JPS6165553A - Power off detection of modulating/demodulating device - Google Patents

Abstract

PURPOSE:To decide a power source of any one of modulating/demodulating devices by transmitting a specific code to the 1st modulating/demodulating device through the 2nd channel for a certain period from said device whose power is turned off immediately after a power source is turned off and polling sequentially codes when the 1st modulating/demodulating device detects the specific code. CONSTITUTION:When the power source of a modulating/demodulating device 3 is turned off, a communications control part 63 of said device 3 transmits the code for informing that the power source is turned off with respect to a modulating/ demodulating device 1 through a communications circuit 5 for a certain period. On the other hand, after said device 1 transmits sure address code, it waits the response from an opposite party. At this time a communications control part 61 detects said code. After said part 61 terminates the detection of said code, it transmits sequentially address codes with respect to all address numbers stored in a memory 7, and checks whether or not the response from the opposite part can be found. Here, since the response with respect to the address code in the address number cannot be obtained, the communications control part 61 can judge that the power source of the modulating/ demodulating device 3 has been turned off.

Description

[Detailed description of the invention] [Industrial application field] The present invention connects one modem to a single modem through a communication line.

This invention relates to a power-off detection method for N modems connected in a multi-drop format.

[Conventional technology]

Conventionally, in a multidrop line, the following method has been adopted as a method for testing a modem using a second channel.

In other words, using a polling-based transmission control procedure, the first modem instructs N modems connected to the first modem via communication lines to which modem the data should be transferred. If the modulator/demodulator that receives the address code is the same as its own address, it returns information as to whether the modulator/demodulator is normal or abnormal. Using the above method, the first modem sequentially sends address codes to the second to Nth modem, receives responses, and sends address codes to all the modems connected on the communication line. I was aware of the situation.

[Problem that the invention seeks to solve]

However, in the conventional system, when the power of the selected modem is turned off or the address code sent from the first modem is If there is a problem with the communication line,
The first modem will no longer be able to obtain a response from the modem. In other words, if the first modem transmits an address code to the second to Nth modem but does not receive a response, it determines whether the power of the corresponding modem is turned off. The problem was that it was difficult to tell whether the communication line between the modem or the modem was bad.

The present invention aims to eliminate the above-mentioned drawbacks, and aims to provide a detection method that allows the first modem to determine that the power of the second to Nth modem is turned off.

[Means for solving problems]

The present invention provides a first modem and a plurality of devices connected to the first modem by a multi-drop communication line and configured to perform data communication with the first modem and the first modem. a data communication line comprising second to Nth modem and demodulators, from the first modem to the second modem;
In the modem device, the modem device sequentially polls the modem device using a second channel and tests each modem device based on a response signal from the modem device. The modem is set to the first mode immediately after the power to the modem is turned off.
means for transmitting a specific code through a second channel for a certain period of time to notify the first modem that the power has been turned off; a memory for storing the numbers of the modulation/demodulation devices that have responded from the second to Nth modulation/demodulation devices, and when the above specific code is detected;
The present invention is characterized by comprising means for sequentially polling all the modulation and demodulation devices stored in the memory and determining which modulation and demodulation device has been powered off.

[For production]

In the present invention, when the power of any one of the second to N-th modems connected to a multi-drop communication line is turned off, the power is turned off immediately after the power is turned off from the turned-off modem. A specific code is sent over a second channel for a certain period of time to notify the modem that the power has been turned off. The first modem determines which modem it modulates by sequentially polling when it detects the specific code according to the memory that stores the numbers of the modems that have responded to polling from the second to Nth modem. It can be determined whether the device is powered off.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

The figure is a block configuration diagram of a power-off detection device of a modulation/demodulation device according to an embodiment of the present invention. In the figure, a modem 1 is connected via a communication line 5 to a modem 2.3.4 in a multi-drop format.

A communication control section 6 for performing data transmission using a second channel is provided in the modem 1.2.3.4, and is connected to the communication line 5, respectively. The modem 811 device 1 includes a modem 2.3 connected to the communication line 5.
．． There is a memory 7 for storing the address number list of 4, and is connected to the communication control section 6.

Here, the feature of the present invention is the power-off detection portion surrounded by a dashed line. Now, modem 2.3.4
are provided with switches 8□-84 for setting the address number of the modulator/demodulator 2.3.4, and are connected to communication control units 6□-64, respectively. Here, it is assumed that the address number of the modulation/demodulation device 2 is set to 2, the address number of the modulation/demodulation device 3 is set to 3, and the address number of the modulation/demodulation device 4 is set to 4.

The operation of the power-off detection device of the modulation/demodulation device having such a configuration will be explained.

In the figure, first, the communication control unit 61 of the modem 1 changes the address code of the address number 2 to the address number 4 in order to check the number of modems connected to the communication channel vA5.
Polling starts sequentially up to the address code of . When this address code is input to the communication control units 6° to 6 of the modem devices 2 to 4 via the communication line 5, the communication control units 6□ to
64 is set by the switches 82 to 84 of the modulators 2 to 4, and compares whether the received address number and the received address code number are the same, and if they are the same, the communication control unit 62
.about.64 transmits a response via the communication line 5. When the communication control unit 61 receives this response, the modulation/demodulation device 1 stores the address number of the modulation/demodulation device that responded in the memory 7, and does not store the number in the memory 7 unless there is a response to the transmitted address code.

Through the above operations, a list of numbers of modems connected to the communication line 5 is created in the memory 7. According to this number list, modem 1 sequentially transmits address codes and receives responses from modems 2 to 4.

Here, the features of the present invention will be explained.

Now, when the power to the modulator/demodulator 3 is turned off, the communication control section 63 of the modulator/demodulator 3 transmits a code for a certain period of time via the communication line 5 to notify the modulator/demodulator 1 that the power is turned off. On the other hand, after transmitting a certain address code, the modulation/demodulation device 1 is waiting for a response from the other party, and at this time, the communication control section 61 detects the above code. After the communication control unit 6° no longer detects the above code, it sequentially sends address codes to all address numbers stored in the memory 7, and checks whether there is a response from the other party. Here, address codes with address numbers 2 to 4 are sent out, but no response is received to the address code with address number 3 because the power to the modulation/demodulation device 3 is turned off. Thereby, the communication control unit 61 can determine that the power to the modem device 3 has been turned off. Further, the communication control unit 6. Since no response was obtained from the modem 3, the list of address number 3 is deleted from the memory 7, and no address code is sent to the modem 3 from the next polling. However, in consideration of the case where the power of the modem device 3 is turned on later, the modem device 1
The communication system '<I11 section 61 periodically transmits the address code of address number 3 at a cycle longer than the polling of the address number list. Here, when the power of the modem device 3 is turned on and the modem device 1 receives a response to the address code of address number 3, the communication control unit 6I sends a list of the address number 3 to the memory 7. Add.

By the above method, the modem 1 can detect which of the modems 2 to 4 connected to the communication line 5 has been powered off. Furthermore, if a failure occurs in the communication line 5 connecting the modem 1 and the modems 2 to 4, there will be no response to the transmission of the address code from the modem 1. It can be determined that a failure has occurred in the communication line 5 between the modem and the modem that did not respond. In this case, the communication control unit 61 of the modulation/demodulation device 1 deletes the address number list for which no response was received from the memory 7, in the same way as when the power is turned off, and for that address number,
Address number list.

Address codes are sent at a longer cycle than polling. If the communication line is restored and a response is received from the modulator/demodulator, the communication controller 6° adds a list of the address numbers to the memory 7.

In addition, although the above description has shown an example in which three modem devices are connected on a communication line in a multi-point manner, in the present invention, the number of modem devices N may be 2 or more and any number.

〔Effect of the invention〕

As explained above, the present invention is capable of controlling the modem when the power of the modem connected to the communication line is cut off.
It has an excellent effect of being able to distinguish between cases where a failure occurs in the communication line. Therefore, there is an advantage that abnormalities in the communication line can be quickly detected.

[Brief explanation of drawings]

The figure is a block configuration diagram of a power-off detection device of a modulation/demodulation device according to an embodiment of the present invention. 1 to 4...Modulator/demodulator, 5...Communication line, 6...
Communication control unit, 7... memory, 8... switch.

Claims (1)

[Claims] (1) A first modem and a plurality of second modems connected to the first modem by a multi-drop communication line and configured to perform data communication with the first modem. to N-th modem, the first modem to the second to N-th modem are polled sequentially using a second channel, and the second to N-th modem In a modem that tests each modem using a response signal from the modem, the second to Nth modem may test the first modem immediately after the power of the modem is turned off. said first modem includes means for transmitting a specific code through a second channel for a period of time to notify that the power has been turned off; When the above specific code is detected, all the modems stored in the memory are sequentially polled to determine which modem it is. 1. A power-off detection method for a modulation/demodulation device, comprising: means for determining whether the device is powered off.