JP2770281B2 - Data transmission method - Google Patents

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 In a case where a plurality of electronic control units (hereinafter, referred to as "ECU") are connected by a common signal line (hereinafter, referred to as "network bus") to mutually transmit data, FIG.
It is conventionally known to use a message having a configuration as shown in FIG.
No.).

In FIG. 1, one message has a SOM (Start of Message) field indicating the start of the message, and a DESNODE (Destin) indicating the destination of the message.
ation Node) field, ECU that received the message
Comprises an ACK (Acknowledge) field for transmitting a reception confirmation signal, a DATA field indicating transmission data, an FCS (Frame Check Sequence) field for performing error detection, and the like. The ECUs that make up the network
Are called nodes.

The DESNODE field has, for example, a 16-bit configuration as shown in FIG. 1B, in which each bit corresponds to each of a plurality of ECUs (nodes N1 to N16) or a physical address (N1 to N16). ) Is converted to a function address, and the function address is displayed.

On the other hand, the ACK field is
Similarly to the E field, the ECU having the configuration as shown in FIG. 3B or the ECU (for example, the EC of the nodes N3, N5 and N8) which has received the message as shown in FIG.
U) is known in which reception acknowledgment signals are transmitted in descending order of priority. In the latter case, one EC
When U detects that the message transmitted by itself and the message on the bus are different (collision of the message), it determines that the message transmitted by the other ECU has a higher priority and suspends the transmission of the message. . When the transmission is stopped, retransmission is performed, and as a result, a reception acknowledgment signal is transmitted in descending order of priority.

[0006]

However, when the ACK field is configured as shown in FIG. 8B, there is a problem that the message becomes longer and the time required for acknowledgment becomes longer. In the case of the configuration shown in FIG. 3C, the receiving ECU always detects the presence / absence of a message collision on the bus when transmitting the reception confirmation signal, and retransmits the message when a collision occurs. This necessitates a problem that communication control of the ECU is complicated.

Particularly, in a control system for a vehicle, it is necessary to transmit detection data of the driving state of the vehicle, and the time required for the transmission must be minimized.

The present invention has been made in view of the above points, and has as its object to provide a data transmission method that can reduce the time required for message reception confirmation and the load on the communication control device. I do.

[0009]

Means for Solving the Problems] To achieve the above object the present invention is mounted on a vehicle, a data transmission method for sending and receiving messages between a plurality of control devices mutually connected by a common signal line, transmission The control device on the side includes a data field composed of data to be transmitted, an address field for defining a transmission destination of the data, and a field for confirming reception of the data.
A message including a response bit and an acknowledgment field consisting of one blank bit is transmitted,
When the control device receives the data normally, the control device
Send an acknowledgment signal in the acknowledgment bit,
The control device on the side sets the acknowledgment bit at two different times.
By sampling at points, the presence or absence of an acknowledgment signal
And if there is the acknowledgment signal, send the data.
It is determined that the communication has been completed .

[0010]

[0011]

The control device on the transmitting side is composed of data to be transmitted.
The data fields to be transmitted and the destination of the data
Address field and confirmation of receipt of the data
1-bit acknowledgment bit
And an acknowledgment fee consisting of one blank bit
Send a message containing the
Acknowledges the acknowledgment
A reception acknowledgment signal in the
The device samples the acknowledgment bit at two different times.
Check if there is a reception confirmation signal by pulling
If the reception confirmation signal is present, the transmission of the data is completed.
Is determined.

[0012]

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 are mutually connected via a network bus 6. The ENG control ECU 1 controls the operation of the engine according to the accelerator pedal operation of the driver of the vehicle. The MISS control ECU 2 controls the automatic transmission according to the driving state of the vehicle. The TCS control ECU 3 controls the automatic transmission. An ECU that detects the slip state of the drive wheels of the vehicle and controls the output torque of the engine, and a suspension control ECU 4 controls the suspension (active suspension) according to the driving state of the vehicle.
U, the brake control ECU 5 is an ECU that detects the locked state of the wheels and performs brake control. These ECUs 1
5 to 5 need to mutually monitor control parameters and operating parameters detected by sensors, are connected via a network bus 6, and mutually transmit and receive 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 includes 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 has a bus line 107
(Random Access Memory) 102 via the
M (Read Only Memory) 103 and a communication control IC (Inte
grated Circuit) 105. Communication control I
C105 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, for example, temporarily storing data being calculated. 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. The transmission terminal of the communication control IC is connected to the base of a transistor 115 via a resistor 114. The emitter of the transistor 115 is connected to the ground, the collector is connected to the network bus 6, and connected to the power supply line VSUP via the resistor 116 and to the non-inverting input of the comparator 111 via the resistor 117. The inverting input of the comparator 111 is
It is connected to the ground via a resistor 113 and to the power supply line VSUP via a resistor 112. The output of the comparator 111 is connected to the receiving terminal of the communication control IC 105.

With the configuration shown in FIG. 3, the output of the comparator 111 changes to high / low in response to the high (high) / low (low) signal level on the network bus 6, and the bus 6
The above signal can be received. Communication control IC
The collector of the transistor 115 changes to low / high in accordance with the high / low of the transmission output of 105, and a signal is sent to the network bus 6.

The ECUs 2 to 5 are basically configured similarly to the ECU 1. Therefore, even if one ECU sends a high-level signal to the network bus 6, the other ECU
When U sends a low level signal, the signal on the bus 6 goes low, so in this embodiment the low level is dominant (dominant) and the high level is recessive (inferior).

FIG. 4 is a diagram showing the format of a message used for data transmission in this embodiment. One message is a SOM field, a DATA ID field, a DESNODE field (address field), and a DATA field (data field). , FC
It consists of an S field, an ACK field (acknowledge field), and an EOM field. In the following description, the ECUs 1 to 5 are referred to as 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 a different identifier is set for all data. The priority of the message is determined by this identifier as described later.

The DESNODE field is a field indicating a data transmission destination, and in this embodiment, is shown in FIG.
As shown in FIG. 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 becomes 10101000000000000000. In this embodiment, since the number of nodes is 5, 11
Although the bits are not used, up to 16 nodes can be handled in consideration of system expansion (node increase).

The DATA field is a field including the length of data to be transmitted and the data. FC
The S field has a CRC (Cyclic Redundancy) for a data string from the SOM field to the DATA field.
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 reception of a message. In the present embodiment, the transmitting side transmits two recessive bits and receives the message. The side performs a reception acknowledgment by overwriting one dominant bit. Therefore, when there are a plurality of nodes to be received, if at least one node performs a reception acknowledgment, the transmitting node determines that data transmission is completed and does not retransmit the data.

With the ACK field having such a configuration, the time required for reception confirmation can be reduced, and the load on the communication control IC can be reduced. Also, if the data transmission rate is increased in order to improve the real-time property of data (for example, about 1 Mbit / sec),
Although there may be a problem due to the transmission delay, as described above, this problem is prevented by forming the ACK field as a two-bit structure and setting the reception acknowledgment signal to one bit, that is, providing one blank bit. be able to. This point will be described with reference to FIGS.

FIG. 5 shows a case in which one blank bit is not provided. If there is a data transmission delay Td, the transmitting node determines at the transmission end time t1 of the FCS field.
It takes at least 2Td until the time t2 when the reception confirmation signal is received. Therefore, the reception acknowledgment signal is output at time ts
, The reception confirmation signal cannot be checked.

On the other hand, in the present embodiment, as shown in FIG. 6, by providing a blank bit and sampling the reception confirmation signal at times tsa and tsb, it is possible to reliably check the reception confirmation signal.

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

In the above-described configuration of the ACK field, if there are a plurality of receiving nodes, it is not possible to perform reception confirmation for each reception node. However, if a reception confirmation signal is returned, at least one of the nodes will surely receive. And if the other nodes fail to receive data normally due to some problem, it can notify the transmitting node by sending an error frame. Therefore, an error can be detected except when the connection is not established.

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

Next, the data transmission procedure will be described.

A node having data to be transmitted first confirms whether or not the network bus 6 is in an idle state (no signal state). When the node is in an idle state, the nodes sequentially transmit messages from the SOM field. By this message transmission, arbitration is performed when a message collision occurs in the DATAID field.

For example, a message including data of the intake pressure Pb is transmitted from the ENG control ECU 1 and the
When a message including data of the vehicle speed V is sent from the SS control ECU 2, the output of the ENG control ECU 1 matches the signal on the bus as shown in FIG. 7, so that the ENG control ECU 1 continues sending the message. . On the other hand, MI
The SS control ECU 2 determines that the arbitration has been lost at this point, and stops the subsequent transmission, because the signal transmitted by the SS control ECU 2 does not match the signal on the bus in the bit indicated by the arrow in FIG. Therefore, the transmission / reception of the intake pressure Pb is performed with priority over the vehicle speed V.

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

[0034]

As described in detail above, in the data transmission method according to the present invention, the control device on the transmitting side transmits the data to be transmitted from
Data field and a destination of the data.
Address field and the reception confirmation of the data.
1-bit acknowledgment bit
And an acknowledgment fee consisting of one blank bit
Send a message containing the
Acknowledges the acknowledgment
A reception acknowledgment signal in the
The device samples the acknowledgment bit at two different times.
Check if there is a reception confirmation signal by pulling
If the reception confirmation signal is present, the transmission of the data is completed.
Received from the control device on the transmitting side.
Data transmission delay time to the control device on the side cannot be ignored
Even in this case, it is possible to reliably perform the reception confirmation, and it is possible to reduce the time required for the reception confirmation and the load on the communication control device.

[Brief description of the 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 illustrating a configuration of an electronic control device that configures the system of FIG. 1;

FIG. 3 is a diagram showing a specific configuration of a bus interface of FIG. 2;

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 a transmission delay cannot be ignored.

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

FIG. 7 is a diagram for explaining arbitration when a message collision occurs.

FIG. 8 is a diagram for explaining a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine control electronic control unit 6 Network bus 101 Central processing unit (CPU) 105 Communication control IC 106 Bus interface

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04L 12/40

Claims (1)

(57) [Claims] In 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, a control device on a transmission side includes a data field including data to be transmitted. And an address field for specifying a destination of the data, and a field for confirming the reception of the data, wherein
A message including an acknowledgment bit and an acknowledgment field consisting of one blank bit is transmitted, and when the control device on the receiving side has normally received the data, the reception acknowledgment bit is received in the acknowledgment bit . And the transmitting control unit sends the acknowledgment bit to two different
Sampling at a certain point in time
A data transmission method comprising: confirming the presence / absence; and determining that the transmission of the data is completed if the reception confirmation signal is present .