 111 determines that the connected HDMI cable is a compatible cable, and controls so as to operate in the compatible mode.

[0180] Similarly, voltage monitor unit 133 of HDMI cable 130-4 monitors that the voltage at point P32 is 4 V, and sends the monitoring result to control unit 132. Based on this monitoring result, control unit 132 determines that the connected source device is a compatible source device, and controls it to operate in the compatible mode.

[0181] Source device 110-4 is controlled to operate in the compatible mode. As shown in Fig. 32, control unit 111 sets switch SW32 to a short-circuit state, and further sets switch SW31 to an open state. Therefore, the voltage at point P32 of the +5V power line becomes 5V. In HDMI cable 130-4, voltage monitor unit 133 monitors that the voltage at point P32 is 5V, and sends the monitoring result to control unit 132. By monitoring that the voltage at point P32 is 5V in this manner, it is confirmed that the source device has identified its own cable as a compatible cable.

[0182] Based on the monitoring result, the control unit 132 changes the state of each switch as shown in Fig. 33 and transitions to normal operation. In this case, first the switch SW33 is opened and then the switch SW35 is shorted so as not to affect the source device 110-4 and the sink device 320. Thereafter, the control unit 132 turns on the LDO regulators 332A and 332B to provide a power supply of 3.3V to the conversion circuits 331A and 331B, which are active circuits, and sets these conversion circuits 331A and 331B to an operating state (Enable).

[0183] By shorting switch SW35, a 5V voltage is sent from source device 110-3 to sink device 320 via the +5V power line, and accordingly a 5V voltage (connection detection signal) is sent from sink device 320 to source device 110-1 via the HPD line. This causes control unit 111 of source device 110-4 to recognize that cable preparation is complete, and transitions to normal operation.

[0184] Although the compatible source device 110-4 may be configured so that the current that can be supplied by the +5V power line is always 55 mA or more and can supply current to the active circuit of the HDMI cable 130-4, which is a compatible cable, the control unit 111 of the source device 110-4 may change the mode to one in which the current that can be supplied by the +5V power line is 55 mA or more when it determines that the connected HDMI cable is a compatible cable. By switching the mode of the current supply amount, the source device 110-4 can reduce the power of the power supply circuit unit. In this case, after determining that the HDMI cable is a compatible cable, the control unit 111 changes the mode to one in which the current that can be supplied is 55 mA or more before opening the switch SW31.

[0185] 31, the HDMI cable 130-3, which is a compatible cable, activates its own active circuit when it determines that the connected source device is a compatible source device that can supply sufficient current to its own active circuit. This allows the active circuit of the HDMI cable 130-4 to operate appropriately, and also prevents the source device from failing due to being unable to withstand the overcurrent.

[0186] Fig. 34 shows a configuration example of a transmission system 10-4A. This transmission system 10-4A is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-4A has a source device 310 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-4 connecting them. In this Fig. 34, parts corresponding to Figs. 4 and 31 are given the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0187] In this transmission system 10-4A, the source device 310 is a non-compliant source device such as a legacy device, and the HDMI cable 130-4 is a compliant cable. In this case, the source device 310 operates normally (see FIG. 6).

[0188] Also, the HDMI cable 130-4 determines that the source device is a non-compatible source device and operates in the non-compatible mode. In this case, in the initial state, the voltage at point P32 of the +5V power line is 5V. The voltage monitor unit 133 of the HDMI cable 130-4 monitors that the voltage at point P32 is 5V, and sends the monitoring result to the control unit 132. The control unit 132 determines that the source device is a non-compatible source device based on this monitoring result, and controls the device to operate in the non-compatible mode.

[0189] In this case, the control unit 132 changes the state of each switch and transitions to normal operation. In this case, in order not to affect the sink device 320, first the switch SW33 is opened, and then the switch SW35 is shorted. In addition, in this case, the control unit 132 keeps the LDO regulators 332A and 332B off, and keeps the conversion circuits 331A and 331B, which are active circuits, in a non-operating state (Disable). This prevents the HDMI cable 130-4 from drawing a current of 55 mA or more from the source device 310, and prevents the source device 310 from being unable to withstand the overcurrent and causing a breakdown.

[0190] Fig. 35 shows a configuration example of a transmission system 10-3B. This transmission system 10-4B is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-4B has a source device 110-4 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 330C connecting them. In this Fig. 35, parts corresponding to Figs. 4 and 31 are given the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0191] In this transmission system 10-4B, the source device 110-4 is a compliant source device, and the HDMI cable 330C is a non-compliant cable such as a legacy cable. In this case, the HDMI cable 330C operates normally (see FIG. 6).

[0192] Source device 110-4 determines that the HDMI cable is a non-compliant cable and operates in a non-compliant mode. In this case, in the initial state, the voltage at point Q31 of the +5V power line is 5V. Voltage monitor unit 112 of source device 110-4 monitors that the voltage at point Q31 is 5V, and sends the monitoring result to control unit 111. Based on this monitoring result and the fact that the HPD line is at a high level (5V), control unit 111 determines that the HDMI cable is a non-compliant cable and controls to operate in a non-compliant mode. In this case, control unit 111 sets switch SW32 to a short-circuit state, sets switch SW31 to an open state, and transitions to normal operation.

[0193] Here, there is a possibility that sink device 320 will start drawing 50 mA when it detects 5 V. If 50 mA is drawn via 100 kΩ resistor R1 in the initial state of Fig. 35, the voltage of the +5V power line from switch SW32 to sink device 320 will drop significantly from 5 V and is expected to deviate significantly from the defined specification range.

[0194] As a way to avoid this, for example, as shown in FIG. 36, an ammeter 113 can be placed between resistor R1 and switch SW31, and when it detects a current increasing from the amount of current I (= 5V / (R1+R2)=5V / 500KΩ=10μA) that flows when both the source device and HDMI cable in FIG. 31 are compatible, switches SW31 and SW32 can be quickly switched so that 50mA can be passed from the source of the +5V power line of source device 110-4 to sink device 320.

[0195] 37 shows an example of a sequence of source device 110-4, which is a corresponding source device. In step ST101, for example, when the power switch is turned on and +5V is raised, the sequence starts and proceeds to step ST102. In this step ST102, control unit 111 judges whether voltage monitor unit 112 detects a predetermined bias voltage (4V).

[0196] When a predetermined bias voltage (4V) is detected, in step ST103, the control unit 111 determines that the HDMI cable is a compatible cable. Then, in step ST104, the control unit 111 changes the switch SW32 from an open state to a short state, and changes the switch SW31 from a short state to an open state. Then, in step ST105, when the control unit 111 detects that the HPD line has become high level (5V), the sequence ends in step ST106.

[0197] Furthermore, when the predetermined bias voltage (4V) is not detected in step ST102, the control unit 111 determines in step ST107 whether or not a high level (5V) of the HPD line is detected. When a high level (5V) of the HPD line is not detected, the process returns to step ST102. On the other hand, when a high level (5V) of the HPD line is detected, in step ST108, the control unit 111 determines that the HDMI cable is a non-compliant cable.

[0198] Then, in step ST109, the switch SW32 is changed from the open state to the short-circuited state, and the switch SW31 is changed from the short-circuited state to the open state by the control section 111. Then, in step ST106, the sequence ends.

[0199] 38 shows an example of a sequence for the HDMI cable 130-4, which is a compatible cable. In step ST111, when the voltage monitor unit 133 detects a voltage of 5V or 4V on the +5V power line, the sequence starts and proceeds to step ST112. In this step ST112, the control unit 132 determines whether the voltage monitor unit 133 detects a predetermined bias voltage (4V).

[0200] When a predetermined bias voltage (4V) is detected, in step ST113, the control unit 132 determines that the source device is a compatible source device. Then, in step ST114, when the voltage monitor unit 133 detects 5V, in step ST115, the control unit 132 changes the switch SW33 from a short-circuited state to an open state. In this case, the detection of 5V by the voltage monitor unit 133 confirms that the source device has determined that its own cable is a compatible cable.

[0201] Next, in step ST116, the switch SW35 is changed from the open state to the short state by the control unit 132. Then, in step ST117, the LDO regulators 332A and 332B are turned on to put the active circuit into an operating state (Enable), and then, in step ST118, the sequence ends.

[0202] Furthermore, when the predetermined bias voltage (4V) is not detected in step ST112, in step ST119, the control unit 132 determines that the source device is a non-compatible source device. Next, in step ST120, the control unit 132 changes the switch SW33 from a short-circuited state to an open state. Then, in step ST121, the control unit 132 changes the switch SW35 from an open state to a short-circuited state, and in step ST118, the sequence ends.

[0203] It should be noted that the switches SW31 and SW32 of the source device 110-4 and the switches SW33 and SW35 of the HDMI cable 130-4 are reset to their initial states when the voltage of the +5V power line drops.

[0204] In the above description, the HDMI cable 130-4, which is a compatible cable, controls the on / off of the LDO regulators 332A and 332B depending on whether the source device is a compatible device or a non-compatible device. However, in this case, if the source device is a non-compatible device, the LDO regulators 332A and 332B are turned off and the active circuit is in an inactive state, making it impossible to transmit data.

[0205] Therefore, when the source device is a non-compliant source device, the HDMI cable 130-4 may guarantee that the current drawn from the source device is 55 mA or less by lowering the data rate, rather than keeping the LDO regulators 332A and 332B in an off state. This allows data transmission even if the source device is a non-compliant source device.

[0206] "Embodiment 5" 39 shows a configuration example of a transmission system 10-5. This transmission system 10-5 is an HDMI transmission system that uses HDMI as a digital interface. This transmission system 10-5 has a source device 110-5 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-5 that connects them.

[0207] The HDMI cable 130-3 in the transmission system 10-3 in Fig. 23 described above does not have a register, but the HDMI cable 130-5 in the transmission system 10-5 has a register 131 similar to that of the HDMI cable 130-1 in the transmission system 10-1 in Fig. 7 described above. In Fig. 39, parts corresponding to those in Fig. 7 and Fig. 23 are given the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0208] The HDMI cable 130-5 is a compatible cable. In addition to AOC configuration circuits such as conversion circuits 331A and 331B, LDO regulators 332A and 332B, and a current driver 333B, the HDMI cable 130-5 includes a control unit 132, voltage monitor units 133 and 134, switches SW3, SW4, and SW5, and a voltage dividing resistor R2.

[0209] Source device 110-5 is a compatible source device. This source device 110-5 has a control unit 111 that controls the operation of each unit, a voltage monitor unit 112, switches SW1 and SW2, and a resistor R1 for voltage division. It is desirable that the resistor R2 of the above-mentioned HDMI cable 130-5 and the resistor R1 of this source device 110-5 each have a relatively large value in order to reduce current consumption. In the following description, R1=100 kΩ and R2=400 kΩ.

[0210] In the transmission system 10-5 shown in Fig. 39, the HDMI cable 130-5 is a compatible cable, and the source device 110-5 is a compatible source device. Therefore, the source device 110-5 determines that the connected HDMI cable is a compatible cable and operates in the compatible mode. Similarly, the HDMI cable 130-5 determines that the connected source device is a compatible source device and operates in the compatible mode.

[0211] The operation of the source device 110-5 and the HDMI cable 130-5 will be described. Although detailed description will be omitted, they operate in the same manner as the source device 110-1 and the HDMI cable 130-1 in the transmission system 10-1 of Fig. 7 described above, and after the control unit 111 of the source device 110-5 accesses (reads / writes) the register 131 of the HDMI cable 130-5, they each transition to normal operation.

[0212] When accessing the register 131, the control unit 111 of the source device 110-5 can write to the register 131 that the control unit 132 of the HDMI cable 130-5 may draw a current of 55 mA or more. After transitioning to normal operation, the control unit 132 of the HDMI cable 130-5 can turn on the LDO regulators 332A and 332B based on the information in the register 131, and draw 55 mA or more from the +5V power line. That is, in the case of the transmission system 10-5 of Fig. 39, the source device 110-5 can notify the HDMI cable 130-5 through the register 131 that the control unit 132 of the HDMI cable 130-5 may draw a current of 55 mA or more.

[0213] In addition, in the transmission system 10-5 shown in FIG. 39, the utility line is used to determine whether the source device and HDMI cable are compatible, but it can also be configured in a similar manner to determine whether the source device and HDMI cable are compatible using the +5V power line (see FIG. 15 and FIG. 31).

[0214] 39, the switch SW5 is kept open until the source device 110-5 finishes accessing the register 131 of the HDMI cable 130-5. Therefore, the access information of the register 131 is not transmitted to the sink device 320 via the DDC line, and it is possible to prevent the sink device 320, whose address is not defined, from malfunctioning.

[0215] 39, after the source device 110-5 finishes accessing the register 131 of the HDMI cable 130-5, the switch SW5 is changed to the short-circuited state, and thereafter the switch SW6 is changed to the short-circuited state. This makes it possible to avoid interference with a communication signal transmitted from the source device 110-5 to the sink device 320 via the DDC line after the sink device 320 transmits a connection detection signal to the source device 110-5.

[0216] 39, the control unit 132 of the HDMI cable 130-5 turns on the LDO regulators 332A and 332B and controls the cable to draw 55 mA or more from the +5V power line based on information transmitted from the source device 110-5 via the register 131 that the cable itself may draw a current of 55 mA or more. This enables the active circuit of the HDMI cable 130-5 to operate appropriately, and also prevents the source device from being unable to withstand the overcurrent and causing a breakdown.

[0217] "Embodiment 6" 40 shows a configuration example of a transmission system 10-3C. This transmission system 10-3C is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-3C has a source device 110-3 as a transmitting device, a repeater 140 as a relay, a sink device 320 as a receiving device, an HDMI cable 330 connecting the source device 110-3 and the repeater 140, and an HDMI cable 130-3 connecting the repeater 140 and the sink device 320.

[0218] In the transmission system 10-3 in Fig. 23 described above, the source device 110-3 and the sink device 320, which are compatible source devices, are directly connected via the HDMI cable 130-3, which is a compatible cable, but in the transmission system 10-3C in Fig. 40, an HDMI cable 330 and a repeater 140 are further inserted in series between the source device 110-3 and the HDMI cable 130-3. In Fig. 40, parts corresponding to Figs. 1 and 23 are denoted by the same reference numerals.

[0219] Here, the repeater 140 has an amplifier 141 on the data line. Also, the repeater 140 has a power supply in a system separate from the +5V power supply line supplied from the source device 110-3, and 5V is supplied to the sink device 320 from this separate power supply through the +5V power supply line. In this case, the +5V power supply line is separated by the repeater 140 between the source device 110-3 and the HDMI cable 130-3. Also, here, it is assumed that the input and output of the control lines such as Utility of the repeater 140 are connected with low impedance.

[0220] 40, a utility line is connected between source device 110-3 and HDMI cable 130-3 via HDMI cable 330, which is a non-compliant cable, and repeater 140. Despite the presence of repeater 140, source device 110-3 and HDMI cable 130-3 perform sequence operations as if they were compatible products.

[0221] In this case, the voltage monitor unit 133 of the HDMI cable 130-3 monitors that the voltage at point P22 is 4V, and sends the monitoring result to the control unit 132. The control unit 132 determines that the source device is a compatible source device based on this monitoring result, and controls it to operate in the compatible mode. Therefore, the switch SW26 is short-circuited, the LDO regulators 332A and 332B are turned on, and the conversion circuits 331A and 331B are put into an operating state, and start drawing current from the +5V line.

[0222] In this case, the actual current source is not the +5V power line of source device 110-3, but the +5V power line of repeater 140. In this case, if repeater 140 does not support a current supply of 55 mA or more, it may break down.

[0223] In this embodiment, in order to avoid such a failure of the repeater 140, the source devices and HDMI cables that make up the transmission system each take into consideration whether a repeater is present or not, and operate differently depending on whether they are compatible or not, and further whether the other party is compatible or not, as shown in Figures 41(a) and (b).

[0224] Compatible source devices (compatible source devices) and non-compatible source devices operate as shown in Fig. 41(a). That is, when a compatible cable (compatible HDMI cable) is connected, a compatible source device operates in a non-compatible mode if a non-compatible repeater is present, and operates in a compatible mode if no repeater is present. Also, a compatible source device operates in a non-compatible mode if a non-compatible cable is connected. Also, a non-compatible source device operates normally whether a compatible cable or a non-compatible cable is connected.

[0225] Also, compatible and non-compatible cables operate as shown in Fig. 41(b). That is, when a compatible source device is connected, a compatible cable operates in a non-compatible mode if a non-compatible repeater is present, and operates in a compatible mode if no repeater is present. Also, a compatible cable operates in a non-compatible mode if a non-compatible source device is connected. Also, a non-compatible cable operates normally whether a compatible or non-compatible source device is connected.

[0226] Also, Figures 41(c) and (d) show the operational relationship between compatible / non-compatible repeaters and compatible / non-compatible cables 2. In the case of a compatible repeater, between the source device and the repeater, the repeater acts like a receiving port for a sink device, and the above-mentioned mode in Figure 6 holds. Between the repeater and the sink device, the repeater acts like a source device output, that is, it has a voltage dividing resistor R and a switch SW just like a compatible source device, so the mode in Figures 41(c) and (d) holds. In this case, the compatible cable does not determine the presence of a repeater, but operates as if it is connected to a source device, but this is not a problem because the compatible repeater can pass 55 mA or more.

[0227] Fig. 42 shows a configuration example of a transmission system 10-6. This transmission system 10-6 is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-6 has a source device 110-6 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-6 that is an AOC that connects them. In this Fig. 42, parts corresponding to Fig. 23 are given the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0228] The HDMI cable 130-6 includes AOC components such as conversion circuits 331A and 331B, LDO regulators 332A and 332B, and a current driver 333B, as well as a control unit 132, voltage monitors 133 and 134, switches SW43, SW44, and SW46, and a voltage dividing resistor R2.

[0229] A series circuit of resistor R2 and switch SW43 is connected between point P42 of the utility line and point P44 of the +5V power line. As a result, 5V is applied to point P42 of the utility line via the series circuit of resistor R2 and switch SW43. A switch SW44 is inserted on the utility line closer to the sink device 320 than point P42. In addition, a switch SW46 is inserted on the +5V power line closer to the sink device 320 than point P44.

[0230] The voltage monitor unit 133 monitors the voltage at point P42 of the utility line and sends the monitoring result to the control unit 132. The voltage monitor unit 134 monitors the voltage at point P43 on the terminal side of the +5V power line from the insertion position of the switch SW46 and sends the monitoring result to the control unit 132. Power is supplied to the LDO regulators 332A and 332B from a point on the +5V power line on the sink device 320 side from the insertion position of the switch SW46. The control unit 132 controls the operation of each part of the HDMI cable 130-6.

[0231] Source device 110-6 is a compatible source device. This source device 110-6 has a control unit 111 that controls the operation of each unit, a voltage monitor unit 112, switches SW41, SW42, SW47, SW48, and resistors R1 and R3 for voltage division. It is desirable that the resistor R2 of the above-mentioned HDMI cable 130-6 and the resistors R1 and R3 of this source device 110-6 each have a relatively large value in order to reduce current consumption. In the following description, R1=400 kΩ, R2=100 kΩ, and R3=500 kΩ.

[0232] A series circuit of resistor R1 and switch SW41 is connected between the ground and point Q41 of the utility line. As a result, 0V, which is the ground voltage, is applied to point Q41 of the utility line via the series circuit of resistor R1 and switch SW41. A switch SW42 is inserted on the opposite side of the utility line from the terminal side of point Q41. A voltage monitor unit 112 monitors the voltage at point Q41 of the utility line and sends the monitoring result to the control unit 111. A voltage of 5V is applied to point Q42 of the +5V power line via a series circuit of resistor R3 and switch SW47. A switch SW48 is inserted on the opposite side of the +5V power line from the terminal side of point Q42.

[0233] In the transmission system 10-6 shown in Fig. 42, the HDMI cable 130-6 is a compatible cable, and the source device 110-6 is a compatible source device. Therefore, the source device 110-6 determines that the connected HDMI cable is a compatible cable and operates in the compatible mode. Similarly, the HDMI cable 130-6 determines that the connected source device is a compatible source device and operates in the compatible mode.

[0234] The operation of source device 110-6 and HDMI cable 130-6 will be described in detail. In Fig. 42, source device 110-6 and HDMI cable 130-6 are shown in an initial state. In source device 110-6, in the initial state, switches SW41 and SW48 are shorted, and switches SW42 and SW47 are open. On the other hand, in HDMI cable 130-6, in the initial state, switch SW43 is shorted, and switches SW44 and SW46 are open.

[0235] In this initial state, SW41 and SW43 are short-circuited, so that resistors R1 and R2 are connected in series between the ground (0V) of source device 110-6 and the +5V power line of HDMI cable 130-6, and a voltage of 4V is obtained at points Q41 and P42 of the utility line through resistive voltage division.

[0236] Voltage monitor section 112 of source device 110-6 monitors that the voltage at point Q41 is 4 V, and sends the monitoring result to control section 111. Based on this monitoring result, control section 111 determines that an HDMI cable, which is a compatible cable, is connected.

[0237] Similarly, voltage monitor unit 133 of HDMI cable 130-6 monitors that the voltage at point P42 is 4 V, and sends the monitoring result to control unit 132. Based on this monitoring result, control unit 132 determines that a source device that is a compatible source device is connected.

[0238] Here, in source device 110-6, switch SW42 is open, so the voltage of 4V is not propagated inside source device 110-6 and does not affect the inside of source device 110-6. Similarly, in HDMI cable 130-6, switch SW44 is open, so the voltage of 4V is not propagated to sink device 320 and does not affect sink device 320.

[0239] Based on the monitoring result of 4V by the voltage monitor unit 133, the control unit 111 of the source device 110-6 shorts the switch SW47 and then opens the switch SW48 as shown in Fig. 43. Here, a resistor R3 is connected in series to the resistors R1 and R2, and a voltage of 2V is obtained at points Q41 and P42 of the utility line by resistor division.

[0240] At this time, if a relay device such as repeater 140 (see FIG. 40) that separates the +5V power line is connected between source device 110-6 and HDMI cable 130-6, there will be no change in the generated voltage due to resistor R3. Therefore, the fact that a voltage of 2V is obtained at points Q41 and P42 of the utility line means that a relay device such as a repeater is not connected.

[0241] Voltage monitor unit 112 of source device 110-6 monitors that the voltage at point Q41 has become 2V, and sends the monitoring result to control unit 111. Based on this monitoring result, control unit 111 determines that no relay device such as a repeater that separates the +5V power line is connected between the compatible cable, and performs control so as to operate in the compatible mode.

[0242] Similarly, voltage monitor unit 133 of HDMI cable 130-6 monitors that the voltage at point P42 has reached 2 V, and sends the monitoring result to control unit 132. Based on this monitoring result, control unit 132 determines that no relay device such as a repeater that separates the +5 V power line is connected between the compatible source device and the compatible source device, and performs control so as to operate in the compatible mode.

[0243] Since source device 110-6 is controlled to operate in the compatible mode, control unit 111 shorts switch SW48, opens switch SW47, and opens switch SW41 as shown in Fig. 44. Therefore, the voltage at point P42 of the utility line becomes 5V. In HDMI cable 130-6, voltage monitor unit 133 monitors that the voltage at point P42 is 5V, and sends the monitoring result to control unit 132. By monitoring that the voltage at point P42 is 5V in this manner, it is confirmed that the source device has determined that its own cable is a compatible cable and that no relay device such as a repeater that separates the +5V power line is present.

[0244] Based on this monitoring result, the control unit 132 changes the state of each switch as shown in Fig. 45 and transitions to normal operation. In this case, in order not to affect the sink device 320, first the switch SW43 is opened, then the switch SW44 is shorted, and finally the switch SW46 is shorted. After that, the control unit 132 turns on the LDO regulators 332A and 332B to provide a power supply of 3.3V to the conversion circuits 331A and 331B, which are active circuits, and sets these conversion circuits 331A and 331B to an operating state (Enable).

[0245] By shorting switch SW46, a 5V voltage is sent from source equipment 110-6 to sink equipment 320 via the +5V power line, and accordingly a 5V voltage (connection detection signal) is sent from sink equipment 320 to source equipment 110-6 via the HPD line. This causes control unit 111 of source equipment 110-6 to recognize that cable preparation is complete, and as shown in Fig. 46, control unit 111 shorts switch SW42 and transitions to normal operation.

[0246] 43, if a voltage of 4V is still obtained at points Q41 and P42 of the utility line, source device 110-6 and HDMI cable 130-6 each operate as follows. In this case, control unit 111 of source device 110-6 determines that a relay device such as a repeater that separates the +5V power line is present, and controls the device to operate in the non-compatible mode. That is, control unit 111 sets switch SW48 to a short-circuited state, switch SW47 to an open state, switch SW41 to an open state, and switch SW42 to a short-circuited state, and transitions to normal operation.

[0247] In this case, the control unit 111 of the HDMI cable 130-6 determines that a relay device such as a repeater that separates the +5V power line is present, and controls the cable to operate in the non-compatible mode. That is, the control unit 132 opens the switch SW43, closes the switch SW44, and closes the switch SW46, and transitions to normal operation.

[0248] The source device 110-6 may be configured so that the current that can be supplied by the +5V power line is always 55 mA or more and can supply current to the active circuit of the HDMI cable 130-6, which is a compatible cable, but the control unit 111 of the source device 110-6 may change the mode to one in which the current that can be supplied by the +5V power line is 55 mA or more when it determines that the connected HDMI cable is a compatible cable and that there is no intermediate device such as a repeater that separates the +5V power line. By switching the mode of the current supply amount, the source device 110-6 can reduce the power of the power supply circuit unit. For example, the control unit 111 changes the mode to one in which the current that can be supplied is 55 mA or more before opening the switch SW41 as described above.

[0249] 42, the HDMI cable 130-6, which is a compatible cable, activates its own active circuit when it determines that the connected source device is a compatible source device capable of supplying sufficient current to its own active circuit and that there is no intermediate relay device such as a repeater that separates the +5V power line. This allows the active circuit of the HDMI cable 130-6 to operate appropriately, and also prevents the source device and relay device such as a repeater from being unable to withstand the overcurrent and causing a breakdown.

[0250] Fig. 47 shows a configuration example of a transmission system 10-6A. This transmission system 10-6A is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-6A has a source device 310 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-6 connecting them. In Fig. 47, parts corresponding to Figs. 4 and 42 are given the same reference numerals, and detailed explanations thereof will be omitted as appropriate.

[0251] In this transmission system 10-6A, the source device 310 is a non-compliant source device such as a legacy device, and the HDMI cable 130-6 is a compliant cable. In this case, the source device 310 operates normally (see FIG. 41).

[0252] Furthermore, the HDMI cable 130-6 determines that the source device is a non-compatible source device and operates in the non-compatible mode. In this case, in the initial state, the voltage at point P42 of the Utility line is 5V. The voltage monitor unit 133 of the HDMI cable 130-6 monitors that the voltage at point P42 is 5V, and sends the monitoring result to the control unit 132. If the voltage at point P42 remains at 5V even though the voltage monitor unit 134 detects 5V, the control unit 132 determines that a non-compatible source device has been connected, and controls the cable to operate in the non-compatible mode.

[0253] In this case, the control unit 132 changes the state of each switch and transitions to normal operation. In this case, in order not to affect the sink device 320, first the switch SW43 is opened, then the switch SW44 is shorted, and finally the switch SW46 is shorted. In addition, in this case, the control unit 132 controls the active circuit so as not to draw a current of 55 mA or more from the +5V power line. For example, the LDO regulators 332A and 332B are kept off, and the conversion circuits 331A and 331B, which are active circuits, are kept in a non-operating state (Disable). This prevents the HDMI cable 130-6 from drawing a current of 55 mA or more from the source device 310, and prevents the source device 310 from being unable to withstand the overcurrent and causing a breakdown.

[0254] In the above description, the HDMI cable 130-6, which is a compatible cable, controls the on / off of the LDO regulators 332A and 332B depending on whether the source device is a compatible device or a non-compatible device. However, in this case, if the source device is a non-compatible device, the LDO regulators 332A and 332B are turned off and the active circuit is in an inactive state, making it impossible to transmit data.

[0255] Therefore, when the source device is a non-compliant source device, the HDMI cable 130-6 may guarantee that the current drawn from the source device is 55 mA or less by lowering the data rate, rather than keeping the LDO regulators 332A and 332B in an off state. This allows data transmission even if the source device is a non-compliant source device.

[0256] Fig. 48 shows a configuration example of a transmission system 10-6B. This transmission system 10-6B is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-6B has a source device 110-6 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 330C connecting them. In this Fig. 48, parts corresponding to Figs. 4 and 42 are given the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0257] In this transmission system 10-6B, the source device 110-6 is a compliant source device, and the HDMI cable 330C is a non-compliant cable such as a legacy cable. In this case, the HDMI cable 330C operates normally (see FIG. 41).

[0258] Source device 110-6 determines that the HDMI cable is a non-compliant cable and operates in the non-compliant mode. In this case, in the initial state, the voltage at point Q41 of the Utility line is 0V. Voltage monitor unit 112 of source device 110-6 monitors that the voltage at point Q41 is 0V, and sends the monitoring result to control unit 111. Based on this monitoring result and the fact that the HPD line is at a high level (5V), control unit 111 determines that the HDMI cable is a non-compliant cable, and controls so as to operate in the non-compliant mode.

[0259] In this case, control unit 111 changes the state of each switch to transition to normal operation. In this case, in order not to affect the inside of source device 110-6, first switch SW41 is opened, and then switch SW42 is shorted.

[0260] 49 shows a configuration example of a transmission system 10-6C. This transmission system 10-6C is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-6C has a source device 110-6 as a transmitting device, a repeater 140 as a relay, a sink device 320 as a receiving device, a cable 330 connecting the source device 110-6 and the repeater 140, and an HDMI cable 130-6 connecting the repeater 140 and the sink device 320.

[0261] In the transmission system 10-6 in Fig. 42 described above, the source device 110-6, which is a compatible source device, and the sink device 320 are directly connected via the compatible cable HDMI cable 130-6, but in the transmission system 10-6C, an HDMI cable 330 and a repeater 140 are further inserted in series between the source device 110-6 and the HDMI cable 130-6. In Fig. 49, parts corresponding to Fig. 40 and Fig. 42 are given the same reference numerals, and detailed description thereof will be omitted as appropriate. It is assumed that the control line is in a state where the IN and OUT are connected within the repeater 140.

[0262] In the transmission system 10-6C shown in Fig. 49, the HDMI cable 130-6 is a compatible cable, and the source device 110-6 is a compatible source device. Therefore, the source device 110-6 determines that an HDMI cable, which is a compatible cable, is connected, but recognizes the presence of the repeater 140 that separates the +5V power line, and operates in a non-compatible mode. Similarly, the HDMI cable 130-6 determines that a source device, which is a compatible source device, is connected, but recognizes the presence of the repeater 140, and operates in a non-compatible mode.

[0263] The operation of the source device 110-6 and the HDMI cable 130-6 in the transmission system 10-6C in Fig. 49 will be described in detail. In Fig. 49, the source device 110-6 and the HDMI cable 130-6 are shown in an initial state. In the source device 110-6, in the initial state, the switches SW41 and SW48 are shorted, and the switches SW42 and SW47 are open. On the other hand, in the HDMI cable 130-6, in the initial state, the switch SW43 is shorted, and the switches SW44 and SW46 are open.

[0264] In this initial state, SW41 and SW43 are short-circuited, and the utility line is connected between source device 110-6 and HDMI cable 130-6 via HDMI cable 330 and repeater 140, so that resistors R1 and R2 are connected in series between the ground (0V) of source device 110-6 and the +5V power line of HDMI cable 130-6, and a voltage of 4V is obtained at points Q41 and P42 of the utility line due to resistive voltage division.

[0265] Voltage monitor section 112 of source device 110-6 monitors that the voltage at point Q41 is 4 V, and sends the monitoring result to control section 111. Based on this monitoring result, control section 111 determines that an HDMI cable, which is a compatible cable, is connected.

[0266] Similarly, voltage monitor unit 133 of HDMI cable 130-6 monitors that the voltage at point P42 is 4 V, and sends the monitoring result to control unit 132. Based on this monitoring result, control unit 132 determines that a source device that is a compatible source device is connected.

[0267] Based on the result of monitoring 4V by voltage monitor 112, control unit 111 of source device 110-6 shorts switch SW47 and then opens switch SW48 as shown in Fig. 50. At this time, since the +5V power line of source device 110-6 and the +5V power line of HDMI cable 130-6 are separated within repeater 140, resistor R3 is not connected in series to resistors R1 and R2, and therefore the voltage at points Q41 and P42 of the Utility line does not fluctuate from 4V.

[0268] Control unit 111 of source device 110-6 determines that a repeater exists between itself and the compatible cable based on the 4V monitoring result by voltage monitor unit 112, and controls the cable to operate in the non-compatible mode. Similarly, control unit 132 of HDMI cable 130-6 determines that a repeater exists between itself and the compatible source device based on the 4V monitoring result by voltage monitor unit 133, and controls the cable to operate in the non-compatible mode.

[0269] 51, the control unit 111 of the source device 110-6 shorts the switch SW48, opens the switch SW47, and also opens the switch SW41. Therefore, the voltage at point P42 of the utility line becomes 5V. In the HDMI cable 130-6, the voltage monitor unit 133 monitors that the voltage at point P42 is 5V, and sends the monitoring result to the control unit 132. By monitoring that the voltage at point P42 is 5V in this manner, it is confirmed that the source device has determined that its own cable is a compatible cable and that a relay device such as a repeater that separates the +5V power line is present.

[0270] Based on the monitoring result, the control unit 132 changes the state of each switch as shown in FIG. 52 and transitions to normal operation. In this case, first the switch SW43 is opened, then the switch SW44 is shorted, and finally the switch SW46 is shorted. In addition, in this case, the control unit 132 controls the active circuit so as not to draw a current of 55 mA or more from the +5V power line. For example, the LDO regulators 332A and 332B are kept off, and the conversion circuits 331A and 331B, which are active circuits, are kept in a non-operating state (Disable). This prevents the HDMI cable 130-6 from drawing a current of 55 mA or more from the repeater 140, and prevents the repeater 140 from being unable to withstand the overcurrent and causing a breakdown.

[0271] Furthermore, by shorting switch SW46, a 5V voltage is sent from repeater 140 to sink device 320 via the +5V power line, and accordingly a 5V voltage (connection detection signal) is sent from sink device 320 to source device 110-6 via the HPD line. This causes control unit 111 of source device 110-6 to recognize that cable preparation has been completed, and as shown in Fig. 53, switch SW42 is shorted, and the system transitions to normal operation.

[0272] 54 shows an example of a sequence of source device 110-6, which is a corresponding source device. In step ST131, for example, when the power switch is turned on and +5V is raised, the sequence starts and proceeds to step ST132. In this step ST132, control unit 111 judges whether voltage monitor unit 112 detects the first bias voltage (4V).

[0273] When the first bias voltage (4V) is detected, in step ST133, the control unit 111 determines that a compatible cable, an HDMI cable, is connected. Then, in step ST134, the control unit 111 changes the switch SW47 from an open state to a short-circuited state, and then changes the switch SW48 from a short-circuited state to an open state.

[0274] Next, in step ST135, the control unit 111 determines whether the second bias voltage (2V) is detected by the voltage monitor unit 112. When the second bias voltage (2V) is detected, the control unit 111 determines that there is no relay device such as a repeater separating the +5V power line from the HDMI cable, and proceeds to step ST136. In this step ST136, the control unit 111 changes the switch SW48 from an open state to a short-circuited state, the switch SW47 from a short-circuited state to an open state, and further changes the switch SW41 from a short-circuited state to an open state.

[0275] Next, when the control unit 111 detects in step ST137 that the HPD line has become high level (5 V), in step ST138 the control unit 111 changes the switch SW42 from an open state to a short state. Then, in step ST139, the sequence ends.

[0276] Furthermore, when the second bias voltage (2V) is not detected in step ST135, the control unit 111 determines that a relay device such as a repeater that separates the +5V power line from the HDMI cable is present, and the process proceeds to step ST140. In this step ST140, the control unit 111 changes the switch SW48 from an open state to a short-circuited state, the switch SW47 from a short-circuited state to an open state, and the switch SW41 from a short-circuited state to an open state. Then, in step ST138, the control unit 111 changes the switch SW42 from an open state to a short-circuited state. Then, in step ST139, the sequence ends.

[0277] Furthermore, when the first bias voltage (4V) is not detected in step ST132, the control unit 111 determines in step ST141 whether or not a high level (5V) of the HPD line is detected. When a high level (5V) of the HPD line is not detected, the process returns to step ST132. On the other hand, when a high level (5V) of the HPD line is detected, in step ST142, the control unit 111 determines that a non-compliant HDMI cable is connected.

[0278] Then, in step ST143, the switch SW41 is changed from the short-circuited state to the open-circuited state. Next, in step ST138, the switch SW42 is changed from the open-circuited state to the short-circuited state by the control section 111. Then, in step ST139, the sequence ends.

[0279] 55 shows an example of a sequence for the HDMI cable 130-6, which is a compatible cable. In step ST151, when the voltage monitor unit 134 detects a voltage of 5V, the sequence starts and proceeds to step ST152. In this step ST152, the control unit 132 determines whether the voltage monitor unit 133 detects the first bias voltage (4V).

[0280] When the first bias voltage (4 V) is detected, in step ST153, the control unit 132 determines that a source device that is a compatible source device is connected. Then, in step ST154, the control unit 132 determines whether the voltage monitor unit 133 has detected the second bias voltage (2 V).

[0281] When the second bias voltage (2V) is detected, the control unit 132 determines that there is no relay device such as a repeater separating the +5V power line between the source device and the control unit 132, and proceeds to step ST155. If the voltage monitor unit 133 detects 5V in step ST155, the control unit 132 changes the switch SW43 from a short-circuited state to an open state, the switch SW44 from an open state to a short-circuited state, and the switch SW46 from an open state to a short-circuited state in step ST156.

[0282] Next, in step ST157, the LDO regulators 332A and 332B are turned on and the active circuit is put into an operating state (Enable), and then in step ST158, the sequence ends.

[0283] Also, when the second bias voltage (2V) is not detected in step ST154, the control unit 132 determines that a relay device such as a repeater is interposed between the source device and the +5V power line, and proceeds to step ST159. In this step ST159, the control unit 132 changes the switch SW43 from a short-circuited state to an open state, the switch SW44 from an open state to a short-circuited state, and the switch SW46 from an open state to a short-circuited state. Then, in step ST158, the sequence ends.

[0284] Also, when the first bias voltage (4V) is not detected in step ST152, the control unit 132 determines in step ST160 that a source device that is a non-compatible source device is connected. Then, in step ST159, the control unit 132 changes the switch SW43 from the short-circuited state to the open-circuited state, the switch SW44 from the open-circuited state to the short-circuited state, and the switch SW46 from the open-circuited state to the short-circuited state. Then, in step ST158, the sequence ends.

[0285] When the voltage of the +5V power line drops, the switches SW41, SW42, SW47, and SW48 of the source device 110-6 and the switches SW43, SW44, and SW46 of the HDMI cable 130-6 are reset to their initial states.

[0286] "Embodiment 7" 56 shows a configuration example of a transmission system 10-7. The transmission system 10-7 is an HDMI transmission system that uses HDMI as a digital interface. The transmission system 10-7 includes a source device 110-7 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-7 that connects them.

[0287] The HDMI cable 130-6 in the transmission system 10-6 in Fig. 42 described above does not have a register, but the HDMI cable 130-7 in the transmission system 10-7 in Fig. 56 has a register 131 similar to that of the HDMI cable 130-1 in the transmission system 10-1 in Fig. 7 described above. In Fig. 56, parts corresponding to those in Fig. 7 and Fig. 42 are given the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0288] The HDMI cable 130-7 is a compatible cable. In addition to AOC configuration circuits such as conversion circuits 331A and 331B, LDO regulators 332A and 332B, and a current driver 333B, the HDMI cable 130-7 includes a control unit 132, voltage monitors 133 and 134, switches SW3, SW4, SW5, and SW6, and a voltage dividing resistor R2.

[0289] Source device 110-7 is a compatible source device. This source device 110-7 has a control unit 111 that controls the operation of each unit, as well as a voltage monitor unit 112, switches SW1, SW2, SW7, SW8, and resistors R1 and R3 for voltage division. It is desirable that the resistor R2 of the above-mentioned HDMI cable 130-7 and the resistors R1 and R3 of this source device 110-7 each have a relatively large value in order to reduce current consumption. In the following description, R1=400 kΩ, R2=100 kΩ, and R3=500 kΩ.

[0290] In the transmission system 10-7 shown in Fig. 56, the HDMI cable 130-7 is a compatible cable, and the source device 110-7 is a compatible source device. Therefore, the source device 110-7 determines that the connected HDMI cable is a compatible cable and operates in the compatible mode. Similarly, the HDMI cable 130-7 determines that the connected source device is a compatible source device and operates in the compatible mode.

[0291] The operation of the source device 110-7 and the HDMI cable 130-7 will be described. Although detailed description will be omitted, they operate in the same manner as the source device 110-1 and the HDMI cable 130-1 in the transmission system 10-1 of Fig. 7 described above, and after the control unit 111 of the source device 110-7 accesses (reads / writes) the register 131 of the HDMI cable 130-7, they each transition to normal operation.

[0292] When accessing the register 131, the control unit 111 of the source device 110-7 can write to the register 131 that the source device itself may draw a current of 55 mA or more. After transitioning to normal operation, the control unit 132 of the HDMI cable 130-7 can set the active circuit to an operating state (Enable) and draw 55 mA or more from the +5V power line based on the information in the register 131. That is, in the case of the transmission system 10-7 in Fig. 56, the source device 110-7 can notify the HDMI cable 130-7 through the register 131 that the source device itself may draw a current of 55 mA or more.

[0293] Although detailed description is omitted, source device 110-7 and HDMI cable 130-7 operate in the same manner as source device 110-6 and HDMI cable 130-6 in transmission system 10-6 in Fig. 42. This allows control unit 111 of source device 110-7 to recognize whether or not a repeater or other relay device that separates the +5V power line is present between the corresponding cable. Similarly, control unit 132 of HDMI cable 130-7 recognizes whether or not a repeater or other relay device that separates the +5V power line is present between the corresponding source device.

[0294] As described above, after transitioning to normal operation, the control unit 132 of the HDMI cable 130-7 can enable the active circuit and draw 55 mA or more from the +5V power line based on the information in the register 131. However, if it is recognized that there is an intermediate device such as a repeater that separates the +5V power line between the compatible source device and the HDMI cable 130-7, the active circuit can be controlled so as not to draw a current of 55 mA or more from the +5V power line, thereby preventing the intermediate device such as the repeater from being unable to withstand the overcurrent and causing a breakdown.

[0295] 56, the switch SW5 is kept open until the source device 110-7 finishes accessing the register 131 of the HDMI cable 130-7. Therefore, the access information of the register 131 is not transmitted to the sink device 320 via the DDC line, and it is possible to prevent the sink device 320, whose address is not defined, from malfunctioning.

[0296] 56, after the source device 110-7 finishes accessing the register 131 of the HDMI cable 130-7, the switch SW5 is changed to the short-circuited state, and thereafter the switch SW6 is changed to the short-circuited state. Therefore, after the sink device 320 sends a connection detection signal to the source device 110-7, the connection detection signal is sent from the source device 110-7 to the sink device 320 through the DDC line, so that the communication signal can be prevented from being blocked.

[0297] 56, the control unit 132 of the HDMI cable 130-7 turns on the LDO regulators 332A and 332B and controls the cable to draw 55 mA or more from the +5V power line based on information transmitted from the source device 110-7 via the register 131 that the cable itself may draw a current of 55 mA or more. This enables the active circuit of the HDMI cable 130-7 to operate appropriately, and also prevents the source device from being unable to withstand the overcurrent and causing a breakdown.

[0298] Furthermore, in the transmission system 10-7 shown in FIG. 56, if there is a relay device such as a repeater that separates the +5V power line between the source device 110-7 and the HDMI cable 130-7, this is recognized and the active circuit of the HDMI cable 130-7 can be controlled so as not to draw a current of more than 55 mA from the +5V power line, thereby preventing the relay device from being unable to withstand the overcurrent and causing a breakdown.

[0299] 42, the second voltage (2V) is generated by providing a configuration in which a voltage of 5V is applied to point Q42 of the +5V power line via a series circuit of resistor R3 and switch SW47. However, a configuration in which resistor R3 is eliminated and the second voltage (2V) is generated by directly varying the 5V potential is also conceivable.

[0300] "Embodiment 8" Fig. 57 shows a configuration example of a transmission system 10-8. This transmission system 10-8 is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-8 has a source device 110-8 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-8 connecting them. In this Fig. 57, parts corresponding to Fig. 7 are given the same reference numerals, and detailed explanations thereof will be omitted as appropriate.

[0301] In the transmission system 10-1 of Figure 7, source device 110-1 reads and writes register 131 provided in cable 130-1 using the I2C (Inter-Integrated Circuit) of the DDC line, thereby enabling information such as the cable ID, parameters for adjusting circuit characteristics, the amount of current consumed by the cable, and transmittable data rate to be exchanged between source device 110-1 and cable 130-1.

[0302] In contrast, the transmission system 10-8 exchanges various information between the source device 110-8 and the HDMI cable 130-8 by changing the resistance value of the variable resistor circuit to change the bias voltage of the utility line, eliminating the need for a register on the DDC line. Therefore, register access information is not transmitted to the sink device 320 via the DDC line, and malfunctions do not occur in the sink device 320 where the corresponding address is not defined.

[0303] The HDMI cable 130-8 is a compatible cable. The HDMI cable 130-8 has a control unit 132, voltage monitor units 133 and 134, switches SW4 and SW6, and a variable resistance circuit 135. A switch SW4 is inserted in the utility line from point P2 to the sink device 320 side. Also, a switch SW6 is inserted in the +5V power line from point P3 to the sink device 320 side.

[0304] The voltage monitor unit 133 monitors the voltage at point P2 of the utility line and sends the monitoring result to the control unit 132. The voltage monitor unit 134 monitors the voltage at point P3 of the +5V power line and sends the monitoring result to the control unit 132. The control unit 132 controls the operation of each part of the HDMI cable 130-8.

[0305] A variable resistance circuit 135 is connected between point P2 of the utility line and the ground (0 V). The variable resistance circuit 135 is configured with a predetermined number of series circuits of resistors and switches connected in parallel. In the illustrated example, a series circuit of resistor R2x and switch SW3x, a series circuit of resistor R2y and switch SW3y, and a series circuit of resistor R2z and switch SW3z are connected in parallel.

[0306] Source device 110-8 is a compatible source device. In addition to control unit 111 that controls the operation of each unit, source device 110-8 has voltage monitor unit 112, switch SW2, and variable resistance circuit 114. Switch SW2 is inserted inward from point Q1 on the utility line. Voltage monitor unit 112 monitors the voltage at point Q2 on the utility line, and sends the monitoring result to control unit 111.

[0307] A variable resistance circuit 114 is connected between the +5V power line and point Q1 of the utility line. The variable resistance circuit 114 is configured with a predetermined number of series circuits of resistors and switches connected in parallel. In the illustrated example, a series circuit of resistor R1x and switch SW1x, a series circuit of resistor R1y and switch SW1y, and a series circuit of resistor R1z and switch SW1z are connected in parallel.

[0308] It is desirable that the resistances R2x, R2y, and R2z of the above-mentioned HDMI cable 130-8 and the resistances R1x, R1y, and R1z of this source device 110-8 each have a relatively large value in order to reduce current consumption. Although not limited to these values, the following description will be given assuming R1x=100 kΩ, R1y=200 kΩ, R1z=300 kΩ, R2x=400 kΩ, R2y=500 kΩ, and R2z=600 kΩ.

[0309] In the transmission system 10-8 shown in Fig. 57, the HDMI cable 130-8 is a compatible cable, and the source device 110-8 is a compatible source device. Therefore, the source device 110-8 determines that the connected HDMI cable is a compatible cable and operates in the compatible mode. Similarly, the HDMI cable 130-8 determines that the connected source device is a compatible source device and operates in the compatible mode.

[0310] The operation of the source device 110-8 and the HDMI cable 130-8 will be described in detail. In Fig. 57, the source device 110-8 and the HDMI cable 130-8 are shown in an initial state. In the source device 110-8, in the initial state, the switch SW1x is short-circuited, and the switches SW1y, SW1z, and SW2 are open. On the other hand, in the HDMI cable 130-8, in the initial state, the switch SW3x is short-circuited, and the switches SW3y, SW3z, SW4, and SW6 are open.

[0311] In this initial state, switches SW1x and SW3x are short-circuited, so that resistors R1x and R2x are connected in series between the +5V power line of source device 110-8 and the ground (0V) of HDMI cable 130-8, and a voltage of 4V (bias voltage) is obtained at points Q1 and P2 of the utility line through resistive voltage division.

[0312] Voltage monitor unit 112 of source device 110-8 monitors that the voltage at point Q1 is 4 V, and sends the monitoring result to control unit 111. Based on this monitoring result, control unit 111 determines that the connected HDMI cable is a compatible cable, and controls so as to operate in the compatible mode.

[0313] Similarly, voltage monitor unit 133 of HDMI cable 130-8 monitors that the voltage at point P2 is 4 V, and sends the monitoring result to control unit 132. Based on this monitoring result, control unit 132 determines that the connected source device is a compatible source device, and controls it to operate in the compatible mode.

[0314] Here, in source device 110-8, switch SW2 is open, so the voltage of 4V is not propagated inside source device 110-8 and does not affect the inside of source device 110-8. Similarly, in HDMI cable 130-8, switch SW4 is open, so the voltage of 4V is not propagated to sink device 320 and does not affect sink device 320.

[0315] The source device 110-8 and the HDMI cable 130-8 each start operating in the corresponding mode, and first transmit and receive information. In this case, the source device 110-8 can transmit various information to the HDMI cable 130-8 by changing the resistance value of the variable resistor circuit 114 to change the bias voltage of the utility line. On the HDMI cable 130-8 side, the monitoring result of the bias voltage at point P2 of the utility line is supplied from the voltage monitor unit 133 to the control unit 132. The control unit 132 refers to a table showing the correspondence between the bias voltage value and information, and understands and acquires the transmission information from the source device 110-8.

[0316] In this case, the HDMI cable 130-8 can transmit various information to the source device 110-8 by changing the bias voltage of the utility line by changing the resistance value of the variable resistor circuit 135. On the source device 110-8 side, the monitoring result of the bias voltage at point Q1 of the utility line is supplied from the voltage monitor unit 112 to the control unit 111. The control unit 111 refers to a table showing the correspondence between the bias voltage value and information, and understands and acquires the transmission information from the HDMI cable 130-8.

[0317] Fig. 58 shows an example of the operation of the variable resistance circuits 114, 135 when transmitting and receiving information between the source device 110-8 and the HDMI cable 130-8. Fig. 58(a) shows the same initial state as Fig. 57. When it is determined that both the source device 110-8 and the HDMI cable 130-8 are compatible, first, as shown in Fig. 58(b), the source device 110-8 switches the switch group of the variable resistance circuit 114 and changes the bias voltage generated by resistor voltage division to transmit information to the HDMI cable 130-8. When the source device 110-8 finishes transmitting information to the HDMI cable 130-8, as shown in Fig. 58(c), it shifts the switch group of the variable resistance circuit 114 to the initial switch state (see Fig. 58(a)) and notifies the HDMI cable 130-8 that the information transmission has finished.

[0318] Thereafter, as shown in Fig. 58(d), the HDMI cable 130-8 switches the switches of the variable resistance circuit 135 to change the bias voltage generated by resistor voltage division, thereby transmitting information to the source device 110-8. When the HDMI cable 130-8 has completed transmitting information to the source device 110-8, it transitions the switches of the variable resistance circuit 135 to the initial switch state (see Fig. 58(a)) as shown in Fig. 58(e), and notifies the source device 110-8 that the information transmission has completed.

[0319] In the transmission system 10-8 of FIG. 57, the variable resistance circuit 114 of the source device 110-8 and the variable resistance circuit 135 of the HDMI cable 130-8 are shown as examples in which three resistors are arranged in parallel, but the number of resistors arranged in parallel is not limited to three.

[0320] For example, as shown in Fig. 59, 256 gradations can be expressed by arranging eight weighted resistors in parallel. In this case, the source device 110-8 and the HDMI cable 130-8 have a common table, for example, as shown in Fig. 60. In this case, when transmitting information from the source device 110-8 to the HDMI cable 130-8, a voltage of a predetermined code in the table is generated, so that the HDMI cable 130-8 can detect that the source device 110-8 supports information of that code. However, in the above implementation example, two gradations are already used.

[0321] The gradation 0, which opens all the switches, is the condition for moving to the next sequence, and another gradation is used as the initial state of the negotiation. Since these two gradations cannot be used for information transmission, if 256 gradations are prepared, 254 gradations can be used freely. In the example of FIG. 60, when the source device 110-8 wants to convey the source version to the HDMI cable 130-8, this can be conveyed by expressing a voltage of either gradation 2 or 3. As a method for switching the gradation, it is possible to continuously switch to the desired gradation, or it is possible to make the source device 110-8 and the HDMI cable 130-8 recognize that they are moving to the next gradation by always returning to a certain determined gradation once.

[0322] In addition, in the transmission system 10-8 of Figure 57, the variable resistance circuit 114 of the source device 110-8 and the variable resistance circuit 135 of the HDMI cable 130-8 are examples in which three resistors are arranged in parallel, and the resistance value is changed by switching between the shorted state and the open state of each switch in the switch group, but it is also possible to configure these variable resistance circuits 114, 135 using a single resistance element (variable resistance element) whose resistance value can be changed.

[0323] When the transmission and reception of information between source device 110-8 and HDMI cable 130-8 is completed, control unit 111 of source device 110-8 opens all switches in the group of switches SW1, as shown in Fig. 61. Therefore, the voltage at point P2 of the utility line becomes 0 V. In the HDMI cable 130-8, voltage monitor unit 133 monitors that the voltage at point P2 is 0 V, and sends the monitoring result to control unit 132.

[0324] Based on the result of this monitoring, the control unit 132 determines that the transmission and reception of information has ended, and changes the states of the switches SW3 group and the switches SW4 and SW6 to transition to normal operation as shown in Fig. 62. In this case, in order not to affect the sink device 320, first all the switches in the switch SW3 group are opened, then the switch SW4 is shorted, and finally the switch SW6 is shorted.

[0325] By shorting switch SW6, a 5V voltage is sent from source equipment 110-8 to sink equipment 320 via the +5V power line, and accordingly a 5V voltage (connection detection signal) is sent from sink equipment 320 to source equipment 110-8 via the HPD line. This causes control unit 111 of source equipment 110-8 to recognize that cable preparation is complete, and as shown in Fig. 63, control unit 111 shorts switch SW2 and transitions to normal operation.

[0326] 57, various information is transmitted and received between the source device 110-8 and the HDMI cable 130-8 by changing the bias voltage of the utility line by changing the resistance values ​​of the variable resistor circuits 114 and 135, and a register is not required on the DDC line. Therefore, register access information is not transmitted to the sink device 320 through the DDC line, and malfunctions do not occur in the sink device 320 where the corresponding address is not defined.

[0327] Fig. 64 shows a configuration example of a transmission system 10-8A. This transmission system 10-8A is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-8A has a source device 310 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-8 connecting them. In Fig. 64, parts corresponding to Figs. 1 and 57 are given the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0328] In this transmission system 10-8A, the source device 310 is a non-compliant source device such as a legacy device, and the HDMI cable 130-8 is a compliant cable. In this case, the source device 310 operates normally (see FIG. 6).

[0329] Furthermore, the HDMI cable 130-8 determines that the source device is a non-compatible source device and operates in the non-compatible mode. In this case, in the initial state, the voltage at point P2 of the Utility line is 0V. The voltage monitor unit 133 of the HDMI cable 130-8 monitors that the voltage at point P2 is 0V, and sends the monitoring result to the control unit 132. The control unit 132 determines that the source device is a non-compatible source device based on this monitoring result and the fact that the +5V power line is at a high level (5V), and controls the device to operate in the non-compatible mode.

[0330] In this case, the control unit 132 changes the state of each switch and transitions to normal operation. In this case, in order not to affect the sink device 320, first all the switches in the switch SW3 group are opened, then the switch SW4 is shorted, and finally the switch SW6 is shorted (see FIG. 63).

[0331] Fig. 65 shows a configuration example of a transmission system 10-8B. This transmission system 10-8B is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-8B has a source device 110-8 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 330 connecting them. In Fig. 65, parts corresponding to Figs. 1 and 57 are given the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0332] In this transmission system 10-8B, the source device 110-8 is a compliant source device, and the HDMI cable 330 is a non-compliant cable such as a legacy cable. In this case, the HDMI cable 330 operates normally (see FIG. 6).

[0333] Source device 110-8 determines that the HDMI cable is a non-compliant cable and operates in the non-compliant mode. In this case, in the initial state, the voltage at point Q1 of the Utility line is 5V. Voltage monitor unit 112 of source device 110-8 monitors that the voltage at point Q1 is 5V, and sends the monitoring result to control unit 111. Based on this monitoring result and the fact that the HPD line is at a high level (5V), control unit 111 determines that the HDMI cable is a non-compliant cable, and controls so as to operate in the non-compliant mode.

[0334] In this case, control unit 111 changes the state of each switch and transitions to normal operation. In this case, first, all switches in the switch SW1 group are opened, and then switch SW2 is shorted (see FIG. 63) so as not to affect the inside of source device 110-8.

[0335] 66 shows an example of a sequence of source device 110-8, which is a corresponding source device. In step ST161, for example, when the power switch is turned on and +5V is raised, the sequence starts and proceeds to step ST162. In this step ST162, control unit 111 judges whether voltage monitor unit 112 detects a predetermined bias voltage (4V).

[0336] When a predetermined bias voltage (4V) is detected, in step ST163, the control unit 111 determines that the HDMI cable is a compatible cable. Then, in step ST164, information is transmitted and received between the HDMI cable and the control unit 111 using changes in resistance value.

[0337] Next, in step ST165, after the transmission and reception of information is completed, all the switches in the switch SW1 group are opened by the control unit 111. After that, in step ST166, when the control unit 111 detects that the HPD line has become high level (5 V), in step ST167, the control unit 111 changes the switch SW2 from the open state to the short state. Then, in step ST168, the sequence ends.

[0338] Furthermore, when the predetermined bias voltage (4V) is not detected in step ST162, the control unit 111 determines in step ST169 whether or not a high level (5V) of the HPD line is detected. When a high level (5V) of the HPD line is not detected, the process returns to step ST162. On the other hand, when a high level (5V) of the HPD line is detected, in step ST170, the control unit 111 determines that the HDMI cable is a non-compliant cable.

[0339] Then, in step ST171, all the switches in the switch SW1 group are opened. Next, in step ST167, the switch SW2 is changed from the open state to the short-circuit state by the control section 111. Then, in step ST168, the sequence ends.

[0340] 67 shows an example of a sequence for the HDMI cable 130-8, which is a compatible cable. In step ST181, when the voltage monitor unit 134 detects a voltage of 5V, the sequence starts and proceeds to step ST182. In this step ST182, the control unit 132 determines whether the voltage monitor unit 133 detects a predetermined bias voltage (4V).

[0341] When a predetermined bias voltage (4V) is detected, in step ST183, the control unit 132 determines that the source device is a compatible source device. Then, in step ST184, information is transmitted and received between the source device and the control unit 132 using a change in resistance value. Next, in step ST185, when the voltage monitor unit 133 detects 0V, in step ST186, the control unit 132 opens all the switches in the switch SW3 group.

[0342] Next, in step ST187, the control unit 132 changes the switch SW4 from the open state to the short state, and then, in step ST188, the control unit 132 changes the switch SW6 from the open state to the short state. Then, in step ST189, the sequence ends.

[0343] Furthermore, when the predetermined bias voltage (4V) is not detected in step ST182, the control unit 132 determines in step ST190 that the source device is a non-compatible source device. Then, in step ST186, the control unit 132 opens all the switches in the group of switches SW3.

[0344] Next, in step ST187, the control unit 132 changes the switch SW4 from the open state to the short state, and then, in step ST188, the control unit 132 changes the switch SW6 from the open state to the short state. Then, in step ST189, the sequence ends.

[0345] When the voltage of the +5V power line drops, each switch of source device 110-8 and each switch of HDMI cable 130-8 are reset to their initial states.

[0346] "Embodiment 9" Fig. 68 shows a configuration example of a transmission system 10-9. This transmission system 10-9 is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-9 has a source device 110-9 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-9 that is an AOC that connects them. In Fig. 68, parts corresponding to Figs. 42 and 57 are given the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0347] The HDMI cable 130-9 has a control unit 132, voltage monitor units 133 and 134, switches SW44 and SW46, and a variable resistor circuit 135 in addition to AOC configuration circuits such as conversion circuits 331A and 331B, LDO regulators 332A and 332B, and a current driver 333B.

[0348] A switch SW44 is inserted in the utility line closer to the sink device 320 than point P42. A variable resistance circuit 135 is connected between point P42 of the utility line and the +5V power line. As a result, 5V is applied to point P42 of the utility line via the variable resistance circuit 135. This variable resistance circuit 135 is configured by connecting in parallel a series circuit of a resistor R2x and a switch SW3x, a series circuit of a resistor R2y and a switch SW3y, and a series circuit of a resistor R2z and a switch SW3z.

[0349] The voltage monitor unit 133 monitors the voltage at point P42 of the utility line and sends the monitoring result to the control unit 132. The voltage monitor unit 134 monitors the voltage at point P43 on the terminal side of the +5V power line from the insertion position of the switch SW46 and sends the monitoring result to the control unit 132. Power is supplied to the LDO regulators 332A and 332B from a point on the +5V power line on the sink device 320 side from the insertion position of the switch SW46. The control unit 132 controls the operation of each part of the HDMI cable 130-9.

