JP2006217580A - Network system, programmable controller and data sharing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a network system capable of reducing the load of each node when data is shared among a plurality of nodes connected to a network. <P>SOLUTION: In the network system, a plurality of nodes 10 are connected to the network 21 (though illustration is omitted, connection is performed via a switching hub). A frames to be transmitted via the network is initially taken into a communication interface 13d, it is determined whether or not its multicast address (BA) is registered in a multicast reception table 13d', if it is registered, the received frame is transferred to an MPU 13a and a RAM 13c and when it is not registered, the communication interface 13d serves to discard it. Thus, the loads of the MPU 13a and a CPU unit are reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a network system, a programmable controller, and a data sharing method.

  A programmable controller (PLC) is used as a control device for factory automation (FA) installed in a production factory (manufacturing site). This PLC is composed of a plurality of units. In other words, the PLC controls and outputs to the power supply unit of the power supply source, the CPU unit that controls the entire PLC, the input unit that inputs the signals of the switches and sensors attached to the FA production equipment and equipment, and the actuator. Various units such as an output unit for outputting the signal and a communication unit for connecting to a communication network.

  The control in the PLC (CPU unit) takes a signal input from the input unit into the I / O memory of the CPU unit (IN refresh) and performs a logical operation based on a user program written in a pre-registered ladder language (calculation) Execution), the operation execution result is written in the I / O memory, sent to the output unit (OUT refresh), and thereafter, so-called peripheral processing is cyclically repeated.

  By the way, in a system including this PLC, a plurality of communication nodes such as PLCs and other controllers are prepared, connected to each other via a network, and data is shared between the nodes, thereby performing synchronization control and cooperative control. There is. In this case, there is a data link method as a method of sharing data between nodes such as PLC.

  In this data link method, as disclosed in Patent Documents 1 and 2, etc., a data link area is set as a virtual memory in a predetermined area of the memory in each node. In this data link area, a local node area for storing data to be shared and a remote node area for storing data sent from other nodes are prepared. These data link areas are set in a continuous memory area. Then, each node transmits its own data stored in its own node area via the network. The transmitted data is acquired by all other nodes connected to the network, and stored in the corresponding other node area (the other node area for the node that transmitted the acquired data). As a result, all nodes participating in the data link can share data with other nodes by transmitting and outputting data stored in their own node areas.

  As shown in FIG. 1, in a network system in which a plurality of nodes (PLC etc.) 1 are connected to each area to be shared via a network 2 as shown in FIG. For this, a data link area (virtual memory) is set.

  Here, in the figure, a black area is a self-node area that stores data held by itself, and a white area is another node area that stores data held by another node. Data reading / writing will be described with reference to the node (1). The node (1) writes data to the virtual memory (1) allocated to itself. Then, the node (1) automatically transmits to the virtual memory (1) of the node (2) to the node (4) via the network 2 by simultaneous broadcast. Conversely, the node (1) receives the data transmitted from the nodes (2) to (4) in the corresponding virtual memories (2), (3), and (4), respectively. The node (1) reads out the data stored in the virtual memories (1) to (4) and uses it. Thereby, the node (1) has the data held by the other nodes (2) to (4) existing on the network 2 in its own virtual memories (2) to (4). Therefore, the application of the node (1) can acquire and use data held by the other nodes (2) to (4) by accessing the virtual memory. That is, inter-node communication can be realized as if reading and writing to the virtual memory without being conscious of the communication procedure with respect to the other nodes 1. The same can be said for the other nodes (2) to (4). Therefore, the data possessed by each node 1 can be shared by the nodes (1) to (4).

  As a result, all nodes output data stored in their own node areas, so that all nodes participating in the data link can share data with other nodes. This data link function is widely used as a method of sharing data between nodes in a PLC network because data can be exchanged between a plurality of nodes (PLC) without creating a ladder program.

  As described above, each node needs to broadcast data stored in its own node area to the network 2. When the network 2 is a half-duplex system, if a frame to which data stored in the virtual memory is added simultaneously from a plurality of nodes, a collision occurs on the network 2 and a transmission error occurs. Therefore, using a normal token passing system, a node that has acquired a token (transmission right) transmits a frame. The image of this token passing system is as shown in FIG.

  That is, data is transmitted when each node holds a token (transmission right), and the token is passed to the next node. As shown in FIG. 2B, the frame transmitted from each node includes a BA (broadcast address) as a transmission destination address, followed by a virtual memory address, data to be actually transmitted, and a token.

  Data transmitted from each node is allocated to a virtual memory address (sometimes called common memory) space. In the receiving node, a memory map table that associates the address of the virtual memory and the address of the memory in the node is set, and according to this table, the necessary data is received from the data flowing in the network and is taken into the memory in the node. .

Patent No. 3329399 Japanese Patent Laid-Open No. 06-014033

  However, when trying to share data by the above-described data link method, there are the following problems. In the token passing method, communication is performed in half duplex on the communication path, so the communication performance depends on the token circulation. Therefore, the communication performance depends on the total time for each node to transmit retained data and the total number of nodes. That is, as shown in FIG. 2A, the node (1) broadcasts and transmits the frame 1 storing the data stored in the area (1) of its own virtual memory, and then the node (2) receives the token. And frame 2 storing the data stored in the area (2) of the own node area is transmitted by broadcast, and then the node (3) acquires the token and stores it in the area (3) of the own node area. The frame 3 storing the stored data is transmitted by broadcast, and then the node (4) acquires the token and transmits the frame 4 storing the data stored in the area (4) of the own node area by broadcast. Then take one round. Therefore, the communication cycle time of one time is the sum of the time when the four nodes transmit frames, and the communication cycle time increases when the number of nodes increases or the data capacity of the own node area to be transmitted increases.

  Many applications often do not require all the data flowing on the network, and many of the communication cycle times are waiting times that are meaningless for the receiving node.

  That is, when attention is paid to the node (1), the data to be transmitted stored in the own node area (1) is not necessarily required by all the other nodes (2) to (4). That is, the data stored in the own node area is data that is required by at least one node 1 among other nodes that perform data links. The other nodes that have received the data transmitted by broadcasting store all the received data in the areas of the corresponding other node areas, but the other nodes 1 normally use a part of the received data. It becomes.

  As an example, if four nodes 1 have data links, the data sent from node (1) includes only data used by node (2) and only node (3). It is assumed that data to be used (data for node (3)) and data to be used by all the nodes (2) to (4) are included. In this case, the node (1) transmits the data stored in the area (1) of its own node area in the virtual memory, but the node (2) receiving the data naturally receives the node (3 ) Data is not used. There are many data received by the node (1) from other nodes that are not required by the node (1).

  As described above, even if data that is received but not used is stored in the memory, it is a wasteful use of the memory, and not only is the data storage area required more than necessary, but also transmission / reception of unused data (communication amount) Increase) and memory read / write operations are required, which is complicated.

  In addition, in order to reduce the memory capacity, each node does not store all received data link data in the memory, but extracts only the necessary data and stores it in the memory. It can also be discarded. However, since all frames transmitted by broadcast are transferred to the MPU or RAM inside the receiving node regardless of the contents, the data unnecessary for the receiving node is the data necessary for the MPU. Whether or not unnecessary data is discarded. Therefore, an extra load is generated on the MPU.

  According to the present invention, when data is shared among a plurality of nodes connected to a network, the load on each node is reduced, and the time required for data transmission / reception processing to be shared in a short time (one round) It is an object of the present invention to provide a network system, a programmable controller, and a data sharing method that can shorten a communication cycle time).

  A network system according to the present invention is a network system capable of sharing data among a plurality of nodes on a network in which a plurality of nodes are connected via a switching hub, and the plurality of nodes are connected to the switching hub. A communication interface capable of transmitting and receiving data by multicast communication in a full-duplex communication system, a virtual memory storing data to be transmitted to other nodes in order to share data among a plurality of nodes, and the virtual A multicast address for transmitting data on the memory to another node and a table associating transmission data are provided. Of the plurality of nodes, the communication interface of the transmission side node has a function of transmitting data by multicast together with a multicast address based on the table. Of the plurality of nodes, the receiving node has multicast address information storage means for storing a multicast address of data required by itself among data transmitted by multicast from other nodes. When the communication interface of the receiving node receives the data transmitted by multicast, the communication interface determines whether or not the data is necessary based on the multicast address stored in the multicast address information storage means. Incorporates only the data required by the node into the node and discards data that is not required by the node. Shared data with other nodes.

  Further, when the association between the multicast address and the transmission data constituting the table is composed of a plurality of sets and a frame for transmission is configured in units of the set, the transmission is performed during one cycle of the transmission timing of the own node. The same identification number is added to a plurality of frames for transmission, and when the plurality of frames are received at the receiving node, if the plurality of frames have different identification numbers, a discard process is performed. It is good to configure.

  The node on the receiving side stores and holds the information for identifying the node on the transmitting side that transmits the data required by itself and the address information of the virtual memory on the transmitting side in the node on the transmitting side. Based on this, it is possible to make an inquiry about the multicast address to the transmitting side node and to make an income.

  The programmable controller according to the present invention includes a communication interface capable of transmitting and receiving data by multicast communication using a full duplex communication method via a switching hub, and data to be transmitted to other nodes in order to share data among a plurality of nodes. Of the virtual memory to be stored, a table in which transmission data is associated with a multicast address for transmitting the data on the virtual memory to another node, and data transmitted by multicast from another node, self is necessary Multicast address information storage means for storing the multicast address of the data to be stored. Then, the communication interface receives the data transmitted by multicast together with the multicast address based on the table, and receives the data transmitted by multicast, the communication interface determines itself based on the multicast address stored in the multicast address information storage means. It is determined whether or not the data is necessary, and only the data required by itself is taken into the node, and if the data is not required by itself, the data is discarded.

  The data sharing method according to the present invention is a data sharing method in a network system capable of sharing data between a plurality of nodes on a network in which a plurality of nodes are connected via a switching hub. Then, the plurality of nodes transmit to the other nodes in order to share data between the plurality of nodes and a communication interface capable of transmitting and receiving data by multicast communication using the full duplex communication method via the switching hub. Assume a configuration including a virtual memory in which data is stored, a table in which transmission data is associated with a multicast address for transmitting data on the virtual memory to another node. Then, the communication interface of the transmission side node among the plurality of nodes transmits the multicast data together with the multicast address based on the table, and the reception side node among the plurality of nodes transmits the multicast data from the other nodes by multicasting. Among the data to be transmitted, it has a multicast address information storage means for storing the multicast address of the data required by itself, and when the communication interface of the node on the receiving side receives the data transmitted by multicast, Based on the multicast address stored in the multicast address information storage means, it is determined whether or not the data is necessary for itself, and only the data required by itself is taken into the node, and if the data is not required by itself, it is discarded. Execute processing That. The transmitting node shared data with the receiving node by cyclically transmitting data at the transmission timing of the own node.

When the association of the multicast address and transmission data constituting the table is composed of a plurality of sets, and a frame for transmission is configured in units of the set, a plurality of transmissions are performed during one cycle of the transmission timing of the own node. Send the frame with the same identification number,
When the plurality of frames are received and the identification numbers of the plurality of frames are different, the receiving node executes a discarding process. In addition, the receiving side node stores and holds the information for identifying the transmitting side node that transmits the data required by itself and the address information of the transmitting side virtual memory in the transmitting side node. Based on the information, a multicast address inquiry is made to the transmitting side node, and a process for obtaining income is executed.

  According to the present invention, since full duplex communication is performed, each node can transmit a frame at an arbitrary timing. Since it is a full duplex type, collision (collision) does not occur, so various services can be mixed on the network. Furthermore, in the present invention, it is not necessary for each node to perform processing such as acquisition of a transmission right such as a token, and protocol implementation is facilitated.

  It is possible to perform processing (data transfer, memory storage, etc.) using only the registered multicast address as a normal received frame at the communication interface of the receiving side node using multicast as the communication method. As a result, in the present invention, unnecessary multicast data flowing on the network can be filtered, and an unnecessary load is not given to the receiving node.

  The memory map of the virtual memory newly devised by this method has an independent address system for each node, so it can be used without being affected by the usage conditions of other nodes, and memory duplication does not occur Therefore, the degree of freedom of memory map setting is improved.

  When data that requires simultaneity is divided into a plurality of frames and transmitted, the same identification number is added to a plurality of frames transmitted in the same communication cycle time, and the plurality of frames are transmitted. When the frame is received as a regular frame and the identification numbers of the plurality of regular frames are different, the discarding process may be performed. This guarantees simultaneity.

  In addition, the reception side node stores and holds information for identifying a transmission side node that transmits data required by itself, and address information of the transmission side virtual memory in the transmission side node. Based on the obtained information, a multicast address can be inquired to the transmitting side node and acquired.

  In the present invention, when data is shared between a plurality of nodes connected to the network, the receiving node determines only a frame that is required by the communication interface as a regular frame and performs a predetermined process, Since unnecessary items are discarded on the communication interface side, the load on each node can be reduced. Since communication is performed in a full-duplex manner, each node transmits data at an arbitrary timing, and transmission from multiple nodes is permitted at the same time. Transmission / reception processing can be performed.

  FIG. 3 shows an example of a network configuration showing an embodiment of the present invention. As shown in FIG. 3, a network system is constructed in which two PLCs 10 are connected to a switching hub 20 serving as a repeater via a network cable 21 so that data can be transmitted and received via the switching hub 20. ing. In the figure, an example in which two PLCs 10 are connected is shown for the sake of convenience, but more PLCs or nodes other than the PLC may be connected.

  The PLC 10 is configured by connecting various units such as a power supply unit 11, a CPU unit 12, a communication unit 13, an input unit 14, an output unit 15, and a special function unit 16. Each unit is connected by a backplane bus, and a system for controlling a control target is configured by transmitting and receiving data in real time via the backplane bus. Of course, the units constituting the PLC 10 are not limited to those shown in the figure, and may be appropriately increased or decreased as necessary.

  The power supply unit 11 supplies power to each unit group constituting the PLC 10. The CPU unit 12 stores a control program and has a function of controlling the system in a programmable manner. The control program is executed based on the IN data fetched from the controlled object via the input unit 14 and the like, and the obtained calculation result (OUT data) is sent to the output unit 15. As an example, the input unit 14 acquires the state (IN data) of an input device such as a limit switch or a sensor. The acquired IN data is transferred to the CPU unit 12 at a predetermined timing (during IN refresh). The output unit 15 causes the connected control target to change based on the OUT data received from the CPU unit 12. For example, by turning on the switch, an external electric device is operated (electrical change), and a pneumatic valve is opened and closed (mechanical change). The special function unit 16 includes a unit that executes a control program in sharing with the CPU unit 12 and a motion controller that controls a motor or the like in response to a command from the CPU unit 12.

