JPH054650U - Multiplexer - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a multiplex communication device capable of promptly detecting a disconnection of a communication line and easily identifying a disconnection point. [Structure] In a multiplex communication device in which a master station and a plurality of slave stations are connected in a multi-drop manner, when normal communication between the master station and each slave station is completed, disconnection detection processing (340) is performed, and the communication line starts from the end to the end. It is determined whether there is a wire break between the two. If it is determined by this disconnection detection process that a disconnection has occurred between the start end and the end of the communication line, a disconnection point search process (360) is performed this time,
For each communication line from the start end to each slave station, it is sequentially determined whether or not a wire break has occurred, and if a wire break has occurred,
The address of the slave station that cannot communicate due to the disconnection is displayed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention comprises a master station connected to the beginning of a communication line and a plurality of slave stations branch-connected to the communication line, and multiplex communication for performing information transmission by multiplexing the communication line under transmission control by the master station. Regarding the device.

[0002]

[Prior Art]

 Conventionally, the master station is connected to the beginning of the communication line and each of the slave stations is branched and connected to the communication line (hereinafter, this connection mode is called multi-drop), and the master station and the slave station perform bidirectional data transmission. Multiplex communication systems are known. For example, in a local area network installed inside a building, the master station is located on the first floor of the building, and one slave station is located on each floor. 2. Description of the Related Art A multiplex communication device is known that is connected by a loop and performs serial bidirectional communication via a communication line multiplexed by a time division method.

[0003]

[Problems to be solved by the device]

 Since this type of multiplex communication equipment uses a communication line, if the communication line is disconnected, communication becomes impossible and accurate data exchange cannot be performed between the master station and slave stations. However, because the conventional multiplex communication device does not have the function of detecting disconnection of the communication line, the master station and slave stations perform communication operations individually until the user notices an abnormality, and the master station side There were various problems, such as a command being issued based on incorrect data.

For example, when such a multiplex communication device is used in a hotel to smoothly perform operations such as guest room management and cleaning, a cleaning instruction from the front does not reach an operator, or conversely, a room where a customer is present. This causes the problem that the cleaning instruction to the worker is delivered to the worker.

Further, even if the user notices the disconnection, it takes a lot of time and labor to specify where the disconnection is, and there is also a problem that the recovery takes time. The present invention has been made in view of these problems, and provides a multiplex communication device capable of promptly detecting the disconnection of a communication line as described above and easily identifying the disconnection point. It was made for the purpose of doing.

[0006]

[Means for Solving the Problems]

 That is, the present invention made to achieve the above object comprises a master station connected to the beginning of a communication line and a plurality of slave stations branch-connected to the communication line, as illustrated in FIG. In a multiplex communication apparatus in which the master station and each of the plurality of slave stations transmit information under the transmission control of the master station, the master station and each of the plurality of slave stations transmit information to the plurality of slave stations. Set the termination switch that connects the terminating resistor to the branch connection point of the slave station, the cutoff switch that disconnects the connection between the communication circuit in the slave station and the communication line, and set whether the slave station is the terminal slave station from the outside. If it is set that the slave station is the terminating slave station, the terminating switch is set to the terminating resistor connection side, and conversely the slave station is not the terminating slave station. If the end switch is When the disconnection detection signal transmitted from the main station is received by the communication circuit and the steady drive means for driving the protection connection and the disconnection switch to the circuit connection side, for a predetermined time, the When the disconnection detection driving means for driving the disconnection switch to the circuit disconnection side and the disconnection confirmation signal including the identification information of the slave station transmitted from the master station in the communication circuit, the disconnection confirmation signal is received from the identification information. Is for the slave station, and if the disconnection confirmation signal is for the slave station, the disconnection switch is driven to the line cutoff side and the termination switch is driven to the termination resistance connection side for a predetermined time. On the contrary, if the disconnection confirmation signal is not for the slave station, the disconnection switch is driven to the line interruption side and the termination switch is driven to the termination resistance interruption side for a predetermined time. A disconnection confirmation driving means is provided, and a disconnection detection signal transmitting means for transmitting the disconnection detection signal to the main station, and the communication line is connected until a predetermined time elapses after the disconnection detection signal is transmitted. A disconnection determination means for determining disconnection of the communication line by energizing, and a disconnection confirmation signal including the identification information for each of the plurality of slave stations when the disconnection determination means determines disconnection of the communication line. Disconnection confirmation signal transmitting means for sequentially transmitting at every predetermined time, and each time the disconnection confirmation signal transmitting means transmits the disconnection confirmation signal, the communication line is energized until a predetermined time elapses thereafter. When the disconnection of the line is judged and the disconnection is judged, the disconnection confirmation registration means for registering the identification information in the disconnection confirmation signal transmitted from the above disconnection confirmation signal transmission means as the incommunicable slave station, and the above disconnection confirmation When the disconnection judgment for all slave stations is completed by the operations of the signal transmission means and the disconnection confirmation registration means, the multiplex communication is provided with a display means for displaying the identification information registered as the above-mentioned incommunicable slave station. The main point is the device.

