JPS5912657A - Transmission line protecting system of multidrop type information transmission system - Google Patents

Abstract

PURPOSE:To improve the reliability of a system, by detecting a station failure including the failure of a line driver, and disconnecting the line driver output side of the failed station from a transmission line. CONSTITUTION:A switch 7A is turnd on normally and selected to the OFF position when a station failure including a failure of a line driver 42 is detected and the output side of the line driver 42 is disconnected from the transmission line 1. Then, a failure detecting signal of a transmission line data monitor circuit 11 is monitored and when an output failure of the driver 42 continues for a prescribed time, it is regarded as the failure of driver of the own station and the disconnecting state of the switch 7A is continued. When the output side of the driver 42 is restored to the normal state after the disconnection of the switch 7A, it is regarded as the failure of other stations, and the switch 7A is restored to the ON state. Thus, the failure occupying the transmission line due to the abnormality of the own station is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for maintaining a transmission line in the event of a failure in a multi-drop information transmission system.

Multi-drop information transmission is as shown in Figure 1.
One transmission line I is branched in the middle section, each branch point is connected to each station such as a computer 2 and a terminal device 3, and one transmission line I is shared between each station 7. versus N
Or exchange information on an N-to-M basis. The coupling circuit between each station and the transmission path I is as shown in the terminal device 3 (here, the line receiver V and the line driver 6 are used as transmission path connection ends, and the received data of the receiver q1 is sent to the data processing device 5. The transmitted data of the data processing device 5 is sent out from the driver h through the inhibit circuit 6.

The inhibit circuit 6 detects a failure in the data processing device 5, etc., or stops transmission (by blocking the transmission of data), when a station failure occurs (this eliminates the occupation of the transmission line I by continuing to send out transmission data from the failed station). It protects the transmission path and allows data exchange between other healthy stations.

This conventional transmission line protection method is based on line driver Hiroshi!
Transmission line I may become unable to transmit due to a failure.
This results in a system failure in which information cannot be transmitted between all stations except those with duplexed transmission lines.

The present invention has been made in view of the above-mentioned circumstances, and detects stay/stop/failure including line driver failure, and disconnects the line driver output side of the faulty station from the transmission path. It is an object of the present invention to provide a transmission line protection system that eliminates the occupation of the transmission line by station f and ensures healthy information transmission between other stations.

FIG. 2 shows one embodiment of the present invention, and is a block diagram of a transmission line protection device of a station. Received data from the transmission line I, which is made into a twisted pair or the like, is taken into the data processing device 5 by the line receiver 1, and data transmitted from the data processing device 5 to another station is transferred to the transmission line I through the line driver h. . The data processing device 5 monitors transmission paths for data, performs encoding/decoding, and serial/parallel conversion.

It is equipped with various transmission function means for transmitting and receiving data between stations, such as a transmitting/receiving buffer, transmission control, and device interface.

The output side of the line driver q is connected to the transmission path I via a switch 7A such as a relay contact, and the switch 7A is turned on and off by a switch operating circuit 7 such as a relay coil. Switch 7A is normally in the ON state, and any malfunction at the station including line driver ψ2 failure [
In response to this, the line driver Hiroshi is operated off! The output side of is disconnected from transmission line I. An on/off operation signal for the switch operation circuit 7 is given from a station separation control circuit 8.

The control circuit 8 includes a device failure detection circuit 9. The above-mentioned on/off operation signal is generated according to the outputs of the driver input monitoring circuit 10 and the transmission line data monitoring circuit 11.

The device failure detection circuit 9 monitors the operation of the data processing device 5. For example, if the data processing device is controlled by a microcomputer, a check by a watchdog timer may cause an error to occur in the device 5. When a fatal failure is detected, a detection signal is given to the station disconnection control circuit 8 to instruct disconnection of the two switches. Driver human power monitoring circuit 10 is driver q
, from the input of the driver LA! The time during which the output continues to be in the on state is monitored, and when it is detected that the on state continues for a predetermined time or more, a signal indicating driver manual power abnormality is given to the station disconnection control circuit 8. The transmission line data monitoring circuit 11 is
It monitors the data on transmission path I, and
One frame data or abnormal data (
When it is detected that the transmission line is in the always-on state (data that rubs) for a millimeter period or more, a transmission line abnormality signal is given to the stillage disconnection control circuit 8.

The station 7 disconnection control circuit 8 performs the determination process shown in the table below based on the combination of the transmission path abnormality signal from the transmission path data monitoring circuit 11 and the driver manual abnormality signal from the driver input monitoring circuit 10.

With this table in mind, in process (a), Kokichi, who has determined that there is an abnormality in his own station, gives an operation signal to the switch operation circuit 7 to turn off the switch 7A, and disconnects the output side of the driver 6 from the transmission line I. . Processing (b) means a failure at the input terminal of the driver, so it is the same as processing (a) that the driver l
The output side of , is disconnected from the transmission line 1. Since the process (c) means a failure on the output side of the driver including the transmission line, after disconnecting the output side of the driver ψ from the transmission line I, the driver <1. In other words, the abnormality detection signal of the transmission line data monitoring circuit 11 is monitored, and when the abnormality on the output side of driver q2 continues for a predetermined period of time even after switch 7A is disconnected, it is assumed that the driver of the own station is abnormal and switch 7A is activated.
If the output side of the driver I11 returns to normal after the switch 7A is cut, the switch 7A is returned to the on state without being considered as an abnormality in other stations.In this way, the station disconnection control circuit 8 automatically For various abnormalities including the station driver, switch 7A
Switch 7A is controlled to be off and disconnected from the transmission line including the driver, and in the event of an abnormality in another station, switch 7A is returned to on control to prevent an accident in which the transmission line is occupied due to an abnormality in the own station, and to disconnect the transmission line between other stations. data transmission possible.

As described above, according to the present invention, each station in a multi-drop information transmission system detects failures in its own station, including failures on the output side of the line driver, and disconnects the output side of the line driver from the transmission path. This has the effect of significantly improving the reliability of the system without causing a single failure to lead to an accident that occupies the transmission line, and without duplicating the transmission line.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional multi-drop information transmission system, and FIG. 2 is a block diagram of a station 7 showing an embodiment of the present invention. I...Transmission line, 2...Electronic computer, 3...Terminal device, 6...Line receiver, 6...Line line controller, 5...Data processing device, 2...・Switch operation circuit, 7A...Switch, 8...Station cutting control circuit, 9...Device failure detection circuit, 10...Dry nozzle human power monitoring circuit, 11...Transmission line data monitoring circuit, [2... Line 7-no (. Ward C9 沫

Claims (1)

[Claims] In a multi-drop information transmission 7 system in which each station is branch-connected to one transmission path, each station has a switch means between the transmission path (a line driver for carrying transmission data and the transmission path). A control means is provided for disconnecting and controlling the above-mentioned switch means when a malfunction of various equipment in the own station is detected, including a malfunction of the own station's line liner, to prevent a transmission line from being occupied due to a malfunction of the own station. A transmission line protection system for multi-drop information transmission/stem, which is characterized by: