JPH02262736A - Communication system by duplex data communication media - Google Patents

Abstract

PURPOSE:To perform the communication of data without delay due to a fault by transmitting the data to both duplex data communication media, handling only the data coming earlier as normal data and deleting the data coming later at a reception side. CONSTITUTION:A communication interface 10 and a communication interface 11 send the data I 18 and 19 from a CPU 4 to the data communication medium A 16 and the data communication medium B 17 as data II 20 and 21, respective ly. A CPU 5 handles the data received earlier, for example, data III 22 as nor mal communication data and deletes the data receiving later, for example, data III 23 in data communication from the communication interface 12 or 13. In such a manner, it is possible to continue the data communication without delay or missing the data compared with the data communication before the fault occurs even when the fault occurs in the data communication medium on one side.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention provides a system for communicating data between multiple devices that do not have a dual configuration using a duplex data communication medium, in which both data communication media are used at all times. The present invention relates to a communication method using a duplex data communication medium in which data communication is performed using a dual data communication medium.

"Prior Art" When performing data communication in a system in which data is communicated between multiple devices that do not have a dual configuration using a redundant data communication medium, in the conventional technology, each device always only uses one of the data communication media. was used for data communication.

"Problem to be Solved by the Invention" In the prior art, in order to perform data communication as described above, when one of the data communication media performing data communication fails, each device detects the failure and then
The data communication was restarted by switching to the other data communication medium. As a result, it takes a certain amount of time to switch the data communication medium, resulting in real-time control of the control system.
In systems where delays in data communication cannot be tolerated, data cannot be sent or received during the period between failure and switching, resulting in data loss.

In addition, if data communication is performed using multiple devices each in a dual configuration, data communication can be continued without data loss even if a failure occurs in the data communication medium, but dual configuration requires complicated and expensive devices. It had some drawbacks.

The present invention solves the above-mentioned drawbacks of the prior art, and includes:
Provides a communication method that allows data communication to continue without data loss when one of the data communication media fails in a system that communicates data between multiple devices that do not have a dual configuration using duplex data communication media. The purpose is to

1. In a system that communicates data between multiple devices that do not have a dual configuration using a duplex data communication medium,
Each device that performs data communication is connected to both duplex data communication media, and the sending device always sends data to both duplex data communication media, and the receiving device , if both types of data are received, only the first-arrived data is treated as regular data.

``Operation'' The data transmitting device transmits data to both of the duplexed data communication media, while the data receiving device receives the same data from both data communication media. , central processing unit (hereinafter abbreviated as CPU)
Since there are only 14 sets, the data is divided into data to be received first and data to be received afterward, and only the data that arrives first is treated as regular data, and the data that arrives later is discarded. In this way, by constantly using duplicated data communication media to perform data communication, even if one data communication medium fails, only the first-arrived data will be received normally by the other data communication medium. , it becomes possible to perform data communication without delay due to failure.

Furthermore, if the device on the receiving side cannot receive data that is supposed to arrive later, it can be assumed that one of the data communication media has failed, so it is also possible to detect a failure in the data communication medium.

Embodiment FIG. 1 shows an example of a data communication system to which the present invention is applied. In the figure, reference numeral 1 denotes a first device for data communication, and a CPU 4 that performs main processing within the device 1.
．． It consists of two sets of communication interfaces 10.11 and an internal bus 7 that interconnects them.

The second device 2 likewise consists of a CPU 5, two communication interfaces 12.13 and an internal bus 8.

3 indicates the n-th device (where n is an integer of 3 or more), and, like the device 1.2, it consists of a CPU 6.2 sets of communication interfaces 1, 4.15, and an internal bus 9. There is.

16.17, respectively, indicate a duplex data communication medium A and a data communication medium B, and communication interfaces 1-0.1-1.12. of each device 1.2 and 3.
Connected to 13.14.15.

In addition, as an example representing the flow of communication data, 18.
19 is the data ■ sent by the CPU 4 of the device 7, and 2
0.21 is the communication interface] 0.7.1 is the data communication medium A ]-6 and data communication medium B 17, and 22.23 is the communication interface 12.13 receives the data and sends it to the CPU of the device 2. The data ■ to be passed to 5 are shown respectively.

Next, with reference to FIGS. 1 to 5, a case will be described in which communication data is sent from device 1 and device 3 to device 2.

The CPtJ 4 of the device 1 adds a destination 38, a source 39, and a sequence number 40 as headers to the data I 18 or 19 to be transmitted, as shown in formats 1 to 1 in FIG. A request is made to the communication interface 11 to send data I 18, and immediately thereafter a request is made to the communication interface 11 to send data I 19.

Here, the sequence number 40 is a value modulo m that increases by 1 each time data is sent to one destination, m
is a natural number.

Figure 3 shows sequence number 4 when CPU 4 transmits.
In the example of adding 0, 24 is the correspondence table between the data destination 38 and the sequence number 40 added to data 2, 25 is the transmission time axis, and 26.27.28.29.30 is the transmission timing. Each is shown below. In this example, the sequence number 1 is transmitted to device 2 at timing 26 and to the nth device 3 at timing 27. Thereafter, in the same manner, timings 28 and 29 are set using sequence number 2.
It is transmitted to device 3 and device 2 at timing 30, and then transmitted to device 3 at timing 30 according to sequence 3.

The communication interface 10 and the communication interface 11 that received the transmission request from the CPU 4
4 data from I 18.19 to data communication medium A
16 and data communication medium B 17 as data II 20.21, respectively.

Note that FIG. 4 shows data I 18 or data II to which a source 38 and a sequence number 40 are added.
The format of I 22.23 is shown.

Next, the communication interfaces 12 and 13 of the device 2
are data communication medium A 16 and data communication medium B
When data 20.21 is received from 17, respectively, data I22.21 is received in the format shown in FIG.
23 and passed to the CPU 5 respectively. At this time, since the communication interfaces 10 and 11 and the communication interfaces 12 and 13 operate independently and asynchronously, it is difficult to determine which of the communication interfaces 12 and 13 passes the data III 22.23 to the CPU 5 first. Indeterminate.

Finally, in the data communication from the communication interface 12 or 13, the CPU 5 treats the data received earlier, for example data III 22, as regular communication data, and treats the data received later, for example data m23.
throw it away. At this time, the source 38 and the sequence number 40
Since it is determined whether the data was received earlier or later, it is possible to distinguish the data even if different data is received from another device between the first arrival and the last arrival.

FIG. 5 shows an example in which the CPU 5 of the device 2 handles the received data 22.23 from the devices 1 and 3, which is the sender 38, where 40 is the sequence number;
41, the data communication medium A 16 and the data communication medium B 17 used are abbreviated as A and B.

31 indicates handling as data. Furthermore, with respect to the time axis 32, the reception timings are shown at 33, 34, 35, 36, and 37, respectively.

In this example, with sequence number 1 from device 1, A,
Two identical pieces of data arrived from both lines of B at timings 33 and 34, so the third data of the first arrival was sent from device 1 at timing 35 using sequence number 2 using 8 lines. , treated as data.

In this case, the accident determination for line A is suspended.

The fourth data is sequence number 1 from the third device.
This data was sent at timing 36 using line A, and this data has the same sequence number and line used as the first data, but the transmission sources are different between device 1 and device 3. Treated as separate data. In this case, failure determination for the 8 lines is suspended.

The 5th data arrived from line A, but since it is the same as the 3rd data sent from line 8, the data is discarded, but the status of line A, which was on hold when the 3rd data was received, is It is determined to be normal.

Furthermore, if the CPU 5 does not receive the later data even after a certain period of time has passed since the CPU 5 received the first data, it can be assumed that one of the duplex data communication media has failed. This also makes it possible to detect failures in the data communication medium.

"Effects of the Invention" As is clear from the above explanation, according to the present invention, when data communication is performed using duplicated data communication media, even if one of the data communication media fails, the data communication is compared with the data communication before the failure. data communication can be continued without delay or data loss.

Furthermore, when a data communication medium fails, the accident can be easily detected.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a data communication system to which the present invention is applied, FIGS. 2 and 4 are diagrams showing the formats of data ■ and data m in FIG. 1, and FIG. In FIG. 1, the device 2 is a diagram showing an example of adding a sequence number when transmitting data, and FIG. 5 is a diagram showing an example of how the device 2 in FIG. be. In the figure, 1.2.3 is the device, ] 6 is the data communication medium A, and 17 is the data communication medium B. Patent applicant: Takatake Seisakusho Co., Ltd.

Claims (1)

[Claims] In a system that communicates data between multiple devices that do not have a dual configuration using a duplex data communication medium,
Each device that performs data communication is connected to both duplex data communication media, and the sending device always sends data to both of the duplex data communication media, and the device receiving the data A communication method using a duplex data communication medium is characterized in that when both types of data are received, only the first-arrived data is treated as regular data.