JPH08163163A - Isolation detection for terminal interface part and loop network system - Google Patents

Abstract

PURPOSE: To prevent communication of erroneous data from being performed between terminals by automatically detecting the isolation of a terminal interface part when the terminals connected to transmission stations parted in different loops by loop back communicate with each other when the looping back is performed by a test, etc., in the normal state of the transmission line of a loop network. CONSTITUTION: The transmission station receiving a loop back command from a control station by a carrier detecting part 21 from the transmission line on one side when a normal operation is being performed performs the loop back of the command from a logic part 22 to the transmission line on the other side. Simultaneously, a pseudo fault signal is transmitted from a fault generating part 24 to a downstream transmission station on the transmission line on one side via a selector 23, and the downstream transmission station recognizes that it is out of a closed loop by receiving the pseudo fault signal, and executes fault processing by detecting the isolation of the terminal interface part of its own station.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting an isolation of a terminal interface unit accommodated in a transmission station that has deviated from a closed loop due to a loopback in a loop network applied to a LAN (local area network) or the like. Is.

[0002]

2. Description of the Related Art In a loop network, as shown in FIG. 10, one control station 101 and a plurality of transmission stations (terminals 1
(Communication control device housing 2, 13, 14, 15, 16)
Data is exchanged between a plurality of terminals or computers distributed by arranging frames on the transmission lines by looping the transmission lines 102 to 106 by the internal and external dual transmission lines 10 and 11.

In such a network, FIG.
When a loopback is performed between the transmission stations 102 and 106 as shown in FIG. 2, the control station 101, the closed loop of the transmission stations 102 and 106, and the transmission stations 103, 104 and 105 are divided into two. If communication is performed between 102 and 103, a state in which communication cannot be performed (a terminal interface unit is isolated) occurs.

In the above loop network, for example, in Japanese Patent Laid-Open No. 5-37540, FIG.
The configuration of the transmission station is as shown in (a) and (b). All the transmission stations are composed of a carrier detection unit 21 and a theoretical unit 22. FIG. 12 (a) shows the state of the transmission station in the normal state, and FIG. 12 (b) shows the state of the transmission station at the time of loopback. ing. Note that in FIG. 12, the carrier detection unit 2 is provided only for one of the transmission lines to simplify the description.
1 and the theoretical section 22 are shown, the carrier detection section and the theoretical section are similarly provided on the other transmission line side.

Next, the operation will be described. As shown in FIG. 11, control stations 101 and 104 and transmission stations 102 and 103,
In a loop network in which 105 and 106 are connected in a loop by internal and external transmission lines 10 and 11,
When a failure occurs in each of the transmission paths between the transmission stations 102 and 103 and 105 and 106, the carrier detection section 21 shown in FIG. 12A detects the failure in the transmission path and notifies the theory section 22 of the failure. Then, from the state of FIG.
In the state shown in (b), the loopback is performed by returning the frame to the transmission path on the other side.

Before a failure occurs, the transmission stations 102, 1
Nos. 03, 105, and 106 were in the state shown in FIG. 12A, but the respective transmission stations 102, 103, 105, and 106
As shown in FIG. 12 (b), by putting the local station in a loopback state, two separated closed loops are formed as shown in FIG. After that, each transmission station (including the control station) 101, 102, 106 of the first closed loop checks whether or not the same terminal interface as the terminal interface existing in the own station exists in the first closed loop.

In this case, each transmission station 101, 102, 10
6 knows from the table showing the state of the loop that the same terminal interface as the terminal interface existing in the first closed loop does not exist in the same closed loop. That is, each of the control stations 101 and 104 has an information table indicating what kind of terminal interface each transmission station accommodates, knows that there is a terminal interface in the closed loop of itself, which has no other party, and Notify the terminal interface unit of no isolation. On the other hand, each transmission station (including control station) 103, 10 of the second closed loop
4, 105 also perform similar processing.

[0008]

In the configuration of the conventional transmission station, the isolation of the terminal interface is detected when a failure occurs in the transmission line and loopback is performed.
When performing loopback for a test or the like in the normal state instead of the fault state, there is a problem that the terminal interface unit in the transmission station does not perform isolation detection.

The present invention has been made in order to solve the above-mentioned problems, and transmission is performed not only when a failure occurs in the transmission line but also when loopback is performed in a normal state in a test or the like. It is an object of the present invention to provide a method for detecting isolation of a terminal interface unit in a station.

[0010]

[Means for Solving the Problems]

(1) A terminal interface isolation detection method according to the present invention loops one control station having a loop control function and a plurality of transmission stations having terminals by a dual transmission path having different transmission directions. In a network connected in a loop, when a closed loop is formed by a transmission station including the control station by looping back the predetermined transmission station according to a command from the control station, the predetermined loopback transmission station is A signal corresponding to loopback execution is transmitted to a transmission station that is out of the closed loop, and the transmission station that receives the transmitted signal recognizes that it is isolated from the loop and detects the isolation of its own terminal interface unit. It is something that is done.

(2) Further, the transmission station is provided with a fault generating section for generating a pseudo fault signal as a signal corresponding to loopback execution, and the loopback transmission station causes a pseudo fault from the fault generating section to the downstream transmission station. The transmitting station that transmits the signal and receives this pseudo fault signal recognizes that it is isolated from the loop, detects the isolation of the terminal interface section of its own station, and causes the isolated terminal to perform predetermined fault processing. It is the one.

(3) Further, the transmission station is provided with a signal generation unit for generating a control frame as a signal corresponding to the loopback execution, and the transmission station that has looped back uses the above-mentioned signal generation unit instead of the normal frame. The control frame is transmitted to the downstream transmission station, and the transmission station that receives this control frame recognizes that it is isolated from the loop, detects the isolation of the terminal interface section of its own station, and this isolated terminal performs a predetermined process. Is to do.

(4) Further, there is a network in which one control station having a loop control function and a plurality of transmission stations having terminals are connected in a loop by dual transmission lines having different transmission directions. Then, when a predetermined transmission station is looped back by a command from the control station and a closed loop is formed by the transmission stations including the control station, the control station displays a loop configuration at normal time built in itself. Determine the out-of-loop transmission station out of the loop by referring to the configuration table,
A signal corresponding to the determination result is transmitted to the transmission station outside the loop, and the transmission station receiving the transmitted signal recognizes that it is isolated from the loop and detects the isolation of the terminal interface section of the own station. It is the one.

(5) In addition, there is a network in which one control station having a loop control function and a plurality of transmission stations having terminals are connected in a loop by dual transmission lines having different transmission directions. Then, an identification code for identifying normality / abnormality of the transmission line is added to the transmission signal between the terminal interface parts to exchange the signal, and a loopback is performed to a predetermined transmission station according to a command from the control station to control the control station. When a closed loop is formed in the transmission station including the above, if the above-mentioned two terminal interface units for transmitting and receiving the transmission signal are in the closed loop and outside the closed loop, the terminal interface unit outside the closed loop should detect an abnormality in the transmission and reception of the transmission signal. Is used to detect isolation.

(6) In a network in which one control station having a loop control function and a plurality of transmission stations having terminals are connected in a loop by dual transmission lines having different transmission directions, When a predetermined transmission station is looped back by a command from the control station and a closed loop is formed by the transmission stations including the control station, the control station displays the communication state immediately before the loopback built in itself By referring to the display table, the out-of-loop transmission station that is out of the loop is determined, the signal corresponding to the determination result is transmitted to the above-mentioned out-loop transmission station, and the transmission station that receives this transmitted signal is isolated from the loop. By recognizing this, the isolation of the terminal interface section of the own station is detected.

(7) Further, when a failure occurs in the transmission line,
The transmission station that detects the lack of a transmission signal loops back itself and notifies the downstream transmission station that it is isolated.

(8) The loop network system according to the present invention uses the isolation detecting method for the terminal interface section according to any one of (1) to (7).

[0018]

[Action]

(1) In the terminal interface isolation detection method of the present invention, when a predetermined transmission station is looped back by a command from the control station to form a closed loop in the transmission stations including the control station, the predetermined loopback is performed. The transmitting station transmits a signal corresponding to the loopback execution to the transmitting station that is out of the closed loop, and the transmitting station that receives the transmitted signal recognizes that it is isolated from the loop and Detect isolation.

(2) Further, the transmission station that loops back is
A pseudo fault signal is transmitted from the fault occurrence section to the downstream transmission station, and the transmission station that receives this pseudo fault signal recognizes that it is isolated from the loop, detects the isolation of the terminal interface section of its own station, and The terminal that has performed the above-mentioned processing is to perform a predetermined failure process.

(3) Also, the transmission station that loops back is
Instead of a normal frame, the control frame is transmitted from the signal generation unit to the downstream transmission station, and the transmission station receiving this signal recognizes that it is isolated from the loop and detects the isolation of the terminal interface unit of its own station. , The isolated terminal performs a predetermined process.

(4) Further, when a predetermined transmission station is looped back by a command from the control station to form a closed loop in the transmission stations including the control station, the control station has a normal loop built in itself. By referring to the loop configuration table that displays the configuration, determine the out-of-loop transmission station that has deviated from the loop, transmit the signal corresponding to the determination result to the above-mentioned out-loop transmission station, and receive the transmitted signal. The station recognizes that it is isolated from the loop and detects the isolation of the terminal interface section of the station.

(5) Also, an identification code for identifying normal / abnormal of the transmission path is added to the transmission signal between the terminal interface parts to exchange the signal, and a predetermined transmission station is looped back by a command from the control station. Then, when a closed loop is formed in the transmission station including the control station, when the two terminal interface units for transmitting and receiving the transmission signal are in the closed loop and outside the closed loop, the terminal interface unit outside the closed loop transmits and receives the transmission signal. Isolation is detected by detecting an abnormality.

(6) Further, when a predetermined transmission station is looped back by a command from the control station and a closed loop is formed by the transmission stations including the control station, the control station immediately before the loopback built in itself is formed. By referring to the communication status display table that displays the communication status, determine the out-of-loop transmission station that is out of the loop, transmit the signal corresponding to the determination result to the above-mentioned out-loop transmission station, and receive this transmitted signal. The transmitting station recognizes that it is isolated from the loop and detects the isolation of the terminal interface section of its own station.

(7) Also, when a failure occurs in the transmission line,
The transmission station, which has detected the lack of the transmission signal, loops back itself and notifies the downstream transmission station that it is isolated.

(8) The loop network system according to the present invention uses the isolation detecting method for the terminal interface section according to any one of (1) to (7) above.

[0026]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. Figure 1 shows the system configuration of the loop network.
One control station 1 and a plurality of transmission stations 2 to 6 that connect the terminals 12 to 16 are connected in a loop by the internal and external duplex transmission lines 10 and 11, and a frame is circulated on the transmission lines to connect the terminals. Communicating.

FIG. 2 shows the configuration of the transmission station of the embodiment. The transmission station includes a carrier detection unit 21 that detects a failure in the transmission path, a theory unit 22 that performs device management and data transmission / reception, a failure occurrence unit 24 that artificially causes a failure in the transmission path, and a normal frame and a pseudo failure signal. 2A shows the state of the transmission station in the normal state, and FIG. 2B shows the state of the transmission station in the loopback. Note that in FIG. 2, the carrier detection unit 2 is provided only for one of the transmission lines to simplify the description.
1, the theoretical unit 22, the selector 23, and the failure occurrence unit 24 are shown, but the respective units are similarly mounted on the other transmission path side.

The operation will be described below. In the loop type network configuration of FIG. 1, the operation will be described by taking as an example the case where a loopback is performed between the transmission stations 2 and 6 while the terminals 12 and 13 and 15 and 16 are communicating with each other. . The frame generated by the control station 1 reaches the transmission station 2 through the transmission line 10. At the transmission station 2, the frame is looped back and looped back to the transmission path 11, and at the same time, transmitted to the downstream transmission stations 3, 4 and 5 through the transmission path 10. Similarly, the frame from the control station 1 reaches the transmission station 6 through the transmission line 11. At the transmission station 6, the frame is looped back and returned to the transmission path 10, and at the same time, passes through the transmission path 11 and the transmission stations 5, 4 and 4, which are downstream stations.
It is also transmitted to 3.

Transmission stations 2 and 6 executing loopback
Has a configuration as shown in FIG.
In No. 2, the transmission path on the opposite side is looped back, and instead of controlling the selector 23 to send a normal frame to the transmission path, a failure occurs due to a signal stop generated by the failure generation unit 24 or generation of an erroneous frame. Communicate the status to the downstream station.

