JPH0556049A - Communication controller - Google Patents

Abstract

PURPOSE:To improve the maintenance performance and the reliability of the system and to prevent a fault of disabled communication consecutiveness due to a fault of a standby side bus by always monitoring the standby side bus of duplicate buses and detecting the fault and locating a fault location when the fault takes place in the bus. CONSTITUTION:An active bus L1 is interconnected to a communication section 1 and an active side bus monitor section 3 by a bus changeover section 2 according to a command of a host communication section 1, the monitor section 3 receives a signal from the bus L1 and when a start delimiter in the received frame signal is detected, it is sent to a clock section 5. However, when the signal is not token frame addressed to a communication controller, a wrong destination signal is sent to the clock section 5 to allow the standby set side bus monitor section 4 to receive the signal from the standby set side bus L2 thereby checking all received frames. When the frame is normal, the clock section 5 is started, the operation of the clock section 5 is stopped by an output from the monitor section 4. Furthermore, when a fault takes place in the standby set side bus L2 while the clock is sent, it is fed to a fault detection section 6 and informed to the communication section 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a LAN (Local).
For example, in the case of Area Network), the present invention relates to a communication control device connected to a duplicated bus, specifically, to detect an abnormality of a standby bus that is not currently used.

[0002]

2. Description of the Related Art In a LAN or the like, FIG. 5 shows an example of a system composed of three communication control devices connected to a dual token bus system bus. This figure is
The communication control devices S1 and S are connected to the redundant buses L1 and L2.
2 is an example of a system in which S3 is connected. In such a system, the same signal (HDLC frame or the like) is sent to both of the duplicated buses L1 and L2, and the communication control devices S1, S2 and S3 receive the frame signal from the bus recognized as normal. The method of doing is common. Then, each of the communication control devices S1, S2, S3, for example, when using the currently recognized side bus (hereinafter referred to as the working side bus) L2, points A of this working side bus L2.
When an abnormality such as a failure or disconnection occurs in the communication control device S1, S2, S3, the communication side control device S1, S2, S3 cannot receive the frame signal for a certain time or more, or cannot receive the token addressed to itself, so that the active bus It is determined that an abnormality has occurred in L2, and the other bus that is not currently used (hereinafter referred to as the standby side bus) L1 is newly set as the active side bus.
Signals are received using this bus L1.

[0003]

The conventional communication control device as described above can detect the abnormality of the working bus and switch to the standby bus to continue the signal receiving operation.
At the time of bus switching, since it is not judged whether the standby side bus is normal, there is a problem that the communication operation after the bus switching cannot be guaranteed. Further, when an abnormality occurs in the standby side bus, it is not possible to specify the abnormal position, so that there is a problem that maintainability is poor.

An object of the present invention is to solve such a problem, and an object thereof is to improve reliability and maintainability of a communication system.

[0005]

According to the present invention, which has solved the above problems, at least two or more units are installed in a dual token bus system bus, and the same frame signal is transmitted to both of the dual buses. In the communication control device, when an abnormality occurs in the currently used bus, the bus switching unit switches from the currently used bus to the standby bus in the standby state according to an instruction from the higher communication unit. The frame delimiter is received from the communication control device and the start delimiter is detected and the start delimiter detection signal is output.
An active-side bus monitor that outputs a destination-difference signal when the frame is not a frame, and a standby-side bus monitor that detects that the frame signal from the standby-side bus is normal and outputs a normal frame detection signal, A timekeeping unit which starts a constant value timekeeping operation upon receiving the start / delimiter detection signal and stops the constant value timekeeping operation upon receipt of the destination error signal or upon receipt of the normal frame detection signal; And a standby-side bus abnormality detection unit that detects that the unit has timed a certain value and retains it as an abnormality in the standby-side bus.

[0006]

In the communication control device of the present invention, the timekeeping section starts the timekeeping operation by the frame signal from the active side bus, and when this frame signal is not the token frame addressed to the communication control device, or from the standby side bus. If the frame signal is normal, the clocking operation is stopped, and in other cases, the clocking unit measures a constant value and the standby side bus is abnormal.
The abnormal position of the standby bus can be specified by the circulation order of token frames in the system and the timekeeping status of the timekeeping section.

[0007]

Embodiments of the communication control apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration block diagram showing a main part of a communication control device of the present invention, and a portion surrounded by a dotted line is a characteristic part of the present invention. In this figure, when the upper communication unit 1 detects an abnormality in the working bus, it gives a switching instruction to the bus switching unit 2, and the bus switching unit 2 switches the bus to be used from the working bus to the standby bus. .. Such a switching method is similar to the conventional method. The bus switching unit 2 is a block that selects either the bus L1 or the bus L2, and connects the working side bus to the higher order communication unit 1 and the working side bus monitoring unit 3 according to the instruction of the higher order communication unit 1. The standby bus is connected to the standby bus monitoring unit 4. The active-side bus monitoring unit 3 receives the signal from the active-side bus and, when detecting the start delimiter in the received frame signal, transmits the start delimiter detection signal to the time counting unit 5. Further, when the received frame signal is not a token frame addressed to the communication control device, a misaddressed signal is transmitted to the clock unit 5. The standby side bus monitoring unit 4 receives the signal from the standby side bus, performs a CRC check on all the received frame signals, determines whether the frame is a normal frame, and if it is normal, detects a normal frame detection signal. Is transmitted to the clock unit 5. When the timekeeping unit 5 receives the start / delimiter detection signal from the active bus monitoring unit 3, it starts the timekeeping,
When the frame received by the active bus monitoring unit 3 is not a token frame addressed to the communication control device, or when a frame normal signal is received from the standby bus monitoring unit 4, the clocking operation is stopped. In addition, when the timekeeping is continued and the timekeeping value reaches a certain value, the standby-side bus abnormality detection unit 6 is notified of that fact. The standby-side bus abnormality detection unit 6 holds the constant value signal of the clock unit 5 as an abnormality detection signal, and when the upper communication unit 1 makes a read request, notifies the held information and normalizes the held information. Initialize itself to represent the state.

Next, the operation of the communication control apparatus of the present invention thus constructed will be described with reference to FIGS. 2, 3 and 4.
Note that this operation example assumes a system in which three communication control devices S1, S2, S3 are connected to the buses L1, L2 as in the example shown in FIG. 5, and the token frame is the device S3-.
It shall be transferred in the order of S2-S1-S3 -.... Then, FIGS. 2, 3 and 4 show the respective operations of the communication control devices S1, S2 and S3 when it is assumed that a bus abnormality such as a disconnection has occurred at a point A on the bus L2 shown in FIG. It is a figure. By detecting the abnormality of the bus L2, each communication control device S
When the current bus is L2, 1, S2 and S3 switch the current bus to the bus L1 and the standby bus to the bus L2. This operation is due to the existing function,
Will be realized. The subsequent operation is peculiar to the present invention.

FIG. 2 shows the bus L as seen from the communication control unit S1.
FIG. 3 is a diagram showing signal transmission / reception in 1 and L 2 and operation of a clock unit 15. First, the device S on the working bus L1
The frame signal from 3 to the device S2 is received. At this time,
Since the standby side bus L2 is disconnected at the point A, the same frame signal from this device S3 to the device S2 is not received on the standby side bus L2. The active-side bus monitoring unit 3 detects the start delimiter in the frame signal from the active-side bus L1, and the time counting unit 5 starts time counting accordingly. After that, the active-side bus monitoring unit 3 finds that this frame signal is not a token frame addressed to the device S1, and the signal is sent to the time counting unit 5 to stop the time counting operation.
Then, a frame signal is sent from the device S2 to the device S1 and is sent to the working bus L1, and the start delimiter causes the clock unit 15 to start clocking. Although this frame signal is a token frame addressed to the device S1, the standby side bus L2 cannot receive a normal frame signal because the standby side bus L2 has a failure at the point A.
The timekeeping operation of is continued, and the timekeeping expires when the timekeeping value reaches a certain value. Then, an abnormal signal of the standby side bus is sent to the standby side bus abnormality detection unit 6. Thereby, the device S2
From this, it is found that the standby bus L2 is abnormal when the frame signal is transmitted to the device S1. still,
When transmitting a frame signal from this device S1 to another device, the timer unit 5 does not measure time.

FIG. 3 is a diagram showing the operation of the signal transmission / reception and the clock unit in the communication control device S2. Working side bus L1
Thus, when the frame signal from the device S3 to the device S2 is received, the active-side bus monitoring unit detects the start delimiter in this frame signal, and the clocking unit starts clocking. At the same time, the standby-side bus monitoring unit determines that the standby-side bus L2
If the same frame signal is also received from the above and the frame is judged to be a normal frame by the CRC check of this frame signal, after the end delimiter is detected, the clock unit stops clocking.
Then, when the frame signal is transmitted from the device S2 to the device S1, the time is not measured. When the active side bus L1 receives the token from the device S1 to the device S3, the standby side bus L2 is disconnected at the point A.
2 does not receive this frame signal from device S1 to device S3. At this time, the active-side bus monitoring unit determines that the bus L1
The start delimiter is detected in the frame signal from, and the time counting unit starts time counting. After that, it is found that this frame signal is not the token frame addressed to the device S2, and the time counting operation is stopped. Therefore, the device S2 does not detect the abnormality of the standby side bus L2.

FIG. 4 is a diagram showing the operation of the signal transmission / reception and the clock unit in the communication control device S3. First, when the device S3 sends a frame signal to the device S2, the device S3 does not perform the timing operation. Next, from the working bus L1,
When the frame signal from the device S2 to the device S1 is received,
The in-use side bus monitoring section detects the start delimiter in this frame signal, and the clock section starts clocking. At the same time, the standby side bus monitoring unit receives the same frame signal from the standby side bus L2, and the CRC of this frame signal is received.
If the check determines that the frame is a normal frame, after the end delimiter is detected, the clock unit stops clocking.
Subsequently, a frame signal is sent from the device S1 to the device S3 to the active bus L1, and the start delimiter causes the clock unit to start clocking. This frame signal is a token frame addressed to the device S3, but the standby-side bus L2 has a failure at point A, so the standby-side bus monitoring unit does not receive a regular frame signal, and the timing of the clock unit continues. When the time count value reaches a certain value, the time count operation is completed, and an error signal is sent to the standby side bus error detection unit. This allows
When the token is sent from the device S1 to the device S3, it is found that the standby side bus L2 is abnormal.

As described above, in the devices S1 and S3, the abnormality detection of the standby bus L2 in this system and the abnormal point A can be specified.

[0013]

According to the communication control device of the present invention, the standby side bus of the redundant bus is constantly monitored, and when an abnormality occurs in this standby side bus, it is possible to detect the abnormality and identify the abnormal portion. As a result, the maintainability of the system can be improved, and when the active bus is switched to the standby bus, it is possible to prevent the trouble that the standby bus fails and communication cannot be continued. , The reliability of the system can be improved.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of a main part of a communication control device of the present invention.

FIG. 2 is a diagram showing an operation of a system using the device of the present invention.

FIG. 3 is a diagram showing an operation of a system using the device of the present invention.

FIG. 4 is a diagram showing an operation of a system using the device of the present invention.

FIG. 5 is an example of a general system using a communication control device.

[Explanation of symbols]

 1 Upper communication unit 2 Bus switching unit 3 Active side bus monitoring unit 4 Standby side bus monitoring unit 5 Timekeeping unit 6 Standby side bus abnormality detection unit S1, S2, S3 Communication control device L1, L2 bus

Claims (1)

[Claims] 1. A dual token bus system bus is installed in at least two units, the same frame signal is sent to both of the duplex buses, and an abnormality occurs in the currently used bus. At this time, in the communication control device in which the bus switching unit switches from the active side bus to the standby side bus in the standby state according to the instruction of the higher-level communication unit, the frame signal from the active side bus is received and its start delimiter is detected. The start side delimiter detection signal and the frame signal from the standby side bus and the working side bus monitoring section that outputs a destination misdirection signal when the frame signal is not a token frame addressed to the communication control device. In response to the standby side bus monitoring unit that detects normality and outputs a normal frame detection signal, and the start delimiter detection signal A timer which stops the constant value time counting operation when the constant value time counting operation is started and the destination-difference signal is received or the normal frame detection signal is received, and a case where the time counting section measures a constant value. A communication control device comprising: a standby-side bus abnormality detection unit that detects and retains the standby-side bus abnormality.