JP3619583B2 - Data transmission system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
According to the present invention, a transmission right is sequentially assigned to each of a plurality of data transmission apparatuses, or a master station transmits a transmission request signal to any one of a plurality of slave stations and sequentially transmits them. The present invention relates to a data transmission system that transmits and receives data by assigning rights.
[0002]
[Prior art]
An example of using such a data transmission system is a control center. In the control center, a master station, which is a data transmission device and a master station, has a transmission memory, and a programmable controller is connected to the transmission memory so that writing and reading are possible. When the programmable controller is a data transmission device in the control center and wants to obtain data from a remote station as a slave station, the programmable controller writes the data in a predetermined area of the transmission memory, thereby the remote station to the master station. Talker address (transmission request signal) is output on the transmission line.
[0003]
Then, in each remote station, if it is determined that the talker address is the address assigned to itself, the data of the motor protection relay owned by itself will be the listener address assigned to the master station ( The master station receives this data and writes it in the reception area of the programmable controller of the transmission memory. Thus, the programmable controller reads this data from the transmission memory and performs processing based on the data.
[0004]
In such a data transmission system, in order to cope with an abnormality such as a short circuit or disconnection of the transmission line, the transmission line is duplicated, and when an abnormality occurs, the system is operated by switching to the other transmission line. There is something to do. In this case, in the conventional data transmission system, an abnormality detection circuit is provided in the data transmission apparatus, and the transmission line is switched by detecting an abnormality of the transmission line in a circuit.
[0005]
[Problems to be solved by the invention]
However, in such a conventional data transmission system, it is necessary to provide an extra buffer circuit for the interface in the data transmission device by duplicating the transmission path, and further provide an abnormality detection circuit. There was a problem that the size of the.
SUMMARY OF THE INVENTION The present invention solves the above problems, and an object thereof is to provide a data transmission system that can detect an abnormality occurring in a transmission line without providing an abnormality detection circuit and can switch to a normal transmission line. It is in.
[0007]
[Means for Solving the Problems]
To achieve the above objective,Claim1The described data transmission system performs transmission / reception of data by sequentially assigning a transmission right to each of a plurality of data transmission apparatuses, and connects a plurality of data transmission apparatuses and selectively uses one of them. A plurality of data transmission devices measure a no-request time during which no transmission or reception request signal is transmitted from the currently used transmission path to the local station. When the request time exceeds a predetermined time, a control means is provided for controlling the transmission path to be switched to the other one by determining that the transmission path is abnormal.
[0008]
Claim2The data transmission system described isThe data transmission device as the master station transmits a transmission request signal to any one of the data transmission devices as the slave stations.Assign sequential transmission rightsHaveIn those that send and receive data byWith a master station and multiple slave stationsAnd has a duplexed transmission line that selectively uses one or the other,The slave station measures the non-request time during which no transmission or reception request signal is transmitted to the local station, and the no-request time is a predetermined time.And a control means for controlling to switch the currently used transmission line to the other when it is determined that the transmission line is abnormal.
[0009]
Claim3In the described data transmission system, the data transmission device as a master station transmits and receives data by transmitting a transmission request signal to any one of the data transmission devices as a plurality of slave stations and sequentially assigning a transmission right. In what is to be performed, a master station and a plurality of slave stations are connected, and a duplex transmission path is used in which one of them is selectively used. Measure the no-signal time, and if the no-signal time exceeds a predetermined time, determine that the transmission line is abnormal and switch the currently used transmission line to the otherAnd send an abnormal signal to the master station.It is characterized by comprising control means for controlling as described above.
[0011]
Claim4In the described data transmission system, the data transmission device as a master station transmits and receives data by transmitting a transmission request signal to any one of the data transmission devices as a plurality of slave stations and sequentially assigning a transmission right. In what is to be performed, a master station and multiple slave stations are connected, and a duplex transmission path is used in which one of them is selectively used. The slave station determines an abnormality from the check code attached to the received data. If this number of determinations exceeds a predetermined number of times, it is determined that the transmission line is abnormal, and the currently used transmission line is switched to the other.And send an abnormal signal to the master station.It is characterized by comprising control means for controlling as described above.
[0012]
Claim 2In this case, when it is determined that the transmission path is abnormal, the control means may transmit an abnormal signal to the master station.5).
Also,In the above case,When it is determined that the transmission line is abnormal, the control unit preferably causes the display unit to display the occurrence of the transmission line abnormality.6).
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. In FIG. 1 schematically showing the entire configuration, two master stations (data transmission apparatuses) 1a and 1b serving as master stations are connected to a plurality of remote stations (data transmission apparatuses) 2 serving as slave stations via transmission paths 3a and 3b. It is connected and is connected to a programmable controller 4 for controlling the entire apparatus.
[0014]
The master stations 1 a and 1 b relay data transmission / reception performed between the programmable controller 4 and the remote station 2. Note that the transmission paths 3a and 3b perform the same data transmission from the programmable controller 4 via the master stations 1a and 1b, but are alternatively selected and used by the remote station 2.
[0015]
The control center 5 is configured by installing a plurality of control units 5a formed by integrating the remote station 2, the motor protection relay 6, the electromagnetic contactor 7 and the like in a cubicle (not shown). The remote station 2 receives operation data sent from the master station 1a or 1b via the transmission line 3a or 3b and sends the operation data to the motor protection relay 6. The motor protection relay 6 opens and closes the main circuit 9 of the induction motor 8 which is a motor by opening and closing the main contact 7a of the electromagnetic contactor 7 according to the given operation data, and performs stop control of the induction motor 8.
[0016]
Further, the motor protection relay 6 transmits state data such as a main circuit current value of the induction motor 8 and power supply abnormal state or failure state data to the remote station 2. Then, the remote station 2 transmits the various data given from the motor protection relay 6 to the master station 1a or 1b via the transmission path 3a or 3b.
[0017]
The programmable controller 4 controls the entire system by controlling, protecting and monitoring the induction motor 8 by exchanging data with a predetermined remote station 2 via the master station 1a or 1b. Yes. The master stations 1a and 1b are provided with indicators 1aa and 1ba as display means.
[0018]
FIG. 2 shows the electrical configuration of the remote station 2. The transmission lines 3a and 3b are connected to input / output terminals 10A and 10B of a driver / receiver circuit (hereinafter referred to as D / R circuit) 10, respectively. The input / output terminal 10A is connected to the input terminal of the input buffer 10Ia and the output terminal of the output buffer 10Oa inside the D / R circuit 10. Similarly, the input / output terminal 10B is connected to the input terminal of the input buffer 10Ib and the output terminal of the output buffer 10Ob.
[0019]
The output terminal of the input buffer 10Ia and the input terminal of the output buffer 10Oa are connected to the input / output terminal 10A ′ of the D / R circuit 10, and the output terminal of the input buffer 10Ib and the input terminal of the output buffer 10Ob are D / R circuit 10 is connected to input / output terminal 10B ′.
[0020]
The input / output terminals 10A ′ and 10B ′ are respectively connected to the terminals 11A and 11B of the connection switching circuit 11, and the terminal 11C of the connection switching circuit 11 is input to a microcomputer (hereinafter referred to as a microcomputer) 12 serving as control means. Connected to the output terminal.
[0021]
The output terminal of the microcomputer 12 is connected to the control terminal DIR of the D / R circuit 10, and the microcomputer 12 gives a high or low level control signal to the D / R circuit 10, and the input buffers 10 Ia and 10 Ib or the output The buffers 10Oa and 10Ob are enabled, and the setting of the D / R circuit 10 is switched to the driver / receiver.
[0022]
The output terminal of the microcomputer 12 is connected to the control terminal A / B of the connection switching circuit 11. The microcomputer 12 gives a high or low level control signal to the connection switching circuit 11, and The connection of the terminal 11C is switched to the terminal 11A or the terminal 11B, that is, the transmission path 3a or 3b. In addition, the microcomputer 12 includes a timer 12a that counts up with a clock signal having a predetermined period and can read out the timer value. The above constitutes the data transmission system 13.
