JPH04103044U - Communication device - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a communication device that can prevent contention by forcibly stopping the transmission state if the transmission state continues beyond a predetermined period for some reason. [Configuration] The network is installed in the hotel HT, and the communication equipment at the front desk and each floor (main station 5 and slave stations 7a to 7
n) is branch-connected to the communication line 3, and the main station 5 and slave station 7a
~7n are each equipped with a communication control section 20. In the communication control unit 20, due to some abnormality, the SIO 20a
is fixed in the transmitting state and the transmitting state is prolonged, the limit signal SLM output from the monitor circuit 20c at the trigger timing immediately before the occurrence of an abnormality is interrupted during the period of the pulse width T, and the transmitting/receiving switching circuit 20d is The transmission/reception switching signal STR is forcibly changed to Low. Therefore, in the transceiver 20, the driver DR is stopped and the receiver RC is started.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention is a communication network that constitutes one station of a multiplex transmission network that transmits information by multiplexing communication lines. related to communication equipment.

0002

[Conventional technology]

Conventionally, each of multiple communication devices is branch-connected to a communication line, and communication lines are multiplexed. A multiplex communication system that transmits data by converting the data into two is known. For example, inside a building A local area network installed in a building with all communications on the ground floor of a building. The communication device to be controlled (hereinafter referred to as the main station) has one communication device (hereinafter referred to as the main station) on each floor. A slave station (hereinafter referred to as "slave station") is installed, and the master station is connected to the start end of the communication line, and other communication lines are Each of the communication devices is branch-connected to the communication line (hereinafter, this connection form is referred to as multi-drive). (referred to as a 3-bit flop), both serially and serially via time-division multiplexed communication lines. A multiplex communication system that performs mutual communication is known.

0003 In this type of multiplex communication system, the master station polls (queries the slave stations). to prompt data transmission)/Selecting (inquiry slave stations and request data transmission) Generally, the entire communication is controlled by a system that prompts the reception of data. i.e. , the master station queries each of the slave stations in a predetermined order, and the slave stations ask whether the master station By responding and transmitting only when an inquiry is made to your own station, This prevents conflicts from occurring.

0004 Furthermore, the communication devices constituting the multiplex communication system, for example, transmit TTL level data. a driver that converts communication data into a signal of a predetermined electrical standard and sends it to a communication line; A receiver that receives signals from a communication line and converts them into TTL level received data. , generates transmitted data, stores received data, and also functions as a driver or receiver. It is equipped with a communication controller that outputs transmission or reception commands to the server. this A microcomputer is connected to the communication controller to provide more advanced communication control. Sometimes God is doing it. In addition, when the communication device is powered down, the driver By opening the output terminal of the driver and putting it in a high impedance state, This is done so as not to interfere with the transmission operations of other slave stations.

[0005] In this way, the above communication system is configured so that contention does not occur. This eliminates the need to determine transmission priorities and content When a collision occurs, it is decided whether to give priority to the own station or the colliding partner station (arbitrator) It is not necessary to provide a circuit for communication), and the communication procedure and circuit configuration of the communication device are simple. In addition, multi-drop connections are easy to wire and install. Because of these advantages, it has been widely adopted.

[0006]

[Problem that the idea aims to solve]

However, in the case of a power failure, the above-mentioned communication equipment cannot maintain content in the multiplex communication system. Although communication controller failure and microcomputer Due to the data going out of control, the communication controller is stuck issuing a transmission command. When the driver continues transmitting, the communication line is occupied by the communication device. When the other station transmits data, contention always occurs and communication becomes impossible. The problem arises that

[0007] Also, if the driver is left in the transmitting state for a long time, it may overheat and cause damage to the internal circuit. Problems also arise, such as failure and destruction. Therefore, in this invention, if the transmission status continues beyond a predetermined period for some reason, the A communication device that can prevent contention by stopping the transmission state automatically. It is about providing.

[0008]

[Means to solve the problem]

The gist of this idea is: A communication device that constitutes one station in a multiplex transmission network that transmits information by multiplexing communication lines. There it is, Generating transmission information and transmitting the transmission information for a period corresponding to the amount of the transmission information. Transmission information generating means for generating a transmission command signal to command; The transmission signal corresponding to the transmission information generated by the transmission information generation means is transmitted to the communication circuit. a transmission means for outputting to the line; Receive a signal from the communication line and reproduce received information corresponding to the received signal. receiving means; When a transmission command signal is input from the transmission information generating means, the transmission means is activated. and stops the receiving means, and when the transmission command signal is interrupted, the transmitting means a transmitting/receiving switching means for stopping the transmitting means and activating the receiving means; If the transmission information generating means continues to generate a transmission command signal for a predetermined period of time, , forcing the transmission/reception switching means to stop the transmission means and switch the transmission/reception. forced switching means for activating the means; A communication device comprising:

[0009]

[Effect]

According to the communication device of the present invention configured as described above, the transmission information generating means In addition to generating transmission information, it also generates a transmission command signal for a period corresponding to the amount of transmission information. do. The transmission/reception switching means starts the transmission means when the transmission command signal is input. and at the same time stop the receiving means. Then, the transmission means corresponds to the transmitted information. Outputs the transmission signal to the communication line. The transmission command signal from the transmission information generation means is interrupted. Then, the transmission/reception switching means stops the transmitting means and starts the receiving means. let Then, the receiving means receives the signal from the communication line and responds to the received signal. Play the received information.

0010 At this point, an abnormality occurs in the transmission information generation means for some reason, and the transmission command signal is not generated. Suppose that it continues to exist and continues for a predetermined period of time. Then, the forced switching means The communication switching means is forced to stop the transmitting means and start the receiving means.

[0011]

【Example】 Embodiments of the present invention will be described below with reference to the drawings. First, Figure 1 is a block diagram showing the configuration of a communication device to which the present invention is applied, and Figure 2 is a block diagram showing the configuration of a communication device to which the present invention is applied. FIG. 1 is a block diagram showing the overall configuration of the Calarea network.

0012 As shown in Figure 2, one system of communication line 3 wired inside the hotel HT has one Communication equipment (hereinafter referred to as the main station) 5 installed at the front desk on each floor and each floor of the hotel HT. Communication devices (hereinafter referred to as slave stations) 7a to 7n arranged one by one are multi-drop local area networks (hereinafter referred to simply as networks). A network (called a network) has been constructed. In this network, the main station 5 The communication line 3 is multiplexed in a time-division manner under communication control, and the main station 5 and slave stations 7a to 7a are multiplexed. 7n, bidirectional data communication is performed using serial bit signals.

[0013] The communication line 3 is composed of, for example, twisted pair wires 3a and 3b, and the starting end LS is connected to the main station 5. Note that the communication line 3 and serial bit signals are, for example, The one that complies with the electrical standards set by the Association of Electrical Engineers (CCITT) is used.

[0014] The master station 5 sends various data to the slave stations 7a to 7 using a polling/selecting method. and receives transmission data from slave stations 7a to 7n. Also, on main station 5 is equipped with a well-known microcomputer (not shown), and processes the creation of transmission data, It is configured to perform various processes on received data and various processes associated with sending and receiving data. There is. Furthermore, an input device and a display device (both not shown) are provided, and each You can input various data related to the usage status of the guest room, and also It is configured so that transmission data etc. from 7a to 7n can be displayed.

[0015] When there is polling or selection from the master station 5, the slave stations 7a to 7n Sends various data to the main station 5 in response to the response request of receive. Further, the slave stations 7a to 7n are also equipped with microcomputers (not shown). Creation process of transmitted data, various processes of received data, various processes associated with sending/receiving execution It is configured to do the following. In addition, input devices and display devices (both shown in the figure) ), and various data regarding the usage status of each guest room on the relevant floor can be entered. Both are configured to display input data, transmission data from the main station 5, etc. There is.

[0016] As shown in FIG. 1, each of the communication devices (main station 5 and slave stations 7a to 7n) includes: A communication control section 20 is provided. This communication control unit 20 controls serial communication. SIO20a connected to communication line 3, and between communication line 3 and SIO20a transceiver 20b that converts the signal level with A monitor circuit 20c that monitors TXD and a transmission request signal (L ow active) The transceiver 20b is placed in transmitting or receiving operation based on RTS. The transmission/reception switching circuit 20d is the main part.

[0017] In this embodiment, the SIO 20a serves as the transmission information generating means, and the monitor circuit 20c serves as the transmission information generating means. This corresponds to forced switching means. SIO20a is connected to a microcomputer (not shown) by bus BS, When there is a transmission command from the microcomputer, the transmission request signal RTS (Low active At the same time, it outputs the signal as a transmittable signal CTS (Low active). Entering this will set it to transmit mode. After a short adjustment time TP, the microphone The parallel transmission data transferred from the microcomputer is converted into serial bit pulses. The communication circuit is converted into transmission data TXD composed of transceiver 20b. Send to line 3. For example, in the case of start-stop serial communication, the transmission data TXD ( 1 character) is the first start bit (1 bit, Low), 1 character data bits (8 bits, high or low), last stop bit The bit pulse configuration is (1 bit, High). Also SIO20 a is set to go into receive mode when there is a receive command from the microcomputer. When the serial receive data RXD is input, the parallel receive data is Convert and transfer to microcomputer. Reception data RXD is also the above transmission data It has a bit/pulse configuration similar to TXD.

[0018] Note that the communication speed (baud rate) is determined by the clock signal φ from the clock circuit CLK. Element timings for transmission and reception generated based on TXC and RX C. In addition, SIO20a is well-known, and even if Bazilog's Z80SIO and NEC's μPD7201A are well known. Therefore, details of its configuration and operation will be omitted.

[0019] The transceiver 20b converts the transmission data TXD from the SIO 20a into a predetermined electrical A driver DR converts the signal into a standard signal and sends it to the communication line 3, and a signal from the communication line 3. It includes a receiver RC that converts the signal into the electrical specifications of the SIO 20a. Tiger In the receiver 20b, the transmission/reception switching signal STR from the transmission/reception switching circuit 20d (High active, details will be explained later) is input, the driver DR starts operating. When the receiver RC stops and the transmission/reception switching signal STR is interrupted (Low) , the receiver RC is configured to operate when the driver DR stops. .

[0020] Driver DR is a differential amplifier, and transmits data TXD from SIO20a. (TTL level bit pulse) to a balanced output signal of a predetermined standard (positive and negative swing) It converts it into a bit pulse (to be transmitted) and sends it to the communication line 3. Also, driver D R has a three-state circuit configuration, and when the power is cut off, the output The end is cut off from the internal circuit and becomes a high impedance state, preventing other stations from transmitting. It is configured so that it does not interfere.

[0021] The receiver RC is also a differential amplifier, and receives the balanced input signal from the communication line 3. It is converted into a fixed electrical specification (TTL level) and output to the SIO 20a. Further, connection terminals Ta and Tb between the communication line 3 and the transceiver 20b are connected to transceivers. impedance matching between the server 20b and the communication line 3 to reduce signal attenuation due to reflection. A terminating resistor RT is provided to reduce the voltage.

[0022] The monitor circuit 20c monitors the timing at which the transmission data TXD is input from the SIO 20a. The circuit revolves around the multivibrator MB, which outputs one-shot pulses when It is a road. That is, in the multivibrator MB, the input transmission data TXD The first trigger (hereinafter referred to as the first trigger) occurs when the logic level of ), which limits the maximum period of the driver DR's transmission state. SLM is output. Additionally, the multivibrator MB is configured to be retriggerable. The transmission data TXD is input again while the limit signal SLM is being output, and its logic is When the level becomes Low, the limit signal SLM is output again at that point. The mit signal SLM is extended beyond a predetermined pulse width T.

[0023] Note that the pulse width T of the limit signal (High active) SLM is determined by the external resistor. The transmission mode of SIO20a is determined by the size of Rext and the capacitance of capacitor Cext. The period is set to be sufficiently longer than the period of the code. Pulse according to instructions by microcomputer The transmission mode is not continued beyond the period of width T, and such a transmission continuation state The main station 5 and slave station 7 may This cannot happen unless some kind of abnormality occurs in a to 7n. This has been confirmed by simulation.

[0024] The transmission/reception switching circuit 20d consists of an inverter NOT and an AND element AND. . The transmission/reception switching circuit 20d inverts the transmission request signal RTS from the SIO 20a. Sending/receiving the AND of the signal SRTS and the limit signal SLM from the monitor circuit 20d A signal switching signal STR is output to the transceiver 20b. In other words, the limit signal During the period when SLM is High, the transmission/reception switching signal STR is a signal corresponding to the inverted signal SRTS. level, and is always Low while the limit signal SLM is Low.

[0025] As shown in FIG. 3, between the main station 5 and the slave stations 7a to 7n configured as described above, Communication is performed according to a predetermined procedure. For example, as shown in column (A) of the figure, when polling, first the main station 5 is a character S representing a synchronization signal to each of slave stations 7a to 7n in a predetermined order. YN, address UAD of destination slave station 7a to 7n, character representing inquiry Send a response request message consisting of ENQ. In response to this transmission, slave stations 7a~ 7n is a guest room on the floor where STX/substations 7a to 7n, which indicate the start of a message, are installed. The guest room number RAD/message (one transmission block) whose data should be changed. In response, a reply message consisting of data ETB representing the termination of h) is sent.

[0026] When there is a response from the slave stations 7a to 7n, the master station 5 sends a character indicating an affirmative response. It sends an acknowledgment message consisting of data ACK and RAD, and in response to this transmission, Stations 7a to 7n transmit various data DAT and text regarding STX and the status of the guest room. respond by sending a text message consisting of ETX indicating the termination of.

[0027] Then, the main station 5 sends an acknowledgment message consisting of ACK and RAD and acknowledges the data. Confirm data reception. Upon receiving this message, the slave stations 7a to 7n terminate the transmission. The character EOT indicating completion is transmitted and communication is terminated.

[0028] As shown in column (B) of the figure, when selecting, main station 5 = transmission (S YN・RAD・ENQ)→Slave stations 7a to 7n=Reply (ACK・RAD)→Main station 5= Transmission (STX/data to be transmitted to slave stations 7a to 7n DAT/RAD/ETX) → Slave stations 7a to 7n = reply (ACK/RAD) → master station 5 = end of communication (EOT). Communication is performed according to the procedure specified.

[0029] Next, regarding the operation of the communication control section 20, the case of the slave stations 7a to 7n will be explained as an example. This will be explained with reference to the timing chart of No. 4. As shown in the figure, when the slave stations 7a to 7n receive polling from the master station 5, the microphone The SIO20a enters the transmission mode according to the command from the computer and sends the transmission request signal RTS. Output. After a short adjustment time TP, a reply message (STX/RAD/ET B) as transmission data TXD and transceiver 20b and multivibrator MB. Output to. Then, the first trigger is applied to the multivibrator MB, and the limit is applied. A signal SLM (High) is output to the transmission/reception switching circuit 20d. Then, sending and receiving The switching circuit 20d sends the transmission/reception switching signal STR (High) to the transceiver 20. The driver DR enters the operating state and sends the transmission data TXD as a balanced output. It is converted into a signal and sent to the communication line 3. Transmission request signal RTS from SIO20a When the transmission/reception switching signal STR is interrupted, the transmission/reception switching signal STR is also interrupted, and as a result, the driver DR is stopped. At the same time, receiver RC enters the operating state. Next, send a text message (S TX/DAT/ETX) transmission → reception of acknowledgment from main station 5 → communication termination ( EOT) transmission and two-way communication will continue.

[0030] In the process of communication progressing normally, multiband transmission occurs during each transmission. Since the ibrator MB is retriggered, the limit signal SLM continues. communication The final trigger is activated when the termination (EOT) is sent, and the pattern starts from that point (t1). After the period of pulse width T has elapsed, the limit signal SLM becomes Low. That is, above Throughout the communication process, the limit signal SLM is held at High level, and the transmission/reception The switching signal STR is connected to switching between the transmission mode and reception mode of SIO20a. and switches between active (High) and non-active (Low).

[0031] If there is a selection from the main station 5 after a certain period of time, it will be the same as polling. A response message (ACK/RAD) is sent in the same way. Next, a text from main station 5 When receiving a message, sends an acknowledgment message (ACK/RAD) . Here, the microcomputer goes out of control while sending the acknowledgment message. An abnormality such as a failure or failure of SIO20a occurs and SIO20a is fixed in the transmitting state. Suppose that

[0032] In this case, the SIO 20a continues to output the transmission request signal RTS and transmit data. TXD becomes idle (High). Therefore, driver DR uses normal transmission. Continue the sending operation beyond the period. However, with the multivibrator MB, the above Since no trigger will be activated after an error occurs, the previous trigger will be the final one. The limit signal SLM output from the time point (tx) is after the predetermined period T has elapsed. becomes Low. As a result, the transmit/receive switching signal STR is interrupted (Low) and the When the receiver DR stops, the receiver RC starts.

[0033] As explained above, in this embodiment, the communication devices (main station 5 and slave stations 7a to 7n) Some kind of abnormality occurs during transmission, and SIO20a is fixed in the transmission state. If the transmission status continues, the output will occur at the trigger timing immediately before the error occurs. Transmission/reception switching occurs when the limit signal SLM is interrupted at the completion of the period of pulse width T. The signal STR is forced to go low, causing the driver DR to stop and the receiver RC activates it. Therefore, any of the communication devices (master station 5 and slave stations 7a to 7n) Even in the event of a failure, contention does not occur in the network and data between other stations is maintained. data communication is ensured.

[0034] Also, since the driver DR is not left in operation for a long time, it may overheat. Therefore, the service life of the driver DR is extended. In addition, in this embodiment, the transmission data TXD of SIO20a is transmitted by a multivibrator. In addition to the MB trigger input, the SIO20a transmission request signal RTS is also used as a trigger input. It may also be used as input. Or monitor program execution on a microcomputer A monitoring circuit (so-called watchdog timer) is installed to utilize the monitoring signal. may be used.

[0035] In addition, although this embodiment has been explained using the case of start-stop type serial communication as an example, In addition, similar effects can be achieved with synchronous serial communication.

[0036]

[Effect of the idea]

As described in detail above, according to the present invention, when a communication device transmits a signal due to some cause. If the sending state continues for a specified period of time, the sending state will be stopped and the receiving state will be forced. Since the configuration is configured to switch automatically, contention in the communication network can be prevented. information transmission between other stations in the communication network can be ensured.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a communication device according to an embodiment.

FIG. 2 is a block diagram representing a local area network installed within a hotel.

FIG. 3 is an explanatory diagram of a communication procedure in a local area network.

FIG. 4 is a timing chart showing the operation of a communication control unit.

[Explanation of symbols]

3...Communication line LS...Starting end 5...Main station 7a-7n...Slave station 20...Communication control unit 20a...Serial communication controller 20b...Transceiver 20c...Monitor circuit 20d...
Transmission/reception switching circuit DR...Driver RC...Receiver MB...Multi-vibrator

Claims (1)

[Scope of utility model registration request] Claim 1: A communication device constituting one station of a multiplex transmission network that transmits information by multiplexing communication lines, the device generating transmission information and transmitting the transmission information for a period corresponding to the amount of the transmission information. a transmission information generating means for generating a transmission command signal for commanding the transmission information, a transmission means for outputting a transmission signal corresponding to the transmission information generated by the transmission information generation means to the communication line, and receiving a signal from the communication line. and when a transmission command signal is input from the transmission information generating means, the transmission means is activated and the reception means is stopped, and the transmission command signal is activated. A transmission/reception switching means that stops the transmission means and starts the reception means when the transmission is interrupted, and when the transmission information generation means continues to generate a transmission command signal for a predetermined period of time, the transmission/reception switching means is forced to transmit the transmission command signal. A communication device comprising forced switching means for stopping the transmitting means and starting the receiving means.