JPH0145786B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmission control device for a loop-type data transmission system connected in a loop by two transmission paths having different directions, and in particular has a function of reconfiguring a transmission network in the event of a failure. The present invention relates to a transmission control device equipped with a transmission control device.

A loop data transmission system consists of a plurality of stations and a loop-shaped transmission line connecting them, but if there is only one loop-shaped transmission line, a failure in one station or the transmission line can cause The entire system stops functioning. In order to prevent this, as shown in FIG.
A configuration in which connections are made between ~8a and 5b~8b is known. In this configuration, normally transmission is performed using one transmission line system (for example, 5a to 8a), and when a failure occurs in this transmission line system, the other transmission line system 5b to 8b is used.
In order to prevent system downtime (backup), and even in the event of a station failure or failure of both transmission lines, the transmission line can be looped back at the stations on both sides of the failure point, connecting all stations with the transmission line. Normal transmission can be maintained (loopback).

Connection control between the duplex transmission path and the station is performed at the station. FIG. 2 is a block diagram showing a conventional example, and shows one station. In the same figure, when there is no abnormality, A
The transmission lines 30 and 31 of the system (B system) are connected to the receiving circuit 1.
0, 12, modulation/demodulation circuits 14, 15, and multiplexers 16, 17 are connected to transmission lines 32, 3 of the same system through priority control circuits 18, 19 and transmission circuits 11, 13.
Connected to 3. Here, priority control circuits 18, 19
The system performs operations such as inserting a flag for priority control of loop transmission into the transmission frame when the system is transmitting signals. The data state of each transmission system, that is, the presence or absence of a signal, or the normality of the signal time width is determined by the data state detection circuit 20,
It is monitored by 21.

Now, assuming that transmission is being performed on the A system of the transmission lines 30 to 32, the microcomputer 26 and the transmission control circuit 24 are connected to the modulation/demodulation circuit 14 via the multiplexer 22 and the signal line 27. At this time, in the B system of the transmission lines 31 to 33, the monitoring signal is merely relayed by the modulation/demodulation circuit 15, and the B system itself is monitored. In such a state, the data state detection circuit 20
When an abnormality is detected in the A-system transmission line, this is input to the transmission line switching control circuit 25 via the multiplexer 23, and each multiplexer 1
7, 18, 22, and 23 are controlled by switching signals S _A to S _D. The multiplexers 17 and 18 change the line configuration, and the multiplexer 22 connects the B-system modulation/demodulation circuit 15 side to the control circuit 24 via the signal line 28.
and connected to the microcomputer 26.

In this way, in the conventional device, either the A-system or B-system modulation/demodulation circuits 14, 15 are connected to the microcomputer 26, and if one of the modulation/demodulation circuits or the transmission line fails, However, the input signal lines 27 and 2 of the multiplexer 22 can be switched to the other side and continue to operate.
8 is parallelized in signal bit units, so
Multiplexing all of the signal lines requires a large amount of hardware for the multiplexer 22, and the control circuit 25 also becomes complex, resulting in low reliability.

SUMMARY OF THE INVENTION An object of the present invention is to provide a transmission control device that solves the problems of the conventional device described above and can switch duplex transmission lines with a small amount of hardware and without data disturbance.

The present invention is characterized in that the transmission control unit and the microcomputer are fixedly connected to one modem circuit, and the line configuration is switched in the transmitting/receiving circuit, which is a serial transmission path. It is.

Hereinafter, the details of the present invention will be explained with reference to Examples. FIG. 3 shows an embodiment of the present invention, in which each transmitter/receiver circuit 10-13 has multiplexers 46-46.
49 are connected, and these switching is performed by switching signals SA1, SA2, SA2,
SB1 and SB2 perform reconfiguration of the transmission path. Since the multiplexers 46 to 49 are all provided on the serial signal transmission path, parallel signal lines 27 and 28 as shown in the conventional example in FIG.
This can be realized with a much simpler configuration than the multiplexer 22 that performs switching. Furthermore, the transmission control circuit 54 that controls this is also simplified. On the other hand, a microcomputer 26 is fixedly connected to the modulation/demodulation circuit 14 of the A-system transmission line via a transmission control circuit 54, and no multiplexer is provided on this parallel signal line 27. Further, the priority control circuit 52, which is essential for loop transmission, is provided only on the output side of the modulation/demodulation circuit 14. Data state detection circuits 20 and 21 for detecting the presence or absence of data signals are provided on the output sides of the modulation and demodulation circuits 14 and 15 of both transmission lines.
is provided in the same manner as in the prior art, and is connected via a multiplexer 53 to a network configuration control circuit 55 that controls transmission line switching. The transmission control circuit 54 and the network configuration control circuit 55 both decode the contents of the data or issue a command to switch the transmission path to the network configuration control circuit 55 using software based on an interrupt from the control circuit 54, etc. It is connected to a microcomputer 26.

Next, a configuration example of the duplex loop transmission line will be explained using FIGS. 4 to 7. FIG. 4 is a simplified diagram of the configuration in which the signal lines 60, 62, and 63 are selected as the output signals of the multiplexers 46, 47, 48, and 49 in FIG. 3, respectively. That is, the modulation/demodulation circuits 14 of the A-system transmission line systems 30 and 32 are fixedly connected to the microcomputer 26,
The transmission lines 31 and 33 of the B system are simply equipped with a modulation/demodulation circuit 15.
Only things are connected. Data is sent and received between stations on the A-system transmission line connected to this microcomputer 26.
Only the monitoring signal is sent through the B-system transmission line.

The connection state shown in FIG. 4 is when there is no failure. From now on, system A will be referred to as the main transmission path, system B will be referred to as the slave transmission path, as names that physically correspond to the transmission paths.
Furthermore, if we call the transmission line that currently performs data transmission and reception between stations the active transmission line, and the transmission line that does not, the standby transmission line.
In the case of FIG. 4, the main transmission line and the active transmission line coincide, and the conventional transmission line and the standby transmission line coincide.

Next, in FIG. 3, the multiplexer 46,
FIG. 5 shows a configuration in which signal lines 61, 63, 60, and 62 are selected as the output signals of 47, 48, and 49, respectively. That is, unlike FIG. 4 above, the slave transmission lines 31 and 33 are connected to the microcomputer 26 and become active transmission lines, and the main transmission lines 30 and 32 become standby transmission lines. This standby transmission line has the role of detecting the location and type of failure. The configuration shown in FIG. 5 corresponds to a backup operation. Further, in FIG. 3, a configuration in which signal lines 60, 62, 61, and 62 are selected as the output signals of multiplexers 46, 47, 48, and 49, respectively, is shown in FIG. This is a case in which the station serves as a turn-back station for constructing a turn-back loop when a failure occurs in both the main system and the conventional transmission line. Data between stations is looped back from the transmission line 30 to the transmission line 31 via the modulation/demodulation circuit 14. The cases shown in FIGS. 6 and 7 above are loopback operations.

Next, the operation for implementing the line configuration as described above will be explained in detail for the backup case shown in FIG. Normally, each station has a configuration as shown in FIG. That is, transmission is performed on the main transmission path side. Furthermore, it has conventionally been possible to check the line status by sending a monitoring signal to the transmission line side. When a failure occurs in the main transmission line, the state detection circuit 20 shown in FIG. 3 detects that the working signal is disconnected. Only one control station in the loop transmission system causes an interrupt to the microcomputer 26 due to the disconnection of the active signal.
At the same time, other ordinary stations shift to a mode of simply relaying data. The control station issues a transmission path switching command to the network configuration control circuit 55 using software in response to the above-mentioned interrupt.
With this command, the control station configuration becomes as shown in FIG. At this point, other stations send slave transmission line switching command data. Each station that receives this executes transmission path switching at the timing of the end of this command data frame. This control is performed by the state detection circuit 20 in FIG.
21, is performed by the network configuration control circuit 55. In this manner, the stations are next switched, and all the stations are configured as shown in FIG. That is, at this point, the active transmission line becomes the slave transmission line, the standby transmission line becomes the main transmission line, and data is transmitted and received through the slave transmission line.
When the main transmission line is repaired and a failure occurs in the conventional transmission line, the above configuration is reversed and the configuration shifts from FIG. 5 to FIG. 4. The switching timing is the same.

FIG. 8 shows a time chart explaining the above operation. In Figure 8, when each station detects a signal disconnection, only the control station (CST) is switched, and the other stations receive a switching command (sent through the slave transmission line) from the control station as described above. is detected and switched to the state shown in FIG. This means that if you switch all at once when the signal is cut off,
This is because it becomes impossible to synchronize the switching timing between the stations.

The same is true for the loopbacks shown in FIGS. 6 and 7, and the switching is also performed by a switching command from the control station.

As is clear from the above embodiments, the present invention has the advantage of eliminating the need for a complicated multiplexer and its control circuit, making it possible to realize smaller hardware and higher reliability.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a transmission system having a duplexed loop transmission line, FIG. 2 is a block diagram showing an example of a conventional transmission control device, FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG. 4 〜FIG. 7 is an explanatory diagram of the line configuration when various switching is performed in the embodiment of FIG. 3,
FIG. 8 is an explanatory diagram of switching timing in the embodiment of FIG. 3. 5-8...Station, 5a-8a, 5b-
8b...Transmission line, 14, 15...Modulation/demodulation circuit, 2
0, 21...State detection circuit, 26...Microcomputer, 30-33...Transmission line, 46-49
...Multiplexer, 54...Transmission control section, 55
...Network configuration control circuit, 52...Priority control circuit.

Claims (1)

[Claims] 1 interconnected through loop-shaped first and second transmission paths whose transmission directions are opposite to each other, each of which processes signals mutually transmitted and received with the first and second relay means, and which constantly A processing means connected to the first relay means, and inputs to the first and second relay means are respectively selected from inputs from the first and second transmission paths, and input to the first and second transmission paths. selecting means for selecting each output from the outputs of the first and second relay means, and monitoring the outputs of the first and second relay means to prevent failures in the first and second transmission paths. and a control means for detecting and controlling the selection means, and the control means includes:
When a failure in one of the first and second transmission lines is detected, the signal is transmitted via the other transmission line and the first relay means connected to the processing means, and one transmission line is connected to the second relay means. A standby system is formed by connecting the first transmission line to the first transmission line and the second transmission line via the first relay means so that when a failure is detected in both the first and second transmission lines, the failure location is removed. 1. A transmission control device comprising a line switching function for performing signal transmission by connecting two transmission lines in a looped manner and connecting a transmission line other than the looped transmission line to a second relay means to form a standby system.