JPH0533088Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a duplex communication control device installed inside a duplex communication station or a non-duplex communication station connected to a duplex bus of a token bus type. .

<Prior art> As shown in FIG. 4, communication buses L1 and L2 are duplicated, and redundant communication stations S1, S2, S3, and S4
In a token bus type communication system to which communication stations are connected, when each communication station starts communication, it sends out a token, obtains the right to use the bus, and then performs communication operations.

In such a communication system, when an abnormality occurs on one bus, the communication station that detects the abnormality performs broadcast communication and prevents all communication stations from using the abnormal bus. Ensure normal communication.

On the other hand, each communication station has a function of generating a new token if no signal is detected from any of the redundant buses for a certain period of time or more. Therefore, in the system shown in FIG. 4, if a failure or disconnection occurs at points A and B, for example, when the abnormality at point A is detected and bus L2 is selected from the viewpoint of communication station S1, communication station S3 becomes an isolated station, and communication station S3 becomes an isolated station. generates and sends an inappropriate token to other normal stations on the abnormal bus L2, interrupting the original communication taking place on the normal bus, and disrupting the entire communication system. There were times when communication became impossible.

Furthermore, even when a non-duplex communication station is connected to the system shown in FIG. 4, a similar problem may occur if a token is sent from the non-duplex communication station to the bus on the side where the abnormality has occurred.

<Problem to be solved by the invention> The problem to be solved by the invention is when a failure occurs in two or more places in a communication system consisting of only redundant communication stations in a token bus type redundant bus communication system, or Even in a communication system where communication stations and non-duplex communication stations coexist, it is possible to prevent inappropriate tokens from being generated, prevent the entire communication system from being unable to communicate, and improve reliability. The purpose is to realize a high quality communication system.

<Means for Solving the Problems> The present invention, which has solved the above problems, is a duplex communication control device installed inside a duplex communication station or a non-duplex communication station connected to a duplex bus of the token bus type. A communication station connection status table that is updated as appropriate by intercepting tokens on the bus and sets the status of each communication station connected to the bus; The token is sent to the communication station having the next highest or lowest station number after the station number of This is a duplex communication control device characterized in that it has an access control section that sends out the following information.

<Operation> In a communication system using a duplex communication station or a non-duplex communication station using the duplex communication control device of the present invention, one communication station circulates tokens on the bus in ascending or descending order of station numbers, and each communication station A communication station connection status table is created internally to intercept this and set the connection status of each communication station, and each communication station refers to this table and performs the optimal communication operation, resulting in the existence of two tokens. Never.

<Embodiment> FIG. 1 shows the configuration of a communication station S including a redundant communication control device 1 implementing the present invention.

In this figure, a communication station S has a duplex communication control device 1 and a normal communication function section 2.

Further, the communication station S has two transceivers 3 as a means for connecting to the communication buses L1 and L2 if the communication station S is a duplex communication station, and one transceiver 3 if the communication station S is a non-duplex communication station, Access control unit 12 is connected.

The access control unit 12 updates the communication station connection state table 13 based on the contents of the token received from the transceiver 3, and
The destination of the token is determined based on the contents of the token, and the token is sent to the communication buses L1 and L2 via the transceiver 3.

An example of a communication system configured using such a communication station S is shown in FIG. 2, and its operation will be explained.

Communication stations S1 and S4 are duplex communication stations and communication station S
2 and S3 are non-duplex communication stations, and each communication bus L
1, connected to L2. Each communication station S1, S
2, S3, S4 are communication station numbers #1, #2, #3,
Has #4.

Each communication station then generates a communication station connection state table 13 based on the station number of the source of the token intercepted from the bus to which it is connected.

For example, if communication station S1 holds a token at a certain point in time, communication station S1 uses bus L1 to communicate with communication station S2 (#1), which is connected to bus L1 and has the next highest station number. #2) Send the token to ().

Communication station S2 is connected only to bus L1, and uses the token given by communication station S1 to communication station S4, which has the next highest station number after itself (#2).
(#4) via the bus L1 ().

The communication station S4 transmits this token to the communication station S1 via the bus L1 () since there is no communication station with a station number larger than its own (#4).

Since the token transmitted by the communication station S1 has now circulated, the communication station S1 then circulates the token to the communication stations connected to the bus L2.

The communication station S1 sends a token to the communication station S3 (#3) connected to the bus L2 and having the next highest station number after its own station number (#1) ().

Communication station S3 is connected only to bus L2, and transfers the token given by communication station S1 to communication station S4, which has the next highest station number after itself (#3).
(#4) is sent from bus L1 ().

The communication station S4 transmits this token to the communication station S1 via the bus L2 () since there is no communication station with a station number larger than its own (#4).

Through the above operations, each communication station intercepts the tokens present on the buses to which it is connected, and creates a communication station connection state table therein.

The contents of the communication station connection status table in each communication station are shown in FIGS. 3a, b, c, and d.

Fig. 3a shows the contents of the connection state table of communication station S1, Fig. 3b shows the contents of the connection state table of communication station S2, Fig. 3c shows the contents of the connection state table of communication station S3, and Fig. 3d shows the contents of the connection state table of communication station S3. The contents of the connection state table of the communication station S4 are shown, and "O" represents the type of communication station connected to the buses L1 and L2.

Thereafter, the above operations are repeated to circulate the token, and when a communication station that requires the use of the bus obtains a token, it uses it and transmits the token again.

Although the above operation shows the case where tokens circulate in ascending order of station numbers, tokens may circulate in descending order of station numbers.

Furthermore, even if an abnormality occurs on one of the redundant buses, each communication station can recognize the bus on which the abnormality has occurred and the type of communication station connected to itself using the communication station connection status table. It is possible to adjust the creation of tokens that are output to the bus when a bus abnormality occurs.

In this way, if a failure or disconnection occurs in two or more places in a communication system with only redundant communication stations,
Alternatively, even if non-duplex communication stations are mixed, the token circulates to all communication stations and by detecting an isolated communication station in the communication station connection status table, the token in the communication system is always unique. Therefore, an inappropriate token will not be generated from an isolated communication station.

<Effects of the invention> In a communication system using a duplex communication station or a non-duplex communication station using the duplex communication control device of the present invention, one communication station circulates tokens on the bus in ascending or descending order of station numbers, and each communication The station intercepts this and creates an internal communication station connection status table that sets the connection status of each communication station, and each communication station refers to this table and performs the optimal communication operation, earning two tokens. Therefore, an inappropriate token will not be generated even if a failure occurs in two or more places in a communication system consisting only of duplex communication stations, or in a communication system in which duplex communication stations and non-duplex communication stations coexist. Therefore, it is possible to prevent the entire communication system from becoming unable to communicate, and to realize a highly reliable communication system.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a communication station including a redundant communication control device implementing the present invention, FIG. 2 is a diagram showing how tokens are circulated in a communication station including the duplex communication control device of the present invention, Figure 3a,
b, c, and d are diagrams representing the contents of the communication station connection status table of each communication station in the system shown in Fig. 2;
The figure shows a state in which communication stations are connected to a duplex bus. 1... Redundant communication control device, 2... Communication function unit, 3... Transmitter/receiver, 12... Access control unit,
13...Communication station connection status table, L1, L2...
...Bus, S, S1, S2, S3, S4...Communication station.

Claims (1)

[Scope of utility model registration request] In a duplex communication control device provided inside a duplex communication station or a non-duplex communication station connected to a duplex bus of the token bus type, the tokens on the bus are updated as appropriate by intercepting the tokens, and the tokens are updated as appropriate and connected to the bus. A communication station connection status table in which the status of each communication station is set; and when the token is received, the token is sent via one bus to a communication station having a station number next higher or smaller than its own station number. Next, when the token is received, an access control unit transmits the token to a communication station having the next highest or lowest station number after the own station number on the other bus.