JPH05191415A - Multiplex communication system - Google Patents

Abstract

PURPOSE:To realize accurate network management by making the return of a reception confirming signal coincident with a substantial normal connection state of a communication node in a multiplex communication system returning the reception confirming signal when a signal is received. CONSTITUTION:The system is provided with plural communication nodes 12 composed of a multiplex module 18 having a transfer section 14 and a reception buffer 16 accumulating a reception signal and of a control section 20 reading a reception signal stored in the reception buffer 16 and controlling a controlled system based on the reception signal. The plural communication nodes 12 are connected to a common transmission line 2 to implement multiplex communication between the communication nodes 12 and the multiplex module 18 returns a reception confirming signal when the reception signal is received. In such a multiplex communication system, only when the control section 20 is in the read enabling state of the reception signal accumulated in the reception buffer 16, the multiplex module 18 returns the reception confirming 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 system used in, for example, a vehicle, in which a communication node for transmitting and receiving signals receives a reception confirmation signal when receiving a signal transmitted from another communication node. The present invention relates to a multiplex communication method for returning a message.

[0002]

2. Description of the Related Art In recent automobiles, the number of electronic control devices mounted has increased with the development of electronic control, and as a result, the problems of enlargement and complication of wiring connecting the electronic control devices have become remarkable. Is coming. Therefore, in order to solve such a problem, signal communication between a plurality of electronic control devices is performed by multiplex communication, that is, a communication node for a plurality of electronic control devices is connected to a common transmission line, and signal communication between the communication nodes is performed. It has been considered to perform multiplex communication and is being put to practical use.

As one of the communication control methods in the above-mentioned multiplex communication, there is known a time division multiplex communication in which a distributed control method in which each communication node independently controls the transmission / reception of signals of each communication node. In such a distributed control method, in order for each communication node to control the transmission / reception of its own signal, whether or not other communication nodes which are connected to the transmission line and constitute the network are normally connected to the transmission line. ,
That is, each communication node is required to grasp and manage whether or not the signal is normally received (connection management of the communication node).

Therefore, conventionally, for example, Japanese Patent Publication No. 58-5
As described in Japanese Laid-Open Patent Publication No. 00348, in performing multiplex communication between a plurality of communication nodes, each communication node returns a reception confirmation signal when receiving a transmitted signal, It is known that the other communication node is configured so that the other communication node can know that the communication node that has returned the reception confirmation signal is normally connected.

As a specific example of the multiplex communication device for confirming the reception as described above, a multiplex module having a communication node, a transmission / reception unit for transmitting and receiving, and a reception buffer for accumulating a received signal received, and the above And a control unit (CPU) for reading the received signal accumulated in the reception buffer and controlling the controlled object based on the read received signal. When the multiplex module receives the signal, the multiplex module stores the received signal in the reception buffer. An apparatus has been considered in which the reception confirmation signal is stored and returned to confirm reception, and the multiplex module and the control unit are simultaneously activated when the multiplex communication system is activated.

[0006]

By the way, in the connection management of the communication node in the multiplex communication as described above, it is not simply grasped and managed whether or not it is formally received, but it is substantially received. It is necessary to grasp and manage whether or not there is control, that is, whether or not control is performed based on the received signal as well as simply receiving.

However, when the control unit and the multiplexing module are simultaneously activated at the time of activation of the multiplex communication system as described above, the control unit performs a failure check of the control unit and the like for a predetermined time after the activation, and then accumulates in the reception buffer. The reception signal can be read out, that is, the reception buffer can be read, and the control target can be controlled based on the reception signal. However, the multiplexing module can perform transmission / reception and return of a reception confirmation signal simultaneously with the activation. Therefore, even if the control unit cannot read the received signal and perform control for a predetermined time after the activation, when the signal is sent, the signal is received by the multiplexing module and accumulated in the receiving buffer. Then, the reception confirmation signal is returned, and the reception confirmation signal causes the other communication node to recognize that the communication node on the reception side (reception node) is normally connected.

Therefore, in the above-mentioned conventional multiplex communication device, the return of the reception confirmation signal and the substantial connection state of the communication node do not coincide with each other until the control unit can read the reception buffer after the activation. Therefore, the other communication nodes mistakenly grasp the connection state of the receiving node, and various inconveniences occur due to the fact that the connection state of such a communication node cannot be accurately grasped and managed. There is a problem that it will occur.

Further, the problem that the return of the reception confirmation signal and the substantial connection state of the communication node do not match as described above may occur not only at the time of activation but also after activation. That is, the control unit is not always capable of reading once it becomes possible to read the reception buffer. For example, the control unit may read the reception buffer because it performs other control unrelated to the reception signal. In some cases, even if a signal is received and a reception confirmation signal is returned, in that case, control based on the received signal is not actually carried out, and the same problem as in the case of the above-mentioned start occurs.

In view of the above circumstances, an object of the present invention is to provide a multiplex communication system in which the return of the reception confirmation signal and the substantial connection state of the communication node are made to coincide with each other, whereby the network management can be accurately performed. To provide.

[0011]

In order to achieve the above object, a multiplex communication system according to the present invention includes a multiplex module having a transmitting / receiving unit for transmitting and receiving and a receiving buffer for accumulating a received signal, and the above receiving unit. A plurality of communication nodes each including a control unit that reads a reception signal accumulated in the buffer and controls a control target based on the read reception signal, and connects the plurality of communication nodes to a common transmission line The multiplex module is a multiplex communication method in which multiplex communication is performed between each communication node and the reception module returns the reception confirmation signal when the reception signal is received. Only when the received signal that has been read is ready to be read,
The multiplexing module is configured to return the reception confirmation signal.

[0012]

As described above, the multiplex communication system according to the present invention allows the multiplex module to receive the reception confirmation signal only when the control section is ready to read the received signal stored in the reception buffer. Is configured to be returned. Therefore, when the reception confirmation signal is returned, the control unit can always read the received signal and control the controlled object based on the signal, that is, the return of the reception confirmation signal and the substantial connection of the communication node. It is possible to match the status, and the reception confirmation signal is sent back despite the formal connection status in which the reception is being performed but the control based on the reception signal is not performed, so that the connection is normally established. It is possible to prevent erroneous recognition that there is an error, and avoid various inconveniences due to incorrect connection management of the communication node.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings. The embodiment described below is a multiplex communication system for a vehicle according to the present invention, which is so-called CSMA /
This is an example applied to a device adopting a network access method called a CD-AMP system. CSMA here
(Carrier Sense Multiple Access) means a method in which each communication node confirms the availability of the transmission path when a transmission request occurs and performs transmission, and CD (Collision Detection) means
Each communication node means a method of monitoring the transmission signal of the transmission line and performing retransmission control when detecting a signal collision.
rbitration onMessage Priority) means a method in which a high-priority message is transmitted as it is without being damaged when signals collide.

<Multiple Transmission Device> This embodiment is implemented by the multiplex communication device shown in FIG. The illustrated device is a common transmission line (bus) 2 composed of a looped twisted pair wire.
Are provided, and four multiplex communication nodes are connected to the transmission line 2. In this embodiment, there are four communication nodes, and an EGI node 4 for performing engine control,
4WS node 6 for performing four-wheel steering control, and ABS / TRC node 8 for performing tire slip control
And a body system node 10 for controlling body-related switches.

Signal transmission between the communication nodes 4, 6, 8 and 10 is carried out via the transmission line 2 by multiplex communication based on the CSMA / CD-AMP system which is a time division distributed control system. Since each communication node controls transmission / reception of its own signal, it has node connection information (information on whether each communication node is normally connected to the transmission line) based on the ACK field described below. There is. In addition, the signal transmitted by any one of the nodes is set to be received by all the other nodes.

The communication nodes 4, 6, 8 and 10 are connected to the transmission line 2 via a connector 12 as shown in FIG. Each of the communication nodes 4, 6, 8 and 10 includes a multiplex module 18 having a transmission / reception unit 14 for transmitting / receiving and a reception buffer 16 for storing received signals, and a control unit 20 which is a host CPU connected to the multiplex module 18. And a reset circuit 22 connected to the control unit 20. The control unit 20 controls the multiplexing module 18 and also controls the input interface 24 and the output interface 26.
The EGI node 4 is connected to an engine as a control target to control the engine, and the 4WS node 6 is connected to a rear wheel steering device as a control target. Then, the rear wheel steering device is controlled, the ABS / TRC node 8 is connected to the brake device or engine as a control target to control the brake device or engine, and the body system node 10 is a switch as a control target. Is connected to the switches to control the switches.

<Signal Frame> Each communication node 4, 6,
In performing the above-mentioned transmission, each of the 8 and 10 transmits information of its own node, such as various vehicle driving information and control information, for each frame by the signal frame F having the configuration shown in FIG. To receive. The frame F includes an SOM code, PRI code, ID code, data length, data 1 to data N, CRC code, E.
It has a structure having an OD code, an ACK field, and an EOM code.

The above-mentioned "SOM code (start of message code)" is a specific code indicating the start of the frame F, and each node recognizes the start of the frame F when receiving this SOM code. .. The above-mentioned "PRI code (priority code)" is a code indicating a priority order that indicates which signal should be preferentially processed when a plurality of communication nodes transmit data at the same time and the signals collide. In this embodiment, the lower the bit value, the higher the priority is assigned. This is because the low level is WIRED-OR in the transmission line 2. If signals are sent from multiple nodes at the same time, the "PRI code" of the node with the higher priority remains on the transmission path 2, and the lower node uses the "PRI code" sent by itself as another code. A collision is detected due to the change, and the self-failed frame is retransmitted. The "ID code (frame ID code)" is a code indicating the transmission source of the corresponding frame. The number of data that follows is written in the "data length". If there are N data, N is sent as the data length. The node receiving this frame reads the data of the data length. In the "data 1 to data N", various information to be transmitted by the frame is written. The "CRC code" is an error detection code, the "EOD code" is an end of data code indicating that the data is at the end, the "ACK field" is a reception confirmation signal area for confirming reception, and the The "EOM code" is an end of message code indicating the end of the frame.

<ACK field> The ACK field is made up of, for example, bits corresponding to the number of communication nodes connected to the transmission path 2 (4 bits because four communication nodes are connected in this embodiment). A predetermined unique bit area is assigned to the communication node.
Each communication node confirms normal reception by each bit area of the ACK field. That is, the communication node (transmission node) that transmits the signal frame sets each bit area of the ACK field to “0” and transmits the signal frame to the transmission line when transmitting the signal frame. Communication node (reception node) on the side that receives this signal frame
Is the data 1 of the frame received by the check code
It is checked whether or not there is an error in the contents of ~ N, and if there is no error, a reception confirmation signal (ACK signal) "1" is transmitted to a predetermined unique bit area for each receiving node. In this case, the transmitting node is also receiving the signal frame at the same time as it is transmitting, and if it is normally received, ACK
The ACK signal “1” is transmitted to the bit area unique to the transmitting node in the field.

Therefore, when each communication node normally receives the transmitted signal frame, all the bit areas of the ACK field on the transmission line 2 are "1", and if any of the receiving nodes is normal. When not receiving, the bit area peculiar to the receiving node which has not received remains “0”. Therefore, the transmitting node is
Upon receiving the field, each receiving node confirms whether or not the signal frame is normally received, and if any of the receiving nodes recognizes that the signal frame is not received, the same signal frame is retransmitted.

Even when the signal frame is retransmitted in this way, the ACK field is included in the signal frame, and when the node that has not previously received the packet recognizes that it has normally received, the signal frame is retransmitted. If it is confirmed that it has not been normally received yet, it is retransmitted further. For example, if it is not received even if it is retransmitted 3 times, it is judged that the node is down and further retransmission is not performed. .

Also, each communication node recognizes that each communication node is normally receiving, that is, is normally connected by reading the ACK field, and the connection information of each communication node is sent to its own node. Hold and update this connection information each time a signal is sent.

<Activation / Deactivation of Multiplexing Module> In the multiplex communication device, only when the control unit 20 is in a state where the received signal accumulated in the receiving buffer 16 can be read out, that is, the receiving buffer 16 The multiplex module is activated only when is ready to be read. In this regard, refer to FIG. 4 showing the relationship between the multiplex module 18, the control unit 20 and the reset circuit 22 and FIG. 5 which is a time chart showing the operating / non-operating state of the control unit 20 and the multiplex module 18. While explaining.

In the multiplex communication device, the communication nodes 2, 4, 6 and 8 are system up by a predetermined activation signal such as an Ig-ON signal. In that case, first, at the time t ₁ based on the predetermined start signal, the reset circuit 22
Outputs an H (HIGH) signal to the reset terminal of the control unit 22, and the control unit 20 is activated in response to the H signal. The control unit 20 first performs a failure check of the control unit 20 and the like after the operation state, and during the failure check, the control unit 20 cannot read the reception buffer 16 of the multiple module, and the failure check ends. The reception buffer can be read only at the time (time t ₂ ). And the control unit
The 20 outputs an H signal from the port to the reset terminal of the multiplex module 18 when the reception buffer can be read, and the multiplex module is activated for the first time by this H signal, and the transmission / reception and reception by the transmission / reception unit 14 are performed. The received signal can be stored in the reception buffer 16, and the reception confirmation signal can be returned when the signal is received.

Further, the control unit 20 may not be able to read the reception buffer 16 not only at the time of a failure check at the time of start-up but also after that for various reasons, for example, because other control is performed. There is. The control unit 20
Even when the reception buffer 16 becomes unreadable after such activation, the port outputs an L (LOW) signal to the reset terminal of the multiplex module 18 to make the multiplex module 18 inoperative, that is, to transmit and receive. The reception confirmation signal is not returned, and when the reception buffer 16 can be read, an H signal is output from the port to the reset terminal of the multiplex module to activate the multiplex module 18 again.

In the multiplex communication system, as described above, the multiplex module 18 returns the reception confirmation signal only when the control unit 20 is ready to read the reception buffer 16 and assigns it to each communication node in the ACK field. The assigned unique bid area is set to "1". Therefore, the return of the reception confirmation signal, that is, the bit area "1" peculiar to each communication node of the ACK field and the reception buffer readable state of the control unit 20 always match and become equivalent, and accurate communication node connection information can be obtained. Yes, network management can be performed accurately.

The multiplex communication system according to the present invention need only be configured so that the multiplex module sends back the reception confirmation signal only when the control unit 20 is ready to read the reception buffer 16. However, in the above embodiment, as described above, the control module 20 activates the multiplexing module only when the reception buffer 16 can be read, and when the reception buffer 16 cannot be read, reception confirmation is simply performed. It is configured not to send back or receive signals, nor to send or receive. With this configuration,
The above embodiment has the following effects.

That is, in the above-described multiplex communication device, for example, signals may be continuously transmitted one after another from a predetermined transmission node, and a predetermined reception node may control the controlled object on the basis of the signal. is there. In such cases,
If the control module 20 cannot read the reception buffer 16 and the multiplex modules 18 receive signals one after another, the signals are sequentially accumulated in the reception buffer 16 and the reception buffer 16 receives the signals.
After 16 is full, it will not receive that signal. Then, after that, when the control unit 20 becomes able to read the reception buffer 16, the control unit 20 reads the old signal accumulated in the reception buffer 16 and controls the control target based on the old signal (of course, the reception target). After all the old signals stored in the buffer 16 have been read out, the multiplexing module
Control is performed based on the new signal received by 18),
Improper control will be performed.

However, in the above-described embodiment, the multiplex module 18 does not receive when the control unit 20 cannot read the reception buffer 16 as described above. The problem that the multiplexing module 18 receives a signal even though the reception buffer 16 cannot be read, and the signal is accumulated in the reception buffer 16, thereby performing control based on the old signal accumulated in the reception buffer 16. Can also be avoided.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a multiplex communication device that implements a multiplex communication system according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a signal frame.

FIG. 3 is a diagram showing an example of a communication node.

FIG. 4 is a diagram showing a relationship among a multiplexing module, a control unit, and a reset circuit.

FIG. 5 is a time chart showing operating / non-operating states of the multiple module and the control unit.

[Explanation of symbols]

 2 Transmission lines 4, 6, 8, 10 Communication node 14 Transmitter / receiver 16 Receive buffer 18 Multiplex module 20 Controller

Claims (1)

[Claims] 1. A multiplexing module having a transmission / reception unit for transmitting and receiving and a reception buffer for accumulating a reception signal, and controlling a control target based on the read reception signal read from the reception signal accumulated in the reception buffer. And a plurality of communication nodes each including a control unit for connecting the plurality of communication nodes to a common transmission line to perform multiplex communication between the communication nodes, and the multiplex module receives the received signal. In the communication node, the multiplex module returns the reception confirmation signal when the control signal is stored in the reception buffer. A multiplex communication system characterized by being configured to return an acknowledgment signal.