JP2009159025A - Communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To specify the failure of a slave or the disconnection of a communication path relating to the slave, and to continue communication between a master and the slave even under the failure of wiring. <P>SOLUTION: Normally, a master 1 performs communication with a switch SWN=ON, switch SWA=OFF and switch SWB=OFF, and when a failure determination section 10 determines that there is no failure and disconnection, communication is performed between the master 1 and a slave 2 by a line A and a line B without using a GND line. When it is detected that the output of a comparator RmN is Low, the master 1 stops the normal communication and continues communication with the slave 2 via a path constituted of the line A and the GND line. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a communication system that performs current communication between a master and a slave.

  Conventionally, for example, Patent Document 1 proposes a data transmission circuit that enables full-duplex communication with a two-wire system. Specifically, in Patent Document 1, a master and a slave are connected by two lines, and data is superimposed on a DC voltage from the master and transmitted to the slave as a voltage signal via the two lines. A method of transmitting data from a slave as a current signal to the master has been proposed.

In other words, the power line and the communication line are shared by the master and the slave, and current communication is performed with both the power supply and the communication function with a small number of wires. In current communication, the master supplies voltage (power) to the slave, and the current consumed by the slave is increased or decreased according to the communication content of the slave. Then, the master detects the current value consumed by the slave, and compares the current value with a threshold value to decode the communication content sent from the slave.
JP-A-6-69911

  However, in the above conventional technique, in current communication, if one or more of a plurality of slaves are broken due to a short circuit failure, all communication using a current path passing through the slaves is hindered. Therefore, it is unknown whether the wiring is short-circuited or which slave is broken. Therefore, there is a problem that it takes much time to identify a fault location and replace a faulty part.

  Therefore, it is conceivable to multiplex communication paths. However, the merit of current communication is that the master and slave can share the power line and the communication line, and can realize low cost with less wiring. Therefore, if the communication path is multiplexed and the wiring is made redundant, the merit of current communication cannot be utilized.

  In view of the above points, the present invention can identify a slave failure and a disconnection of a communication path related to the slave, and can continue communication between the master and the slave even when a wiring failure occurs. The purpose is to provide a system.

  In order to achieve the above object, according to the first aspect of the present invention, current flows between the master (1) and the slave (2) through a plurality of wirings (A, B, B0, B1, B2, C). A communication system having a GND line common to the master and the slave connected to the GND (3) of each of the master and the slave, wherein the master is connected between each of the plurality of wirings and the GND line. A plurality of GND voltage adjusting units (6, 8, 16) that are connected to generate a potential difference between the wiring and the GND line, and connected between the wirings, between one wiring and the other wiring. Voltage adjustment unit (4, 14) that generates a potential difference between the GND, potential difference information indicating whether or not a potential difference is generated from the voltage adjustment unit between GND and the voltage adjustment unit between wirings, and a wiring potential indicating the potential of each wiring Information and A failure determination unit (10) for determining a failure of any of the slave and the plurality of wirings based on the input potential difference information and the wiring potential information, and any of the plurality of wirings is in failure Each voltage adjusting unit forms a path composed of a non-failed wiring and a GND line among a plurality of wirings, and communication between the master and the slave is continued by the path. It is characterized by.

  According to this, since only the potential difference information and the wiring potential information of the inter-GND voltage adjusting unit and the inter-wiring voltage adjusting unit are determined, it is possible to identify the failure location in a short time. Even if any of the plurality of wirings fails, a communication path that passes through the non-failing wiring and the GND line is formed, so that communication between the master and the slave can be continued.

  According to the second aspect of the present invention, when the failure determination unit determines that there is no failure in either the slave or the plurality of wirings, the plurality of GND voltage adjustment units and the plurality of wirings are used without using the GND line. Thus, communication can be performed between the master and the slave.

  As in the third aspect of the invention, when the failure determination unit determines that there is no failure in either the slave or the plurality of wires, communication is performed without using the GND line. When the load is high, communication can be performed with two systems.

  As described in the fourth aspect of the invention, the inter-wiring voltage adjustment unit includes means for detecting the consumption current consumed by the slave, and generates potential difference information according to the magnitude of the consumption current. It is characterized by.

