Communication device and communication system

Abstract

[Problem] To provide a communication device and a communication system that perform serial communication at low power and at high speed. [Solution] The communication device comprises: a state-switching control unit for controlling switching between a first state that establishes synchronization for performing communication with a communication partner device, a second state that initiates communication after synchronization is established in the first state, a third state that causes communication to be intermittently stopped without losing the establishment of synchronization, and a fourth state that reestablishes synchronization with the communication partner device when communication is resumed after being stopped for a longer period than in the third state; a first communication control unit for repeating, on a first cycle, the operation of continuously transmitting a first signal within a first signal interval to the communication partner device when in the fourth state; a second communication control unit which, when a second signal outputted from the communication partner device in response to the first signal is received, transmits a third signal that is synchronized to the second signal to the communication partner device. The switching control unit causes transition from the fourth state to the first state when the second communication control unit transmits the third signal.

Description

[Technical Field]

[0001] The present disclosure relates to a communication device and a communication system. [Background technology]

[0002] A technology for performing high-speed serial communication between multiple devices has been proposed (Patent Document 1). This type of high-speed serial communication is used in a variety of fields, including communication between in-vehicle devices, for example. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-239011 Summary of the Invention [Problem to be solved by the invention]

[0004] Advances in autonomous driving and electronics technology are increasing the need for high-speed communication between in-vehicle devices. The Automotive SerDes Alliance (ASA) envisions time division duplexing (TDD) communication between root and leaf devices connected via a cable.

[0005] Since the root device and leaf devices do not always communicate with each other, if communication does not occur for a predetermined period of time, the states of the root device and leaf device are changed to reduce power consumption.

[0006] The ASA standard ver. 1.01 defines light sleep and deep sleep states. In light sleep, communication is temporarily suspended for a time interval equal to or greater than the TDD switching time but shorter than the time required to maintain synchronization between devices. Because synchronization between devices is maintained even during periods of suspension, communication can be resumed quickly. In contrast, in deep sleep, communication is suspended for an extended period of time, and synchronization must be reestablished between devices when communication resumes.

[0007] Root devices have an internal ECU, so they can transition from deep sleep to normal mode on their own. In contrast, leaf devices do not have an internal ECU, so they must have a mechanism for transitioning from deep sleep to normal mode. The ASA standard ver. 1.01 does not specify the processing procedure for leaf devices to transition from deep sleep to normal mode, which raises the risk that leaf devices may not be able to transition from deep sleep to normal mode quickly.

[0008] Therefore, the present disclosure provides a communication device and a communication system that are capable of performing serial communication at high speed with low power consumption. [Means for solving the problem]

[0009] In order to solve the above problem, according to the present disclosure, there is provided a state switching control unit that controls switching between a first state in which synchronization is established for communication with a communication partner device, a second state in which the communication is started after synchronization is established in the first state, a third state in which the communication is intermittently stopped without losing synchronization, and a fourth state in which the communication is stopped for a longer period than in the third state and synchronization is re-established with the communication partner device when the communication is resumed; a first communication control unit that repeats an operation of continuously transmitting a first signal to the communication partner device within a first signal section in a first cycle when in the fourth state; a second communication control unit that, upon receiving a second signal output from the communication partner device in response to the first signal, transmits a third signal synchronized with the second signal to the communication partner device; The communication device is configured such that, when the second communication control unit transmits the third signal, the state switching control unit transitions from the fourth state to the first state.

[0010] According to the present disclosure, a first state switching control unit controls switching between a first state in which synchronization is established for communication with a first communication partner device, a second state in which the communication is started after synchronization is established in the first state, a third state in which the communication is intermittently stopped without losing synchronization, and a fourth state in which the communication is stopped for a longer period than in the third state and synchronization is re-established with the first communication partner device when the communication is resumed; a second state switching control unit that controls switching between the first state, the second state, the third state, and the fourth state with a second communication partner device; a first communication control unit that, when the second communication partner device is in the fourth state, repeatedly receives a first signal in a first period, the first signal being continuously transmitted from the second communication partner device within a first signal section, and transmits the received first signal to the first communication partner device; a second communication control unit that, upon receiving a second signal in response to the first signal from the first communication partner device, transmits the second signal to the second communication partner device; The communication device is provided such that the first state switching control unit transitions from the fourth state to the first state when the first communication partner device transmits the second signal.

[0011] When the second state switching control unit receives the first signal from the second communication partner device while in the fourth state, it may transition to the first state if the first communication partner device is in the first state, the second state, or the third state.

[0012] The first communication control unit may repeat, in the first period, an operation of continuously transmitting the first signal generated using a pseudorandom number within the first signal section.

[0013] The first communication control unit is X 23 +X 5 The first signal may be generated based on a polynomial of +1.

[0014] According to the present disclosure, a state switching control unit controls switching between a first state in which synchronization is established for communication with a communication partner device, a second state in which the communication is performed after synchronization is established in the first state, a third state in which the communication is intermittently stopped without losing synchronization, and a fourth state in which the communication is stopped for a longer period than in the third state and synchronization is re-established with the communication partner device when the communication is resumed; a first communication control unit that, when the communication partner device is in the fourth state, repeatedly receives, in a first period, a first signal that is continuously transmitted from the communication partner device within a first signal section; A communication device is provided, comprising: a second communication control unit configured to transmit, to the communication partner device, a second signal synchronized with the first signal received by the first communication control unit.

[0015] The signal amplitude of the first signal may be equal to or less than the signal amplitude of the second signal.

[0016] The signal amplitude of the first signal may be 0.2 times or more and 0.8 times or less than the signal amplitude of the second signal.

[0017] The signal amplitude of the first signal may be 0.4 times or more and 0.6 times or less than the signal amplitude of the second signal.

[0018] The signal amplitude of the first signal may be 0.5 times the signal amplitude of the second signal.

[0019] The first signal section may be equal to or shorter than a second signal section in which the second signal is continuously output.

[0020] The first signal section may be 0.5 times the second signal section.

[0021] The first signal section may be 768 [nsec], and the first period may be 4816 [nsec].

[0022] The first signal section may be 1536 [nsec], and the first period may be 3280 [nsec].

[0023] The first signal and the second signal may have the same signal amplitude and the same period, and the length of the first signal section may be the same as the length of the second signal section in which the second signal is output continuously.

[0024] The first signal section and the second signal section may be 1536 [nsec], and the period of the first signal and the second signal may be 3280 [nsec].

[0025] Information may be transmitted and received alternately between the communication partner device and the communication partner device within an allocated period in a TDD (Time Division Duplex) communication system.

[0026] According to the present disclosure, a first communication device; a second communication device that alternately transmits and receives information to and from the first communication device within an allocated period in a TDD (Time Division Duplex) communication method; The second communication device a state switching control unit that controls switching between a first state in which synchronization is established for communication with the first communication device, a second state in which the communication is performed after synchronization is established in the first state, a third state in which the communication is intermittently stopped without losing synchronization, and a fourth state in which the communication is stopped for a longer period than in the third state and synchronization is re-established with the first communication device when the communication is resumed; a first communication control unit that repeats an operation of continuously transmitting a first signal within a first signal section to the first communication device in a first cycle when in the fourth state; A communication system is provided having a second communication control unit that, when receiving a second signal output from the first communication device in response to the first signal, transmits a third signal synchronized with the second signal and transitions from the fourth state to the first state.

[0027] a third communication device that alternately transmits and receives information to and from the first communication device within a period allocated by the TDD communication method, and that alternately transmits and receives information to and from the second communication device within a period allocated by the TDD communication method; the third communication device, a first communication control unit that, when the second communication device is in the fourth state, repeatedly receives a first signal, which is continuously transmitted within a first signal section from the second communication device, in a first period, and transmits the received first signal to the first communication device; a second communication unit that, upon receiving a second signal in response to the first signal from the first communication device, transmits the second signal to the second communication device; The communication control unit may also have a second communication control unit that, upon receiving a third signal synchronized with the second signal from the second communication device, transmits the third signal to the first communication device and transitions from the fourth state to the first state.

[0028] a plurality of the third communication devices are connected in a daisy chain between the first communication device and the second communication device; When the multiple third communication devices and the second communication device are in the fourth state, each of the multiple third communication devices may sequentially transmit the first signal of the first period that is transmitted continuously from the second communication device within the first signal section to the third communication device or the first communication device that is closer to the first communication device, and may sequentially receive a second signal synchronized with the first signal transmitted from the first communication device and transmit it to the third communication device or the second communication device that is closer to the second communication device, and may transition from the fourth state to the first state. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a block diagram showing a schematic configuration of a communication system according to the present disclosure. [Figure 2] A diagram explaining TDD communication that complies with the ASA standard. [Figure 3] State transition diagram of a communication system that complies with the ASA standard. [Figure 4] 1 is a flowchart showing the startup sequence steps performed when the root device and leaf device are in the startup state. [Figure 5] Timing diagram of the startup sequence. [Figure 6] 2 is a block diagram showing the internal configuration of the PHY unit in the root device and the PHY unit in the leaf device in FIG. 1. [Figure 7] 10 is a flowchart showing the processing steps of the wake-up sequence performed by a Leaf device. [Figure 8] A flowchart showing the wake-up sequence procedure performed by a rooted device. [Figure 9] Timing diagram for the wake-up sequence. [Figure 10] FIG. 10 is a timing diagram of a wake-up request signal. [Figure 11] FIG. 1 is a timing diagram showing the relationship between a wake-up request signal and a Phase 1G signal. [Figure 12] 1 is a block diagram showing a schematic configuration of a communication system 1a including a root device, a leaf device, and a branch device. [Figure 13] FIG. 2 is a block diagram showing the internal configuration of a plurality of PHY units. [Figure 14] 10 is a flowchart showing the processing procedure of the PHY unit that is the far-side PHY. [Figure 15] 10 is a flowchart showing the processing procedure of a PHY unit that is a Near-side PHY. [Figure 16] Block diagram of a communication system in which multiple Branch devices are daisy-chained. [Figure 17] FIG. 10 is a timing diagram of a wake-up of the communication system 1 according to the second embodiment. [Figure 18] FIG. 10 is a timing diagram of a wake-up request signal. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, an embodiment of a communication device and a communication system 1 will be described with reference to the drawings. The following description will focus on the main components of the communication device and the communication system 1, but the communication device and the communication system 1 may include components and functions that are not shown or described. The following description does not exclude components and functions that are not shown or described.

[0031] A communication system 1 according to the present disclosure performs time division multiplexing (TDD) communication between a plurality of communication devices. The following mainly describes the communication devices and communication system 1 that comply with the ASA standard.

[0032] FIG. 1 is a block diagram showing a schematic configuration of a communication system 1 according to the present disclosure. The communication system 1 in FIG. 1 includes a root device (10) and a leaf device (20) that comply with the ASA standard. The root device (10) and the leaf device (20) alternately perform TDD communication. In this specification, a path for transmitting information from the root device (10) to the leaf device (20) is called an uplink, and a path for transmitting information from the leaf device (20) to the root device (10) is called a downlink. The uplink and downlink are provided on the same cable (30).

[0033] The root device (10) has an ECU (10-1), an ASE / ASD unit (10-2), a DLL unit (10-3), and a PHY unit (10-4). The ECU (10-1) controls the entire system and also receives and processes application signals, such as video signals, transmitted from the leaf devices (20). The ECU (10-1) generates control signals for controlling each unit. The ASE / ASD unit (10-2) performs ASE processing to encapsulate control signals from the ECU (10-1) and ASD processing to decode the encapsulated application signals from the leaf devices (20) back into the original application signals. The DLL unit (10-3) generates uplink packets containing the application signals encapsulated by the ASE / ASD unit (10-2), extracts the application signals contained in downlink packets transmitted from the leaf devices (20), and sends them to the ASE / ASD unit (10-2). The PHY unit (10-4) outputs a signal including an uplink packet generated by the DLL unit (10-3) to the cable (30) in accordance with the timing of the TDD, and also receives a signal including a downlink packet sent from the leaf device (20) to the cable (30), and sends the received downlink packet to the DLL unit (10-3).

[0034] The leaf device 20 includes an application unit 20-1, an ASE / ASD unit 20-2, a DLL unit 20-3, and a PHY unit 20-4. The leaf device 20 operates in accordance with a control signal transmitted from the root device 10 via an uplink, and transmits a downlink packet including an application signal generated by the application unit 20-1 of the leaf device 20 to the root device 10 via the downlink.

[0035] The application unit (20-1) generates application signals such as video signals and audio signals. The ASE / ASD unit (20-2) performs ASE processing to encapsulate the application signals and ASD processing to decode the encapsulated control signals from the root device (10).

[0036] The DLL unit (20-3) generates a downlink packet including the application signal encapsulated by the ASE / ASD unit (20-2), and extracts the encapsulated control signal from the uplink packet transmitted from the root device (10) and sends it to the ASE / ASD unit (20-2).

[0037] The PHY unit (20-4) outputs a signal including a downlink packet generated by the DLL unit (20-3) to the cable (30) in accordance with the timing of the TDD, and also receives a signal including an uplink packet sent from the root device (10) to the cable (30), and sends the received uplink packet to the DLL unit (20-3).

[0038] Figure 2 is a diagram explaining TDD communication conforming to the ASA standard. As shown in Figure 2, in the ASA standard, one cycle (time t0 to t4) of the TDD communication method is 27,376 ns. Times t0 to t1 and times t2 to t3 are signal switching periods between uplink signals and downlink signals. Times t1 to t2 are the transmission period for uplink packets, and times t3 to t4 are the transmission period for downlink packets.

[0039] Typically, the signal capacity of an application signal output from a leaf device (20) is much larger than the signal capacity of a control signal output from a root device (10). For this reason, as shown in Figure 2, in the ASA standard using the TDD communication method, the period (time t3 to t4) allocated to the downlink for transmitting application signals and the like is set longer than the period (time t1 to t2) allocated to the uplink for transmitting control signals and the like.

[0040] FIG. 3 is a state transition diagram for a communication system 1 that complies with the ASA standard. FIG. 3 shows an overview of the state transitions in the communication system 1 and is not the exact state transition diagram described in the ASA standard. The root device (10) and leaf device (20) in FIG. 1 change states according to the state transition diagram in FIG. 3. As shown in FIG. 3, the communication system 1 that complies with the ASA standard has a startup state (first state) S2, a normal state (second state) S3, a light sleep state (third state) S4, a fail state S5, and a deep sleep state (fourth state) S6. As described above, the light sleep state is a state in which communication is temporarily suspended for a time interval equal to or longer than the TDD switching time and equal to or shorter than the time required to maintain synchronization between devices. More simply, it is a state in which communication is suspended intermittently without losing synchronization.

