JPH088979A - Digital transmission system - Google Patents

Abstract

PURPOSE:To enable monitoring of a transmission line by the presence or absence of the changed point of data in even nonframe data by transmitting the correlation result of original data and a clock to a transmission line. CONSTITUTION:In a transmitter 10, original data to be transmitted is transmitted to a transmission line 8 via an encoding means 12. At this time, an encoding means 12 performs an encoding destroying the continuity of '0' or the continuity of '1' in original data by using a clock signal synchronizing with transmitted data in the transmission line. In a receiver 20, a decoding is performed by a decoding means 21 and an original signal is obtained. As a transmission line monitoring device 22, the pulse generation means of a retriggerable operation is provided, and a trigger is performed by the transmission data from the transmission line 8. When prescribed time passes after the trigger, an output generation operation is performed and an abnormality detection output is generated. As a result, the monitoring of the transmission line by the presence or absence of the changed point of data becomes possible in even nonframe data, and the normal data delivery/reception from a transmission side to a reception side can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital transmission system for communicating digital signals, and more particularly, to a transmission line monitoring device for monitoring a transmission line so that it can carry out a monitoring operation without trouble even in non-frame data transmission. The present invention relates to a digital transmission system.

[0002]

2. Description of the Related Art In a conventional digital communication system, the presence or absence of data is monitored to monitor a transmission line. The presence / absence of data is monitored by monitoring the presence / absence of a change point of the frame bit on the receiving side when the transmitting side has added the frame bit to the data.

FIG. 12A shows an example of data with frame bits, in which a frame bit of "01" is added every period T. In this way, when the frame bit of the data is added, for example, the data is all zero (ALL ZERO) or all 1 (ALL ON).
Even in the case of E), the change point from "0" to "1" always appears every cycle T. Therefore, a circuit that can monitor the change point of data on the receiving device side, for example, a trigger oscillator that can freely change the pulse width such as a one-shot multivibrator (monostable multivibrator) is used, and the change point occurs. In that case, transmission line monitoring can be easily monitored by generating a pulse.

FIG. 12B shows a conventional configuration example using a one-shot multivibrator IC (integrated circuit).
FIG. 13 shows a timing chart showing the operation of FIG.

In FIG. 12 (b), 1 is a transmitter and 3 is a transmitter.
Is a transmission line, 4 is a receiving device, and 5 is a one-shot multivibrator IC. A conventional transmission line monitoring device in a digital transmission system is as shown in FIG.
A one-shot multivibrator IC (integrated circuit, for example, C-MOS type IC of model number HC4538) 5 is used for the input stage from the transmission line 3. The one-shot multivibrator IC 5 is connected to a circuit composed of a resistor R1 and a capacitor C1 as a time constant circuit, and a transmission line 3 is connected to a clock input terminal, and data transmitted through this transmission line 3 is used as a trigger. , Operates to generate a pulse.

One-shot multivibrator IC 5
As shown in FIG. 13 (a), is a negative displacement of the data transmitted through the transmission path 3, that is, the leading edge of the signal when the digital signal changes from "1" to "0" is used as a trigger. It operates as shown in FIG. 13B, and generates a pulse with a time lag corresponding to the time td set by the time constant circuit.

As described above, the one-shot multivibrator IC 5 is triggered by the negative displacement of the transmission data on the transmission line 3 and operates with a time lag corresponding to the time td set by the time constant circuit. The shot multivibrator IC 5 is retriggerable (restarting type that restarts from the beginning each time it receives a trigger), and when retriggered, it operates with a time lag corresponding to the time td from this point.

With such a structure, when the transmission line 3 becomes untransmittable due to a failure such as disconnection, the output of the one-shot multivibrator IC 5 is always "0", and otherwise the output is always "0". It becomes 1 ”and the transmission line can be monitored.

However, in the case of the method of monitoring the state of the transmission line 3 at such a data change point (trigger point), the transmitted data is added with frame bits as shown in FIG. 12 (a). However, in the case of transmitting non-frame data, there arises a problem that the transmission path cannot be monitored. In other words, in the case of non-frame data data, sometimes the transmission data is all zero,
In some cases, it is impossible to determine whether the transmission data is in the state of all zeros, all ones, or the failure of the transmission path.

