JP4407838B2 - Communication master station startup control method - Google Patents

Description

  The present invention relates to a communication master station startup control method applied to a PLC system in which a communication master station and a communication slave station are connected by a bus network.

  A programmable logic controller device (PLC device) having a communication function and one or more I / O terminal devices having a communication function are connected by a bus network, and the PLC device having a communication function is used as a communication master station; Each I / O terminal device having a communication function is a communication slave station, and in the operating state, each of the corresponding communication slave stations shifts the timing relative to the simultaneous broadcast transmission of the polling frame from the communication master station. A PLC system that exchanges various data between a communication master station and each communication slave station by repeating a series of operations for returning a response frame to the communication master station has been known. (For example, refer to Patent Document 1). Here, the “I / O terminal device” is a general term for an input terminal device, an output terminal device, and an input / output terminal device.

  There are various realization forms as a “PLC device having a communication function” to be a communication master station. For example, (1) a building block PLC that can be expanded with various functions in units, with a communication master unit installed, and (2) various functions can be expanded in units. In a building block type PLC with a built-in communication function in the CPU unit itself, (3) In an all-in-one type PLC in which all basic functions necessary for the PLC such as an arithmetic processing unit and an input / output unit are accommodated in one housing. Assuming that the functions are further built in, (4) All-in-one type PLC with all the basic functions necessary for PLC such as arithmetic processing unit and input / output unit accommodated in one housing, with external communication master unit Is done. The building block type PLC includes a type in which each unit is attached to a base board and a type in which each unit is attached to a DIN rail and each unit is connected to each other by a through connector provided in each unit.

Similarly, various implementations exist for the “I / O terminal device having a communication function” to be a communication slave station. For example, (1) an all-in-one type I / O terminal device in which all basic functions necessary for an I / O terminal device such as a terminal block and an input / output circuit are accommodated in one housing. (2) In an all-in-one type I / O terminal device that houses all the basic functions necessary for an I / O terminal device such as a terminal block and input / output circuit in one housing, the communication slave unit is connected via a cable. (3) A communication slave unit is installed in a building block type I / O terminal device in which basic functions required for I / O terminal devices such as terminal blocks and input / output circuits can be expanded in units. (4) Repeaters that exist on the network As long as they have less, it can also be included as an I / O terminal.
JP-A-9-128019

  In the communication master station in this type of PLC system, a startup control method is adopted in which, after startup, a link establishment process is performed to shift to an operating state. In the link establishment process, polling frames are sent to all connectable communication slave stations in a batch or divided into several slave station groups, and based on whether or not a response frame is received from the communication slave station. The connection frame is confirmed. Each communication slave station recognizes the response frame transmission request for itself based on the matching match between the destination address attached to the polling frame and its own set address, and sends the necessary response frame to the timing specific to that slave station. Reply with.

  In general, the address of the communication slave station is manually set on site by a DIP switch or the like. In addition, in a large-scale production line represented by an automobile production line or a liquid crystal production line, the number of communication slave stations becomes enormous, and nearly 60 communication slave stations are connected to one communication master station via a network. It is also assumed that it is connected. For this reason, duplication of communication slave stations based on erroneous address settings is relatively easy, and various countermeasures for slave duplication have been proposed.

  On the other hand, as shown in FIG. 11A, there are many communication slave stations (S1, S2,... Sn) on the network, whereas the communication master station (M1) is basically the same. Since there is only one unit on the network (1: N), and the master station address is not of the nature that is manually set in the field, there is no discussion about countermeasures for duplication of communication master stations. It was.

  However, in recent years, in a large-scale production line represented by an automobile production line or a liquid crystal production line, the laying distance of the network can be several tens of meters, and the network cables constituting the network are complicated in the factory. Since the correspondence between the communication master station and the network cable is difficult to understand, the communication master station of one network is changed between the two networks that are physically adjacent in the factory. Even if the communication master station is already connected due to incorrect connection to the network cable of the network or due to poor visibility in the factory, the same communication master station is mistakenly connected. 11 (b) due to incorrect connection such as connecting to the network cable of the other network. As shown, has led to two or more communication master stations on the same network (M1, M2) state are simultaneously present (hereinafter, referred to as "master plurality") is a concern that occurs discussed.

  In addition, recently, instead of the conventional PLC system that allows the presence of only one communication master station on the network, a PLC system product that allows the presence of two or more communication master stations on the network has appeared in the market. The user may misunderstand that the PLC system product allows the presence of two or more communication master stations on the network, and may connect two or more communication master stations to a network cable corresponding to the same network. Has also been discussed.

  When such master duplication occurs, frames from both communication master stations are mixed or collided on the network, and one of the communication slave stations becomes inoperable. There is also a risk of unexpected behavior in response to the issued polling frame.

  The present invention has been made paying attention to the above-mentioned problems, and the object of the present invention is to provide two or more communication master stations for a PLC system that allows only one communication master station on the network. An object of the present invention is to provide a start-up control method for a communication master station that can reliably prevent malfunction of the PLC system even when a situation of being connected occurs.

  Other objects and operational effects of the present invention will be easily understood by those skilled in the art by referring to the following description of the specification.

  The start-up control method for a communication master station according to the present invention connects a PLC device having a communication function and one or more I / O terminal devices having a communication function through a bus network, and also has a PLC having a communication function. Each device is a communication master station and each I / O terminal device having a communication function is a communication slave station. In the operating state, the corresponding communication slave station responds to the transmission of a polling frame from the communication master station. Is returned to the communication master station, so that the present invention is applied to a PLC system in which various data are exchanged between the communication master station and each communication slave station.

  Here, when sending a frame on a normal bus communication line or a multi-drop line, the polling frame is transmitted by a frame that is not received by all slave stations and is received only by a specific slave station. There are cases. The meaning of “the communication slave station returns a response frame to the communication master station” includes a case where the slave station returns a frame by a general polling selection method or a talk passing method. For example, a communication master station identifies one communication slave station and transmits a polling frame, and one communication slave station that receives the frame returns data, and the communication master station receives the data. Including. It also includes one that repeats one-to-one communication between the communication master station and each communication slave station in order.

  In addition, the communication slaves pass tokens in order, and the slave station that acquired the tokens sequentially transmits response frames to the master station. In each invention described below, the transmission of a polling frame and the meaning of “the communication slave station returns a response frame to the communication master station” are the same.

  More specifically, the method of the present invention is executed prior to the link establishment process in the process of going through the link establishment process after activation and before entering the link establishment process, and there are duplicate communication master stations on the network. The master duplication determination process for determining whether or not to perform is performed, and when it is determined by the master duplication determination process that is executed prior to the link establishment process that the communication master station is duplicated, the process proceeds to the link establishment process. The master duplication determination process executed prior to the link establishment process is a frame transmitted only by the communication slave station prior to the link establishment process. Based on the reception, it is determined that the master is duplicated.

  In another preferred embodiment of the present invention, the master duplication determination process executed prior to the link establishment process is based on the reception of a frame transmitted only by the communication slave station prior to the link establishment process. You may determine with duplication.

  According to such a configuration, when a communication master station is mistakenly connected to a network cable that constitutes a network of an already operating PLC system, the power supply of the additionally connected communication master station is turned on. After being input and started, a communication frame transmitted by the communication slave station is received prior to the link establishment process. Based on this, it is possible to determine master duplication.

  In other words, a polling frame from the communication master station is repeatedly sent to the network cable constituting the network of the already operating PLC system with a predetermined transmission cycle, and a response frame from the communication slave station responding thereto is also sent. Therefore, receiving a communication frame (response frame) transmitted by a communication slave station prior to link establishment processing indirectly means that another communication master station already exists (master duplication). Based on this, it can be determined that the master is duplicated.

  Moreover, according to this determination method, there are at most response frames for the number of connected communication slave stations within the period of the polling frame, and it is only necessary to receive one of them. Although it is a typical determination, there is an advantage that a highly reliable determination result can be obtained from the point of determination algorithm.

  In this determination method, in the communication frame format, the code indicating the content of the frame code part indicating the type of the communication frame corresponds to one of a plurality of known types of codes transmitted only by the communication slave station. This can be realized by determining.

  In another preferred embodiment of the present invention, in addition to the master duplication determination process executed prior to the link establishment process, the master duplication judgment process is executed in parallel with the link establishment process, and the link establishment process When it is determined that the communication master station is duplicated by the master duplication judgment process executed in parallel, the transition to the predetermined master duplication avoidance process is made without going to the operation state, In addition, a master duplication determination process executed in parallel with the link establishment process transmits a polling frame to each of all connectable communication slave stations and stores whether or not a response frame is received from the communication slave station In the connection frame confirmation process for establishment, no response frame reception confirmation can be obtained from any communication slave station. Or it may be determined that the master plurality based on.

  According to such a configuration, in addition to the master duplication determination process executed prior to the link establishment process, the master duplication determination process is executed in parallel with the link establishment process. Even when it is determined by the master duplication determination process that there are duplicate communication master stations, the process proceeds to the predetermined master duplication avoidance process without shifting to the operation state. For this reason, even when a situation occurs in which two or more communication master stations are connected to a PLC system that allows only one communication master station on the network, the malfunction of the PLC system is ensured. Can be prevented.

  In addition, when a PLC system is newly installed or when operation is resumed after maintenance, the network cable constituting one network is mistakenly identified as a system that allows two or more communication master stations, and 2 from the beginning. Even when more than one communication master station is connected, it is possible to reliably determine master duplication in parallel with the link establishment processing.

  That is, when two or more communication master stations are connected to the network from the time of starting the system in this way, there is a high possibility that these communication master stations will be activated simultaneously by turning on the power or operating the reset switch, In that case, in the link establishment process immediately after startup, polling frames are transmitted from each communication master station at almost the same timing, so these polling frames collide on the network and are invalidated, and each communication slave There is a high possibility that the response frame is not transmitted from the station. Therefore, even though a polling frame is transmitted to each of all connectable communication slave stations, no response slave reception confirmation can be obtained from any communication slave station. The existence of a station (master duplication) can be estimated with considerable probability, and based on this, it can be determined that there is a master duplication.

  In addition, in this determination method, a dedicated polling frame transmission process is not provided for the master duplication determination, but the polling frame transmission process executed in the link establishment process is diverted. There is also an advantage that the time required for shifting from the reset state to the operation state is not increased.

  In another preferred embodiment of the present invention, in addition to the master duplication determination process executed prior to the link establishment process, the master duplication judgment process is executed in parallel with the link establishment process, and the link establishment process When it is determined that the communication master station is duplicated by the master duplication judgment process executed in parallel, the transition to the predetermined master duplication avoidance process is made without going to the operation state, In addition, a master duplication determination process executed in parallel with the link establishment process transmits a polling frame to each of all connectable communication slave stations and stores whether or not a response frame is received from the communication slave station In the connection frame confirmation process for establishment, the master duplication is based on the reception of the frame transmitted only by the communication master station. Or it may be determined.

  Even with such a configuration, when a PLC system is newly installed or when operation is resumed after maintenance, the network cable constituting one network is mistakenly identified as a system that permits two or more communication master stations. Even when two or more communication master stations are connected from the beginning, it is possible to reliably determine the master duplication in parallel with the link establishment process.

  In other words, when two or more communication master stations are connected to the network from the time of starting the system in this way, there is a high possibility that these communication master stations will be activated simultaneously by turning on the power or operating the reset switch. However, since each communication master unit still operates asynchronously, the polling frame transmission timing from each communication master station is slightly shifted, and the polling transmitted from each communication master station by another communication master station It is also possible to receive a frame. Therefore, a polling frame is transmitted to each connectable communication slave station, and only the communication master station transmits it in the connection frame confirmation process for establishing a link that stores the presence / absence of reception of a response frame from the communication slave station. The fact that two or more communication master stations exist (master duplication) can be estimated with considerable establishment, and based on this, it can be determined as master duplication.

  Moreover, even in this determination method, a separate dedicated polling frame transmission process is not provided for master duplication determination, but the polling frame transmission process executed in the link establishment process is diverted. There is also an advantage that the time required for shifting from the reset state to the operation state is not increased.

  In another preferred embodiment of the present invention, in addition to the master duplication determination process executed prior to the link establishment process, the master duplication judgment process is executed in parallel with the link establishment process, and the link establishment process When it is determined that the communication master station is duplicated by the master duplication judgment process executed in parallel, the transition to the predetermined master duplication avoidance process is made without going to the operation state, Furthermore, the master duplication determination process executed in parallel with the link establishment process divides all connectable communication slave stations into at least two groups and transmits a polling frame for each group. The frame transmitted only by the communication master station in the connection frame confirmation process for establishing a link that stores whether or not a response frame is received. Based on the reception of the is intended to determine the master plurality, and randomly changed the transmission interval of the polling frame in each group may be one.

  Even with such a configuration, when a PLC system is newly installed or when operation is resumed after maintenance, the network cable constituting one network is mistakenly identified as a system that permits two or more communication master stations. Even when two or more communication master stations are connected from the beginning, it is possible to reliably determine the master duplication in parallel with the link establishment process.

  In other words, as described above, when two or more communication master stations are connected to the network since the system was started, these communication master stations can be activated simultaneously by turning on the power or operating the reset switch. Although each communication master unit still operates asynchronously, the timing of polling frame transmission from each communication master station is slightly shifted, so that each communication master station is connected to another communication master station. It is also possible to receive a polling frame transmitted by. At this time, if the polling frame transmission interval is randomly changed for each group, the collision establishment of polling frames transmitted from each of the two or more communication master stations is reduced, and each communication master station can communicate with other communication master stations. The probability of receiving a master station polling frame is increased. For this reason, the process of determining the master duplication based on the reception of the frame transmitted only by the communication master station acts more effectively, and the master duplication can be more reliably determined.

  In another preferred embodiment of the present invention, the predetermined master duplication avoidance process may be a process of leaving the network. Here, “leave processing from the network” means that the connection of the line is physically disconnected through the switch, and that the frame is physically connected to the line, but no frame such as a polling frame is transmitted. It includes both cases of hibernation.

