JPH05316124A - Data transmission method - Google Patents

Abstract

PURPOSE:To prevent a defect of data caused by a transmission delay and to increase the transmission speed in the data transmission system comprising plural controllers. CONSTITUTION:A message used for data transmission consists of a SOM field indicating the start of the message, a DATAID field representing an identifier of data, a DESNODE field representing a destination of the data, a DATA being data to be sent, an FCS field representing the result of error check calculation, an ACK field for acknowledge of reception and an EOM field representing the end of the message. The DATAID field consists of the identifier and idle bits, and the ACK field consists of bits for reception acknowledge and idle bits. Since idle bits are provided to the fields, even when a transmission delay in data is not negligible, arbitration and acknowledge of reception are accurately implemented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission method for transmitting and receiving data between a plurality of electronic control units mounted on a vehicle.

[0002]

2. Description of the Related Art When a plurality of electronic control units (hereinafter referred to as "ECU") are connected by a common signal line (hereinafter referred to as "network bus") and data is mutually transmitted, CSM is used.
A / CD (Carrier Sense Multiple Access / Collision)
A method of performing bit arbitration in an arbitration field for determining the priority of a message based on the detection method has been conventionally known (SAE standard J.
1850, CAN proposed by Bosch, Germany
(Controller Area Network) etc.).

Here, the bit arbitration is, for example, a high-level bit is a dominant bit (dominant bit) and a low-level bit is a recessive bit (inferior bit) on a network bus, and when two or more messages compete with each other, a dominant bit. Is prioritized to determine the priority of the message.

Further, the message in the above-mentioned system includes an acknowledge field for confirming the reception of the message, and the ECU on the receiving side sends back a reception confirmation signal to the transmitting side.

[0005]

When the above-mentioned conventional data transmission method is applied to a data transmission system including a plurality of ECUs mounted on a vehicle, it is necessary to increase the transmission speed in order to transmit data at high speed. .. However, since a transmission delay occurs in the message transmission / reception circuit and the network bus, this delay cannot be ignored when the transmission speed is increased, and the following problems occur. In addition,
In the following description, each ECU that makes up the network
Is called a node.

Consider, for example, a case where the messages sent from the node A and the node B compete with each other and there is a transmission delay Td.
Here, if the arbitration field of the message sent by the node A is "1001100" and the arbitration field of the message sent by the node B is "1001000", if the transmission delay Td is so small that it can be ignored, the node A sends it. The message wins mediation. That is,
Since "1" is the dominant, the signal on the bus is "1001100", and the node A determines that the sending signal and the receiving signal match and that the arbitration has been won.

However, as shown in FIG. 9, the transmission delay Td
Is large enough to be ignored, it takes time T until the output signal of the node B ((b) in the figure) is received by the node A.
With a delay of d ((c) in the figure), the received signal of the node A becomes as shown in (d) in the figure. Therefore, the time points ts1 to t
In s7, when the received signal is sampled, the sampled signal becomes "1101100", and the node A
Will be different from the transmission signal of. As a result, node A becomes
Although it is supposed to win the arbitration, it will be mistakenly judged that it has lost.

When the node A sends a message to the node B and the node B returns a reception confirmation signal, it takes 2Td from the time when the node A finishes sending the data.
The reception confirmation signal is received after the elapse, and if the transmission delay Td is too large to be ignored, the reception confirmation signal may not be normally confirmed in the node A (see FIG. 5).

The present invention has been made in view of the above points, and it is an object of the present invention to provide a data transmission method capable of preventing an adverse effect caused by a data transmission delay and increasing a data transmission rate.

[0010]

In order to achieve the above object, the present invention provides a data transmission method for transmitting and receiving a message between a plurality of control devices mounted on a vehicle and connected by a common signal line. The message includes at least an arbitration field for determining the priority of data to be transmitted, and the arbitration field is designed to have a predetermined redundancy.

In order to achieve the same object, the present invention provides a data transmission method for transmitting and receiving a message between a plurality of control devices mounted on a vehicle and connected by a common signal line, wherein at least the message is transmitted. A field for confirming receipt of a message is included, and the field is configured to have a predetermined redundancy.

Further, it is preferable that the predetermined redundancy is such that the bit time is made longer than that of other fields, or that blank bits are inserted.

