JP2017046053A - Master node - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a master node that prevents a wakeup signal from being undetected.SOLUTION: A master node is connected with a slave node via communication wiring and includes a transceiver and a microcomputer. The transceiver includes a transmitter, a receiver, and a comparison unit that outputs a comparison signal indicating comparison between a transmission signal input into the transmitter and a reception signal input into the receiver to the microcomputer. The microcomputer determines whether or not the slave node has output a wakeup signal to the communication wiring on the basis of the comparison signal from the start of output of a sleep signal.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a master node that is communicably connected to a plurality of slave nodes via communication wiring.

  As shown in Patent Document 1, a communication system in which a plurality of slaves and one master are connected via a bus communication path is known. The slave and the master operate in a wake-up mode or a sleep mode.

  The master sends a sleep signal to the slave when the sleep prohibition factor disappears. Then, the master determines whether or not to receive a dominant pulse after a predetermined time elapses after the sleep signal is output. When receiving the dominant pulse, the master continues the wake-up mode. On the other hand, if the dominant pulse is not received, the master enters the sleep mode.

Japanese Patent No. 5617795

  As described above, the master of the communication system described in Patent Document 1 detects the dominant pulse (wake-up signal) after confirming the end of the output of the sleep signal. Therefore, a time lag for confirmation occurs between the end of outputting the sleep signal and the detection of the wake-up signal. Therefore, in this time lag, the master cannot detect the wakeup signal, and there is a possibility that the wakeup mode cannot be continued.

  In view of the above problems, an object of the present invention is to provide a master node in which detection of a wakeup signal cannot be performed.

One of the disclosed inventions for achieving the above object is a master node communicably connected to a plurality of slave nodes (10) via a communication wiring (30),
A transceiver (50) connected to the communication wiring;
A microcomputer (40) connected to the communication wiring via the transceiver,
Transceiver
A transmitter (51) for outputting a transmission signal output from the microcomputer to the communication wiring;
A receiver (52) for outputting a reception signal input from the communication wiring to the microcomputer;
A comparison unit (53) for outputting a comparison signal obtained by comparing the transmission signal input to the transmitter and the reception signal input to the receiver to the microcomputer;
Each of the plurality of slave nodes and the transceiver has a communication mode and a power saving mode as operation modes.
Each of the plurality of slave nodes has a function of outputting, to the communication wiring, a wakeup signal that causes each of the plurality of slave nodes to shift from the power saving mode to the communication mode.
The microcomputer has a sleep signal that causes each of the plurality of slave nodes to shift from the communication mode to the power saving mode as a transmission signal,
The microcomputer determines whether or not a wake-up signal is output to the communication wiring based on the comparison signal after starting to output the sleep signal.

  The transmission signal input to the transmitter (51) and the reception signal input to the receiver (52) are substantially the same from when the sleep signal is output from the microcomputer (40) to when it is output. Become. Further, even when the slave node (10) does not output the wakeup signal after the sleep signal is output, the transmission signal and the reception signal are substantially the same. However, when the slave node (10) outputs the wakeup signal after the sleep signal is output, the transmission signal and the reception signal are substantially different. As described above, the transmission signal and the reception signal are substantially different depending on the presence or absence of the wake-up signal. Therefore, it can be determined whether or not the wake-up signal is output to the communication wiring (30) based on the comparison signal obtained by comparing the transmission signal and the reception signal.

  By the way, in the case of detecting the wake-up signal after confirming the end of outputting the sleep signal, a time lag for confirmation occurs between the end of outputting the sleep signal and detecting the wake-up signal. . Therefore, the wakeup signal cannot be detected at this time lag.

  On the other hand, in the present invention, as described above, the detection of the wakeup signal based on the comparison signal is performed from the beginning of outputting the sleep signal. For this reason, unlike the above-described comparison configuration, it is possible to prevent the detection of the wake-up signal.