[0041] When the root device (10) and leaf device (20) are powered on (S1), both devices transition to a startup state S2, in which synchronization is established between the connected root device (10) and leaf device (20) in order to start TDD communication.

[0042] When the synchronization establishment process between the root device (10) and the leaf device (20) is completed, the state transitions to normal state S3. In the normal state, the root device (10) and the leaf device (20) alternately send and receive information using the TDD communication method.

[0043] The root device (10) and leaf devices (20) may transition from the normal state to the light sleep state. When they transition to the light sleep state, they stop TDD communication for a set period of approximately 100 ms, and then they repeat the process of returning to the normal state after the set period has elapsed. Alternatively, if they cannot transition from the light sleep state to the normal state, they return to the startup state and start over from the synchronization establishment process between the root device (10) and leaf devices (20).

[0044] If a TDD communication error occurs consecutively while in the normal state or light sleep state, the system transitions to the fail state. After that, the system transitions from the fail state to the startup state, and the synchronization establishment process between the root device (10) and the leaf device (20) is restarted.

[0045] 4 is a flowchart showing the startup sequence performed when the root device (10) and leaf devices (20) are in the startup state. First, a 1 GHz clock signal is synchronized between the root device (10) and leaf devices (20) (step S11). In this specification, this clock signal is called the Phase 1G signal (second signal).

[0046] Next, synchronization of the TDD cycle is established (step S12). In step S12, the Root device (10) and the Leaf device (20) transmit and receive a Phase SGA signal.

[0047] Next, the downlink and uplink signal sections within one TDD cycle are set to the same as in the normal state, and TDD communication is established (steps S13 and S14). After that, the state transitions to the normal state, and TDD communication begins. In this specification, step S11 is referred to as Phase 1G processing, step S12 as Phase SGA processing, step S13 as Phase SGB processing, and step S14 as Phase SGC processing.

[0048] Figure 5 is a timing diagram of the startup sequence. Figure 5 shows the timing of the Phase 1G signal and Phase SGA signal transmitted on the uplink and downlink when processing steps S11 and S12 in Figure 4. At time t50, the root device (10) and leaf device (20) are powered on, and initial settings are performed on each device. After the initial settings, the leaf device (20) enters a standby state to receive the Phase 1G signal transmitted from the root device (10).

[0049] The root device (10) outputs a Phase 1G signal to the uplink starting at time t51, after the time required for initial setup and other operations has elapsed (5-1). The Phase 1G signal is a 1 GHz signal consisting of a specific pattern including a control signal followed by a predetermined PRBS (Pseudo-Random Bit Sequence) signal. One signal interval during which the Phase 1G signal is output is 1536 [nsec]. The root device (10) repeatedly transmits the Phase 1G signal at a cycle of 3280 [nsec], which includes one signal interval.

[0050] After receiving the Phase 1G signal output from the Root device (10), the Leaf device (20) becomes capable of outputting a Phase 1G signal itself, and transmits a Phase 1G signal (third signal) 104 [nsec] after the end of one signal section of the Phase 1G signal from the Root device (10) (5-2).

[0051] As shown in Fig. 5, the Root device (10) and the Leaf device (20) alternately transmit and receive Phase 1G signals, and use the received Phase 1G signals to synchronize the clocks of the Phase 1G signals they transmit. Once the Root device (10) and the Leaf device (20) have completed clock synchronization and are able to correctly receive the Phase 1G signals, they write information indicating that preparations for transition to Phase SGA in step S12 of Fig. 4 have been completed into the control signal included in the Phase 1G signal they transmit, and then transmit the Phase 1G signal.

[0052] When both the Root device (10) and the Leaf device (20) are able to correctly receive the Phase 1G signal and can confirm from the control signal contained in the simultaneously received Phase 1G signal that the other party has also correctly received the Phase 1G signal, the process proceeds from step S11 to step S12 in FIG. 4 (time t53).

[0053] 4, the Root device (10) outputs a Phase SGA signal (5-3) to the Uplink. The Phase SGA signal is a signal consisting of a specific pattern including a control signal followed by a predetermined PRBS signal, and one signal interval is 13,584 [nsec]. The Root device (10) repeatedly transmits the Phase SGA signal at a cycle of 27,376 [nsec], which includes one signal interval.

[0054] In step S12, the Leaf device (20) starts outputting the Phase SGA signal (5-4) 104 [nsec] after one signal period of the Phase SGA signal output by the Root device (10) has ended.

[0055] As shown in FIG. 5, the Root device (10) and the Leaf device (20) alternately transmit and receive Phase SGA signals, and use the received Phase SGA signals to train the receiving equalizer and synchronize the TDD cycle.

[0056] As shown in FIG. 4, the process of step S13 is performed after step S12, and after the process in the startup state is completed, the state transitions to the normal state S3.

[0057] The state transition diagram in Figure 3 includes a deep sleep state S6, in which devices in the ASA-compliant communication system 1 are inactive for a much longer period of time than in the light sleep state S4. However, the current ASA standard, version 1.01, does not specify the details of the operation of the deep sleep state.

[0058] 1 is, for example, a display and the Root device (10) is, for example, a video player, it is assumed that a user will touch the screen of the display to start the communication system 1 and watch a video while the communication system 1 is paused. In this case, the Leaf device (20) which is a display is required to start the Root device (10) which is a video player by some means.

[0059] Furthermore, if the Leaf device (20) is, for example, a camera module, when only the camera unit operates and detects an image, it is assumed that the Leaf device (20) requests the Root device (10) to be activated in order to notify the Root device (10). For example, when a surveillance camera detects a face or skin color from image data of a certain area and determines that a person has approached the monitored object, it is assumed that the surveillance camera activates the communication system 1 to determine how to respond. However, the current ASA standard ver. 1.01 does not specify a procedure for activating the Root device (10) from a Leaf device (20) in a deep sleep state.

[0060] Therefore, the communication device and communication system 1 of the present disclosure are characterized by being able to solve the above-mentioned problems.

[0061] (First embodiment) The communication device and communication system 1 according to the first embodiment have the same block configuration as that shown in Fig. 1. Both the root device (10, first communication device) and the leaf device (20, second communication device) in Fig. 1 correspond to the communication device according to the first embodiment.

[0062] Figure 6 is a block diagram showing the internal configuration of the PHY unit (10-4) in the Root device (10) and the PHY unit (20-4) in the Leaf device (20) in Figure 1. As shown in Figure 6, the PHY units (10-4) and (20-4) in both devices have the same configuration. The PHY units (10-4) and (20-4) in Figure 6 are configured to receive a wake-up request signal (first signal) from another communication device (Root device (10) or Leaf device (20)). A timing diagram for the wake-up request signal will be described later. Figure 6 illustrates the block configuration related to the wake-up sequence in the PHY units (10-4) and (20-4).

[0063] The PHY units (10-4) and (20-4) in FIG. 6 include a state machine unit (FSM, state switching control unit) (80-1), a startup generation unit (start up Gen, second communication control unit, 80-2), a wakeup signal generation unit (Wakeup Signal Gen, first communication control unit, 80-3), a signal detector (80-4), a multiplexer (Mux, 80-5), a demultiplexer (DeMux, 80-6), a TDD controller 80-9, a driver (80-7), and a receiver (80-8).

[0064] The FSM (80-1) is a state machine that controls the wake-up sequence according to Figure 3 and Figures 9 and 10 described later. The FSM (80-1) receives a wake-up request initiation command or a startup state transition command from the communication partner device.

[0065] The startup generation unit (80-2) generates signals required for the startup sequence shown in FIG. 4 and outputs them to the multiplexer (80-5).

[0066] The wake-up signal generating unit (80-3) generates a wake-up request signal, which will be described later, and outputs it to the multiplexer (80-5).

[0067] The multiplexer 80-5 selects the data packet output from the DLL unit 10-3, 20-3, the signal output from the startup generation unit 80-2, or the wake-up request signal output from the wake-up signal generation unit 80-3 based on a control signal from the FSM 80-1, and outputs the selected signal to the driver 80-7. The driver 80-7 outputs the signal selected by the multiplexer 80-5 to the cable 80-10 in accordance with instructions from the TDD controller 80-9.

[0068] More specifically, the driver 80-7 outputs the signal selected by the multiplexer 80-5 to the corresponding device via the cable 80-10 in the TDD communication format shown in Fig. 2. Here, the cable 80-10 is the cable 80-10 that connects the root device 10 and the leaf device 20 shown in Fig. 1.

[0069] The receiver 80-8 receives a signal output from a connected device via a cable 80-10. The demultiplexer 80-6 outputs the signal received by the receiver 80-8 to the signal detector 80-4 or the DLL units 10-3, 20-3 under control of the FSM 80-1. More specifically, the demultiplexer 80-6 outputs a data packet, which is the received signal, to the signal detector 80-4 in the startup state S2 or the deep sleep state S6, and to the DLL units 10-3, 20-3 in the normal state S3, the light sleep state S4, or the fail state S5.

[0070] The signal detector (80-4) detects a Phase 1G signal or a wake-up request signal received via the cable (80-10), receiver (80-8), and demultiplexer (80-6), and outputs the detection result to the FSM (80-1).

[0071] As will be described later, the state machine unit (80-1) controls switching between a startup state, a normal state, a light sleep state, and a deep sleep state with the root device (10). The wake-up signal generation unit (80-3) repeats an operation of continuously transmitting a wake-up request signal to the root device (10) during a first signal interval in a first cycle when in the deep sleep state. When the startup generation unit (80-2) receives a Phase 1G signal output from the root device (10) in response to the wake-up request signal, the startup generation unit (80-2) transmits a Phase 1G signal synchronized with the Phase 1G signal to the root device (10). When the startup generation unit (80-2) transmits the Phase 1G signal, the state machine unit (80-1) transitions from the deep sleep state to the startup state.

[0072] The following describes the wake-up sequence performed by the leaf device (20) and the root device (10) assuming that the entire communication system 1 is in the deep sleep state S6. In the deep sleep state S6, the power of the entire communication system 1 is on, but communication between the root device (10) and the leaf device (20) is stopped.

[0073] 7 is a flowchart showing the procedure for the wake-up sequence performed by the leaf device 20. A controller (not shown) in the leaf device 20 in the deep sleep state sends a wake-up request start command to the FSM 80-1 to transition to the normal state (S21 is Yes).

[0074] In response to this command, the FSM (80-1) of the leaf device (20) issues a wake-up request signal (S22). More specifically, the FSM (80-1) controls the wake-up signal generator (80-3) to generate a wake-up request signal for one signal section. The FSM (80-1) also controls the multiplexer (80-5) to cause the multiplexer (80-5) to select the wake-up request signal generated by the wake-up signal generator (80-3). The FSM (80-1) then controls the TDD controller (80-9). As a result, the TDD controller (80-9) controls the driver (80-7) to output the wake-up request signal to the cable (80-10) for one signal section (S22).

[0075] The signal detector (80-4) detects the Phase 1G signal output from the Root device (10) during a period other than one signal section of the wake-up request signal output by itself, and outputs the detection result to the FSM (80-1).

[0076] When the FSM (80-1) of the leaf device (20) detects the Phase 1G signal from the root device (10), it determines that the root device (10) has transitioned to the startup state S2, and it also transitions to the startup state S2 (YES in S23). From then on, the startup sequence shown in Figure 4 is executed.

[0077] In this way, after outputting a wake-up request signal to the cable 80-10, the leaf device 20 transitions from the deep sleep state to the startup state when it receives a Phase 1G signal from the root device 10.

[0078] If the FSM 80-1 of the leaf device 20 does not detect the Phase 1G signal, it determines that the root device 10 is in the deep sleep state S6 and repeats the processes from S22 onward to send a wake-up request signal again (NO in S23). As a result, the leaf device 20 periodically outputs a wake-up request signal until it receives the Phase 1G signal from the root device 10.

[0079] Figure 8 is a flowchart showing the processing procedure of the wake-up sequence performed by the root device (10). When the root device (10) is in the deep sleep state S6, the ECU (10-1) in Figure 1 instructs the FSM (80-1) to wait for the input of a start-up state transition command ("move to start-up state"). At this time, the signal detector (80-4) enters a state in which it detects a wake-up request signal.

[0080] When a startup state transition command is input to the FSM (80-1) or the signal detector (80-4) detects a wake-up request signal, the FSM (80-1) immediately transitions from the deep sleep state S6 to the startup state S2 (S31 is YES). From then on, the startup sequence shown in Figure 4 is executed.

[0081] In step S31, if the startup state transition command is not input to the FSM (80-1) or the signal detector (80-4) does not detect a wake-up request signal, the deep sleep state S6 is maintained. The FSM (80-1) waits for the startup state transition command to be input, and the signal detector (80-4) continues to detect the wake-up request signal.

[0082] By the above procedure, a wake-up operation from the leaf device (20) of the communication system 1 shown in FIG. 1, in which the root device (10) and the leaf device (20) are connected, can be realized.

[0083] Figure 9 is a timing diagram of the wake-up sequence, Figure 10 is a timing diagram of the wake-up request signal, and Figure 11 is a timing diagram showing the relationship between the wake-up request signal and the Phase 1G signal. Figure 9 shows the timing at which the Leaf device (20) outputs a wake-up request signal when the entire communication system 1 is in a deep sleep state.

[0084] As shown in FIG. 10, the wake-up request signal generated by the wake-up signal generating unit (80-3) in FIG. 6 is expressed by the polynomial X 23 +X 5 It is composed of a PRBS signal represented by +1, and its maximum frequency is nominally 1 GHz. The wake-up request signal outputs the PRBS signal within one signal interval of 768 [nsec], then stops, and after 4048 [nsec] has elapsed, it repeats the operation of outputting the PRBS signal again within one signal interval of 768 [nsec]. In this way, the wake-up request signal is a periodic signal that repeatedly outputs the PRBS signal within one signal interval of 768 [nsec] with a cycle of 4816 [nsec].

[0085] As shown in Figures 9 and 10, a leaf device (20) in a deep sleep state periodically outputs the above-mentioned wake-up request signal to a cable (80-10). This wake-up request signal is transmitted to a root device (10) via a cable (80-10) in a downlink of a TDD communication system. The leaf device (20) periodically transmits the wake-up request signal until it receives a Phase 1G signal from the root device (10). Upon receiving the Phase 1G signal, the leaf device (20) immediately stops transmitting the wake-up request signal.

[0086] 9 and 11, when the root device (10) receives a wake-up request signal, it outputs a Phase 1G signal to the cable (80-10) within one signal section of 1536 [nsec] at a cycle of 3280 [nsec]. This Phase 1G signal is transmitted to the leaf device (20) via the cable (80-10) by the uplink of the TDD communication method.

[0087] As shown in Figure 11, the signal amplitude of the wake-up request signal is less than or equal to the signal amplitude of the Phase 1G signal. Desirably, the signal amplitude of the wake-up request signal is 0.2 times or more and 0.8 times or less than the signal amplitude of the Phase 1G signal. More desirably, the signal amplitude of the wake-up request signal is 0.4 times or more and 0.6 times or less than the signal amplitude of the Phase 1G signal. Even more desirably, the signal amplitude of the wake-up request signal is 0.5 times or more than the signal amplitude of the Phase 1G signal. In this way, by making the signal amplitude of the wake-up request signal smaller than the signal amplitude of the Phase 1G signal, adverse electrical effects such as damage to circuit components in the Root device (10) and the Leaf device (20) can be prevented even if both signals are transmitted and received at the same time.

[0088] 11, when the Root device (10) outputs a Phase 1G signal in response to a wake-up request signal from the Leaf device (20), a time region is secured in which the wake-up request signal and the Phase 1G signal do not overlap each other, making it easier for the Leaf device (20) to detect the Phase 1G signal and for the Root device (10) to detect the wake-up request signal.

[0089] As shown in FIG. 9, when the Leaf device (20) receives a Phase 1G signal from the Root device (10), it synchronizes with the received Phase 1G signal and outputs a Phase 1G signal of the same signal level, thereby transitioning to a startup state.

[0090] The ASA standard also assumes that the root device 10 and leaf devices 20 are connected via a branch device 40. FIG. 12 is a block diagram showing a schematic configuration of a communication system 1a including the root device 10, leaf devices 20, and branch devices 40. The internal configurations of the root device 10 and leaf devices 20 in FIG. 12 are the same as those in FIG. 1. The branch device 40 in FIG. 12 includes an application unit 40-1, an ASE / ASD unit 40-2, a router 40-7, multiple DLL units 40-3 and 40-4, and multiple PHY units 40-4 and 40-6. In the communication system 1a in FIG. 12, the root device 10 is assumed to recognize in advance that the leaf device 20 and branch device 40 may transmit wake-up request signals.

[0091] FIG. 13 is a block diagram showing the internal configuration of multiple PHY units (40-4) and (40-6). As shown in FIG. 13, the PHY unit (40-4) has an FSM (80-1a, first state switching control unit), and the PHY unit (40-5) has an FSM (80-1b, second state switching control unit). A wake-up request initiation command or a startup state transition command from the root device (10) is input to the FSM (80-1a). A wake-up request initiation command or a startup state transition command from the leaf device (20) is input to the FSM (80-1b). Note that although FIG. 13 omits all but the FSM (80-1a) and FSM (80-1b), the PHY units (40-4) and (40-6) have the same internal configuration as FIG. 6.

[0092] The FSM 80-1a in the PHY unit 40-4 and the FSM 80-1b in the PHY unit 40-6 exchange information with each other. Specifically, the FSM 80-1b in the PHY unit 40-6 notifies the FSM 80-1a in the PHY unit 40-4 that a wake-up request start command has been received from the leaf device 20, and notifies it of the state of the leaf device 20 (13-1). The FSM 80-a in the PHY unit 40-4 notifies the FSM 80-1b in the PHY unit 40-6 of a request to transition to the setup state, and notifies it of the state of the root device 10 (13-2).

[0093] The router (40-7) determines the destination of the transmission packet, determining whether the packet is intended for the Branch device (40) itself or for another device, and transmits the encapsulated information to the DLL unit (40-3), the DLL unit (40-5), or the ASE / ASD unit (40-2).

[0094] Even when a branch device 40 is connected between a root device 10 and a leaf device 20 as shown in Figure 12, each device undergoes the state transition shown in Figure 3. The leaf device 20 enters the deep sleep state when the entire communication system 1a is in the deep sleep state, or when the root device 10 to the branch device 40 are in the normal or light sleep state and the branch device 40 to the leaf device 20 are in the deep sleep state. As described above, the leaf device 20 is expected to enter the deep sleep state in one of the two cases described above. In either case, it is necessary for the leaf device 20 to be able to return from the deep sleep state to the normal state at its own will.

[0095] Below, the processing procedure for the Leaf device (20) to perform a wake-up operation when the Root device (10) and the Leaf device (20) are connected via the Branch device (40) shown in Figure 12 will be explained separately for the two cases mentioned above.

[0096] As described above, the branch device (40) shown in Figure 12 has two systems of PHY and DLL. The PHY unit (40-6) and the DLL unit (40-5) are one system, and the PHY unit (40-4) and the DLL unit (40-3) are another system. Here, the PHY unit (40-6) connected to the leaf device (20) is called the far-side PHY, and the PHY unit (40-4) connected to the root device (10) is called the near-side PHY.

[0097] The FSM (80-1a) controls switching between the startup state, normal state, light sleep state, and deep sleep state with the root device (10). The FSM (80-1b) controls switching between the startup state, normal state, light sleep state, and deep sleep state with the leaf device (20).

[0098] When the leaf device 20 is in a deep sleep state, the PHY unit 40-4 repeatedly receives a wake-up request signal, which is continuously transmitted from the leaf device 20 within a first signal interval, in a first cycle, and transmits the received wake-up request signal to the root device 10. When the PHY unit 40-6 receives a Phase 1G signal from the root device 10 in response to the wake-up request signal, the PHY unit 40-6 transmits the Phase 1G signal to the leaf device 20. When the root device 10 transmits the Phase 1G signal, the FSM 80-1a transitions from the deep sleep state to the startup state.

[0099] 14 is a flowchart showing the processing procedure of the PHY unit (40-6) which is the far-side PHY, and FIG. 15 is a flowchart showing the processing procedure of the PHY unit (40-4) which is the near-side PHY. The PHY unit (40-4) and the PHY unit (40-6) have the internal configuration shown in FIG.

[0100] First, a case where the leaf device 20 performs a wake-up operation when all devices are in a deep sleep state will be described. The leaf device 20 performs the operation according to the flowchart in FIG. 7, and therefore, the description will be omitted.

[0101] When the far-side PHY of the branch device (40) is in a deep sleep state, if the signal detector (80-4) of the far-side PHY receives a wake-up request signal from the leaf device (20) (YES in S42), it checks the state of the near-side PHY (13-2 in FIG. 13).

[0102] If the Near-side PHY is in the normal state S3 or the light sleep state S4 (YES in S43), the startup operation is immediately initiated. Thereafter, the startup sequence of FIG. 4 is executed in the same manner as described for the Root device (10). In this way, when the Branch device (40) receives a wake-up request signal from the Leaf device (20), if the Root device (10) is in the normal state S3 or the light sleep state S4, the Branch device (40) immediately transitions from the deep sleep state to the startup state.

[0103] On the other hand, when a wake-up request signal is received from the leaf device (20), if the near-side PHY is not in the normal state S3 or the light sleep state S4 (NO in S43), the branch device (40) issues a command (13-1 in FIG. 13) to the far-side PHY to start a wake-up operation to establish communication with the root device (10) (S44). In this case, the branch device (40) maintains the deep sleep state S6 until communication between the near-side PHY and the root device (10) is established.

[0104] When the Near Side PHY transitions to the normal state S3 and receives the startup state transition command (13-2 in Figure 13) for the Far Side (S41 is YES), it immediately transitions to the startup state S2. After that, the startup sequence (Figure 4) is executed, as explained for the Root device (10). These operations cause the Leaf device (20) and Branch device (40) to perform wake-up operations.

[0105] Next, the wake-up sequence when the Near Side PHY of the Branch device 40 is in the deep sleep state will be described with reference to the flowchart of FIG. 15. When a wake-up operation start command (13-1 in FIG. 13) is received from the Far Side PHY (YES in S51), the Near Side PHY immediately outputs a wake-up request signal to establish communication with the Root device 10 (S52, first communication control unit). This wake-up request signal is transmitted to the Root device 10 via the cable 80-10. The Near Side PHY of the Branch device 40 then performs the same operation as in FIG. 7. That is, when the FSM 80-1 of the Branch device 40 detects a Phase 1G signal from the Root device 10, it determines that the Root device 10 has transitioned to the startup state S2, and it also transitions to the startup state S2 (YES in S23).

[0106] When the Near Side PHY of the Branch device (40) establishes communication with the Root device (10), it issues an instruction (13-2 in FIG. 13) to the Far Side PHY of the Branch device (40) to transition to the startup state S2, and the Branch device (40) itself transitions to the normal state S3 (S54).

[0107] The procedure by which the Root device (10) in the deep sleep state receives a wake-up request signal from the Near-side PHY of the Branch device (40) and transitions to the startup state S2 is the same as that shown in the flowchart of FIG.

[0108] According to the above procedure, when the Leaf device (20) shown in FIG. 12 is in a deep sleep state, each device can be transitioned to a startup state by transmitting a wake-up request signal from the Leaf device (20).

[0109] The processing procedure of the branch device (40) described above can also be applied to a communication system 1b in which a plurality of branch devices (40) are daisy-chained between a root device (10) and a leaf device (20) as shown in Fig. 16. Each branch device (40) in Fig. 16 has the same internal configuration as the branch device (40) in Fig. 12. Also, the PHY unit in each branch device (40) in Fig. 15 has the same internal configuration as that in Fig. 13.

[0110] At startup, the root device (10) in Figure 16 reads information from the built-in registers of each device (20, 40, 100, 110) to determine whether each device supports deep sleep and whether it can transition from deep sleep to another state. If all connected devices can transition from deep sleep, the following processing is allowed.

[0111] When all devices are in the deep sleep state and a wake-up operation is performed from the leaf device (20), the above-described processing procedure is performed to perform the wake-up operation in the order of the leaf device (20), the branch device (40), the branch device (40), the branch device (110), the branch device (100), and the root device (10), thereby transitioning the root device (10) to the startup state S2. This establishes communication between the root device (10) and each branch device (40), (110), (100), and then establishes communication between the branch devices (40) toward the leaf device (20), and finally establishes communication between the branch device (40) and the leaf device (20). In this way, communication is established between the multiple branch devices in order from the side closest to the root device (10).

[0112] In addition, in the system shown in FIG. 16, when it is desired to establish communication between devices starting from a branch device (40) in the network, for example, a branch device (110), and ending at the root device (10), the near-side PHY of the branch device (110) starts a wake-up operation from its own application or controller (S51 in FIG. 15) as shown in FIG. 15, and communication from the branch device (110) to the root device (10) can be established according to the procedure described above.

[0113] As described above, in the communication system 1 according to the first embodiment, when the Leaf device (20) is in a deep sleep state, the Leaf device (20) repeatedly outputs a wake-up request signal, and when the Leaf device (20) receives a Phase 1G signal transmitted by the Root device (10) that has received the wake-up request signal, the output of the wake-up request signal is stopped, and the Leaf device (20) outputs a Phase 1G signal synchronized with the received Phase 1G signal, thereby transitioning to a startup state. This allows the Leaf device (20) to take action on its own to exit the deep sleep state.

[0114] Furthermore, when a branch device 40 is connected between a root device 10 and a leaf device 20, the wake-up request signal output by the leaf device 20 is transmitted to the root device 10 via the branch device 40. When the branch device 40 receives a Phase 1G signal from the root device 10, it immediately transitions to a startup state. Furthermore, the branch device 40 transmits the Phase 1G signal output by the root device 10 that has received the wake-up request signal to the leaf device 20 via the branch device 40. When the leaf device 20 receives the Phase 1G signal, it can stop outputting the wake-up request signal and transition to a startup state.

[0115] (Second embodiment) 9 and 11, in the communication system according to the first embodiment, the signal amplitude of the wake-up request signal output by the Leaf device (20) is set to be less than (e.g., about 0.5 times) the signal amplitude of the Phase 1G signal output by the Root device (10), and one signal interval of the wake-up request signal is set to be less than (e.g., about 0.5 times) one signal interval of the Phase 1G signal. The Leaf device (20) originally has the function of generating a signal with the same signal amplitude and the same one signal interval as the Phase 1G signal output from the Root device (10). In addition to this function, as described above, the Leaf device (20) needs to be provided with the function of generating a wake-up request signal with a different signal amplitude and one signal interval from the Phase 1G signal. In contrast, in the second embodiment, a wake-up request signal is generated with the same signal amplitude and the same one signal interval as the Phase 1G signal.

[0116] The communication system 1 according to the second embodiment has the same configuration as that shown in Fig. 1, 12, or 16. The internal configuration of each device in the communication system 1 according to the second embodiment is the same as that shown in Fig. 1, 6, 12, or 13.

[0117] 17 is a timing diagram of a wake-up of the communication system 1 according to the second embodiment, and FIG. 18 is a timing diagram of a wake-up request signal. A leaf device (20) in a deep sleep state repeatedly outputs a wake-up request signal with the same signal amplitude and the same signal interval as the Phase 1G signal generated by the root device (10), at the same cycle as the Phase 1G signal. The leaf device (20) is originally equipped with the function of generating a Phase 1G signal, and can easily generate a wake-up request signal with the same signal amplitude and the same signal interval as the Phase 1G signal.

[0118] When the root device (10) receives a wake-up request signal from the leaf device (20), it understands that the leaf device (20) has started a wake-up sequence and outputs a Phase 1G signal. The wake-up request signal has the same signal amplitude and one signal period as the Phase 1G signal, but since it is a signal sent to the deep sleep state, the root device (10) determines that it is a wake-up request signal. The root device (10) outputs the Phase 1G signal at a timing that does not overlap with one signal period of the wake-up request signal.

[0119] When the leaf device (20) receives the Phase 1G signal from the root device (10), it immediately stops outputting the wake-up request signal, synchronizes with the Phase 1G signal from the root device (10), outputs a Phase 1G signal with the same signal amplitude and one signal period, and transitions to a startup state.

