JPS6120449A - Duplex communication channel control system - Google Patents

Abstract

PURPOSE:To switch a loop-shaped communication channel without making the information which is being transmitted disappear, when a fault is generated in the communication channel concerned, by providing a means for storing a communication frame which is being transmitted, on a control station, and constituting said station so that the communication frame in the storage means is retransmitted after executing switching of the loop-shaped communication channel. CONSTITUTION:A control part 25 receives a communication frame which makes a round of a loop-shaped communication channel, from a receiving circuit 21 or 33, and constitutes the next communication frame and transmits it. In this case, the communication frame to be transmitted is stored in a storage device 26. When the generation of a fault is detected, the control part 25 connects a transmitting circuit 22 and a receiving circuit 23 of a stand-by system by controlling a switching device 24, and also decides a faulty point and switches the communication channel constitution by controlling each terminal station by a control line which is not shown in the figure. Thereafter, the control part 25 reads out the communication frame from the storage device 26, edits it and sends it out to the communication channel from the transmitting circuit 22, and thereafter, it is returned to the same control as the normal time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to communication control of a loop-shaped communication path, and more particularly to a control method when switching a duplicated loop-shaped communication path.

2. Description of the Related Art A communication system using a loop-shaped communication path is widely used, in which terminal stations that communicate with each other and a control station that controls those communications are connected in series through a communication path to form one loop.

In such a system, the communication path system is duplicated to prevent communication of the entire system from being disabled due to a failure in the communication path or the terminal station.

The present invention relates to the storage of transmitted data when switching such a duplex loop communication path system.

[Conventional technology]

FIG. 2 is a diagram showing an example of a communication system configured with a double-wired loop-shaped communication path.

This system is composed of control station 1 and terminal station 2-1.2-2.2.
-3, etc. are sequentially connected through communication paths 3-1.3-2--3-4, and a second loop is connected through communication paths 4-1.4-2-4-4.

゛ The control station 1 creates a communication frame in a predetermined format and transmits it to the communication path 3-1. For example, as shown in FIG.
-11-1.1 The main body part lined up by the number of terminal stations as shown in 10-3, and the flag 11-1.1 that indicates the delimitation of communication frames before and after it.
It shall consist of 1-2.

Each terminal station 2-1, 2-2, etc. detects the head flag of the arriving communication frame and counts slots 0-1, etc. from the head to detect the own station slot assigned to it. , receives the contents of its own station slot, and if there is transmission information, replaces the own station slot with the transmission information, and if there is no transmission information, it is relayed as is.

Note that each terminal station relays the received flag and slots other than its own slot as is.

In this way, the communication frame relayed through each terminal station is returned to the control station 1, so the control station 1 identifies the destination end station from the transmission information of the slot of each terminal station and matches the slot of the destination end station. A communication frame in which transmission information is arranged is constructed and sent to the communication path 3-1 as described above, and communication between terminal stations is performed by repeating the above steps.

After transmitting a communication frame, the control station 1 monitors the time it takes to receive the communication frame after going around the loop-shaped communication path, checks the format of the received communication frame, etc. Detects the occurrence of a failure in the communication path (including the relay function of each terminal station) due to no reception or an abnormality in the format of the communication frame.

When the control station 1 detects the occurrence of a failure, it determines the failure point using a known method such as a loop bank.

Based on the results, the backup system of the loop communication path was put into use,
Also, the communication path configuration is changed, such as by setting a bypass to exclude the faulty terminal station from the loop.

[Problem that the invention seeks to solve]

As is clear from the above explanation, when a failure occurs,
There is a high possibility that the information in the communication frames transmitted through the loop-shaped communication path will disappear or have incorrect contents after the point of failure.

Therefore, even if communication becomes possible after the above measures, the lost information will have to be reconstructed and retransmitted, or the lost information will have to be reconstructed and retransmitted before the communication that continued from before the failure actually resumed. It is necessary to give and receive alternative information,
Such processing was one of the causes of delays in restarting operations.