The downstream transmission stations 3, 4, and 5 have the configuration shown in FIG. 2A, and the carrier detection unit 21 in the transmission station detects a failure in both the transmission lines 10 and 11. By detecting the failure on both transmission lines in this way, the transmission stations 3, 4, and 5 know that they have been disconnected from the closed loop, and judge that the terminal interface unit accommodated in the transmission station is isolated. The terminal interface units of the transmission stations 3, 4 and 5 isolated by the above process perform a predetermined failure process. In this way, communication due to incorrect data between terminals can be prevented.

Note that the failure processing is processing for notifying the terminal that the data is not valid.
In the case of RC-232C, set RD to all "1",
Turn off the CD and notify the terminal. When viewed from the terminal,
Since it is unclear whether the data from the network is correct or not, if the communication with the partner terminal is not possible (whether it is a failure or a test), failure processing is performed.

When an actual failure occurs in the transmission path, the carrier detecting section 21 of each transmission station detects this failure and recognizes that it is isolated. The same operation is performed when a failure occurs in the following embodiments. Further, this operation is the same as that described in the conventional technique.

Example 2. Embodiment 2 of the present invention will be described below with reference to the drawings. FIG. 1 shows a system configuration of a loop type network, in which one control station 1 and a plurality of transmission stations 2 to 6 for connecting terminals 12 to 16 are internal and external duplex transmission lines 10 and 11.
Are connected in a loop, and a frame is circulated on the transmission path to perform communication between terminals. This is the same as in the first embodiment.

FIG. 3 shows the configuration of the transmission station of the embodiment. The transmission station includes a carrier detection unit 21 that detects a failure in a transmission path, a logic unit 22 that performs device management and data transmission / reception, a signal generation unit 25 that generates a control frame or a dedicated command, and a control frame that is generated by the signal generation unit. The signal detection unit 26 detects a dedicated command and the like, and a selector 23 that selectively outputs a normal frame and a control frame or a dedicated command and the like to a transmission path.

FIG. 3A shows the state of the transmission station in the normal state, and FIG. 3B shows the state of the transmission station at the time of loopback. Note that FIG. 3 shows the carrier detection unit 21, the logic unit 22, the selector 23, the signal generation unit 25, and the signal detection unit 26 for only one transmission path for simplification of description, but the other transmission path side. Similarly, each part is mounted.

The operation will be described below. In the loop type network configuration of FIG. 1, terminals 12, 13, 15
In the state of the opposite communication between the transmission stations 2 and 6
The operation will be described by taking the case where the loopback is performed in the example. The frame generated by the control station 1 reaches the transmission station 2 through the transmission line 10. At the transmission station 2, the frame is looped back and returned to the transmission line 11, and at the same time,
It is also transmitted to the transmission stations 3, 4 and 5 which are the downstream stations through the transmission line 10. Similarly, the frame from the control station 1 reaches the transmission station 6 through the transmission line 11. At the transmission station 6, the frame is looped back and returned to the transmission path 10, and at the same time, the frame passes through the transmission path 11 and is a downstream station.
It is also transmitted to 4, 3. This operation is similar to that of the first embodiment.

Transmission stations 2 and 6 executing loopback
Has a configuration as shown in FIG.
2 indicates that the transmission station generated by the signal generation unit 25 is in a loopback state, instead of performing loopback to the transmission path on the opposite side and controlling the selector 23 to send a normal frame to the transmission path. It transmits a control frame or a dedicated command to the downstream station.

The downstream transmissions 3, 4, and 5 have the configuration shown in FIG. 3A, and the signal detection unit 26 in the transmission station is provided.
At 1, it is detected that a transmission station in a loopback state on both the transmission lines 10 and 11 exists in the upstream station. In this way, by detecting a control frame or a dedicated command indicating the existence of a loopback transmission station on both transmission paths, the transmission stations 3, 4 and 5 know that they have been disconnected from the closed loop, and It is determined that the accommodated terminal interface unit is isolated, and thus the isolated transmission stations 3, 4,
Each terminal interface unit 5 performs a predetermined fault process.

The control frame of this embodiment is more complex in its generation method than the pseudo fault signal of the first embodiment because it generates a frame, but various information other than the signal notifying the isolation of the terminal interface unit is also present. There is a merit that it can be transmitted to the downstream station. In order to generate a frame, it is necessary to output a signal of a predetermined bit in a period of a fixed period, so a circuit such as a time management or a counter is required, which complicates frame generation.

In comparison with this, the pseudo-fault signal of the first embodiment can be easily generated, for example, by fixing the data for the downstream station to all "1" or all "0".
Further, when the optical transmitter is used, there is an advantage that it can be generated only by stopping the clock input to the optical transmitter or by inputting a meaningful signal to the optical output stop terminal provided in the optical transmitter. However, the downstream station cannot distinguish between a true failure and a pseudo failure intentionally generated. Since the signal generated in the control frame is a dedicated command, there is no difference between the two.

Example 3. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a system configuration of a loop type network, in which one control station 1 and a plurality of transmission stations 2 to 6 for connecting terminals 12 to 16 are internal and external duplex transmission lines 10 and 11.
Are connected in a loop, and a frame is circulated on the transmission path to perform communication between terminals. This is the same as in the first embodiment.

The configuration of the transmission station is the same as that of the prior art configuration. As shown in FIG. 12, the transmission station includes a carrier detection unit 21 for detecting a failure of a transmission line and a theory unit 22 for device management and data transmission / reception. 12A shows the state of the transmission station in the normal state, and FIG. 12B shows the state in the transmission station at the time of loopback.

The structure of the control station is shown in FIG. The loopback command unit 30 generates a command signal for looping back a predetermined transmission station when performing a test or the like.
The loop configuration table 31 is a table showing a loop configuration in a normal state, and the contents thereof are, as shown in FIG. 3 shows the connection order of the transmission stations to which the frame is transmitted. Out-of-loop transmission station determination unit 32
Obtains information on the loopback transmission station from the loopback command unit 30 and refers to the loop configuration content of the loop configuration table 31 to determine the transmission station outside the loop.

The operation will be described below. In the loop type network configuration of FIG. 1, terminals 12, 13, 15
In the state of the opposite communication between the transmission stations 2 and 6
The operation will be described by taking the case where the loopback is performed in the example. The frame generated by the control station 1 reaches the transmission station 2 through the transmission line 10. At the transmission station 2, the frame is looped back and returned to the transmission line 11, and at the same time,
It is also transmitted to the transmission stations 3, 4 and 5 which are the downstream stations through the transmission line 10. Similarly, the frame from the control station 1 reaches the transmission station 6 through the transmission line 11. At the transmission station 6, the frame is looped back and returned to the transmission path 10, and at the same time, the frame passes through the transmission path 11 and is a downstream station.
It is also transmitted to 4, 3.

The operation of the control station 1 will be described in detail with reference to FIG. 4 and FIG. 5. In the control station 1, the transmission stations 2 and 6 which execute loopback are instructed by the loopback instruction section to transmit the transmission stations 2 and 6.
Execute a loopback of. On the other hand, the out-loop transmission station determination unit refers to the information obtained by looping back the transmission stations 2 and 6 from the loopback command unit and the loop configuration table 31 as shown in FIG. 5, and controls the transmission lines 10 and 11. Station 1
It is confirmed that the transmission station 2 is looping back from the control station 1 and the control station 1 is looping back from the transmission station 6.

From the result, in the control station 1, the transmission stations outside the closed loop of the control station 1, the transmission stations 2 and 6 are the transmission stations 3 and 3.
4, 5 and determines that the transmission line 10 is transmitted to the transmission stations 3, 4, and 5.
Or use 11 to signal that it is out of the closed loop. The transmission stations 3, 4, and 5 know that they are disconnected from the closed loop, and judge that the terminal interface unit accommodated in the transmission station is isolated, and thereby the isolated terminal interface units of the transmission stations 3, 4, and 5 are isolated. Then, the predetermined failure processing is performed.

Example 4. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a system configuration of a loop type network, in which one control station 1 and a plurality of transmission stations 2 to 6 for connecting terminals 12 to 16 are internal and external duplex transmission lines 10 and 11.
Are connected in a loop, and a frame is circulated on the transmission path to perform communication between terminals.

The configuration of the transmission station is the same as that of the prior art configuration. As shown in FIG. 12, the transmission station includes a carrier detection unit 21 for detecting a failure of a transmission line and a theory unit 22 for device management and data transmission / reception. 12A shows the state of the transmission station in the normal state, and FIG. 12B shows the state in the transmission station at the time of loopback.

In this embodiment, when communicating between terminals, the transmitting station transmits the identification code in addition to the data necessary for communication as shown in FIG. 6 (a). The identification code is shown in Figure (b).
As shown in, it is assigned to each opposite terminal,
When normal, one terminal is assigned "1", the other terminal is assigned "2", and when an abnormality is detected, one terminal is assigned "3" and the other is assigned "4". The identification code is an example, and for example, the identification code at the time of abnormality may be the identification code cracked in the partner terminal at the time of normality.

The operation will be described below. In the loop type network configuration of FIG. 1, terminals 12, 13, 15
In the state of the opposite communication between the transmission stations 2 and 6
The operation will be described by taking the case where the loopback is performed as an example. The frame generated by the control station 1 is transmitted by the transmission line 10
To reach the transmission station 2. The frame at the transmission station 2 is
At the same time as being looped back and returned to the transmission path 11, the transmission station 3, 4, 5 which is a downstream station passes through the transmission path 10.
Can also be told. Similarly, the frame from control station 1
The transmission station 6 is reached via the transmission line 11. At the transmission station 6, the frame is looped back and returned to the transmission line 10, and at the same time, transmitted to the downstream transmission stations 5, 4, and 3 through the transmission line 11.

Here, the loop is separated by the loopback, and the terminals 12 and 13 in which the terminal interface section is isolated.
The case will be described. Transmission stations 2 and 3 are terminals 12 and 1
Data from No. 3 is transmitted in every frame in a format as shown in FIG. 6 (a) with an identification code as shown in FIG. 6 (b). Figure 7 shows the data transfer sequence
Shown in

First, when not looping back, the terminals 12 and 13 can communicate with each other. The transmission station 2 to which the terminal 12 is connected sends the data with the identification code "1" indicating the normal state to the transmission station 3 to which the terminal 13 is connected, and the transmission station 3 identifies the identification code "1".
It is recognized that the transmission station 2 including the terminal 12 is normal by receiving the. On the other hand, even the transmission station 3 to which the terminal 13 is connected sends the data with the identification code "2" indicating the normal state to the transmission station 2 to which the terminal 12 is connected. By receiving the identification code "2", the transmission station 2 recognizes that the transmission station 3 including the terminal 13 is normal.

Next, in the case of looping back, as shown in FIG.
The data from the terminal 12 is transmitted to the terminal 13 via the transmission station 2, the transmission line 10, and the transmission station 3 as shown in FIG.
The data from 3 is connected to the transmission station 2 because the transmission station 6 loops back when the transmission line 10 is used and the transmission station 2 loops back even when the transmission line 11 is used. It does not reach the terminal 12. Therefore, the transmission station 3 which has received the identification code "1" indicating the normal state from the transmission station 2 to which the terminal 12 is connected transmits the data with the identification code "2" indicating the normal state to the terminal 12 connected. Although it is sent to the transmitting station 2 which is present, it is not transmitted to the transmitting station 2 because it is looped back.

The transmission station 2 detects that the transmission station 3 including the terminal 13 is abnormal and attaches an identification code "3" indicating that the abnormality is detected to the terminal 13 via the transmission line 10.
The transmission station to which is connected sends to 3. The transmission station 3 detects the abnormality by receiving the identification code "3" and determines that the terminal interface unit accommodated in the transmission station is isolated, and thereby each terminal interface unit in the transmission station performs failure processing. .

Example 5. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a system configuration of a loop type network, in which one control station 1 and a plurality of transmission stations 2 to 6 for connecting terminals 12 to 16 are internal and external duplex transmission lines 10 and 11.
Are connected in a loop, and a frame is circulated on the transmission path to perform communication between terminals. This is the same as in the first embodiment.

The configuration of the transmission station is the same as that of the prior art configuration. As shown in FIG. 12, the transmission station includes a carrier detection unit 21 for detecting a failure of a transmission line and a theory unit 22 for device management and data transmission / reception. 12A shows the state of the transmission station in the normal state, and FIG. 12B shows the state in the transmission station at the time of loopback.

The structure of the control station is shown in FIG. The loopback command unit 30 generates a command signal for looping back a predetermined transmission station when performing a test or the like.
The communication status display table 41 is a table that displays the communication status immediately before the loopback.

The contents of the communication status display table 41 are shown in FIG. 9, and in the control station 1, what kind of terminal is accommodated in each transmission station, and which transmission station each terminal currently has. It indicates which terminal of the terminal is communicating with. In FIG. 9, "○" indicates the state of communication,
“X” indicates a state in which communication is not performed. In the illustrated example, the terminal 12 of the transmission station 2 and the terminal 13 of the transmission station 3 are in the communication state,
Further, the terminal 15 of the transmission station 5 and the terminal 16 of the transmission station 6 are in communication with each other.

The communication state judging section 42 obtains information on the looped back transmission station from the loopback command section 30 and refers to the communication state of the communication state display table 41,
Determine the transmission station outside the loop.

The operation will be described below. In the loop type network configuration of FIG. 1, terminals 12, 13, 15
In the state of the opposite communication between the transmission stations 2 and 6
The operation will be described by taking the case where the loopback is performed as an example.

The frame generated by the control station 1 reaches the transmission station 2 through the transmission line 10. At the transmission station 2, the frame is looped back and returned to the transmission line 11, and at the same time, the frame passes through the transmission line 10 and the transmission stations 3, 4, which are downstream stations.
It is also transmitted to 5. Similarly, the frame from the control station 1 reaches the transmission station 6 through the transmission line 11. Transmission station 6
At the same time, the frame is looped back and returned to the transmission line 10 and, at the same time, transmitted to the transmission stations 5, 4 and 3 which are downstream stations through the transmission line 11.

The operation of the control station 1 will be described with reference to FIGS. 8 and 9. In the control station 1, the loop stations of the transmission stations 2 and 6 are instructed by the loopback command section to instruct the transmission stations 2 and 6 that execute loopback. Execute back. On the other hand, the communication state determination unit includes information on looping back the transmission stations 2 and 6 from the loopback command unit, and the communication state display table 41 as shown in FIG.
It is confirmed that the control station 1 and the transmission station 2 are looping back and the control station 1 and the transmission station 6 are looping back on the transmission paths 10 and 11 with reference to.

From the result, in the control station 1, the transmission stations outside the closed loop of the control station 1, the transmission stations 2 and 6 are the transmission stations 3 and 3.
4, 5 and determines that the transmission line 10 is transmitted to the transmission stations 3, 4, and 5.
Or use 11 to signal that it is out of the closed loop. The transmission stations 3, 4, and 5 know that they are disconnected from the closed loop, and judge that the terminal interface unit accommodated in the transmission station is isolated, and thereby the isolated terminal interface units of the transmission stations 3, 4, and 5 are isolated. Then, the predetermined failure processing is performed.

Example 6. In each of the above-mentioned embodiments, the isolation of the terminal interface is detected both in the case of looping back even in the normal state as in the test and in the case of looping back due to an actual failure in the transmission path. Although the example in which the method is applied to the loop network system has been described, the method may be applied only to the case where the loopback is performed even in the normal state as in the test.

[0065]

As described above, according to the present invention, an isolated terminal interface unit is automatically detected when a loopback is performed by a test or the like in a normal state of the transmission line. This has the effect of preventing communication due to incorrect data.

[Brief description of drawings]

FIG. 1 is a system configuration diagram during loopback according to the present invention.

FIG. 2 is a configuration diagram of a transmission station according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram of a transmission station according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a main part of a control station according to a third embodiment of the present invention.

FIG. 5 is a diagram of a loop configuration table according to the third embodiment of the present invention.

FIG. 6 is a diagram showing the contents of an identification code in Example 4 of the present invention.

FIG. 7 is a diagram showing a data transfer sequence for explaining the operation of the fourth embodiment of the present invention.

FIG. 8 is a configuration diagram of a main part of a control station according to a fifth embodiment of the present invention.

FIG. 9 is a diagram showing a communication status display table according to the fifth embodiment of the present invention.

FIG. 10 is a configuration diagram of a conventional loop type network system.

FIG. 11 is a system configuration diagram in a case where a conventional loop type network system is in a loopback state.

FIG. 12 is a block diagram of a conventional transmission station.

[Explanation of symbols]

1 control station, 2 to 6 transmission stations, 10 and 11 transmission lines, 1
2 to 16 terminals, 21 carrier detection unit, 22 logic unit, 23 selector, 24 failure generation unit, 25 signal generation unit, 26 signal detection unit, 30 loopback execution command unit, 31 loop configuration table, 32 loop outside transmission station determination Section, 41 communication status display table, 42 communication status determination section, 101 control station, 102 to 103 transmission station.

Claims (8)

[Claims] 1. A network in which one control station having a loop control function and a plurality of transmission stations having terminals are connected in a loop by dual transmission lines having different transmission directions, When a transmission station including the control station forms a closed loop by looping back the predetermined transmission station according to a command from the control station, the predetermined loopback transmission station outputs a signal corresponding to loopback execution from the closed loop. A terminal interface characterized by transmitting to a deviating transmitting station and recognizing that the transmitting station receiving this transmitted signal is isolated from the loop, and detecting the isolation of the terminal interface section of the own station. Method for detecting part isolation. 2. The transmission station looped back according to claim 1, wherein the transmission station is provided with a fault generating unit that generates a pseudo fault signal as a signal corresponding to loopback execution.
The pseudo fault signal is transmitted from the fault generating unit to the downstream transmission station, and the transmission station which receives the pseudo fault signal recognizes that it is isolated from the loop and detects the isolation of the terminal interface section of its own station. A method for detecting isolation of a terminal interface unit, characterized in that an isolated terminal performs a predetermined failure process. 3. The transmission station according to claim 1, wherein the transmission station is provided with a signal generation unit that generates a control frame as a signal corresponding to loopback execution,
Instead of a normal frame, the control frame is transmitted from the signal generation unit to the downstream transmission station, and the transmission station that receives this control frame recognizes that it is isolated from the loop, and isolates its own terminal interface unit. As well as detect
A method for detecting isolation of a terminal interface unit, characterized in that the isolated terminal performs a predetermined process. 4. A network in which one control station having a loop control function and a plurality of transmission stations having terminals are connected in a loop by dual transmission lines having different transmission directions, When a predetermined transmission station is looped back by a command from the control station and a closed loop is formed by the transmission stations including the control station, the control station displays a loop configuration table that displays the normal loop configuration built in itself. Referring to, determine the loop outside transmission station out of the loop, and transmit the signal corresponding to the determination result to the above loop outside transmission station,
A transmission station that receives the transmitted signal recognizes that the transmission station is isolated from the loop, and detects the isolation of the terminal interface section of the local station. 5. A terminal in a network in which one control station having a loop control function and a plurality of transmission stations having terminals are connected in a loop by dual transmission lines having different transmission directions from each other, Transmission and reception of signals by adding an identification code for identifying normal / abnormal of the transmission line to the transmission signal between the interface parts, and looping back a predetermined transmission station according to a command from the control station to perform transmission including the control station. When a closed loop is formed in a station, if the above-mentioned two terminal interface units for transmitting / receiving a transmission signal are in a closed loop and outside the closed loop, the terminal interface unit outside the closed loop detects an abnormality in the transmission / reception of the transmission signal and thereby isolates itself. A method for detecting isolation of a terminal interface unit, which is characterized in that the detection is performed. 6. A network in which one control station having a loop control function and a plurality of transmission stations having terminals are connected in a loop by dual transmission lines having different transmission directions, When a predetermined transmission station is looped back by a command from the control station and a closed loop is formed by the transmission stations including the control station, the control station displays the communication state immediately before the loopback built in itself By referring to the table, the out-of-loop transmission station that is out of the loop is determined, the signal corresponding to the determination result is transmitted to the above-mentioned out-loop transmission station, and the transmission station that receives this transmitted signal is isolated from the loop. A method for detecting isolation of a terminal interface unit, which is characterized by detecting the fact that the terminal interface unit of the own station is isolated. 7. The method according to any one of claims 1 to 6,
When a failure occurs in the transmission line, the transmission station that detects the lack of the transmission signal loops back itself and notifies the downstream transmission station that it is isolated. Method for detecting part isolation. 8. A loop network system using the isolation detection method for a terminal interface unit according to claim 1. Description: