JPH09284317A - Communication control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit an operator to recognize a defective part from any station by executing TDR by means of the respective stations when a fault of one bus is reported and reporting the result to the other stations. SOLUTION: When transmission as against the bus is executed in vain, a fault detecting means 24 detects a fault. When the fault in one bus is detected in the self station, a fault reporting means 25 reports the fault in one side to the other stations through the use of the normal side bus. When the fault of one bus is reported, an executing means 26 executes TDR as against the fault side bus. A multi-address communicating means 27 reports the result of TDR executed in its own station by multi-address communication. A storage means 28 makes table of the result of TDR executed in its own station and the result of TDR reported from the other stations and stores it. The other stations are constituted in the same as the station 21 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication control method in which a plurality of stations are connected to a redundant bus and communication is performed between the stations. More specifically, the present invention relates to a communication control method improved in order to reduce the number of steps for identifying a failure location when one of the duplicated buses fails.

[0002]

2. Description of the Related Art Generally, in a communication system using an HF bus, Vnet, etc., the buses are duplicated and both buses are always used alternately. If one bus fails, the other bus continues communication. ing.

As a method for detecting the distance to a failure point, TDR (Time Domain Reflect)
There is a "metry". TDR transmits a communication frame of a certain length from its own station, and this communication frame is also received by its own station, so that the coupler of the own station has a failure and the cable has a failure (disconnection, short circuit).
This is a method of detecting the distance to the failure point when the occurrence of the above occurs. In TDR, the distance to the failure point is detected as follows. That is, when the bus is out of order,
The communication frame sent from the own station is reflected at the failure point and returns to the own station. The returned communication frame interferes with the communication frame sent by the own station, and the signal waveform is distorted. The station can receive the communication frame up to the point where the signal waveform is distorted. Since the communication frame reciprocates between the self station and the failure location, (length of communication frame received by the self station) / 2 is proportional to the distance to the failure location. Therefore,
The distance to the fault location is detected based on the length of the communication frame received by the own station. In the conventional communication system, there is no one that automatically executes TDR when a failure is detected to specify the failure location. For this reason, the operator himself had to carry out the TDR to identify the failure location. Moreover, in the HF bus, when one bus fails, it is not possible to know in detail which part of the bus has failed. The only information available was which station failed to send the communication frame to which station. Thus, when one of the buses fails, it is extremely difficult to identify the failure location.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and when a failure of one bus is notified, each station executes TDR, and the result is transferred to other stations. To all the stations, and all stations can know the failure point from any station by storing the TDR result executed by the own station and the TDR result notified from other stations. The purpose is to realize.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a communication control method for connecting a plurality of stations to a redundant bus and performing communication between the stations, when one of the redundant buses fails. The communication control method is characterized in that communication is performed through the steps. When each station is notified of the failure of one of the buses, a TDR is executed for the failed bus. Each station notifies other stations of the TDR result. A process in which all stations store the TDR result executed by the own station and the TDR result notified from other stations.

[0006]

According to the present invention as described above, when the failure of one of the buses is notified, each station executes TDR on the bus on the failed side and notifies the other station of the result of the TDR. All stations executed at their own station
DR result and TDR notified from other stations
And the result of.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a communication system for carrying out the present invention. In FIG. 1, 1 ₁ and 1 ₂ are duplicated buses, 2 ₁ and 2 ₂ , ... Are stations connected to the buses 1 ₁ and 1 ₂ . The buses 1 ₁ and 1 ₂ are, for example, LAN
(Local Area Network). A communication control device is provided in each of the stations 2 ₁ , 2 ₂ , ...

At station 2 ₁ , 21 ₁ , 21 ₂ and 2
Reference numerals 2 ₁ and 22 ₂ denote drivers and receivers provided for transmitting and receiving, and these are provided for each bus. 23
Is a communication means for communicating via the drivers 21 ₁ and 21 ₂ and the receivers 22 ₁ and 22 ₂ . The communication frame sent from the driver is reflected at the failure point and returns to the own station. The returned communication frame interferes with the transmitted communication frame, and the signal waveform is distorted. The receiver can receive the communication frame up to the point where the signal waveform is distorted.
The distance from (the length of the communication frame received by the receiver) / 2 to the failure location is detected. In this way, TDR is executed. Reference numeral 24 is a failure detecting means for detecting a failure of the bus. The failure detecting means 24 detects a failure when transmission to the bus fails. Reference numeral 25 is a failure notifying means, which notifies the other station of the failure of one bus by using the bus on the normal side when the failure of one bus is detected in the own station. This notification is performed by placing status information on the token or by broadcast communication. Reference numeral 26 denotes an execution unit that executes TDR on the bus on the failure side when a failure on one bus is notified. 27 is a broadcast communication means for notifying the result of the TDR executed in the own station. The notification is made by, for example, broadcast communication. 28
The storage means stores a result of the TDR executed by the own station and a result of the TDR notified from another station as a list. The other stations also have the same configuration as the station 2 ₁ .

The operation of the communication system of FIG. 1 will be described. FIG. 2 is a flowchart showing the operation procedure of the communication system of FIG. The operation will be described according to the order of steps in the flowchart. In this flowchart, an example is shown in which failure information is placed on a token and notified.

The operation will be described when the bus 1 ₂ is disconnected between the stations 2 ₁ and 2 ₂ as shown in FIG. The X portion in FIG. 3 is a cut point. (S1) Station 2 ₁ fails to send a token on bus 1 ₂ . (S2) The station 2 ₁ succeeds in transmitting the token on the bus 1 ₁ . (S3) The station 2 ₁ detects the failure of the bus 1 ₂ . (S4) Station 2 ₁ notifies all stations of the failure of bus 1 ₂ . This notification is made using a token that goes around the bus 1 ₁ . That is, the token is station 2
Place the status information indicating the failure of the bus 1 ₂ when that has been turned into ₁ in the token. By putting the failure information on the token, it is possible to promptly notify all stations of the failure of the bus. (S5) The station 2 ₂ receives the token, recognizes the failure of the bus 1 ₂ from the status information put on the token, and executes TDR on the bus 1 ₂ . (S6) The station 2 ₂ broadcasts the TDR result. Broadcast communication is carried out using the bus 1 _1. (S7) Each station to which the tokens other than the stations 2 ₁ and 2 ₂ come around executes the processes of S5 and S6. (S8) The station 2 ₁ executes TDR when the token makes a round and returns, and broadcasts the result. As a result, all the stations can collect the TDR result executed by the own station and the TDR result broadcast from other stations. (S9) All stations store the collected TDR results as a list. (S10) Each station broadcasts the TDR result at regular intervals until the bus returns to normal. by this,
Information (the result of TDR) is prevented from being lost due to a transient factor. Here, the information loss due to a transient factor means that the communication frame is lost due to disturbance, for example.

As a result, the operator who notices the abnormality of one of the buses can refer to the TDR result list from any station and specify the failure location.

FIG. 4 is a diagram showing an example of the result of TDR. “O” in FIG. 4 means that there is a phenomenon, and “−” means that there is no phenomenon. When the list shown in FIG. 4 (a) is obtained, a bus failure occurs at a position corresponding to (8 bytes / 2) from station 2 ₁ and (6 bytes / 2) corresponding to station 2 _2. Can be determined to have occurred. The conversion to the actual length is calculated from the data transmission rate and the cable transmission delay rate. When the list shown in FIG. 4B is obtained, it can be determined that the coupler of the station 2 ₁ is out of order.

In the embodiment, the case where the failure information is placed on the token and notified to the other stations has been described, but the failure information may be broadcast to the other stations to notify the other stations of the failure. In addition, CSMA / CD (C
arrier SenseMultiple Acce
The same operation as in the embodiment can be performed with a bus of the ss Collision Detect type.

According to the present invention, when the failure of one of the buses is notified, each station executes the TDR and notifies the other station of the result. Therefore, all stations store the TDR result executed by the own station and the TDR result notified from other stations.
As a result, the operator can know the failure point from any station, and the man-hour for identifying the failure point can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration example of a communication system for implementing the present invention.

FIG. 2 is a flowchart showing an operation procedure of the communication system of FIG.

FIG. 3 is a diagram showing an example of a failure that has occurred in a bus.

FIG. 4 is a diagram showing an example of a result of TDR.

[Explanation of symbols]

1 ₁ , 1 ₂ Bus 2 ₁ , 2 ₂ , ... Stations 21 ₁ , 21 ₂ Driver 22 ₁ , 22 ₂ Receiver 23 Communication means 24 Failure detection means 25 Failure notification means 26 Execution means 27 Broadcast communication means 28 Storage means

Claims (1)

[Claims] 1. A communication control method in which a plurality of stations are connected to a redundant bus and communication is performed between the stations, and when one of the redundant buses fails, communication is performed through the following steps. And a communication control method. When each station is notified of the failure of one of the buses, a TDR is executed for the failed bus. Each station notifies other stations of the TDR result. A process in which all stations store the TDR result executed by the own station and the TDR result notified from other stations.