JP2012182512A - Ring type network system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to continue communication by allowing loopback even if a logical disconnection state occurs such that normal communication cannot be performed although electric connection is maintained.SOLUTION: A master station 1 generates and transmits a disconnection detection frame to adjacent slave stations #1 (2), #4 (5) when detecting continuous transmission failures. The slave station #4 (5) responds when it receives the disconnection detection frame, and if its own station is not an end terminal station, it transmits the disconnection detection frame to an adjacent station #3 (4) other than the transmission source station. Then, the slave station #4 (5) performs loopback regarding its own station as an end terminal station, if it cannot receive a response from the adjacent station #3 (4) even when a prescribed time has elapsed since it sent the disconnection detection frame.

Description

  In the present invention, a ring type transmission path is formed by connecting a plurality of nodes (stations) in a daisy chain and turning back a line (signal line) between the stations connected at both ends of the daisy chain. Related to network system.

  FIG. 6 is a configuration diagram illustrating an example of a ring network system. This ring network system is configured by daisy chaining a master station and a plurality of slave stations # 1, # 2, # 3, and # 4 to a line. Then, the slave stations # 2 and # 3 located at the end detect that the station is not connected to one side and loop back inside to form a ring-shaped transmission path.

  All the stations constituting such a ring network system monitor the network signal lines in the physical layer, and because of the reason that the amplitude (potential) is not detected or is small, it is caused by disconnection or connector disconnection. It is determined that it is “disconnected”. In this case, the station near the disconnection point detects a communication error, loops back the line, and maintains the line in a connected state so that data exchange between stations other than the disconnected station is continued. It is configured.

  In the ring network system shown in FIG. 6, the slave station # 4 detects a disconnection because the amplitude is not detected from the signal line with the slave station # 3, and loops back to detect a ring-shaped transmission path. Is maintained.

  For example, Patent Document 1 discloses a technique for recovering a network from a disconnected state by monitoring a beacon frame that does not affect the state of each station in a network system in which loopback is performed. Further, in Patent Document 2, in a loop-back network system having a main transmission line and a sub-transmission line, disconnection is detected once, and a Low signal is output to the transmission line on the side where an abnormality is detected. A technique is disclosed that can detect a disconnection correctly even when one of the transmission lines is disconnected by detecting a disconnection. All of the inventions described in these patent documents are methods for detecting disconnection by monitoring the signal level.

JP 2001-7830 A JP-A-3-185951

  However, according to the above-described prior art, even if the amplitude (potential) of the signal propagating through the signal line can be detected, even if the signal is electrically connected due to damage of the network cable or the like, the CRC is not suitable for reasons such as poor contact. (Cyclic Redundancy Check) If a logical disconnection occurs that prevents normal communication due to frequent abnormalities, loopback cannot be performed, and communication cannot be continued. .

  The present invention has been made in view of the above-described problems, and the object of the present invention is to provide a loopback even in the case where a logical disconnection state occurs in which communication cannot be normally performed while being electrically connected. It is an object of the present invention to provide a ring network system that enables communication to be continued.

  In order to solve the above problems, a ring network system of the present invention is a ring network system in which a plurality of stations including a master station and a slave station are daisy chain connected to form a ring-shaped line. The station includes a frame transmission unit that circulates the frame on the ring-shaped line, a logical disconnection detection unit that detects that the frame transmitted by the frame transmission unit does not return, and the logical disconnection detection unit. A disconnection detection frame transmitting means for transmitting a disconnection detection frame to a slave station adjacent to the master station when it is detected that no return is made, and a response frame for the disconnection detection frame is transmitted to the master station after transmitting the disconnection detection frame. Connection from the slave station adjacent to the And a first loopback control means for disconnecting from the slave station and looping back the line when the disconnection detection response frame is not received from a slave station adjacent to the master station. A response frame transmitting means for receiving the disconnection detection frame transmitted from the adjacent station that transmitted the disconnection detection frame and transmitting the response frame to the adjacent station; When the station is an intermediate station, the disconnection detection frame relay means for relaying the disconnection detection frame to a slave station connected downstream of the own station, and after the disconnection detection frame is relayed by the disconnection detection frame relay means, When a response frame to the disconnection detection frame is received from a slave station connected downstream of the own station, the connection with the slave station is maintained, When the disconnection detection response frame is not received from a slave station connected downstream of the own station, a second loop that disconnects the slave station connected downstream of the own station and loops back the line And a second communication control unit having a back control means.

  According to the present invention, when the master station continuously detects a communication failure, the master station transmits a disconnection detection frame to an adjacent slave station, and the slave station that has received this disconnection detection frame is not disconnected. Is returned, and a disconnection detection frame is transmitted to the other adjacent station. Then, the master station or slave station that has transmitted the disconnection detection frame determines that it is disconnected when there is no response within a predetermined period, and loops back with the local station as the terminal station. For this reason, it is possible to identify the location where the disconnection occurs even in a logical disconnection state where normal communication is not possible due to deterioration of the network cable, etc. Can continue.

  In the ring network system of the present invention, the disconnection detection frame transmitting means transmits the disconnection detection frame only to the slave station connected to one end of the master station when the master station is a terminal station. When the station is an intermediate station, the disconnection detection frame is transmitted to each of the slave stations at both ends adjacent to each other.

  According to the ring network system of the present invention, even if a logical disconnection state occurs in which electrical communication is not possible but normal communication is possible, loopback is possible and communication is continued. Can do.

It is a figure which shows the structure of the ring type network system which concerns on embodiment of this invention. It is a block diagram which shows the structure of the master station of the ring type network system which concerns on embodiment of this invention, and a slave station. It is a sequence diagram which shows operation | movement of the ring type network system which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the master station of the ring type network system which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the slave station of the ring type network system which concerns on embodiment of this invention. It is a figure which shows the structure of the conventional ring type network system.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments (hereinafter, this embodiment) according to the present invention will be described in detail with reference to the drawings.
(Configuration of the embodiment)
FIG. 1 is a diagram showing a configuration of a ring network system according to the present embodiment. In FIG. 1, in the ring network system 10, a master station 1 and a plurality of slave stations # 1 (2), # 2 (3), # 3 (4), # 4 (5) are daisy chain connected. ing. Then, the line 6 is ring-shaped by turning back the lines by the stations # 2 (3) and # 3 (4) which are the terminal stations.

  As shown in FIG. 2, the master station 1 includes a master communication control unit 11A including a loopback control unit 115. The master communication control unit 11A generates a disconnection detection frame when detecting that transmission has failed continuously, and transmits the disconnection detection frame to the adjacent slave stations # 1 (2) and # 4 (5). When a disconnection detection response frame cannot be received even after a predetermined time has elapsed since the transmission of, the loopback control unit 11B has a function of looping back with the local station as a terminal station.

  As shown in FIG. 2, the master communication control unit 11A includes a main control unit 110, a transmission / reception unit 111, a logical disconnection detection unit 112, a disconnection detection frame generation unit 113, a response determination unit 114, and a loopback control. Part 115.

  The transmission / reception unit 111 transmits / receives a frame via the line 6 to / from adjacent slave stations # 1 (2) and # 4 (5). The logical disconnection detection unit 112 checks whether the frame transmitted to the line 6 via the transmission / reception unit 111 has returned to normal after going around the line 6. Then, when detecting that the transmitted frame does not return continuously for a predetermined time, the logical disconnection detection unit 112 determines “logical disconnection” and starts the disconnection detection frame generation process in the disconnection detection frame generation unit 113. Let That is, the logical disconnection detection unit 112 detects a logical disconnection when frame transmission by the transmission / reception unit 111 fails continuously for a predetermined time, and instructs the disconnection detection frame generation unit 113 to generate a disconnection detection frame.

  Under this instruction, the disconnection detection frame generation unit 113 generates a disconnection detection frame and transmits it to the adjacent slave stations # 1 (2) and # 4 (5) via the transmission / reception unit 111. The response determination unit 114 detects the inability to communicate with the adjacent station when the disconnection detection response frame cannot be received from the adjacent station even after a predetermined time has elapsed since the transmission / reception unit 111 transmits the disconnection detection frame. Based on the detection of the inability to communicate with the adjacent station, the main control unit 110 causes the loopback control unit 11B to perform loopback control with the local station as the terminal station.

  When the logical disconnection is detected by the logical disconnection detection unit 112, the main control unit 110 automatically detects the disconnection detection frame generated by the disconnection detection frame generation unit when the local station is not a terminal station, that is, an intermediate station. The transmission / reception unit 111 is instructed to transmit to slave stations # 1 (2) and # 4 (5) at both ends of the station.

  On the other hand, the slave station # 4 (5) includes a slave communication control unit 15A including a loopback control unit 154, as shown in FIG. When the slave communication control unit 15A receives the disconnection detection frame, the slave communication control unit 15A generates a disconnection detection response frame and sends it back to the transmission source station that has transmitted the disconnection detection frame. It has a function of transmitting (relaying) a disconnection detection frame to adjacent stations other than the transmission source station. Further, the slave communication control unit 15A has a function of connecting to an adjacent station when communication is possible between adjacent stations, and looping back the line 6 when communication is not possible between adjacent stations.

The slave communication control unit 15A includes a main control unit 150, a transmission / reception unit 151, a disconnection detection frame rotation control unit 152, a response determination unit 153, and a loopback control unit 154.
The transmission / reception unit 151 transmits / receives a frame to / from the adjacent master station 1 and slave station # 3 (4) via the line 6. When the own station is a terminal station, the disconnection detection frame circulatory control unit 152 receives the disconnection detection response frame via the transmission / reception unit 151, and transmits the disconnection detection response frame to the adjacent transmission source station that has transmitted the disconnection detection frame. Reply to Further, when the own station is not a terminal station, that is, when it is an intermediate station, the disconnection detection frame circulatory control unit 152 receives the disconnection detection response frame when the disconnection detection frame is received, and the adjacent transmission that has transmitted the disconnection detection frame. A reply is sent to the original station, and a disconnection detection frame is transmitted (relayed) to the adjacent station connected to the other station. The response determination unit 153 causes the loopback control unit 154 to execute loopback using the local station as a terminal station when the disconnection detection response frame cannot be received even after a predetermined time has elapsed since the disconnection detection frame was transmitted (relayed). .

  The main control unit 150 determines whether or not the own station is a terminal station. When the own station is not a terminal station (intermediate station), the main control unit 150 generates a disconnection detection response frame at the time of receiving the disconnection detection frame and transmits the disconnection detection frame to the transmission source station (adjacent station). A function to send a disconnection detection frame to an adjacent station other than the transmission source station, and if the disconnection detection response frame cannot be received even after a predetermined time has elapsed since the disconnection detection frame was transmitted, In order to realize the function of causing the loopback by the loopback control unit 15B, that is, the function as the “slave communication control unit 15A”, the transmission / reception unit 151, the disconnection detection frame circulation control unit 152, The response determination unit 153 and the loopback control unit 154 are controlled (details will be described later).

  That is, the main control unit 150 monitors the disconnection detection frame. When the disconnection detection frame is not received, the main control unit 150 transmits the received normal frame to the slave station # 3 (4) adjacent downstream to transmit the normal frame to the line. The frame is controlled so as to circulate at 6. Further, when the reception of the disconnection detection frame is confirmed, the main control unit 150 performs frame circulation control so as to return a disconnection detection response frame indicating a response to the disconnection detection frame to the master station 1 that is the transmission source. . Further, the main control unit 150 maintains the connection state of the line 6 if the own station is a terminal station, and detects disconnection with respect to the slave station # 3 (4) located adjacent to the downstream if it is an intermediate station. Controls the circulation of frames that relay frames.

The slave stations # 1 (2), # 2 (3), and # 3 (4) all have the same configuration as that of the slave station # 4 (5), and thus the description of the configuration is omitted to avoid duplication. To do.
(Operation of the embodiment)
FIG. 3 is a sequence diagram showing the operation of the ring network system 10 according to the present embodiment. First, the schematic operation of the ring network system 10 shown in FIG. 1 will be described with reference to the sequence diagram of FIG.

  FIG. 3A shows how the frame circulates during normal communication. The frame generated by the master station 1 returns after sequentially circling adjacent slave stations # 1 (2), # 2 (3), # 3 (4), and # 4 (5). At this time, the master station 1 performs a CRC check in order to detect an abnormality such as garbled data in the frame that has returned after being circulated. As shown in FIG. 3B, it is assumed that a logical disconnection occurs between slave station # 3 (4) and slave station # 4 (5). The master station 1 detects this logical disconnection by, for example, continuously failing communication for 10 [ms], that is, by not normally receiving a circulating frame continuously for 10 [ms]. At this time, as shown in FIG. 3C, the master station 1 transmits a disconnection detection frame to each of the adjacent slave stations # 1 (2) and # 4 (5).

  As shown in FIG. 3D, the slave station # 1 (2) that has received the disconnection detection frame notifies the master station 1 that is the transmission source station of the disconnection detection frame to the disconnection detection response frame. Reply by sending At the same time, the slave station # 1 (2) transmits (relays) the disconnection detection frame to the slave station # 2 (3) that is adjacent and located downstream, and circulates the disconnection detection frame. Similarly, the slave station # 4 (5) that has received the disconnection detection frame responds that it is not disconnected by transmitting a disconnection detection response frame to the master station 1 that is the transmission source station of the disconnection detection frame. At the same time, slave station # 4 (5) transmits (relays) the disconnection detection frame to slave station # 3 (4) that is adjacent and located downstream, and circulates the disconnection detection frame.

  At this time, as shown in FIG. 3 (e), the slave station # 4 (5) has received a response of 10 [ms] from the slave station # 3 (4) for the disconnection detection frame transmitted by itself. Therefore, a disconnection is detected, and loopback is performed with the local station as the terminal station. Thereafter, as shown in FIG. 3F, the slave station # 3 (4) is disconnected from the network (line 6), and the frame is circulated in a degenerated configuration.

  Next, operations of the master communication control unit 11A in the master station 1 and the slave communication control unit 15A in the slave station # 4 (5) will be described in detail with reference to the flowcharts shown in FIGS. To do.

  As shown in FIG. 4, the master station 1 transmits a frame generated by itself through the transmission / reception unit 111. After this transmission, the master station 1 constantly monitors whether the transmitted frame is normally circulated via the slave stations # 1 (2), # 2 (3), # 3 (4), # 4 (5). (Steps S11 and S12). For example, when the logical disconnection detection unit 112 detects that the frame does not return continuously for 10 ms (step S12 “NO”), the logical disconnection detection unit 112 generates a disconnection detection frame to the disconnection detection frame generation unit 113. Instruct.

  At this time, the main control unit 110 determines whether or not the own station is a terminal station (step S13). If it is not the terminal station (step S13 “NO”), the disconnection detection frame generated by the disconnection detection frame generation unit 113 is transmitted to the slave stations # 1 (2) and # 4 (5) connected to both ends of the local station. ) Is transmitted to the transmission / reception unit 111 (step S15). On the other hand, for example, when the slave station on the left side of the master station 1 is not connected, the master station 1 operates as a terminal station, but if the own station is a terminal station (step S13 “YES”), Only the connected slave station # 1 (2) is instructed to the transmission / reception unit 111 to transmit the disconnection detection frame (step S14).

  As a method for detecting whether or not the own station is a terminal station, it can be determined by detecting the reception carrier of the reception port of the own station. For example, if the reception carrier of both reception ports is detected, the local station is not a terminal station, and if only the carrier of one reception port is detected, the local station is determined to be a terminal station. When the carriers of both reception ports are not detected, it is determined that the local station is not connected to the network and is isolated.

  Further, the master station 1 monitors whether or not a response frame is received with respect to the transmitted disconnection detection frame by the response determination unit 114 (step S16). For example, when a disconnection detection response frame is not received even after 2 ms have elapsed after transmission of a disconnection detection frame (timeout occurrence: step S17 “YES”), the response determination unit 114 cannot communicate with an adjacent station. Is detected and notified to the main control unit 110. With this notification, the main control unit 110 instructs the loopback control unit 115 to perform loopback, and loops back with the local station as the terminal station (step S18). If a disconnection detection response frame can be received without detecting a timeout (“NO” in step S17), the response determination unit 114 notifies the main control unit 110 that the disconnection detection response frame has been received. Under this notification, the main control unit 110 maintains the instruction to the loopback control unit 115 as it is, and maintains the connection state of the line.

  Next, the operation of slave station # 4 (5) will be described. In FIG. 5, the slave station # 4 (5) monitors the disconnection detection frame transmitted from the master station 1 and received by the transmission / reception unit 151 by the main control unit 150 (step S21). When the disconnection detection frame is not received (step S21 “NO”), the main control unit 150 instructs the transmission / reception unit 151 to transmit the received normal frame to the slave station # 3 (4) adjacent downstream, A normal frame is circulated on the line 6.

  When the reception of the disconnection detection frame is confirmed (step S21 “YES”), the main control unit 150 returns a disconnection detection response frame indicating a response to the disconnection detection frame to the transmission source master station 1 (step S22). ). Thereafter, the main control unit 150 determines whether or not the own station is a terminal station (step S23). If the own station is a terminal station (step S23 “YES”), an instruction to the loopback control unit is given. Maintain the line connection status. When the own station is not a terminal station, that is, an intermediate station (step S23 “NO”), the main control unit 150 transmits a disconnection detection frame to slave station # 3 (4) located adjacent to the downstream ( Instruct the disconnection detection frame circuit controller 152 to relay (step S24). Then, the slave station # 4 (5) monitors the response from the slave station # 3 (4) for the transmitted disconnection detection frame by the response determination unit 153 (step S25).

The method for detecting whether or not the own station is a terminal station is the same as that for the master station described above.
Here, for example, when the disconnection detection response frame is not received within 2 ms after the disconnection detection frame is transmitted to the slave station # 3 (4) (step S26 “YES”), the response determination unit 153 sets a timeout. The main control unit 150 is notified of timeout detection. Under this notification, the main control unit 150 instructs the loopback control unit 154 to perform loopback, and loops back with the local station as the terminal station (step S27). As a result, the line 6 is disconnected from the station downstream from the slave station # 4 (5), and the ring-shaped transmission path is reconstructed only by the station upstream from the slave station # 3 (4). Thereafter, the frame is circulated with the station being degenerated.

If a disconnection detection response frame can be received from slave station # 2 (3) without detecting a timeout in step S26 (step S26 “NO”), response determination section 153 mainly receives the disconnection detection response frame. Notify the control unit 150. Based on this notification, the main control unit 150 maintains the instruction to the loopback control unit 154 as it is, and maintains the connection state of the line.
(Effect of embodiment)
As described above, according to the ring network system 10 according to the present embodiment, the master station 1 generates a disconnection detection frame when detecting that transmission has continuously failed, and is adjacent to the slave station # 1. (2) Transmit to # 4 (5). The slave station # 4 (5) responds when the disconnection detection frame is received, and when the own station is not a terminal station, that is, when it is an intermediate station, the slave station # 4 (5) A disconnection detection frame is transmitted. Then, when the slave station # 4 (5) cannot receive a response from the adjacent station # 3 (4) even after a predetermined time has elapsed after transmitting the disconnection detection frame, the slave station # 4 (5) loops back with its own station as the terminal station. . At this time, slave station # 3 (4) is disconnected from the network, and communication is continued in a degenerate configuration. Therefore, for example, it is possible to identify the location where the disconnection occurs even in a logical disconnection state where normal communication is not possible even if it is electrically connected due to deterioration of the network cable, etc. Can continue.

  The route passing through (Step S12 “YES”), (Step S17 “NO”), (Step S21 “NO”), (Step S23 “YES”), and (Step S26 “NO”) The state will be maintained. For this reason, once the loopback is activated and the line is degenerated, the state is maintained. In other words, the present invention operates so as to maintain the line only in the degenerate direction even if the network cable is damaged or poorly contacted, so that the communication where the station is repeatedly dropped and joined is unstable. Therefore, a highly reliable ring network system can be provided.

  As mentioned above, although preferred embodiment of this invention was explained in full detail, it cannot be overemphasized that the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiments. Further, it is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  4 corresponds to the frame transmission means, step S12 in FIG. 4 corresponds to the logical disconnection detection means, and steps S14 and S15 in FIG. 4 correspond to the disconnection detection frame transmission means. Steps S16 to S18 correspond to the first loopback control means.

  Further, step S21 in FIG. 5 and step S22 related to step S21 correspond to response frame transmission means, step S24 in FIG. 5 corresponds to disconnection detection frame relay means, and step S27 related to step S26 and step S26 in FIG. Corresponds to the second loopback control means.

1 Master station 2, 3, 4, 5 Slave station # 1 to # 4
6 lines 10 ring network system 11A master communication control unit 12A slave communication control unit 110, 150 main control unit 111, 151 transmission / reception unit 112 logical disconnection detection unit 113 disconnection detection frame generation unit 114, 153 response determination unit 115, 154 loopback Control unit 152 Disconnection detection frame rotation control unit

Claims (2)

A ring network system in which a plurality of stations including a master station and a slave station are daisy chain connected to form a ring-shaped line,
The master station
Frame transmitting means for circulating a frame around the ring-shaped line;
Logical disconnection detecting means for detecting that the frame transmitted by the frame transmitting means does not return;
A disconnection detection frame transmitting means for transmitting a disconnection detection frame to a slave station adjacent to the master station when the logical disconnection detection means detects that the frame does not return;
After transmitting the disconnection detection frame, when a response frame for the disconnection detection frame is received from a slave station adjacent to the master station, the connection with the slave station is maintained, and the disconnection detection response frame is adjacent to the master station. A first communication control unit having first loopback control means for disconnecting from the slave station when not receiving from the slave station and looping back the line;
The slave station
Response frame transmitting means for receiving the disconnection detection frame transmitted from the adjacent station that has transmitted the disconnection detection frame, and transmitting the response frame to the adjacent station;
Disconnection detection frame relay means for relaying the disconnection detection frame to a slave station connected downstream of the local station when the local station is an intermediate station;
After the disconnection detection frame is relayed by the disconnection detection frame relay means, when a response frame for the disconnection detection frame is received from a slave station connected downstream of the own station, the connection with the slave station is maintained, When a disconnection detection response frame is not received from a slave station connected downstream of the own station, a connection with the slave station connected downstream of the own station is disconnected, and a second loopback for looping back the line A ring network system comprising a second communication control unit having control means. The ring network system according to claim 1,
The disconnection detection frame transmission means includes:
When the master station is a terminal station, the disconnection detection frame is transmitted only to the slave station connected to one end of the master station, and when the master station is an intermediate station, the master station is connected to the slave stations at both ends adjacent to each other. A ring network system characterized by transmitting a disconnection detection frame.

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