JPH03201741A - Transmission request reply method for transmission circuit - Google Patents

Abstract

PURPOSE:To improve the system response by fetching data in plural nodes when a data requested by one node is sent from other node to a bus. CONSTITUTION:When nodes A-C sends a data in response to a transmission request of a node D through a bus BL, one node D and the remaining nodes A-C, namely, the nodes A-C requiring the data fetch the data sent through the bus BL. Thus, it is not required for the plural nodes A-C to request individually the same data to the other node D and the transmission of the same data for each node request is not required by the nodes A-C. As a result, the frame occupancy rate of the bus BL is low. Thus, even a request from a node with low priority is quickly coped with and the system response is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a transmission request response method of a transmission circuit in multiplex transmission communication.

(Prior art and problems to be solved) As shown in Fig. 5, a multiplex transmission system adopted in automobiles transmits multiple multiplex signals via a multiplex transmission line (hereinafter referred to as "bus") BL made of twisted pair wires, etc. Nodes (hereinafter simply referred to as "nodes") A to D (e.g., front multiplex node, combination switch, meter, rear multiplex node, etc.) are connected and data is transmitted frame by frame from any one of these nodes. However, there is a multiplex transmission method in which when the receiving node receives the frame normally, it returns a reception confirmation signal following this frame.

By the way, some of these nodes have their respective memories reset when the key switch is turned on when the vehicle is started, and new data (
Information) will be received and updated. As a result, if these nodes all send transmission request frames to a certain node all at once, the bus will become busy. For example, as shown in FIG. 6, when nodes A to C each request speed data (ID=△△) from node D (speedometer), each sends a transmission request frame ID △△ to bus BL separately. becomes. Also, nodes A and B send request frame ID △△ to node D.
It is also possible that another node C sends a transmission request frame ID ΔΔ to the node D after the node D sends the data of the requested ID ΔΔ to the bus BL. In that case, node D responds again to node C's transmission request frame and sends out a data frame with ID ΔΔ.

Alternatively, if each node A-C issues a transmission request to node D to have it send data, the nonid D may send data with ID △△ to each node A-C many times. There is a possibility that it will become.

In this way, when multiple nodes send transmission request frames to a certain node all at once, for example, CS M
A/ CD (Carrier 5ense Mess
ageArbitration Colution D
In the case of the (etect) method, the frame occupancy rate of the bus increases and there is no margin, and accordingly, transmission requests from nodes with low priority are postponed, resulting in poor responsiveness of the transmission system. Furthermore, as the frame occupancy rate of the bus increases, when a new node is added, the bus occupancy rate will further increase, making it difficult to guarantee the responsiveness required by the specifications. As a result, upgrading such as increasing the transmission speed is required, which ultimately makes the transmission system expensive. Therefore, it is preferable to keep the frame occupancy rate of the bus as low as possible and keep it as open as possible.

The present invention has been made in view of the above points, and when a plurality of nodes request data transmission from a certain node, only one of the nodes sends the transmission request frame to the bus, and the remaining The node cancels the transmission request and makes it wait, and when the data requested by the first node is sent to the bus, the nodes that need the data take in the data, thereby reducing the bus frame occupancy rate. It is an object of the present invention to provide a transmission request response method for a transmission circuit that reduces the transmission request.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, a large number of nodes are connected to a common bus, a certain node requests data transmission from another node, and the other node requests data transmission from the other node. In a transmission request response method for a transmission system in which a node sends requested data to a bus, a plurality of nodes make a transmission request to another node, and one node among the plurality of nodes sends a transmission request. is sent onto the bus for the first time, the remaining nodes confirm that the transmission request has been made and cancel their own transmission requests, and the data requested by the one node is transferred from the other node to the bus. When the data is sent out, the plurality of nodes take in the data.

(Operation) When multiple nodes request the same data from a certain node, when one of these nodes sets a transmission flag for a transmission request frame, the remaining nodes
When checking the transmission flag of the one node, it determines that another node is requesting the same node to transmit the same data, resets the transmission flag of its own transmission request frame, and waits.

When the transmitting node sends data to the bus in response to the transmission request of the one node, the one node and the remaining nodes, that is, each node that requires the data, transmits the data sent to the bus. take in. This eliminates the need for a plurality of nodes to individually request the same data from a certain node, and also eliminates the need for the corresponding node to send out the same data for each request from each node. As a result, the frame occupancy rate of the bus decreases.

(Example) An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an outline of the present invention, in which a plurality of, for example, four nodes A to D are connected to a bus BL, and these nodes A to D exchange data with each other via a common bus BL. Sending and receiving are possible.

The node D is, for example, a speedometer, and the other nodes A to C can request data (speed information) from this node D as needed. Transmission/reception control employs the so-called C8MA/CD system. CSMA/CD allows bus connection and is advantageous as an in-vehicle communication system. However, as the bus occupancy increases, low-priority signals experience significant transmission delays.

For example, the frame F that transmits vehicle driving information has an SD (Start Delimiter) as shown in FIG.
The frame has a frame structure including a code, a priority code, a type code, a frame ID code, data, and a check code. Furthermore, ACK after check code
A field (reception confirmation signal area) is provided, and each node returns an ACK signal unique to each node in the reception confirmation signal area corresponding to the bit area corresponding to these nodes to confirm normal reception. I have to.

Furthermore, the frame G requesting data transmission is, for example, the third
As shown in the figure, S D (Start Delimit
er) code, priority code, type code, request ID code, check code, and ACK field, and is shaped like a data area is missing.

The SD code is a specific code representing the start of frame F, and the receiving node recognizes the start of frame F when receiving this SD code. The priority code is a code used for priority control, and indicates the priority order that instructs which signal will be transmitted preferentially when multiple nodes transmit data at the same time and the signals collide. be. If a collision occurs between multiple pieces of data, data with a higher priority is transmitted first. The type code is an area indicating the type of frame, and is defined such that, for example, if it is "0", it is a frame F1 that transmits data, and if it is "1", it is a frame G that requests data.

The frame ID code is a code that identifies what kind of data is assigned to each bit of the data area in the frame, and it indicates what kind of data is combined to make up the data area. . The receiving node can identify the content of the data in the data area of the transmitted frame by this frame ID code. In the case of data transmission request frame G, the identification number of the requested data is shown.

When each node A to D requests data from another node, each node sends a transmission flag F of the transmission request frame ID.
Set 1. When flag F1 is set, it is sent when it has the highest priority among the transmission flags of other transmission data frames and transmission request data frames set at the corresponding node, and when the multiplex transmission path BL is empty. If successful, flag F is lowered.

The transmission request frame G is received by all connected functioning nodes. If the ID number of that frame is the ID number that a certain node should transmit, it transmits the data frame F with the corresponding ID number.

The action will be explained below.

For example, node A, node D whose BSC is a speedometer
shall request data (speed information) from. Furthermore, the ID of the speed data is assumed to be △△. and,
Assume that node A among these three nodes A to C first requests node D to send data. Node A is
In order to request node D to send data, the transmission flag F1 of the transmission request frame ID △△ is set, and if F has the highest priority among the transmission flags set in node A, and the frame is empty. When the transmission request frame ID ΔΔ is present, the transmission request frame ID ΔΔ is sent to the bus BL (FIG. 4).

When this transmission request frame ID△△ is sent to bus BL, flag F1 of node A is cleared, and node B-D
receives this frame.

When nodes B and C receive the transmission request frame ID△△ on bus BL, they determine that node A has requested node D to send data, that is, speed information, and if they If the speed signal transmission request flag F2 for node D is set, it is canceled.

That is, nodes B and C each transmit request frame ID Δ
Reset each transmission flag F1 of Δ. Then, it waits for the data for the transmission request frame ID ΔΔ of the node A to be sent from the node D to the bus BL.

On the other hand, upon receiving the transmission request frame ID ΔΔ transmitted from the node A, the node D transmits data (speed information) for the frame ID ΔΔ to the bus BL. Therefore, each node A to C takes in the data (speed information) sent from node D to bus BL. This eliminates the need for each of nodes A to C to request the same data from node D, and node D also
There is no need to send the same data to the bus BL every time a request is made by ~C. As a result, the frame occupancy rate of the bus BL becomes low (1/3), and the bus BL becomes vacant for a large amount of time. As the free time on the bus BL increases, the response time to other low-priority transmission requests becomes shorter.

Further, as described above, if nodes B and C send not only the transmission request frame but also the transmission data sent from node D, that is, the speed data of ID ΔΔ, If the transmission flag F1 of the transmission request frame is set, by clearing it, the frame occupation rate can be reduced and the response speed can be increased.

(Effects of the Invention) As explained above, according to the present invention, a large number of nodes are connected to a common bus, a certain node requests another node to send data, and the other node receives the request. In a transmission request response method for a transmission system that sends data to a bus, multiple nodes make a transmission request to another node, and one of the nodes sends the transmission request to the bus first. The remaining nodes confirm that the transmission request has been made and cancel their own transmission requests, and when the data requested by the one node is sent from the one node to the bus, the remaining nodes confirm that the transmission request has been made and cancel their own transmission request. By allowing the nodes to take in the data, the frame occupancy rate of the bus can be lowered, and requests from nodes with lower priority can be quickly responded to, thereby improving the system performance. It is possible to improve responsiveness. Furthermore, it is possible to add new nodes without upgrading the system, and there are excellent effects such as the ability to utilize the transmission system more effectively.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a transmission circuit to which the transmission request response method for a transmission circuit according to the present invention is applied, and FIG. FIG. 3 is a diagram showing another example of the frame structure for transmitting information used in the transmission circuit of FIG. 1, and FIG. An explanatory diagram of a transmission request response method in a circuit, FIG. 5 is a block diagram of a transmission circuit to which a conventional transmission request response method is applied, and FIG. 6 is a diagram showing a conventional transmission request response method in the transmission circuit shown in FIG. It is. BL...Bus, A-D...Node, F...Frame.

Claims (1)

[Claims] A transmission request response method for a transmission system in which a large number of nodes are connected to a common bus, one node requests another node to transmit data, and the other node transmits the requested data to the bus. In , multiple nodes make a transmission request to another node, and when one of the nodes sends a transmission request to the bus first, the remaining nodes do not know that the transmission request has been made. Transmission characterized in that the plurality of nodes confirm and cancel their own transmission request, and when the data requested by the one node is sent to the bus from the other node, the plurality of nodes take in the data. Circuit transmission request response method.