JPH11251977A - Transmission line fault detection system and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To monitor a fault in a transmission line without adding a signal line for monitoring the same. SOLUTION: A pulse generation circuit 2 generates pulse signals of a fixed cycle shorter than input signals inputted to the signal line. Then, the exclusive ORs of the input signals and the pulse signals are obtained in an EXOR circuit 3 and are transmitted through a signal line 1A. On a reception side, the transmitted signals are inputted to an integration circuit 4 and the input signals are restored. In a disconnection detection circuit 5, the rise or fall of the transmitted signals is detected, but if the rise or the fall is not detected for a prescribed time, a fault in a transmission line is judged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for detecting a fault in a transmission line, for example, a technique for detecting a break in a cable.

[0002]

2. Description of the Related Art Conventionally, disconnection monitoring of a cable has been performed by DC level monitoring using an unused wire. FIG.
FIG. 3 is a block diagram showing a conventional cable disconnection monitoring method. In this conventional example, as shown in FIG. 3, a cable disconnection monitoring line 31, an earth 32 set to a low level at a connection source, and
A reception buffer 33 for detecting a reception level and a pull-up unit 34 for performing a pull-up immediately before the reception buffer 33 are provided.

In the cable disconnection monitoring circuit configured as described above, when the cable is normally connected, a low level from the ground 32 of the connection source is detected, and when the cable is disconnected, the input becomes open. The high level is detected by the pull-up 34 on the receiving side. That is,
The receiving side performs level detection, and if the level is low, it is determined that the cable connection is normal, and if the level is high, the cable connection is disconnected.

[0004]

However, when the above-described cable disconnection monitoring circuit is used, the number of lines in the cable is fixed. There was a problem that a monitoring line could not be provided. Therefore, an object of the present invention is to provide a technique capable of monitoring a transmission line failure without adding a signal line for monitoring a transmission line failure.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a transmission path failure detection system for detecting a failure in a transmission path, comprising a pulse generating means for generating a pulse signal at a constant period, and an input signal input to a signal line. Pulse signal superimposing means for superimposing the pulse signal, and detecting means for detecting a pulse from the input signal on which the pulse signal is superimposed, and detecting a fault in the transmission path based on the state of the pulse. I do.

[0006] It is preferable that the transmission path failure detection system further includes extraction means for extracting only an input signal from the input signal on which the pulse signal is superimposed. Further, the pulse signal has a shorter period than the input signal. The present invention relates to a transmission path failure detection system for detecting a failure in a transmission path, wherein the pulse generation circuit generates a pulse signal having a period shorter than an input signal input to a signal line and a fixed period, An EXOR circuit that takes an exclusive OR of a signal and the pulse signal, an integration circuit that restores the input signal from an output signal of the EXOR circuit, and an output signal of the EXOR circuit, and a rising edge of this signal or A transmission path failure determination circuit that determines that the transmission path has failed if the fall is not detected within a predetermined time.

The present invention relates to a transmission line fault detecting method for detecting a fault in a transmission line, wherein an exclusive OR of an input signal input to a signal line and a pulse signal of a fixed period is obtained, and this signal is converted to a signal. Outputting the signal to the transmission line, receiving the signal from the signal line, detecting the rising or falling of the received signal, and transmitting the signal to the transmission path when the rising or falling of the received signal is not detected for a predetermined time. Determining that a failure has occurred.

It is preferable that the transmission path failure detection method further includes a step of removing a pulse component of the received signal and restoring an input signal.

[0009]

Embodiments of the present invention will be described.
In the present embodiment, a description will be given of a case where a cable is disconnected as a typical example of a failure in a transmission path. FIG. 1 is a block diagram of the present embodiment.

In FIG. 1, 1A to 1N are signal lines in a cable. 2 is a pulse signal generation circuit. The pulse signal generation circuit 2 generates a pulse signal having a constant cycle and a cycle shorter than a change cycle (not constant) of the DC output signal A input to the signal line 1A. 3 is an EXOR circuit. The EXOR circuit 3 generates an exclusive OR (EXO) of the pulse signal of the pulse signal generation circuit 2 and the DC output signal A.
R), and outputs this to the signal line 1A as a transmission signal.

An integration circuit 4 extracts (restores) the DC output signal A from the received input signal. D as described above
When the change cycle of the C output signal A is compared with the cycle of the pulse signal, the cycle of the pulse signal is shorter. Therefore, the integration circuit 4 smoothes the waveform by performing integration with a long time constant on the received signal, removes the pulse component by shaping the waveform through a buffer, and restores a signal equivalent to the DC output signal A. .

A disconnection detection circuit 5 detects a pulse from the received signal and detects a disconnection of the cable from the state of the pulse. The disconnection detection circuit 5 is configured by a mono-multi circuit (one-shot circuit). The mono-multi circuit is a type of edge detection circuit. When a signal containing a pulse is input to the mono-multi circuit, a high-level output is generated for a certain period of time by either rising or falling of the pulse, regardless of the pulse width. do. Therefore, when a pulse is input periodically, the mono-multi circuit continuously outputs a high level output. On the other hand, when there is no rising or falling input, the output changes from high level to low level after a certain period of time. Therefore, the disconnection detection circuit 5 determines that the cable is disconnected when the received signal does not include the pulse signal and becomes a fixed level due to the disconnection of the cable and the output of the mono-multi circuit changes to a low level. Note that the high-level time when a pulse is input is longer than the period of the pulse signal generated by the pulse signal generation circuit 2.

Next, the operation of this embodiment will be described. FIG. 2 is a timing chart for explaining the operation of the present embodiment. First, a DC output signal A shown in FIG.
The pulse signal shown in (B) is input to the EXOR circuit 3. The EXOR circuit 3 takes an exclusive OR of the DC output signal A and the pulse signal and outputs the output signal shown in (C) to the signal line 1A.

The signal shown in (D) is received on the receiving side, and the received signal is branched and input to the integrating circuit 4 and the disconnection detecting circuit 5. The integration circuit 4 smoothes the waveform by integrating the input signal with a long time constant, removes the pulse component by shaping the waveform through a buffer, and removes the DC output signal as shown in (E). Restore the same signal as A.

On the other hand, the mono-multi circuit of the disconnection detection circuit 5 outputs a high-level signal at the rise of the pulse of the input signal. At this time, the time of the signal output in response to the rising of the pulse is longer than the period of the pulse signal. Therefore, the signal output from the mono-multi circuit is
(F). Here, it is assumed that a cable break occurs at time T. Then, the signals input to the integration circuit 4 and the disconnection detection circuit 5 become signals of a constant level.

Therefore, the signal input to the mono-multi circuit of the disconnection detection circuit 5 does not include a pulse component, and after a predetermined time has elapsed, the signal output from the mono-multi circuit becomes a low level signal. This makes it possible to detect that the cable has been disconnected.

[0017]

As described above, according to the present invention, since a pulse signal serving as connection information is superimposed on a used signal line in a cable, it is not necessary to newly provide a signal line for determining connection. Therefore, there is an excellent effect that it is not necessary to change the number of core wires to a large number for monitoring, and that it is not necessary to change a connector (a large number of signals that can be handled) due to an increase in the number of signal lines.

[Brief description of the drawings]

FIG. 1 is a block diagram of the present embodiment.

FIG. 2 is a timing chart for explaining the operation of the present embodiment.

FIG. 3 is a block diagram of a conventional example.

[Explanation of symbols]

 1A to 1N signal line 2 pulse signal generation circuit 3 EXOR circuit 4 integration circuit 5 disconnection detection circuit

Claims (6)

[Claims] 1. A transmission line fault detection system for detecting a fault in a transmission line, comprising: a pulse generation means for generating a pulse signal at a constant period; and a pulse for superimposing the pulse signal on an input signal input to a signal line. A transmission path fault detection system comprising: signal superposition means; and detection means for detecting a pulse from the input signal on which the pulse signal is superimposed, and detecting a fault in the transmission path based on a state of the pulse. 2. The transmission path fault detection system according to claim 1, further comprising an extracting unit that extracts only an input signal from the input signal on which the pulse signal is superimposed. 3. The transmission line fault detection system according to claim 1, wherein the pulse signal has a shorter period than an input signal. 4. A transmission line failure detection system for detecting a failure in a transmission line, comprising: a pulse generation circuit that generates a pulse signal having a shorter period and a fixed period than an input signal input to a signal line; An EXOR circuit that takes an exclusive OR of an input signal and the pulse signal; an integration circuit that restores the input signal from an output signal of the EXOR circuit; and an output signal of the EXOR circuit, A transmission path failure detection system comprising: a transmission path failure determination circuit that determines a failure in the transmission path when a fall is not detected within a predetermined time. 5. A transmission line fault detection method for detecting a fault in a transmission line, comprising: obtaining an exclusive OR of an input signal input to a signal line and a pulse signal having a predetermined period; Outputting the signal, receiving the signal from the signal line, and detecting the rising or falling of the received signal.If the rising or falling of the received signal is not detected for a predetermined period of time, the transmission path has a fault. Determining that a transmission line has occurred. 6. The transmission path failure detection method according to claim 5, further comprising a step of removing a pulse component of the received signal and restoring an input signal.