JP3750636B2 - Data relay apparatus and multiplex communication system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a data relay device and a multiple communication system.
[0002]
[Prior art]
In recent years, the advancement of information communication has progressed especially against the background of advances in computer technology. For example, even in automobiles, the amount of information exchanged between control units that control mounted electrical components has increased rapidly. Yes. Thus, multiple communication systems are being adopted to reduce the number of wire harnesses that transmit information. In a multiplex communication system, a communication node such as a control ECU that transmits and receives data is connected to a common multiplex communication line, and data communication is performed between the communication nodes via the multiplex communication line. The data includes the data main body and the type of information, and the received communication node can understand the contents of the data. In the case of the above-mentioned automobiles having various control types, a plurality of communication lines and nodes connected to the multiple communication lines are used in order to efficiently perform data communication according to a difference in required communication speed. There is a communication system that communicates between nodes belonging to different communication systems through a data relay device.
[0003]
In Japanese Patent Laid-Open No. 2000-244548, a data relay apparatus is provided with a buffer group including buffers that temporarily hold data to be relayed for each type of data body, and the buffer data is overwritten only by the same type of data. In this way, there is one that improves the reliability of data communication without preparing a huge buffer for temporarily storing relay data.
[0004]
[Problems to be solved by the invention]
By the way, if the communication speed differs greatly between communication systems, data relayed from a communication system with a high communication speed to a low-speed communication system may explosively increase. For this reason, the communication load becomes extremely high in a low-speed communication system, and communication is difficult to be established. For this reason, for example, in a data transfer process in which data received by a multiplex communication line of a high-speed communication system that is a relay source is first transferred from a reception buffer that temporarily holds data to the buffer group, a cycle of performing the transfer process is increased to some extent As a result, a sufficient time during which data transfer is not performed after completion of data transfer is provided so that the communication load of the relay destination communication system is not excessively increased.
[0005]
On the other hand, if the interval of the data transfer process from the reception buffer to the buffer group is sufficiently large so that the communication load of the relay destination communication system is not excessively increased, the data transfer to the buffer group is not performed in the reception buffer. Before it is done, the reception buffer is overwritten by the next reception data, and there is a high risk that the original data will be lost.
[0006]
In order to solve this problem, it is conceivable to secure the time until the reception buffer is overwritten with new data by sequentially transferring data from the reception buffer to the buffer group by FIFO. In the end, it is necessary to prepare a considerable number of reception buffers, and it is not always possible to sufficiently reduce the buffer size.
[0007]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a data relay apparatus and a multiplex communication system having a simple configuration with sufficient data communication reliability.
[0008]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided a data relay device for relaying a plurality of types of data interposed between multiple communication lines for transmitting data including the type of information together with the data body, In a data relay device having a buffer group consisting of buffers temporarily held for each data type,
The buffer group includes a first buffer group that temporarily holds data received on the relay source multiplex communication line, and data from the first buffer group is transferred to the relay destination multiplex communication line for transmission. The second buffer group temporarily holds data in advance, and in each buffer group, a buffer is assigned to each data type on a one-to-one basis.
[0009]
When data enters from the communication system of the relay source, the data is written in the buffer corresponding to the type of data in the first buffer group. This data is transferred from the buffer of the first buffer group to the buffer of the second buffer group. The communication load at the relay destination can be suppressed by increasing the interval of the transfer process. Here, even if a large amount of data enters the data relay device from the relay source communication system, the buffer of the first buffer group is overwritten only by the latest data of the same type, and the specific type of data is lost. There is no end to it. Accordingly, it is possible to reduce both the communication load at the relay destination by increasing the transfer processing interval and the prevention of the loss of other types of data due to the received data. In addition, since the buffers need only be provided in the number of types of data to be relayed in each buffer group, the configuration is simple.
[0010]
According to a second aspect of the present invention, the data relay device and a plurality of communication systems in which communication nodes for transmitting and receiving data are connected to the multiplex communication line are multiplexed so as not to impair the reliability of data communication due to loss of relay data. A communication system can be constructed.
[0011]
In the invention of claim 3, the plurality of communication systems are configured by communication systems having different communication speeds.
The first buffer group is used for temporarily storing received data using a communication system with a higher communication speed as a relay source.
[0012]
If the communication system of the relay source is a communication system having a high communication speed, a situation in which relay data tends to concentrate on a communication system having a low communication speed is likely to occur. By using the high-speed communication system as a relay source for temporarily storing received data, it is particularly effective to achieve both data relay reliability and a reduction in communication load in a communication system with a low communication speed.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
1A and 1B show a data relay device and a multiple communication system according to the present invention. The multiplex communication system is composed of a plurality (2 in the example) of communication systems 11 and 12 and a data relay device 4. Each communication system 11, 12 has communication nodes 31, 32 connected to multiple communication lines 21, 22, and transmits / receives data using a predetermined protocol between the communication nodes 31, 32 of each communication system 11, 12. It is like that. Here, the first communication system 11 has a protocol of CAN and a communication speed of 500 kbps, and the second communication system 12 has a protocol of BEAN and the communication speed is 10 kbps which is sufficiently slower than the communication speed of the first communication system 11. Suppose that The first communication system (hereinafter, appropriately referred to as a high-speed communication system) 11 is a communication system in which an ECU for engine control and an ECU for ABS control are connected to a multiplex communication line 21 as a communication node 31, for example. The second communication system (hereinafter referred to as a low-speed communication system as appropriate) 12 includes, for example, an ECU for controlling opening / closing of a door or an ECU for controlling air conditioning in a vehicle interior as a communication node 32 on a multiplex communication line 22. It is a connected communication system.
[0014]
Each of the multiple communication lines 21 and 22 is connected to the data relay device 4, and the data relay device 4 transfers the data transmitted from the communication nodes 31 and 32 to the communication nodes 32 and 31 belonging to different communication systems 11 and 12. It comes to relay.
[0015]
The data relay device 4 is constituted by a communication IC that interfaces with the multiple communication lines 21 and 22, a control microcomputer, and the like, and is represented by its functional block in the figure, and the reception buffers 411 and 412. , Transmission buffers 421 and 422, a buffer unit 43, a data controller 44, and the like.
[0016]
The reception buffers 411 and 412 and the transmission buffers 421 and 422 are provided for each of the multiple communication lines 21 and 22 in a one-to-one correspondence. In the reception buffers 411 and 412, data from the communication nodes 31 and 32 received by the multiplex communication lines 21 and 22 are first written and temporarily held. In the transmission buffers 421 and 422, data to be transmitted to the communication nodes 31 and 32 of the relay destination communication systems 11 and 12 is written immediately before transmission.
[0017]
The buffer unit 43 is a buffer group including a plurality of buffers 431. Each buffer 431 temporarily holds data written in the reception buffers 411 and 412 before being transferred to the transmission buffers 421 and 422, as will be described in detail later. It is like that. There are as many buffers 431 as the number of types of data bodies of data to be relayed (hereinafter referred to as data types as appropriate), and there is a one-to-one correspondence between each buffer 431 and a data type to which a part of the header portion of data is assigned. is doing. For example, if there are five types of data bodies to be transferred, five buffers 431 are prepared, and each buffer 431 is associated with the type of data to be written. The data type specifies what is meant by information such as a numerical value of the data body. For example, it is known that the data body indicates the engine speed. The data type corresponds to “ID” for the CAN protocol, and “DATAID” for the BEAN protocol. The data area of the buffer unit 43 is allocated on the RAM constituting the microcomputer.
[0018]
Further, as shown in FIG. 1B, the reception buffer 411 for the high-speed communication system 11 is a buffer group composed of a plurality of buffers 4111, and each buffer 4111 is provided corresponding to each data type on a one-to-one basis. is there. The configuration is similar to that of the buffer unit 43. On the other hand, the data type of data stored in the buffer 431 of the buffer unit 43 is the data type of data relayed from the communication system 11 to the communication system 12 and the data type of data relayed from the communication system 12 to the communication system 11. Is different in that the data type of data stored in the buffer 4111 of the reception buffer 411 is only the data type of data relayed from the communication system 11 to the communication system 12.
[0019]
The data controller 44 transfers data received on the multiplex communication lines 21 and 22 to the transmission buffers 421 and 422 for the communication systems 11 and 12 as relay destinations, and is executed by a CPU constituting the microcomputer. Realized above.
[0020]
FIG. 2 shows the contents of data transfer processing for transferring data received by the multiplex communication line 21 of the high-speed communication system 11 to the transmission buffer 422 for the low-speed communication system 12. In step S101, data reception processing is executed. FIG. 3 shows the contents of the data reception process. In step S201, processing for fetching data from the multiplex communication line 21 of the high-speed communication system 11 is executed. In step S202, the type of captured data is determined.
[0021]
In the subsequent step S203, the fetched data is set in the buffer 4111 corresponding to the determined data type, and the reception process is ended. In FIG. 3, a buffer n, a buffer m, and a buffer l mean a buffer 4111 corresponding to the data type n, the data type m, and the data type l, respectively.
[0022]
The data reception process is executed not only in the data transfer process but also by an interrupt, and all data to be relayed can be set in the corresponding buffer 4111 of the reception buffer 411. The processing speed is set in consideration of the communication speed of the high-speed communication system 11.
[0023]
In step S102, it is determined whether there is reception data in the buffer 4111 of the reception buffer 411. If a positive determination is made, the process proceeds to step S103, and if a negative determination is made, the process returns to step S101. In step S103, data is fetched from the buffer 4111, and transfer processing is executed in step S104. In the transfer process, the data is written into the buffer 431 of the corresponding data type in the buffer unit 43. This is executed for all the buffers 4111 of the reception buffer 411 in which data is written.
[0024]
For example, the presence or absence of data may be checked sequentially for all the buffers 4111, and if there is data, writing to the buffer 431 may be executed, or when data is received from the high-speed communication system 11 In addition, the data types may be listed in a list provided on the RAM, and the listed data types may be written to the buffer 431. After the writing to the buffer 431 is completed, the data in the buffer 4111 of the data type and the data type on the list are deleted.
[0025]
Further, a schedule is set so that the transfer process is started at a predetermined interval. This predetermined interval defines the communication load in the low-speed communication system 12 as will be described later. When the transfer process is performed, the process returns to step S102.
[0026]
The reception buffer 421 for the low-speed communication system 12 is a single-stage buffer similar to the conventional one or a multi-stage buffer that is read by a FIFO or the like, and received data is written as needed. Then, the data is transferred to the buffer 431 of the buffer unit 43 corresponding to the data type. The transfer process can be executed together with the transfer process from the reception buffer 411 for the high-speed communication system 11 to the buffer unit 43 in step S104.
[0027]
The data stored in the buffer 431 of the buffer unit 43 is transferred by the data controller 44 to the transmission buffers 421 and 422 corresponding one-to-one with the data type according to the data type. Similar to the transfer process from the reception buffer 411 to the buffer unit 43, the transfer process is performed by checking the presence / absence of data in all the buffers 431, or by listing the data type of the buffer 431 in which the data has been written. It is executed based on the list. The transfer destination is specified based on the transfer destination table that associates the transmission buffers 421 and 422 of the transfer destination with the data type.
