JP3163521B2 - Communication cable automatic recovery system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disconnection of a communication cable in a communication system in which a relay station is connected between terminal stations via a communication cable, and a terminal resistor is connected to each terminal station. Regarding automatic recovery system.

[0002]

2. Description of the Related Art Conventionally, in a communication system in which several control devices are connected to a communication cable, there is generally no countermeasure against a disconnection of the communication cable itself. As described above, if no countermeasure is taken, it is necessary to find the broken part and restore it, or to reconnect the cable, and the system remains in a communication failure during that time. There is also a system in which a spare communication cable is drawn in advance to minimize the time during which communication failure occurs, and the communication cable is manually switched when the cable is disconnected. However, in this system, the communication cable is a normal 2 cable.
The communication failure state is maintained until the operator responds because it is manually operated.

[0003]

FIG. 4 is a diagram showing the configuration of a system in which a conventional control device is connected by a communication cable. A terminal resistor R0 is connected to each of the terminal stations 51 and 55, and a relay station 5 is provided between the terminal stations 51 and 55.
2 to 54 are connected in series by a communication cable 56.

FIG. 5 is a diagram showing a state where the communication cable 56 is disconnected in the system of FIG. For example, when the communication cable 56 between the relay station 52 and the relay station 53 is disconnected at one place, it is natural that communication between the separated relay station 52 and the relay station 53 cannot be performed, and it is still connected. Between the existing relay station 53 and the terminal station 55,
Cannot function as a terminating station because there is no terminating resistor, and even if the communication is performed as it is, the communication operation becomes unstable or a communication failure occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and has been made in view of the above circumstances. An object of the present invention is to provide an automatic recovery system for disconnection of a cable.

[0006]

SUMMARY OF THE INVENTION A communication cable disconnection automatic recovery system according to the present invention is mutually connected by a pair of signal lines via a normally open contact, and each is connected via a normally open contact. A pair of terminating stations having a terminating resistor, and between the terminating station and the terminating station and connected in series by a pair of signal lines between the opposite side, and between the pair of signal lines A relay station having a terminating resistor connected via a normally open contact, connected between the terminating stations, between the relay stations, between the relay stations, between the relay station and the terminating station, and between the terminating stations, respectively And a pair of disconnection detection signal lines. The terminal station and the relay station respectively detect the disconnection of the disconnection detection signal line, and the relay station that has detected the disconnection closes the normally open contact of its own station, connects the terminal resistance between the signal lines, and Is notified to the terminal station that did not detect the disconnection. As a result, the normally open contacts of the terminal stations are closed and the normally open contacts are opened to enable the signal lines of the terminal stations and to open the terminal resistance. Therefore, a new network is formed in which the terminal station or the relay station sandwiching the disconnected communication cable becomes the terminal station. The terminal station and the relay station are constituted by, for example, a PC or another control device.

[0007]

FIG. 1 is a block diagram conceptually showing a configuration of an automatic disconnection recovery system according to an embodiment of the present invention, and FIG. 2 is a programmable controller (hereinafter, referred to as a PC) used as a control device thereof. FIG. 3 is a diagram showing a connection relationship of FIG. As shown, stations # 0 to # 4 of the PC 14
Are connected in a ring shape. The # 0 station 10 includes a power supply module 21a and a CPU module 2 as shown in FIG.
2a, PC link module 23a, output module 2
4a and the input module 25a, and the other # 1 stations 11 to # 4 stations 14 also include the same module. The PC link module 23a of the # 0 station 10 is a control module for exchanging communication data with another station, and the terminals X1 and X2 of the PC link module 23a of the # 0 station 10 are two-pair twisted shielded cables (hereinafter referred to as cable). ) Are connected to terminals X1 and X2 of the PC link module 23b of the # 1 station 11 via a pair of signal lines 27. Further, the terminals X1 and X2 of the PC link module 23a of the # 0 station 10 are connected to a pair of relay contacts R1a which are normally open, and the relay contacts R1a further connect the pair of signal lines 27 of the cable 26. A pair of relay contacts R1 similarly provided on the # 4 station 14 side via
e. And the relay contact R1e is # 4 station 1
Terminals X1, X of the PC link module (not shown)
2 are connected.

