Data transmission method for communication controller

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a communication control device connected to a multiplex transmission line to transmit a message, and more particularly to a data transmission method of a communication control device for transmitting data.

【0002】

[Conventional technology]

Conventionally, as shown in FIG. 6, a multiplex node having this type of communication control device includes a communication control device (LSI) 11 connected to a multiplex transmission line (multiplex bus) MB composed of a pair of electric wires and the like, and a control circuit (a control circuit). It consists of a CPU) 12 and an input / output interface (I / F) circuit 13. The CPU 12 takes in events (data) from various switches and the like via the I / F circuit 13, and the LSI 11 has a transmission buffer memory for storing the data of the message input from the CPU 12 and the data ID for identifying the data. The message in the transmission buffer memory is being transmitted to the multiple bus MB. In addition, some multiple nodes that have an LSI that controls communication do not have a CPU. In this case, after storing the data and data ID captured via the I / F circuit 13 in the data buffer memory, It was stored in the transmission buffer memory and transmitted to the multiple bus MB. These multiple nodes are connected to multiple buses to form a network, and CSMA / CD (Carrier Sense Multiple Access / Collision) It is used for multiplex transmission of data in automobiles, for example, by using a detection) transmission method. In the node where the event has changed, the CPU 12 writes the transmission data to the transmission buffer memory of the LSI 11 and generates a transmission request. Upon receiving the transmission request, the LSI 11 starts transmitting the transmission data, and the CPU 12 can write the next transmission data after the transmission of the LSI 11 is completed and the transmission buffer memory becomes empty. ing.

【0003】

FIG. 7 is a diagram showing an embodiment of a message format of a data frame transmitted between multiple nodes. In the figure, the above data frame is followed by an SOM (Start Of Message) indicating the start of a message, a priority (PRI) that determines the priority when a plurality of multiple nodes simultaneously transmit data to a multiple bus, and a subsequent data frame. A message ID indicating the contents of each data (DATA), a control data area (CONT) containing data indicating the data length, a data area of a length (variable length) indicated by CONT (DATA1 to DATA4), CRC, etc. Error check code, EOD (End Of Data) indicating the end of data, ACK signal area for returning ACK signal with bit support from all multiple nodes, and ACK signal returned from all registered nodes. It has a 1-bit ACK confirmation area indicating that data transmission has been completed and an EOM (End Of Message) indicating the end of the message.

【0004】

Here, as shown in FIG. 8, the transmission multiplex node transmits a data frame consisting of SOM to EOD via the multiplex bus, and the other multiplex nodes receive the data normally without any error in advance. The ACK signal is returned to the specified ACK signal area. When the basic multiplex node having the ACK management function confirms that the ACK signal has been returned from all the registered nodes, it sends a dominant ACK confirmation bit to the ACK confirmation area. In FIG. 8, the transmit multiplex node A and the receive multiplex node E correspond to the basic multiplex nodes, and the receive multiplex nodes B, C, and D are simple multiplex nodes without an ACK management function. Now, if there is no ACK return from the receive multiplex node B, the transmit multiplex node A does not send the ACK confirmation bit and retransmits the data frame. This retransmission operation ends after being repeated a certain number of times, for example, X times, and if the registration of the receiving multiplex node B is deleted, the retransmission is repeated indefinitely when a certain node fails and does not return an ACK signal. There is no such thing as a node. When the simple multiplex node transmits a data frame, when the above ACK confirmation bit is received, it is determined that the data transmission has been performed normally and the transmission is terminated, and when the above ACK confirmation bit is not received, transmission is performed. Resend after determining that an error has occurred. This retransmission operation was also completed after X times.

【0005】

Further, when new data to be transmitted occurs before the transmission is completed, the transmission request of the data already written in the transmission buffer memory may be canceled and new data may be written.

【0006】

[Problems to be Solved by the Invention]

However, in the above-mentioned conventional example, when the data stored in the transmission buffer memory is in the state of waiting for transmission, even if the event changes, the latest data is transmitted only after the data in the transmission buffer memory is transmitted. Can not do it. For example, in the case of data transmission in an automobile, when the data called wiper-on is stored in the transmission buffer memory, even if the horn data changes from off to on, the wiper-on data in the transmission buffer memory is transmitted. There is a problem that the latest horn-on data cannot be transmitted until after this is done, and the transmission of the more necessary latest data is delayed.

【0007】

Further, if the transmission request of the data already stored in the transmission buffer memory is canceled, there is a problem that the data is lost. Therefore, there is a problem that a buffer memory for a queue is required and the cost is increased. Also, if a transmission error occurs when sending a certain message and the transmission request is canceled during retransmission, the data held by both will differ between the node that was able to receive the message and the node that was not able to receive it. There was a problem that it would end up.

【0008】

The present invention has been made in view of the above problems, and an object of the present invention is to provide a data transmission method of a communication control device capable of quickly transmitting the latest data with high necessity.

【0009】

[Means for solving problems]

In order to solve the above object, the present invention has a transmission storage means connected to the multiple transmission line and storing the data of the message to be transmitted to the multiple transmission line, and the input data of the data is transmitted. In the data transmission method of the communication control device that temporarily stores the data in the storage means and then transmits the data to the multiple transmission line, a change in the input data is detected, and when the change in the data is detected, the data is stored in the transmission storage means. It detects whether or not the transmitted data is in the state of being retransmitted, and when the data stored in the transmission storage means is in the state of being retransmitted, the changed data is sent to the transmission storage means. A data transmission method of a communication control device is provided, in which the storage is stopped until the retransmission of the data stored in the transmission storage means is completed. According to claim 2, when the data stored in the transmission storage means is data that can be received differently between the nodes, the data stored in the transmission storage means is being retransmitted. Also, by storing the input data in the transmission storage means, there is provided a data transmission method of a communication control device capable of transmitting the input data more quickly.

【0010】

[Action]

Only when the data stored in the transmission storage means consisting of the transmission buffer memory is being retransmitted, the storage of the latest changed data in the transmission storage means is stopped, and in the state of waiting for transmission, the latest data It enables storage in the transmission storage means. Therefore, the latest data with high necessity can be quickly transmitted without the data being different between the nodes on the network, and the reliability of data transmission in the communication control device can be improved.

【0011】

[Example]

An embodiment of the present invention will be described with reference to the drawings of FIGS. 1 to 5. FIG. 1 is a configuration block diagram showing a configuration of a communication control device according to the present invention. In this figure, a simple multiplex node having no CPU and no ACK management function is shown. In the figure, the input port 21 takes in data from various switches and the like as a parallel signal as in FIG. The communication control device includes an input port 21, an output port 22, a port control unit 23, a transmission buffer memory 24 for storing transmission data, a reception buffer memory 25 for storing received data, and a communication control unit 26. The node shown in this embodiment has only one type of transmission ID, and the content of the transmission frame is as shown in FIG. That is, the transmission ID is data that identifies the node, and one bit of the data area corresponds to one input port. If even one of the above input ports changes, the data of all ports will be latched, and the data of input port A will be in the area of DATA1, and the data of input ports B, C, and D will be in DATA2, 3, and 4, respectively. It is stored in the area and sent.

【0012】

The port control unit 23 detects a change in the parallel data input from the input port 21, and sets an input port change flag when there is a change in the input data. When there is a change in the input data, the flag indicating that the data is being retransmitted in the communication control unit 26 is checked, and only when the data is not being retransmitted, the data is stored in the transmission buffer memory 24 and a transmission request is sent to the communication control unit 26. appear. Further, the port control unit 23 outputs the data stored in the reception buffer memory 25 by the communication control unit 26 to the output port 22.

【0013】

When the communication control unit 26 receives a transmission request, the communication control unit 26 detects the idle state of the multiple bus MB, and when the multiple bus MB is in a free state in which no multiple node is used, the data in the transmission buffer memory 24. Is transmitted via the multiple bus MB, and when the above transmission is completed, the dominant ACK confirmation bit sent from the basic multiplex node having the ACK management function to the multiple bus MB is received, depending on the presence or absence of the ACK confirmation bit. It is determined whether or not the data stored in the transmission buffer memory 24 needs to be retransmitted, and if retransmitting is not necessary, the retransmission flag is turned off. Further, when the communication control unit 26 receives the frame data as shown in FIG. 7 via the multiple bus MB, the communication control unit 26 stores the received data in the reception buffer memory 25.

【0014】

As described above, FIG. 2 is a diagram showing the contents of the transmission frame transmitted by the communication control device. When the state abcdefgh of the input port A changes from 00000000 to 10000000, all ports A, B, The data of C and D are latched and stored in the transmission buffer memory 24, and a transmission request is generated. However, when the multiple bus MB is busy and waiting for transmission, if the data on port A changes and the status of input port A becomes "11000000", the new data "11000000" is sent to the transmission buffer memory 24. Since it is stored, the communication control unit 26 can transmit the latest data in one frame. When there are multiple types of transmission IDs, the data of different transmission IDs may change. Therefore, it is necessary to prepare a plurality of transmission buffer memories to prepare for transmission waiting, but in this embodiment, the transmission ID is Since there is only one type, the latest data can be sent by preparing one transmission buffer memory, discarding the data waiting to be transmitted, and sending only new data.

【0015】

Next, the operation of data transmission of the communication control device shown in FIG. 1 will be described with reference to the drawings of FIGS. 3 to 5. First, the port control unit 23 detects whether or not the input port change flag of the input port 21 is set (step 101). Here, when the above flag is not set, there is no change in the input data from the input port 21, and the state waits until the data changes. If the above flag is set, the input data has changed, so the above data (parallel data) is latched as transmission data (step 102). At this time, the communication control unit 26 detects the idle state of the multiple bus MB (step 103).

【0016】

Here, when the multiplex bus MB is in a free state where no multiple nodes are used, the port control unit 23 stores the latched data in the transmission buffer memory 24 and sends a transmission request to the communication control unit 26. appear. Upon receiving the transmission request, the communication control unit 26 transmits the SOM of the transmission data in the transmission buffer memory 24 to the multiple bus MB to fix the transmission data (step 104), and then from PRI to EOD shown in FIG. Data frame is transmitted (step 105). Then, it is determined whether or not there is a competition loss with another node (step 106).

【0017】

Here, if there is no competition or loss with other nodes, the communication control unit 26 transmits an ACK signal to a predetermined ACK area after transmitting the above data frame as shown in FIG. 4 (step). 107), It is determined whether the ACK confirmation area for storing the ACK confirmation bit sent by the basic multiplex node having a CPU is dominant (step 108).

【0018】

Here, when the ACK confirmation area is dominant, the retransmission counter provided in the communication control unit 26 that counts the number of retransmissions is turned off, and the flag indicating that the communication is being retransmitted is turned off. Clear the count value (step 109), return to step 101, and determine if the input port change flag is set. If the ACK confirmation area is in the passive state, it is determined that the transmission data will be retransmitted, the retransmission flag is turned on (step 110), and the count value of the retransmission counter is added by 1 (step 111). , Determine if the above retransmission is completed X times (step 112).

【0019】

Here, when the retransmission is completed X times, the communication control device returns to step 101 and performs the same operation as described above, and when the retransmission is not completed X times, the communication control device goes to step 103. It returns to detect the idle state of the multiple bus MB, and when the multiple bus MB becomes free, the data in the transmission buffer memory 24 is retransmitted. If the multiple bus MB is in use in step 103, or if the competition is lost in step 106 (the communication control device is in the reception state), the transmission data in the transmission buffer memory 24 is as shown in FIG. Is determined by the retransmission flag whether the communication control unit 26 is retransmitting (step 113), and when the above flag is off, the transmission data is not being retransmitted, and the input port change flag is set (step 114). ) Has a change in the transmission data (input of new transmission data), so the transmission data is latched from the input port 21 (step 115).

【0020】

Further, in step 113, when the retransmission flag is set and the transmission data is being retransmitted, when the input port change flag is not set in step 114, or when the transmission data is latched in step 115, step 103 Return to to detect the idle state of the multiple bus MB. Therefore, in this embodiment, the retransmission flag determines whether to store the latest data from the input port 21 in the transmission buffer memory 24, and only when the data stored in the transmission buffer memory 24 is being retransmitted. The storage of the changed latest data in the transmission buffer memory 24 is stopped, the latest data is stored in the transmission buffer memory 24 after the retransmission is completed, and the data stored in the transmission buffer memory 24 is transmitted even once. In the state of waiting for transmission, the latest data can be stored in the transmission buffer memory 24. Therefore, it is possible to quickly transmit the latest data that is highly needed.

【0021】

When the data held by both nodes may differ between the node that was able to receive the message being retransmitted and the node that was not able to receive it, or when the highest priority data is generated. Since data may be stored in the transmission buffer memory 24 even during retransmission, it is possible to set, for example, whether to stop storing the latest data changed in the transmission buffer memory 24 during retransmission with an external terminal, for example. If set to, the versatility will be higher.

【0022】

In this embodiment, the case where the data transmission method according to the present invention is used for a multiple node without a CPU has been described, but the present invention is not limited to this, and the present invention can also be used for a multiple node having a CPU. ..

【0023】

[Effect of the invention]

As described above, the present invention has a transmission storage means that is connected to the multiple transmission line and stores the data of the message to be transmitted to the multiple transmission line, and temporarily stores the input data in the transmission storage means. Then, in the data transmission method of the communication control device that transmits the data to the multiple transmission path, a change in the input data is detected, and when the change in the data is detected, the data stored in the transmission storage means is stored. It is necessary because the retransmission is detected and the storage of the changed data in the transmission storage means according to the detection result of the retransmission is stopped until the retransmission of the data stored in the transmission storage means is completed. The latest highly reliable data can be transmitted quickly, and the reliability of data transmission in the communication control device can be improved.

[Simple explanation of drawings]

[Figure 1]

It is a block diagram which shows the schematic structure of the communication control device for demonstrating the data transmission method which concerns on this invention.

[Figure 2]

It is a figure which shows the content of the transmission frame transmitted by the communication control device shown in FIG.

[Fig. 3]

It is a figure which shows the flowchart for demonstrating the transmission operation of the communication control device shown in FIG.

[Fig. 4]

It is a figure which shows the flowchart for demonstrating the transmission operation of the communication control device shown in FIG.

[Fig. 5]

It is a figure which shows the flowchart for demonstrating the transmission operation of the communication control device shown in FIG.

[Fig. 6]

It is a block diagram which shows the schematic structure of the multiple node.

[Fig. 7]

It is a figure which shows the structure of the frame of the signal transmitted between multiple nodes.

[Fig. 8]

It is a figure for demonstrating data transmission between multiple nodes.

[Explanation of symbols]

11 Communication control circuit (LSI) 12 Control circuit (CPU) 13 Input / output interface (I / F) circuit 21 Input port 22 Output port 23 Port control unit 24 transmit buffer memory 25 Receive buffer memory 26 Communication control unit MB multiplex transmission line (multiplex bus)