JPH0736557B2 - Data transmission method and network system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a data transmission system of a network system, and is particularly suitable for use in collecting shared information such as maintenance information used by communication terminals in a network. Regarding data transmission method.

[Prior Art] In a network system, when a failure occurs in a device forming a network, it is required to quickly identify a failure point and take a recovery measure. Therefore, it is necessary to have a function of monitoring the state of the constituent devices in the network, collecting the monitoring information in the monitoring device of the network, and notifying the maintenance personnel via the display device such as a monitor.

In order to realize this function, the network needs a data transmission method capable of efficiently transmitting the data used for the normal communication between terminals and the data used for the above state monitoring.

In the network system used in the field of process control, the above two types of data have the following characteristics. The data used for terminal-to-terminal communication is used for process control, so it has high real-time property (several ms to several hundred ms), and the data used for state monitoring does not require real-time property as much as the former, but knows the state that changes sequentially. In order to achieve this, data transmission with a cycle of several seconds is required.

As a method of transmitting different types of data,
A method of performing time slot multiplexing and determining a fixed or variable area for transmitting each information, and Japanese Patent Laid-Open No. 63-13
As described in Japanese Patent No. 3736, there is a method of packetizing data, prioritizing it, and transmitting it.

Further, in Japanese Patent Laid-Open No. 1-221042, in a packet switch, priority information of both immediacy and discardability is added to each packet to be transmitted according to the data type, and the packet in the queue is Regarding the above, it is disclosed that the line transmission order is determined according to the priority of immediacy, and when the queue overflows, packets including the packets in the queue are discarded according to the priority of discardability. There is.

[Problems to be Solved by the Invention] In the above-mentioned conventional technology, the focus is only on the efficient transmission of data having various characteristics, and each communication such as maintenance information, management information, and history information in a network is performed. It is not discussed how each communication terminal specifically collects data that is shared by the terminals or data that is convenient to hold in each communication terminal (hereinafter referred to as shared information or shared data). .

Multiple communication terminals (stations) in a network such as a LAN
In order to collect shared information, one master station is defined and information is periodically transmitted from each station to the master station.
Alternatively, the master station may make a 1: 1 inquiry to each station. However, these communications become a steady load,
This causes a wait for normal data communication.
Further, when the master station fails, the master station needs to be replaced, but the replacement procedure becomes complicated, which is inconvenient.

An object of the present invention is to provide a plurality of inquiry stations at the same time in a network system that collects information about each communication terminal, so that even if a failure occurs in one inquiry station, data transmission in which collection and securing of shared information are maintained To provide a method.

Another object of the present invention is to provide a data transmission method for efficiently transmitting information shared by each communication terminal among information handled in a network system without hindering transmission of other data.

[Means for Solving the Problems] In order to achieve the above object, a data transmission method according to the present invention is a data transmission method for periodically collecting information about each communication terminal device in a network to which a plurality of communication terminal devices are connected. In this method, a) an inquiry frame for inquiring information regarding other communication terminal devices to a plurality of communication terminal devices is formed, a) forming a chain of addresses that makes a round among all communication terminal devices that are the targets of information collection. Is provided, and the function of transmitting the inquiry frame with the priority of the inquiry frame is provided.
c) The inquiry frame is transmitted to the next communication terminal device that follows the chain of addresses, and d) The communication terminal device that has received the inquiry frame writes its own information in the inquiry frame, and the next communication terminal device. When a plurality of inquiry frames to be transmitted to the next communication terminal device compete with each other, the inquiry frame with the lower priority is discarded by referring to the priority, and e) the above The communication terminal device that has generated and transmitted the inquiry frame, when receiving the inquiry frame that has made a round, captures the information collected for each of the communication terminal devices and notifies other communication terminal devices of the collected information. The notification frame is sent as a notification frame.

In each of the communication terminal devices, it is desirable to prioritize transmission of normal data other than the inquiry frame over transmission of the collection information.

The frame has at least a destination address of transmission, a frame type indicating whether the frame is an “inquiry” or a “notification”, a priority of the frame, and fields for writing the information to be collected. In the process e), the frame type of the inquiry frame that has made a round is rewritten from “inquiry” to “notification” and transmitted to another communication terminal device.

Preferably, when one communication terminal device competes for a plurality of notification frames to be transmitted to the next communication terminal device during one round of the notification frame, the notification frame with the lower priority is discarded.

