JP3217397B2 - Data transmission method of communication control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication control device connected to a multiplex transmission line for transmitting a message, and more particularly to a data transmission method of a communication control device for transmitting data.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 6, a multiplex node having a communication control device of this type includes a communication control device (LSI) 11 connected to a multiplex transmission line (multiplex bus) MB composed of a pair of electric wires. And a control circuit (CPU) 12 and an input / output interface (I / F) circuit 13. The CPU 12 captures events (data) from various switches and the like via the I / F circuit 13, and the LSI 11
It has a transmission buffer memory for storing the data of the message input from the PU 12 and the data ID for identifying the data, and transmits the message in the transmission buffer memory to the multiplex bus MB. Further, some multiplex nodes having an LSI for performing communication control do not have a CPU. In this case, after storing the data and data ID fetched via the I / F circuit 13 in the data buffer memory,
The data is stored in the transmission buffer memory and transmitted to the multiplex bus MB. These multiplex nodes are connected to a multiplex bus to form a network, and a CSMA / CD (Carrier Sense Multiple
Access / Collision Detection) is used, for example, for multiplex transmission of data in automobiles. At the node where the event has changed, the CPU 12
The transmission data is written into the transmission buffer memory 11 to generate a transmission request. The LSI 11 receiving the transmission request starts transmitting the transmission data, and the CPU 12
After the transmission of 1 is completed and the transmission buffer memory becomes empty, the next transmission data can be written.

FIG. 7 is a diagram showing an embodiment of a message format of a data frame transmitted between multiple nodes. In the figure, the data frame includes a start of message (SOM) indicating the beginning of a message and a priority (PRI) for determining the priority when a plurality of multiplex nodes simultaneously transmit data to a multiplex bus.
, A message ID indicating the content of each succeeding data (DATA), a control data area (CONT) including data indicating the data length, and a length indicated by CONT (variable length)
Data area (DATA1 to DATA4), error check codes such as CRC, and EOD (End Of Data) indicating the end of data.
a), an ACK signal area for returning an ACK signal on a bit basis from all multiplexed nodes, and a 1-bit ACK determination area indicating that the ACK signal has been returned from all registered nodes and data transmission has been completed. And EOM (End Of Message) indicating the end of the message.

Here, as shown in FIG. 8, a transmission multiplex node transmits a data frame including SOM to EOD via a multiplex bus, and other multiplex nodes transmit data frames normally without error. Returns an ACK signal to a predetermined ACK signal area. When confirming that all registered nodes have returned ACK signals, the basic multiplex node having the ACK management function sends a dominant ACK determination bit to the ACK determination area. In FIG. 8, a transmission multiplex node A and a reception multiplex node E correspond to a basic multiplex node, and reception multiplex nodes B, C, and D are simple multiplex nodes without an ACK management function. If there is no ACK returned from the receiving multiplex node B, the transmitting multiplex node A does not transmit the ACK determination bit and retransmits the data frame. This retransmission operation ends when it is repeated a certain number of times, for example, X times. If the registration of the reception multiplex node B is deleted, a certain node fails and ACK is received.
When a signal is not returned, retransmission is not repeated indefinitely. When the simple multiplex node transmits a data frame, when the ACK determination bit is received, it is determined that data transmission has been normally performed, and transmission is terminated. When the ACK determination bit is not received, transmission is performed. It determines that an error has occurred and resends. This retransmission operation
Similarly, it ended X times.

Further, when new data to be transmitted is generated before the transmission is completed, a request for transmitting data already written in the transmission buffer memory is canceled and new data can be written. is there.

[0006]

However, in the above-mentioned conventional example, when the data stored in the transmission buffer memory is in a transmission waiting state, the data in the transmission buffer memory is transmitted even if the event changes. Only afterwards can the latest data be transmitted. For example, in the case of data transmission in a car, even when the data of the horn changes from off to on while the data of the wiper on is stored in the transmission buffer memory, the data of the wiper on in the transmission buffer memory is transmitted. Only after that, the latest horn-on data cannot be transmitted, and there is a problem in that the transmission of the more necessary newest data is delayed.

Further, if a transmission request for data already stored in the transmission buffer memory is canceled, the data is lost. for that reason,
There is a problem that a buffer memory for the queue is required and the cost increases. Also, if a transmission error occurs during transmission of a certain message and the transmission request is canceled during retransmission, the data held by the node that received the message and the data that the two nodes could not receive differed. There was a problem that would.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a data transmission method of a communication control device capable of rapidly transmitting the latest data having high necessity.

[0009]

According to the present invention, there is provided a transmission storage means connected to a multiplex transmission line and storing data of a message to be transmitted to the multiplex transmission line. In a data transmission method of a communication control device for temporarily storing input data of the data in the transmission storage means and transmitting the input data to the multiplex transmission line, a change in the input data is detected, and a change in the data is detected. Then
Wherein stored in the transmission memory means data is being retransmitted
Is stored in the transmission storage means.
When the transmitted data is in a state of being retransmitted ,
There is provided a data transmission method of a communication control device that stops storing the changed data in the transmission storage unit until retransmission of the data stored in the transmission storage unit ends. In the second aspect, the data stored in the transmission storage means is stored.
Data may be received differently between each node.
When the data is stored in the transmission storage means,
Even if the data is being retransmitted,
By storing the input data in the transmission storage means,
Communication controller data that can be transmitted more quickly
A transmission method is provided.

[0010]

The storage of the latest changed data in the transmission storage unit is stopped only when the data stored in the transmission storage unit comprising the transmission buffer memory is being retransmitted. Can be stored in the transmission storage means. Therefore, the latest data with high necessity can be transmitted quickly without the data between the nodes on the network being different, and the reliability of data transmission in the communication control device can be improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. 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 without a CPU and without an ACK management function is shown. In the figure, the input port 21 receives 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 contents of the transmission frame are as shown in FIG. That is, the transmission ID is data for identifying the node, and one bit of the data area corresponds to one input port. When even one of the input ports changes, the data of all the ports is latched, the data of the input port A is stored in the area of DATA1, and the data of the input ports B, C and D are similarly stored in the areas of DATA2 and DATA2, respectively.
The data is stored and transmitted in areas 3 and 4.

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. If there is a change in the input data, the communication control unit 26 checks the flag indicating that retransmission is in progress, and stores the data in the transmission buffer memory 24 only when the retransmission is not in progress.
Generates a transmission request. 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.

When receiving the transmission request, the communication control unit 26 detects the idle state of the multiplex bus MB, and when the multiplex bus MB is in an idle state in which no multiplex node is used, the transmission buffer memory 24 Multiplex bus M
B, upon completion of the transmission, receives a dominant ACK determination bit sent to the multiplex bus MB from the basic multiplex node having an ACK management function, and
It is determined whether or not the data stored in the transmission buffer memory 24 needs to be retransmitted according to the presence or absence of the K determination bit,
If retransmission is unnecessary, the retransmission flag is turned off. Further, upon receiving frame data as shown in FIG. 7 via the multiplex bus MB, the communication control unit 26 stores the received data in the reception buffer memory 25.

FIG. 2 is a diagram showing the contents of a transmission frame transmitted by the communication control device as described above, and the state "abcdefgh" of the input port A is set to "00000000".
When the number changes from "0" to "10000000", the data of all ports A, B, C, and D are latched and stored in the transmission buffer memory 24 to generate a transmission request.
In the state of transmission waiting in crowded multiplex bus MB, port A
Of the input port A changes to "11000
000 ”, the new data“ 1100000 ”
Since "0" is stored in the transmission buffer memory 24, the communication control unit 26 can transmit the latest data in one frame. When there are a plurality of types of transmission IDs, data of different transmission IDs change. Therefore, it is necessary to prepare a plurality of transmission buffer memories to prepare for transmission waiting, but in this embodiment, since there is only one type of transmission ID,
If one transmission buffer memory is prepared and data waiting for transmission is discarded and only new data is transmitted, the latest data can be transmitted.

Next, the data transmission operation of the communication control apparatus shown in FIG. 1 will be described with reference to FIGS. First, the port control unit 23 detects whether the input port change flag of the input port 21 is set (Step 101). Here, when the flag is not set, there is no change in the input data from the input port 21, so that the apparatus enters a standby state until the data changes. If the flag is set, there is a change in the input data, so that the data (parallel data) is latched as transmission data (step 102). At this time, the communication control unit 26 detects the idle state of the multiplex bus MB (Step 103).

Here, when the multiplex bus MB is in an idle state in which no multiplex node is used, the port control unit 23 stores the latched data in the transmission buffer memory 2.
4 and a transmission request is issued to the communication control unit 26. 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 multiplex bus MB to fix the transmission data (step 104), and then transmits the SOM from the PRI to EOD shown in FIG. Is transmitted (step 105). Then, it is determined whether or not there is a competition loss with another node (step 106).

Here, if there is no loss of competition with another node, as shown in FIG. 4, the communication control unit 26, after transmitting the data frame, stores the A in a predetermined ACK area.
A CK signal is transmitted (step 107), and it is determined whether or not the ACK determination area storing the ACK determination bit transmitted by the basic multiplex node having the CPU is dominant (step 108).

If the ACK determination area is dominant, the flag indicating that retransmission is being performed in the communication control unit 26 is turned off, and the number of retransmissions provided in the communication control unit 26 is counted. The count value of the retransmission counter is cleared (step 109), and the process returns to step 101 to determine whether the input port change flag is set. If the ACK determination area is in the passive state, it is determined that retransmission of transmission data is to be performed, the retransmission flag is turned on (step 110), and the count value of the retransmission counter is set to 1
After the addition (step 111), it is determined whether the retransmission has been completed X times (step 112).