[0350] Source device 110-9 is a compatible source device. This source device 110-9 has a voltage monitor unit 112, SW42, SW47, SW48, a resistor R3 for voltage division, and a variable resistor circuit 114 in addition to a control unit 111 that controls the operation of each unit.

[0351] A variable resistance circuit 114 is connected between the ground and point Q41 of the utility line. As a result, 0 V is applied to point Q41 of the utility line via the variable resistance circuit 114. This variable resistance circuit 114 is configured by connecting in parallel a series circuit of a resistor R1x and a switch SW1x, a series circuit of a resistor R1y and a switch SW1y, and a series circuit of a resistor R1z and a switch SW1z.

[0352] The resistors R2x, R2y, and R2z of the above-mentioned HDMI cable 130-9 and the resistors R1x, R1y, R1z, and R3 of this source device 110-9 are preferably relatively large in value in order to reduce current consumption. Although not limited to these values, the following description will be given assuming R1x=400 kΩ, R1y=500 kΩ, R1z=600 kΩ, R2x=100 kΩ, R2y=200 kΩ, R2z=300 kΩ, and R3=500 kΩ.

[0353] A switch SW42 is inserted on the opposite side of the terminal side of point Q41 of the utility line. A voltage monitor unit 112 monitors the voltage at point Q41 of the utility line and sends the monitoring result to control unit 111. A voltage of 5V is applied to point Q42 of the +5V power line via a series circuit of resistor R3 and switch SW47. A switch SW48 is inserted on the opposite side of the terminal side of point Q42 of the +5V power line.

[0354] In the transmission system 10-9 shown in Fig. 68, the HDMI cable 130-9 is a compatible cable, and the source device 110-9 is a compatible source device. Therefore, the source device 110-9 determines that the connected HDMI cable is a compatible cable and operates in the compatible mode. Similarly, the HDMI cable 130-9 determines that the connected source device is a compatible source device and operates in the compatible mode.

[0355] The operation of the source device 110-9 and the HDMI cable 130-9 will be described in detail. In Fig. 68, the source device 110-9 and the HDMI cable 130-9 are shown in an initial state. In the source device 110-9, the switches SW1x and SW48 are short-circuited, and the switches SW1y, SW1z, SW42, and SW47 are open. On the other hand, in the HDMI cable 130-9, in the initial state, the switch SW3x is short-circuited, and the switches SW3y, SW3z, SW44, and SW46 are open.

[0356] In this initial state, SW1x and SW3x are short-circuited, so that resistors R1x and R2x are connected in series between the ground (0V) of source device 110-9 and the +5V power line of HDMI cable 130-9, and a voltage of 4V is obtained at points Q41 and P42 of the Utility line through resistive voltage division.

[0357] Voltage monitor section 112 of source device 110-9 monitors that the voltage at point Q41 is 4 V, and sends the monitoring result to control section 111. Based on this monitoring result, control section 111 determines that an HDMI cable, which is a compatible cable, is connected.

[0358] Similarly, the voltage monitor unit 133 of the HDMI cable 130-9 monitors that the voltage at point P42 is 4 V, and sends the monitoring result to the control unit 132. Based on the monitoring result, the control unit 132 determines that a source device that is a compatible source device is connected.

[0359] Here, in source device 110-9, switch SW42 is open, so the voltage of 4 V is not propagated inside source device 110-9 and does not affect the inside of source device 110-9. Similarly, in HDMI cable 130-9, switch SW44 is open, so the voltage of 4 V is not propagated to sink device 320 and does not affect sink device 320.

[0360] Based on the monitoring result of 4V by the voltage monitor unit 112, the control unit 111 of the source device 110-9 shorts the switch SW47 and then opens the switch SW48 as shown in Fig. 69. Here, a resistor R3 is connected in series to the resistors R1x and R2x, and a voltage of 2V is obtained at points Q41 and P42 of the utility line by resistor division.

[0361] At this time, if a relay device such as repeater 140 that separates the +5V power line is connected between source device 110-9 and HDMI cable 130-9 (see the case where switch SW47 is shorted and switch SW48 is open in FIG. 75 described later), the power line between source device 110-9 and HDMI cable 130-9 is separated by repeater 140, so no change occurs in the generated voltage due to resistor R3. Therefore, the fact that a voltage of 2V is obtained at points Q41 and P42 of the utility line means that a relay device such as a repeater is not connected.

[0362] Voltage monitor unit 112 of source device 110-9 monitors that the voltage at point Q41 has become 2V, and sends the monitoring result to control unit 111. Based on this monitoring result, control unit 111 determines that no relay device such as a repeater that separates the +5V power line is connected between the compatible cable, and performs control to operate in the compatible mode.

[0363] Similarly, the voltage monitor unit 133 of the HDMI cable 130-9 monitors that the voltage at point P42 has reached 2 V, and sends the monitoring result to the control unit 132. Based on this monitoring result, the control unit 132 determines that no relay device such as a repeater that separates the +5 V power line is connected between the compatible source device and the compatible source device, and performs control so as to operate in the compatible mode.

[0364] The source device 110-9 and the HDMI cable 130-9 each start operating in the corresponding mode, and first transmit and receive information. In this case, the source device 110-9 can transmit various information to the HDMI cable 130-9 by changing the resistance value of the variable resistor circuit 114 to change the bias voltage of the utility line. On the HDMI cable 130-9 side, the monitoring result of the bias voltage at point P42 of the utility line is supplied from the voltage monitor unit 133 to the control unit 132. The control unit 132 refers to a table showing the correspondence between the bias voltage value and information, and understands and acquires the transmission information from the source device 110-9.

[0365] In this case, the HDMI cable 130-9 can transmit various information to the source device 110-9 by changing the bias voltage of the utility line by changing the resistance value of the variable resistor circuit 135. On the source device 110-9 side, the monitoring result of the bias voltage at point Q41 of the utility line is supplied from the voltage monitor unit 112 to the control unit 111. The control unit 111 refers to a table showing the correspondence between the bias voltage value and information, and understands and acquires the transmission information from the HDMI cable 130-9.

[0366] When the transmission and reception of information between source device 110-9 and HDMI cable 130-9 is completed, as shown in Fig. 70, control unit 111 of source device 110-9 sets switch SW48 to a short-circuited state, switch SW47 to an open state, and further sets all switches in the switch SW1 group to an open state. Therefore, the voltage at point P42 of the utility line becomes 5V. In HDMI cable 130-9, voltage monitor unit 133 monitors that the voltage at point P42 is 5V, and sends the monitoring result to control unit 132.

[0367] Based on the result of this monitoring, the control unit 132 determines that the transmission and reception of information has ended, and changes the states of the switch SW3 group and the switches SW44 and SW46 to transition to normal operation as shown in Fig. 71. In this case, in order not to affect the sink device 320, first all the switches in the switch SW3 group are opened, then the switch SW44 is shorted, and finally the switch SW46 is shorted.

[0368] By shorting switch SW46, a 5V voltage is sent from source equipment 110-9 to sink equipment 320 via the +5V power line, and accordingly a 5V voltage (connection detection signal) is sent from sink equipment 320 to source equipment 110-9 via the HPD line. This causes control unit 111 of source equipment 110-9 to recognize that cable preparation is complete, and as shown in Fig. 72, control unit 111 shorts switch SW42 and transitions to normal operation.

[0369] 69, if a voltage of 4V is still obtained at points Q41 and P42 of the utility line, source device 110-9 and HDMI cable 130-9 each operate as follows. In this case, control unit 111 of source device 110-9 determines that a relay device such as a repeater that separates the +5V power line is present, and controls the device to operate in the non-compatible mode. That is, control unit 111 switches SW48 to a short-circuited state, switches SW47 to an open state, all switches in the switch SW1 group to an open state, and further switches SW42 to a short-circuited state, and transitions to normal operation.

[0370] In this case, the control unit 111 of the HDMI cable 130-9 determines that a relay device such as a repeater that separates the +5V power line is present, and controls the cable to operate in the non-compatible mode. That is, the control unit 132 opens all of the switches SW3, closes the switch SW44, and closes the switch SW46, and transitions to normal operation.

[0371] The source device 110-9 may be configured so that the current that can be supplied by the +5V power line is always 55 mA or more and can supply current to the active circuit of the HDMI cable 130-9, which is a compatible cable, but the control unit 111 of the source device 110-9 may change the mode to one in which the current that can be supplied by the +5V power line is 55 mA or more when it determines that the connected HDMI cable is a compatible cable and that there is no intermediate device such as a repeater that separates the +5V power line. By switching the mode of the current supply amount, the source device 110-9 can reduce the power of the power supply circuit unit. For example, the control unit 111 changes the mode to one in which the current that can be supplied is 55 mA or more before opening all the switches in the switch SW1 group as described above.

[0372] In this manner, in the transmission system 10-9 shown in Fig. 68, similarly to the transmission system 10-8 shown in Fig. 57 described above, various information is transmitted and received between the source device 110-9 and the HDMI cable 130-9 by changing the resistance values ​​of the variable resistance circuits 114, 135 to change the bias voltage of the utility line, and a register is not required on the DDC line. Therefore, register access information is not transmitted to the sink device 320 through the DDC line, and malfunctions do not occur in the sink device 320 where the corresponding address is not defined.

[0373] Also, in the transmission system 10-9 shown in Fig. 68, similarly to the transmission system 10-6 shown in Fig. 42, the HDMI cable 130-9, which is a compatible cable, activates its own active circuit when it determines that the connected source device is a compatible source device capable of supplying sufficient current to its own active circuit and that no relay device such as a repeater is present to separate the +5V power line. This allows the active circuit of the HDMI cable 130-9 to operate appropriately, and also prevents the source device and relay device such as a repeater from failing to withstand the overcurrent and causing a breakdown.

[0374] Fig. 73 shows a configuration example of a transmission system 10-9A. This transmission system 10-9A is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-9A has a source device 310 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-9 connecting them. In Fig. 73, parts corresponding to Figs. 4 and 68 are given the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0375] In this transmission system 10-9A, the source device 310 is a non-compliant source device such as a legacy device, and the HDMI cable 130-9 is a compliant cable. In this case, the source device 310 operates normally (see FIG. 41).

[0376] Also, the HDMI cable 130-9 determines that the source device is a non-compatible source device and operates in the non-compatible mode. In this case, in the initial state, the voltage at point P42 of the Utility line is 5V. The voltage monitor unit 133 of the HDMI cable 130-6 monitors that the voltage at point P42 is 5V, and sends the monitoring result to the control unit 132. If the voltage at point P42 remains at 5V even though the voltage monitor unit 134 detects 5V, the control unit 132 determines that a non-compatible source device has been connected, and controls the cable to operate in the non-compatible mode.

[0377] In this case, the control unit 132 changes the state of each switch and transitions to normal operation. In this case, in order not to affect the sink device 320, first all of the switches SW3 are opened, then the switch SW44 is shorted, and finally the switch SW46 is shorted. In addition, in this case, the control unit 132 controls the active circuit so as not to draw a current of 55 mA or more from the +5V power line. For example, the LDO regulators 332A and 332B are kept off, and the conversion circuits 331A and 331B, which are active circuits, are kept in a non-operating state (Disable). This prevents the HDMI cable 130-9 from drawing a current of 55 mA or more from the source device 310, and prevents the source device 310 from being unable to withstand the overcurrent and causing a breakdown.

[0378] In the above description, the HDMI cable 130-9, which is a compatible cable, controls the on / off of the LDO regulators 332A and 332B depending on whether the source device is a compatible device or a non-compatible device. However, in this case, if the source device is a non-compatible device, the LDO regulators 332A and 332B are turned off and the active circuit is in an inactive state, making it impossible to transmit data.

[0379] Therefore, when the source device is a non-compliant source device, the HDMI cable 130-9 may guarantee that the current drawn from the source device is 55 mA or less by lowering the data rate, rather than keeping the LDO regulators 332A and 332B in an off state. This allows data transmission even if the source device is a non-compliant source device.

[0380] Fig. 74 shows a configuration example of a transmission system 10-9B. This transmission system 10-9B is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-9B has a source device 110-9 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 330C connecting them. In Fig. 74, parts corresponding to Figs. 4 and 68 are given the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0381] In this transmission system 10-9B, the source device 110-9 is a compliant source device, and the HDMI cable 330C is a non-compliant cable such as a legacy cable. In this case, the HDMI cable 330C operates normally (see FIG. 41).

[0382] Source device 110-9 determines that the HDMI cable is a non-compliant cable and operates in the non-compliant mode. In this case, in the initial state, the voltage at point Q41 of the Utility line is 0V. Voltage monitor unit 112 of source device 110-9 monitors that the voltage at point Q41 is 0V, and sends the monitoring result to control unit 111. Based on this monitoring result and the fact that the HPD line is at a high level (5V), control unit 111 determines that the HDMI cable is a non-compliant cable, and controls so as to operate in the non-compliant mode.

[0383] In this case, control unit 111 changes the state of each switch to transition to normal operation. In this case, in order not to affect the inside of source device 110-9, first all switches in the switch SW1 group are opened, and then switch SW42 is shorted.

[0384] 75 shows a configuration example of a transmission system 10-9C in which a repeater 140 that separates a +5V power line is connected between a source device 110-9 and an HDMI cable 130-9 (details will be omitted). In this transmission system 10-9C, an HDMI cable 330 and a repeater 140 are inserted in series between the source device 110-9 and the HDMI cable 130-9. Note that the control line is in a state where the IN and OUT are connected within the repeater 140.

[0385] In such a transmission system 10-9C, as described above, the source device 110-9 and the HDMI cable 130-9 can detect the presence of the repeater 140, and for example, the HDMI cable 130-9 can avoid accidentally drawing a current of 55 mA or more from the repeater 140, making it possible to prevent a breakdown in the repeater 140.

[0386] 76 shows an example of a sequence of source device 110-9, which is a corresponding source device. In step ST191, for example, when the power switch is turned on and +5V is raised, the sequence starts and proceeds to step ST192. In this step ST192, control unit 111 judges whether voltage monitor unit 112 detects the first bias voltage (4V).

[0387] When the first bias voltage (4V) is detected, in step ST193, the control unit 111 determines that a compatible cable, an HDMI cable, is connected. Then, in step ST194, the control unit 111 changes the switch SW47 from an open state to a short-circuited state, and then changes the switch SW48 from a short-circuited state to an open state.

[0388] Next, in step ST195, the control unit 111 judges whether the second bias voltage (2V) is detected by the voltage monitor unit 112. When the second bias voltage (2V) is detected, the control unit 111 judges that there is no relay device such as a repeater separating the +5V power line between the HDMI cable, and proceeds to step ST196. In this step ST196, information is transmitted and received between the HDMI cable using changes in resistance value.

[0389] Next, in step ST197, the control section 111 changes the switch SW48 from the open state to the shorted state, the switch SW47 from the shorted state to the open state, and further, all the switches in the switch SW1 group are set to the open state.

[0390] Next, when the control unit 111 detects in step ST198 that the HPD line has become high level (5 V), in step ST199, the control unit 111 changes the switch SW42 from an open state to a short state. Then, in step ST200, the sequence ends.

[0391] Furthermore, when the second bias voltage (2V) is not detected in step ST195, the control unit 111 determines that a relay device such as a repeater that separates the +5V power line from the HDMI cable is present, and the process proceeds to step ST201. In this step ST201, the control unit 111 changes the switch SW48 from an open state to a short state, changes the switch SW47 from a short state to an open state, and further changes all the switches in the switch SW1 group to an open state. Then, in step ST199, the control unit 111 changes the switch SW42 from an open state to a short state. Then, in step ST200, the sequence ends.