[0023]
Next, the operation of this embodiment will be described. Here, the microcomputer 12 gives a high level control signal to the connection switching circuit 11, connects the input / output terminals to the transmission line 3a, and gives a high level control signal to the D / R circuit 10. Assume that the input buffers 10Ia and 10Ib are enabled and the D / R circuit 10 is set as a receiver.
[0024]
In FIG. 3 which shows the flowchart of the control contents of the microcomputer 12, the microcomputer 12 starts the timer 12a in the “timer start” processing step R1 and starts counting time, and determines “There is address transmission?”. The process proceeds to step R2. In the determination step R2, the microcomputer 12 determines whether any address is transmitted from the master station 1a onto the transmission path 3a. If it is determined that there is no address transmission and “NO” in the determination step S2, the process proceeds to a determination step R3 of “timer value> constant value?”.
[0025]
In the determination step S3, the microcomputer 12 reads the timer value of the timer 12a and determines whether or not the no-signal time (time during which no address is transmitted) indicated by the timer value exceeds a predetermined value, that is, It is determined whether or not a predetermined time has elapsed. If "NO" is determined in the determination step R3, the process proceeds to step R2, and the microcomputer 12 determines whether an address is transmitted again.
[0026]
In the determination step R2, if the address is transmitted and it is determined “YES”, the process proceeds to the “timer clear” processing step R6 to clear the timer 12a and stop the time measurement. Then, the process proceeds to the next determination step R7 of “your address?”. In determination step R7, the microcomputer 12 determines whether or not the address received in step R2 is a talker or listener address (transmission or reception request signal) assigned to itself. In the determination step R7, if the transmitted address is not assigned to itself and the microcomputer 12 determines “NO”, the process proceeds to step R1 to start counting the no-signal time again.
[0027]
If it is determined in the determination step R7 that the transmitted address is assigned to itself and the microcomputer 12 determines “YES”, the process proceeds to the processing step R8 of “transmission / reception processing”. In processing step R8, the microcomputer 12 performs transmission or reception processing from the remote station 2 to the master station 1 in response to reception of a talker or listener address. When performing transmission processing, a low-level control signal is given to the D / R circuit 10, the output buffers 10Oa and 10Ob are enabled, and the D / R circuit 10 is set as a driver. Then, the process proceeds to step R1.
[0028]
Here, it is assumed that a disconnection or a short circuit accident has occurred in the transmission line 3a. Then, since the address is not transmitted from the master station 1a, the microcomputer 12 repeats the loop of steps R2 and R3. Then, the count value of the timer 12a gradually increases, and when it exceeds a predetermined constant value, “YES” is determined in Step R3, and the process proceeds to the processing step R4 of “Transmission path switching”.
[0029]
In the processing step R4, the microcomputer 12 gives a low-level control signal to the connection switching circuit 11, and switches the input / output terminal to the transmission line 3b for connection. Then, the process proceeds to processing step R5 of “abnormal processing”. In processing step R5, when the talker address assigned to the microcomputer 12 is transmitted from the master station 1b, the microcomputer 12 transmits data indicating that an abnormality has occurred in the transmission path 3a together with the listener address for the master station 1b. . Then, the process proceeds to step R1.
[0030]
Thus, when the master station 1b receives the data together with the listener address, the master station 1b informs that an abnormality has occurred in the transmission line 3a, for example, by turning on a lamp of the display 1ba. Then, when the process proceeds to the “timer clear” processing step R9 to clear the timer 12a, the process proceeds to step R1.
[0031]
As described above, according to the present embodiment, when master stations 1a and 1b and a plurality of remote stations 2 are connected by duplexed transmission paths 3a and 3b, data transmission is performed using the transmission path 3a. In addition, the microcomputer 12 of the remote station 2 determines that an abnormality has occurred in the transmission line 3a when the no-signal time during which no address is transmitted exceeds a certain time, and switches to the transmission line 3b for use. .
[0032]
Therefore, since the program of the microcomputer 12 can reliably detect an abnormality such as a disconnection or a ground fault in the transmission path 3a and can be used by switching to a sound transmission path 3b, transmission to the remote station 2 is different from the conventional one. There is no need to provide a circuit for detecting a road abnormality, and the remote station 2 can be made compact.
