JPS60132439A - Communication system - Google Patents

Abstract

PURPOSE:To avoid the relaying of communication in case the circuits of both communication systems have faults at a time by checking the actuation of the circuit of one side before the circuit of the other side has a fault in said communication systems which exchange information with each other. CONSTITUTION:A parallel redundant constitution is attained to perform mutual switching between circuits of both using and queuing systems. When a time-out state is detected at a station S1, a station 1 transmits a switch command frame F1 via a circuit 1a. The station which received the command F1 turns off a switch SW1 then turns on a switch SW2 to open the circuit 1a. In this case, the command F1 is transmitted en bloc to all stations. Thus all stations perform the circuit switching at a time.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention relates to a system in which individual stations that mutually perform distributed processing are connected to multiplexed, particularly duplexed communication lines through switches, and mutually exchange information. 5 related to communication systems.

[Prior art and its problems]

By distributing the processing using several control devices such as microprocessors and exchanging information with each other, temperature control is performed as a whole.In the 5-distributed processing system, a common control system is used between each control device. They are connected by a communication line, and in order to further improve system reliability, the communication line is often converted to 2i to create a redundant configuration. FIG. 1 is a system configuration diagram showing a conventional example of a darning system.

In the 5112''M configuration shown in the figure, normally the line 1a is connected to the line 1.c, and when a failure occurs in the line 1a, the suppressing devices I-''L5a to 3d switch the used line to line 15. , control can be continued without stopping communication. However, in such a duplex configuration, the standby system does not operate while the regular system is operating, and when the regular system fails, the °C standby system is activated first.
If the standby system has already failed while the regular system is operating 1. j results in interruption of communication when a failure occurs in the regular system, resulting in a problem that the reliability of the system is impaired.

[Purpose of the invention]

This invention has been made in view of this point, and it is an object of the present invention to prevent communication from being interrupted due to simultaneous failure of both lines by checking the operation of one line before the other line fails. With the goal.

[Key points of the invention]

This invention has a parallel redundant configuration in which one side of the multiplexed communication line is used as a regular line and the other as a standby line (rather than being fixed as a front thread), the lines for the regular use and the standby line can be switched to each other. , by periodically switching the lines used (regular lines), it is intended to prevent both lines from failing at the same time and communication being interrupted.In other words, by switching between the lines and using them, the lines can be used normally. Since it is confirmed each time, this point is used to improve reliability. However, if a failure occurs between the last use and the current use, Since there is little chance that a failure will occur in the line being used, there is virtually no problem in practical use.

[Embodiments of the invention]

FIG. 2 is a block diagram showing an embodiment of the present invention, in which each control device 3a=3d includes two communication control units 2a.

Communication lines 1a, 1b□ via 2a' to 2d, 2d'
It is connected to the. FIG. 3 is a block diagram showing the internal configuration of each station. Communication control unit 2a controls line 1a, and 2a' controls line 1b. Transmission and reception data on the lines is transmitted via communication buffer 8. The processor CPU5 is then notified.

cpu5 uses switch SW1.8W2 to switch to 2a, 2a
' You can select either communication control section, switch SW1
When is on, line 1a is on, and switch SW2 is on.
When N, each line 1b is used. Each of the connecting stations 81 to S4 has a timer 9 that counts the same fixed period T, and the CPU 5 executes a line switching operation in response to a timeout interrupt of the timer 9.

Now, suppose that connected stations S1 to S4 are communicating using line 1a and station s1 has detected a timeout, and station S1 transmits a switching command frame F1 via line 1a. The station receiving Fl turns off the switch SW1 to close the line 1a, and then turns on the switch SW2 to open the line iIJ1a, thereby switching the line. At this time, the switching command F1 is simultaneously transmitted to all stations connected to the line 1aiC, so that all stations can switch the line at the same time.

FIG. 4 is a flowchart showing the line switching program.

In other words, in the line switching program shown in the same figure, if a failure was detected in the standby line when it last operated, the line switching command F1 for the standby system -\ is not sent, and as a result, the failure has already occurred Switching operations are also prevented from being performed on lines where this is occurring. In addition, in order to prevent unnecessary line switching from occurring even if each connected station operates its timer independently, if a line switching command is received from another station while the timer of the own station is operating, the timer of the own station is When the output is out, the switching operation is not performed (see eD).

Therefore, only stations that have not received a line switching command from another station since the previous timeout,
Check whether the line on standby is already out of order (see O), confirm that it is not out of order, and issue the line switching command F1.
to all stations at the same time (see θ), disconnect the line currently in use (see O), switch S
W1. After switching SW2 (see ■) and switching to the line that is on standby (see O), the timer 9 is reset (see [Yes]) to complete the series of operations.

FIG. 5 is a link/fming chart for explaining the operation at the time of line switching.

This is the case where there are three stations 81, 82 and S5, and each station S1,
The operating waveforms of 82 and S3 are shown as (a), (b) and (c), respectively. It is clear from the same figure (a) that the timer 9 of station S1 is
It can be seen that timeout occurs first, and as a result, the command F1 is given to each station, and the switch of each station is changed from SW1 to SW2. In addition, the operation period of the timer is given as T, so that within one hour after the timeout is detected at C1 station S1, for example, (B) or (C) in the same figure
Even if a timeout is detected at station S2, 83, the line will not be switched.

By doing this, there is no need to provide 5 common parts to centrally control line switching operations of all stations connected to a communication line, and any station can take the initiative in switching other stations. According to 1, it is possible to perform control at a predetermined period T.

In the above embodiment, a bus-type communication line is used, but the same operation as described above can also be carried out using a loop-type communication line.

〔Effect of the invention〕

According to this invention, in a multiplexed communication system, particularly a redundant communication system, the line in use is periodically switched when the line is normal, so that it is possible to confirm that the other line is available before one line fails. 1), it is possible to prevent communication from being interrupted due to failure of both lines. In addition, line switching control is not performed centrally at a specific station, but is configured so that each station can perform the control equally, so even if one station is inoperable, line switching will continue at regular intervals. C5, and is useful for improving the reliability of communication systems.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional example of a communication system, Fig. 2 is a block diagram showing an embodiment of the present invention, Fig. 6 is a block diagram showing the configuration of a station, and Fig. 4 is a flow chart showing a line switching program. , FIG. 5 is a timing chart illustrating the operation at the time of line switching. Code explanation 1 (1a, , 1b) -------・Line, 2 (
2a to 2d, 2a' to 2d'... communication control unit,
3 (5a-3d)... Control device, 4...
・Terminal part, 5...Microprocessor (cpu
), 6...Program memory (ROM), 7.
...Temporary memory (RAM), 8...
Communication (tufa, 9...timer, S1 to S4)
...Distributed processing station, swi, SW2...
...Switch agent Patent attorney Akio Namiki Agent Patent attorney Kiyoshi Matsuzaki Figure 1 Figure 2 Figure 3 J Figure 5

Claims (1)

[Claims] In a communication system in which individual stations are arranged in a distributed manner and perform predetermined data processing (1) and are connected to multiplexed communication lines via switches and exchange information with each other, each station is provided with a predetermined cycle. A timer is provided that outputs a predetermined output for each station, and the temperature from the predetermined station that receives the output from the timer to all stations is
A communication system characterized in that multiplexed communication lines are switched between each other at a predetermined cycle and used by issuing a switching command to the switch.