Further, a terminating resistor R is connected in parallel to terminals X1 and X2 of the PC link module 23a of the # 0 station 10 via a pair of relays R2a which are normally closed. Terminal X of PC link module of # 4 station 14
Similarly, a terminating resistor R0 is connected in parallel to 1 and X2 via a pair of relays R2d which are normally closed. Therefore, since the relay contacts R1a and R1e are open but the relay contacts R2a and R2e are closed, the # 0 station 1
Although the signal line 27 between the station 0 and the # 4 station 14 is not connected, the terminating resistor R0 is connected. on the other hand,#
The relays R1a and R1d in the 1st station 11 to the # 3 station 13
There is no relay contact corresponding to, and signal lines 2 are connected to terminals X1 and X2.
7 are directly connected, and a pair of relays R2b, R2 which are constantly open are connected to the terminals X1, X2.
A terminating resistor R0 is connected in parallel via c and R2d. Therefore, in the # 1 station 11 to the # 3 station 13, the terminating resistor R0 is not constantly connected in parallel. Each of the PC link modules 23a, 23b,... Has its SHD terminal connected to the ASHD terminal of another module via the shielded wire of the cable 26.

Relay coils RCa, RCb are connected to one terminal of the output modules 24a, 24b, respectively. When the relay coil RCa is excited by the output module 24a of the # 0 station 10, the relay contact R1a is opened and the relay contact R2a is closed. When the relay coil (not shown) is excited by the output module 24 (not shown) of the # 4 station 14, the relay contact R1e is opened and the relay contact R2e is closed. As a result, # 0 station 10 and # 4 station 1
4, the signal line 27 is connected, the terminating resistor R0 is removed, and the terminal does not function as a terminating station. Also,
In the case of # 1 station 11 to # 3 station 13, when their relay coils RCb are excited, conversely, relay contact R2
are closed, and the terminating resistor R0 is connected, so that it can function as a terminating station.

Each of the input modules 25a, 25b...
Are connected to the ground terminal of the other station via the signal line of the cable 26, respectively. For example, the terminal I0 of the input module 25a of the # 0 station 10 is connected to the ground terminal of the # 1 station 11, and the terminal I1 of the # 0 station 10 is connected to the # 4 station 1
4 ground terminal. This connection relation is # 1 station 11
The same applies to the input module 25b of the # 14 station 14. The terminals I of the input modules 25a, 25b ...
The presence / absence of disconnection is determined based on the input signals 0 and I1.
Therefore, among the signal lines of the cable 26, the input module 2
The signal lines connected to the terminals I0, I1 of 5a, 25b... Are referred to as disconnection detection signal lines 28. When the cable 26 is disconnected, the individual signal lines may be disconnected. However, here, it is assumed that an intruder disconnects intentionally as in a monitoring system. It is assumed that all signal lines including the signal line 27 are disconnected.

FIG. 3 is an explanatory diagram showing the operation of the above-described system at the time of disconnection. As shown, # 1 station 11 and # 2 station 12
The case where the cable 26 between the two is disconnected will be described. The CPU modules 21a, 21b,... Of each station take in the signals of the input modules 25a, 25b,... At regular intervals, and determine whether the signals at the terminals I0, I1 are at the ground potential. If the signals at the terminals I0 and I1 are at the ground potential, the cable 26 is normal.
If the signal of I1 is not at the ground potential, the cable 2
6 is determined to be disconnected. # 1 station 11 and # 2 station 1
2 is disconnected, the potential of the terminal I0 of the input module 25b of the # 1 station 11 and the potential of the terminal I0 of the input module 25 of the # 2 station 12 are not ground potentials. The CPU module 21a of the # 1 station 11 and the CPU module (not shown) of the # 2 station determine that the cable 26 between them has been disconnected based on the potential change of the terminals, and the output modules 24b... Is set to "1", and the relay coils RCb are driven. Thereby, the relay contacts R2b and # 2 of the # 1 station 11
The relay contacts R2c of the stations 12 are respectively closed, and the terminating resistors R0 are connected to the respective stations. As a result, the network of the # 0 station 10 and the # 1 station 11 and the # 2 stations 12 to # 4
Two groups of stations 14 are created (step 1).

Next, the # 1 station 11, which has newly become the terminal station, is disconnected from the # 0 station 10, and the # 2 station 12 is disconnected from the # 4 station 14, indicating that the own station has become the terminal station. Are transmitted via the PC link modules 23b. CPU modules 21b and # of station # 0 station 10, which is a conventional terminal station
When the CPU modules of the four stations 14 receive the signal, they output a signal to a predetermined terminal of the output module 24b to excite the relay coil RCb, and the relay contact R1
a, R1e is opened, and the relay contacts R2a, R2e are closed, so that the signal line 2 between the # 0 station 10 and the # 4 station 14
7 is made valid and the terminating resistor R0 is released (step 2). By the above processing, # 1 station 11 and # 2 station 12
Are formed as new terminal networks.

In the above-described embodiment, the example of the relay contacts whose opening and closing are controlled by the excitation of the relay coil has been described. However, these contacts in the present invention may be realized by an electronic switch or the like. Further, although an example of a PC has been described as the control device, another control device may be used. In the above-described embodiment, the disconnection detection is performed by detecting a potential change of the disconnection detection signal line. However, the present invention is not limited to this. For example, a change in current value may be detected, or an optical signal may be configured using an optical fiber line. The disconnection may be detected based on the presence / absence.

[0014]

As described above, according to the present invention, the terminal station and the relay station respectively detect the disconnection of the disconnection detection signal line, and the relay station which has detected the disconnection puts the terminal resistance of its own station between the signal lines. Connect and inform the end station that the end station has changed,
Since the signal lines of the terminal stations are made effective and the terminating resistors are opened, a new network is automatically formed in which the terminal station or the relay station, which is disconnected and sandwiches the communication cable, becomes the terminal station. For this reason, even if there is a disconnection, the communication is immediately restored, and stable communication in which communication between all the stations can be continued is enabled.

[Brief description of the drawings]

FIG. 1 is a block diagram conceptually showing the configuration of an automatic disconnection recovery system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a connection relationship of PCs used in the control device of FIG.

FIG. 3 is an explanatory diagram showing an operation at the time of disconnection in the system of the embodiment of FIG. 1;

FIG. 4 is a diagram showing a configuration of a system in which a conventional control device is connected by a communication cable.

FIG. 5 is a diagram showing a state where a communication cable 56 is disconnected in the system of FIG. 4;

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Kuramoto 1-1171 Tenjincho, Kodaira-shi, Tokyo Koyo Electronics Industry Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) H04B 1 / 74 H04B 3/46

Claims (2)

(57) [Claims] A pair of terminal stations connected to each other by a pair of signal lines via a normally open contact, each having a terminating resistor connected to each other via a normally open contact; A relay station having a terminating resistor connected in series between the pair of signal lines between the opposite sides of the pair of signal lines, and connected through a normally open contact between the pair of signal lines; A pair of disconnection detection signal lines respectively connected to the station, between the relay stations, between the relay station and the terminal station, and between the terminal stations, and the terminal station and the relay station detect the disconnection. Each of the disconnection of the signal lines is detected, and the relay station that has detected the disconnection closes the normally open contact of the own station, connects a terminating resistor between the signal lines, and notifies the terminal station that the terminal station has changed. By transmitting the normally open contact of the terminal station and opening the normally open contact of the terminal station, Automatic communication cable disconnection recovery system that enables the wires and opens the terminating resistor. 2. The system according to claim 1, wherein each of the terminal station and the relay station comprises a programmable controller.