  The communication unit 13 communicates with other devices (nodes) via the network cable 21. In this embodiment, since Ethernet (registered trademark) is used as the network, the communication unit 13 is a unit corresponding to Ethernet (registered trademark). By communicating with PLCs that are physically separated by the communication unit 13, it is possible to perform control in cooperation with the remote PLC 10.

  FIG. 4 shows an internal configuration of the CPU unit 12 and the communication unit 13 constituting the PLC 10. The CPU unit 12 is a unit that controls the entire PLC 10. The hardware configuration includes an MPU 12a that is a microprocessor that controls the operation of the entire CPU unit 12, a ROM 12b that is a memory for storing system firmware, and a system work. RAM 12c, which is used as a memory, user memory (UM) 12d, which is a memory for storing user programs, ASIC 12e for a control program that performs user program (command) execution processing / communication unit interface processing / memory access bus arbitration processing An IO memory (IOM) 12f which is a memory area such as a contact area (an area for storing IN data fetched from the input unit, output data to be sent to the output unit, etc.), a data area, and the bus interface 12 Are connected to the internal bus 12h, and can transfer data to each other in the unit via the internal bus 12h, and are connected to the backplane bus 10a via the bus interface 12g, Can be transferred to and from.

  The communication unit 13 includes an MPU 13a that is a microprocessor that controls the operation of the entire communication unit, a ROM 13b that is a memory that stores system firmware, a RAM 13c that is a memory used as system work, and a bus connected to the backplane bus 10a. An interface 13g is provided. Furthermore, the communication interface 13d corresponding to Ethernet (registered trademark) is connected to the external network 21 and communicates with other nodes. These are also connected to the internal bus 13f, and can transfer data to each other via the internal bus 13f, and connected to the backplane bus 10a via the bus interface 13g. Data can be transferred to and from the unit. Furthermore, in addition to the system firmware, the ROM 13b stores a memory map of a virtual memory in relation to the present invention.

  FIG. 5 is a schematic diagram of a network configuration focusing on the data transmission side. Each node such as the PLC 10 transmits data allocated to the virtual memory address space (data stored in the conventional local node area) by multicast. The virtual memory of each node shown in FIG. 5 corresponds to the own node area shown in FIG. In this embodiment, the data stored in each virtual memory address space is divided into one frame or a plurality of frames and transmitted. FIG. 5 shows an example in which the transmission is divided into three frames in all nodes, but the number of divisions may be different in each node, and there may be some that are not divided.

  Each virtual memory address space is assigned an individual multicast address for each frame to be transmitted. In the present embodiment, “MA”, “node address”, “−” “identification number” are multicast addresses. For example, the multicast address of the first virtual memory address 1-1 of the node (1) is “MA1-1”, and the multicast address of the second virtual memory address 1-2 of the node (1) is “MA1-2”, and the multicast address of the third virtual memory address 1-3 of the node (1) is “MA1-3”. The data structure of the transmission frame is “multicast address + virtual memory address + data”, and no token is added as in the conventional case.

  Each node transmits the data allocated to its own virtual memory address space by multicast. Then, in multicast transmission, the same frame is transferred to all nodes joining the network 21 by the switching hub 20. Each node transmits data at an arbitrary timing.

  FIG. 6 shows an example of the internal structure of the communication unit 13, which is a main part of the present invention, focusing on the function on the receiving side. A multicast reception table 13d 'is provided in the Ethernet (registered trademark) compatible communication interface 13d. The multicast reception table 13d stores and holds the multicast address attached to the receivable frame (transmits necessary data used by itself). In the illustrated example, “MA1-1” and “MA1-2” of the node (2).

  The communication interface 13d once fetches the frame transmitted by this multicast by the communication interface 13d, determines whether or not the multicast address of the received frame is registered in the multicast reception table 13d ′, and is registered The received frame is transferred to the MPU 13a or the RAM 13c, and the unregistered frame is discarded by the communication interface 13d.

  Therefore, for example, as shown in FIG. 5, when there are three data to be transmitted and stored in the node (1), that is, virtual memory address 1-1, virtual memory address 1-2, and virtual memory address 1-3, Three transmission frames having multicast addresses “MA1-1”, “MA1-2”, and “MA1-3” are sequentially transmitted from the node (1) to the network cable 21. Then, since the switching hub 20 that has received each transmission frame is a transmission frame by multicast, the switching hub 20 transmits the transmission frame to all nodes that join the network. Accordingly, as shown in FIG. 7, the node (2) once captures all of the multicast transmission frames transmitted from the node (1), but as shown in FIG. 6, the multicast of the communication unit 13 of the node (2). Since “MA1-1” and “MA1-2” are registered in the reception table 13d ′ and “MA1-3” is not registered, the communication interface 13d transmits the received two frames to the MPU 13a and the RAM 13c. And the unregistered “MA1-3” frame is discarded.

  Therefore, data unnecessary for the receiving node (in the illustrated example, the frame “MA1-3”) is discarded by the communication interface 13d, so that no additional load is applied to the internal MPU 13a and the CPU unit 12. Of course, the transmission frame by multicast sent from the other nodes (3) and (4) via the switching hub 20 is not registered in the multicast reception table 13d ′ of the node (2), so the communication interface 13d. All are destroyed at.

  Next, as described above, the communication interface 13d receives only frames necessary for its own node and transfers them to the MPU 13a and RAM 13c, and multicasts to the multicast reception table 13d 'necessary for discarding unnecessary frames. Address registration and registration of information necessary for transferring received data to a predetermined memory area will be described.

  In the ROM 13b of the communication unit 13, a memory map table 13b ′ in which the following three items (1) to (3) are associated is set.

(1) Virtual memory address (virtual memory address) included in the frame to be received
(2) Address of receiving node memory for storing the received data included in the frame on the receiving node side (reception actual memory address)
(3) Data capacity of the data (reception size)
Further, the memory map table 13b 'stores the multicast address itself of the frame to be received or information for acquiring the multicast address in association with each other.

  In accordance with the information stored in the memory map table 13b ′, the MPU 13a registers a multicast address for acquiring necessary data from the data flowing in the network in the multicast reception table 13d ′.

  FIG. 8 shows an example of the data structure of the memory map table 13b ′ in which data of the multicast address itself is associated. As shown in the figure, the memory map table 13b ′ includes the received real memory address in the own node that records the received data, the multicast address of the received frame, the virtual memory address of the transmission source, and the reception size. It is a related table. If all the virtual memory addresses and multicast addresses on the transmission side necessary for reception are stored in the memory map table 13b 'on the reception side, the multicast address is already known on the reception node side. The multicast address stored in the table 13b ′ can be registered in the multicast reception table 13d ′. This registration process has an advantage that it can be performed without making an inquiry from the receiving node to the transmitting node. However, the association between the virtual memory address and the multicast address must be strictly determined in advance on both the transmission node and the reception node side.

  FIG. 9 shows another example of the data structure of the memory map table 13b ′. The memory map table 13b 'includes a received real memory address in the own node that records received data, and a node address of a transmitting node for specifying a transmitting node that transmits a received frame (for example, IP (Internet Protocol)). Address), the virtual memory address of the transmission source, and the reception size. That is, as compared with the one shown in FIG. 8, in this example, the node address of the transmission node is registered instead of the specific registration of the multicast address.

  In the case of the memory map table 13b ′ having this data structure, prior to transmission / reception of an actual multicast transmission frame, the reception node needs to acquire a multicast address of the transmission frame necessary (to be received) by itself. Therefore, a multicast address is inquired from the receiving node to the transmitting node based on the transmitting node address stored in the memory map table 13b ′ and the virtual address on the transmitting side, and is acquired. In this way, the association between the virtual memory address and the multicast address need only be decided only by the transmitting side node.

  The specific procedure for acquiring the multicast address is as follows. That is, assume that the memory map table 13b 'on the transmission side and the memory map table 13b' on the reception side are as shown in FIGS. Then, as shown in FIG. 12, the receiving node (2) inquires of the transmitting node (1) about the multicast address of data to be received together with the transmitting virtual memory address. Upon receiving this inquiry, the sending node (1) searches its own memory map table (FIG. 10) based on the received virtual memory address, extracts the corresponding multicast address, and sends the extracted multicast address as a response. To the receiving node (2). The node (2) on the receiving side registers the received multicast address in the multicast reception table 13d ′.

  Each node repeatedly executes the process of making an inquiry about the multicast address from the receiving side node to the transmitting side node and registering the multicast address acquired by the response from the transmitting side in the multicast receiving table 13d ′. Thus, the multicast address of the transmission frame required by itself can be acquired.

  When the initial process is completed, the process shifts to normal data communication. That is, the transmission side node (1) sequentially transmits the data to be transmitted together with the multicast address, and the reception side node receives only the frame stored in the multicast address reception table 13d ′, and the other The frame is discarded at the communication interface 13d.

  FIG. 13 shows an example of the transmission status of the communication frame of this embodiment. As shown in FIG. 13, each node sequentially transmits transmission frames stored in its own virtual memory for each communication cycle time. This communication cycle time does not depend on the total amount of data and the number of nodes in the network, but a time unique to each transmission node is set in such a manner that it depends on the number of transmission data of each transmission node. Actually, an appropriate value of the communication cycle time of each node is determined in the entire network in consideration of the transmission capability limit of the transmission node, the reception capability limit of the reception node, the transfer capability limit of the switching hub 20, and the like. To do.

  FIG. 14 shows a main part of the second embodiment of the present invention. That is, data transmitted by the multicast address is often used for equipment control, and data simultaneity may be required. For example, in the case of a large virtual memory, it is necessary to divide it into a plurality of transmission frames for transmission. The simultaneity means that a frame divided into a plurality of times in one communication cycle (for example, frames 1-1 to 1-3 transmitted from the node (1)) is a snapshot of data in the virtual memory (frame 1). It means that the data of −1 to 1-3 is configured by the state of being taken out from the virtual memory at the same time. However, if data of different times are mixed, the data of the frames 1-1 to 1-3 are lost in synchronism, and there is a risk that control such as strict interlock cannot be performed.

  For example, consider a case where a plurality of data on the virtual memory of the node (1) is used as an interlock condition. Moreover, when the plurality of data is transmitted as data of different frames, frames of different snapshots are transmitted every communication cycle. At this time, if the received node (2) cannot distinguish whether the received frame is the same snapshot frame, the data of different snapshots may be used as the interlock condition, and the interlock condition is satisfied. The legitimacy of will be lost.

  In order to guarantee such simultaneity, in this embodiment, serial number data is added to the transmission frame as shown in FIG. This serial number data is counter information that is incremented and updated by 1 each time a communication cycle is updated. The transmission data belonging to the same communication cycle (for example, frames 1-1 to 1-3) takes the same value. That is, for example, the serial number added to the frames 1-1 to 1-3 transmitted at the first communication cycle time is “1”, and the frames 1-1 to 1-3 transmitted at the second communication cycle time are added. The serial number is “2”.

  The node on the receiving side checks the serial number stored in each received frame, and determines whether or not they are the same value. That is, if frames 1-1 and 1-2 are received, and if the serial numbers of both frames are the same value, it can be determined that the frames are transmitted at the same communication cycle time. Conversely, when the serial numbers stored in the frames 1-1 and 1-2 are different, each frame can be determined as a frame transmitted at a different communication cycle time. Therefore, simultaneity is guaranteed for data stored in frames having the same serial number, but simultaneity cannot be guaranteed for data stored in a plurality of frames having different serial numbers. Only when the serial number data has the same value, it is taken in as official received data, and when it is different, the received data is discarded. In this way, simultaneity can be ensured. Note that examples of cases where the serial number data are different include frame discard due to noise, frame order relation misplacement due to communication path control, and the like.

  As a specific function for ensuring the above-mentioned data simultaneity, a frame received according to the multicast address stored in the multicast address reception table 13d 'is not immediately transferred to the reception real memory, but As shown in the data flow diagram shown in FIG. 15, the following serial number control is executed at the receiving node.

  In the figure, “reception frame” is reception data transferred from the communication interface 13d to the MPU 13a and the RAM 13c, and has passed the multicast filter (the communication interface 13d is determined to be a frame registered in the multicast reception table 13d ′. It is a thing. In the present embodiment, a primary storage buffer for temporarily storing received frames is set in the RAM 13c or MPU 13a. In the case of the node (2) shown in FIG. 6, the multicast reception table 13d ′ receives two frames sent by multicast from the node (1) “MA1-1” and “MA1-2”. Therefore, the buffer also has a “frame 1-1 buffer” for storing the frame 1-1 with the multicast address MA1-1 and a “frame for storing the frame 1-2 with the multicast address MA1-2”. Two “1-2 buffers” were prepared.

  When receiving the received frame (the frame that has passed the multicast filter), the simultaneity determination processing unit 13a ′ implemented in the MPU 13a compares the received frame with the serial number data of the previously received frame stored in the primary storage buffer. It is determined whether or not sex is secured. On the condition that simultaneity is ensured, the data of the data part in the frame is stored in the memory area of the reception real memory 13 'in the RAM 13c set in the memory map table 13b'. As a result, the data stored in the reception actual memory 13c ′ is only a formal reception frame and data in which simultaneity is ensured.

  16 and 17 show specific processing functions of the simultaneity determination processing unit 13a ′. Note that the flowcharts shown in FIGS. 16 and 17 are for the simultaneity determination processing unit 13a ′ in the node (2) described above, and a received frame that requires simultaneity has a multicast address of MA1-1. Two frames, a frame 1-1 and a frame 1-2 with a multicast address of MA1-2, are used.

  The simultaneity determination processing unit 13a ′ receives the multicast frame received by the communication interface 13d, and acquires a received frame determined to be a frame addressed to the own node based on the multicast reception table 13d ′ (S11).

  The simultaneity determination processing unit 13a ′ determines whether or not the received frame is the frame 1-1 (S12). If the received frame is the frame 1-1, the received data is stored in the frame 1-2 primary storage buffer. It is determined whether or not (S13). When the reception data is not stored in the frame 1-2 primary storage buffer (No in the branch determination in S13), the simultaneity determination processing unit 13a ′ stores the reception data in the frame 1-1 primary storage buffer. It is determined whether or not (S14), and if received, the received data received this time is stored in the frame 1-1 primary storage buffer after discarding the received old data (S15). (S16). If the received data is not stored in the frame 1-1 primary storage buffer (No in S14), the simultaneity determination processing unit 13a 'uses the received data received this time as it is as the frame 1-1 primary. Store in the storage buffer (S16).

  On the other hand, when the reception data is already stored in the frame 1-2 primary storage buffer (Yes in S13), the concurrency determination processing unit 13a ′ receives the reception stored in the frame 1-2 primary storage buffer. It is determined whether the serial number data of the frame (frame 1-2) and the serial number data of the frame 1-1 received this time are the same (S17). If they are the same, the received frame 1-1 and frame 1-2 are determined. Since it can be determined that the frame 1-2 stored in the primary storage buffer has been transmitted in the same communication cycle time, the two received frames are copied to the actual reception memory (S18). Thereafter, the simultaneity determination processing unit 13a ′ discards the received frame 1-1 and data temporarily stored in the primary storage buffer of the frame 1-2 (S19).

  If the serial number data of the received frame 1-1 and the serial number data stored in the primary storage buffer of the frame 1-2 are different (No in the branch determination in S17), the process jumps to the processing step S14 and the above-described processing is performed. Execute.

  On the other hand, if the received data is not the frame 1-1, the branch determination process step S12 is No, so the process jumps to the process step S22 to determine whether the received data is the frame 1-2 (S22). In the case of the frame 1-2, it is determined whether or not received data is stored in the frame 1-1 primary storage buffer (S23). When the reception data is not stored in the frame 1-1 primary storage buffer (No in S23 branch determination), the simultaneity determination processing unit 13a 'stores the reception data in the frame 1-2 primary storage buffer. Whether the received data is received or not is discarded (S25), and the received data received this time is stored in the frame 1-2 primary storage buffer. (S26). In addition, when the reception data is not stored in the frame 1-2 primary storage buffer (No in S24 branch determination), the concurrency determination processing unit 13a ′ uses the reception data received this time as it is as the frame 1-2 primary. Store in the storage buffer (S26).

  On the other hand, when the reception data is already stored in the frame 1-1 primary storage buffer (Yes in S23), the concurrency determination processing unit 13a 'receives the reception stored in the frame 1-1 primary storage buffer. It is determined whether or not the serial number data of the frame (frame 1-1) and the serial number data of the frame 1-2 received this time are the same (S27). If they are the same, the received frames 1-2 and 1-1 are received. Since it can be determined that the frame 1-1 stored in the primary storage buffer has been transmitted in the same communication cycle time, these two received frames are copied to the actual reception memory (S28). Thereafter, the simultaneity determination processing unit 13a ′ discards the received frame 1-2 and the data temporarily stored in the frame 1-1 primary storage buffer (S29).

  If the serial number data of the received frame 1-2 is different from the serial number data stored in the frame 1-1 primary storage buffer (No in the branch determination in S27), the process jumps to the processing step S24, and the above-described processing is performed. Execute.

  If the received data is neither the frame 1-1 nor the frame 1-2, the branch determination processing step S22 is No, so the process returns to the processing step S11, and the concurrency determination processing unit 13a ' Wait for reception. Of course, when data other than the frames 1-1 and 1-2 is received, other data processing and protocol processing are executed.

  Normally, as shown in FIG. 13, the transmission side node (1) transmits in the order of “frame 1-1” → “frame 1-2”. There is also an idea that only “Frame 1-1 primary storage buffer” should be provided, assuming that “1” is always received first. However, in the Internet protocol (IP), the datagram type communication data used in multicast may not be able to guarantee the context, so the reception order of frames transmitted with the same communication cycle time is not necessarily the order of transmission. The frame 1-2 may be received first. Assuming such a case, the frame 1-2 primary storage buffer is also provided in this embodiment.

  The present embodiment shown in FIG. 15 to FIG. 17 is shown based on a simple example of two reception frames. Of course, there may be three or more reception frames for which simultaneity is required. Depending on the number of received frames, the number of primary storage buffers is increased, or the determination processing flow shown in FIGS.

It is a figure explaining the conventional data link. It is a figure explaining a talk passing system. It is a figure which shows an example of the network structure which shows one Embodiment of this invention. FIG. 2 is a diagram illustrating an internal configuration of a CPU unit 12 and a communication unit 13 that constitute a PLC 10. It is the schematic which shows a network structure. It is a figure which shows an example of the internal structure of the communication unit 13 used as the principal part of this invention paying attention to the function of the receiving side. It is a figure explaining the effect | action of this embodiment. It is a figure which shows the memory map table which linked | related data of the multicast address itself. It is a figure which shows an example of another data structure of a memory map table. It is a figure which shows a specific example of the memory map table of a transmission side. It is a figure which shows a specific example of the memory map table on the receiving side. It is a figure which shows the procedure of the concrete acquisition of the multicast address based on the memory map table of FIG. 10, FIG. It is a figure which shows an example of the transmission condition of the communication frame of this embodiment. It is a figure which shows the principal part of 2nd Embodiment of this invention. It is a figure which shows the data flow diagram of this embodiment. It is a part of flowchart which shows the function of a simultaneity determination processing part. It is a part of flowchart which shows the function of a simultaneity determination processing part.

Explanation of symbols

10 PLC (node)
12 CPU unit 13 Communication unit 13a MPU
13a 'concurrency judgment processing office 13b ROM
13b 'Memory map table 13c RAM
13c 'real memory for reception 13d communication interface 13d' multicast reception table 20 switching hub 21 network cable

Claims (7)

A network system capable of sharing data between a plurality of nodes on a network in which a plurality of nodes are connected via a switching hub,
The plurality of nodes include a communication interface capable of transmitting and receiving data by multicast communication using the full duplex communication method via the switching hub;
A virtual memory for storing data to be transmitted to other nodes in order to share data among a plurality of nodes;
A table for associating a multicast address and transmission data for transmitting data on the virtual memory to another node;
Of the plurality of nodes, the communication interface of the transmission side node has a function of transmitting data by multicast together with a multicast address based on the table,
Among the plurality of nodes, the receiving node has multicast address information storage means for storing a multicast address of data required by itself among data transmitted by multicast from other nodes,
When the communication interface of the node on the receiving side receives the data transmitted by multicast, the communication interface determines whether or not the data is necessary based on the multicast address stored in the multicast address information storage means. Incorporates only the data required by the node into the node, and in the case of data that does not need itself, has a function to discard,
The network system according to claim 1, wherein the transmitting side node shares data with the receiving side node by cyclically transmitting data at a transmission timing of the own node. When the association of the multicast address and transmission data constituting the table is composed of a plurality of sets, and a frame for transmission is configured in units of the set, a plurality of transmissions are performed during one cycle of the transmission timing of the own node. Send the frame with the same identification number,
2. The network system according to claim 1, wherein when the plurality of frames are received, the receiving-side node performs discard processing if the plurality of frames have different identification numbers.   The receiving-side node stores and holds information for identifying a transmitting-side node that transmits data required by itself, and address information of the transmitting-side virtual memory in the transmitting-side node, and the stored and held information 3. The network system according to claim 1, wherein a multicast address is inquired to the transmission side node based on the information and income is obtained. A communication interface capable of transmitting and receiving data by multicast communication in a full duplex communication system via a switching hub;
A virtual memory for storing data to be transmitted to other nodes in order to share data among a plurality of nodes;
A table associating a multicast address and transmission data for transmitting the data on the virtual memory to another node;
Multicast address information storage means for storing a multicast address of data required by itself among data transmitted by multicast from other nodes,
The communication interface is
A function of transmitting data by multicast together with a multicast address based on the table;
When receiving data transmitted by multicast, it is determined whether or not it is necessary data based on the multicast address stored in the multicast address information storage means, and only the data required by itself is taken into the node, A programmable controller characterized by having a function of discarding data that is not required by the device. A data sharing method in a network system capable of sharing data between a plurality of nodes on a network in which a plurality of nodes are connected via a switching hub,
The plurality of nodes include a communication interface capable of transmitting and receiving data by multicast communication using the full duplex communication method via the switching hub;
A virtual memory for storing data to be transmitted to other nodes in order to share data among a plurality of nodes;
A table for associating a multicast address and transmission data for transmitting data on the virtual memory to another node;
The communication interface of the transmitting node among the plurality of nodes transmits data by multicast together with a multicast address based on the table,
The receiving node of the plurality of nodes has multicast address information storage means for storing a multicast address of data required by itself among the data transmitted by multicast from other nodes. When the communication interface of the node receives the data transmitted by multicast, the node determines whether the data is necessary or not based on the multicast address stored in the multicast address information storage means. If the data is taken into the node and the data is not necessary, execute the discarding process,
The data sharing method, wherein the transmitting side node shares data with the receiving side node by cyclically transmitting data at the transmission timing of the own node. When the association of the multicast address and transmission data constituting the table is composed of a plurality of sets, and a frame for transmission is configured in units of the set, a plurality of transmissions are performed during one cycle of the transmission timing of the own node. Send the frame with the same identification number,
6. The data sharing method according to claim 5, wherein when the plurality of frames are received, the receiving node executes a discarding process when the plurality of frames have different identification numbers.   The receiving-side node stores and holds information for identifying a transmitting-side node that transmits data required by itself, and address information of the transmitting-side virtual memory in the transmitting-side node, and the stored and held information 7. The data sharing method according to claim 5, wherein a process of making an inquiry about a multicast address is performed to the transmitting side node and income is obtained.

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