JP6452427B2 - Time synchronization monitoring method, communication system, and master device - Google Patents

Description

  The present invention relates to a time synchronization monitoring method, a communication system, and a master device that monitor time synchronization between a master device and a slave device by exchanging time synchronization packets between the master device and the slave device. It is.

  In recent years, with packetization of data in network communication, a method of performing time synchronization on a packet basis has been proposed. For example, IEEE (The Institute of Electrical and Electronics Engineers) 1588 defines PTP (Precision Time Protocol) (see Non-Patent Document 1). The time synchronization accuracy of PTP is in units of microseconds or nanoseconds, and is higher than that of NTP (Network Time Protocol), which is a time synchronization protocol having time synchronization accuracy in milliseconds.

  PTP is applied to a communication system including a master device (master device) having a reference time (master clock) and a slave device (slave device) having a reference time (slave clock). In PTP, time synchronization packets are periodically exchanged between a master device and a slave device, and the reference time of the slave device is corrected based on information obtained in the process.

The PTP time synchronization process has the following processing steps.
First, the master device transmits a Sync message (Clock Sync message), which is a time synchronization packet, to the slave device.
Second, the master device transmits a Followup message (Clock Sync Followup message) that is a time synchronization packet to the slave device. The Followup message includes information indicating the time T1 (time based on the master clock) when the Sync message is transmitted from the master device. The slave device records time T1 (time based on the master clock) and time T2 (time based on the slave clock) when the Sync message is received.
Thirdly, the slave device transmits a Delay_Req message (Clock Delay Request message), which is a time synchronization packet, to the master device. The master device records time T4 (time based on the master clock) which is the time when the Delay_Req message is received.
Fourth, the master device transmits a Delay_Resp message (Clock Delay Response message), which is a time synchronization packet, to the slave device. The Delay_Resp message includes information indicating time T4 (time based on the master clock). Since the slave device can confirm that the master device has received the Delay_Req message by receiving the Delay_Resp message, the slave device records time T3 (time based on the slave clock) when the Delay_Req message is transmitted.

  Since the slave device records times T1, T2, T3, and T4 (that is, four time stamps), a time difference (T2−) that is a propagation time (propagation time) from the master device to the slave device. T1) and a time difference (T4-T3) that is a propagation time in the direction from the slave device to the master device can be calculated. The slave device calculates the average value ((T2-T1) + (T4-T3)) / 2 of the two time differences as a value indicating the propagation time (delay time) in the transmission path from these two time differences. Is calculated.

  Furthermore, by subtracting the average value (((T2-T1) + (T4-T3)) / 2) from the time difference (T2-T1) which is the propagation time in the direction from the master device to the slave device, The offset value ((T2-T1)-(T4-T3)) / used to correct the time of the slave device (time based on the slave clock) based on the time of the master device (time based on the master clock) 2 is calculated. The slave device can be synchronized with the reference time (master clock) of the master device by correcting the reference time (slave clock) so that the offset value becomes 0.

IEEE Std 1588 (TM) -2008, “IEEE Standard for a Precise Clock Synchronized Protocol for Network for Networked and Roc. )

  As described above, in the PTP, the slave device calculates the propagation time (delay time) and the offset value of the transmission path using the four time stamps, and based on these values, the slave device calculates the reference time. This is a protocol for performing correction.

  Thus, in PTP, there are four synchronization packet transmissions for obtaining four time stamps, but there is no sequence for notifying the master device of the synchronization accuracy of the reference time of the slave device. For this reason, the master device cannot determine whether or not the synchronization processing of the reference time of the slave device is completed. Similarly, since there is no sequence for monitoring the slave clock in the master device, this cannot be detected when a time shift occurs in the master clock or the slave clock.

  In other words, since the master device cannot determine the completion of the synchronization processing of the reference time in the slave device and detect the time lag of the master clock or the slave clock, the master device can synchronize the reference time of the slave device. There is a problem that it is difficult to ensure quality, maintain and manage accuracy. Further, in order to solve such a problem, in addition to the process of transmitting / receiving four time synchronization packets in the PTP, a sequence for transmitting a completion notification of the synchronization processing of the reference time of the slave device to the master device It is necessary to take measures such as adding a hardware or hardware for detecting completion of time synchronization processing to the slave device.

  Therefore, the present invention has been made in view of the above-described problems of the prior art, and provides a time synchronization monitoring method, a communication system, and a master device that enable highly accurate time synchronization between a master device and a slave device. The purpose is to provide.

  A time synchronization monitoring method according to an aspect of the present invention is a time synchronization monitoring method for monitoring synchronization between a master clock of a master device and a slave clock of a slave device, wherein the master device is based on the master clock. A first message transmission / reception step of transmitting a first message at a first time, and wherein the slave device receives the first message at a second time based on the slave clock; and the master device indicates the first time. A second message transmitting / receiving step of transmitting a second message including information, wherein the slave device receives the second message; and the slave device indicates the third time at a third time based on the slave clock. A third message including information is transmitted, and the master device transmits a request message for receiving the third message. Transmitting a fourth message including information indicating a fourth time which is a time based on the master clock and the time when the third message is received, and the slave device The response message transmission / reception step for receiving the fourth message and whether the master device has a monitoring time difference that is a difference between the fourth time and the third time within a predetermined allowable range. A determination step of determining whether or not to output the result of the determination.

  According to another aspect of the present invention, there is provided a time synchronization monitoring method in which synchronization between a master clock of a master device and first to Mth slave clocks of first to Mth (M is an integer of 2 or more) slave devices. Is a time synchronization monitoring method for monitoring synchronization between the master clock and the m-th slave clock of the m-th (m is an integer of 1 to M) slave device. In the synchronization monitoring process, the master device transmits a first message at a first time based on the master clock, and the m-th slave device transmits the first message at a second time based on the m-th slave clock. A first message transmission / reception step for receiving the message, the master device transmits a second message including information indicating the first time, and the m-th slave device receives the second message. A second message transmission / reception step, wherein the m-th slave device transmits a third message including information indicating the third time at a third time based on the m-th slave clock; A request message transmission / reception step for receiving the third message, and information indicating a fourth time that is a time based on the master clock and when the master device receives the third message, A response message transmitting and receiving step in which the mth slave device receives the fourth message, and the master device is a monitoring time that is a difference between the fourth time and the third time. And determining whether or not the difference is within a predetermined allowable range, and outputting a result of the determination.

  According to one aspect of the present invention, the master device determines whether the time synchronization processing of the slave clock of the slave device is completed based on the monitoring time difference between the master clock and the slave clock. Can do.

  According to another aspect of the present invention, the master device completes the time synchronization processing of the slave clocks of the plurality of slave devices based on the plurality of monitoring time differences between the master clock and the plurality of slave clocks. Furthermore, it is possible to determine whether there is a time lag in either the master clock or the plurality of slave clocks, or a time lag has occurred in the master clock of the master device. Can do.

It is a block diagram which shows the structure of the communication system of a comparative example. It is a sequence diagram which shows PTP as a time synchronization method which a comparative example employ | adopts. It is a block diagram which shows the structure of the communication system which implements the time synchronous monitoring method of Embodiment 1 of this invention. FIG. 3 is a sequence diagram showing a PTP that employs the time synchronization monitoring method of the first embodiment. 4 is a flowchart illustrating an operation of a synchronization accuracy monitoring unit of the master device according to the first embodiment. It is a block diagram which shows the structure of the communication system which implements the time synchronous monitoring method of Embodiment 2 of this invention. FIG. 10 is a sequence diagram showing a PTP that employs the time synchronization monitoring method of the second embodiment. 10 is a flowchart illustrating an operation of a synchronization accuracy monitoring unit of the master device according to the second embodiment. It is a block diagram which shows the structure of the communication system which implements the time synchronous monitoring method of Embodiment 3 of this invention. FIG. 10 is a hardware configuration diagram of a modified example of the master device according to the first to third embodiments.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, first, a comparative example will be described based on FIGS. 1 and 2, and then Embodiments 1 to 3 and a modified example will be described in detail based on FIGS. 3 to 10. The present invention is not limited to Embodiments 1 to 3 and modifications described below.

《Comparative example》
FIG. 1 is a block diagram illustrating a configuration of a communication system of a comparative example using PTP. As shown in FIG. 1, this communication system includes a master device 1 and a slave device 2. The master device 1 and the slave device 2 are connected by a wired line 3. The master device 1 includes a transmission / reception unit 11 that performs communication with the host device, a transmission / reception unit 12 that performs communication with the slave device 2, a packet extraction unit 13, a time synchronization processing unit 14, and a time synchronization packet generation unit 15. And a reference time acquisition unit 16. The slave device 2 includes a transmission / reception unit 21 that communicates with the master device 1, a transmission / reception unit 22 that communicates with a lower-level device, a packet extraction unit 23, a time synchronization processing unit 24, and a time synchronization packet generation unit 25. And a time information processing unit 26.

FIG. 2 is a sequence diagram showing PTP as a time synchronization method adopted by the comparative example of FIG. The PTP time synchronization process has the following processing steps.
First, the time synchronization processing unit 14 in the master device 1 acquires the master clock from the reference time acquisition unit 16. Based on the acquired master clock, the time synchronization processing unit 14 generates a Sync message that is a time synchronization packet in the time synchronization packet generation unit 15, and sends the Sync message to the slave device 2 at time T 1. Send. The slave device receives the Sync message at time T2, and stores information indicating the time T2 when the Sync message is received.

  Second, the time synchronization processing unit 14 in the master device 1 generates a Followup message, which is a time synchronization packet including information indicating the time T1, in the time synchronization packet generation unit 15 and sends it to the slave device 2. To send. The packet extraction unit 23 in the slave device 2 extracts the Followup message from the downlink packet, and the time synchronization processing unit 24 indicates the information indicating the time T1 acquired from the extracted Followup message and the stored time T2. Information is transmitted to the time information processing unit 26.

  Third, the time synchronization processing unit 24 in the slave device 2 acquires a slave clock from the time information processing unit 26. Based on the acquired slave clock, the time synchronization processing unit 24 causes the time synchronization packet generation unit 25 to generate a Delay_Req message, which is a time synchronization packet, and transmits it to the master device 1 at time T3. .

  Fourth, the packet extraction unit 13 in the master device 1 extracts the Delay_Req message from the uplink packet received by the transmission / reception unit 12, and the time synchronization processing unit 14 receives the Delay_Req message as a trigger for the time synchronization packet. The generation unit 15 generates a Delay_Resp message that is a time synchronization packet including information indicating the time T <b> 4 when the master device 1 receives the Delay_Req message, and transmits the generated message to the slave device 2. The packet extraction unit 23 in the slave device 2 extracts the Delay_Resp message from the downlink packet, and the time synchronization processing unit 24 transmits information indicating the time T4 acquired from the Delay_Resp message to the time information processing unit 26.

  The time information processing unit 26 in the slave device 2 uses the information indicating the times T1, T2, T3, and T4, the propagation time (T2-T1) in the direction from the master device 1 to the slave device 2, and the slave device 2. The propagation time (T4-T3) in the direction from to the master device 1 is calculated. From the above two propagation times (that is, delay times), the average value of the propagation times in the transmission path is calculated by the following equation: ((T2-T1) + (T4-T3)) / 2. Further, from the propagation time (T2−T1) in the direction from the master device 1 to the slave device 2 and the average value of the propagation time in the transmission path (((T2−T1) + (T4−T3)) / 2), the slave The offset value of the device 2 is calculated by the following equation ((T2-T1)-(T4-T3)) / 2, and in the slave device 2, the reference time (so that the offset value becomes the value “0”) (Slave clock) is corrected. Such correction of the reference time is periodically repeated, for example.

  However, in the comparative example, there is no sequence in which the master device 1 notifies the master device 1 of the synchronization accuracy of the reference time of the slave device 2. For this reason, the master device 1 cannot determine whether or not the synchronization processing of the reference time of the slave device 2 has been completed. On the other hand, in the following first to third embodiments and modifications, the master device uses the monitoring time difference (T4-T3) to determine whether or not the slave device reference time synchronization processing is completed. Can be determined.

Embodiment 1
FIG. 3 is a block diagram illustrating a configuration of a communication system that implements the time synchronization monitoring method according to the first embodiment. 3, components that are the same as or correspond to the components shown in FIG. 1 (comparative example) are assigned the same reference numerals as those shown in FIG. As shown in FIG. 3, the communication system includes a master device 1a and a slave device 2a. In the following description, a master device and a slave device are both devices having a communication function, for example, a station side communication device and a terminal side (subscriber side) communication device. The master device 1a and the slave device 2a are connected by a wired line 3. The wired line 3 may include a network, but needs to be a PTP-compatible network. The master device 1a of the first embodiment shown in FIG. 3 includes a transmission / reception unit 11, a transmission / reception unit 12, a packet extraction unit 13, a time synchronization processing unit 14, a time synchronization packet generation unit 15, and a reference time acquisition. It differs from the master device 1 shown in FIG. 1 in that a synchronization accuracy monitoring unit 17 is provided in addition to the unit 16. 3 includes a transmission / reception unit 21, a transmission / reception unit 22, a packet extraction unit 23, a time synchronization processing unit 24a (reference numeral 24 in FIG. 1), and a time synchronization unit. Although common to the slave device 2 shown in FIG. 1 in that the packet generation unit 25 and the time information processing unit 26 are provided, the time synchronization packet generation unit 25 generates based on an instruction from the time synchronization processing unit 24a. 1 is different from the slave device 2 of the comparative example shown in FIG. 1 in that the Delay_Req message, which is a time synchronization packet, includes information indicating the time T3 (time based on the slave clock) when the Delay_Req message is transmitted. .

  The master device 1a includes transmission / reception units 11 and 12, a packet extraction unit 13, a time synchronization processing unit 14, a time synchronization packet generation unit 15, a reference time acquisition unit 16, and a synchronization accuracy monitoring unit 17. You may provide the control part and information storage part (memory) which control the various operation | movement of the whole master apparatus 1a including. In addition to the monitoring unit that monitors the synchronization accuracy, the synchronization accuracy monitoring unit 17 may include a calculation unit that performs calculation and a storage unit that temporarily stores the calculated value. In addition, the slave device 2a includes the transmission / reception units 21 and 22, the packet extraction unit 23, the time synchronization processing unit 24a, the time synchronization packet generation unit 25, and the time information processing unit 26. You may provide the control part and information storage part (memory) which control various operation | movement.

  FIG. 4 is a sequence diagram showing a PTP that employs the time synchronization monitoring method of the first embodiment. The sequence shown in FIG. 4 includes information indicating time T3 (time based on the slave clock) when the Delay_Req message is transmitted by the time synchronization processing unit 24a of the slave device 2a. The sequence of the comparative example shown in FIG.

  As shown in FIG. 4, in the time synchronization monitoring method of the first embodiment, as the first process (first message transmission / reception step S1), the master device 1a operates at time T1 (first time) based on the master clock. A Sync message (Clock Sync message) is transmitted as a time synchronization message (first message), and the slave device 2a receives the Sync message at time T2 (second time) based on the slave clock. The slave device 2a temporarily stores information indicating the time T2 in the memory.

  As the next second processing (second message transmission / reception step S2), the master device 1a transmits a Sync_Followup message (Clock Sync Followup message) as a time synchronization message (second message) including information indicating the time T1, The slave device 2a receives this Sync_Followup message. The slave device 2a temporarily stores information indicating the time T1 in the memory.

  As the next third processing (request message transmission / reception step S3), the slave device 2a at time T3 (third time) based on the slave clock as a time synchronization message (third message) including information indicating this time T3. The Delay_Req message (Clock Delay Request message) is transmitted, and the master device 1a receives the Delay_Req message at time T4. The slave device 2a temporarily stores information indicating the time T3 in the memory. The master device 1a temporarily stores information indicating the time T3 and information indicating the time T4 in the memory.

  As the next fourth process (response message transmission / reception step S4), time T4 (fourth time), which is the time when the master device 1a receives the time synchronization clock (third message) based on the master clock. ), A Delay_Resp message (Clock Delay Response message) is transmitted as a fourth message, and the slave device 2a receives the Delay_Resp message. The slave device 2a temporarily stores information indicating the time T4 in the memory.

  Next, the slave device 2a uses the time T1 based on the master clock, the time T2 based on the slave clock, the time T3 based on the slave clock, and the time T4 based on the master clock to obtain the slave clock that is the reference time of the slave device 2a. Correct. The correction at this time is the same as the correction method described in the comparative example. For example, the time information processing unit 26 of the slave device 2a calculates the average value of the propagation time (delay time) in the transmission path by ((T2-T1) + (T4-T3)) / 2. Next, the time information processing unit 26 of the slave device 2a determines the average propagation time (((T2-T1) + ((T2-T1) + (T2)) from the propagation time (T2-T1) in the direction from the master device 1a to the slave device 2a. By subtracting T4-T3)) / 2), the offset value of the slave device 2a is calculated as ((T2-T1)-(T4-T3)) / 2, and the time information processing unit 26 of the slave device 2a is calculated. Corrects the reference time (slave clock) so that the offset value becomes the value “0”.

  Furthermore, in the first embodiment, the synchronization accuracy monitoring unit 17 of the master device 1a has a monitoring time difference (T4-T3) that is a difference between the time T4 and the time T3 within a predetermined allowable range. It has a determination step of determining whether or not there is and outputting the result of the determination. When it is determined in the determination step that the monitoring time difference (T4-T3) is outside the allowable range, the determination result indicates that there is a time lag in the slave clock that is the reference time of the slave device 2a. Information. When it is determined that the monitoring time difference (T4-T3) is within the allowable range, the determination result is information indicating that there is no time shift in the slave clock that is the reference time of the slave device 2a. This information is notified to the higher-level device through the transmission / reception unit 11, for example.

  FIG. 5 is a flowchart illustrating the operation of the synchronization accuracy monitoring unit 17 of the master device 1a according to the first embodiment. The operation of the synchronization accuracy monitoring unit 17 will be described based on FIG.

  Each time the synchronization accuracy monitoring unit 17 of the master device 1a receives the Delay_Req message from the slave device 2a (step S11), the master device 1a transmits the Delay_Resp message at time T3 when the Delay_Req message is transmitted from the slave device 2a. Using the time T4 at the time of calculation, a monitoring time difference (T4-T3) that is a propagation time (ie, delay time) in the direction from the slave device 2 to the master device 1a is calculated (steps S12 and S13), and This is recorded (step S14).

  When the monitoring time difference (T4−T3) is within a predetermined allowable range (step S15), the synchronization accuracy monitoring unit 17 of the master device 1a determines that the slave clock has been corrected by the offset value, and the slave device It is determined that the time synchronization in 2a is completed (step S16). If the monitoring time difference (T4-T3) does not fall within the allowable range, the synchronization accuracy monitoring unit 17 determines that the slave clock is not corrected by the offset value, and the time synchronization in the slave device 2a is not completed. (Step S17).

  In FIG. 5, the case where it is determined that correction is completed (step S <b> 17) when the monitoring time difference (T <b> 4 − T <b> 3) is within the allowable range has been described in step S <b> 15. The determination of the monitoring time difference (T4-T3) (determination corresponding to step S15) may be repeated a plurality of times. In this case, for example, when the monitoring time difference (T4−T3) is within the allowable range for 10 consecutive times (also referred to as “when converged within the allowable range” when the determination is repeated a plurality of times). The determination in step S15 may be YES.

  As described above, according to the time synchronization monitoring method, the communication device, and the master device 1a of the first embodiment, the synchronization accuracy monitoring unit 17 of the master device 1a calculates and records the monitoring time difference, and further varies. By performing monitoring, it is possible to monitor the time synchronization accuracy of the slave device 2 from the master device 1a without adding a sequence or adding a hardware function. Further, by notifying the determination result (monitoring result) of the master device 1a to the host device from the transmission / reception unit 11 of the master device 1a, a communication system having an alarm function can be provided, and the reliability and quickness of maintenance Will improve.

<< Embodiment 2 >>
FIG. 6 is a block diagram illustrating a configuration of a communication system that implements the time synchronization monitoring method according to the second embodiment. 6, components that are the same as or correspond to the components shown in FIG. 3 (Embodiment 1) are given the same reference numerals as those shown in FIG. As shown in FIG. 6, this communication system includes a master device 1b and first to Mth slave devices 2_1, 2_2,..., 2_M (M is an integer equal to or greater than 2). The master device 1b is connected to each of the first to Mth slave devices 2_1, 2_2,..., 2_M via the switching hub 41. The master device 1b according to the second embodiment shown in FIG. 6 includes a transmission / reception unit 11 that communicates with a host device, a transmission / reception unit 12 that communicates with each slave device, a packet extraction unit 13, and a time synchronization processing unit. 14, a time synchronization packet generation unit 15, a reference time acquisition unit 16, and a synchronization accuracy monitoring unit 17 a. When any one of the first to Mth (M is an integer of 2 or more) slave devices 2_1, 2_2,..., 2_M is shown, the mth slave device 2_m (or slave device 2_m ). It has the same configuration as slave device 2a in the first embodiment.