  In this way, the master can communicate with the slave by acquiring the potential difference information from the consumption current consumed by the slave. In this case, the master can select a communication path according to the potential difference information.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. The communication system according to the present embodiment includes, for example, a slave such as a sensor and a master such as an ECU that performs constant control based on a signal from the sensor. The master and the slave are mounted on a vehicle, for example. Used for vehicle control and the like.

  FIG. 1 is a block diagram of a communication system according to the first embodiment of the present invention. As shown in this figure, the communication system includes a master 1 and a slave 2, and the master 1 and the slave 2 are connected by lines A and B for current communication. The GND 3 of the master 1 and the GND 3 of the slave 2 are connected by a common GND line (body earth or the like in the vehicle) not shown.

  The GND line is a line that is not normally used for communication. Here, “normal time” refers to a time when the communication system can perform the maximum performance using the line A and the line B. On the other hand, the “non-normal time” refers to a case where failure diagnosis is performed or communication is performed with reduced performance.

  Between the lines A and B, the inter-wiring voltage adjustment unit 4 is connected. The inter-wiring voltage adjustment unit 4 includes a switch SWN, a constant potential VN, a resistor 5, and a comparator RmN.

  The switch SWN is connected to the master 1 side of the line A. A constant potential VN and a resistor 5 are directly connected to the switch SWN, and the master 1 side of the line B is connected to the resistor 5. Then, a potential between the constant voltage VN and the resistor 5 is input to one input terminal of the comparator RmN. When the switch SWN is turned on, the potential of the line A becomes a constant potential VN.

  For example, the potential of the line B is input to the other input terminal of the comparator RmN as the reference potential (ref Nm). As long as it is a reference potential, it may be a constant potential generated by a circuit in the master 1. Accordingly, the comparator RmN outputs a Hi or Low signal based on the potential difference between both ends of the resistor 5, that is, the current consumption of the resistor 5.

  In the master 1, an inter-GND voltage adjusting unit 6 is connected between the line A and the GND 3. The GND voltage adjustment unit 6 includes a switch SWA, a constant voltage VA, a resistor 7, and a comparator RmA. The switch SWA, the constant voltage VA, and the resistor 7 are connected in series.

  A potential between the constant voltage VA and the resistor 7 is input to one input terminal of the comparator RmA. For example, a reference potential (ref Am) generated in the master 1 is input to the other input terminal of the comparator RmA. Accordingly, the comparator RmA outputs a Hi or Low signal based on the current consumption of the resistor 7.

  Furthermore, a GND voltage adjusting unit 8 is connected between the line B and the GND 3 in the master 1. The GND voltage adjustment unit 8 includes a switch SWB, a constant voltage VB, a resistor 9, and a comparator RmB. The switch SWB, the constant voltage VB, and the resistor 9 are connected in series.

  A potential between the constant voltage VB and the resistor 9 is input to one input terminal of the comparator RmB, and a reference potential (ref Bm) generated in the master 1 is input to the other input terminal of the comparator RmB, for example. The Thereby, the comparator RmB outputs a Hi or Low signal based on the current consumption of the resistor 9.

  The switch SWN, the switch SWA, and the switch SWB are constituted by transistors, for example, and are controlled by a control circuit (not shown) provided in the master 1. The on / off status of the switch SWN, the switch SWA, and the switch SWB and the outputs of the comparator RmN, the comparator RmA, and the comparator RmB are input to the failure determination unit 10 in the master 1.

  The failure determination unit 10 determines whether the slave 2 is functioning normally by combining the ON / OFF state of the switch SWN, the switch SWA, and the switch SWB and the outputs of the comparator RmN, the comparator RmA, and the comparator RmB. It diagnoses failures and diagnoses the disconnection of line A and line B.

  On the other hand, the transistor TsN and the resistor 11 are connected in series between the line A and the line B in the slave 2. In addition, the slave 2 side of the line A is connected to one input terminal of the comparator RsA, and the potential of the line A is input to the input terminal.

  A reference potential (ref As) generated in the slave 2, for example, the potential of GND3, is input to the other input terminal of the comparator RsA. Thereby, the comparator RsA outputs a Hi or Low signal based on the potential difference between the potential of GND3 and the line A.

  In the slave 2, a transistor TsA and a resistor 12 are connected in series between the line A and GND3. The transistor TsA is used when current communication is performed between the master 1 and the slave 2 using a path formed by the line A and the GND line.

  Further, the slave 2 side of the line B is connected to one input terminal of the comparator RsB, and the potential of the line B is input to the input terminal. A reference potential (ref Bs) generated in the slave 2, for example, the potential of GND3, is input to the other input terminal of the comparator RsB. Accordingly, the comparator RsB outputs a Hi or Low signal based on the potential difference between the potential of GND3 and the line B.

  The outputs of the comparators RsA and RsB are used in the slave 2 as judgment materials for the operation that the slave 2 should take.

  In the slave 2, a transistor TsB and a resistor 13 are connected in series between the line B and GND3. The transistor TsB is used when performing current communication between the master 1 and the slave 2 using a path formed by the line B and the GND line.

  The above is the overall configuration of the communication system according to the present embodiment. Each component in the master 1 and the slave 2 is incorporated into the master 1 and the slave 2 as discrete parts, for example, or packaged on one circuit board and incorporated into the master 1 and the slave 2.

  Next, operation and failure diagnosis in the communication system will be described with reference to the drawings. FIG. 2 is a table showing the determination contents of the failure determination unit 10 based on the ON / OFF state of the switch SWN, the switch SWA, and the switch SWB and the combination of the outputs of the comparator RmN, the comparator RmA, and the comparator RmB. FIG. 3 shows the movement of the slave 2 in a table.

  In the communication system having the above configuration, communication is stopped when all of the switch SWN, the switch SWA, and the switch SWB are turned off. Normally, the master 1 communicates with the slave 2 with the switch SWN = ON, the switch SWA = OFF, and the switch SWB = OFF.

  In this case, when the failure determination unit 10 determines that there is no failure or disconnection, communication is performed between the master 1 and the slave 2 using the line A and the line B without using the GND line. That is, the switch SWA and the switch SWB are turned off and the switch SWN is turned on, and normal communication is performed between the master 1 and the slave 2 using the path formed by the lines A and B.

  When the master 1 detects a communication interruption or the like, the master 1 stops normal communication and performs diagnosis. That is, when the current of the slave 2 is not consumed and the output of the comparator RmN is Low, the failure determination unit 10 specifies the failure location by failure diagnosis.

  Specifically, the failure determination unit 10 of the master 1 sets the switch SWN = OFF, the switch SWA = ON, and the switch SWB = ON. In this case, if communication is received by the comparator RmA, it can be determined that the line A and the line B are normal. At this time, in order to perform communication only on the line A, the transistor TsA is turned on in the slave 2 and the transistor TsB is turned off, so that communication is performed through a path constituted by the line A and the GND line. At this time, since no current flows through the line B, the output of the comparator RmB is Low. Further, the possibility of failure of the transistor TsN of the slave 2 can also be determined.

  On the other hand, when the comparator RmA is disconnected or the communication is received by the comparator RmB, it can be determined that the line A has failed such as disconnection.

  Further, if the switch SWN = OFF, the switch SWA = OFF, and the switch SWB = ON, and communication is received by the comparator RmB, it can be determined that the line B is normal. In this case, in order to perform communication using only the line B, the transistor TsA is turned off in the slave 2 and the transistor TsB is turned on, so that communication is performed using a path constituted by the line B and the GND line. At this time, since no current flows through the line A, the output of the comparator RmA becomes Low.

  When the comparator RmB is disconnected, it can be determined that the line B has failed. When the comparator RmA receives a signal, it can be determined that the line A has failed.

  Note that the ON / OFF state of the switch SWN, the switch SWA, and the switch SWB corresponds to the potential difference information of the present invention. Each output of the comparator RmN, the comparator RmA, and the comparator RmB corresponds to the wiring potential information of the present invention.

  The slave 2 performs communication using one of the line A and the line B depending on the combination of the outputs of the comparator RsA and RsB. Specifically, as shown in FIG. 3, when the output of the comparator RsA is Hi and the output of the comparator RsB is Low, the transistor TsN is turned on, and the lines A and B are used without using the GND line. Normal communication was performed.

  On the other hand, when the output of the comparator RsA is Hi and the output of the comparator RsB is Hi, for example, the line B may be broken. Therefore, the slave 2 turns on the transistor TsA and turns off the transistor TsB to enable communication using the line A and the GND line in order to communicate via a path formed by the line A and the GND line.

  Further, when the output of the comparator RsA is Low and the output of the comparator RsB is Hi, for example, the line A may be broken. Therefore, the slave 2 turns off the transistor TsA and turns on the transistor TsB to enable communication using the line B and the GND line in order to communicate via the path formed by the line B and the GND line.

  When the output of the comparator RsA is Low and the output of the comparator RsB is Low, the communication is normal, but the slave 2 determines that the communication is stopped.

  As described above, when a failure is found by the failure determination unit 10, the master 1 issues a diagnosis when the failure is found or when the master 1 holds the result of finding the failure. Thereby, in the communication system, it is not necessary to inspect which part of the line A, the line B, and the slave 2 is out of order, and the parts can be easily replaced.

  In addition, when a failure in line A or line B is found, a path composed of the non-failed wiring and the GND line of line A and line B is formed, and the master 1 and slave 2 are connected by the path. Current communication continues between them.

  As described above, in the present embodiment, normally two or more lines, that is, the line A and the line B are used to perform highly reliable current communication, and the failure determination unit 10 performs a failure diagnosis to perform slave diagnosis. If an abnormality such as line A is detected, use the third wiring that was not normally used, that is, the GND line, and carry out communication with the slave 2 for the purpose of continuing data transmission and reception. Is a feature.

  Thereby, the redundancy and high reliability of the communication function can be realized by providing the master 1 and the slave 2 with two or more switches SWN, SWA, and SWB without making the entire communication function redundant. When performing failure diagnosis, it is only necessary to perform failure determination based on the on / off state of the switch SWN, switch SWA, and switch SWB and the outputs of the comparator RmN, comparator RmA, and comparator RmB. Can be identified. Even if a failure occurs in the wiring or the like, communication between the master 1 and the slave 2 can be continued by forming a communication path using the GND line.

  Further, since the lines connecting the master 1 and the slave 2 are only the line A, the line B, and the GND line, redundant communication can be handled without increasing the wiring cost.

(Second Embodiment)
In the present embodiment, only different parts from the first embodiment will be described. In the first embodiment, the one-to-one communication system between the master 1 and the slave 2 has been described. However, the present embodiment is characterized in that the master 1 and the slave 2 are one-to-many communication systems.

  FIG. 4 is a block diagram of the communication system according to the present embodiment. As shown in this figure, line A and line B are branched from one master 1 and connected to a plurality of slaves 2. The configuration of each slave 2 is the same as that shown in FIG.

  In the present embodiment, for example, time division communication is performed between the master 1 and the slave 2 so that the communication of each slave 2 does not interfere.

  FIG. 5 is a table showing the determination contents of the failure determination unit 10 by a combination of the switch SWA, the switch SWB, the comparator RmN, the comparator RmA, and the comparator RmB. Even when the master 1 communicates with a plurality of slaves 2 as in the present embodiment, the same failure determination is performed as when the master 1 and the slave 2 communicate one-to-one.

  When the switch SWN = ON, the switch SWA = OFF, and the switch SWB = OFF, and the master 1 is performing time division communication with the plurality of slaves 2, the slave X of the plurality of slaves 2 is normal, If the communication interruption of the slave N among the plurality of slaves 2 is detected by the output of the comparator RmN, a failure of the slave N other than the slave X or one of the lines A and B connected to the slave N has failed. Can be determined.

  Further, when the switch SWN = OFF, the switch SWA = ON, and the switch SWB = ON, if the communication interruption of the slave N is detected by the output of the comparator RmA, either the line A or the line B connected to the slave N is detected. Can be determined to be malfunctioning. Furthermore, if only the slave N can communicate with the output of the comparator RmB, it can be determined that the line A connected to the slave N has failed.

  When the switch SWN = OFF, the switch SWA = OFF, and the switch SWB = ON, if the communication interruption of the slave N is detected by the output of the comparator RmB, it can be determined that the line B connected to the slave N is broken. . If only the slave N can communicate with the output of the comparator RmA, it can be determined that the line A connected to the slave N is broken.

  As described above, even in the one-to-many communication, it is possible to determine the failure of any one of the slaves 2 and the line A and the line B connected to each slave 2.

(Third embodiment)
In the present embodiment, only different portions from the above embodiments will be described. This embodiment is characterized by using a communication line in which one communication line is branched into a plurality.

  FIG. 6 is a block diagram of a communication system according to the present embodiment. As shown in this figure, line B0 is branched into line B1 and line B2. Thereby, a path using line A, line B0, and line B1 is formed between the master 1 and the plurality of slaves 2, and communication between the slave 1 of the plurality of slaves 2 and the master 1 is possible. It becomes.

  The line B1 is connected to the comparator RsB of the slave 1 in the slave 2, and the line B2 is connected to the comparator RsA of the slave 2 in the slave 2.

  Further, a path using the line B0, the line B2, and the line C is formed, and communication between the slave 2 of the plurality of slaves 2 and the master 1 is possible.

  In such a wiring configuration, the inter-wiring voltage adjustment unit 14 is connected between the line B0 and the resistor 5 and between the line C. The inter-wiring voltage adjustment unit 14 includes a switch SW2N, a constant potential V2N, a resistor 15, and a comparator RmN2.

  The switch SW2N is connected to the line B0, and the constant potential V2N and the resistor 15 are directly connected to the switch SW2N. A potential between the constant voltage V2N and the resistor 15 is input to one input terminal of the comparator RmN2. When the switch SW2N is turned on, the potential of the line B0 becomes a constant potential V2N.

  For example, the potential of the line C is input to the other input terminal of the comparator RmN2 as the reference potential (ref N2m). As long as it is a reference potential, it may be a constant potential generated by a circuit in the master 1. Accordingly, the comparator RmN2 outputs a Hi or Low signal based on the potential difference between both ends of the resistor 15, that is, the consumption current of the resistor 15.

  In the master 1, an inter-GND voltage adjusting unit 16 is connected between the line C and the GND 3. The GND voltage adjustment unit 16 includes a switch SWC, a constant voltage VC, and a resistor 17. The switch SWC, the constant voltage VC, and the resistor 17 are connected in series.

  A potential between the constant voltage VC and the resistor 17 is input to one input terminal of the comparator RmC. For example, a reference potential (ref Cm) generated in the master 1 is input to the other input terminal of the comparator RmC. Thereby, the comparator RmC outputs a Hi or Low signal based on the current consumption of the resistor 17.

  Note that the switch SW1N, the constant potential V1N, and the comparator RmN1 shown in FIG. 6 correspond to the switch SWN, the constant potential VN, and the comparator RmN shown in FIG. 1, respectively. The outputs of the comparator RmN1, the comparator RmN2, the comparator RmA, the comparator RmB, and the comparator RmC are respectively input to the failure determination unit.

  FIG. 7 is a table showing the determination contents of the failure determination unit 10 by the combination of each switch and each comparator in the present embodiment. Even when the master 1 communicates with a plurality of slaves 2 as in the present embodiment, the same failure determination is performed as when the master 1 and the slave 2 communicate one-to-one.

  As shown in FIG. 7, when only the switch SW1N is turned on, if communication is possible with the comparator RmN1, normal communication with the slave 1 out of the slaves 2 is possible by the path of the lines A, B1, and B0. When the output of the comparator RmN1 is Low in such a path, it can be determined that there is a failure in any of the paths.

  Further, when only the switch SW2N is turned on, if communication is possible with the comparator RmN2, normal communication with the slave 2 out of the slaves 2 is possible by the path by the lines B0, B2, and C. When the output of the comparator RmN2 is Low, it can be determined that there is a failure in any of the paths.

  A circuit configuration in which the switch SW1N and the switch SW2N are turned off and communication is performed using the GND line. When only the switch SWA and the switch SWB are turned on, the communication is performed through the path of the line A, the line B1, and the line B0. It becomes. In this case, if communication is possible with the comparator RmA and the output of the comparator RmB is Low, it can be determined that the line A is normal. If the output of the comparator RmA is Low, it can be determined that the line A has failed.

  On the other hand, if communication is possible with the comparator RmB, it can be determined that the line A is faulty, the lines B0 and B1 are normal, and the communication is continued through a path constituted by the lines B0, B1 and GND. .

  When only the switch SWB is turned on, communication is performed through the path constituted by the line B0, the line B1, and the GND line as described above. For this reason, the output of the comparator RmA is Low, and it is determined that the line B0 and the line B1 are normal as described above.

  However, in the circuit configuration, when the output of the comparator RmB becomes Low, it is determined that one of the line B0 and the line B1 is out of order. Further, if communication is possible by the comparator RmA, it can be determined that the line A has failed.

  Then, when only the switch SWB and the switch SWC are turned on, communication is performed along the path of the line B0, the line B2, and the line C. In this case, communication is possible with the comparator RmB, and if the output of the comparator RmC is Low, it can be determined that the line B0 and the line B2 are normal. If the output of the comparator RmB is Low, it can be determined that one of the line B0 and the line B2 has failed.

  In addition, when only the switch SWC is turned on, communication is performed through a path constituted by the line C and the GND line. In this case, if the output of the comparator RmB becomes Low, it can be determined that the line C is normal. However, if the output of the comparator RmC is Low, it is determined that the line C is faulty. On the other hand, if communication is possible with the comparator RmB, it is determined that one of the line B0 and the line B2 is out of order.

  As described above, even if the communication system includes a plurality of slaves 2 and the line B0 is branched into the lines B1 and B2, it is possible to determine whether there is a failure in each line.

(Other embodiments)
As the timing when the master 1 performs the failure diagnosis, as in each of the above-described embodiments, in addition to during normal communication, for example, when power is supplied to the communication system, for each period preset in the master 1, external The failure diagnosis may be performed at each timing such as operation from the master to the master 1.

  The circuit configurations of the inter-wiring voltage adjustment units 4 and 14 and the GND voltage adjustment units 6, 8, and 16 shown in the above embodiments are merely examples, and may be configured by other circuits.

  In addition, the number of slaves 2 and the branching of the wiring are also examples shown in the above embodiments, and can be appropriately changed according to the situation where the communication system is used.

  As described above, when the failure determination unit 10 determines that there is no failure in either the slave 2 or each line, communication is performed without using the GND line. It can also be done.

  The inter-wiring voltage adjustment units 4 and 14 are provided with means for detecting the consumption current consumed by the slave, and have other configurations as long as they generate potential difference information corresponding to the magnitude of the consumption current. It doesn't matter. In other words, the inter-wiring voltage adjustment units 4 and 14 may be configured by other than the comparator RmN and the switch SWN.

1 is a block diagram of a communication system according to a first embodiment of the present invention. It is the figure which represented the determination content of the failure determination part by the combination of each switch and each comparator as a table | surface. It is the figure which showed the motion of the slave as a table | surface. It is a block diagram of the communication system which concerns on 2nd Embodiment of this invention. In 2nd Embodiment, it is the figure which represented the determination content of the failure determination part by the combination of each switch and each comparator as a table | surface. It is a block diagram of the communication system which concerns on 3rd Embodiment of this invention. In 3rd Embodiment, it is the figure which represented the determination content of the failure determination part by the combination of each switch and each comparator as a table | surface.

Explanation of symbols

1 Master 2 Slave 3 GND
4, 14 Voltage adjustment unit between wirings 6, 8, 16 Voltage adjustment unit between GND 10 Failure determination unit A, B, C line

Claims (4)

Current communication is performed between the master (1) and the slave (2) via a plurality of wirings (A, B, B0, B1, B2, C), and the GND ( A communication system having a common GND line for the master and the slave connected to 3),
The master
A plurality of GND voltage adjusting units (6, 8, 16) connected between each of the plurality of wirings and the GND line, and generating a potential difference between the wiring and the GND line;
An inter-wiring voltage adjusting unit (4, 14) connected between the wirings and generating a potential difference between one wiring and the other wiring;
The potential difference information indicating whether or not the potential difference is generated from the GND voltage adjusting unit and the wiring voltage adjusting unit and the wiring potential information indicating the potential of each wiring are input, and the potential difference information and the wiring potential are input. A failure determination unit (10) for determining a failure of any of the slave and the plurality of wirings based on the information;
When any of the plurality of wirings is faulty, the voltage adjusting unit forms a path constituted by the wiring that is not faulty among the plurality of wirings and the GND line, and A communication system, wherein communication between the master and the slave is continued.   When the failure determination unit determines that there is no failure in either the slave or the plurality of wirings, the master is controlled by the plurality of GND voltage adjustment units and the plurality of wirings without using the GND line. The communication system according to claim 1, wherein communication is performed between the slave and the slave.   When the failure determination unit determines that there is no failure in either the slave or the plurality of wirings, communication is performed without using the GND line. The communication system according to claim 1 or 2, wherein communication is performed.   The inter-wiring voltage adjustment unit includes means for detecting current consumption consumed by the slave, and generates potential difference information corresponding to the magnitude of the current consumption. Item 4. The communication system according to any one of Items 1 to 3.

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