Here, the communication control device determines that the retransmission is X
If the retransmission has not been completed X times, the process returns to step 103 to detect the idle state of the multiplex bus MB, and returns to step 101 to perform the same operation as described above. When the bus MB becomes empty, the data in the transmission buffer memory 24 is retransmitted. If the multiplex bus MB is in use in step 103,
Alternatively, in the case where the contention is lost (the communication control device is in the reception state) in step 106, the transmission data in the transmission buffer memory 24 is transferred to the communication control unit 26 as shown in FIG.
Is determined by the retransmission flag (step 113). If the flag is off and the transmission data is not being retransmitted and the input port change flag is set (step 114), the transmission is performed. Since there is a change in data (input of new transmission data), the transmission data is latched from the input port 21 (step 115).

In step 113, if the retransmission flag is set and the transmission data is being retransmitted, if the input port change flag is not set in step 114, or if the transmission data is latched in step 115, Returning to step 103, the idle state of the multiplex bus MB is detected. Therefore, in this embodiment, it is determined whether the latest data from the input port 21 is stored in the transmission buffer memory 24 based on the retransmission flag, and only when the data stored in the transmission buffer memory 24 is being retransmitted, Transmission buffer memory 2 for changed latest data
4 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 in a state of waiting for transmission that has never been transmitted. 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 necessary.

In the case where the data which has been retransmitted may be different between the node which has been able to receive the message and the node which has not been able to receive the retransmitted message, or the case where the highest-priority data occurs. In this case, the data may be stored in the transmission buffer memory 24 even during the retransmission. Therefore, whether to stop storing the latest data changed in the transmission buffer memory 24 during the retransmission is determined by, for example, an external terminal. If it can be set, versatility will be higher.

In this embodiment, the case where the data transmission method according to the present invention is used for a multiplex node having no CPU has been described. However, the present invention is not limited to this, and may be used for a multiplex node having a CPU. It is possible.

[0023]

As described above, according to the present invention, there is provided transmission storage means which is connected to a multiplex transmission line and stores data of a message to be transmitted to the multiplex transmission line. Once stored in the storage means, in the data transmission method of the communication control device for transmitting to the multiplex transmission path, the change of the input data is detected, and when the change of the data is detected, the transmission storage means Detecting retransmission of the stored data and storing the changed data in the transmission storage means in accordance with the detection result of the retransmission until the retransmission of the data stored in the transmission storage means is completed. Since the operation is stopped, the latest data with high necessity can be transmitted quickly, and the reliability of data transmission in the communication control device can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a schematic configuration of a communication control device for explaining a data transmission method according to the present invention.

FIG. 2 is a diagram showing the contents of a transmission frame transmitted by the communication control device shown in FIG.

FIG. 3 is a diagram showing a flowchart for explaining a transmission operation of the communication control device shown in FIG. 1;

FIG. 4 is a diagram illustrating a flowchart for describing a transmission operation of the communication control device illustrated in FIG. 1;

FIG. 5 is a diagram showing a flowchart for explaining a transmission operation of the communication control device shown in FIG. 1;

FIG. 6 is a configuration diagram illustrating a schematic configuration of a multiplex node.

FIG. 7 is a diagram illustrating a configuration of a frame of a signal transmitted between multiple nodes.

FIG. 8 is a diagram for explaining data transmission between multiple nodes.

[Description of Signs] 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 Transmission buffer memory 25 Receive buffer memory 26 Communication control unit MB multiplex transmission path (multiplex bus)

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yoshikazu Shinnobu 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (72) Inventor Hiroaki Sakamoto 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (56) References JP-A-61-100043 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 13/08 H04J 3/00 H04L 29/08 H04L 12/18

Claims (2)

(57) [Claims] 1. A transmission storage means connected to a multiplex transmission path and storing data of a message to be transmitted to the multiplex transmission path, wherein the input data of the data is temporarily stored in the transmission storage means. after, Oite the data transmitting method of a communication control device to be transmitted to the multiplex transmission line, wherein the detecting a change in the input data, the change of the data is detected, the stored in the transmission memory means data is re Detecting whether or not data is being transmitted , and when data stored in the transmission storage means is being retransmitted
It is stored into the transmission memory means of the data the changes to retransmission of data stored in the transmission memory means is ended, the data transmission method of a communication control device, characterized in that the stop. 2. A multiplex transmission line connected to a multiplex transmission line.
Transmission record that stores the data of the message to be transmitted to the transmission path
Storage means for storing the input data of the data in the transmission record.
After temporarily storing it in the storage means, it is transmitted to the multiplex transmission path.
In the data transmission method of the communication control device, a change in the input data is detected, and when a change in the data is detected, the data is stored in the transmission storage unit.
The stored data is received differently between each node
Is acceptable data, the changed input data
Data is stored in the transmission storage means, and the data stored in the transmission storage means is other than the above data.
When the data is stored in the transmission storage means,
Detecting whether or not the transmitted data is being retransmitted, and when the data stored in the transmission storage means is being retransmitted.
Storing the changed data in the transmission storage means
The retransmission of the data stored in the transmission storage means is terminated.
A data transmission method for a communication control device, wherein the data transmission is stopped until completion .