  FIG. 7 is a sequence diagram showing a PTP that employs the time synchronization monitoring method of the second embodiment. FIG. 7 shows PTP between the master device 1b and the first to Mth slave devices 2_1, 2_2,..., 2_M-1, 2_M.

  As shown in FIG. 7, in the time synchronization monitoring method according to the second embodiment, as the first process (first message transmission / reception step), the master device 1b sets the time at time T1_1 (first time) based on the master clock. A first sync message (clock sync message) is transmitted as a synchronization message (first message), and the first slave device 2_1 receives the first sync message at time T2_1 (second time) based on the slave clock. To do.

  As the next second processing (second message transmission / reception step), the master device 1b receives a first Sync_Followup message (Clock Sync) as a time synchronization message (second message) including information indicating the time T1_1 (first time). (Followup message) is transmitted, and the slave device 2_1 receives the second message.

  Thereafter, the first process (first message transmission / reception step) and the second process (second message transmission / reception step) are sequentially executed between the second to M-th slave devices 2_2,.

  As the next third processing (request message transmission / reception step), the first to M-th slave devices 2_1, 2_2,..., 2_M perform the times T3_1, T3_2, ..., T3_M (third time) based on the slave clock. First to M-th Delay_Req messages (Clock Delay Request messages) as time synchronization messages (third messages) including information indicating times T3_1, T3_2,..., T3_M (third time) are sequentially transmitted, and the master device 1b. However, the first to Mth slave devices 2_1, 2_2,..., 2_M receive the first to Mth Delay_Req messages.

  As the next fourth process (response message transmission / reception step), times T4_1, T4_2,..., Which are times when the master device 1b receives the time synchronization clock (third message) based on the master clock. The first to Mth Delay_Resp messages (Clock Delay Response messages) as the fourth message are sequentially transmitted, including information indicating T4_M (fourth time), and the slave devices 2_1, 2_2,..., 2_M-1, 2_M , 1st to Mth Delay_Resp messages are received.

  Next, the first to M-th slave devices 2_1, 2_2,..., 2_M have times T1_1, T1_2,..., T1_M based on the master clock, times T2_1, T2_2,. , T3_M based on the master clock and times T4_1, T4_2,..., T4_M based on the master clock are used to correct the first to Mth slave devices 2_1, 2_2,. To do.

  In the next determination step, the master device 1b determines the monitoring time differences (T4_1-T3_1) and (T4_2-T3_2) which are the differences between the times T4_1, T4_2,..., T4_M and the times T3_1, T3_2,. ),..., (T4_M-T3_M) are determined within a predetermined allowable range, and the determination result is output. When it is determined in the determination step that the monitoring time difference is outside the allowable range, the determination result is information indicating that the slave clock has a time lag. Of the time synchronization monitoring method performed by the master device 1b of the second embodiment, the processing between the master device 1b and each of the first to Mth slave devices 2_1, 2_2,. This is the same as the time monitoring method 1. However, in the time synchronization monitoring method of the second embodiment, the status of the communication system is determined using all the monitoring difference values for the first to M-th slave devices 2_1, 2_2, ..., 2_M generated by the master device 1b. Is judged. Below, operation | movement of the synchronous precision monitoring part 17a of the master apparatus 1b which performs these determination is demonstrated.

  FIG. 7 is a flowchart illustrating the operation of the synchronization accuracy monitoring unit 17a of the master device 1b according to the second embodiment. The operation of the synchronization accuracy monitoring unit 17a will be described with reference to FIG.

  Each time the synchronization accuracy monitoring unit 17a of the master device 1b receives the Delay_Req message from the slave device 2_m (step S21), the master device 1b transmits the Delay_Resp message at time T3_m when the Delay_Req message is transmitted from the slave device 2b. The time difference for monitoring (T4_m−T3_m), which is the propagation time in the direction from the slave device 2_m to the master device 1b, is calculated using the time T4_m at the time (steps S22 and S23) and recorded (step S24). ).

  When the monitoring time difference (T4_m−T3_m) falls within a predetermined allowable range (step S25), the synchronization accuracy monitoring unit 17a determines that the slave clock is corrected by the offset value, and performs time synchronization in the slave device 2_m. Is determined to be completed (step S26). When the monitoring time difference (T4_m−T3_m) does not fall within the allowable range and continues to fluctuate, the synchronization accuracy monitoring unit 17a determines that the slave clock is not corrected by the offset value, and time synchronization in the slave device 2_m is completed. It determines with not having carried out (step S27). Note that the processing in steps S21 to S27 in FIG. 8 is the same as the processing in steps S11 to S17 in FIG. 5 described in the first embodiment. After the processes from step S21 to S27 in FIG. 8 are repeated M times, the process of the synchronization accuracy monitoring unit 17a proceeds to step S28.

  Each time the master device 1b receives the Delay_Req message from the first to Mth slave devices 2_1,..., 2_M in the steps before step S28, the Delay_Req message is changed from the first to Mth slave devices 2_1,. Time information indicating the time T3 (ie, T3_1,..., T3_M) and the time T4 when the master device 1b receives the Delay_Req message from the first to M-th slave devices 2_1,. That is, using the time information indicating T4_1,..., T4_M), the monitoring time difference (T4-T3) in the direction from the first to M-th slave devices 2_1,. T4_1-T3_1),... (T4_M-T3_M)) for each slave device 2_1, , It is calculated for 2_M record.

  In step S28, the synchronization accuracy monitoring unit 17a of the master device 1b determines that all of the plurality of monitoring time differences (T4_1-T3_1),..., (T4_M-T3_M) recorded in the slave devices 2_1,. If it falls within the allowable range (YES in step S28), it is determined that there is no time difference between the master clock and each slave clock. In step S28, the synchronization accuracy monitoring unit 17a of the master device 1b includes a part of the plurality of monitoring time differences (T4_1-T3_1),..., (T4_M-T3_M) in the recorded slave devices 2_1,. Alternatively, when all of them do not fall within the allowable range (NO in step S28), the process proceeds to step S30, and all of the plurality of monitoring time differences (T4_1-T3_1),..., (T4_M-T3_M) , It is determined whether the displacement is within a certain range and in the same direction. Here, the upper limit of the certain range is a value lower than the upper limit of the allowable range. Further, the shift in the same direction means a case where all the codes of (T4_1-T3_1),..., (T4_M-T3_M) are the same code. Since T4_m is a time based on the master clock and T3_m is a time based on the slave clock, (T4_m−T3_m) may be not only a positive value but also a negative value.

  If it is determined in step S30 that all of the M monitoring time differences (T4_1−T3_1),..., (T4_M−T3_M) are within a certain range and are in the same direction (in step S30) YES), it is determined that a master clock shift has occurred (step S31). On the other hand, if the determination is NO in step S30, that is, “when there is one or more monitoring time differences that do not fall within a certain range” or “a positive value and a negative value among the M monitoring time differences”. If there is a value, a time shift (time shift within the allowable range used in step S25) has occurred in any of the first to M-th slave devices, or another fault (for example, any It is determined that a failure or a transmission path failure has occurred in the slave device (step S32). The time synchronization monitoring method of the present invention is not limited to the flowchart of FIG.

  As described above, according to the time synchronization monitoring method of the second embodiment, when there is no time lag exceeding the allowable range, monitoring of the master clock and slave clock (step S29), monitoring of the master clock ( Step S31) and failure detection of each slave device and the transmission path (step S32) are possible. Therefore, according to the time synchronization monitoring method of the second embodiment, the synchronization accuracy monitoring unit 17a of the master device 1b calculates the monitoring time differences in the plurality of slave devices 2_1, ..., 2_M, and records the calculation results. By monitoring the variation in the monitoring time difference, it is possible to monitor the master clock and the slave clock and monitor the failure of the slave device and the transmission path without adding a sequence or a hardware function.

<< Embodiment 3 >>
The first and second embodiments have described the method in which the master device can monitor the time synchronization accuracy of the slave device even when the operation clock frequency of the master device and the operation clock frequency of the slave device are asynchronous. In the third embodiment, as shown in FIG. 9, the master device 1c and the slave device 2c include synchronous Ethernet (registered trademark) (Sync-E) processing units 20 and 30, and the frequency synchronization is performed using the Sync-E function. It is related with the communication system of the state. In the third embodiment, a time synchronization monitoring method in a state where the master device 1c and the slave device 2c are synchronized in the operation clock frequency by the Sync-E function will be described.

  FIG. 9 is a block diagram illustrating a configuration of a communication system that implements the time synchronization monitoring method according to the third embodiment. 9, components that are the same as or correspond to the components shown in FIG. 3 (Embodiment 1) are given the same reference numerals as those shown in FIG. As shown in FIG. 9, the communication system includes a master device 1c and a slave device 2c. The master device 1c and the slave device 2c are connected by a wired line 3. The master device 1c of the third embodiment shown in FIG. 9 includes a transmission / reception unit 11, a transmission / reception unit 12, a packet extraction unit 13, a time synchronization processing unit 14, a time synchronization packet generation unit 15, and a reference time acquisition. It differs from the master device 1a of the first embodiment in that it includes a clock source 18, a frequency distribution unit 19, and a Sync-E processing unit 20 in addition to the unit 16 and the synchronization accuracy monitoring unit 17. 9 includes a transmission / reception unit 21, a transmission / reception unit 22, a packet extraction unit 23, a time synchronization processing unit 24a, a time synchronization packet generation unit 25, and a time In addition to the information processing unit 26, the frequency distribution unit 29 and the Sync-E processing unit 30 are different from the slave device 2a of the first embodiment.

  The relationship between the Sync-E function shown in FIG. 9 and time synchronization processing will be described. The master device 1c operates by distributing the reference frequency obtained from the clock source 18 in the device by the frequency distribution unit 19. The Sync-E processing unit 20 of the master device 1c transmits a frequency synchronization frame including information on the reference frequency in the direction from the master device 1c to the slave device 2c. In the slave device 2c that has received the frequency synchronization frame, the Sync-E processing unit 30 extracts the reference frequency information, and the frequency distribution unit 29 distributes the information in the slave device 2c. Therefore, the master device 1c and the slave device 2c operate in a state where the frequency is synchronized with the reference frequency. Since the master device 1c and the slave device 2c are frequency-synchronized, the difference in information indicating the time monitoring packet in both is smaller than in the comparative example of FIG.

