JPH11353293A - Failure detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a failure detector which detects only the failure of a duplex communication device. SOLUTION: The failure detectors installed in two duplex communication devices which perform the communication with each opposite party device have the communication break detection means 21 and 31 which detect that the communication commands given from the opposite party devices are broken for the communication break detection time, the state notification means 22 and 32 which notify the opposite party devices of the communication unable states based on the detection results of the means 21 and 31, and the failure decision means 23 and 33 which decide the failures of the opposite party devices when one of both duplex communication devices is unable to perform the communication and then decide the failures of their own devices when one of both duplex communication devices is enable to perform the communication when the failure decision time passed after the breaks of communication are detected by the means 21 and 31.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure detection device for a duplex communication device for communicating with a partner device, and more particularly to a failure detection device for detecting only a failure of a duplex communication device.

[0002]

2. Description of the Related Art Conventionally, in a system for performing communication between a higher-level device (communication master) and a lower-level device (communication slave), the lower-level device causes a communication error from the communication master to be interrupted for a predetermined time due to a communication abnormality. Is detected by the internal communication disconnection detecting means.

[0003] Such an apparatus is shown and described in FIG. In the figure, an upper device 1 is communicating with lower devices 2 and 3 via a communication line L. Lower device 2, 3
Constitutes a duplex communication device, and if one device fails, switches to the other device. And the lower device 2,
3 has communication disconnection detecting means 21 and 31, respectively. The communication disconnection detecting means 21 and 31 detect that the communication command from the upper device 1 has been interrupted for a certain period of time.

[0004] The operation of such a device will be described below.
The communication disconnection detecting units 21 and 31 monitor communication commands from the upper device 1 and detect that the communication commands have been interrupted for a certain period of time. The lower device 2,
3 requests the other lower-side devices 3 and 2 to switch by a switching signal, stops the operation of itself as a failure, and the other lower-side devices 3 and 2 start a communication operation.

[0005]

In such a device,
Even if the communication failure is monitored by the communication disconnection detecting means 21 and 31, it is determined whether the lower device 2 or 3 has failed or the upper device has failed (the communication line L has been disconnected or the upper device 1 has failed). Cannot be determined.

In such a case, in the case of a failure on the upper side,
The lower-side devices 2 and 3 stop operating at the same time, and keep issuing switching requests.

Further, when the lower devices 2 and 3 perform analog output, a transient output is inevitably generated at the time of switching. Therefore, it is desired to prevent the lower devices 2 and 3 from switching due to an upper fault. There was a problem that it could not be prevented.

[0008] When the upper device 1 is removed for inspection or the like, it is not possible to prevent unnecessary switching such that the lower devices 2 and 3 are switched.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a failure detecting device that detects only a failure of a duplex communication device.

[0010]

According to the present invention, there is provided a failure detecting apparatus provided in a duplex communication device for communicating with a partner device, wherein the communication disconnection detecting that the communication command from the partner device has lost the communication disconnection detection time. Detecting means, state notifying means for notifying the other of the redundant communication devices that communication is impossible by detecting the communication disconnection detecting means, and after the failure determination time elapses from the communication disconnection detection of the communication disconnection detecting means, the duplex communication device And a failure determination unit that determines that the other device is out of order when the other device is not communicable, and determines that the other device is out of service when the other device is communicable.

According to the present invention, the communication disconnection detecting means detects that the communication command has been interrupted during the communication disconnection detection time. By this detection, the status notification means notifies the other of the redundant communication devices that communication is impossible. Then, after the failure determination time elapses from the detection of the communication disconnection, the failure determination means determines whether the other communication device has a failure or its own communication device based on the other state of the duplex communication device.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing one embodiment of the present invention. In the figure, an upper device 1 is a partner device and communicates with lower devices 2 and 3 via a communication line L. The lower devices 2 and 3 constitute a duplex communication device, and if one device fails, the lower device 2 or 3 switches to the other device. The lower-level devices 2 and 3 have communication disconnection detecting units 21 and 31, status notifying units 22 and 32, and failure determining units 23 and 33, respectively. Communication disconnection detecting means 21 and 31, state notifying means 22,
32 and the failure determination means 23 and 33 constitute a failure detection device, and these are generally created by a program.

The communication disconnection detecting means 21 and 31 detect that the communication command from the upper device 1 has been interrupted for the communication disconnection detection time Ta. The status notifying means 22 and 32 detect the communication disconnection detecting means 21 and 31, respectively,
Notify 2 that communication is not possible. The failure determination means 23, 33
After the failure determination time Tb elapses after the communication disconnection detection unit 21 detects the communication disconnection, when the other lower-side devices 3 and 2 cannot communicate, it determines that the upper-side device has failed and the other lower-side devices 3 and 2 can communicate. At this time, it is determined that the local lower-side devices 2 and 3 are out of order. Here, for example, the failure determination time Tb = (interval communication command interval from the higher-level device 1 to the lower-level devices 2 and 3) + (error time of the time count of the communication disconnection time Ta).

The operation of such a device is described below.
FIG. 2 is a diagram for explaining the operation of the device of FIG. In the figure, the left side shows the state of the lower device 2, and the right side shows the state of the lower device 3.

At first, it is assumed that the lower device 2 is a service and the lower device 3 is on standby. During normal operation, the status notification means 22, 32 of the lower-level devices 2, 3 output a COMRDY (COMUNICASION READY) signal (high level) in a communicable state (S1).

The communication disconnection detecting means 2 of the lower device 2
2 is in a communication disabled state when the communication command from the upper device 1 is interrupted by the communication disconnection detection time Ta! COMDY
Outputs a signal (low level). At this time, the states of the lower-side devices 2 and 3 do not change, and the lower-side device 2 is in service and the lower-side device 3 is on standby (S2).

If the failure determination time Tb has elapsed and the signal from the status notification means 32 of the lower device 3 is a COMRDY signal, the failure determination device 23 determines that the lower device 2 has failed. As a result, the lower device 2 fails and sends a switching signal to the lower device 3, and the lower device 3
It becomes a service (S3).

When the failure determination time Tb elapses, the failure determination means 23 outputs a signal from the state notification means 32 of the lower device 3 to! If the signal is a COMRDY signal, it is determined that an upper failure has occurred. Thus, the lower-side devices 2 and 3 do not change the state. That is, the lower device 2 is a service, and the lower device 3 is on standby (S4).

Also, from the normal state (S1), when the communication disconnection detecting means 32 of the lower device 3 loses the communication disconnection detection time Ta from the upper device 1, the communication is disabled! Outputs COMRDY signal (low level).
At this time, the state of the lower-side devices 2 and 3 does not change, and the lower-side device 2 is in service and the lower-side device 3 is in standby (S5).

The failure determination means 33 determines that a failure has occurred if the failure determination time Tb has elapsed and the signal from the state notification means 22 of the lower device 2 is a COMRDY signal. As a result, the lower device 3 fails, and the lower device 2
Remains a service (S6).

Further, when the failure determination time Tb elapses, the failure determination means 33 outputs a signal from the state notification means 22 of the lower device 2 to! If the signal is a COMRDY signal, it is determined that an upper failure has occurred. Thus, the lower-side devices 2 and 3 do not change the state. That is, the lower device 2 is a service, and the lower device 3 is on standby (S4).

As described above, the other communication states are notified by the state notification means 22 and 32, and the failure determination means 23 and 33 determine the failure of the lower-level devices 2 and 3 based on this notification and their own communication states. It is determined whether the failure is in the upper-level device or in the upper-level device.
3 can be a failure. That is, the lower device 2,
Switch only when you have to switch 3,
Unnecessary switching operation is eliminated.

The present invention is not limited to this, and the higher-level device 1 may be duplicated and similarly configured. That is, the upper device 1 is a duplex communication device, and the lower devices 2 and 3 are partner devices.

[0024]

According to the present invention, the following effects can be obtained. The other communication state of the duplex communication device is notified by the state notification unit, and by this notification and its own communication state,
Since the failure determination means determines whether the failure is in the own communication device or the failure in the partner device, it is possible to switch to the other duplex communication device only in the case of the failure in the own communication device. In other words, switching is performed only when switching of the redundant communication device is required, and unnecessary switching operation is eliminated.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the device of FIG. 1;

FIG. 3 is a configuration diagram showing a conventional failure determination device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper device 2, 3 Lower device 21, 31 Communication disconnection detection means 22, 32 Status notification means 23, 33 Failure determination means

Claims (1)

[Claims] 1. A failure detection device provided in a duplex communication device that communicates with a counterpart device, comprising: a communication disconnection detection unit configured to detect that a communication command from the counterpart device has lost communication disconnection detection time; By means of the detection, state notification means for notifying the other of the redundant communication devices that communication is impossible, and after the failure determination time elapses from the communication disconnection detection of the communication disconnection detection means, when the other of the redundant communication equipment is unable to communicate, A failure detection device comprising: a failure determination unit that determines that the other device has failed and determines that the own communication device has failed when the other device is communicable.