JPH0690238A - Duplex communication control equipment - Google Patents

Abstract

PURPOSE:To prevent communication performance from being lowered due to erroneous bus status information by quickly and surely notifying information (bus status information) representing the fault or the restored state of duplexed communication lines to each communication station. CONSTITUTION:Each communication station ST is comprised by providing a bus status list 21 which houses the bus status information representing whether or not communication can be performed by using first and second communication lines L1, L2 by each communication station connected to the first and second communication lines, a token generating means 22 which transmits a token frame by putting the latest bus status information provided by its own, a list update means 23 which receives the token frame outputted on to the first and second communication lines and updates the content of its own bus status list according to the bus status information on the token frame, and transmission/reception means 11-15 which select one of the duplexed communication lines based on the bus status information and perform the communication.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a duplicated communication control device applied to a communication system comprising a plurality of communication stations connected to a duplicated communication line (network), and more specifically to a duplicated communication line. Each communication station connected to is a duplex communication control device that communicates with each other by carrying communication rights (tokens), and a situation occurs where one of the duplex communication lines fails. Also, the present invention relates to a duplex communication control device that enables other communication stations to continue normal communication without being affected by the influence.

[0002]

2. Description of the Related Art In a distributed control system which requires high reliability, a control station in charge of process control and a communication line connected to these have a dual structure. Is configured to be backed up by.

FIG. 6 is a conceptual diagram of a communication system in which a communication line has a dual structure. In the figure, ST1, S
T2 ... ST4 are communication stations and correspond to the above-mentioned distributedly arranged control stations. BS1, B
S2 is a duplicated communication line. In such a communication system, a duplexed communication line BS is shown.
1, BS2, one communication line, for example, BS1
If a failure occurs on the local side, communication station ST
When the token turns to 1, the communication station ST
If No. 1 first transmits a frame to the communication station ST2 using the first communication line BS1, the transmission fails due to a failure at the point A. For this reason, the communication station ST1 subsequently carries out a frame transmission using the second communication line BS2, which is successful.

In this case, the communication station ST1 causes the failure (failure) of the first communication line BS1 to all the communication stations connected to the communication line when the token next arrives at the communication station ST1. Broadcast to All communication stations that received this,
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 for performing such communication control has the following problems. (A) The communication station ST1 is the first communication line BS
Since the failure of the first communication line BS1 is broadcast to other communication stations when the token comes back to the communication station after the failure of No. 1 is detected, the token is returned for the second time. The other communication station cannot recognize the failure of the first communication line BS1 until the turn of the. (B) If there is a communication station that has once failed to receive the broadcast indicating that the first communication line has a failure, the communication station cannot recognize the failure of the communication line BS1 forever. (C) If there is a communication station that does not recognize the failure of one communication line, the communication station repeats the operation for detecting the failure of one communication line each time a token comes around to it. This will decrease the communication performance. In addition, a warning message indicating that the one-sided communication line is out of order is repeatedly issued. (D) If there is a communication station newly joined to the communication line while one communication line is broken, the communication station cannot recognize the failure of the one communication line.

The present invention has been made in view of such a problem, and when a failure occurs in any one of the communication lines of the duplex configuration, the communication stations connected to the communication line can reliably and reliably An object of the present invention is to provide a highly reliable duplex communication control device that enables quick recognition of the failure information and minimizes the influence on the normal communication operation.

Further, another object of the present invention is that, even when a communication station is newly connected to a communication line to newly add to the communication, the newly added communication station does not take a complicated procedure. , And to provide a duplex communication control device capable of quickly grasping the state of each communication line and smoothly participating in token path communication.

[0008]

SUMMARY OF THE INVENTION The present invention to achieve such an object is to perform transmission / reception (transmission) of data between a plurality of communication stations connected to duplicated first and second communication lines. In the duplex communication control device, which is configured to carry around a right (token), each communication station connected to each of the first and second communication lines is connected to the first and second communication lines. A bus status list storing bus status information indicating whether or not each of the communication stations being used can communicate using the first and second communication lines, and the latest bus status information held by itself in the token frame And token status output on the first and second communication lines, and 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 its own bus status list with the latest information according to the bus status information in the token frame when the token comes around to itself. To be updated.

The transmitting / receiving means grasps the failure / recovery status of the redundant communication line (bus) from the latest bus status information stored in the bus status list, and selects the communication line on the side without a failure. Perform data transmission.
When the token is sent to the next communication station, the token generation means carries the latest bus status information possessed by the token frame and transmits it.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a conceptual diagram showing the construction of an embodiment of the present invention. In the figure, L1 and L2 are duplexed 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, for example, distributedly arranged. These correspond to a control station and an operator station that performs control operation and monitoring, and each communication station performs data transmission / reception (transmission) communication by carrying communication rights (tokens).

In each of the communication stations ST1, ST2, ..., 11 and 12 are receivers for receiving communication frames sent through the communication lines L1 and L2, and 13 and 14 are for sending communication frames to the communication lines L1 and L2. A driver 15 for communication is a communication control means, which has a function of performing communication control of a token pass system, a function of transmitting and receiving a communication frame, a function of checking data, and the like.

Reference numeral 21 is a bus status list, which is the first and the first.
Each communication station connected to the second communication lines L1 and L2 stores bus status information indicating whether or not communication is possible using the first and second communication lines. It is provided in the section. Reference numeral 22 is a token generation means for transmitting the latest bus status information possessed by the token frame, and 23 is a token frame output on the first and second communication lines L1 and L2.
It is a list updating means for updating the contents of its own bus status list 21 according to the bus status information contained in the token frame.

When transmitting the communication frame, the communication control means 15 refers to the bus status list 21 and selects and selects the communication line on the side where no fault has occurred from the duplicated communication lines L1 and L2. It is configured to send a communication frame to the communication line side. FIG. 2 is a conceptual diagram of the configuration of a token frame indicating the communication right in the communication frame output from the communication control means 15. PR
A is a preamble part indicating the beginning of a frame, DA is address information of a destination communication station, SA is address information of a source communication station, LG is communication frame length information, and CTL is control information. It includes information indicating the type and control information for transmitting information. BI is the latest bus status information (information indicating whether each of the communication lines L1 and L2 can be used). CRC is a check code.
The type of token frame is, for example, a normal token command that sends a token only to the communication stations currently participating in communication, or a token to a communication station that is not currently participating in communication but may participate at some point. There are diagnostic tokens to turn.

FIG. 3 is a structural conceptual diagram of the bus status list 21 provided in each communication station. For each of the communication lines L1 and L2, the latest state of the communication line indicating normal (for example, "1") or abnormal (for example, "0") is stored here. Such bus status information can be known whether the transmission has failed or succeeded when the token is acquired and the communication frame is transmitted, and the latest bus status information obtained is Stored in a list. Also, 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 thus configured 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 on the token frame, and specifies the destination address of the next communication station ST2. Bus status list 2
Transmission is performed using a communication line that indicates normality, such as L1 (step 1). And the token transmission is
By confirming the response signal from the partner communication station,
It is determined whether or not it has succeeded (step 2). If the token transmission is successful here, the token moves to the partner communication station ST2 side.

In step 2, if the token transmission fails, that is, if no response is returned from the other communication station, the communication station ST1 determines that the communication line L1 is broken, and the communication line L1 is broken. The bus status information indicating that the communication is being performed is placed on the token, and this time, the token is transmitted using the communication line L2 (step 3), and subsequently, the token transmission using the communication line L2 is successful. Whether or not it is determined (step 4).

When it is determined that the transmission is successful, 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 that has received this token, the list updating means 23 causes the bus status information (communication line L1) on the token.
The bus status list 21 of its own is updated to the latest one (step 5).

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

By carrying out such a procedure, when the token makes a round in each communication station participating in the communication, the bus status of each communication station
The contents of the list will be updated to show the latest status. 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 the confirmation processing, for example, the token transmission using the communication line L2 is executed again to confirm whether a valid response is returned, and the token transmission is performed in the same manner using the communication line L1. If no response is returned, communication lines L1, L
If 2 is abnormal, it is processing such as detection of a failure point.

FIG. 5 is a block diagram showing the configuration of the second embodiment of the present invention. In this embodiment, the diagnostic token generating means 31 is provided in each communication station. The diagnostic token is a token for encouraging a communication station, which is newly connected to the first and second communication lines or is turned on to newly join the communication, to join the communication. , This diagnostic token is configured to be transmitted with the latest bus status information that it has.

When receiving this diagnostic token, 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 is a live list showing the operating state of each communication station connected to or connected to the communication lines L1 and L2. Shows inactive, and if it is not yet participating in communication, inactive is displayed. The live list is updated upon receiving information indicating that the communication station is in an active state, which is broadcast by each communication station at regular intervals.

The diagnostic token generating means 31 refers to the live list 40, and transmits the diagnostic token to the communication station showing inactivity in the live list 40 at a constant cycle. In addition, in the live list 40, the normal token generated by the token generation means 21 is
It patrols the communication stations that are active.

According to this embodiment, a communication station that newly joins the token path communication can send the status information of the duplicated communication line to other communication stations without performing a complicated procedure when joining the communication. Can be matched.

[0025]

As described in detail above, according to the present invention, each communication station is notified of information (bus status information) indicating a failure or recovery status of a duplicated communication line, quickly and reliably. Therefore, it is possible to prevent a decrease in communication performance based on incorrect bus status information. Further, in the case of recovery from a failure, the normal operation of the duplex communication line can be swiftly performed, so that a highly reliable duplexer can be realized.

Further, according to the second embodiment, even in a communication station newly joining the token path communication,
Without complicated procedures when joining the communication,
It is possible to match the status information of the communication line of the duplex configuration with that of another communication station, and prevent deterioration of communication performance.

[Brief description of drawings]

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

FIG. 2 is a conceptual diagram showing the configuration of a token frame indicating a communication right in the communication frame output from the communication control means.

FIG. 3 is a conceptual diagram showing the configuration 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 conceptual diagram of a configuration of a communication system in which a communication line has a dual 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 generating means 23 List updating means 31 Diagnostic token generating means 40 Live list

Claims (2)

[Claims] 1. Duplex communication in which data transmission / reception (transmission) is carried out by carrying communication rights (tokens) among a plurality of communication stations connected to the duplicated first and second communication lines. In the controller, each communication station connected to each of the first and second communication lines is the communication station connected to each of 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 generation means for transmitting the latest bus status information possessed by a token frame and transmitting the token status; 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 contained in the token frame. And a transmission / reception means for selecting one of the duplicated communication lines on the basis of the bus status list and performing communication. 2. A communication token connected to the first and second communication lines and newly added to each communication station, has a diagnostic token for prompting the communication station to join the communication, and has the latest bus status that it has. When a diagnostic token generating means for transmitting information is provided, and the list updating means receives this diagnostic token,
2. The duplex communication control device according to claim 1, wherein the contents of its own bus status list are updated according to the bus status information contained in the diagnostic token frame.