JPH04142139A - Monitoring device - Google Patents

Abstract

PURPOSE:To enhance reliability for fault detection by providing first and second reception means which compare the differential amplitude of signals receiving from each signal transmission line with each threshold value and a logical operation means which performs the logical operation of comparison results from those reception means corresponding to a fetching result. CONSTITUTION:The same output can be obtained at the first and second reception means 11, 12 in an ordinary operation, however, the differential amplitude of input signals can be decreased when abnormality occurs, and no signal can be detected from the reception means with high threshold value, therefore, the output of the reception means goes to a different one from the one obtained from the reception means with low threshold value, and the detection of abnormality is performed by performing the logical operation of the output with the logical operation means 13. Thereby, since it is possible to detect the abnormality in real time by performing the logical operation of the output from the first and second reception means 11, 12, the reliability for the fault detection can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a monitoring device for monitoring failures in a balanced communication system using at least two signal transmission lines.

(Prior Art) Conventionally, a balanced communication system using this type of monitoring device is composed of two signal transmission lines and a plurality of nodes that are connected to the signal transmission lines and transmit and receive signals. , used for data transmission in automobiles. Each node is equipped with two receiving circuits (comparators, etc.) with different reception threshold levels so that even if one signal transmission line fails, communication can be performed using the other signal transmission line. One receiving circuit has the same low threshold level as a normal receiving circuit, and the other receiving circuit can receive normal reception against potential failures (for example, short circuits in signal transmission lines). The outputs of these duplexers were selectively received through a selection circuit to monitor failures in the signal transmission line.

In other words, under normal conditions, the monitoring device transmits and receives signals using the receiving circuit with the lower reception threshold level among the two receiving circuits provided in the communication circuit, and when a certain period of time or a certain condition is met. monitor for failures if
During monitoring, the receiving circuit with a higher reception threshold level is used to perform reception, and the potential failure is monitored.

(Problem to be Solved by the Invention) However, in the above-mentioned monitoring device, failure monitoring is performed only at a certain time interval or when a certain condition is met. However, there was a problem in that failures could not be detected instantaneously, and failure detection was unreliable.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a monitoring device that can instantly detect an abnormality when a failure occurs.

(Means for Solving the Problem) In order to achieve the above object, the present invention provides at least two
In a communication circuit in a balanced communication system that is connected to two signal transmission lines, and when one of the signal transmission lines suffers a communication failure, data is communicated via the other signal transmission line, each having different differential amplitude thresholds. first and second receiving means that compare the differential amplitudes of the signals received from the respective signal transmission lines with the respective threshold values set and the comparison results from the first and second receiving means are taken in; A monitoring device is provided that includes a logical operation means that performs a logical operation according to a result.

(Function) Normally, the outputs from the first and second receiving means are the same, but when an abnormality occurs, the differential amplitude of the input signal becomes smaller, and the receiving means with a higher threshold detects the signal. Therefore, the output is different from that from the receiving means with a low threshold value, and abnormality detection is performed by performing a logical operation on the output by the logical operation means.

Therefore, the monitoring device can detect abnormalities in real time by performing logical operations on the outputs from the first and second receiving means.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings of FIGS. 1 and 2.

FIG. 1 is a block diagram showing the configuration of a monitoring device according to the present invention. In the figure, a monitoring device 10 includes receiving circuits 11 and 12, which are composed of comparators, etc., connected to data buses A and B, which are signal transmission lines, and capacitors 01 to C4 for AC coupling, and the receiving circuit 11
．． Exclusive OR (hereinafter referred to as “E
It is called "XOR". ) circuit 13, a filter path 14 that takes in the output from the EXOR circuit 13, a communication control circuit 15 that takes in the output data from the reception circuit 11 and controls data transmission and reception, and a control circuit that controls the communication control circuit 15 ( CPU) 16.

The receiving circuit 11.12 subtracts the output level (amplitude peak voltage VAVB) of the signal input from the data bus AXB to obtain a differential amplitude, and further compares the result with a preset differential reception threshold level. Then, it is converted to a corresponding digital signal and output. The receiving circuit 11 is
The differential reception threshold level VSL is set low as shown by the dotted line in Figure 2(a) so that the signal can be received even if the differential amplitude of the signal is halved due to a failure in the communication system. There is. Furthermore, when there is no failure in the communication system and the differential amplitude is large, the receiving circuit 12 can detect the differential amplitude of the signal input from the data bus, but when a failure occurs and the differential amplitude of the signal is small, the receiving circuit 12 can detect the differential amplitude of the signal input from the data bus. In order to prevent the differential amplitude of the signal from being detected, the differential reception threshold level VSO is set higher than the differential reception threshold level VSL of the receiving circuit 11, as shown by the dashed line in FIG. 2(a). There is.

The EXOR circuit 13 performs logical operations based on digital signals input from the receiving circuits 11.12. For example, as shown in FIGS. 2(b) and 2(c), receiving circuits 11 and 1
When the digital signals 20 and 21 are both output from the EXOR circuit 20 and 21 at the "1" level, or when the digital signals 20 and 21 are both at the "0" level, the output signal from the EXOR circuit 13 is as shown in FIG. 2(d). As shown in FIG.
The output signal from the circuit 13 becomes "1" level.

The filter circuit 14 is composed of a bandpass filter or the like that passes signals in a predetermined frequency range (frequency range corresponding to the output signal from the EXOR circuit 13).

The communication control circuit 15 controls the receiving circuits 11, 12 and a transmitting circuit (not shown) to exchange signals with the data buses A and B.

The control circuit 16 controls the communication control circuit 15 to input and output data, and also takes in the output from the filter circuit 14 to monitor whether a failure has occurred in the data bus.

Next, the data bus monitoring operation of the monitoring device shown in FIG. 1 will be explained.

When the data buses A and B are in normal operation with no failure, the differential amplitudes of the signals input from the data buses A and B to the receiving circuit 11 and 12 are as shown in Fig. 2 (a). Since the amplitude of the waveform is the same, the receiving circuits 11 and 12 both detect the above waveform and output a digital signal 20 and 21 having an l'' level waveform as shown in FIGS. 2(b) and 2(c).EXO
When the R circuit 13 takes in the digital signal from the receiving circuit 11.12, it performs a logical operation according to the signal.

In this case, since both of the captured signals have waveforms at the 'l' level, the EXOR circuit 13 passes the '0' level signals to the control circuit through the filter circuit 14, as shown in FIG. 2(d). 16.The control circuit 16 outputs the above “O
``When the level signal is taken in, it is determined that there is no failure on the data bus and that it is normal.

In addition, in the case of an abnormal situation where a failure occurs in the data buses A and B, the differential amplitudes of the signals input from the data buses A and B to the receiving circuits 11 and 12 are shown in FIG. 2(a), respectively. Since the waveform amplitude at abnormal times is approximately half of the waveform amplitude at normal times, the receiving circuit 11 detects the above waveform,
A digital signal 22 with a "1" level waveform shown in FIG. 2(b) is output, but the receiving circuit 12 cannot detect the above waveform and outputs a "0" level signal shown in FIG. 2(C). do.

When the EXOR circuit 13 takes in the digital signal from the receiving circuit 11.12, it performs a logical operation according to the signal. In this case, since the captured signal has a waveform of "1" and "0" levels, the EXOR circuit 13
As shown in FIG.
A is connected to the control circuit 16 via the control circuit 16. When the control circuit 16 receives the above-mentioned "beam level" signal indicating the occurrence of a failure, it determines that a failure has occurred in the data bus and that an abnormality is occurring.

Therefore, in this embodiment, the signals inputted from both data buses are detected at different differential reception threshold levels, and the detected signals are subjected to a logical operation using an EXOR circuit, and the differential amplitude at the time of abnormality is reduced. Since a signal indicating abnormality detection is output only at certain times, the control circuit 16 can detect an abnormality in the data bus at the same time as a failure occurs in the data bus.

(Effects of the Invention) As explained above, in the present invention, connection is made with at least two signal transmission lines, and when one of the signal transmission lines has a communication failure, data communication is performed via the other signal transmission line. Different differential amplitude thresholds are set in communication circuits in balanced communication systems that perform
first and second receiving means that compare the differential amplitude of the signals received from each of the signal transmission lines with the respective thresholds; and receiving the comparison results from the first and second receiving means and responding to the results. Since the present invention is equipped with a logical calculation means for performing logical calculations, it is possible to instantly detect an abnormality when a failure occurs in the signal transmission line, thereby increasing the reliability of failure detection.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a monitoring device according to the present invention, and FIG. 2 is a waveform diagram showing signal waveforms at various parts of the monitoring device shown in FIG. 11.12...Reception circuit, 13...EXOR circuit,
14... Filter circuit, 15... Communication control circuit, 1
6...Control circuit, A, B...Signal transmission line (data bus).

Claims (2)

[Claims] (1) There are different differences between communication circuits in a balanced communication system that is connected to at least two signal transmission lines, and when one of the signal transmission lines becomes defective, data is communicated via the other signal transmission line. first and second receiving means, each of which has a dynamic amplitude threshold set, and which compares each threshold with the differential amplitude of the signal received from each of the signal transmission lines;
taking in the comparison results from the first and second receiving means;
A monitoring device comprising: logical operation means for performing a logical operation according to the result. (2) The monitoring device according to claim 1, wherein the logical operation means comprises an exclusive OR circuit.