JP4341466B2 - Synchronous communication system - Google Patents

Description

  The present invention relates to a synchronous communication system in which a plurality of nodes each having a prescribed data transmission timing transmit and receive data in synchronization with each other on a network.

Conventionally, as this type of synchronous communication system, there is an in-vehicle synchronous communication system in which a large number of electronic control units (ECUs) are communicably connected to a network such as an in-vehicle LAN (Local Area Network) (for example, Patent Document 1). reference). On the network constituting such a synchronous communication system, a large number of data are sequentially transmitted and received between the electronic control devices. For this reason, in such a system, each node is required to avoid collision of transmission data on the network and avoid communication delay of transmission data (delay from generation of a transmission request until data is actually transmitted on the network). These nodes are synchronized by preliminarily defining the transmission timing of each node. Specifically, each node receives a data frame periodically transmitted by some of the nodes constituting the network, so that synchronization is established, and transmission data is collided so as to maintain the synchronization. I try to avoid it.
JP 2003-333048 A

  By the way, by synchronizing between the nodes as described above, it is theoretically possible to avoid collision of transmission data. However, in this case, the following new inconvenience occurs.

  That is, a node that periodically transmits data must continue to send fixed-length data regardless of the presence or absence of significant data. Even when there is no significant data, the node transmits fixed-length data for the purpose of maintaining synchronization. It will be. Therefore, for example, when the node A that cannot transmit significant data only by the assigned transmission timing and the node B that frequently transmits data only for the purpose of maintaining synchronization exist simultaneously on the network, the node B Node A cannot transmit significant data at the timing when fixed-length data is transmitted for the purpose of maintaining synchronization. As a result, the delay of the transmission data from the node A increases, and in the worst case, the node A discards the significant data, which may cause a situation in which the significant data is not transmitted from the node A. It might be.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a synchronous communication system capable of efficiently reducing delay of transmission data and realizing more prompt data communication. There is to do.

In order to achieve such an object, in the synchronous communication system according to claim 1, as a synchronous communication system in which a plurality of nodes, each of which has a prescribed data transmission timing, transmit and receive data in synchronization with each other on the network, Each node has a delegable transmission timing notification means for notifying other nodes that there is a delegable transmission timing, which is a timing for transmitting meaningless data, and the source node by receiving this delegable transmission timing notification a transmission timing transfer request means for requesting the transfer of the transmission timing by receiving this transmission timing delegation request together and a transmission timing transfer notifying means for notifying whether the transmission timing delegated to the requesting node, is the transceiver The transmission timing of each node is assigned A fixed-length data portion composed of a fixed-length data sequence, a variable-length data portion composed of a variable-length data sequence, and an idle portion to which no data is transmitted are configured as one cycle, and can be delegated by each node Notification to other nodes having timing, transmission timing delegation request to the transmission source node based on the notification, and notification of availability of transmission timing delegation to the request source node based on the delegation request The transmission is performed using the transmission timing .

By adopting such a configuration for each node on the network, a node having a delegable transmission timing that is a timing for transmitting meaningless data is notified to the other nodes through the delegable transmission timing notification means. The other node that has received this delegable transmission timing notification knows that there is a delegable transmission timing, and if there is significant data desired to be transmitted to its own node, the above transmission timing delegation request Through the means, the transmission source node is requested to delegate the transmission timing. In this case, the transmission source node of the delegable transmission timing notification that has received this transmission timing delegation request notifies the requesting node whether or not transmission timing delegation is possible through the transmission timing delegation notification means. That is, if there is no significant data to be transmitted at the transmission timing of the own node and it is known in advance that meaningless data is to be transmitted, the right of data transmission can be transferred to another node having significant data. Thus, the other node to which the right is transferred can transmit the significant data even when there is significant data exceeding the prescribed data transmission timing. As a result, as a whole, the delay of transmission data is efficiently reduced, and as a result, faster data communication is realized. Further, the data used for communication of the various notifications and requests is not necessarily equal to the data length of the fixed-length data portion. Therefore, in this way, by using the transmission timing of the variable length data portion to transmit and receive data used for the various notifications and requests, the variable length data portion is equivalent to the data used for the communication. As a result, data used for communication of these various notifications and requests can be transmitted and received more efficiently.

  Further, in such a synchronous communication system, as in the invention according to claim 2, the transmission timing delegation notification means of the node having a delegable transmission timing that does not transmit the significant data is used as the transmission timing delegation notification means of the own node. A transmission timing interval that can be delegated is calculated as a transmission cycle interval by comparing a transmission timing interval that does not transmit significant data with a transmission timing interval that is requested to be delegated, and transmission timing can be delegated to the requesting node. When notifying the fact, the calculated transmission cycle interval is combined with an offset that is a cycle difference from the transmission cycle including the timing at which the transmission timing transfer notification is transmitted to the transmission cycle including the first transmission timing transferred. By configuring it as a notification, the delegation of the above transmission timing In the case cormorants, so the transmission timing of significant data they transfer can be appropriately maintained. In this case, the degree of freedom of the transmission timing delegation mode is also greatly increased.

That is, in this case, when there are a plurality of request source nodes that have requested the delegation of the transmission timing, for example, according to the invention of claim 3,
The transmission timing delegation notifying means of a node having a delegable transmission timing that does not transmit the significant data notifies the plurality of request source nodes together with the calculated transmission cycle interval and the offset. Constitution.
Alternatively, as in the invention according to claim 4,
The transmission timing delegation notifying means of a node having a delegable transmission timing that does not transmit significant data, the calculated transmission cycle interval and the offset only for a specific node among the plurality of request source nodes The configuration that notifies together.
It becomes possible to control the delegation mode freely.

Also, in the synchronous communication system according to claim 5, wherein the transmission timing transfer notifying means nodes having delegable transmission timing does not transmit the pre-Symbol significant data, the delegable transmission timing notified by the timing of the idle portion The transmission timing delegation request of other nodes based on the above is received, and among the nodes having the transmission timing delegation request, the transmission timing is preferentially given to the node with the short transmission interval of significant data notified together with the request. A delegation notice will be sent.

  According to such a configuration, reception settings for the transmission timing delegation request, that is, various settings related to delegation of data transmission right, are performed at the timing of the idle part, which is a transmission period break, and time is wasted. In addition, the delegation of transmission timing with less waste can be realized as a whole network by preferentially assigning the delegation request to a node having a short significant data transmission interval.

Also, in the synchronous communication system according to claim 6, wherein the transmission timing transfer notifying means nodes having delegable transmission timing does not transmit the pre-Symbol significant data, the delegable transmission timing notified by the timing of the idle portion It is assumed that the transmission timing delegation request of another node based on the above is received and the delegation notification of the transmission timing is preferentially performed to a node having a communication distance close to the own node among the nodes having the delegation request.

  Even with such a configuration, reception processing of the transmission timing delegation request is performed at the timing of the idle unit, thereby saving time and delegation of transmission timing. By preferentially allocating the delegation request to nodes that are close to each other, it is possible to reduce the influence of physical wiring delay. That is, this reduces variations in the transmission timing of fixed-length data and makes it difficult for synchronization between nodes to shift.

On the other hand, in a synchronous communication system according to claim 7, when the prior SL fixed-length data unit initially, be only the transmission timing of the node having a delegable transmission timing does not transmit the significant data is allocated The transmission timing delegation notification unit of the node performs transmission timing delegation notification in order from the node that has completed initialization and has transmitted the transmission timing delegation request to the transmission source node based on the transmission timing delegation notification. .

  According to such a configuration, the transmission timing required for the nodes is sequentially delegated from the node where the initialization, that is, the initialization of the hardware or software by the reset accompanying the start of the power supply for each node is completed. Therefore, it is not necessary to determine the transmission timing of each node in advance, and it becomes easy to add and delete nodes.

  Hereinafter, an embodiment of a synchronous communication system according to the present invention will be described in detail with reference to the drawings. Note that the synchronous communication system of this embodiment is also basically a vehicle such as an automobile, as in the conventional synchronous communication system, and a plurality of nodes each having a prescribed data transmission timing are mutually connected on the network. This is a system that transmits and receives data in synchronization. However, in the synchronous communication system of this embodiment, the delay of transmission data is shortened through communication control described below, and as a result, more efficient data communication can be realized.

First, the configuration of the synchronous communication system according to this embodiment will be described with reference to FIG.
FIG. 1 is a schematic configuration diagram showing an example of a synchronous communication system according to this embodiment.

  As shown in FIG. 1, this synchronous communication system is a so-called bus network composed of four nodes. Four nodes A to D are connected via a communication bus 1, and each of these nodes is connected. Serial data is transmitted and received between them. When each node receives the data, each node decodes the received data and executes control of various actuators and other processes according to the decoded contents. Note that termination resistors 2 and 3 are provided at the termination portion of the network to prevent an electrical signal transmitted through the network from being reflected by the termination portion and generating noise.

By the way, as seen in a multiplex communication system for automobiles, this synchronous communication system is, for example, a control system related to a power train, and each node (arranged in an engine, a transmission, a brake system, a steering system, etc.) If the electronic control unit) is connected by the communication bus 1,
・ Engine control.
・ Shift control.
・ Brake control.
-ABS (anti-brake system) control.
・ Power assist steering control.
Various controls are performed in a multiplexed manner through the transmission / reception of data between the nodes described above.

Although not shown for convenience, each of the above nodes includes a communication control circuit, a host computer dedicated to the node, a memory, and the like.
Among these, the communication control circuit is a circuit that controls transmission and reception of data during data communication between the communication bus 1 and the node. In particular,
(A1) “Delegable transmission timing notification” is made through the delegable transmission timing notification means when there is a delegable transmission timing to the own node.
(A2) A node that cannot transmit significant data, which is data meaningful to the transmission timing assigned to the own node, transmits “transmission timing” to the node that has transmitted the “delegable transmission timing notification” through the transmission timing delegation request unit. Send delegation request.
(A3) The node that has received the “transmission timing delegation request” transmits a “transmission timing delegation notification” to the transmission source node through the transmission timing delegation notification means.
(A4) When the “delegable transmission timing notification” is returned, the delegable transmission timing interval is calculated. Further, when transmitting the “transmission timing delegation request”, a transmission timing interval at which delegation is to be requested is calculated. When transmitting the “transmission timing delegation notification”, an offset that is a period difference from the transmission cycle including the timing at which the “transmission timing delegation notification” is transmitted to the transmission cycle including the first transmission timing delegated is calculated. Do.
Process such as.

In addition, the host computer is mainly
(B1) When data is received through the communication control circuit, the received data is decoded, and various actuators assigned to the node are driven according to the decoded contents.
(B2) When sensing is performed at the node by sensors, the sensing information is encoded and transmitted to the communication bus 1 through the communication control circuit.
(B3) As a result of decoding the received data, if this is a request for a reply of a predetermined code, the reply code registered in advance in its built-in memory is sent to the communication bus 1 through the communication control circuit. Send.
It is a part that performs such processing.

Next, the data structure of data exchanged in the synchronous communication system according to this embodiment will be described in detail with reference to FIG.
The synchronous communication system according to this embodiment employs a time slot (time interval) communication method, and a plurality of nodes each having a prescribed data transmission timing transmit and receive data in synchronization with each other on the network. By doing so, the data to be transmitted can be sent within a certain time (transmission timing).

  FIG. 2 is a data stream showing an example of the transmission timing of the fixed length data portion, the transmission timing of the variable length data portion, and the timing of the idle portion of each node in this time slot (time interval) communication method. Here, the data stream is a data flow, and is data transfer in units of bytes. Here, the transmission cycle of such a data stream and each transmission timing are shown visually for convenience.

In the example of FIG. 2, the four nodes are respectively
Node A transmits data A1 and data A2.
Node B transmits data B2.
Node C does not send data.
Node D transmits data D4.
The configuration of the data stream in the case of As shown in FIG. 2, the transmission cycle is set such that the transmission timing of the fixed length data portion, the transmission timing of the variable length data portion, and the timing of the idle portion are one cycle. Then, the transmission timing of the fixed-length data portion is composed of transmission timings of data A1, data B2, data A3, and data D4.

  Note that significant data that cannot be transmitted at the transmission timing of the fixed-length data portion is transmitted at the transmission timing of the variable-length data portion. Further, in the present embodiment, using the transmission timing of this variable length data part, the above-mentioned “delegable transmission timing notification”, “transmission timing delegation request”, “transmission timing delegation notification”, and “transmission timing delegation” Data such as “rejection notification” is transmitted and received. By the way, “significant data” here is “significant data”, for example, sensing information (for example, engine speed) detected by a sensor, etc. It is data reflected in. In addition, there is “insignificant data” for this “significant data”, and this “insignificant data” is exclusively composed of, for example, “0 (zero)”, etc., and maintains synchronization exclusively. Fixed value data transmitted for the purpose.

  On the other hand, in this embodiment, a node having a delegable transmission timing receives a “transmission timing delegation request” from another node at the timing of the idle unit and performs a series of data transmission right delegation settings, etc. And For this reason, the actual transmission right delegation based on this delegation setting is performed at the transmission timing of the variable length data after the timing of the idle part that has performed this delegation setting.

The data transmission right delegation process by the synchronous communication system according to this embodiment will be described in detail below with reference to FIGS.
First, the concept of the data transmission right delegation process performed here will be described with reference to FIG. Incidentally, in the synchronous communication system according to this embodiment, significant data is transmitted from a node transmitting meaningless data (fixed length data) to another node in place of this meaningless data for the purpose of maintaining synchronization. By providing a procedure for transferring the right to do so, data delay or data destruction is avoided.

FIG. 3 is a sequence chart showing an example of a data transmission right delegation process executed in the synchronous communication system according to this embodiment.
Here, first, the data transmission mode before transmission right delegation, which is a premise of the data transmission right delegation processing in this example, is listed below with reference to FIG.
The node A uses all the transmission timings of the fixed length data portions of the data A1 and data A3, and further transmits the data A1 ′ every four times the transmission cycle using the transmission timing of the variable length data portion.
The node B transmits significant data every twice the transmission cycle at the transmission timing of the fixed-length data part of the data B2, and transmits meaningless data for the remaining transmission cycle.
Node C transmits data C2 ′ every four times the transmission period using the transmission timing of the variable length data portion.
The node D uses all the transmission timings of the fixed length data portion of the data D4, and further transmits the data D3 ′ irregularly using the transmission timing of the variable length data portion.

  In this example, under such circumstances, the transmission right of the data A1 'or the data C2' is transferred from the node B to the node A and the node C. This also allows the irregular data D3 'transmitted by the node D to be transmitted constantly.

Therefore, in this example, as shown in FIG. 3, as a data transmission right delegation process, a sequence in the mode listed below is executed.
(B) The node B indicates that it is possible to delegate the transmission timing corresponding to the fixed-length data for “data B2” at a rate twice the transmission cycle through the “delegable transmission timing notification”. Notification is given to a certain node A, node C, and node D.
(B) Node A and node C transmit a “transmission timing delegation request” to node B, thereby delegating transmission timing corresponding to fixed-length data for data B2 at a rate four times the transmission period. Request.
(C) Upon receiving this, the node B, as a “transmission timing delegation notification”, transmits the above-described offset, that is, the node A, together with the transmission timing (four-fold interval) to be delegated to the node A and the node C. Is notified of “from the next transmission cycle”, and the node C is notified of “after three cycles”.

  Thus, by notifying all of the periodic transmission timings to one node by notifying the above offset as a “transmission timing delegation notification” as well, for example, as in the example here, the node A And node C can be divided and delegated.

Hereinafter, the data transmission right delegation process illustrated in FIG. 3 will be further described with reference to FIGS. 4 and 5 by comparing specific examples of data streams before and after delegation.
FIG. 4 shows the data stream before the transmission right transfer process shown in FIG. 3 as described above.

  Here, for example, at the transmission timing of the variable length data portion, the transmission cycle interval at which the data A1 ′ is transmitted first is defined as the first cycle, and the transmission cycle interval at which the data C2 ′ is transmitted is defined as the third cycle. The data stream at that time can be expressed as shown in FIG. That is, here, a series of data transfer is repeatedly executed at intervals of four cycles, such as the first cycle to the fourth cycle or the fifth cycle to the eighth cycle. In this case, in the first period, the third period, the fifth period, and the seventh period, the data A1 'or the data C2' is transmitted using a part of the transmission timing of the variable length data portion. For this reason, the transmission of the data D3 'that the node D transmits irregularly is not guaranteed, and there may be a problem such as delay or discard of the data D3'. That is, regarding the data D3 'transmitted irregularly, it is necessary to always reserve a part of the transmission timing of the variable length data portion for the data D3' so that the data D3 'can be always communicated. Therefore, in this example, by delegating the transmission right of the node B transmitting meaningless data every other period to the node A and the node C, the data A1 ′ and the data C2 ′ is transmitted at the transmission timing of the fixed length data portion of the data B2.

In this way, it is the data stream after the transmission right transfer process shown in FIG. 5 that guarantees the transmission of the irregular data D3 ′.
Note that the data stream shown in FIG. 5 shows a state in which, after delegation setting is performed in the idle unit, all actual transmission rights are delegated based on the delegation setting. Also, here, at the transmission timing of the fixed-length data portion, the transmission cycle interval at which the data A1 ′ is transmitted first is defined as the first cycle, and the transmission cycle interval at which the data C2 ′ is transmitted is defined as the third cycle. ing.

  As shown in FIG. 5, when the transmission timing transfer is completed in the above-described manner, the transmission timing of the data B2 of the fixed-length data portion is in the order of node A, node B, node C, and node B, respectively. Data will be sent. Thereby, the node A, the node B, and the node C transmit only at the transmission timing of the fixed length data portion, and the irregular data D3 ′ transmitted by the node D can always be transmitted at the transmission timing of the variable length data portion. .

  Next, with reference to FIGS. 6 to 10, a process related to the data transmission right delegation setting will be described in more detail. This delegation setting is repeatedly executed at the timing of the idle unit through a communication control circuit having a common control structure provided in each node.

That is, in this embodiment, the communication control circuit performs the data transmission right delegation setting according to the processing procedure shown in FIG.
First, with reference to FIG. 6, an outline of processing (delegation processing) according to the data transmission right delegation setting according to this embodiment will be described.

  In the data transmission right delegation process, each communication control circuit first determines whether or not there is a “transmission timing delegation request” in each reception buffer as the “transmission timing delegation request” reception process in step S100. Search for. If there is a “transmission timing delegation request”, it is determined whether or not there is a transmission timing that can be delegated. If there is a delegation transmission timing, a “transmission timing delegation notification” is transmitted. On the other hand, if the transmission timing cannot be transferred, a “transmission timing transfer rejection notice” is transmitted.

  In addition, each communication control circuit does not transmit significant data to its own node, that is, there is a transmission timing of a fixed-length data part that can be delegated, as the “delegation possible transmission timing notification” transmission process of step S200. Judge whether or not. If there is such a delegable transmission timing, the delegable transmission timing interval is calculated, and a “delegable transmission timing notification” is transmitted to another node.

  Further, each communication control circuit receives “transmission timing delegation notification” or “transmission timing delegation rejection notification” in each reception buffer as a “transmission timing delegation (rejection) notification” reception process that is the process of step S300. Search for existence. If there is a “transmission timing delegation notification”, the node that has transmitted the above “transmission timing delegation request” performs a setting to transmit data using this delegation transmission timing, and is in a delegation request state Is released. On the other hand, when there is a “transmission timing delegation rejection notification”, the node cancels the delegation request state without performing new transmission settings for the data.

  Then, each of the communication control circuits searches for whether or not there is a “delegable transmission timing notification” in each reception buffer as the “delegable transmission timing notification” reception process of step S400. In other words, in response to the presence of this “delegable transmission timing notification”, the node that has insufficient transmission timing of the fixed-length data portion calculates the transmission timing interval requested by itself, along with the calculation result, “Transmission timing delegation request” is transmitted.

Hereinafter, with reference to FIG. 7 to FIG. 10, the details of the specific processing in each of the above-described steps S100 to S400 will be further described.
First, the process in step S100, that is, the “transmission timing transfer request” reception process will be described in detail with reference to FIG.

  As shown in FIG. 7, this “transmission timing delegation request” reception process searches for whether or not there is a “transmission timing delegation request” in each reception buffer provided in each of the communication control circuits. It starts (step S101). In step S102, it is determined whether there is a “transmission timing transfer request”. If it is determined that there is no “transmission timing delegation request”, the “transmission timing delegation request” reception process is skipped, and the “delegation possible transmission timing notification” transmission process, which is the next step S200, is performed. Migrate to

  On the other hand, if it is determined in step S102 that there is a “transmission timing delegation request”, it is determined whether there is a transmission timing that can be delegated to its own node (step S103). Then, if there is a transmission timing that can be delegated with respect to the transmission timing interval for requesting delegation sent together with the “transmission timing delegation request”, it is determined that delegation is possible. And the derivable transmission timing interval (cycle) and the offset are calculated. Then, a “transmission timing delegation notice” is transmitted together with the calculation result (step S104). On the other hand, if there is no transmission timing at which delegation is possible, it is determined that delegation is not possible, and a “transmission timing delegation rejection notification” is transmitted (step S105). Note that, in the case where there are a plurality of “transmission timing delegation requests” in the reception buffer, the same processing is repeatedly executed for all of these “transmission timing delegation requests”. The

Next, the process in step S200, that is, the “delegable transmission timing notification” transmission process will be described in detail with reference to FIG.
As shown in FIG. 8, the “delegation possible transmission timing notification” transmission process is started by determining whether or not there is a transmission timing that can be delegated to the own node (step S201). If it is determined that the node does not have this delegable transmission timing, the process leaves the “delegable transmission timing notification” transmission process and “transmission timing delegation (rejection)” is the process of the next step S300. The process proceeds to the “notification” reception process.

  On the other hand, when it is determined in step S201 that there is a transmission timing that can be delegated to the own node, the interval of the transmission timing that can be delegated is calculated. That is, if there is a transmission timing of the fixed-length data portion that does not transmit significant data, the interval is calculated as a delegable transmission timing interval (step S202). Then, the “delegation possible transmission timing notification” is transmitted together with the calculation result (step S203). Thereafter, the process proceeds to the “transmission timing delegation (rejection) notification” reception process, which is the process of step S300.

Next, the process in step S300, that is, the “transmission timing delegation (rejection) notification” reception process will be described in detail with reference to FIG.
As shown in FIG. 9, this “transmission timing delegation (rejection) notification” reception process searches for a “transmission timing delegation notification” or a “transmission timing delegation rejection notification” in the reception buffer. (Step S301). That is, first, in step S302, it is determined whether or not there is a “transmission timing transfer notification”. If it is determined that there is a “transmission timing delegation notification” in the reception buffer, a setting is made to transmit data using the delegated transmission timing interval (step S303), and the delegation request state is released. (Step S304). In this way, in step S303, the data transmission timing is set on the premise that the delegated transmission timing is used. In this case, actual data transmission based on the setting is performed after the offset sent together with the “transmission timing delegation notification”. Then, the process proceeds to the “delegation possible transmission timing notification” reception process which is the process of step S400.

  On the other hand, if it is determined in step S302 that there is no “transmission timing delegation notification”, it is next determined whether or not there is a “transmission timing delegation rejection notification” (step S305). If it is determined in step S305 that there is a “transmission timing delegation rejection notification”, the state during the delegation request is canceled without performing any new data transmission setting as described above (step S306). Then, the process proceeds to the “delegation possible transmission timing notification” reception process which is the process of step S400.

Next, the process in step S400, that is, the “delegation possible transmission timing notification” reception process will be described in detail with reference to FIG.
As illustrated in FIG. 10, the “delegable transmission timing notification” reception process is started by searching for “delegable transmission timing notification” in the reception buffer (step S 401). Then, in step S402, it is determined whether or not the “delegable transmission timing notification” is present (step S402). Here, when it is determined that there is no “delegable transmission timing notification”, the “delegable transmission timing notification” reception process is exited.

  On the other hand, if it is determined in step S402 that there is a “delegable transmission timing notification”, it is determined whether or not the current state is a request for delegation (step S403). If it is determined that the current state is already in the delegation request state, the “delegation possible transmission timing notification” reception process is exited.

  On the other hand, if it is determined in step S403 that the current state is not yet a request for delegation, it is next determined whether or not the transmission timing of the fixed-length data portion is insufficient in the own node. (Step S404). When it is determined that the transmission timing of the fixed-length data portion is not insufficient, the “delegable transmission timing notification” reception process is exited.

  On the other hand, if it is determined in step S404 that the transmission timing of the fixed-length data portion is insufficient, a transmission timing interval for requesting delegation is calculated (step S405), and along with the calculation result, A “transmission timing delegation request” is transmitted (step S406). Then, this state is set as a state during delegation request (step S407).

  In the example shown in FIG. 3, such processing is sequentially performed between the node B, the node A, and the node C, so that the data stream illustrated in FIG. 4 is changed in the manner illustrated in FIG. This means that the irregular data D3 ′ transmitted by the node D can always be transmitted.

As described above in detail, according to the synchronous communication system according to this embodiment, the excellent effects listed below can be obtained.
(1) A node having a delegable transmission timing that does not transmit significant data is notified to another node through the “delegable transmission timing notification” (step S200). Upon receiving this delegable transmission timing notification, the other node knows that there is a delegable transmission timing, and if there is significant data desired to be transmitted to the own node, the above-mentioned "transmission timing delegation request" The transmission source node is requested to delegate the transmission timing (step S400). That is, if it is known in advance that there is no significant data to be transmitted at the transmission timing of the own node, the right of data transmission can be transferred to another node having significant data (“transmission timing delegation notification”). (Step S100). The other node to which the right is transferred can transmit this data even when there is significant data that exceeds the prescribed data transmission timing. As a result, the delay of the transmission data is efficiently reduced as a whole system, and more prompt data communication is realized.

  (2) This is used as a transmission timing delegation notification means of a node having a delegable transmission timing that does not transmit significant data, and this is compared with the transmission timing interval of the node that does not transmit significant data and the transmission timing interval for which the delegation is requested. Thus, the transmission timing interval that can be delegated is calculated as the transmission cycle interval. At the same time, when notifying the requesting node that transmission timing can be delegated, the first transmission period including the calculated transmission period interval and the transmission period including the timing at which the transmission timing delegation notification is transmitted is used. An offset that is a period difference up to the transmission period including the transmission timing is also notified (step S104 in FIG. 7). As a result, even when the transmission timing is delegated, the transmission timing of the significant data to be delegated can be appropriately maintained. In this case, the degree of freedom of the transmission timing delegation mode is also greatly increased.

  (3) The calculated transmission cycle interval and the offset are notified to each of a plurality of request source nodes (steps S101 to S104 in FIG. 7). Thus, by notifying each node together with the calculated transmission cycle interval and offset, not only delegating all of the periodic transmission timings to one node, but also dividing into a plurality of It is also possible to delegate to a node. As a result, the communication delay of the transmission data can be efficiently shortened more efficiently.

  (4) Data transmission / reception such as “delegation possible transmission timing notification” (step S200), “transmission timing delegation request” (step S400), “transmission timing delegation (rejection) notification” (step S100), etc. Data used for communication of various notifications and requests is transmitted at the transmission timing of the variable length data part. By transmitting the data using such a transmission timing, the variable length data portion is used for the data used for the communication of the data, and used for communication of these various notifications and requests. Data can be transmitted and received more efficiently.

Note that the synchronous communication system according to the present invention is not limited to the above-described embodiment, and can be implemented as, for example, the following form, which is appropriately modified from the embodiment.
In the above embodiment, when specifying the transmission timing to be delegated by the transmission period interval and the offset from the transmission timing delegation notification, the nodes A and C are selected as delegation destination nodes. As a node, any node that can be delegated may be selectively designated. That is, as a transmission right delegation process, as shown in FIG. 11 as a sequence chart corresponding to FIG. 3, for example, all the transmission timings of meaningless data of node B are delegated to node A. It can also be set not to delegate. In particular, in the example shown in FIG. 11, since the transmission right is delegated to only one node (node A), the transmission timing is transmitted to this one node (node A) at “double intervals” from the next cycle. Can be delegated. FIG. 12 shows the data stream after the transmission right transfer in this case. That is, in this case, at each transmission period of data B2, in this case, “data A1 ′” of node A, “data B2” of node B, “insignificant data” of node A, “data of node B” Data is transmitted in the order of “B2”. In this way, even by delegating the transmission right to only one node, the transmission timing of meaningless data is suppressed as compared to before the delegation, for example, delay or discard of irregular data D3 ′ transmitted by the node D is suppressed. Will be able to. In this case, the process of step S405 in the “delegation possible transmission timing notification” reception process shown in FIG. 10, that is, the delegation transmission timing interval calculation process may be omitted.

  In the above embodiment, each of the nodes A to D includes a communication control circuit, a node-dedicated host computer, and a memory. However, the configuration of each node is not limited thereto. That is, the configuration of the node may be any configuration that can perform the data transmission right delegation process as described above, and the configuration is also arbitrary.

In the above embodiment, for the sake of simplicity, the case where the synchronous communication system is configured with four nodes A to D is illustrated, but the number of nodes is arbitrary.
In addition, when the synchronous communication system is configured by a large number of nodes, it is effective to preferentially assign the delegation request to a node with a short transmission interval of significant data as the delegation destination of the transmission timing described above . This makes it possible to realize transmission timing delegation with less waste for the entire network.

  Similarly, it is also effective to give priority to a node having a short communication distance from the delegation source node as a transmission timing delegation destination. In this case, since the influence of the physical wiring is reduced, variation in the transmission timing of the fixed-length data portion is reduced, and synchronization between the nodes can be made difficult to shift.

  In such a synchronous communication system, only the transmission timing of a node having a delegable transmission timing that does not transmit the significant data may be initially allocated to the fixed-length data portion. That is, in this case, initialization is completed in the other nodes, and the transmission timing delegation notification is sequentially performed from the node that transmitted the “transmission timing delegation request” to the transmission source node based on the “transmission timing delegation notification”. In this way, by sequentially delegating the necessary transmission timings from the nodes that have been initialized, it is not necessary to decide the distribution of the transmission timings of each node, and it is also easy to add and delete nodes. it can. Here, the initialization is a reset associated with the start of power supply for each node, and is initialization of hardware and software.

  In the above embodiment, the data to be transmitted / received includes a fixed-length data portion consisting of a fixed-length data sequence to which the transmission timing of each node is allocated, a variable-length data portion consisting of a variable-length data sequence, and any data Although it is assumed that the idle part that is not transmitted is configured as one cycle, these data structures (data stream structures) are arbitrary. In this case, the above-mentioned various notifications and requests including data transmission such as the above-mentioned “delegable transmission timing notification”, “transmission timing delegation request”, “transmission timing delegation notification”, and “transmission timing delegation rejection notification”, etc. The transmission timing of data used for the communication is arbitrary, and an appropriate timing in the employed data structure can be used.

  In this case, the processing timing of the processes shown in FIGS. 6 to 10 is also arbitrary, and an appropriate timing in the data structure to be employed can be used. Of course, when the above-mentioned idle part exists in these data structures, it is more desirable that this process is also executed at the timing of this idle part.

  In the above embodiment, the network structure is a bus network, but the network structure is not limited to the bus network. That is, the network connection form is arbitrary. For example, such a network connection form may be a star type, a ring type, or the like.

  In the above embodiment, the time slot (time interval) communication method is exemplified, but the communication method is not limited to such a time slot (time interval) communication method. In other words, any communication method may be used as long as the nodes are synchronized and the transmission timing of each node is defined in advance.

  -Although the synchronous communication system mounted in vehicles, such as a motor vehicle, was illustrated in the said embodiment, this synchronous communication system is not limited to what is called vehicle mounting.

The block diagram which shows the whole structure about one Embodiment of the synchronous communication system concerning this invention. The data stream figure which shows the example of a data structure employ | adopted with the synchronous communication system of the embodiment. The sequence chart which shows the example about the delegation aspect of the transmission timing by the system of the embodiment. The data stream figure which shows the example of a data structure before transfer of the said transmission timing. The data stream figure which shows the example of a data structure after transfer of the said transmission timing. The flowchart which shows the whole process sequence about the delegation process of the data transmission timing by the embodiment. The flowchart which shows the process sequence about the "transmission timing transfer request" reception process among the said transfer processes. The flowchart which shows the process sequence about the "delegation possible transmission timing notification" transmission process among the said delegation processes. The flowchart which shows the process sequence about the "transmission timing transfer (rejection) notification" reception process of the said transfer processes. The flowchart which shows the process sequence about the "delegation possible transmission timing notification" reception process of the said delegation processes. The sequence chart which shows the modification about the transfer aspect of the said transmission timing. The data stream figure which shows the example of a data structure after the transmission timing transfer by the modification of FIG.

Explanation of symbols

  1 ... communication bus, 2,3 ... termination resistor.

Claims (7)

In a synchronous communication system in which a plurality of nodes, each of which has a data transmission timing defined therein, transmit and receive data in synchronization with each other on the network,
Each node transmits a delegable transmission timing notifying means for notifying other nodes that there is a delegable transmission timing, which is a timing for transmitting meaningless data, and the transmission source by receiving this delegable transmission timing notification. A transmission timing delegation requesting means for requesting the node to delegate transmission timing, and a transmission timing delegation notifying means for notifying the requesting node whether or not transmission timing delegation is possible by receiving this transmission timing delegation request ;
The data to be transmitted / received includes a fixed-length data portion composed of a fixed-length data sequence to which transmission timing of each node is assigned, a variable-length data portion composed of a variable-length data sequence, and an idle portion where no data is transmitted. Configured as one cycle, notification to other nodes that there is a transmission timing that can be delegated by each node, transmission timing delegation request to a transmission source node based on the notification, and request source node based on the delegation request A synchronous communication system, characterized in that a transmission timing delegation notification is performed using the transmission timing of the variable length data portion .   The transmission timing delegation notifying means of a node having a delegable transmission timing that does not transmit significant data compares the transmission timing interval of the node that does not transmit significant data with the transmission timing interval for which the delegation is requested. The derivable transmission timing interval is calculated as a transmission cycle interval, and when the requesting node is notified that transmission timing can be delegated, the calculated transmission cycle interval and the transmission timing delegation notification are transmitted. 2. The synchronous communication system according to claim 1, wherein an offset that is a period difference from a transmission cycle including timing to a transmission cycle including a first transmission timing delegated is also notified.   When there are a plurality of request source nodes that have requested the transmission timing delegation, the transmission timing delegation notification means of a node having a delegable transmission timing that does not transmit significant data is provided for each of the plurality of request source nodes. The synchronous communication system according to claim 2, wherein the calculated transmission cycle interval and the offset are notified together.   When there are a plurality of request source nodes that request the transmission timing delegation, the transmission timing delegation notification means of the node having a delegable transmission timing that does not transmit the significant data is specified among the plurality of request source nodes. The synchronous communication system according to claim 2, wherein the calculated transmission cycle interval and the offset are notified together only to the node. The transmission timing delegation notifying means of a node having a delegable transmission timing that does not transmit the significant data receives a transmission timing delegation request of another node based on the delegable transmission timing notification at the timing of the idle unit, 2. The synchronous communication system according to claim 1 , wherein a delegation notification of a transmission timing is preferentially performed to a node having a short transmission interval of significant data notified together with the delegation request. The transmission timing delegation notifying means of a node having a delegable transmission timing that does not transmit the significant data receives a transmission timing delegation request of another node based on the delegable transmission timing notification at the timing of the idle unit, 2. The synchronous communication system according to claim 1 , wherein a delegation notification of a transmission timing is preferentially performed to a node having a communication distance close to the own node among the nodes having the delegation request. Initially, only the transmission timing of a node having a delegable transmission timing that does not transmit significant data is allocated to the fixed-length data portion, and the transmission timing delegation notifying means of the node has been initialized. The synchronous communication system according to claim 1 , wherein the transmission timing delegation notification is performed in order from the node that has transmitted the transmission timing delegation request to the transmission source node based on the transmission timing delegation notification.

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