[0028]
Since the actual interval at which data is transferred from the buffer 431 to the transmission buffers 421 and 422 of the buffer unit 43 is not shorter than the interval of the transfer processing from the reception buffers 411 and 412 to the buffer 431, the buffer 431 is slow. The interval of data transfer processing to the transmission buffer 422 for the communication system 12 depends on the predetermined interval, which is the interval of transfer processing from the reception buffer 411 for the high-speed communication system 11 to the buffer 431. The longer the predetermined interval, the longer, and the communication load of the low-speed communication system 12 is reduced.
[0029]
On the other hand, every time data to be relayed is transmitted from the communication node 31 of the high-speed communication system 11 to the low-speed communication system 12, the data is written in the reception buffer 411. In the reception buffer 411, each buffer 4111 is the same. Overwritten only by type of data. Therefore, even if the transfer interval from the reception buffer 411 to the buffer 431 is set long as described above, data of a specific data type is not lost when a large amount of data is transmitted from the high-speed communication system 11. .
[0030]
The data stored in the buffer 431 is transferred to the transmission buffer 422 for the low-speed communication system 12 at a predetermined cycle, but the transfer interval from the reception buffer 411 to the buffer unit 43 is suppressed, so that the processing interval is suppressed. Does not increase the communication load in the communication system.
[0031]
When a receive buffer for a high-speed communication system is used in a FIFO, if a large-scale buffer configuration is used, the loss of data in the receive buffer can be substantially prevented, but the data is stored in the buffer unit that is the transfer destination. , The data is overwritten by the same type of data and disappears. Therefore, even if the reception buffer is allowed to be overwritten with the same type of data as in this data relay apparatus, there is no disadvantage compared to the FIFO reception buffer. Rather, the configuration in which the reception buffer is used in the FIFO has to increase the number of stages of the reception buffer according to the communication speed of the high-speed communication system, whereas the size of the reception buffer does not depend on the communication speed of the high-speed communication system, It can be said that the configuration is superior to that in which the reception buffer is a FIFO system in that it can be surely prevented from being overwritten by data of different data types.
[0032]
Further, the reception buffer 412 for the low-speed communication system 12 includes a plurality of buffers corresponding to the data types relayed from the low-speed communication system 12 to the high-speed communication system 11 like the reception buffer 411 for the high-speed communication system 11. A buffer group consisting of Problems such as failure to establish control due to loss of received data can be reliably prevented.
[0033]
Further, although the description has been given of the multiplex communication system having two communication systems, the present invention can be applied to a communication system having three or more communication systems.
[Brief description of the drawings]
1A is a configuration diagram of a data relay device and a multiplex communication system according to the present invention, and FIG. 1B is a main part of the data relay device.
FIG. 2 is a first flowchart showing control executed in a data controller of the data relay device.
FIG. 3 is a second flowchart showing control executed in a data controller of the data relay device.
[Explanation of symbols]
11, 12 Communication systems 21, 22 Multiple communication lines 31, 32 Communication node 4 Data relay device 411, 412 Reception buffer (first buffer group)
4111 Buffers 421 and 422 Transmission buffer 43 Buffer unit (second buffer group)
431 Buffer 44 Data controller

Claims (3)

A data relay device that relays a plurality of types of data interposed between multiple communication lines that transmit data including the type of information together with the data body, and temporarily stores the data to be relayed for each type of data In a data relay device having a buffer group consisting of buffers,
The buffer group includes a first buffer group that temporarily holds data received on the relay source multiplex communication line, and data from the first buffer group is transferred to the relay destination multiplex communication line for transmission. A data relay apparatus comprising: a second buffer group that temporarily holds data in advance, and in each buffer group, a buffer is assigned to each data type on a one-to-one basis. A multiplex communication system comprising: the data relay device according to claim 1; and a plurality of communication systems in which communication nodes for transmitting and receiving data are connected to the multiplex communication line. The multiplex communication system according to claim 2, wherein the plurality of communication systems are configured by communication systems having different communication speeds.
A multiplex communication system in which the first buffer group is used for temporarily storing received data using a communication system having a higher communication speed as a relay source.

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