JPH06224927A - Loop communication system - Google Patents

Abstract

PURPOSE:To allow the system to be restored surely against the occurrence of various faults automatically by resetting its own station when the state of absence of a carrier on a transmission line for a prescribed time or over is detected. CONSTITUTION:A carrier detection section 21 detects a carrier of transmission lines 7, 8 for each prescribed time by a control signal from a watchdog timer section 22 and outputs a pulse of a prescribed period to a carrier interruption timer 23 on the occurrence of a carrier interrupt state. The timer 23 calculates the input pulses and sends a reset signal to a logic section 24 when the carrier interrupt state lasts for a prescribed time or over and outputs a control signal to a counter 26. A carrier stop section 25 stops the carrier of the transmission lines 7, 8 for a prescribed time with the carrier stop signal from the logic section 24. When the counter 26 calculates a prescribed count, a transmission stop signal is outputted to a transmission stop section 27.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loop type communication system having a double transmission path for transmitting frames flowing in mutually opposite directions.

[0002]

2. Description of the Related Art Conventionally, a loop type communication system has been
Various measures have been taken to restore the system when a failure occurs, but none of them are the best, and each has its own drawbacks.
Therefore, it is desired that the loop communication system has a highly complete automatic recovery function.

As shown in FIG. 5, a conventional loop communication system is composed of a plurality of stations, for example, control stations 51 to 53, a transmission station 54 and the like, which are connected to dual transmission lines 55 and 56, respectively. At least one of the control stations 51 to 53 is the master station, and this master station is the dual transmission path 55, 56.
The frame is circulated in the opposite direction and the control area of the frame is used to perform various controls in the system.

In such a loop type communication system, various measures as shown in FIGS. 6 to 8 are taken in consideration of various failures.

As shown in FIG. 6, for example, transmission lines 55, 5
6 is assumed, the transmission line 55,
An auxiliary line 61 different from 56 is provided, and the auxiliary line 61 is used to transmit a reset signal to the faulty station to reset the faulty station.

However, in this case, which control station 51
It is necessary to provide an enormous number of auxiliary lines 61 so as to reset the faulty station from ~ 53 as well, which increases the amount of hardware, resulting in cost increase and system redundancy.

Further, as shown in FIG. 7, transmission lines 55, 5
When an abnormality of a specific station on 6 is assumed, each station has a logic unit 71 for controlling communication of control information and each transmission line 55,
The reset circuit unit 72 may be provided between the circuit 56 and 56.

In this case, the reset circuit section 72 constantly monitors the control area of the frame that circulates on each of the transmission lines 55 and 56, and another station inserts a reset command into the control area of the frame to circulate the frame, and When the reset circuit unit 72 of the faulty station receives the reset command from the reset circuit unit 72, the reset circuit unit 72 resets the logic unit 71.

However, in this case, if the faulty station on the transmission lines 55 and 56 cannot receive the reset command, resetting is impossible. Also, if the faulty station is the master station and the receiving functions of both systems have become abnormal, the other control stations 52 and 53 will try to become the master station and flow frames, so the system will be manually restored. In the meantime
Other normal stations on the transmission lines 55, 56 will be adversely affected endlessly.

Therefore, as shown in FIG. 8, in addition to the reset circuit section 72, a logic section 82 incorporating a software called a watchdog timer (hereinafter referred to as WDT) 81.
Some are equipped with.

In this case, in the normal operating state, the logic unit 82 clears the WDT 81 at regular intervals. When the logic unit 82 cannot clear WDT81, WDT8
1 times out and resets the logic unit 82.

As a result, the logic unit 82 can be reset even if the reset command cannot be received. However, when a software failure occurs such that the WDT 81 does not time out, resetting to the logic unit 82 becomes impossible and, eventually, the auxiliary unit. There is no choice but to use a huge amount of hardware called line 61. When the auxiliary line 61 is not used together, the operator may directly operate the logic unit 82 to reset it, but this requires manual intervention, which increases the cost during maintenance and automatically restores the system. In terms of sex, there is no point in incorporating WDT81.

[0013]

As described above, in the above-mentioned conventional loop communication system, various countermeasures are taken in preparation for various failures, but all of them are incomplete as the automatic recovery function. There is a problem that some parts may have to be manually restored depending on the part where the abnormality occurs.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a loop type communication system capable of surely performing automatic recovery in response to various failures.

[0015]

In order to achieve the above-mentioned object, the loop communication system of the present invention has a plurality of stations respectively connected to a loop-shaped transmission line, and these stations connect carriers to the transmission line. In a loop communication system in which various control information is propagated by transmitting to perform communication,
Each of the stations detects a carrier-free state on the transmission path, and a carrier-detecting means detects the carrier-free state on the transmission path, and resets its own station when a certain time or more has elapsed. Resetting means for resetting.

Further, in this loop type communication system, a plurality of stations are respectively connected to a loop-shaped transmission line, and these stations transmit carriers to the transmission lines to propagate various control information for communication. In a loop communication system, each station detects a carrier communication state in which each carrier transmits a carrier to a downstream station on the transmission path, carries control information on the carrier and propagates the carrier, and a carrier disconnection state in which there is no carrier on the transmission path. A carrier detecting section, a monitoring section for transmitting a signal to the carrier detecting section at regular time intervals to detect the carrier disconnection state, and to the data communication means when the carrier disconnection state continues for a predetermined time or more. A carrier disconnect timer for resetting by sending a reset signal and a reset time for the data communication means from the carrier disconnect timer. Counted, and includes a counter for delivering a transmission stop signal when adapted to send a stop condition, and a transmission stop unit stopping the transmission of said data communication means by transmitting a stop signal from this counter.

[0017]

In the loop communication system of the present invention, when a specific station among a plurality of stations connected to the transmission line is reset,
Carrier transmission from the upstream station to the downstream specific station side is stopped.

On the other hand, if the specific station does not receive the carrier, if the station is a transmission station, it resets itself after a lapse of a predetermined time, and the transmission station cannot leave itself so that it leaves the loop network.

When the station is a control station, it resets itself after a predetermined time has elapsed, and then starts transmission of control information by itself to affect other stations, but again there is no carrier on the transmission path. Therefore, the operation is reset again and such an operation is repeated. At this time, since the number of resets is counted by the counter, the transmission of the control information is stopped by the transmission stop unit when the number of resets meets the transmission stop condition. After leaving completely, it will not affect other stations.

That is, if the abnormal station does not receive the control information but continues to have no carrier on the transmission line, it does not have to provide an auxiliary line separate from the transmission line and does not rely on software such as WDT for manual operation. Without any intervention, the loop network will recover without the station by reliably resetting itself and leaving the loop network.

[0021]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a loop type communication system according to an embodiment of the present invention, and FIG. 2 is a diagram showing an internal configuration of an arbitrary station of this system.

As shown in FIG. 1, in the loop communication system, a plurality of stations, for example, two control stations 1 and 2 and transmission stations 3, 4, 5, and 6 are loop-shaped double transmission lines. It is configured to be connected via transmission lines 7 and 8.

As shown in FIG. 2, for example, the control station 1 includes a carrier detection unit 21, a monitoring timer unit 22, a carrier loss timer 23, a logic unit 24, a carrier stop unit 25, and a counter 2.
6, a transmission stop unit 27 and the like. The other stations 2 to 6 are also configured similarly to the control station 1.

The carrier detection unit 21 performs an operation of detecting the carrier on the transmission lines 7 and 8 at regular time intervals according to the control signal from the monitoring timer unit 22, and when no carrier is present (carrier cut state), the carrier cut timer is set. A pulse having a predetermined cycle is output to 23. The carrier disconnection timer 23 counts the input pulses, and when the carrier disconnection state is a predetermined time or more, sends a reset signal to the logic unit 24 and outputs a control signal to the counter 26. The logic unit 24 is external,
For example, when various control information is delivered from an interface board or the like, a carrier is transmitted to a downstream station on the transmission path, and a frame in which the control information is inserted is placed on the carrier and propagated to perform communication. Further, the logic unit 24 notifies the control station of the value counted in the counter of its own station by an instruction from the master station, or sends the count value given from the master station to the counter of its own station by the instruction from the master station. It has a function to set. The carrier stop unit 25 stops the carriers on the transmission lines 7 and 8 for a certain period of time in response to a carrier stop signal from the logic unit 25. The counter 26 counts the number of times the reset signal is output. When the counter 26 counts a constant value, it outputs a transmission stop signal to the transmission stop unit 27. Then, the count value of the counter 26 is returned to the initial value when the power is turned on or by the count clear signal from the logic unit 24. The transmission stop unit 27 stops the transmission of various control information from the logic unit 24 to the transmission paths 7 and 8 by the transmission stop signal from the counter 26.

Next, the operation of this loop communication system will be described with reference to the flowchart of FIG.

In this loop communication system, when the system power is turned on, the count values of the monitoring timer unit 22, the carrier loss timer 23, the counter 26, etc. are reset, and the time of the monitoring timer unit 22 and the carrier loss timer 23 is reset. Measurement starts (step 301). Then, the monitoring timer unit 22 times out after a lapse of a predetermined time (step 302), and sends a carrier detection command to each carrier detection unit 21. As a result, the carrier detection unit 21 performs the carrier detection operation of each system (transmission path 7 or transmission path 8) (step 303).

As a result of this detection, for example, if there is a carrier in at least one of the two systems (step 304).
), A count clear signal is output from the carrier detection unit 21, and the count value of the carrier break timer 23 is cleared (step 305).

On the other hand, when the carrier is not detected from the two systems (step 304), for example, the master station detects the abnormality of this station by the diagnostic packet, and on the transmission lines 7 and 8 downstream of the station where the abnormality occurs. When the two stations are instructed to stop the carrier transmission, the carrier detection unit 21 outputs a count signal (pulse signal) and the carrier disconnection timer 23
Is incremented by 1 (step 306).

When the above operation is repeated several times and the count value of the carrier disconnection timer 23 exceeds a predetermined value (step 307), the carrier disconnection timer 23 times out, which causes both systems of the transmission lines 7 and 8. That is, the carrier-free state has continued for a predetermined time.

When the carrier loss timer 23 times out, it outputs a count signal to the counter 26 and advances the count value of the counter by one (step 308). At the same time, the carrier loss timer 23 outputs a reset signal to the logic unit 24 to reset the logic unit 24 (step 309).

In the case of this loop communication system, the logic unit 24 is reset by the reset signal output from the carrier loss timer 23.
The subsequent recovery operation differs depending on whether the station with is a control station or a transmission station.

When the abnormal station is the control station, for example, when the control station 1 is the master station and the master station is in an abnormal state,
The logic unit 24 is reset, but since the control station 1 has the information necessary for starting up, it starts up by itself after resetting.

When the control station 1 starts up, it sends out a carrier by itself and transmits a control signal instructing a parent determination process in an attempt to determine a parent with another parent station. This control signal causes another control station 2 to start the control operation. This control operation continues unless the control station 1 stops transmitting the control signal.
However, since there is no carrier for the own station on the transmission lines 7 and 8, the control station 1 resets itself again after a certain time has elapsed. While repeating this operation, the count value of the counter 26 of the control station 1 exceeds a predetermined value (matches the transmission stop condition) (step 310). Then, the counter 26
A transmission stop signal is output from and is input to the transmission stop unit 26. Then, the transmission stop unit 26 stops the transmission of various control information to the transmission lines 7 and 8 of the logic unit 24 (step 311), and the control station 1 leaves the loop network for the first time, affecting other stations. Disappear.

On the other hand, as shown in FIG.
For example, in the case of the transmission station 5, carrier transmission from the station 4 to the station 5 using the transmission line 7 and carrier transmission from the station 6 to the station 5 using the transmission line 8 are performed. You need to stop the transmission.

Therefore, the master station (control station 1) instructs the stations 4 and 6 to stop carrier transmission. Then, the station 4 stops carrier transmission to the transmission line 7. The station 6 also stops carrier transmission to the transmission line 8.

As a result, carrier transmission to the station 5 is stopped in both systems, and the carrier loss timer 23 of the station 5 starts operating. When the carriers of both systems are stopped until the carrier disconnection timer 23 of the station 5 times out, the logic unit 24 of the station 5 is reset, the station 5 leaves the loop network, and the station 5 does not have the loop network. Will be restored. After that, the station 5 receives the information from the master station and tries to start up, but while the carriers of both systems are stopped, the station 5 cannot receive the information necessary for starting itself and cannot start up. However, this does not adversely affect other stations.

After that, when the control station 1 issues an instruction to restore the carrier transmission to the respective logic units 24 of the stations 4 and 6,
Carrier transmission to station 5 is resumed, allowing station 5 to join the loop network when it comes back up.

Needless to say, the same operation is performed when the transmission lines 7 and 8 (both systems) both fail and the carrier does not reach.

As described above, according to the loop type communication system of this embodiment, when the receiving parts of the control stations 1 and 2 and the transmission stations 3 to 6 are abnormal, or the transmission lines 7 and 8 are broken, etc. In addition, the abnormal station cannot receive a reset command or the like and cannot be remotely controlled through the transmission lines 7 and 8. However, the hardware such as the carrier interruption timer 23 or the counter 26 that does not affect the software failure can be surely used. The logic 24 can be reset. Therefore, unlike the conventional case, it is not necessary to provide another auxiliary line other than the transmission line, to rely on software, or to intervene manually. Further, when the control station 1 becomes abnormal, the control station 1 tries to start up and affects other stations at first, but at least the reset by the carrier loss timer 23 is repeated and the count value of the counter 26 meets the transmission stop condition. It is possible to recover the loop network by limiting the time within a fixed time.

[0041]

As described above, according to the loop type communication system of the present invention, each station monitors the carrier of the transmission path at every predetermined time, and when the carrier disconnection state exceeds a certain time, the carrier disconnection timer Since hardware such as a counter and a counter resets itself from the loop network by resetting itself, there is no need to provide auxiliary lines to each station, no need to rely on software, no human intervention, etc. It is possible to reliably recover the loop network in response to a major failure.

[Brief description of drawings]

FIG. 1 is a block diagram showing a loop communication system according to an embodiment of the present invention.

2 is a block diagram showing an internal configuration of each station of the loop communication system of FIG.

FIG. 3 is a flowchart showing an operation of the loop communication system of the present invention.

FIG. 4 is a diagram showing an example of an actual reset operation of the loop communication system of the present invention.

FIG. 5 is a diagram showing a conventional loop communication system.

FIG. 6 is a diagram showing an example in which an auxiliary line is provided as a configuration for resetting a logic unit in a conventional loop communication system.

FIG. 7 is a diagram showing an example in which a reset circuit unit is provided as one configuration for resetting a logic unit in a conventional loop communication system.

FIG. 8 is a diagram showing an example in which a WDT is provided as one configuration for resetting a logic unit in a conventional loop communication system.

[Explanation of symbols]

1, 2 ... Control station, 3, 4, 5, 6 ... Station, 7, 8 ... Transmission path, 21 ... Carrier detection section, 22 ... Monitoring timer section, 23
... carrier cut timer, 24 ... logic part, 25 ... carrier stop part, 26 ... counter, 27 ... transmission stop part.

Claims (2)

[Claims] 1. A loop communication system in which a plurality of stations are respectively connected to a loop-shaped transmission line, and these stations transmit various carriers by transmitting carriers to the transmission line to carry out communication. Each station detects carrier-free state on the transmission path, and carrier detecting means for detecting the carrier-free state on the transmission path by the carrier detecting means, and resets its own station when a certain time or more has elapsed. A loop communication system comprising: reset means. 2. A loop type communication system in which a plurality of stations are respectively connected to transmission lines on a loop, and these stations transmit carriers to the transmission lines to propagate various control information to perform communication. Is a data communication unit that transmits a carrier to a downstream station on the transmission line and propagates control information on the carrier, and a carrier detection unit that detects a carrier disconnection state in which there is no carrier on the transmission line, A monitoring unit that sends a detection signal to the carrier detection unit at fixed time intervals to detect the carrier disconnection state, and sends a reset signal to the data communication unit when the carrier disconnection state continues for a fixed time or longer. The carrier loss timer to be reset and the number of resets from the carrier loss timer to the data communication means are counted, and the transmission stop condition is set. A loop communication system comprising: a counter which sends out a transmission stop signal when matched, and a transmission stop unit which stops transmission of control information from the data communication means by a transmission stop signal from the counter.