JPH0420543B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] This is a method for monitoring transmission failures in a ring-shaped communication path. A configuration control device that connects nodes to a ring-shaped communication channel is provided with frame detection means corresponding to each node, which detects a communication frame flowing through the communication channel and outputs a signal indicating that the frame is continuing. For example, if those display signals are simultaneously observed and compared using an observation device, an abnormal node can be easily detected.

[Industrial Application Field] The present invention relates to a method for monitoring transmission failures in a ring-shaped communication path of a data communication system.

2. Description of the Related Art A data communication system using a ring-shaped communication path is well known, in which a plurality of nodes are connected in series in a ring-shaped data transmission path.

In a ring-shaped communication path, a fault at one location often affects the entire system, so it is especially desirable that the fault location can be detected quickly.

[Problems to be solved by conventional technology and invention]

FIG. 3 is a block diagram showing an example of the configuration of a ring-shaped communication channel communication system.

In the figure, numeral 1 denotes nodes that communicate with each other through this communication system, and are connected in series to a ring-shaped communication path 3 by a configuration control device 2 .

The ring-shaped communication path 4 provided separately is a path that constitutes a known so-called loop back for configuring a ring excluding the faulty part when a failure occurs in the ring-shaped communication path 3.

As is well known, when an abnormal state occurs in the ring-shaped communication path 3, the configuration control device 2 performs the following depending on the situation:
It has a function to control the configuration of the communication path so that communication can be continued by bypassing the failed node 1 as shown in path 5 shown by a broken line, or by setting a loop back as shown in path 6. .

Each node 1 transmits a ring-shaped communication path 3,
For example, a frame having the configuration shown in FIG. In Figure 4e,
FS is the start code of the frame, and FE is the end code, and the control information and data to be transmitted are placed in the DT section sandwiched between the two codes.

The FS and FE codes, and each byte of the DT part are, for example, 9-bit bytes shown in FIG. By setting both bits of FS and FE to the same value, it is possible to distinguish them from general data bytes.

Further, in a state where no frame is transmitted, for example, repeating 0 and 1 is transmitted so as not to match any byte in FIG. 4b.

As mentioned above, frames are regenerated at each node 1, so if one of the nodes 1 has a failure, normal frames will not arrive at each node 1 connected downstream from it, so There is a possibility that nodes 1 will not be able to communicate with each other, and such nodes 1 must be bypassed as soon as possible.

To this end, it is desirable that each configuration control device 2 be able to quickly detect nodes 1 in an abnormal state.
Conventionally, no means for easily performing such detection has been provided.

[Means for solving problems]

FIG. 1 is a block diagram showing the principle structure of the present invention.

In the figure, reference numeral 10 denotes a frame detection unit provided in the configuration control device 12 corresponding to each node 1, which outputs a signal indicating that the frame is being continued to the output signal line 11.

[Effect]

The frame detection unit 10 detects a frame in a predetermined format as described above from the signal of the ring-shaped communication channel 3, and detects the frame from the start to the end of the frame as a signal 11.
Output as .

By comparing and monitoring each signal 11 output from the frame detection unit 10 corresponding to each node 1, for example, in the monitoring unit 13, abnormal points can be easily detected from differences in frame duration, timing, etc. indicated by the signals 11. can do.

〔Example〕

FIG. 2a is a block diagram showing the configuration of an embodiment of the frame detection section 10 of the present invention, and FIG. 2b is a time chart thereof.

The received signal from the ring-shaped communication path 3 is input to the reception shift register 20 in bit series.

The FS detection gate 21 is connected to the reception shift register 2.
When the bit pattern of the FS code in the frame format shown in FIG. Turn on line 22.

The output line 22 turns on the output FSPTN of the flip-flop 23 in the next cycle, turns on the output FSD of the flip-flop 24 in the next cycle, and sets the so-called JK type flip-flop 25 on in the next cycle. and hold it. The output RXFRM turns on the output CRXFM of the flip-flop 26.

The output RXFRM is output to the output signal line 11 to indicate that the frame is continuing.

