JPH09130873A - Transmitting and receiving circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the installing operation and maintenance operation such as the check and correction of connection by attaining correct transmission and connection without executing connection again even when erroneous connection is generated. SOLUTION: A transmission circuit 2 is provided with a transmission signal processing circuit 21 inverting and noninverting transmission data TxD corresponding to the contents of a pole switching signal POL. On the other hand a reception circuit 3 consists of an input gate circuit 31 with an input terminal and an inverting input terminal, a switching circuit 32 selecting one of the input terminal and the inverting input terminal corresponding the contents of the pole switching signal POL, and a receiving signal processing circuit 33 executing inversion and noninversion corresponding the contents of the pole switching signal POL to output. As this transmitting and receiving circuit 1 switches the contents of the pole switching signal POL when a break signal is detected in the output of the receiving signal processing circuit 33, correct transmission and reception is attained without executing connection again even when generating an erroneous connection between equipments connecting plural equipments.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is installed in a state in which a set of equipment such as an outdoor unit and an indoor unit of an air conditioner are separated from each other, so that control signals can be exchanged between the two equipments in a balanced type. When configured to be done via
The present invention relates to a transmission / reception circuit provided for transmitting and receiving the control signal.

[0002]

2. Description of the Related Art Conventionally, when this kind of wiring is carried out, RS-
A transmission / reception circuit based on the 485 system or the like is provided, and two electric wires called twisted pair wires are connected by twisting each other between these transmission / reception circuits. By doing so, the same IEEE standard R defined by
Compared with the S-232C method, the number of electric wires between devices is reduced, and a dedicated connector is not required, so that the connection work can be simplified and the cost can be reduced.

[0003]

However, in the above-mentioned conventional RS-485 system and the like, since two lines have polarities, there is a possibility that an erroneous connection may occur during the above-mentioned connection work. However, when this erroneous connection occurs, the control signal cannot be correctly transmitted.

As a means for solving the above-mentioned problems, a method has been proposed in which two receiving circuits are prepared and each of them is reversely connected to prepare for the above-mentioned erroneous connection. The output needs to be doubled, which causes another problem such as an enormous burden on the transmission circuit side and an increase in size, and a solution to these points becomes an issue.

[0005]

As a concrete means for solving the above-mentioned conventional problems, the present invention performs communication between devices via a balanced type two lines to which a transmission circuit and a reception circuit are connected. In the transmission / reception circuit, the transmission circuit of the transmission / reception circuit has a transmission signal processing circuit that inverts and non-inverts the transmission data according to the content of the pole switching signal, and an input terminal is connected to the output of the transmission signal processing circuit and transmission enable is performed. An output gate circuit that has a terminal, an output terminal connected to one line, and an inverting output terminal connected to the other line, and that produces an output by the transmission enable terminal; An input gate circuit having an input terminal connected to the line and an inverting input terminal connected to the other line, and what is provided between the input terminal and the inverting input terminal depending on the content of the pole switching signal. And a reception signal processing circuit which is connected to the output of the input gate circuit and which inverts and non-inverts the output from the input gate circuit according to the content of the pole switching signal and outputs the inverted signal. The problem is solved by providing a transmission / reception circuit characterized in that the content of the pole switching signal is switched when a break signal is detected at the output of the reception signal processing circuit.

[0006]

Next, the present invention will be described in detail based on an embodiment shown in the drawings. Reference numeral 1 in FIG. 1 denotes a transmitter / receiver circuit according to the present invention. This transmitter / receiver circuit 1 is based on the RS-485 system and is composed of a transmitter circuit 2 and a receiver circuit 3. Is similar to that of the conventional example.

Here, in the present invention, the transmission circuit 2 is constituted by the transmission signal processing circuit 21 and the output gate circuit 22, and the reception circuit 3 is constituted by the input gate circuit 31, the switching circuit 32 and the reception signal processing circuit 33. In this way, it is possible to cope with the erroneous connection of the balanced type two lines at the time of installation.

The transmitter circuit 2 and the receiver circuit 3 will be described in more detail below. First, the transmitter circuit 2 will be described.
Specifically, the transmission signal processing circuit 21 provided in 1 is configured by a two-input exclusive OR circuit (XOR), the negative logical value of the transmission data TxD is input to one input terminal, and the other one is input. A signal from the pole switching signal POL is input to the input terminal, and the transmission data TxD is non-inverted or inverted depending on the content of the pole switching signal POL.

The output gate circuit 22 is provided with an output terminal X connected to one of the balanced two lines and an inverting output terminal Y connected to the other line of the same balanced two lines. When the transmission enable signal TxE is input, the signal from the transmission signal processing circuit 21 is output to the output terminal X at the same time, and at the same time, the signal from the transmission signal processing circuit 21 is inverted and output to the inverted output terminal Y. . A terminating resistor R1 is connected between the output terminal X and the inverting output terminal Y.

Further, the input gate circuit 3 of the receiving circuit 3
1 is provided with an input terminal connected to the output terminal X through a resistor R2, and an inverting input terminal connected to the inverting output terminal Y through a resistor R3, and the input terminal is The output of the exclusive OR circuit 32a to which the pole switching signal POL and the "H" level such as the power source are input is input via the bias resistor R4.

The output of the exclusive OR circuit 32b, to which the pole switching signal POL and the "L" level such as ground are input to the inverting input terminal, is input via a bias resistor R5, and the exclusive logic is input. A switching circuit 32 is configured by the sum circuit 32a and the exclusive OR circuit 32b.

A received signal processing circuit 33 is connected to the output of the input gate circuit 31, and the received signal processing circuit 33 is specifically configured by a 2-input exclusive OR circuit, and one of As described above, the output of the input gate circuit 31 is input to the input end, the signal from the pole switching signal POL is input to the other input end, and the reception data RxD (negative logic) is obtained at the output end. The transmission data Tx
Each of D, the transmission enable signal TxE, the pole switching signal POL, and the reception data RxD is a microcomputer CPU.
Connected to.

The transmission circuit 2 configured as described above
2 is a truth table showing the input / output relationship of the receiver circuit 3 and FIG. 3 is a truth table showing the input / output relationship of the receiving circuit 3 according to the present invention. The features of the transmission / reception circuit 1 are listed below.

First, in the transmitter circuit 2, when the transmission enable signal TxE is not input, the output terminal X and the inverted output terminal Y are set regardless of the contents of the transmission data TxD and the pole switching signal POL. Both are in the high impedance state "Z", indicating that there is no signal.

As described above, when both the output terminal X and the inverting output terminal Y are in the high impedance state "Z", the receiving circuit 3 outputs the received data RxD as "irrespective of the content of the pole switching signal POL. It outputs an H "level to indicate that the line is in a no signal state.

Secondly, regardless of the content ("H" level or "L" level) of the pole switching signal POL, the transmission data TxD input to the transmission circuit 2 of its own.
Is re-inverted in the received signal processing circuit 33 even if it is inverted in the transmitted signal processing circuit 21, and is output to the received data RxD as the input normal state.

Therefore, for example, the pair of transmitting and receiving circuits 1 are connected to the output terminal X and the output terminal X, and the inverting output terminal Y and the inverting output terminal Y.
If the pole switching signal POL has the same contents, the transmission data TxD and the reception data RxD will have the same contents, and the communication will be performed correctly.

Further, when one output terminal X and the other inverting output terminal Y and the one inverting output terminal Y and the other output terminal X are erroneously connected, the pole switching signal POL of the one transmitting / receiving circuit 1 is made. If the contents of the above is "H" level, the contents are changed so that the contents of the pole switching signal POL of the other transmission / reception circuit 1 are set to the "L" level, so that the communication is correctly performed.

Therefore, in the transmitter / receiver circuit 1 of the present invention, if the line connection is determined to be correct or incorrect by an appropriate means, the contents of the pole switching signal POL can be switched according to the determination to perform correct communication. The procedure of the above determination will be described based on an example of connection of an air conditioner including one outdoor unit 4 and a plurality of, for example, three indoor units 5a to 5c shown in FIG.

At this time, the outdoor unit 4 and the indoor unit 5 are
Output terminals X of the transmission / reception circuit 1 provided in each of a to 5c
The inverted output terminal Y is connected by the twisted pair wire 6 and the installation work is physically completed.
By performing the following procedure in this state, the installation work is completed electrically.

First, the outdoor unit 4 and the indoor units 5a-5
c is set so that the contents of the pole switching signal POL are the same when the power is turned on at the time of shipment (“L” in this example).
It is described as a level). The outdoor unit 4 is provided with an initial setting button 4a and the like, and is used as a base unit that serves as a reference for determination. In addition, the above-mentioned parent device is the indoor unit 5a-5
Although it may be provided on the c side, it is preferable to provide it on the outdoor unit 4 in terms of cost, etc., since there will be a plurality of units.

When the operator presses the initial setting button 4a of the outdoor unit 4 when the air conditioner is installed, the microcomputer CPU connected to the transmitting / receiving circuit 1 provided in the outdoor unit 4 enables transmission. “H” for signal TxE
Since the level is output and the transmission data TxD is not output at this time, a continuous space (“H” level) is output to the output terminal X.

Therefore, in the indoor unit 5a and the indoor unit 5b to which the output terminal X and the output terminal X are accurately connected, the reception data RxD which becomes a continuous space can be obtained, and the reception data RxD has been detected. The computer CPU does nothing, and thus the pole switching signal POL of the indoor unit 5a and the indoor unit 5b is held at the "L" level.

On the other hand, in the indoor unit 5c which has been erroneously connected, when the initial setting button 4a of the outdoor unit 4 is turned on, a break signal of "L" level continuous to the received data RxD is output. Therefore, the microcomputer CPU of the indoor unit 5c outputs the pole switching signal P when the break signal is continuously output for a predetermined time (for example, 1 second).
It is assumed that the OL is switched to the “H” level and accurate transmission / reception can be performed.

At this time, the microcomputer C
In the PU, the pole switching signal P set according to the above procedure is set.
A non-volatile memory NVM for storing the contents of the OL is provided (see FIG. 1). After that, when the power is turned on again, the pole switching signal POL is set by the contents of the non-volatile memory NVM, and, for example, when a power failure occurs. It is said that it can also handle.

The outdoor unit 4 is not provided with the initial setting button 4a, and the outdoor unit 4 automatically performs the above-described sequence each time the power is turned on, and the pole switching signal POL is output each time. It is also possible to set the setting freely, and at this time, the nonvolatile memory NVM can be omitted.

[0027]

As described above, according to the present invention, the transmission circuit has the transmission signal processing circuit for inverting and non-inverting the transmission data according to the contents of the pole switching signal, and the receiving circuit has the input terminal and the inverting input terminal. An input gate circuit having, a switching circuit for selecting one of an input terminal and an inverting input terminal according to the content of the pole switching signal, and a reception signal processing circuit for performing inversion and non-inversion according to the content of the pole switching signal and outputting. And the transmission / reception circuit that switches the content of the pole switching signal when a break signal is detected at the output of the reception signal processing circuit,
For example, even in an air conditioner composed of one outdoor unit and a plurality of indoor units, when an erroneous connection occurs between the respective devices,
As a device that can perform correct transmission and reception without re-connection, it has an extremely excellent effect of simplifying installation work and maintenance.

Further, since the transmitter / receiver circuit can judge the erroneous connection by detecting the break signal as described above, the judgment of the erroneous connection made at the time of installation can be extremely easily carried out, so that the microcomputer can be mounted. This also has the effect of simplifying the software for determining the incorrect connection.

[Brief description of the drawings]

FIG. 1 is a wiring diagram showing an embodiment of a transmission / reception circuit according to the present invention.

FIG. 2 is an explanatory diagram showing the operation of the transmission circuit in the same embodiment as a truth value.

FIG. 3 is an explanatory diagram showing the operation of the receiving circuit in the same embodiment as a truth value.

FIG. 4 is an explanatory diagram showing an example of a usage state of a transmission / reception circuit according to the present invention.

[Explanation of symbols]

 1 ... Transmission / reception circuit 2 ... Transmission circuit 21 ... Transmission signal processing circuit 22 ... Output gate circuit 3 ... Reception circuit 31 ... Input gate circuit 32 ... Switching circuit 33 ... Reception signal processing circuit 4 ... Outdoor Machine 4a …… Initial setting buttons 5a to 5c …… Indoor unit 6 …… Twisted pair wire X …… Output terminal Y …… Inverted output terminal TxD …… Transmission data RxD …… Reception data TxE …… Transmission enable signal POL …… Pole switching signal CPU …… Microcomputer NVM …… Nonvolatile memory

Claims (2)

[Claims] 1. A transmitter / receiver circuit when communication is performed between devices via a balanced type two-line connecting a transmitter circuit and a receiver circuit, wherein the transmitter circuit of the transmitter / receiver circuit transmits data according to the contents of a pole switching signal. A transmission signal processing circuit for inverting and non-inverting, a transmission enable terminal having an input terminal connected to the output of the transmission signal processing circuit, an output terminal connected to one line, and an inverting output terminal connected to the other line. An input gate circuit having an input terminal connected to one line and an inverting input terminal connected to the other line. And a switching circuit for selecting one of the input terminal and the inverting input terminal according to the content of the pole switching signal, and the pole switching by being connected to the output of the input gate circuit. A reception signal processing circuit that inverts and non-inverts the output from the input gate circuit according to the content of the signal and outputs the output. When a break signal is detected at the output of the reception signal processing circuit, the content of the pole switching signal is changed. A transmission / reception circuit characterized by switching. 2. The contents of the pole switching signal are stored in a non-volatile memory, and when the power supply of the transmission / reception circuit is once cut off and then turned on again, the contents are read out and the contents are reset. The transmission / reception circuit according to claim 1, which is characterized in that.