JP4006605B2 - Reduction of repeater delay effect - Google Patents

Description

  The present invention relates to a communication system for controlling an FA device or the like that includes a master station that manages a network, a slave station that connects an I / O device, and a relay station that shapes and amplifies a communication frame in a bus network. Is.

  A remote I / O network of a programmable controller (PLC) composed of a single master station, a plurality of slave stations, and a plurality of relay stations is already known. An example of the network is shown in FIG.

  As shown in the figure, this network system is roughly composed of a master station 70, slave stations 80a to 80d (slave # 1 to 4), and relay stations 90a to 90d (repeaters # 1 to 4). The network is configured with two relay stations (repeaters).

  A building block type PLC includes a CPU unit for executing a user program, an input / output unit (I / O unit) connected to input devices and output devices (hereinafter, collectively referred to as I / O devices), a remote I / O unit, and the like. Each unit such as a communication master unit that connects an O network and communicates input / output data (I / O data) with a slave station is combined.

  The master station 70 may be regarded as corresponding to a set of programmable controllers, or may be regarded as a PLC communication master unit. In the figure, the programmable controller is represented as a master station. This network is configured as a bus network, and the master station manages the network and is incorporated in the programmable controller.

  The slave station is connected to an I / O device (not shown), controls the output device based on the OUT data stored in the communication frame received from the master station, and responds to a request from the master station. Then, IN data fetched from the input device is stored in a response frame and returned to the master station.

  The relay station performs waveform shaping and amplification processing on communication frames transmitted and received on the network. Therefore, when request frames transmitted from the master station to each slave station and response frames from each slave station are communicated, shaping / amplification processing is performed every time it passes through the relay station. A delay of a certain time required for processing (repeater delay) occurs.

  FIG. 21 shows an operation model showing, in time series, the request frame transmitted from the master station and the response frame responded by each slave station at the observation points A, B, C, and D shown in FIG. .

  As shown in FIG. 17, slave station # 1 is connected to the master station without passing through the relay station. Therefore, since the response of the slave station (# 1) 80a at the observation point A in FIG. 21 does not cause a repeater delay, the response frame from the slave station (# 1) 80 is displayed together with the end of the request frame from the master station 70. Has been sent.

  On the other hand, there is one relay station between the slave station (# 2) 80b and the master station 70, and the slave stations (# 3) 80c and (# 4) 80d are connected to the master station 70. There are two relay stations. Therefore, the request frame transmitted to the slave stations (# 2, # 3, # 4) causes a repeater delay every time it passes through the relay station, and the response frames from those slave stations also pass through the relay station in the same way. Repeater delay occurs every time.

  For this reason, conventionally, in consideration of the repeater delay that occurs in the relay station, as shown in the figure, a gap is left in the response of each slave so that the responses do not collide (for example, Patent Document 1). reference).

  Similarly, at the observation points B, C and D shown in FIG. 17, in order to cope with the repeater delay, as shown in FIG. To send.

  Further, since the system is a bus type system, the relay station relays all communication frames flowing upstream and downstream. In the system configuration as shown in FIG. 17, the response frame of the slave station (# 3) 80c is transmitted to the master station and other slave stations via the four relay stations (relay stations 90d, 90c, 90a, 90b). Arrives at the slave station (# 4) 80d.

At this time, the slave station (# 4) 80d arrives after “repeater delay × 4” time. For this reason, in order to avoid the collision of response frames from all the slave stations, it is necessary to leave a gap of time corresponding to “repeater delay × 4” on the average at the observation point A. . Therefore, the communication cycle is
Communication cycle = Request frame time
+ (Response frame time + repeater delay x maximum number of repeater stages x 2)
× Slave number.

Furthermore, as described above, the conventional relay station relays all communication frames flowing upstream and downstream. More specifically, for example, the response frame transmitted from the slave station (# 1) 80a shown in FIG. 21 is not only transmitted to the master station 70, but also other slave stations (# 2, # 3, # 4). This is clear from the fact that the response frame from the slave station (# 1) is known at all of the observation points A, B, C, and D. Similarly, response frames from all slave stations are known at all observation points A, B, C, and D.
JP 2004-280304 A

  In the conventional method, the repeater delay generated at each relay station is taken into consideration so that there is a gap between the responses of each slave station so that the responses do not collide with each other. There has been a problem of increasing the number of people.

  In addition, the communication frame addressed to the master station transmitted from each slave station on the network is also relayed to other slave stations, resulting in an increase in the occupation rate of the communication path, leading to a decrease in communication performance. .

  The present invention has been made paying attention to the above-mentioned problems, and the object of the present invention is to provide a relay station capable of preventing the responses of the slave stations from colliding with each other without increasing the communication cycle. It is an object of the present invention to provide a method for reducing the influence of delay and a system for realizing the method.

  Another object of the present invention is to determine the type of communication frame to be relayed by a relay station on the network and relay only necessary information, thereby reducing the network occupancy rate and improving the network efficiency. It is to improve.

  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.

  In the communication system of the present invention, a master station, which is a programmable controller having a communication function, and one or more slave stations, which are I / O terminal devices having a communication function, are connected by a network and are connected to the network. In a communication system in which a relay station functioning as a repeater is interposed in one or more stages on a path connecting a master station located upstream and a slave station located downstream, on a network The communication frame transmitted and received includes a communication frame having identification information for identifying that the first frame type is issued only from the slave station to the master station. An upstream port connected to the upstream network and a downstream port connected to the downstream network. When the identification information of the frame received at the downstream port is identified as the first frame type, the received frame is relayed only in the direction from the downstream port to the upstream port. It is characterized by performing.

  With such a configuration, the response frame transmitted from the slave station to the master station is transmitted only to the master station, and is not transmitted to other slave stations as in the conventional example. Therefore, unnecessary frame transmission is not performed, and it is possible to minimize the gap between the response timings of the slave stations provided so that the responses do not collide with each other on the network.

  As a preferred embodiment, the communication frame transmitted / received on the network further includes identification information for identifying the second frame type transmitted only from the master station to the slave station. When the communication frame is included and the relay station identifies that the identification information of the frame received at the upstream port or the downstream port is the second frame type, the relay station The relay processing may be performed only in the direction from the downstream port to the downstream port.

  Similarly, in another preferred embodiment, the communication frame transmitted / received on the network is a third frame type that is transmitted bidirectionally between the master station and the slave station. A communication frame having identification information for identifying the frame, and when the relay station identifies that the identification information of the frame received at the upstream port or the downstream port is the third frame type, the reception The received frame may be subjected to relay processing in the direction from the received upstream port to the downstream port or in the direction from the received downstream port to the upstream port.

  According to a preferred embodiment, the master station transmits a specific communication frame to the slave station, reads the number of passing stages of the relay station from the response frame from the slave station for the specific communication frame, and reads the read relay Based on the number of passing stages of the station, the slave station calculates a time domain for setting a timing for returning a response frame to the communication frame from the master station, and performs a writing process to the slave station of the time domain. Also good.

  With such a configuration, based on information obtained from a communication frame to be transmitted, it is possible to grasp the position on the network configuration with the slave station that transmitted the frame (for example, from the master station to the slave station). How many relay stations are on the route to the top). And in the time domain for setting the response timing in each slave station calculated by the master station, it becomes possible to reduce the gap between the response timings of each slave station and realize a high-speed communication cycle.

  At this time, in the slave station, the time domain for setting the timing for transmitting the response frame for the communication frame from the master station is calculated so that the master station can receive a plurality of response frames without gaps. Also good.

  With such a configuration, it is possible to reduce a response gap provided when transmitting a response frame to a frame from the master station, and to reduce the influence of repeater delay caused by the relay station.

  Here, “repeater delay” refers to the time required for various communication frames transmitted on the network to pass through the relay station. Since various processes such as waveform shaping and amplification are performed on the communication frame to be relayed in the relay station, a delay occurs as compared with the case where there is no relay station each time the communication frame is relayed. The repeater delay means this delay, that is, the time required for relay processing in the relay station. The same applies to “repeater communication” described below.

  As a preferred embodiment, the specific communication frame transmitted from the master station to the slave station can include information on the address value of the relay station that has passed through and information on the number of relay station stages. When the specific communication frame passes, the station performs processing for including information on the address value of the local station and information on a value obtained by adding +1 to the number of relay station stages in the specific communication frame. The station extracts, from the specific communication frame, the processing for extracting the address value information of the relay station adjacent to the upper side of the own station and the information on the number of relay station stages, and the specific communication in the response frame to the master station. You may make it perform the process which includes the information of the address value of the relay station adjacent to the high-order side of the own station read from the flame | frame, and the information of the number of relay station steps.

  As a preferred embodiment, in a communication frame transmitted / received on the network, an in-frame for the slave station to return the IN data input from the input device connected to the slave station as a response to the master station. The slave station returns an in-frame response as soon as the repeater delay time based on the time domain held by the local station, and the relay station upstream from the downstream port for the in-frame. The relay process may be performed only in the direction toward the port.

  In a preferred embodiment, the slave station transmits a connection frame for the master station to confirm the existence of the slave station, and the master station transmits a connection frame to the slave station. The slave station transmits a connection frame as a response to the trigger frame earlier by the repeater delay time based on the time domain, and the relay station transmits the connection frame as a response to the trigger frame. May perform relay processing only from the downstream to the upstream direction.

  Further, the communication system of the present invention as seen from another aspect includes a master station that is a programmable controller having a communication function and one or more slave stations that are I / O terminal devices having a communication function in a network. A relay station that functions as a repeater over one stage or two or more stages is connected on a route that is connected and on the network and connects a master station located upstream and a slave station located downstream. In a communication system, a communication frame transmitted / received on a network includes a communication frame having a first frame type that is transmitted only from a slave station to a master station. Identify received frames with an upstream port connected to the other network and a downstream port connected to the downstream network When it is identified that the information is of the first frame type, the received frame is relayed only in the direction from the downstream port to the upstream port, and the slave station communicates with the master station. The time domain for setting the timing at which the slave station returns a response frame to the communication frame from the master station, which is determined based on the number of relay stations intervening in the master station, is stored in advance. It is determined that the master station can receive a plurality of response frames without gaps.

  With such a configuration, the response frame transmitted from the slave station to the master station is transmitted only to the master station, and is not transmitted to other slave stations as in the conventional example. Therefore, unnecessary frame transmission is not performed, and it is possible to minimize the gap between the response timings of the slave stations provided so that the responses do not collide with each other on the network. Then, it is possible to reduce the response gap provided when transmitting the response frame to the frame from the master station, and to reduce the influence of repeater delay caused by the relay station.

In a preferred embodiment, the slave station transmits a connection frame for the master station to confirm the existence of the slave station, and the master station transmits a connection frame to the slave station. Sending the requested trigger frame,
Based on the time domain, the slave station returns a response to the connection frame as early as the repeater delay time, and the relay station relays only the connection frame from downstream to upstream. Also good.

  As a preferred embodiment, the communication frame includes an in-frame for transmitting IN data of the I / O terminal device which is a slave station to the master station. The slave station is based on the time domain. In response to the in-frame including the IN data of the I / O terminal device, the master station returns a response so that a plurality of response frames can be received without gaps. You may make it perform a relay process only with respect to a direction.

According to another aspect of the present invention, a master station that is a programmable controller having a communication function and one or more slave stations that are I / O terminal devices having a communication function are connected by a network. Relay in a communication system in which a relay station functioning as a repeater is interposed over one or two or more stages on a path connecting a master station located upstream and a slave station located downstream An apparatus, an upstream port connected to an upstream network and a downstream port connected to a downstream network;
The receiving means for receiving various communication frames from the upstream port or the downstream port, the identifying means for identifying the type of the communication frame received by the receiving means from the identification information included therein, and the type of the communication frame identified by the identifying means is the slave In the case of the first frame type issued only from the station to the master station, relay control means for performing relay processing only in the direction from the downstream port to the upstream port is provided.

  With such a configuration, the response frame transmitted from the slave station to the master station is transmitted only to the master station, and is not transmitted to other slave stations as in the conventional example.

  At this time, if the type of the communication frame identified by the identifying means by the relay control means is the second frame type issued only from the master station to the slave station, the direction from the upstream port to the downstream port The relay processing may be performed only on the.

  Further, when the type of the communication frame identified by the relay control unit by the identifying unit is the third frame type issued bi-directionally between the master station and the slave station, the upstream port is changed to the downstream port. Or the relay process may be performed in the direction from the downstream port to the upstream port.

  As is apparent from the above description, according to the present invention, the relay station on the network discriminates the type of communication frame to be relayed and relays only necessary information, thereby reducing the network occupancy rate. It is possible to improve efficiency and speed up the communication cycle.

  In the following, a preferred embodiment of 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, reference numeral 3 denotes a setting device using a personal computer, and various settings are made for each device / apparatus serving as a node on the network such as the PLC device 1, the master unit 10, the communication slave station, and the relay device 4. With the ability to do. Sometimes referred to as “setting tool device” or “network configurator”. 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, the OUT data in the I / O memory 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. Written in the IN area.

  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 into the IN area of the RAM 103 in the communication master unit 10, and the CPU unit 20 takes in from the communication master unit 10 by the I / O refresh operation. The CPU unit 20 executes the user program based on the IN data, and sets the execution result as OUT data. The CPU unit 20 sends OUT data to the communication master unit 10 by the I / O refresh operation. The communication master unit 10 stores the OUT data in the OUT area of the RAM 103. Then, the communication master unit 10 transmits OUT data in the OUT area of the RAM 103 to the corresponding I / O terminal device 2 asynchronously with the I / O refresh.

  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 control the 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 and the like, I / O 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.

  Then, between the communication master unit 10 and each I / O terminal device 2, through 1-N master-slave communication with the communication master unit 10 as a communication master station and each I / O terminal device 2 as a communication slave station. , I / O data is exchanged.

  Specifically, the OUT data received from the communication master unit 10 is sent to the I / O device 7 (output device) via the I / O unit 207 of the I / O terminal device 2, and the I / O device The IN data taken into the I / O terminal device 2 via the I / O unit 207 from 7 (input device) is transmitted to the communication master unit 10.

  Next, FIG. 4 shows a hardware configuration diagram inside the repeater functioning as a relay device. As shown in the figure, the repeater 4 is mounted between the communication interfaces 401 and 402 connected to the master side and the slave side, and the data (signal) transmitted between the communication interfaces 401 and 402, respectively. It includes a repeater ASIC 403 that performs predetermined processing, and a CPU 407 that is configured mainly by a microprocessor and controls the entire apparatus. Furthermore, a power supply unit 404 is provided that steps down the input voltage (24 V) to 5 V and supplies power to each element in the repeater 4. Furthermore, an LED display unit 405 indicating an operating state (communication state), abnormality / normality, and a setting switch 406 for setting a node address and the like are provided.

  In the delay reduction of the repeater (relay station) in the present invention, it is preferable that each relay station on the network recognizes the installation position (that is, the network configuration) on the network. In the network configured as described above, an example of a search path for transmitted information frames and an example of a network configuration information teaching method therefor will be described.

  The communication master station (M), the communication slave station (S), and the relay station (R) described above with reference to FIG. 1 have unique addresses on the PLC system network. Individual identification is performed by this address. The network configuration information teaching method of the present embodiment is applied from network startup management to normal communication.

  First, the relay station (R) to the relay station (R) and the relay station (R) to the slave station (S) through the first frame broadcasted simultaneously (one-to-N communication) from the master station (M). ), The relay station (R) and the slave station (S) generate and store the “upper neighbor station information of the own station” in the network.

  This operation may be performed at a stage before the master station recognizes the relay station and slave station connected to the network, such as when the power is turned on, or the master station is connected to the network during network operation. It may be optionally performed at a stage after recognizing the connected relay station and slave station.

  In this embodiment, a search frame (generally called a SolicitFrame, a BeaconFrame, or the like is applicable. Hereinafter, it is described as BeaconFrame, and is abbreviated as BF, but both mean to include SolicitFrame) is used. A block diagram showing the frame format of the BF is shown in FIG.

  As shown in the figure, the BF flowing through the field bus 6 includes a BF identification header 501 for identifying the BF, and a relay station that is updated with the address value of the relay station every time it passes through the relay station. It includes at least an address 502, a relay station counter 503 whose value is incremented by +1 every time it passes through the relay station, and a transmission speed 504 indicating the communication transfer speed of the BF.

  The communication master station (M) broadcasts the BF simultaneously so that the BF is transmitted to all relay stations and communication slave stations (S) connected to the network. Then, the BF that has been broadcast simultaneously reaches the slave station (S) directly, or reaches the slave station via one or more relay stations. At this time, although the BF flowing through each path is slightly delayed by the line delay time of the path and the relay delay time of the passing relay station, it can be considered that the BF reaches each relay station and each slave station at almost the same time as a whole. it can.

  An explanatory diagram (part 1) of the frame transmission / reception sequence is shown in FIG. As shown in the figure, from the master station (address 10), a BF having a relay station address value of “10” and a relay station counter value of “0” is broadcast on the network. The

  When the relay station (address 100) receives the broadcasted BF from its upper port, the value “10” of the relay station address 502 in the BF and the value “0” of the relay station counter 503 are read from the BF. And stored in a memory in the relay station (address 100). As a result, the relay station (address 100) can recognize the relative position of its own station, assuming that the station address of the station adjacent to the upper side is “10”. In this case, the content of “upper neighbor information of own station” generated by the relay station (address 100) is “upper neighbor information of own station” (station address “10”).

  Thereafter, the value of the relay station address 502 in the BF is replaced with “100” (relay station address: own station address) from “10” (master station address: the station address of the station adjacent to the upper side). . At the same time, the value “0” of the relay station counter 503 is incremented by +1 to “1”. Thus, a new BF in which the value of the relay station address 502 is rewritten and the value of the relay station counter 503 is incremented by +1 is transmitted from the lower port to the slave station (address 101) located in the next stage. .

  When the slave station (address 101) receives the BF transmitted from the relay station (address 100), the value “100” of the relay station address 502 in the BF and the value “1” of the relay station counter 503 are read from the BF. , Stored and held in a memory in the slave station (address 101). As a result, the slave station (address 101) can recognize the relative position of its own station, assuming that the station address of the station adjacent to the upper side is “100”. In this case, since the station address of the station adjacent to the upper side is “100”, the content of the “higher side neighboring station information of the own station” generated by the slave station (address 101) Side adjacent station information "(station address" 100 ").

  In this way, when the information storage phase (phase I) is executed, the master station (address 10) to the relay station (address 100), the relay station (address 100) via the BF broadcast simultaneously from the master station. ) From the slave station (address 101) to the relay station (address 100), the relay station (address 100) and the slave station (address 101) are respectively notified of the higher-level neighboring station information and the relay station counter in the network. Values are generated and stored.

  In the example shown in FIG. 6, only one relay station is interposed between the master station and the slave station, but two or more relay stations are interposed between these stations. Even when no relay station is interposed between the master station and the slave station, the operation of each relay station and each slave station is the same.

  FIG. 7 shows a processing flow (No. 1) when the relay station receives BF. The process shown in this flow is executed by the CPU 407 in the repeater 4 shown in FIG.

  In the figure, when processing is started, first, frame reception standby processing is executed (step 701). In this state, when any frame is received (YES in step 702) and it is determined that the frame is BF based on the BF identification header 501 of the frame (YES in step 703), the following processing (steps 704 to 709) is performed. Are executed sequentially.

  First, the frame is analyzed and the structure of the frame is recognized (step 704). Next, address information (relay station address 502) and counter information (relay station counter 503) in the frame are read out and stored in a predetermined memory (steps 705 and 706). Next, the address information (relay station address 502) in the frame is replaced with its own address (step 707). Next, the counter information (relay station counter 503) in the frame is replaced with a value incremented by +1 (step 708). Finally, the new frame thus obtained is output to the lower port (709).

  FIG. 8 shows a processing flow (No. 1) at the time of BF reception of the communication slave station. The processing shown in this flow is executed by the CPU 203 in the I / O terminal device 2 shown in FIG.

  In the figure, when processing is started, first, frame reception standby processing is executed (step 801). In this state, when any frame is received (YES in step 802) and the frame is determined to be a BF header based on the BF identification header 501 of the frame (YES in step 803), the following processing (steps 804 to 806) is performed. It is executed sequentially.

  First, the frame is analyzed, and the structure of the frame is recognized (step 804). Next, in-frame address information (relay station address 502) and in-frame counter information (relay station counter 503) are read out and stored in a predetermined memory as “upper neighbor information of own station” (step 805). 806).

  In this way, each of the relay station and the slave station generates and stores the higher-side neighboring station information of the own station and the relay station counter value in the network, and this information is fed back to the master station. The system diagram of the entire system can be grasped. In addition to the method using BF, there is a network configuration information teaching method. For example, a method may be used in which an operator confirms the number of relay stations intervening with the master station in each slave station from the actual network configuration and registers the result in the master station. That is, a method may be used in which the setting device 3 transmits and writes the stage number information of the relay station of each slave station to the master station. If this method is used, then the stage number information of the relay station is transmitted from the master station to each slave station and written.

  As another method, for example, an operator may check the number of relay stations intervening with the master station in each slave station from the actual network configuration, and register the result in the slave station. That is, a method of transmitting and writing the relay station stage number information directly from the setting device 3 to each slave station may be used. Another method for registering the relay station stage number directly to each slave station is to provide an operation button on the slave station, and the operator can register by pressing the operation button on the slave station by the same number as the relay station stage number. It is good also as such a method.

  Next, a method for reducing a repeater delay generated in a relay station on a network, which is a main part of the present invention, will be described in detail with reference to FIGS. In these figures, reference numeral 30 is a master station, 40a to e are slave stations (parts 1 to 5), 50a and b are relay stations (parts 1 and 2), 31 is a network trunk line, and 32 is a network trunk line. Network branch lines 1 and 33 branch from the network trunk line, and network branch lines 2 branch from the network trunk line respectively.

  In the PLC system according to the present invention, a dedicated frame (for example, BeaconFrame, OutFrame, TrgFrame) issued only from the master station to the slave station described below, and a dedicated frame issued only from the slave station to the master station There is a frame (for example, ConnectionFrame, InFrame), a frame that is emitted in both directions (for example, EventFrame), the relay station distinguishes the frame type, and the relay station transfers only in the necessary direction. . The BeaconFrame (beacon frame) is the above-described search frame, which is periodically transmitted from the master station, and serves to notify the slave station of the transmission transmission rate and the number of repeater passing stages. OutFrame is a PLC user program execution result or the like as OUT data and is transmitted from the master station to the slave station. TrgFrame (trigger frame) is used to request a ConnectionFrame response from the master station to the slave station. The connection frame (connection frame) is a reply to the master station when the slave station receives the trigger frame and is designated by the trigger frame. The master station performs existence confirmation (YES in step 1103 in FIG. 18) or join processing (steps 1104 and 1105 in FIG. 18) for the slave station that has returned this ConnectionFrame. InFrame (in-frame) is for transmitting IN data captured by the slave station from the input device to the master station. The EventFrame (event frame) is a frame for the slave station to transmit some data to the master station in response to a request from the master station, in addition to the in-frame.

  As shown in FIG. 10 and FIG. 11, the PLC system in the present embodiment shapes a master station 30 that manages a network, a slave station 40 that controls I / O, and a communication frame in a bus network. -It is comprised from the relay station 50 to amplify.

  The basic structure of each frame is shown in FIG. As shown in the figure, each frame has a start code 901 indicating that the frame starts, a frame identification header 902 indicating the type of the frame, frame data 903 indicating the content of the frame, and a check indicating the validity of the frame. It includes at least four elements of code 904 (CRC data or the like). When the relay station 50 on the network recognizes the start code 901, it shapes the waveform and starts output to the other port. By shaping this waveform, it is possible to extend the laying distance of the network.

  However, when relay processing is performed at the stage where the start code 901 is determined, data transmitted from the slave station 40 to the master station 30 is also relayed to other slave stations. However, the data was transmitted and the occupation efficiency of the network was reduced.

  FIG. 10 shows a case where frame transmission from the master station 30 to the slave station 40 is performed. Since the frame from the master station 30 to the slave station 40 is a broadcast frame, it can be handled by relaying all the frames simultaneously. As shown in the figure, a frame transmitted from the master station 30 is transmitted not only to the slave station 40a but also to the slave station 40d and the slave station 40e via the relay station 50a. Although not shown, the data is also transmitted to the slave station 40b and the slave station 40c via the relay station 50b.

  On the other hand, FIG. 11 shows a case where frame transmission from the slave station 40 to the master station 30 is performed. As shown in the figure, for example, when a frame is transmitted from the slave station 40d to the master station 30, the relay station 50a shapes and amplifies the frame and transmits the frame to the master station 30. However, conventionally, the relay station 50b simultaneously receives the frame and transmits the frame to the lower port. For this reason, the slave stations 40b and 40c have not been able to secure the network idle time that can be transmitted to the master 30 station, and the network communication efficiency has been reduced.

  FIG. 12 shows the network occupation ratio in the above case. As shown in the figure, a frame addressed to the master station from the slave station 40d arranged on the network branch line 32 is relayed from the network branch line 32 by the relay station 50a and sent to the network trunk line 31 to be the master station. 30. However, it is transmitted to the master station 30, relayed by the relay station 50b installed on the network branch line 33, and transmitted to the slave station 40b. The frame originally from the slave station 40d addressed to the master station is also transmitted to the slave station 40b via the network branch line 32 and the relay station 50b. As a result, the frame addressed to the master station 30 is relayed from the slave station 40d on the network branch line 33, resulting in an extra occupation, and the transmission of the frame addressed to the master station 30 from the slave station 40b is delayed accordingly. ing.

  Although not shown in the figure, a frame transmitted from the slave station 40b to the master station 30 is also transmitted to the slave stations 40d and 40e via the relay station 50a, and an extra set work is placed on the network branch line 32. Occupation occurred.

  FIG. 13 shows a case where a frame received by each relay station is identified and unnecessary relay processing is not performed. It is clear by comparing FIG. 12 with FIG. 12, but the relay station 50b identifies the frame addressed to the master station 30 from the slave station 40d and prevents the relay process from being performed, so that the network on the network branch line 33 It is possible to smoothly transmit a frame addressed to the master station 30 from the slave station 40b without causing extra network occupation. Thus, by determining the frame identification header at the relay station and performing the relay process only in the necessary direction, the communication time of the network branch line 33 can be secured, the slave stations 40b and 40c can communicate, and the network efficiency is improved. An improvement can be realized. Here, it is described that the communication time of the network branch line 33 is secured, but it goes without saying that the efficiency of the entire network is improved by performing the same processing in other relay stations.

  FIG. 14 shows a functional block diagram of a relay station that identifies frames and prevents unnecessary relaying as described above. As shown in the figure, each relay station has an upper port 411 and a lower port 417 connected to the network by a bidirectional serial bus.

  First, a case where a frame is transmitted from the upper port 411 side will be described. The frame (received data) sent to the upper port 411 via the bidirectional serial bus is sent to the start code detector 412. The received data is accumulated in the data buffering unit 413 from the start code detection unit 412 and later sent to the repeat frame generation unit 416. At this time, the start code detection unit 412 transmits the reception data to the data buffering unit 413 and also transmits the reception data and the start code detection signal to the frame type identification unit 414. Next, when a start code detection signal is sent to the frame type identification unit 414, the type of the frame is identified, and the identification result is sent to the lower repeat control unit 415 as a frame type information signal. The lower repeat control unit 415 determines whether the received frame is a repeat target frame according to the type of frame specified by the frame type information signal.

  The determination method in the lower repeat control unit 415 is as follows. As described above, each relay station on the network knows its own position on the network and a relative position with other relay stations and slave stations by using the network configuration information teaching method. In this case, since the determination is made with respect to the frame received on the upper port 411 side, it is determined whether or not the frame transmitted from the upstream in the network is relayed further downstream from the relay station. Therefore, for example, if the received data is a frame addressed from the master station to the slave station, it is determined that the frame is to be transmitted from the upstream side of the network and is to be relayed further downstream via the lower port. . On the other hand, if the received data is a frame addressed from the slave station to the master station, the master station is located upstream from the relay station, so there is no need to perform relay processing (repeat) downstream via the lower port. It is determined to be a frame.

  When it is determined through such determination processing that the target frame is a frame that needs to be relayed, a repeat start signal is transmitted to the repeat frame generation unit 416. The repeat frame generation unit 416 that has received this repeat start signal transmits the reception data stored in the data buffering unit 413 as repeat transmission frame data to the network via the lower port 417. The lower repeat control unit 415 transmits a repeat start signal to the repeat frame generation unit 416 and also transmits a suppression signal to the upper repeat control unit 421. In the relay station, the frame transmitted by itself may be received by itself. To prevent this, when transmitting frame data from the lower port 417, a signal for suppressing reception at the upper port 411 via the upper repeat control unit 421 is sent to the lower repeat control unit 415. To send.

  When the lower repeat control unit 415 determines that it is not necessary to perform relay, a repeat start signal is not generated and the received data is not relayed.

  Similarly, a case where a frame is transmitted from the lower port 417 side will be described below. The frame (received data) sent to the lower port 417 via the bidirectional serial bus is sent to the start code detector 418. The received data is accumulated in the data buffering unit 419 from the start code detection unit 418 and later sent to the repeat frame generation unit 422. At this time, the received data is sent to the data buffering unit 419, and the received data and the start code detection signal are also sent to the frame type identifying unit 420. Next, when a start code detection signal is sent to the frame type identification unit 420, the type of the frame is identified, and the identification result is sent to the upper repeat control unit 421 as a frame type information signal. The upper repeat control unit 421 determines whether or not to perform further relay processing (repeat) via the upper port 411 according to the frame type defined by the frame type information signal.

  The determination method in the upper repeat control unit 421 is the same as that at the time of reception from the upper port 411 described above, but in this case, since the determination is for the frame received on the lower port 417 side, it has been transmitted from the downstream in the network. It becomes a frame. Therefore, if the received data is a frame addressed from the slave station to the master station, it is determined that the frame is to be transmitted from the downstream side of the network and is to be relayed further upstream via the upper port. On the other hand, if the received data is a frame addressed to the slave station from the master station, the slave station is located downstream from the relay station, so the relay process (repeat) to the master station located upstream via the upper port is It is determined that the frame does not need to be performed.

  When it is determined that it is necessary to perform relaying through such determination processing, a repeat start signal is transmitted to the repeat frame generation unit 422. The repeat frame generation unit 422 that has received this repeat start signal transmits the reception data stored in the data buffering unit 419 to the network via the upper port 411 as repeat transmission frame data. The upper repeat control unit 421 transmits a repeat start signal to the repeat frame generation unit 422 and also transmits a suppression signal to the lower repeat control unit 415. In the relay station, the frame transmitted by itself may be received by itself. To prevent this, when transmitting frame data from the upper port 411, a signal for suppressing reception at the lower port 417 via the lower repeat control unit 415 is sent to the upper repeat control unit 421. To send.

  If the upper repeat control unit 421 determines that it is not necessary to perform relay, a repeat start signal is not generated and received data is not relayed.

  The processing performed at the relay station is shown in the flowchart of FIG. As shown in the figure, the host port side first starts in a standby state waiting for frame reception (step 1501). After receiving the frame, the start code of the received frame is detected (step 1502). When the start code of the frame is detected, header identification (frame type identification) is performed based on the frame identification header included in the frame described above with reference to FIG. 9, and whether or not the frame type is a repeat target frame. Is determined (step 1503). If the target frame is a repeat target frame (step 1503, repeat target frame), a signal for stopping reception and repeat to the lower port is transmitted (step 1504), and then repeat processing to the lower port is started (step 150). 1505). On the other hand, if the target frame is a non-repeatable frame (step 1503, non-repeatable frame), the process returns to step 1501 and waits for the next received frame.

  Similarly, the lower port side starts in a standby state waiting for frame reception (step 1506). After receiving the frame, the start code of the received frame is detected (step 1507). When the start code of the frame is detected, header identification (frame type identification) is performed based on the frame identification header included in the frame, and it is determined whether or not the frame type is a repeat target frame (step 1508). ). If the target frame is a repeat target frame (step 1508, repeat target frame), a signal for stopping reception and repeat to the higher port is transmitted (step 1509), and then repeat processing to the higher port is started (step 1509). 1510). On the other hand, if the target frame is a non-repeatable frame (step 1508, non-repeatable frame), the process returns to step 1506 and waits for the next received frame.

  With such a configuration, each relay station can determine the type of received frame and relay only frames that need to be relayed. In the above embodiment, the network configuration is described as two relay stations and five slave stations. However, the same effect can be obtained by performing the same processing in different networks.

  In addition, a relay station having such a function can switch between a frame to be relayed and a frame not to be relayed by setting. Similarly, it is also possible to provide a period (time) during which no relay process is performed by setting.

  Furthermore, in the above configuration, the relay operation itself of an arbitrary relay station can be stopped. As a result, an independent network separated by relay stations whose relay operation has been stopped can exist.

  An example in which an independent network is configured with one relay station in the network as a partition is shown in FIG. In this figure, the basic configuration is the same as that of FIG. 10 and FIG. 11 described above, so the same reference numerals are given to the same components and the description thereof is omitted. 16 differs from the network configurations of FIGS. 10 and 11 in that a submaster (submaster) station 60 is installed on the network branch line 32. In such a network configuration, by setting so as to stop the relay operation in the relay station 50a on the network branch line 32, it is possible to configure an independent network separated by the relay station 50a in which the relay operation is stopped. Become. More specifically, in the network of FIG. 3, the network branch line 32 divided by the relay station 50a, the slave station 40d, the slave station 40e installed on the network branch line 32, and the newly installed submaster. Station 60 is configured as an independent network. Then, by connecting the sub master station 60 to this independent network, high-speed communication within the independent network becomes possible.

  When this independent network is incorporated into the same network again, a return instruction frame is transmitted from the sub-master station 60 to the relay station 50a. When the relay station 50a receives the return instruction frame, the relay station 50a returns a frame indicating a status of returning to the master station 30 and restarts the relay operation. This restores the network.

  In the case of the above-described return method, it may take time to return. In this case, it may be set such that the relay operation is stopped only for a predetermined time from the reception of a specific frame at the upper port of the target relay station (the relay station 50a in this example) for which the relay operation is stopped. With such a configuration, it normally operates as a part of the network, and when a predetermined frame is received from the master station, the relay operation is stopped for a predetermined period, and an independent network separated from the network is configured. If the sub-master 60 is set to operate only during the period when the relay station stops the relay operation, it operates as an independent network for a predetermined period, and when the period expires, the relay operation can be reunited and returned to the normal network. It becomes possible. In this way, an independent network partitioned by the relay station is efficiently formed, high-speed communication within the independent network is realized, and return to the normal network is facilitated.

  Next, the flow of communication frames in a network to which the present invention is applied will be described with reference to FIGS. FIG. 17 is a system configuration diagram of the network used in the description of the conventional example. The case where the present invention is used in the same system configuration will be described below. Needless to say, since the configuration of FIG. 17 has already been described in detail in the description of the conventional example, description thereof is omitted here.

  The operation of the master station in the network system having such a configuration will be described with reference to the flowchart shown in FIG. As shown in the figure, the master station first transmits a BF (Beacon frame) (step 1101). This BF is transmitted simultaneously at predetermined intervals, and has a function of notifying each slave station how many (how many) relay stations exist on the transmission path from the master station. Subsequently, a trigger frame is transmitted (step 1102). This trigger frame is transmitted to a specific address, and includes an instruction to transmit the CN frame after reception at the target slave station. Therefore, the master station confirms whether a CN frame has been returned from the slave station after transmitting the trigger frame (step 1103). The CN frame referred to here is a response frame of the slave station to the trigger frame transmitted by the master station. The master station performs the following joining process on the slave that has returned the CN frame. If a CN frame has been returned (step 1103, YES), the slave station that is the transmission source of the CN frame is joined. As the joining process, a StatusRead frame for performing a slave information reading process is transmitted (step 1104). Although this reading process is omitted in the flowchart of the figure, transmission of StatusRead to the target slave station and reception of the response are executed. Then, the process of reading the type information of the target slave station included in the response from the slave station and the number of relay station passing stages of the corresponding slave is performed. The master station grasps the network configuration from the slave station information obtained by this reading process, and creates a time domain based on the information. Then, as another process of the subscription process, an information write process (step 1105) for the slave by StatusWrite is performed. Also in this write process, although not shown in the flowchart of FIG. 6, a process of transmitting StatusWrite to the target slave station is performed. This StatusWrite includes the created time domain, and instructs the slave station side to perform response processing at the timing specified in the time domain on the slave station side. When these processes are completed, the process returns to Step 1101 again.

  Next, the operation on the slave station side will be described with reference to FIG. Based on the BF from the master station, the frame transmission rate and the number of relay station passing stages are ascertained using the method described above (step 1201). When this grasping process is completed, the state transitions to a state where a trigger frame from the master station can be received (step 1202). Whether or not a trigger frame is received from the master station is confirmed (step 1203). At this time, if the reception of the trigger frame cannot be confirmed (step 1203, NO), the process waits until the trigger frame is received. If reception of the trigger frame from the master station can be confirmed (step 1203, YES), it is identified whether the trigger frame is addressed to the own station (whether it is a CN response corresponding node) (step 1204). At this time, if the node is not a CN response corresponding node (step 1204, NO), the process returns to step 1203 and waits for the next trigger frame. If the node is a corresponding CN response node (step 1204, YES), a CN frame is returned to the master station (step 1205). Subsequently, it waits for the reception of StatusRead from the master station (step 1206 and step 1206, NO). If StatusRead from the master station is received (step 1206, YES), it returns the number of passing steps of its own relay station to the master station as a response to the received StatusRead (step 1207). Subsequently, it waits for reception of StatusWrite from the master station (step 1208 and step 1208, NO). When StatusWrite is received from the master station (step 1208, YES), the state is changed to the subscription state by the parameter of StatusWrite and the time domain is reflected (step 1209). The reflection of the time domain is to set the own station so as to transmit a response frame at a response timing specified in the time domain created by the master station.

  As described above, when the initial processing is completed for the master unit and all the slave units, a communication cycle for exchanging I / O information is executed as follows. The master unit broadcasts a request frame including output data to the slaves. Each slave unit sequentially transmits response frames including input data based on the time domain received from the master unit. After all the slave units have transmitted the response frame, the master unit broadcasts the request frame again and repeats the I / O information exchange communication cycle.

  FIG. 20 shows an operation model showing, in time series, the request frame transmitted from the master station and the response frame responded by each slave station at the four observation points A to D shown in FIG. As shown in the figure, at observation point A, in addition to the request frame from the master station, response frames from each slave station are known, but at other observation points B, C, and D, Only the request frame from the master station and the response frame from the slave station located downstream from each observation point in the network configuration are known, and unnecessary frames are not relayed as in the conventional example shown in FIG. Is clear.

  In this embodiment, each relay station is set to relay the response frame only from the downstream to the upstream, and each response frame passes so that the interval between the response frames can be minimized at the observation point A. It is set to respond quickly by the repeater delay time corresponding to the number of relay stations. With this setting, the interval between the response frames at the observation point A can be minimized, and as shown in FIG. 20, a reduction in repeater delay is realized in each response frame.

The transmission timing of the response frame in each slave station is
Response time transmission start of the corresponding slave station response frame after receiving the request frame = Position of the response frame of the corresponding slave station at observation point A
Request frame arrival delay
-Time until the corresponding slave station response frame arrives at observation point A = position of the corresponding slave station response frame at observation point A
-Repeater delay x number of repeater (relay station) stages to the corresponding slave x 2
It becomes.

At this time, the communication cycle is
Communication cycle =
Requested frame time + repeater delay x maximum number of repeater stages
+ (Response frame time) x number of slaves.

  Therefore, compared with the conventional example, the communication cycle becomes faster by the amount of “repeater delay × maximum repeater stage number × (2 × number of slaves−1)”.

  In addition, when the cycle time of the communication network using the conventional technology and the communication network having the same network configuration and applying the present invention was compared, the cycle time of 1.8 ms in the conventional example was By applying the present invention, the time was reduced to 1.2 ms.

  As is apparent from the above description, according to the present invention, the relay station on the network discriminates the type of communication frame to be relayed and relays only necessary information, thereby reducing the network occupancy rate. It is possible to improve efficiency and speed up the communication cycle.

It is a block diagram of a PLC system including a communication master station, a communication slave station, and a relay station. It is a hardware block diagram of a communication master station. It is a hardware block diagram of a communication slave station. It is a hardware block diagram of a relay station. It is a frame block diagram of a BEACON frame. It is a schematic diagram of transmission / reception of a frame. It is a process flowchart at the time of BF reception of a relay station. It is a process flowchart at the time of BF reception of a slave station. It is a frame block diagram of a frame. It is a figure explaining frame transmission from a master station to a slave station. It is a figure explaining the frame transmission from a slave station to a master station. It is a figure explaining the network occupation rate of a prior art. It is a figure explaining the network occupation rate in this invention. It is a functional block diagram for demonstrating operation | movement of a relay station. It is a flowchart which shows the process of a relay station. It is a figure explaining the structure of the independent network using a submaster station. FIG. 2 is a system configuration diagram of a network configured with two relay station stages. It is a flowchart of the initial process of a master station. It is a flowchart of the initial process of a slave station. It is a frame operation model (the present invention) in a relay station two-stage configuration. It is a frame operation model (conventional example) in a two-stage relay station configuration.

Explanation of symbols

1 PLC
2 Slave station 3 PC
4 relay station 5 terminator 6 field bus 7 I / O device 10 communication master unit 20 CPU unit 30 master station 31 network trunk line 32 network branch line 1
33 Network branch line 2
40a-40e Slave station

Claims (14)

A master station, which is a programmable controller having a communication function, and one or more slave stations, which are I / O terminal devices having a communication function, are connected by a network and are located on the network and located upstream. In a communication system in which a relay station functioning as a repeater is interposed over one stage or two or more stages on a path connecting a station and a slave station located downstream ,
Some communication frames that will be transmitted or received on the network,
Communication frame cage containing Marete with identification information for identifying that it is the first frame type emanating from the slave station only to the master station,
The relay station
When the upstream port connected to the upstream network and the downstream port connected to the downstream network are provided, and the identification information of the frame received at the upstream port or the downstream port is identified as the first frame type, A communication system, wherein a received frame is relayed only in the direction from the downstream port to the upstream port . Some communication frames sent and received on the network
Communication frame cage containing Marete with identification information for identifying that the master station is a second frame type emitted only to the slave station,
The relay station
When the identification information of the frame received at the upstream port or the downstream port is identified as the second frame type, the received frame is relayed only in the direction from the upstream port to the downstream port. line cormorants communication system according to claim 1, characterized in that. Some of the communication frame transmitted and received by the network further
Communication frame cage containing Marete with identification information for identifying that it is the third frame type emitted in both directions between the master station and the slave station,
The relay station
When the identification information of the frame received at the upstream port or the downstream port identifies that it is the third frame type, for the received frame , the direction from the received upstream port to the downstream port or the received downstream The communication system according to claim 1 , wherein relay processing is performed in a direction from the port to the upstream port . The master station
Transmits a communication frame specific to the slave station, reads the passage number of the relay station from the response frame from the slave station for the particular communication frame, based on the passage number of the read relay station, the slave station calculates the time domain for setting a timing for returning the response frame to the communication frame from the master station performs the writing process to the slave station of the time domain, to any one of claims 1-3, characterized in that The communication system described. The time domain for setting the timing for transmitting a response frame for the communication frame from the master station in the slave station is calculated so that the master station can receive a plurality of response frames without gaps. Item 5. The communication system according to Item 4 . The specific communication frame transmitted from the master station to the slave station can include information on the address value of the relay station that has passed and information on the number of relay station stages,
The relay station
When the specific communication frame passes, the address information of the own station and the information of the value obtained by adding +1 to the number of relay station stages are included in the specific communication frame ,
Slave station
From the specific communication frame , a process of extracting information on the address value of the relay station adjacent to the upper side of the own station and information on the number of relay station stages;
A process of including, in the response frame to the master station, information on the address value of the relay station adjacent to the upper side of the own station read from the specific communication frame and information on the number of relay station stages, The communication system according to claim 4 . A communication frame that will be transmitted or received over a network is included in-frame to the IN data input from the input device connected to the slave station slave station replies in response to the master station,
Slave station
Based on the time domain held by the local station, the response is sent back in-frame earlier by the repeater delay time.
The relay station
6. The communication system according to claim 5 , wherein relay processing is performed only in the direction from the downstream port to the upstream port for in-frame. Slave station
The master station transmits a connection frame for confirming the existence of the slave station to the master station.
The master station
Sends a trigger frame requesting the slave station to send a connection frame,
Slave station
Based on the time domain, a connection frame as a response to the trigger frame is returned earlier by the repeater delay time,
The relay station
6. The communication system according to claim 5 , wherein the connection frame is relayed only from the downstream to the upstream direction. A master station, which is a programmable controller having a communication function, and one or more slave stations, which are I / O terminal devices having a communication function, are connected by a network and are located on the network and located upstream. In a communication system in which a relay station functioning as a repeater is interposed over one stage or two or more stages on a path connecting a station and a slave station located downstream ,
Among the communication frames sent and received on the network,
Communication frame having a first frame type emanating from the slave station only to the master station cage contains Marete,
The relay station
It includes a downstream port connected to the upstream port and the downstream side of the network connected to the upstream side of the network, when the identification information of the received frame is identified to be the first frame type, for a frame in which the received Performs relay processing only in the direction from the downstream port to the upstream port ,
Slave station
The time domain for setting the timing at which the slave station returns a response frame to the communication frame from the master station, determined based on the number of relay stations intervening with the master station, is stored in advance. The time domain is determined so that the master station can receive a plurality of response frames without gaps. Slave station
The master station transmits a connection frame for confirming the existence of the slave station to the master station.
The master station
Sends a trigger frame requesting the slave station to send a connection frame,
Based on the time domain, the slave station returns a response to the connection frame earlier by a repeater delay time,
The communication system according to claim 9 , wherein the relay station performs a relay process only for a connection frame from downstream to upstream. In the communication frame,
In-frame for transmitting IN data of I / O terminal device, which is a slave station , to the master station is included.
Slave station
Based on the time domain , the master station returns a response so that the master station can receive a plurality of response frames without any gaps, including the IN data of the I / O terminal device,
The relay station
The communication system according to claim 9 , wherein the in-frame is subjected to relay processing only from downstream to upstream. A master station which is a programmable controller having a communication function, linked with one or more slave stations are I / O terminal devices having the communication function in the network, and by Tsu near the network, located upstream A relay device in a communication system in which a relay station that functions as a repeater is interposed over one or more stages on a path connecting a master station and a slave station located downstream ,
An upstream port connected to the upstream network and a downstream port connected to the downstream network;
Receiving means for receiving various communication frames from the upstream port or the downstream port ;
Identifying means for identifying the type of communication frame received by the receiving means from the identification information included therein ;
When the type of the communication frame identified by the identification unit is the first frame type that is issued only from the slave station to the master station, the relay process is performed only in the direction from the downstream port to the upstream port. A relay apparatus comprising: a relay control unit. Relay control means
When the type of the communication frame identified by the identifying means is the second frame type issued only from the master station to the slave station, the relay process is performed only in the direction from the upstream port to the downstream port. The relay apparatus according to claim 12. Relay control means
When the type of the communication frame identified by the identification means is the third frame type that is transmitted bidirectionally between the master station and the slave station , the direction from the upstream port to the downstream port or the upstream from the downstream port The relay apparatus according to claim 12, wherein relay processing is performed in a direction toward a port .

Images