JPH01268236A - Line switching device for data transmission system - Google Patents

Abstract

PURPOSE:To instantaneously cope with disconnection, etc., of a line by switching a signal line and loop back line at a line switching device by means of the 1st and 2nd switching circuits which are operated by the detecting outputs of the 1st and 2nd detection circuits for detecting input states. CONSTITUTION:The detection circuits 6 and 7 can send actuating signals to the switching circuit 3, 4, and 9 upon instantaneously detecting signals transmitted through a signal line SG and loop back line LB and each relay switch (a) to (f) constituting the switching circuits 3, 4, and 9 can operate at high speeds (for example, in the order of msec). Therefore, even if the signal line SG or loop back line LB is cut off, the disconnection can be coped with immediately by switching the line. Since the interrupting time of data transmission can be made extremely shorter in such way, a transmission system whose function is not stopped due to lost data is obtained.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a line switching device in a data transmission system, and more specifically, the present invention relates to a line switching device in a data transmission system.
In a line switching device in a data transmission system connected in a loop through a transmission line consisting of a signal line and a loopback line, by switching the line between the signal line and the loopback line at each station, it is possible to quickly respond to line breaks, etc. The present invention relates to a line switching device in a data transmission system that can be used.

<Conventional technology> A local area network (hereinafter referred to as LAN) is
Due to cost reductions resulting from the current development of computer technology, it has been widely incorporated into factory automation systems and small-scale systems such as office automation (OA) systems.

Among the above LANs, multiple slave stations are connected to one master station,
A loop-type LAN connected in a loop using transmission lines such as optical fibers, coaxial cables, and twisted pair cables.
I will explain about it.

Loop-type LAN transmission lines usually have a signal line that transmits signals in one direction of the loop, and a loopback line that transmits signals in the opposite direction in order to cope with line disconnections. It is configured.

FIG. 7 is a diagram showing the configuration of such a transmission system, in which a master station (A) and a plurality of terminal stations (B) are attached and connected in a loop through a transmission path (C). The above master station (
A) consists of a control master station (A') and a line switching device (P), and a terminal station (B) consists of 1. It consists of a control slave station (B') and a line switching device (P). A plurality of loads (D) are connected to the control slave station (B').

The transmission path (C) is composed of a signal line (SC) and a loopback line (LB) that transmit signals in opposite directions.

According to the above system, the control master station (A') is connected to the signal line (
The self-generated data can be sent to the control slave station (B') and the loopback line (LB), and sequentially supplied to the control slave station (B'). Each control slave station (B') receives the above data and sends response data regarding the state of the load (D) to the signal line (
SG) and loopback line (LB) to the master station (A
).

When the transmission line (C) is disconnected or the like and data that should be input from the signal line (SC) is interrupted, the data that should be input from the loopback line (LB') is input from the loopback line (LB') at the terminal station (B) that first detected the data interruption. Folds the data back to the signal line output side. In addition, when data to be input from the loopback line (LB) is interrupted, the data input from the signal line (SG) is folded to the loopback line output side at the terminal station (B) that first detected the data interruption. return. In order to realize these loopback states, the terminal station (B) constantly monitors the data input from the signal line (SG) and the loopback line (LB), and if the input data is interrupted, the terminal station (B) ), it is necessary to switch from which of the loopback lines (LB) to acquire data, and whether to send the data to be looped back to the signal line (SG) or to the loopback line (LB). This switching is automatically controlled in response to the presence or absence of signal line input and loop-tock line input.

Specifically, the signal line input and the loop line (
If there is re-input of LB), the terminal station (B)
Data through state in which the input is output as is (Figure 8)
(See A). If there is no loop line input, for example, if the loop line input side, that is, the signal line output side is disconnected, the signal line input is looped back to the loop back line (LB) and sent out. (see figure (B)).

If there is no signal line input, that is, if the signal line input side is disconnected, connect the loopback line input to the signal line (SC
) (see FIG. 8(C)). If there is no input, the state is switched to transmitting its own data to the signal line (SG) and loopback line (LB) (see FIG. 2(D)).

Therefore, if there is no disconnection between any of the stations, a loop-like connection will be formed as shown in Figure 1, but if there is no disconnection between any of the stations. If this has occurred, for example, as shown in Figure 9, if there is a disconnection between the terminal station (Bl) and (B2), the terminal station (B1) will return the signal line input to the loopback line (LB). At the same time, the terminal station (
B2) is switched and controlled so that the loopback line input is looped back to the signal line (SC).

As a result, the master station (A)
data can be transmitted to all terminal stations (B).

In order to switch the line in the above line switching device (F), a signal line (SC) and a loopback line (LB) are required.
A signal detecting means for determining the presence or absence of a signal input from each terminal, and a connection control means for operating a switch to realize a predetermined connection state depending on the presence or absence of a signal are required.

Conventionally, signal detection and connection control were carried out by each station (A
) (B) It was realized by the software of the provided microcomputer. In other words, a detector detects the signal input state, and when a timer measures the absence of a signal for a certain period of time, it is determined that there is no input signal, and a predetermined switch is activated to return the signal. was.

<Problem to be solved by the invention> However, in the line switching device in the data transmission system described above, both the signal detection means and the connection control means are realized by software, so it takes a certain amount of time for determination and processing (for example, a total of 2 seconds). For this reason,
During the above judgment and processing, there was a problem in that data input was interrupted for a while due to the influence of line disconnection. Particularly in high-speed LANs with high data transmission speeds, the amount of data that is lost is relatively large, which poses problems such as interfering with system operation.

This invention was made in view of the above-mentioned problems.In a loop transmission system in which a plurality of stations are interposed using a transmission line consisting of a signal line and a loopback line, data may be lost due to line breakage, etc. An object of the present invention is to provide a line switching device in a data transmission system that can quickly switch the line and acquire data when the line is interrupted.

Means for Solving the Problems> To achieve the above object, a line switching device of the present invention includes a first detection circuit that detects an input state from a signal line, and a first detection circuit that detects an input state from a loopback line. a second detection circuit for detection, a first switch circuit provided on the signal line input and loopback line output sides and operated by the output of the first detection circuit, and a first switch circuit provided on the signal line output and loopback line input sides. and a second switch circuit operated by the output of the second detection circuit, and a state in which the signal line input is sent to the signal line output side and the loopback line input is sent to the loopback line output side, and the signal line input is This function switches the state in which the signal line is looped back to the loopback line output side, the loopback line input is folded back to the signal line output side, or the data generated at the station is sent to the output side of the signal line and loopback line. be.

Function> With the line switching device in the data transmission system described above, when the rain detection circuit detects a state where there is no line disconnection and signal line input and loopback line input are present, the first switch circuit switches the signal line The input is connected to a second switch circuit, and a signal is sent from the second switch circuit to the output side of the signal line. Further, the loopback line input is directly sent to the output side of the loopback line through the second switch circuit and the first switch circuit.

Next, when the loopback line input is disconnected, the second detection circuit detects this and switches the state of the second switch circuit. Then, the signal supplied from the first switch circuit is turned back by the second switch circuit and supplied to the output side of the loopback line. In this way, the signal line input can be looped back to the loopback line.

Next, when the signal line input is disconnected, the first detection circuit detects the disconnection of the signal line input and switches the state of the first switch circuit. Then, the loopback signal coming from the second switch circuit is looped back at the first switch circuit,
It is connected to the second switch circuit directly or via a signal processing section. Then, a signal is supplied to the output side of the signal line through the second switch circuit. This allows the loopback line input to be looped back to the signal line.

When both the signal line input and the loopback line input are disconnected, the first and second detection circuits detect the disconnection of the signal line input and the loopback line input, and switch the states of the first and second switch circuits. . Then, the signal generated at the station is sent out to the output side of the loopback line through the second switch circuit, and is also sent out to the output side of the signal line through the first switch circuit. This allows the data generated at the station to be sent out to the transmission line.

<Example> Hereinafter, embodiments will be described in detail with reference to the accompanying drawings showing examples.

FIG. 1 is a schematic circuit diagram showing the configuration of a line switching device of the present invention, in which a line switching device (1) is installed in the middle of a transmission line consisting of a signal line (SG) and a loopback line (LB) that are parallel to each other. It has been inserted. Then, the line switching device (1
) is connected to a control master station or a control slave station (hereinafter collectively referred to as "connection station (2)").

More specifically, a first switch circuit (3) is provided on the signal line input and loopback line output sides, and a second switch circuit (4) is provided on the signal line output and loopback line input sides. A third terminal is provided between the connecting station (2) and the
A switch circuit (5) is interposed. A first detection circuit (6) detects the signal line input and operates the first switch circuit (3), and a first detection circuit (6) detects the loopback line input and operates the second switch circuit (4). A second detection circuit (7) is provided. Also, based on the output of the AND circuit (8) and the AND circuit (8) which operates when both the output of the first detection circuit (6) and the output of the second detection surface path (7) are present, - A fourth switch circuit (9) is provided which is activated.

Furthermore, a third switch circuit detects the state of the signal passing through the entrance/exit of the connection station (2) and operates the third switch circuit (5).
A detection circuit (10) is provided. Each of the detection circuits described above uses, for example, a current transformer.

To explain the specific connection state, the first switch circuit (
3) has two relay switches (a) and (b). The input side signal line (SG) is connected to the b contact (represented by a black circle in the figure) of one relay switch (a), and the output side signal line (SG) is connected to the b contact of the other relay switch (b). A loopback line (LB) is connected. The second switch circuit (4) has three relay switches (C) to (
e), the B contact of the relay switch (C) is connected to the common terminal of the relay switch (a), and the common terminal of the relay switch (C) is connected to the input side loopback line (LB
)It is connected to the. The B contact of the relay switch (d) is the A contact of the relay switch (a) (represented by a white circle in the diagram)
The a contact of the relay switch (d) is connected to the loopback line (LB) on the output side. Also, the fourth
The switch circuit (9) has one relay switch (f), and the a contact of the relay switch (f) is the common terminal of the relay switch (d), and the a contact of the relay switch (b)
It is connected to the contact point and the a contact point of the relay switch (e). The common terminal of the relay switch (f) and the b contact of the relay switch (e) are connected to the output side signal line (SG). Further, the third switch circuit (5) has two relay switches (g) and (h), and the common terminal of the relay switch (g) is connected to the common terminal of the relay switch (b). The common terminals of (h) are respectively connected to the common terminals of relay switches (e). The a contact of the relay switch (g) is connected to the input side of the connection station (2), and the a contact of the relay switch (h) is connected to the output side of the connection station 0). Further, the b contacts of the relay switches (g) and (h) are connected to each other.

The operation of the above circuit will be explained.

First, if the connecting station (2) does not exist, or if the connecting station (
When using 2) separately, use the relay switch (
When g) and (h) are respectively turned to the B contact side, the B contacts are connected and the connecting station ■ is electrically disconnected.

If a signal line input and a loopback line input are present in this state, the first detection circuit (6) and second detection circuit σ) detect these inputs, and relay switches (a) and (b) )
, turn relay switches (c), (d), and (e) to the b contact side, respectively. As a result, the loopback line input is connected to the loopback line output side, and the signal line input is connected to the signal line output side via the relay switches (g) and (h) (see Figures 2 and 1). (Refer to the table, the black circle in the table indicates the state where the contact is pushed down to the B contact). In other words, the line switching device functions as a repeater.

Table 1 Next, when there is a connecting station (2), the third switch circuit (5) detects a predetermined signal output from the connecting station (2) and connects the relay switches (g) and (h) to the a contact. Flip it to the side and connect the line switching device (1) and the connection station (2). If a signal line input and a loopback line input are present in this state, the first detection circuit (6) and second detection circuit (7) detect these inputs, and the relay switches (a), (b), Turn each relay switch (c), (d), and (e) to the b contact side.

As a result, the loopback line input is connected to the loopback line output side, and the signal line input is connected to the signal line output side via the connection station (2) (see Figure 3 and Table 2, Table The white circle indicates the state where the a contact is bent).

As a result, the connecting station (2) can acquire data input from the signal line (SG) and send the data as is to the output side of the signal line (SC) to provide it to the adjacent station. can.

Table 2 If there is a break in the signal line (SG) and there is no signal line input, the first detection circuit (6) detects the absence of the signal line input and turns on the relay switches (a) and (b). Since it is turned to the A contact side, the loopback line input is connected to the relay switch (C
), relay switch (a), relay switch (d), relay switch (b), relay switch (g) to connect station (2), connect station (2) Garari relay switch (h) relay switch (e) to the signal line output (see Figure 4 and Table 3). In other words, a state is realized in which the loopback line input is supplied to the connecting station (2) and the supplied data is looped back to the signal line output side.

Table 3 Next, if there is a break in the loopback line (L B ) and there is no loopback line input, the second detection circuit (
7) detects the absence of loop) g) and enters the connecting station (2) via the connecting station (2).
) to relay switch (h), relay switch (e),
It goes out to the loopback line output via the relay switch (d) (see Figure 5 and Table 4). As a result, a state is realized in which the signal line input is supplied to the connecting station (2) and the supplied data is returned as is to the loopback line output.

Table 4: If both the signal line (SG) and the loopback line (LB) are disconnected, and neither the signal line input nor the loopback line input exists, the rain detection circuit (6) and (7) will each be =
18- Detect the absence of signal line input and loopback line input, and turn relay switches (a) to (e) to a contact. At the same time, the AND circuit (8) receives the detection output of the rain detection circuit (6> (7)) and turns the relay switch (f) to the a contact side.

As a result, the output of the connected station (2) is connected to the relay switch (h).
, is sent from the relay switch (e) to the signal line output via the relay switch (f), and the relay switch (
e) to the loopback line output via the relay switch (d). Along with this, the relay switch (
e) to relay switch (b), relay switch (g)
and returns to the connecting station (2) (see Figure 6 and Table 5). As a result, a state is realized in which the connection station (2) outputs its own signals to the signal line (SG) and the loopback line (LB), respectively. With this, for example, when the connecting station (2) is a controlling master station, command data for the slave station can be sent through the signal line (SG) and the loopback line (LB). If the connected station (2) is a controlled slave station, load data for the master station is sent to the signal line (SC).
), it can be sent out through the loopback line (LB).

= 19 - Table 5 In the operations explained above, the detection circuits (6) and (7) instantaneously detect the signals transmitted through the signal line (SG) and the loopback line (LB) and switch the switch circuits (3) and ( 4), (9
) can send an operating signal to the switch circuit (3),
Each relay switch (a) to (4) and (9) constitutes
f) can also operate at high speed (for example, on the order of m5eQ), so signal lines (SC) and loopback lines (L
Even if there is a line disconnection in B), the line can be switched immediately.

It should be noted that the present invention is not limited to the above-described embodiments; for example, the switch circuit may be configured with a logic gate instead of a relay. The operating time of a logic gate is
Since it is on the order of n5eC, the operation time can be further shortened by using logic gates.

Various other design changes can be made without changing the gist of the invention.

<Effects of the Invention> As described above, the present invention has first and second detection circuits that detect the input state from the transmission line, and a first detection circuit that operates based on the detection outputs of the first and second detection circuits. , and a second switch circuit, and can switch the signal line and loopback line in the line switching device by operating the first and second switch circuits, and can instantly respond to line disconnections, etc. be able to. Therefore, the interruption time of data transmission can be made extremely short, so it is possible to realize a transmission system in which the system function does not stop due to data loss.

[Brief explanation of the drawing]

Figure 1 shows the data transmission system of this invention = 21
- Schematic configuration diagram showing an example of a line switching device, Figures 2 to 6
The figure is an operation diagram explaining the switching state of the line, Figure 7 is a schematic diagram showing the overall configuration and signal flow of a transmission system using the line switching device, and Figure 8 shows the switching status of each line of the line switching device. FIG. 9 is a schematic diagram showing the flow of signals in the transmission system when line switching is performed. (1)...Line switching device, (3)...First switch circuit, (4)...29th switch circuit, (6)...First detection circuit, (7)...・Second detection circuit,

Claims (1)

[Claims] 1. Signals that transmit data in opposite directions consisting of wires and loopback wires Along with laying the transmission line in a loop Multiple stations are interposed in the loop, and each station signal line input and loopback line input signal line at the relevant station depending on the power status. and loopback line connection status. Data that can be switched by a switch A line switching device in a transmission system. So, The first one detects the input state from the signal line. detection circuit and input from the loopback line. a second detection circuit for detecting the force state; Installed on the line input and loopback line output sides is activated by the output of the first detection circuit. a first switch circuit, a signal line output, Provided on the loopback line input side, the second A second circuit operated by the output of the detection circuit of It has a switch circuit, Loop the signal line input to the signal line output side. Back line input to loop back line output side Check the sending status and signal line input for each. state where the loop back line is folded back to the output side. Fold back line input to signal line output side status or signal line and loopback The data generated at the station is sent to the output side of the It is characterized by switching to the sending state. Line switching in data transmission systems Device.