JPH07177162A - Multiplex communication - Google Patents

Abstract

PURPOSE:To surely detect a hit in any communication equipment with respect to the multiplex communication equipment in which a receiver side communication equipment returns a reply signal representing a reception state of data to a sender side communication equipment so as to detect, the communication state. CONSTITUTION:Plural communication equipments 10 are connected via a common bus line 12. A connector 30 is provided with a circuit setting a withstand voltage of a bus line 12 to be a betaV (>alphaV) when the connector 30 and an ECU 20 are in contact with each other and setting the withstand voltage of the bus line 12 to be reduced to an alphaV when the connector 30 and the ECU 20 are momentarily interrupted. Upon the receipt of data from the bus line 12, the ECU 20 discriminates whether or not reception is implemented normally, and provides an output of a reply signal whose peak level is a betaV when the data reception is normal and an output of a reply signal whose peak level is a 0V when the data reception is not normal. A communication equipment sending data discriminates the communication state depending on a peak level of the received reply signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiplex communication device,
Especially when data is mutually communicated between a plurality of communication devices, a data signal is returned from the communication device on the receiving side to the communication device on the transmitting side and a response signal indicating the reception state of the data is returned. The present invention relates to a multiplex communication device that retransmits data to ensure high reliability.

[0002]

2. Description of the Related Art Conventionally, as a multiplex communication device for connecting a plurality of communication devices via a common bus line to perform mutual communication, for example, a device disclosed in Japanese Patent Application Laid-Open No. 2-1647 is known. .

In this device, one of a plurality of communication devices, which is a communication device on the receiving side, returns a response signal according to the reception state when receiving data, and the communication device on the transmitting side returns the response. It is a device that determines whether or not data transmission to a plurality of communication devices has been normally performed based on a signal.

Here, the apparatus described in the above publication can be realized by mutually communicating data of transmission frames as shown in FIG. 4, for example. That is, when the start bit is transmitted from the transmitting communication device toward the bus line, the other communication device can recognize that the data communication is started.

Next, when the ID signal is transmitted on the bus line, the receiving side communication device can recognize from which communication device the data is transmitted. Therefore, if a message is sent subsequently to this, it is possible to identify from which communication device the message was sent by the receiving communication device, even though multiple communication devices are connected to the bus line. can do.

The error detection bit transmitted following the message is a code preset by the transmitting side and the receiving side. That is, if the communication state is normal, a predetermined set value should be transmitted as the error detection bit, and it can be judged whether the received message is normal or not depending on whether this bit is normal or not.

If each receiving communication device sets a response signal depending on whether the message is normal or not in the response bit and returns the data of the transmission frame shown in FIG. 4, this is received. The original communication device on the transmitting side can judge whether the data transmitted by itself is normally received by another communication device.

Here, the apparatus described in the above publication executes multiplex communication assuming three types of response signals as shown in FIG. That is, FIG. 5A shows a response signal (hereinafter referred to as ACK) output from each communication device to the bus line when the data is normally received, and the passive level “1” and the dominant level are shown. A 2-bit signal of "10" is obtained by combining with "0".

This ACK signal is converted into a "1" consisting of 2 bits.
The reason why it is represented by "0" is that "1" represents that communication is normal and that "0" represents that the communication device is functioning normally.

That is, in the multiplex communication device, the potential of the bus line is generally maintained at a level corresponding to "1", and "0" signal is positively output from any of the communication devices. It does not fall to a level equivalent to ". Therefore, if the response signal is simply represented as "1" by the 1-bit signal, it is not possible to determine whether the response signal represents a normal reception state or the communication device itself is in a state of being cut off from the bus line. .

FIG. 5B shows a response signal (hereinafter referred to as NACK) output when the received data is abnormal, and is a 2-bit signal "00" for the same reason.

FIG. 5C shows a state in which no response signal is transmitted from the receiving communication device, that is, when the connection between the receiving communication device and the bus line is momentarily disconnected. That is, in the device described in the above publication, when the potential on the bus line is maintained at the level corresponding to “11” at the timing when the response signal is returned,
Thereby, it is intended to recognize the instantaneous interruption of the communication device on the receiving side.

By the way, in general, in a multiplex communication device, the potential of the bus line does not decrease unless a "0" signal is transmitted by any one of the communication devices, as described above. If "0" is output from a communication device, "1" is output from another communication device.
Even if is output, the potential of the bus line drops to a level corresponding to "0".

Therefore, in the above conventional device, at least one communication device among the plurality of communication devices is connected to the NAC.
If the K signal is transmitted, "00" will appear on the bus line as the response signal, and in the transmitting side communication device,
As a result, the communication abnormality can be recognized.

[0015]

However, in such a configuration, even if an interruption occurs in any of the communication devices, if another communication device normally receives the data and transmits the ACK signal. After all, a response signal of "10" appears on the bus line.

In other words, the above-mentioned conventional multiplex communication device can recognize the state as a communication abnormality when all the receiving communication devices are instantaneously disconnected or the transmitting communication device is instantaneously disconnected. However, there is a problem in that some communication devices on the receiving side cannot be recognized as a communication error.

The present invention has been made in view of the above points, and when the receiving side communication device normally receives the data, it cannot receive the high level signal as the ACK signal and the normal data. In this case, a low level signal is returned as a NACK signal, and the potential of the bus line is lowered to a predetermined level between a high level and a low level at the time of a momentary interruption, thereby providing a multiplex communication device that solves the above problems. The purpose is to

[0018]

FIG. 1 is a block diagram showing the principle of a multiplex communication device that achieves the above object. That is, the above-mentioned purpose is, as shown in FIG. 1, a common bus line M1.
Upon communication between a plurality of communication devices connected to the receiver, the communication device M2 on the receiving side returns a response signal according to the reception state when receiving the data, and the communication device M3 on the transmitting side receives the data based on the response signal. A multiplex communication device for determining a data reception state in the side communication device M2, wherein the reception side device M2 includes reception state determination means M4 for determining whether or not the data received from the bus line M1 is normal, When the reception state determination means M4 determines that the data is normal, it outputs a high-level signal to the bus line M1, and when the data is determined to be abnormal, the potential of the bus line M1 is changed. Reception state response means M5 for outputting a low level signal, and the reception side communication device M2
Is cut off from the bus line M1 by a short time, the bus potential lowering means M6 for lowering the potential of the bus line M1 to a predetermined level lower than the high level is provided. Data transmitting means M7 for transmitting data including error detection data used by the communication device M2 to judge the state of received data toward the bus line M1.
A level determination means M8 for determining the potential level of the bus line M1 when the reception state response signal is returned from the reception side communication device M2, and the level determination means M8.
This is achieved by a multiplex communication device that includes a communication state determination unit M9 that determines the communication state between a plurality of communication devices based on the determination result of 1.

[0019]

In the multiplex communication device according to the present invention, the data transmission means M7 of the transmission side communication device M3 transmits data including error detection data when transmitting data to the bus line M1.

The reception state determination means M4 of the reception side communication device M2 receives the data supplied from the bus line M1 and determines whether the error detection data included in the data is normal. Based on this, it is determined whether or not the data has been normally received.

Then, the reception state response means M5 supplies a high level signal to the bus line M1 when the data reception is normally performed, and the data reception is normally performed. If not, a signal for setting the bus line M1 to the low level is supplied.

Therefore, in the level determining means M8 of the transmitting side communication device M3, when all the receiving side communication devices M2 connected to the bus line M1 receive data normally, a response signal is sent. It is determined that the potential of the bus line M1 at the time of returning is at high level. When data is not normally received by any of the receiving side communication devices M2, the potential of the bus line M1 changes due to the influence of the reception state response signal transmitted from the receiving side communication device M2. It is determined to be low level.

On the other hand, when the receiving side communication device M2 is momentarily disconnected from the bus line M1, the bus potential lowering means M6.
Lowers the potential of the bus line M1 below a predetermined level lower than the high level. That is, the bus line M1
When at least one receiving communication device M2 among the receiving communication devices M2 connected to the above has a momentary interruption, even if data is normally received by all the other receiving communication devices M2, the response signal is returned when the response signal is returned. The potential of the bus line M1 never rises to a high level.

Then, the level determining means M8 of the transmitting side communication device M3 determines whether the potential of the bus line M1 is at a high level or a low level, and also at any receiving side communication device M2. It is determined whether or not the level is a predetermined level that occurs when the communication occurs, and the communication state determination means M9
Determines the communication state of the data transmitted by the data transmitting means M7 based on the result.

[0025]

FIG. 2 is a block diagram of a communication device 10 which constitutes a multiplex communication device according to an embodiment of the present invention. The communication device 10 of the present embodiment has the functions of the above-mentioned receiving side communication device M2 and transmitting side communication device M3.

That is, the communication device 10 is connected via a bus line 12 to a plurality of communication devices of similar construction (not shown) to form a multiplex communication device. And bus line 1
2 functions as the above-mentioned transmitting side communication device M3 when transmitting data to itself, and when receiving data from the bus line 12, the above receiving side communication device M2.
Function as.

The communication device 10 has the above-mentioned reception state determination means M4, reception state response means M5, data transmission means M7,
An electronic control unit (ECU) 20 that realizes the level determination means M8 and the communication state determination means M9 and a function corresponding to the bus potential lowering means M6 described above are built-in, and the bus line 12 and the power source are provided to the communication device 10. The connector 30 connects the line 14 and the ground line 16.

In the multiplex communication apparatus of this embodiment, when it is necessary to use the detection result of the same sensor in a plurality of communication apparatuses, it is necessary to use the calculation result of one of the communication apparatuses in another communication apparatus. It is effective when there is a plurality of vehicle-mounted ECUs.
When each is configured as each communication device, its function can be effectively exhibited.

The ECU 20 is a device mainly composed of a CPU 22. The CPU 22 performs predetermined arithmetic processing based on the supplied data, and at the same time, executes a plurality of other ECUs.
It has a multiplex communication function to realize multiplex communication with.

That is, the multiplex communication apparatus of the present embodiment also performs communication by the same method as the conventional multiplex communication apparatus except for the response signal, and performs mutual data communication by serial communication via the bus line 12. Therefore, the protocol is defined. Then, the CPU 22 performs a process of transmitting data to the bus line 12 or receiving data from the bus line according to the protocol. Incidentally, in the present embodiment, as in the case of the conventional apparatus, data is exchanged according to the transmission frame shown in FIG.

The drive circuit 24 is a circuit for applying a predetermined shaping to the signal output from the CPU 24 and outputting the signal to the bus line 12. That is, in this embodiment, the output voltage of only the response signal is increased as compared with the start signal, the ID signal, the message signal, the error detection signal, and the end signal among the signals output from the CPU 22 for the reason described later. The drive circuit 24 performs a shaping process for realizing such a function.

More specifically, from the CPU 22 shown in FIG.
When the signal transmission is started in accordance with the transmission frame shown in FIG. 5, the drive circuit 24 directs the output level (hereinafter referred to as αV) of the CPU 22 to the bus line 12 from the start signal to the error detection signal and the end signal. Output. Then, the CPU 22 only for the response signal
The output level of (a) is amplified (hereinafter, the output level after amplification is represented by βV) and output toward the bus line 12.

In this sense, in the multiplex communication device of the present embodiment, the CPU 22 and the drive circuit 24 correspond to the reception state response means M4 and the data transmission means M7 described above. Further, in the present embodiment, the CPU 22 outputs "0".
When a signal corresponding to “1” is output from the CPU 22 to the low level of the potential (hereinafter, referred to as 0 V) when the signal corresponding to is output, and the signal is amplified by the drive circuit 22, The potential βV corresponds to the above-mentioned high level.

The response signal level detection circuit 26 is a circuit for monitoring the potential of the bus line 12 and detecting its level when a response signal is transmitted from another ECU (not shown) to the bus line 12. In this embodiment, 0
It has a function of distinguishing and detecting three levels of V, αV, and βV. The response signal level detection circuit 26
Corresponds to the level determining means M8 described above.

The connector 30 is a member detachably attached to the ECU 20 and has a function of controlling the connection between the ECU 20 and a wire harness such as the bus line 12 and the power supply line 14, and the above-mentioned bus. It is a main part of this embodiment having a function as the potential lowering means M6.

That is, the connector 30 includes the connector 3
A circuit that guards the electric potential of the bus line 12 to αV or less when there is a momentary disconnection between 0 and the ECU 20 is built in. This circuit includes a Zener diode 32 having a Zener voltage αV connected to a bus line 12, an inverter 34 having a low level of 0 V and a high level of (β−α) V or more, and a resistor 36 for driving the inverter 34. , 38.

The input terminal of the inverter 34 is the ECU 20.
It is grounded via a terminal provided at and is also connected to the power supply voltage via a resistor 36 functioning as a pull-up resistor. Therefore, if the ECU 20 and the connector 30 are in proper contact, the input terminal 3 of the inverter 34
4 is grounded, and a voltage of (β-α) V or higher showing a high level appears at its output terminal.

In this case, the Zener diode 32 connected to the output terminal of the inverter 34 exhibits a withstand voltage obtained by adding the Zener voltage αV to the output voltage of the inverter 32, and the bus line 12 eventually exceeds βV. Withstand voltage (the upper limit is determined by the characteristics of the inverter 34) is provided.

On the other hand, when the contact between the connector 30 and the ECU 20 is not proper and the input terminal of the inverter 34 is in a state of floating above the ground level, the potential thereof is the resistance 3
6 rises to the power supply voltage level connected. Therefore, the output terminal voltage of the inverter 34 becomes low level, that is, 0 V, and therefore the breakdown voltage of the bus line 12 becomes αV which is the Zener voltage of the Zener diode 32 as it is.

That is, in the multiplex communication apparatus of this embodiment, when the connector 30 and the ECU 20 are in proper contact, the withstand voltage of the bus line 12 is βV or more, and when the connection is not appropriate. Then, the breakdown voltage of the bus line 12 drops to αV. Then, such a function is not realized only between the illustrated connector 30 and the ECU 20, but is realized in all communication devices (connector and ECU) connected to the bus line 12.

By the way, in the multiplex communication apparatus of the present embodiment, the transmission frame shown in FIG. 4 is used, and the response signal is binary 0V-βV, and in other cases it is binary 0V-αV. As described above, the data signal is transmitted / received by the signal shown.

FIGS. 3A and 3B show the potential of the bus line 12 when a data signal is transmitted according to such a protocol, and FIG. 3A shows that data is normally stored in all communication devices. Is received, that is, when the ACK signal is transmitted from all the communication devices, FIG. 6B shows that when at least one communication device has a data reception error, that is, at least one communication device. It shows the case where the device sends a NACK signal.

In this case, assuming that the ECU 20 is the communication device on the transmission side, the response signal level detection circuit 26 in FIG.
For the state of (A), “βV, 0
A 2-bit signal consisting of V ″ is detected, and FIG.
In response to the above condition, a response signal composed of "0V, 0V" is detected.

On the other hand, when a disconnection between the connector and the ECU occurs in any one of the communication devices connected to the bus line 12, the breakdown voltage of the bus line 12 decreases to αV. In this case, the signal transmitted by each communication device instead of the response signal is originally a signal having an upper limit of αV and is not affected at all, but the response signal is affected.

In other words, even if all communication devices except the communication device in which the instantaneous interruption occurs receive data normally and an ACK signal is transmitted to it, the bus line 1
As shown in FIG. 3 (C), a response signal consisting of “αV, 0V” is generated on the upper part of FIG. 2, which is different from the response signal shown in FIG. 3 (A).

The CPU 22 uses the response signal level detection circuit 2
It is possible to recognize such a change in the situation via 6 and distinguish that some communication devices are in a non-response state due to a momentary interruption from the case where all communication devices normally transmit an ACK signal. You can figure it out. In this sense, αV in this embodiment corresponds to the above-mentioned predetermined level.

Incidentally, a momentary interruption occurs in some communication devices,
When a NACK signal is transmitted from another communication device together with this, the NACK signal appears preferentially on the bus line 12, but the instantaneous interruption is common to the data reception abnormality in that it is a communication abnormality. However, since there is little real benefit to distinguish between the two, this phenomenon is not a hindrance.

As described above, according to the multiplex communication apparatus of the present embodiment, in performing mutual data communication between a plurality of communication apparatuses, in addition to whether or not the data communication is normally performed, the instantaneous value of the connector is changed. It is possible to reliably detect even no response caused by disconnection or the like. Therefore, by taking measures such as retransmitting data when an abnormality such as a momentary interruption is detected, it is possible to secure high reliability as a multiplex communication device.

Such a momentary disconnection of the connector has conventionally been a problem in an in-vehicle ECU used under an environment where vibration is constantly applied. When the multiplex communication device of this embodiment is applied to a network including these in-vehicle ECUs, , Especially effective.

By the way, the response signals shown in FIGS. 3A to 3C are formed by 2 bits in consideration of the reliability of data transfer. However, in the multiplex communication apparatus of the present embodiment, it is not always necessary. The response signal does not have to be a 2-bit signal.

In other words, a high level as a signal to be sent and received,
In a conventional device that can use only low level binary, it is necessary to generate a low level signal in order to indicate that the communication device is operating. Is shown in FIG.
A 2-bit signal is always required as shown in FIG.

On the other hand, the multiplex communication apparatus of this embodiment is
It is possible to indicate that the communication device is operating by emitting the signal of the peak value βV. Therefore, if it is sufficient to detect the situation where some communication devices do not operate, the response signal can be configured by 1 bit.

In this case, as in the case where the response signal is formed by using 2 bits, a case where some communication devices are not operating and some communication devices are operating (FIG. 3C) Can be distinguished from the case where all communication devices are not operating (the response signal of αV appears in both 2 bits), but it can be determined whether or not the entire multiplex communication device is in a normal state. It is possible to shorten the data length while ensuring the function.

[0054]

As described above, according to the present invention, the response signal issued by the receiving side communication device at the normal time is at a high level, the response signal issued at the time of an abnormality is at the low level, and the response signal at the momentary interruption is high level and low. By setting a predetermined level between the levels, the response signal when any one of the communication devices on the receiving side receives a momentary interruption from the response signal when the communication device on the receiving side normally receives the data. It can be prioritized, and priority can be given to the case where normal reception of data cannot be performed in any of the receiving side communication devices over the response signal when any one of the receiving side communication devices is interrupted.

In this case, all the receiving side communication devices normally receive the data, and it is not necessary to take measures such as resending of the data thereafter, and a momentary interruption or an abnormality in any of the receiving side communication devices. It becomes possible to individually recognize the situation in which reception is necessary and the situation in which it is necessary to take measures such as resending of data.

Further, the multiplex communication apparatus according to the present invention represents three situations to be distinguished by 1-bit signals of high level, predetermined level and low level. Therefore, it has a feature that the data length can be shortened as compared with the conventional device which requires 2 bits as a response signal.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of a multiplex communication device according to the present invention.

FIG. 2 is a configuration diagram of a communication device that constitutes a multiplex communication device that is an embodiment of the present invention.

FIG. 3 is a diagram for explaining the operation of the multiplex communication device of this embodiment.

FIG. 4 is an example of a transmission frame in multiplex communication.

FIG. 5 is a diagram for explaining the operation of a conventional multiplex communication device.

[Explanation of symbols]

 M1, 12 bus line M2 receiving side communication device M3 transmitting side communication device M4 receiving state judging means M5 receiving state responding means M6 bus potential lowering means M7 data transmitting means M8 level judging means M9 communication state judging means 10 communication device 20 electronic control device (ECU) 22 CPU 24 Drive circuit 26 Response signal level detection circuit 30 Connector 32 Zener diode 34 Inverter 36, 38 Resistance

Claims (1)

[Claims] 1. When performing communication between a plurality of communication devices connected to a common bus line, a receiving communication device returns a response signal according to a receiving state when data is received, and the transmitting communication device sends the response signal. A multiplex communication device that determines a data reception state in the reception side communication device based on a response signal, wherein the reception side device determines whether or not the data received from the bus line is normal. A high level signal is output to the bus line when the reception state determination means determines that the data is normal, and a potential of the bus line is changed when the data is determined to be abnormal. A reception state response means for outputting a signal of low level, and a potential of the bus line lower than the high level when the receiving side communication device is momentarily disconnected from the bus line Bus potential lowering means for lowering to a predetermined level, wherein the transmitting side communication device transmits data including error detection data used by the receiving side communication device for judging the state of received data to the bus line. Transmitting means, level determining means for determining a potential level of the bus line when a reception state response signal is returned from the receiving side communication device, and between the plurality of communication devices based on the determination result of the level determining means. A multiplex communication apparatus, comprising: a communication state determining means for determining a communication state.