JP6992346B2 - Network system - Google Patents

Description

The present invention relates to a network system having a ring-type logical topology and a synchronization method in the network system.

A logical topology refers to a logical form of a data transmission path in a communication system. The logical topology in the communication system does not always match the physical topology which is the physical connection form of each node device in the communication system. For example, even if the communication system has a bus-type physical topology in which each node device is connected in a straight line, the data transmission path is folded back at the node devices at both ends, and the data is relayed twice at each node device, going back and forth. Therefore, a ring-type logical topology can be realized.

As an example of a system having a ring-type logical topology, a control system in a factory or a plant is known. Control systems often employ a ring-type physical topology to avoid outages due to communication interruptions. In the case of a bus-type physical topology, if a disconnection occurs in one place of the communication line between the node devices, the function of the entire system is impaired. On the other hand, in the case of a ring-type physical topology, it is possible to continue operation as a bus-type physical topology by performing loopback processing on each of the two node devices adjacent to the disconnection point. ..

In this explanation, it is assumed that the logical topology is a ring type, and if the physical topology is a bus type, it is called "bus type (control) system", "bus type network", etc., and if the physical topology is a ring type, it is called. It shall be called "ring-type (control) system", "ring-type network", or the like.

In a control system, timer synchronization technology is extremely important because a plurality of node devices cooperate to execute processing.

Network Time Protocol (NTP) or IEEE1588 is widely known as a timer synchronization method in a network.

Here, Patent Document 1 discloses a timer synchronization technique in a ring-type control system in which two ring-type data transmission paths having opposite data transmission directions are formed.

Further, Patent Document 2 discloses a time synchronization method in a bus-type network having a ring-type logic topology.

Patent Document 2 proposes a network system in which a plurality of nodes are connected in a bus type and a ring-shaped transmission path is formed by folding back a line at both nodes, and a synchronization method in the network system. There is.

In the prior art,
The reference time of each station is synchronized in the order of (1) delay time measurement → (2) delay time collection → (3) delay time setting → (4) master time distribution.

Since the crystal that is the basis of the reference time of each station gradually has a clock error within the range of the PPM specifications, the reference time of each synchronized station shifts with the passage of time, and the error expands. go. Therefore, in order to maintain the synchronization accuracy within a certain range, "(4) Master time distribution" is periodically carried out to adjust the time to the master station. Generally, in order to maintain the synchronization accuracy of 1us or less, it is necessary to perform "(4) Master time distribution" once every several tens of ms (milliseconds).

Further, in the ring-shaped network or the like in which a plurality of nodes are connected in a ring shape to form a transmission path, when a disconnection occurs, a station adjacent to the disconnection portion automatically executes disconnection detection and loopback processing. That is, each station has a function of detecting the presence or absence of disconnection of the line directly connected to the station based on the link state of the physical layer, and a function of reestablishing the communication path by looping back at the time of detecting the disconnection. From this, when a disconnection occurs at one location, the station adjacent to the disconnection detects the disconnection and automatically loops back to bypass the disconnection and reestablish the communication path so that all stations can communicate. It enables continuous operation of the system.

Japanese Unexamined Patent Publication No. 6-21460 Japanese Unexamined Patent Publication No. 2011-9829

As described above, in a ring-type network or the like, when the communication path is re-established due to disconnection, the "(4) Master time distribution" that is regularly performed is within the same control cycle or re-established. If it is implemented immediately after, "(4) Master time distribution" will be performed on the route after re-establishment, which is different from the route premised on the delay time distributed in advance in "(3) Delay time distribution". May be. In this case, erroneous synchronization correction will be performed for all stations on the downstream side of the disconnection point, and interstation synchronization of the entire system cannot be maintained.

An object of the present invention is to provide a network system or the like that can prevent erroneous synchronization correction from being performed even when a route change is performed due to a disconnection in a network or the like having a ring-type logic topology.

In the network system of the present invention, in a network having a master station and a plurality of slave stations and having a ring-type logical topology, each transmission delay time, which is the communication time between the master station and each slave station, and each from the master station. It is a network system that synchronizes the timer of each slave station with the timer of the master station by periodically distributing the master time to the slaves, and has the following means.

The master station
An overall disconnection determination means for determining the presence or absence of disconnection in the entire network,
When it is determined by the overall disconnection determining means that there is a disconnection in the entire network, the master time distribution is temporarily suspended, and then a confirmation request is transmitted to each slave station to confirm the disconnection / connection status with the adjacent station. As a means of requesting confirmation of disconnection and connection,
After a predetermined time or more has elapsed from the transmission of the confirmation request, each slave station is recalculated to set each transmission delay time, and then the master time distribution is restarted .
The predetermined time is the time from when the confirmation request is transmitted until it becomes possible to assume that the station corresponding to the disconnection point is in the loopback state regardless of where the disconnection occurs on the network. possible.

Each of the slave stations
In response to the confirmation request from the disconnection / connection confirmation requesting means, the disconnection / connection confirmation means for confirming the disconnection / connection state with the adjacent station, and the disconnection / connection confirmation means.
As a result of confirming the disconnection connection state with the adjacent station by the disconnection connection confirmation means, it has a loopback means for looping back when it is determined that there is a disconnection.

According to the network system or the like of the present invention, in a network or the like having a ring-type logical topology, it is possible to prevent erroneous synchronization correction from being performed even when the route is changed due to the occurrence of disconnection.

It is a figure (the 1) which shows an example of the network system to which this method is applied. It is a figure (the 2) which shows an example of the network system to which this method is applied. It is an example of data transmission in the network system of FIGS. 1 and 2. It is a figure which shows the example of the disconnection occurrence in the network system of FIG. It is an example of a ring type network system applied to the example of FIGS. 6 and 7. (A) and (b) are diagrams showing the operation of the previous method. (A) and (b) are diagrams showing the operation of this method. It is a figure which shows the flow of processing of the whole network system. It is a processing flowchart of a master station. It is a processing flowchart diagram of a slave station. This is a configuration example of a node device. It is a processing flowchart diagram of the master station in the case of the configuration of FIG. 11. It is a processing flowchart figure of the slave station in the case of the configuration of FIG. (A) is an image of the process for discriminating between the ring type and the bus type, and (b) is an image of the data obtained by the process. It is a functional block diagram of each node device.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 and 2 are diagrams showing an example of a network system to which this method is applied.

This method assumes that the above-mentioned logical topology is a ring-type network system, and that the logical topology is always ring-type and does not change. In this description, this premise will not be described one by one, and in the following description, "bus type" and "ring type" mean physical topology.

1 and 2 show an example of a "ring-shaped network". In this example, this "ring-shaped network" is, for example, a network in which two ring-shaped data transmission paths having opposite data transmission directions are formed. Further, the "ring-type network" may be changed to the "bus-type network" due to the occurrence of disconnection as described later. As mentioned above, the "bus type" and "ring type" here all mean the physical topology, and this is the same in the following description (the following will not be described one by one).

The "ring-type network" in this example can be continuously operated as a "bus-type network" even if a disconnection occurs. That is, the "ring-type network" presupposed in this example has, for example, two communication lines and forms two rings. Then, when a disconnection occurs, one ring is formed by connecting two communication lines (in a loopback state) at each of the two node devices adjacent to the disconnection point, thereby forming a bus-type network configuration. And.

The network system 1 in the example of FIGS. 1 and 2 has five node devices 10 (10A, 10B, 10C, 10D, 10E). Each node device 10 is connected to the other two node devices 10 by a communication line 2 (2a, 2b, 2c, 2d, 2e), respectively. For example, the node device 10A is connected to the node device 10B by the illustrated communication line 2a and is connected to the node device 10E by the communication line 2e.

Here, for any node device 10, another node device 10 directly connected by the communication line 2 is referred to as an "adjacent station", an "adjacent node", or the like. In the above example, the adjacent stations for the node device 10A are the node device 10B and the node device 10E.

Further, each node device 10 has network connection portions NW1 and NW2. The network connection portions NW1 and NW2 each have an input terminal and an output terminal (not shown). One end of each of the above communication lines 2 (communication line connecting between any two node devices 10) is connected to the network connection portion NW1 of one node device 10, and the other end is connected to the other node device. It is connected to the network connection unit NW2 of 10. In the above example, as shown in the figure, one end of the communication line 2a is connected to the network connection portion NW2 of the node device 10A, and the other end is connected to the network connection section NW1 of the node device 10B.

Although not shown, the communication line 2 is composed of two communication lines, and each communication line is connected to an input terminal and an output terminal (not shown) of the network connection portions NW1 and NW2, respectively. In the above example, one end of the communication line 2a is connected to an input terminal and an output terminal (not shown) of the network connection portion NW2 of the node device 10A, and the other end is not shown of the network connection portion NW1 of the node device 10B. It is connected to the input terminal and the output terminal of.

Further, one end of each of the two communication lines is connected to the input terminal, and the other end is connected to the output terminal. In the above example, one end of one of the two communication lines of the communication line 2a is connected to an input terminal (not shown) of the network connection portion NW2 of the node device 10A, and the other end is a network connection portion of the node device 10B. It is connected to an output terminal (not shown) of NW1. The other end of the two communication lines of the communication line 2a is connected to an output terminal (not shown) of the network connection part NW2 of the node device 10A at one end, and the other end is an input (not shown) of the network connection part NW1 of the node device 10B. It is connected to the terminal.

By connecting the communication lines 2, in the network system of FIG. 1, a first data transmission path D1 shown by a solid line and a second data transmission path D2 shown by a dotted line in FIG. 2 are formed. That is, two rings are formed. Then, for example, in the case of normal operation during normal operation (no disconnection; ring type), communication processing is performed using only one of the two rings (in this example, only the data transmission path D1 is used). Is done. Here, the first data transmission path D1 is described as being transmitted in the clockwise direction, and the second data transmission path D2 is described as being transmitted in the counterclockwise direction, but the present invention is not limited to this example. However, basically, the first data transmission path D1 and the second data transmission path D2 are transmitted in opposite directions to each other.

As shown in FIG. 2, as an example here, each node device 10 has a processing unit. Here, the sign of the processing unit is changed between the master and the slave as shown in the figure. This is because the processing content of the processing unit differs between the master and the slave. Here, it is assumed that the node device 10A is the master and the others (10B, 10C, 10D, 10E) are slaves.

From this, as shown in the figure, only the master node device 10A is referred to as the processing unit 11a, and the slave node devices 10B, 10C, 10D, and 10E are all referred to as the processing unit 11. The processing content of the processing unit 11 is basically the same for all slaves. The processing content of the processing unit 11a is different from that of the processing unit 11. As an example, the left side of FIGS. 9 and 12, which will be described later, shows the processing of the processing unit 11a, and the left side of FIGS. 10 and 13 shows the processing of the processing unit 11.

In FIG. 2, data transmission / reception by the first data transmission path D1 goes through the processing units 11 and 11a, but data transmission / reception by the second data transmission path D2 does not go through the processing units 11 and 11b (transferred as it is).

FIGS. 3 (a) and 3 (b) show an example of the normal operation in the normal time.
As shown in FIG. 3A, in the case of the above example, the packet goes around the network clockwise via the first data transmission path D1, and all the node devices 10 receive this packet. That is, for example, the packet transmitted from the node device 10A, which is the master, follows the first data transmission path D1 in the order of node device 10A → node device 10B → node device 10C → node device 10D → node device 10E → node device 10A. It goes around the network via the network and returns to the source (node device 10A). That is, each node device 10 sequentially relays the packet in the relay format, so that the packet goes around the network, and all the node devices 10 can receive the packet.

Further, as shown in FIG. 3B, in each node device 10, a certain processing time is required for packet relay (from reception from the upstream side to transfer to the downstream side). This is mainly a process for executing a predetermined process in the processing unit 11 or the processing unit 11a (for example, acquiring data from a packet or storing own station data (for example, the latest sensor measurement value) in the packet). Etc.) It is the time it takes.

In FIG. 3A, the second data transmission path D2 is omitted.
In the case of passing through the second data transmission path D2, since it does not go through the processing unit 11 or the processing unit 11a (because it is relayed and transferred as it is), the above-mentioned constant processing time does not take. The second data transmission path D2 will be used when the bus type is changed due to the disconnection.

In the network system of the configuration and operation shown in FIGS. 1, 2, and 3, when a disconnection occurs at an arbitrary position, the physical topology changes to the bus type as described above, but the operation can be continued.

FIG. 4 is a diagram showing an example of disconnection occurrence in the network system of FIG. 1 and the like.
FIG. 4 shows a state after the occurrence of disconnection and after the transition to the loopback state is completed. In other words, it shows the state after changing to the bus type. In addition, the forwarding status of the packet in this state is indicated by an arrow.

In the example shown in FIG. 4, it is assumed that a disconnection has occurred between the node device 10E and the node device 10D (on the communication line 2d). In this example, the node devices 10 adjacent to the disconnection points are the node device 10E and the node device 10D.

As mentioned above, each station (each node device) has a function to detect the presence or absence of disconnection of the communication line directly connected to its own station based on the link state of the physical layer, and puts the side where the disconnection is detected into a loopback state. By having a function to reestablish the communication path, the operation can be continued as a bus-type network system. From this, in the case of the previously considered method (referred to as the previous method) in the example of FIG. 4, when the disconnection occurs, the node device 10E and the node device 10D each independently detect the disconnection. Then, it becomes a loopback state. This method is also the same as the previous method in that the node device 10E and the node device 10D are finally in a loopback state, but the devices 10E and 10D are not "unique" but the master station. It differs from the previous method in that it goes into a loopback state based on the initiative.

When a station in a loopback state receives a packet from any one of the data transmission paths D1 and D2, the station transmits this packet to the other data transmission path to the adjacent station to the source. Loop back. In the case of the node device 10D, the packet transmitted from the node device 10C via the first data transmission path D1 is transmitted (looped back) to the node device 10C via the second data transmission path D2.

From this, in the example of FIG. 4, when the node device 10E and the node device 10D are in the loopback state, the transmission packet from the node device 10A is transmitted by the following procedure.

The packet is first transmitted by the first data transmission path D1 in the order of node device 10A → node device 10B → node device 10C → node device 10D. Then, the packet is looped back by the node device 10D, and the packet is transmitted by the second data transmission path D2 in the order of the node device 10D → the node device 10C → the node device 10B → the node device 10A → the node device 10E. Then, it is looped back by the node device 10E, and this time, it is transmitted from the node device 10E to the node device 10A by the first data transmission path D1, and is passed to the processing unit 11 of the node device 10A. Packet transmission is completed when 11 determines that the packet transmitted by itself has returned.

The fact that the physical topology changes from a "ring-type network" to a "bus-type network" due to such a disconnection is the same in both the above-mentioned previous method and this method. The previous method and this method are the same in that the final result is as shown in FIG. 4, but the process is different (in the previous method, the corresponding node device 10 independently transitioned to the loopback state, but in this method, the master is used. The corresponding node device 10 shifts to the loopback state on the initiative). This will be described with reference to FIGS. 5, 6, and 7.

First, here, as a specific example, FIG. 5 is used instead of FIG. 4, but as shown in the figure, the same configuration as that of FIG. 4 is given the same sign (10, 11, 11a, etc.). ..

FIG. 5 shows an example of a ring-type network system consisting of one master station (M station) and four slave stations. Each of these stations may be the same as the node device 10. The four slave stations are slave 1 (S1 station), slave 2 (S2 station), slave 3 (S3 station), and slave 4 (S4 station) in the figure.

Further, in FIG. 5, the packet transfer status is indicated by an arrow, but unlike FIG. 4, the packet transfer status is shown in FIG. 5 before the disconnection occurs.

In FIG. 5, before the disconnection occurs, the transmission packet from the master station is transmitted in the order of master station → slave 1 → slave 2 → slave 3 → slave 4 by the first data transmission path D1 and returns to the master station. This completes the packet transmission. Since it is a "ring-type network" before the disconnection occurs, the second data transmission path D2 is not used in this example.

On the other hand, in FIG. 5, for example, when a disconnection occurs between the slave 2 and the slave 3 as shown in the drawing, loopback is performed in the slave 2 and the slave 3, respectively, so that transmission is performed although not shown in FIG. The route is as follows.

The transmission packet from the master station is transmitted in the order of master station → slave 1 → slave 2 by the first data transmission path D1, looped back by the slave 2, and this time by the second data transmission path D2, the slave 2 → Slave 1 → Master station → Slave 4 → Slave 3 are transmitted in this order. Then, it is looped back by the slave 3, is transmitted in the order of slave 3 → slave 4 → master station by the first data transmission path D1, and returns to the master station to complete the packet transmission.

Ultimately, such a state itself is the same in both the previous method and the present method. However, the process for that is different between the previous method and the present method, as shown in FIGS. 6 (b) and 7 (b).

Note that FIG. 5 further shows a communication unit 16 and a communication unit 18 for each node device 10. The communication units 16 and 18 are communication function units corresponding to, for example, the network connection units NW1 and NW2, respectively, and have an input terminal and an output terminal to communicate with an adjacent station to be connected.

Here, FIG. 6A shows a schematic operation from the time when the power of the network system of FIG. 5 in the previous method is turned on. Then, FIG. 6 (b) shows the detailed operation of the previous method when the disconnection occurs at an arbitrary timing during this schematic operation.

As shown in FIG. 6A, when the power is turned on in each node device 10, a predetermined initial process is first executed, and then a synchronization sequence is executed. This synchronization sequence may be an existing technique, and for example, a timer synchronization technique such as Patent Document 1 may be used. As a result of the synchronization sequence, each slave station holds the transmission delay time between the master station and its own station (the time required for packet transmission from the master station to its own station). As a result, each station can synchronize the timer of its own station with the timer of the master station. After that, the operation starts, a predetermined periodic process is repeatedly executed, and the master time is distributed periodically, so that accurate timer synchronization can be maintained.

FIG. 6B shows the detailed operation of the previous method when a disconnection occurs during such an operation.

As shown in FIG. 6B, in the operation during operation, TF frame transmission / reception → MC frame transmission / reception → MSG frame transmission / reception are performed at predetermined tact cycles. In addition, the master time is distributed periodically using the MSG frame transmission / reception band.

The TF frame is a frame for the master station to input the data of each slave station. When each slave station receives a TF frame, it adds its own station data (current data such as sensor measurement values) to the TF frame and then transfers the data to an adjacent station. When the TF frame goes around the network and returns to the master station, the master station can acquire the data of all the slave stations, and based on this, it is possible to perform a predetermined operation to obtain the output data. This output data is transmitted to each slave station by the MC frame.

When each slave station receives the MC frame, it acquires the output data of the master station included in the MC frame and then transfers the data to the adjacent station. From this, as the MC frame goes around the network, all the slave stations can acquire the output data of the master station.

Further, since the MSG frame is a frame for transmitting an arbitrary message, it may be transmitted only when a message occurs. Also, unlike the TF frame and MC frame, it is not necessary to transmit the current state data in real time, so another data may be transmitted using the MSG frame transmission / reception band (hence, for example). Master time distribution is performed).

Each slave is required based on the distributed master time, the time of its own station at the time of distribution reception (timer value of its own station, etc.), and the above-mentioned transmission delay time between its own station and the master station. By correcting the timer of the own station, the timer of the own station is synchronized with the timer of the master station. For example, taking the S3 station as an example, the distributed master time is 0 minutes 00 seconds 00, the transmission delay time is 00 seconds 07, and the time of the own station at the time of distribution reception is 0 minutes 00 seconds 07. Then, since it matches with "distributed master time + transmission delay time (= 0 minutes 00 seconds 00 + 00 seconds 07 = 0 minutes 00 seconds 07)", it is not necessary to correct the timer of the own station.

Then, when a disconnection occurs between the S2 station and the S3 station at any time as shown in the figure, these S2 stations and S3 stations, which are adjacent stations of the disconnection point, immediately detect the disconnection (for example, in a few μs to several ms). Then, it becomes a loopback state. In the illustrated example, the TF frame transmitted between the start of the disconnection and the start of the loopback disappears in the middle (when transferred from the S2 station to the S3 station), but after that (after that). The MC frame etc.) is normally transmitted by loopback as shown in the figure. However, the transmission path has changed.

That is, in FIG. 6B, the transmission path in the loopback state is M station → S1 station → S2 station → S2 station loopback → S1 station → M station → as shown by the solid line arrow and the dotted line arrow in the figure. S4 station-> S3 station-> S3 station loopback-> S4 station-> M station. The solid line arrow in the figure indicates data transmission by the data transmission path D1, and the dotted line arrow indicates data transmission by the data transmission path D2.

In this way, the packet goes around all stations and can continue to operate even after the disconnection, but since the transmission path has changed as described above, the master time is distributed in the loopback state as shown in the figure. If so, the above-mentioned problems will occur.

For example, in the S3 station, the "time of the own station at the time of distribution reception" in the above specific example will change. As described above, in the S3 station, the route from the master station is longer after the disconnection than before the disconnection, so that the "time of the own station at the time of distribution reception" is later after the disconnection than before the disconnection. In the above specific example, if the "time of the own station at the time of distribution reception" is 0 minutes 00 seconds 11 in the loopback state, "distributed master time + delay time (= 0 minutes 00 seconds 00 + 00 seconds)" Since it does not match with "07 = 0 minutes 00 seconds 07)", the timer of the own station is corrected (the amount of deviation (corrects only by the amount of = 00 seconds 04). However, in reality, the timers are synchronized as described above. Since it is a state and does not need to be corrected, the timer synchronization will be out of order by correcting it.

On the other hand, at the stations upstream of the disconnection point (S1 station and S2 station in this example), the transmission delay time (in other words, the route from the master station to the own station) does not change between before and after the disconnection. Such a problem does not occur. Such a problem may occur at a station on the downstream side of the disconnection point.

Here, FIG. 7A shows a schematic operation from the time when the power of the network system of FIG. 5 in this method is turned on. Then, FIG. 7B shows a detailed operation of this method when a disconnection occurs at an arbitrary timing during this schematic operation.

First, since the overall schematic operation itself shown in FIG. 7A is almost the same as the previous method shown in FIG. 6A, no particular description thereof will be given.

As shown in FIG. 7 (b), when a disconnection occurs at an arbitrary time, the operation of the M station itself in the tact cycle immediately after that is the same as in FIG. 6 (b). That is, since the M station has not yet recognized the occurrence of the disconnection at this stage, the normal operation is maintained, and it is assumed that the master time distribution timing is accidentally in this example. As a result, the M station sequentially sends out three types of frames (TF frame, MC frame, and time distribution frame) as shown in the figure. As described above, this operation itself is the same as in FIG. 6 (b), but the transmission state of each of these frames is different from that in FIG. 6 (b) as shown in the figure.

That is, in this method, since each slave station does not perform loopback independently, the S2 station and S3 station are not yet in the loopback state at this timing. Therefore, the S2 station transfers the received frame to the S3 station on the downstream side as usual, but it does not reach the S3 station due to the disconnection (it disappears on the way). Therefore, none of the above three types of frames reaches the stations downstream from the disconnection point (S3 station, S4 station). In this way, the time distribution frame does not reach the stations downstream from the disconnection point (S3 station, S4 station), so that the above-mentioned problem of timer synchronization failure does not occur.

Then, in this method, the master station (M station) determines that a disconnection has occurred somewhere in the entire network because a plurality of frames do not return. From this, here, the above three types of frames in the tact cycle immediately after the occurrence of the disconnection do not return, so it is determined that there is a disconnection somewhere in the entire network, and the normal operation is temporarily stopped in the next tact cycle. Then, it becomes an operation mode for constructing a new transmission path.

In this operation mode, the master station transmits a predetermined specific frame (referred to as an LLD frame) to both systems in the MSG band. Transmission to both systems means transmission to both the data transmission path D1 and the data transmission path D2, in other words, transmission to both adjacent stations. From this, in the illustrated example, the master station (M station) transmits the LLD frame to the S1 station (slave 1) via the data transmission path D1 and the S4 station (slave) via the data transmission path D2. Send to 4).

Here, as described above, each slave station relays and transfers the frame received via the data transmission path D1 via the processing unit 11, and the frame received via the data transmission path D2 transmits the processing unit 11. Relay and transfer as it is without going through. However, these are normal operations and there are exceptions. First, each slave station has a function of temporarily latching a received frame and checking its type and the like. For example, it is checked whether or not the received frame is the above-mentioned specific frame (LLD frame).

Then, when the received frame is the specific frame (LLD frame), each slave station executes the following operation different from the normal operation.

-When an LLD frame from one adjacent station is received, a predetermined response frame is returned to the one adjacent station, and the LLD frame is transmitted (transferred) to the other adjacent station. Then, it waits for the response frame to be returned from the other adjacent station. If there is no reply from the response frame even after waiting for a certain period of time, it is determined that there is a disconnection between the other adjacent station and the loopback state is set.

In the figure, the LLD frame is indicated by a thick line solid line arrow, and the response frame is indicated by a thick line dotted line arrow.

Regarding the TF frame, MC frame, and MSG frame, as in FIG. 6B, the solid line arrow indicates the data transmission by the data transmission path D1, and the dotted line arrow indicates the data transmission by the data transmission path D2.

In the illustrated example, a response frame is returned from the S1 station to the M station for the LLD frame transmitted from the M station to the S1 station, and S2 is returned for the LLD frame transmitted from the S1 station to the S2 station. A response frame is returned from the station to the S1 station. However, since the LLD frame transmitted from the S2 station to the S3 station does not reach the S3 station due to the disconnection, there is no reply of the response frame from the S3 station to the S2 station. From this, the S2 station determines that there is a disconnection between the S2 station and the S3 station, and puts it in a loopback state.

Similarly, in the illustrated example, for the LLD frame transmitted from the M station to the S4 station, a response frame is returned from the S4 station to the M station, and for the LLD frame transmitted from the S4 station to the S3 station. Then, the response frame is returned from the S3 station to the S4 station. However, since the LLD frame transmitted from the S3 station to the S2 station does not reach the S2 station due to the disconnection, there is no reply of the response frame from the S2 station to the S3 station. From this, the S3 station determines that there is a disconnection between the S3 station and the S2 station, and puts it in a loopback state.

From the above, in the illustrated example, the S3 station and the S2 station are in a loopback state. The master station returns to normal operation after the next tact cycle (however, at this time, the master time distribution is still interrupted), but as shown in the figure, as in the previous method shown in FIG. 6 (b), S3 A new transmission path is formed by the loopback of the station and the S2 station, and the frame can go around all the stations, so that it can be operated normally.

After that, as shown in FIG. 7A, the synchronization sequence is re-executed, and each transmission delay time according to the new transmission path is obtained and set in each slave station. Here, the re-executed synchronization sequence is different from the normal synchronization sequence (after the initial processing). As will be described in detail later, since it is always a ring type in normal times, a synchronization sequence is performed according to the ring type, but after a disconnection occurs, the loopback state may occur and the bus type may change. If it is a bus type, it is necessary to perform a synchronization sequence according to the bus type. Details will be described later.

When the re-execution of the above synchronization sequence is completed, the master time distribution is restarted. In this state, even if the master time is distributed, the above-mentioned problem does not occur. This is because, as described above, the transmission delay time (time required for data transmission between the own station and the master station) is set for each slave station according to the new transmission path.

The difference between the operation of this method shown in FIG. 7 and the operation of the previous method shown in FIG. 6 is that the method does not always enter the loopback state until after the master time distribution is temporarily suspended. be. Furthermore, after the loopback state is reached, after the re-execution of the synchronization sequence is completed (that is, after the transmission delay time according to the new transmission path is calculated and installed in each slave station), the master time is distributed. Is to cancel the suspension of. By doing so, it is possible to prevent the occurrence of malfunction due to the distribution of the master time.

Hereinafter, the processing of each station (each node device 10) that realizes the present method will be described with reference to the flowcharts of FIGS. 8, 9, 10, 12, and 13.

As described above, one of the plurality of node devices 10 is used as a master station, and the others are used as slave stations.

FIG. 8 shows the processing flow of the entire network system. The processing operations of the master station and the slave station are shown in FIGS. 9, 10 or 12, 12 and 13 according to the flow of this processing.

In FIG. 8, first, the master station constantly checks whether or not the frame transmitted by the master station has returned to the own station. Then, for example, when the frame does not return a plurality of times in succession, it is determined that a disconnection has occurred somewhere in the entire network (step S1), and the processes after step S2 are executed.

The master station first suspends the master time distribution (step S2).
Subsequently, the process of step S3 is performed. In step S3, starting from the master station, each station sequentially transmits the above LLD frame to an adjacent station of its own station and confirms whether or not there is a response frame reply. In step S3, for example, first, the master station transmits the LLD frame to both systems (both adjacent stations) and waits for a reply of the response frame. When each slave station receives an LLD frame from one adjacent station, it returns a response frame, transmits (transfers) the LLD frame to the other adjacent station, and waits for a reply of the response frame. If there is no reply from the response frame even after a certain period of time has passed since the LLD frame was transmitted, both the master station and each slave station are considered to have a disconnection with the adjacent station and are in a loopback state. .. By doing so, the two stations adjacent to the disconnection point are in a loopback state.

Then, when a predetermined time has elapsed from the LLD frame transmission, the master station re-executes the time synchronization process (synchronization sequence) (step S4). This "predetermined time" is arbitrarily set in advance, but for example, the time required for all the stations constituting the network to confirm the presence / absence of the transmission of the LLD frame and the reply of the response frame (further in this time). It may be a time with some margin added), but it is set by the developer and the like.

By the process of step S4, as described above, a new transmission delay time corresponding to the new transmission path formed by the loopback is calculated and set for each slave station.

Then, when the processing of step S4 is completed, the master station restarts the master time distribution (step S5). As described above, even if the master time is distributed in this state, no problem occurs.

The processing flow of FIG. 8 is realized by, for example, the processing of the master station shown in FIG. 9 and the processing of the slave station shown in FIG. In this example, the processing of the master station is mainly executed by the processing unit 11a, and the processing of the slave station is mainly executed by the processing unit 11.

First, in FIG. 9, when the master station determines that a disconnection has occurred somewhere in the entire network (step S11), the master station executes the processes after step S12. In step S12, the master time distribution is temporarily stopped. Steps S11 and S12 may be the same as steps S1 and S2, and the description thereof will be omitted.

The master station subsequently transmits a confirmation request frame (corresponding to the above LLD frame), which is a specific frame, to both systems (both adjacent stations) (step S13), and the confirmation response frame (corresponding to the above response frame). ) Waits for a reply (step S14). When a confirmation response frame is returned from the adjacent station within a certain period of time (step S14, YES), it is determined that the connection state (no disconnection) between the own station and the adjacent station is made (step S17). On the other hand, if there is no response frame from the adjacent station even after a certain period of time has passed (step S14, NO), it is determined that there is a disconnection between the own station and the adjacent station (step S15), and a loopback state is established. (Step S16).

The processes of steps S14 to S17 are executed for each of the two systems. Therefore, it may occur that one system is determined to be connected and the other system is determined to be disconnected.

Here, the above-mentioned fixed time is, for example, a value obtained by adding a predetermined margin to the time normally required for communication (transmission and reply) with an adjacent station, and is arbitrarily determined and set by the developer or the like in advance. On the other hand, the predetermined time in step S18 described below may be the same as the predetermined time described in step S4. That is, the predetermined time in step S18 may be set to a time during which the loopback state should be in the adjacent station at the disconnection point regardless of where the disconnection occurs on the network when the predetermined time elapses. It is desirable, and the developer or the like arbitrarily decides and sets it in advance.

The master station re-executes the time synchronization process (step S19) when a predetermined time has elapsed from the time when the confirmation request frame is transmitted to both systems (step S18, YES), and resumes the master time distribution when the re-execution is completed (step S18, YES). Step S20). The processing of steps S19 and S20 may be the same as those of steps S4 and S5, and the description thereof will be omitted.

On the other hand, as shown in FIG. 10, for example, when the confirmation request frame is sent from one of the two adjacent stations (steps S31, YES), each slave station first receives the one adjacent station. The above confirmation response frame is returned to the user (step S32). Subsequently, a confirmation request frame is transmitted (transferred) to the other adjacent station (step S33). If the confirmation response frame is returned from the other adjacent station within a certain period of time (step S34, YES), it is determined that there is no disconnection (connection) between the own station and the other adjacent station. (Step S36), this process is terminated as it is. On the other hand, if the confirmation response frame is not returned from the other adjacent station even after a certain period of time has elapsed (step S34, NO), it is determined that there is a disconnection between the own station and the other adjacent station (step S34, NO). Step S35), the loopback state is set (step S37).

If the slave station that executes this process is an adjacent station to the master station, the "one adjacent station" in step S31 is the master station.

The processing units 11 and 11a have, for example, an arithmetic processor such as a CPU and a storage unit such as a memory. A predetermined application program is stored in advance in the storage unit. When the arithmetic processor executes this application program, for example, the process of FIG. 9 or the process of FIG. 10 is realized.

12 and 13 are processing flowcharts of a master station and a slave station when the configuration of the node device 10 is an example shown in FIG.

Here, a configuration example of the node device 10 shown in FIG. 11 will be described before the description of FIGS. 12 and 13.

In the illustrated example, the node device 10 includes a processing unit (11 or 11a), a timer 12, two latches 13 and 14, a logical connection confirmation unit 15 and a communication unit 16 which are configured to relate to one adjacent station, and the other. It has a logical connection confirmation unit 17 and a communication unit 18 which are configured to be related to the adjacent stations of the above. As an example, it is considered that one related to the adjacent station corresponds to, for example, the network connection portion NW1, and the other adjacent station corresponds to, for example, the network connection portion NW2. You may. Among these configurations, substantially the same configurations as those shown in FIGS. 2 and 5, etc. are designated by the same reference numerals. Therefore, regarding the processing unit, the node device 10 as the master station has the processing unit 11a, and the node device 10 as the slave station includes the processing unit 11.

However, the processing units (11a, 11) in the configuration example of FIG. 11 execute, for example, the processing on the left side in FIGS. 12 and 13, which will be described later, instead of the processing of FIGS. 9 and 10. This is mainly, in the case of the configuration example of FIG. 11, the logical connection confirmation unit 15 is configured to specialize in processing related to the specific frame (LLD frame, etc.) separately from the processing units (11a, 11). , 17 are provided.

Further, among the configurations shown in the figure, configurations other than the communication units 16 and 18 and the logical connection confirmation units 15 and 17 may be provided on one arithmetic processor. That is, if it is a master station, the processing unit 11a, the timer 12, the two latches 13 and 14, and the logical connection confirmation units 15 and 17 may be provided on one arithmetic processor. Similarly, if it is a slave station, the processing unit 11, the timer 12, the two latches 13 and 14, and the logical connection confirmation units 15 and 17 may be provided on one arithmetic processor. The passing of various data indicated by the illustrated solid line arrow, short dotted line arrow, long dotted line arrow, one-dot chain line arrow, and the like may be realized by a function (not shown) provided in this arithmetic processor.

However, the present invention is not limited to this example, and for example, the logical connection confirmation units 15 and 17 may be provided on a processor different from the above-mentioned one arithmetic processor.

Here, the logical connection confirmation units 15 and 17 function only at the time of processing when a disconnection occurs, and do not function at normal times. From this, the operation in the normal state will be described first with respect to the configuration of FIG. 11, but it is assumed that the logical connection confirmation units 15 and 17 do not exist.

The communication units 16 and 18 perform communication processing with adjacent stations, respectively. Here, from the above, it is expressed that the communication unit 16 communicates with one adjacent station and the communication unit 18 communicates with the other adjacent station.

Further, the communication units 16 and 18 monitor the physical connection for performing bit transfer on the transmission medium (electric signal or optical), and notify the processing unit (11, 11a) of the physical link state. In addition to this, signal conversion from the transmission medium into the node or vice versa is performed.

The communication units 16 and 18 have an input terminal and an output terminal, respectively. In the illustrated example, the communication unit 16 has an input terminal related to the first data transmission path D1, and the communication unit 18 has an output terminal related to the first data transmission path D1. From this, the frame received from the input terminal of the communication unit 16 is passed to the processing unit (11, 11a) via the latch circuit 13 as shown by the solid line arrow in the figure, and the processing unit (11, 11a) is this. The frame is output from the output terminal of the communication unit 18. This is because, as described above, in this example, the frame relay related to the first data transmission path D1 is performed via the processing unit (11, 11a).

On the other hand, the frame received from the input terminal of the communication unit 18 basically does not go through the processing unit (11, 11a), but as shown by the solid line arrow in the figure, the frame of the communication unit 16 passes through the latch circuit 14. It is output from the output terminal.

However, the above operation is a ring type operation (before the disconnection occurs), and is different from the above operation in the loopback state. Further, the latch circuits 13 and 14 basically have a function of temporarily latching (holding) the received frame and monitoring the type of the received frame and the like. Then, when the received frame passes through the latch circuit 13 or the latch circuit 14, the latch circuits 13 and 14 may determine the type of the frame. The timer 12 is the timer to be synchronized as described above.

Further, the operation when either the communication unit 16 side or the communication unit 18 side is in the loopback state will be described below.

First, when the communication unit 18 side is in a loopback state, that is, when a disconnection with the other adjacent station is detected, the processing unit (11, 11a) passes through the input terminal of the communication unit 16. When the received frame is received, the frame is output from the output terminal of the communication unit 16 (as indicated by the alternate long and short dash arrow and the solid line arrow). In other words, the frame transmitted from the one adjacent station via the data transmission path D1 is looped back and transmitted to the adjacent station via the data transmission path D2.

On the other hand, when the communication unit 16 side is in a loopback state due to the detection of a broken line with one of the adjacent stations, the communication unit 16 is received via the input terminal of the communication unit 18 and latched by the latch circuit 14. The frame is taken into the processing unit (11, 11a) (as indicated by the alternate long and short dash arrow in the figure). This control is performed by, for example, an arithmetic processor (not shown). The processing unit (11, 11a) outputs the captured frame from the output terminal of the communication unit 18 (as shown by the solid line arrow in the figure). In other words, the frame transmitted from the other adjacent station via the data transmission path D2 is looped back and transmitted to the other adjacent station via the data transmission path D1.

The processing units (11, 11a) determine and process transmission frames generated by a request from a higher-level processing system (not shown) existing in each node device 10, relaying or deleting frames received from the input terminals, and the like. It is carried out.

The six dotted arrows between the processing unit (11, 11a) and the logical connection confirmation unit (15, 17) shown in FIG. 11 are simply the processing unit (11, 11a) -logical connection confirmation unit (15, 17) It only shows an image of data exchange between them, and is not described here in particular.

Here, as described above, when the disconnection occurs, the logical connection confirmation units 15 and 17 function. When a specific request is received from the processing units (11, 11a), the logical connection confirmation units 15 and 17 perform an operation in response to the request. Further, the logical connection confirmation units 15 and 17 constantly monitor the received frame. That is, the logical connection confirmation unit 15 monitors the frame input from the input terminal of the communication unit 16, and the logical connection confirmation unit 17 monitors the frame input from the input terminal of the communication unit 18. Then, by this monitoring, when the received frame is a frame of a specific type, the logical connection confirmation units 15 and 17 perform processing according to this type.

If the received frame is a frame of the specific type, the logical connection confirmation units 15 and 17 prevent the received frame from being latched by the latches (13, 14) (processing units (11, 11a). ) May also have a function (to prevent acquisition).

Further, as shown in FIGS. 12 and 13, the logical connection confirmation units 15 and 17 have different processing contents depending on whether the slave station or the master station is used. Here, even if the processing contents are different, the same sign (15, 17) is attached.

12 and 13 show processing examples of the node device 10 having the configuration shown in FIG. FIG. 12 is a processing example of the master station, and FIG. 13 is a processing example of the slave station.

First, as shown in FIG. 12, when the processing unit 11a of the master station determines that a disconnection has occurred somewhere in the entire network (step S41), first, the master time distribution is temporarily stopped (step S42). The processing of steps S41 and S42 may be the same as that of steps S11 and S12, and the description thereof will be omitted.

The processing unit 11a of the master station subsequently notifies the confirmation units of both systems (that is, both the logical connection confirmation units 15 and 17) of the connection confirmation request (step S43). Then, the state waits for a response from each confirmation unit to this notification (step S44).

When the logical connection confirmation unit 15 and 17 are notified of the connection confirmation request from the processing unit 11a as described above, the logical connection confirmation units 15 and 17 respectively send a confirmation request frame to the logical connection confirmation unit of the adjacent station to which they are involved in response to this request. Transmit (step S51). In this process, in the case of the logical connection confirmation unit 15, the confirmation request frame is notified to one of the adjacent stations by transmitting the confirmation request frame from the output terminal of the communication unit 16. In the case of the logical connection confirmation unit 17, the confirmation request frame is notified to the other adjacent station by transmitting the confirmation request frame from the output terminal of the communication unit 18.

Then, it becomes a response waiting state. If there is no disconnection between the adjacent station and the adjacent station, the adjacent station returns the confirmation response frame to the confirmation request frame within a certain period of time. From this, if the confirmation response frame is returned from the adjacent station within a certain period of time (step S52, YES), it is determined that the connection (no disconnection) is made (step S54), and if there is no reply (step S52). S52, NO) It is determined that there is a disconnection (step S53).

Then, the processing unit 11a is notified of the disconnection presence / absence determination result (step S55). If an acknowledgment frame is received, it is deleted (step S56).

When the processing unit 11a receives the notification of the disconnection presence / absence determination result from each logical connection confirmation unit in step S55 (step S44, YES), and if any one of them is determined to be disconnected (step S45, YES). ), The side where the disconnection is made is put into a loopback state (step S46). The operation in the loopback state has already been described and will not be described here. Then, the process proceeds to step S47. On the other hand, if both of the two logical connection confirmation units 15 and 17 are determined to be connected, the process proceeds to step S47 as it is.

The processing unit 11a determines whether or not a predetermined time has elapsed from the time of notification in step S43 (step S47), and when the predetermined time has elapsed (steps S47, YES), the time synchronization process is re-executed (step S48). After the re-execution is completed, the master time distribution is restarted (step S49). The predetermined time in step S47 may be the same as the predetermined time in step S18, step S48 may be the same as step S19, and step S49 may be the same as step S20, and the description thereof will be omitted.

Further, in the example shown in FIG. 13, the processes of the logical connection confirmation units 15 and 17 of the slave stations are generally the processes of steps S72 and S73 when step S71 becomes YES, and step S74 is performed. When YES, the processes of steps S75 to S80 are executed. As described above, the logical connection confirmation units 15 and 17 constantly monitor the type of the received frame, and if the received frame is a confirmation request frame, step S71 becomes YES and the received frame is confirmed. If it is a response frame, step S76 is YES. The logical connection confirmation units 15 and 17 do nothing (do not function) when the type of the received frame is other than these confirmation request frames and confirmation response frames.

Basically, if step S71 is YES in any one of the two logical connection confirmation units 15 and 17, then step S74 is YES in the other logical connection confirmation unit.

When any one of the two logical connection confirmation units 15 and 17 receives the confirmation request frame transmitted from the logical connection confirmation unit of the adjacent station (step S71, YES), the confirmation response frame is returned to the adjacent station. At the same time (step S72), the processing unit 11 is notified that the confirmation request frame has been received (step S73).

In step S71, if the adjacent station is a master station, the confirmation request frame transmitted in step S51 is received, and if the adjacent station is a slave station, the confirmation request transmitted in step S75 described later is received. You will receive the frame.

Further, due to the reply of the confirmation response frame in step S72, the adjacent station becomes YES in step S52 or step S76 described later.

When the processing unit 11 receives a confirmation request frame reception notification in step S73 from any one of the logical connection confirmation units (steps S62, YES), the processing unit 11 notifies the other logical connection confirmation unit of the connection confirmation request (step S62, YES). Step S63).

When the processing units 11 notify the logical connection confirmation units 15 and 17 in step S63 (steps S74, YES), the logical connection confirmation units 15 and 17 transmit a confirmation request frame to the adjacent station to which they are involved (step S75). If there is no disconnection between the adjacent station and the adjacent station, the logical connection confirmation unit of the adjacent station returns the confirmation response frame in step S72.

From this, if the confirmation response frame is returned within a certain time from the processing time of step S75 (step S76, YES), it is determined that the connection with the adjacent station is in a connected state (no disconnection) (step S77). .. If there is no reply from the confirmation response frame within a certain period of time (step S76, NO), it is determined that there is a disconnection with the adjacent station (step S78). Then, the determination result is notified to the processing unit 11 (step S79). The received confirmation response frame is deleted (step S80).

When the processing unit 11 receives the notification of the determination result in step S79 (step S64, YES) and the determination result has a disconnection (step S65, YES), the processing unit 11 loops back to the logical connection confirmation unit side of the notification source. The state is set (step S66). If the determination result is a connection (step S65, NO), the process of step S66 is not performed.

By the above processes of FIGS. 12 and 13, each slave station sequentially determines the connection state of the communication line connected to its own device under the initiative of the master station, and if the line is disconnected, the loopback state. It becomes. Of course, the master station itself also determines the connection state of the communication line connected to its own device, and if it is disconnected, it will be in a loopback state. In this way, each slave station is put into a loopback state under the control of the master station, so that the corresponding station is put into a loopback state after the master station temporarily stops the master time distribution. Therefore, the above problem does not occur due to the master time distribution.

Here, the re-execution of the above-mentioned synchronous sequence will be described.
Basically, the existing process may be used for the synchronization sequence re-execution itself.

However, in the situation assumed by this method, the physical topology may change from the ring type to the bus type. If the physical topology is a ring type, for example, the timer synchronization technique of Patent Document 1 may be used. If the physical topology is a bus type, for example, the timer synchronization technique of Patent Document 2 may be used. From this, if it is determined whether the physical topology of the current network is a ring type or a bus type, it is possible to realize the re-execution of the synchronous sequence using the existing technology.

From this, the method of determining whether the physical topology of the current network is a ring type or a bus type will be described below.

In the above description, it is assumed that a loopback state is always generated, but this is premised on the fact that a disconnection has actually occurred. Even though no disconnection has actually occurred, there are cases where communication is temporarily interrupted for some reason such as noise, which causes the master station to "disconnect somewhere in the entire network." May occur. Then, for example, when the processes of FIGS. 9 and 10 are performed by this, if the communication blackout has already been resolved, the station where the processes of steps S16 and S37 are performed (the station in the loopback state) is There will be no one. Therefore, in this case, the physical topology remains ring-shaped.

Due to the circumstances described above, it is not always changed to the bus type, so it is necessary to determine whether the physical topology of the current network is the ring type or the bus type.

From the above, in the above-mentioned various explanations, the explanation that the corresponding node device 10 (node device 10 adjacent to the disconnection point) shifts to the loopback state is described as "when the disconnection really occurs. It is assumed that "is".

First, each node device 10 recognizes the result of confirming the logical connection with the adjacent stations of both systems by the above-mentioned processing. That is, the master station transmits the confirmation request frame to the adjacent stations of both systems as described above, and recognizes the logical connection confirmation result depending on the presence or absence of the reply (response) of the confirmation response frame to the transmission. Further, each slave station can recognize the logical connection confirmation result (= there is a connection of the adjacent station) by receiving the confirmation request frame transmitted from the adjacent station for one adjacent station, but further, the confirmation request frame to the adjacent station. May be sent to confirm the logical connection for the presence or absence of a response. Further, the confirmation request frame is transmitted to the other adjacent station, and the logical connection confirmation result is recognized depending on the presence or absence of a reply (response) of the confirmation response frame to the confirmation request frame.

Further, as described above, the presence or absence of disconnection is detected based on the link state of the physical layer in the past, and in this example as well, for example, the communication units 16 and 18 detect the physical link state (for example, lower PHY (physical)). Layer; always acquired from layer 1) etc.).

An image of the above processing is shown in FIG.
FIG. 14A is an image of the process for discriminating between the ring type and the bus type, and FIG. 14B is an image of the data obtained by the process.

As shown in FIG. 14A, the processing unit 11 acquires the logical connection confirmation result and the physical link state of the A system from the logical connection confirmation unit 15 and the communication unit 16 of the A system, and the logical connection confirmation unit of the B system. 17. The logical connection confirmation result and the physical link state of the B system are acquired from the communication unit 18. Note that the physical link state can always be acquired, unlike the logical connection confirmation result.

As shown in the figure, the communication unit 16 side is defined as the A system and the communication unit 18 side is defined as the B system.
Each node device 10 determines the logical link state of its own station for each of the A system and the B system as follows, based on the logical connection confirmation result and the physical link state.

-If the logical connection confirmation result = "no response (reply)" or the physical link status = "unlinked", the logical link status = "unlinked". The reason for making such a determination is that if either the logical connection or the physical link fails, communication cannot be performed either way.

-If the logical connection confirmation result = "response (reply)" and the physical link status = "link available", the logical link status = "link available".

As described above, the determination of the logical link state is performed for both systems (each of the two adjacent stations), and the logical link state of the A system and the logical link state of the B system are obtained.

In the case of the master station, the logical link state determination process is executed, for example, before the process of step S19 in FIG. 9 or before the process of step S48 in FIG. 12 is executed. In the case of a slave station, the logical link state determination process is executed, for example, after the process of step S37 or S36 in FIG. 10 is executed, or after the determination process of step S65 in FIG. 13 is executed.

After executing the above-mentioned logical link state determination process, the processing unit 11 of the master station subsequently transmits a specific frame (referred to as a logical link state information collection frame) for collecting the logical link state of each station, for example, data transmission. It is transmitted via the path D1. When the received frame is the logical link state information collection frame, the processing unit 11 of each slave station adds the logical link state of the own station determined above to the logical link state information collection frame and downstream. Relay to the adjacent station of. From this, when the logical link state information collection frame goes around the network and returns to the master station, the master station finally adds the logical link state of its own station to the logical link state information collection frame, thereby making the logic logical. The link state information collection frame is in a state in which the above logical link states of all the node devices 10 on the network are stored.

FIG. 14B shows an example of the data configuration of the logical link state information collection frame and an example of the state after the cycle of each station.

As shown in the figure, each station adds and stores the station number of its own station, the determined logical link state of the A system, and the logical link state of the B system to the received logical link state information collection frame. As an example, when the logical link state information collection frame is transmitted from the node device 10A, it goes around the network in the order of node device 10B → node device 10C → node device 10D → node device 10E, and returns to the node device 10A. come. The station number and the logical link state of each station are added to the logical link state information collection frame in this order, and the last node device 10A adds the station number and the logical link state of the own station to the logical link state information collection frame. The state shown on the right side of FIG. 14B is obtained.

From this, the processing unit 11 of the master station determines the physical topology as described below based on the stored data of the logical link state information collection frame.

-If both systems have a logical link status = "with link" in all stations, it is judged as a ring topology.

-If there is even a part of the logical link status = "unlinked", it is judged as a bus type topology.

Then, the transmission delay time is calculated by the calculation method according to the determined topology. This can be done using existing methods. That is, when it is determined that the current state is the bus type topology, for example, the method of calculating the transmission delay time described in Patent Document 2 may be used.

On the other hand, when it is determined that the current state is the ring-type topology, for example, the method for calculating the transmission delay time described in Patent Document 1 may be used. In this case, when each node device 10 inputs a predetermined command (such as a time inquiry command in Patent Document 1) from the input terminal of the communication unit 18, the processing unit 11 acquires this command and determines the predetermined command. After performing the processing, it may be output from the output terminal of the communication unit 16. That is, the time required for this predetermined command to go around the network may be the same in the case of the first data transmission path D1 and the case of the second data transmission path D2.

When the method for calculating the transmission delay time described in Patent Document 1 is used on this premise, it is roughly as follows, for example.

The master station simultaneously transmits the time inquiry commands _QA and QB to both the main route (D1) and the _subroute (D2). Here, as an example, it is assumed that these commands specify a specific destination station. When each slave station receives these time inquiry commands QA and _QB , it relays and transfers to the downstream _side , but in the case of the destination station, it relays by adding the timer value of its own timer 12 at the time of reception. Forward. Based on the above premise, the two time inquiry commands _QA and QB go around the network and return to the master station at the same time, and the master station measures the time _tL required from the transmission of these commands to the return. is doing. Further, the master station acquires the timer value TA which is the timer value related to the main route of the destination station and the timer value TB which is the timer value related to the sub route.

From these data, the transmission delay time tA to the destination station related to the main route can be obtained by the following formula.

tA = {tL + (| TA-TB |)} / 2

Of course, the present invention is not limited to these examples, and any existing calculation method may be used.

For example, when the method for calculating the transmission delay time described in Patent Document 2 is used, it is roughly as follows, for example.

First, like the latch circuit in Patent Document 2, each of the above latch circuits 13 and 14 acquires the timer value of the timer 12 when the received frame is a timer latch instruction message, and processes it as the timer value and the flag “1”. It also has a function of notifying the unit (11, 11a). When the processing unit (11, 11a) receives the timer value collection message, the processing unit (11, 11a) sets the timer value and the flag “1” acquired by either one or both of the latch circuits 13 and 14 to the timer value. Store in the specified area of the collected message (store in order from the beginning).

The master station first transmits the timer latch instruction message on the data transmission path D1, and then transmits the timer value collection message on the data transmission path D1. By adding the timer value of the own station and the flag "1" to the returned timer value collection message, the timer value collection message includes the timer values of all stations.

From this, since the timer value and the order of each station can be known from the stored data of the timer value collection message, it can be known which station is adjacent to each other. From this, the transmission time between each adjacent station can be obtained as follows.

As an example, the node device 10B and the node device 10C, which are adjacent stations to each other, are taken as an example. When the processing time is _Tα , the transmission time LBC between the node device 10B and the node device 10C can be calculated by the following equation.

LBC = {(TB2-TB1)-(TC2-TC1) _-Tα } / 2

The transmission time between all adjacent stations is calculated in the same way.
By using the transmission time between the adjacent stations, the transmission delay time between the master station and each slave station can be obtained.

FIG. 15 is a functional block diagram of the network system of this example.
Here, in a network having a master station and a plurality of slave stations and having a ring-type logical topology, each transmission delay time, which is the communication time between the master station and each slave station, and a timer from the master station to each slave are scheduled. It is premised on a network system that synchronizes the timer of each slave station with the timer of the master station by distributing the master time.

In the illustrated example, the master station 20 includes an overall disconnection determination unit 21, a disconnection connection confirmation request unit 22, a restart control unit 23, a topology determination unit 24, a disconnection connection confirmation unit 25, a loopback unit 26, and the like.

The slave station 30 has a disconnection connection confirmation unit 31, a loopback unit 32, and the like.
In the master station 20, the overall disconnection determination unit 21 determines whether or not there is a disconnection in the entire network (whether or not there is a disconnection somewhere in the entire network; the location where the disconnection occurs is unknown).

When the disconnection connection confirmation request unit 22 determines that there is a disconnection in the entire network by the overall disconnection determination unit 21, the master time distribution is temporarily suspended, and then the slave station 30 is disconnected from the adjacent station. Have them check the connection status. This transmits, for example, a predetermined request for confirming the disconnection / connection state to each slave station 30 in the form of a relay. That is, for example, the master station issues the above request to an adjacent station of its own station, and this adjacent station relays the above request to the adjacent station of its own station. By repeating this, all slave stations 30 will receive the above request.

In each slave station 30, the disconnection / connection confirmation unit 31 confirms the disconnection / connection state with the adjacent station of its own station according to the disconnection / connection confirmation request unit 22 (for example, when the request is received).

The loopback unit 32 is put into a loopback state when it is determined that there is a disconnection as a result of confirming the disconnection / connection state with the adjacent station by the disconnection / connection confirmation unit 31. In the loopback state, the packet is not relayed to the adjacent station with the disconnection, and when the packet from the other adjacent station is received, the packet is returned to the other adjacent station (loopback).

Further, the master station 20 also has a disconnection connection confirmation unit 31 of the slave station 30, a disconnection connection confirmation unit 25 having the same processing function as the loopback unit 32, and a loopback unit 26. However, the disconnection / connection confirmation unit 25 confirms the disconnection / connection state by the determination by the overall disconnection determination unit 21 that there is a disconnection even if the above request is not received. Then, when it is confirmed that there is a disconnection, the loopback unit 26 shifts to the loopback state.

Then, in the master station 20, the restart control unit 23 obtains the transmission delay time again after the stations corresponding to the disconnection points (including not only the slave station but also the own station) enter the loopback state. The slave station 30 is set, and then the master time distribution is restarted. In the restart control unit 23, for example, after the disconnection connection confirmation request unit 22 issues the above request and a predetermined predetermined time elapses, the station corresponding to the disconnection location (including its own station) is in the loopback state. It is regarded as a thing.

In the loopback state, a transmission path for avoiding the disconnection point is newly constructed, and the restart control unit 23 obtains a transmission delay time according to the new transmission path.

In the network system of this example of FIG. 15, while the master time distribution is temporarily suspended by the processing functions of the master station 20 and the slave station 30, the corresponding station is in a loopback state and new transmission is performed. A path is formed, and a transmission delay time corresponding to the new transmission path is set for each slave station. As a result, it is possible to prevent the timer synchronization from being out of order due to the master time distribution.

Further, by constructing the new transmission path, the physical topology of the network may change from a ring type to a bus type. From this, the master station may further have the topology determination unit 24 for determining whether the physical topology of the network in which the new transmission path is constructed is a ring type or a bus type. Then, the restart control unit 23 again obtains the transmission delay time by using the calculation method according to the determined physical topology.

However, not limited to this example, if it is considered that the loopback state has occurred after the disconnection has occurred without making a judgment by the topology determination unit 24, it is regarded as having become a bus type, and a calculation method according to the bus type is used. The transmission delay time may be obtained again.

Further, for example, the disconnection / connection confirmation request unit 22 of the master station may transmit a specific packet to an adjacent station of the own station. In the case of this embodiment, for example, when the disconnection connection confirmation unit 31 of the slave station receives the specific packet from one adjacent station, it returns a specific response packet to the one adjacent station and identifies it to the other adjacent station. A packet is transmitted, and the state of disconnection and connection between the own station and the other adjacent station is confirmed by the presence or absence of a reply of the specific response packet from the other adjacent station to the transmitted specific packet. You may.

Further, in the case of the above embodiment, the disconnection / connection confirmation request unit 22 of the master station between the own station and the adjacent station depending on whether or not the specific response packet is returned from the adjacent station to the transmitted specific packet. You may check the disconnection and connection state. That is, the disconnection / connection confirmation request unit 22 may confirm the disconnection / connection state instead of the disconnection / connection confirmation unit 25. Of course, in this form, the disconnection / connection confirmation unit 25 is not required.

Then, in the case of this embodiment, when the loopback unit 26 of the master station determines that there is a disconnection with the adjacent station as a result of confirming the disconnection / connection state with the adjacent station by the disconnection / connection confirmation request unit 22. Puts it in a loopback state.

Further, as another form, for example, the master station and the slave station may each have two logical connection confirmation units (not shown) for confirming the disconnection / connection state with the adjacent station of the own station. .. In the case of this configuration, for example, when the master station determines that there is a disconnection in the entire network, the two logical connection confirmation units (not shown) of the master station each confirm the logical connection (not shown) of the adjacent station. A specific packet is transmitted to the unit, and if there is a response, it is determined that there is no disconnection with the adjacent station.

In the case of this configuration, when one of the logical connection confirmation units in the own station receives the specific packet, the one logical connection confirmation unit returns a specific response packet to the source and at the same time, the slave station returns a specific response packet to the source. When the other logical connection confirmation unit of the own station transmits the specific packet (relays to the downstream side) and the specific response packet is not returned to the transmitted specific packet, there is a disconnection with the adjacent station. judge.

The master station 20 and the slave station 30 have an arithmetic processor such as a CPU and an MPU (not shown) and a storage unit such as a memory, and the arithmetic processor executes a predetermined application program stored in the storage unit in advance. As a result, the processing functions of the various functional units shown in FIG. 15 are realized.

According to the present invention, in a network system that can have a bus-type or ring-type configuration, it is possible to synchronize the timers of each node even if a disconnection occurs at one place.

In the previous method, at the time of disconnection, the station at the disconnection point (particularly the slave station) detects the disconnection by monitoring the link state of the physical layer, and automatically loops back to reestablish the communication path.

However, since the master station does not immediately know the re-establishment of this communication path, the master time is distributed, and as a result, there is a possibility that erroneous synchronization correction is performed in all the downstream stations of the disconnection point.

In response to this problem, in the present invention, the slave station does not loop back and reestablish the communication path without permission, but the master station takes the initiative in reestablishing the communication path. At that time, the master time distribution is temporarily suspended.

That is, the master station determines that a disconnection has occurred somewhere in the network because the transmission frame of its own station does not return, temporarily suspends the master time distribution, and determines whether or not each slave station has a disconnection. , If there is a disconnection, loopback is performed to reestablish the communication path. After that, the transmission delay time according to the reestablished communication path is obtained and set in each slave station, and then the master time distribution is restarted. As a result, each slave station performs timer synchronization by the correct transmission delay time according to the reestablished communication path and the master time distribution, so that the timer synchronization does not go wrong.

As described above, according to the network system or the like of the present invention, it is possible to prevent erroneous synchronization correction from being performed even when the route is changed due to the occurrence of disconnection in a network or the like having a ring-type logic topology.

2 (2a, 2b, 2c, 2d, 2e) Communication line NW1, NW2 Network connection unit 10 (10A, 10B, 10C, 10D, 10E) Node device 11, 11a Processing unit 12 Timer 13 Latch circuit 14 Latch circuit 15 Logical connection Confirmation unit 16 Communication unit 17 Logical connection confirmation unit 18 Communication unit D1, D2 Data transmission path 20 Master station 21 Overall disconnection judgment unit 22 Disconnection connection confirmation request unit 23 Resume control unit 24 Topology determination unit 25 Disconnection connection confirmation unit 26 Loopback unit 30 Slave station 31 Disconnection connection confirmation unit 32 Loopback unit

Claims (9)

In a network having a master station and a plurality of slave stations and having a ring-type logical topology, each transmission delay time, which is the communication time between the master station and each slave station, and a periodic master from the master station to each slave. It is a network system that synchronizes the timer of each slave station with the timer of the master station by time distribution.
The master station
An overall disconnection determination means for determining the presence or absence of disconnection in the entire network,
When it is determined by the overall disconnection determining means that there is a disconnection in the entire network, the master time distribution is temporarily suspended, and then a confirmation request is transmitted to each slave station to confirm the disconnection / connection status with the adjacent station. As a means of requesting confirmation of disconnection and connection,
It has a restart control means that, after a predetermined time or more has elapsed from the transmission of the confirmation request, the transmission delay time is obtained again and set in each slave station, and then the master time distribution is restarted .
Each of the slave stations
In response to the confirmation request from the disconnection / connection confirmation requesting means, the disconnection / connection confirmation means for confirming the disconnection / connection state with the adjacent station, and the disconnection / connection confirmation means.
As a result of confirming the disconnection connection state with the adjacent station by the disconnection connection confirmation means, it has a loopback means for making a loopback state when it is determined that there is a disconnection.
The predetermined time is the time from when the confirmation request is transmitted until it becomes possible to assume that the station corresponding to the disconnection point is in the loopback state regardless of where the disconnection occurs on the network. Is,
A network system characterized by that . The restart control means of the master station is
When the predetermined time or more has elapsed since the confirmation request was transmitted, it is considered that the station corresponding to the disconnection point has entered the loopback state, and the transmission delay time is obtained again and set in each slave station. The network system according to claim 1, wherein the master time distribution is resumed thereafter. Due to the loopback state, a new transmission path that avoids disconnection points is constructed.
The network system according to claim 2, wherein the restart control means obtains the transmission delay time according to the new transmission path. The network system according to claim 3, wherein the physical topology of the network may change from a ring type to a bus type due to the construction of the new transmission path. The master station further has a topology determining means for determining whether the physical topology of the network in which the new transmission path is constructed is a ring type or a bus type.
The network system according to claim 4, wherein the restart control means obtains the transmission delay time again by using a calculation method according to the determined physical topology. The master station also has the disconnection / connection confirmation means and the loopback means.
The network system according to claim 1, wherein the network system according to claim 1 is characterized in that the connection state between the own station and the adjacent station of the own station is confirmed and the loopback state is set when there is a disconnection. The disconnection / connection confirmation requesting means of the master station transmits a specific packet for the confirmation request to an adjacent station of its own station.
When the disconnection / connection confirmation means of the slave station receives the specific packet from one adjacent station, it returns a specific response packet to the one adjacent station and transmits the specific packet to the other adjacent station. Claims 1 to 1, wherein the disconnection connection state between the own station and the other adjacent station is confirmed by the presence or absence of a reply of the specific response packet from the other adjacent station to the transmitted specific packet. The network system according to any one of 5. The disconnection / connection confirmation requesting means of the master station confirms the disconnection / connection state between the own station and the adjacent station depending on the presence / absence of a reply of the specific response packet from the adjacent station to the transmitted specific packet. ,
The master station is further characterized by having a loopback means for making a loopback state when it is determined that there is a disconnection with an adjacent station as a result of confirming the disconnection / connection state with the adjacent station by the disconnection / connection confirmation requesting means. The network system according to claim 7. Each of the master station and the slave station has two logical connection confirmation units for confirming the disconnection / connection state with the adjacent station of the own station.
When the master station determines that there is a disconnection in the entire network, the two logical connection confirmation units of the master station each send a specific packet for the confirmation request to the logical connection confirmation unit of the adjacent station. If there is a response after sending , it is determined that there is no disconnection with the adjacent station, and
In the slave station, when one of the logical connection confirmation units receives the specific packet, the one logical connection confirmation unit returns a specific response packet to the source, and the other logical connection confirmation unit receives the specific response packet. The network system according to claim 6, wherein the specific packet is transmitted, and it is determined that there is a disconnection with an adjacent station when the specific response packet is not returned to the transmitted specific packet.

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