[0010]

As described above, the transmission line monitoring in the digital transmission system is performed using the retriggerable one-shot multivibrator.
This is because the retriggerable one-shot multivibrator uses the property that the pulse generation time is postponed by the retrigger, and the retrigger is performed at each change point of the transmission data. Since the bit content always changes at regular intervals, this is used to perform a retrigger each time a data change occurs, so that the time lag range of the one-shot multivibrator can be used when transmission data is being transmitted. The one-shot multivibrator prevents the output from being repeatedly retriggered by, and the abnormality can be detected by utilizing the fact that the retrigger is not applied after the transmission line is disconnected.

However, in the conventional method of monitoring the status by using the output of the one-shot multivibrator, the transmission path is monitored depending on the presence or absence of the change point of the data, so that all zero (ALL) is transmitted when transmitting non-frame data.
There is a problem that the transmission line cannot be monitored because it is not possible to distinguish between "0" or all 1 (ALL "1") data and the transmission line failure (disconnection).

Therefore, the object of the present invention is to
It is an object of the present invention to provide a transmission line monitoring apparatus which solves this problem and can monitor a transmission line even with non-frame data depending on the presence or absence of a data change point.

[0013]

In order to achieve the above object, the present invention is configured as follows. That is, a configuration is provided in which the receiving side is provided with a transmission line monitoring device that detects an abnormality in the transmission line connecting the transmitting side and the receiving side by monitoring a pulse change in the transmission line transmission data signal during a predetermined monitoring period. In the digital transmission system described above, the transmitting side is provided with an encoding means for breaking a sequence of 0s or a sequence of 1s in the original data by using a clock signal synchronized with the data to be transmitted, and the data is transmitted through the encoding means. Retriggerable pulse generation, which is sent to the channel and is triggered on the receiving side by the transmission data from this channel as the channel monitoring device, and an output is generated and an abnormality detection output is generated when a predetermined time has elapsed after the trigger. And means for restoring the data obtained via the transmission path to the original data before encoding.

The encoding means and the restoring means are constructed by using an exclusive OR circuit, and the exclusive OR circuit of the encoding means stores the exclusive OR result of the original data and the clock signal. In addition to outputting the output, the exclusive OR circuit of the restoring means outputs the exclusive OR result of the data received from the transmission line and the clock signal.

Further, the encoding means and the restoring means are constructed by using an exclusive NOR logic circuit, and the exclusive NOR logic circuit of the encoding means has an exclusive NOR logic result of the original data and the clock signal. And an exclusive NOR logic circuit of the restoring means outputs an exclusive NOR logic result of the data received from the transmission line and the clock signal.

[0016]

In the above construction, the transmitting side sends the original data to be transmitted to the transmission line via the encoding means, and the encoding means uses the clock signal synchronized with the data to be transmitted on the transmission line. Consecutive "0" or "1" in data
Encoding that breaks the sequence of. Then, on the receiving side, this is decoded by the restoring means to obtain the original signal. On the other hand, on the other hand, the receiving side is provided with pulse generation means for retriggerable operation as a transmission line monitoring device, and is triggered by transmission data from the transmission line. The output generation operation is performed when a predetermined time has elapsed after the trigger, and an abnormality detection output is generated.

The transmitted data is encoded by the encoding means so that the content changes in synchronization with the clock signal even when "0" or "1" continues in the original data. Even if the original data is a series of "1" or a series of "0", it is in the form of data that alternates. Therefore, the pulse generating means is repeatedly retriggered as long as the data is normally transmitted, and is not retriggered when the transmission path is cut off, so that an abnormality detection output is generated.

Therefore, according to the present invention, it becomes possible to monitor the transmission path even for non-frame data depending on the presence or absence of a change point of data, and also it is possible to normally send and receive data from the transmitting side to the receiving side.

Further, according to the present invention, the clock and the exclusive OR (EXO) at the stage of outputting the original data coming into the transmitting side.
R) or exclusive NOR (EXNOR) and output. A circuit and an EXO that can monitor the change point of data and detect anomalies based on the existence of the change point
Prepare R or EXNOR or flip-flop.

