Patent Description:
In recent years, drones, wearable devices, automobiles, and the like equipped with a plurality of cameras are rapidly increasing. High-speed interface specifications such as C-PHY specification and D-PHY specification that have been developed by the MIPI (Mobile Industry Processor Interface) alliance are applied in a case where image data from a plurality of cameras is transmitted to an application processor and the like. PTL <NUM> proposes a technology for signal transmission in the D-PHY specification.

PTL <NUM> discloses a bus system including three or more devices which are coupled to a bus. The three or more devices include one or a plurality of imaging devices, and transmit or receive data signals in a time-division manner.

Incidentally, in the MIPI, data transmission is point-to-point transmission; therefore, there are many issues to be solved to support a plurality of cameras, such as limitations on the number of pins on an application processor side, an increase in size of a transmission path, and product design. Multipoint bus transmission shows promise for support of a plurality of cameras. However, in existing multipoint bus transmission, waveform quality is greatly deteriorated by an influence of reflection and the like, which causes an issue that the existing multipoint bus transmission is not suitable for high-speed transmission. It is therefore desirable to provide a communication system and a communication method that make it possible to achieve multipoint bus transmission suitable for high-speed transmission.

According to a first aspect, the present invention provides a communication system according to independent claim <NUM>. According to a second aspect, the present invention provides a communication method according to independent claim <NUM>. Further aspects of the present invention are set forth in the dependent claims, the drawings and the following description. A communication system according to an embodiment of the present disclosure is a communication system that transmits data from a plurality of transmission devices to one reception device via a pair of signal lines. In the communication system, each of the transmission devices includes: a mode controller that controls a transmission mode; a transmission data generator that generates the data in accordance with the transmission mode controlled by the mode controller; and a data transmitter that transmits the data generated by the transmission data generator to the reception device. In a case where the transmission mode of a first transmission device of the plurality of the transmission devices is an HS (High Speed) mode, the mode controller of a second transmission device of the plurality of the transmission devices turns the transmission mode of the second transmission device to a termination mode in which an output terminal of the second transmission device is terminated.

A communication method according to an embodiment of the present disclosure is a communication method of transmitting data from a plurality of transmission devices to one reception device via a pair of signal lines, and includes the following step. In a case where a transmission mode of a first transmission device of the plurality of the transmission devices is an HS mode, a transmission mode of a second transmission device of the plurality of transmission devices is turned to a termination mode in which an output terminal of the second transmission device is terminated.

In the communication system and the communication method according to the embodiments of the present disclosure, in the case where the transmission mode of the first transmission device of the plurality of transmission devices is the HS mode, the transmission mode of the second transmission mode of the plurality of transmission devices is turned to the termination mode in which the output terminal of the second device is terminated. Accordingly, total reflection in the second transmission device is suppressed in the case where the transmission mode of the first transmission device is the HS mode. In addition, it is possible to perform transmission while performing switching between the HS mode and the LP mode.

Hereinafter, some embodiments of the present disclosure are described in detail with reference to the drawings. It should be noted that the description is given in the following order.

Description is given of a communication system <NUM> according to an embodiment of the present disclosure. <FIG> illustrates an overview of the communication system <NUM>. The communication system <NUM> is applied to transmission of a data signal and a clock signal, and includes transmission devices <NUM> and <NUM> and a reception device <NUM>. The communication system <NUM> includes a clock lane CL a data lane DL over the transmission devices <NUM> and <NUM> and the reception device <NUM>. The clock lane CL transmits the clock signal, and the data lane DL transmits the data signal such as image data, for example. That is, the communication system <NUM> is configured to perform multipoint bus transmission.

The transmission devices <NUM> and <NUM> each include a digital transmitter circuit and an analog transmitter circuit. The reception device <NUM> includes a digital receiver circuit and an analog receiver circuit. For example, a <NUM>-bit or <NUM>-bit parallel signal is transmitted between the digital transmitter circuit and the analog transmitter circuit. In addition, for example, a <NUM>-bit or <NUM>-bit parallel signal is transmitted between the digital receiver circuit and the analog receiver circuit. In the clock lane CL, the analog transmitter circuit and the analog receiver circuit are coupled to each other by a clock signal line <NUM> that transmits a differential clock signal. In the data lane DL, the analog transmitter circuit and the analog receiver circuit are coupled to each other by a data signal line <NUM> that transmits a differential data signal. The clock signal line <NUM> includes a pair of a positive signal line Cp and a negative signal line Cn that transmit a differential signal. The data signal line <NUM> includes a pair of a positive signal line Dp and a negative signal line Dn that transmit a differential signal. For example, a <NUM>-bit serial signal is transmitted to each of the clock signal line <NUM> and the data signal line <NUM>.

The transmission device <NUM> includes a clock transmitter circuit <NUM> and a data transmitter circuit <NUM>. The transmission device <NUM> includes a clock transmitter circuit <NUM> and a data transmitter circuit <NUM>. The reception device <NUM> includes a clock receiver circuit <NUM> and a data receiver circuit <NUM>. In the clock lane CL, the clock transmitter circuits <NUM> and <NUM> and the clock receiver circuit <NUM> are coupled to each other by the clock signal line <NUM> described above. In the data lane DL, the data transmitter circuits <NUM> and <NUM> and the data receiver circuit <NUM> are coupled to each other by the data signal line <NUM> described above. Each of the clock transmitter circuits <NUM> and <NUM> is a differential signal transmitter circuit that generates a differential clock signal as the clock signal and outputs the thus-generated differential clock signal to the clock signal line <NUM>. Each of the data transmitter circuits <NUM> and <NUM> is a differential signal transmitter circuit that generates a differential data signal as the data signal and outputs the thus-generated differential data signal to the data signal line <NUM>. The clock receiver circuit <NUM> is a differential signal receiver circuit that receives the differential clock signal as the clock signal via the clock signal line <NUM> and performs predetermined processing on the received differential clock signal. The data receiver circuit <NUM> is a differential signal receiver circuit that receives the differential data signal as the data signal via the data signal line <NUM> and performs predetermined processing on the received differential data signal. It should be noted that each of the clock transmission devices <NUM> and <NUM> and the data transmission devices <NUM> and <NUM> may be a ternary signal transmitter circuit that outputs a ternary level signal. In addition, each of the clock receiver circuit <NUM> and the data receiver circuit <NUM> may be a ternary signal receiver circuit.

<FIG> illustrates an example of a configuration of the communication system <NUM>. The communication system <NUM> illustrated in <FIG> represents the communication system <NUM> illustrated in <FIG> with functional blocks.

The transmission device <NUM> includes, in the clock lane CL, a transmission mode controller <NUM>, a clock generator <NUM>, and a clock transmitter <NUM>. The transmission device <NUM> includes, in the data lane DL, a transmission data generator <NUM> and a data transmitter <NUM>. The transmission mode controller <NUM> decides a transmission mode in accordance with an instruction from an upper layer (e.g., three control signals HSEN, DRVEN, and PU_EN as illustrated in <FIG> and <FIG>).

Here, the control signal HSEN is a signal for setting Enable and Disable of an HS mode. The control signal DRVEN is a signal for setting Enable and Disable of the HS mode or an LP mode. The control signal PU_EN is a signal for setting Enable and Disable of a PU (PullUp) mode. The transmission mode controller <NUM> sets various modes in accordance with a combination of the three control signals HSEN, DRVEN, and PU_EN), for example, as illustrated in <FIG>.

For example, in a case of (HSEN, DRVEN, PU_EN) = (<NUM>, <NUM>, <NUM>), the transmission mode controller <NUM> sets the HS mode. In addition, for example, in a case of (HSEN, DRVEN, PU_EN) = (<NUM>, <NUM>, <NUM>), the transmission mode controller <NUM> sets the LP mode. In addition, for example, in a case of (HSEN, DRVEN, PU_EN) = (<NUM>, <NUM>, <NUM>), the transmission mode controller <NUM> further sets the PullUp mode in the LP mode (hereinafter referred to as "LP mode + PullUp mode"). In addition, for example, in a case of (HSEN, DRVEN, PU_EN) = (<NUM>, <NUM>, <NUM>), the transmission mode controller <NUM> sets the PullUp mode. In addition, for example, in a case of (HSEN, DRVEN, PU_EN) = (<NUM>, <NUM>, <NUM>), the transmission mode controller <NUM> sets a high impedance (HiZ) mode.

The PullUp mode indicates a mode in which a voltage of a pair of output terminals 40A and 40B is pulled up to a predetermined voltage value. The LP mode + PullUp mode indicates a mode in which the voltage of the pair of output terminals 40A and 40B is pulled up to a predetermined voltage value in addition to setting the LP mode. The HiZ mode indicates that the pair of output terminals 40A and 40B are turned to a floating state.

The transmission mode controller <NUM> further performs control corresponding to a decided transmission mode, on the clock generator <NUM> and the transmission data generator <NUM>. The clock generator <NUM> generates a clock signal with a clock frequency corresponding to a transmission mode in accordance with an instruction of the transmission mode controller <NUM>. The clock generator <NUM> outputs the generated clock signal to the clock transmitter <NUM> and the transmission data generator <NUM>. The clock transmitter <NUM> outputs the clock signal generated by the clock generator <NUM> to the clock signal line <NUM>. That is, the clock transmitter <NUM> outputs the clock signal generated by the clock generator <NUM> to a clock receiver <NUM> via the clock signal line <NUM>.

The transmission data generator <NUM> performs, in accordance with an instruction of the transmission mode controller <NUM>, various kinds of processing such as communication protocol control, decoding of data inputted from an upper layer, insertion of a control command, and parallel-serial conversion, on an inputted data signal (e.g., high-speed transmission data HS-TxData or low-speed transmission data LP-TxData), thereby generating a data signal. The transmission data generator <NUM> outputs the generated data signal to the data transmitter <NUM>. The transmission data generator <NUM> switches various kinds of processing described above in accordance with an instruction of the transmission mode controller <NUM>. The data transmitter <NUM> outputs the data signal generated by the transmission data generator <NUM> to a data signal line. That is, the data transmitter <NUM> outputs the data signal generated by the transmission data generator <NUM> to a data receiver <NUM> via the data signal line.

The transmission device <NUM> includes, in the clock lane CL, a transmission mode controller <NUM>, a clock generator <NUM>, and a clock transmitter <NUM>. The transmission device <NUM> includes, in the data lane DL, a transmission data generator <NUM> and a data transmitter <NUM>. The transmission mode controller <NUM> decides a transmission mode in accordance with an instruction from an upper layer (e.g., three control signals HSEN, DRVEN, and PU_EN). The transmission mode controller <NUM> further performs control corresponding to a decided transmission mode, on the clock generator <NUM> and the transmission data generator <NUM>. The clock generator <NUM> generates a clock signal with a clock frequency corresponding to a transmission mode in accordance with an instruction of the transmission mode controller <NUM>. The clock generator <NUM> outputs the generated clock signal to the clock transmitter <NUM> and the transmission data generator <NUM>. The clock transmitter <NUM> outputs the clock signal generated by the clock generator <NUM> to the clock signal line <NUM>. That is, the clock transmitter <NUM> outputs the clock signal generated by the clock generator <NUM> to the clock receiver <NUM> via the clock signal line <NUM>.

The transmission data generator <NUM> performs, in accordance with an instruction of the transmission mode controller <NUM>, various kinds of processing such as communication protocol control, decoding of data inputted from an upper layer, insertion of a control command, and parallel-serial conversion, on an inputted data signal (e.g., high-speed transmission data HS-TxData or low-speed transmission data LP-TxData), thereby generating a data signal. The transmission data generator <NUM> outputs the generated data signal to the data transmitter <NUM>. The transmission data generator <NUM> switches various kinds of processing described above in accordance with an instruction of the transmission mode controller <NUM>. The data transmitter <NUM> outputs the data signal generated by the transmission data generator <NUM> to a data signal line. That is, the data transmitter <NUM> outputs the data signal generated by the transmission data generator <NUM> to the data receiver <NUM> via the data signal line.

The reception device <NUM> includes the clock receiver <NUM> in the clock lane CL. The reception device <NUM> includes, in the data lane DL, the data receiver <NUM> and a received data interpreter <NUM>. The clock receiver <NUM> receives the clock signal outputted from the clock transmitter <NUM> or the clock transmitter <NUM> via the clock signal line <NUM>. The clock receiver <NUM> outputs the received clock signal to the received data interpreter <NUM>. The data receiver <NUM> receives the data signal outputted from the data transmitter <NUM> or the data transmitter <NUM> via the data signal line <NUM>. The data receiver <NUM> outputs the received data signal to the received data interpreter <NUM>. The received data interpreter <NUM> performs, on the basis of the inputted clock signal, various kinds of processing such as serial-parallel conversion, detection of a control command, decoding of signal data, and communication protocol control, on the inputted data signal, thereby generating a data signal to be provided to a subsequent stage. The received data interpreter <NUM> switches various kinds of processing described above in accordance with the inputted clock signal, for example. The received data interpreter <NUM> outputs the generated data signal (e.g., high-speed reception data HS-RxData or low-speed reception data LP-RxData) to a circuit of a subsequent stage.

<FIG> illustrates an example of the data transmitters <NUM> and <NUM> in the communication system <NUM>. Each of the data transmitters <NUM> and <NUM> includes a driver HS-TX for signal transmission in the HS mode, a driver LP-TX for signal transmission in the LP mode, and a driver LP-RX for signal reception in the LP mode. Each of the data transmitters <NUM> and <NUM> further includes a terminator resistor RT and a pull-up resistor PU. The terminator resistor RT is configured to turn on and off termination of the pair of output terminals 40A and 40B coupled to a pair of data signal lines <NUM>, and the pull-up resistor PU is configured to pull up the pair of output terminals 40A and 40B coupled to the pair of data signal lines <NUM>. The pull-up resistor PU controls on and off of a pull-up resistor on the basis of a control signal PUON for controlling pull-up. Each of the data transmitters <NUM> and <NUM> includes a terminator controller PHY-FSM.

The driver HS-TX outputs the low-speed transmission data LP-TxData inputted from the transmission data generators <NUM> and <NUM> to the pair of data signal lines <NUM> via the pair of output terminals 40A and 40B on the basis of control signals from the transmission data generators <NUM> and <NUM>. The driver HS-TX outputs the low-speed transmission data LP-TxData inputted from the transmission data generators <NUM> and <NUM> to the pair of data signal lines <NUM> via the pair of output terminals 40A and 40B on the basis of control signals from the transmission data generators <NUM> and <NUM>. The termination controller PHY-FSM detects a transmission mode in any other transmission device on the basis of the voltage of the pair of output terminals 40A and 40B. Examples of kinds of transmission modes to be detected by the termination controller PHY-FSM include LP-<NUM> of the LP mode, LP-<NUM> of the LP mode, LP-<NUM> of the LP mode, or the like.

The termination controller PHY-FSM further controls on and off of the terminator resistor RT on the basis of the detected transmission mode (a result of detection). <FIG> illustrates an example of a function of the termination controller PHY-FSM. <FIG> illustrates an example of a circuit of the termination controller PHY-FSM. Suppose that the termination controller PHY-FSM detects that any other transmission device is in LP-<NUM> of the LP mode on the basis of LPdata_p and LPdata_n, for example. At this time, in both the transmission devices <NUM> and <NUM>, state variation is stopped. Suppose that, for example, the termination controller PHY-FSM detects that the other transmission device is turned to LP-<NUM> of the LP mode on the basis of LPdata_p and LPdata_n after detecting that the other transmission device is in LP-<NUM> of the LP mode. At this time, the other transmission device has started a transition of a state from LP-<NUM> of the LP mode to the HS mode. Suppose that, for example, the termination controller PHY-FSM detects that the other transmission device is turned to LP-<NUM> of the LP mode on the basis of LPdata_p and LPdata_n after detecting that the other transmission device is turned to LP-<NUM> of the LP mode. At this time, the other transmission device is preparing for being turned to the HS mode. Accordingly, in a case where the termination controller PHY-FSM is detecting that the other transmission device is turned to LP-<NUM> of the LP mode (during detection of LP-<NUM> of the LP mode), for example, the termination controller PHY-FSM outputs, to the terminator resistor RT, a control signal for turning the terminator resistor RT from off to on as a control signal RTON. Thus, the terminator resistor RT is turned from off to on.

The mode of the other transmission device is detected by determining the voltage of the pair of output terminals 40A and 40B by a predetermined threshold value, for example. Suppose that the other transmission device starts a transition to the HS mode, and thereafter is transitioned to the HS mode, ends the HS mode, and starts a transition from the HS mode to the LP mode. The voltage of the output terminals 40A and 40B at this time is detected by the predetermined threshold value, thereby generating LPdata_p and LPdata_n. The termination controller PHY-FSM uses the LPdata_p and the LPdata_n as input data, and outputs, to the terminator resistor RT, a control signal for turning on or off the terminator resistor RT. Thus, the terminator resistor RT is turned on or off.

<FIG> illustrates an example of waveforms of the communication system <NUM>. As illustrated in <FIG>, in the transmission devices <NUM> and <NUM>, a transmission device that outputs HS-TxData, LP-TxData, and PullUp to the data signal line <NUM> (the pair of the positive signal line Dp and the negative signal line Dn) is indicated by "FRONT", and a transmission device in the Hi-Z mode is indicated by "REAR". The reception device <NUM> receives the high-speed transmission data HS-TxData alternately outputted from the transmission devices <NUM> and <NUM> via the data signal line <NUM> (the pair of the positive signal line Dp and the negative signal line Dn). Accordingly, as illustrated in (C) of <FIG>, it looks as if the reception device <NUM> receives the high-speed transmission data HS-TxData and LP-TxData from a single transmission device.

Here, in a case where the transmission mode of a first transmission device (the transmission device <NUM>) of the transmission devices <NUM> and <NUM> is the HS mode, a mode controller (the transmission mode controller <NUM>) of a second transmission device (the transmission device <NUM>) of the transmission devices <NUM> and <NUM> turns the transmission mode of the second transmission device (the transmission device <NUM>) to a termination mode in which the output terminals 40A and 40B of the second transmission device (the transmission device <NUM>) are terminated. In contrast, in a case where the transmission mode of the second transmission device (the transmission device <NUM>) of the transmission devices <NUM> and <NUM> is the HS mode, a mode controller (the transmission mode controller <NUM>) of the first transmission device (the transmission device <NUM>) of the transmission devices <NUM> and <NUM> turns the transmission mode of the first transmission device (the transmission device <NUM>) to a termination mode in which the output terminals 40A and 40B of the first transmission device (the transmission device <NUM>) are terminated.

In addition, the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>) turns the terminator resistor RT from off to on in a case where desired successive transitions to LP-<NUM>, LP-<NUM>, and LP-<NUM> (LP-<NUM> →LP-<NUM> → LP-<NUM>) are detected in the transmission mode of the other transmission device (the transmission device <NUM>). In contrast, the termination controller PHY-FSM of the second transmission device (the transmission device <NUM>) turns the terminator resistor RT from off to on in a case where desired successive transitions to LP-<NUM>, LP-<NUM>, and LP-<NUM> are detected in the transmission mode of the other transmission device (the transmission device <NUM>).

In addition, the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>) turns the terminator resistor RT from off to on in a case where the voltage of the pair of output terminals 40A and 40B is determined by a predetermined threshold value to detect a desired transition. In contrast, the termination controller PHY-FSM of the second transmission device (the transmission device <NUM>) turns the terminator resistor RT from off to on in a case where the voltage of the pair of output terminals 40A and 40B is determined by the predetermined threshold value to detect a desired transition.

In addition, the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>) turns the terminator resistor RT from on to off in a case where the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>) detects that the transmission mode of the other transmission device (the transmission device <NUM>) is LP-<NUM> of the LP mode. In contrast, the termination controller PHY-FSM of the second transmission device (the transmission device <NUM>) turns the terminator resistor RT from on to off in a case where the termination controller PHY-FSM of the second transmission device (the transmission device <NUM>) detects that the transmission mode of the other transmission device (the transmission device <NUM>) is LP-<NUM> of the LP mode.

In addition, the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>) turns the terminator resistor RT from on to off in a case where the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>) detects that the voltage of the pair of output terminals 40A and 40B exceeds a predetermined threshold value. In contrast, the termination controller PHY-FSM of the second transmission device (the transmission device <NUM>) turns the terminator resistor RT from on to off in a case where the termination controller PHY-FSM of the second transmission device (the transmission device <NUM>) detects that the voltage of the pair of output terminals 40A and 40B exceeds the predetermined threshold value.

In addition, in the first transmission device (the transmission device <NUM>), in a case where the transmission mode is displaced from the HS mode to the LP mode, the transmission mode controller <NUM> inserts the PullUp mode in which the voltage of the pair of output terminals 40A and 40B is pulled up. In contrast, in the second transmission device (the transmission device <NUM>), in a case where the transmission mode is displaced from the HS mode to the LP mode, the transmission mode controller <NUM> inserts, after such displacement, the PullUp mode in which the voltage of the pair of output terminals 40A and 40B is pulled up.

In addition, in the first transmission device (the transmission device <NUM>), the mode controller <NUM> inserts, before and after the termination mode, the HiZ mode in which the voltage of the pair of output terminals 40A and 40B is set to high impedance. In contrast, in the second transmission device (the transmission device <NUM>), the mode controller <NUM> inserts, before and after the termination mode, the HiZ mode in which the voltage of the pair of output terminals 40A and 40B is set to high impedance.

Next, description is given of effects of the communication system <NUM> according to the present embodiment.

In recent years, drones, wearable devices, automobiles, and the like equipped with a plurality of cameras are rapidly increasing. High-speed interface specifications such as C-PHY specification and D-PHY specification that have been developed by the MIPI alliance are applied in a case where image data from a plurality of cameras is transmitted to an application processor and the like.

Incidentally, in the MIPI, data transmission is point-to-point transmission; therefore, there are many issues to be solved to support a plurality of cameras, such as limitations on the number of pins on an application processor side, an increase in size of a transmission path, and product design. Multipoint bus transmission shows promise for support of a plurality of cameras. However, in existing multipoint bus transmission, waveform quality is greatly deteriorated by an influence of reflection and the like, which causes an issue that the existing multipoint bus transmission is not suitable for high-speed transmission.

In contrast, in the present embodiment, in a case where the transmission mode of the first transmission device (the transmission device <NUM>) of the transmission devices <NUM> and <NUM> is the HS mode, the transmission mode of the second transmission device (the transmission device <NUM>) of the transmission devices <NUM> and <NUM> is the termination mode in which the output terminals 40A and 40B of the second transmission device (the transmission device <NUM>) are terminated. This makes it possible to suppress total reflection in the second transmission device (the transmission device <NUM>) in a case where the transmission mode of the first transmission device (the transmission device <NUM>) is the HS mode. In addition, it is possible to perform transmission while performing switching between the HS mode and the LP mode. This consequently makes it possible to achieve multipoint bus transmission suitable for high-speed transmission.

In addition, in the present embodiment, each of the data transmitters <NUM> and <NUM> includes the terminator resistor RT that is configured to turn on and off termination of the pair of output terminals 40A and 40B coupled to the data signal line <NUM>. Further, the transmission mode of any other transmission device is detected on the basis of the voltage of the pair of output terminals 40A and 40B, and on and off of the terminator resistor RT is controlled on the basis of a result of such detection. This makes it possible to suppress total reflection in the second transmission device (the transmission device <NUM>) in a case where the transmission mode of the first transmission device (the transmission device <NUM>) is the HS mode. In addition, it is possible to perform transmission while performing switching between the HS mode and the LP mode. This consequently makes it possible to achieve multipoint bus transmission suitable for high-speed transmission.

In addition, in the present embodiment, in the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>), the terminator resistor RT is turned from off to on in a case where desired successive transitions to LP-<NUM>, LP-<NUM>, and LP-<NUM> are detected in the transmission mode of the other transmission device (the transmission device <NUM>). Accordingly, total reflection in the second transmission device (the transmission device <NUM>) is suppressed by the terminator resistor RT in a case where the transmission mode of the first transmission device (the transmission device <NUM>) is the HS mode. This consequently makes it possible to achieve multipoint bus transmission suitable for high-speed transmission.

In addition, in the present embodiment, in the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>), the terminator resistor RT is turned from off to on in a case where the pair of output terminals 40A and 40B is determined by the predetermined threshold value to detect a desired transition. This makes it possible to suppress total reflection in the second transmission device (the transmission device <NUM>) by the terminator resistor RT in a case where the transmission mode of the first transmission device (the transmission device <NUM>) is the HS mode. This consequently makes it possible to achieve multipoint bus transmission suitable for high-speed transmission.

In addition, in the present embodiment, in the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>), the terminator resistor RT is turned from on to off in a case where the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>) detects that the transmission mode of the other transmission device (the transmission device <NUM>) is LP-<NUM> of the LP mode. This makes it possible to perform transmission while performing switching between the HS mode and the LP mode. This consequently makes it possible to achieve multipoint bus transmission suitable for high-speed transmission.

In addition, in the present embodiment, in the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>), the terminator resistor RT is turned from on to off in a case where the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>) detects that the voltage of the pair of output terminals 40A and 40B exceeds the predetermined threshold value. This makes it possible to perform transmission while performing switching between the HS mode and the LP mode. A This consequently makes it possible to achieve multipoint bus transmission suitable for high-speed transmission.

In addition, in the present embodiment, in the first transmission device (the transmission device <NUM>), in a case where the transmission mode is displaced from the HS mode to the LP mode, the transmission mode controller <NUM> inserts the PullUp mode in which the voltage of the pair of output terminals 40A and 40B is pulled up. This makes it possible to reduce the possibility that an unintended unnecessary current flows by superimposing LP-<NUM> sections of the LP mode on each other in a case where transmission is performed while performing switching between the transmission device <NUM> and the transmission device <NUM>. This consequently makes it possible to perform transmission while performing switching between the HS mode and the LP mode. Accordingly, it is possible to achieve multipoint bus transmission suitable for high-speed transmission.

In addition, in the present embodiment, in the first transmission device (the transmission device <NUM>), the mode controller <NUM> inserts, before and after the termination mode, the HiZ mode in which the voltage of the pair of output terminals 40A and 40B is set to high impedance. The first transmission device is turned to the HiZ mode in a case where the second transmission device performs HS mode transmission and LP mode transmission. In addition, the second transmission device is turned to the HiZ mode in a case where the first transmission device performs HS mode transmission and LP mode transmission. The first transmission device and the second transmission device exclusively use the HS mode · LP mode and the HiZ mode in such a manner, which makes it possible to achieve time-divisional use of a multipoint bus transmission path by the first transmission device and the second transmission device. Accordingly, it is possible to achieve multipoint bus transmission suitable for high-speed transmission.

In addition, in the present embodiment, the transmission mode (the HS mode, the LP mode, the pullup mode, or a high impedance mode) is decided on the basis of a combination of the three control signals HSEN, DRVEN, and PU_EN. This makes it possible to achieve multipoint bus transmission suitable for high-speed transmission by a simple control method.

<FIG> illustrates a modification example of the configuration of the communication system <NUM> according to the embodiment described above. The communication system <NUM> according to the embodiment described above may include three or more transmission devices. The communication system <NUM> according to the present modification example includes, for example, transmission devices <NUM>, <NUM>, and <NUM> and the reception device <NUM>. The communication system <NUM> includes the clock lane CL the data lane DL over the transmission devices <NUM>, <NUM>, and <NUM> and the reception device <NUM>. The clock lane CL transmits the clock signal, and the data lane DL transmits the data signal such as image data, for example. That is, the communication system <NUM> is configured to perform multipoint bus transmission.

The transmission device <NUM> includes a digital transmitter circuit and an analog transmitter circuit, as with the transmission devices <NUM> and <NUM>. For example, a <NUM>-bit or <NUM>-bit parallel signal is transmitted between the digital transmitter circuit and the analog transmitter circuit. In addition, a <NUM>-bit or <NUM>-bit parallel signal is transmitted between the digital receiver circuit and the analog receiver circuit. In the clock lane CL, the analog transmitter circuit and the analog receiver circuit are coupled to each other by the clock signal line <NUM> that transmits a differential clock signal. In the data lane DL, the analog transmitter circuit and the analog receiver circuit are coupled to each other by the data signal line <NUM> that transmits a differential data signal. The clock signal line <NUM> includes a pair of the positive signal line Cp and the negative signal line Cn that transmit a differential signal. The data signal line <NUM> includes a pair of the positive signal line Dp and the negative signal line Dn that transmit a differential signal. For example, a <NUM>-bit serial signal is transmitted to each of the clock signal line <NUM> and the data signal line <NUM>.

The transmission device <NUM> includes the clock transmitter circuit <NUM> and the data transmitter circuit <NUM>, for example, as with the transmission device <NUM>. In the clock lane CL, the clock transmitter circuits <NUM> and <NUM> and the clock receiver circuit <NUM> are coupled to each other by the clock signal line <NUM> described above. In the data lane DL, the data transmitter circuits <NUM> and <NUM> and the data receiver circuit <NUM> are coupled to each other by the data signal line <NUM> described above. Each of the clock transmitter circuits <NUM> and <NUM> is a differential signal transmitter circuit that generates a differential clock signal as the clock signal and outputs the thus-generated differential clock signal to the clock signal line <NUM>. Each of the data transmitter circuits <NUM> and <NUM> is a differential signal transmitter circuit that generates a differential data signal as the data signal and outputs the thus-generated differential data signal to the data signal line <NUM>. The clock receiver circuit <NUM> is a differential signal receiver circuit that receives the differential clock signal as the clock signal via the clock signal line <NUM> and performs predetermined processing on the received differential clock signal. The data receiver circuit <NUM> is a differential signal receiver circuit that receives the differential data signal as the data signal via the data signal line <NUM> and performs predetermined processing on the received differential data signal. It should be noted that each of the clock transmission devices <NUM> and <NUM> and the data transmission devices <NUM> and <NUM> may be a ternary signal transmitter circuit that outputs a ternary level signal. In addition, each of the clock receiver circuit <NUM> and the data receiver circuit <NUM> may be a ternary signal receiver circuit.

The transmission device <NUM> includes, in the clock lane CL, a transmission mode controller <NUM>, a clock generator <NUM>, and a clock transmitter <NUM>, for example, as illustrated in <FIG>. The transmission device <NUM> includes, in the data lane DL, a transmission data generator <NUM> and a data transmitter <NUM>, for example, as illustrated in <FIG>. The transmission mode controller <NUM> decides a transmission mode in accordance with an instruction from an upper layer (e.g., three control signals HSEN, DRVEN, and PU_EN). The transmission mode controller <NUM> further performs control corresponding to a decided transmission mode, on the clock generator <NUM> and the transmission data generator <NUM>. The clock generator <NUM> generates a clock signal with a clock frequency corresponding to a transmission mode in accordance with an instruction of the transmission mode controller <NUM>. The clock generator <NUM> outputs the generated clock signal to the clock transmitter <NUM> and the transmission data generator <NUM>. The clock transmitter <NUM> outputs the clock signal generated by the clock generator <NUM> to the clock signal line <NUM>. That is, the clock transmitter <NUM> outputs the clock signal generated by the clock generator <NUM> to the clock receiver <NUM> via the clock signal line <NUM>.

The transmission data generator <NUM> performs, in accordance with an instruction of the transmission mode controller <NUM>, various kinds of processing such as communication protocol control, decoding of data inputted from an upper layer, insertion of a control command, and parallel-serial conversion, on an inputted data signal (e.g., high-speed transmission data HS-TxData or low-speed transmission data LP-TxData), thereby generating a data signal. The transmission data generator <NUM> outputs the generated data signal to the data transmitter <NUM>. The transmission data generator <NUM> switches various kinds of processing described above in accordance with an instruction of the transmission mode controller <NUM>. The data transmitter <NUM> outputs the data signal generated by the transmission data generator <NUM> to a data signal line. That is, the data transmitter <NUM> outputs the data signal generated by the transmission data generator <NUM> to the data receiver <NUM> via the data signal line. The data transmitter <NUM> has, for example, a configuration similar to that of the data transmitters <NUM> and <NUM>, as illustrated in <FIG>.

<FIG> illustrates an example of waveforms of the communication system <NUM> according to the present modification example. As illustrated in <FIG>, the transmission devices <NUM>, <NUM>, and <NUM> sequentially output the high-speed transmission data HS-TxData and the low-speed transmission data LP-TxData to a data signal line <NUM> (the pair of the positive signal line Dp and the negative signal line Dn). It should be noted that in <FIG>, a transmission device that outputs HS-TxData, LP-TxData, and PullUp is indicated by "FRONT", and a transmission device in the Hi-Z mode is indicated by "REAR". The reception device <NUM> receives the high-speed transmission data HS-TxData and the low-speed transition data LP-TxData alternately outputted from the transmission devices <NUM>, <NUM>, and <NUM> via the data signal line <NUM> (the pair of the positive signal line Dp and the negative signal line Dn). Accordingly, as illustrated in (C) of <FIG>, it looks as if the reception device <NUM> receives HS-TxData and LP-TxData from a single transmission device.

Here, in a case where the transmission mode of a first transmission device (the transmission device <NUM>) of the transmission devices <NUM>, <NUM>, and <NUM> is the HS mode, mode controllers (the transmission mode controllers <NUM> and <NUM>) of a second transmission device (the transmission device <NUM>) and a third transmission device (the transmission device <NUM>) of the transmission devices <NUM>, <NUM>, and <NUM> turn the transmission modes of the second transmission device (the transmission device <NUM>) and the third transmission device (the transmission device <NUM>) to a termination mode in which the output terminals 40A and 40B of the second transmission device (the transmission device <NUM>) and the third transmission device (the transmission device <NUM>) are terminated. In addition, in a case where the transmission mode of the second transmission device (the transmission device <NUM>) of the transmission devices <NUM>, <NUM>, and <NUM> is the HS mode, mode controllers (the transmission mode controllers <NUM>) of the first transmission device (the transmission device <NUM>) and the third transmission device (the transmission device <NUM>) of the transmission devices <NUM>, <NUM>, and <NUM> turn the transmission modes of the first transmission device (the transmission device <NUM>) and the third transmission device (the transmission device <NUM>) to a termination mode in which the output terminals 40A and 40B of the first transmission device (the transmission device <NUM>) and the third transmission device (the transmission device <NUM>) are terminated. In addition, in a case where the transmission mode of the third transmission device (the transmission device <NUM>) of the transmission devices <NUM>, <NUM>, and <NUM> is the HS mode, mode controllers (the transmission mode controllers <NUM>) of the first transmission device (the transmission device <NUM>) and the second transmission device <NUM> of the transmission devices <NUM>, <NUM>, and <NUM> turn the transmission modes of the first transmission device (the transmission device <NUM>) and the second transmission device (the transmission device <NUM>) to a termination mode in which the output terminals 40A and 40B of the first transmission device (the transmission device <NUM>) and the second transmission device (the transmission device <NUM>) are terminated.

In addition, the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>) turns the terminator resistor RT from off to on in a case where desired successive transitions to LP-<NUM>, LP-<NUM>, and LP-<NUM> are detected in the transmission modes of the other transmission devices (the transmission devices <NUM> and <NUM>). In addition, the termination controller PHY-FSM of the second transmission device (the transmission device <NUM>) turns the terminator resistor RT from off to on in a case where desired successive transitions to LP-<NUM>, LP-<NUM>, and LP-<NUM> are detected in the transmission modes of the other transmission devices (the transmission devices <NUM> and <NUM>). In addition, the termination controller PHY-FSM of the third transmission device (the transmission device <NUM>) turns the terminator resistor RT from off to on in a case where desired successive transitions to LP-<NUM>, LP-<NUM>, and LP-<NUM> are detected in the transmission modes of the other transmission devices (the transmission devices <NUM> and <NUM>).

In addition, the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>) turns the terminator resistor RT from off to on in a case where the voltage of the pair of output terminals 40A and 40B is determined by a predetermined threshold value to detect a desired transition. In addition, the termination controller PHY-FSM of the second transmission device (the transmission device <NUM>) turns the terminator resistor RT from off to on in a case where the voltage of the pair of output terminals 40A and 40B is determined by the predetermined threshold value to detect a desired transition. In addition, the termination controller PHY-FSM of the third transmission device (the transmission device <NUM>) turns the terminator resistor RT from off to on in a case where the voltage of the pair of output terminals 40A and 40B is determined by the predetermined threshold value to detect a desired transition.

In addition, the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>) turns the terminator resistor RT from on to off in a case where desired successive transitions to LP-<NUM>, LP-<NUM>, and LP-<NUM> are detected in the transmission modes of the other transmission devices (the transmission devices <NUM> and <NUM>). In addition, the termination controller PHY-FSM of the second transmission device (the transmission device <NUM>) turns the terminator resistor RT from on to off in a case where desired successive transitions to LP-<NUM>, LP-<NUM>, and LP-<NUM> are detected in the transmission modes of the other transmission devices (the transmission devices <NUM> and <NUM>). In addition, the termination controller PHY-FSM of the third transmission device (the transmission device <NUM>) turns the terminator resistor RT from on to off in a case where desired successive transitions to LP-<NUM>, LP-<NUM>, and LP-<NUM> are detected in the transmission modes of the other transmission devices (the transmission devices <NUM> and <NUM>).

In addition, the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>) turns the terminator resistor RT from on to off in a case where the voltage of the pair of output terminals 40A and 40B is determined by a predetermined threshold value to detect a desired transition. In addition, the termination controller PHY-FSM of the second transmission device (the transmission device <NUM>) turns the terminator resistor RT from on to off in a case where the voltage of the pair of output terminals 40A and 40B is determined by the predetermined threshold value to detect a desired transition. In addition, the termination controller PHY-FSM of the third transmission device (the transmission device <NUM>) turns the terminator resistor RT from on to off in a case where the voltage of the pair of output terminals 40A and 40B is determined by the predetermined threshold value to detect a desired transition.

In addition, in the first transmission device (the transmission device <NUM>), in a case where the transmission mode is displaced from the HS mode to the LP mode, the transmission mode controller <NUM> inserts the PullUp mode in which the voltage of the pair of output terminals 40A and 40B is pulled up. In addition, in the second transmission device (the transmission device <NUM>), in a case where the transmission mode is displaced from the HS mode to the LP mode, the transmission mode controller <NUM> inserts the PullUp mode in which the voltage of the pair of output terminals 40A and 40B is pulled up. In addition, in the third transmission device (the transmission device <NUM>), in a case where the transmission mode is displaced from the HS mode to the LP mode, the transmission mode controller <NUM> inserts the PullUp mode in which the voltage of the pair of output terminals 40A and 40B is pulled up.

In addition, in the first transmission device (the transmission device <NUM>), the mode controller <NUM> inserts, before and after the termination mode, the HiZ mode in which the voltage of the pair of output terminals 40A and 40B is set to high impedance. In addition, in the second transmission device (the transmission device <NUM>), the mode controller <NUM> inserts, before and after the termination mode, the HiZ mode in which the voltage of the pair of output terminals 40A and 40B is set to high impedance. In addition, in the third transmission device (the transmission device <NUM>), the mode controller <NUM> inserts, before and after the termination mode, the HiZ mode in which the voltage of the pair of output terminals 40A and 40B is set to high impedance.

Next, description is given of effects of the communication system <NUM> according to the present modification example.

In the present modification example, in a case where the transmission mode of the first transmission device (the transmission device <NUM>) of the transmission devices <NUM>, <NUM>, and <NUM> is the HS mode, the transmission modes of the second transmission device (the transmission device <NUM>) and the third transmission device (the transmission device <NUM>) of the transmission devices <NUM>, <NUM>, and <NUM> are the termination mode in which the output terminals 40A and 40B of the second transmission device (the transmission device <NUM>) and the third transmission device (the transmission device <NUM>) are terminated. This makes it possible to suppress total reflection in the second transmission device (the transmission device <NUM>) and the third transmission device (the transmission device <NUM>) in a case where the transmission mode of the first transmission device (the transmission device <NUM>) is the HS mode. In addition, it is possible to perform transmission while performing switching between the HS mode and the LP mode. This consequently makes it possible to achieve multipoint bus transmission suitable for high-speed transmission.

In addition, in the present modification example, each of the data transmitters <NUM>, <NUM>, and <NUM> includes the terminator resistor RT that is configured to turn on and off termination of the pair of output terminals 40A and 40B coupled to the data signal line <NUM>. Further, the transmission modes of the other transmission devices are detected on the basis of the voltage of the pair of output terminals 40A and 40B, and on and off of the terminator resistor RT is controlled on the basis of a result of such detection. This makes it possible to suppress total reflection in the second transmission device (the transmission device <NUM>) and the third transmission device (the transmission device <NUM>) in a case where the transmission mode of the first transmission device (the transmission device <NUM>) is the HS mode. In addition, it is possible to perform transmission while performing switching between the HS mode and the LP mode. This consequently makes it possible to achieve multipoint bus transmission suitable for high-speed transmission.

In addition, in the present modification example, in the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>), the terminator resistor RT is turned from off to on in a case where desired successive transitions to LP-<NUM>, LP-<NUM>, and LP-<NUM> are detected in the transmission modes of the other transmission devices (the transmission devices <NUM> and <NUM>). Accordingly, total reflection in the second transmission device (the transmission device <NUM>) and the third transmission device (the transmission device <NUM>) is suppressed by the terminator resistor RT in a case where the transmission mode of the first transmission device (the transmission device <NUM>) is the HS mode. This consequently makes it possible to achieve multipoint bus transmission suitable for high-speed transmission.

In addition, in the present modification example, in the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>), the terminator resistor RT is turned from off to on in a case where the pair of output terminals 40A and 40B is determined by the predetermined threshold value to detect a desired transition. This makes it possible to suppress total reflection in the second transmission device (the transmission device <NUM>) and the third transmission device (the transmission device <NUM>) by the terminator resistor RT in a case where the transmission mode of the first transmission device (the transmission device <NUM>) is the HS mode. This consequently makes it possible to achieve multipoint bus transmission suitable for high-speed transmission.

In addition, in the present modification example, in the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>), the terminator resistor RT is turned from on to off in a case where the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>) detects that the transmission modes of the other transmission devices (the transmission devices <NUM> and <NUM>) are LP-<NUM> of the LP mode. This makes it possible to perform transmission while performing switching between the HS mode and the LP mode. This consequently makes it possible to achieve multipoint bus transmission suitable for high-speed transmission.

In addition, in the present modification example, in the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>), the terminator resistor RT is turned from on to off in a case where the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>) detects that the voltage of the pair of output terminals 40A and 40B exceeds the predetermined threshold value. This makes it possible to perform transmission while performing switching between the HS mode and the LP mode. This consequently makes it possible to achieve multipoint bus transmission suitable for high-speed transmission.

In addition, in the present modification example, in the first transmission device (the transmission device <NUM>), in a case where the transmission mode is displaced from the HS mode to the LP mode, the transmission mode controller <NUM> inserts the PullUp mode in which the voltage of the pair of output terminals 40A and 40B is pulled up. This makes it possible to reduce the possibility that an unintended unnecessary current flows by superimposing LP-<NUM> sections of the LP mode on each other in a case where transmission is performed while sequentially performing switching among the transmission device <NUM>, the transmission device <NUM>, and the transmission device <NUM>. This consequently makes it possible to perform transmission while performing switching between the HS mode and the LP mode. Accordingly, it is possible to achieve multipoint bus transmission suitable for high-speed transmission.

In addition, in the present modification example, in the first transmission device (the transmission device <NUM>), the mode controller <NUM> inserts, before and after the termination mode, the HiZ mode in which the voltage of the pair of output terminals 40A and 40B is set to high impedance. The first transmission device is turned to the HiZ mode in a case where the second transmission device or the third transmission device performs HS mode transmission and LP mode transmission. In addition, the second transmission device is turned to the HiZ mode in a case where the first transmission device or the third transmission device performs HS mode transmission and LP mode transmission. The third transmission device is turned to the HiZ mode in a case where the first transmission device or the second transmission device performs HS mode transmission and LP mode transmission. The first transmission device, the second transmission device, and the third transmission device exclusively use the HS mode · LP mode and the HiZ mode in such a manner, which makes it possible to achieve time-divisional use of a multipoint bus transmission path by the first transmission device, the second transmission device, and the third transmission device. Accordingly, it is possible to achieve multipoint bus transmission suitable for high-speed transmission.

In addition, in the present modification example, the transmission mode (the HS mode, the LP mode, the pullup mode, or the high impedance mode) is decided on the basis of a combination of the three control signals HSEN, DRVEN, and PU_EN. This makes it possible to achieve multipoint bus transmission suitable for high-speed transmission by a simple control method.

<FIG> illustrates a modification example of waveforms of the communication system <NUM> according to the modification example A described above. In the present modification example, the transmission device <NUM> does not output the high-speed transmission data HS-TxData and the low-speed transmission data LP-TxData, and the transmission device <NUM> is in a mode (specifically the high impedance mode) other than the HS mode and the LP mode, for example, as illustrated in (C) of <FIG>. Accordingly, in the present modification example, the reception device <NUM> receives the high-speed transmission data HS-TxData and the low-speed transmission data LP-TxData alternately outputted from the transmission devices <NUM> and <NUM> via the data signal line <NUM> (the pair of the positive signal line Dp and the negative signal line Dn), for example, as illustrated in (D) of <FIG>. Even in a case where some transmission devices of a plurality of transmission devices are in a mode (specifically, the high impedance mode) other than the HS mode and the LP mode in such a manner, effects similar to those in the embodiment descried above are achieved.

<FIG> illustrates an example of a circuit configuration of the communication system <NUM> according to the embodiment described above. The communication system <NUM> according to the embodiment described above may include, for example, a transmission device TX1 serving as the transmission device <NUM>, a transmission device TX2 serving as the transmission device <NUM>, and a reception device RX serving as the reception device <NUM>, as illustrated in <FIG>. The communication system <NUM> according to the embodiment described above may further include a transmission path P that couples the respective transmission devices TX1 and TX2 and the reception device RX to each other, for example, as illustrated in <FIG>.

The transmission path P is branched at a midpoint into three, and has branch points Hp and Hn. A transmission path P<NUM> that is one of branches couples the transmission device TX1 and the branch points Hp and Hn to each other. The transmission path P<NUM> includes a pair of signal lines P1p and P1n that transmit a differential signal. The signal line P1p is coupled to the branch point Hp, and the signal line P1n is coupled to the branch point Hn. A terminator resistor RT/<NUM> of the transmission device TX1 is provided for each of the signal lines P1p and P1n.

A transmission path P<NUM> that is one of the branches couples the transmission device TX2 and the branch points Hp and Hn to each other. The transmission path P<NUM> includes a pair of signal lines P2p and P2n that transmit a differential signal. The signal line P2p is coupled to the branch point Hp, and the signal line P2n is coupled to the branch point Hn. The terminator resistor RT/<NUM> of the transmission device TX2 is provided for each of the signal lines P2p and P2n.

A transmission path P<NUM> that is one of the branches couples the reception device RX and the branch points Hp and Hn to each other. The transmission path P<NUM> includes a pair of signal lines P3p and P3n that transmit a differential signal. The signal line P3p is coupled to the branch point Hp, and the signal line P3n is coupled to the branch point Hn. The terminator resistor RT/<NUM> of the reception device RX is provided for each of the signal lines P3p and P3n.

Each of the signal lines P1p, P2p, and P3p includes a resistor element R in proximity to the branch point Hp. Further, each of the signal lines P1n, P2n, and P3n also includes the resistor element R in proximity to the branch point Hn. Here, the resistor element R has a resistance value represented by the following expression (<NUM>), where a characteristic impedance of each of the signal lines P1p, P1n, P2p, P2n, P3p, and P3n is Z<NUM>, each of the terminator resistors for the respective signal lines P1p, P1n, P2p, and P2n of the respective transmission devices TX1 and TX2 is RT/<NUM>, and each of the terminator resistors for the respective signal lines P3p and P3n of the reception device RX is RT/<NUM>.

In a case where the characteristic impedance Z<NUM> is <NUM> ohms and the terminator resistor RT/<NUM> has <NUM> / <NUM> = <NUM> ohms, the resistor element R has <NUM> ohms. At this time, each of the signal lines P1p, P1n, P2p, P2n, P3p, and P3n has <NUM> ohms (Rs) as viewed from any port of the transmission devices TX1 and TX2 and the reception device RX, and is a transmission path achieving impedance matching.

To suppress deterioration in transmission characteristics by reflection, the respective resistor elements R are disposed as close to the branch points Hp and Hn as possible. In addition, to suppress deterioration in skew characteristics in a lane of the transmission path P, the signal lines P1p and P1n are disposed to lay wiring patterns of the signal line P1p and the signal line P1n in as approximate a layout as possible. Similarly, the signal lines P2p and P2n are disposed to lay wiring patterns of the signal line P2p and the signal line P2n in as approximate a layout as possible. Similarly, the signal lines P3p and P3n are disposed to lay wiring patterns of the signal line P3p and the signal line P3n in as approximate a layout as possible. In addition, to suppress deterioration in skew characteristic between lanes of the transmission path P, the respective signal lines P1p, P1n, P2p, P2n, P3p, and P3n are disposed to lay wiring patterns of different lanes in as approximate a layout as possible.

