JPH01143533A - Multiplex transmission system - Google Patents

Abstract

PURPOSE:To prevent malfunction and to improve the reliability by initializing a multiplex node so as to receive a transmission data from other multiplex node at the start of each multiplex node. CONSTITUTION:In the event of a started multiplex node after reset after power application or runaway, a destination address and an address to send a signal to all multiplex nodes are designated to all 1 within a prescribed time from the reset, a transmission request code frame ID (=1) is added to a frame ID, the frame ID of a required data is added to a data area and the result is sent to a multiplex transmission line MB. The multiplex node receiving the frame discriminates the frame ID code and detects the frame ID required by a transmission multiplex node from the inside of the data area. Then the multiplex node having the corresponding ID code as a transmission data sends its transmission data to the transmission line. Thus, a required data is obtained from other multiplex nodes started already.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a so-called C3MA/CD (Carrier
SenseMultiple Access/C
The present invention relates to a multiplex transmission system using a transmission system (O11ision Detection), and specifically relates to a method for initializing a multiplex transmission system.

(Prior Art) Conventionally, multiplex transmission systems for automobiles include a plurality of multiplexed nodes interconnected via multiplexed transmission paths, and data is transmitted from one of the multiplexed nodes for each frame having a destination address. , when the multiplex node specified by this destination address successfully receives the frame, a distributed control multiplex transmission system using the C5MA/CO transmission system returns a reception confirmation signal from the specified node following this frame. Proposed.

Now, if we show a schematic configuration diagram of a multiplex transmission system for automobiles using this C3MA/CD transmission system, it will be as shown in Figure 8. In this figure, a multiplex transmission line (bus) consisting of twisted pair wires A plurality of multiplex nodes, namely, a front multiplex node FN, a combination switch multiplex node C81, a meter multiplex node MT, and a rear multiplex node RN are connected via the MB.

Incidentally, a front turn light signal lamp 6, a front turn left signal lamp 7, a front small lamp 8, and a horn 9 are connected to the front multiplex node FN, and a turn light switch 10 is connected to the combination switch multiplex node C3. , turn left switch 11, small lamp switch 12, horn switch 1
3. A headlamp high beam switch 14 is connected, a turn light indicator 15, a turn left indicator 16, and a headlamp high beam indicator 17 are connected to the meter multiplex node MT, and the rear multiplex node RN has a rear turn A light signal lamp 18, a rear turn light signal lamp 19, and a tail lamp 20 (this tail lamp 20 is turned on when the small lamp switch 12 is turned on) are connected.

By the way, in such a multiplex transmission system for automobiles, as shown in FIG.
Vehicle driving information is transmitted for each frame F having the configuration shown in a). Here, this frame F includes an 8-bit (Start Delimiter) code, destination address, own station address, data length, and data 1.
-The frame has a data N1 check code.

First, the SD code is a specific code representing the start of frame F, and the receiving multiplex node recognizes the start of frame F when it receives this SD code symbol. If each multiple node in the network used in such a transmission method has its own address and destination address specified in 8 pintos, then 0 to (2" -1
) = Any number up to 255 is assigned as an address. That is, a maximum of 256 multiple nodes can be connected within the network, and each multiple node has
oooooooo~1111111 in different binary numbers
Addresses up to 1 are assigned. In reality, when 11111111 is specified as a destination address, it is called a global address, and a function of simultaneous broadcasting to all nodes is added, and 25 nodes that can connect to the network are added.
There are many cases where there are 5 pieces.

Therefore, in such a conventional automobile multiplex transmission system,
When transmitting a frame once, there are only two ways to send it: to one multiplex node or to all multiplex nodes. The address of the node is written, and the multiple node that receives this frame can know from which multiple node the frame was sent.

The number of data that follows is written in the data length,
In this case, if there are N pieces of data, N is sent as the data length. The multi-node that receives this frame reads only the contents of the data length. The transmitted content that follows the data is a check code (error detection code), and by checking this, it is possible to know that the frame is at its end. In order to ensure data transmission, the receiving node uses a check code to check whether there are any errors in the contents of the received frame. After time 7, it sends its own address as a reception confirmation signal (ACK signal) A to the multiplex transmission path MB.

The multiplex node that transmitted frame F receives this ACK signal light, and the receiving side recognizes that the data has been received normally.

When data is not received correctly on the receiving side (when an error is detected by the check code) or when a framing error occurs (when the actually sent data is shorter or longer than the length specified by the data length) In this case, as shown in Figure 10 (bl), the receiving side does not return an ACK signal.In this case, as shown in Figure 10 fa+, the transmitting side must return an ACK signal within a certain time T! after frame transmission is completed. , determines that the transmission of frame F has failed, and starts retransmission of the same frame F.

Figure 11 shows a case where a frame for simultaneous broadcasting is transmitted from a certain multiplex node.The structure of the transmitted frame is the same as that for transmission to one multiplex node as shown in Figure 11 (al), but the destination address is Global address (11
111111) is sent. In this case, the multiplex transmission path MB
All multiplex nodes connected to will receive this data. Assuming that all the multiplex nodes are receiving normally, as shown in Figure 11 (bl), after a certain time ↑, (〈Tyo) time from the end of the frame, they will simultaneously send their own address as an ACK signal A. Send it back.

In the above-mentioned C5MA/CD transmission system, instead of constantly transmitting data to the multiplex transmission path MB, the event is to effectively utilize the multiplex transmission path MB and improve reliability by making each multiplex node equal. I'm trying.

For example, in the combination switch front multiplex node C8 in FIG.
The information is transmitted to the meter multiplex node MT and the rear multiplex node RN, and the respective multiplex nodes perform operations such as lighting the small lamp 8, dimming the meter, and lighting the tail lamp 20.

In the automobile multiplex transmission system, as shown in Figure 12, due to differences in how each electrical component is used, a 10B power supply, accessories (
There are three power start timings: ACC) power supply and ignition (IGI) power supply. +B power supply is for operating electrical components even when the ignition key is not turned on, and is used for front multiple node FN and rear multiple node R.
N and combination switch multiple node C8 is 10B
It is necessary to operate with a power supply, and a 10B power supply is also supplied to the multiplex control circuit in each multiplex node. Accessories (A
CC>The ignition key is turned on, but -
In a, the engine is not rotating and is therefore not generating electricity to operate electrical components, and radios and the like are operated by the accessory power source. The ignition power source is used to operate electrical components when the engine is rotating and the vehicle is running, and the meter multiple node MT is supplied with the ignition power source. +Bt[ is a power supply that is constantly supplied when connected to a battery, and the accessory power supply and ignition power supply are power supplies that are supplied by the ignition key, and the timings at which they are supplied are different.

(Problems to be Solved by the Invention) However, in the conventional multiplex transmission system, in the following three cases, a multiple node connected to a multiplex transmission line matches the content of data to be transmitted from another multiple node. There is a problem in that it may retain data that is not intended for use.

First, in transmission between multiple nodes that operate on dissimilar power supplies, that is, power sources that start being supplied at different times, a multiple node that is activated later cannot obtain information about a multiple node that is activated earlier. There is a problem. As shown in Figure 8, when only the meter multiplex node MT operates on the ignition IGI power source and the other multiplex nodes operate on the 10B power source, the 10B power source is supplied but the ignition IGI power source is not supplied. When the small lamp ON signal is transmitted from the combination switch multiplex node C8 in the state, the front multiplex node FN and the rear multiplex node RN respectively light the front small lamp 8 and the tail lamp 20, but the ignition signal is not sent to the meter multiplex node MT. The small lamp on signal cannot be received because the IG1 power is not supplied. Later, even if the ignition IGI power is supplied to the meter multiplex node MT, the small lamp switch 12 remains on in the combination switch multiplex node C8. Since it does not change, it does not transmit a small lamp on signal. Therefore, at the meter multiplex node MT, the indicator remains un-dimmed.

Second, even among multiple nodes that operate on the same type of power source, due to differences in the rise characteristics of internal constant voltage power supplies, multiple nodes that are started later are activated and operated earlier. There is a problem that it is not possible to receive signals from. In an automotive multiplex transmission system, each multiplex node has +B supplied externally to operate the logic circuit.
It is equipped with a constant voltage circuit that converts +12V to +5V. As shown in FIG. 13, these constant voltage circuits have different characteristics depending on the multiplexed nodes, so that their rise times also differ, and there is a difference in the operation start time of each multiplexed node. In FIG. 13, the output A of the constant voltage circuit reaches the operation start level earlier, and the output B reaches the operation start level later.

Furthermore, to explain in detail the transmission between the air conditioner switch multiple node 21 and the air conditioner unit multiple node 23 with reference to FIG. 14, the signal processing section 21a of the air conditioner switch multiple node 21 monitors the state of the air conditioner switch 22, When there is a change in state, the transmission control section 21b transmits a switch multiplex signal to the air conditioner unit multiplex node 23. The transmission control section 23b of the air conditioner unit multiplex node 23 receives this multiplexed signal, the signal processing section 23a decodes it, and energizes various actuators 24 for the air conditioner according to the contents of the switch multiplexed signal 5. Air conditioner switch multiple node 2
If the constant voltage power supply No. 1 rises earlier than that of the air conditioner unit multiple node 23, the air conditioner switch multiple node 21 is activated and the air conditioner unit multiple node 23 is not activated, that is, point A in FIG. Even if the state of the air conditioner switch 22 changes between the point and the point B, the air conditioner unit multiplex node 23 cannot receive the switch multiplex signal and therefore does not operate normally.

Thirdly, even if power is supplied to all multiplex nodes, if a certain multiplex node goes out of control and a signal processing unit heliset signal is applied from the runaway detection circuit in that multiplex node, for example, if the multiplex node's power supply Even when the circuit is reset to zero by a low-voltage reset signal and the previously stored data is cleared, the internal state of the signal processing unit is initialized, making it impossible to know the current state of other multiple nodes. There is a problem. To explain in detail with reference to FIG. 8, all four multiplex nodes are activated, the small lamp switch 12 of the combination switch multiplex node C8 is in the on state, and the small lamp 8 of the front multiplex node FN is in the lit state. If a reset signal is applied to the signal processing section of the rear multiplex node RN when the tail lamp 20 of the rear multiplex node RN is in the lighting state and the indicator of the meter multiplex node MT is in the dimmed state, the rear multiplex node RN The internal data of is initialized and the tail lamp 20 is turned off. Since the combination switch multiplex node C3 does not know about the reset of this rear multiplex node RN and there is no change in the event of the small lamp switch 12, the combination switch multiplex node C3 does not transmit the small lamp switch on signal again. In this case, even after returning from reset, it is impossible to know the state of a switch that remains unchanged after reset.

The present invention was developed in view of the above circumstances, and prevents malfunctions and improves reliability by initializing each multiplex node to receive transmission data from other multiplex nodes when starting up. The purpose of this invention is to provide a multiplex transmission system that allows

(Means for Solving the Problem) In order to achieve the above object, according to the present invention, each multiplex node is provided with a plurality of multiplex nodes connected to a common multiplex transmission path, and when an event occurs, the corresponding multiplex In a multiplex transmission method in which a node transmits data of its event via the multiplex transmission path, a multiplex transmission method is provided in which, when each multiplex node is activated, the activated multiplex node transmits a frame indicating a transmission request to other multiplex nodes. be done.

(Operation) If there is a lag in the startup time of multiple nodes that are activated by different types of power sources or the same type of power source, or if multiple nodes are reset after activation, each multiple node that is activated later will not be connected to other multiple nodes at the time of activation. A frame indicating a transmission request is sent to the node, and data from other multiple nodes at that time is received to prevent malfunctions and improve reliability.

(Example) Hereinafter, an example of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a diagram showing the general format of a frame F used in the multiplex transmission system of the present invention.
It consists of a D code, data length, data, and check code. As mentioned above, the SD code is located at the beginning of frame F and indicates the start of that frame, the destination address specifies the multi-node to which the transmitted data should be received, and the own station address specifies the frame F. Indicates the multiplex node to be transmitted, the data length gives the length of the next data, data data...N is written in the data area, and the check code is CRC.

It consists of codes such as checksum and parity, and is used to check the contents of the received frame F. The frame ID code is a code that indicates the allocation of data allocated to each bit of the data area, and the receiving side multiplex node can recognize the contents of the data by the frame ID code.Normally, the transmitting multiplex node The receiver specifies the address of the destination multiplex node as the destination address, then specifies the address of the transmitting multiplex node as its own address, specifies the frame ID code of the frame and the length of the data to be sent, Data is sent to the data area, a check code is added to all bits, and the data is sent to the multiplex transmission path.

When the power of each multiplex node is turned on, if the activated multiplex node sends a specific transmission request frame shown in FIG. Send all data that should be sent. In other words, the activated multiplex node specifies the destination address as the aforementioned global address (all 1) that should send a signal to all multiplex nodes within a predetermined time from the reset after power-on or the reset upon recovery from the aforementioned runaway. and send the transmission request code (frame ID=1) to frame I.
D, a frame ID code of the required data is added to the data area, and the frame ID code is sent to the multiplex transmission path. The multiplex node that received this frame judges the frame ID code, detects that the multiplex node represented by its own station address has issued a transmission request message, and selects the frame required by the transmitting multiplex node from inside the data area. A multiplex node that detects the ID and has the corresponding frame ID code as transmission data sends the transmission data to the multiplex transmission path. As a result, a multiple node that issues a transmission request message when the power is turned on can obtain necessary data from other multiple nodes that are already activated. Here, if the frame ID code of the transmission request frame is used as the frame ID code of all frames to be received by the transmitting multiplex node, the transmitting multiplex node can, in principle, collect all necessary data at that point. Therefore, each multiplex node can receive data that it should originally receive even if the power supplies are turned on at different times. In this embodiment, the number of frames requested to be transmitted is one, but by expanding the data area of the transmission request frame, requests for transmission of multiple frames can be easily accommodated.

Assuming that the meter multiplex node MT that was activated later, as mentioned in Problem 1 above, transmits the transmission request frame shown in FIG. Transmission request from meter multiple node MT from address (meter=2) (frame ID-1)
of the frame requested to be transmitted from the code in the data area. It is detected that the D code is 2. The front multiplex node FN and rear multiplex node RN in FIG. 8 do not have frame ID=2 as transmission data and therefore do not transmit anything, but combination switch multiplex switch C8 has frame ID=2 as transmission data. , transmits the frame of FIG. 3 to the meter multiplex node MT. The meter multiplex node MT learns from the data area (small lamp lit) of the frame shown in FIG. 3 that the small lamp is lit.

FIG. 4 is a diagram showing an example of a transmission request frame in which one multi-node is designated as the destination without using the global address as the destination address when there is only one frame to be transmitted. The destination address is designated as Combi 5W-3, indicating Combination Switch multiplex node sc.

In the embodiments described above, the processing of the received signal is somewhat slow because the multiplex node that receives the transmission request frame needs to determine the requested frame ID. 3 [It's rough.

FIG. 5 shows another embodiment of the transmission request frame,
This frame has neither a destination address nor a local address specified, and does not include data indicating the requested frame ID code in the data area. configured to send. FIG. 6 also shows another embodiment of a request to transmit frame requesting all multiplex nodes to transmit all frames they have. The destination address is specified by a global address, and the local address is specified by the address of the multiple node that issued the transmission request. When all multiplex nodes transmit all frames, the traffic on the multiplex transmission path increases when the system starts up in a multiplex transmission system with a large number of multiplex nodes and a large number of frames to be processed, such as when many multiplex nodes start up at the same time. Rather than transmitting all frames since this may affect the response, it can be configured to transmit all frames whose data differs from the initial value. In other words, if the data to be sent is the same as the initial value, there is no need to send it after a reset because the data on the multiple nodes is the initial value and the sending and receiving sides have the same data value. When the system is started, which is likely to increase, much of the data remains at its initial value, and there is less need to send it, which eliminates the impact on responsiveness when the system starts.

FIG. 7 is a diagram showing an example of a transmission request frame in a multiplex transmission system that performs priority control. Priority control is such that when signals are returned all at once from other multiple nodes in response to a transmission request frame from one multiple node, the signals are accepted in order of priority to prevent the signals from colliding with each other. This is to restore the condition. Since the transmission request frame is an important signal for unifying the data held by each multiplex node, it is given the highest priority in priority control in order to quickly complete its processing.

(Effects of the Invention) As explained above, according to the present invention, each multiplex node is provided with a plurality of multiplex nodes connected to a common multiplex transmission path, and when an event occurs, the corresponding multiplex node transmits data of the event. In the multiplex transmission method that transmits data via the multiplex transmission path, when each multiplex node starts up, the activated multiplex node transmits a frame indicating a transmission request to other multiplexed nodes, thereby reducing startup delays caused by different types of power sources and power supply circuit failures. In the case of startup delays due to variations in startup times due to variations in characteristics, or startup delays due to resets of multiple nodes in a multiplex transmission system, each multiplex node is returned to its normal state, preventing system malfunctions and improving performance. The effect of being able to achieve this goal is obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a general format of a frame used in the multiplex transmission system of the present invention, FIG. 2 is a diagram showing an embodiment of a transmission request frame, FIG. 3 is a diagram showing an example of a response frame, and FIG. 7 to 7 are diagrams showing other embodiments of transmission request frames, FIG. 8 is a schematic configuration diagram showing a multiplex transmission system for automobiles using the CSMA/CD multiplex transmission system, and FIGS.
Fig. 11 is a diagram showing the frame format 7 in the conventional multiplex transmission system for automobiles, Fig. 12 is a diagram explaining startup timing based on various sources, and Fig. 13 is a rise characteristic of a constant voltage circuit in a multiple node. A diagram explaining the variation in
FIG. 14 is a diagram illustrating signal transmission between the air conditioner switch multiple node and the air conditioner unit multiple node. 6...Front turn light signal lamp, 7...
・Front turn left signal lamp, 9... Horn, 10... Turn light switch, 11... Turn left switch, 15... Turn light indicator, 16... Turn left indicator, 18...
Rear turn light signal lamp, 19... Rear turn left signal lamp, A, A3. A5...Reception confirmation signal (ACK signal), cs...Combination switch multiple node, FN...Front multiple node, F
...Frame, MB...Multiple transmission line, MT...Meter multiplex node, RN...Rear multiplex node.

Claims (4)

[Claims] (1) In a multiplex transmission method, each multiplex node includes a plurality of multiplex nodes connected to a common multiplex transmission path, and when an event occurs, the corresponding multiplex node transmits data of the event via the multiplex transmission path, A multiplex transmission system characterized in that when each multiplex node is activated, the activated multiplex node transmits a frame indicating a transmission request to other multiplex nodes. (2) The multiplex transmission system according to claim 1, wherein the other multiplex node transmits all frames that can be transmitted from the other multiplex node to the activated multiplex node. (3) The multiplex transmission according to claim 1, wherein the other multiplex node transmits all frames in which the data in the data area within the frame is different from the initial value, out of all the frames that can be transmitted from the other multiplex node. method. (4) The multiplex transmission system according to any one of claims 1 to 3, wherein the frame indicating the transmission request is given the highest priority among all frames and transmitted.