[0120] As described above, in the second embodiment, the leaf device 20 outputs a wake-up request signal having the same signal amplitude and the same signal duration as the Phase 1G signal output from the root device 10, at the same cycle as the Phase 1G signal. This makes it easier for the leaf device 20 to generate a wake-up request signal, and simplifies the internal configuration of the leaf device 20.

[0121] The present technology can be configured as follows: (1) A state switching control unit that controls switching between a first state in which synchronization is established for communication with a communication partner device, a second state in which the communication is started after synchronization is established in the first state, a third state in which the communication is intermittently stopped without losing synchronization, and a fourth state in which the communication is stopped for a longer period than in the third state and synchronization is re-established with the communication partner device when the communication is resumed; a first communication control unit that repeats an operation of continuously transmitting a first signal to the communication partner device within a first signal section in a first cycle when in the fourth state; a second communication control unit that, upon receiving a second signal output from the communication partner device in response to the first signal, transmits a third signal synchronized with the second signal to the communication partner device; The state switching control unit transitions the communication device from the fourth state to the first state when the second communication control unit transmits the third signal. (2) a first state switching control unit that controls switching between a first state in which synchronization is established for communication with a first communication partner device, a second state in which the communication is started after synchronization is established in the first state, a third state in which the communication is intermittently stopped without losing synchronization, and a fourth state in which the communication is stopped for a longer period than in the third state and synchronization is re-established with the first communication partner device when the communication is resumed; a second state switching control unit that controls switching between the first state, the second state, the third state, and the fourth state with a second communication partner device; a first communication control unit that, when the second communication partner device is in the fourth state, repeatedly receives a first signal in a first period, the first signal being continuously transmitted from the second communication partner device within a first signal section, and transmits the received first signal to the first communication partner device; a second communication control unit that, upon receiving a second signal in response to the first signal from the first communication partner device, transmits the second signal to the second communication partner device; The communication device, wherein the first state switching control unit transitions from the fourth state to the first state when the first communication partner device transmits the second signal. (3) The communication device described in (2), wherein the second state switching control unit, when receiving the first signal from the second communication partner device while in the fourth state, transitions the first communication partner device to the first state if the first communication partner device is in the first state, the second state, or the third state. (4) A communication device described in any one of (1) to (3), wherein the first communication control unit repeats the operation of continuously transmitting the first signal generated using pseudorandom numbers within the first signal section in the first period. (5) The first communication control unit is X 23 +X 5The communication device according to (4), wherein the first signal is generated based on a +1 polynomial. (6) A state switching control unit that controls switching among a first state in which synchronization is established for communication with a communication partner device, a second state in which the communication is performed after synchronization is established in the first state, a third state in which the communication is intermittently stopped without losing synchronization, and a fourth state in which the communication is stopped for a longer period than in the third state and synchronization is re-established with the communication partner device when the communication is resumed. a first communication control unit that, when the communication partner device is in the fourth state, repeatedly receives, in a first period, a first signal that is continuously transmitted from the communication partner device within a first signal section; a second communication control unit configured to transmit to the communication partner device a second signal synchronized with the first signal received by the first communication control unit. (7) The communication device according to any one of (1) to (6), wherein the signal amplitude of the first signal is equal to or less than the signal amplitude of the second signal. (8) The communication device according to (7), wherein the signal amplitude of the first signal is 0.2 times or more and 0.8 times or less than the signal amplitude of the second signal. (9) The communication device according to (8), wherein the signal amplitude of the first signal is 0.4 times or more and 0.6 times or less than the signal amplitude of the second signal. (10) The communication device according to (9), wherein the signal amplitude of the first signal is 0.5 times the signal amplitude of the second signal. (11) The communication device according to any one of (1) to (10), wherein the first signal section is equal to or shorter than a second signal section in which the second signal is continuously output. (12) The communication device according to (11), wherein the first signal section is 0.5 times the second signal section. (13) A communication device according to any one of (1) to (12), wherein the first signal section is 768 [nsec] and the first period is 4816 [nsec]. (14) A communication device according to any one of (1) to (12), wherein the first signal section is 1536 [nsec] and the first period is 3280 [nsec]. (15) A communication device described in any one of (1) to (6), wherein the first signal and the second signal have the same signal amplitude and the same period, and the length of the first signal section is the same as the length of the second signal section in which the second signal is output continuously. (16) The communication device described in (15), wherein the first signal section and the second signal section are 1536 [nsec], and the period of the first signal and the second signal is 3280 [nsec]. (17) The communication device according to (1) or (6), which alternately transmits and receives information to and from the communication partner device within an allocated period in a TDD (Time Division Duplex) communication method. (18) a first communication device; a second communication device that alternately transmits and receives information to and from the first communication device within an allocated period in a TDD (Time Division Duplex) communication method; The second communication device a state switching control unit that controls switching between a first state in which synchronization is established for communication with the first communication device, a second state in which the communication is performed after synchronization is established in the first state, a third state in which the communication is intermittently stopped without losing synchronization, and a fourth state in which the communication is stopped for a longer period than in the third state and synchronization is re-established with the first communication device when the communication is resumed; a first communication control unit that repeats an operation of continuously transmitting a first signal within a first signal section to the first communication device in a first cycle when in the fourth state; a second communication control unit that, upon receiving a second signal output from the first communication device in response to the first signal, transmits a third signal synchronized with the second signal and transitions from the fourth state to the first state. (19) A third communication device is provided which alternately transmits and receives information to and from the first communication device within a period allocated by the TDD communication method, and alternately transmits and receives information to and from the second communication device within a period allocated by the TDD communication method, the third communication device, a first communication control unit that, when the second communication device is in the fourth state, repeatedly receives a first signal, which is continuously transmitted within a first signal section from the second communication device, in a first period, and transmits the received first signal to the first communication device; a second communication unit that, upon receiving a second signal in response to the first signal from the first communication device, transmits the second signal to the second communication device; A communication system as described in (18), further comprising a second communication control unit that, upon receiving a third signal synchronized with the second signal from the second communication device, transmits the third signal to the first communication device and transitions from the fourth state to the first state. (20) A plurality of the third communication devices are connected in a daisy chain between the first communication device and the second communication device, The communication system described in (19), wherein, when the plurality of third communication devices and the second communication device are in the fourth state, each of the plurality of third communication devices sequentially transmits the first signal of the first period transmitted continuously from the second communication device within the first signal section to the third communication device or the first communication device that is closer to the first communication device, sequentially receives a second signal synchronized with the first signal transmitted from the first communication device, and transmits it to the third communication device or the second communication device that is closer to the second communication device, and transitions from the fourth state to the first state.

[0122] The aspects of the present disclosure are not limited to the individual embodiments described above, but include various modifications that may be conceived by those skilled in the art, and the effects of the present disclosure are not limited to the above-described contents. In other words, various additions, modifications, and partial deletions are possible within the scope of the conceptual idea and spirit of the present disclosure, which is derived from the contents defined in the claims and their equivalents. [Explanation of symbols]

[0123] 1, 1a, 1b Communication system, 10 Root device, 10-2 ASE / ASD section, 10-3 DLL section, 10-4 PHY section, 20 Leaf device, 20-1 Application section, 20-2 ASE / ASD section, 20-3 DLL section, 20-4 PHY section, 30 Cable, 40 Branch device, 40-1 Application section, 40-2 ASE / ASD section, 40-3 DLL section, 40-4, 40-5, 40-6 PHY section, 40-7 Router, 80-1 State machine section, 80-10 Cable, 80-2 Startup generation section, 80-3 Wake-up signal generation section, 80-4 Signal detector, 80-5 Multiplexer, 80-6 Demultiplexer, 80-7 Driver, 80-8 Receiver, 80-9 TDD controller, 100, 110 Branch device

Claims

1. a state switching control unit that controls switching between a first state in which synchronization is established for communication with a communication partner device, a second state in which the communication is started after synchronization is established in the first state, a third state in which the communication is intermittently stopped without losing synchronization, and a fourth state in which the communication is stopped for a longer period than in the third state, awaits a response from the communication partner device, and re-establishes synchronization with the communication partner device when the communication is resumed in response to the response; a first communication control unit that repeats an operation of continuously transmitting a first signal to the communication partner device within a first signal section in a first cycle when the communication partner device itself is in the fourth state; a second communication control unit that, upon receiving a second signal output from the communication partner device in response to the first signal, transmits a third signal synchronized with the second signal to the communication partner device; The communication device, wherein the state switching control unit transitions from the fourth state to the first state when the second communication control unit transmits the third signal.

2. a first state switching control unit that controls switching between a first state in which synchronization is established for communication with a first communication partner device, a second state in which the communication is started after synchronization is established in the first state, a third state in which the communication is intermittently stopped without losing synchronization, and a fourth state in which the communication is stopped for a longer period than in the third state, awaits a response from the first communication partner device, and re-establishes synchronization with the first communication partner device when the communication is resumed in response to the response; a second state switching control unit that controls switching between the first state, the second state, the third state, or the fourth state that waits for a response from the second communication partner device and re-establishes synchronization with the second communication partner device when the communication is resumed in response to the response; a first communication control unit that, when the second communication partner device is in the fourth state, repeatedly receives a first signal, which is continuously transmitted within a first signal section from the second communication partner device, in a first period, and transmits the received first signal to the first communication partner device; a second communication control unit that, upon receiving a second signal in response to the first signal from the first communication partner device, transmits the second signal to the second communication partner device; The communication device, wherein the first state switching control unit transitions from the fourth state to the first state when receiving the second signal transmitted from the first communication partner device.

3. 3. The communication device according to claim 2, wherein the second state switching control unit transitions to the first state when the first communication partner device is in the first state, the second state, or the third state when the second state switching control unit receives the first signal from the second communication partner device while the communication device is in the fourth state.

4. The communication device according to claim 1 , wherein the first communication control unit repeats, in the first period, an operation of continuously transmitting the first signal generated using a pseudorandom number within the first signal section.

5. The first communication control unit is X 23 +X 5 The communication device of claim 4 , wherein the first signal is generated based on a +1 polynomial.

6. a state switching control unit that controls switching between a first state in which synchronization is established for communication with a communication partner device, a second state in which the communication is performed after synchronization is established in the first state, a third state in which the communication is intermittently stopped without losing synchronization, and a fourth state in which the communication is stopped for a longer period than in the third state, awaits a response from the communication partner device, and re-establishes synchronization with the communication partner device when the communication is resumed in response to the response; a first communication control unit that, when the communication partner device is in the fourth state, repeatedly receives, in a first period, a first signal that is continuously transmitted from the communication partner device within a first signal section; a second communication control unit configured to transmit to the communication partner device a second signal synchronized with the first signal received by the first communication control unit.

7. The communication device according to claim 1 , wherein the signal amplitude of the first signal is equal to or less than the signal amplitude of the second signal.

8. The communication device according to claim 7 , wherein the signal amplitude of the first signal is not less than 0.2 times and not more than 0.8 times the signal amplitude of the second signal.

9. The communication device according to claim 8 , wherein the signal amplitude of the first signal is equal to or greater than 0.4 times and equal to or less than 0.6 times the signal amplitude of the second signal.

10. The communication device according to claim 9 , wherein the signal amplitude of the first signal is 0.5 times the signal amplitude of the second signal.

11. The communication device according to claim 1 , wherein the first signal section is equal to or shorter than a second signal section in which the second signal is continuously output.

12. The communication device according to claim 11 , wherein the first signal section is 0.5 times the second signal section.

13. 2. The communication device according to claim 1, wherein the first signal section is 768 [nsec] and the first period is 4816 [nsec].

14. 2. The communication device according to claim 1, wherein the first signal section is 1536 [nsec] and the first period is 3280 [nsec].

15. 2. The communication device according to claim 1, wherein the first signal and the second signal have the same signal amplitude and the same period, and the length of the first signal section is the same as the length of the second signal section in which the second signal is output continuously.

16. 16. The communication device according to claim 15, wherein the first signal section and the second signal section are 1536 [nsec], and the period of the first signal and the second signal is 3280 [nsec].

17. 2. The communication device according to claim 1, wherein information is alternately transmitted and received between the communication device and the communication partner device within an allocated period in a TDD (Time Division Duplex) communication system.

18. a first communication device; a second communication device that alternately transmits and receives information to and from the first communication device within an allocated period in a TDD (Time Division Duplex) communication system; the second communication device, a state switching control unit that controls switching between a first state in which synchronization is established for communication with the first communication device, a second state in which the communication is performed after synchronization is established in the first state, a third state in which the communication is intermittently stopped without losing synchronization, and a fourth state in which the communication is stopped for a longer period than in the third state, awaits a response from the first communication device, and re-establishes synchronization with the first communication device when the communication is resumed in response to the response; a first communication control unit that repeats an operation of continuously transmitting a first signal to the first communication device within a first signal section in a first cycle when the first communication control unit itself is in the fourth state; a second communication control unit that, upon receiving a second signal output from the first communication device in response to the first signal, transmits a third signal synchronized with the second signal and transitions from the fourth state to the first state.

19. a third communication device that alternately transmits and receives information to and from the first communication device within a period allocated by the TDD communication method, and that alternately transmits and receives information to and from the second communication device within a period allocated by the TDD communication method; the third communication device, a first communication control unit that, when the second communication device is in the fourth state, repeatedly receives a first signal, which is continuously transmitted within a first signal section from the second communication device, in a first period, and transmits the received first signal to the first communication device; a second communication unit that, upon receiving a second signal in response to the first signal from the first communication device, transmits the second signal to the second communication device; 19. The communication system according to claim 18, further comprising: a second communication control unit that, upon receiving a third signal synchronized with the second signal from the second communication device, transmits the third signal to the first communication device and transitions from the fourth state to the first state.

20. a plurality of the third communication devices are connected in a daisy chain between the first communication device and the second communication device; 20. The communication system of claim 19, wherein, when the plurality of third communication devices and the second communication device are in the fourth state, each of the plurality of third communication devices sequentially transmits the first signal of the first period transmitted continuously from the second communication device within the first signal section to the third communication device or the first communication device that is closer to the first communication device, sequentially receives a second signal synchronized with the first signal transmitted from the first communication device, and transmits it to the third communication device or the second communication device that is closer to the second communication device, and transitions from the fourth state to the first state.

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