JPH0427241A - Multiplex transmission method - Google Patents

Abstract

PURPOSE:To send out the message of every data in order corresponding to the occurrence frequency, etc., by providing a data priority bit for showing the priority of each data and a node priority bit for showing the priority of each node. CONSTITUTION:A message 7 to be sent out is configured by data PB 4 for showing the priority of data handled by each ECU being a node, a node PB 5 for showing the priority of each ECU, and a data bit 6 for showing the contents of each data. The data handled by each ECU is classified into plural groups in accordance with the occurrence frequency or every response delay allowable time, and the priority of the data is allocated in order of from that of the high occurrence frequency to that of the low occurrence frequency, or from that of a short allowable time to that of a long allowable time. For instance, in the case the data is classified into four groups, in order from the highest priority, for instance, '0001', '0010', '0011', and '0100' are allocated as the data PB 4 of 4 bits. Subsequently, the message of every data is sent out to the bus from the ECU in order corresponding to its occurrence frequency, etc.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is applicable to CS SMA/CD (Carrie
r 5ense Multiple Access w
The present invention relates to a multiplex transmission method for multiplex transmission of messages using a method (column detection).

[Conventional technology]

Conventionally, there are various control methods for transmitting a plurality of pieces of information through one transmission path, but the CSMA/CD method is generally adopted for multiplex transmission in automobiles.

By the way, to briefly explain the multiplex transmission method using the CSMA/CD method in automobiles, when transmitting data from sensors etc. via a bus between ECUs corresponding to nodes installed in various parts of the car. , When multiple ECUs transmit data at the same time and a data collision occurs, the transmission is stopped starting with the data with the lowest priority, the data with the highest priority is transmitted first, and the transmission is stopped after an arbitrary amount of time has elapsed. This is to retransmit the data.

In this way, in order to determine which data should be prioritized, a priority is conventionally assigned to each ECU that is a node, and node priority bits (hereinafter referred to as priority pits) representing the priority of each assigned ECU are used. PB) is transmitted together with the data to be transmitted.

That is, as shown in FIG. 7, message 3 consisting of a node PBI representing the priority of the ECU and data bit 2 representing data content is sent from the ECU to the bus, and message 3 is sent from multiple ECUs simultaneously. Each ECU that sent message 3 when a conflict occurred
By each, the node PBI of conflicting message 3
The ECU determines the transmission order based on the priority of the node P that has a higher priority than its own priority.
When it is determined that there is a message 3 consisting of B1, the transmission of the message 3 by the ECU is stopped, and the message 3 is transmitted again after an arbitrary period of time has elapsed.

By the way, in the case of multiplex transmission in automobiles, each ECU handles many types of data, and one ECU
Among the data handled by the system, there are data that has a high degree of occurrence and should be transmitted in a high order, and data that has a low degree of origin and should be transmitted in a low order, and there are multiple pieces of data that have different degrees of occurrence.

In this way, when one ECU handles multiple data with different raw [f[, the degree of generation of the message sent by the ECU is synchronized with the highest degree of generation of each data handled by this ECU. However, the priority according to the highest generation opening degree among the generation opening degrees of each data is assigned as the priority of the ECU.

[Problem to be solved by the invention]

Therefore, in the conventional case, all the data handled by one ECU with different degrees of opening are sent out at once as one message, resulting in a very long message length, resulting in a decrease in line utilization efficiency, and In some cases, it is necessary to increase the transmission speed to ensure response time, and the increase in transmission speed has the problem of increasing radiated noise.

Therefore, this invention was made to solve the above-mentioned problems, and it is possible to prevent a decrease in line usage efficiency and improve line utilization efficiency without increasing the transmission speed in message multiplex transmission using the CSMA/CD method. The purpose is to enable effective use of.

[Means to solve the problem]

The multiplex transmission method according to the present invention provides a CS between a plurality of nodes.
In a multiplex transmission method that performs multiplex transmission of messages using the MA/CD method, the message is expressed as a data priority bias representing the priority of a plurality of data handled by each of the nodes, and a priority of each of the nodes. It is composed of a node priority bit and a data bit representing the content of each data, and each node determines the transmission order based on the priority according to the data priority bit, and the priority according to the data priority bit is equal. In this case, the transmission order is determined based on the priority determined by the node priority bit.

[Effect]

In this invention, a data priority bit representing the priority of each data and a node priority bit representing the priority of each node are provided, and the transmission order is first determined based on the priority by the data priority bit. Then, to determine the transmission order based on the priority by the node priority bit,
Even when one node handles multiple pieces of data with different frequencies of occurrence and allowable response delay times, messages for each piece of data are sent from the node to the bus in order according to their frequency of occurrence, etc., and one message is processed. The line length does not become as long as in the past, and there is no need to increase the transmission speed to ensure response time, and line utilization efficiency can be improved.

〔Example〕

FIG. 1 is an explanatory diagram of a message format in an embodiment in which the multiplex transmission method of the present invention is applied to transmission in an automobile.

As shown in the figure, there is data PB4 (PB is a priority bit) that represents the priority of multiple data handled by each ECU, which is a node, a node PB5 that represents the priority of each ECU, and the contents of each data. The message 7 to be sent is constituted by the data bits 6 representing the message.

At this time, the data handled by each ECU is classified into multiple groups according to frequency of occurrence or allowable response delay time.
If data priorities are assigned in order of occurrence frequency to group, or from short to long allowable time groups, and are classified into four groups, for example, 4 bits are assigned in descending order of priority. As data PB4, "0001"0010""0
011" and "0100" are assigned.

In comparison with the conventional message format shown in FIG. 7, by providing the data PB4, one message 7 contains only one data, and one ECU handles multiple data with different occurrence frequencies, etc. Even in cases where messages are sent from the ECU to the bus in accordance with their frequency of occurrence, the length of one message does not become as long as in the past.

Here, the length of the data bit 6 is not particularly fixed.

Next, FIG. 2 is a block diagram of a transmission system in an automobile that multiplex transmits messages in the format shown in FIG. 1. As shown in FIG.
, a third ECUIO1 for the meter, and a fourth ECUll for the driver's door control are connected to the bus 12, respectively,
Messages are sent from each ECU 3 to 11 to bus 12, and multiplex transmission of messages is performed between each ECU 3 to 11 via bus 12.

By the way, for example, each EC with the first ECU 8 as a high priority
Priorities are assigned to U3-11, and each ECU3-11 is assigned priority.
11, for example, as a 4-bit node PB5, “
00010 “0010” “0011°,”0100
” etc., message formats corresponding to each data handled by each ECU 3 to 11 are shown in FIGS. 3 to 6, respectively.

However, FIGS. 3 to 6 show some examples of messages sent from each ECU 3 to 11,
As mentioned above, if the data PB4 is 4 bits, the number of messages that one ECU can send is 16. Furthermore, if the node PB5 is 4 bits as described above, the number of ECUs that can be connected to the bus 12 is 16. .

The message sent from the first ECU 8 for engine control is message 7.7 7 as shown in Fig. 3, and the message ^I A2° ^3 - 7Al is as shown in Fig. 3(a). For example, the data content is the throttle close signal 5C (3) and the throttle open signal So (3), which occur frequently (10 ss), and the message 7^2 is, as shown in FIG. High degree (100+s) oil pressure data OIL
, each indicator data P, N, R of the torque converter (hereinafter referred to as torque converter).

D and L are data contents, and message 7A3 is shown in the same figure (
Engine control diagnosis data EG-D (8) with low occurrence frequency (500ss) as shown in e)
Let be the data content.

Next, the message sent from the second ECU 9 for brake control is the message 7Bl"B2"B3 as shown in FIG. 4, and the message 7B□ is the opening degree as shown in FIG. The data content is the shock absorber control signal SAB (3) with a high value (10 S), and the message 7B2 is as shown in FIG.
Next, the parking brake signal PBK (1) with the highest opening degree (100ss) and the warning lamp signal LP
The data content of the message 7B3 is the brake control diagnosis data BK-D (8), which has a low occurrence frequency (500 ss), as shown in FIG. 7(e).

Furthermore, the message sent from the third ECU 10 for the meter is message 7. as shown in FIG. 7.
7, but as shown in the same figure (b), CI C2C
Since there is no data content corresponding to message 7c2, which has the second highest occurrence frequency (100+s), only messages 7 and 7c3 are actually sent, and message 7°1 is ), the speed signal 5P (8) has a high frequency of occurrence (10ms).
The data content of the message 7.3 is the meter diagnosis data MT-D (8), which has a low occurrence frequency (500 ms), as shown in FIG. 7(C).

Further, messages sent from the fourth ECU 11 for driver's door control are message 7. as shown in FIG. 7. 7, but the same Di D2
03 As shown in Figure (a), there is no data content corresponding to message 7D1, which occurs frequently (10 S), so only message 7.7 is actually sent.
3, and message 7D2 occurs in the passenger seat with the second highest occurrence frequency (100ss), as shown in FIG. 3(b).

Up control signal P/ for each power window on the left and right rear seats
W UP FL, P/W UP RL, P
/W UP RR, and power window down control signal for passenger seat and rear left and right seats P/W DNFL,
The data contents are P/W DN RL and P/W DN RR, and message 7D3 contains door control diagnosis data DR-D (8) with a low occurrence frequency (500+ns) as shown in the same figure (C). Data content.

Therefore, for example, if message 7 from the first ECU 3 and message 7Bl from the second ECU 9 are sent to the bus 12 at the same time, the first ECU 8 determines the priority of the message 7Bl based on the data PB4, and at the same time the message 7Bl from the second ECU 9 is sent to the bus 12. The priority of message 7Al according to data PB4 is determined, and as a result of the determination, the priority according to data P^l old B4 of both messages 7.7 is the same, so message 7
．． The priority of node PB5 of 7 is determined in the same way as in the old AI.

As a result of the judgment, node PB5 of message 7Al
Since the priority given by node PB5 is higher than the priority given by message 7Bl to node PB5, sending of message 7B+ from second ECU 9 is stopped and message 7^1 from first ECU 8 is preferentially transmitted over the bus.

Further, even if messages are sent from three or more ECUs at the same time, the same processing is performed.

In this way, the data PB4 representing the priority of each data handled by each ECU 3 to 11 and the node PB5 representing the priority of each ECU 3 to 11 are provided.
The transmission order is determined based on the priority given by the node PB5, and if the priorities are the same, the transmission order is determined based on the priority given by the node PB5. Even when handling messages, messages for each data are EC-coded in order according to their frequency of occurrence, etc.
U to bus 12, the length of one message can be prevented from increasing as in the past, there is no need to increase the transmission speed to ensure response time, and the efficiency of line usage can be improved. can be achieved.

Note that in the above embodiment, the data PB4 and the node PB5
Although the description has been made using the case where each bit is 4 bits, the present invention is not limited to this.

Furthermore, in the above embodiment, the case where four ECUs were used as nodes was explained, but two or three ECUs were used as nodes.
U, even when using 5 or more ECUs,
Of course, this invention can be implemented in a similar manner.

Furthermore, although the above embodiment describes the case where it is applied to an automobile, the application target is not limited to automobiles in particular, and the present invention can be applied to various devices and two devices that adopt multiplex transmission using the CSMA/CD method. Needless to say, it can be applied.

〔Effect of the invention〕

As described above, according to the multiplex transmission method of the present invention, data priority bits representing the priority of each data and node priority bits representing the priority of each node are provided. Even when handling data, messages for each piece of data can be sent from the node to the bus in an order based on the frequency of occurrence, etc., and the length of one message can be prevented from increasing as in the past. There is no need to increase the transmission speed to ensure response time, and the line usage efficiency can be improved, making effective use of the line, and is particularly effective in multiplex transmission in automobiles.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a message format in an embodiment of the multiplex transmission method of the present invention, FIG. 2 is a block diagram of a transmission system that transmits the message format of FIG. 1, and FIGS. FIG. 7 is an explanatory diagram of a message sent from a transmission system node in the figure, and FIG. 7 is an explanatory diagram of a message format in a conventional multiplex transmission method. 4...Data PB (data priority bit) 5
...Node PB (node priority bit) 6.
...Data bit 7...Message 8-11...1st to 11th ECU

Claims (1)

[Claims] (1) In a multiplex transmission method for multiplexing messages between a plurality of nodes using the CSMA/CD method, each of the nodes includes a data priority bit representing the priority of a plurality of data handled by each of the nodes; consists of a node priority bit representing the priority of the data, and a data bit representing the content of each data, and each node determines the transmission order based on the priority based on the data priority bit, and A multiplex transmission method characterized in that, when priorities are equal, transmission order is determined based on priorities determined by the node priority bits.