In the communication system <NUM>, in a case where the transmission device TX1 outputs a signal, for example, as illustrated in <FIG>, output of the transmission device TX2 is stopped, and further, the transmission device TX2 is differentially terminated. Similarly, in the communication system <NUM>, in a case where the transmission device TX2 outputs a signal, output of the transmission device TX1 is stopped, and further, the transmission device TX1 is differentially terminated.

<FIG> illustrates an example of pass characteristics in the communication system <NUM>. <FIG> illustrates an example of reflection characteristics in the communication system <NUM>. <FIG> illustrates an example of an eye diagram in the communication system <NUM>. In <FIG>, a lower waveform of two waveforms is a result of pass characteristics as viewed from the transmission devices TX1 and TX2, and an upper waveform of the two waveforms is a result of pass characteristics as viewed from the reception device RX. In <FIG>, a result of reflection characteristics as viewed from the transmission devices TX1 and TX2 and a result of reflection characteristics as viewed from the reception device RX are superimposed on each other.

In <FIG>, a signal level around <NUM> is -<NUM> dB. This means that the signal level is decreased to about a half by insertion of the resistor element R. In addition, in <FIG>, a signal level around <NUM> is -<NUM> dB. In <FIG>, an eye of the eye diagram is clearly open.

In the present modification example, the three-branched branch points Hp and Hn are provided in the transmission path P, and the resistor element R is provided for each of signal lines at the three-branched branch points Hp and Hn. Thus, in the present modification example, only providing branches to the transmission path P by an extremely simple configuration makes it possible to achieve multipoint bus transmission suitable for high-speed transmission.

In addition, in the present modification example, each of the resistor elements R provided in the transmission path P has a resistance value represented by the expression (<NUM>) described above. Accordingly, each of the signal lines P1p, P1n, P2p, P2n, P3p, and P3n has <NUM> ohms (Rs) as viewed from any port of the transmission devices TX1 and TX2 and the reception device RX, and is a transmission path achieving impedance matching. This makes it possible to achieve multipoint bus transmission suitable for high-speed transmission.

In addition, in the present modification example, a transmission device (e.g., the transmission device TX2) that does not output a signal is differentially terminated. This makes it possible to reduce noise in the transmission path P, as compared with a case where the transmission device that does not output a signal becomes a released end. This makes it possible to achieve multipoint bus transmission suitable for high-speed transmission.

<FIG> illustrates a modification example of a circuit of each of the transmission data generators <NUM>, <NUM>, and <NUM> according to the embodiment and the modification examples A, B, and C described above. In the present modification example, the driver LP-TX, the driver LP-RX, and the pull-up resistor PU are not included in each of the transmission data generators <NUM>, <NUM>, and <NUM>. In the present modification example, each of the transmission data generators <NUM>, <NUM>, and <NUM> includes a driver HS-TX, the terminator resistor RT, a pull-up/pull-down resistor PU/PD, and comparators CMP1 and CMP2.

The pull-up/pull-down resistor PU/PD includes a pull-down resistor and a pull-up resistor. The pull-down resistor is coupled to the positive signal line Dp and allows for pulling down, and the pull-up resistor is coupled to the negative signal line Dn and allows for pulling up. The pull-up/pull-down resistor PU/PD controls on and off of the pull-down resistor and the pull-up resistor on the basis of a control signal PUPDON for controlling pulling up and pulling down. The comparator CMP1 outputs a result of comparison between a voltage of the positive signal line Dp and a threshold value Vth to the termination controller PHY-FSM. The comparator CMP2 outputs a result of comparison between a voltage of the negative signal line Dn and the threshold value Vth to the termination controller PHY-FSM. The comparators CMP1 and CMP2 input, as <NUM>-bit signals, two outputs of the LP-RX determined by the single threshold value Vth to the PHY-FSM of a subsequent stage.

<FIG> illustrates an example of waveforms of the communication system <NUM> including the transmission data generators <NUM> and <NUM> in <FIG>. In the present modification example, the transmission devices <NUM> and <NUM> alternately output the high-speed transmission data HS-TxData to the data signal line <NUM> (the pair of the positive signal line Dp and the negative signal line Dn), as illustrated in <FIG>. It should be noted that <FIG> illustrates, as an example, a case where the transmission data generators <NUM> and <NUM> output DIF-P and DIF-N before and after outputting the high-speed transmission data HS-TxData.

Here, in a case where the transmission mode of the first transmission device (the transmission device <NUM>) of the transmission devices <NUM> and <NUM> is the HS mode, the mode controller (the transmission mode controller <NUM>) of the second transmission device (the transmission device <NUM>) of the transmission devices <NUM> and <NUM> turns the transmission mode of the second transmission device (the transmission device <NUM>) to the termination mode in which the output terminals 40A and 40B of the second transmission device (the transmission device <NUM>) are terminated. In contrast, in a case where the transmission mode of the second transmission device (the transmission device <NUM>) of the transmission devices <NUM> and <NUM> is the HS mode, the mode controller (the transmission mode controller <NUM>) of the first transmission device (the transmission device <NUM>) of the transmission devices <NUM> and <NUM> turns the transmission mode of the first transmission device (the transmission device <NUM>) to the termination mode in which the output terminals 40A and 40B of the first transmission device (the transmission device <NUM>) are terminated.

In addition, the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>) turns the terminator resistor RT from off to on in a case where the transmission mode of the other transmission device (the transmission device <NUM>) is transitioned from a DIF-N mode to a DIF-P mode. In contrast, the termination controller PHY-FSM of the second transmission device (the transmission device <NUM>) turns the terminator resistor RT from off to on in a case where the transmission mode of the other transmission device (the transmission device <NUM>) is transitioned from the DIF-N mode to the DIF-P mode.

In addition, the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>) turns the terminator resistor RT from on to off in a case where the termination controller PHY-FSM of the first transmission device (the transmission device <NUM>) detects that the transmission mode of the other transmission device (the transmission device <NUM>) is transitioned to the DIF-N mode and an amplitude in DIF-N is equal to or smaller than a predetermined threshold value. In contrast, the termination controller PHY-FSM of the second transmission device (the transmission device <NUM>) turns the terminator resistor RT from on to off in a case where the termination controller PHY-FSM of the second transmission device (the transmission device <NUM>) detects that the transmission mode of the other transmission device (the transmission device <NUM>) is transitioned to the DIF-N mode and an amplitude in DIF-N is equal to or smaller than the predetermined threshold value.

In addition, in the first transmission device (the transmission device <NUM>), in a case where the transmission mode is displaced from the DIF-N mode to the HiZ mode, to maintain a voltage level in the DIF-N mode, the transmission mode controller <NUM> inserts the PullUp mode in which the voltage of the pair of output terminals 40A and 40B is pulled up. In contrast, in the second transmission device (the transmission device <NUM>), in a case where the transmission mode is displaced from the DIF-N mode to the HiZ mode, to maintain a voltage level in the DIF-N mode, the transmission mode controller <NUM> inserts the PullUp mode in which the voltage of the pair of output terminals 40A and 40B is pulled up.

In the present modification example, in a case where the transmission mode of the first transmission device (the transmission device <NUM>) of the transmission devices <NUM> and <NUM> is the HS mode, the transmission mode of the second transmission device (the transmission device <NUM>) of the transmission devices <NUM> and <NUM> is the termination mode in which the output terminals 40A and 40B of the second transmission device (the transmission device <NUM>) are terminated. Accordingly, total reflection in the second transmission device (the transmission device <NUM>) is suppressed in a case where the transmission mode of the first transmission device (the transmission device <NUM>) is the HS mode. In addition, it is possible to perform transmission while performing switching between the HS mode and the DIF-N mode. This consequently makes it possible to achieve multipoint bus transmission suitable for high-speed transmission.

In the following, description is given of application examples of the communication system <NUM> according to any of the embodiment and the modification examples A to D thereof described above.

<FIG> illustrates an appearance of a smartphone <NUM> (a multifunctional mobile phone) to which the communication system <NUM> according to any of the embodiment and the modification examples A to D thereof described above is applied. Various devices are mounted in the smartphone <NUM>. The communication system according to any of the respective embodiments described above is applied to a communication system in which data are exchanged among these devices.

<FIG> illustrates a configuration example of an application processor <NUM> to be used in the smartphone <NUM>. The application processor <NUM> includes a CPU (Central Processing Unit) <NUM>, a memory controller <NUM>, a power source controller <NUM>, an external interface <NUM>, a GPU (Gaphics Processing Unit) <NUM>, a media processor <NUM>, a display controller <NUM>, and an MIPI interface <NUM>. In this example, the CPU <NUM>, the memory controller <NUM>, the power source controller <NUM>, the external interface <NUM>, the GPU <NUM>, the media processor <NUM>, and the display controller <NUM> are each coupled to a system bus <NUM> to allow for data exchange with one another via the system bus <NUM>.