  In addition, the code | symbol with the parenthesis is attached | subjected to the element as described in the claim as described in a claim, and each means for solving a subject. The reference numerals in parentheses are for simply indicating the correspondence with each component described in the embodiment, and do not necessarily indicate the element itself described in the embodiment. The description of the reference numerals with parentheses does not unnecessarily narrow the scope of the claims.

1 is a block diagram illustrating a schematic configuration of a communication system according to a first embodiment. 1 is a circuit diagram showing a schematic configuration of a master transceiver according to a first embodiment. FIG. It is a timing chart which shows the delay of the signal inputted into a comparison part, and a wake-up signal. It is a timing chart for demonstrating the sleep process of a master. It is a timing chart for demonstrating the sleep process of a master. It is a flowchart for demonstrating the sleep process of a master. It is a timing chart for demonstrating the modification of a sleep process. It is a flowchart for demonstrating the modification of a sleep process. It is a flowchart for demonstrating the modification of a sleep process. It is a block diagram which shows schematic structure of the communication system which concerns on 2nd Embodiment. It is a circuit diagram which shows schematic structure of the transceiver of the master which concerns on 2nd Embodiment. It is a timing chart for demonstrating the sleep process of a master. It is a flowchart for demonstrating the sleep process of a master. It is a flowchart for demonstrating the determination process of a mode determination part. It is a circuit diagram which shows schematic structure of the modification of a transceiver. It is a timing chart for demonstrating the modification of a determination process. It is a flowchart for demonstrating the modification of a determination process.

DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment when the present invention is applied to a vehicle communication system will be described with reference to the drawings.
(First embodiment)
A communication system according to the present embodiment will be described with reference to FIGS. In FIGS. 3 to 5, the sleep signal, the detection state of the wake-up signal, and the power saving mode are hatched in order to clarify the signals and states.

  As shown in FIG. 1, in the communication system 100, a plurality of slave nodes 10 and one master node 20 are electrically connected via a communication wiring 30 so that signals can be transmitted and received (communicable). In this embodiment, LIN communication is adopted as a communication protocol. The master node 20 transmits a transmission request (header) to the communication wiring 30 (LIN bus), and the slave node 10 transmits data (response) corresponding to the transmission request to the communication wiring 30. The master node 20 also transmits a frame including a header and a response to the communication wiring 30.

  The timing at which the master node 20 transmits the header and the frame to the communication wiring 30 is determined by the LIN schedule. Thereby, it is avoided that different signals collide in the communication wiring 30. Hereinafter, the slave node 10 and the master node 20 are simply referred to as a slave 10 and a master 20, respectively.

  As shown in FIG. 4, a communication signal input / output between the slave 10 and the master 20 is composed of a Lo level and a Hi level. Lo level is dominant and Hi level is recessive.

  Each of the slave 10 and the master 20 has a communication mode for performing LIN communication and a power saving mode with lower power consumption than the communication mode. When each of the slave 10 and the master 20 is in the power saving mode, when a signal instructing activation is input to one of the plurality of slaves 10 from an external host ECU or the like, the slave 10 sends a wake-up signal to the communication wiring. Output to 30. As a result, each of the other slaves 10 and the master 20 performs activation processing, and shifts from the power saving mode to the communication mode.

  When each of the slave 10 and the master 20 is in the communication mode, when the master 20 outputs a sleep signal to the communication wiring 30, each of the plurality of slaves 10 performs a sleep process and shifts from the communication mode to the power saving mode. As will be described later, the master 20 detects a wake-up signal in the sleep process. When the master 20 determines that the wakeup signal is not input, the master 20 shifts from the communication mode to the power saving mode. On the other hand, when it is determined that the wake-up signal is input, the master 20 continues the communication mode.

  As shown in FIG. 1, the master 20 includes a microcomputer 40 and a transceiver 50. The microcomputer 40 and the transceiver 50 are connected via four terminals, a Tx terminal, an EN terminal, a DiffEN terminal, and an Rx terminal. Thereby, the microcomputer 40 is connected to the communication wiring 30 via the transceiver 50. Hereinafter, the microcomputer 40 is simply referred to as the microcomputer 40.

  The microcomputer 40 outputs a header or a frame as a transmission signal to the Tx terminal. The microcomputer 40 outputs an operation mode switching signal for instructing switching of the operation mode of the transceiver 50 to the EN terminal. Further, the microcomputer 40 outputs a detection state switching signal for instructing the transceiver 50 to switch the detection state of the wakeup signal to the DiffEN terminal. A signal (received signal) from the communication wiring 30 and a comparison signal described later are input to the microcomputer 40 via the Rx terminal.

  In the following, the signals at the Tx terminal, EN terminal, DiffEN terminal, and Rx terminal are simply denoted as Tx, EN, DiffEN, and Rx, respectively. The same applies to the drawings.

  As shown in FIG. 2, the transceiver 50 includes a transmitter 51, a receiver 52, a comparison unit 53, and a connection switching unit 54. The comparison unit 53 includes a comparator 55 and a filter 56, and the connection switching unit 54 includes a switch 57 and an AND gate 58. In the power saving mode, the driving of the transmitter 51 of the transceiver 50 is stopped. The same applies to the slave 10, and the transmitter of the slave 10 is stopped in the power saving mode.

  An output terminal of the transmitter 51 is connected to the communication wiring 30 and an input terminal thereof is connected to the Tx terminal. The transmitter 51 is also connected to an EN terminal. An input terminal of the receiver 52 is connected to the communication wiring 30, and an output terminal thereof is connected to the first input terminal of the AND gate 58. The non-inverting input terminal of the comparator 55 is connected to the communication wiring 30 and the inverting input terminal is connected to the Tx terminal. The output terminal of the comparator 55 is connected to the second input terminal of the AND gate 58 through the filter 56 and the switch 57. The switch 57 is provided between the high-level reference potential and the AND gate 58, and between the filter 56 and the AND gate 58, and is connected to the DiffEN terminal. The output terminal of the AND gate 58 is connected to the Rx terminal.

  The transmitter 51 switches to the communication mode or the power saving mode according to the EN voltage level (operation mode switching signal). The transmitter 51 of the present embodiment is in the communication mode when EN is at the Hi level, and is in the power saving mode when at the Lo level. The transmitter 51 outputs a transmission signal to the communication wiring 30 when it enters the communication mode, and stops outputting the transmission signal to the communication wiring 30 when it enters the power saving mode.

  The receiver 52 outputs a reception signal input from the communication wiring 30 to the AND gate 58. The AND gate 58 outputs a Hi level signal when both of the two input signals are at the Hi level, and outputs a Lo level signal when at least one of the two input signals is at the Lo level. As will be described later, when the wake-up signal is not detected, the AND gate 58 is connected to the reference potential via the switch 57. Therefore, when the wakeup signal is not detected, the output of the AND gate 58 is the same as the received signal. That is, Rx is the same as the received signal.

  The reception signal is input to the non-inverting input terminal of the comparator 55 of the comparator 53, and the transmission signal is output to the inverting input terminal. Therefore, when the voltage level of the received signal is lower than that of the transmitted signal, the comparator 55 outputs the Lo level. In contrast, when the received signal has a higher voltage level than the transmitted signal, the comparator 55 outputs a Hi level. Even when the reception signal and the transmission signal have the same voltage level, the comparator 55 outputs the Hi level.

  As described above, when the microcomputer 40 of the master 20 outputs the sleep signal shown in FIG. 3, it is expected that the reception signal and the transmission signal are substantially the same. However, due to signal delay, the input timing of the sleep signal to the non-inverting input terminal and the inverting input terminal is shifted by the delay time. Therefore, although the transmission signal and the reception signal are substantially the same, the comparator 55 may output the Lo level continuously for the delay time instead of the Hi level.

  On the other hand, when the slave 10 outputs the wake-up signal shown in FIG. 3, the transmission signal and the reception signal are substantially different. As shown in FIG. 3, the wake-up signal is a Lo level signal for a specified time longer than the delay time. Therefore, while the wake-up signal is input to the comparator 55, the comparator 55 outputs the Lo level continuously for a specified time. Note that after the slave 10 outputs the wake-up signal, the transmission signal and the reception signal are kept at the Hi level unless the master 20 outputs a header or a frame.

