JPH05183567A - Loop type communication system - Google Patents

Abstract

PURPOSE:To provide a loop type communication system in which integration of a time slot management table is simply implemented at the time of re-integration of separated loops. CONSTITUTION:A control station 1 and plural stations 3-1... are connected by transmission lines 7 in duplicate, a frame having plural time slots is circulated onto the transmission lines 7, plural time slots are allocated to the stations 3-1..., the stations 3-1... use the allocated time slot to make communication and loopback is implemented on the occurrence of a fault. In such a loop communication system, return of a time slot to a control station is suppressed in the loopback state.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a loop communication system.

[0002]

2. Description of the Related Art With the development of information processing technology, various systems have been developed in which a plurality of distributed information processing apparatuses are connected to transmission lines via stations and information is transmitted between these information processing apparatuses. Has been done. As something like this,
Connect the control station and multiple stations in a loop by a transmission line,
There is a loop communication system in which an information processing device is connected to each station and a frame is circulated on a transmission path for communication.

By the way, in such a loop communication system, when a certain station communicates, it is necessary to allocate a time slot to the station. Then, as one of such time slot allocation methods, there is a predictive allocation method. In this predictive allocation method, each station is assigned a predetermined time slot in advance, and when each station runs out of pre-allocated time slots, it requests the control station to assign a certain amount of time slots, and the control station Ask them to allocate a certain amount of time slots. When the communication ends and the free time slot in the own station exceeds a certain amount, a predetermined amount of time slots are returned to the control station.

Further, as a countermeasure against such a failure of the loop type communication system, there are a loopback method and a parental alternation method.

In loopback, the transmission lines are duplicated in advance, and when a failure occurs in a part of the system (transmission path or station), the transmission paths are folded back within the stations at both ends of the failure point to form a loop, It is intended to continue the operation of the system.

In the parental substitution system, the function of the control station is given to a plurality of stations, and when a failure occurs in the operating control station,
The station on standby becomes the control station and takes over the management of the system.

FIG. 7 shows a loop type communication system having these two countermeasures for failure. In this loop type communication system, when a failure occurs at a plurality of points, the loop is divided into two or more, and each of them is divided into two or more. The loop begins to operate autonomously.

As shown in FIG. 7A, the control station 1 and a plurality of stations 3-1 3-2, ..., 3-having the functions of the control station are provided.
m and the ordinary stations 5-1, 5-2, ..., 5-n are connected in a loop by a double transmission line 7, and the transmission line 7
The frame is circulated around and communication is performed.

In such a loop communication system, as shown in FIG.
When a failure occurs at points A and B shown in (a), the loop is divided into two. In one loop, station 1 is the control station as it is, and in the other loop, station 3-2 is the control station.

The control station has a time slot management table 21 as shown in FIG. FIG. 8 shows FIG.
7 shows a time slot management table held by the control station 1 in a state before the loop shown in FIG. For example, the first time slot is assigned to station 3-1 and the second time slot is assigned to station 5-1.
It can be seen that the third time slot is an empty time slot.

As shown in FIG. 7A, when the loop is divided into two, and the station 1 and the station 3-2 become the divided control stations, each has its own time slot management table. Become.

In the state immediately after the loop separation, the two time slot management tables are equivalent, but the two separated loops are operated independently. Co-located time slots may be assigned to different stations.

For example, as shown in FIG. 7A, the eighth time slot is assigned to the station 3-1 in one loop, and the eighth time slot is assigned to the station 5-2 in the other loop. Happens.

Therefore, when the failure is recovered and the two loops are re-integrated, a time slot (eighth time slot) assigned to the same position collides as shown in FIG. 7B. Occurs.

In order to avoid such a collision, it can be considered to suppress acquisition of an empty time slot from the control station by the above-mentioned predictive allocation method in the loopback state.

However, if the acquisition of time slots is only suppressed, excess time slots are returned from each station, resulting in inconsistency of the time slot management table between the control stations, and the control stations are integrated into one at the time of loop reintegration. At this time, there arises a problem that it becomes difficult to integrate the time slot management tables.

[0017]

As described above, in the conventional loop communication system, there is a problem that it becomes difficult to integrate the time slot management tables at the time of re-unifying the separated loops.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a loop type communication system which can easily integrate time slot management tables when re-unifying separated loops. To provide.

[0019]

In order to achieve the above-mentioned object, the present invention provides a control station and a plurality of stations connected by a duplicated transmission line, and a frame having a plurality of time slots on the transmission line. In a loop communication system in which a plurality of time slots are circulated, each station is assigned to each station, each station requests the control station to add a time slot and returns the time slot, and loops back in the event of a failure. Sometimes, the loop communication system is characterized in that the return of the time slot from each of the stations to the control station is suppressed.

[0020]

According to the present invention, the time slot management tables can be easily integrated when the separated loops are integrated again.

[0021]

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

FIG. 1 shows a schematic configuration of a loop type communication system according to an embodiment of the present invention. The control station 1 and a plurality of stations 3-1, 3-2, ... 3-
m and the ordinary stations 5-1, 5-2, ..., 5-n are connected in a loop by a double transmission line 7, and the transmission line 7
The frame is circulated around and communication is performed.

FIG. 2 is a format diagram of a frame. The frame includes a frame synchronization area 11 and a control area 1.
3, data communication area 15.

The frame synchronization area 11 indicates the beginning of a frame.

The control area 13 has a fixed length and is used for controlling the control station 1 and each station 3-1. The data communication area 15 is composed of a plurality of time slots, and each station 3
-1 ... Communicate using the time slots of the data communication area 15.

A certain amount of time slots is given to each station 3-1, ..., 5-n, and each station 3-1 ... Communicates using the time slot assigned to itself. Then, when the communication amount increases and the time slot allocated to the own station becomes insufficient, the control area 13 is used to request the control station 1 for a certain amount of time slots. The control station 1 refers to the time slot management table for this request, and allocates the required amount of empty time slots to the station. For example, when the station 3-1 makes a request for two time slots to the control station 1, the control station 1 allocates the third time slot and the seventh time slot to the station 3-1 as shown in FIG. 3, for example. ..

On the contrary, when the communication volume at a certain station decreases and the empty time slot of the own station becomes available, and the number reaches a certain amount, a certain amount in the empty time slot is used in the control area 13. And returns it to the control station 1. For example, station 3-2
When the communication traffic decreases and it becomes unnecessary to use the fourth time slot assigned to the station 3-2, the fourth time slot is returned to the control station 1.

In the present embodiment, when a failure occurs in the system and a loopback state occurs, each station 3-1, ..., 5-n
The above-described time slot acquisition processing and time return processing are suppressed, and time slot acquisition and return cannot be performed.

That is, in the loopback state, the state of the time slot management table of the control station is fixed regardless of the number of empty time slots of each station 3-1.

In such a loop type communication system, as shown in FIG. 4, when a failure occurs at C, a loop is formed by folding back the transmission path at the stations 3-m and 5-n, and this loop is used. Communication takes place.

Further, as shown in FIG. 5, when a failure occurs in the control station 1, the transmission lines are folded back at the stations 5-1 and 5-n, and the station 3-2 becomes the control station for communication. Be seen. In this way, when loopback is performed, as described above, each station 3-1 ... 5-n can suppress the above-described time slot acquisition processing and time return processing, and can perform time slot acquisition and time return. Can not.

As shown in FIG. 6, when a failure occurs at two points A and B in the system, the system is separated into two loops. In one loop, the station 1 is the control station as it is, and in the other loop, the station 3-2 is the control station. Each of the control stations 1 and 3-2 has a time slot management table, and the time slot management table remains immovable while holding the state immediately before the loop is separated.

In other words, in the two separated loops, even if there is a time slot acquisition and return request from each station, the control stations 1 and 3-2 ignore it and write the time slot management table of each. There is no change.

For this reason, even if the failure is recovered and the two separated loops are re-integrated, the two time slot management tables are in the equivalent state, so that a situation of time slot collision occurs. There is no. In this case, the system operation can be continued simply by deciding which station is the control station in the integrated loop. In addition, in the above-described embodiment, as shown in FIG. 5, the case where the loop is separated into two loops is described, but it is obvious that the present invention can be applied to the case where the loop is separated into three or more loops.

[0035]

As described above in detail, according to the present invention, it is possible to provide a loop communication system in which the time slot management tables can be easily integrated at the time of reintegration of separated loops.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a frame format.

FIG. 3 is a diagram showing a time slot management table.

FIG. 4 is a diagram showing a loopback in the case where a failure occurs in one part of the loop.

FIG. 5 is a diagram showing a case where a failure occurs in the control station 1 and loopback and parental change are performed.

FIG. 6 is a diagram showing a loopback when a failure occurs at two points in the loop.

FIG. 7 is a diagram showing a situation where time slot collision occurs when loops are reintegrated in a conventional loop communication system.

FIG. 8 is a diagram showing a time slot management table.

[Explanation of symbols]

 1 ... Control station 3-1 to 3-n ... Station having control function 5-1 to 5-n ... Station 7 ... Transmission line 21 ... Time slot management table A, B, C ...... the obstacle

Claims (1)

[Claims] 1. A control station and a plurality of stations are connected by a duplicated transmission line, a frame having a plurality of time slots is circulated on the transmission line, the plurality of time slots are assigned to each station, and each station is controlled. In a loop communication system that requests a time slot premium and returns time slots to a station and loops back in the event of a failure, suppresses the time slot return from each station to the control station when in a loopback state A loop communication system characterized by the above.