[Means for solving problems]

SUMMARY OF THE INVENTION An object of the present invention is to provide a redundant communication channel control system that can switch the communication channel without losing information being transmitted when a failure occurs in the loop communication channel.

The purpose of this is to connect a control station and a plurality of terminal stations sequentially through a redundant communication path to form a two-system loop communication path, and to communicate between the control station and a plurality of terminal stations using communication frames transmitted on one system of the loop communication path. In a system in which communication is performed between terminal stations, and if a failure is detected in the system in use, the communication is performed using a communication frame transmitted in the other system, the control station This is achieved by the duplex communication channel control method of the present invention, which has means for storing frames, and is configured to retransmit the communication frames stored in the storage means after switching the loop-shaped communication channel system. .

[Effect]

That is, the communication frame being transmitted at the control station is stored,
After a failure is detected, when switching the communication channel configuration and restarting communication, it starts with retransmission of the stored communication frame, so when each terminal station restarts communication, it starts with communication processing for the previous communication frame. As a result, it is possible to smoothly and easily continue communication with the communication that existed before the failure occurred.

〔Example〕

FIG. 1 is a block diagram showing the configuration of a control station 1 in an embodiment of the present invention.

In the figure, the transmitting circuit 20 and the receiving circuit 21 are connected to the communication path 3.
-1 and 3-4 to form a working communication path system, and the transmitting circuit 22 and receiving circuit 23 are connected to communication paths 4-4 and 4-1 to form a backup system.

The communication path may be, for example, an optical fiber line, in which case,
The transmitting circuit 20.22 and the receiving circuit 21.23 include a photoelectric conversion circuit.

``The switch 24 switches the control unit 25 to the active communication channel or the backup communication path, and is controlled by the control unit 25.

The control unit 25 follows the known communication control as described above.
A communication frame is constructed and sent to the transmission circuit 20 or 22. According to the present invention, the control unit 25 simultaneously stores the communication frame to be sent in the storage device 26 at this time.

The control unit 25 receives the communication frame that has made one circuit around the loop-shaped communication channel from the receiving circuit 21 or 23, configures the next communication frame by the communication control process as described above, and transmits the frame. At this time, as in the case of the previous communication frame, the communication frame to be transmitted is stored in the storage device 26, so the communication frame currently being transmitted is held and the previous communication frame is erased.

The control unit 25 also monitors the occurrence of a failure in the communication path as described above.

When detecting the occurrence of a fault, the control unit 25 controls the switching device 24 to connect to the backup transmitting circuit 22 and receiving circuit 23, and also controls each terminal station via a control line (not shown) to determine the fault point. and switch the communication path configuration.

After that, the control unit 25 reads out the communication frame from the storage device 26, edits it, and sends it from the transmission circuit 22 to the communication path.
After that, the control will return to the same as normal.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, when switching a duplex loop-shaped communication path at the time of a failure, loss of information being transmitted is prevented, so recovery after switching is accelerated and the communication system is improved. There is a significant industrial effect of improving availability.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a control station according to an embodiment of the present invention, FIG. 2 is a configuration diagram of a communication system, and FIG. 3 is an explanatory diagram of the configuration of a communication frame. In the figure, ■ is a control station, 2-1 to 2-3 are terminal stations, 3-1
~4-4 is a communication path, 10-1-10-3 is a slot,
11-1 and 11-2 are flags, 20.22 is a transmitting circuit, 21.23 is a receiving circuit, 24 is a switch, 25 is a control unit, and 26 is a storage device. 1st m Figure Z

Claims (1)

[Claims] A control station and a plurality of terminal stations are sequentially connected through a duplex communication path to form a two-system loop communication path, and communication frames transmitted through one system of the loop communication path are used to communicate between the control station and the terminal stations. In a system that performs communication and, if a failure is detected in the system in use, switches to perform the communication using a communication frame transmitted by the other system, the control station stores the communication frame that is being transmitted. 1. A duplex communication channel control system, comprising means for retransmitting communication frames stored in said storage means after switching said loop-shaped communication channel system.