[0392] Furthermore, when the first bias voltage (4V) is not detected in step ST192, in step ST202, the control unit 111 determines whether or not a high level (5V) of the HPD line is detected. When a high level (5V) of the HPD line is not detected, the process returns to step ST192. On the other hand, when a high level (5V) of the HPD line is detected, in step ST203, the control unit 111 determines that a non-compliant HDMI cable is connected.

[0393] Then, in step ST204, all the switches in the switch SW1 group are changed to the open state. Next, in step ST199, the switch SW42 is changed from the open state to the short state by the control unit 111. Then, in step ST200, the sequence ends.

[0394] 77 shows an example of a sequence for the HDMI cable 130-9, which is a compatible cable. In step ST211, when the voltage monitor unit 134 detects a voltage of 5V, the sequence starts and proceeds to step ST212. In this step ST212, the control unit 132 determines whether the voltage monitor unit 133 detects the first bias voltage (4V).

[0395] When the first bias voltage (4 V) is detected, in step ST213, the control unit 132 determines that a source device that is a compatible source device is connected. Then, in step ST214, the control unit 132 determines whether the voltage monitor unit 133 has detected the second bias voltage (2 V).

[0396] When the second bias voltage (2V) is detected, the control unit 132 determines that there is no relay device such as a repeater separating the +5V power line between the source device and the control unit 132, and proceeds to step ST215. In this step ST215, information is transmitted and received between the source device and the control unit 132 using changes in resistance value.

[0397] Next, in step ST216, when 5V is detected by the voltage monitor unit 133, in step ST217, the control unit 132 opens all switches in the switch SW3 group, changes switch SW44 from the open state to the short-circuit state, and further changes switch SW46 from the open state to the short-circuit state.

[0398] Next, in step ST218, the LDO regulators 332A and 332B are turned on and the active circuit is put into an operating state (Enable), and then in step ST219, the sequence ends.

[0399] Furthermore, when the second bias voltage (2V) is not detected in step ST214, the control unit 132 determines that a relay device such as a repeater is interposed between the source device and the +5V power line, and proceeds to step ST220. In this step ST220, the control unit 132 opens all the switches in the switch SW3 group, changes the switch SW44 from the open state to the short state, and further changes the switch SW46 from the open state to the short state. Then, in step ST219, the sequence ends.

[0400] Furthermore, when the first bias voltage (4V) is not detected in step ST212, the control unit 132 determines in step ST221 that a source device that is a non-compatible source device is connected. Then, in step ST220, the control unit 132 opens all the switches in the switch SW3 group, changes the switch SW44 from the open state to the short state, and further changes the switch SW46 from the open state to the short state. Then, in step ST219, the sequence ends.

[0401] When the voltage of the +5V power line drops, each switch of the source device 110-9 and each switch of the HDMI cable 130-9 are reset to their initial states.

[0402] "Embodiment 10" For example, in the transmission system 10-9 shown in Fig. 68 above, power supply to the active circuit may be performed from the outside, for example by providing a power supply terminal other than the pins specified in HDMI, rather than from the source device 110-9 via the +5V power line. This external power supply is connected only to the active circuit, and there is no problem if it is used only to supply current to the active circuit.

[0403] However, for example, when directly connected to the +5V power line as in the transmission system 10-9D shown in Fig. 78, the timing at which the HPD returns to the source device 110-9 cannot be controlled, and the sequence described above does not hold. Although not described in detail, the transmission system 10-9D has a source device 110-9 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-9D having an external power supply terminal that connects them.

[0404] In order to avoid the above inconvenience, as shown in the transmission system 10-10 of Fig. 79, a switch SW49 is provided between the external power supply terminal and the +5V power line, and the switch SW49 is closed after all sequences are completed. Alternatively, instead of providing a switch between the external power supply terminal and the +5V power line, a switch may be provided on the sink device 320 side from the connection point between the external power supply terminal and +5V. Although detailed description will be omitted, the transmission system 10-10 has a source device 110-9 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-10 that has an external power supply terminal and is provided with a switch SW49, which connects them.

[0405] "Embodiment 10" Fig. 80 shows a configuration example of a transmission system 10-10. This transmission system 10-10 is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-10 has a source device 110-10 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-10 connecting them. In Fig. 80, parts corresponding to Figs. 42 and 7 are given the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0406] The HDMI cable 130-10 is a compatible cable that has a resistor 131. In addition to the resistor 131, the HDMI cable 130-10 has a control unit 132, voltage monitor units 133 and 134, switches SW3, SW4, SW5, and SW6, and a resistor R2 for voltage division.

[0407] The resistor 131 is connected to a point P1 of the DDC line. A switch SW5 is inserted on the DDC line closer to the sink device 320 than point P1. A series circuit of a resistor R2 and a switch SW3 is connected between point P2 of the utility line and point P3 of the +5V power line. This allows 5V to be applied to point P2 of the utility line via the series circuit of the resistor R2 and the switch SW3. A switch SW4 is inserted on the utility line closer to the sink device 320 than point P2. In addition, a switch SW6 is inserted on the +5V power line closer to the sink device 320 than point P3.

[0408] The voltage monitor unit 133 monitors the voltage at point P2 of the utility line and sends the monitoring result to the control unit 132. The voltage monitor unit 134 monitors the voltage at point P3 of the +5V power line and sends the monitoring result to the control unit 132. The control unit 132 controls the operation of each part of the HDMI cable 130-10.

[0409] Source device 110-10 is a compatible source device. In addition to control unit 111 that controls the operation of each unit, source device 110-10 has voltage monitor unit 112, switches SW1, SW2, SW7, SW8, and voltage dividing resistors R1 and R3. It is desirable that resistor R2 of HDMI cable 130-10 and resistors R1 and R3 of source device 110-10 have relatively large values ​​to reduce current consumption. In the following description, R1=400 kΩ, R2=100 kΩ, and R3=500 kΩ.

[0410] A series circuit of resistor R1 and switch SW1 is connected between the ground and point Q1 of the utility line. As a result, 0V, which is the ground voltage, is applied to point Q1 of the utility line via the series circuit of resistor R1 and switch SW1. A switch SW2 is inserted on the opposite side of the terminal side of point Q1 of the utility line. A voltage monitor unit 112 monitors the voltage at point Q1 of the utility line and sends the monitoring result to the control unit 111. In addition, a 5V power supply is applied to point Q2 of the +5V power line via a series circuit of resistor R3 and switch SW7. A switch SW8 is inserted on the opposite side of the terminal side of point Q2 of the +5V power line.

[0411] In the transmission system 10-10 shown in Fig. 80, the HDMI cable 130-10 is a compatible cable, and the source device 110-10 is a compatible source device. Therefore, the source device 110-10 determines that the connected HDMI cable is a compatible cable and operates in the compatible mode. Similarly, the HDMI cable 130-10 determines that the connected source device is a compatible source device and operates in the compatible mode.

[0412] The operation of the source device 110-10 and the HDMI cable 130-10 will be described in detail. In Fig. 80, the source device 110-10 and the HDMI cable 130-10 are shown in an initial state. In the source device 110-10, in the initial state, the switches SW1 and SW8 are shorted, and the switches SW2 and SW7 are open. On the other hand, in the HDMI cable 130-10, in the initial state, the switches SW3, SW4, SW5, and SW6 are open.

[0413] When the control unit 132 of the HDMI cable 130-10 receives the monitoring result of the voltage monitor unit 134 and detects that the voltage at point P3 of the +5V power line, that is, the voltage of the +5V power line, has stabilized at 5V, it sets the switch SW3 to a short-circuit state as shown in Fig. 81. By setting the switch SW3 to a short-circuit state after the voltage of the power line has stabilized at 5V in this way, it is possible to prevent deviation in the timing of starting negotiation between the source device 110-10 and the HDMI cable 130-10 due to an unstable state of the power line voltage at the time the cable is inserted.

[0414] When switch SW3 is short-circuited, resistors R1 and R2 are connected in series between the ground (0V) of source device 110-10 and the +5V power line of HDMI cable 130-10, and a voltage of 4V is obtained at points Q1 and P2 of the utility line due to resistive voltage division.

[0415] Voltage monitor unit 112 of source device 110-10 monitors that the voltage at point Q1 is 4V, and sends the monitoring result to control unit 111. Based on this monitoring result, control unit 111 determines that a compatible cable, an HDMI cable, is connected. Similarly, voltage monitor unit 133 of HDMI cable 130-10 monitors that the voltage at point P2 is 4V, and sends the monitoring result to control unit 132. Based on this monitoring result, control unit 132 determines that a compatible source device, a source device, is connected.

[0416] Here, in source device 110-10, switch SW2 is open, so the voltage of 4 V is not propagated inside source device 110-10 and does not affect the inside of source device 110-10. Similarly, in HDMI cable 130-10, switch SW4 is open, so the voltage of 4 V is not propagated to sink device 320 and does not affect sink device 320.

[0417] Based on the monitoring result of 4V by the voltage monitor unit 112, the control unit 111 of the source device 110-10 shorts the switch SW7 and then opens the switch SW8 as shown in Fig. 82. Here, a resistor R3 is connected in series to the resistors R1 and R2, and a voltage of 2V is obtained at points Q1 and P2 of the utility line by resistor division.

[0418] Here, if a relay device such as repeater 140 (see FIG. 50) that separates the +5V power line is connected between source device 110-10 and HDMI cable 130-10, there will be no change in the generated voltage due to resistor R3. Therefore, the fact that a voltage of 2V is obtained at points Q1 and P2 of the utility line means that a relay device such as a repeater is not connected.

[0419] Voltage monitor unit 112 of source device 110-10 monitors that the voltage at point Q1 has become 2V, and sends the monitoring result to control unit 111. Based on this monitoring result, control unit 111 determines that no relay device such as a repeater that separates the +5V power line is connected between the compatible cable, and controls the device to operate in the compatible mode.

[0420] Similarly, voltage monitor unit 133 of HDMI cable 130-10 monitors that the voltage at point P2 has reached 2 V, and sends the monitoring result to control unit 132. Based on this monitoring result, control unit 132 determines that no relay device such as a repeater that separates the +5 V power line is connected between the compatible source device and the compatible source device, and performs control to operate in the compatible mode.

[0421] Note that, if a relay device such as a repeater is connected between source device 110-10 and HDMI cable 130-10, even if switch SW7 is shorted and switch SW8 is open, the voltage at points Q1 and P2 of the utility line will remain at 4 V. In this case, control unit 111 of source device 110-10 controls the switching of the states of switches SW7 and SW8 by itself, and therefore it can be determined that a relay device such as a repeater is connected between source device 110-10 and HDMI cable 130-10 because the voltage at point Q1 remains at 4 V even if the states of switches SW7 and SW8 are switched.

[0422] However, because the control unit 132 of the HDMI cable 130-10 does not know the timing at which the states of the switches SW7 and SW8 of the source device 110-10 are switched, it cannot determine from the monitoring result of the voltage at point P2 that a relay device such as a repeater is connected between the source device 110-10 and the HDMI cable 130-10. In this case, the control unit 111 of the source device 110-10 opens the switch SW1, sets the voltage at point P2 of the Utility line to 5V, and notifies the control unit 132 of the HDMI cable 130-10 that a relay device such as a repeater is connected between the source device 110-10 and the HDMI cable 130-10.

[0423] In this way, when a relay device such as a repeater is connected between the source device 110-10 and the HDMI cable 130-10, the source device 110-10 and the HDMI cable 130-10 go through a predetermined procedure to transition to normal operation.

[0424] When no relay device such as a repeater is connected between the source device 110-10 and the HDMI cable 130-10, the source device 110-10 is controlled to operate in the corresponding mode. Therefore, the control unit 111 accesses (reads / writes) the register 131 of the HDMI cable 130-10 via the DDC line. In this case, the control unit 111 can read and use the specification information of the HDMI cable 130-10 present in the register 131, and can also write information on the current supply capacity of the source device 110-10. After transitioning to normal operation, the control unit 132 of the HDMI cable 130-10 can read and use the information on the current supply capacity of the source device 110-10 written in the register 131.

[0425] When the control unit 111 accesses (reads / writes) the register 131 via the DDC line, the switch SW5 is in the open state, so that the access information of the register 131 is prevented from being transmitted to the sink device 320, and thus malfunction of the sink device 320 in which the corresponding address is not defined is avoided.

[0426] After the access (read / write) to the register 131 described above is completed, the control unit 111 of the source device 110-10 shorts the switch SW8 and opens the switch SW7 as shown in Fig. 83. Therefore, the voltage at the point P2 of the utility line becomes 4V again. In the HDMI cable 130-10, the voltage monitor unit 133 monitors that the voltage at the point P2 becomes 4V, and sends the monitoring result to the control unit 132.

[0427] Based on the result of this monitoring, control unit 132 shorts switch SW6 as shown in Fig. 84. By shorting switch SW6 in this way, when 5V voltage is sent from source device 110-10 to sink device 320 via the +5V power line, it becomes possible to send a 5V voltage (connection detection signal) from sink device 320 to source device 110-10 via the HPD line.

[0428] In this case, switch SW1 of source device 110-10 is in a short-circuited state, and switch SW3 of HDMI cable 130-10 is also in a short-circuited state, so that the voltage at point Q1 of the utility line is 4 V. Therefore, when HDMI cable 130-10 is removed from source device 110-10, control unit 111 of source device 110-10 can detect this from the monitoring result of voltage monitor unit 112, and can take measures such as returning the switches to their initial states to prevent malfunction.

[0429] 85, when sink device 320 is in a state of being disconnected from HDMI cable 130-10, a state continues in which a 5V voltage (connection detection signal) is not sent from sink device 320 to source device 110-10 via the HPD line. In this state, when HDMI cable 130-10 is removed from source device 110-10, the voltage at point Q1 of the Utility line changes from 4V to 0V. This allows control unit 111 of source device 110-10 to detect that HDMI cable 130-10 has been removed from source device 110-10.

[0430] When a 5V voltage (connection detection signal) is sent from sink device 320 to source device 110-6 via the HPD line, control unit 111 of source device 110-10 recognizes that cable preparation is complete, and opens switch SW1 as shown in Fig. 86. Therefore, the voltage at point P2 of the Utility line becomes 5V.

[0431] In the HDMI cable 130-10, the voltage monitor unit 133 monitors that the voltage at point P2 is 5 V, and sends the monitoring result to the control unit 132.

[0432] Based on the monitoring result, the control unit 132 changes the state of each switch as shown in Fig. 87, and transitions to normal operation. In this case, in order not to affect the sink device 320, first the switch SW3 is opened, then the switch SW4 is shorted, and the switch SW5 is shorted. After waiting for a certain period of time after opening the switch SW1, the control unit 111 of the source device 110-10 transitions to normal operation by shorting the switch SW2 as shown in Fig. 88.

[0433] In the above, a case has been described in which the register 131 exists in the HDMI cable 130-10, but if it is known that there will be no register access from the source device 110-10, the HDMI cable 130-10 does not need to have the register 131 and the switch SW5. Note that, if it is unknown whether there will be register access from the source device 110-10, even if the HDMI cable 130-10 does not have the register 131, by providing the switch SW5, it is possible to prevent an undefined address from being sent to the sink device 320, and to prevent malfunctions in the sink device 320 from occurring.

[0434] 80, after the voltage of the +5V power supply line stabilizes at 5V, the switch SW3 of the HDMI cable 130-10 is shorted, resistors R1 and R2 are connected in series between the ground (0V) of the source device 110-10 and the +5V power supply line of the HDMI cable 130-10, and a voltage of 4V is obtained at points Q1 and P2 of the Utility line. Therefore, the source device 110-10 can determine that a compatible HDMI cable is connected, and the HDMI cable 130-10 can determine that a compatible source device is connected.

[0435] 80, switch SW7 is shorted, switch SW8 is open, resistors R1, R2, and R3 are connected in series between the ground (0 V) of source device 110-10 and a 5 V power supply, and a voltage of 2 V is obtained at points Q1 and P2 of the utility line. Therefore, it is possible to determine that there is no intermediate relay device such as a repeater that separates the +5 V power supply line between source device 110-10 and HDMI cable 130-10.

[0436] 80, until source device 110-10 receives a connection detection signal from sink device 320 via the HPD line, switch SW1 is short-circuited and a voltage of 4 V is obtained at point Q1 of the utility line. Therefore, when HDMI cable 130-10 is removed from source device 110-10, the voltage at point Q1 of the utility line changes from 4 V to 0 V, so that source device 110-10 can detect the removal and can take measures such as returning the switch to the initial state to prevent malfunction.

[0437] 89 shows an example of a sequence of source device 110-10, which is a corresponding source device. In step ST231, for example, when the power switch is turned on and +5V is raised, the sequence starts and proceeds to step ST232. In this step ST232, control unit 111 judges whether voltage monitor unit 112 detects the first bias voltage (4V).

[0438] When the first bias voltage (4V) is detected, in step ST233, the control unit 111 determines that a compatible cable, an HDMI cable, is connected. Then, in step ST234, the control unit 111 changes the switch SW7 from an open state to a short-circuited state, and then changes the switch SW8 from a short-circuited state to an open state.

[0439] Next, in step ST235, the control unit 111 judges whether the second bias voltage (2V) is detected by the voltage monitor unit 112. When the second bias voltage (2V) is detected, the control unit 111 judges that there is no relay device such as a repeater separating the +5V power line from the HDMI cable, and proceeds to step ST236. In this step 236, the control unit 111 accesses (reads / writes) the register of the HDMI cable.

[0440] Then, after the access to the register of the HDMI cable is completed, in step ST237, control section 111 changes switch SW8 from the open state to the short-circuited state, and changes switch SW7 from the short-circuited state to the open state.

[0441] Next, when the control unit 111 detects that the HPD line has become high level (5V) in step ST238, the control unit 111 changes the switch SW1 from a shorted state to an open state in step ST239. Then, after waiting for a certain period of time, the control unit 111 changes the switch SW2 from an open state to a shorted state in step ST240, and then the sequence ends in step ST241.

[0442] Furthermore, when the second bias voltage (2V) is not detected in step S235, the control unit 111 determines that a relay device such as a repeater that separates the +5V power line from the HDMI cable is present, and the process proceeds to step ST242. In this step ST242, the control unit 111 changes the switch SW8 from an open state to a short-circuited state, the switch SW7 from a short-circuited state to an open state, and the switch SW1 from a short-circuited state to an open state. Then, in step ST240, the control unit 111 changes the switch SW2 from an open state to a short-circuited state. Then, in step ST241, the sequence ends.

[0443] Furthermore, when the first bias voltage (4V) is not detected in step ST232, control unit 111 determines in step ST243 whether or not a high level (5V) of the HPD line is detected. When a high level (5V) of the HPD line is not detected, the process returns to step ST232. On the other hand, when a high level (5V) of the HPD line is detected, control unit 111 determines in step ST244 that a non-compliant HDMI cable is connected.

[0444] Then, in step ST245, switch SW1 is changed from the short-circuited state to the open-circuited state. Next, in step ST240, switch SW2 is changed from the open-circuited state to the short-circuited state by control section 111. Then, in step ST241, the sequence ends.

[0445] 90 shows an example of a sequence for the HDMI cable 130-10, which is a compatible cable. In step ST251, when the voltage monitor unit 134 detects a voltage of 5V, the sequence starts and proceeds to step ST252. In this step ST252, the control unit 132 changes the switch SW3 from an open state to a short state after the voltage of 5V on the +5V power line has stabilized.

[0446] Next, in step ST253, the control unit 132 determines whether the first bias voltage (4 V) is detected by the voltage monitor unit 133. When the first bias voltage (4 V) is detected, in step ST254, the control unit 132 determines that a source device that is a compatible source device is connected.

[0447] Next, in step ST255, the control unit 132 judges whether the second bias voltage (2V) has been detected by the voltage monitor unit 133. If the second bias voltage (2V) is detected, the control unit 132 judges that there is no relay device such as a repeater separating the +5V power line between the source device and the control unit 132, and proceeds to step ST256. If the voltage monitor unit 133 detects the first bias voltage (4V) in this step ST256, the control unit 132 proceeds to step ST257.

[0448] In step ST257, the control unit 132 changes the switch SW6 from an open state to a short-circuited state. Next, when 5V is detected by the voltage monitor unit 133 in step ST258, the control unit 132 changes the switch SW3 from a short-circuited state to an open state, the switch SW4 from an open state to a short-circuited state, and the switch SW5 from an open state to a short-circuited state in step ST259. Then, in step ST260, the sequence ends.

[0449] Also, when the second bias voltage (2V) is not detected in step ST255, after the voltage monitor unit 133 detects 5V, the control unit 132 determines that a relay device such as a repeater is interposed between the source device and the +5V power line, and proceeds to step ST261. In this step ST261, the control unit 132 changes the switch SW3 from the short-circuited state to the open-circuited state, the switch SW4 from the open-circuited state to the short-circuited state, the switch SW5 from the open-circuited state to the short-circuited state, and the switch SW6 from the open-circuited state to the short-circuited state. Then, in step ST260, the sequence ends.

[0450] Also, when the first bias voltage (4V) is not detected in step ST253, in step ST262, the control unit 132 determines that a source device that is a non-compatible source device is connected. Then, in step ST261, the control unit 132 changes the switch SW3 from the short-circuited state to the open-circuited state, the switch SW4 from the open-circuited state to the short-circuited state, the switch SW5 from the open-circuited state to the short-circuited state, and the switch SW6 from the open-circuited state to the short-circuited state. Then, in step ST260, the sequence ends.

[0451] When the voltage of the +5V power line drops, the switches SW1, SW2, SW7, and SW8 of the source device 110-10 and the switches SW3, SW4, SW5, and SW6 of the HDMI cable 130-10 are reset to their initial states.

[0452] "Embodiment 11" Fig. 91 shows a configuration example of a transmission system 10-11. This transmission system 10-11 is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-11 has a source device 110-11 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-11 connecting them. In Fig. 91, parts corresponding to Fig. 80 and Fig. 39 are given the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0453] The source device 110-11 has the same configuration as the source device 110-10 in the transmission system 10-10 in Fig. 80. The HDMI cable 130-11 is an AOC (Active Optical Cable), whereas the HDMI cable 130-10 in the transmission system 10-10 in Fig. 80 is a normal HDMI cable.

[0454] Therefore, the HDMI cable 130-11 has AOC components such as conversion circuits 331A and 331B, LDO regulators 332A and 332B, and a current driver 333B in addition to a register 131, a control unit 132, voltage monitor units 133 and 134, and switches SW3, SW4, SW5, and SW6.

[0455] Although detailed description will be omitted, this transmission system 10-11 operates in the same manner as the transmission system 10-10 in FIG. 80, and can provide the same effects.

[0456] In this transmission system 10-11, the control unit 132 of the HDMI cable 130-11 can control the LDO regulators 332A and 332B to turn on and draw 55 mA or more from the +5V power line based on the current supply capability information transmitted from the source device 110-11 through the register 131, that is, information that the control unit 132 may draw a current of 55 mA or more. In this case, for example, in the HDMI cable sequence of Fig. 90, after the process of step ST259, the LDO regulators 332A and 332B are turned on and the active circuit is set to an operating state (Enable). This enables the active circuit of the HDMI cable 130-11 to operate appropriately, and also prevents the source device from failing due to being unable to withstand the overcurrent.

[0457] In addition, if the HDMI cable 130-11 does not have the resistor 131, the control unit 132 of the HDMI cable 130-11, based on the determination that the source device 110-11 is a compatible cable, may assume that the source device 110-11 has sufficient current supply capability information, and may turn on the LDO regulators 332A, 332B to control the cable to draw 55 mA or more from the +5V power line.

[0458] "Embodiment 12" Fig. 92 shows a configuration example of a transmission system 10-12. This transmission system 10-12 is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-12 has a source device 110-12 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-12 connecting them. In Fig. 92, parts corresponding to those in Fig. 80 are given the same reference numerals, and detailed explanations thereof will be omitted as appropriate.

[0459] The HDMI cable 130-12 has the same configuration as the HDMI cable 130-10 in the transmission system 10-10 in Fig. 80. Whereas the source device 110-10 in the transmission system 10-10 in Fig. 80 is provided with a switch SW7, the source device 110-12 excludes this switch SW7, and otherwise has the same configuration and operates in the same manner.

[0460] Although detailed description will be omitted, this transmission system 10-12 operates in the same manner as the transmission system 10-10 in FIG. 80, and can provide the same effects.

[0461] "Embodiment 13" Fig. 93 shows a configuration example of a transmission system 10-13. This transmission system 10-13 is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-13 has a source device 110-13 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-13 connecting them. In Fig. 93, parts corresponding to those in Fig. 91 are given the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0462] The HDMI cable 130-13 has the same configuration as the HDMI cable 130-11 in the transmission system 10-11 in Fig. 91. Whereas the source device 110-11 in the transmission system 10-11 in Fig. 91 is provided with a switch SW7, the source device 110-13 excludes this switch SW7, and otherwise has the same configuration and operates in the same manner.

[0463] Although detailed description will be omitted, this transmission system 10-13 operates in the same manner as the transmission system 10-11 in FIG. 91 and can provide the same effects. "Embodiment 14" Fig. 94 shows a configuration example of a transmission system 10-14. This transmission system 10-14 is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-14 has a source device 110-14 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-14 connecting them. In Fig. 94, parts corresponding to Figs. 80 and 92 are given the same reference numerals, and detailed explanations thereof will be omitted as appropriate.

[0464] The HDMI cable 130-14 has the same configuration as the HDMI cable 130-12 in the transmission system 10-12 in Fig. 92. Whereas the source device 110-12 in the transmission system 10-12 in Fig. 92 is provided with resistor R3, the source device 110-14 is provided with an LDO (Low Drop Out) regulator 115 instead. This LDO regulator 115 is controlled by the control unit 111, and is controlled to generate a voltage of 3 V when the switch SW8 is opened, and to generate a voltage of 5 V when the switch SW8 is short-circuited.

[0465] In this way, the LDO regulator 115 generates a voltage of 3V when the switch SW8 is opened, so that the resistors R1 and R2 are connected in series between the ground (0V) of the source device 110-14 and the 3V power supply, and a voltage of 2V is obtained at points Q1 and P2 of the utility line. As a result, it is possible to determine that there is no intermediate relay device such as a repeater that separates the +5V power supply line between the source device 110-14 and the HDMI cable 130-14, similar to the transmission systems 10-10 and 10-12 in Figs. 80 and 92.

[0466] Although detailed description is omitted, this transmission system 10-14 operates in the same manner as the transmission systems 10-10 and 10-12 in Figs. 80 and 92, and can obtain the same effects. In addition, in this transmission system 10-14, by using an LDO regulator 115 instead of the resistor R3, when the switch SW8 is opened, a stable voltage of 3V is applied to the +5V power line, and a voltage of 2V can be accurately generated at points Q1 and P2 of the utility line, making it possible to accurately determine that no relay device such as a repeater is present. Incidentally, when using the voltage drop due to the resistor R3, if a large current is drawn through the resistor R3 other than the current flowing through the series resistors R1 and R2, the voltage drop in the resistor R3 becomes large, and there is a possibility that a voltage less than 3V is applied to the +5V power line.

[0467] "Embodiment 15" Fig. 95 shows a configuration example of a transmission system 10-15. This transmission system 10-15 is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-15 has a source device 110-15 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-15 connecting them. In Fig. 95, parts corresponding to Figs. 93 and 94 are given the same reference numerals, and detailed explanations thereof will be omitted as appropriate.

[0468] The HDMI cable 130-15 has the same configuration as the HDMI cable 130-13 in the transmission system 10-13 in Fig. 93. Whereas the source device 110-13 in the transmission system 10-13 in Fig. 93 is provided with resistor R3, the source device 110-15 is provided with an LDO (Low Drop Out) regulator 115 instead. This LDO regulator 115 is controlled by the control unit 111, and is controlled to generate a voltage of 3 V when the switch SW8 is opened, and to generate a voltage of 5 V when the switch SW8 is short-circuited.

[0469] Although detailed description will be omitted, this transmission system 10-15 operates in the same manner as the transmission systems 10-13 and 10-14 in Figs. 93 and 94, and can provide the same effects. "Embodiment 16" Fig. 96 shows a configuration example of a transmission system 10-16. This transmission system 10-16 is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-16 has a source device 110-16 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-16 connecting them. In Fig. 96, parts corresponding to Figs. 80, 92, and 94 are given the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0470] The HDMI cable 130-14 has the same configuration as the HDMI cable 130-14 in the transmission system 10-14 in Fig. 94. Whereas the source device 110-14 in the transmission system 10-14 in Fig. 94 is provided with the LDO regulator 115 and the switch SW8, the source device 110-16 is provided with an LDO regulator 116 that sets the voltage of the +5V power line. This LDO regulator 116 is controlled by the control unit 111, and is controlled to generate a voltage of 3V at the same timing as when the switch SW8 is opened in the transmission system 10-14 in Fig. 94, and to generate a voltage of 5V at other times.

[0471] In this way, the LDO regulator 116 generates a voltage of 3V at the same timing as when the switch SW8 is opened in the transmission system 10-14 in Fig. 94, so that the resistors R1 and R2 are connected in series between the ground (0V) of the source device 110-16 and the 3V power supply, and a voltage of 2V is obtained at points Q1 and P2 of the utility line. As a result, it is possible to determine that there is no intermediate equipment such as a repeater that separates the +5V power supply line between the source device 110-16 and the HDMI cable 130-16, similar to the transmission systems 10-10, 10-12, and 10-14 in Figs. 80, 92, and 94.

[0472] Although detailed description is omitted, this transmission system 10-16 operates in the same manner as the transmission systems 10-10, 10-12, and 10-14 in Fig. 80, Fig. 92, and Fig. 94, and can obtain the same effects. Moreover, since the transmission system 10-16 does not use the switch SW8, it is possible to avoid unstable operation due to ripples that are generated when the switch SW8 is switched between open and short-circuited.

[0473] "Embodiment 17" Fig. 97 shows a configuration example of a transmission system 10-17. This transmission system 10-17 is an HDMI transmission system using HDMI as a digital interface. This transmission system 10-17 has a source device 110-17 as a transmitting device, a sink device 320 as a receiving device, and an HDMI cable 130-17 connecting them. In Fig. 97, parts corresponding to Figs. 95 and 96 are given the same reference numerals, and detailed explanations thereof will be omitted as appropriate.

[0474] The HDMI cable 130-17 has the same configuration as the HDMI cable 130-15 in the transmission system 10-15 in Fig. 95. Whereas the source device 110-15 in the transmission system 10-15 in Fig. 95 is provided with the LDO regulator 115 and the switch SW8, the source device 110-17 is provided with an LDO regulator 116 that sets the voltage of the +5V power line instead. This LDO regulator 116 is controlled by the control unit 111, and is controlled to generate a voltage of 3V at the same timing as when the switch SW8 is opened in the transmission system 10-15 in Fig. 95, and to generate a voltage of 5V at other times.

[0475] Although detailed description will be omitted, this transmission system 10-17 operates in the same manner as the transmission systems 10-15 and 10-16 in Figs. 95 and 96, and can provide the same effects.

[0476] <2. Modifications> In the above-mentioned embodiments 10 to 17, until the source device receives a connection detection signal from the sink device via the HPD line, switch SW1 is short-circuited and a voltage of 4V is obtained at point Q1 of the Utility line, so that when the HDMI cable is removed from the source device, the source device can detect this. Although detailed description is omitted, it is also possible to obtain the same effect by using a similar configuration in the other embodiments.

[0477] In addition, in the above embodiment, an example was shown in which a utility line and a power line were used to determine whether the source device and the HDMI cable are compatible, but the lines used are not limited to these, and other lines may also be used.

[0478] In the above embodiment, a transmission system in which a source device and a sink device are connected by an HDMI cable has been described as an example. However, the present technology can also be applied to a cable that uses a mechanism defined in the "VESA Plug and Display (P&D) Specification" between a transmitting device and a receiving device, and therefore can also be applied to DVI, MHL, Display Port, and the like. The present technology can also be applied to wireless communication, etc., not limited to AOC and ACC. Furthermore, the present technology can of course also be applied to USB cables, etc.

[0479] For example, let us briefly explain the configuration when using "Display Port". Figure 98(a) shows the pin arrangement of "Display Port". AuX+ / - corresponds to HDMI's DDC, and 3.3V corresponds to HDMI's +5V. Hot plug detection corresponds to HDMI's HPD.

[0480] In the configuration shown in Figure 15, this is possible if a 3.3V power line is used instead of the +5V power line. In the configuration in Figure 7, the GND of pin 14 can be used instead of the Utility line. If one side is a non-compliant product such as legacy, switch SW2 or switch SW4 shown in Figure 7 does not exist, and so there will be a short with GND, but if the source device is non-compliant as in Figure 11, there is no problem as the cable side is also 0V. Even if the cable is non-compliant as in Figure 12, there is no problem as the 3.3V is connected to GND via 100kΩ, and the leakage current is very small at 33μA.

[0481] This technology can also be applied to "Thunderbolt." Figure 98(b) shows the pin arrangement for "Thunderbolt." In the case of "Thunderbolt," "DPPWR" corresponds to the +5V line. HPD is provided from the beginning. In the example of HDMI, the Utility line is used to perform resistive voltage division between the source and the cable, but in the case of "Thunderbolt," it is sufficient to use the reserve of No. 10 or No. 12.

[0482] The present technology can also be configured as follows. (1) A cable connected between a first electronic device and a second electronic device, a determination unit that determines whether the first electronic device is a compatible electronic device; and a control unit that controls the first electronic device to operate in a compatible mode when the first electronic device is a compatible electronic device and to operate in a non-compatible mode when the first electronic device is not a compatible electronic device based on a determination result of the determination unit. cable. (2) The determination unit determines whether the first electronic device is a compatible electronic device based on a voltage monitoring result of a predetermined line to which a predetermined voltage is applied via a voltage dividing resistor. The cable described in (1) above. (3) a first switch is connected in series with the voltage dividing resistor; The first switch is shorted when the determination is made. The cable described in (2) above. (4) a second switch is inserted on the second electronic device side from the point where the voltage monitoring is performed on the predetermined line; The second switch is in an open state when the determination is made. The cable described in (3) above. (5) In the corresponding mode, when the voltage monitor detects that the voltage of the predetermined line has reached the predetermined voltage, the control unit changes the first switch from a short-circuited state to an open state, and then changes the second switch from an open state to a short-circuited state. The cable described in (4) above. (6) further comprising a register connected to the communication line; a third switch is connected to the communication line on the second electronic device side from a point where the register is connected; In the corresponding mode, the control unit changes the third switch from an open state to a short state after confirming that the register has been accessed from the first electronic device. A cable according to any one of (1) to (5). (7) The control unit confirms that the register has been accessed from the first electronic device based on a voltage monitoring result of a predetermined line to which a predetermined voltage is applied via a voltage dividing resistor. The cable described in (6) above. (8) A fourth switch is inserted in the power line, In the corresponding mode, the control unit changes the third switch from an open state to a short-circuit state, and then changes the fourth switch from an open state to a short-circuit state. The cable according to (6) or (7) above. (9) In the non-compatible mode, the control unit changes the third switch from an open state to a short state without confirming that the register has been accessed from the first electronic device. A cable according to any one of (6) to (8). (10) A fourth switch is inserted in the power line, In the non-compatible mode, the control unit changes the third switch from an open state to a short-circuit state, and then changes the fourth switch from an open state to a short-circuit state. The cable described in (9) above. (11) Further comprising a current consuming unit connected to the power supply line, In the compatible mode, the control unit changes the current consumption unit from a current non-consuming state to a current consuming state after confirming that the first electronic device has determined that its own cable is a compatible cable. A cable according to any one of (1) to (5). (12) a fifth switch is inserted in the power supply line; In the compatible mode, the control unit changes the fifth switch from an open state to a short state after confirming that the first electronic device has determined that its own cable is a compatible cable. The cable described in (11) above. (13) The control unit confirms that the first electronic device has determined that its own cable is a compatible cable based on a voltage monitoring result of a predetermined line to which a predetermined voltage is applied via a voltage dividing resistor. The cable described in (11) above. (14) In the non-compatible mode, the control unit changes the fifth switch from an open state to a short state without confirming that the first electronic device has determined that its own cable is a compatible cable. The cable described in (12) above. (15) The control unit controls the first electronic device to operate in the corresponding mode when the first electronic device is a corresponding electronic device and no relay device is interposed between the first electronic device and the corresponding electronic device to separate a power line. A cable as described in (1) or (2). (16) The control unit determines that the first electronic device is a compatible electronic device when the voltage of a predetermined line to which a predetermined voltage is applied via a voltage dividing resistor becomes a first voltage, and then determines that the relay device is not present between the first electronic device and the control unit when the voltage of the predetermined line changes to a second voltage. The cable described in (15) above. (17) The information transmitting unit, which functions when the device operates in the corresponding mode, transmits information to and from the first electronic device. A cable as described in (1) or (2). (18) The information transmission unit is A variable resistance circuit is connected to a predetermined line, By changing the resistance value of the variable resistor circuit, arbitrary information is transmitted to the first electronic device. The cable described in (17) above. (19) The information transmission unit is The resistance value of the variable resistor circuit is fixed to a predetermined value, and a voltage of the predetermined line is monitored to receive predetermined information from the first electronic device. The cable described in (18) above. (20) A method for controlling a cable connected between a first electronic device and a second electronic device, comprising the steps of: a determination step in which a determination unit determines whether the first electronic device is a compatible electronic device; A control step is included in which a control unit controls the first electronic device to operate in a compatible mode when the first electronic device is a compatible electronic device, and to operate in a non-compatible mode when the first electronic device is not a compatible electronic device, based on a determination result of the determination unit. How the cable is controlled. (21) A connection device connected between a first electronic device and a second electronic device, comprising: a determination unit that determines whether the first electronic device is a compatible electronic device; and a control unit that controls the first electronic device to operate in a compatible mode when the first electronic device is a compatible electronic device and to operate in a non-compatible mode when the first electronic device is not a compatible electronic device based on a determination result of the determination unit. Connection device. (22) An electronic device that is connected to an external device via a cable, A determination unit that determines whether the cable is a compatible cable; and a control unit that performs control so that the cable operates in a compatible mode when the cable is a compatible cable and operates in a non-compatible mode when the cable is not a compatible cable based on a determination result of the determination unit. electronic equipment. (23) The determination unit determines whether the cable is a compliant cable based on a voltage monitor result of a predetermined line to which a predetermined voltage is applied via a voltage dividing resistor. The electronic device according to (22). (24) a first switch is connected in series with the voltage dividing resistor; The first switch is shorted when the determination is made. The electronic device according to (23) above. (25) a second switch is inserted on the side of the predetermined line opposite to the terminal side of the point where the voltage monitoring is performed; The second switch is in an open state when the determination is made. 2. The electronic device according to claim 1 , (26) In the corresponding mode, the control unit changes the first switch from a short-circuited state to an open state after detecting that the connection detection line has become a high level. 20. The electronic device according to claim 24 or 25. (27) In the non-compatible mode, the control unit changes the first switch from a short-circuited state to an open state. 2. The electronic device according to claim 1 , (28) In the corresponding mode, the control unit accesses a register of the cable through a communication line before changing the first switch from a short-circuited state to an open state. The electronic device according to any one of (24) to (26). (29) In the corresponding mode, the control unit changes a current that can be supplied by the power line from a first current to a second current that is higher than the first current before changing the first switch from a short-circuited state to an open state. The electronic device according to any one of (24) to (26). (30) The control unit controls the cable to operate in the corresponding mode when the cable is a corresponding cable and no relay device is interposed between the cable and the corresponding cable to separate a power line. 2. The electronic device according to claim 1 , (31) The control unit determines that the cable is a compatible cable when the voltage of a specific line to which a specific voltage is applied via a voltage dividing resistor becomes a first voltage, and then determines that the relay device is not present between the cable and the specific line when the voltage of the specific line changes to a second voltage. The electronic device according to (30) above. (32) The device further includes an information transmission unit that functions when the device operates in the corresponding mode and transmits information to and from the cable. 2. The electronic device according to claim 1 , (33) The information transmission unit is A variable resistance circuit is connected to a predetermined line, By changing the resistance value of the variable resistor circuit, arbitrary information can be transmitted to the cable. The electronic device according to (32) above. (34) The information transmission unit is The resistance value of the variable resistor circuit is fixed to a predetermined value, and the voltage of the predetermined line is monitored to receive predetermined information from the cable. The electronic device according to (33) above. (35) A method for controlling an electronic device connected to an external device via a cable, comprising: a determining step in which a determining unit determines whether the cable is a compatible cable; A control step is provided in which a control unit controls the device to operate in a compatible mode when the cable is a compatible cable, and to operate in a non-compatible mode when the cable is not a compatible cable, based on a determination result of the determination unit. A method for controlling electronic devices. (36) An electronic device that is connected to an external device via a connection device, a determination unit for determining whether the connection device is a compatible connection device; and a control unit that controls the connection device to operate in a compatible mode when the connection device is a compatible connection device and to operate in a non-compatible mode when the connection device is not a compatible connection device based on a determination result of the determination unit. electronic equipment. [Explanation of symbols]

[0483] 10-1~10-17, 10-1A~10-4A, 10-1B~10-4B, 10-6B~10-6C, 10-8A~10-8B, 10-9A~10-9D...Transmission system 110-1~110-17 Source device 111 Control unit 112 Voltage monitor section 113...Ammeter 114,135... Variable resistor circuit 115,116···LDO regulator 130-1~130-17, 130-9D, 330, 330C...HDMI cable 131 Register 132 Control section 133, 134 Voltage monitor section 140 Repeater 141 Amplifier 310...Source device 311...Control section 320...Sink device 321...EDID ROM 322 Control section 331A, 331B...Conversion circuit 332A, 332B...LDO Regulators 333B...Current driver SW1~SW8, SW11~SW15, SW21~SW24, SW26, SW31~SW33, SW35, SW41~SW44, SW46~SW49... Switches R1, R2, R3: Voltage dividing resistors

Claims

1. A connection device connected between a first electronic device and a second electronic device, a determination unit that is connected to the first electronic device via a line of a High-Definition Multimedia Interface (HDMI) cable and determines whether the first electronic device is a compatible electronic device based on a voltage monitor result of a predetermined line to which a predetermined voltage is applied via a voltage dividing resistor; a control unit that controls the first electronic device to operate in a compatible mode when the first electronic device is a compatible electronic device and to operate in a non-compatible mode when the first electronic device is not a compatible electronic device based on a determination result of the determination unit; a register including its own specification information and accessed by the first electronic device via a Display Data Channel (DDC) line of the HDMI cable; The control unit is A control for accepting writing of information relating to a supply capacity of the first electronic device from the first electronic device to the register; performing control based on access from the first electronic device to the register; The HDMI cable is an optical cable for optical communication. Data transmission from the first electronic device over at least one TMDS channel is controlled in response to accessing the register. Connection device.

2. An electronic device that is connected to an external device via a High-Definition Multimedia Interface (HDMI) cable line, a determination unit that determines whether the HDMI cable is a compatible HDMI cable based on a voltage monitor result of a predetermined line to which a predetermined voltage is applied via a voltage dividing resistor; and a control unit that performs control so that the HDMI cable operates in a compatible mode when the HDMI cable is a compatible HDMI cable, and operates in a non-compatible mode when the HDMI cable is not a compatible HDMI cable, based on a determination result of the determination unit. electronic equipment.

3. a first switch is connected in series with the voltage dividing resistor; The first switch is shorted when the determination is made.

3. The electronic device according to claim 2.

4. a second switch is inserted on the opposite side of the terminal side of the predetermined line at which the voltage monitoring is performed; The second switch is in an open state when the determination is made.

4. The electronic device according to claim 3.

5. In the corresponding mode, the control unit changes the first switch from a short-circuited state to an open state after detecting that the connection detection line has become a high level.

4. The electronic device according to claim 3.

6. The control unit changes the first switch from a short-circuited state to an open state in the non-compatible mode.

4. The electronic device according to claim 3.

7. In the corresponding mode, the control unit accesses a register of the HDMI cable through a communication line before changing the first switch from a short-circuited state to an open state.

4. The electronic device according to claim 3.

8. In the corresponding mode, the control unit changes a current that can be supplied by the power line from a first current to a second current that is higher than the first current before changing the first switch from a short-circuited state to an open state.

4. The electronic device according to claim 3.

9. The control unit controls the HDMI cable to operate in the corresponding mode when the HDMI cable is a corresponding HDMI cable and no relay device is interposed between the HDMI cable and the corresponding HDMI cable to separate a power line.

3. The electronic device according to claim 2.

10. The control unit determines that the HDMI cable is a compatible HDMI cable when the voltage of a specific line to which a specific voltage is applied via a voltage dividing resistor becomes a first voltage, and then determines that the relay device is not present between the HDMI cable and the specific line when the voltage of the specific line subsequently changes to a second voltage.

10. The electronic device according to claim 9.

11. and an information transmission unit that functions when the device operates in the corresponding mode and transmits information to and from the HDMI cable.

3. The electronic device according to claim 2.

12. The information transmission unit is A variable resistance circuit is connected to a predetermined line, By changing the resistance value of the variable resistor circuit, arbitrary information can be transmitted to the HDMI cable. The electronic device according to claim 11.

13. The information transmission unit is The resistance value of the variable resistor circuit is fixed to a predetermined value, and the voltage of the predetermined line is monitored to receive predetermined information from the HDMI cable.

13. The electronic device according to claim 12.

14. A method for controlling an electronic device connected to an external device via a High-Definition Multimedia Interface (HDMI) cable line, comprising: a determination step in which a determination unit determines whether the HDMI cable is a compatible HDMI cable based on a voltage monitor result of a predetermined line to which a predetermined voltage is applied via a voltage dividing resistor; A control step is provided in which a control unit controls the HDMI cable to operate in a compatible mode when the HDMI cable is a compatible HDMI cable, and to operate in a non-compatible mode when the HDMI cable is not a compatible HDMI cable, based on a determination result of the determination unit. A method for controlling electronic devices.

15. An electronic device that is connected to an external device via a connection device, a determination unit that is connected to the connection device via a line of a High-Definition Multimedia Interface (HDMI) cable and determines whether the connection device is a compatible connection device based on a voltage monitor result of a predetermined line to which a predetermined voltage is applied via a voltage dividing resistor; a control unit that controls the connection device to operate in a compatible mode when the connection device is a compatible connection device and to operate in a non-compatible mode when the connection device is not a compatible connection device based on a determination result of the determination unit; The HDMI cable is an optical cable for optical communication. electronic equipment.

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