  The filter 56 outputs the Hi level when the input signal is at the Hi level and when the continuous input time of the Lo level input signal is shorter than the specified time. The filter 56 continues to output the Lo level when the continuous input time of the Lo level input signal is longer than the specified time. Therefore, after the microcomputer 40 outputs the sleep signal, the filter 56 continues to output the Hi level when the wakeup signal is not input to the comparator 55. In contrast, when the wakeup signal is input to the comparator 55, the filter 56 continues to output the Lo level. The output of the filter 56 corresponds to a comparison signal.

  As described above, the comparison unit 53 continues to output the Hi level comparison signal when the wakeup signal is not detected, and continues to output the Lo level comparison signal when the wakeup signal is detected. Note that if the set time is a time longer than the delay time and shorter than the specified time, the filter 56 may operate as described below. That is, the filter 56 outputs a high level comparison signal when the input signal is at the high level and when the continuous input time of the low level input signal is shorter than the set time. The filter 56 may continue to output the Lo level comparison signal when the continuous input time of the Lo level input signal is longer than the set time.

  The switch 57 of the connection switching unit 54 connects the reference potential and the AND gate 58 when the voltage level of DiffEN (detection state switching signal) is Lo level. On the contrary, when DiffEN is at the Hi level, the switch 57 connects the filter 56 and the AND gate 58. As a result, when DiffEN is at the Lo level, a reception signal is input to the Rx terminal. When DiffEN is at the Hi level, a signal (comparison signal) corresponding to the detection of the wakeup signal of the comparison unit 53 is input to the Rx terminal.

  As shown in FIGS. 4 and 5, the microcomputer 40 sets DiffEN to Lo level until it starts outputting the sleep signal. Thereby, the microcomputer 40 receives the reception signal from the Rx terminal. Further, the microcomputer 40 switches DiffEN from the Lo level to the Hi level when starting to output the sleep signal. Thereby, the microcomputer 40 receives the comparison signal from the Rx terminal.

  Next, the sleep process of the master 20 will be described based on FIG. 4 and FIG. At the beginning of FIGS. 4 and 5, each of the plurality of slaves 10 and one master 20 is in a communication mode. At this time, EN is fixed at the Hi level, and the transmitter 51 is in the communication mode. DiffEN is fixed at Lo level, Rx is the same as the communication wiring 30 (LIN bus), and the master 20 is in a non-detection state of the wakeup signal. The master 20 outputs a header and a frame to the Tx terminal according to the LIN schedule, and the slave 10 outputs a response corresponding to the header output from the master 20 to its own Tx terminal.

  When the master 20 outputs a sleep signal to perform the sleep process in such a communication state, each slave 10 switches from the communication mode to the power saving mode. When the master 20 starts outputting the sleep signal, it switches DiffEN from the Lo level to the Hi level. As a result, Rx becomes the same as the output (comparison signal) of the comparator 53. As a result, the master 20 shifts to a wake-up signal detection state.

  The microcomputer 40 raises DiffEN from the Lo level to the Hi level, and then determines whether or not Rx changes from the Hi level to the Lo level. That is, the microcomputer 40 determines whether or not a wakeup signal is detected. If the wakeup signal is not detected even after the determination time has elapsed since DiffEN was raised from Lo level to Hi level, the microcomputer 40 switches EN from Hi level to Lo level as shown in FIG. Thereby, the transmitter 51 is switched from the communication mode to the power saving mode. Although not shown in the drawing, when a wakeup signal is detected thereafter, the microcomputer 40 switches EN from the Lo level to the Hi level, and switches DiffEN from the Hi level to the Lo level. As a result, the transmitter 51 switches from the power saving mode to the communication mode, and the master 20 shifts to a non-detection state of the wakeup signal.

