JPH0644764B2 - Data transmission system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a data transmission system, and in particular, includes a master station, a plurality of slave stations, and a transmission path connecting these, and performs data transmission between these stations. Data transmission system.

[Prior Art] In this type of transmission system, a failure may occur in a slave station. In that case, conventionally, the failure is dealt with by manually operating a switch for switching lines. It is also proposed that the master station detect the failure of the slave station and the master station deal with the failure.

[Problems to be Solved by the Invention] In the former case, it is necessary to detect a faulty station first.
In addition, the line down time for data transmission was long due to manual switching, and it took a lot of manpower and time to secure the line.

In the latter case, if the slave station constantly outputs data due to a failure in the transmission / reception circuit, data collision will occur between the master station and all slave stations, and data communication will be disabled. .

[Means for Solving the Problems] According to the present invention, in a data transmission system including a master station, a plurality of slave stations, and a transmission path connecting these stations, the plurality of slaves are provided in a data transmission system for performing data transmission between these stations. Each of the stations is interposed between a data transmission / reception circuit, the transmission line and the data transmission / reception circuit, the data transmission / reception circuit is connected in series to the transmission line when energized, and the data is transmitted from the transmission line when de-energized. A relay circuit that forms a bypass circuit in the transmission path that separates the transmission / reception circuit and bypasses the data transmission / reception circuit; a detection circuit that detects the presence / absence of a failure of the data transmission / reception circuit and generates a detection signal indicating the presence / absence of the failure; ，
A relay that controls the relay circuit according to the detection signal, energizes the relay circuit when the detection signal represents the absence of the fault, and disconnects energization of the relay circuit when the detection signal represents the absence of the fault. A data transmission system characterized by including a control circuit is obtained.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a main part of a data transmission system according to an embodiment of the present invention. In the figure, reference numeral 1 is a master station, and slave station 2
1, 22, and 23 are connected so that data can be transmitted from the master station to the slave station and from the slave station to the master station via the data transmission paths 7 and 8. That is, when the slave stations 21, 22, 23 are normal, the data from the master station 1 is transmitted to the slave stations 21, 22, 23 via the transmission path 7, and the data from each of the slave stations 21, 22, 23 is transmitted. Is sent to the master station 1 via the transmission line 8.

Each of the slave stations 21, 22, 23 has a data transmission / reception circuit 31,
Includes 32. Transmission lines 7 and 8 and data transmission / reception circuit 3
Relay circuits 61 and 62 are interposed between the relay circuits 1 and 32. The relay circuits 61 and 62 are connected to the transmission line 7 when energized.
8 is connected in series with the data transmission / reception circuits 31 and 32, and the data transmission / reception circuits 31 and 32 are connected from the transmission lines 7 and 8 when the power is not supplied.
And a bypass circuit for separating the data transmission / reception circuits 31 and 32 is formed in the transmission lines 7 and 8.

The data transmission / reception circuits 31 and 32 are connected to fault detection circuits 41 and 42 that detect the presence or absence of these faults and generate detection signals indicating the presence or absence of the faults. Further, relay control circuits 51 and 52 for controlling the relay circuits 61 and 62 are connected to the failure detection circuits 41 and 42. The relay control circuits 51 and 52 energize the relay circuits 61 and 62 when the detection signal indicates the absence of the fault, and cut off the energization of the relay circuits 61 and 62 when the detection signal indicates the absence of the fault. is there.

In the normal state, the relay circuit 61 is in the power-on state,
The contact is broken and the bypass circuit of the data transmission line 7 is opened. At this time, the data from the data transmitting / receiving circuit 31 is transmitted to the data transmitting / receiving circuit of the next slave station 22 via the transmission path 7.

Now, consider a case where a failure occurs in the transmission / reception circuit 31 in the slave station 21. The fault detection circuit 41 detects the occurrence of a fault in the transmission / reception circuit 31, controls the relay control circuit 51 by the detection signal, and turns off the power supply of the relay circuit 61. The relay circuit 61 is connected from the transmission / reception circuit 31 to the transmission path 7 when the power is off.
A signal path to the data transmission line 7 is opened, and a bypass circuit that bypasses the data transmission / reception circuit 31 is formed in the data transmission line 7.

As a result, when a data transmission / reception circuit of a child station fails,
The transmission path from the data transmission / reception circuit to the data transmission path is disconnected. At the same time, a data transmission line that bypasses the slave station is automatically configured. Therefore, it does not hinder the data transmission between other normal slave stations and the master station.

Also, since the relay circuit has a break contact for bypassing the transmission line, a similar bypass circuit is configured even when the power of the station of the slave station is cut off or the panel of the data transmission / reception circuit is not mounted. be able to.

As described above, according to the data transmission system of the present invention,
When a failure occurs in the data transmission / reception circuit of the slave station or when the power of the station is down, the data transmission / reception circuit of the failed station is automatically disconnected from the data transmission path and a bypass of the data transmission path is formed. . Moreover, since this fault countermeasure function is given to each of the plurality of slave stations, it is completely unrelated to the predetermined functions of the other slave stations and the master station, and is also completely unrelated to the transmission / reception function of the data transmission / reception circuit of the own station. When a failure occurs, the failure countermeasure is executed without impairing the predetermined functions of the data transmission / reception circuits of other slave stations, master stations, and own station.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of a data transmission system according to an embodiment of the present invention. 1 ... Parent station, 21, 22, 23 ... Child station, 31, 32 ...
... Data transmission / reception circuit, 41, 42 ... Fault detection circuit, 5
1, 52 ... Relay control circuit, 61, 62 ... Relay circuit, 7, 8 ... Data transmission path

Claims (1)

[Claims] 1. In a data transmission system including a master station, a plurality of slave stations, and a transmission path connecting these stations, and performing data transmission between these stations, each of the plurality of slave stations includes a data transmission / reception circuit, The data transmission / reception circuit is interposed between the transmission line and the data transmission / reception circuit, the data transmission / reception circuit is connected in series to the transmission line when energized, and the data transmission / reception circuit is disconnected from the transmission line when de-energized. A relay circuit that forms a bypass circuit for bypassing in the transmission path, a detection circuit that detects the presence / absence of a fault in the data transmission / reception circuit, and generates a detection signal indicating the presence / absence of the fault, and the relay circuit according to the detection signal. The relay circuit is energized when the detection signal represents the absence of the fault, and the relay circuit is energized when the detection signal represents the absence of the fault. One data transmission system which comprises a relay control circuit.