JPH01221955A - System for controlling loopback of loop network - Google Patents

Abstract

PURPOSE:To omit the installation of a managing station and to shorten a time required for the accomplishment of loopback at the time of generating abnormality by providing prescribed plural functions in a node station which performs the input/output of data between a terminal equipment. CONSTITUTION:In the node stations 1-6, one end side of the node station N is designated as a terminal P and the other end side as a terminal Q for the transmission directions of a master system loop 7 and a slave system loop 8. The station N, when the disconnection of a reception signal from the terminal P side being generated, stops the transmission of a signal from the terminal P, and sets the terminal Q side at a loopback state. Meanwhile, when the disconnection of the reception signal at the terminal Q side is generated, the terminal P side is set at the loopback state, and a burst signal is sent from the terminal Q side intermittently, and it is decided whether or not the intermittent signal is returned in a synchronous state, and when no synchronous state is generated, the loopback state is continued, and when synchronization is obtained, the loopback state is cancelled, then, a loop is recovered to a normal loop.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the improvement of a loop network that interconnects information devices distributed in factories, buildings, etc. to maximize the OA rate. In particular, the present invention relates to improvements in a loopback control method provided to avoid stopping the entire system when a failure occurs in a portion of a loop transmission line.

[Prior Art and Problems] There are systems called star type and bus type in LAN, which connect multi-functional terminal equipment to form a network that can be controlled all at once, but with the development of information equipment and As a result, the number of installed terminal devices is increasing, and today, loop networks with simple wiring have become mainstream.

As shown in FIG. 6, such a loop network connects node stations 11, 12, 13, 14 and 15, which are input and output to terminal equipment (not shown), to transmission lines 7 and 8 made of optical fibers. They are connected in a loop in sequence. Generally, such a station includes a management station 10 for managing and controlling the entire system, and the general node station serving as an input/output field to the network.

On the other hand, the transmission line has a duplex configuration, consisting of a main loop 7 running clockwise in the figure and a slave loop 8 running counterclockwise. In such a configuration, data transmission between terminals is performed using the main loop 7 during normal operation, and the slave loop 8 is used as a backup system and constantly sends signals representing data such as "1". In the event of a road disconnection or station abnormality, the standby system is used to loop back around the abnormal location to prevent the entire system from being disconnected.

Assume now that a transmission line disconnection occurs between node stations 12 and 13, as shown in FIG.

The management station 10 normally sends check data to each node station, and when this is delayed, it is possible to detect an abnormality in the loop transmission path.

Conventionally, when the management station 10 detects an abnormality as described above, it has generally entered a loopback state using the following procedure.

(b) The main loop 7 is the sending side, the slave loop 8 is the receiving side, and the main loop 7 is viewed from the management station IO.
A loopback command is issued to 15, which is the farthest station (Igt downstream station), to return the main system data to the slave system, and then test data is transmitted.

(b) If test data is not returned as described above, a loopback command is issued to the station 14 that is one level upstream, and the test data is transmitted in the same manner as above.

If no response data is returned even after this, the same process is performed sequentially with another upstream station. In the case of FIG. 6, loopback 12a is performed for the first time at station 12, and the response is Data will be returned.

(C) Next, the management station 10 uses the slave loop 8 as the transmitter and the master loop 7 as the receiver, and sends the slave data to the master loop 7 to the adjacent station 13 of the loopback station 12 determined above. Issue a command to return to.

(iv) The management station 10 transmits test data and checks the response. Thereafter, the management station 10 puts the slave loop 8 into a relay state (allows data to pass through) and resumes transmission using the master loop 7 for both transmission and reception.

Loopback is completed by the steps (a) to (d) described above, but in such conventional systems, the steps are extremely complicated as described above, and the resulting time delay until transmission is restored has become a problem. In other words, there are not many problems when the number of node stations is small, but as the system scale expands and the number of node stations increases, searching for an abnormality using the trial and error procedure described above becomes surprisingly time-consuming, and abnormalities in the transmission path are detected. The time from occurrence to completion of loopback becomes extremely long, and data transmission is stopped during that time, which cannot be overlooked in a system that requires a high degree of reliability.

In addition to the above, failure of the management station 10 itself is also possible, and to protect against this, it is necessary to duplicate the management station itself, and as the situation becomes more and more complex, There is.

[Object of the Invention] The present invention eliminates the drawbacks of the prior art as described above, and not only makes it possible to omit the installation of a management station in a loop network, but also greatly reduces the time required to complete a loopback when an abnormality occurs. The aim is to provide a new loopback control method that can shorten the time required.

[Summary of the Invention] According to the present invention, a node station that performs data input/output with a terminal device has the following two functions.

In other words, if the received signal from one end is disconnected, the signal transmission from that end is stopped and the other end is placed in a loopback state, and the received signal from the other end is disconnected. In this case, the other #i side is put into a loopback state, and the end where the received signal is cut off sends an intermittent signal, and it is determined whether or not the intermittent signal appears synchronously on the receiving side, and synchronization is performed. These two functions are to continue the loopback state if no condition occurs, and to cancel the loopback condition if synchronization occurs.

If such a function is installed and maintained, if an abnormality occurs in the transmission line, the R function will automatically operate to form a loopback that automatically avoids the abnormality, and the abnormality will be prevented. When the system returns to normal, the loopback is automatically released and the normal loop is restored.

[Example] The present invention will be sequentially described below with reference to the drawings of the embodiment.

Figure 1 shows 1. Node station 1, 2, 3, 4°5.
6 is a schematic explanatory diagram of a loop network according to the present invention in which the main loop 7 and the slave loop 8 are connected in a loop.

Unlike the conventional example shown in FIG. 6, the loop network according to the present invention does not include a management station. Each of the node stations 1 to 6 is provided with the following two functions.

Now, such a typical node station N is shown in FIG. With respect to the transmission direction of the main loop 7 and the slave loop 8, one end of the node station N is P#i and the other end is the Q end. Here, node station N
If the received signal from the P side is disconnected, the P
It has a first function of stopping signal transmission from the end and putting the C[ side in a loopback state. On the other hand, if the received signal on the Q end side is interrupted, the P end side is put into a loopback state, and a burst signal is sent out intermittently from the Q end, and the intermittent signal is returned in a synchronous state. It has a second function that determines whether or not a synchronization occurs, continues the loopback state if no synchronization occurs, and cancels the loopback state and returns to the normal loop if synchronization occurs.

FIG. 7 is a block diagram showing a specific circuit configuration for causing the node station N to perform the above two functions. That is, in FIG. 7, 20.22 is an optical transmitter, 21.23 is an optical receiver, 24 to 26 are signal detection circuits, 27 to 29 are signal selection circuits, 30 is a regeneration circuit, 31 is a timer, and 32 is a 33 is a data transmitting circuit, 34 is a data receiving circuit, 35.37 is an optical signal output, 36.38 is an optical signal input, and 39 is an optical transmission prohibition signal.

Next, each node station 1, 2゜3.4
．． In the loop network according to the present invention shown in FIG. The loopback control related to this will be specifically explained.

The station 4 detects that the reception signal of the main system 7 is disconnected, and forms a loopback 4b according to the first function, while prohibiting the transmission of the slave system signal to the station 5. On the other hand, in station 5, when the slave signal from station 4 is disconnected, the second function is activated to form a loopback 5a,
At the same time, the burst signal 51 is sent to the station 4, and it is determined whether the synchronization signal 41 is returned via the circuit 4a of the station 4. In this case, effective transmission codes for the burst optical signal are codes with a mark rate of 50% such as DMI or CMI, or codes with a mark rate of 10 to 9 such as PWM.
A sign of 0% is appropriate, and the circuit can immediately determine the presence or absence of an optically received signal.

In FIG. 3, (a) shows the transmitted signal of the burst signal 51 at the station 5, and (b) shows the received signal 41.
It is a time chart showing.

In FIG. 3, Tl is the period during which the transmission line disconnection occurs, and the burst signal 51 is transmitted at time 11T4, but the received signal 41 is not obtained. T2 is the period immediately after the transmission line failure has been recovered. period, here burst signal 5
A synchronous reception signal 41 corresponding to 1 is obtained. As a result, the reception of the synchronization signal 41 is confirmed for a predetermined period of time, and the circuit determines that the fault in the transmission path has been recovered, and the station 5 releases the loopback state at time T5, and for a period of time T3. enter the state of

In station 4, the loopback state is released at time Ta, which is slightly later than time T5. In this case, the delay time until the time Ttx at which station 4 determines the reception of the main signal that started being transmitted from station 5 at time T5 and releases the loopback is set to be longer than the time width T4 of the burst signal. is appropriate. If such a setting is made, there is no risk of erroneously canceling the loopback during the synchronization determination period Tz.

As described above, according to the loop network according to the present invention, in the event of a transmission line disconnection, the functions provided in each node station automatically operate, and the adjacent station where the transmission line disconnection occurs automatically operates. A loopback is formed, and when the transmission path is restored, the loopback is automatically canceled and the normal transmission path is restored. Moreover, such operations do not require control by a management station, and are realized only by hardware, and the complicated trial and error required to find the point of failure in the conventional example is not necessary, so the loopback can be completed quickly. , system reliability can be greatly improved.

Note that FIG. 4 shows a case where a disconnection occurs in the main system loop in the loop network according to the present invention, and station 4 that detects the main system disconnection stops transmitting to the slave system and forms a loopback 4b. When the slave system is stopped, the station 5 forms a loopback 5a and transmits a burst signal 51, as described below.

FIG. 5 shows a case where a disconnection occurs in the slave system loose signal, and the station 5 detects the slave system signal disconnection and forms a loopback 5a, while sending out a burst signal 51. Upon receiving the burst signal 51, the station 4 detects the disconnection of the main system signal, forms a loopback 4b, and begins the operation described above.

In this way, even if a transmission line disconnection occurs in either the main or slave system,
There is no difference in loopback formation operation.

[Effects of the Invention] As described above, according to the loopback control method according to the present invention, the following excellent effects can be achieved.

(1) The fault point detection algorithm is extremely simplified,
A management control station that monitors and controls the entire loop becomes unnecessary.

(2) When a failure occurs, the time required to create a bus that detours around the failure point is greatly shortened, making it possible to significantly improve system reliability.

(3) Since the configuration of each data input/output station is simplified, costs are reduced and reliability is improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the case where a failure occurs in the transmission line of the loop network according to the present invention, FIG. 2 is an explanatory diagram of the end of the node station, and FIG. 3 is a time chart before and after the failure is recovered. 4 and 5 are explanatory diagrams showing the case where a failure occurs in either one of the transmission paths, FIG. 6 is an explanatory diagram showing the case where a transmission path failure occurs in a conventional loop network, and FIG. FIG. 2 is a block diagram showing an example of a circuit configuration of such a node station. 1 to 6: Node station, 4b, 5a: Loopback, 7: Main loop, 8: Slave loop. Agent Patent Attorney Fujio Sato No. I Figure 3 Figure 4 b

Claims (1)

[Claims] (1) In a loop network in which each node station is connected by a loop transmission method with duplex transmission paths, each node station has a signal from one end when the received signal from that end is interrupted. The first function is to stop signal transmission from the other end and place the other end in a loopback state, and when the received signal from the other end is cut off, the other end is put in a loopback state and the received signal is cut off. An intermittent signal is sent from the end that has become synchronized, and it is determined whether or not the intermittent signal appears in synchronization on the receiving side.If synchronization does not occur, the loopback state is continued and synchronization is detected. A loopback control method for a loop network that controls loopback by providing a second function for canceling the loopback state when the loopback occurs.