JPH1084400A - Data transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain data transmission without intermission even on the occurrence of a fault in a modem of a line by connecting a plurality of modems whose transmission protocol differs to one and same line and transmitting multiplexed same data. SOLUTION: The transmitter is provided with an in-phase modem 50 and a quadrature modem 51 whose phases differ from each other by 90 degrees. Then the in-phase modem 50 and the quadrature modem 51 whose phases differ from each other by 90 degrees conduct transmission reception of signals whose phases differ from each other by 90 degrees. Furthermore, an external input output section 33 connects the in-phase modem 50, the quadrature modem 51 and a control section 11, and the external input output section 33 outputs each output from the in-phase modem 50 and the quadrature modem 51 to the control section 11 and an output from the control section 11 is outputted to the in-phase modem 50. Since same data are multiplexed and transmitted with phases shifted by 90 degrees by using the two modems, data are transmitted uninterruptibly even on the occurrence of a modem of one line and the high reliability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission device suitable for use in a process monitoring and control system installed in a sewage treatment plant, a building factory facility, a production plant, or the like.

[0002]

2. Description of the Related Art The above-mentioned process monitoring control system is provided with a data transmission device for transmitting data between a monitoring side and a monitoring target side.

FIG. 5 is a block diagram showing a schematic configuration of a conventional process monitoring control system. As shown in this figure, two data transmission devices 3A and 3B are provided between the monitoring device 1 and the controller 2. The data transmission devices 3A and 3B are connected by a line 4 using an electric wire or an optical fiber cable, and data transmission between the monitoring device 1 and the controller 2 is performed via the line 4.

The structure of the data transmission device will be described with reference to a data transmission device 3B on the controller 2 side. The data transmission device 3B controls a modem (a so-called modem) 10 and various parts of the device as shown in the block diagram of FIG. Control unit 11,
External input / output unit 12 for connecting control unit 11 and modem 10
And the internal bus line 20 of the controller 11 and the controller 2
And an internal bus input / output unit 13 for connecting the internal bus.
The data transmission device 3A of the monitoring device 1 has basically the same configuration.

The modem 10 modulates signals and data from the control unit 11 and outputs the modulated signals and data to the line 4, and demodulates signals and data transmitted via the line 4 and outputs the demodulated signals and data to the control unit 11. The control unit 11 outputs signals and data from the modem 10 to the internal bus line 20 of the controller 2 via the internal bus input / output unit 13. Further, the control unit 11 outputs signals and data from the controller 10 to the modem 10. The controller 2 controls the process equipment 5 and the process equipment 5
Is output to the monitoring device 1. Note that the line 4 shown in FIG. 6 is a metallic two-wire type, and a shield line covering them is grounded via the housing of the data transmission device 3B.

[0006]

By the way, in the above-mentioned conventional data transmission apparatus, if any one of the line 2 and the modem 10 has an abnormality, the data transmission between the other data transmission apparatus is stopped. Therefore, there is a problem that reliability cannot be obtained.

Therefore, as shown in the block diagram of FIG.
In preparation for the abnormality of the line 4 or the modem 10, the number of the lines 31 in addition to the line 4 is increased, and one modem 32 for the line 31 is added in addition to the modem 10 to include one of the modems 10 in use. Unused line 31 when an error occurs on line 4
There is also a data transmission apparatus in which redundancy is enhanced by switching to a modem 32.

However, even in this data transmission device, if there is an abnormality in the line 4 and an abnormality in the modem 32, for example, the data transmission stops, and one of the line 4 or the line 31 and the other line In other words, if one of the four lines is broken, data transmission becomes impossible.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a data transmission device capable of improving reliability in data transmission.

[0010]

In order to increase redundancy, multiplexing of modems and multiplexing of lines are indispensable. In particular, modems and lines do not correspond one-to-one but correspond to n-to-n. Better. In addition, by adding wireless data transmission in addition to wired data transmission, redundancy can be further enhanced.

In the case of one line (metallic two-wire system), simply multiplexing modems makes data transmission overlapping, so that redundancy is impossible. Therefore, it is possible to multiplex modems by changing the data transmission format.
In order to change the data transmission format, for example, modems having different modulation schemes may be used. Modulation methods include amplitude modulation, frequency modulation, and phase modulation. In particular, in the phase modulation method, it is possible to multiplex a modem only by changing the phase of a signal.

On the other hand, in the case of a multiplex line, a switch circuit for selecting which line carries a signal from the modem is provided. In this case, the number of lines is not limited to an even number, and n (n ≧ 2)
Two of the books are selected. This increases the margin of the line.

Since high speed is required for selecting a line, a reflected wave is used. If the signal emitted from one end of the line has an open end, a reflected wave exists from the open end. By detecting the presence or absence of the reflected wave, it can be determined whether or not the line is disconnected.

According to the first and second aspects of the present invention, a plurality of modems having different transmission formats are provided, and these modems are connected to the same line to perform multiplex transmission of the same data. Each modem inputs and outputs data in a transmission format based on any one of amplitude modulation, frequency modulation, and phase modulation.

According to this configuration, a plurality of modems having different transmission formats are connected to the same line, and multiplex transmission of the same data is performed. Therefore, data transmission can be performed without interruption even when the modem is abnormal on one line.

The invention according to claim 3 further comprises a line selecting means for selecting a sound line by detecting a reflected wave at the time of data transmission in each of the plurality of lines and connecting to each of the modems. is there.

According to this configuration, if there is a reflected wave at the time of data transmission in the currently selected line among the plurality of lines, the line is determined to be abnormal and switched to another line. In this case, it is also determined whether or not there is a reflected wave during data transmission. In this way, switching to a healthy line is performed. Therefore, data transmission can be performed without interruption even when the line is abnormal.

Further, the invention according to claim 4 further comprises wireless communication means for transmitting and receiving data, wherein the line selecting means connects each modem to the wireless communication means when all of the plurality of lines are abnormal. is there.

According to this configuration, when all of the plurality of lines become abnormal, each modem is connected to the wireless communication means and wireless data transmission is started. Therefore, data transmission can be performed without interruption even when all the lines are abnormal.

[0020]

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

<First Embodiment> FIG. 1 is a block diagram showing a configuration of a data transmission apparatus according to a first embodiment of the present invention. In this figure, FIG. 6 and FIG.
The same reference numerals are given to the same parts as those described above, and the description thereof will be omitted. Although the data transmission device 40B shown in FIG. 1 is installed on the controller 2 (see FIG. 2) side, the configuration and function are substantially the same as those installed on the monitoring device 1 side.
The difference is that the data transmission device 40B installed on the controller 2 side has its internal bus input / output unit 13 connected to the internal bus line 20 of the controller 2,
The data transmission device 40A installed on the monitoring device 1 side has an internal bus input / output unit 13 connected to an internal bus line (not shown) of the monitoring device 1.

In the first embodiment, multiplexing is performed by only one line, and a normal-mode modem 50 and a quadrature modem 51 having phases different from each other by 90 degrees are provided. FIG. 2 is a diagram showing the difference between the phases of the normal-mode modem 50 and the quadrature modem 51, where 50A is the phase of the normal-mode modem 50 and 51A is the phase of the quadrature modem 51. Transmission and reception of signals having phases different from each other by 90 degrees are performed. In this way, even if one of the modems fails, data transmission by the other modem is established, so that data transmission is performed without interruption.

The external input / output unit 33 is provided with a normal-phase modem 50.
And the quadrature modem 51 and the control unit 11 are connected. The output of each of the normal-phase modem 50 and the quadrature modem 51 is output to the control unit 11 by the external input / output unit 33, and the output of the control unit 11 is Normal phase modem 50 and quadrature modem 5
1 is output.

As described above, in the first embodiment, two modems, ie, the normal-phase modem 50 and the quadrature modem 51, are used.
The same data is multiplexed with a phase shifted by 90 degrees and transmitted. Therefore, data can be transmitted without interruption even when a modem in one line is abnormal, and high reliability is obtained.

<Second Embodiment> FIG. 3 is a block diagram showing a configuration of a data transmission apparatus according to a second embodiment of the present invention.

The data transmission device 6 according to the second embodiment
0B is a line multiplex of the data transmission apparatus 40B of the first embodiment, and a switch unit 62 is provided between the normal-mode modem 50 and the quadrature modem 51 and the four lines 61a to 61d. . The switch unit 62 includes a microcomputer, a changeover switch, and the like. The switch unit 62 constantly monitors the status of each of the four lines 61a to 61d, and connects the normal line 61a to 61d with the normal-phase modem 50 and the quadrature. Connect the modem 51. Whether the lines 61a to 61d are normal or not is determined based on the reflected wave. If the line is broken, the reflected wave does not return. Therefore, it is determined that the line is abnormal and the other line is determined. Switch. In this case, since the other data transmission device 60A also has the same configuration as the data transmission device 60B, if one switches the line, the other switches the line following it.
That is, since both sides always select the same line, data transmission is performed without interruption. Switch part 62
Determines that the reflected waves return in all of the lines 61a to 61d, the in-phase modem 50 and the quadrature modem 51
Connection to the lines 61a to 61d and the wireless communication unit 64
Connect to Thus, wireless data transmission is started.

Here, the operation of the switch section 62 will be described with reference to the flowchart shown in FIG.

First, the reflected wave on the line established at the present time is monitored, and it is determined whether or not the line has an abnormality (steps S10 and S12). In this determination, if it is determined that there is an abnormality, the process proceeds to step S14, and the currently established line is changed to a healthy line. Next, it is determined whether or not the number of the changed transmission lines is one or less (step S16). If it is determined that there is one or more lines, the process returns to step S10. Is canceled to change to the wireless transmission method (step S18). That is, the normal-phase modem 50 and the quadrature modem 51 are connected to the wireless communication unit 64.

As described above, in the second embodiment,
Using two modems, a normal-phase modem 50 and a quadrature modem 51, the same data is multiplexed with a phase shifted by 90 degrees and transmitted, and the lines are multiplexed to select a sound line at all times. Is determined by using the reflected wave. If all the lines are abnormal, the in-phase modem 50 and the quadrature modem 51 are connected to the line 61a.
To 61d, and connected to the wireless communication unit 64 to perform wireless data transmission.

Therefore, data transmission can be performed without interruption even when a modem or line is abnormal, so that the reliability is greatly improved.

The first embodiment and the second embodiment
In the embodiment, the in-phase modem 50 using the phase modulation is used.
Although the same data is multiplexed with a phase shifted by 90 degrees using the quadrature modem 51, the multiplexing may be performed using amplitude modulation or frequency modulation.

Further, in the second embodiment, four lines 61a to 61d are used, but the number is not limited as long as the number is two or more. As the number increases, the reliability can be improved.

[0033]

As described above, according to the data transmission apparatus of the first and second aspects, a plurality of modems having different transmission formats are connected to the same line to perform multiplex transmission of the same data. Therefore, even if the modem is abnormal on one line, data transmission can be performed without interruption, and high reliability can be obtained.

According to the data transmission device of the third aspect,
If there is a reflected wave at the time of data transmission on the currently selected one of the multiple lines, it is determined that the line is abnormal and switched to another line. And high reliability can be obtained.

According to the data transmission apparatus of the fourth aspect,
Each modem is connected to the wireless communication means when all of the multiple lines become abnormal, and data is transmitted wirelessly, so even if all lines are abnormal, data can be transmitted without interruption. Reliability can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a data transmission device according to the present invention.

FIG. 2 is a diagram for explaining a data transmission method of the data transmission device according to the first embodiment.

FIG. 3 is a block diagram illustrating a configuration of a data transmission device according to a second embodiment of the present invention.

FIG. 4 is a flowchart illustrating an operation of a switch unit of the data transmission device according to the second embodiment.

FIG. 5 is a block diagram showing a configuration of a process monitoring control system using a conventional data transmission device.

FIG. 6 is a block diagram illustrating a configuration of a conventional data transmission device.

FIG. 7 is a block diagram showing a configuration of a conventional data transmission device.

[Explanation of symbols]

 4, 61a to 61d Line 40B Data transmission device 50, 51 Modem 62 Switch unit (line selection unit) 64 Wireless communication unit (wireless communication unit)

Claims (4)

[Claims] 1. A data transmission apparatus comprising a plurality of modems having different transmission formats, each of which is connected to the same line to perform multiplex transmission of the same data. 2. The data transmission apparatus according to claim 1, wherein each of the modems inputs and outputs data in a transmission format based on any one of amplitude modulation, frequency modulation, and phase modulation. 3. A line selecting means for selecting a sound line by detecting a reflected wave at the time of data transmission in each of the plurality of lines and connecting to each of the modems. 3. The data transmission device according to any one of claims 1 to 2. 4. A wireless communication unit for transmitting and receiving data, wherein the line selecting unit connects each of the modems to the wireless communication unit when all of the plurality of lines are abnormal. The data transmission device according to any one of claims 1 to 3, wherein: