JP6971679B2 - Communication system, communication equipment, and communication control method - Google Patents

Description

The present invention relates to communication systems, communication devices, and communication control methods.

Currently, a communication system in which a master unit and a plurality of slave units are connected to each other by a communication line pair is known. For example, Patent Document 1 describes a signal transmission system in which a central processing unit and a plurality of terminals are connected by a pair of transmission lines.

In the signal transmission system described in Patent Document 1, the central processing apparatus transmits data to the terminal by voltage transmission, and the terminal transmits data to the central processing apparatus by current transmission. In this signal transmission system, the terminal cannot know whether or not another terminal is transmitting current. Therefore, in this signal transmission system, in order to avoid collision of current transmission, polling by a central processing unit, transmission of a synchronization signal, and the like are required.

Japanese Unexamined Patent Publication No. 2-210935

However, if an attempt is made to avoid a collision of current transmission by polling or transmission of a synchronization signal, the processing load increases and the throughput of the communication system decreases. Therefore, there is a demand for a technique for suppressing collision of current transmission without reducing the throughput of the communication system.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a communication system, a communication device, and a communication control method that suppress a collision of current transmission without reducing the throughput of the communication system. ..

In order to achieve the above object, the communication system according to the present invention is
A master unit having a master unit side terminal pair, a first slave unit having a first slave unit side terminal pair, and a second slave unit having a second slave unit side terminal pair are provided, and the master unit side terminal is provided. A communication system in which a pair, the first handset side terminal pair, and the second handset side terminal pair are connected to each other by a communication line pair.
The master unit is a voltage provided with a voltage reduction circuit that applies a voltage between the master unit side terminal pairs and reduces the voltage applied between the master unit side terminal pairs when a current flows between the master unit side terminal pairs. With the application circuit
Reception that receives the first serial data from the first slave unit and receives the second serial data from the second slave unit by detecting the presence or absence of a current flowing between the terminal pairs on the master unit side. With a circuit,
The first slave unit includes a transmission circuit that transmits the first serial data to the master unit by controlling the conduction / non-conduction state between the terminal pairs on the first slave unit side.
The second handset is
A transmission circuit that transmits the second serial data to the master unit by controlling the conduction / non-conduction state between the terminal pairs on the second slave unit side.
A voltage drop detection circuit that detects that the voltage applied between the second handset side terminal pair has dropped, and
When the voltage drop detection circuit does not detect that the voltage applied between the second handset side terminal pairs has dropped, the second serial data is transmitted to the transmission circuit included in the second handset. for example Bei and a control circuit which,
The voltage application circuit is a transmission circuit that transmits third serial data to the second slave unit by switching the polarity of the voltage applied between the master unit side terminal pairs.
The second slave unit includes a receiving circuit that receives the third serial data from the master unit by detecting the polarity of the voltage applied between the terminal pairs on the second slave unit side.
The control circuit has the third serial based on the polarity detected by the receiving circuit included in the second slave unit when the third serial data is not transmitted from the transmitting circuit included in the master unit. Determine the logic of the data .

In the present invention, when the voltage applied between the master unit side terminal pairs decreases and the voltage applied between the slave unit side terminal pairs does not decrease when a current flows between the master unit side terminal pairs, the slave unit Serial data is sent. Therefore, according to the present invention, it is possible to suppress the collision of current transmission without reducing the throughput of the communication system.

Configuration diagram of the communication system according to the embodiment of the present invention Configuration diagram of the master unit and the slave unit according to the embodiment of the present invention. A flowchart showing a data transmission process executed by the slave unit according to the embodiment of the present invention. A flowchart showing a data reception process executed by the slave unit according to the embodiment of the present invention.

(Embodiment)
Embodiments of the present invention will be described with reference to the drawings. First, the communication system 1000 according to the embodiment of the present invention will be described with reference to FIG. The communication system 1000 is a system including a master unit 100 and a plurality of slave units (slave unit 200, slave unit 300, slave unit 400), and the master unit 100 and the plurality of slave units communicate with each other. The communication system 1000 is, for example, a lighting system including a lighting control device and a plurality of lighting devices. In this case, the master unit 100 corresponds to the lighting control device, and the plurality of slave units each correspond to the plurality of lighting devices.

The master unit 100 includes a DC power supply (not shown) and supplies electric power to a plurality of slave units. The plurality of slave units operate with the electric power supplied from the master unit 100. The master unit 100 transmits data to a plurality of slave units by a voltage signal, and the plurality of slave units transmit data to the master unit 100 by a current signal. In the present embodiment, full-duplex communication is possible between the master unit 100 and one slave unit. For example, when the master unit 100 transmits data to the slave unit 200, the slave unit 200 can transmit data to the master unit 100.

Further, the plurality of slave units can voluntarily transmit data to the master unit 100 as long as the transmission timings do not conflict with each other. For example, the slave unit 200 can spontaneously transmit data to the master unit 100 when the slave unit 300 and the slave unit 400 are not transmitting data to the master unit 100. Data is not transmitted or received between the plurality of slave units. Further, in the present embodiment, the data transmitted / received between the master unit 100 and the plurality of slave units is binary data to which 0 or 1 is assigned to each bit, and is serial data transferred to each bit. be.

The master unit 100 and the plurality of slave units are connected to each other by a plurality of communication line pairs (communication line pair 13, communication line pair 23, communication line pair 33), and communicate with each other via the plurality of communication line pairs. .. Specifically, the terminal pair 143 included in the master unit 100 and the terminal pair 243 included in the slave unit 200 are connected by a communication line pair 13, and the master unit 100 and the slave unit 200 are connected. More specifically, the terminal 141 included in the master unit 100 and the terminal 241 included in the slave unit 200 are connected by the communication line 11, and the terminal 142 included in the master unit 100 and the terminal 242 included in the slave unit 200 are connected by the communication line 12. Be connected.

Further, the terminal pair 243 included in the slave unit 200 and the terminal pair 343 included in the slave unit 300 are connected by a communication line pair 23, and the slave unit 200 and the slave unit 300 are connected. More specifically, the terminal 241 included in the slave unit 200 and the terminal 341 included in the slave unit 300 are connected by the communication line 21, and the terminal 242 included in the slave unit 200 and the terminal 342 included in the slave unit 300 are connected by the communication line 22. Be connected. Further, the terminal pair 343 included in the slave unit 300 and the terminal pair 443 included in the slave unit 400 are connected by a communication line pair 33, and the slave unit 300 and the slave unit 400 are connected. More specifically, the terminal 341 of the handset 300 and the terminal 441 of the handset 400 are connected by the communication line 31, and the terminal 342 of the handset 300 and the terminal 442 of the handset 400 are connected by the communication line 32. Be connected.

Therefore, the terminal 141 included in the master unit 100, the terminal 241 included in the slave unit 200, the terminal 341 included in the slave unit 300, and the terminal 441 included in the slave unit 400 are interconnected. Further, the terminal 142 included in the master unit 100, the terminal 242 included in the slave unit 200, the terminal 342 included in the slave unit 300, and the terminal 442 included in the slave unit 400 are interconnected.

Here, the master unit 100 can supply DC power and transmit data to the slave unit 200, the slave unit 300, and the slave unit 400 by switching the polarity of the voltage applied between the terminal pairs 143. .. On the other hand, the slave unit 200 obtains DC power by rectifying the voltage applied between the terminal pairs 243. Further, the slave unit 200 can receive data from the master unit 100 by determining the polarity of the voltage applied between the terminal pairs 243. Similarly, the slave unit 300 obtains DC power by rectifying the voltage applied between the terminal pairs 343. Further, the slave unit 300 can receive data from the master unit 100 by determining the polarity of the voltage applied between the terminal pairs 343. The same applies to the handset 400.

Further, the master unit 100 can receive data from the slave unit 200, the slave unit 300, and the slave unit 400 by detecting the presence / absence of a current flowing between the terminal pairs 143. On the other hand, the slave unit 200 can transmit data to the master unit 100 by controlling the conduction / non-conduction state between the terminal pairs 243. Further, the slave unit 300 can transmit data to the master unit 100 by controlling the conduction / non-conduction state between the terminal pairs 343. The same applies to the handset 400.

Here, in the master unit 100, when data is transmitted by any of the slave unit 200, the slave unit 300, and the slave unit 400 and a current flows between the terminal pairs 143, the voltage applied between the terminal pairs 143 is lowered. Let me. On the other hand, when the slave unit 200 detects that the voltage applied between the terminal pairs 243 has decreased, it can be considered that the slave unit 300 or the slave unit 400 is transmitting data to the master unit 100. .. Similarly, when the slave unit 300 detects that the voltage applied between the terminal pairs 343 has dropped, it may be considered that the slave unit 200 or the slave unit 400 is transmitting data to the master unit 100. can. The same applies to the slave unit 400.

Next, the configurations of the master unit 100 and the slave unit 200 will be described with reference to FIG. Since the configurations of the slave unit 300 and the slave unit 400 are basically the same as the configurations of the slave unit 200, the description thereof will be omitted.

The master unit 100 includes a transmission circuit 110, a reception circuit 120, a control unit 130, a terminal pair 143, a power supply terminal 161 and a capacitor 162, and a ground terminal 163.

The transmission circuit 110 transmits data by a voltage signal according to the control by the control unit 130. The transmission circuit 110 switches the polarity of the voltage applied between the terminal pairs 143 between + V1 and −V1. Specifically, in the transmission circuit 110, an H level voltage (for example, 5V) is output from the transmission terminal 131 (terminal indicated by Tx1) included in the control unit 130, and the transmission terminal 132 (Tx2) included in the control unit 130 outputs the H level voltage. When an L level voltage (for example, 0V) is output from the terminal shown), 0V is applied to the terminal 141 and V1 is applied to the terminal 142. On the other hand, when the L level voltage is output from the transmission terminal 131 and the H level voltage is output from the transmission terminal 132, the transmission circuit 110 applies V1 to the terminal 141 and 0V to the terminal 142. V1 is the power supply voltage of the master unit 100, for example, 24V. Since the transmission circuit 110 always applies a voltage between the terminal pairs 143, it can be said to be a voltage application circuit.

The transmission circuit 110 includes an NPN (Negative Positive Negative) transistor 111, an NPN transistor 112, a resistor 113, an NPN transistor 114, an NPN transistor 115, a resistor 116, a PNP (Positive Negative Positive) transistor 117, and a PNP transistor. It is equipped with 118. The collector of the NPN transistor 111 and the collector of the NPN transistor 114 are connected to the power supply terminal 161. The base of the NPN transistor 111, the collector of the NPN transistor 112, and the base of the PNP transistor 117 are connected to the transmission terminal 131. The emitter of the NPN transistor 111 is connected to the base of the NPN transistor 112 and one end of the resistor 113. The emitter of the NPN transistor 112, the other end of the resistor 113, and the emitter of the PNP transistor 117 are connected to the terminal 142.

The base of the NPN transistor 114, the collector of the NPN transistor 115, and the base of the PNP transistor 118 are connected to the transmission terminal 132. The emitter of the NPN transistor 114 is connected to the base of the NPN transistor 115 and one end of the resistor 116. The emitter of the NPN transistor 115, the other end of the resistor 116, and the emitter of the PNP transistor 118 are connected to the terminal 141. The collector of the PNP transistor 117 and the collector of the PNP transistor 118 are connected to the non-inverting input terminal of the operational amplifier 122 via the capacitor 123, and are connected to the ground terminal 128 via the resistor 126.

The NPN transistor 111, the NPN transistor 112, and the resistor 113 constitute a current limiting circuit 151 that limits the magnitude of the current flowing from the terminals 142 to the terminals 141 (current flowing between the terminals 143). The current limiting circuit 151 has a function of increasing the voltage between the power supply terminal 161 and the terminal 142 as the current flowing from the terminal 142 to the terminal 141 increases. Here, the higher voltage between the power supply terminal 161 and the terminal 142 means that the voltage between the terminal 141 and the terminal 142 to which 0 V is applied (the voltage applied between the terminals 143) becomes lower. Means. That is, the current limiting circuit 151 can be said to be a voltage drop circuit that lowers the voltage applied between the terminal pairs 143 when a current flows between the terminal pairs 143. Hereinafter, the operation of the current limiting circuit 151 will be described.

First, it is assumed that the terminal pair 143 is controlled in a non-conducting state. When the slave unit 200 controls the terminal pair 243 to the non-conducting state, the slave unit 300 controls the terminal pair 343 to the non-conducting state, and the slave unit 400 controls the terminal pair 443 to the non-conducting state. , The terminal pair 143 is controlled to be in a non-conducting state. First, when an L-level voltage is output from the transmission terminal 132, the NPN transistor 114 and the NPN transistor 115 are turned off, and the PNP transistor 118 is turned on. Further, when the H level voltage is output from the transmission terminal 131, the NPN transistor 111 and the NPN transistor 112 are turned on, and the PNP transistor 117 is turned off. However, no current flows between the terminals 143, and the voltage of the terminals 142 is about the same as V1 which is the voltage of the power supply terminal 161. That is, in this case, the current limiting circuit 151 does not exert the function of limiting the current or lowering the voltage.

Next, it is assumed that the terminal pair 143 is controlled to be in a conductive state. The slave unit 200 controls the terminal pair 243 to be in a conductive state, the slave unit 300 controls the terminal pair 343 to be in a conductive state, or the slave unit 400 controls the terminal pair 443 to be in a conductive state. In this case, the connection between the terminal pairs and 143 is controlled to be in a conductive state. First, when an L-level voltage is output from the transmission terminal 132, the NPN transistor 114 and the NPN transistor 115 are turned off, and the PNP transistor 118 is turned on. Here, when an H-level voltage is output from the transmission terminal 131, the current flowing through the current path of the NPN transistor 111 and the resistor 113 gradually increases.

However, the base-emitter voltage of the NPN transistor 112, which is the voltage across the resistor 113 (the product of the current value of the current flowing through the resistor 113 and the resistance value of the resistor 113), is a predetermined voltage (for example, 0.6 V). ) Is reached, a current starts to flow in the current path of the NPN transistor 112, and the current flowing in the base of the NPN transistor 111 does not increase. As a result, the current value of the current flowing between the terminal pairs 143 settles to a constant value, and the voltage between the current paths of the NPN transistor 111 and the voltage across the resistor 113 settle to a constant value. That is, in this case, the current limiting circuit 151 exerts a function of limiting the current or lowering the voltage. By adjusting the resistance value of the resistor 113, the upper limit value of the current flowing between the terminal pairs 143 can be adjusted. For example, assuming that the resistance value of the resistor 113 is 0.6Ω, the upper limit of the current flowing between the terminal pairs 143 is 0.6V / 0.6Ω = 1A.

The NPN transistor 114, the NPN transistor 115, and the resistor 116 form a current limiting circuit 152 that limits the magnitude of the current flowing from the terminals 141 to the terminals 142 (current flowing between the terminals 143). The current limiting circuit 152 has a function of increasing the voltage between the power supply terminal 161 and the terminal 141 as the current flowing from the terminal 141 to the terminal 142 increases. Here, the higher voltage between the power supply terminal 161 and the terminal 141 means that the voltage between the terminal 142 and the terminal 141 to which 0 V is applied (the voltage applied between the terminals 143) becomes lower. Means. That is, the current limiting circuit 152 can be said to be a voltage drop circuit that lowers the voltage applied between the terminal pairs 143 when a current flows between the terminal pairs 143. Since the operation of the current limiting circuit 152 is basically the same as the operation of the current limiting circuit 151, the description thereof will be omitted.

The receiving circuit 120 supplies a voltage signal corresponding to data (bit data) transmitted as a current signal from any of the slave units to the control unit 130. When the receiving circuit 120 detects that the current flowing through the communication line pair 13 exceeds a predetermined threshold value, the receiving circuit 120 sends an L level voltage signal to the receiving terminal 133 (terminal indicated by Rx) included in the control unit 130. Supply. On the other hand, when the receiving circuit 120 detects that the current flowing through the communication line pair 13 is less than this threshold value, the receiving circuit 120 supplies an H level voltage signal to the receiving terminal. In the slave unit 200, the slave unit 300, and the slave unit 400, a current flows between the terminal pairs 143 when transmitting the bit corresponding to 0, and a current flows between the terminal pairs 143 when transmitting the bit corresponding to 1. Do not shed. Therefore, the receiving circuit 120 considers that the bit corresponding to 0 is received when the L level voltage signal is applied to the receiving terminal 133, and when the H level voltage signal is applied to the receiving terminal 133. It is considered that the bit corresponding to 1 has been received.

The receiving circuit 120 includes a power supply terminal 121, an operational amplifier 122, a capacitor 123, a resistor 124, a resistor 125, a resistor 126, a ground terminal 127, and a ground terminal 128. The power supply terminal 121 is connected to a DC power supply (not shown) that outputs V3 (for example, 5V) as a power supply voltage, and V3 is applied. The DC power supply that outputs V3 is generated from the DC power supply (not shown) that outputs V1. The operational amplifier 122 compares the reference voltage applied to the non-inverting input terminal with the input voltage applied to the inverting input terminal. When the input voltage is higher than the reference voltage, the operational amplifier 122 outputs the L level voltage from the output terminal, and when the input voltage is lower than the reference voltage, the operational amplifier 122 outputs the H level voltage from the output terminal.

The capacitor 123 cuts off the DC component supplied to the inverting input terminal of the operational amplifier 122. The resistor 124 and the resistor 125 are connected in series between the power supply terminal 121 and the ground terminal 127. The resistor 124 and the resistor 125 apply a reference voltage obtained by dividing the power supply voltage to the non-inverting input terminal of the operational amplifier 122. The resistor 126 limits the current flowing from the power supply terminal 161 to the ground terminal 128. The ground terminal 127 and the ground terminal 128 are connected to a DC power supply (not shown) included in the master unit 100, and 0 V is applied.

The control unit 130 controls the overall operation of the master unit 100. The control unit 130 controls the transmission circuit 110 to transmit data to any of the slave units. For example, the control unit 130 outputs a voltage at a level corresponding to the bit data to be transmitted from the transmission terminal 131. The control unit 130 outputs a voltage at a level opposite to the level of the voltage output from the transmission terminal 131 from the transmission terminal 132. Further, the control unit 130 identifies the data transmitted from any of the slave units based on the voltage signal supplied from the reception circuit 120. For example, the control unit 130 samples bit data according to the level of the voltage applied to the receiving terminal 133, and identifies the transmitted data from the bit data string obtained by the sampling.

In the present embodiment, when the bit corresponding to 1 is transmitted, the control unit 130 outputs an H level voltage from the transmission terminal 131 and outputs an L level voltage from the transmission terminal 132. Further, when transmitting the bit corresponding to 0, the control unit 130 outputs an L level voltage from the transmission terminal 131 and outputs an H level voltage from the transmission terminal 132. Therefore, the voltage of the terminal 142 becomes higher than the voltage of the terminal 141 when the bit corresponding to 1 is transmitted, and the voltage of the terminal 142 is lower than the voltage of the terminal 141 when the bit corresponding to 0 is transmitted. Become. Further, the control unit 130 shall transmit a bit corresponding to 1 in the idle state.

The control unit 130 is composed of, for example, a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like.

The terminal pair 143 is a terminal pair to which a communication line pair 13 for transmitting / receiving data to / from a plurality of slave units is connected. The terminal pair 143 includes a terminal 141 and a terminal 142. The terminal pair 143 is connected to the terminal pair 243 via the communication line pair 13. That is, the terminal 141 is connected to the terminal 241 via the communication line 11, and the terminal 142 is connected to the terminal 242 via the communication line 12.

The power supply terminal 161 is connected to a DC power supply (not shown) that outputs V1 (for example, 24V), and V1 which is a power supply voltage is applied. The capacitor 162 is provided between the power supply terminal 161 and the ground terminal 163, and an AC component (high frequency component) output from the power supply terminal 161 flows to the ground terminal 163. The ground terminal 163 is connected to a DC power supply included in the master unit 100, and 0 V is applied.

The slave unit 200 includes a transmission circuit 210, a reception circuit 220, a control unit 230, a terminal pair 243, a rectifier circuit 250, a voltage drop detection circuit 260, and a power supply terminal 271.

The transmission circuit 210 transmits data to the master unit 100 by a current signal according to the control by the control unit 230. The transmission circuit 210 controls the current flowing through the communication line pair 13 by controlling the conduction / non-conduction state between the terminal pair 243. That is, the transmission circuit 210 controls the terminal pair 243 to be in a conductive state when a current is passed through the communication line pair 13, and controls the terminal pair 243 to be in a non-conducting state when the current is not passed through the communication line pair 13. ..

The transmission circuit 210 includes an NPN transistor 211 and a resistor 212. The collector of the NPN transistor 211 is connected to the power supply terminal 271. The base of the NPN transistor 211 is connected to the transmission terminal 231 (terminal indicated by Tx) included in the control unit 230. The emitter of the NPN transistor 211 is connected to a reference terminal (terminal indicated by S0) included in the control unit 230 via a resistor 212. The NPN transistor 211 is turned on when an H level voltage is applied to the base, and turned off when an L level voltage is applied to the base. When the NPN transistor 211 is turned off, no current flows through the communication line pair 13. On the other hand, when the NPN transistor 211 is turned on, a current flows through the communication line pair 13.

If the NPN transistor 211 is turned on when the voltage of the terminal 241 is higher than the voltage of the terminal 242, the power supply terminal 161 → NPN transistor 114 → resistor 116 → terminal 141 → communication line 11 → terminal 241 → diode 253 → power supply terminal 271. → NPN transistor 211 → Resistance 212 → Diode 252 → Terminal 242 → Communication line 12 → Terminal 142 → PNP transistor 117 → Resistance 126 → Ground terminal 128. On the other hand, if the NPN transistor 211 is turned on when the voltage of the terminal 241 is lower than the voltage of the terminal 242, the power supply terminal 161 → NPN transistor 111 → resistor 113 → terminal 142 → communication line 12 → terminal 242 → diode 254 → power supply. Current flows through the route of terminal 271 → NPN transistor 211 → resistor 212 → diode 251 → terminal 241 → communication line 11 → terminal 141 → PNP transistor 118 → resistor 126 → ground terminal 128. The resistor 212 is a load resistor and limits the current flowing in the current path of the NPN transistor 211.

The receiving circuit 220 supplies a voltage signal corresponding to data (bit data) transmitted as a voltage signal from the master unit 100 to the control unit 230. When the voltage of the terminal 242 is higher than the voltage of the terminal 241, the receiving circuit 220 supplies an H level (for example, 5V) voltage signal to the receiving terminal 232 (terminal indicated by Rx) included in the control unit 230. On the other hand, when the voltage of the terminal 241 is higher than the voltage of the terminal 242, the receiving circuit 220 supplies an L level (for example, 0V) voltage signal to the receiving terminal 232 included in the control unit 230. The receiving circuit 220 can also be said to be a polarity detecting circuit that detects the polarity (+ V1 or −V1) of the voltage applied between the terminal pairs 243. The receiving circuit 220 outputs a voltage corresponding to the voltage applied to the terminal 242 of the terminal pair 243.

The receiving circuit 220 includes a Zener diode 221, a resistor 222, and a resistor 223. The anode of the Zener diode 221 is connected to the reference terminal 233, and the cathode of the Zener diode 221 is connected to the receiving terminal 232. The Zener diode 221 prevents the voltage of the receiving terminal 232 from becoming higher than the breakdown voltage (for example, 5V) with respect to the voltage of the reference terminal 233. The resistor 222 is provided between the terminal 242 and the receiving terminal 232 and limits the voltage applied to the receiving terminal 232. The resistor 223 is provided between the reference terminal 233 and the receiving terminal 232 in parallel with the Zener diode 221.

The control unit 230 controls the overall operation of the slave unit 200. The control unit 230 controls the transmission circuit 210 to transmit data to the master unit 100. For example, the control unit 230 outputs a voltage at a level corresponding to the bit data to be transmitted from the transmission terminal 231. For example, when transmitting a bit corresponding to 0, the control unit 230 outputs an H level voltage signal from the transmission terminal 231 and causes a current to flow between the terminals 243. When transmitting the bit corresponding to 1, the control unit 230 outputs an L-level voltage signal from the transmission terminal 231 and does not pass a current between the terminals 243.

Here, the control unit 230 confirms that the other slave unit has not transmitted data to the master unit 100, and then causes the transmission circuit 210 to transmit data to the master unit 100. Here, while the other slave unit transmits data to the master unit 100, a period in which a current flows between the terminals 143 occurs. When a current flows between the terminal pairs 143, the voltage applied between the terminal pairs 143 is reduced by the action of the current limiting circuit 151 (or the current limiting circuit 152) that functions as a voltage lowering circuit. At this time, the voltage drop detection circuit 260 detects a drop in the voltage applied between the terminal pairs 143, and the voltage drop detection circuit 260 applies an L level voltage to the detection terminal 234 included in the control unit 230. Therefore, when it is confirmed that the L level is not applied to the detection terminal 234 for a predetermined time, the control unit 230 causes the transmission circuit 210 to transmit data to the master unit 100.

Further, when the control unit 230 detects that the L level voltage is applied to the detection terminal 234 while the current is not flowing between the terminal pairs 143 by the transmission circuit 210, the control unit 230 transmits the data by the transmission circuit 210. Abort. Then, it is possible to avoid a communication abnormality that occurs when the slave unit 200 and another slave unit (slave unit 300 or slave unit 400) simultaneously transmit data to the master unit 100.

Further, the control unit 230 identifies the data transmitted from the master unit 100 based on the voltage signal supplied from the reception circuit 220. That is, the control unit 230 samples the bit data according to the level of the voltage applied to the reception terminal 232, and identifies the transmitted data from the bit data string obtained by the sampling.

Here, the control unit 230 is based on the polarity of the voltage applied between the terminal pairs 243 when the data is not transmitted by the master unit 100, that is, when the master unit 100 is in the idle state. The logic of the data received from the machine 100 can be determined. For example, it is assumed that the master unit 100 transmits a bit corresponding to 1 when it is in an idle state. Here, when transmitting the bit corresponding to 1, the control unit 130 outputs an H level voltage from the transmission terminal 131 and outputs an L level voltage from the transmission terminal 132. Therefore, when the master unit 100 is in the idle state, the voltage of the terminal 142 becomes higher than the voltage of the terminal 141.

Here, as shown in FIG. 2, it is assumed that the terminal 141 and the terminal 241 are connected by the communication line 11, and the terminal 142 and the terminal 242 are connected by the communication line 12. In this case, when the master unit 100 is in the idle state, the voltage of the terminal 242 becomes higher than the voltage of the terminal 241. Therefore, when the master unit 100 is in the idle state, an H level voltage is applied to the receiving terminal 232. Therefore, the control unit 230 considers that the bit corresponding to 1 is received when the H level voltage is applied to the receiving terminal 232, and when the L level voltage is applied to the receiving terminal 232. It is considered that the bit corresponding to 0 has been received.

On the other hand, unlike the connection shown in FIG. 2, it is assumed that the terminal 141 and the terminal 242 are connected by the communication line 11, and the terminal 142 and the terminal 241 are connected by the communication line 12. In this case, when the master unit 100 is in the idle state, the voltage of the terminal 242 is lower than the voltage of the terminal 241. Therefore, when the master unit 100 is in the idle state, an L level voltage is applied to the receiving terminal 232. Therefore, the control unit 230 considers that the bit corresponding to 1 is received when the L level voltage is applied to the receiving terminal 232, and when the H level voltage is applied to the receiving terminal 232. It is considered that the bit corresponding to 0 has been received.

In this way, the control unit 230 determines the level of the voltage signal supplied from the reception circuit 220 that functions as the polarity detection circuit when the master unit 100 is in the idle state, and determines the logic of the received data. Therefore, the control unit 230 can appropriately receive the data transmitted from the master unit 100 regardless of the connection polarity of the communication line pair 13. Further, the control unit 230 executes lighting control (not shown) according to the control by the master unit 100. The control unit 230 is composed of, for example, a microcomputer including a CPU, a ROM, a RAM, and the like.

Here, the threshold value for the control unit 230 to discriminate the level of the voltage signal supplied from the receiving circuit 220, that is, the threshold value for discriminating the polarity of the voltage applied between the terminal pairs 243 is the communication line pair 13. It is set to a value that is not affected by the flow of return current. That is, when the return current flows through the communication line pair 13, the voltage applied between the terminal pairs 243 decreases due to the voltage drop in the communication line pair 13. Further, when the return current flows through the communication line pair 13, the voltage applied between the terminal pairs 143 decreases due to the action of the voltage drop circuits (current limiting circuits 151 and 152), and as a result, the voltage is applied between the terminal pairs 243. The voltage to be applied drops further. Therefore, the threshold value is set to a value that does not affect the discrimination result even if the return current flows through the communication line pair 13 and the voltage applied between the terminal pairs 243 decreases.

More specifically, the threshold is such that when a voltage of the first polarity is applied between the terminal pairs 143 by the voltage application circuit (transmission circuit 110), a current flows between the terminal pairs 143 and the voltage drop circuit (current limit). Even when the voltage applied between the terminal pairs 143 is reduced by the circuits 151 and 152) and the voltage between the terminal pairs 243 is reduced due to the voltage drop due to the communication line pair 13 connecting the terminal pair 143 and the terminal pair 243. , Is set to be less than the voltage between the terminals 243. When a voltage of the first polarity is applied between the terminals 243, for example, the voltage applied to the terminals 242 is higher than the voltage applied to the terminals 241. On the other hand, when a voltage of the second polarity is applied between the terminals 243, for example, the voltage applied to the terminals 242 is lower than the voltage applied to the terminals 241.

Further, the above threshold is set when a voltage having a second polarity opposite to that of the first polarity is applied between the terminal pairs 143 by the voltage application circuit (transmission circuit 110), a current is applied between the terminal pairs 143. It does not flow, the voltage applied between the terminal pairs 143 by the voltage drop circuit (current limiting circuits 151, 152) does not drop, and the terminal pair due to the voltage drop due to the communication line pair 13 connecting the terminal pair 143 and the terminal pair 243. Even when the voltage between 243 does not decrease, it is set to be equal to or higher than the voltage between the terminals and 243.

If the control unit 230 cannot adjust the threshold value, the voltage output by the receiving circuit 220 (polarity detection circuit) may be adjusted by adjusting the resistance value of the resistor 222, the resistance value of the resistor 223, and the like. In this case, in the receiving circuit 220 (polarity detection circuit), when a voltage of the first polarity is applied between the terminal pairs 143 by the voltage application circuit (transmission circuit 110), a current flows between the terminal pairs 143 and the voltage drops. The voltage applied between the terminal pairs 143 is reduced by the circuit (current limiting circuits 151 and 152), and the voltage between the terminal pairs 243 is reduced by the voltage drop due to the communication line pair 13 connecting the terminal pair 143 and the terminal pair 243. Even in this case, a voltage equal to or higher than the above threshold is output.

Further, the receiving circuit 220 (polarity detecting circuit) is a terminal when a voltage having a second polarity opposite to the first polarity is applied between the terminal pairs 143 by the voltage applying circuit (transmitting circuit 110). No current flows between the pair 143, the voltage applied between the terminal pairs 143 by the voltage drop circuit (current limiting circuits 151, 152) does not drop, and the communication line pair 13 connecting the terminal pair 143 and the terminal pair 243 is connected. Even when the voltage between the terminals and the 243 does not decrease due to the voltage drop due to the above, a voltage less than the above threshold is output.

In this way, the receiving circuit 220 (polarity detecting circuit) can detect the polarity without being affected by the voltage drop due to the return current flowing through the communication line pair 13. According to such a configuration, transmission from the master unit 100 to the slave unit 200 (or the slave unit 300) and transmission from the slave unit 200 (or the slave unit 300) to the master unit 100 can be executed at the same time. can. As a result, the communication throughput is improved.

The terminal pair 243 is a terminal pair to which a communication line pair 13 for transmitting / receiving data to / from the master unit 100 is connected. The terminal pair 243 includes a terminal 241 and a terminal 242. The terminal pair 243 is connected to the terminal pair 143 via the communication line pair 13. That is, the terminal 241 is connected to the terminal 141 via the communication line 11, and the terminal 242 is connected to the terminal 142 via the communication line 12. Further, the terminal pair 243 is also a terminal pair for connecting the terminal pair 143 included in the master unit 100, the terminal pair 343 included in the slave unit 300, and the terminal pair 443 included in the slave unit 400. Therefore, the terminal pair 243 is connected to the terminal pair 343 via the communication line pair 23. That is, the terminal 241 is connected to the terminal 341 via the communication line 21, and the terminal 242 is connected to the terminal 242 via the communication line 22.

The rectifier circuit 250 rectifies + V1 and −V1 which are positive and negative power supply voltages applied between the terminal pairs 243, and generates V2 which is an operating power supply of the slave unit 200. The operating power supply V2 of the slave unit 200 has a voltage (for example, 24V) similar to that of V1 which is the power supply voltage of the master unit 100, and is supplied to each module from the power supply terminal 271. The rectifier circuit 250 includes a diode 251, a diode 252, a diode 253, and a diode 254. Further, the rectifier circuit 250 includes an AC input terminal pair (not shown) to which the terminal pair 243 is connected and a DC output terminal pair (not shown) through which a current obtained by rectifying the current supplied via the AC input terminal pair flows. ) And. The anode of the diode 251 and the anode of the diode 252 are connected to one DC output terminal (DC output terminal on the low voltage side). The cathode of the diode 253 and the cathode of the diode 254 are connected to the other DC output terminal (DC output terminal on the high voltage side). The cathode of the diode 251 and the anode of the diode 253 are connected to the terminal 241 (one AC input terminal). The cathode of the diode 252 and the anode of the diode 254 are connected to terminal 242 (the other AC input terminal).

The voltage drop detection circuit 260 is a circuit that detects that the voltage applied between the terminal pairs 243 has dropped. When the voltage drop detection circuit 260 detects that the power supply voltage output from the rectifier circuit 250 is equal to or lower than a predetermined threshold value, the voltage drop detection circuit 260 sets the L level to the detection terminal 234 (terminal indicated by CS) provided in the control unit 230. Supply the voltage signal of. On the other hand, when the voltage drop detection circuit 260 detects that the power supply voltage output from the rectifier circuit 250 exceeds a predetermined threshold value, the voltage drop detection circuit 260 supplies an H level voltage signal to the detection terminal 234 included in the control unit 230. do.

The voltage drop detection circuit 260 includes a power supply terminal 261, an operational amplifier 262, a capacitor 263, a resistor 264, a resistor 265, and a ground terminal 266. The power supply terminal 261 is connected to a DC power supply (not shown) that outputs V4 (for example, 5V) as a power supply voltage, and V4 is applied. The DC power supply that outputs V4 is generated from the DC power supply (not shown) that outputs V2. The operational amplifier 262 compares the reference voltage applied to the inverting input terminal with the input voltage applied to the non-inverting input terminal. The operational amplifier 262 outputs an H level voltage from the output terminal when the input voltage is higher than the reference voltage, and outputs an L level voltage from the output terminal when the input voltage is lower than the reference voltage.

The voltage drop detection circuit 260 detects that the voltage applied between the DC output terminal pairs included in the rectifier circuit 250 has dropped, thereby detecting that the voltage applied between the terminal pairs 243 has dropped. As described above, the voltage drop detection circuit 260 detects that the voltage after rectification has dropped, and does not detect the polarity (or change in polarity) of the voltage applied between the terminal pairs 243. Therefore, the voltage drop detection circuit 260 does not have a configuration for detecting the polarity of the voltage applied between the terminal pairs 243, and detects the return current flowed by another slave unit (slave unit other than the slave unit 200). can do.

The capacitor 263 cuts off the DC component supplied to the non-inverting input terminal of the operational amplifier 262. The resistor 264 and the resistor 265 are connected in series between the power supply terminal 261 and the ground terminal 266. The resistor 264 and the resistor 265 apply a reference voltage obtained by dividing the power supply voltage to the inverting input terminal of the operational amplifier 262. The ground terminal 266 is connected to a DC power supply (not shown) included in the slave unit 200, and 0 V is applied.

The power supply terminal 271 is a power supply terminal for supplying V2, which is the operating power supply of the slave unit 200 generated by the rectifier circuit 250, to each module. Since the configurations of the slave unit 300 and the slave unit 400 are basically the same as the configurations of the slave unit 200, the description thereof will be omitted.

Next, the data transmission process executed by the slave unit 200 will be described with reference to the flowchart shown in FIG. The slave unit 200 is connected to, for example, the master unit 100, and when the power is turned on, the data transmission process is started. Since the data transmission process executed by the slave units 300 and 400 is basically the same as the data transmission process executed by the slave unit 200, the description thereof will be omitted or simplified.

First, the control unit 230 determines whether or not the data transmission condition is satisfied (step S101). The data transmission condition is satisfied, for example, when data requesting a response is received from the master unit 100, or when a predetermined interrupt occurs. In this embodiment, the slave unit 200 can voluntarily transmit data to the master unit 100 without being instructed by the master unit 100. When the control unit 230 completes the process of step S101, the control unit 230 generates a bit string of data to be transmitted (step S102).

When the control unit 230 completes the process of step S102, the control unit 230 monitors the level of the detection terminal 234 (step S103). When the process of step S103 is completed, the control unit 230 determines whether or not the detection terminal 234 continuously maintains the H level (step S104). The continuous maintenance of the H level by the detection terminal 234 means that the data is not being transmitted by another slave unit.

When the control unit 230 determines that the detection terminal 234 does not continuously maintain the H level (step S104: NO), the control unit 230 returns the process to step S103. On the other hand, when the control unit 230 determines that the detection terminal 234 continuously maintains the H level (step S104: YES), the control unit 230 selects a bit to be transmitted (step S105). The bits are selected in order from the beginning of the generated bit string. When the control unit 230 completes the process of step S105, the control unit 230 sets the transmission terminal 231 to a level corresponding to the selected bit (step S106). For example, if the selected bit is 0, the transmit terminal 231 is set to H level (eg, 5V), and if the selected bit is 1, the transmit terminal 231 is set to L level (eg, 0V). Will be done.

When the process of step S106 is completed, the control unit 230 determines whether or not the level of the transmission terminal 231 is the L level (step S107). The fact that the level of the transmission terminal 231 is the L level means that the transmission circuit 210 controls the terminal pair 243 to be in a non-conducting state, and no current is flowing. When the control unit 230 determines that the level of the transmission terminal 231 is the L level (step S107: YES), the control unit 230 monitors the level of the detection terminal 234 (step S108).

When the process of step S108 is completed, the control unit 230 determines whether or not the level of the detection terminal 234 is the H level (step S109). When the level of the detection terminal 234 is H level, it means that no current is passed by any of the slave units and the terminal pair 143 is controlled to be in a non-conducting state. On the other hand, the fact that the level of the detection terminal 234 is the L level means that a current is flowing by one of the slave units and the terminal pair 143 is controlled to be in a conductive state.

When the control unit 230 determines that the level of the detection terminal 234 is not the H level (step S109: NO), the control unit 230 stops the data transmission and returns the process to step S103. When the control unit 230 determines that the level of the transmission terminal 231 is not the L level (step S107: NO) or determines that the level of the detection terminal 234 is the H level (step S109: YES), 1 bit. It is determined whether or not the minute time has elapsed (step S110).

When the control unit 230 determines that the time for one bit has not elapsed (step S110: NO), the process returns to step S107. On the other hand, when the control unit 230 determines that the time for one bit has elapsed (step S110: YES), the control unit 230 determines whether or not all the bits have been selected (step S111). When the control unit 230 determines that all the bits have been selected (step S111: YES), the control unit 230 considers that the data transmission has been completed, and returns the process to step S101. On the other hand, when the control unit 230 determines that any of the bits has not been selected (step S111: NO), the process returns to step S105 and selects the next bit.

Next, the data reception process executed by the slave unit 200 will be described with reference to the flowchart shown in FIG. The slave unit 200 is connected to, for example, the master unit 100, and when the power is turned on, the data reception process is started. Since the data reception process executed by the slave units 300 and 400 is basically the same as the data reception process executed by the slave unit 200, the description thereof will be omitted or simplified.

First, the control unit 230 monitors the level of the receiving terminal 232 (step S201). That is, the control unit 230 samples the level of the voltage applied from the reception circuit 220 to the reception terminal 232. When the process of step S201 is completed, the control unit 230 determines whether or not the receiving terminal 232 continuously maintains one level (step S202). The fact that the receiving terminal 232 continuously maintains one level means that the master unit 100 is in an idle state.

When the control unit 230 determines that the reception terminal 232 does not continuously maintain one of the levels (step S202: NO), the control unit 230 returns the process to step S201. On the other hand, when the control unit 230 determines that the receiving terminal 232 continuously maintains one level (step S202: YES), the control unit 230 sets the maintained level to the idle level (step S203). The idle level is the level of the voltage applied to the receiving terminal 232 when the bit corresponding to 1 is transmitted.

When the process of step S203 is completed, the control unit 230 monitors the level of the receiving terminal 232 (step S204). That is, the control unit 230 samples the level of the voltage applied from the reception circuit 220 to the reception terminal 232. When the process of step S204 is completed, the control unit 230 determines whether or not there is a change in the level of the receiving terminal 232 (step S205). Note that the change in the level of the receiving terminal 232 means that the master unit 100 has started transmitting data and the first bit (for example, the start bit) has been transmitted.

When the control unit 230 determines that the level of the reception terminal 232 has not changed (step S205: NO), the control unit 230 returns the process to step S204. On the other hand, when the control unit 230 determines that the level of the receiving terminal 232 has changed (step S205: YES), the control unit 230 acquires a bit string for one frame (step S206). When the control unit 230 completes the process of step S206, the control unit 230 converts the bit string into data (step S207). When the control unit 230 completes the process of step S207, the control unit 230 returns the process to step S204.

In the present embodiment, when the voltage applied between the terminal pairs 143 decreases when the current flows between the terminal pairs 143 and the voltage applied between the terminal pairs 243 does not decrease, serial data is transmitted from the slave unit 200. Will be done. Therefore, according to the present invention, the collision of current transmission can be suppressed without lowering the throughput of the communication system 1000.

Further, in the present embodiment, while the slave unit 200 is transmitting data to the master unit 100, another slave unit (for example, the slave unit 300 or the slave unit 400) is transmitting data to the master unit 100. If this is detected by the handset 200, the data transmission by the handset 200 is stopped. Therefore, according to the present embodiment, the collision of current transmission can be further suppressed.

In this case, it is preferable to assign priorities to a plurality of slave units, and when current transmissions by the plurality of slave units collide, stop the current transmission to the slave unit having the lowest priority as much as possible. For example, the smaller the address number indicated by the 4-bit digital data, the higher the priority. Then, among the bit strings constituting the data to be transmitted to the master unit 100, the bit string immediately after the start bit is set as the bit string indicating the address number of the slave unit. Then, for example, 0000 is assigned as the address number of the slave unit 200, 0001 is assigned as the address number of the slave unit 300, and 0010 is assigned as the address number of the slave unit 400.

Here, in response to the broadcast by the master unit 100 or in response to the power being turned on to the master unit 100, the slave unit 200, the slave unit 300, and the slave unit 400 simultaneously transmit data to the master unit 100. It is assumed that you have started sending. The slave unit 200, the slave unit 300, and the slave unit 400 allow a return current to flow when transmitting a bit corresponding to 0, and do not allow a return current to flow when transmitting a bit corresponding to 1. Further, the slave unit 200, the slave unit 300, and the slave unit 400 check whether the return current is being passed by another slave unit when transmitting the bit corresponding to 1.

Therefore, the slave unit 200 sends a return current for 4 bits. On the other hand, after passing the return current for 3 bits, the slave unit 300 detects that the return current is being passed by another slave unit at the 4th bit, and stops the data transmission. Further, the slave unit 300 detects that the return current is being passed by another slave unit at the third bit after passing the return current for 2 bits, and stops the data transmission. According to such a configuration, when the collision of the current transmission is suppressed, it is possible to prevent the data transmission by the slave unit having a high priority from being interrupted.

Further, in the present embodiment, the current limiting circuit 151 and the current limiting circuit 152 are adopted as the voltage drop circuit. Therefore, according to the present embodiment, it is possible to reduce the voltage between the terminals 143 while maintaining the current flowing between the terminals 143.

Further, in the present embodiment, the logic of the serial data transmitted by the master unit 100 is determined according to the polarity applied between the terminal pairs 243 when the master unit 100 is idle. Therefore, according to the present embodiment, the logic of serial data can be specified regardless of the connection polarity between the terminal pair 143 and the terminal pair 243.

(Modification example)
Although the embodiments of the present invention have been described above, various modifications and applications are possible in carrying out the present invention.

In the present invention, which part of the configuration, function, and operation described in the above embodiment is adopted is arbitrary. Further, in the present invention, in addition to the above-mentioned configurations, functions, and operations, further configurations, functions, and operations may be adopted.

In the embodiment, an example in which the communication system 1000 is a lighting system, the master unit 100 is a lighting control device, and the slave unit 200, the slave unit 300, and the slave unit 400 are lighting devices has been described. Of course, in the present invention, the communication system may be another system. For example, the communication system 1000 may be an air conditioning system, the master unit 100 may be an outdoor unit, and the slave unit 200, the slave unit 300, and the slave unit 400 may be indoor units. Further, the number of slave units is not limited to three, and may be two or four or more.

In the embodiment, an example in which one slave unit is connected to one master unit or one slave unit has been described. The connection relationship between the master unit and the slave unit is not limited to this example. For example, two or more slave units may be connected to one master unit, or two or more slave units may be connected to one slave unit.

Further, the logic of the data is not limited to the example shown in the embodiment. For example, an input voltage may be applied to the non-inverting input of the operational amplifier 122, and a reference voltage may be applied to the inverting input of the operational amplifier 122. In this case, it is preferable that the control unit 230 outputs an H level voltage from the transmission terminal 231 when transmitting the bit corresponding to 1. In this case, the bit corresponding to 1 corresponds to the H level.

In the embodiment, an example in which the current limiting circuit 151 and the current limiting circuit 152 are adopted as the voltage drop circuit has been described. In the present invention, another circuit may be adopted as the voltage drop circuit. For example, a circuit excluding the NPN transistor 112 from the current limiting circuit 151, that is, a circuit including the NPN transistor 111 and the resistor 113 can be adopted as the current limiting circuit. Similarly, a circuit in which the NPN transistor 115 is excluded from the current limiting circuit 152, that is, a circuit including the NPN transistor 114 and the resistor 116 can be adopted as the current limiting circuit.

The present invention allows for various embodiments and modifications without departing from the broad spirit and scope of the invention. Further, the above-described embodiment is for explaining the present invention, and does not limit the scope of the present invention. That is, the scope of the present invention is indicated by the scope of claims, not by embodiments. And, various modifications made within the scope of the claims and within the scope of the equivalent invention are considered to be within the scope of the present invention.

The present invention is applicable to a communication system in which a master unit and a plurality of slave units communicate with each other.

11,12,21,22,31,32 communication line, 13,23,33 communication line pair, 100 master unit, 110,210 transmission circuit, 111,112,114,115,211 NPN transistor, 117,118 PNP transistor , 120, 220 receiving circuit, 121,161,261,171 power supply terminal, 122,262 operational capacitor, 123,162,263 capacitor, 113,116,124,125,126,212,222,223,264,265 resistor, 127,128,163,266 Ground terminal, 130,230 Control unit, 131,132,231 Transmission terminal, 133,232 Receiving terminal, 141,142,241,242,341,342,441,442 terminal, 143,243 , 343,443 terminal pair, 151,152 current limiting circuit, 200,300,400 slave unit, 221 Zener diode, 233 reference terminal, 234 detection terminal, 250 rectifier circuit, 251,252,253,254 diode, 260 voltage drop Detection circuit, 1000 communication system

Claims (8)

A master unit having a master unit side terminal pair, a first slave unit having a first slave unit side terminal pair, and a second slave unit having a second slave unit side terminal pair are provided, and the master unit side terminal is provided. A communication system in which a pair, the first handset side terminal pair, and the second handset side terminal pair are connected to each other by a communication line pair.
The master unit is a voltage provided with a voltage reduction circuit that applies a voltage between the master unit side terminal pairs and reduces the voltage applied between the master unit side terminal pairs when a current flows between the master unit side terminal pairs. With the application circuit
Reception that receives the first serial data from the first slave unit and receives the second serial data from the second slave unit by detecting the presence or absence of a current flowing between the terminal pairs on the master unit side. With a circuit,
The first slave unit includes a transmission circuit that transmits the first serial data to the master unit by controlling the conduction / non-conduction state between the terminal pairs on the first slave unit side.
The second handset is
A transmission circuit that transmits the second serial data to the master unit by controlling the conduction / non-conduction state between the terminal pairs on the second slave unit side.
A voltage drop detection circuit that detects that the voltage applied between the second handset side terminal pair has dropped, and
When the voltage drop detection circuit does not detect that the voltage applied between the second handset side terminal pairs has dropped, the second serial data is transmitted to the transmission circuit included in the second handset. for example Bei and a control circuit which,
The voltage application circuit is a transmission circuit that transmits third serial data to the second slave unit by switching the polarity of the voltage applied between the master unit side terminal pairs.
The second slave unit includes a receiving circuit that receives the third serial data from the master unit by detecting the polarity of the voltage applied between the terminal pairs on the second slave unit side.
The control circuit has the third serial based on the polarity detected by the receiving circuit included in the second slave unit when the third serial data is not transmitted from the transmitting circuit included in the master unit. Determine the logic of the data,
Communications system. A master unit having a master unit side terminal pair, a first slave unit having a first slave unit side terminal pair, and a second slave unit having a second slave unit side terminal pair are provided, and the master unit side terminal is provided. A communication system in which a pair, the first handset side terminal pair, and the second handset side terminal pair are connected to each other by a communication line pair.
The master unit is a voltage provided with a voltage reduction circuit that applies a voltage between the master unit side terminal pairs and reduces the voltage applied between the master unit side terminal pairs when a current flows between the master unit side terminal pairs. With the application circuit
Reception that receives the first serial data from the first slave unit and receives the second serial data from the second slave unit by detecting the presence or absence of a current flowing between the terminal pairs on the master unit side. With a circuit,
The first slave unit includes a transmission circuit that transmits the first serial data to the master unit by controlling the conduction / non-conduction state between the terminal pairs on the first slave unit side.
The second handset is
A transmission circuit that transmits the second serial data to the master unit by controlling the conduction / non-conduction state between the terminal pairs on the second slave unit side.
A voltage drop detection circuit that detects that the voltage applied between the second handset side terminal pair has dropped, and
When the voltage drop detection circuit does not detect that the voltage applied between the second handset side terminal pairs has dropped, the second serial data is transmitted to the transmission circuit provided in the second handset. for example Bei and a control circuit which,
The voltage application circuit is a transmission circuit that transmits third serial data to the second slave unit by switching the polarity of the voltage applied between the master unit side terminal pairs.
The second slave unit includes a receiving circuit that receives the third serial data from the master unit by detecting the polarity of the voltage applied between the terminal pairs on the second slave unit side.
The receiving circuit included in the second handset outputs a voltage corresponding to the voltage applied to one of the terminals of the second handset side terminal pair.
The control circuit determines whether or not the voltage output from the receiving circuit included in the second handset is equal to or higher than the threshold value.
In the receiving circuit included in the second slave unit, when a voltage of the first polarity is applied between the master unit side terminal pairs by the voltage application circuit, a current flows between the master unit side terminal pairs. The voltage applied between the master unit side terminal pairs is reduced by the voltage drop circuit, and the voltage drop due to the communication line pair connecting the master unit side terminal pair and the second slave unit side terminal pair causes the first. Even when the voltage between the terminal pairs on the slave unit side of 2 drops, the voltage above the threshold is output.
In the receiving circuit included in the second slave unit, when a voltage having a second polarity opposite to that of the first polarity is applied between the terminal pairs on the master unit side by the voltage applying circuit. No current flows between the master unit side terminal pairs, the voltage applied between the master unit side terminal pairs does not decrease due to the voltage reduction circuit, and the master unit side terminal pair and the second slave unit side terminal do not decrease. Even when the voltage between the second slave unit side terminal pair does not decrease due to the voltage drop due to the communication line pair connecting the pair, a voltage less than the threshold value is output.
Communications system. The master unit includes a power supply terminal to which the power supply voltage of the master unit is applied.
The voltage drop circuit increases the voltage applied between the power supply terminal and one of the terminals of the master unit side terminal pair as the current flowing between the master unit side terminal pairs increases, and at the same time, the voltage drop circuit increases the voltage applied between the power supply terminal and one of the master unit side terminal pairs. It is a current limiting circuit that suppresses the current flowing between the pair of terminals on the master unit side to a predetermined threshold or less.
The communication system according to claim 1 or 2. Before Stories second slave unit, before Symbol second and AC input terminal pair handset terminal pair is connected, the DC output terminal of the current obtained by rectifying the current supplied via the AC input terminal pair to flow comprising a rectifier circuitry having pairs and, a,
The voltage drop detection circuit detects that the voltage applied between the DC output terminal pairs has dropped, thereby detecting that the voltage applied between the second slave unit side terminal pairs has dropped. ,
The communication system according to any one of claims 1 to 3. A terminal pair connected to the master unit and the slave unit by a communication line pair to which voltage is applied,
A transmission circuit that transmits serial data to the master unit by controlling the conduction / non-conduction state between the terminal pairs, and
A voltage drop detection circuit that detects that the voltage applied between the terminal pairs has dropped,
A communication device including a control circuit for causing the transmission circuit to transmit the serial data when the voltage drop detection circuit does not detect that the voltage applied between the terminal pairs has dropped.
The master unit transmits the second serial data to the communication device by switching the polarity of the voltage applied between the communication line pairs.
A receiving circuit for receiving the second serial data from the master unit by detecting the polarity of the voltage applied between the terminal pairs is provided.
The control circuit determines the logic of the second serial data based on the polarity detected by the receiving circuit when the second serial data is not transmitted from the master unit.
Communication equipment. A terminal pair connected to the master unit and the slave unit by a communication line pair to which voltage is applied,
A transmission circuit that transmits serial data to the master unit by controlling the conduction / non-conduction state between the terminal pairs, and
A voltage drop detection circuit that detects that the voltage applied between the terminal pairs has dropped,
A communication device including a control circuit for causing the transmission circuit to transmit the serial data when the voltage drop detection circuit does not detect that the voltage applied between the terminal pairs has dropped.
The master unit transmits the second serial data to the communication device by switching the polarity of the voltage applied between the communication line pairs.
A receiving circuit for receiving the second serial data from the master unit by detecting the polarity of the voltage applied between the terminal pairs is provided.
The receiving circuit outputs a voltage corresponding to the voltage applied to one of the terminals of the terminal pair.
The control circuit determines whether or not the voltage output from the receiving circuit is equal to or higher than the threshold value, and determines whether or not the voltage is equal to or higher than the threshold value.
In the receiving circuit, when a voltage of the first polarity is applied between the communication line pairs by the master unit, a current flows between the communication line pairs and the voltage applied between the communication line pairs decreases. Even when the voltage between the terminal pairs drops due to the voltage drop due to the communication line pair, a voltage equal to or higher than the threshold value is output.
In the receiving circuit, when a voltage having a second polarity opposite to the first polarity is applied between the communication line pairs by the master unit, no current flows between the communication line pairs. Even when the voltage applied between the communication line pairs does not decrease and the voltage between the terminal pairs does not decrease due to the voltage drop due to the communication line pair, the voltage less than the threshold value is output.
Communication equipment. A master unit having a master unit side terminal pair, a first slave unit having a first slave unit side terminal pair, and a second slave unit having a second slave unit side terminal pair are provided, and the master unit side terminal is provided. It is a communication control method in a communication system in which a pair, the first handset side terminal pair, and the second handset side terminal pair are connected to each other by a communication line pair.
A voltage is applied between the pair of terminals on the master unit side to
By controlling the conduction / non-conduction state between the terminal pairs on the first slave unit side, the first slave unit transmits the first serial data to the master unit.
When a current flows between the master unit side terminal pairs, the voltage applied between the master unit side terminal pairs is reduced.
When the voltage applied between the second handset side terminal pairs does not decrease, the second handset can be used as the parent by controlling the conduction / non-conduction state between the second handset side terminal pairs. Send the second serial data to the machine,
The master unit receives the first serial data from the first slave unit by detecting the presence or absence of a current flowing between the terminal pairs on the master unit side, and the second slave unit receives the first serial data. receives the serial data,
By switching the polarity of the voltage applied between the terminal pairs on the master unit side, the master unit transmits the third serial data to the second slave unit.
The second slave unit receives the third serial data from the master unit by detecting the polarity of the voltage applied between the terminal pairs on the second slave unit side.
The logic of the third serial data is determined based on the polarity detected by the second slave unit when the third serial data is not transmitted from the master unit.
Communication control method. A master unit having a master unit side terminal pair, a first slave unit having a first slave unit side terminal pair, and a second slave unit having a second slave unit side terminal pair are provided, and the master unit side terminal is provided. It is a communication control method in a communication system in which a pair, the first handset side terminal pair, and the second handset side terminal pair are connected to each other by a communication line pair.
A voltage is applied between the pair of terminals on the master unit side to
By controlling the conduction / non-conduction state between the terminal pairs on the first slave unit side, the first slave unit transmits the first serial data to the master unit.
When a current flows between the master unit side terminal pairs, the voltage applied between the master unit side terminal pairs is reduced.
When the voltage applied between the second handset side terminal pairs does not decrease, the second handset can be used as the parent by controlling the conduction / non-conduction state between the second handset side terminal pairs. Send the second serial data to the machine,
The master unit receives the first serial data from the first slave unit by detecting the presence or absence of a current flowing between the terminal pairs on the master unit side, and the second slave unit receives the first serial data. receives the serial data,
By switching the polarity of the voltage applied between the terminal pairs on the master unit side, the master unit transmits the third serial data to the second slave unit.
The second slave unit receives the third serial data from the master unit by detecting the polarity of the voltage applied between the terminal pairs on the second slave unit side.
The second handset outputs a voltage corresponding to the voltage applied to one of the terminals of the second handset side terminal pair.
The second handset determines whether or not the output voltage is equal to or higher than the threshold value.
In the second slave unit, when a voltage of the first polarity is applied between the master unit side terminal pairs by the master unit, a current flows between the master unit side terminal pairs and the master unit side terminal pair. The voltage applied between them decreases, and the voltage between the second slave unit side terminal pair increases due to the voltage drop caused by the communication line pair connecting the master unit side terminal pair and the second slave unit side terminal pair. Even if it drops, it outputs a voltage above the threshold and outputs it.
When a voltage having a second polarity opposite to that of the first polarity is applied between the master unit side terminal pair by the master unit, the second slave unit has the master unit side terminal pair. No current flows between them, the voltage applied between the master unit side terminal pairs does not decrease, and the voltage due to the communication line pair connecting the master unit side terminal pair and the second slave unit side terminal pair. Even if the voltage between the second handset side terminal pairs does not drop due to the drop, a voltage less than the threshold is output.
Communication control method.

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