The CPU <NUM> processes various pieces of information handled in the smartphone <NUM> in accordance with a program. The memory controller <NUM> controls a memory <NUM> to be used in a case where the CPU <NUM> performs information processing. The power source controller <NUM> controls a power source of the smartphone <NUM>.

The external interface <NUM> is an interface for communication with external devices. In this example, the external interface <NUM> is coupled to a wireless communication section <NUM> and to an image sensor <NUM>. The wireless communication section <NUM> performs wireless communication with mobile phone base stations. The wireless communication section <NUM> includes, for example, a baseband section, an RF (radio frequency) front end section, and the like. The image sensor <NUM> acquires an image, and includes, for example, a CMOS sensor. For example, the communication system according to any of the embodiment and the modification examples A to D described above is applied to a communication system between the external interface <NUM> and the image sensor <NUM>.

The GPU <NUM> performs image processing. The media processor <NUM> processes information such as voice, characters, and graphics. The display controller <NUM> controls a display <NUM> via the MIPI interface <NUM>.

The MIPI interface <NUM> transmits an image signal to the display <NUM>. As the image signal, for example, a signal such as a YUV-format signal and an RGB-format signal is usable. For example, the communication system according to the embodiment and the modification examples A to D described above is applied to a communication system between the MIPI interface <NUM> and the display <NUM>.

<FIG> illustrates a configuration example of the image sensor <NUM>. The image sensor <NUM> includes a sensor section <NUM>, an ISP (Image Signal Processor) <NUM>, a JPEG (Joint Photographic Experts Group) encoder <NUM>, a CPU <NUM>, a RAM (Random Access Memorr) <NUM>, a ROM (Read Only Memory) <NUM>, a power source controller <NUM>, an I<NUM>C (Inter-Integrated Circuit) interface <NUM>, and an MIPI interface <NUM>. In this example, these respective blocks are coupled to a system bus <NUM> to allow for data exchange with one another via the system bus <NUM>.

The sensor section <NUM> acquires an image, and includes, for example, a CMOS sensor. The ISP <NUM> performs predetermined processing on the image acquired by the sensor section <NUM>. The JPEG encoder <NUM> encodes the image processed by the ISP <NUM> to generate a JPEG-format image. The CPU <NUM> controls respective blocks of the image sensor <NUM> in accordance with a program. The RAM <NUM> is a memory to be used in a case where the CPU <NUM> performs information processing. The ROM <NUM> stores a program to be executed in the CPU <NUM>. The power source controller <NUM> controls a power source of the image sensor <NUM>. The I<NUM>C interface <NUM> receives a control signal from the application processor <NUM>. In addition, although not illustrated, the image sensor <NUM> also receives a clock signal from the application processor <NUM>, in addition to the control signal. Specifically, the image sensor <NUM> is configured to be operable on the basis of clock signals with various frequencies.

The MIPI interface <NUM> transmits an image signal to the application processor <NUM>. As the image signal, for example, a signal such as a YUV-format signal and an RGB-format signal is usable. For example, the communication system according to any of the respective embodiments described above is applied to a communication system between the MIPI interface <NUM> and the application processor <NUM>.

<FIG> and <FIG> each illustrate a configuration example of a vehicle-mounted camera as an application example to an imaging device. <FIG> illustrates an installation example of the vehicle-mounted camera, and <FIG> illustrates an internal configuration example of the vehicle-mounted camera.

For example, vehicle-mounted cameras <NUM>, <NUM>, <NUM>, and <NUM> are respectively mounted on the front (front), left, right, and rear (rear) of a vehicle <NUM>, as illustrated in <FIG>. The vehicle-mounted cameras <NUM> to <NUM> are each coupled to an ECU (Electrical Control Unit) <NUM> via an in-vehicle network.

An image capturing angle of the vehicle-mounted camera <NUM> mounted on the front of the vehicle <NUM> is within a range indicated by "a" in <FIG>, for example. An image capturing angle of the vehicle-mounted camera <NUM> is within a range indicated by "b" in <FIG>, for example. An image capturing angle of the vehicle-mounted camera <NUM> is within a range indicated by "c" in <FIG>, for example. An image capturing angle of the vehicle-mounted camera <NUM> is within a range indicated by "d" in <FIG>, for example. Each of the vehicle-mounted cameras <NUM> to <NUM> outputs a captured image to the ECU <NUM>. This consequently makes it possible to capture a <NUM>-degree (omnidirectional) image on the front, right, left, and rear of the vehicle <NUM> in the ECU <NUM>.

For example, each of the vehicle-mounted cameras <NUM> to <NUM> includes an image sensor <NUM>, a DSP (Digital Signal Processing) circuit <NUM>, a selector <NUM>, and a SerDes (SERializer/DESerializer) circuit <NUM>, as illustrated in <FIG>.

The DSP circuit <NUM> performs various kinds of image signal processing on an imaging signal outputted from the image sensor <NUM>. The SerDes circuit <NUM> performs serial-parallel conversion of a signal, and includes, for example, a vehicle-mounted interface chip such as FPD-Link III.

The selector <NUM> selects whether to output the imaging signal outputted from the image sensor <NUM> via the DSP circuit <NUM> or not via the DSP circuit <NUM>.

The communication system according to any of the respective embodiments described above is applicable to, for example, a coupling interface <NUM> between the image sensor <NUM> and the DSP circuit <NUM>. Moreover, the communication system according to any of the respective embodiments described above is applicable to, for example, a coupling interface <NUM> between the image sensor <NUM> and the selector <NUM>.

Although the present disclosure has been described above referring to a plurality of embodiments and the modification examples thereof, the present disclosure is not limited to the embodiments and the like described above, and may be modified in a variety of ways. It should be noted that effects described herein are merely illustrative. The effects of the present disclosure are not limited to those described in the specification. The present disclosure may have effects other than those described in the specification.

According to the communication system and the communication method according to the embodiments of the present disclosure, in a case where the transmission mode of the first transmission device of the plurality of transmission devices is the HS mode, the transmission mode of the second transmission device of the plurality of transmission devices is turned to the termination mode in which the output terminal of the second transmission device is terminated, which makes it possible to achieve multipoint bus transmission suitable for high-speed transmission. It should be noted that the effects of the present disclosure are not necessarily limited to the effects described here, and may be any of the effects described in the specification.

This application claims the benefit of Japanese Priority Patent Application <CIT>.

Claim 1:
A communication system (<NUM>) that is configured to transmit data from a plurality of transmission devices (<NUM>, <NUM>, <NUM>) to one reception device (<NUM>) via a pair of signal lines (<NUM>), each of the transmission devices (<NUM>, <NUM>, <NUM>) comprising:
a mode controller (<NUM>, <NUM>, <NUM>) that is configured to control a transmission mode;
a transmission data generator (<NUM>, <NUM>, <NUM>) that is configured to generate the data in accordance with the transmission mode controlled by the mode controller (<NUM>, <NUM>, <NUM>); and
a data transmitter (<NUM>, <NUM>, <NUM>) that is configured to transmit the data generated by the transmission data generator (<NUM>, <NUM>, <NUM>) to the reception device, in a case where the transmission mode of a first transmission device (<NUM>) of the plurality of the transmission devices (<NUM>, <NUM>, <NUM>) is an High Speed, HS, mode, the mode controller (<NUM>, <NUM>) of any second transmission device (<NUM>, <NUM>) of the plurality of the transmission devices (<NUM>, <NUM>, <NUM>) is configured to turn the transmission mode of the second transmission device (<NUM>, <NUM>) to a termination mode in which a pair of output terminals (40A, 40B) of the second transmission device (<NUM>, <NUM>) is terminated, wherein
each of the data transmitters (<NUM>, <NUM>) includes:
a terminator resistor (RT) that is configured to turn on and off termination of the pair of output terminals (40A, 40B) coupled to the pair of signal lines (<NUM>), and
a termination controller (PHY-FSM) that is configured to detect the transmission mode of other transmission devices (<NUM>, <NUM>, <NUM>) on a basis of a voltage of the pair of output terminals (40A, 40B) and to control on and off of the terminator resistor (RT) on a basis of a result of such detection.