The counter 27 always repeatedly counts from '0' to '8', but the flip-flop 24
By turning on the output FSD, '8' is forcibly set regardless of the count value at that time, and when FSD is turned off in the next cycle, counting restarts from '0'.

Since the counter 27 has a binary display output line 28, its ²³ -digit output line RXCN3 is turned on only when the count value is '8'.

The sixth and eighth bits of the receive shift register 20 are input to an exclusive OR (EOR) gate 29, so when both inputs are both 0 or both 1, the output of the gate 28 is 0. its negative output
NDP is input to the AND (A) gate 30 along with the aforementioned signals CRXFM and RXCN3, and the AND gate 30
The output becomes the reset input of the flip-flop 25.

Therefore, after the CRXFM is turned on, when the count value of the counter 27 is '8', and the 6th and 8th bits of the receive shift register 20 become the same value (an example of the bit values in this state is Flip-flop 25 (shown below the dashed line in receive shift register 20) is reset and RXFRM is restored off.

This condition indicates the end of the frame if the frame is received normally, as is clear from the frame structure and the bit structure of each byte.
The FE code is the 0th to 8th of the receiving shift register 20.
Since it is only satisfied when shifted into a bit position, signal RXFRM indicates the duration of the frame.

Therefore, for example, by using the rise of RXFRM as a trigger, observing the frame duration when RXFRM is turned on, and comparing this observation with respect to the output signal line 11 of each frame detection unit 10 corresponding to each node 1, all Under normal conditions, all frames should be observed as having the same duration.

However, if a byte with an incorrect bit configuration that differs from the frame configuration is transmitted due to some kind of failure, the FS code may not be detected, a signal that is not an FS code may be incorrectly identified as an FS code, or an FE code may be detected. There is a large possibility that the RXFRM signal is controlled at a timing different from that of the frame detection unit 10 which normally receives the frame, such as by generating a reset signal for the flip-flop 25 using a general data byte that is not received.

Therefore, the monitoring unit 13 receives, for example, output signals in the same state from the frame detection units 10 corresponding to two nodes 1, and receives output signals of the same state from the frame detection units 10 corresponding to the subsequent nodes that are abnormally longer than the previous two nodes, or If there is an output signal indicating a short duration, it is possible to detect that there is an abnormality. can be easily determined.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, in a ring-shaped communication channel communication system, a configuration control device monitors nodes connected to it,
Since it becomes easier to determine a faulty node, there is a significant industrial effect of improving the availability of the communication system by speeding up the response to faults, etc.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the principle configuration of the present invention.
FIG. 2a is a block diagram of an embodiment of the present invention;
FIG. b is a time chart, FIG. 3 is a block diagram of an example of the configuration of a communication system, and FIG. 4 is an explanatory diagram of a frame configuration. In the figure, 1 is a node, 2 and 12 are configuration control devices, 3 and 4 are ring-shaped communication channels, 10 is a frame detection section, 11 is an output signal line, 13 is a monitoring section, and 20
is the reception shift register, 21 is the FS detection gate,
23, 24, 25, 26 are flip-flops, 2
7 is a counter, 29 is an exclusive OR gate, 30
indicates an AND gate.

Claims (1)

[Scope of Claims] 1. A ring-shaped communication path 3 formed by connecting one or more configuration control devices 12 in series, wherein each configuration control device 12 connects one or more nodes 1 to the ring-shaped communication path 3. In a communication system configured to be connected to a communication system, the configuration control device 12 is provided with a monitoring unit 13 and a frame detection unit 10 corresponding to each node 1, and the frame detection unit 10 is configured to connect to a predetermined format of communication. The monitoring unit 13 detects the frame and outputs a signal 11 indicating that the communication frame is continuing, and the monitoring unit 13 determines the length of the communication frame duration indicated by the signal output from the frame detection unit 10. 1. A transmission failure monitoring method, characterized in that the system is configured to determine the normality of the node 1 by identifying the node 1 according to predetermined conditions.