A network system according to the present invention is a network system including a common transmission line and a plurality of communication terminal devices connected to the transmission line and each having a unique address, wherein the plurality of communication terminal devices form a circular address chain. At least two of the plurality of communication terminal devices are provided with a configuring unit, and periodically generate an inquiry frame to collect information about other communication terminal devices, and in the frame, communication in the next order of the address chain is performed. Each communication terminal device in the system including at least two of the communication devices has a means for transmitting information added with information indicating the priority of the frame, using the terminal device as a destination address, and an inquiry generated by another communication terminal device. When a frame is received, its own information is added to the inquiry frame and is transmitted to the next communication terminal device. When detecting conflicts inquiry frame from the terminal device, by referring to the priority of the frame, it is characterized in that it has a means for discarding the frame of the lower priority.

Preferably, the at least two communication terminal devices capture the information collected in the inquiry frame and rewrite the inquiry frame into a notification frame and transmit the inquiry frame when the inquiry frame sent by itself goes around the address chain. Each communication terminal device in the system including the above-mentioned at least two units has a unit that, when receiving the notification frame generated by another communication terminal device, acquires the information collected in the notification frame.

As the priority of the frame, for example, the address of the communication terminal device can be used.

[Operation] In the data transmission method according to the present invention, at least two, and preferably all communication terminals collect shared information. As a result, the communication terminals can be made masterless and shared information can be secured in each communication terminal. However, this configuration may cause a plurality of inquiry frame transmission requests to occur in each communication terminal, which increases the load on the communication terminal, but this adverse effect is resolved as follows. That is, the content of the shared information at a certain time is the same regardless of which communication terminal collects, and the inquiry frame generated by each communication terminal does not need to go around all the terminal devices, but at least one inquiry frame goes around. By doing so, the same shared information can be collected. Focusing on this, when the inquiry frames compete (collide) with each other, only the one with the higher priority is utilized and the one with the lower priority is discarded. by this,
It is possible to reduce the load on the communication terminal. The communication frame that generated its own inquiry frame does not return to the communication terminal that generated the inquiry frame that was discarded due to contention, but the shared information collected by the communication terminal that won the competition is sent as a notification frame. no problem.

The specific functions or actions of the means are as follows.

The chain of addresses formed by the communication terminals (hereinafter referred to as address ring) is used to determine the order in which the communication terminals transmit inquiry / notification frames.

The function to send out the inquiry frame and the function to add own information when the inquiry frame is received enable the communication terminal that generated / transmitted the inquiry frame to collect the information of each communication terminal by going through the address ring of the inquiry frame. To do.

Also, when receiving inquiry frames, the function that determines priority when multiple inquiry frame transmission requests collide and discards frames with low priority is only for frames with high priority when the transmission load of the network increases. To prevent an increase in load due to an increase in inquiry frames.

Furthermore, the function of rewriting the inquiry frame to the notification frame when it makes a round in the address ring and distributing the collected information to each communication terminal correctly collects the shared information even in the communication terminal that sent the inquiry frame discarded in the above priority judgment. Guarantee that it can be collected. Similarly to the inquiry frame, the notification frame is discarded by the one with the lower priority when contention occurs when the communication terminals in the system are sequentially cycled. Since the contention has already been adjusted for the inquiry frame, the possibility of contention for the notification frame is considered to be lower than that for the inquiry frame. When transmitting the notification frame, the destination address may be transmitted as a common address common to each communication terminal.

Embodiments Embodiments of the present invention will be described in detail below with reference to the drawings.

1 and 2 show the inquiry frame or notification frame of the node station 1 (hereinafter, referred to as a feature of the present invention).
FIG. 1 shows an operation of transmitting / receiving an inquiry / notification frame), FIG. 1 shows an operation when the inquiry / notification frame is received from another node station, and FIG. 2 generates an inquiry / notification frame by itself. It shows the operation when it is done.

FIG. 3 shows an example of the configuration of a network system to which the present invention can be applied. A node station 1 is built in a communication terminal 2 and connected to a trunk cable 3 via a drop cable 5 to form a bus type network. Configure the system. The node station 1 is composed of, for example, a communication control board mounted on the communication terminal 2. The trunk cable 5 is terminated by a terminator 4 to prevent electric reflection. As shown by the broken line in FIG. 3, the address ring is chained from the highest node address to the lowest node address, such as 3 → 2 → 1 → 3 ... It is a logical ring that connects to things.
The present invention is not limited to the bus type network, but can be similarly applied to a ring type, a star type and the like.

FIG. 4 shows the format of the inquiry / notification frame used between the node stations 1 in this embodiment. This format uses the frame destination node address DA16 and the frame source node address SA
17, node address MSA18 that first generated the frame on the address ring, control information C19 indicating the type of inquiry / notification of the frame, area or field IN to write the information of each node station collected in the inquiry frame
F20 and frame error check code FCS21. Note that the MSA 18 functions as a priority in the case of contention for transmission of inquiry / notification frames, and in this embodiment, the node address is used as it is, but a priority different from the node address may be defined. Also, in this embodiment,
The INF 21 is further divided into areas 1 to 128 for writing information for each node station. (128 is the maximum number of node stations in this system.) The shared information in this embodiment is life / death information (1 bit for each node station) indicating whether or not each node station is in a normal operating state. Although explained as an example, the type of shared information and the data capacity are not limited to this example.

FIG. 5 shows the internal structure of the node station 1. The node station 1 mainly includes the MPU 6, a ROM 8 for storing the MPU 6 program, a RAM 9 used for a data transmission / reception buffer and a program work area, a communication control LSI 7 for configuring an address ring and performing transmission right control, and the inside of the node station. Of the modulator / demodulator 11 for converting the digital signal of the above into an analog signal on the transmission line, the interface circuit 10 and the interface line 13 for connecting the node station 1 and the communication terminal 2, the internal timer 14, the DIPSW15 for address setting, and the MPU6. An internal bus 12 is used to control each unit.

FIG. 6 shows the state of the transmission waiting queue in each node station, the details of which will be described later.

The operation of the embodiment of the present invention will be described below.

First, in each node station 1, when the power is turned on, the MPU6 initializes the internal circuit, reads the address set from DIPSW15 in the process, sets it in the communication control LSI 7, and performs the start-up process. . The communication control LSI 7 whose startup is performed by the MPU 6 constitutes an address ring as shown by the broken line in FIG. 3 according to the built-in protocol. As a result, the transmission right is sequentially transmitted in the chain direction of this address ring. The address ring is reconfigured when a new address ring is generated or a failure occurs in the node station. In the present embodiment, the protocol conforms to IEEE802.4 (token bus) and is not directly related to the present invention, so a detailed description thereof will be omitted here.

After the address ring is configured, the MPU 6 which receives the completion notification from the communication control LSI 7 activates the internal timer 14. The internal timer 14 sends an interrupt notification to the MPU 6 via the internal bus 12 after a certain period of time set by the MPU 6 has passed. Upon receiving this notification, the MPU 6 operates according to the flow shown in FIG.

First, the MPU 6 generates an inquiry frame (S20). Therefore, the communication control LS17 reads out the next node address stored at the time of configuring the address ring, and stores it as the DA16 in the work area of the RAM 9 used for creating the inquiry frame. Next, the MPU 6 stores the own node address read from the DIPSW 15 as SA17 and MSA18. In the work area corresponding to C19, the code "0" indicating that the frame is an "inquiry frame" (8 is used because C is 1 byte)
Bit is all “0”. ) Is stored. Furthermore, IN
In the area corresponding to F20, set the code "1" (only the least significant bit of 1 byte is "1") to indicate "live" of the life and death information in the area corresponding to the address of the own node station. However, the code "0" indicating "death" is set in other areas.

When the inquiry frame to be transmitted to the work area of RAM9 is generated, MPU6 refers to the inquiry frame transmission waiting queue 61 in the transmission waiting queue as shown in FIG. 6 prepared in RAM9 and previously registered in the queue. It is checked whether or not there are any remaining items (S21), and when empty, the query frame created in the work area is registered in the queue 61. On the other hand, if there is something already registered in the queue, the size of the MSA of the query frame already registered in the queue and the size of the MSA of the query frame newly created in the work area are compared (S24). Discard the latter if greater than or equal to,
When the former is smaller than the latter, the former is removed from the queue and the latter is newly registered in the queue (S25). That is, the one with the larger MSA is prioritized. On the contrary, there is no problem if the smaller MSA is prioritized. After the queue registration, the MPU 6 refers to the three waiting queues 61 to 63, assigns a higher priority in the order of the data frame, the notification frame, and the inquiry frame from the communication terminal, and is registered in each waiting queue according to this priority. The transmission frames are copied from the work area to the transmission buffer 64 one by one, and the queues are sequentially processed. That is, it is checked whether or not the transmission data from the transmission terminal exists (S26), and if there is, the transmission process is prioritized. If there is only an inquiry frame (or a notification frame), the frame remaining in the priority determination is transmitted (S27). For frame transmission, the MPU 6 prepares a transmission frame in the transmission buffer 64 and instructs the communication control LSI 7 to transmit, so that the communication control LSI 7 acquires the transmission right on the transmission path and then the transmission buffer
This is done by reading 64 frames, adding FCS21, and sending them to the transmission path.

The inquiry frame transmitted as described above is received by the next node station of the address ring shown in DA15, and the frame reception process of FIG. 1 is performed.

In the receiving process of FIG. 1, the node station that generated the frame confirms that the notification frame has gone around the address ring by using the mechanism described above (S3
1), discard (S32), and complete a series of information collection operations.
After that, when the internal timer 14 is activated again, a series of operations is restarted. The information collected in each node station can be collected from the communication terminal via the interface line 13 and the interface circuit 10, and the communication terminal can always collect the life / death information of the node station maintained.

When the node 1 receives the inquiry 1 notification frame, it first determines whether the frame is an inquiry frame or a notification frame by referring to C19 of the frame (S
1). At this time, the data frame from the communication terminal is also determined. When the inquiry frame is received, the node station 1 operates as shown in FIG. The received inquiry frame is stored in the reception buffer in the RAM 9 by the communication control LSI 7 of the node station 1. MP
U6 rewrites DA16 of the received inquiry frame to the next node address of the address ring, rewrites SA17 to its own node station, and sets the code "1" indicating "raw" to the area assigned to its own node station of INF20. ,
Create an inquiry frame to send (S2). The processes S3 to S9 related to frame transmission thereafter are the same as the above-described process S21
~ It is exactly the same as S27.

Returning to FIG. 2, when the inquiry frame makes one round in the address ring and returns to the generating node station (S28), the INF20 of the frame contains the life / death information of all the node stations in the network system. It has been written. That is, in the node station which is operating correctly, the code "1" indicating "raw" is written in the area assigned to the INF 20, and the code "0" indicating "dead" remains in the other areas. One round confirmation of the received inquiry frame is performed by comparing the MSA18 of the frame stored in the reception buffer with that of the MPU6 of DIPSW15 and confirming the coincidence. After one round of confirmation of the inquiry frame, the MPU 6 stores the INF 20 of the frame in the area different from the reception buffer in the RAM 9 (S29). Then, the next node address of the address ring is set in DA16 of the received frame, its own address is set in SA17, and the code "1" indicating the notification frame is set in C19, and the notification frame is transmitted (S30). The frame transmission operation at this time is almost the same as the above-mentioned operation, and the only difference is that the transmission waiting queue referred to when the priority determination is performed by the MSA 18 becomes the notification frame transmission waiting queue.

The notification frame is sequentially transmitted in accordance with the address ring just like the inquiry frame. When each node station receives the notification frame, the MPU 6 stores the INF 20 of the frame in the RAM 9 and rewrites the DA 16 and SA 17 to be transmitted to the next node station.

Next, a case where normal transmission data is generated in the communication terminal 2 will be described. In this case, the transmission data and the destination address are set in the RAM 9 via the interface circuit 10 and the interface line 13, and the MPU 6 is activated for transmission. Upon receiving the transmission activation, the MPU 6 registers in the data transmission waiting queue from the communication terminal shown in FIG. Thereafter, as described above, each transmission waiting queue is given a priority and processed with the highest priority, whereby the transmission / reception operation of the inquiry / notification frame can be prevented from interfering with other communication.

In the present invention, a plurality of node stations in the network system have a function of generating the inquiry / notification frame as described above and transmitting / receiving it. As a result, for example, even if a failure occurs in the node station with the node address = 3 in FIG.
By making the other node stations maintain the information collecting operation, the backup is possible. That is,
Node address = 3 is "dead", node address = 1, 2
You can collect life and death information that is "live". The adverse effect of increasing the load other than the normal processing due to having the above function in multiple node stations is eliminated by discarding the one with the lower priority when the inquiry / notification frame transmissions compete in each node station. Therefore, it is preferable that all the node stations have the function.

The communication control LSI 7 reconfigures a new address ring excluding the node station where the failure has occurred.

In the embodiment described above, the inquiry frame and the notification frame are sequentially designated and transmitted with the following addresses, but the notification frame may be transmitted with a common address common to each communication terminal. .

EFFECT OF THE INVENTION According to the present invention, an inquiry /
Shared information can be collected by sending and receiving notification frames. Even if there are a plurality of inquiry stations, when the transmission request conflicts of a plurality of inquiry / notification frames are detected, the one with a lower priority is discarded, so that the load is not increased. Further, if all communication terminals are used as the inquiry station, the information collecting operation can be maintained even if any communication terminal fails. Further, by increasing the priority of the normal data frame when transmitting the inquiry / notification frame, the shared information can be collected without hindering the normal communication.

[Brief description of drawings]

FIG. 1 is a flow chart showing the operation of the node station when receiving an inquiry / notification frame from another node station, FIG. 2 is a flow chart showing the operation of the node station that generates an inquiry frame, and FIG. 3 is an application of the present invention. 4 is an inquiry / notification frame format, FIG. 5 is an internal configuration diagram of a node station, and FIG. 6 is a frame transmission waiting queue configuration diagram of the node station. 1 ... Node station, 2 ... Communication terminal, 6 ... MP
U, 7 ... Communication control LSI, 9 ... RAM, 61 ... Inquiry frame transmission waiting queue, 62 ... Communication frame transmission waiting queue, 63 ... Data transmission waiting queue from communication terminal, 64 ...
… Send buffer.

Front page continuation (72) Inventor Hideaki Masuko 5-2-1 Omika-cho, Hitachi-shi, Ibaraki Inside the Omika factory, Hitachi Ltd. (72) Masato Satake 5-2-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Omika factory

Claims (8)

[Claims] 1. A data transmission method for periodically collecting information about each communication terminal device in a network to which a plurality of communication terminal devices are connected, comprising: a) Between all communication terminal devices to be collected. B) at least two communication terminal devices, and at least the destination address of the transmission and "inquiry" or "notification".
"Inquiry" is set to the frame type of the frame having each field for writing the frame type indicating any of the above, the priority of the frame, and the information to be collected,
By setting the address of the next communication terminal device to the destination address, by setting the priority of the predetermined own communication terminal device to the priority of the frame, to inquire information about other communication terminal devices A function of generating and transmitting an inquiry frame is provided, c) each of the at least two communication terminal devices periodically transmits the inquiry frame to the next communication terminal device that follows the chain of addresses, d ) The communication terminal device that has received the inquiry frame rewrites its destination address to the address of the next communication terminal device, and writes its own information in the field of the information to be collected of the inquiry frame, When a plurality of inquiry frames to be transmitted to the next communication terminal device compete with each other, the priority of the frame is transmitted. When reference so as to discard the lower inquiry frame of priority, the communication terminal apparatus generates and transmits the e) the inquiry frame, having received the inquiry frame that has run its course,
While capturing the information collected about each of the communication terminal devices, by rewriting the frame type field of the inquiry frame to "notification", as a notification frame for notifying the other communication terminal device of the collected information, A data transmission method characterized by transmitting rewritten frames. 2. The data transmission method according to claim 1, wherein in each of the communication terminal devices, transmission of normal data other than the inquiry frame is prioritized over transmission of the collected information. 3. The data transmission system according to claim 1, wherein the address of the communication terminal device is used as the priority of the frame. 4. When one communication terminal device competes for a plurality of notification frames to be transmitted to the next communication terminal device during one cycle of the notification frame, the notification frame having a lower priority is discarded. The data transmission method according to claim 1, wherein 5. A network system comprising a common transmission line and a plurality of communication terminal devices connected to the transmission line and each having a unique address, wherein the plurality of communication terminal devices form an annular address chain. At least two of the plurality of communication terminal devices are provided with at least a destination address of transmission and “inquiry” or “notification”.
Establishing an "inquiry" in the frame type of the frame having each field for writing the frame type indicating any of the above, the priority of the frame, and the information to be collected,
Inquiry for setting the address of the next communication terminal device to the destination address, setting the predetermined priority of the own communication terminal device to the priority of the frame, and inquiring information about other communication terminal devices. Each communication terminal device in the system including at least two units periodically generates and transmits a frame, and each communication terminal device receives information held by itself when receiving an inquiry frame generated by another communication terminal device. While adding to the field of the information to be collected of the inquiry frame, rewriting the destination address to the address of the next communication terminal device, means for transmitting the rewritten inquiry frame, and a plurality of communication terminal devices And a means for discarding a frame with a lower priority by referring to the priority of the frame when detecting a conflict in the inquiry frame. A network system characterized in that 6. The at least two communication terminal devices take in the information collected in the inquiry frame and “notify” the frame type field when the inquiry frame sent by itself goes around the address chain.
Each communication terminal device in the system including at least two of the communication frames when the notification frame generated by another communication terminal device is received. 6. The network system according to claim 5, further comprising means for fetching the information collected in. 7. The network system according to claim 5, wherein the address of the communication terminal device is used as the priority of the frame. 8. Each of the communication terminal devices including the at least two units, an inquiry frame transmission waiting queue for storing inquiry frames to be transmitted, a notification frame transmission waiting queue for storing notification frames to be transmitted, and a normal It has a data transmission waiting queue for storing data to be transmitted, and these queues are set to have a high transmission priority in the order of a data transmission waiting queue, a notification frame transmission waiting queue, and an inquiry frame transmission waiting queue. Claim 6
The described network system.