JPS62208737A - Operating state decision method in multiplex communication system - Google Patents

Abstract

PURPOSE:To grasp the operating state of a node by sending a data from each node on a communication line at each prescribed period, monitoring the data on the communication line in the timing at which no data is sent and detecting the node without transmission at each said period. CONSTITUTION:Input/output terminals 1a-6a of plural nodes 1-6 having a transmission/reception function are connected by one communication line 1 and each node applies time division multiplex transmission in the titled multiplex communication system, then each node sends a data at each prescribed period and monitors the data on the line 1 in the timing when no transmission exists, a node without transmission in the said period is detected and if a node having no detection of transmission one or plural times consecutively exists, it is decided that the transmission function of the said node is stopped. Thus, the node where no transmission exists supervises other nodes and the operating state of each node is accurately grasped without changing the system constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for determining the operating state of a multiplex communication system suitable for use in, for example, a multiplex communication system mounted on a vehicle.

"Prior Art" It is desirable for a transmitting system or a receiving system mounted on a vehicle to have a simple configuration and be lightweight. Therefore, a multiplex communication system has been developed in which multiple nodes can transmit and receive data through a single communication line. FIG. 3 is a block diagram showing the configuration of a transmitting/receiving system that employs this multiplex communication method.

In this figure, 1 is an audio unit (node) mounted on the vehicle, 2 is an air suspension unit (node) that adjusts the vehicle height, and 3 and 4 are radio switch units for controlling each of the above units. (node)
and air suspension switch unit (node)
It is. The radio switch unit 3 and air suspension switch unit 4 are operated by the driver. Further, 5 is a radio switch unit operated by a fellow passenger, and 6 is a display unit (node) that displays the operating status of the audio unit 1 and the air suspension unit 2.

The input and output terminals of each of the units l to 6 described above are each connected to one data line 10, and this data line I
Data is exchanged only through O.

Also, as can be seen from the above explanation, each unit is LA
N (Local Area Network).

Next, lb to 6b are communication control units that control data exchange between the units 1 to 6, and each unit has a built-in microcomputer. In this case, the output terminal 1c of the communication control section 1b is connected to the base of the transistor Tr via a resistor, as shown in FIG. transistor T
r has a collector connected to the positive power supply terminal (voltage Vcc), and is also connected to the data line 10 via the input/output terminal 1a, and has an emitter grounded.

In addition, the input terminal 1d of the communication control section 1b is the direct input/output terminal 1.
connected to a. The communication control sections 2a to 6a in each of the units 2 to 6 have the same configuration as the communication control section Ib described above.

Now, to explain the characteristics of the data line IO,
This data line 10 is connected to the collector of the transistor at the input/output terminal of each unit I to 6, so if any transistor T+4<1 is turned on, the data line 10 is forced to turn on regardless of the state of the other transistors Tr. It becomes ground level (low level). That is, the data line 10 is configured to give priority to the low level side, and when any one of the units 1 to 6 is outputting a low level signal, the other units cannot output a high level signal. The structure is as follows.

Next, data transfer in each unit 1 to 6 will be explained.

The signals output from units 1 to 6 are asynchronous signals as shown in FIG.
It consists of TR (1 or 5.5 bits), a high level start bit S1 data part B (8 bits), a parity bit, and a high level end signal.The start bit, data bit B1 and parity bit are , the first half of each bit is the content of that bit (see drawing S
or D), and the latter 0.5 bit is a gap G at a level that is the inversion of the bit content. One of the reasons why the gap G is provided in this way is to easily detect the usage state of the data line IO. That is, according to the above-mentioned signal format, as shown in FIG.
When a signal is being output, it is always at a low level for a period exceeding at least 0.5 bits. Therefore, it is possible to know whether the data line 10 is in use by detecting whether the state of the line is low for a period exceeding 0.5 bits (for example, 1 bit).

Furthermore, the data transfer between the audio unit 1, the air suspension unit 2, and the display unit 6 is unidirectional data transfer, as shown in FIG. 3, and is asynchronously transmitted. The format of the transmitted data in this asynchronous transmission is as shown in FIG. 6(a). Data D shown in this figure is the receiving unit address (i.e., the address of display unit address 6)
This is address data consisting of and a transmitting unit address, and data D and the following are various data used for display. In this case, the data DI start signal ST
R is set to 5.5 bits (hereinafter referred to as STR1),
The start signal STR for data D, , D, . . . is set to 1 bit (hereinafter referred to as 5TR2). Therefore, the display unit 6 shows that the start signal is STn l
By determining whether the received data is address data or display data, it is possible to know whether the received data is address data or display data.

Next, the audio unit l and radio switch units 3 and 5 are in a mask and slave relationship, respectively.
Similarly, the relationship between the air suspension unit 2 and the air suspension switch unit 4 is that of a mask and a slave.

In order to exchange data between the mask and the slave, the mask side first outputs the data request signal shown in FIG. 6(b), and then the slave side outputs the data request signal shown in FIG. 6(c) under the control of the mask side. It is designed to output a data return signal. The bidirectional arrows shown in FIG. 3 indicate the direction of the data transfer. The data request signal in this case is
As shown in FIG. 6(b), it is a signal containing only data D1, and this data D1 is a signal similar to data D shown in FIG. 6(a). In addition, the data reply signal consists of only data components, as shown in FIG.
The data D + , D x , etc. shown in this figure are not shown in the same figure (a), and the data D t , D s , etc.
・This is the same data.

Next, in the above system, the operation of data collision avoidance when two or more units compete with each other and start transmission will be described.

Now, as shown in FIG. 7, it is assumed that the audio unit 1 and the air suspension unit 2 on the mask side start transmitting at the same time. In this case, the transmission signal is the 6th
Since the signal is one of those shown in FIGS. (a) and (b), the address data of the receiving unit is sent out after the start signal and start bit. And time t. Up to time t, the data of audio unit I and air suspension unit 2 are the same. It is assumed that these data are different thereafter.

In this case, time t. Previously, data line IO
The level of the output signal of each unit 1.2 is equal to the level of the output signal of each unit 1.2, but at time t. In this case, the level of the output signal of the air suspension unit 2 is different from the level of the data line IO. This is because, as mentioned above, the data line IO is configured to give priority to the lower level side.
It's time. This is because the low level signal of the audio unit 1 in is given priority. In the air suspension unit 2, it is determined that a data collision has occurred when a difference between the level of the output signal and the level of the data line IO is detected, and as a result, a collision is detected at time t0. After that, the air suspension unit 2 suspends transmission. Then, only audio unit l continues to transmit, and collisions are avoided. Note that collision detection for audio unit I is also performed in exactly the same manner as described above. In conventional systems, data collisions are avoided as described above, and as a result, data can be exchanged between a plurality of units via a single communication line.

In addition, in the above system, data is sent only when there is a change in the data to be displayed or when there is a change in the operating status of a switch, and when data does not need to be changed, Prevents data transmission. As a result, only the necessary data is sent to the data line IO, which increases its utilization efficiency, and also has the advantage of shortening the time from when a data sending request is made until it is sent onto the data line 10. It was done.

"Problems to be Solved by the Invention" By the way, in the conventional system described above, when data is not sent on the data line 10, either the transmission is not performed because there is no data to be transmitted, or the transmission is not performed. There was a problem in that it was not possible to determine whether data was not being transmitted because the transmission function of the node that was supposed to perform this was stopped, and the operating state could not be determined.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a method for determining the operating state in a multiplex communication system that can monitor the operating state of nodes and grasp the situation.

"Means for Solving the Problems" In order to solve the above problems, the present invention provides that the input/output ends of a plurality of nodes having transmitting/receiving functions are each connected by one communication line, and each of the nodes In a multiplex communication system configured to perform time division multiplex transmission, each node transmits data at predetermined intervals, and
At the timing when no transmission is performed, the data on the communication line is monitored to detect nodes that are not transmitting at each predetermined period, and if there is a node for which transmission is not detected one or more times in a row, It is determined that the transmission function of the node in question has stopped.

"Effect" Since each node detects the transmission status of other nodes at times when they are not transmitting, the nodes in the system mutually monitor each other.

``Example'' Hereinafter, an example of the present invention will be described with reference to the drawings.Here, as an example of the present invention, FIGS.
An embodiment in which the invention is applied to the multiplex communication system shown in FIG. 7 will be described.

First, an overview of this embodiment will be explained.

First, in the case of asynchronous transmission, each unit
Transmission is repeated at every predetermined period T as shown in FIG. 2, and in the case of synchronous transmission, reply data is sent at every predetermined period T as shown in FIG. In this case, in asynchronous transmission, if there is no change in the data, the same data is retransmitted, and if there is a change in data, new data is transmitted; teeth,
When there is no data request signal, the same data as the previously sent data is sent out, and when there is a data request signal, new data at the current time is sent out.

In addition, the above-mentioned period T is set to be sufficiently long compared to the time for one transmission of each unit, so that all the transmissions and receptions of all units can be completed within the period T (the figure is shown for illustrative purposes only). (The data part is displayed for a long time).

In addition, each unit monitors the signal on the data line 10 at a time when it is not transmitting data,
The monitoring operation shown in the flowchart of FIG. 1 is performed. below,
The monitoring operation of this embodiment will be explained based on FIG.

First, in step SPI, the communication control unit ib~6
Clears the timer in the microcomputer provided in the microcomputer installed in the controller.b (see FIG. 3). This timer measures the transmission period T described above. Next, step SP
2, it is determined whether a signal has been sent on the data line 10. If no signal is sent on the data line 10, this determination is rNOJ and the process moves to step SP5, where it is determined whether the timer has finished counting the period T. If not, the determination at step SP5 is rNOJ, and the process returns to step SP2.

On the other hand, the determination in step SP2 is rY E S J
If so, move to step SP3, and execute this step SP3.
The data on the data line 10 is read at the step. Then, identify the sending unit from this read data,
Next, the process moves to step SP4, and a data reception flag provided corresponding to the unit is set. When the process of step SP4 is completed, the process moves to step SP5, and it is determined whether the timer has finished counting the period T. If this determination is rNOJ, the process returns to step SP2 and the above process is executed again.

Next, when the timer finishes counting the period T and the determination in step SP5 becomes rY E S J, the process proceeds to step SP
6, it is determined whether the data reception flag has not been set for a predetermined number of times or more. The determination in step SP6 is performed for each unit recognized in the reception operation in step SP3, and rY E S
For the unit determined to be J, it is determined in step SP8 that a failure has occurred, and then the failure is displayed in step SP9. On the other hand, for the unit for which the determination is "NO" in step SP6, step S
At P7, the reception flag of the corresponding unit is reset, and the process returns to step SPI to repeat the above operation.

In the above operation, the reception flag becomes unset when the corresponding unit does not transmit during the period T, and there are two cases described below. One case is when the transmission function of the unit is out of order, and the other case is when the unit attempts to transmit after the period T and another unit is transmitting. In other words, when another unit is transmitting, the unit enters a transmission standby state and starts transmitting only after the transmitting unit finishes transmitting, so the data transmission interval becomes longer than the period T. It is. However, in this case, when the monitoring unit executes step SP2 again, it is determined to be rYEsJ, so at this time, the data reception flag is set via step SP3.4. Therefore, unless there is a failure in the unit, the non-set state of the data reception flag will not be continuously detected. The determination at step SP6 described above is a process for determining whether the unit is malfunctioning or not. If the non-set state of the data reception flag continues for a preset number of times or more, the microcomputer's processing is SP
8 to perform failure-by-failure identification.

Therefore, for example, if the predetermined number of times is set to two,
In both cases of asynchronous and synchronous transmission, the second
At timing t1 shown in FIG. 3(C), it is determined that the transmission function of the unit has stopped.

Note that in the flowchart shown in FIG. 1, after the determination in step SP6, the process is divided into the process in step SP8.9 and the process in step SP7, but in actual operation of the microcomputer, these processes are performed in a time-sharing manner. It looks like this. For example, “NO” in step SP6
If there is a unit that is determined to be ``rYES,'' then step SP8.9 is performed for that unit, and then step S is performed for the unit that is determined to be ``rYES''.
Processing from P7 onwards is performed.

Furthermore, in this embodiment, it is determined in step SP6 whether the data reception flag has been in the non-set state for a predetermined number of times or more, but when this invention is applied to a system configured to prevent transmission conflicts, Alternatively, if the non-set state is detected even once, it may be immediately determined that a failure has occurred.

"Effects of the Invention" As explained above, according to the present invention, the input/output ends of a plurality of nodes having transmitting/receiving functions are each connected by one communication line, and each node can transmit time-division multiplexing. In a multiplex communication system configured to perform this, each node transmits data at predetermined intervals, and when not transmitting data, monitors data on the communication line and transmits data within the predetermined cycle. If there is a node where transmission is not detected once or several times in a row, it is determined that the transmission function of that node has stopped, so transmission is not performed. Nodes mutually monitor other nodes, thereby making it possible to accurately grasp the operating status of each node without changing the configuration of the system.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram showing a transmission signal in an embodiment of the present invention, FIG. 2 is a waveform diagram illustrating transmission abort processing after collision detection in the same embodiment, and FIG. 3 is a waveform diagram showing a transmission signal mounted on a vehicle. FIG. 4 is a block diagram showing the configuration of the multiplex communication system. FIG. 4 is a circuit diagram showing the configuration of the data line IO of the system shown in FIG. 1. FIG. 5 is a waveform diagram showing the output signals in the system. FIG. 7 is a conceptual diagram showing an aspect of transmission data in the system, and is a waveform diagram for explaining transmission interruption processing when a conventional priority setting method is used. I~6...Unit (node), la~6a・
...Input/output terminal, 1b to 6b...Communication control section, 10...Data line, STR...
・Start signal.

Claims (1)

[Claims] In a multiplex communication system in which the input and output ends of a plurality of nodes having transmitting and receiving functions are each connected by a single communication line, and each of the nodes is configured to perform time division multiplex transmission, each of the nodes has a predetermined Data is transmitted every cycle, and when data is not being transmitted, the data on the communication line is monitored and nodes to which transmission has not been performed are detected every predetermined cycle, and the data is transmitted one or more times in succession. A method for determining an operating state in a multiplex communication system, characterized in that if there is a node for which transmission is not detected, it is determined that the transmission function of the node is stopped.