  Unlike this, as shown in FIG. 5, immediately after the master 20 outputs the sleep signal, Rx changes from the Hi level to the Lo level, and when the microcomputer 40 detects the wake-up signal, the microcomputer 40 sets DiffEN to Hi. Switch from level to Lo level. Then, EN is maintained at the Hi level. As a result, the transmitter 51 maintains the communication mode, and the master 20 shifts to a non-detection state of the wakeup signal. Note that the above determination time is several times longer than the specified time of the wake-up signal.

  Next, the sleep process of the microcomputer 40 will be described with reference to FIG. However, when performing the sleep process, the master 20 is in the communication mode and EN is at the Hi level.

  First, in step S10, the microcomputer 40 determines whether or not the slave 10 is allowed to sleep. If sleep is permitted, the microcomputer 40 proceeds to step S20. On the other hand, if sleep is prohibited, the microcomputer 40 repeats step S10 and waits until sleep is permitted.

  In step S20, the microcomputer 40 changes DiffEN from the Lo level to the Hi level. As a result, the master 20 enters a detection state of the wakeup signal, and the microcomputer 40 detects the comparison signal via the Rx terminal. After this, the microcomputer 40 proceeds to step S30.

  In step S30, the microcomputer 40 outputs a sleep signal. Thereby, the microcomputer 40 shifts the slave 10 to the sleep mode. After this, the microcomputer 40 proceeds to step S40.

  In step S40, the microcomputer 40 determines whether or not Rx has changed from the Hi level to the Lo level. That is, the microcomputer 40 determines whether there is a wake-up signal. If Rx is at the Lo level, the microcomputer 40 determines that there is a wake-up signal and proceeds to step S50. On the other hand, if Rx is at the Hi level, the microcomputer 40 determines that there is no wake-up signal, and proceeds to step S60.

  In step S50, the microcomputer 40 changes DiffEN from the Hi level to the Lo level. Further, the microcomputer 40 sets EN to Hi level and ends the sleep process.

  In step S60, the microcomputer 40 determines whether or not the determination time has elapsed after switching DiffEN to the Hi level. If the determination time has elapsed, the microcomputer 40 proceeds to step S70. In contrast, if the determination time has not elapsed, the microcomputer 40 returns to step S40. Therefore, if Rx does not change from the Hi level to the Lo level in step S40, the microcomputer 40 repeats steps S40 and S60 until the determination time elapses.

  In step S70, the microcomputer 40 changes EN from the Hi level to the Lo level. As a result, the master 20 shifts from the communication mode to the power saving mode. Thereafter, the microcomputer 40 returns to step S40. In this case, since the determination time has elapsed, the microcomputer 40 repeats steps S40, S60, and S70 until Rx changes from the Hi level to the Lo level.

  Next, operational effects of the communication system 100 according to the present embodiment will be described. As described above, the master 20 starts detecting the wakeup signal when outputting the sleep signal. Therefore, unlike the configuration in which the wakeup signal is detected after the end of outputting the sleep signal is confirmed, a time lag for the confirmation does not occur, and the wakeup signal cannot be detected.

  In the present embodiment, when Rx is at the Hi level, the microcomputer 40 shows an example in which EN is changed from the Hi level to the Lo level when the determination time has elapsed after the DiffEN is switched to the Hi level. However, unlike this, as shown in FIGS. 7 and 8, EN may be changed from the Hi level to the Lo level after a predetermined time, which is shorter than the determination time. This predetermined time is the time required to finish outputting the sleep signal after switching DiffEN to Hi level.

  In the case of this modification, the microcomputer 40 sets EN to Lo level when a predetermined time elapses after switching DiffEN to Hi level. By doing so, the microcomputer 40 switches the transmitter 51 from the communication mode to the power saving mode at the end of outputting the sleep signal. When it is detected that Rx has become Lo level, the microcomputer 40 sets DiffEN to Lo level and EN to Hi level. As a result, the master 20 enters a non-detection state of the wake-up signal, and the transmitter 51 switches to the communication mode. When Rx remains at the Hi level, the microcomputer 40 keeps DiffEN at the Hi level and EN at the Lo level.

  In the case of this modification, the microcomputer 40 performs step S80 instead of step S60 as shown in FIG. The microcomputer 40 determines whether or not a predetermined time has elapsed in step S80, and proceeds to step S70 if it has elapsed, and returns to step S40 if it has not elapsed.

  As described above, in the case of this modification, the transmitter 51 switches to the power saving mode after a predetermined time elapses (the end of outputting the sleep signal). Thereby, the power consumption in the master 20 is reduced.

  Unlike the above modification, the microcomputer 40 may determine the end of the output of the sleep signal instead of determining whether the predetermined time has elapsed. In the case of this further modification, as shown in FIG. 9, the microcomputer 40 performs step S90 instead of step S80. If the microcomputer 40 determines the end of the output of the sleep signal in step S90 and determines that the output has been completed, the microcomputer 40 proceeds to step S70, and if determined that the output has not been completed, returns to step S40.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. The communication system according to the second embodiment has much in common with the above-described embodiment. Therefore, in the following description, description of common parts is omitted, and different parts are mainly described. In the following description, the same reference numerals are given to the same elements as those described in the above embodiment.

  In the first embodiment, the example in which the microcomputer 40 and the transceiver 50 are connected via the four terminals of the Tx terminal, the EN terminal, the DiffEN terminal, and the Rx terminal is shown. On the other hand, the present embodiment is characterized in that the microcomputer 40 and the transceiver 50 are connected via three terminals of a Tx terminal, a DiffEN terminal, and an Rx terminal as shown in FIG.

  Further, as shown in FIG. 11, the transceiver 50 has a mode switching unit 59.

  In the first embodiment, the En terminal is connected to the transmitter 51, and the operation mode of the transmitter 51 is determined according to the EN voltage level (operation mode switching signal). However, DiffEN is input to the transmitter 51 via the mode switching unit 59 as shown in FIG. The operation mode of the transmitter 51 is determined by the output of the mode switching unit 59. The transmitter 51 of this embodiment is in the power saving mode when the output of the mode switching unit 59 is at the Hi level, and is in the communication mode when it is at the Lo level.

  The mode switching unit 59 detects the rising edge and the falling edge of DiffEN. When the rising edge of DiffEN is detected, the mode switching unit 59 starts measuring time. Then, as shown in FIG. 12, when a predetermined time elapses, the mode switching unit 59 outputs Hi level DiffEN to the transmitter 51. As a result, the transmitter 51 is switched to the power saving mode. Further, when the mode switching unit 59 detects the falling edge of DiffEN, the mode switching unit 59 stops the output to the transmitter 51 immediately. As a result, a Lo level signal is input to the transmitter 51, and the transmitter 51 is switched to the communication mode.

  Next, the sleep process of the microcomputer 40 will be described with reference to FIG. In the case of the present embodiment, as shown in FIG. 12, the microcomputer 40 performs steps S10 to S30 described in the first embodiment in the sleep process. However, if the sleep signal is output in step S30, the microcomputer 40 proceeds to step S100.

  In step S100, the microcomputer 40 determines whether or not Rx has changed from the Hi level to the Lo level. If Rx is at the Lo level, the process proceeds to step S110. On the other hand, when Rx remains at the Hi level, the microcomputer 40 repeats Step S100 and waits until a wakeup signal is detected.

  In step S110, the microcomputer 40 changes DiffEN from the Hi level to the Lo level. As a result, the master 20 shifts to the non-detection state of the wakeup signal. Thereafter, the microcomputer 40 ends the sleep process.

  Next, the operation mode switching determination process of the mode switching unit 59 will be described with reference to FIG. First, in step S210, the mode switching unit 59 determines whether or not DiffEN has changed from the Lo level to the Hi level. That is, the mode switching unit 59 determines whether DiffEN has risen. If DiffEN has risen, the mode switching unit 59 proceeds to step S220. On the other hand, if DiffEN has not risen, the mode switching unit 59 repeats step S210 and waits until DiffEN rises. The mode switching unit 59 proceeds to step S220 when the microcomputer 40 performs step S20 shown in FIG.

