Electricity: electrical systems and devices – Polarity reversing – Automatic
Patent
1991-04-11
1993-10-26
Gaffin, Jeffrey A.
Electricity: electrical systems and devices
Polarity reversing
Automatic
178 3, 375 36, H04B 302, H04L 2500
Patent
active
052571602
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a device which uses the transmission of polar serial signals and which is capable of switching the polarity of the signals, and more specifically to a transmission device for serial signals which is used for signal transmission between control devices on air conditioners, and to a method for determining the polarity of such transmission devices.
BACKGROUND ART
An air conditioning system commonly comprises a remote controller, an indoor apparatus and an outdoor apparatus. It is known that signal transmission between these apparatuses can be done with a two-wire crossover wiring system utilizing serially encoded signal transmission technology so as to reduce the number of wires used. According to this method, it is currently possible for a single controller to control a plurality of indoor and outdoor apparatuses. FIG. 5 shows a basic scheme of a conventional two-wire crossover wiring system for serial signal transmission. Also, FIG. 6 shows a conventional differential transmission circuit as an example of a serial transmission interface. In FIGS. 5 and 6, a remote controller 1' is connected to indoor apparatuses 2a' and 2b' and outdoor apparatuses 3a' and 3b' through a crossover wiring 5' so that the control and monitoring of air conditioning systems can be centralized.
Each apparatus (the remote controller 1', the indoor apparatuses 2a' and 2b', and the outdoor apparatuses 3a' and 3b') has a serial transmission interface 6' and a microcomputer 7'. When the microcomputer 7' carries out transmission and reception of signals, it controls control signals DE and RE of a differential line driver/receiver IC 8'.
In the example of FIG. 5, the two wires of the crossover wiring 5' have polarity, and line A and line B have to be connected to terminal A and terminal B at the signal terminal 4', respectively. In a conventional system, it has been a problem that, when this connection is reversed, normal signal transmission operation becomes impossible, and the air conditioners cannot be operated properly.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a serial signal transmission device and a control method for determining polarity so as to resolve the above-mentioned problem associated with conventional systems.
The serial signal transmission device of the present invention is characterized in that, in a serial signal transmission device which carries out signal transmission between a plurality of control devices using two transmission wires with fixed polarity, the serial transmission interface of each control device is equipped with two pairs of differential drivers and receivers, and the driver outputs and receiver inputs of different polarity in these two pairs of drivers and receivers are connected to each other.
According to the serial signal transmission device of the present invention, it becomes possible to transmit signals properly, for example, by including a function of switching the polarity of signal wires in a serial transmission interface of each control device and by choosing a driver and a receiver with correct polarity from two pairs of drivers and receivers having different polarity.
Also, the control method for determining polarity of the present invention is characterized in that, in a serial signal transmission device which uses two transmission lines with predetermined polarity to carry out signal transmission in both directions between a plurality of control devices, which each control device has two pairs of differential drivers and receivers in its serial transmission interface, and in which a driver output and a receiver input with different polarity of these two pairs of drivers and receivers are connected to each other, the polarity of each signal transmission device is adjusted by transmitting, a random number of times and between signal transmission devices, data packets containing data as to whether polarity has been determined and whether the polarity is in order or in reverse and data expressing the addr
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Aoi Fumio
Hirose Atsushi
Isomichi Kanji
Ninagawa Chuzo
Yasuda Hitoshi
Elms Richard T.
Gaffin Jeffrey A.
Mitsubishi Jukogyo Kabushiki Kaisha
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