  The operation of the synchronization accuracy monitoring unit 17 in FIG. 9 will be described. The synchronization accuracy monitoring unit 17 uses the information indicating the time T3 when the Delay_Req message is transmitted from the slave device 2c and the information indicating the time T4 when the master device 1c transmits the Delay_Resp message, from the slave device 2c to the master. The monitoring time difference (T4-T3), which is the propagation time in the direction to the device 1c, is calculated and recorded. When the monitoring time difference converges within a predetermined allowable range, the synchronization accuracy monitoring unit 17 determines that the slave clock has been corrected by the offset value, and determines that the time synchronization in the slave device 2c has been completed. When the monitoring time difference (T4-T3) continues to fluctuate without converging, it is determined that the slave clock is not corrected by the offset value, and it is determined that the time synchronization in the slave device 2c is not completed. In the third embodiment, the master device 1c and the slave device 2c are frequency-synchronized by the Sync-E function, and the time difference between the time monitoring packets in both is reduced. The monitoring time difference converges to a narrower range. Therefore, by synchronizing the frequency between the devices using the Sync-E function and monitoring the synchronization accuracy according to the present invention, the time synchronization accuracy can be monitored more accurately than in the first and second embodiments.

<Modification>
FIG. 10 is a hardware configuration diagram showing the configuration of the master device according to the first to third embodiments. The master device shown in FIG. 10 includes a memory 91 as a storage device that stores a program as software, and a processor 92 as an information processing unit that executes the program stored in the memory 91. The master device shown in FIG. 10 shows a specific example of the structure of the slave station device according to the first to third embodiments. The operation of the apparatus shown in FIG. 10 is the same as that of the master apparatus according to the first to third embodiments.

  When the apparatus shown in FIG. 10 realizes the processing in the master apparatus according to the first to third embodiments, each configuration of the master apparatus shown in FIG. 10 causes the processor 92 to execute a program stored in the memory 91. This is realized. In addition, in order to implement | achieve each structure of a master apparatus, the case where it used with the processor 92 and the memory 91 was illustrated, However, A part of each structure of a master apparatus is implement | achieved by the processor 92 and the memory 91, and another part is hardware It may be realized by a circuit. The time synchronization monitoring method described in the first to third embodiments can be realized by the master device shown in FIG.

  1a, 1b, 1c Master device (main device), 2a, 2_1, 2_2, ..., 2_M, 2c Slave device (slave device), 3 Wired line, 11, 12, 21, 22 Transceiver, 13, 23 Packet extractor 14, 24 Time synchronization processing unit, 15, 25 Time synchronization packet generation unit, 16 Reference time acquisition unit, 17, 17a Synchronization accuracy monitoring unit, 18 Clock source, 19 Frequency distribution unit, 20 Sync-E processing unit, 26 Time information processing unit, 29 frequency distribution unit, 30 Sync-E processing unit, 41 switching hub.

Claims (12)

A time synchronization monitoring method for monitoring synchronization between a master clock of a master device and a slave clock of a slave device,
A first message transmission / reception step in which the master device transmits a first message at a first time based on the master clock, and the slave device receives the first message at a second time based on the slave clock;
A second message transmitting / receiving step in which the master device transmits a second message including information indicating the first time, and the slave device receives the second message;
A request message transmission / reception step in which the slave device transmits a third message including information indicating the third time at a third time based on the slave clock, and the master device receives the third message;
The master device transmits a fourth message including information indicating a fourth time that is a time based on the master clock and is a time when the third message is received, and the slave device transmits the fourth message A response message sending and receiving step for receiving a message;
The master device determines whether or not a monitoring time difference that is a difference between the fourth time and the third time is within a predetermined allowable range, and outputs the result of the determination A time synchronization monitoring method comprising: a determination step. The determination result is information indicating that there is a time lag in the slave clock when the time difference for monitoring is determined to be outside the allowable range in the determination step. The time synchronization monitoring method according to 1.   The slave device further includes a time correction step of correcting the slave clock based on the first time, the second time, the third time, and the fourth time. 2. The time synchronization monitoring method according to 2.   Before the first message transmission / reception step, the master device transmits first operation clock frequency information indicating the operation clock frequency of the master device to the slave device, and the slave device operates the operation clock of the slave device. 4. The time synchronization monitoring method according to claim 1, further comprising a step of matching a frequency with an operation clock frequency of the master device. 5. A time synchronization monitoring method for monitoring synchronization between a master clock of a master device and first to Mth slave clocks of first to Mth (M is an integer of 2 or more) slave devices, the master clock And the time synchronization monitoring process executed for monitoring the synchronization between the slave device and the m-th slave clock of the m-th (m is an integer of 1 to M) slave device,
The master device transmits a first message at a first time based on the master clock, and the m-th slave device receives the first message at a second time based on the m-th slave clock. A message sending and receiving step;
A second message transmitting / receiving step in which the master device transmits a second message including information indicating the first time, and the m-th slave device receives the second message;
The m-th slave device transmits a third message including information indicating the third time at a third time based on the m-th slave clock, and the master device receives the third message. A message sending and receiving step;
The master device transmits a fourth message including information indicating a fourth time that is a time based on the master clock and is a time when the third message is received, and the m-th slave device includes: A response message transmission / reception step for receiving the fourth message;
The master device determines whether or not a monitoring time difference that is a difference between the fourth time and the third time is within a predetermined allowable range, and outputs the result of the determination A time synchronization monitoring method comprising: a determination step. In the determination step, when it is determined that the monitoring time difference is within the allowable range for all of the first to M-th slave devices, the determination result is the master clock and the first clock. The time synchronization monitoring method according to claim 5, wherein the time synchronization monitoring method is information indicating that there is no time lag in any of the first to Mth slave clocks. For all of the first to Mth slave devices, in the determination step, the monitoring time difference is within a predetermined range, and for all of the first to Mth slave devices, the monitoring is performed. The time synchronization monitoring method according to claim 5 or 6, wherein, when the codes of the time differences for use are the same, the result of the determination is information indicating that there is a time lag in the master clock.   The time synchronization monitoring process executed for monitoring the synchronization between the master clock and the m-th slave clock of the m-th (m is an integer from 1 to M) slave device includes the first message transmission / reception step. Before the master device transmits first operation clock frequency information indicating an operation clock frequency of the master device to the m-th slave device, and the m-th slave device transmits the m-th slave device. The time synchronization monitoring method according to claim 5, further comprising a step of causing the operation clock frequency of the master device to coincide with the operation clock frequency of the master device. A master device;
A slave device communicating with the master device,
A communication system for monitoring synchronization between a master clock of the master device and a slave clock of the slave device,
The master device transmits a first message at a first time based on the master clock, and the slave device receives the first message at a second time based on the slave clock;
The master device transmits a second message including information indicating the first time, the slave device receives the second message,
The slave device transmits a third message including information indicating the third time at a third time based on the slave clock, and the master device receives the third message,
The master device transmits a fourth message including information indicating a fourth time that is a time based on the master clock and is a time when the third message is received, and the slave device transmits the fourth message Receive the message,
The master device determines whether or not a monitoring time difference that is a difference between the fourth time and the third time is within a predetermined allowable range, and outputs the result of the determination A communication system characterized by the above. A master device;
First to Mth (M is an integer of 2 or more) slave devices communicating with the master device,
A communication system for monitoring synchronization between a master clock of the master device and slave clocks of the first to M-th slave devices,
In a time synchronization monitoring process executed for monitoring synchronization between the master clock and the m-th slave clock of the m-th (m is an integer of 1 to M) slave device,
The master device transmits a first message at a first time based on the master clock, and the m-th slave device receives the first message at a second time based on the m-th slave clock;
The master device transmits a second message including information indicating the first time; the m-th slave device receives the second message;
The mth slave device transmits a third message including information indicating the third time at a third time based on the mth slave clock, and the master device receives the third message,
The master device transmits a fourth message including information indicating a fourth time that is a time based on the master clock and is a time when the third message is received, and the m-th slave device includes: Receiving the fourth message;
The master device determines whether or not a monitoring time difference that is a difference between the fourth time and the third time is within a predetermined allowable range, and outputs the result of the determination A communication system characterized by the above. A master device that communicates with a slave device,
A transceiver unit;
A reference time acquisition unit for outputting a master clock;
A time synchronization packet generator for generating a time synchronization packet;
A packet extraction unit for extracting a time synchronization packet from a signal transmitted from the slave device;
A synchronization accuracy monitoring unit that monitors the synchronization accuracy between the master clock and the slave clock of the slave device;
Have
The master device transmits a first message at a first time based on the master clock, and the slave device receives the first message at a second time based on the slave clock;
The master device transmits a second message including information indicating the first time, the slave device receives the second message,
The slave device transmits a third message including information indicating the third time at a third time based on the slave clock, and the master device receives the third message,
The master device transmits a fourth message including information indicating a fourth time that is a time based on the master clock and is a time when the third message is received, and the slave device transmits the fourth message Receive the message,
The master device determines whether or not a monitoring time difference that is a difference between the fourth time and the third time is within a predetermined allowable range, and outputs the result of the determination A master device characterized by that. A master device that communicates with first to Mth slave devices (M is an integer of 2 or more),
A transceiver unit;
A reference time acquisition unit for outputting a master clock;
A time synchronization packet generator for generating a time synchronization packet;
A packet extraction unit for extracting a time synchronization packet from a signal transmitted from the first to M-th slave devices;
A synchronization accuracy monitoring unit that monitors the synchronization accuracy between the master clock and the slave clocks of the first to M-th slave devices;
Have
In a time synchronization monitoring process executed for monitoring synchronization between the master clock and the m-th slave clock of the m-th (m is an integer of 1 to M) slave device,
The master device transmits a first message at a first time based on the master clock, and the m-th slave device receives the first message at a second time based on the m-th slave clock;
The master device transmits a second message including information indicating the first time; the m-th slave device receives the second message;
The mth slave device transmits a third message including information indicating the third time at a third time based on the mth slave clock, and the master device receives the third message,
The master device transmits a fourth message including information indicating a fourth time that is a time based on the master clock and is a time when the third message is received, and the m-th slave device includes: Receiving the fourth message;
The master device determines whether or not a monitoring time difference that is a difference between the fourth time and the third time is within a predetermined allowable range, and outputs the result of the determination A master device characterized by that.

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