JP3106827B2 - Multiplex communication device - Google Patents

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,
In particular, when mutually communicating data between a plurality of communication devices, a response signal indicating a data reception state is returned from the receiving communication device to the transmitting communication device, and if a communication error is detected by the response signal, the data is transmitted. And a multiplex communication device for ensuring high reliability by retransmitting the multiplex communication.

[0002]

2. Description of the Related Art Hitherto, as a multiplex communication apparatus for connecting a plurality of communication apparatuses via a common bus line and performing mutual communication, for example, an apparatus disclosed in Japanese Patent Laid-Open No. 2-1647 is known. .

[0003] In this device, a communication device which becomes a receiving communication device among a plurality of communication devices returns a response signal according to a reception state when receiving data. This device determines whether data transmission to a plurality of communication devices has been normally performed based on a signal.

[0004] The apparatus described in the above publication can be realized by mutually transmitting data of a transmission frame as shown in FIG. 4 for example. That is, when a start bit is transmitted from the transmitting communication device to the bus line, the other communication devices can recognize that data communication is started.

Next, when an ID signal is transmitted on the bus line, the receiving communication device can recognize from which communication device data transmission is performed. Therefore, if a message is transmitted subsequently, even if a plurality of communication devices are connected to the bus line, the communication device on the receiving side specifies which communication device the message was transmitted from. can do.

The error detection bit transmitted after the message is a code set in advance on the transmitting side and the receiving side. That is, if the communication state is normal, a predetermined value should be transmitted as the error detection bit, and it can be determined whether the received message is normal based on whether this bit is normal.

If each receiving communication device sets a response signal according to whether the message is normal or not to the response bit and returns the data of the transmission frame shown in FIG. The originating communication device that has made the transmission can determine whether the data transmitted by itself has been normally received by another communication device.

Here, the apparatus described in the above publication performs multiplex communication on the assumption of 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 data is normally received, and includes a passive level “1” and a dominant level. A two-bit signal “10” is obtained by combining “0”.

[0009] This ACK signal is represented by a 2-bit "1".
The reason why it is represented by "0" is that "1" indicates that communication is normal and "0" indicates that the communication device is functioning normally.

That is, in a multiplex communication device, the potential of a bus line is generally maintained at a level corresponding to "1", and unless a communication device actively outputs a "0" signal, the potential of the bus line becomes "0". Does not drop to a level corresponding to "". Therefore, if the response signal is simply expressed as "1" by a 1-bit signal, it cannot be determined whether the response signal indicates a normal reception state or the communication device itself is disconnected 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 where 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 interrupted. In other words, the device described in the above-mentioned publication discloses that 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, the instantaneous interruption of the receiving communication device is to be recognized.

By the way, in a multiplex communication apparatus, as described above, the potential of the bus line does not decrease unless a "0" signal is transmitted in any of the communication apparatuses as described above. If “0” is output from the communication device, “1” is output from another communication device.
Is output, the potential of the bus line drops to a level corresponding to “0”.

Therefore, in the above-mentioned conventional device, the NAC is transmitted from at least one of the plurality of communication devices.
When the K signal is transmitted, “00” appears on the bus line as a response signal.
As a result, a communication abnormality can be recognized.

[0015]

However, in such a configuration, even if an instantaneous interruption occurs in any of the communication devices, if the data is normally received in another communication device and the ACK signal is transmitted. Finally, a response signal "10" appears on the bus line.

That is, the above-mentioned conventional multiplex communication apparatus can recognize the state as a communication abnormality when all the receiving communication apparatuses are instantaneously interrupted at the same time or when the transmitting communication apparatus is instantaneously interrupted. However, there has been a problem that a momentary interruption of some of the receiving communication devices cannot be recognized as a communication abnormality.

The present invention has been made in view of the above points, and when a receiving-side communication device has normally received data, a high-level signal as an ACK signal has not been received normally. In such a case, there is provided a multiplex communication apparatus that solves the above problem by returning a low-level signal as a NACK signal and lowering the potential of the bus line to a predetermined level between a high level and a low level at the time of an instantaneous interruption. The purpose is to:

[0018]

FIG. 1 is a block diagram showing the principle of a multiplex communication apparatus which achieves the above object. That is, as shown in FIG.
When performing communication between a plurality of communication devices connected to the receiving device, the receiving communication device M2 returns a response signal according to the receiving state upon receiving the data, and the transmitting communication device M3 performs the receiving based on the response signal. A multiplex communication device for judging a data reception state in the side communication device M2, wherein the reception side device M2 includes a reception state judgment unit M4 for judging whether or not data received from the bus line M1 is normal; When the data is determined to be normal by the reception state determination means M4, a high-level signal is output to the bus line M1, and when the data is determined to be abnormal, the potential of the bus line M1 is changed. Receiving state responding means M5 for outputting a signal to be low level;
And a bus potential lowering means M6 for lowering the potential of the bus line M1 to a predetermined level lower than the high level when the bus is disconnected from the bus line M1. A data transmission unit M7 for transmitting data including error detection data used by the communication device M2 to determine the state of received data to the bus line M1;
A level determining means M8 for determining the potential level of the bus line M1 when a receiving state response signal is returned from the receiving side communication device M2;
And a communication state determination unit M9 that determines a communication state between the plurality of communication apparatuses based on the determination result.

[0019]

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

The receiving state determining means M4 of the receiving 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. Then, it is determined whether or not the data has been received normally.

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

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

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 an instantaneous interruption occurs in at least one of the receiving communication devices M2 among the receiving communication devices M2 connected to the communication device M2, even if data is normally received in 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 does not rise to a high level.

The level determining means M8 of the transmitting communication device M3 determines whether the potential of the bus line M1 is at a high level or a low level, and instantaneously interrupts at any of the receiving communication devices M2. It is determined whether the level is a predetermined level generated when the communication has occurred, and the communication state determining means M9
Determines the communication state of the data transmitted by the data transmission means M7 based on the result.

[0025]

FIG. 2 is a block diagram showing a communication apparatus 10 constituting a multiplex communication apparatus according to an embodiment of the present invention. The communication device 10 of the present embodiment has the functions of the above-described receiving communication device M2 and transmitting communication device M3.

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

The communication device 10 includes the above-mentioned receiving state determining means M4, receiving state responding means M5, data transmitting means M7,
An electronic control unit (ECU) 20 for realizing the level determination unit M8 and the communication state determination unit M9, and a function corresponding to the bus potential lowering unit M6 described above are incorporated. It comprises a connector 30 for connecting 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 operation result of one of the communication apparatuses in another communication apparatus. It is effective when there is, for example, a plurality of in-vehicle ECUs mounted on a vehicle to perform various vehicle controls
Is configured as each communication device, the function can be effectively exhibited.

The ECU 20 is a device mainly composed of a CPU 22. The CPU 22 performs a predetermined calculation process based on the supplied data, and executes a plurality of other ECUs.
It has a multiplex communication function for realizing multiplex communication with the device.

That is, the multiplex communication apparatus of this embodiment also performs communication in the same manner as the conventional multiplex communication apparatus except for the response signal, and performs mutual data communication by serial communication via the bus line 12. The protocol has been determined. 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. In this embodiment, data transmission and reception are performed in accordance with the transmission frame shown in FIG. 4 as in the conventional apparatus.

The drive circuit 24 is a circuit that performs predetermined shaping on the signal output from the CPU 24 and outputs the signal to the bus line 12. That is, in the present embodiment, the output voltage of only the response signal is increased compared to the start signal, the ID signal, the message signal, the error detection signal, and the end signal among the signals output by the CPU 22 for the reasons described later. The drive circuit 24 performs a shaping process for realizing such a function.

More specifically, FIG.
When the transmission of a signal is started in accordance with the transmission frame shown in (1), the drive circuit 24 directs the output level (hereinafter, referred to as αV) of the CPU 22 from the start signal to the error detection signal and the end signal to the bus line 12 as it is. Output. Then, the CPU 22 only responds to the response signal.
(Hereinafter, the amplified output level is referred to as βV) and output to the bus line 12.

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

The response signal level detection circuit 26 is a circuit for monitoring the potential of the bus line 12 and detecting the 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 detecting three levels of V, αV, and βV separately. The response signal level detection circuit 26
Corresponds to the level determination means M8 described above.

The connector 30 is a member provided detachably with respect to the ECU 20, has a function of controlling the connection between the ECU 20 and a wire harness such as the bus line 12, the power supply line 14, and the like. This is a main part of this embodiment having a function as a potential lowering unit M6.

That is, the connector 30 includes the connector 3
A circuit is provided for guarding the potential of the bus line 12 to αV or less when there is an instantaneous interruption between 0 and the ECU 20. This circuit includes a Zener diode 32 connected to the bus line 12 and having a Zener voltage αV, 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 connected to the ECU 20
Are 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 higher than (β-α) V representing a high level appears at its output terminal.

In this case, the Zener diode 32 connected to the output terminal of the inverter 34 has 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. It has a withstand voltage (the upper limit is determined by the characteristics of the inverter 34).

On the other hand, if the contact between the connector 30 and the ECU 20 is not appropriate and the input terminal of the inverter 34 rises from the ground level, the potential of the
6 rises to the power supply voltage level connected via. Therefore, the output terminal voltage of the inverter 34 becomes low level, that is, 0 V, and the withstand 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 properly in contact with each other, the withstand voltage of the bus line 12 is maintained at βV or more, and when the connection is not appropriate. , The breakdown voltage of the bus line 12 decreases to αV. Such a function is not realized only between the illustrated connector 30 and the ECU 20, but is realized in all communication devices (connectors and ECUs) connected to the bus line 12.

By the way, in the multiplex communication apparatus of this embodiment, the transmission frame shown in FIG. 4 is used, and the response signal is represented by binary values of 0V-βV, and in other cases, it is represented by binary values of 0V-αV. The transmission and reception of the data signal by the represented signal is as described above.

FIGS. 3A and 3B show the potential of the bus line 12 when a data signal is transmitted according to such a protocol. FIG. FIG. 2B shows a case where data reception abnormality has occurred in at least one communication device, that is, at least one communication device has received an ACK signal from all communication devices. It shows a case where the device has transmitted a NACK signal.

In this case, if the ECU 20 is a transmitting-side communication device, the response signal level detection circuit 26
For the state of (A), “βV, 0” is used as a response signal.
V "is detected, and FIG. 3 (B)
With respect to the state, a response signal consisting of "0 V, 0 V" is detected.

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

That is, even if normal data reception is performed in all communication devices except for the communication device in which the instantaneous interruption has occurred and an ACK signal is transmitted in response thereto, the bus line 1
As shown in FIG. 3 (C), a response signal consisting of “αV, 0V” is generated on the line 2, which is different from the response signal shown in FIG. 3 (A).

The CPU 22 has a response signal level detection circuit 2
6, the change of the situation can be recognized, and the fact that some of the communication devices are in the non-response state due to the momentary interruption is distinguished from the case where all the communication devices normally transmit the ACK signal. You can figure out. In this sense, αV in this embodiment corresponds to the above-mentioned predetermined level.

Incidentally, an instantaneous interruption occurs in some communication devices,
At the same time, when a NACK signal is transmitted from another communication device, the NACK signal appears preferentially on the bus line 12, but the instantaneous interruption is a communication abnormality and is common to the data reception abnormality. However, there is little benefit in distinguishing the two, so this phenomenon is not a problem.

As described above, according to the multiplex communication apparatus of the present embodiment, when performing mutual data communication between a plurality of communication apparatuses, it is determined whether or not the data communication is normally performed and the instantaneous state of the connector. A non-response resulting from a disconnection or the like can also be reliably detected. Therefore, if measures such as resending data when an abnormality such as an instantaneous interruption is detected are taken, it is possible to secure high reliability as a multiplex communication device.

The instantaneous interruption of the connector has conventionally been a problem in an in-vehicle ECU used in an environment where vibrations are constantly applied, and the multiplex communication apparatus of the present embodiment is applied to a network composed of these in-vehicle ECUs. Especially effective.

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, the response signals are not necessarily formed. The response signal does not need to be a 2-bit signal.

That is, a high level signal is transmitted and received,
In a conventional device that can use only low-level and low-level binary signals, it is necessary to generate a low-level signal to indicate that the communication device is operating. Is the above FIG. 5 (A)
As shown in (1), a 2-bit signal was always required.

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 a situation in which some of the communication devices do not operate, the response signal may be configured with one bit.

In this case, as in the case where a response signal is formed using two bits, some communication devices do not operate and some communication devices are operating (FIG. 3C). Cannot be distinguished from the case where all the communication devices are not operating (the response signal of αV appears for 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 securing the function.

[0054]

As described above, according to the present invention, the response signal generated when the receiving side communication device is normal is high, the response signal generated when abnormal is low, and the response signal generated when the receiving communication device is momentarily interrupted is high and low. By setting the predetermined level between the levels, a response signal when an instantaneous interruption occurs in any of the receiving communication devices is obtained from a response signal when normal data reception is performed in all the receiving communication devices. Priority can be given, and priority can be given to a case where normal data cannot be received in any of the receiving communication devices over a response signal in a case where an instantaneous interruption has occurred in any of the receiving communication devices.

In this case, data is normally received in all the receiving communication apparatuses, and it is not necessary to take measures such as retransmission of data thereafter. It is possible to individually recognize situations in which measures such as data reception and data retransmission need to be taken.

Further, the multiplex communication apparatus according to the present invention shows three situations in which a 1-bit signal of a high level, a predetermined level, and a low level should be distinguished. Therefore, there is also a feature that the data length can be shortened as compared with a conventional device that requires 2 bits as a response signal.

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram of a communication device constituting a multiplex communication device according to an embodiment of the present invention.

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

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

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

[Description of Signs] M1, 12 bus lines M2 reception side communication device M3 transmission side communication device M4 reception state determination unit M5 reception state response unit M6 bus potential reduction unit M7 data transmission unit M8 level determination unit M9 communication state determination unit 10 communication Device 20 Electronic control unit (ECU) 22 CPU 24 Drive circuit 26 Response signal level detection circuit 30 Connector 32 Zener diode 34 Inverter 36, 38 Resistance

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H04L 12/28 H04L 25/00

Claims (1)

(57) [Claims] 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 reception state upon receiving data, and the transmitting communication device transmits the response signal according to a reception state. 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 data received from the bus line is normal. When the reception state determination means determines that the data is normal, a high-level signal is output to the bus line, and when the data is determined to be abnormal, the potential of the bus line is changed. Receiving state response means for outputting a signal to be set to a low level; and when the receiving side communication device is momentarily disconnected from the bus line, the potential of the bus line is lower than the high level. 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 to determine 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 receiving state response signal is returned from the receiving communication apparatus; and a plurality of communication apparatuses based on the determination result of the level determining means. A multiplex communication apparatus comprising: a communication state determination unit that determines a communication state.