  According to such a configuration, when the master duplication is determined after the power is turned on and before the link establishment process, no disturbance is caused to the operating PLC system. On the other hand, if it is determined that the master is duplicated during the link establishment process, all communication master stations will be disconnected from the network. Can be avoided.

  As described above, the object of the present invention is that a situation has occurred in which two or more communication master stations are connected to a PLC system that allows only one communication master station on the network. Even in this case, as described above, it is to surely prevent the malfunction of the PLC system. In consideration of such an object, various forms other than the “departure processing from the network” can be adopted as the “predetermined master duplication avoidance process”.

  As another form of the “predetermined master duplication avoiding process”, for example, (1) if it is determined that the master is duplicated before the link establishment process, the process does not proceed to the link establishment process, but later The additionally connected communication master station impersonates a communication slave station, transmits a response frame to the original communication master station and notifies the original communication master station of the master duplication, and (2) during link establishment processing, If it is determined that the master is duplicated, the communication master station sends a predetermined error code to all the communication slave stations at random timing and then arrives first without shifting to the operation state. For example, the operation of all communication slave stations can be suspended by using an error code.

  The present invention viewed from another aspect can also be understood as a PLC system. That is, this PLC connects one PLC device having a communication function and one or more I / O terminal devices having a communication function through a bus network, and the PLC device having the communication function is used as a communication master station. Each I / O terminal device that has a communication function is a communication slave station, and in operation, the corresponding communication slave station returns a response frame to the communication master station in response to transmission of a polling frame from the communication master station. By repeating this series of operations, various data are exchanged between the communication master station and each communication slave station.

  Then, in the communication master station, whether or not there are duplicate communication master stations on the network, which is executed prior to the link establishment process in the process of transitioning to the operation state after starting the link establishment process. When it is determined that there is a duplicate communication master station by the master duplication judgment means for judging whether or not and the master duplication judgment processing executed prior to the link establishment processing, it is determined without proceeding to the link establishment processing. First master duplication avoiding means for shifting to the master duplication avoiding process.

  Furthermore, the present invention viewed from another aspect can be regarded as a master station of a PLC system. That is, this master station connects one PLC device having a communication function and one or more I / O terminal devices having a communication function by a bus network, and the PLC device having the communication function is a communication master station. In addition, each I / O terminal device having a communication function is a communication slave station, and in operation, the corresponding communication slave station sends a response frame to the communication master station in response to transmission of a polling frame from the communication master station. By returning it, the present invention is applied to a PLC system in which various data are exchanged between the communication master station and each communication slave station.

  Then, in this master station, it is executed prior to the link establishment process in the process of going through the link establishment process to the operational state after startup, and whether or not there are duplicate communication master stations on the network. When it is determined that the communication master station is duplicated by the first master duplication judgment means for judging whether the first master duplication judgment process is executed prior to the link establishment process, the process proceeds to the link establishment process. First master duplication avoiding means for shifting to a predetermined master duplication avoiding process without further processing, and further, a first master duplication determining means executed prior to the link establishing process is provided. Prior to processing, master duplication is determined based on reception of a frame transmitted by a communication slave station.

  In addition, the present invention connects one PLC device having a communication function and one or more I / O terminal devices having a communication function by a bus network, and the PLC device having the communication function serves as a communication master station; Each I / O terminal device having a communication function is set as a communication slave station, and in operation, the communication slave station corresponding to the frame transmission from the communication master station returns a response frame to the communication master station. , A communication master station start-up control method applied to a PLC system adapted to exchange various data between the communication master station and each communication slave station, after starting, through link establishment processing, In the process of transitioning to the operational state, this is executed prior to link establishment processing, and there are duplicate communication master stations on the network. The master duplication determination process is performed to determine whether or not the communication master station is duplicated by the master duplication determination process executed prior to the link establishment process, and the process proceeds to the link establishment process. Without being transferred to a predetermined master duplication avoiding process.

  In addition, the PLC system of the present invention connects one PLC device having a communication function and one or more I / O terminal devices having a communication function by a bus network, and also connects the PLC device having the communication function to a communication master. Each I / O terminal device that has a communication function as a communication station is a communication slave station, and in operation, the corresponding communication slave station sends a response frame to the communication master station in response to frame transmission from the communication master station. A PLC system in which various data are exchanged between the communication master station and each communication slave station by returning the data to the communication master station. In the process of transitioning to a state, it is executed prior to link establishment processing, and there are duplicate communication master stations on the network. If it is determined that there is a duplicate communication master station by the master duplication judgment means for judging whether or not and the master duplication judgment processing executed prior to the link establishment processing, the process does not proceed to the link establishment processing. And a first master duplication avoiding means for shifting to a predetermined master duplication avoiding process.

  According to the present invention, when it is determined by the master duplication determination process executed prior to the link establishment process that the communication master station is duplicated, the process proceeds to the predetermined master duplication avoidance process without shifting to the link establishment process. When the communication master station is determined to be duplicated by the master duplication determination process executed in parallel with the link establishment process, the process proceeds to the predetermined master duplication avoidance process without shifting to the operation state. Therefore, even if a situation occurs in which two or more communication master stations are connected to a PLC system that allows only one communication master station on the network, the malfunction of the PLC system is ensured. Can be prevented.

  Hereinafter, a preferred embodiment of a start-up control method for a communication master station according to the present invention will be described in detail with reference to the accompanying drawings.

  A block diagram of the entire PLC system including a communication master station and a communication slave station is shown in FIG. As shown in the figure, this PLC system includes a PLC device 1 having a communication function as a communication master station, and I / O terminal devices 2, 2... Having a plurality of communication functions as communication slave stations. Are connected by a field bus 6 which is a bus network. In the figure, 4 is a repeater that functions as a relay device, and 5 is a termination device that reduces reflection at the end of the fieldbus.

  The illustrated PLC device 1 has a large number of connectors arranged on a backplane (not shown) on which a parallel bus is laid, and a CPU unit, an I / O unit, various other high-performance units, etc. are connected to these connectors. A so-called building block type PLC device that can be arbitrarily attached is employed. In particular, in this example, a “PLC device having a communication function” is configured by attaching a communication master unit to one connector on the backplane. In the figure, among these units, only the CPU unit 20 and the communication master unit 10 are denoted by reference numerals.

  A hardware configuration diagram showing an internal configuration of the communication master unit 10 is shown in FIG. As shown in the figure, the communication master unit 10 includes a communication interface (communication I / F) 101 that functions as a communication physical layer, and a master ASIC 102 that is a circuit that realizes a desired communication function as an LSI. , A buffer area for transmission / reception data transferred to / from the CPU unit 20, a RAM 103 functioning as a calculation work area for the CPU 104, which will be described later, and a CPU 104 that is configured mainly by a microprocessor and controls the entire apparatus. A nonvolatile memory (EEPROM) 105 in which various setting data are stored, an LED display 106 for performing various operation displays, a setting switch 107 used for various setting operations, and a CPU unit Internal bus interface that functions as an interface to the internal bus leading to 20 Esu and an (internal bus I / F) 108.

  As is well known to those skilled in the art, in this type of PLC system, the CPU unit 20 repeatedly executes a common process, an I / O refresh process, a user program execution process, a peripheral service process, and the like. When executing the I / O refresh process, the I / O refresh process is performed not only between the local I / O unit mounted on the backplane but also with the RAM 103 in the communication master unit 10. Execute.

  Specifically, OUT data in the I / O memory (not shown) of the CPU unit 20 is written to the OUT area in the RAM 103 of the communication master unit 10, and the IN data in the RAM 103 is stored in the I / O memory of the CPU unit 20. / O written to the IN area in the memory.

  On the other hand, as will be described in detail later, communication via the field bus 6 is performed between the communication master unit 10 and each I / O terminal device 2 asynchronously with the I / O refresh operation of the CPU unit 20. As a result, a kind of I / O refresh process is also executed between each I / O terminal device 2 and the RAM 103 in the communication master unit 10.

  Specifically, the IN data received from the I / O terminal device 2 is written in the IN area of the RAM 103 in the communication master unit 10, and the OUT data in the OUT area of the RAM 103 is the corresponding I / O terminal device. 2 is transmitted.

  In this way, the I / O refresh process is executed between the I / O memory in the CPU unit 20 and each I / O terminal device 2, 2,... As described above, the CPU unit 20 can handle I / O devices connected to the remotely installed I / O terminal devices 2, 2,.

  Next, FIG. 3 shows a hardware configuration diagram inside the I / O terminal device. As shown in the figure, the I / O terminal device 2 is a master for an LSI that includes a communication interface (communication I / F) 201 functioning as a communication physical layer and a circuit for realizing a desired communication function. An ASIC 202, a CPU 203 mainly composed of a microprocessor for controlling the entire apparatus, a nonvolatile memory (EEPROM) 204 for storing various setting data, and an LED display for displaying various operations Device 205, setting switch 206 used for various setting operations, I / F unit 207 for exchanging data with I / O device 7, and a stabilized DC power supply for the entire apparatus And a DC power supply unit 208 having a transforming function.

  As described in detail later, between the communication master unit 10 and each I / O terminal device 2, the communication master unit 10 is a communication master station, and each I / O terminal device 2 is a communication slave station. I / O data is exchanged through N-master / slave communication.

  Specifically, OUT data received from the communication master unit 10 is sent to an output device of the I / O device 7 via the I / F unit 207 of the I / O terminal device 2. Then, the IN data taken into the I / O terminal device 2 from the input device of the I / O device 7 via the I / F unit 207 is transmitted to the communication master unit 10. A specific example of the output device is a drive system actuator or the like, and a specific example of the input device is a sensor or a switch.

  Next, details of the 1-to-N master / slave communication by the polling / selecting method including the main part of the present invention will be described with reference to FIGS.

  A configuration diagram of the format of the communication frame is shown in FIG. As shown in the figure, the communication frame flowing in the field bus 6 includes a start code portion 401 in which a start code indicating the head of the frame is stored, and a frame in which a frame code for determining the frame type is stored. At least a code part 402, a data part 403 for storing data and the like, and a check code part 404 for storing a check code such as a CRC code and a parity bit are prepared.

  Various communication frames flow on the field bus 6, and there are frames that can be transmitted only by the communication master station and frames that can be transmitted only by the communication slave station. The identification of these frames can be performed based on the contents of the frame code portion 402.

  In this example, the frame that can be transmitted only by the communication master station includes (1) the presence confirmation of the communication slave station, the data transmission to the communication slave station, and the data transmission permission from the communication slave station at the same time. Network synchronization and output data frame (OUT_Frame), which has three roles: synchronization, connection confirmation, output data transmission, (2) existence confirmation of communication slave station, and data transmission permission from communication slave station at the same time Network synchronization frame (TRG_Frame) that has the role of network synchronization and connection confirmation, (3) Output data frame (OUT_NT_Frame), which transmits data to the communication slave station, and has the role of output data transmission, ( 4) Four types of search frames (BEACON_Frame) for notifying the communication slave station of the current transmission rate. There exist.

In addition, frames that can be transmitted only by the communication slave station include (1) a presence response frame (CN_Frame) for making a response to the presence confirmation (OUT_Frame or TRG_Frame) from the communication master station to the communication slave station, and (2) to the master station. There are two types of frames, an input data frame (IN_Frame) for performing the data transmission. Then, a code is determined in advance so that the six types of frames can be distinguished, and code information is stored in the frame code unit 402. Note that there are alternatives for determining the code information. For example, the frame code is a combination of a station type code indicating whether the transmission source is a communication master station or a communication slave station and a content code indicating the frame content. It may be stored in the unit 402.

  In the operation state in this PLC system, in response to the simultaneous broadcast transmission of the polling frame from the communication master station, each of the corresponding communication slave stations returns a response frame to the communication master station with the timing shifted from each other. By repeating the operation, various data are exchanged between the communication master station and each communication slave station.

  Specifically, the communication master station broadcasts polling frames (corresponding to the previously described network synchronization / output data frame (OUT_Frame), network synchronization frame (TRG_Frame), etc.) addressed to all of the first to fourth frames. When broadcast transmission is performed, a response frame (the above-described presence response frame (CN_Frame) or input data frame (CN_Frame) or input data frame (CN_Frame) is transmitted from each slave station in the order of the first slave station, the second slave station, the third slave station, and the fourth slave station. Is equivalent to IN_Frame). At this time, as to how to determine the return timing of each communication slave, for example, as seen in Japanese Patent Laid-Open No. 9-128019, reception of self-addressed data in the network frame for synchronization and output (OUT_Frame) A method of determining a reply timing by adding a basic idle time in consideration of a frame length and a physical delay to timing is conventionally known.

  Note that a destination can be specified for a polling frame transmitted simultaneously. For example, in the above example, if the third frame is excluded from the destination designation, the third slave station that receives the third frame recognizes that it is not a self-addressed polling frame, and does not return a response frame.

  In this way, although the communication master station broadcasts polling frames to all communication slave stations, each communication slave station specifies its own address for the polling frame that is broadcast simultaneously. Since no response frame is sent back unless there exists, this data transmission procedure can be said to be a polling / selecting method substantially.

  Next, the startup control method for the communication master station, which is the main part of the present invention, will be described. As described above, the start-up control method of the communication master station of the present invention is performed in the process of transitioning to the operating state after the start of the link establishment process and prior to the link establishment process and / or the link. In parallel with the establishment process, a master duplication determination process is performed to detect that there are duplicate communication master stations on the network. The master duplication determination process is executed prior to the link establishment process. When it is determined that there is a duplicate, the communication master station moves to a predetermined master duplication avoidance process without going to the link establishment process and the master duplication judgment process executed in parallel with the link establishment process. When it is determined that there is a duplication, the process shifts to a predetermined master duplication avoiding process without shifting to the operation state. That.

  FIG. 6 shows a flowchart (part 1) showing the master station process executed prior to the link establishment process. Note that the processing shown in this flowchart is executed by the CPU 104 in the communication master unit 10 shown in FIG.

  In the figure, when the process is started by turning on the power, the initialization process (step 601) is first executed, the flags and registers are initialized, and a timer for determining the monitoring time is set. The monitoring time is set after being set (step 602). The monitoring time of the timer set here is determined to be sufficiently longer than the polling frame transmission period (transmission time interval) in the operating state of the system.

  Thereafter, until the timer expires (NO in step 604), it is repeatedly determined whether or not any frame is normally received (NO in step 603). Here, whether or not any frame has been received can be determined by detecting the presence or absence of a check code such as a CRC code or a parity bit stored in the check code unit 404 of the frame.

  If it is determined that some frame has been received before the timer expires (NO in step 604) (step 603 YES), a master station duplication detection process is executed (step 605), and a predetermined master duplication detection flag F1 Is set to “1”, a transition to a network leaving process is performed to avoid master duplication (step 606).

  The reason why such a process is adopted is that if another communication master station is already connected to the network to which the communication master station is connected and operated, the monitoring time ends and the timer times out. This is because a polling frame transmitted from an existing communication master station or a response frame transmitted from each communication slave station in response thereto should be received.

  In the network disconnection process, the connection of the line may be physically disconnected through the switch, or it is physically connected to the line but does not transmit any frame such as a polling frame. It is good also as a state.

  In contrast, if no frame is normally received (NO in step 603) and the timer expires (YES in step 604), frame transmission permission processing is executed (step 607), and a predetermined frame transmission permission flag F2 is set. After being set to “1”, a transition to a link establishment process is performed (step 608).

  Such processing is adopted because if no other communication master station is connected to the network to which the communication master station is connected, the polling frame or response will be sent before the monitoring time expires and the timer times out. This is because there is no way to receive the frame.

  According to the above example, if a communication master station is accidentally connected to a network cable that constitutes a network of an already operating PLC system, the additional connected communication master station is powered on. Then, any communication frame that flows on the network is received within a monitoring period that is sufficiently longer than the simultaneous broadcast transmission period of polling frames in the operating state. Duplicates can be determined and a departure from the network can be achieved.

  The "broadcast transmission cycle" here refers to, for example, a communication master station specifying one communication slave station and transmitting a polling frame, and one communication slave station receiving it returns data. If the communication master station receives the data and repeats the one-to-one communication between the communication master station and each communication slave station, the communication that performs the one-to-one communication It also includes the meaning of the period. Also in the embodiments described below, the meaning of “broadcast transmission period” is the same.

  According to such processing of the master station, it is possible to determine master duplication only by detecting the presence of, for example, a check code (corresponding to a CRC code, a parity bit, etc.) attached to all communication frames. There is an advantage that the judgment algorithm is simple and can be immediately introduced into an existing system.

  Next, FIG. 7 shows a flowchart (No. 2) showing the process of the master station executed prior to the link establishment process. The processing shown in this flowchart is also executed by the CPU 104 in the communication master unit 10 shown in FIG.

  In the flowchart of FIG. 7, the difference from the flowchart of FIG. 6 is that the transmission source is between the process of determining whether or not the frame is normally received (step 603) and the master station duplication detection process (step 605). The process (step 609) for determining whether or not it is a master is newly added.

  That is, in this example, even if it is determined that some frame has been received before the timer expires (step 604 NO) (step 603 YES), the master station duplication detection process (step 605) is immediately performed. In addition, it is determined whether or not the transmission source is the master (step 609), and only when it is determined that the transmission source is the master (YES in step 609), the master duplication detection process is performed. (Step 605), and after the predetermined master duplication detection flag F1 is set to "1", the routine proceeds to network disconnection processing to avoid master duplication (Step 606).

  Here, the determination as to whether or not the transmission source is a master is made by determining whether or not a code indicating the content of the frame code part indicating the type of communication frame is a plurality of known types transmitted only by the communication master station. Code ((1) Communication slave station existence confirmation, data transmission to communication slave station, data frame for network synchronization and output (OUT_Frame) for simultaneously permitting data transmission from communication slave station, (2) communication slave Network synchronization frame (TRG_Frame) for simultaneously confirming the existence of the station and permitting data transmission from the communication slave station, (3) Output data frame (OUT_NT_Frame) for performing data transmission to the communication slave station, (4 ) 4 types of search frames (BEACON_Frame) to notify the communication slave station of the current transmission rate It corresponds to one of those) can be achieved by determining the. If the code is composed of a station type code indicating whether the transmission source is a communication master station or a communication slave station and a content code indicating the frame content, the code from the station type code in the frame code part is used. It can also be realized by discrimination.

  Even if the transmission source of the received frame is not the master (transmission source is the slave) (NO in step 609), the monitoring time determined by the timer is set sufficiently longer than the transmission period of the polling frame. Therefore, as long as master duplication occurs, until the timer expires (NO in step 604), a polling frame transmitted from another master is always detected (YES in step 609). After execution (step 605), a shift to the network leaving process is performed (step 606).

  On the other hand, if there is no master duplication, the polling frame transmitted from the master is not received (step 609 NO) and the timer is timed up (step 604 YES). In this case, the frame transmission permission process After (step 607), the transition to the link establishment process is performed (step 608).

  Even in the above example, if the communication master station is mistakenly connected to the network cable that constitutes the network of the PLC system that is already in operation, when the communication master station is turned on and started, After that, since the communication frame transmitted only by the communication master station is received within the monitoring period sufficiently longer than the simultaneous broadcast transmission period of the polling frame in the operating state, the master duplication is determined based on this, and the network Achieving withdrawal from

  According to such processing of the master station, since the polling frame from the communication master station repeatedly flows in the network cable constituting the network of the already operating PLC system with a predetermined transmission cycle, The fact that a communication frame (such as a polling frame) transmitted only by the communication master station is received within a monitoring period sufficiently longer than the simultaneous broadcast transmission period of the polling frame means that another communication master station already exists. (Master duplication) directly means that there is an advantage that the master duplication determination can be more reliably performed based on this.

  Next, FIG. 8 shows a flowchart (No. 3) showing the process of the master station executed prior to the link establishment process. The processing shown in this flowchart is also executed by the CPU 104 in the communication master unit 10 shown in FIG.

  In the flowchart of FIG. 8, the difference from the flowchart of FIG. 6 is that the transmission source is between the determination process of whether or not the frame is normally received (step 603) and the master station duplication detection process (step 605). The process (step 610) for determining whether or not it is a slave is newly added.

  That is, in this example, even if it is determined that some frame has been received before the timer expires (step 604 NO) (step 603 YES), the master station duplication detection process (step 605) is immediately performed. In addition, it is determined whether or not the transmission source is a slave (step 610). Only when it is determined that the transmission source is a slave (YES in step 610), the master duplication detection process is performed. (Step 605), and after the predetermined master duplication detection flag F1 is set to "1", the routine proceeds to network disconnection processing to avoid master duplication (Step 606).

  Here, whether or not the transmission source is a slave is determined by determining whether or not a code indicating the content of the frame code part indicating the type of the communication frame is a plurality of known types transmitted only by the communication slave station in the communication frame format. Code ((1) Presence response frame (CN_Frame) for responding to the presence confirmation (OUT_Frame or TRG_Frame) from the communication master station to the communication slave station, (2) Data frame for input to transmit data to the master station (Corresponding to two types of frames (IN_Frame)). If the code is composed of a station type code indicating whether the transmission source is a communication master station or a communication slave station and a content code indicating the frame content, the code from the station type code in the frame code part is used. It can also be realized by discrimination.

  Even if the transmission source of the received frame is not a slave (transmission source is the master) (NO in step 610), the monitoring time determined by the timer is set sufficiently longer than the transmission period of the polling frame. Therefore, as long as the master duplication occurs, the response frame transmitted from the slave is surely detected until the timer expires (step 604 NO) (step 610 YES), and the master duplication detection process is executed. Then (step 605), the shift to the network leaving process is performed (step 606).

  On the other hand, if there is no master duplication, the response frame transmitted from the slave is not received (step 610 NO), and the timer is timed up (step 604 YES). In this case, the frame transmission permission process After (step 607), the transition to the link establishment process is performed (step 608).

  Even in the above example, if the communication master station is mistakenly connected to the network cable that constitutes the network of the PLC system that is already in operation, when the communication master station is turned on and started, After that, since the communication frame transmitted only by the communication slave station is received within the monitoring period sufficiently longer than the simultaneous broadcast transmission period of the polling frame in the operating state, the master duplication is determined based on this, and the network Achieving withdrawal from

  Moreover, according to such processing of the master station, there are at most response frames for the number of connected communication slave stations within the period of the polling frame, and it is only necessary to receive one of them. Therefore, although it is an indirect determination, there is also an advantage that a highly reliable determination result can be obtained from the viewpoint of the determination algorithm.

  Next, a flowchart showing processing of the master station during link establishment processing is shown in FIG. 9 (first half) and FIG. 10 (second half). As shown in FIG. 5, the master station that is in the process of establishing a link individually transmits a polling frame to each of all connectable communication slave stations, and stores whether or not a response frame has been received from the communication slave station. While performing connection slave confirmation processing for link establishment, master duplication determination processing is performed.

  In FIG. 9, when the link establishment process is started, first, various pre-processes necessary for the link establishment process are executed (step 701), and then a polling frame transmission process (step 702) and a monitoring time are set. A timer set process (step 703) is executed.

  Thereafter, until the timer expires (NO in step 708), it waits for whether or not any frame has been normally received (NO in step 704). Here, whether or not any frame has been received can be determined by detecting the presence or absence of a check code such as a CRC code or a parity bit stored in the check code unit 404 of the frame.

  By the way, in the polling frame transmitted simultaneously by the polling frame transmission processing (step 702), it is possible to specify the destination, while each communication slave station has a function of transmitting a response frame by shifting the timing from each other. It is. For this reason, there is not a single method of polling for connection slave confirmation processing.

  If there are four communication slave stations for one communication master station, (1) broadcast transmission of one polling frame specifying all destinations of the first to fourth slave stations When polling all communication slave stations, (2) the slave stations to be polled are divided into a group including the first and second slave stations and a group including the third slave station and the fourth slave station. When polling all communication slave stations by dividing the two polling frames into two groups and broadcasting the two polling frames specifying the slave stations included in each group in two broadcasts, (3 ) All the communication threads are transmitted by broadcasting the 4 polling frames that specify the address of the 4 slave stations to be polled for each station in 4 batches. When placing a poll the blanking station, etc. is assumed. The example of the communication sequence explanatory diagram described above with reference to FIG. 5 corresponds to the case of (3) above.

  As can be seen from FIG. 5, the master station identifies one communication slave station, transmits a polling frame, and confirms the connection frame based on whether or not a response frame has been received from one communication slave station that has received it. I do. Next, a polling frame is transmitted to another communication slave station, and a connection frame is confirmed based on whether or not a response frame is received from the communication slave station that has received the polling frame.

  The link establishment process is performed by repeating this in order. The meaning of this simultaneous broadcast includes a case in which all slave stations do not perform reception processing and transmit a polling frame that only a specific slave station receives. Even a frame transmitted on a normal bus communication line or a multi-drop line is included in the meaning of “broadcasting” here.

  Here, for convenience of explanation, in the example shown in the flowchart of FIG. 9, as shown in FIG. 5, the polling frame transmission process (step 703) is executed in accordance with the case (3) above. Assuming that

  On this assumption, when the polling frame transmission process (step 702) is executed and the polling frame for specifying the destination of the first slave station is transmitted, if the master is not in a normal state, Before the timer expires (step 708 NO), a response frame from the first slave station is received (step 704 YES, step 705 NO, step 706 YES), and a response reception process (step 707) is executed to obtain the first slave station. The connection confirmation flag F11 corresponding to is set to “1”.

  Thereafter, from the second slave station to the fourth slave station (FIG. 10, step 701 NO), the destination is changed and the polling frame transmission processing is repeated (step 702). In this example, the second to fourth slave stations are repeated. Since all the stations are connected, response reception processing is executed each time (step 707), and the connection confirmation flags F12, F13, and F14 corresponding to the second to fourth slave stations are sequentially set to “1”. Set.

  If any of the first to fourth slave stations is not connected, the timer times out while waiting for receiving a response frame corresponding to the slave station (YES in step 708), so the connection confirmation for the nth slave station is performed. The flag F1n is maintained in the “0” state.

  In this way, when transmission of polling frames to all slave stations is completed (step 709 YES), whether or not response frames have been received from one or more slave stations based on the contents of the connection confirmation flags F11 to F14. If a determination is made (step 710) and an affirmative determination is obtained here (YES in step 710), the link establishment process is terminated and the operation state is shifted.

  In this operational state, as described above, in response to simultaneous transmission of polling frames from the communication master station, the corresponding communication slave stations shift the timing with respect to each other and send response frames to the communication master station. By repeating a series of returning operations, various data are exchanged between the communication master station and each communication slave station.

  Various data exchanges between the communication master station and each communication slave station may be performed by a general polling selection method or a token passing method. For example, the communication master station identifies one communication slave station and transmits a polling frame, and one communication slave station that receives the frame returns data, and the communication master station receives the data. Thus, one-to-one communication may be sequentially performed between the communication master station and each communication slave station. Each communication slave may pass tokens in order, and the slave station that has acquired the token may sequentially send response frames to the master station. The meaning of “each of the communication slave stations returns the response frame to the communication master station with the timing shifted from each other” includes such a method.

  Next, master duplication determination processing for avoiding master duplication performed in parallel with the above link establishment processing will be described.

  When a PLC system is newly installed or when operation is resumed after maintenance, two or more units have been mistakenly identified as a network cable that constitutes one network, or a system that allows two or more communication master stations. It is assumed that the communication master station is connected.

  In this way, when two or more communication master stations are connected to the network from the time of system startup, these communication master stations are likely to be activated at the same time by turning on the power or operating the reset switch. In the link establishment process immediately after startup, polling frames are transmitted from each communication master station at almost the same timing, so these polling frames collide on the network and are invalidated. There is a high possibility that the response frame will not be transmitted. Therefore, even though a polling frame is transmitted to each of all connectable communication slave stations, no response slave reception confirmation can be obtained from any communication slave station. The existence of a station (master duplication) can be estimated with considerable probability, and based on this, it can be determined that there is a master duplication.

  That is, in the flowcharts of FIGS. 9 and 10, when it is determined that a response frame is not received from any slave station (NO in step 710) even though polling frames are transmitted to all slaves (YES in step 709), A process for detecting line abnormality or master duplication (step 712) is executed, and a predetermined flag F3 indicating line abnormality or master duplication detection is set to "1", and then a shift to the network disconnection process is performed. (First process).

  According to such a configuration, when a PLC system is newly installed or when operation is resumed after maintenance, the network cable constituting one network is mistakenly identified as a system that permits two or more communication master stations. Even if two or more communication master stations have been connected from the beginning, in parallel with the link establishment process, the master duplication is reliably determined, and all the duplicating communication master stations are determined. It is possible to voluntarily leave the line and prevent malfunction of the PLC system due to master duplication.

  On the other hand, if two or more communication master stations have been connected to the network since the system was started up, there is a high possibility that these communication master stations will be activated simultaneously by turning on the power or operating the reset switch. However, since each communication master unit operates asynchronously, the polling frame transmission timing from each communication master station is slightly shifted, and each communication master station receives a polling frame transmitted from another communication master station. It is possible to do. Therefore, a polling frame is transmitted to each connectable communication slave station, and only the communication master station transmits it in the connection frame confirmation process for establishing a link that stores the presence / absence of reception of a response frame from the communication slave station. The fact that two or more communication master stations exist (master duplication) can be estimated with considerable establishment, and based on this, it can be determined that there is a master duplication.

  That is, in the flowcharts of FIGS. 9 and 10, if it is determined that a frame from the master station has been received while waiting for a response frame from any slave station (YES in step 705), a master station duplication detection process (step 705) is performed. 711) is executed and the flag F4 indicating the master station duplication detection is set to "1", and then the shift to the network disconnection process is performed (second process).

  Even with such a configuration, when a PLC system is newly installed or when operation is resumed after maintenance, the network cable constituting one network is mistakenly identified as a system that permits two or more communication master stations. Even if two or more communication master stations have been connected from the beginning, in parallel with the link establishment process, master duplication is reliably determined and all duplicate communication master stations are spontaneously Thus, it is possible to prevent the PLC system from malfunctioning due to the master duplication.

  In addition, according to the first process and the second process described above, the polling frame transmission process executed in the link establishment process is used instead of providing a separate dedicated polling frame transmission process for determining the master overlap. Therefore, there is also an advantage that the time required for shifting from the power-on or reset to the operation state is not increased easily.

  In the second processing described above, other communication master stations use other masters by using the accidental transmission timing shift of the polling frames transmitted from each of the two overlapping communication master stations. Although the reception of the polling frame of the station is detected, the transmission period of the polling frame in the link establishment process is changed for each master station in advance, or the timer is set in the timer in the timer setting process (step 703). If the monitoring time data is set to a random value using a random number generator, the transmission timing of polling frames transmitted from each of the two overlapping communication master stations can be positively shifted. Increases the possibility of receiving polling frames when there is a master duplication, and improves the reliability of master duplication judgment. Can.

  That is, when such a configuration is adopted, the establishment of collision of polling frames transmitted from each of two or more communication master stations is reduced, and each communication master station is established to receive polling frames of other communication master stations. As a result, the process of determining master duplication based on the reception of a frame transmitted only by the communication master station acts more effectively, and the master duplication can be more reliably determined.

  According to the present invention, when it is determined by the master duplication determination process executed prior to the link establishment process that the communication master station is duplicated, the process proceeds to the predetermined master duplication avoidance process without shifting to the link establishment process. When the communication master station is determined to be duplicated by the master duplication determination process executed in parallel with the link establishment process, the process proceeds to the predetermined master duplication avoidance process without shifting to the operating state. Therefore, even if a situation occurs in which two or more communication master stations are connected to a PLC system that allows only one communication master station on the network, the malfunction of the PLC system is ensured. Can be prevented.

It is a block diagram of a PLC system including a communication master station and a communication slave station. It is a hardware block diagram of a communication master unit. It is a hardware block diagram of an I / O terminal device. It is a block diagram of the format of a communication frame. It is explanatory drawing which shows an example of a basic communication sequence. It is a flowchart (the 1) which shows the process of the master station performed prior to a link establishment process. It is a flowchart (the 2) which shows the process of the master station performed prior to a link establishment process. It is a flowchart (the 3) which shows the process of the master station performed prior to a link establishment process. It is a flowchart (first half) which shows the process of the master station in process of link establishment. It is a flowchart (second half) which shows the process of the master station in process of link establishment It is a figure for demonstrating the problem of a prior art.

Explanation of symbols

M1 Original communication master station M2 Master station added by mistake 1 PLC device with communication function 2 I / O terminal device with communication function 3 Personal computer 4 Repeater 5 Termination device 6 Fieldbus 7 I / O device 10 Communication master unit 20 CPU unit 101 Communication interface 102 ASIC for master
103 RAM
104 CPU
105 EEPROM
106 LED Display 107 Setting Switch 108 Internal Buzz Interface 201 Communication Interface 202 Slave ASIC
203 CPU
204 EEPROM
205 LED display 206 Setting switch 207 I / F section

Claims (12)

