JPH021647A - On-vehicle data transmission protocol - Google Patents

Abstract

PURPOSE:To improve transmission efficiency by priority-returning an error detection code and stopping the transmission of an error non-detection code when reception recognition codes having the detection code showing the presence of an error and the non-detection code showing the absence of the error collide. CONSTITUTION:When a node 1a judges that the error is present in a message M which it itself has read among nodes 1a-1d, it transmits an NAK signal on a network 2. An ACK signal is simultaneously transmitted from the other nodes 1b-1d. The nodes 1b-1d detect that there are the detection codes in priority higher than the error non-detection code which they themselves have outputted, and stop the transmission of the ACK signal hereafter, in the step transmitting the 1st bit of the ACK signal. The node 1f reads the NAK signal transmitted on the network 2, judges that there is the error in the reception of the message M of the node 1a and re-transmits the message M. Thus, the occupied time of the network is shortened and much more data can be transmitted.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an in-vehicle data transmission protocol used in a network that controls auxiliary equipment, and in particular relates to an in-vehicle data transmission protocol that improves message transmission efficiency. Concerning transmission protocols.

[Prior Art] FIG. 2 is a diagram showing the configuration of a part of an in-vehicle network provided in a vehicle V.

In this figure, Ia and Ib are nodes attached to the left and right sides of the front of the vehicle V, and control the lighting of various lights attached to the front of the vehicle (2).

I c and I d are nodes attached to the rear left and right sides of the vehicle V, and control the lighting of various lights attached to the rear of the vehicle (■). ! Reference character e is a node installed near a wiper motor (not shown) installed inside the vehicle V, and controls the operation of this wiper motor. The IF is a node that manually inputs signals from various switches attached to the driver's seat operation surface (not shown). These nodes L a - If are each assigned an identification code (hereinafter referred to as an address code) so that they can be distinguished from each other, and use this address code to exchange information with each other. In this case, messages in a predetermined format are used for information exchange. 2 is a network connecting nodes la to 1f.

Figure 4 is a diagram showing an example of a message format applied to the in-vehicle data transmission protocol. As shown in this figure, a message consists of a start bit, priority, message type, function code, sending node address, data ( (0 to 8 bytes), data end code, error check code, and reception confirmation code (#1 to N) area.

The priority of these areas is the message's priority.
It represents the priority of network use, and the message type represents the type of message, such as 1-to-I transmission, 1-to-N transmission, etc. The function code area differs depending on the message type, but in the case of one-to-one transmission, the address code of the node to which this message is sent is entered, and in the case of one-to-N transmission, the address code of the node to which the message is sent is entered. Contains the address group code. The sending node address represents the address code of the node that sends this message M onto the odd work 2. For example, from node Ir to node 1
When transmitting data to a=ld, the address code of node If is written in the sending node address area. In the data area, 0 to N pieces of data are written, each unit being 1 byte (for example, 8 bits is !byte). This data includes 0N10F'F data, U
There is P/D0 W N data, etc. Receipt confirmation code #1
-N is the ACK signal or NAK signal of each note returned from the node to which this message is sent. In this case, the number of ACK signals and NAK signals corresponding to the failure of the node receiving the message is written in the reception confirmation area. The ACK signal and NAK signal contain the address code of the node. The ACK signal is used to notify the transmitting node when the receiving node determines that it has received the transmitted message M without error. Further, the NAK signal is used to notify the transmitting node when it is determined that an error has occurred in the reception of the Moeki message M.

Here, an example of the specifications of an in-vehicle network is shown below for reference.

Table 1 Next, the data transmission protocol in the in-vehicle network will be explained based on the above-mentioned messages.

For example, when a switch for an illumination light (not shown) provided on the operation surface of the car V is turned on, a signal output from the switch is supplied to the node tr, which turns on the headlights and taillights. message is created.

At this time, since the transmission is 1-to-N, the code of the node group related to lighting the lights is written in the function code area, and the data for lighting the headlights and taillights is written in the data area. The created message is then sent to the network 2 and read by all nodes except node tr. At this time, each receiving node uses a function code to determine whether the message is necessary or not, and if it is not necessary, does not listen to the response (in this case, node le).

When each of the nodes and mills 1d that require a message determines that it has received the read message without error, it sends an ACK signal to the network 2. At this time, ACK signals are transmitted from four nodes at the same time, and there is a possibility that a collision will occur on the line, but the data string of the ACK signal directly represents the priority order, and the priority order can be determined by arbitration using the priority method. They are sent in order from highest to lowest. If bit "0" has priority over bit "1", for example, the priorities in the data string of the reception confirmation codes of nodes la to ld shown in FIG. 3 are as follows. That is, at the second bit, the node 1b becomes "L", so the node 1b stops sending out the ACK signal at this point. Next, at the 5th bit, the node IC becomes 1'', so at this point, the node lc becomes AC
Stop sending the K signal. Next, at the 7th bit, the node Id becomes "l", so at this point the node Id becomes "l".
stops sending the ACK signal. Thus, the ACK signal of node la remains and is sent to the network 2 up to the final bit. Thereafter, BACK signals are sent to the network 2 in order of priority, ie, node ld, node lc, and node lb.

Then, each ACK signal output to the network 2 is sequentially read into the node l'.
knows that the message was received correctly by all nodes that need it.

On the other hand, for example, if the node la determines that the message it has read contains an error, it sends a NAK signal to the network 2. At this time, the other nodes send an ACK signal to the network 2.

In this case, as above, N
An AK signal and an ACK signal are sent to the network 2.

Then, the NAK signal and ACK signal sent to network 2 are read into node 1.
Node Ir learns that an error occurred in the transmission of the message and retransmits the message.

Next, when a wiper switch (not shown) provided on the operation surface is turned on, a signal is supplied from the switch to the node If, and a message for operating the wiper motor is created. At this time, the message type area contains l pairs! A code indicating transmission is written in the function code area, an address code of the node le is written in the function code area, and data for operating the wiper motor is written in the data area. The created message is then read into the node le via the network 2. At this time, node Ie
When determining that it has received the read message without error, it sends an ACK signal to the network 2. and,
The ACK signal sent to the network 2 is read into the node 1r.

On the other hand, if the node Ie determines that there was an error in receiving the read message, it sends a NAK signal to the network 2.
Send to. And the NA sent out to network 2
The K signal is read into node If. At this time, since there is only one receiving node, there is also only one reception confirmation code.

[Problems to be Solved by the Invention] As mentioned above, when controlling auxiliary equipment, there are cases where a single switch, such as a wiper, operates one auxiliary equipment, and a single switch, such as a lighting device, operates multiple auxiliary equipment. auxiliary equipment may be operated.

By the way, when controlling one auxiliary device, the sending node only needs to receive one reception confirmation code from the receiving node, but when controlling multiple auxiliary devices, it is necessary to receive a large number of reception confirmation codes. becomes longer. Therefore, there was a problem in that the transmission time became long.

Here, the message length will be calculated with reference to the message format shown in FIG.

■For example, the start bit length is 2 bits, the priority is 5 bits, the message is being transmitted is 3 bits, the function code is 8 bits, the sending node address is 8 bits, the data is 8 x 8 bits, the data end code is 1 bit, and the error is 1 bit. If the check code is 8 bits, when l-to-l transmission is performed, the address code for one node (assuming 8 bits) and the 1-bit ACK/NAK signal are written in the ACK area, so the message length is 2+8+8+8+8X
8+1+8+9=108 people I.

On the other hand, if one-to-eight transmission is performed in each area in the same manner as above, the message length is 2+8+8+8+8x8+
I+8+8x9=171 bits. In this case, the message length will be approximately 1.5 times as compared to the above.

(2) On the other hand, if the data is 8 bits and one-to-one transmission is performed, the message length will be 52 bits.

On the other hand, when 1:8 transmission is performed, the message length is 115 pits. In this case, the message length will be approximately twice that of the above.

In this way, when 1:N transmission is performed, the message length becomes longer and the transmission time becomes longer than when 1:1 transmission is performed.

A countermeasure against this problem is to increase the message transmission speed, but increasing the transmission speed causes the problem that it becomes more susceptible to the effects of noise.

This invention was made in view of the above-mentioned circumstances, so even when performing 1-to-N transmission, the transmission time can be shortened to the same level as 1-to-1 transmission without increasing the transmission speed. The purpose is to provide an in-vehicle data transmission protocol.

[Means for solving the problem 1] In order to solve the above-mentioned problems, according to the present invention, it is possible to prevent an error from occurring during message transmission during message formatting in a distributed control network constructed from several notebooks. A reception confirmation code field indicating the presence or absence is provided, and the message data string corresponds to the priority order of network use, and each message is arbitrated bit by bit when a collision occurs between the messages on the network. In an in-vehicle data transmission protocol that transmits a high-priority message without destroying it, and returns a reception confirmation code sent from a node that receives the transmitted message to the notebook that sent the message, the message The reception confirmation code field is for one node, and the reception confirmation code is composed of a detection code indicating whether or not an error has occurred during the message transmission, and this reception confirmation code is made up of the address code of the node to which the reply is to be sent. When a reception confirmation code having an error detection code indicating that there is no error and a reception confirmation code having an error non-detection code indicating no error collide on the network, the reception confirmation code having the error detection code is given priority and the message is transmitted. When you reply to the node,
The present invention is characterized in that a node that returns a reception confirmation code that replaces the error non-detection code stops sending the reception confirmation code.

[Effect] As in the case of ``Two Footprints'', the error detection code has priority over the error non-detection code, and the reception confirmation code sent over the network is only for one note, so that if a certain note becomes the target. If a message is sent to a node that
The least of the nodes that received this message
If the notebook determines that there was an error in the message transmission, the notebook sends an error detection code over the network. Then, when the error detection code is sent out, other nodes that received the message without error detect that there is an error detection signal on the network that has a higher priority than the error non-detection code that they output on the network. and stops sending the confirmation signal onto the network. Therefore, the node that sent the message can know the existence of a node that could not normally receive the message by receiving the error detection code sent out on the network.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the format of a message M applied to an in-vehicle data transmission protocol, which is an embodiment of the present invention. Note that this data transmission protocol is applied to distributed control of a network.

In this figure, the format of message M is the conventional message format (see Figure 4) except for the reception confirmation code field.
It is similar to Specifically, the ACK signal is rlj+r
The address code "NAK signal is roJ+r address code".

In this case, bit "0" and bit "l" are error detection display codes that indicate whether an error has occurred in the transmission of message M. Of these, "0" indicates that an error has occurred, and rN is Each indicates that no error has occurred, and the priority is set as "0">"I". This error detection indication code is then assigned to the most significant bit of the reception confirmation code.

Here, the reason why a reception confirmation code is allocated to one node during message formatting is as follows.

By giving the right to preferentially use Bubuto Work 2 (see Figure 2) to the node that outputs the NAK signal,
The note that sent message M reads the reception confirmation code for one node on network 2, and checks whether the message transmission was completed without error on all the notes.
Alternatively, it can be known whether an error has occurred in message transmission in at least one node. That is,
There is no need to check for each node that reads the message M whether the message M has been transmitted without error. Therefore, the notebook that transmits the message M only has to transmit the message M repeatedly a predetermined number of times until the ACK signal is output on the network 2.

In this way, it is possible to determine whether or not to retransmit message M depending on whether the reception confirmation code for one note output on network 2 is 80K or NAK. There is no need to receive an acknowledgment signal from the node. Therefore, it is sufficient to allocate the reception confirmation code for one node during the formatting of the message M.

Next, a data transmission protocol in a vehicle network will be explained based on the message M described above with reference to FIG.

For example, if a message M is sent onto network 2 from node 1r, which has set the function code so that the message will be received by node 1a-1 (I), if there is no collision, all nodes other than node 1r (Ia ~ le), and it is determined whether the message M is necessary or not based on the function code in the message M. In this case, as described above, the message M is set to be imported into the node Ia-1d. Then, when each node l mill 1d determines that the message M that it has taken in is accurate, it outputs an ACK signal onto the network 2. At this time, the ACK signal is simultaneously received from the four nodes. is output, so a collision occurs, but since the 1st bit is the same ACK signal for all 4 nodes, output continues, and the address code with the highest priority is selected by arbitration based on the priorities of the address codes themselves from the 2nd bit onward. The ACK signal output from the holding node ultimately remains.

Then, the ΔCK signal remaining on network 2 until the end is read into node ld. As a result, node 1r
determines that each of the nodes Ia=I+4 has received the message M without error, and does not retransmit the message M.

- For example, note t that read message M”
When node 1a among nodes Ia to 1d determines that the message M that it has read contains an error, it sends a NAK signal onto network 2. At this time, an ACK signal is simultaneously sent from other nodes 1 b - 1 d to network 2 north, but at the stage of sending the first bit of the ACK signal, node I b - 1 d detects that its own output j and error detection are not detected. It is detected that an error detection code with a higher priority than the code exists on the network 2, and subsequent transmission of ACK signals is stopped. Then, N sent out on network 2
The AK signal is read into node If. Thus, node 1'' Ir determines that an error has occurred in the reception of message M by node la, and retransmits message M.

In this way, the node that sent the NAK signal uses network 2 with priority over the node that sent the ACK signal, so if even one node determines that there was an error in the transmission of message M, network 2 A NAK signal is sent. Therefore, the node that transmitted the message M can determine whether or not it is necessary to retransmit the message M by simply reading the reception confirmation signal for one node sent onto the network 2. This is no different from the conventional case in which a node that sent a message examines the reception confirmation signals returned from all the nodes to which the message was sent and determines whether retransmission is necessary. No inconvenience will occur.

[Effects of the Invention] According to the present invention, in a distributed control network constructed by several m nodes, a reception confirmation code column is provided during message formatting to indicate whether an error has occurred during message transmission, and the message data The priority order of network use corresponds to the column, and when a collision occurs between the messages on the network, each message is arbitrated bit by bit, so that the message with a higher priority is transmitted without being destroyed. , in an in-vehicle data transmission protocol in which a reception confirmation code sent from a node that receives the transmitted message is returned to the node that sent the message, the reception confirmation code field of the message is for one node; The reception confirmation code is composed of a detection code indicating whether or not an error has occurred during the message transmission, and an address code of the node that returns this reception confirmation code, and a reception confirmation code having an error detection code indicating that there is an error and an error detection code indicating that there is no error. If a reception confirmation code having an error non-detection code or a reception confirmation code having an error detection code collides on the network, the reception confirmation code having the error detection code is given priority and is returned to the node that sent the message, and the reception confirmation code having the error non-detection code is returned to the node that sent the message. Since the sending of the reception confirmation code of the node that returns the confirmation code is stopped, even in the case of 1-to-N transmission, the length of the message is 1 pair! The length will be the same as for transmission. Therefore, in the case of l-to-N transmission, the length of the message is reduced compared to conventional transmission. The network occupancy time is shortened and more data can be transmitted (transmission efficiency is improved). Furthermore, since there is no need to increase the transmission speed, there is no need to increase the transmission speed, so there is no influence from noise.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a message format applied to an embodiment of the present invention, Fig. 2 is a diagram showing a part of the configuration of a network installed in a car, and Fig. 3 explains an example of priority order. FIG. 4 is a diagram showing a message format applied to a conventional in-vehicle data transmission protocol. 2...Network, 1a=1f...Node, M...Message.

Claims (1)

[Claims] In a distributed control network constructed by multiple nodes, a reception confirmation code field is provided in the message format to indicate whether an error occurred during message transmission, and the priority of network use corresponds to the message data string. When a collision occurs between the messages on the network, by arbitrating each message bit by bit, messages with higher priority are transmitted without being destroyed, and the transmitted messages are transmitted from the node receiving them. In an in-vehicle data transmission protocol that returns a reception confirmation code to the node that sent the message, the reception confirmation code field of the message is for one node, and the reception confirmation code is sent to the node that sends the message. The reception confirmation code is composed of a detection code indicating an error and an address code of a node that returns this reception confirmation code, and a reception confirmation code having an error detection code indicating that there is an error and a reception confirmation code having an error non-detection code indicating that there is no error. If there is a collision, the reception confirmation code having the error detection code is given priority and is returned to the node that sent the message, and the reception confirmation code of the node that returns the reception confirmation code having the error non-detection code is An in-vehicle data transmission protocol characterized by stopping transmission.