JP2888038B2 - Redundant communication controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a duplex communication controller applied to a communication system comprising a plurality of communication stations connected to a duplex communication line (network), and more particularly, to a duplex communication line. Is a duplex communication control device in which each communication station connected to the communication station communicates with each other by carrying a communication right (token), and a situation occurs in which one of the duplicated communication lines breaks down. The present invention also relates to a duplex communication control device that allows other communication stations to continue communication normally without being affected by the influence.

[0002]

2. Description of the Related Art In a distributed control system requiring high reliability, a control station in charge of controlling a process and a communication line to which the control stations are connected have a duplex configuration. It is configured so that it can be backed up.

FIG. 6 is a conceptual diagram of a communication system having a duplex communication line. In the figure, ST1, S
T2... ST4 are communication stations, which correspond to the above-mentioned distributed control stations. BS1, B
S2 is a duplex communication line. In such a communication system, a communication line BS having a duplex configuration shown in the figure is used.
1 and BS2, one communication line, for example, BS1
Communication station ST
When the token is turned to 1, the communication station ST
Assuming that the transmission of the frame 1 to the communication station ST2 using the first communication line BS1 first, the transmission fails due to a failure at the point A. For this reason, the communication station ST1 subsequently executes frame transmission using the second communication line BS2, which is successful.

[0004] In this case, the communication station ST1 notifies the failure (failure) of the first communication line BS1 to all the communication stations connected to the communication line when the token comes to itself next time. Broadcast to All communication stations receiving this will
Upon recognizing the failure of the first communication line BS1, the communication function using the first communication line BS1 is stopped, and thereafter the communication is continued using the second communication line BS2.

[0005]

However, a communication system that performs such communication control has the following problems. (A) The communication station ST1 has a first communication line BS
Since the failure of the first communication line BS1 is broadcast to another communication station when the token is returned to the communication station after detecting the failure of the first communication station, the token is transmitted for the second time. Until, the other communication station cannot recognize the failure of the first communication line BS1. (B) If there is a communication station that has once failed to receive the broadcast indicating that the first communication line is faulty, the communication station cannot recognize the fault of the communication line BS1 forever. (C) If there is a communication station that does not recognize the failure of one of the communication lines, the communication station repeats the operation for detecting the failure of one of the communication lines every time a token comes to itself. As a result, the communication performance decreases. In addition, a warning message indicating that one of the communication lines is out of order is repeatedly issued. (D) If one communication line is out of order and there is a communication station newly subscribed to the communication line, the communication station cannot recognize the failure of the other communication line.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and in the event that a failure occurs in any communication line of a duplex configuration, each of the communication stations connected to the communication line reliably and reliably. It is an object of the present invention to provide a highly reliable duplex communication control device capable of promptly recognizing the fault information, minimizing the influence on normal communication operations.

Another object of the present invention is to provide a communication station which newly joins without taking complicated procedures even when a new communication station is added to the communication by connecting a new communication station to a communication line. Another object of the present invention is to provide a duplex communication control device that can quickly grasp the state of each communication line and smoothly participate in token path communication.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for transmitting and receiving data (transmission) between a plurality of communication stations connected to duplexed first and second communication lines. In a duplex communication control device, the communication stations are connected to the first and second communication lines, and each of the communication stations is connected to the first and second communication lines. Status list storing bus status information indicating whether each communication station is capable of communicating using the first and second communication lines, and the latest bus status information stored in the token frame. And token generation means for transmitting the token frame output on the first and second communication lines, and receiving bus status information on the token frame. Thus configured with their a list updating means for updating the contents of the bus status list, and a receiving means for one of redundant communication lines performs the selected communication based on the bus status list.

[0009]

In each communication station, the list updating means updates the contents of the bus status list of the communication station with the latest information according to the bus status information carried in the token frame when the token comes to itself. Update so that

[0010] The transmission / reception means grasps the failure / recovery status of the communication line (bus) of the duplex configuration based on the latest bus status information stored in the bus status list, and selects the communication line on the side with no failure. Perform data transmission.
When sending the token to the next communication station, the token generating means transmits the token frame with the latest bus status information of the token frame.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a conceptual diagram showing the configuration of an embodiment of the present invention. In the figure, L1 and L2 are duplicated first and second communication lines, ST1, ST2... Are a plurality of communication stations respectively connected to these duplicated communication lines L1 and L2, and these are distributed and arranged, for example. Control stations and operator stations that perform control operations and monitoring. Each communication station performs data transmission / reception (transmission) communication by carrying a communication right (token).

In each of the communication stations ST1, ST2,..., 11 and 12 are receivers for receiving communication frames transmitted through the communication lines L1 and L2, and 13 and 14 send communication frames to the communication lines L1 and L2. And a communication control means 15 for performing communication control of the token pass system, a function of transmitting / receiving a communication frame, a function of checking data, and the like.

Reference numeral 21 denotes a bus status list.
Each communication station connected to the second communication lines L1 and L2 stores bus status information indicating whether communication is possible using the first and second communication lines. Section. 22 is a token generating means for transmitting the latest bus status information possessed by the self on the token frame and transmitting it; 23 receives the token frame output on the first and second communication lines L1 and L2;
This is a list updating means for updating the contents of its own bus status list 21 according to the bus status information in the token frame.

When transmitting a communication frame, the communication control means 15 refers to the bus status list 21 to select a communication line on the side on which no failure has occurred among the duplicated communication lines L1 and L2, and has selected the communication line. It is configured to transmit a communication frame to the communication line side. FIG. 2 is a conceptual diagram of a token frame indicating a communication right in a communication frame output from the communication control unit 15. PR
A is a preamble part indicating the beginning of the frame, DA is address information of the communication station of the destination, SA is address information of the communication station of the transmission source, LG is length information of the communication frame, CTL is control information, and CTL is control information. Information indicating the type, control information for information transmission, and the like are included. BI is the latest bus status information (information indicating whether each of the communication lines L1 and L2 can be used or not). CRC is a check code.
The types of token frames include, for example, a normal token command that sends a token only to the communication station that is currently participating in communication, and a token that is not currently participating in communication, but is sent to a communication station that is likely to participate in the future. There is a diagnostic token to turn.

FIG. 3 is a conceptual diagram showing the structure of the bus status list 21 provided in each communication station. For each of the communication lines L1 and L2, the state of the latest communication line indicating normal (for example, "1") and abnormal (for example, "0") is stored here. Such bus status information can be determined by whether the transmission has failed or succeeded when the communication frame is transmitted by acquiring the token, and the obtained latest bus status information is Stored in the list. On the receiving side, when the token is received, the list updating means based on the bus status information on the token,
The contents of the list are updated, whereby the contents of the bus status list 21 are quickly updated to the latest bus status information.

The operation of the apparatus having the above configuration will be described below. FIG. 4 is a flowchart showing the operation of one communication station ST1 connected to the communication line. For example, first, the communication station ST1 has a token, and the communication control means 15 refers to its own bus status list 21, puts the information in the token frame, and specifies the destination address of the next communication station ST2. And bus status list 2
The transmission is performed using a communication line indicating normality, for example, L1 (step 1). And the token transmission,
By checking the response signal from the destination communication station,
It is determined whether or not the process has succeeded (step 2). If the token transmission is successful, the token moves to the destination communication station ST2.

In step 2, if the transmission of the token fails, that is, if no response is returned from the other communication station, the communication station ST1 determines that the communication line L1 has failed, and the communication line L1 has failed. The token is transmitted using the communication line L2 (step 3), and the token transmission using the communication line L2 succeeds. Is determined (step 4).

If it is determined that the transmission has succeeded, the communication station ST1 updates the contents of its own bus status list 21 so that the communication line L1 indicates a failure. Also in the communication station ST2 receiving this token, the list updating means 23 transmits the bus status information (communication line L1
The bus status list 21 is updated to the latest one based on the information indicating that the bus has failed (step 5).

The communication station ST that has acquired the token
2, if there is a communication request such as data transmission, the communication operation is executed, and then, according to the contents of the own bus status list 21, the next communication station is addressed using the communication line L2 (communication station ST3). Is transmitted in the same procedure as described above, that is, with the bus status information added to the token.

By performing such a procedure, when the token goes round each communication station participating in the communication, the bus status and the
The contents of the list will be updated to indicate the latest state. If it is determined in step 4 that the token transmission using the communication line L2 has failed, a predetermined confirmation process or the like is performed. As this confirmation processing, for example, the token transmission using the communication line L2 is executed again to confirm whether a valid response is not returned, and the token transmission is similarly performed using the communication line L1 to perform the same. If no response is returned, the communication lines L1, L
2 is abnormal, and processing such as detection of a failure location is performed.

FIG. 5 is a block diagram showing the configuration of a second embodiment of the present invention. In this embodiment, a diagnostic token generating means 31 is provided in each communication station. This diagnostic tone is a token for urging a communication station newly connected to the first or second communication line or newly joining the communication when the power is turned on to join the communication. The diagnostic token is configured to transmit the latest bus status information of the diagnostic token.

When the diagnostic token is received, the list updating means 23 updates the contents of its own bus status list 21 in accordance with the bus status information contained in the diagnostic token frame. Reference numeral 40 denotes a live list indicating an operation state of each communication station connected to or connected to the communication lines L1 and L2, and includes a communication station in a state of participating in communication (an operation state). Indicates active, and if it has not yet participated in communication, inactive is displayed. This live list is updated in response to information that each communication station broadcasts at regular intervals and indicates that it is in an active state.

The diagnostic token generating means 31 refers to the live list 40 and transmits the diagnostic token to the communication station indicating inactivity in the live list 40 at a constant cycle. Note that a normal token generated by the token generation means 21 is included in the live list 40.
It patrols to the communication station indicating active.

According to this embodiment, a communication station newly subscribing to token-pass communication can transmit status information of a duplex communication line to another communication station without performing complicated procedures when subscribing to communication. Can be matched.

[0025]

As described above in detail, according to the present invention, information (bus status information) indicating a failure or recovery state of a duplexed communication line is promptly and reliably notified to each communication station. It is possible to prevent a decrease in communication performance based on incorrect bus status information. In addition, when recovery from a failure occurs, normal operation as a duplex communication line can be promptly performed, so that a highly reliable duplex device can be realized.

According to the second embodiment, the communication station newly joining the token pass communication also
Without complicated procedures when subscribing to communications,
The status information of the duplex communication line can be matched with that of another communication station, thereby preventing a decrease in communication performance.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a conceptual diagram of a token frame indicating a communication right in a communication frame output from a communication control unit.

FIG. 3 is a conceptual diagram of a bus status list provided in each communication station.

FIG. 4 is a flowchart showing the operation of one communication station connected to a communication line.

FIG. 5 is a configuration block diagram showing another embodiment of the present invention.

FIG. 6 is a configuration conceptual diagram of a communication system in which a communication line has a duplex configuration.

[Explanation of symbols]

 L1, L2 First and second communication lines ST1, ST2 Communication station 11, 12 Receiver 13, 14 Driver 15 Communication control means 21 Bus status list 22 Token generation means 23 List updating means 31 Diagnostic token generation means 40 Live list

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-175046 (JP, A) JP-A-62-150948 (JP, A) JP-A-60-132439 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H04L 12/28

Claims (2)

(57) [Claims] 1. Duplex communication in which data is transmitted and received (transmitted) between a plurality of communication stations connected to duplicated first and second communication lines by carrying a communication right (token). A control device, wherein each of the communication stations connected to the first and second communication lines includes: a communication station connected to the first and second communication lines; A bus status list storing bus status information indicating whether or not communication is possible using a line; a token generating means for transmitting the latest bus status information possessed by the user on a token frame; Receives the token frame output on the second communication line, and updates the contents of its own bus status list according to the bus status information on the token frame A duplex communication control device comprising: a list updating unit that performs communication; and a transmitting / receiving unit that performs communication by selecting one of the duplicated communication lines based on the bus status list. 2. A communication device according to claim 1, wherein each of the communication stations is connected to a first and a second communication line and newly added to the communication station. A diagnostic token generating means for transmitting the information is provided, and the list updating means, when receiving the diagnostic token,
2. The duplex communication control device according to claim 1, wherein the content of its own bus status list is updated according to the bus status information carried in the diagnostic token frame.