JP6391373B2 - Master / slave network device - Google Patents

Description

  The present invention relates to a network device having a master / slave configuration, and more particularly to a master / slave network device in which a master / slave is composed of devices of the same product number.

  As a conventional technique related to a network device having a master / slave configuration, for example, those described in Patent Documents 1 to 3 are known. In Patent Document 1, a master device and a slave device are distinguished in advance, and a technique for setting an ID to a plurality of slave devices is described. A power line and a switch are provided for setting IDs in a plurality of slave devices, and the configuration is high. Patent Document 2 describes a technique for setting an ID in a slave device without providing a switch. Further, Patent Document 3 describes a technique for setting IDs to a plurality of slave LAN devices, and a management data line is provided for setting IDs.

  As a network device having a master / slave configuration, for example, a device in which a plurality of ECUs (Electric Control Units) mounted on a vehicle are connected to a vehicle CAN (Controller Area Network) bus is known. An example of a network device mounted on a vehicle is shown in FIG. In the figure, a network device 90 is shown in which two ECUs 93 and 94 are further connected to a vehicle bus 92 to which a host ECU 91 is connected. Here, the ECU 93 is a master ECU, and the ECU 94 is a slave ECU. The vehicle bus 92 forms a CAN bus.

  The master ECU 93 receives information from the slave ECU 94 via the vehicle bus 92 and integrates this information with its own information to perform a predetermined process. Further, the master ECU 93 exchanges information with the host ECU 91 such as outputting the processing result to the host ECU 91 via the vehicle bus 92. The slave ECU 94 transmits information obtained by control or the like to the master ECU 93 via the vehicle bus 92.

  In the master / slave network device 90 illustrated in FIG. 4, when two ECUs 93 and 94 use the same hardware, software, and setting parameters, it is necessary to recognize that each is a master or a slave. The following four methods are conceivable as a method for making each ECU recognize master or slave.

  Method 1: A master or slave setting value is written in a predetermined parameter of each ECU before shipment, and shipment is performed after writing the parameter. When each ECU is attached to the vehicle, the ECU in which the master setting value is written in the parameter is attached to the vehicle as the master ECU 93, and the ECU in which the slave setting value is written is attached as the slave ECU 94.

  Method 2: After each ECU is shipped and before installation on the vehicle, the dealer sets each ECU as a master or slave, and the master on which the master is set is attached to the vehicle as a master ECU 93, and the slave is set. The attached ECU is attached as a slave ECU 94. This method differs from Method 1 in that the two ECUs are not distinguished from each other at the time of shipment, and can be shipped as ECUs of the same product.

  Method 3: A switch for selecting a master or a slave is installed in each ECU before shipment, and when the switch is attached to a vehicle, the switch is selected as a master or a slave. Thereby, each ECU can recognize whether it is a master or a slave by the electrical signal from a switch. This method is similar to Method 2 in that the two ECUs do not distinguish between the master and the slave at the time of shipment. In this method, however, the master or slave is electrically distinguished using an electrical signal from the switch. Yes.

  Method 4: At least one of an interface connector for connecting the master ECU 93 to the vehicle bus 92 and an interface connector for connecting the slave ECU 94 is provided with a pin for identifying the master / slave. As an example, FIG. 5 shows a case where pins are provided only on the interface connector to which the master ECU 93 is connected. In the figure, a pin 97 is provided only in the interface connector 95 that connects the master ECU 93, and no pin is provided in the interface connector 96 that connects the slave ECU 94. The ECU connected to the interface connector 95 recognizes that it is a master ECU by reading the information on the pin 97, and the ECU connected to the interface connector 96 is a slave because it cannot obtain the pin information. Can be recognized.

  Among the above-described methods 1 to 4, in method 1, the set values of the parameters differ between the ECU used for the master ECU 93 and the ECU used for the slave ECU 94 at the time of shipment. Therefore, it is necessary to manage each ECU separately from a master and a slave after shipment, and it is necessary to distinguish each ECU and attach it to the vehicle. On the other hand, in the methods 2 to 4, there is no distinction between master and slave in each ECU at the time of shipment, and the hardware, software, and set parameters are all the same. Hereinafter, ECUs having the same hardware, software, and setting parameters are referred to as the same product number ECU. In the methods 2 to 4, the distinction between the master and the slave is added to each ECU immediately before or after the ECU is attached to the vehicle.

  In the above methods 2 to 4, since the same product number ECU is used for the master ECU 93 and the slave ECU 94, the ECU manufacturer side and the user side can manage each ECU as a same type of device without distinguishing each ECU. It has the advantage that the management cost can be reduced.

JP 2003-152741 A Japanese Patent No. 4957813 Japanese Patent No. 2959403

  However, in the prior art described in Patent Documents 1 to 3, a master device and a slave device are distinguished in advance, and there is no technique for causing a master and a slave to recognize each using a device having the same product number. There is no description. When the master device and the slave device are distinguished from each other and used in the network device, there is a problem in that the management cost increases because it is necessary to manage each device separately. In Patent Document 1, a power supply line and a switch are required, and in Patent Document 3, a management data line is required, which causes a problem of high cost.

  Further, in the master / slave network device including a plurality of ECUs, the above four methods for recognizing whether each ECU is a master or a slave have the following problems. In Method 1, since the master ECU and the slave ECU are preliminarily distinguished and shipped as different product numbers, it is necessary to manage each separately separately as in Patent Documents 1 to 3, and there is a problem of high cost. .

  The methods 2 to 4 have the advantage that the management cost can be reduced because the same product number ECU is used for the master ECU and the slave ECU, but each has the following problems. First, in method 2, since the dealer needs to set the master or slave in each ECU, a new man-hour is generated at the dealer. There is also a problem that a CAN communication tool is newly required to set each ECU as a master or a slave.

  In the method 3, it is necessary for the dealer to select a master or a slave by operating a switch, and a new man-hour is generated at the dealer. Moreover, since it is necessary to install a switch in each ECU beforehand, it leads to an increase in cost.

  Further, in the method 4, a pin for identifying the master / slave is provided in advance in the interface connector that connects the same product number ECU so that a predetermined difference (for example, whether or not a predetermined voltage is applied) is given between the master and the slave. It is necessary to. Thus, it is necessary to use different connectors for the ECU used for the master and the ECU used for the slave. In addition, it is necessary to prepare one dedicated pin for the interface connector for this application, which increases the number of pins of the connector and leads to an increase in cost.

  Furthermore, in the conventional network device in which both the master ECU and the slave ECU are connected to the vehicle bus, information is transmitted from the slave ECU to the master ECU via the vehicle bus, so the amount of information transmitted to the vehicle bus increases. There is also a problem that the communication load increases.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a master / slave network device capable of automatically recognizing whether each device is a master or a slave using the same product number. And

A first aspect of the master / slave network device of the present invention is a master / slave network device configured by arranging one or more devices serving as slaves with respect to one device serving as a master, The master device and the slave device are devices of the same product number with the same hardware, software, and parameter setting values, each having a master / slave determination unit that automatically recognizes the master or slave, Each bus has two ports and is a backbone bus that supervises the entire system as a bus for transmitting information. A main bus to which one port of the master device is connected, and the other port of the master device And a local bus to which one port of the slave device is connected, and The star / slave determination unit determines whether or not the one port is connected to the main bus by a predetermined process, and when determining that the one port is connected to the main bus, the device becomes the master. The device automatically recognizes this, outputs a slave recognition signal to the other port, and automatically recognizes that the device becomes the slave when the slave recognition signal is input from the one port. .

  According to another aspect of the master / slave network device of the present invention, the master / slave determination unit inputs the information transmitted from the one port to the main bus as the predetermined process. It is characterized by determining that it is connected.

  In another aspect of the master / slave network device of the present invention, the master / slave determination unit performs the main communication when performing predetermined communication with another device connected to the main bus as the predetermined processing. It is determined that it is connected to a bus.

  In another aspect of the master / slave network device of the present invention, each of the devices has a non-volatile memory, and the master / slave determination unit determines whether the device automatically recognizes the master or the slave. When the result of automatic recognition stored in the memory is saved in the memory, the automatic recognition result is read from the memory and the device is automatically recognized as the master or the slave. It is characterized by that.

  In another aspect of the master / slave network device of the present invention, the device includes a gateway unit that outputs a signal input from one of the two ports to the other port, and The gateway unit of the device to be transmitted / receives a signal between another device connected to the main bus and the device to be the slave, and the gateway unit of the device to be the slave is processed inoperatively It is characterized by.

  According to another aspect of the master / slave network device of the present invention, two or more devices serving as the slave are connected by connecting the device serving as the master or another device serving as the slave to the two ports of the device serving as the slave. When the slave recognition signal is input from one of the two ports and connected to the daisy chain, it automatically recognizes that the device is the slave and recognizes the slave to the other of the two ports. A signal is output.

  According to the present invention, it is possible to provide a master / slave network device capable of automatically recognizing whether each is a master or a slave by using devices of the same product number.

It is a block diagram which shows the structure of the master / slave network apparatus of 1st Embodiment of this invention. It is a block diagram which shows the structure of the master / slave network apparatus of 2nd Embodiment. It is a block diagram which shows the structure of the master / slave network apparatus of 3rd Embodiment. It is a block diagram which shows an example of the conventional network device mounted in the vehicle. It is a block diagram which shows an example of the conventional network device by which the pin was provided in the interface connector which connects master ECU.

  A master / slave network device according to a preferred embodiment of the present invention will be described in detail with reference to the drawings. In addition, about each structural part which has the same function, the same code | symbol is attached | subjected and shown for simplification of illustration and description. In the following, a master / slave network apparatus configured by connecting a plurality of ECUs mounted on a vehicle to a CAN bus of the vehicle will be described as an example. However, the present invention is not limited to this.

(First embodiment)
A master / slave network device according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram illustrating a configuration of a master / slave network device 100 according to the present embodiment. The master / slave network device 100 of the present embodiment includes a vehicle bus 110 that is a main bus, a master ECU 120 connected to the vehicle bus 110, and a slave ECU 130 connected to the master ECU 120 via a local bus 140. Yes. The host bus 10 is connected to a host ECU 10 positioned above the master ECU 120 and the slave ECU 130.

  The master ECU 120 and the slave ECU 130 are the same part number ECU with the same hardware, software, and set parameters. Further, the vehicle bus 110 and the local bus 140 together form a CAN bus. Each of the master ECU 120 and the slave ECU 130 has two CAN ports. In FIG. 1, the master ECU 120 has CAN ports 121 and 122, and the slave ECU 130 has CAN ports 131 and 132.

  In the master / slave network device 100 of this embodiment, one CAN port 121 of the master ECU 120 is connected to the vehicle bus 110, and one CAN port 131 of the slave ECU 130 is connected to another one of the master ECU 120 via the local bus 140. It is connected to the CAN port 122.

  By connecting the master ECU 120 and the slave ECU 130 to the vehicle bus 110 and the local bus 140, respectively, in this embodiment, it is possible to automatically recognize that the ECU 120 is the master and the ECU 130 is the slave as follows. .

  First, since the CAN port 121 is connected to the vehicle bus 110, the ECU 120 can input information transmitted to the vehicle bus 110 from the CAN port 121 and can communicate with the host ECU 10. . On the other hand, since the ECU 130 is not connected to the vehicle bus 110 with the CAN ports 131 and 132, information transmitted to the vehicle bus 110 cannot be input and communication with the host ECU 10 is not possible. In the master / slave network device 100 of the present embodiment, it is determined whether or not it is a master depending on whether or not processing via the vehicle bus 110 is possible.

  In order to determine whether or not it is a master, the ECUs 120 and 130 each include a master / slave determination unit 101. The master / slave determination unit 101 determines whether or not the ECU is a master depending on whether or not a predetermined process can be performed via the vehicle bus 110. As described above, there is input of information transmitted to the vehicle bus 110 or communication with the host ECU 10 as described above, and whether or not these processes are possible is determined to determine whether or not the master is a master. be able to.

  Since the CAN port 121 is connected to the vehicle bus 110, the ECU 120 can input information transmitted from the CAN port 121 to the vehicle bus 110. By determining that the information has been input, the ECU 120 The ECU 120 can automatically recognize that it is the master. On the other hand, since the ECU 130 is not connected to the vehicle bus 110 with the CAN ports 131 and 132, information transmitted to the vehicle bus 110 cannot be input, and automatic recognition of the master is not performed. .

  As information transmitted to the vehicle bus 110, for example, information such as a vehicle speed and a brake state can be selected in advance, and when this information is input, it can be determined that the vehicle is a master. Alternatively, when some information is input, it may be determined that the user is the master. Since no information is transmitted to the local bus 140 at the time of activation, the ECU 130 does not input any information and determine that it is the master.

  As a predetermined process via the vehicle bus 110 by the master / slave determination unit 101, it may be determined whether or not communication with the host ECU 10 is possible. As an example, it is determined whether or not the upper ECU 10 has received a predetermined packet output at a predetermined cycle, and when it is determined that it has been received, the ECU 120 is automatically recognized as a master.

  Alternatively, when each master / slave determination unit 101 of each of the ECUs 120 and 130 outputs a predetermined confirmation signal to each CAN port and receives a response signal from the higher-level ECU 10, the ECU 120 is the master. You may make it recognize automatically. Since the confirmation signal output from the master / slave determination unit 101 of the ECU 120 is transmitted from the CAN port 121 to the host ECU 10 via the vehicle bus 110, a response signal is transmitted from the host ECU 10 to determine the master / slave determination of the ECU 120. The unit 101 can input the response signal from the CAN port 121.

  On the other hand, the confirmation signal output from the master / slave determination unit 101 of the ECU 130 cannot be output to the vehicle bus 110 from any of the CAN ports 131 and 132. Further, even if the host ECU 10 outputs a response signal to the vehicle bus 110 in response to the confirmation signal from the ECU 120, the master / slave determination unit 101 of the ECU 130 cannot input it. Therefore, the ECU 130 is not automatically recognized as the master.

  When the ECU 120 is automatically recognized as a master, the master / slave determination unit 101 of the ECU 120 outputs a slave recognition signal to a CAN port 122 different from the CAN port 121 connected to the vehicle bus 110. Since the CAN port 122 is connected to the local bus 140, and the local bus 140 is connected to the CAN port 131 of the ECU 130, the slave recognition signal output to the CAN port 122 of the ECU 120 is sent to the ECU 130 via the local bus 140. Communicated. When a slave recognition signal is input from the CAN port 131, the master / slave determination unit 101 of the ECU 130 automatically recognizes that the ECU 130 is a slave.

  The master / slave determination unit 101 provided in the ECUs 120 and 130 starts the above processing when the vehicle is powered on and the ECUs 120 and 130 are activated. Then, when each of them is automatically recognized by the master or slave, the processing of the master / slave determination unit 101 is terminated. When the ECUs 120 and 130 are automatically recognized by the master and slave, respectively, the results can be stored in the respective memories 102. As the memory 102, for example, NVM (Non-Volatile Memory) may be used. As a result, when the ECUs 120 and 130 are subsequently activated, the automatic recognition results stored in the memory 102 can be read and set as masters and slaves, respectively.

  On the other hand, the automatic recognition result may not be stored in the memory 102 but the master / slave determination unit 101 may automatically perform master / slave recognition each time the ECUs 120 and 130 are activated. In this case, it is not necessary to check whether each ECU was a master or a slave before removal when it is once removed from the vehicle due to a malfunction of the ECU, etc. The effect such as is obtained. For example, even if the ECU 130 is attached to the master position and the ECU 120 is attached to the slave position, the master / slave determination unit 101 automatically recognizes that the ECUs 130 and 120 are the master and slave, respectively.

  As described above, in the master / slave network device 100 of this embodiment, the master ECU and the slave ECU can have the same product number, which reduces the management cost at the time of shipment of the ECU and after shipment. Can be made. In addition, each ECU connected to the vehicle bus 110 and the local bus 140 can be automatically recognized using the master / slave determination unit 101 as a master or a slave. As a result, work by a dealer or the like, special hardware, or the like is unnecessary, and an increase in cost can be suppressed.

  Furthermore, in the master / slave network device 100 of the present embodiment, data transmission / reception between the master ECU 120 and the slave ECU 130 is performed using the local bus 140 instead of the vehicle bus 110, so that the communication of the vehicle bus 110 is performed. An effect of not increasing the load is also obtained. In particular, since the CAN bus is a low-speed bus, it is a great advantage not to increase the load on the vehicle bus by using the local bus.

(Second Embodiment)
A master / slave network device according to a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the master / slave network device 200 of this embodiment. In the master / slave network device 100 of the first embodiment, only the master ECU 120 can communicate directly with the host ECU 10, and the slave ECU 130 cannot communicate directly with the host ECU 10. On the other hand, it is conceivable that the slave ECU 130 also needs direct communication with the host ECU 10. For example, when software is downloaded from the host ECU 10 to each of the ECUs 120 and 130, or when failure information is transmitted, direct communication may be required between the host ECU 10 and each of the ECUs 120 and 130.

  Therefore, in the master / slave network device 200 of the present embodiment, the gateway unit 202 is provided in each of the master ECU 220 and the slave ECU 230. The gateway unit 202 of the master ECU 220 transfers a packet input from one of the two CAN ports 221 and 222 to the other CAN port and outputs it. Thus, direct communication between the host ECU 10 and the slave ECU 230 is performed using the gateway 202 of the master ECU 220.

  More specifically, a packet directly transmitted from the host ECU 10 to the slave ECU 230 is transmitted from the host ECU 10 to the CAN port 221 of the master ECU 220, and is transferred from the CAN port 221 to the CAN port 222 by the gateway 202 of the master ECU 220. The data is transmitted from the port 222 to the CAN port 231 of the slave ECU 230. Further, a packet directly transmitted from the slave ECU 230 to the host ECU 10 is transmitted from the CAN port 231 of the slave ECU 230 to the CAN port 222 of the master ECU 220, transferred from the CAN port 222 to the CAN port 221 by the gateway 202 of the master ECU 220, and CAN. It is transmitted from the port 221 to the host ECU 10.

  Since the master ECU 220 and the slave ECU 230 have the same product number, the gateway unit 202 is also provided in the slave ECU 230. However, since another ECU is not connected to the CAN port 232 of the slave ECU 230, it is necessary to perform processing so that the gateway unit 202 of the slave ECU 230 does not operate.

  In order to enable proper direct communication between the host ECU 10 and the ECUs 220 and 230, it is possible to identify whether the communication packet is transmitted to the ECU 220 or the ECU 230. It is necessary to keep. Therefore, a unique ID corresponding to the ECU 220 or 230 is added to the communication packet. Thereby, when the ID of the master ECU 220 is added to the packet transmitted from the host ECU 10, the master ECU 220 receives the ID. When the ID of the slave ECU 230 is added to the packet transmitted from the host ECU 10, the slave ECU 230 receives this via the gateway unit 202 of the master ECU 220.

  According to the master / slave network apparatus 200 of this embodiment, not only the master ECU 220 but also the slave ECU 230 can directly communicate with the host ECU 10.

(Third embodiment)
A master / slave network device according to a third embodiment of the present invention will be described with reference to FIG. FIG. 3 is a block diagram showing the configuration of the master / slave network device 300 of this embodiment. The master / slave network device 300 of this embodiment is configured by connecting a plurality of slave ECUs 330 to the master ECU 320 in a daisy chain, and in FIG. 3, three slave ECUs 330 are connected. Hereinafter, the three slave ECUs 330 are represented by 330 (1) to 330 (3), respectively.

  In the slave ECU 330 (1), the CAN port 331 (1) is connected to the CAN port 322 of the master ECU 320 via the local bus 341, and the CAN port 332 (1) is connected to the local bus 342. The slave ECU 330 (2) has a CAN port 331 (2) connected to the CAN port 332 (1) of the slave ECU 330 (1) via the local bus 342, and the CAN port 332 (2) connected to the local bus 343. Yes. Further, in the slave ECU 330 (3), the CAN port 331 (3) is connected to the CAN port 332 (2) of the slave ECU 330 (2) via the local bus 343, and nothing is connected to the CAN port 332 (3). .

  Also in this embodiment, the master ECU 320 and the slave ECUs 330 (1) to 330 (3) all use the same part number ECU, and automatically recognize each master / slave using the respective master / slave determination unit 301. . Here, in the slave ECU 330 (1) connected to the master ECU 320, the master / slave determination unit 301 inputs the slave recognition signal output from the master ECU 320 from the CAN port 331 (1) and automatically recognizes that it is a slave. Then, a slave recognition signal is output to the CAN port 332 (1).

  In the slave ECU 330 (2) connected to the slave ECU 330 (1) by the local bus 342, the master / slave determination unit 301 inputs a slave recognition signal from the CAN port 331 (2) and automatically recognizes that it is a slave. Thereafter, the slave recognition signal is output to the CAN port 332 (2). Further, in the slave ECU 330 (3) connected to the slave ECU 330 (2) via the local bus 343, the master / slave determination unit 301 inputs a slave recognition signal from the CAN port 331 (3) to automatically recognize that it is a slave. To do. Thereafter, the slave recognition signal is output to the CAN port 332 (3). However, since another slave ECU is not connected to the CAN port 332 (3), the slave automatic recognition processing is completed.

  As described above, in the master / slave network apparatus 300 according to the present embodiment, when the master / slave determination unit 301 of the slave ECU 330 inputs the slave recognition signal from the CAN port 331, the slave recognition signal is automatically recognized after being recognized as a slave. It is configured to output to the CAN port 332. Thereby, even when a plurality of slave ECUs (hereinafter referred to as n (natural number)) are connected in a daisy chain, all n slave ECUs can automatically recognize that they are slaves. It has become.

  The master / slave network device 300 of the present embodiment can also be configured to have the gateway unit 202 so that each slave ECU 330 can directly communicate with the host ECU 10. In this case, since the master ECU 320 and the n slave ECUs 330 (1) to 330 (n) all use the same part number, all of the master ECU 320 and the n slave ECUs 330 (1) to 330 (n) are used. Has a gateway unit 202.

  Since the n slave ECUs 330 (1) to 330 (n) are sequentially daisy chained, another slave ECU 330 is connected to the CAN port 332 (n) of the nth slave ECU 330 (n). Absent. Therefore, it is necessary to perform processing so that the gateway unit 202 of the nth slave ECU 330 (n) does not operate. Therefore, the gateway unit 202 of the slave ECU 330 (n) is automatically deactivated by automatically recognizing that the nth slave ECU 330 (n) is connected to the final end as follows. can do.

  When the master / slave determination unit 301 of each slave ECU 330 receives a slave recognition signal from the CAN port 331, a predetermined response signal is output to the CAN port 331. The response signal is transmitted from the CAN port 331 to the CAN port 332 of the slave ECU 330 that is the transmission source of the slave recognition signal via the local bus. Therefore, the master / slave determination unit 301 of each slave ECU 330 waits for a response signal from the transmission destination to be returned to the CAN port 332 after outputting the slave recognition signal to the CAN port 332. At this time, if a response signal is not returned even after a predetermined time has elapsed since the slave recognition signal was output, the master / slave determination unit 301 determines that the slave ECU 330 is the last slave ECU 330. When it is determined that the slave ECU 330 is at the final end, processing is performed so that the gateway unit 202 of the slave ECU 330 does not operate.

  In the master / slave network apparatus 300 according to the present embodiment, the master ECU 320 and the n slave ECUs 330 can have the same product number, and can automatically recognize the master or slave respectively. As a result, the management cost at the time of shipment of the ECU and after the shipment can be reduced, and work by a dealer or special hardware or the like becomes unnecessary, and an increase in cost can be suppressed.

  Note that the description in the present embodiment shows an example of the master / slave network device according to the present invention, and the present invention is not limited to this. The detailed configuration and detailed operation of the master / slave network device according to the present embodiment can be appropriately changed without departing from the gist of the present invention.

10 Host ECU
100, 200, 300 Master / slave network device 101, 301 Master / slave determination unit 102 Memory 110 Vehicle bus 120, 220, 320 Master ECU
130, 230, 330 Slave ECU
121, 122, 131, 132, 221, 222, 231, 232, 321, 322, 331, 332 CAN port 140, 341-343 Local bus 202 Gateway unit

Claims (6)

A master / slave network device configured by arranging one or more devices as slaves with respect to one device as a master,
The master device and the slave device are devices of the same product number with the same hardware, software, and parameter setting values, each having a master / slave determination unit that automatically recognizes the master or slave ,
Each of the devices has two ports,
As a bus for transmitting information, a main bus that controls the entire system and is connected to a main bus to which one port of the master device is connected; one of the other port of the master device and the slave device A local bus to which the port is connected,
The master / slave determination unit
It is determined whether or not the one port is connected to the main bus by a predetermined process, and when it is determined that the one port is connected to the main bus, the device is automatically recognized as the master, Outputs a slave recognition signal to the other port;
The master / slave network device, wherein when the slave recognition signal is input from the one port, the device is automatically recognized as the slave. The master / slave determination unit determines that it is connected to the main bus when the information transmitted from the one port to the main bus is input as the predetermined processing. 2. The master / slave network device according to 1. The master / slave determination unit determines, as the predetermined process, that it is connected to the main bus when performing predetermined communication with another device connected to the main bus. The master / slave network device according to claim 1 . Each of the devices has a non-volatile memory,
The master / slave determination unit stores the result of automatic recognition of the device as the master or the slave in the memory, and when the result of automatic recognition is stored in the memory, The master / slave network device according to any one of claims 1 to 3 , wherein a result of automatic recognition is read to automatically recognize that the device is the master or the slave. The devices each have a gateway unit that outputs a signal input from one of the two ports to the other port,
The gateway unit of the master device transmits and receives signals between another device connected to the main bus and the slave device,
The master / slave network device according to claim 1 , wherein the gateway unit of the slave device is processed inoperative. The master device or another slave device is connected to the two ports of the slave device, and two or more slave devices are connected in a daisy chain,
When the slave recognition signal is input from one of the two ports, the device automatically recognizes that the device becomes the slave, and outputs the slave recognition signal to the other of the two ports. The master / slave network device according to claim 1 .

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