A PLC device having a communication function and one or more I / O terminal devices having a communication function are connected by a bus network, and the PLC device having the communication function is used as a communication master station and has an I / O function. Each of the O terminal devices is a communication slave station. In an operating state, the communication slave station returns a response frame to the communication master station in response to transmission of a polling frame from the communication master station. A communication master station start-up control method applied to a PLC system configured to exchange various data between a station and each communication slave station,
After starting, in the process of going through the link establishment process and going to the operational state, execute the master duplication judgment process to judge whether there are duplicate communication master stations on the network prior to the link establishment process ,
Configured when the communication master station by the master plurality determination process performed in advance of the link establishment process is determined to be present in duplicate, without shifting to the link establishment process, the process proceeds to a predetermined master plurality avoidance process And
Furthermore, the master duplication determination process executed prior to the link establishment process is a master duplication determination based on the reception of the frame transmitted by the communication slave station prior to the link establishment process.
A communication master station start-up control method characterized by the above. In addition to the master duplication determination process executed prior to the link establishment process, the master duplication judgment process is executed in parallel with the link establishment process,
When it is determined by the master duplication determination process that is executed in parallel with the link establishment process that the communication master station is duplicated, the process shifts to the predetermined master duplication avoidance process without shifting to the operation state. Configured,
Further, link master plurality determination process in parallel with the link establishment process Ru is executed, transmits a polling frame addressed to the respective connectable all communication slave station, stores the received presence or absence of a response frame from the communication slave station 2. The communication according to claim 1, wherein in the connection frame confirmation processing for establishment, master duplication is determined on the basis that no response frame reception confirmation can be obtained from any communication slave station. Master station startup control method. In addition to the master duplication determination process executed prior to the link establishment process, the master duplication judgment process is executed in parallel with the link establishment process,
When it is determined by the master duplication determination process that is executed in parallel with the link establishment process that the communication master station is duplicated, the process shifts to the predetermined master duplication avoidance process without shifting to the operation state. Configured,
Further, link master plurality determination process in parallel with the link establishment process Ru is executed, transmits a polling frame addressed to the respective connectable all communication slave station, stores the received presence or absence of a response frame from the communication slave station 2. The communication master station start-up according to claim 1, wherein in the connection frame confirmation processing for establishment, it is determined that the master is duplicated based on reception of a frame transmitted only by the communication master station. Time control method. In addition to the master duplication determination process executed prior to the link establishment process, the master duplication judgment process is executed in parallel with the link establishment process,
When it is determined by the master duplication determination process that is executed in parallel with the link establishment process that the communication master station is duplicated, the process shifts to the predetermined master duplication avoidance process without shifting to the operation state. Configured,
Furthermore, the master plurality determination process in parallel with the link establishment process Ru is executed, all the communication slave stations connectable divided into at least two groups, transmits a polling frame for each group, from the communication slave station In connection frame confirmation processing for establishing a link for storing the presence / absence of reception of the response frame, it is determined that the master is duplicated based on the reception of the frame transmitted only by the communication master station, and the transmission interval of the polling frame The communication master station startup control method according to claim 1, wherein the communication master station is randomly changed for each group. A PLC device having a communication function and one or more I / O terminal devices having a communication function are connected by a bus network, and the PLC device having the communication function is used as a communication master station and has an I / O function. Each of the O terminal devices is a communication slave station. In an operating state, the communication slave station returns a response frame to the communication master station in response to transmission of a polling frame from the communication master station. A PLC system that exchanges various data between a station and each communication slave station,
In the communication master station,
Master duplication determination means that is executed prior to link establishment processing in the process of transitioning to the operating state after starting link establishment processing, and determining whether or not there are duplicate communication master stations on the network. When,
When the master plurality determination means that will be performed prior to the link establishment process is determined and the communication master station is present in duplicate, without shifting to the link establishment process, the first to migrate to a predetermined master plurality avoidance process Master duplication avoidance means,
There has been provided,
Furthermore, the first master duplication determination means that is executed prior to the link establishment process determines master duplication based on the reception of the frame transmitted by the communication slave station prior to the link establishment process. A PLC system characterized by that. A second master duplication determination unit that is executed in parallel with the link establishment process and determines whether or not there are duplicate communication master stations on the network;
When the second master duplication judgment unit executed in parallel with the link establishment process determines that there is a duplicate communication master station, the process proceeds to a predetermined master duplication avoidance process without shifting to the operation state. A second master duplication avoiding means for migrating;
Further, a second master plurality determination unit that runs in parallel with the link establishment process, transmits a polling frame addressed to the respective connectable all communication slave station, the reception whether a response frame from the communication slave station in connection frame confirmation process for storing link establishment, it is to determine the master plurality based on the fact that can not be obtained acknowledgment of the response frame from any communication slave station, it in claim 5, wherein The described PLC system . Second master duplication determination means that is executed in parallel with the link establishment process and determines whether or not there are duplicate communication master stations on the network;
When the second master duplication judgment unit executed in parallel with the link establishment process determines that there is a duplicate communication master station, the process proceeds to a predetermined master duplication avoidance process without shifting to the operation state. A second master duplication avoiding means for migrating;
Further, a second master plurality determination unit that runs in parallel with the link establishment process, transmits a polling frame addressed to the respective connectable all communication slave station, the reception whether a response frame from the communication slave station 6. The PLC system according to claim 5 , wherein, in the connection frame confirmation processing for establishing the link to be stored, the master duplication is determined based on reception of a frame transmitted only by the communication master station. . Second master duplication determination means that is executed in parallel with the link establishment process and determines whether or not there are duplicate communication master stations on the network;
When the second master duplication judgment unit executed in parallel with the link establishment process determines that there is a duplicate communication master station, the process proceeds to a predetermined master duplication avoidance process without shifting to the operation state. A second master duplication avoiding means for migrating;
Further, a second master plurality determination means with the link establishment process Ru are executed in parallel is, the total communication slave stations connectable divided into at least two groups, transmits a polling frame for each group, the communication In connection frame confirmation processing for establishing a link that stores whether or not a response frame is received from a slave station, it is determined that the master is duplicated based on reception of a frame transmitted only by the communication master station, and a polling frame 6. The PLC system according to claim 5 , wherein the transmission interval is randomly changed for each group. A PLC device having a communication function and one or more I / O terminal devices having a communication function are connected by a bus network, and the PLC device having the communication function is used as a communication master station and has an I / O function. Each of the O terminal devices is a communication slave station. In an operating state, the communication slave station returns a response frame to the communication master station in response to transmission of a polling frame from the communication master station. A communication master station applied to a PLC system that exchanges various data between a station and each communication slave station,
The first master that is executed prior to the link establishment process and determines whether or not there are duplicate communication master stations on the network in the process of transitioning to the operation state through the link establishment process after activation. Duplicate determination means;
When the first master plurality determination process that will be performed prior to the link establishment process is determined and the communication master station is present in duplicate, without shifting to the link establishment process, the transition to a predetermined master plurality avoidance process First master duplication avoiding means,
There has been provided,
Furthermore, the first master duplication determination means that is executed prior to the link establishment process determines master duplication based on the reception of the frame transmitted by the communication slave station prior to the link establishment process. A communication master station of a PLC system. Second master duplication determination means that is executed in parallel with the link establishment process and determines whether or not there are duplicate communication master stations on the network;
When the second master duplication judgment unit executed in parallel with the link establishment process determines that there is a duplicate communication master station, the process proceeds to a predetermined master duplication avoidance process without shifting to the operation state. A second master duplication avoiding means for migrating;
Further, a second master plurality determination unit that runs in parallel with the link establishment process, transmits a polling frame addressed to the respective connectable all communication slave station, the reception whether a response frame from the communication slave station in connection frame confirmation process for storing link establishment, it is to determine the master plurality based on the fact that can not be obtained acknowledgment of the response frame from any communication slave station, it in claim 9, wherein The communication master station of the described PLC system . Second master duplication determination means that is executed in parallel with the link establishment process and determines whether or not there are duplicate communication master stations on the network;
When the second master duplication judgment unit executed in parallel with the link establishment process determines that there is a duplicate communication master station, the process proceeds to a predetermined master duplication avoidance process without shifting to the operation state. A second master duplication avoiding means for migrating;
Further, a second master plurality determination unit that runs in parallel with the link establishment process, transmits a polling frame addressed to the respective connectable all communication slave station, the reception whether a response frame from the communication slave station 10. The PLC system according to claim 9 , wherein in the connection frame confirmation process for establishing the link to be stored, it is determined that the master is duplicated based on the reception of the frame transmitted only by the communication master station. Communication master station . Second master duplication determination means that is executed in parallel with the link establishment process and determines whether or not there are duplicate communication master stations on the network;
When the second master duplication judgment unit executed in parallel with the link establishment process determines that there is a duplicate communication master station, the process proceeds to a predetermined master duplication avoidance process without shifting to the operation state. A second master duplication avoiding means for migrating;
Further, a second master plurality determination means with the link establishment process Ru are executed in parallel is, the total communication slave stations connectable divided into at least two groups, transmits a polling frame for each group, the communication In connection frame confirmation processing for establishing a link that stores whether or not a response frame is received from a slave station, it is determined that the master is duplicated based on reception of a frame transmitted only by the communication master station, and a polling frame The communication master station of the PLC system according to claim 9 , wherein the transmission interval is randomly changed for each group.

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