JPH08191315A - Multiplex transmission equipment - Google Patents

Abstract

PURPOSE: To accurately receive a signal from a transmission line at low cost and with simple constitution even if such a fault that the transmission line is disconnected occurs. CONSTITUTION: If a 1st transmission line 10 is disconnected, a potential Va which is converted by a 1st potential converting circuit 21 connected to this transmission line is so converted that (reference potential Vc) < (potential Va) > (potential Vb at passive time). If a disconnection fault occurs to a 2nd transmission line 11, a potential Vb which is converted by a 2nd potential converting circuit 22 connected to this transmission line is so converted that (reference potential Vd) > (potential Vb) < (potential Va at passive time). One of comparators 23-25, therefore, outputs a normal signal at all times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiplex transmission device for detecting signals that are multiplex-transmitted on a transmission line.

[0002]

2. Description of the Related Art Conventionally, this type of multiplex transmission device has a CS
MA / CD (Carrier Sense Multiple Access / Collision)
Detection) method and NDA (Non Destructive Arbitrat)
There has been a system used in a transmission system in which an ion (Ion) method is combined or a transmission system in a LAN (Local Area Network) using a token. Further, in the above device, N
When communication is performed in the baseband using the RZ code, the logic has a high level (hereinafter referred to as “H”) or a low level (hereinafter referred to as “L”) as many bits. Since then, the bit synchronization between the multiplex transmission devices is deviated, so the bit stuff rule is used. That is, according to the bit stuffing rule, the stuff bit of logic "L" is given when the logic "H" continues for a certain length (for example, 5 bits), and the stuff bit of logic "H" when the logic "L" continues for a certain length. , And there was a thing that synchronizes at the edge of this stuff bit. By this transmission method, it was possible to prevent the "H" state for a certain time (for example, 6 bits) or more during normal communication. An example of such a multiplex transmission device is described in Japanese Patent Laid-Open No. 5-284135. In the above-mentioned multiplex transmission device, signals on the first and second transmission lines as shown in FIG. 5A are transmitted to predetermined potentials Va and Vb (see FIG.
(B)) first and second potential conversion circuits,
A first comparator (see FIG. 5D) that compares the converted potentials Va and Vb with a second comparator that compares the converted potential Va of the first transmission path with a reference potential Vc. Vessel (Fig. 5
(See (e)), the converted potential Vb of the second transmission line
And a third comparator (see FIG. 5 (f)) that compares the reference potential Vd with the reference potential Vd, and when one of the two first and second transmission lines fails, each comparator is configured by the logic synthesis circuit. By selecting the failure communication mode in which the sum of the above is used as the reception data and outputting the reception data to the multiplex transmission control circuit, reception is possible even if one of the transmission paths fails.

[0003]

However, in a system provided with the above-mentioned multiplex transmission device, for example, the multiplex transmission device is connected to a transmission line via a branch line, and one of the branch lines of the receiving-side multiplex transmission device (for example, the first line). When the receiving side multiplex transmission device receives a signal in a failure state in which a branch line connected to the transmission line is disconnected, the receiving side multiplex transmission device detects a failure of the transmission line and transmits data in the failure communication mode. However, since the relationship between the converted potential and the reference potential is as shown in FIG. 5C, the first and third comparators can be used as shown in FIGS. 5D and 5F. There is a large difference in the width of the output signal.

This tendency increases as the potential Va from the first potential conversion circuit becomes closer to the passive side of the potential Vb from the second potential conversion circuit as shown in FIG. 5C. Was becoming. Further, in this case, the output of the second comparator is in the "H" state as shown in FIG. 5 (e). In this case, the logical sum of the outputs of the first to third comparators is selected as the reception signal, and as a result, the output of the first comparator is selected.
As shown in (d), in the passive signal and the dominant signal, since the pulse width of the passive signal becomes narrow, the communication control circuit may not be able to detect the passive signal, which causes a communication error. There was a problem.

Further, when a disconnection fault occurs in the first transmission line when the ground potential of the receiving-side multiplex transmission device is higher than the ground potential of the transmitting-side multiplex transmission device, for example, the first and second The relationship between the potentials Va and Vb from the second potential conversion circuit and the reference potentials Vc and Vd is as shown in FIG. 6, and the potential Va and the reference potentials Vc and Vd of the first potential conversion circuit are the generated ground potential difference. Only V1 rises to the passive potential Vb (= V2) side of the output of the second potential conversion circuit.

At this time, (Va + V1 <V2) is necessary for the first comparator to receive the signal, and (Vd + V1 <V2) for the third comparator to be able to receive the signal.
V2). Therefore, the ground potential difference is (V2−
Above Va) and below (V2-Vd), the output of the third comparator is selected as the received signal and the signal can be transmitted.

However, the ground potential difference is (V2-Va ± VOF).
F) (however, VOFF is the range of the offset voltage of the first comparator), the output of the first comparator becomes indefinite, and as a result, the originally expected signal cannot be obtained in the received signal and communication is performed. An error occurs. That is, the range of the ground potential difference at which the signal can be transmitted must be less than (V2-Va) excluding the above range (V2-Va ± VOFF), which makes the signal receiving operation unstable. There was a problem.

The present invention has been made in view of the above problems, and even if a failure occurs such that the transmission line is disconnected, a signal on the transmission line can be accurately received at a low cost and with a simple structure. An object is to provide a multiplex transmission device.

[0009]

In order to achieve the above object, according to the present invention, at least two common transmission lines (including branch lines) are connected to each other and the signals of the respective transmission lines are connected. Corresponding to the first potential comparing means (comparator) for comparing the respective predetermined potentials, and the second comparing means (comparator) comparing the potential of the converted one transmission line with a predetermined reference potential. ), A third comparing means (comparator) for comparing the converted potential of the other transmission line with a predetermined reference voltage, and a logic synthesizing means (logic synthesizing circuit) for logically synthesizing the outputs of the respective comparators. And a communication control means (communication control circuit) for receiving the synthesis result of the logic synthesis circuit, in the case of converting the signal of the one transmission path to a first predetermined potential, If the transmission line is broken (reference potential of the second comparator) (First predetermined potential)> (second predetermined potential when passive) The first potential conversion means (potential conversion circuit) for converting the potential so as to satisfy the condition, and the signal of the other transmission line. When the other transmission line is disconnected during conversion to the second predetermined potential, (reference potential of the third comparator)> (second predetermined potential) <(the first predetermined when passive) A multiplex transmission device including a second potential conversion unit (potential conversion circuit) that converts a potential so as to satisfy the condition (potential).

According to a second aspect of the present invention, when the one transmission line is disconnected, the first bias means (bias circuit) for applying a power supply potential to the one transmission line and the other transmission line are disconnected when the other transmission line is disconnected. Second bias means (bias circuit) for applying a ground potential to the other transmission path.

[0011]

When one of the transmission lines is disconnected, the potential converted by the first potential conversion circuit connected to this transmission line is changed to the second potential conversion circuit which is normally connected to the other transmission line. Is converted to a value greater than the passive potential and greater than the reference potential of the second comparator. When the other transmission line is disconnected, the potential converted by the second potential conversion circuit connected to this transmission line is changed by the first potential conversion circuit connected to one normal transmission line. The converted potential is always smaller than the passive potential and smaller than the reference potential of the third comparator. As a result, even if a disconnection failure occurs on one side of the transmission path, one of the three comparators always outputs a normal signal and signal communication becomes possible. In the second aspect, the first and second bias circuits give a potential to the transmission path so as to satisfy the conditions of the first and second potential conversion circuits, thereby enabling more normal signal communication. .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a multiplex transmission apparatus according to the present invention will be described below with reference to the drawings of FIGS. FIG. 1 is a configuration block diagram showing a first embodiment of the configuration of a multiplex transmission device according to the present invention. In the figure, the multiplex transmission devices 20 and 40 according to the present invention include two first and second transmission lines 10 and 10.
Each of the communication systems 11 is connected in parallel and has the same communication function. Therefore, of these communication systems, the reception system of the multiplex transmission device 20 will be described as a representative.

In the multiplex transmission device 20, the first and second potential conversion circuits 21 and 22 are connected to the first and second transmission paths 10 and 11 via branch lines 12 and 13, respectively. There are three first to third comparators 23 to 2 in the 21 and 22.
5 are connected to each other. First potential conversion circuit 21
Converts the signal on the transmission line 10 to a predetermined potential Va, and the second potential conversion circuit 22 converts the signal on the transmission line 11 to a predetermined potential Vb. In addition, the first comparator 23,
The voltages Va and Vb from both transmission lines 10 and 11 are compared,
The second comparator 24 compares the voltage Va from the transmission line 10 with a preset reference voltage Vc, and the third comparator 25 with the voltage Vb from the transmission line 11 is preset. The reference voltage Vd is compared with the reference voltage Vd.

The signals of the first and second transmission lines 10 and 11 in the normal state have the potential waveform shown in FIG. 2 (a). Here, the passive signal is a state in which there is no signal on the transmission path, "L" is expected in the input of the communication control circuit 30 described later, that is, the output MSI of the logic synthesis circuit 29, and the dominant signal is the above-mentioned transmission. There is a signal on the street,
This is a signal on the transmission line for which "H" is expected at the output MSI.

The first potential conversion circuit 21 includes a resistor 21a connected to the branch line 12, a resistor 21b connected between the resistor 21a and each comparator and between the power source Vcc, and a resistor 21a. It is composed of a resistor 21c connected between the comparators and the ground GND, and converts the signal on the transmission line 10 into the potential Va shown in FIG. 2B. The potential Va is determined by the ratio of the resistance values of the resistors 21b and 21c when the first transmission line 10 has a disconnection failure. In the resistors 21b and 21c, the potential Va is the second value.
The resistance values are selected so that the potential Vb converted by the potential conversion circuit 22 is larger than the potential in the passive state and larger than the reference potential Vc.

The second potential conversion circuit 22 includes a resistor 22a connected to the branch line 13, a resistor 22b connected between the resistor 22a and each comparator, and between the ground GND and a resistor 22b.
It is composed of a resistor 22a and a resistor 22c connected between the comparators and between the power source Vcc and converts the signal on the transmission line 11 into the potential Vb shown in FIG. 2 (b). The potential Vb is determined by the ratio of the resistance values of the resistors 22b and 22c when the second transmission line 11 has a disconnection failure. In the resistors 22b and 22c, the potential Vb is the first value.
The resistance values are selected so that the potential Va converted by the potential conversion circuit 21 is smaller than the passive potential and smaller than the reference potential Vd.

That is, the resistance values of the resistors 21b and 21c and the resistors 22b and 22c take values that satisfy the following relational expression. When the first transmission line 10 has a disconnection failure (reference potential Vc) <(potential Va)> (potential Vb when passive) (1) When the second transmission line 11 has a disconnection failure (reference potential Vd)> (Potential Vb) <(potential Va at the time of passive) (2) The outputs a to c of the first to third comparators 23 to 25 are input to the corresponding output control circuits 26 to 28. To be done. The output control circuits 26, 27, 28 include counter units 26a, 27a, 28a and an AND gate 26, respectively.
b, 27b, 28b. Each comparator 2
The outputs of 3 to 25 are counters 26a to 28a, respectively.
And AND gates 26b to 28b.

The counters 26a to 28a normally output "L", but the outputs of the comparators 23 to 25 are equal to or longer than the longest possible data in the data frame to be transmitted, that is, T1. Whether it is in the "H" state for a time or more is detected, and if it is in the "H" state for the T1 time or more, "H" is output. The outputs of the counter units 26a to 28a are inverted and are AND gates 26b to 28, respectively.
In addition to being input to b, it is input to the logic synthesis circuit 29. The time T1 is the same as the counter units 26a-28.
It may be different for each a.

The AND gates 26b to 28b are used for the comparator 2.
The logical product of the outputs 3 to 25 and the inverted outputs of the counter units 26a to 28a is output to the logic synthesis circuit 29. The logic synthesizing circuit 29 is composed of OR gates 29a, 29b, 29d and an AND gate 29c. OR gate 29
The outputs of the counter units 26a to 28a are respectively input to a, and the OR gate 29a outputs the logical sum of these inputs to the AND gate 29c. The outputs e and f of the AND gates 27b and 28b are input to the OR gate 29b, and the OR gate 29b is
The logical sum of these inputs is output to the AND gate 29c.

The AND gate 29c is the OR gate 2.
The logical product of the outputs of 9a and 29b is output to the OR gate 29d. The output of the AND gate 29c and the output d of the AND gate 26b are input to the OR gate 29d, and the OR gate 29d outputs the logical sum of these inputs to the communication control circuit 30 as a reception signal MSI. There is.

When the communication control circuit 30 takes in the output (received signal) of the OR gate 29d, it performs processing such as data decoding according to the received signal, and controls, for example, each connected device (not shown). I do. Next, the operation of the multiplex transmission apparatus shown in FIG. 1 will be described for each communication mode shown in Table 1. Table 1 shows the relationship between the states of the first and second transmission lines 10 and 11 and the outputs of the comparators 23 to 25.

[0022]

[Table 1] First, in the normal communication mode, the first and second transmission lines 1
The signals shown in FIG. 2A are transmitted to 0 and 11, and the signals are the first and second potential conversion circuits 21 and 22.
Are converted into potentials Va and Vb as shown in FIG. 2B and are input to the comparators 23 to 25. As shown in Table 1, the outputs of the comparators 23 to 25 are in the "L" state in the passive state and in the "H" state in the dominant state (see FIGS. 2C to 2E). Therefore, when the transmission lines 10 and 11 are in a normal state, there is no continuous "H" signal longer than the time T1. Therefore, the counter unit 26a-
28a always outputs "L", and AND gate 26b ...
28b is opened by the above output and the comparators 23-25
The respective outputs a to c are output.

However, since the outputs of the counter sections 26a to 28a are "L", the output of the OR gate 29a is "L". Therefore, since the AND gate 29c is closed, the outputs b and c of the second and third comparators 24 and 25 are not output, and only the output a of the first comparator 23 passes through the OR gate 29d and the received signal is received. The MSI is input to the communication control circuit 30 and data communication is performed.

Next, for example, as shown in FIG. 1, of the branch lines 12 and 13 connected to the first and second transmission lines 10 and 11, the failure communication mode in the state where the branch line 12 is broken by an X mark. The case will be described. In this case, the first and second transmission lines 1
The signals on 0 and 11 correspond to the first and second potential conversion circuits 21 and
It is converted into potentials Va and Vb as shown in FIG. 3A by 22 and input to the comparators 23 to 25. As shown in Table 1, the output c of the third comparator 25 is in the "L" state in the passive state and in the "H" state in the dominant state (see FIG. 3 (d)).

However, as shown in FIG. 3A, the potential V
Since a becomes larger than that in the passive state of the potential Vb due to the disconnection, the outputs a and b of the first and second comparators 23 and 24 are
Is always in the “H” state regardless of whether the signals on the first and second transmission lines 10 and 11 are in the passive state or the dominant state (see FIGS. 3B and 3C). . Therefore, since the AND gates 26b and 27b are closed, the outputs a and b of the first and second comparators 23 and 24 are not output to the outputs d and e, and they are always in the "L" state.

Further, in the third comparator 25, FIG.
Since the signal from the second transmission line 11 is received as shown in FIG. 5, "L" is output from the counter unit 28a to open the AND gate 28b, and the third comparator 2 is output at the output f.
The output c of 5 is output. In addition, the counter units 26a, 2
Since the output of 7a is "H", the output of the OR gate 29a is "H". Therefore, since the AND gate 29c is opened, the outputs a to c of the first to third comparators 23 to 25 are ORed, and the output c of the third comparator 25 becomes the reception signal MSI.

As a result, even if the first transmission line 10 is broken, only the output of one of the three comparators, in this case, the output c of the third comparator 25 passes through the OR gate 29d. , To the communication control circuit 30. That is, a ground potential difference is generated between the multiplex transmission devices, and the first
When the transmission line 10 is disconnected, the first potential conversion circuit 21 connected to the first transmission line 10 outputs the potential Va satisfying the condition of the expression (1), and thus is connected to the normal transmission line 11. A normal signal is output only from the third comparator 25 which is operated, and the outputs of the first and second comparators 23 and 24 are always in the "H" state. As a result, the ground potential difference becomes the second
Within the difference (Vb-Vd) between the passive potential of the potential Vb converted from the potential conversion circuit 22 and the reference potential Vd, the signal can be satisfactorily transmitted only by the second transmission path 11. .

Also in the failure communication mode in the state where the second transmission line 11 is broken, the second potential conversion circuit 2 is similarly provided.
2 outputs the potential Vb that satisfies the condition of the equation (2), the second comparator 2 connected to the normal transmission line 10
A normal signal is output from only 4 and the outputs of the first and third comparators 23 and 25 are always in the "H" state. As a result,
If the ground potential difference is within the difference (Va-Vc) between the passive potential of the potential Va converted from the first potential conversion circuit 21 and the reference potential Vc, the first transmission path 10 can be used satisfactorily. It becomes possible to transmit signals.

Therefore, in the present embodiment, when one side of the transmission line is broken, only one of the three comparators outputs a signal, so that it is not affected by the outputs of the other two comparators. , It becomes possible to communicate accurately. Further, in this embodiment,
Since the passive signal and the dominant signal received have the same pulse width, the signal on the transmission path can be accurately received and the communication error can be prevented.

FIG. 4 is a configuration block diagram showing a second embodiment of the configuration of the multiplex transmission apparatus according to the present invention. In the figure, in the second embodiment, in addition to the components of the first embodiment, a first bias circuit 31 connected between the branch line 12 and the power supply Vcc, and a connection between the branch line 13 and the ground GND. And a second bias circuit 32 that has been set. The first bias circuit 31 realizes the formula (1) by biasing the potential Va converted by the first potential conversion circuit 21 to the power supply side potential when the first transmission line 10 is disconnected. .

The second bias circuit 32 realizes the equation (2) by biasing the potential Vb converted by the second potential conversion circuit 22 to the ground side potential when the second transmission line 11 is broken. are doing. Therefore, also in this embodiment, as in the case of the first embodiment, when a disconnection failure occurs on one side of the transmission line, a signal is output from only one comparator, and the influence of the outputs of the other two comparators is affected. Communication is possible without being affected.

[0032]

As described above, according to the present invention, the respective predetermined potentials which are connected to each other through at least two common transmission lines and which are converted corresponding to the signals of the respective transmission lines are provided. The first comparing means for comparing, the second comparing means for comparing the converted potential of the one transmission path with a predetermined reference potential, and the second comparing means for comparing the converted potential of the other transmission path with the predetermined reference voltage. In the multiplex transmission device having third comparing means for comparing, logical synthesizing means for logically synthesizing the outputs of the respective comparing means, and communication control means for receiving the synthetic result of the logical synthesizing means, the one transmission path When the signal is converted to the first predetermined potential, if the one transmission line is broken, the first predetermined potential is larger than the reference potential of the second comparison means, and the second one when passive is used. Satisfies the condition of becoming larger than the specified potential of When converting the signal of the other transmission line to the second predetermined potential when the other transmission line is disconnected, the second predetermined potential is changed to the second potential. And the second potential conversion means for converting the potential so as to satisfy the condition of being smaller than the reference potential of the comparison means of 3 and smaller than the first predetermined potential in the passive state, so that the transmission line is disconnected. Even if such a failure occurs, the signal on the transmission path can be accurately received at a low cost and with a simple configuration.

In the second aspect, when the one transmission line is broken, the first predetermined potential is higher than the reference potential of the second comparing means and is lower than the second predetermined potential in the passive state. When the first bias means for applying a power supply potential to the one transmission path and the other transmission path are disconnected so that the condition is satisfied, the second predetermined potential is the reference potential of the third comparison means. Since the second bias means for applying a ground potential to the other transmission line is provided so as to satisfy the condition of being smaller and smaller than the first predetermined potential in the passive state, communication of a more normal signal is provided. Can be possible.

[Brief description of drawings]

FIG. 1 is a configuration block diagram showing a first embodiment of a multiplex transmission device according to the present invention.

FIG. 2 is a diagram showing potentials in a transmission line and respective parts of a multiplex transmission device in a normal state.

FIG. 3 is a diagram showing the potentials of the transmission line and each part of the multiplex transmission device when a disconnection failure occurs in the transmission line.

FIG. 4 is a configuration block diagram showing a second embodiment of the multiplex transmission device according to the present invention.

FIG. 5 is a diagram showing potentials at various parts of a conventional transmission line and multiplex transmission device.

FIG. 6 is a diagram showing a potential after conversion by a conventional potential conversion circuit when a ground potential difference occurs.

[Explanation of symbols]

 10, 11 Transmission line 12, 13 Branch line 20, 40 Multiplex transmission device 21, 22 Potential conversion circuit 23-25 Comparator 26-28 Output control circuit 26a-28a Counter section 26b-28b, 29c AND gate 29 Logic combination circuit 29a, 29b, 29d OR gate 30 communication control circuit 31, 32 bias circuit

Claims (3)

[Claims] 1. A first comparing means, which is connected to each other through at least two common transmission lines, and which compares respective predetermined potentials converted corresponding to signals of the respective transmission lines, Second comparing means for comparing the converted potential of one transmission path with a predetermined reference potential; third comparing means for comparing the converted potential of the other transmission path with a predetermined reference voltage; In a multiplex transmission apparatus having logic synthesizing means for logically synthesizing outputs of respective comparing means and communication control means for receiving a synthesis result of the logic synthesizing means, a signal of the one transmission path is converted into a first predetermined potential. In this case, when the one transmission line is disconnected, the condition that the first predetermined potential is higher than the reference potential of the second comparison means and higher than the second predetermined potential in the passive state is satisfied. Potential conversion that converts potentials And the other transmission line is disconnected when converting the signal of the other transmission line to the second predetermined potential, the second predetermined potential is smaller than the reference potential of the third comparison means. And a second electric potential converting means for converting electric potential so as to satisfy a condition of being smaller than the first predetermined electric potential in the passive state. 2. The multiplex transmission device according to claim 2, wherein when the one transmission line is broken, the first predetermined potential is higher than a reference potential of the second comparison means and the second transmission device is passive.
A first biasing means for applying a power supply potential to the one transmission path so as to satisfy the condition of becoming larger than the predetermined potential of
When the other transmission line is disconnected, the second predetermined potential is smaller than the reference potential of the third comparing means and smaller than the first predetermined potential in the passive state, so that the condition is satisfied. 2. The multiplex transmission device according to claim 1, further comprising a second bias unit that applies a ground potential to the other transmission line. 3. The multiplex transmission device according to claim 1, wherein the multiplex transmission device is connected to the transmission line via a branch line.