[0013]

The arbitration field is made redundant, and the influence of transmission delay in bit arbitration is eliminated.

The field for confirming the reception of the transmitted message is made redundant, and the influence of the transmission delay in the reception confirmation of the message is removed.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of a vehicle control system according to an embodiment of the present invention.
1 to 5 (referred to as “CU”) are connected to each other via a network bus 6. The ENG control ECU 1 is an ECU that controls the operation of the engine according to the accelerator pedal operation of the vehicle driver, the MISS control ECU 2 is an ECU that controls the automatic transmission according to the operating state of the vehicle, and the TCS control ECU 3 is The ECU that controls the output torque of the engine by detecting the slip state of the drive wheels of the vehicle, and the suspension control ECU 4 controls the suspension (active suspension) according to the operating state of the vehicle.
The U and brake control ECU 5 is an ECU that detects the locked state of the wheels and performs brake control. These ECU1
5 to 5 need to mutually monitor the operating parameters detected by the control parameters and the sensors, and are therefore connected via the network bus 6 to transmit and receive mutually necessary data.

FIG. 2 is a block diagram showing the configuration of the ENG control ECU 1. A central processing unit (hereinafter referred to as "CPU") 101 has a plurality of sensors 11 and actuators 12 such as fuel injection valves via an input / output interface 104.
It is connected to the. The CPU 101 uses the bus line 107
RAM (Random Access Memory) 102, RO
M (Read Only Memory) 103 and communication control IC (Inte
grated circuit) 105. Communication control I
The C 105 is connected to the network bus 6 via the bus interface 106.

The CPU 101 determines a control parameter based on the detection value of the sensor 11 according to a program stored in the ROM 103, and drives the actuator 12. The RAM 102 is used for temporary storage of data being calculated and the like. Further, the communication control IC controls transmission of a message to the network bus and reception of a message from the network bus.

FIG. 3 is a diagram showing a specific configuration of the bus interface 106 and the network bus 6. The network bus 6 is composed of twisted pair wires 6b and 6c terminated by a terminating resistor 6a.

The first transmission terminal of the communication control IC 105 is connected to the base of the transistor 119 via the resistor 115. The emitter of the transistor 119 is the power supply line V
The collector is connected to the SUP, and the collector is connected via the resistor 116 to the inverting input of the comparator 111 and one twisted pair wire 6
connected to b.

The second transmission terminal of the communication control IC 105 is connected to the base of the transistor 120 via the resistor 117. The emitter of the transistor 120 is connected to the ground, and the collector is connected via the resistor 118 to the comparator 11
It is connected to one non-inverting input and the other twisted pair line 6c.

The non-inverting input of the comparator 111 is a resistor 1
It is connected to the power supply line VSUP via 12 and is also connected to the inverting input of the comparator 111 via the resistor 113. The inverting input of the comparator 111 is connected to the ground via the resistor 114, and the comparator 1
The output of 11 is connected to the reception terminal of the communication control IC 105.

In the circuit of FIG. 3, resistors 116 and 11
8 is about 30Ω, resistors 112 and 114 are about 2 kΩ,
The resistance 113 is about 200Ω, and the terminating resistance 6a is about 100Ω.

Pulse signals whose phases are opposite to each other are output to the first and second transmission terminals of the communication control IC, and the first transmission terminal has a low level (low) and the second transmission terminal has a high level (high). At this time, both the transistors 119 and 120 are turned on, one twisted pair line 6b becomes high, and the other twisted pair line 6c becomes low. When the first transmission terminal is high and the second transmission terminal is low, both the transistors 119 and 120 are turned off, one twisted pair line 6b is low, and the other twisted pair line 6c is high. In this way, the signal is transmitted on the network bus 6.

The output of the comparator 111 changes to low / high corresponding to the high / low of one twisted pair line 6b, and the signal on the network bus 6 is received.

The ECUs 2 to 5 are basically constructed similarly to the ECU 1. Therefore, even if one ECU sends a signal that one twisted pair line 6b is low (6c is high), when another ECU sends a signal that is high, the signal on the twisted pair line 6b is high. So
In this embodiment, the state where the twisted pair line 6b is high (6c is low) is dominant (predominant), and the opposite state is recessive (inferior).

FIG. 4 is a diagram showing a format of a message used for data transmission in this embodiment. One message is an SOM field, a DATA ID field (arbitration field), a DESNODE field, a DATA field, an FCS field, It consists of an ACK field (acknowledge field) and an EOM field. In the following description, ECUs 1-5
Are called nodes 1 to 5.

The SOM field is a field indicating the start of a message. The DATAID field is a data identifier field, and different identifiers are set for all data. This identifier determines the priority of the message as described later.

Specifically, the DATA ID field is composed of a 7-bit identifier and a 7-bit blank bit (recessive bit) as shown in FIG. 4B. The blank bit is inserted so that arbitration, that is, determination of the priority order is appropriately performed even if there is a transmission delay, and the details will be described later.

The DESNODE field is a field indicating the destination of data, and in this embodiment, it is shown in FIG.
As shown in, the 16-bit field is used. One bit is assigned to one node, and the bit corresponding to the destination node is set to logic "1". For example, node 1,
When transmitting to 3 and 5, the DESNODE field is 1010100000000000000. In addition,
In this embodiment, the number of nodes is 5, so 11 bits are not used, but in consideration of system expansion (increase of nodes), up to 16 nodes can be supported.

The DATA field is a field including the length of data to be transmitted and the data. FC
The S field is a CRC (Cyclic Redundancy) for the data string from the SOM field to the DATA field.
This field indicates the result of performing (Check). It is calculated using the generator polynomial G (X) of the following equation (1).

G (X) = X ¹⁶ + X ¹² + X ⁵ +1 (1) The ACK field is a field for confirming the reception of the message, and in this embodiment, the transmitting side sends out two recessive bits and receives them. The side performs a reception confirmation response by overwriting one dominant bit. Therefore, when there are a plurality of nodes to be received, if at least one node makes a reception confirmation response, the transmitting node determines that the data transmission is completed and does not retransmit the data.

By configuring the ACK field in this way, the time required for confirmation of reception can be shortened and the load on the communication control IC can be reduced. In addition, if the data transmission rate is increased to improve the real-time property of the data (for example, about 1 megabit / second),
Although there is a possibility that a transmission delay may cause an adverse effect, this adverse effect can be prevented by configuring the entire ACK field as 2 bits and setting the reception confirmation signal to 1 bit, that is, by providing a blank bit of 1 bit. be able to. This point will be described with reference to FIGS. 5 and 6. Note that the transmission delay here is the sum of the delay generated in the transmission / reception unit of each node and the delay of the transmission line,
The delay of the transmission line is about 5 nsec / m for the twisted pair line.

FIG. 5 shows a case in which one blank bit is not provided, and if there is a data transmission delay Td, the transmitting node ends the transmission of the FCS field at time t1.
It takes at least 2Td until the time t2 at which the reception confirmation signal is received. Therefore, the reception confirmation signal is transmitted at the time point ts.
Even if sampling is done with, the reception confirmation signal cannot be checked.

On the other hand, in this embodiment, as shown in FIG. 6, a blank bit is provided and the reception confirmation signal is sampled at the times tsa and tsb, so that the reception confirmation signal can be surely checked.

Instead of providing the blank bit as described above, the bit time (1 bit time) of the ACK field may be set longer than the other fields as shown in FIG. Thus, if sampling is performed at the time point ts, the reception confirmation signal can be surely checked.

The structure of the ACK field may be, for example, 4 bits as a whole, and the receiving node may overwrite the 2-bit reception confirmation signal.

The EOM field is a field indicating the end of the message.

Next, a data transmission procedure will be described.

The node having data to be transmitted first confirms whether or not the network bus 6 is in the idle state (no signal state), and when it is in the idle state, sequentially sends messages from the SOM field. By sending this message, arbitration is performed when a message collision occurs in the DATAID field.

For example, the ENG control ECU 1 sends a message including the data of the intake pressure Pb, and at the same time MI
When a message including the vehicle speed V data is sent from the SS control ECU 2, the ENG control ECU 1 continues to send the message because the output of the ENG control ECU 1 matches the signal on the bus, as shown in FIG. .. On the other hand, MI
In the bit indicated by the arrow in the figure, the SS control ECU 2 does not match the signal sent by itself with the signal on the bus, so at this point, the SS control ECU 2 determines that it has lost arbitration, and stops the subsequent sending. Therefore, the intake pressure Pb is transmitted / received with priority over the vehicle speed V.

In this embodiment, the logic "1" corresponds to the dominant and the logic "0" corresponds to the recessive. Also, 3
The same arbitration is performed when the above messages conflict.

Next, a case where a data transmission delay becomes a problem will be described with reference to FIGS. 9 and 10. In these figures, the ENG ECU is a node A and the MISS ECU is a node B.

FIG. 9 shows a state in which the sending messages of the node A and the node B compete with each other when no blank bit is provided in the DATA ID field. As described above, since each node confirms that the bus 6 is in the idle state and starts sending the message, the message sending by the node B is the maximum with respect to the message sending by the node A, and the transmission between the nodes AB is the maximum. Delay by Td. Therefore, FIG. 9 shows this case.

Since the message sent by the node B ((b) in the figure) is as shown in (c) of the figure at the position of the node A, the received message of the node A is as shown in (d) of the figure. Become. Therefore, when sampling is performed at time points ts1 to ts7, the sampled signal becomes “1101100”, which is different from the transmission message “1001100” of the node A. As a result, although the node A should originally win the arbitration, it will make a wrong judgment that it has lost.

On the other hand, in this embodiment, since the blank bit is provided as described above, the output of the node A and the node B
And the output of node B at the position of node A is
10A to 10C, respectively, and the received message of the node A is as shown in FIG. 10D.
Therefore, the time points ts1a, ts1b, ts2a, ...,
Sampling is performed at ts7b, and tsia and ts
By taking the logical sum of the results of sampling with ib (i = 1 to 7), correct data (identifier) "1001100" can be obtained.

As described above, in the present embodiment, the blank bit is provided in the DATA ID field for arbitration when two or more messages compete with each other. Therefore, even if the transmission delay Td is not negligible, Accurate mediation (priority determination) can be performed.

Instead of providing a blank bit,
As shown in FIG. 11, the bit time may be set longer than other fields. Thus, by sampling the received message of the node A at the time points ts1 to ts7, correct data (identifier) “1001100” can be obtained.

[0049]

As described above in detail, according to the data transmission method of the present invention, data transmission is performed by a message having a predetermined redundancy in the arbitration field and / or the field for confirming reception of the transmitted message. Therefore, it is possible to prevent the adverse effect caused by the transmission delay and increase the data transmission rate.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a vehicle control system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an electronic control device that constitutes the system of FIG.

FIG. 3 is a diagram showing a specific configuration of the bus interface of FIG.

FIG. 4 is a diagram showing a configuration of a message transmitted and received between electronic control devices.

FIG. 5 is a timing chart for explaining reception confirmation when the transmission delay cannot be ignored.

FIG. 6 is a timing chart for explaining reception confirmation when transmission delay cannot be ignored.

FIG. 7 is a timing chart for explaining reception confirmation when the transmission delay cannot be ignored.

FIG. 8 is a diagram for explaining arbitration when a message collision occurs.

FIG. 9 is a timing chart for explaining arbitration when the transmission delay cannot be ignored.

FIG. 10 is a timing chart for explaining arbitration when the transmission delay cannot be ignored.

FIG. 11 is a timing chart for explaining arbitration when the transmission delay cannot be ignored.

[Explanation of symbols]

 1 Engine Control Electronic Control Device 6 Network Bus 101 Central Processing Unit (CPU) 105 Communication Control IC 106 Bus Interface

Claims (4)

[Claims] 1. A data transmission method for transmitting and receiving a message between a plurality of control devices mounted on a vehicle and connected by a common signal line, wherein the message determines at least a priority of data to be transmitted. A data transmission method, comprising: an arbitration field for, wherein the arbitration field is provided with predetermined redundancy. 2. A data transmission method for transmitting / receiving a message between a plurality of control devices mounted on a vehicle and connected by a common signal line, wherein the message is for at least confirming reception of the transmitted message. A data transmission method comprising a field, the field having a predetermined redundancy. 3. The data transmission method according to claim 1, wherein the predetermined redundancy is to make a bit time longer than other fields. 4. The data transmission method according to claim 1, wherein the predetermined redundancy is to insert a blank bit.