[0033]
Further, according to this embodiment, when the remote station 2 detects an abnormality in the transmission line 3a, the remote station 2 transmits data indicating that an abnormality has occurred to the master station 1b, so that the master station 1b has an abnormality in the transmission line 3a. You can recognize what happened. In addition, since the master station 1b notifies an operator or the like that an abnormality has occurred in the transmission line 3a by the display 1ba, maintenance management of the control center 5 can be easily performed.
[0034]
Further, according to this embodiment, when the master stations 1a and 1b are provided corresponding to the duplexed transmission lines 3a and 3b, and the abnormality occurs in the transmission line 3a, the master station 1b Since the transmission path 3a and the transmission path 3b are separated so as to transmit and receive data, the influence of reflection due to impedance mismatch occurring in the transmission path 3a in which an abnormality has occurred does not reach the switched transmission path 3b. Stable data transmission can be performed.
[0035]
FIG. 4 shows a second embodiment of the present invention. The configuration of the second embodiment is the same as that of the first embodiment, and different operations will be described below.
In FIG. 4 which shows the flowchart of the control contents of the microcomputer 12, when the microcomputer 12 starts the timer 12a in the “timer start” processing step S1 and starts measuring time, “has its own address transmitted?” The process proceeds to the determination step S2. In the determination step S2, the microcomputer 12 determines whether or not the talker or listener address assigned to itself is transmitted from the master station 1a. If it is determined in the determination step S2 that the talker or listener address is not transmitted and “NO”, the process proceeds to a determination step S3 of “timer value> constant value?”.
[0036]
In the determination step S3, the microcomputer 12 reads the timer value of the timer 12a and sets a predetermined value for a time during which the talker or listener address assigned to the timer 12a is not transmitted, that is, a no-request time. It is determined whether or not it has exceeded, that is, whether or not a certain time has passed. Thus, if the microcomputer 12 determines “NO” in the determination step S3, the microcomputer 12 proceeds to step S2 and determines again whether the talker or listener address has been transmitted.
[0037]
In the determination step S2, when the microcomputer 12 transmits its own talker or listener address and determines “YES”, the microcomputer 12 proceeds to the processing step S6 of “transmission / reception processing”. In the processing step S6, the microcomputer 12 performs the transmission or reception processing from the remote station 2 to the master station 1a in response to the reception of the talker or listener address, as in step R8 of the first embodiment. The process proceeds to process step S7. When the microcomputer 12 clears the built-in timer 12a to zero in process step S7, the process proceeds to step S1.
[0038]
Here, when a disconnection or a short circuit accident occurs in the transmission line 3a, since its own talker or listener address is not transmitted, the microcomputer 12 continues to determine “NO” in step S2, and the timer value of the timer 12a. If it exceeds a certain value, “YES” is determined in the step S3. The subsequent processes in steps S4, S5 and S9 are performed in the same manner as steps R4, R5 and R9 in the first embodiment.
[0039]
As described above, according to the second embodiment, the microcomputer 12 determines that an abnormality has occurred in the transmission line 3a when the time during which the talker or listener address assigned to it is not transmitted exceeds a certain time. Since the transmission line 3b is switched to use, the same effect as in the first embodiment can be obtained.
[0040]
FIG. 5 shows a third embodiment of the present invention. The configuration of the third embodiment is the same as that of the first embodiment, and different operations will be described below.
In FIG. 5 showing the flowchart of the control contents of the microcomputer 12, the microcomputer 12 determines “YES” when the talker address assigned to itself is transmitted in the determination step T1 of “transmission request address?”. , The process proceeds to process step T2 of “transmission process”, and the stored data is transmitted to the master station 1a. Then, similarly to the case where “NO” is determined in the determination step T1, the process proceeds to the determination step T3 of “There is a reception request address?”.
[0041]
In the determination step T3, if the microcomputer 12 determines that the listener address of the microcomputer 12 is transmitted and “YES”, the microcomputer 12 proceeds to the process step T4 of the “reception process” and transmits the transmission added after the listener address. Receive data. Then, the process proceeds to a determination step T5 of "Is the check code normal?" If “NO” is determined in the determination step T3, the process proceeds to step T1.
[0042]
In the third embodiment, a cyclic redundancy code generated from transmission data, that is, a CRC (Cyclic Redundancy Check) code, for example, is added to the data transmitted from the master station 1 as a check code. Thus, in the determination step T5, the CRC code is read to determine whether or not the transmission data indicates a normal state with no error. In determination step T5, if the CRC code indicates a normal state and the microcomputer 12 determines “YES”, the process proceeds to step T1.
[0043]
Further, when noise is added to the transmission line 3a or the transmission line 3a causes a ground fault, and any error occurs in the transmission data, and the CRC code does not indicate a normal state according to this, the microcomputer 12 If “NO” is determined in the determination step T5, the process proceeds to the processing step T6 of “N ← N + 1”. In process step T6, the microcomputer 12 increments the value of the counter N (which is cleared to 0 in the initial process) that counts the number of times transmission data errors are detected by the CRC code. Then, the process proceeds to the next “N> 3?” Determination step T7.
[0044]
In the determination step T7, the microcomputer 12 determines whether or not the count value of the counter N has exceeded “3” as the predetermined number of times. If it is determined that the count value does not exceed “3” and “NO”, the process proceeds to step T1. If the count value exceeds “3” and “YES” is determined, the process proceeds to process steps T8 and T9, and the same process as in steps R4 and R5 of the first embodiment is performed. Then, the process proceeds to “N ← 0” processing step T10, and when the count value of the counter N is cleared to zero, the process proceeds to step T1.
[0045]
As described above, according to the third embodiment, when the CRC code added to the transmission data exceeds the number “3” of detecting the error in the transmission data, an abnormality has occurred in the transmission line 3a. Therefore, even if a noise superposition or a ground fault occurs on the transmission path 3a, the abnormality can be reliably detected.
[0046]
The present invention is not limited to the embodiments described above and shown in the drawings, and the following modifications or expansions are possible.
The transmission path 3b may be used first, and when an abnormality occurs in the transmission path 3b, the transmission path 3b may be switched to.
The check code in the third embodiment is not limited to the CRC code, but may be a Hamming code or a parity check code. The predetermined number of times is not limited to “3” and may be changed as appropriate.
[0047]
Instead of providing the timer 12a in the microcomputer 12 to measure the no-signal time or the no-transmission time, the microcomputer 12 may measure the time by a software timer that counts the number of timer interruptions by the system timer.
Instead of providing the display units 1aa and 1ba in the master stations 1a and 1b, providing a display unit in the programmable controller 4 and transmitting data indicating that an abnormality has occurred in the transmission path from the remote station 2, You may make it display on the indicator of the programmable controller 4. FIG.
[0048]
Even when the transmission paths 3a and 3b are connected to the master station 1a and the transmission paths are switched, data may be transmitted and received from the master station 1a.
In the data transmission system 13, the master station 1 as a master station transmits and receives data by transmitting a talker or listener address to the remote station 2 as a slave station. The present invention may be applied to a data transmission system in which a data transmission right (right to become a bus master) is sequentially assigned to each of the data transmission apparatuses between a plurality of data transmission apparatuses having no station-slave station relationship.
[0049]
【The invention's effect】
Since this invention is as having demonstrated above, there exist the following effects.
Claim 1 or2According to the described data transmission system, the plurality of data transmission apparatuses or the control means of the slave stations are used in the transmission line currently used in the transmission line.No request for transmission or reception request signal not transmitted from own station to own stationMeasure time, norequestTime is predeterminedoneWhen the specified time is exceeded, it is determined that the transmission line is abnormal and the currently used transmission line is switched to the other. Therefore, even if the data transmission device is not provided with a circuit for detecting a transmission line abnormality, Since the occurrence of an accident such as a ground fault can be detected, the apparatus can be made small.
[0051]
Claim3According to the described data transmission system,The slave station control means measures the no-signal time of the currently used transmission line of the transmission lines, and determines that the transmission line is abnormal when the no-signal time exceeds a predetermined time. Since the transmission line is controlled so that it is switched to the other, it is possible to detect the occurrence of an accident such as a disconnection or a ground fault without providing a circuit for detecting an abnormality in the transmission line in the data transmission device. can do.
According to the data transmission system of claim 4,The slave station control means determines the abnormality from the check code attached to the received data from the currently used transmission line of the transmission lines, and transmits when the number of times of determination exceeds a predetermined number of times. Since it is determined that there is a path abnormality and the currently used transmission line is switched to the other, it is possible to detect the abnormality reliably even if an abnormality such as noise superposition or ground fault occurs on the transmission line. it can.
Further, when the control means determines that the transmission line is abnormal, it transmits an abnormal signal to the master station to notify the transmission line abnormality, so that the master station can recognize that an abnormality has occurred in the transmission line. (Claim 3 or 4).
[0052]
Claim5According to the described data transmission system,In the case of claim 2,When the control means determines that the transmission line is abnormal, it transmits an abnormality signal to the master station to notify the transmission line abnormality, so that the master station can recognize that an abnormality has occurred in the transmission line.
[0053]
Claim6According to the described data transmission system, the control means causes the display means to display that an abnormality has occurred in the transmission line, so that the operator or the like can be notified that an abnormality has occurred in the transmission line. And maintenance management becomes easy.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram showing a first embodiment of the present invention.
FIG. 2 is a diagram showing an electrical configuration of a remote station
FIG. 3 is a flowchart showing the control contents of the microcomputer of the remote station.
FIG. 4 is a view corresponding to FIG. 3, showing a second embodiment of the present invention.
FIG. 5 is a view corresponding to FIG. 3, showing a third embodiment of the present invention.
[Explanation of symbols]
1a and 1b are master stations (data transmission device, master station), 1aa and 1ba are indicators (display means), 2 is a remote station (data transmission device, slave station), 3a and 3b are transmission paths, and 12 is a microcomputer. (Control means) 13 indicates a data transmission system.

Claims (6)

In a data transmission system that transmits and receives data by sequentially assigning a transmission right to each of a plurality of data transmission devices,
A plurality of data transmission devices are connected to each other, and a duplexed transmission path in which one of them is selectively used,
The plurality of data transmission devices measure a non-request time during which no transmission or reception request signal is transmitted from the currently used transmission path to the local station, and the no- request time is predetermined. A data transmission system comprising control means for determining that a transmission path is abnormal when a predetermined time is exceeded and switching a currently used transmission path to the other. In the data transmission system for transmitting and receiving data by being assigned a sequential transmission right master station serving the data transmission device transmits a transmission request signal or to one of the plurality of slave stations serving data transmission device,
Connecting the master station and a plurality of slave stations, and comprising a duplexed transmission path in which either one is selectively used;
The slave station measures a non-request time during which no transmission or reception request signal is transmitted to the local station, and determines that a transmission path is abnormal when the non-request time exceeds a predetermined time, and is currently used. A data transmission system comprising a control means for controlling to switch the transmission line used to the other. In the data transmission system for transmitting and receiving data by being assigned a sequential transmission right master station serving the data transmission device transmits a transmission request signal or to one of the plurality of slave stations serving data transmission device,
Connecting the master station and a plurality of slave stations, and comprising a duplexed transmission path in which either one is selectively used;
The slave station measures the no-signal time of the currently used transmission line of the transmission lines, and determines that the transmission line is abnormal when the no-signal time exceeds a predetermined time. A data transmission system comprising a control means for switching a transmission path to the other and controlling to transmit an abnormal signal to the master station . In a data transmission system in which a data transmission device as a master station transmits and receives data by transmitting a transmission request signal to any one of a plurality of data transmission devices as slave stations and sequentially assigning a transmission right,
Connecting the master station and a plurality of slave stations, and comprising a duplexed transmission path in which either one is selectively used;
The slave station determines an abnormality from the check code attached to the received data, and determines that the transmission line is abnormal when the number of times of determination exceeds a predetermined number of times. And a control means for controlling to transmit an abnormal signal to the master station . 3. The data transmission system according to claim 2, wherein the control means transmits an abnormal signal to the master station when determining that the transmission path is abnormal . 6. The data transmission system according to claim 1, wherein the control means causes the display means to display the occurrence of the transmission path abnormality when it is determined that the transmission path is abnormal .

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