In the present invention, the clock and the exclusive OR (EXOR) at the stage of outputting the original data coming into the transmitting side.
Or because it outputs by taking exclusive NOR (EXNOR), it is transmitted even if there is no change in the original data such as all zero (ALL “0”) or all 1 (ALL “1”). Encoded outgoing data (transmission data) that goes out to the road does not have data of the same kind of bit content continuous and always repeats alternating, so it is like a one-shot multivibrator on the receiving side. If only the change point is monitored, the transmission line can be monitored.

Also, on the transmitting side, with respect to the original data and the clock, exclusive OR (EXOR) or exclusive NOR (E
The data obtained by (XNOR) can be reproduced as the original data by providing an EXOR, EXNOR or a flip-flop on the receiving side.

Therefore, according to the present invention, it is possible to provide a digital transmission system having a transmission line monitoring apparatus capable of monitoring a transmission line even with non-frame data depending on the presence or absence of a data change point.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a block diagram showing a first embodiment of the present invention, and is a block diagram showing an overall configuration of a digital communication system to which the present invention is applied. In the figure, 10 is a transmitter, 20 is a receiver, and 3 is a transmission path. The transmission device 10 is a device for transmitting the original data to be transmitted to the transmission path 3, and the data obtained by encoding the original data is used as transmission data, and this transmission data and 1 / of the transmission data are transmitted. Two
It outputs a transmission clock having a cycle of, and has at least a transmission control unit 11 and a transmission data conversion circuit 12.

The transmission controller 11 controls the transmission of the transmission data to the transmission line 3, and the transmission data conversion circuit 12
Has a transmission data conversion circuit that converts transmission data output from the transmission control unit 11 into alternating data in synchronization with a transmission clock (data whose bit value changes every clock in synchronization with the transmission clock). There is. The output from the transmission data conversion circuit 12 and the transmission clock are sent to the transmission line 3. The transmission clock is twice as large as the transmission data, and the transmission clock and the transmission data are in a synchronous relationship with each other.

The receiving device 20 receives and takes in the data transmitted through the transmission path 3, and the receiving data conversion circuit 21, the monitoring circuit 22, and the reception control section 23.
have.

The reception data conversion circuit 21 is a circuit for converting the data transmitted through the transmission line 3 into the original data, and the monitoring circuit 22 monitors the signal state of the reception data from the transmission line 3. The abnormality detection output is generated when the signal change does not occur even after a predetermined time. Further, the reception control unit 23 is a reception unit for receiving and controlling the signal (data) output from the reception data conversion circuit 21.

In the present apparatus having such a configuration, on the transmission device 10 side, the original data, which is the data to be transmitted, is converted into a predetermined transmission rate and sent from the transmission control unit 11 together with the transmission clock. A transmission data conversion circuit 12 is provided in the output stage of the transmission data conversion circuit 12, and the transmission data conversion circuit 12 receives the transmission data and the transmission clock from the transmission control unit 11 and converts them into an alternating signal. That is, the data is converted (encoded) into data whose bit value changes every clock in synchronization with the transmission clock, and this is output to the transmission line 3 as transmission data.

On the other hand, the receiving device 20 side receives the transmission clock and the data (transmission data) converted into the alternating signal via the transmission line 3, and the reception data conversion circuit 21 synchronizes with the transmission clock for each clock. The received data (transmission data) is returned to the original data. That is, it is decrypted. Then, the reception data conversion circuit 21 gives the decoded data to the monitoring circuit 22 and the reception control unit 23. Reception control unit 2
At 3, the data is received by receiving this data and the transmission clock.

Further, the monitoring circuit 22 receives the transmission data of the transmission path 3 and monitors the change of the signal state, and when the signal state does not change even after a predetermined time, an abnormality detection output is generated as a detection result.

As a result, even when all "0" s or all "1s" continue in the data string of the original data, it becomes possible to monitor, and an abnormality such as disconnection of the transmission line can be distinguished from the occurrence. .

FIG. 2 is a circuit diagram specifically showing a configuration example of the main part of the system of FIG. 1, and is a circuit diagram as a first embodiment of the present invention. In FIG. 2, 10 is a transmitter,
Reference numeral 12 is a transmission data conversion circuit, which is configured by using an exclusive OR (exclusive OR circuit) EXOR1 in this figure. The EXOR1 receives the transmission data DATA and the transmission clock CLK from the transmission control unit 11 and calculates and outputs the exclusive OR of them.

Reference numeral 20 is a receiving device, 21 is a received data conversion circuit, and 22 is a monitoring circuit. In this example, the received data conversion circuit 21 uses an exclusive OR (exclusive OR circuit) EXOR2. . The exclusive OR circuit EXOR2 receives the transmission data and the transmission clock from the transmission line 3 and calculates and outputs the exclusive OR of them.

The monitoring circuit 22 is constructed by using a one-shot multivibrator MM, and outputs the output pulse as a monitoring result signal, that is, an alarm signal.

FIG. 3 is a timing chart showing the circuit operation of FIG. 2, which will be described with reference to this. The present apparatus having the above-described configuration is capable of processing the original data A (see FIG.
(A)) and the transmission clock B (CLK in FIG. 3B) are transmitted to the transmission line 3 immediately before the EXOR1 performs an exclusive OR of the original data A and the transmission clock B. The result of the sum is output to the transmission line 3 as transmission data. The exclusive OR is a logic "1" when two inputs are different and a logic "0" is output when two inputs are the same. As shown in FIGS. 3 (a) and 3 (b), if the transmission clock B is a positive multiple of the transmission data (sending data) C, the clock is transmitted more than the transmission period per bit of the transmission data. , The signal state always changes within the transmission period per bit of the transmission data, whereby the data C as shown in FIG. 3C is transmitted to the transmission line 3.

On the other hand, on the receiving device 20 side, the transmission data (sending data) and the transmission clock transmitted via the transmission line 3 are fetched via the EXOR 2. EXOR2 takes the exclusive OR of the transmission data and the transmission clock. As a result, original data is restored and obtained from EXOR2 (see reproduced data D in FIG. 3D).

On the receiving device 20 side, the data sent via the transmission line 3 is also input to the one-shot multivibrator MM which constitutes the monitoring circuit 22. The one-shot multivibrator MM is a retriggerable monostable oscillator whose pulse width can be freely changed. In other words, retrigger is a one-shot multivibrator that generates a pulse when a certain set time has elapsed since it was triggered. This is an operating function. Therefore, if the operating time of the one-shot multivibrator MM is set to a setting time of several bits of transmission data (the timing chart shows the pulse width setting as 3 clocks), the last trigger A pulse (see (e) E in FIG. 3, a negative level output in FIG. 3) is generated at the time when the set time has elapsed after the output of the signal is given, and no detection output is generated during the period when the transmission line 3 is normal. (In FIG. 3, a positive level output state). In addition,
In (e) of FIG. 3, "1" is normal and "0" is abnormal.

As described above, the exclusive-OR circuit is provided on the transmitting side to perform the exclusive-OR of the transmission data and the transmission clock having a higher rate than the transmission clock for encoding, and the data is always transmitted even if there is no change in the original data. Data conversion processing is performed so that the state changes within each bit period of data, and this is transmitted as transmission data on the transmission path, and at the receiving side, the exclusive OR circuit is provided and the transmitted data and the transmission clock. By taking the exclusive OR of the data, the data is restored to the original data, and the one-shot multi-vibrator MM that can be retriggered as a monitoring circuit of the transmission line on the receiving side is used.
The one-shot multivibrator is triggered by the data that has been subjected to the data conversion processing that has been transmitted through the transmission line, and the one-shot multivibrator is used when there is no change in the state of the data beyond the retrigger setting time. Since the abnormality detection signal as the detection result is obtained by generating the output, it becomes possible to monitor the transmission path even for non-frame data depending on the presence or absence of a data change point.

(Second Embodiment) FIG. 4 shows another embodiment in which the configuration of the reception data conversion circuit 21 on the receiving device 20 side is different from that of the first embodiment. The configuration of the transmission device 10 side is the same as that of FIG. 2, but the reception data conversion circuit 21 is composed of a flip-flop FF and a delay line DL.

The transmission data from the transmission line 3 is input to the D input terminal of the flip-flop FF, and the transmission line 3
Is transmitted to the clock input terminal of the flip-flop FF via the delay line DL. The flip-flop FF is a D flip-flop and operates in synchronization with the clock of the clock input terminal. The delay line DL is set so as to delay the phase of the input signal by 135 ° ± 180 N ° (where N is an integer).

FIG. 5 is a timing chart showing the operation of the circuit of FIG. According to this timing chart, FIG.
The operation of the circuit will be described. The data C ((c) in FIG. 5) transmitted through the transmission line 3 is input to the D input terminal of the flip-flop FF, while the transmission clock (in FIG. 5 (b)) is input.
CLK) is input to the clock input terminal of the flip-flop FF via the delay line DL to operate the flip-flop FF.

As a result, the flip-flop FF latches the transmission data, which is the input data, with the clock whose phase is shifted by 135 ° ± 180 N ° (where N is an integer) by the delay line DL. Data can be reproduced as shown in (e) of 5. FIG. 6 shows an enlarged view of the I portion of the timing chart of FIG.

The operation of the method of monitoring the transmission line 3 is the same as that described with reference to FIG. (Third Embodiment) In the third embodiment, the configurations of the transmission data conversion circuit 12 on the transmission device 10 side and the reception data conversion circuit 21 on the reception device 20 side are the exclusive OR circuits (EXOR1, EXOR1, It is configured by replacing EXOR2) with exclusive NOR logic circuits (EXNOR1, EXNOR2), and details thereof are shown in FIG. Further, FIG. 8 shows an operation timing chart of the configuration of FIG. 7 as an example.

In FIG. 7, reference numeral 10 is a transmitter, and 1
Reference numeral 2 is a transmission data conversion circuit, which is configured by using an exclusive NOR (exclusive NOR logic circuit) EXOR1 in this figure. The EXNOR 1 receives the transmission data DATA and the transmission clock CLK from the transmission control unit 11 and calculates and outputs the exclusive NOR logic of them.

Reference numeral 20 is a receiver, 21 is a received data conversion circuit, and 22 is a monitoring circuit. In this example, the received data conversion circuit 21 uses an exclusive NOR (exclusive NOR logic circuit) EXNOR2. . This EXN
The OR2 receives the transmission data and the transmission clock from the transmission line 3, calculates the exclusive NOR logic of them, and outputs them.

Further, the monitoring circuit 22 is constructed by using a one-shot multivibrator MM, and outputs the output pulse as a monitoring result signal, that is, an alarm signal.

In this embodiment, the exclusive NOR logic is set by EXNOR1 immediately before transmitting the original data A (FIG. 8A) and the transmission clock B (FIG. 8B) in the transmitter 10 to the transmission line 3. As shown in FIG.
Transmission data C as shown in (c) is transmitted.

The exclusive NOR logic is to output a logic "0" when two inputs are different and to output a logic "1" when two inputs are the same. Then, as shown in FIGS. 3A and 3B, if the transmission clock B is twice as large as the transmission data A, the transmission clock changes faster than the transmission period per bit of the transmission data. So 1 of the transmitted data
The signal state always changes within the transmission period per bit, and as a result, the transmission data (transmission data) C as shown in (c) of FIG. 8 is encoded and transmitted to the transmission line 3.

On the other hand, on the receiving device 20 side, the data and the transmission clock sent through the transmission line 3 are EXNORed.
Take in via 2. EXNOR2 takes an exclusive NOR logic between the reception data and the transmission clock. As a result, EXN
Original data is restored and obtained from OR2 (see (d) D in FIG. 8).

On the receiving device 20 side, the data sent via the transmission line 3 is also input to the one-shot multivibrator MM forming the monitoring circuit 22. The one-shot multivibrator MM is a retriggerable monostable oscillator whose pulse width can be freely changed.

That is, the retrigger is a one-shot multivibrator that generates a pulse when a certain set time has elapsed after being triggered, and operates so that a pulse is generated at the time when the set time elapses from that time each time the trigger is triggered. Therefore, if the operation time of the one-shot multivibrator MM is set to a setting time of about several bits of transmission data (the pulse width is set to 3 clocks in the timing chart), A pulse (see (e) in FIG. 8, negative level output in FIG. 3) is generated when the set time has elapsed since the last trigger was given, and the detection output is generated during the period when the transmission path is normal. It will not be performed (positive level output state in FIG. 8). In addition, in FIG. 8E, "1" is normal,
"0" is abnormal.

In this embodiment, since the transmission data (original data) and the transmission clock are transmitted after taking the exclusive NOR logic, the data C sent to the transmission path is the original data shown in FIG.
Even if “0” is continuous or “1” is continuous, as in (a) of FIG.

Therefore, by providing the one-shot multivibrator 5 which is a retriggerable monostable oscillator capable of freely changing the pulse width on the receiving device 20 side (the timing chart shows the setting of the pulse width as 3 clocks). ), The transmission line 3 can be monitored. Then, the data is reproduced by EXNOR in the input unit of the receiver 20.
Since it can be easily implemented by providing, there is no problem in implementing.

As described above, by providing the exclusive NOR logic circuit on the transmission side and taking the exclusive NOR logic of the transmission data and the transmission clock having a faster rate than this, each transmission data is sure to be transmitted even if there is no change in the data. An exclusive NOR logic between the transmission data and the transmission clock, which is processed by converting the data into a form in which the state changes within the bit period and transmitting it through the transmission path, and also by setting up an exclusive NOR logic circuit on the receiving side. By retrieving the data, a retriggerable one-shot multivibrator MM is provided on the receiving side as a monitoring circuit of the transmission line on the receiving side, and the data conversion processed data transmitted through the transmission line This one-shot multi-vibrator is triggered when the one-shot multi-vibrator is triggered and there is no change in the data state over the retrigger setting time. By generating an output from Bureta, since to obtain an abnormality detection signal as a detection result, it becomes possible to monitor the transmission path by the presence or absence of a change point of the data in the data non-frames.

(Fourth Embodiment) FIG. 9 shows another embodiment in which the configuration of the reception data conversion circuit 21 on the receiving device 20 side is different from that of the third embodiment. The configuration of the transmitting device 10 side is the same as that of FIG.
Is composed of a flip-flop FF and a delay line DL.

The transmission data from the transmission line 3 is input to the D input terminal of the flip-flop FF, and the transmission line 3
Is transmitted to the clock input terminal of the flip-flop FF via the delay line DL. The flip-flop FF is a D flip-flop and operates in synchronization with the clock of the clock input terminal. The delay line DL is set to delay the phase of the input signal by 45 ° ± 180 N ° (where N is an integer).

FIG. 10 is a timing chart showing the operation of the circuit of FIG. The operation of the circuit of FIG. 9 will be described according to this timing chart. The data C ((c) in FIG. 10) transmitted through the transmission path 3 is input to the D input terminal of the flip-flop FF, while the transmission clock ((b) in FIG. 10) is transmitted via the delay line DL. A predetermined delay is given, and the delayed clock ((d) of FIG. 10) is input to the clock input terminal of the flip-flop FF to operate the flip-flop FF.

As a result, the flip-flop FF latches the transmission data, which is the input data, with the clock whose phase is shifted by 45 ° ± 180 N ° by the delay line DL, and as a result, as shown in (e) of FIG. The data can be played back.

The flip-flop F, which operates in synchronization with the transmission clock whose phase is shifted by 45 ° ± 180 N ° on the delay line DL, of the transmission data C thus coming through the transmission path 3
By latching with F, the original data can be reproduced. FIG. 11 is an enlarged view of part II of the timing chart of FIG.
Shown in The transmission line monitoring method of the transmission line 3 by the one-shot multivibrator MM is the same as the operation described in FIG.

Incidentally. The present invention is not limited to the embodiments described above and shown in the drawings, and can be appropriately modified and implemented within the scope of the invention. This system is
When transmitting the original data and the clock in the transmitter to the transmission path, the exclusive OR or the exclusive NOR logic of the original data and the clock is obtained by EXOR or EXNOR, and the result is output as the transmission data. As a result, the transmitted data has an alternating waveform even when "0" is continuous or "1" is continuous in the original data.

Therefore, by providing a one-shot multivibrator, which is a retriggerable monostable oscillator whose pulse width can be freely changed, on the receiving device side, the transmission line can be monitored by the operation output of the one-shot multivibrator. Become. Data reproduction can be easily performed by providing EXOR, EXNOR, or the like at the input unit of the receiving device.

[0061]

As described above, according to the present invention, the result obtained by taking EXOR or EXNOR of the original data and the clock is sent to the output line of the digital transmission system and transmitted to the transmission line. Therefore, it becomes possible to encode data with alternating changes, and by using this data for monitoring, it becomes possible to monitor the transmission line depending on the presence or absence of data change points, even though it is non-frame data. A digital transmission system can be provided.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention,
The block diagram which shows the whole structure of this invention system schematically.

FIG. 2 is a diagram for explaining an embodiment of the present invention,
The circuit diagram showing the important section composition of the system of the present invention.

FIG. 3 is a diagram for explaining an embodiment of the present invention,
The timing chart explaining operation | movement of this invention system.

FIG. 4 is a diagram for explaining an embodiment of the present invention,
First, the configuration of the reception data conversion circuit 21 on the reception device 20 side is
FIG. 8 is a diagram showing another embodiment having a configuration different from that of the embodiment of FIG.

FIG. 5 is a diagram for explaining an embodiment of the present invention,
5 is a timing chart showing the operation of the circuit of FIG. 4.

FIG. 6 is a diagram for explaining an embodiment of the present invention,
FIG. 6 is an enlarged view of part I of the timing chart of FIG. 5.

FIG. 7 is a diagram for explaining an embodiment of the present invention,
The circuit diagram which shows the 3rd Example of this invention.

FIG. 8 is a diagram for explaining an embodiment of the present invention,
FIG. 8 is a diagram showing an operation timing chart of the configuration of FIG. 7.

FIG. 9 is a diagram for explaining an embodiment of the present invention,
The circuit diagram which shows another Example which made the structure of the receiving data conversion circuit 21 of the receiving device 20 side different from the case of a 3rd Example.

FIG. 10 is a diagram for explaining the embodiment of the present invention, which is a timing chart showing the operation of the circuit of FIG. 9;

FIG. 11 is a diagram for explaining the embodiment of the present invention and is an enlarged view of a II portion of the timing chart of FIG. 10.

FIG. 12 is a diagram for explaining a conventional technique.

FIG. 13 is a diagram for explaining a conventional technique.

[Explanation of symbols]

1, 10 ... Transmitting device 3 ... Transmission path 4, 20 ... Receiving device 11 ... Transmission control unit 12 ... Transmission data conversion circuit 21 ... Reception data conversion circuit 22 ... Monitoring circuit 23 ... Reception control unit EXOR1, EXOR2 ... Exclusive OR (exclusive) OR circuit EXNOR1, EXNOR2 ... Exclusive NOR logic circuit MM ... One-shot multivibrator FF ... Flip-flop (D flip-flop) DL ... Delay line

Claims (4)

[Claims] 1. A transmission line monitoring apparatus for detecting an abnormality in a transmission line connecting a transmission side and a reception side by monitoring a pulse change in a transmission line transmission data signal in a predetermined monitoring period. In the provided digital transmission system, the transmitting side is provided with an encoding means for breaking a sequence of 0s or a sequence of 1s in the original data by using a clock signal synchronized with the data to be transmitted. A retriggerable operation in which data is sent to a transmission line, and the reception side is triggered by the transmission data from this transmission line as the transmission line monitoring device and an output generation operation is performed when a predetermined time has elapsed after the trigger to generate an abnormality detection output. Is equipped with pulse generation means of
Also, a digital transmission system characterized in that it is provided with a restoring means for restoring the data obtained through the transmission path to the original data before encoding. 2. The encoding means and the restoring means are configured by using an exclusive OR circuit, and the exclusive OR circuit of the encoding means stores an exclusive OR result of the original data and the clock signal. 2. The digital transmission according to claim 1, wherein the exclusive OR circuit of the restoring means outputs the exclusive OR result of the data received from the transmission line and the clock signal, in addition to the output. system. 3. The encoding means and the restoring means are configured by using an exclusive NOR logic circuit, and the exclusive NOR logic circuit of the encoding means stores an exclusive NOR logic result of the original data and the clock signal. 2. The digital transmission according to claim 1, wherein the exclusive NOR logic circuit of the restoring means outputs the exclusive NOR logic result of the data received from the transmission line and the clock signal while outputting the exclusive NOR logic result. system. 4. The restoring means comprises delay means for phase-shifting the clock signal, and D flip-flop which operates in synchronization with the clock signal obtained through the delay means and takes in data from the transmission path. The digital transmission system according to claim 2, wherein the digital transmission system comprises: