JPH11205321A - Communication path switching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need of a special connector for terminating and to easily specify a fault generation part by providing a switching part for switching the connection destination of a communication path and a changeover control part for controlling connection. SOLUTION: The changeover control part 12A switches the connection of the switching part 10A when the slave communication equipment 1B of a poststage is connected and the output signals of a driver 31B are confirmed. The changeover control part 12B maintains the connection of the switching part 10B since the slave communication equipment of the poststage is not connected and the output signals can not be confirmed in a communication return path. By the operation, since the output of the driver 31B of the slave communication equipment 1B of a final stage is connected to the communication return path and returned to a main control part 21, the communication route of going and returning signals is connected without connecting the special connector for terminating. Also, by sequentially changing the connection route of the switching parts 10A and 10B by the command of the main control part 21 and finding the maximum slave communication equipment connection state of reception signals from the communication return path, the fault generation part is specified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication path switching apparatus for connecting a plurality of slave communication apparatuses to a master communication apparatus electrically using a loop communication path.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional master communication apparatus connected to a plurality of slave communication apparatuses via a bus, that is, an electrically looped communication path. FIG. 3 is a block diagram illustrating an example of a communication device connected by using a connection cable that integrates an outgoing path and a return path. Communication data output from the main control unit 21 of the master communication device 2 includes a driver 31 and a connection cable 4.
0, which is input to the communication processing unit 11a via the receiver 32A of the slave communication device 1a. The communication processing unit 11a exchanges necessary data and outputs communication data to a subsequent communication device. Similarly, the communication data output from the communication processing unit 11a of the slave communication device 1a is
1A, the connection cable 41, and the receiver 32B of the slave communication device 1b are input to the communication processing unit 11b.
The communication processing unit 11a exchanges necessary data and outputs communication data to a subsequent communication device. The communication data output from the communication processing unit 11b of the slave communication device 1b is transmitted via the driver 31B, the special termination connector 42B connecting the forward and return signals, the connection cables 41 and 40, and the receiver 32 of the master communication device 2. Main control unit 21
, And a communication path in which the forward and return signals are connected in a loop is secured. In this example, the description is for a case where there are two slave communication devices. However, even if the number of slave communication devices to be connected is increased, it is possible to connect and operate in the same manner.

[0003]

In a conventional communication device in which a plurality of slave communication devices are connected to a master communication device via a bus, the forward and return signals are connected to the connector of the last slave communication device as described above. It is necessary to connect a special terminal connector, and it has been desired to remove the special terminal connector from the viewpoint of workability. In a communication device in which a plurality of slave communication devices are connected to a conventional master communication device via a bus, when a failure occurs in a part of the communication path, the communication path is interrupted. there were. For example, when a disconnection failure occurs in the communication path 50 in FIG. 5, the communication processing unit 11 a of the slave communication device 1 a detects the disconnection and transmits a disconnection detection to the main control unit 21 of the master communication device 2, whereby the disconnection is performed. It can be specified that the location is between the main control unit 21 and the communication processing unit 11a. Similarly, when a disconnection occurs in the communication paths 51 and 52, the communication processing unit 11 b of the slave communication device 1 b detects the disconnection and transmits the disconnection detection to the main control unit 21 of the master communication device 2. Is between the communication processing unit 11a and the communication processing unit 11b. However, the communication paths 53, 54,
If a disconnection occurs in any of 55, 56, 57, and 58, even if the main control unit 21 of the master communication device 2 detects a disconnection, it can only confirm that the disconnection is on the communication return path, and all slave communication devices However, there is a problem that the disconnection point cannot be specified without checking all the connection cables.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and there is no need to connect a special terminating connector. It is an object of the present invention to obtain a communication device that connects the slave communication devices through a bus.

[0005]

A communication path switching apparatus according to the present invention includes a switching section for switching a connection destination of a communication return path in a slave communication apparatus, and a switching control section for controlling connection of the switching section. It has a function of switching the switching unit according to the presence or absence of a command from a device or an output signal from a slave communication device at a subsequent stage connected to the switching control unit.

[0006]

FIG. 1 is a block diagram showing an embodiment of a communication path switching device for connecting a plurality of slave communication devices to a master communication device via a bus according to the present invention. The functions and processes indicated by the same notations as those in FIG. In the communication path switching device according to this embodiment, after the power is turned on, the switching control units 12A and 12B check whether there is an output signal on the return path of the slave communication device from the connected subsequent stage. In the block diagram illustrating the embodiment of FIG. 1, the switching control unit 12A of the slave communication device 1A includes:
Since the slave communication device 1B at the subsequent stage is connected, the output signal from the driver 31B can be confirmed. The switching control unit 12A that has confirmed the signal switches the connection of the switching unit 10A. On the other hand, the switching control unit 12B of the slave communication device 1B cannot confirm the output signal on the communication return path because the slave communication device of the subsequent stage is not connected. In this case, the switching control unit 12B keeps the connection of the switching unit 10B without switching. By the above operation, the output of the driver 31B of the slave communication device 1B at the last stage is connected to the communication return route and returned to the main control unit 21 of the master communication device 2, so that it is not necessary to connect a special terminal connector. The communication path of the return signal can be connected. FIG. 2 is a diagram illustrating a connection state after the switching of the switching unit is completed by initialization. In the above description, the switching unit has been described as using an electric contact element as an example in the case of using an electric signal in the communication path. Or the direct switching of the optical waveguide by the optical selector.

FIG. 3 is a block diagram showing another example of the operation of the communication path switching device for connecting three slave communication devices to the master communication device by bus according to the present invention. The operation of the communication path switching device will be described. In the block diagram of the present embodiment, the slave communication devices 1A, 1B,
1C are connected, and each switching unit 10
A state in which the connection of A, 10B, and 10C is determined is shown. Here, when a disconnection occurs in the communication channel 56, the driver 31C of the slave communication device 1C sends the communication channel 55, 56,
The output signal to the main control unit 21 via the receivers 32, 57, 58, 59, 60, 61 is cut off. Here, the switching controllers 12A, 12A of the slave communication devices 1A, 1B
B confirms that there is no signal of the communication return path from the subsequent stage, and changes the connection path of the switching units 10A and 10B to each slave communication apparatus 1A
Change to the driver 31A, 31B output side in 1B. However, in the switching control unit 12A of the slave communication device 1A, a signal on the return path from the slave communication device 1B at the subsequent stage is output from the driver 31B by the switching unit 10B. Change to return signal side from. With the above operation, it is possible to secure the communication path without the path in which the disconnection has occurred, and the main control unit 21 of the master communication device 2 communicates with the communication paths 50, 51, 52,
In the paths 58, 59, 60, and 61, good connections can be confirmed, and the communication paths 53, 54, and 5 where disconnection may have occurred.
Since the paths of 5, 56, and 57 can be limited, it is not necessary to confirm the failure of the connection cables 40, 41, the master communication device 2, and the slave communication device 1A when a failure occurs. The location can be specified and recovery can be facilitated. In the above description, the case where the connection paths of the switching units 10A and 10B are switched according to the presence or absence of the signal of the communication return path by the slave communication devices 12A and 12B has been described.
By sequentially changing the connection paths of the switching units 10A, 10B, and 10C according to the instruction from the main unit 1, the main control unit 21 determines the presence or absence of a reception signal from the communication return path and finds the maximum slave communication device connection state. It is also possible to specify the location of a failure in the communication path.

[0008]

As described above, according to the communication path switching apparatus for connecting a plurality of slave communication apparatuses to the master communication apparatus by bus, the switching section for switching the connection destination of the communication path and the connection of the switching section are controlled. By having a switching control unit to
The communication path of the bus connection can be secured without connecting a special termination connector, and the disconnection location can be limited by changing the connection of the communication path when a disconnection occurs.
Recovery in the event of a failure can be facilitated.

[0009]

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an embodiment of a communication path switching device according to the present invention.

FIG. 2 is a block diagram showing a connection at the time of completion of initialization of the communication path switching device of FIG. 1 of the present invention.

FIG. 3 is a block diagram showing an embodiment for explaining an operation at the time of disconnection of the communication path switching device of the present invention.

FIG. 4 is a block diagram illustrating an embodiment of a conventional communication device.

FIG. 5 is a block diagram showing an embodiment for explaining an operation at the time of disconnection of a conventional communication device.

[Explanation of symbols]

1A, 1B, 1C Slave communication device, 10A, 10
B, 10C switching unit, 11A, 11B, 11C communication processing unit, 12A, 12B, 12C switching control unit, 2 master communication device, 21 main control unit, 31, 31A, 31B,
31C driver, 32, 32A, 32B, 32C receiver, 40-43 connection cable, 42B termination connector, 50-61 communication path.

Claims (3)

[Claims] 1. A communication device for connecting a plurality of slave communication devices to a master communication device using an electrically looped communication path, wherein the switching unit switches a connection destination of a communication return path in the slave communication device, and the switching unit A communication path switching device comprising a switching control unit for controlling connection of units. 2. The communication path switching device according to claim 1, wherein said switching control section switches said switching section according to the presence or absence of an output signal from a slave communication apparatus at a subsequent stage. 3. The communication path switching device according to claim 1, wherein the switching control unit of the slave communication device switches the switching unit in response to a command from the master communication device. .