  In step S220, the mode switching unit 59 determines whether or not a predetermined time has elapsed since DiffEN started up. If the predetermined time has elapsed, the mode switching unit 59 proceeds to step S230. On the other hand, if the predetermined time has not elapsed, the mode switching unit 59 repeats step S220 and waits until the predetermined time elapses. That is, the mode switching unit 59 waits until the sleep signal is output.

  In step S230, the mode switching unit 59 outputs Hi-level DiffEN to the transmitter 51. As a result, the transmitter 51 is switched to the power saving mode. Thereafter, the mode switching unit 59 proceeds to step S240.

  In step S240, the mode switching unit 59 determines whether DiffEN has changed from the Hi level to the Lo level. That is, the mode switching unit 59 determines whether DiffEN has fallen. When DiffEN falls, the mode switching unit 59 proceeds to step S250. In contrast, if DiffEN has not fallen, the mode switching unit 59 repeats step S240 and waits until DiffEN falls. The mode switching unit 59 proceeds to step S250 when the microcomputer 40 performs step S110 shown in FIG.

  In step S250, the mode switching unit 59 stops the output of DiffEN to the transmitter 51. Accordingly, the Lo level is input to the transmitter 51 as the output of the mode switching unit 59, and the transmitter 51 is switched to the communication mode.

  As described above, in the communication system 100 according to the present embodiment, the microcomputer 40 and the transceiver 50 are connected via the three terminals of the Tx terminal, the DiffEN terminal, and the Rx terminal. Therefore, the number of connection terminals between the microcomputer 40 and the transceiver 50 is reduced.

  In addition, the transmitter 51 switches to the power saving mode after a predetermined time has elapsed (when the output of the sleep signal ends). Thereby, the power consumption in the master 20 is reduced.

  The mode switching unit 59 of the present embodiment has shown an example in which the operation mode of the transmitter 51 is switched based on the rise and fall of DiffEN. However, unlike this, the mode switching unit 59 may switch the operation mode of the transmitter 51 based on the sleep signal and DiffEN as shown in FIGS. 15 and 16.

  In the case of this modification, when the mode switching unit 59 detects the end of the output of the sleep signal, it outputs Hi level DiffEN to the transmitter 51. In this way, the transmitter 51 is switched to the power saving mode. When the falling edge of DiffEN is detected, the mode switching unit 59 stops the output to the transmitter 51. As a result, a Lo level signal is input to the transmitter 51, and the transmitter 51 is switched to the communication mode.

  As shown in FIG. 17, the mode switching unit 59 of this modification example performs step S260 instead of step S220 in the operation mode switching determination processing. In step S260, the mode switching unit 59 determines the end of the output of the sleep signal. If the mode switching unit 59 determines that the output has been completed, the process proceeds to step S230.

  The mode switching unit 59 has been described as an example of switching the operation mode of the transmitter 51 by outputting and stopping DiffEN to the transmitter 51. However, unlike this, the mode switching unit 59 may switch the operation mode of the transmitter 51 by generating a control signal corresponding to the voltage level of DiffEN and outputting the control signal to the transmitter 51.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In this embodiment, the example which applied the master 20 of this invention to the communication system of a vehicle was demonstrated. However, the present invention is not limited to the communication system having the slave 10 and the communication wiring 30 in addition to the master 20. However, the slave 10 outputs a wakeup signal in the power saving mode. The master 20 of the present invention may be applied to communication with the slave 10 having this function.

  In this embodiment, an example in which LIN communication is employed as a communication protocol has been described. However, the communication protocol is not limited to the above example, and for example, CAN (registered trademark) communication can be adopted.

DESCRIPTION OF SYMBOLS 10 ... Slave 20 ... Master 30 ... Communication wiring 40 ... Microcomputer 50 ... Transceiver 51 ... Transmitter 52 ... Receiver 53 ... Comparison part 100 ... Communication system

Claims (9)

A master node communicably connected to a plurality of slave nodes (10) via a communication wiring (30),
A transceiver (50) connected to the communication wiring;
A microcomputer (40) connected to the communication wiring via the transceiver,
The transceiver is
A transmitter (51) for outputting a transmission signal output from the microcomputer to the communication wiring;
A receiver (52) for outputting a reception signal input from the communication wiring to the microcomputer;
A comparison unit (53) that outputs a comparison signal obtained by comparing the transmission signal input to the transmitter and the reception signal input to the receiver to the microcomputer;
Each of the plurality of slave nodes and the transceiver has a communication mode and a power saving mode as operation modes,
Each of the plurality of slave nodes has a function of outputting, to the communication wiring, a wake-up signal that causes each of the plurality of slave nodes to shift from the power saving mode to the communication mode.
The microcomputer has a sleep signal that causes each of the plurality of slave nodes to shift from the communication mode to the power saving mode as the transmission signal,
The microcomputer determines whether or not the wake-up signal is output to the communication line based on the comparison signal after the microcomputer starts outputting the sleep signal. The wake-up signal is a Lo level signal for a specified time,
The comparison unit has a Hi level as the comparison signal when the time during which the transmission signal input to the transmitter and the reception signal input to the receiver are continuously different is shorter than the specified time. 2. The master node according to claim 1, wherein a signal is output, and if the signal is equal to or longer than the specified time, the Lo level signal is continuously output as the comparison signal. The transceiver includes an AND gate (58) to which the reception signal of the receiver and the comparison signal of the comparison unit are input and an output terminal is connected to the microcomputer, and the AND gate and the comparison unit. And a switch (57) for switching the connection and the connection between the AND gate and the reference potential of the Hi level,
The microcomputer outputs a switching signal to the switch,
The switch connects the AND gate and the reference potential when the switching signal is one of the Lo level and the Hi level, and the AND when the switching signal is the other of the Lo level and the Hi level. Connecting the gate and the comparison section,
3. The master node according to claim 2, wherein when the microcomputer starts outputting the sleep signal, the switching signal is set to the other of the Lo level and the Hi level to connect the AND gate and the comparison unit. .   4. The microcomputer shifts the transceiver from the communication mode to the power saving mode when the comparison signal is at the Hi level from when the microcomputer starts to output the sleep signal until the determination time elapses. Master node.   The microcomputer switches the switching signal to one of the Lo level and the Hi level when the comparison signal becomes the Lo level when the switching signal is set to the other of the Lo level and the Hi level. The master node according to claim 3 or claim 4. The microcomputer is
When a predetermined time has elapsed after starting to output the sleep signal, the transceiver shifts from the communication mode to the power saving mode,
When the switching signal is the other of the Lo level and the Hi level, when the comparison signal becomes the Lo level, the switching signal is set to one of the Lo level and the Hi level, and the transceiver is The master node according to claim 3, wherein the master node is switched from the power saving mode to the communication mode.   The master node according to claim 1, wherein the microcomputer outputs an operation mode switching signal for determining the operation mode of the transceiver to the transceiver. The transceiver includes a mode switching unit (59) for switching the operation mode of the transmitter based on switching of the voltage level of the switching signal.
The mode switching unit switches the transmitter from the communication mode to the power saving mode after elapse of a predetermined time when detecting the switching of the switching signal from one of the Lo level and the Hi level to the other. 4. The master node according to claim 3, wherein the transmitter is switched from the power saving mode to the communication mode when a switching signal from the other of the Lo level and the Hi level to the other is detected. 5. The transceiver includes a mode switching unit (59) that switches the operation mode of the transmitter based on the end of the output of the sleep signal and the switching of the switching signal from the other of the Lo level and the Hi level to the other. )
When detecting the end of output of the sleep signal, the mode switching unit switches the transmitter from the communication mode to the power saving mode, and switches the switching signal from the other of the Lo level and the Hi level to one. The master node according to claim 3, wherein the transmitter is switched from the power saving mode to the communication mode when a change is detected.

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