JPH06214060A - Time synchronizing method - Google Patents

Abstract

PURPOSE:To provide a time synchronizing method capable of precisely grasping a required time for transmission in a loop type network and precisely keeping the time synchronization of all stations on the network. CONSTITUTION:Time inquiry commands QA, QB are outputted from a main station 1 to main and sub transmission routes 3, 4, loop transmission required times tL for circulating the commands in the transmission routes and returning to the self station are measured, and one-way transmission required times tA, tB to a slave station are calculated from these times and internal times TA, TB stored in time responses AA, AB from the slave station according to the commands, and the internal time of the slave station is reset by a time set command considering these as a time set delay time DELTAT to the slave station.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time synchronization method for a loop network, and more particularly to a time synchronization method for a loop network suitable for processing events occurring at each station in the network in time series. Is.

[0002]

2. Description of the Related Art Conventionally, as a method of synchronizing the times of stations connected to a network, as shown in FIG. 7, half of the round-trip time required for transmission information between a master station and a slave station is set as a one-way time, and Based on this, a method of correcting the time of the slave station and synchronizing the time of both stations has been proposed (for example, JP-A-63-52089).

In FIG. 1, reference numeral 101 denotes a central processing unit of the master station M, which has a clock section 102 for generating time and a communication line 1.
A transmission / reception unit 106 that transmits / receives various data via 10,
A detection unit 103 that detects and outputs a transmission time required from the transmission of the time reading request to the slave station S to the reception of a response, a simulation unit 104 that artificially generates correction data for the slave station S based on this transmission time, the correction data The correction unit 105 that corrects the time read from the slave station S, compares the corrected time of the slave station S with the time of the master station M when the read request is transmitted, and if there is a time difference between the two, adjusts this difference to the slave station S. Control unit 1 that controls the comparison unit 107 that outputs data and the console 109 to perform time synchronization processing
It is composed of 08.

Reference numeral 111 denotes a central control unit of the slave station S, which includes a clock unit 112 for generating time, a transmitter / receiver unit 116 for transmitting / receiving various data via the communication line 110, and a clock unit 112 for transmitting / receiving the set time data. A time adjustment unit 117 that adjusts the time and a control unit 118 that controls each unit to perform time synchronization processing are configured.

Next, the conventional time correction processing operation in such a configuration will be described with reference to the sequence diagram shown in FIG. In the figure, 121 is a time reading command from the master station M to the slave station S, 122 is a time response to the time reading command 121, and 123 is a time adjustment command from the master station M to the slave station S. Further, T _M0 and T _S0 are internal times in the master station M and the slave station S when the time reading command 121 is transmitted, T _S1 is an internal time in the slave station S when the time reading command is received, and t is a time response reception from the time reading command transmission. T _M2 and T _S2 are internal times in the master station M and the slave station S when the timed command is received, and T _S2 'is the internal time in the slave station S after the timed.

First, in response to a time correction instruction from the console 109, the control unit 108 of the master station M reads the current internal time, that is, T _M0 from the clock unit 102, stores it in the comparison unit 107, and the transmission / reception unit 106 corrects the time. The time reading command 121 is sent to the slave station S which performs
The detection unit 103 is controlled to start measuring the required transmission time. At this time, the internal time of the slave station S is T _S0 . afterwards,
The control unit 118 of the slave station S reads the current internal time T _S1 from the clock unit 112 according to the time reading command 121 from the master station M, and uses this internal time T _S1 as the time response 122 via the transmission / reception unit 116. Send it back.

In response to the time response 122, the control unit 108 of the master station M stops the required time measuring operation of the detection unit 103 and obtains the required transmission time t. Subsequently, the pseudoizing unit 104 generates correction data t / 2 with half of the required transmission time t as a transmission delay from the master station M to the slave station S, and further the correction unit 1
In 05, the correction data t / 2 is subtracted from the internal time T _S1 of the slave station S received by the time response 122 to correct and calculate the internal time T _S0 of the slave station S when the time read command 121 is issued.

Next, the main station M at the time of issuing the time reading command 121 stored in advance in the comparing section 107.
Internal time T _M0 and corrected time reading command 1
21 Compare the internal time T _S0 of the slave station S at the time of calling,
When there is a time difference between the two, the time adjustment command 123 for the slave station S is transmitted with this difference T _M0 -T _S0 as ΔT. In response to this, the control unit 118 of the slave station S determines that the current internal time T
Add ΔT to _S2 and adjust to T _S2 '(= T _M2 ). Through the series of time synchronization processing as described above, the internal times of the master station M and the slave stations S are synchronized.

[0009]

Therefore, in such a conventional time synchronization method, it is assumed that half of the round-trip transmission time between the master station and the slave stations corresponds to the one-way transmission time from the master station to the slave stations. Since the internal time of both stations is compared and the internal time of the slave station is corrected by the difference between them, the received data is transferred one after another, and in some cases, transmission may be required due to the difference in the round-trip transmission path between the master station and the slave station. In a loop type network where the time is different, there is a problem that the above-mentioned premise is not satisfied, an internal time error occurs at each station, and accurate time synchronization cannot be obtained. The present invention is for solving such a problem, and it is a time synchronization method in a loop network that can accurately grasp the required transmission time even in a loop network and maintain the time synchronization of all stations on the neckwork with high accuracy. Is intended to provide.

[0010]

In order to achieve such an object, the time synchronization method according to the present invention uses, as a transmission time measuring process, a master station to simultaneously transmit data to an arbitrary slave station via a main and a sub-channel. While sending the time inquiry command, it started measuring the time required for loop transmission until the time inquiry command goes around both transmission paths and returns to the own station, and the slave station receives each received via each transmission path. A time response is sent back to each of the time inquiry commands via the corresponding transmission line, and the master station determines from the master station to the slave station based on the loop transmission required time and each slave station's internal time stored in each time response. The process of calculating the required one-way transmission time for each main and sub-transmission path is executed for all slave stations, and transmission is performed at the master station as a time synchronization process. Of the required one-way transmission times for each slave station calculated by the inter-station measurement process, the one-way transmission required time corresponding to the transmission path that sends the time setting command is added to the internal time of the own station when the time setting command is sent. The time setting command is sent to the slave stations as the set time, and the slave station executes the process of resetting the internal time of its own station in response to the time setting command to all slave stations and executes the transmission time measurement process. After that, the time synchronization process is executed at regular intervals.

Further, the present invention is characterized in that such a transmission time measuring process is executed at regular intervals.

Further, each station is provided with a monitor timer which has its own time limit and is reset by a predetermined command from the master station, and the station whose timer has expired first becomes the master station, and thereafter the other stations become slave stations. It is characterized in that the transmission time measurement process and the time synchronization process are carried out.

[0013]

Therefore, the time inquiry command sent from the master station is separately received by the slave station via the main and sub transmission lines, and the time response storing the internal time when the time inquiry command is received is sent to the slave station. To the main station via the corresponding transmission lines. From the internal time of the slave station stored in these time responses and the time required for loop transmission until the time inquiry command is sent and it goes around the transmission line and returns to the master station, The one-way transmission required time is calculated, and this is calculated for all slave stations as the transmission delay time of the time setting command sent from the master station to the slave station. Based on this, the internal time of the master station is corrected and the set time for the slave station is set. The internal time of each slave station is reset by the time setting command, and all slave stations are synchronized with the internal time of the master station.

The required one-way transmission time from the master station to each slave station is calculated again at regular intervals, and the time synchronization processing is executed from the master station to the slave stations based on this.

Further, when the predetermined command indicating the normal operation from the main station is not repeatedly received within the predetermined time, it is judged that the main station cannot execute the time synchronization processing for some reason, and either one of them is first. The station whose time has expired becomes the main station, and time synchronization processing is executed for other stations.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a loop network that is an embodiment of the present invention. In the figure, 1 is the main station M, 2
Are slave stations S1 to Sn, and the master station 1 and the slave station 2 are connected by a double loop transmission line 5 composed of a main route 3 and a sub route 4 having different signal transmission directions.

Further, the master station 1 includes a clock section 11 for generating an internal time, a detecting section 12 and a detecting section 12 for measuring a time required for loop transmission from transmission of a time inquiry command to an arbitrary slave station 2 to reception thereof again. One-way transmission required time for each route from the master station 1 to the slave station 2 based on the measured loop transmission required time and the internal time of the slave station 2 obtained by the inquiry command transmitted via the main route 3 and the sub route 4. Calculating unit 13 for calculating
Via the main route 3 and the sub-route 4, the correction unit 14 for outputting the correction time for the slave station 2 based on the calculation result of the above, the control unit 15 for transmitting the time inquiry command and the time setting command to control the time synchronization processing for the slave station 2. Transmission / reception units 16 and 17 for transmitting / receiving various data to / from other stations
It consists of

Further, the slave station 2 reads the internal time from the clock section 21 in response to a time inquiry command from the clock section 21 which generates the internal time and the main station 1, and returns it to the main station 1.
5, the clock unit 21 according to the time setting command from the main station 1
And a transmitting / receiving unit 26 and 27 for transmitting / receiving various data to / from other stations via the main route 3 and the sub route 4.

Usually, the transmission / reception units 16, 17, 26, 27 provided in the master station 1 and the slave station 2 monitor the corresponding main route 3 or sub route 4 and receive the data received from the station in the preceding stage of the own station. When receiving the data addressed to the own station while performing the transfer processing to transfer to the station of the next stage, the reception processing of incorporating this into the processing unit (not shown) as the reception data, and the processing from this processing unit Data transmission between stations is realized by performing a transmission process of transmitting the transmission data to the next-stage station after confirming that the route to be used is empty according to the transmission request.

Next, the operation of the present invention will be described with reference to FIGS. 2 is a flowchart showing the processing procedure of the transmission time measurement process from the master station 1 to each slave station 2 in the time synchronization processing, and FIG. 3 is the master station 1 in the time synchronization processing.
Is a flowchart showing a processing procedure of a time synchronization process for each slave station 2, and FIG. 4 is a sequence diagram showing a series of time synchronization processing operations.

The transmission time measurement process executed for each slave station 2 in order to measure the time required for command transmission from the master station 1 to each slave station 2 will be described below. First, the main station 1 sends a time inquiry command to the station 2 according to the internal time T ₀ . At this time, the control unit 15 controls the transmitting / receiving unit 16,
The time inquiry commands Q _A and Q _B are simultaneously sent to both the main route 3 and the sub route 4 via 17 (step 30) and the loop transmission required time t _L for each route is counted to the detection unit 12. The operation is started (step 31).

Subsequently, the time inquiry commands Q _A and Q _B sent to both routes 3 and 4 are transmitted / received by the transceivers 26 and 2 of each station.
It is transferred in the reverse direction by 7 and returns to the main station 1 which is the command transmission source at the same time after the time t _{L has} elapsed from the transmission of this command. This is because the number of stations connected to both routes is the same, so the time required for the time inquiry commands Q _A and Q _B to go around each route by the transfer processing in the transceivers 26 and 27 of each station, that is, the loop transmission is required. Time t _L
Are the same. The detection unit 12 of the main station 1 includes a transmission / reception unit 16,
The time inquiry commands Q _A and Q _B sent from the own station via 17 are received (step 32), the counting operation is ended (step 33), and this count value is output as the loop transmission required time t _L. (Step 34).

On the other hand, the slave station 2 sends the time inquiry command Q
_A, is received by each control unit 25 via the transceiver 26, 27 are connected respectively to Q _B on the main route 3 and sub-route 4. The control unit 25 controls the current internal time T from the clock unit 21 for each time inquiry command.
_A, read the T _B, via its transceiver unit 26 or 27 corresponding to the root that has received the command time in response to the main station 1 A _A, and returns the A _B.

That is, from the main route 3 to the transmitting / receiving section 2
When the time inquiry command is received at the internal time T _A via 6 (step 40), the clock unit 21 is accordingly responded.
The internal time T _A at the time of reception is read (step 4
1), this is sent to the main route 3 via the transmission / reception unit 26 as the time response A _A (step 42). When the time inquiry command is received from the sub-route 4 via the transmission / reception unit 27 (step 43), the internal time T _B at the time of reception is read from the clock unit 21 accordingly (step 44), and this is set as the time. The response A _B is sent to the sub route 4 via the transmitting / receiving unit 27 (step 45).

The main station 1 receives the respective time responses A _A and A _B in the control unit 15 via the transmission / reception units 16 and 17 corresponding to the main route 3 and the sub route 4 (steps 35 and 36). Subsequently, calculation is performed based on the loop transmission required time t _L output from the detection unit 12 and the internal times T _A and T _B of the slave station 2 stored in the time responses A _A and A _B received for each route. The time required for one-way transmission from the master station 1 to the slave station 2 on the main route 3 and the sub route 4 is calculated by the unit 13 (step 3).
7).

Here, the one-way transmission time from the master station 1 to the slave station 2 when the main route 3 is used is t _A ,
If the one-way transmission required time from the master station 1 to the slave station 2 when the sub-route 4 is used is t _B , the one-way transmission required time difference from the master station 1 to the slave station 2 due to the difference in the route used t _A -t _B, each time query command Q _a sent simultaneously, the internal time difference slave station 2 is Q _B reaches T _a
Since it is equal to −T _B , t _A −t _B = T _A −T _B.

Further, since the loop transmission required time t _L required for the command to go around the route is the same regardless of which route is used, the time inquiry command Q _A that reaches the slave station 2 via the main route 3. (Time required t _A )
However, the time t _L −t _A required for further transfer from the slave station 2 to return to the master station 1 is required for the time inquiry command Q _B to be transferred from the master station 1 to the slave station 2 using the subroute 4. It becomes equal to time or t _B and t _L −t _A = t _B or t _A + t _B = t _L.

Therefore, t _A = {t _L + (│T _A -T _B │)} / 2 t _B = {t _L- (│T _A -T _B │)} / 2, the main route 3 and the sub route The required one-way transmission times t _A and t _B from the master station 1 to the slave station 2 when 4 is used are calculated and stored in the memory inside the calculation unit 13. As described above, the time required for the transmission between the master station 1 and each slave station 2 is measured, that is, the transmission time measurement process is performed for each slave station 2 and is performed for all slave stations (step 38). Go to process.

Next, a time synchronization process for synchronizing the internal time of each slave station 2 with the internal time of the master station 1 (see FIG. 3).
Will be described. First, in the correction unit 14 of the master station 1, the slave station 2 that has received the time setting command S calculates the slave station setting time T _SET that can be set to the clock unit 21 as it is (step 50). This process corrects the time required for the time setting command S sent from the master station 1 to be transmitted to the slave station 2 with respect to the current internal time of the master station 1, that is, the time at which the time setting command is sent. belongs to.

Therefore, this correction amount is the time setting command S
When the main route 3 is used, the one-way transmission required time tA when the main route 3 for the slave station 2 is used is read from the memory inside the arithmetic unit 13 and T the _SET = T _N + t _a. Further, when the sub route 4 is used, the one-way transmission required time t _B when the sub route 4 is used is read in the same manner, and T _SET = T _N + t _B.

Subsequently, the control unit 15 controls the correction unit 14 corresponding to the arbitrarily selected main route 3 or sub route 4.
In response to the output T _SET of (1), the time setting command S is sent to the slave station 2 via the transmitting / receiving unit 16 or 17 corresponding to the route (step 51).

After the lapse of t _A from this time T _N , the slave station 2
(Internal time T _S ) receives this time setting command S via either route (step 55), and the time setting unit 28
Thus, the clock section 21 is reset based on T _SET stored in this command (step 56). As a result, the internal time T _S of the slave station 2 becomes T _S '(= T _SET ),
This means that the internal time (T _N + t _A ) of the master station 1 and the internal time (T _S ') of the slave station 2 are synchronized, and is similarly executed for all slave stations (step 52). The time synchronization process is repeatedly executed every predetermined time (step 53).

In the above embodiment, as the time synchronization processing, the case where the transmission time measurement process is executed for all slave stations and then the time synchronization process is executed for all slave stations has been described. As a second embodiment in the above, as shown in FIG. 5, these transmission time measurement process (step 60) and time synchronization process (step 61) are performed.
May be repeatedly performed in a timely manner, for example, every predetermined time (step 62). As a result, even when the loop configuration changes due to bypass of the slave station, the required transmission time corresponding to the new loop configuration can be immediately measured, so that the time synchronization can always be maintained with high accuracy.

Further, referring to FIG. 6 as another embodiment of the present invention, when the main station cannot perform the time synchronization processing for some reason, another station becomes the main station. What was made to implement is demonstrated. FIG. 6 is a block diagram of a loop network that is the third embodiment of the present invention.

In the figure, S1 to Sn are stations 7 of the same type.
0, as in FIG. 1, these stations 70 are connected by a double loop transmission line 5 consisting of a main route 3 and a sub route 4 in which the signal transmission directions are different. Further, there is no fixed master station or slave station as shown in FIG. 1, and any one station 70 serves as a master station and all other stations serve as slave stations.

In FIG. 6, the station 70 includes a clock section 11 for generating an internal time, a detecting section 72 for measuring a time required for loop transmission from transmitting a time inquiry command to a slave station and receiving the command again, and a detecting section 72 for measuring. Based on the time required for loop transmission and the internal times of the slave stations respectively received when the main route 3 and the sub route 4 are used,
A calculation unit 13 that calculates a one-way transmission required time for each route to the slave station, a correction unit 74 that outputs a correction time for the slave station based on the calculation result of the calculation unit 13 and resets the clock unit 11 according to a time setting command. , A control unit 75 for transmitting a time inquiry command and a time setting command to control time synchronization processing for a slave station, and transmission / reception units 16 and 17 for transmitting / receiving various data to / from other stations via the main route 3 and the sub route 4. There is.

Further, the station 70 receives a predetermined command such as a time inquiry command or a time setting command from the main station as means for judging whether or not another station is normally operating as the main station. Monitoring timer 7 which is reset to the time, and which has a time longer than the period in which the main station transmits the time inquiry command or the time setting command and which adds a value proportional to the station number unique to each station
Eight. Therefore, the time-up time limit of the monitoring timer 78 is different for each station. Also,
The time-up signal of the monitoring timer 78 is output to the control unit 75. When the time is up, the control unit 75 operates its own station as the master station, and when it is not up, it operates as the slave station.

The detecting section 72 and the calculating section 13 calculate the required transmission time only when the own station is operating as the main station, and the correcting section 74 is operating the own station as the main station. In this case, the correction time for the slave station is calculated, and when the slave station is operating, the clock unit 11 is reset by the time setting command.

Next, the operation of each station based on such a configuration will be described. First, when there is no station in operation on the network and a station enters the operating state,
Since there is no time inquiry command or time setting command sent by another station on the network, the monitoring timer 7
In response to the time-up of 8, the station starts the main station operation, that is, the time synchronization processing operation including the transmission time setting process and the time synchronization process described above. In response to the time inquiry command or the time setting command from the master station, the monitor timers 78 of the other stations are reset and each operates as a slave station.

Next, when the station operating as the main station leaves the network for some reason such as power failure, the time inquiry command or the time setting command is not transmitted from this station, and accordingly Of the other operating stations, the station whose monitoring timer 78 is first timed up becomes the main station. Therefore, one of the stations on the network always executes the master station operation, that is, the time synchronization processing operation described above, and it is possible to avoid the situation where the entire network goes down because this operation is not executed.

[0041]

As described above, according to the present invention, the master station measures the time required for transmission to each slave station via the main route and the sub route, and based on this, the time is corrected and synchronized for each slave station. As a result, highly accurate time synchronization processing can be realized in a network in which the required round-trip transmission times from the master station to the slave stations are different. Further, by repeatedly performing the time synchronization processing in a timely manner, even if there is a change in the configuration of the network loop, it is possible to immediately measure the required transmission time and perform the accurate time synchronization processing.

Furthermore, without fixing the master station or the slave station,
In addition to having both functions in all stations and providing a means to monitor the time synchronization processing, when the time synchronization processing by the master station is no longer detected, one of the slave stations immediately becomes the master station and performs the time synchronization processing. I decided to restart it,
Even if the main station fails, it will be possible to back up immediately. Therefore, in the time synchronization method of the loop type network system, the synchronization accuracy is increased, the network change is accurately dealt with, and the reliability of the network is improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a loop network according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a transmission time measurement process.

FIG. 3 is a flowchart showing a time synchronization process.

FIG. 4 is a sequence diagram showing a time synchronization processing operation.

FIG. 5 is a flowchart showing a time synchronization process according to the second embodiment of the present invention.

FIG. 6 is a block diagram of a loop network according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a conventional time synchronization process.

FIG. 8 is a sequence diagram showing a conventional time synchronization process.

[Explanation of symbols]

 1 Master station 2 Slave station 3 Main route 4 Sub route 5 Double loop transmission line 11 Clock section 12 Detection section 13 Calculation section 14 Correction section 15 Control section 16, 17 Transmission / reception section 21 Clock section 25 Control section 26, 27 Transmission / reception section 28 Time adjustment Part 70 Station 72 Detection part 74 Correction part 75 Control part 78 Monitoring timer

Claims (3)

[Claims] 1. A time inquiry command and time for one station among a plurality of stations coupled to a loop type network having main and sub transmission lines propagating signals in opposite directions and each having a time generation function. This time inquiry command is used as the master station that sends the setting command, and as the slave station that reads the internal time at that time in response to the time inquiry command and returns the time response and resets the internal time in response to the time setting command. And a time synchronization method for synchronizing the internal time of the slave station with the internal time of the master station by a time setting command, as a transmission time measurement process, in the master station, at the same time to any of the slave stations via the main and sub transmission lines. While sending the time inquiry command, this time inquiry command goes around the transmission line and returns to the own station. Start the measurement of the time required for loop transmission until it comes, in the slave station, return a time response via the transmission path corresponding to each of the time inquiry commands received via the transmission path, Further, in the master station, the one-way transmission time from the master station to the slave station is calculated for each of the main and sub transmission lines based on the loop transmission time and each internal time of the slave station stored in each time response. In the master station, as a time synchronization process, the time calculated from the transmission time measurement process for each slave station is calculated as a time synchronization process. The one-way transmission required time corresponding to the transmission path for sending the setting command is added to the internal time of the own station at the time of sending the time setting command. Sending the time setting command as a reset time for the slave station, executing a process of resetting the internal time of the self station in the slave station according to the time setting command for all the slave stations, A time synchronization method comprising performing the time measurement process at regular intervals after executing the time measurement process. 2. The time synchronization method according to claim 1, wherein the transmission time measurement process is executed at regular intervals. 3. The time synchronization method according to claim 1 or 2, wherein each of the stations is provided with a monitoring timer which has its own time limit and is reset by a predetermined command from the main station. The time synchronization method is characterized in that the designated station becomes the master station, and thereafter the other stations are regarded as slave stations to execute the transmission time measurement process and the time synchronization process.