[0007]

[Action]

 In the multiplex communication device of the present invention configured as described above, the terminating switch for connecting the terminating resistor to the communication line on each slave side is normally a steady drive means, and the slave station whose own station is the terminating terminal If it is set to be present, it will be driven to the terminating resistor connection side, and conversely, if it is set to be not the end slave station, it will be driven to the terminating resistor connection side. Further, the cutoff switch that cuts off the connection between the communication line and the communication circuit on each slave side is normally driven to the line connection side by the steady driving means.

Therefore, in the multiplex communication device of the present invention, the communication circuit of each slave station and the communication circuit are normally connected so that each slave station can communicate with the master station, and the slave station position at the end is set. Since a terminating resistor is connected to the communication line at, the occurrence of communication failure due to reflection from the communication line is prevented.

Next, in this state, when the disconnection detection signal transmitting means of the main station operates and transmits the disconnection detection signal, the disconnection detection driving means provided in each slave station responds to the disconnection detection signal, The disconnection switch is driven to disconnect the connection between the communication line and the communication circuit for a predetermined time. That is, by transmitting a disconnection detection signal from the master station to disconnect the communication circuit and communication line of each slave station, only the terminating resistor provided in the terminating slave station is connected to the communication line. In this state, the disconnection determination means of the main station energizes the communication line to determine the disconnection of the communication line. As a result, the disconnection determining means determines the disconnection of the communication line from the main station to the terminating slave station.

If the disconnection determining means determines the disconnection of the communication line in this way, and if it is found that the communication line from the main station to the terminating slave station is disconnected, it is provided in the main station. The disconnection confirmation signal transmitting means sequentially transmits a disconnection confirmation signal including identification information of the slave station to each of the plurality of slave stations at predetermined time intervals.

The disconnection confirmation signal is received by the communication circuit of each slave station, but on each slave station side, the disconnection confirmation drive means generates a disconnection confirmation signal from the identification information included in the received disconnection confirmation signal. If the disconnection confirmation signal is for the local station, the disconnection switch is driven to the circuit interruption side and the terminating switch is driven to the termination resistor connection side for the prescribed time, and conversely the disconnection confirmation is performed. If the signal is not for its own station, the disconnection switch is driven to the circuit interruption side and the termination switch is driven to the termination resistance interruption side for a fixed time. As a result, only the terminating resistor of the specific slave station corresponding to the identification information included in the disconnection detection signal transmitted by the disconnection confirmation signal transmitting means is connected to the communication line, and the communication line is opened on the other slave station side.

Further, on the main station side, every time the disconnection confirmation signal transmitting means transmits a disconnection confirmation signal, the disconnection confirmation registration means energizes the communication line to determine the disconnection of the communication line. The identification information included in the disconnection confirmation signal transmitted from the confirmation signal transmitting means is registered as the incommunicable slave station. In other words, the connection position of the terminating resistor to the communication line is sequentially changed for each slave station, and each time the communication line is energized, the slave station that cannot communicate due to disconnection is detected and the slave station that cannot communicate is detected. To register. When the disconnection position confirmation operation is completed, the display means on the master station side displays the identification information registered as the communication disabled slave station.

[0013]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 2 is a block diagram showing the configuration of the entire multiplex communication apparatus of the embodiment to which the present invention is applied.

As shown in the figure, the multiplex communication device of this embodiment includes a master station 3 arranged at the front of a hotel and a large number of slave stations 5a, 5b, ..., 5n arranged on each floor of the hotel. It consists of a twisted pair communication line 7 wired inside the hotel. The master station 3 is connected to one end of the communication line 7 via a terminal T0, and the slave stations 5a to By sequentially branching and connecting 5b, the master station 3 and the slave stations 5a to 5n are connected by multi-drop.

Here, the master station 3 manages the guest room condition of the hotel and the like by performing serial communication with the slave stations 5a to 5n, and as shown in FIG. 3, the slave stations 5a to 5n. A transceiver 10 conforming to RS-485 is provided for serial communication with the communication standard RS-485.

In addition, the master station 3 creates transmission data to be transmitted to the slave stations 5 a to 5 n via the transceiver 10, processes received data received via the transceiver 10, and inputs serial data to the transceiver 10. A CPU 12, a ROM 14, a RAM 16, a timer 18, parallel input / output ports 20 and 22, a serial communication controller (SIO) 24, and a bus line 26 connecting these parts are provided to output data. The parallel input / output port 20 is connected to a display unit 28 such as a CRT and a key input unit 29 for inputting data from the outside.

Next, the transceiver 10 is connected to the communication line 7 via the terminal T0. The signal lines 31 and 32 connecting the terminal T0 and the transceiver 10 are respectively connected with the signal lines 31 and 32. A relay switch SWX that opens and closes is provided, and a terminating resistor RT 0 is connected between the signal lines 31 and 32 on the transceiver 10 side of the relay switch SWX.

The relay switch SWX is composed of a pair of opening / closing switches provided for each of the signal lines 31 and 32. Each opening / closing switch closes the signal lines 31 and 32 to connect the transceiver 10 and the communication line 7. An a contact to be connected and a b contact for opening the signal lines 31 and 32 to disconnect the transceiver 10 and the communication line 7 are provided.

Further, to the contact b of the relay switch SWX, the power supply voltage V CC is applied to the b contact on the signal line 31 side, and the communication line is supplied from the voltage across the grounding resistor R1 connected to the b contact on the signal line 32 side. A disconnection detection circuit 34, which includes a detection resistor R2, a signal stabilizing capacitor C1, and an inverter INV, for detecting disconnection of 7 is connected, and the disconnection detection circuit 34 connects the transceiver 10 and the communication line 7. When cut off, the communication line 7 is energized so that disconnection of the communication line 7 can be detected.

The relay switch SWX is switched to the contact a side or the contact b side through the coil of the relay X, which is energized and controlled by the switching signal output from the parallel input / output port 22, and the disconnection detection circuit 34. The detection signal from is input to the parallel input / output port 22.

On the other hand, each of the slave stations 5a to 5n is for transmitting various data to the master station 3 in response to the transmission data from the master station 3. As shown in FIG. A transceiver 40 as a communication circuit suitable for −485, a CPU 42, a ROM 44, a RAM 46, a timer 48, parallel input / output ports 50 and 52, a serial communication controller (SIO) 54, and a bus line 56 connecting these parts. Is equipped with. The parallel input / output port 50 has a data input unit 58 for inputting the transmission data to be transmitted to the main station 3 from the outside, and data for outputting the input data and the transmission data from the main station 3 to an external device. The output unit 59 is connected.

Next, the transceiver 40 is branched and connected to the communication line 7 on the side of the main station 3 via the terminal T1, but the signal lines 61 and 62 connecting the terminal T1 and the transceiver 40 are connected to each other by a signal. A relay switch SWX1 for opening and closing the lines 61 and 62, respectively, is provided, and a series circuit including a terminal resistance RT1 and a relay switch SWX2 is provided between the signal lines 61 and 62 on the terminal T1 side of the relay switch SWX1. ing.

The relay switch SWX1 is composed of a pair of open / close switches provided for each of the signal lines 61, 62, and each open / close switch closes the signal lines 61, 62 to connect the transceiver 40 and the communication line 7. It is provided with an a-contact to be connected and a b-contact for opening the signal lines 61 and 62 to disconnect the transceiver 40 and the communication line 7. The relay switch SWX1 corresponds to the above-mentioned cutoff switch, and is connected to the contact a side or the contact b side via the coil of the relay X1 whose energization is controlled by the switching signal output from the parallel input / output port 52. Can be switched to the side.

The relay switch SWX2 corresponds to the above-mentioned termination switch, and is opened / closed via the coil of the relay X2 whose energization is controlled by the switching signal output from the parallel input / output port 52, and the communication line 7 The connection state of the terminating resistor RT1 to is switched.

Next, the parallel input / output port 52 is supplied with the power supply voltage Vcc through the resistor R3, and the input end thereof is connected to the other end of the manual switch SW1 whose one end is grounded. There is. The manual switch SW1 is used to set that the slave station is the slave station at the end farthest from the master station 3 by an external operation. The manual switch SW1 is turned on by an external operation, and the parallel input / output is performed. When the input end of the port 52 is at the low level, the CPU 42 detects that the own station is the terminating slave station. The manual switch SW1 corresponds to the above-mentioned operation unit.

Each of the master station 3 and the slave stations 5a to 5n configured as described above operates according to a control program stored in advance in the ROM 14 or 44. Therefore, the operation of each of these units will be described below with reference to the flow charts shown in FIGS.

First, FIG. 5 is a flow chart showing a communication process individually executed by each of the slave stations 5a to 5n. As shown in the figure, when this process is started, first, in step 100, the initial setting of each part in the slave station is performed, and then in step 110, the contact of the relay X1 (that is, the relay switch SWX1) is set to the contact a side. By switching to, the transceiver 40 and the communication line 7 are connected, and the slave station is set in a state in which communication with the master station 3 is possible. Further, in the following step 120, it is determined whether or not the manual switch SW1 is in the ON state, that is, whether or not the slave switch is set as the terminal slave station by the manual switch SW1. If it is set that the slave station is the terminal slave station, the process proceeds to step 130, the contact of the relay X2 (that is, the relay switch SWX2) is closed, and the terminating resistor RT1 is connected to the communication line 7. The process proceeds to step 140, and if it is not set that the slave station is the terminal slave station, the process directly proceeds to step 140. The processing of steps 110 to 130 corresponds to the above-mentioned steady driving means.

Next, at step 140, the input data from the data input unit 58 is stored in the RAM 46 as the transmission data to the main station 3, and the input data is sent from the data output unit 59 to an external device as necessary. Execute the data input process to output to. Further, in the subsequent step 150, it is determined whether the transmission signal from the main station 3 has been input via the transceiver 40. If the transmission signal from the main station 3 has not been input, the process proceeds to step 110 again to repeat the processing of steps 110 to 140.

On the other hand, when it is determined in step 150 that the transmission signal from the main station 3 is input, the process proceeds to step 160, and the transmission signal normally transmits data to and from the main station 3. It is determined whether the signal is for communication. If the transmission signal from the master station 3 is a transmission signal for normal communication, the process proceeds to step 170, the process for normal communication corresponding to the transmission signal is performed, and the process proceeds to step 110 again. On the contrary, if the transmission signal from the main station is not the transmission signal for normal communication, the process proceeds to step 180.

In step 180, it is determined whether or not the transmission signal from the main station 3 is a disconnection detection start signal output by the main station 3 for detecting disconnection, and the transmission signal from the main station 3 is disconnected. If it is a detection start signal, the process proceeds to step 190 and the timer 48 is started to start measuring the time from the present time. Then, in the following step 200, the connection between the transceiver 40 and the communication line 7 is cut off by switching the contact of the relay X1 (that is, the relay switch SWX1) to the contact b side, and in the following step 210, in the above step 190. By determining whether or not the time measured by the activated timer 48 has reached 0.5 seconds, the connection between the transceiver 40 and the communication line 7 is cut off and waits for 0.5 seconds. Then, when 0.5 seconds elapses, the process proceeds to step 110 again to execute the processing of step 110 and subsequent steps. The processing of steps 190 to 210 corresponds to the disconnection detection driving means described above.

Next, at step 180, when it is determined that the transmission signal from the main station 3 is not the disconnection detection start signal, that is, the transmission signal from the main station 3 is for the main station 3 to search for a disconnection point. If the signal is a disconnection confirmation signal output to the later-described, the process proceeds to step 220, and similarly to step 190, the timer 48 is started to start measuring the time from the present time.

Then, in the following step 230, it is determined whether or not the address for identifying the slave station included in the disconnection confirmation signal from the master station 3 is the preset address of the own station, and If it is the address, the process proceeds to step 240, the contact of the relay X2 (that is, the relay switch SWX2) is closed, and the terminating resistor RT1 is connected to the communication line 7. If it is not the address of the own station, the process proceeds to step 250 and the relay The contact of X2 (immediately, the relay switch SWX2) is opened to cut off the connection of the terminating resistor RT1 to the communication line 7.

Further, in the following step 260, the contact between the relay X1 (that is, the relay switch SWX1) is switched to the contact b side as in the case of the above step 200, thereby disconnecting the connection between the transceiver 40 and the communication line 7, and continuing. In step 270, it is judged whether the time measured by the timer 48 started in step 220 reaches 0.5 seconds or not, so that the connection between the transceiver 40 and the communication line 7 is cut off and the value of 0. Wait for 5 seconds. Then, when 0.5 seconds has elapsed, the process proceeds to step 110 again, and the processes of step 110 and the subsequent steps are executed. The processing of steps 220 to 270 corresponds to the disconnection confirmation driving means described above.

Next, FIG. 6 is a flowchart showing a communication process executed by the main station 3. As shown in the figure, when this process is started, first, in step 300, each part in the main station 3 is initialized, and then the process proceeds to step 310, in which the relay switch SWX of the relay X is connected to the contact a side. Then, the communication line 7 and the transceiver 10 are connected to each other by switching to, and the process proceeds to the subsequent step 320 to execute a normal communication process for performing data transmission with each of the master stations 5a to 5n.

Then, in the following step 330, it is judged whether or not the normal communication with all the slave stations is completed. If the normal communication with all the slave stations is not completed, step 320 is executed again, and the normal communication with all the slave stations is completed. When it is finished, the process proceeds to step 340, and the disconnection detection process is executed according to the following procedure.

That is, as shown in FIG. 7, in this disconnection detection process, first, at step 410, a disconnection detection start signal for disconnection detection is transmitted to the slave side. As described above, when the slave stations 5a to 5b receive the disconnection detection start signal, the processing of steps 190 to 210 disconnects the connection between the transceiver 40 and the communication line 7 for 0.5 seconds. After the disconnection detection start signal is transmitted in this step 410, only the terminating resistor RT1 provided in the terminating slave station 5n is connected to the communication line 7 until 0.5 seconds elapses. Become.

Then, in the subsequent step 420, the timer 18 is started to start measuring the time from the present time, and then in step 430, the contact of the relay X (that is, the relay switch SWX) is set to the contact b. By switching to the side, the communication line 7 is connected to the disconnection detection circuit 34, and in step 440, the detection signal indicating the presence or absence of the disconnection output from the disconnection detection circuit 34 is read. Further, in step 450, it is determined whether or not the time measured by the timer 18 started in step 420 has reached 0.5 seconds, and then waiting for 0.5 seconds after the disconnection detection start signal is transmitted, After 5 seconds, in step 460, the contact of the relay X (that is, the relay switch SWX) is switched to the contact a side, thereby connecting the communication line 7 to the transceiver 10 and ending the disconnection detection process.

In other words, in the disconnection detection process, the disconnection detection circuit 34 is operated by connecting the terminating resistor RT1 to the end of the communication line 7 so that the disconnection detection circuit 34 operates from the beginning to the end of the communication line 7. Detects whether there is a wire break between them. In this embodiment, the process of step 410 corresponds to the disconnection detection signal transmitting means described above, and the processes of steps 420 to 460 and the process of step 350 described later correspond to the disconnection determining means described above.

Returning to FIG. 6, when the disconnection detection process is executed in step 340 as described above, the process proceeds to step 350, and whether or not the disconnection of the communication line 7 is detected by the disconnection detection process. To judge. This determination is made based on the detection signal from the disconnection detection circuit 34 read at the time of executing the disconnection detection process. If the detection signal from the disconnection detection circuit 34 is at the low level, it is determined that the communication line 7 is not disconnected. Then, the process shifts to the normal communication process of step 320 as it is, and conversely, if the detection signal from the disconnection detection circuit 34 is at the high level, it is determined that the communication line 7 is disconnected, and the process proceeds to step 360. After executing the disconnection point search process in the following procedure, the process proceeds to the normal communication process of step 320.

As shown in FIG. 8, in the disconnection point search processing, first, at step 510, a disconnection confirmation signal including the slave station address is transmitted to the slave station side. The process of step 510 is a process for sequentially connecting the terminating resistor RT1 to each of the slave stations 5a to 5n, and the address of the slave station included in the disconnection confirmation signal is sequentially changed every time the step 510 is executed. It Then, in the following step 520, the timer 18 is started to start measuring the time from the present time.

In the next step 530, the communication line 7 is connected to the disconnection detection circuit 34 by switching the contact of the relay X (that is, the relay switch SW X) to the contact b side. In step 540, the disconnection detection is performed. A detection signal that is output from the circuit 34 and indicates whether or not there is a disconnection is read. Then, in the following step 550, it is judged whether or not the time measured by the timer 18 started in the above step 520 has reached 0.5 seconds, thereby waiting for 0.5 seconds after the disconnection detection start signal is transmitted and 0 After a lapse of 5 seconds, the communication line 7 is connected to the transceiver 10 by switching the contact of the relay X (that is, the relay switch SWX) to the contact a side at step 560.

Next, at step 570, it is determined whether or not the detection signal from the disconnection detection circuit 34 read at step 540 is at the low level, that is, whether the disconnection detection circuit 34 has detected the disconnection of the communication line 7. If it is determined that the detection signal is at the low level and the disconnection of the communication line 7 is not detected, the process directly proceeds to step 590. When the detection signal from the disconnection detection circuit 34 is at the high level and it is determined that the disconnection of the communication line 7 is detected, the process proceeds to step 580 and the address of the disconnection confirmation signal transmitted in step 510. Is registered as an incommunicable slave station, the process proceeds to step 590.

Then, in the following step 590, it is determined whether or not the processes of steps 510 to 580 have been performed for all slave stations. If not, the process proceeds to step 510 again. In step 510, in order to change the address of the disconnection confirmation signal to an address of the slave station different from that of the previously transmitted disconnection confirmation signal, the processes of steps 510 to 580 are repeatedly executed, and thus steps 510 to 510 are performed. The processing of step 580 will be executed for all slave stations.

If it is determined in step 590 that the processes of steps 510 to 580 have been executed for all slave stations, the process proceeds to step 600, and the address of the slave station registered as the incommunicable slave station in step 580. Is displayed on the display unit 28, and the disconnection point search processing is ended.

In the present embodiment, the processing of step 510 corresponds to the disconnection confirmation signal transmitting means described above, the processing of steps 520 to 580 corresponds to the disconnection confirmation registration means, and the processing of step 600 described above. It corresponds to the display means described above. As described above, in the multiplex communication device of the present embodiment, the disconnection detection process is performed every time the normal communication between the master station 3 and each of the slave stations 5a to 5n is completed, and the disconnection between the beginning and the end of the communication line 7 is performed. It is determined whether or not has occurred. If it is determined by this disconnection detection process that a disconnection has occurred from the beginning to the end of the communication line 7, the disconnection point search process is performed this time, and the slave stations to which the terminating resistor RT1 is connected are sequentially connected. By changing it, it is sequentially judged whether or not there is a disconnection for each communication line from the start end to each of the slave stations 5a to 5n. If a disconnection occurs, the slave station that cannot communicate due to the disconnection. Register the address of, and finally display the registered address.

Therefore, according to this embodiment, the user can detect the disconnection of the communication line from the display state of the address, and even if the slave stations 5a to 5n output incorrect information due to the disconnection, there is a problem. Can be dealt with without. In addition, since the slave station in which communication cannot be performed can be detected from the display state of the address, it is possible to quickly identify the disconnection point and quickly perform the recovery work for the disconnection. Further, in the present embodiment, the circuit connected to the communication line 7 is only changed when the disconnection is detected, and no special circuit is connected to the communication line 7 during the data transmission, so that the disconnection can be performed without adversely affecting the data transmission. Detection etc. can be performed.

[0047]

[Effect of the device]

 As described above, in the multiplex communication device of the present invention, each subordinate station is provided with a cutoff switch for cutting off the connection between the communication line and the communication circuit, and a termination switch for connecting a terminating resistor to the communication line. By driving the switch, the disconnection of the communication line from the master station to the terminal is judged.If the communication line from the master station to the terminal is broken, the communication line from the master station to each slave station is further broken. By detecting the disconnection sequentially, the slave stations that cannot communicate due to the disconnection are detected and the result is displayed.

Therefore, the user can detect the disconnection of the disconnection of the communication line from the display state, and even if incorrect information is output from each slave station due to the disconnection, it can be dealt with without any problem. In addition, since it is possible to detect a slave station in which communication is impossible from the displayed state, it is possible to quickly identify the disconnection point on the communication line and quickly perform the recovery work for the disconnection.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating a basic configuration of the present invention.

FIG. 2 is a block diagram showing a configuration of an entire multiplex communication device according to an embodiment.

FIG. 3 is an explanatory diagram illustrating a configuration of a main station according to an embodiment.

FIG. 4 is an explanatory diagram illustrating a configuration of each slave station according to the embodiment.

FIG. 5 is a flowchart showing a communication process executed by a slave station.

FIG. 6 is a flowchart showing a communication process executed by the master station.

FIG. 7 is a flowchart showing a disconnection detection process executed in step 340 of FIG.

8 is a flowchart showing a disconnection point search process executed in step 360 of FIG.

[Explanation of symbols]

3 ... Master station 5a to 5n ... Slave station 7 ... Communication line 1
2, 42 ... CPU 14, 44 ... ROM 16, 46 ... RAM 18,
48 ... Timer 10, 40 ... Transceiver 22, 52 ... Parallel I / O port 28 ... Display section 31, 32, 61, 62 ... Signal line
34 ... Disconnection detection circuit RT0, RT1 ... Termination resistance X, X1, X2 ... Relay SWX, SWX1, SWX2 ... Relay switch SW
1 ... Manual switch

Claims (1)

Claims for utility model registration: 1. A master station connected to the beginning of a communication line and a plurality of slave stations branch-connected to the communication line. In a multiplex communication device in which a communication line is multiplexed to transmit information between the master station and each of the plurality of slave stations, a terminating resistor is connected to each of the plurality of slave stations at a branch connection point of the slave station of the communication line. Terminating switch, a cutoff switch for cutting off the connection between the communication circuit in the slave station and the communication line, an operation unit for externally setting whether the slave station is the terminal slave station, and the operation unit. If the slave station is set to be the terminating slave station, the terminating switch is set to the terminating resistor connection side. Conversely, if the slave station is set to be the terminating slave station, the terminating switch is set to the terminating resistor non-connecting side. Drive and above When the disconnection detection signal transmitted from the main station is received by the communication circuit and the steady drive means for driving the disconnection switch to the line connection side, the disconnection detection for driving the disconnection switch to the line disconnection side for a predetermined time. When the disconnection confirmation signal including the identification information of the slave station transmitted from the master station by the driving means and the communication circuit is received, it is determined from the identification information whether the disconnection confirmation signal is for the slave station. If the disconnection confirmation signal is for the slave station,
The disconnection switch is driven to the line cut-off side and the termination switch is driven to the termination resistance connection side for a predetermined time. Conversely, if the disconnection confirmation signal is not for the slave station, the disconnection switch is disconnected for the predetermined time. Disconnection confirmation drive means for driving the disconnection detection signal to the main station, and disconnection confirmation driving means for driving the termination switch to the termination resistance cutoff side, and disconnection detection signal transmitting means for transmitting the disconnection detection signal to the main station. After the transmission, until the predetermined time elapses, the communication line is energized to determine the disconnection of the communication line, and the disconnection determining unit determines the disconnection of the communication line,
To each of the plurality of slave stations, a disconnection confirmation signal including the identification information, a disconnection confirmation signal transmitting unit that sequentially transmits at predetermined time intervals, and each time the disconnection confirmation signal transmission unit transmits the disconnection confirmation signal, After that, the communication line is energized to determine the disconnection of the communication line until a predetermined time elapses, and when the disconnection is determined, the identification information in the disconnection confirmation signal transmitted from the disconnection confirmation signal transmitting means is set to the incommunicable slave station. When the disconnection determination for all slave stations is completed by the operation of the disconnection confirmation registration means registered as, and the operation of the disconnection confirmation signal transmission means and the disconnection confirmation registration means, the display means for displaying the identification information registered as the communication-disabled slave station, A multiplex communication device characterized by being provided.