JPH1116076A - Signal transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce signal lines in the case of adding the other pair of equipments to the installation place of a pair of the equipments by outputting prescribed electric signals based on the plural kinds of signals from a digital signal synthesis means corresponding to the state of output signals from the plural equipments and adding and transmitting the electric signals. SOLUTION: A data synthesis part 3 outputs the three kinds [N=2<n> -1 where (n) is the number of the equipments] of the signals from three output terminals TL1-TL3 corresponding to the output signals T1 and T2 of the equipments 1 and 11. A current output addition part 4 outputs the prescribed amount of currents relating to the digital signals, adds them in an adder 6 and sends them out through a cable to a reception part 202. In the reception part 202, current signals sent out from the adder 6 are converted into voltage signals by a current/voltage converter 7, turned into ON/OFF signals corresponding to the output of TL1-TL3 by a comparator 8, decoded to the signals R1 and R2 corresponding to T1 and T2 by a data decoding part 10 and sent out to the equipments 2 and 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal transmission system in which a physical quantity to be measured is converted into an electric signal and a digital signal obtained by processing the electric signal is received via a signal line. The present invention relates to a signal transmission method for reducing the number of signal lines or the number of cores when receiving a plurality of devices with a plurality of devices.

[0002]

2. Description of the Related Art FIG. 4 shows the state of a cable when serial data communication is performed from one device 1 arranged in a certain area to one device 2 arranged in another area. For example, RS422 or the like is used as the communication cable. The RS422 cable has four cores, and requires a pair of transmission lines and a pair of reception lines.

[0003]

By the way, two such devices are newly provided in a certain area A and another area B, respectively, or another device is provided in a place where a pair of devices (1, 2) is already installed. When adding a pair of devices (11, 22), a communication cable is required between the respective devices as shown in FIG. FIG. 5 shows an example in which two sets of the signal transmission system of FIG. 4 are provided. The present invention aims at reducing the number of signal lines in such a case.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a plurality of devices for outputting digital signals to be transmitted and an output signal from the plurality of devices. , Depending on the state of the signal, more types of digital signals N (N = 2 ⁿ −
1 where n is the number of devices) and a transmitting unit that outputs a predetermined electric signal based on a plurality of types of signals from the digital signal synthesizing unit and adds and outputs the electric signals. And a signal converter for inputting a signal from the transmitting unit and outputting a plurality of types of digital signals corresponding to the output signal of the data synthesizing unit, and inputting a signal from the signal converter and outputting the signals from the plurality of devices. A receiver comprising signal decoding means for outputting a signal corresponding to a signal, and a plurality of devices corresponding to the plurality of devices for receiving a signal from the receiver are provided.

[0005]

[Operation] Digital signal synthesizing means receives respective output signals from a plurality of devices and sends out more types of digital signals than these signals in accordance with the state of those signals. The signal adding means outputs a predetermined amount of current in relation to the digital signal, adds the currents, and sends the sum to a receiving unit via a cable. The signal converter of the receiving unit receives a signal from the transmitting unit and outputs a plurality of types of digital signals. The signal decoding means inputs a signal from the signal converter and outputs a plurality of types of digital signals corresponding to a plurality of types of devices based on the signal.

[0006]

DESCRIPTION OF THE PREFERRED 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 one embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a relationship between a combination of signals of devices and output signals. Parts having the same functions as those of the conventional signal transmission system shown in FIG. 3 are denoted by the same reference numerals, and the description thereof will be appropriately omitted.

In FIG. 1, reference numerals 1 and 11 denote devices installed in an area A, and output terminals of these devices are connected to input terminals of a data synthesizing unit 3. Reference numeral 4 denotes a current output adder, which includes a current output unit 5 and an adder 6. The data combiner 3 and the current output adder constitute a transmission unit 101. A receiving unit 202 includes the current / voltage converter 7, the comparator 8, and the data decoding unit 10. The output terminal of the receiving unit is connected to the input terminals of the devices 2 and 22.

In the above configuration, a PLD (programmable logic device) constituting the data synthesizing unit 3
Although inputs the output signals T _1, T ₂ of the device 1, 11, and outputs the three kinds of signals shown in FIG. 2 from three output terminals TL ₁ ~TL ₃ in response to the signal. In other words, if the output signals of the transmission unit are both on (1, 1), TL _{1 to} TL ₃ are all turned on, and if both are off (0, 0), T
L _{1 to} TL ₃ are all off outputs. Also, T ₁ is off,
If T ₂ is ON (0,1), TL ₁ is turned on, TL
₂ outputs an ON signal and TL ₃ outputs an OFF signal. Further, when T ₁ is turned on, T ₂ is off (1, 0), TL ₁ is turned on, TL ₂ is turned off, TL ₃ outputs a signal off.

The output terminals TL ₁ to TL ₁ of the data synthesizing unit 3
The current output devices 5 respectively connected to the TL ₃ output a current of, for example, 10 mA only when the output is on. Therefore, T
When all of L _{1 to} TL ₃ are on outputs, the output of the adder 6 is 3
At 0 mA, the output is 0 mA when all are off, 20 mA when T ₁ is off, T ₂ is on, and 10 mA when T ₁ is on and T ₂ is off.

[0010] A current signal corresponding to the output of the devices 1 and 11 is transmitted to the receiving unit 202 installed in the area B via the cable 20. In the receiving unit 202, the transmitting unit 101
The reverse procedure performed in is performed. That is, the current signal sent from the adder 6 is converted into a voltage signal by the current-voltage converter 7, turned into an on / off signal corresponding to the outputs of TL ₁ to TL ₃ by the comparator 8, and converted into T ₁ , The signals are decoded into signals R ₁ and R ₂ corresponding to T ₂ and sent to the devices 2 and 22.

Although not shown in the figure, response signals from the devices 2 and 22 are also transmitted to the devices 1 and 11 via the transmission / reception units having the same configuration. In this embodiment, two devices on the area A side and two devices on the area B side are used.
An example in which transmission is performed between two devices using two pairs of cables has been described. By devising the logic of the data synthesizing unit and the data decoding unit, three devices on the area A side and three devices on the area B side can be connected. Can be transmitted by two pairs of cables.

In this case, the output signals of the numbers T ₁ , T ₂ , and T ₃ of the devices and the PLD 10 constituting the data synthesizing unit 3 based on these signals generate seven kinds of signals as shown in FIG. . Similarly, when the number of devices increases, PLD becomes N = 2 ⁿ −
Generate one type of signal.

[0013]

As described above, according to the present invention, asynchronous serial data transmission from a plurality of devices to a plurality of devices is possible with a pair of cables (in the embodiment, the devices are not limited to the above). The combination of the device 1 and the device 11 and the combination of the device 2 and the device 22 are fixed, and communication settings such as an arbitrary parity check and a baud rate can be respectively performed.
Therefore, by connecting the transmitting and receiving units, each of which has the transmitting unit 101 and the receiving unit 202 as one unit, it is possible to transmit and receive between two devices with two pairs of cables.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is an explanatory diagram showing one embodiment of data synthesis used in the present invention.

FIG. 3 is an explanatory diagram showing another embodiment of data synthesis used in the present invention.

FIG. 4 is a configuration diagram of a conventional example in which a cable is transmitted between devices in different areas.

FIG. 5 is a configuration diagram of a conventional example in which a cable is transmitted between two pairs of devices in different areas.

[Explanation of symbols]

1, 11, 2, 22 Equipment 3 Data synthesis section (programmable logic device) 4 Current output addition section 5 Current output section 6 Adder 7 Current / voltage converter 8 Comparator 10 Data decoding section ((Programmable logic device) ) 101 transmitting unit 202 receiving unit

Claims (1)

[Claims] 1. A plurality of devices that output digital signals to be transmitted, and input signals output from the plurality of devices, and more types of digital signals than the plurality of output signals according to the state of the signals. Digital signal synthesizing means for transmitting N (N = 2 ⁿ -1 where n is the number of devices) and outputting predetermined electric signals based on a plurality of types of signals from the digital signal synthesizing means and outputting these electric signals A transmitting unit for adding and outputting, a signal converter for receiving a signal from the transmitting unit and outputting a plurality of types of digital signals corresponding to an output signal of the data combining unit, and a signal from the signal converter; A receiving unit comprising signal decoding means for outputting signals corresponding to output signals of the plurality of devices; and a plurality of devices corresponding to the plurality of devices for receiving signals from the receiving unit. A signal transmission method characterized by the above.