JPH0527292B2 - - Google Patents

Description

[Detailed description of the invention]

Technical Field The present invention relates to a token-passing network control system in which communication rights are transferred between a plurality of communication stations connected by communication lines, and the communication station that has the communication rights can communicate. The present invention relates to a network control method that allows for easy transfer and recognition of communication stations that participate in communication as quickly as possible. BACKGROUND OF THE INVENTION In recent years, with the rise of office automation, so-called local area networks (hereinafter referred to as LANs), which connect various types of office equipment via low-cost and simple network transmission lines, have been in the spotlight. In this type of LAN, a large number of stations are generally connected to a single common communication transmission path, and the transmission path is commonly used to communicate between the stations. Therefore, if two or more stations start communication at the same time, there is a risk that communication signals will be disrupted, or a so-called "communication collision" may occur. Therefore, in order to avoid that "communication collision",
Several network control methods have been proposed so far to adjust the transmission start timing of all stations in the network, but among them, the TOKEN PASSING method is generally known as one of the better methods. It is being In this token passing method, a communication right is logically established that allows one station to occupy and use a network transmission path, and there is only one station in the network that has this communication right. This is based on the principle that when the station that has the communication right finishes its communication operation, or when there is no need to communicate from the beginning, the communication right is delegated to another station. Furthermore, in this token passing method, in order to give each station in the network an equal opportunity to communicate, a station that has finished communicating passes the communication rights to the adjacent downstream station one after another, and the communication rights are transferred to the network. The so-called go-ahead (GO) circulates in a predetermined direction within the workpiece transmission path.
AHEAD) format is generally widely adopted. Furthermore, since communication operations within the network are generally carried out based on predetermined protocols (communication rules), each station is equipped with a processor for this purpose, and communication control operations are performed using predetermined firmware. I'm going. By the way, the above-mentioned network control system based on the token passing method is being applied to networks using optical fibers or in a ring shape.
The reason for this is the GO-Ahead (GO) mentioned above.
This is because the AHEAD) type communication rights circulation system is very well suited to the physical form of a ring-shaped network. For example, as shown in Figure 1, in a link network, the signal flow on the transmission path a is usually unidirectional, so some kind of gate circuit is provided to block the signals on the transmission path.
By turning this on and off, communication rights are sequentially transferred to adjacent downstream stations b to g as shown by the arrows in the figure. type communication rights circulation system can be easily realized. On the other hand, the conventional communication method using the token passing method, for example, the one disclosed in Japanese Patent Publication No. 19779, uses a predetermined communication station or, if a predetermined communication station is unable to communicate, a next available communication method. communication rights were delegated to the communication station. However, in this case, it is difficult to recognize a communication station that joins the communication in the middle, and there is a possibility that communication rights cannot be promptly transferred to the communication station that joins in the middle. Purpose The present invention eliminates the drawbacks of the prior art described above, and allows communication rights to be delegated efficiently, as well as allowing communication stations that participate in communication to be recognized as quickly as possible. The purpose is to provide a network control method. EXAMPLES Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 2 shows an example of the configuration of a local area network according to the present invention, where a is a ring-shaped network transmission line, b to g are transmitting/receiving stations connected to this transmission line a, and the station b is Each address number (station number) of -g is arbitrarily assigned, for example, as shown in the following table, regardless of the connection position of the station.

[Table] When transferring communication rights, station b mentioned above
.about.g, the station that has the communication right delegates the communication right to the station that has the address number that is closest to its own address number and has a larger value. In this way, the communication rights are transferred sequentially, so as shown by the arrows in Figure 3, the communication rights are transferred one after another in the order of address numbers, and the transmission path a.
I will be patrolling inside. That is, as shown by the arrow in Fig. 2, the communication right is from station d→b→
Since the delegation is in the order of f → g → c → e → d...,
At first glance, this appears to be irregular compared to the conventional form of communication rights delegation, in which communication rights are delegated to adjacent downstream stations as shown in Figure 1, but in reality, communication rights are delegated as shown in Figure 3. Tracking the station addresses that go will result in a complete go-ahead type delegation that concatenates in address number order from 1 to 6. FIG. 4 shows an example in which the present invention is applied to a bus-like network, where A is a bus-like network transmission line, and each transmission/reception station b to g connected to this transmission line A and their address numbers 1 to 1 are connected to the transmission line A. 6 and the communication rights delegation method are the same as in the first embodiment described above. As a result, as shown by the arrows in FIG. 4, the order in which communication rights are handed over is the same as shown in FIG.
As in the case of the ring-shaped network shown in the figure, a go-ahead type network control mode is adopted. In this way, in the conventional method, communication rights are delegated to adjacent downstream stations for circulation, which requires a closed loop transmission path, but in this method, communication rights are delegated in the order of station address numbers. Therefore, it is not affected by the physical shape of the transmission path of the network, and can be applied to both the bus-shaped transmission path A and the ring-shaped transmission path a. By the way, the control operation examples of the first and second embodiments shown in FIGS. 2 and 4 are based on the assumption that all stations b to g in the network are in an operable state. be. but,
In reality, some stations often become inoperable due to power being cut off while the network is in operation, or due to malfunction or other reasons, resulting in a situation where valid station addresses are not continuous and the station is left blank. Therefore, it is necessary to select only operable stations within the network and perform the go-ahead type communication rights circulation operation controlled in the order of addresses as described above. An example of the control operation of the embodiment of the present invention shown in FIGS. 5 and 6 in response to this request will be explained with reference to the flowchart shown in FIG. 7. In FIGS. 5 and 6, stations d and f marked with an X are inoperable stations. Additionally, each network is equipped with the following communication control procedures. (T1) Station b via transmission line a or A
The communication data transmitted between . The data of this communication right transfer command includes the address code (address number) of the receiving station that should not receive the command. Further, when this communication rights transfer command is transmitted from a station, only the station having an address number matching the receiving station address receives the communication rights transfer command. (T2) When the receiving station receives the communication rights transfer command described above (step S1), response communication data indicating that the command has been received is returned from the receiving station to the transmitting station that sent the command (step S2). . (T3) Furthermore, in order to ensure the above-mentioned transfer of communication rights and the cyclic operation thereof, each of the stations b to g has a communication control means that performs the following processing. Note that all of these means can be realized using communication control firmware. That is, the station that receives the communication rights transfer command ends its own communication processing, or if no communication processing exists from the beginning, attempts to issue a communication rights transfer command to another station. However, immediately after the network system starts up, for example, immediately after the power is turned on, each station does not remember the station address to which it should next transfer communication rights.
S3). This station address refers to the address of a station that is closest to its own station address and can operate with a larger address number. Therefore, the station to which communication rights are to be delegated first sequentially performs the following trial and determination processing. (t-1) First, if the station has just been started up, jump from step S3 to step S7, clear the count value, and then create a recipient address by adding +1 to the own station address (step S8). This is sent along with the communication rights transfer command (step S11). After that, if there is no response (response communication data) indicating that the command has been received within the specified time (step S12),
It is assumed that the station with that recipient address does not exist in the network or is in an inoperable state due to a power cut or other reason, and the process returns to step S8. Furthermore, "+1" is added to the above-mentioned recipient address. , repeat the same steps as above until a response is received. (t-2) Next, when the above-mentioned recipient address reaches the maximum station address predefined in the network and there is still no response indicating that the command has been received (step S9), the maximum station address predefined in the network is reached (step S9). The recipient address is reset to the station address (step S10), and a communication right transfer command is sent (step S11). (t-3) Here, if there are two or more operable stations in the network, the above (t-3)
-1) and step S11 shown in (t-2)
In response to the command issuing operation, a response indicating that the command has been received should always be returned. When the response is received (step S12), the communication rights transfer operation ends, but at that time, the receiving station address is stored in the memory (RAM) of the station to which the communication rights have been transferred (step S12).
S13) In order to improve communication efficiency by omitting the processing in (t-1) and (t-2) above, in subsequent communication rights transfer operations, this memorized receiving station address is attached to the communication rights transfer operation. (Step S6). (t-4) However, taking into account cases in which a station becomes inoperable due to a power cut or other reasons during network operation, and cases in which a station that becomes operational newly joins the communication network,
After completing the communication rights transfer operation a predetermined number of times (steps S4 and S5), the processing of stations S7 to S12 in the above-mentioned (t-1) and (t-2) sections is performed without using the memorized receiving station address. and updates the memory of the station address to which communication rights should be transferred (step S13). (t-5) Also, step (t-3) above
A communication rights transfer command was issued using the recipient address discovered in the process of S12 (step
S6 and 11), if no response is received to the effect that the command has been received (step S12), it is assumed that the station to which communication rights have been delegated has become inoperable, and the process described above (t-1) is resumed. Then, return to the process from step S8 of the (t-2) term,
Detects a new station to which communication rights are to be transferred. The communication control processing described above enables communication rights delegation operations as in the third and fourth embodiments shown in FIGS. 5 and 6. In the figure, the arrow indicates the destination to which the communication right is transferred, and FIG. 8 shows how the station address to which the communication right is transferred at this time is tracked. FIG. 9 shows an example of the configuration of each station in FIGS. 2 and 4 to 6, where 11 is a transceiver that performs transmission and reception with network transmission path a (or A), and 13 is coupled to transceiver 11. It is a serial controller that is provided according to the data transmission type on transmission path a (or A) and has the function of acting as an intermediary with transmission path a (or A). Communication data as shown in FIG. 10 on transmission path a (or A) is transmitted from the transceiver 11 to the DMA controller 1 via the serial controller 13.
5 and further stored in the memory 16. The central processing unit (CPU) 17 analyzes the network address of the received communication data according to the flowchart of FIG. 7 described above. 18 is an address switch connected to CPU 17,
19 is an interface control unit that is also connected to the CPU 17;
performs input/output control of various office equipment 20. FIG. 10 shows an example of the format of communication data used in each of the networks shown in FIGS. 2 and 4 to 6, where 31 is the recipient address;
32 is a sender address, 33 is a data type, and 34 is a data area. Effects As explained above, according to the present invention, the communication station that has the communication right executes a search process for searching for a communication station to which the communication right is to be transferred every time the communication right is transferred a predetermined number of times. As a result, communication efficiency can be improved compared to a method in which search processing is performed each time communication rights are transferred.Furthermore, the present invention does not perform search processing at all, but transfers communication rights a predetermined number of times. If this is done, a search process is executed, so that it is possible to recognize communication stations that participate in communication as quickly as possible.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of the configuration of a local area network according to a conventional method, FIG. 2 is an explanatory diagram showing an example of the configuration of a local area network according to the present invention, and FIG. FIG. 4 to FIG. 6 are explanatory diagrams showing other configuration examples of the local area network according to the present invention, and FIG. 7 is an explanatory diagram showing an example of the control operation of FIGS. 5 and 6. Flowchart, Figure 8 is 5th
An explanatory diagram showing the order of communication rights delegation in FIGS.
FIG. 9 is a block diagram showing an example of the configuration of each station shown in FIGS. 2 and 4 to 6, and FIG. FIG. 3 is an explanatory diagram showing a format example. A, a...Network transmission line, b-g...Sending/receiving station, 1-6...Station address.

Claims (1)

[Scope of Claims] 1. A token passing network control system in which communication rights are transferred between a plurality of communication stations connected by a communication line, and a communication station having communication rights can communicate, comprising: Each of the communication stations to which the communication rights have been transferred searches for a communication station with which it can communicate in order to transfer the communication rights, and transfers the communication rights to the communication stations that are searched by the search process and is capable of communication. , stores the address information of the communication station to which the communication right has been transferred in the memory, and the next time the communication right is transferred, the communication right is received without performing the search process to the communication station for the address information stored in the memory. Further, each of the communication stations executes a search process of searching for the communication station with which the communication is possible every time the communication rights are transferred a predetermined number of times based on the address information stored in the memory. A network control method characterized by: