JP5430469B2 - Master device, slave device, time synchronization method, and program - Google Patents

Description

  The present invention relates to a technique for synchronizing time between a master device and a plurality of slave devices in a communication system including a master device and a plurality of slave devices.

  In the conventional synchronization method, the master device and the slave device are synchronized by measuring and correcting the propagation delay between the master device (hereinafter also simply referred to as the master) and the slave device (hereinafter also simply referred to as the slave). (For example, patent document 1).

Japanese Patent Laid-Open No. 01-231618

Patent Document 1 discloses measuring and correcting a propagation delay between a master and a slave.
However, only the technique between the master and one slave is described, and the synchronization between the master and a plurality of slaves is not disclosed.
Further, in the synchronous system, clock deviation and jitter of propagation delay occur with time, so it is necessary to periodically measure and correct the propagation delay. However, when the correction is implemented periodically in Patent Document 1, the slave device However, there is a problem that synchronization deviation accumulates between the slaves and the synchronization accuracy is greatly deteriorated.

  The main object of the present invention is to solve such a problem, and when synchronizing the times of the master device and the plurality of slave devices and periodically performing correction, there is a synchronization error between the slave devices. The main purpose is to prevent accumulation and deterioration of synchronization accuracy.

The master device according to the present invention is:
A master device that manages a plurality of slave devices provided with a frame transfer order,
A synchronization point setting unit that sets a time point after a predetermined time from the transmission time of the synchronization frame as a synchronization point for synchronizing the time in the plurality of slave devices;
A measurement frame processing unit that transmits a measurement frame for delay measurement to a start point slave device that is a start point of a transfer order, and receives a measurement response frame that is a response to the measurement frame from the start point slave device;
Based on the time from transmission of the measurement frame to reception of the measurement response frame, a delay time that occurs when the frame is transmitted from the master device to the start slave device is calculated, and the calculated delay time is subtracted from the synchronization point. A correction value generation unit for generating correction values
A correction frame processing unit that transmits a correction frame including the correction value to the start point slave device;
The start-point slave device receives the correction frame, and based on a time from reception of the measurement frame to transmission of the measurement response frame in the start-point slave device and the correction value included in the correction frame, the start-point slave Calculating an offset time from the reception time of the synchronization frame to the synchronization point in a device, transmitting a measurement frame to a slave device in the next transfer order and receiving a measurement response frame from the slave device in the next transfer order, Based on the time from the transmission of the measurement frame to the reception of the measurement response frame, the delay time that occurs when the frame is transmitted from the start slave device to the slave device in the next transfer order is calculated, and the calculated delay time is the offset A correction value is generated by subtracting from the time, and a correction frame that includes the correction value is generated. The over-time after sending to the slave device of the next transfer sequence, the plurality of slave devices at later similar procedure to calculate each offset time according to the transfer order,
A synchronization frame whose reception time in each slave device is a starting point of the offset time of each slave device is transmitted to the start slave device, the synchronization frame is transferred between the plurality of slave devices according to a transfer order, and the slave device in each slave device A synchronization frame processing unit that causes each slave device to derive the synchronization point by adding the synchronization frame reception time and the offset time calculated by each slave device, and synchronizes the time of each slave device at the synchronization point; It is characterized by.

  According to the present invention, after a plurality of slave devices calculate their respective offset times, the synchronization frame is transferred between the plurality of slave devices according to the transfer order, and the reception time of the synchronization frame at each slave device and the calculation at each slave device. Slaves generated by a synchronization method that synchronizes in stages between multiple slave devices in order to synchronize the time of each slave device at the synchronization point by deriving a synchronization point from each slave device by adding to the offset time Accumulation of synchronization deviation between devices can be avoided, and high-precision synchronization can be realized.

1 is a diagram illustrating a configuration example of a communication system according to Embodiment 1. FIG. FIG. 3 shows a configuration example of a master device according to the first embodiment. FIG. 3 illustrates a configuration example of a slave device according to the first embodiment. FIG. 3 shows an example of a frame format such as a measurement frame according to the first embodiment. FIG. 3 is a diagram illustrating an operation principle of a master device and a slave device according to the first embodiment. FIG. 6 is a diagram for explaining a synchronization shift according to the first embodiment. FIG. 5 shows a delay measurement procedure according to the first embodiment. FIG. 5 shows a delay measurement procedure according to the first embodiment. FIG. 9 shows a delay measurement procedure according to the second embodiment. FIG. 3 is a flowchart showing an operation example of a master device according to the first embodiment. FIG. 3 is a flowchart showing an operation example of the slave device according to the first embodiment. FIG. 3 is a flowchart showing an operation example of the slave device according to the first embodiment. The figure which shows the hardware structural example of the master apparatus which concerns on Embodiment 1, and a slave apparatus.

Embodiment 1 FIG.
FIG. 1 shows a configuration example of a communication system according to the present embodiment.
In the example of FIG. 1, it is composed of one master device 100 and three slave devices 200.
The number of slave devices 200 may not be three, but may be any number.
The slave device 200 has two or more communication ports, and the master device 100 and the slave device 200 are connected by a daisy chain with a cable.
Master device 100 transmits a frame for management of slave device 200.
The slave device 200 has a frame transfer order. In the example of FIG. 1, the frame transmitted from the master device 100 is transferred in the order of the slave device 1, the slave device 2, and the slave device 3.
Conversely, a response to the frame from the master device 100 is transferred in the order of the slave device 3, the slave device 2, and the slave device 1.
Note that the slave device 200, which is the start point of the transfer order when transferring a frame from the master device 100, is also referred to as a start point slave device. In the example of FIG. 1, the slave device 1 is a start slave device.

  In the present embodiment, the frame propagation delay of the cable connecting between the master device 100 or the slave device 200 and the processing time required when the slave device 200 relays the frame are the uplink communication (from the slave device 200). Communication in the direction to the master device 100) and downlink communication (communication in the direction from the master device 100 to the slave device 200) are the same.

  Next, a configuration example of the master device 100 according to the present embodiment will be described with reference to FIG.

In FIG. 2, the synchronization point setting unit 101 sets a time point after a predetermined time from a transmission time of a synchronization frame, which will be described later, as a synchronization point that synchronizes time between the master device 100 and the plurality of slave devices 200.
For example, the synchronization point setting unit 101 sets a synchronization point at 10 seconds after the transmission time of the synchronization frame, and sets the time with the plurality of slave devices 200 when a synchronization processing unit 106 described later passes 10 seconds from the transmission time of the synchronization frame. Synchronize.
As will be described later, the slave device 1 calculates an offset time, which is an adjustment time from the reception time of the synchronization frame, and synchronizes the time when the offset time (for example, 9 seconds later) is added to the reception time of the synchronization frame. Derived as a point, receives the synchronization frame from the master device 100, transfers the received synchronization frame to the slave device 2, and further, when 9 seconds have elapsed from the reception time of the synchronization frame, the master device 100 and other slave devices 200 and time are synchronized.
Similarly, the slave device 2 calculates an offset time, which is an adjustment time in the slave device 2, and derives a time point obtained by adding an offset time (for example, 8 seconds later) to the reception time of the synchronization frame as a synchronization point. The synchronization frame is received from 1, the received synchronization frame is transferred to the slave device 3, and the time is synchronized with the master device 100 and the other slave devices 200 when 8 seconds have elapsed from the reception time of the synchronization frame.
Further, the slave device 3 calculates an offset time that is an adjustment time in the slave device 3, derives a time point obtained by adding the offset time (for example, after 7 seconds) to the reception time of the synchronization frame as a synchronization point, and the slave device 2 Then, the time is synchronized with the master device 100 and the other slave devices 200 when 7 seconds have elapsed from the reception time of the synchronization frame.

The synchronization point storage unit 102 stores the synchronization point determined by the synchronization point setting unit 101.
Further, the synchronization point storage unit 102 notifies the correction value generation unit 103 of the stored synchronization points.

The correction value generation unit 103 generates a correction value to be notified to the slave device 1.
More specifically, the correction value generation unit 103 receives a propagation delay value from the propagation delay measurement unit 104, receives a synchronization point from the synchronization point storage unit 102, and calculates a correction value from the propagation delay value and the synchronization point. To do.
The procedure for generating the correction value will be described later.

  The propagation delay measurement unit 104 is notified of a measurement frame transmission timing and a measurement response frame reception timing, which will be described later, and measures a time (delay measurement value) from the measurement frame transmission timing to the measurement response frame reception timing.

The frame processing unit 105 transmits a measurement frame to the slave device 1, receives a measurement response frame from the slave device 1, transmits a correction frame to the slave device 1, and receives a correction completion frame from the slave device 1. An update frame and a synchronization frame are transmitted to the slave device 1.
The frame processing unit 105 is an example of a measurement frame processing unit, a correction frame processing unit, an update frame processing unit, and a synchronization frame processing unit.

Here, the measurement frame is a frame for instructing the start of measurement of the propagation delay of the network.
The measurement response frame is a response of the slave device 1 to the measurement frame, and is a frame for instructing the end of the measurement of the propagation delay of the network.
The correction frame is a frame that includes the correction value generated by the correction value generation unit 103 and notifies the slave device 1 of the correction value.
The correction completion frame is a frame for notifying the master device 100 that the offset time calculation has been completed in all the slave devices 200.
The update frame is a frame that instructs each slave device 200 to select an offset time calculated in the current synchronization processing session and derive a synchronization point.
The synchronization processing session will be described later.
The synchronization frame is a frame in which the reception time at each slave device 200 is the starting point of the offset time of each slave device 200.

The frame processing unit 105 notifies the propagation delay measurement unit 104 of the transmission timing of the measurement frame and the reception timing of the measurement response frame.
Further, the frame processing unit 105 receives the correction value from the correction value generation unit 103 and transmits the correction value to the slave device 1 as a correction frame.
Further, as will be described in detail later, the frame processing unit 105 generates an offset time for each slave device 200 and transmits an update frame after receiving a correction completion frame from the slave device 1. Send.
Then, the frame processing unit 105 transfers the synchronization frame between the plurality of slave devices 200 according to the transfer order, and adds each synchronization device reception time of each synchronization device 200 to the offset time calculated by each slave device 200. The device derives a synchronization point and synchronizes the time of each slave device 200 at the synchronization point.

In the present embodiment, the period from the transmission of the measurement frame to the slave device 1 by the frame processing unit 105 to the time synchronization in each slave device 200 after the transmission of the synchronization frame by the frame processing unit 105 is referred to as a synchronization processing session.
In the present embodiment, the master device 100 and the plurality of slave devices 200 repeatedly perform a synchronization processing session every predetermined period.
For this reason, each slave device 200 calculates the offset time for each synchronization processing session.
The update frame is a frame for instructing to derive a synchronization point by selecting an offset time generated in the current (latest) synchronization processing session from the offset times calculated for each synchronization processing session.
A session ID (Identification) that is an identifier is set for each synchronization processing session.
Hereinafter, the session ID is also referred to as a measurement ID.
As will be described later, the session ID is described in the measurement frame, measurement response frame, correction frame, correction completion frame, update frame, and synchronization frame.

  Next, a configuration example of the slave device 200 according to the present embodiment will be described with reference to FIG.

In FIG. 3, the frame processing unit 201 receives a measurement frame from the master device 100 or the slave device 200 in the previous transfer order, and transmits a measurement response frame to the master device 100 or the slave device 200 in the previous transfer order.
Further, the frame processing unit 201 transmits a measurement frame to the slave device 200 in the next transfer order, and receives a measurement response frame from the slave device 200 in the next transfer order.
Also, the frame processing unit 201 receives the correction frame from the master device 100 or the slave device 200 in the previous transfer order, and transfers the correction frame including the correction value generated by the correction value generation unit 207 described later to the next transfer. Transmit to the slave device 200 in the order.
Further, the frame processing unit 201 receives the correction completion frame from the slave device 200 in the next transfer order, and transfers the correction completion frame to the master device 100 or the slave device 200 in the previous transfer order.
Further, the frame processing unit 201 receives an update frame from the master device 100 or the slave device 200 in the previous transfer order, and transmits the received update frame to the slave device 200 in the next transfer order.
Also, the frame processing unit 201 receives a synchronization frame from the master device 100 or the slave device 200 in the previous transfer order, and transmits the received synchronization frame to the slave device 200 in the next transfer order.

In addition, the frame processing unit 201 describes the reception timing of the measurement frame from the master device 100 or the slave device 200 in the previous transfer order and the transmission timing of the measurement response frame to the master device 100 or the slave device 200 in the previous transfer order. The propagation delay measuring unit 206 is notified.
Further, the frame processing unit 201 notifies the later-described propagation delay measurement unit 206 of the transmission timing of the measurement frame to the slave device 200 in the next transfer order and the reception timing of the measurement response frame from the slave device 200 in the next transfer order. To do.
In addition, the frame processing unit 201 notifies the correction time included in the correction frame to an offset time calculation unit 202 described later.
Also, the frame processing unit 201 receives a correction value from a correction value generation unit 207, which will be described later, and notifies this correction value to the slave device 200 in the next transfer order using a correction frame.
In addition, the frame processing unit 201 notifies the later-described effective offset time selection unit 205 that the update frame has been received.
In addition, the frame processing unit 201 notifies a synchronization point calculation unit 208 described later that the synchronization frame has been received.
The frame processing unit 201 includes a first measurement frame processing unit, a second measurement frame processing unit, a first correction frame processing unit, a second correction frame processing unit, an update frame processing unit, and a synchronization frame processing unit. It is an example.

  The offset time calculation unit 202 includes a time from reception of the measurement frame from the master device 100 or the slave device 200 in the previous transfer order to transmission of the measurement response frame to the master device 100 or the slave device 200 in the previous transfer order. Based on the correction value included in the received correction frame, an offset time is calculated from the reception time of the synchronization frame to the synchronization point, which is a timing for synchronizing the time with the other slave devices 200 and the master device 100.

The first storage unit 203 receives the offset time from the offset time calculation unit 202 and stores it.
The second storage unit 204 also receives the offset time from the offset time calculation unit 202 and stores it.
The first storage unit 203 and the second storage unit 204 store the offset time calculated in different synchronization processing sessions in association with the session ID of the target synchronization processing session.
For example, the first storage unit 203 stores the offset time calculated in the nth synchronization processing session, for example, in association with the session ID: n, and the second storage unit 204 stores the offset time in the n + 1th synchronization processing session. For example, the calculated offset time is stored in association with the session ID: n + 1.
Further, the first storage unit 203 and the second storage unit 204 notify the stored offset time to an effective offset time selection unit 205 described later.
The first storage unit 203 and the second storage unit 204 are examples of storage units.

The effective offset time selection unit 205 notifies the frame processing unit 201 of the session ID described in the update frame when the frame processing unit 201 receives the update frame from the master device 100 or the slave device 200 in the previous transfer order. Is done.
The effective offset time selection unit 205 receives the offset time and the session ID from each of the first storage unit 203 and the second storage unit 204, and sets the session ID that matches the session ID notified from the frame processing unit 201. The associated offset time is selected as the offset time used to derive the synchronization point.
Then, the effective offset time selection unit 205 notifies the synchronization point calculation unit 208 of the selected offset time.

The propagation delay measurement unit 206 receives the measurement frame reception timing from the master device 100 or the slave device 200 in the previous transfer order from the frame processing unit 201 and the measurement response to the slave device 200 in the master device 100 or the previous transfer order. Upon receiving notification of the frame transmission timing, the time (delay measurement value) from the reception timing to the transmission timing is measured.
The propagation delay measurement unit 206 also notifies the transmission timing of the measurement frame from the frame processing unit 201 to the slave device 200 in the next transfer order and the reception timing of the measurement response frame from the slave device 200 in the next transfer order. Then, the time (delay measurement value) from the transmission timing to the reception timing is measured.

The correction value generation unit 207 receives the delay measurement value from the propagation delay measurement unit 206. This delay measurement value is the time between the reception timing of the measurement frame from the master device 100 or the slave device 200 in the previous transfer order and the transmission timing of the measurement response frame to the slave device 200 in the master device 100 or the previous transfer order. It is.
Further, the correction value generation unit 207 receives a notification of the offset time from the offset time calculation unit 202.
Then, the correction value generation unit 207 generates a correction value from the delay measurement value and the offset time.
The generated correction value is notified as a correction frame to the slave device 200 in the next transfer order.
A correction value generation procedure by the correction value generation unit 207 will be described later.

The synchronization point calculation unit 208 receives the valid offset time from the valid offset time selection unit 205.
In addition, the synchronization point calculation unit 208 receives a notification of reception of a synchronization frame from the frame processing unit 201.
Then, the synchronization point calculation unit 208 calculates the time of the synchronization point from the notification of reception of the synchronization frame and the offset time.
More specifically, synchronization point calculation section 208 derives a synchronization point by adding the offset time received from effective offset time selection section 205 to the reception time of the synchronization frame.
Then, the synchronization point calculation unit 208 synchronizes the time with the other slave devices 200 and the master device 100 at the derived synchronization point.
The synchronization point calculation unit 298 is an example of a synchronization processing unit.

FIG. 4 is a configuration diagram showing a format of a frame transmitted / received between the master device 100 and the slave device 200 according to the present embodiment.
4A shows the frame format of the measurement frame, and FIG. 4B shows the frame format of the measurement response frame.
4C shows the frame format of the correction frame, and FIG. 4D shows the frame format of the correction completion frame.
FIG. 4E shows the frame format of the update frame, and FIG. 4F shows the frame format of the synchronization frame.
The following information is stored in the fields defined in each frame.
The destination field stores an ID for identifying the master device 100 or the slave device 200 that receives the frame.
In order for all the master devices 100 or slave devices 200 to receive, a specific address called a broadcast address is designated.
The transmission source field stores an ID for identifying the master device 100 or the slave device 200 that transmits the frame.
The frame type field stores an ID for identifying the frame type.
In the measurement ID field, an ID for identifying the order of delay measurement performed by the master device 100 or the slave device 200 is stored.
That is, the measurement ID field stores an ID (session ID) for identifying the synchronization processing session.
A common session ID (measurement ID) is stored in the measurement frame, measurement frame, correction frame, correction completion frame, update frame, and synchronization frame transmitted and received in the same synchronization processing session.
The correction frame includes a correction value.

As a premise of the communication system according to the present embodiment, the processing time for the slave device 200 to relay a frame is equal to the time for returning the frame.
Note that frame relay refers to a process of transmitting a frame received from one communication port A from another communication port B.
In addition, frame folding refers to a process of transmitting a frame received from a certain communication port A from the same communication port A.

FIG. 5 shows an outline of the synchronization method according to the present embodiment.
In the present embodiment, first, the master device 100 transmits and receives a measurement frame and a measurement response frame to and from the adjacent slave device 200 (start point slave device), and causes the adjacent slave device 200 to calculate an offset time for calculating a synchronization point. The adjacent slave device 200 that has calculated the offset time replaces the master device 100 and transmits / receives a measurement frame and a measurement response frame to / from the adjacent slave device 200 to cause the next slave device 200 to calculate an offset time for calculating the synchronization point. .
By repeating the above operation, the master device and all slave devices share the synchronization point, and the time is synchronized at the synchronization point.

Using FIG. 5 as an example, the principle of the synchronization method according to the present embodiment is shown.
The following (1) to (8) correspond to (1) to (8) shown in FIG.

(1) First, the master device 100 sets a synchronization point that is a timing for synchronizing the entire slave.
(2) The master device 100 transmits a measurement frame with the adjacent slave device 1 as a destination. Simultaneously with transmission, master device 100 starts measuring propagation delay.
(3) The slave device 1 that has received the measurement frame addressed to itself transmits a measurement response frame to the master device 100 that is the transmission source of the measurement frame.
At this time, the slave device 1 measures the time from reception of the measurement frame to transmission of the measurement response frame.
(4) The master device 100 that has received the measurement response frame ends the measurement of the propagation delay.
The master device 100 calculates a correction value based on the measured propagation delay time and synchronization point. The correction value is calculated by Equation 1.
Note that cal_delay is a propagation delay time measured by the master device 100.

(5) Further, the master device 100 transmits the calculated correction value to the slave device 1 in a correction frame.
(6) The slave device 1 receives the correction value from the master device 100.
Further, the slave device 1 calculates an offset time from the received correction value to the synchronization point.
The offset time is calculated from Equation 2.
Thus, the slave device 1 can recognize that the timing corrected by the offset time after receiving the synchronization frame transmitted for synchronization is the synchronization point, and can synchronize with the master device 100.
Note that cal_delay in Expression 2 is a propagation delay time measured by the slave device 1.

(7) The synchronized slave device 1 synchronizes with the slave device 2 adjacent to itself in the same manner as the procedure of the master device 100 from (1) to (6).
(8) By repeating the procedures from (1) to (7) by the master device 100 and all the slave devices 200, the master device 100 and all the slave devices 200 can be synchronized.

Once the master device 100 and the slave device 200 are synchronized, a synchronization shift occurs with time due to various factors.
In order to prevent this, by performing the above sequence periodically, it is possible to periodically correct the synchronization error and maintain the synchronization accuracy.

However, when the master device and the slave device are synchronized step by step as in the method shown in FIG. 5, there is a problem of accumulation of synchronization deviation.
FIG. 6 shows an outline of the synchronization loss accumulation.

First, it is assumed that the slave device 3 has been synchronized from the master device and the slave device 1, and the synchronization is shifted for some reason thereafter.
Here, as shown in FIG. 6A, the synchronization shift between the master device and the slave device 1 is α1, the synchronization shift between the slave device 1 and the slave device 2 is α2, and the synchronization shift between the slave device 2 and the slave device 3 is α3. Suppose that

  As shown in FIG. 6B, when the master device and the slave device 1 are synchronized, the synchronization deviation between the master device and the slave device 1 disappears, but the synchronization deviation between the slave device 1 and the slave device 2 is α1 + α2, and the synchronization deviation occurs. Accumulates.

  Next, as shown in FIG. 6C, when the slave device 1 and the slave device 2 are synchronized, there is no synchronization shift between the master device, the slave device 1 and the slave device 2, but the slave device 2 and the slave device 3 The synchronization deviation becomes α1 + α2 + α3, and the synchronization deviation accumulates.

In order to prevent such accumulation of synchronization deviation, in the present embodiment, the slave device 200 has two portions for storing offset times.
This corresponds to the first storage unit 203 and the second storage unit 204 of the slave device 200.
In the present embodiment, when a certain slave device 200 calculates the offset time, the offset time is not immediately effective and is temporarily stored.
Thereafter, the master device 100 transmits an update frame that makes the offset time valid to all the slave devices 200.
Each slave device 200 validates the offset time when receiving this update frame.
Until an update frame is received, synchronization is performed using the previous offset time.

Next, the communication sequence of the synchronization method according to the present embodiment will be described using the examples shown in FIGS.
The following (1) to (12) correspond to (1) to (12) shown in FIGS. 7 and 8.
Further, the sequence shown in FIGS. 7 and 8 is performed at the start of system operation, for example.

(1) The master device 100 determines a measurement ID (session ID).
In the example of this figure, measurement ID = 0 is set.
Further, the master device 100 transmits a measurement frame to the adjacent slave device 1.
At this time, the field of the measurement frame is set such that destination = slave device 1, transmission source = master device, and measurement ID = 0.
Simultaneously with transmission, the master device 100 starts propagation delay measurement.

(2) The slave device 1 that has received the destination measurement frame transmits a measurement response frame to the master device 100 that is the transmission source of the measurement frame.
At this time, the fields of the measurement response frame are set such that destination = master device, transmission source = slave device 1, and measurement ID = 0.
The measurement ID of the measurement response frame is equal to the measurement ID of the received measurement frame.
The slave device 1 also measures the propagation delay time.

(3) The master device 100 that has received the measurement response frame ends the propagation delay measurement.
Further, the master device 100 calculates a correction value based on the measured propagation delay time and synchronization point.

(4) The master device 100 transmits the calculated correction value to the adjacent slave device 1 in a correction frame.
At this time, in the correction frame field, destination = master device, transmission source = slave device 1, measurement ID = 0, correction value = calculated correction value (A in the example in the figure) is set.
Note that the measurement ID of the correction frame is equal to the measurement ID of the received measurement response frame.
The slave device 1 that has received the correction value calculates an offset time from the correction value and stores it in the first storage unit 203 (f (A) in the example in the figure).
The slave device 1 knows that the time corrected by the offset time after receiving the synchronization frame is the synchronization point.
At this time, the received offset time is not valid and is temporarily stored.
Although not defined in the present embodiment, a response frame of the correction frame is defined in advance, and the slave device 1 returns a response to the master device after this processing, so that the master device can respond to the slave device 1. The reception of the correction frame may be confirmed.

Next, the slave device 1 executes the same processing as that of the master device 100 described above on the adjacent slave device 2.
Specifically, (5) a measurement frame is transmitted to the slave device 2, (6) a measurement response frame is received from the slave device 2, and (7) a correction value is generated by the same procedure as that of the master device 100, and correction is performed. The frame is transmitted to the slave device 2.
The measurement ID of the measurement frame, measurement response frame, and correction frame at this time is equal to the measurement ID of the correction frame received by the slave device 1 from the master device 100.

(8) When the slave device 3 at the end of the network receives the correction value from the slave device 2 and calculates the offset time, the slave device 3 transmits the slave device 3 to the master device 100 to notify the master device 100 that the delay correction has been completed. 2. A correction completion frame is transmitted to the master device 100 via the slave device 1.
At this time, the field of the correction completion frame is set such that destination = master device, transmission source = slave device 3, and measurement ID = 0.
Note that the measurement ID of the correction completion frame is equal to the measurement ID of the correction frame received by the slave device 3.

(9) The master device 100 that has received the correction completion frame compares the measurement ID of the received correction completion frame with the measurement ID that is initially set by itself.
(A) When the two match, the master device 100 transmits an update frame by broadcast in order to validate the offset time of each slave device 200.
The update frame fields are set such that destination = broadcast address, transmission source = master device, and measurement ID = 0.
The measurement ID of the update frame is equal to the measurement ID of the correction completion frame received by itself.
(A) On the other hand, when the measurement IDs do not match, the process restarts from (2).

(10) The slave device 200 that has received the update frame validates the offset time corresponding to the measurement ID of the update frame.
Thereafter, when a synchronization frame is received, a synchronization point is calculated using an effective offset time.
Although not defined in the present embodiment, a frame for response of an update frame is defined in advance, and the slave device that has received the update frame after this processing returns a response to the master device. However, the reception of the update frame of the slave device may be confirmed.

(11) Next, the master device 100 transmits a synchronization frame to all the slave devices 200.
It can be seen that all the slave devices 200 have the same standby time for the effective offset time from the reception time of the synchronization frame in all the master devices 100 and the slave devices 200.
With this as a reference (synchronization point), all the master devices 100 and slave devices 200 are synchronized.

(12) When starting the next synchronization processing session, the master device 100 sets the measurement ID to another value, and performs the processing from (1) to (11).

Next, details of operations of the master device 100 and the slave device 200 shown in FIGS. 7 and 8 will be described with reference to FIGS.
10 shows an operation example of the master device 100, and FIGS. 11 and 12 show an operation example of the slave device 200. FIG.

First, in the master device 100, the synchronization point setting unit 101 sets a synchronization point that is a timing for synchronizing the entire slave device 200 (FIG. 10: S1001) (synchronization point setting step).
Further, the synchronization point storage unit 102 stores the synchronization point set by the synchronization point setting unit 101.
At this time, the synchronization point setting unit 101 determines the session ID (measurement ID) of the current synchronization processing session.

Next, in the master device 100, the frame processing unit 105 generates a measurement frame destined for the adjacent slave device 1 and transmits the measurement frame (FIG. 10: S1002) (measurement frame processing step).
This measurement frame includes the measurement ID determined by the synchronization point setting unit 101.
The same measurement ID is also used in a measurement response frame, a correction frame, a correction completion frame, an update frame, and a synchronization frame, which will be described later.
Simultaneously with the transmission of the measurement frame, the frame processing unit 105 notifies the propagation delay measurement unit 104 of the transmission of the measurement frame, and the propagation delay measurement unit 104 starts measuring the propagation delay.

In the slave device 1, the frame processing unit 201 receives the measurement frame addressed to itself (FIG. 11: S2001) (first measurement frame processing step), and sends it to the master device 100 that is the transmission source of the measurement frame. A measurement response frame is transmitted (FIG. 11: S2002) (first measurement frame processing step).
At this time, in the slave device 1, the frame processing unit 201 notifies the propagation delay measurement unit 206 of the reception timing of the measurement frame and the transmission timing of the measurement response frame, and the propagation delay measurement unit 206 receives the measurement response from the reception of the measurement frame. Measure the time until frame transmission.

Next, in the master device 100, the frame processing unit 105 receives the measurement response frame (FIG. 10: S1003) (measurement frame processing step), notifies the propagation delay measurement unit 104 of the reception of the measurement response frame, and transmits the propagation delay. The measurement unit 104 ends the measurement of the propagation delay.
Next, in the master device 100, the correction value generation unit 103 calculates a correction value based on the propagation delay time measured by the propagation delay measurement unit 104 and the synchronization point stored in the synchronization point storage unit 102 ( FIG. 10: S1004) (correction value generation step).
The correction value is calculated by Equation 1 described above.
Here, Equation 1 is presented again.
Note that cal_delay is a propagation delay time measured by the propagation delay measurement unit 104 (time from transmission of a measurement frame to reception of a measurement response frame).

  Next, in the master device 100, the frame processing unit 105 generates a correction frame including the correction value generated by the correction value generation unit 103, and transmits the correction frame to the adjacent slave device 1 (FIG. 10: S1005). (Correction frame processing step).

In the slave device 1, the frame processing unit 201 receives the correction frame (FIG. 11: S2003) (first correction frame processing step).
Next, in the slave device 1, the offset time calculation unit 202 receives the correction value from the frame processing unit 201, and calculates the offset time from the correction value and the propagation delay time measured by the propagation delay measurement unit 206 (FIG. 11: S2004) (offset time calculation step).
The offset time calculation unit 202 calculates the offset time according to the above equation 2.
Here, Equation 2 is presented again.
Note that cal_delay in Expression 2 is a propagation delay time (time from reception of a measurement frame to transmission of a measurement response frame) measured by the slave device 1.

Thereafter, the slave device 1 stores the calculated offset time in the first storage unit 203 or the second storage unit 204 (FIG. 11: S2005).
As a result, the slave device 1 knows that the time when the offset time has elapsed after receiving the synchronization frame transmitted for synchronization is the synchronization point, and synchronizes with the master device 100 at the synchronization point when the synchronization frame is received. can do.

The slave device 1 that has calculated the offset time performs the above procedure with the slave device 2 instead of the master device 100 itself, and causes the slave device 2 to calculate the offset time.
Since the slave device 1 includes the slave device 2 that is the slave device in the next transfer order (FIG. 11: YES in S2006), the frame processing unit 201 transmits a measurement frame to the slave device 2 (FIG. 11: S2007). (Second measurement frame processing step).
At this time, the propagation delay measuring unit 206 starts measuring the propagation delay time.
In the slave device 1, the frame processing unit 201 receives the measurement response frame from the slave device 2 (FIG. 11: S2008) (second measurement frame processing step).
The propagation delay measuring unit 206 ends the measurement of the propagation delay time upon reception of the measurement response frame.
The operation of the slave device 2 at this time is as shown in S2001 and S2002 of FIG.

Next, in the slave device 1, the correction value generation unit 207 generates a correction value based on the propagation delay time (transmission of measurement frame to reception of measurement response frame) measured by the propagation delay measurement unit 206 and the offset time. (FIG. 11: S2009) (correction value generation step).
The correction value calculation formula by the correction value generation unit 207 is as the following formula 3.

  Next, in the slave device 1, the frame processing unit 201 generates a correction frame including the correction value generated by the correction value generation unit 207, and transmits the correction frame to the slave device 2 (FIG. 11: S2010) (first step). 2 correction frame processing step).

In the slave device 2, the frame processing unit 201 receives the correction frame (FIG. 11: S2003) (first correction frame processing step).
In the slave device 2, the offset time calculation unit 202 receives the correction value from the frame processing unit 201, and calculates the offset time from the correction value and the propagation delay time measured by the propagation delay measurement unit 206 (FIG. 11). : S2004) (offset time calculating step), the calculated offset time is stored in the first storage unit 203 or the second storage unit 204 (FIG. 11: S2005).
Calculation of the offset time by the offset time calculation unit 202 is based on Equation 2 above.

  In this way, the offset times are sequentially calculated in the plurality of slave devices 200 according to the transfer order.

  7 and 8, when the calculation and storage of the offset time is completed in the slave device 3 (FIG. 11: S2005), the slave device 3 does not have the slave device 200 in the next transfer order (FIG. 11: FIG. 11). In S2006, the frame processing unit 201 of the slave device 3 transmits a correction completion frame notifying that the calculation of the offset time has been completed to the slave device 2 (FIG. 11: S2012).

In the slave device 2, the frame processing unit 201 receives the correction completion frame transmitted from the slave device 3 (FIG. 11: S2011) and transmits it to the slave device 1 (FIG. 11: S2012).
In the slave device 1, the frame processing unit 201 receives the correction completion frame transmitted from the slave device 2 (FIG. 11: S2011), and transmits it to the master device 100 (FIG. 11: S2012).

In the master device 100, the frame processing unit 105 receives the correction completion frame transmitted from the slave device 1 (FIG. 10: S1006), and updates if the session ID of the correction completion frame matches the session ID set in S1001. The frame is transmitted to the slave device 1 (FIG. 10: S1007).
In the slave device 1, the frame processing unit 201 receives the update frame (FIG. 12: S2013), and the effective offset time selection unit 205 stores the offset time stored in the first storage unit 203 and the second storage unit. Among them, the offset time associated with the same session ID as the session ID included in the update frame is selected (FIG. 12: S2014).
Further, since the slave device 1 has the slave device 2 that is the slave device in the next transfer order (FIG. 12: YES in S2015), the frame processing unit 201 transmits the update frame to the slave device 2 (FIG. 12: S2015).
Similarly, the slave device 2 and the slave device 3 receive the update frame and select the offset time.

Next, in the master device 100, the frame processing unit 201 transmits a synchronization frame to the slave device 1 (FIG. 10: S1008) (synchronization frame processing step).
In the slave device 1, since the frame processing unit 201 receives the synchronization frame (FIG. 12: S2017) (synchronization frame processing step), there is the slave device 2 that is the slave device in the next transfer order (FIG. 12: S2018). The frame processing unit 201 transmits a synchronization frame to the slave device 2 (FIG. 12: S2019) (synchronization frame processing step).

In the slave device 1, the synchronization point calculation unit 208 derives the synchronization point by adding the offset time selected in S2014 to the reception time of the synchronization frame in S2017 (FIG. 12: S2020) (synchronization processing step). The time is synchronized at (FIG. 12: S2021) (synchronization processing step).
Similarly, the slave device 2 and the slave device 3 receive the synchronization frame, derive the synchronization point, and synchronize the time at the synchronization point.
Similarly, also in the master device 100, the synchronization processing unit 106 synchronizes the time at the synchronization point (FIG. 10: S1009).

In addition to the above operation, in the present embodiment, master device 100 transmits a synchronization frame at a constant cycle (a cycle shorter than the cycle of the synchronization processing session) before the correction completion frame is returned.
For example, the synchronization frame shown as the (re) sync frame in FIG. 8 is transmitted from the master device 100 before the correction completion frame is returned.
This is because even if the correction completion frame is returned and before the update frame is transmitted, synchronization is performed using the offset time calculated in the previous synchronization processing session on the basis of the (re) sync frame. is there.
The field values of the (re) sync frame in FIG. 8 are (BC, M, 0).
This indicates that destination address = broadcast address, transmission source address = master device 100, and measurement ID = 0.
In the second delay measurement (second synchronization processing session), measurement ID = 1 is used in the measurement frame, measurement response frame, correction frame, etc., but the measurement ID of this (re) synchronous frame has a value of 0. is there.
Before the (re) synchronization frame is transmitted, the correction frame (measurement ID = 1) is transmitted, and the slave device 200 calculates the offset time in the second synchronization processing session based on the correction frame, and the second It is stored in the storage unit. For example, in the slave device 1, offset time = f (A ′) is stored in the second storage unit for ID = 1. On the other hand, offset time = f (A) (offset time in the first synchronization processing session) is stored for ID = 0 in the first storage unit.
In the slave device 1 that has received the (re) synchronization frame with the measurement ID = 0, the effective offset time selection unit 205 has the offset time in the first storage unit = f ( A) is selected, and the synchronization point calculation unit 208 calculates the synchronization point by adding the offset time = f (A) selected by the effective offset time selection unit 205 to the reception time of the (re) synchronization frame. The master device 100 and the other slave devices 200 are synchronized when the point arrives.
The (re) synchronization frame is transferred in the order of the slave device 1, the slave device 2, and the slave device 3 in the same manner as the synchronization frame, and each slave device is synchronized using the offset time in the first storage unit. It is done.
Further, when an update frame including measurement ID = 1 is transmitted from the master device 100 and the slave device 1 receives this update frame, the effective offset time selection unit 205 determines that the update frame measurement ID = 1, When the offset time in the second storage unit = f (A ′) is selected and the synchronization frame (measurement ID = 1) is received, the synchronization point calculation unit 208 selects the effective offset time selection unit at the reception time of the synchronization frame. The synchronization point is calculated by adding the offset time = f (A ′) selected in 205, and synchronization is established with the master device 100 and the other slave devices 200 when the synchronization point arrives.

Although not shown in FIG. 7, after the synchronization frame is transmitted in the first delay measurement (first synchronization processing session) and the master device 100 and each slave device 200 are synchronized at the synchronization point, A (re) synchronization frame (measurement ID = 0) may be transmitted before the second delay measurement (second synchronization processing session) starts.
Also in this case, in each slave device 200, the effective offset time selection unit 205 selects the offset time = f (A) in the first storage unit based on the measurement ID = 0 of the (re) sync frame, and synchronizes. The point calculation unit 208 calculates a synchronization point by adding the offset time = f (A) selected by the effective offset time selection unit 205 to the reception time of the (re) synchronization frame, and the master device 100 at the arrival of the synchronization point And other slave devices 200 are synchronized.

As described above, the slave device 200 according to the present embodiment has a storage unit that stores a plurality of offset times calculated in a plurality of synchronization processing sessions.
In the slave device 200, the synchronization point calculation unit 208 synchronizes the time at the synchronization point in the n (n ≧ 1) synchronization processing session, and further, the offset time calculation unit 202 in the n + 1th synchronization processing session. After the new offset time is calculated and before the update frame is received, the resynchronization frame may be received from the master device 100 or the slave device 200 in the previous transfer order.
In such a case, the synchronization point calculation unit 208 extracts the offset time calculated in the n-th synchronization processing session from one of the storage units, and receives the resynchronization frame reception time in the n-th synchronization processing session. The calculated offset time is added to derive the synchronization point again, and the time is synchronized again with the other slave devices 200 and the master device 100 at the derived synchronization point.

In the slave device 200 according to the present embodiment, in the n (n ≧ 1) -th synchronization processing session, after the synchronization point calculation unit 208 synchronizes the time at the synchronization point, the n + 1-th synchronization is performed. Before the processing session starts, a resynchronization frame may be received from the master device 100 or the slave device 200 in the previous transfer order.
In such a case, the synchronization point calculation unit 208 extracts the offset time calculated in the n-th synchronization processing session from one of the storage units, and receives the resynchronization frame reception time in the n-th synchronization processing session. The calculated offset time is added to derive the synchronization point again, and the time is synchronized again with the other slave devices 200 and the master device 100 at the derived synchronization point.

  As described above, according to the present embodiment, after the plurality of slave devices calculate the respective offset times, the synchronization frame is transferred between the plurality of slave devices according to the transfer order, and the reception time of the synchronization frame in each slave device and each Synchronization method that synchronizes multiple slave devices step by step to synchronize the time of each slave device at the synchronization point by deriving the synchronization point to each slave device by adding to the offset time calculated by the slave device Thus, it is possible to avoid accumulation of synchronization deviation between slave devices, and to achieve highly accurate synchronization.

  Further, by repeating the synchronization processing session at a constant period, synchronization can be periodically performed between the master apparatus and the plurality of slave apparatuses, and accumulation of synchronization deviation can be avoided.

  Further, by transmitting the resynchronization frame before transmission of the update frame, synchronization can be achieved before transmission of the update frame, and accumulation of synchronization deviation can be avoided.

As described above, in the present embodiment, the function and sequence for preventing the accumulation of synchronization deviation have been described in the communication system including the master device and a plurality of slave devices.
Specifically, the function and sequence for enabling the information set for synchronization by the slave device to be temporarily stored without being used immediately for synchronization, and for the information temporarily stored after the master device command is received. explained.

  Further, in the present embodiment, the synchronization for synchronizing the processing timing with the master device or other slave devices based on the master device that transmits predetermined information and the information transmitted by the master device or the information transmitted by the slave device. A synchronization network and a synchronization system including a plurality of slave devices that calculate time (synchronization points) have been described.

In the present embodiment,
It has been described that the master device includes the following means.
(A) Frame processing unit Transmits or receives the following frames to the slave device.
A frame (measurement frame) for instructing the start of measurement of network propagation delay.
A frame (measurement response frame) for instructing the end of measurement of network propagation delay.
A frame (correction frame) for notifying other slave devices of the correction value.
Frame for notifying the master of completion of synchronization (correction completion frame).
A frame (update frame) for notifying other slave devices that the offset time is valid.
A frame (synchronization frame) for instructing another slave device to start synchronization.
The transmission timing and reception timing of the frame are notified to a propagation delay measurement unit described later.
A correction value is received from a correction value generation unit described later, and the correction value is transmitted as a correction frame to another slave device.
(B) Propagation delay measurement unit Receives the reception timing of the measurement frame and the transmission timing of the measurement response frame from the frame processing unit, and measures the time (delay measurement value) from the transmission timing to the reception timing.
The measured value is notified to a correction value generation unit described later.
(C) Correction value generation unit Receives a propagation delay value from the propagation delay measurement unit.
A synchronization point is received from a synchronization point storage unit described later.
A correction value is calculated from the propagation delay value and the synchronization point.
The correction value is notified to the frame processing unit.
(D) Synchronization point storage unit Stores synchronization points.
The synchronization point is notified to the correction value generation unit.

In the present embodiment, the slave device including the following means has been described.
(A) Frame processing unit The following frame is transmitted to the master device or another slave device.
Measurement frame,
Measurement response frame,
Correction frame,
Update frame,
Correction complete frame,
Sync frame.
The frame is received from the master device or another slave device.
The transmission timing and reception timing of the frame and the frame information are notified to a propagation delay measuring unit described later.
Notifies an effective offset time selection section (to be described later) that an update frame has been received.
A correction value is received from a correction value generation unit to be described later, and this correction value is notified to other slave devices in a correction frame.
A synchronization point calculation unit described later is notified that a synchronization frame has been received.
(B) First storage unit Receives and stores the offset time.
The stored offset time is notified to an effective offset time selection section described later.
(C) Second storage unit Receives and stores the offset time.
The stored offset time is notified to an effective offset time selection section described later.
(D) Effective offset time selection unit Receives an offset time from the first storage unit.
The offset time is received from the second storage unit.
A frame reception notification for notifying other slave devices that the offset time is valid is received from the frame processing unit.
The effective offset time is determined from the above three pieces of information, and the effective offset time is notified to a synchronization point calculation unit described later and a correction value generation unit described later.
(D) Synchronization point calculation unit Receives an effective offset time from the effective offset time selection unit.
A frame reception notification for instructing the start of synchronization is received from the frame processing unit.
The time of the synchronization point is calculated from the notification of frame reception and the offset time.
(E) Propagation delay measurement unit Receives the reception timing of the measurement frame and the transmission timing of the measurement response frame from the frame processing unit, and measures the time (delay measurement value) from the transmission timing to the reception timing.
The transmission timing of the measurement frame and the reception timing of the measurement response frame are received from the frame processing unit, and the time (delay measurement value) from the reception timing to the transmission timing is measured.
The measured value is notified to a correction value generation unit described later.
(F) Correction value generation unit Receives a propagation delay value from the propagation delay measurement unit.
Receives offset time.
A correction value is calculated from the propagation delay value and the offset time.
The correction value is notified to the frame processing unit.

Further, in the present embodiment, the synchronization system that realizes synchronization in the following processing sequence has been described.
The master device transmits a measurement frame with the adjacent slave device as a destination. Simultaneously with the transmission, the master device and the slave device start propagation delay measurement.
The slave device that has received the destination measurement frame transmits a measurement response frame to the transmission source of the measurement frame.
The master device that has received the measurement response frame ends the propagation delay measurement. A correction value is calculated based on the measured propagation delay time and synchronization point.
The calculated correction value is transmitted to the adjacent slave device.
The slave device that has received the correction value calculates an offset time and stores the offset time.
It can be seen that the time corrected by the offset time after receiving the synchronization frame is the synchronization point. At this time, the generated offset time is not valid.
Next, the slave device executes the same process as that of the master device described above for the adjacent slave device.
When the slave device at the end of the network receives the correction value, a correction completion frame is transmitted to the master device in order to notify the master device that the delay correction has been completed.
The master device transmits an update frame.
The slave device that has received the update frame sets the last calculated offset time as the effective offset time. Thereafter, the synchronization point is calculated using the reception time of the synchronization frame and the valid offset time.
The master device transmits a synchronization frame to all slave devices. It can be seen that the slave device that has received the synchronization frame has the same standby time for the effective offset time in all master devices and slave devices.

In the present embodiment, the master device and the slave device transmit a measurement frame, a measurement response frame, a correction frame, and an update frame at the start of system operation, and a synchronous system in which all master and slave devices are synchronized. explained.
Although the transmission order of the frames is specified, synchronization can be realized even if frames other than those used for synchronization are transmitted in between.

Embodiment 2. FIG.
In the first embodiment, for example, when user data is not transmitted and received between the master device 100 and the slave device 200, such as at the start of system operation, an example is described in which measurement frames are transmitted and received to synchronize. .
However, the synchronization method described in the first embodiment can perform synchronization correction by sharing with other communication (for example, communication of user data).
In particular, if you want to perform periodic communication (periodic communication) at high speed, you can reduce the frame transmission for synchronization correction and save the communication band by carrying out synchronization correction information together with periodic communication, It is possible to realize high-speed periodic communication and high synchronization accuracy.
In the following, an embodiment of carpooling for synchronization correction will be shown by taking a certain periodic communication protocol as an example.
Note that the synchronous correction carpooling is not limited to the periodic communication protocol given as an example.

  When carrying out carpooling, the frame destination, transmission source, and frame type defined in the first embodiment may be unified with the frame field defined in the periodic communication protocol.

  For example, the periodic communication protocol that is the subject of the synchronization correction is shown in FIG.

The periodic communication protocol in FIG. 9 transmits a downlink communication frame from the master apparatus to the slave apparatus 1 in the period i and the period i + 2.
In the downlink communication frame from the master device, user data addressed to the slave device 3, user data addressed to the slave device 2, and user data addressed to the slave device 1 are arranged in this order after the header, and transmission is started in this order.
The slave device 1 receives the downlink communication frame, transfers user data addressed to the slave device 3 that is not addressed to the own device, and user data addressed to the slave device 2 to the slave device 2, and only user data addressed to the slave device 1 is transmitted. get.
Similarly, in the slave device 2, user data addressed to the slave device 3 is transferred to the slave device 3, and only user data addressed to the slave device 2 is acquired.

In the cycle i + 1, each slave device transmits an uplink communication frame.
Specifically, first, slave device 1 transmits user data from its own device, then slave device 2 transmits user data from its own device, and then slave device 3 receives user data from its own device. Send data.
The slave device 2 starts receiving the user data from the slave device 3 at the timing when the transmission of the user data of the slave device 2 is completed, and transfers the user data from the slave device 3 following the user data of the slave device 2. To start. Note that the header from the slave device 3 is discarded.
The slave device 1 starts receiving user data from the slave device 2 at the timing when the transmission of user data from the slave device 1 is completed, and transfers user data from the slave device 2 following the user data from the slave device 1. To start. Note that the header from the slave device 2 is discarded.
In addition, at the timing when the transmission of user data from the slave device 2 is completed, the reception of user data from the slave device 3 is started, and the user data from the slave device 3 is transferred following the user data from the slave device 2. Start.

An example in which a frame for synchronization correction is added to the periodic communication protocol will be described below.
The following (1) to (8) correspond to (1) to (8) in FIG.

(1) The master device performs downlink communication of periodic communication at a timing determined by the periodic communication protocol.
The downlink communication frame includes information that the frame functions as a measurement frame, information for identifying a master device or a slave device that performs correction, and information for identifying a slave device that performs correction.
In the example of FIG. 9, a device that performs correction is a master device, and a device that performs correction is a slave device 1.
After transmitting the downlink communication frame, the master device starts delay measurement.

(2) Each slave device that has received the downlink communication frame (measurement frame) determines whether or not the subject to be corrected is itself, and starts delay measurement if it is itself.
In the example of FIG. 9, the slave device 1 starts delay measurement after receiving a downlink communication frame.

(3) The slave device 1 transmits an uplink communication frame at a timing determined by the periodic communication protocol.
The uplink communication frame includes information indicating that this frame functions as a measurement response frame and information for identifying the destination of the measurement response frame (a device that performs correction).
Thereafter, the delay measurement is terminated.

(4) The master device and the slave device that have received the uplink communication frame determine whether the destination of the measurement response frame is itself.
If it is itself, the delay measurement is terminated.
In the example of FIG. 9, the master device is the destination of the measurement response frame, and the delay measurement ends.

(5) The master device and the slave device that have received the measurement response frame calculate a correction value from the delay measurement value and the synchronization point (or offset time) measured by the master device and the slave device.
The calculation formula is Formula 1 or Formula 3 shown in Embodiment 1.
In the example of FIG. 9, the master device calculates a correction value.

(6) The master device performs downlink communication at a timing determined by the periodic communication protocol.
The downlink communication frame includes information that the frame includes a correction frame, information for identifying a slave device that is a target for delay correction, and information on a correction value calculated by the master device.
In the example of FIG. 9, the delay correction target is the slave device 1.

(7) Each slave device that has received the downlink communication frame (including the correction frame) determines whether or not the delay correction target is itself. calculate.
The formula for calculating the offset time is the formula 2 shown in the first embodiment.
In the example of FIG. 9, the slave device 1 calculates an offset time after receiving a downlink communication frame.
Thus, the slave device 1 can recognize that the time corrected by the offset time after receiving the synchronization frame transmitted for synchronization is the synchronization point, and can synchronize with the master device.
In order to confirm that the measurement frame is received by the slave device, a response frame of the measurement frame may be defined in advance, and the slave device 1 may return a response to the master device after this processing.

(8) Next, the slave device 1 becomes a device that performs correction, and the slave device 2 becomes a device that performs correction, and performs the processes (1) to (7).
The calculation formula used when the slave device 1 calculates the correction value is the formula 3 shown in the first embodiment.
All slave devices perform the processes (1) to (7), and all slave devices calculate the offset time, so that all master devices and slave devices can know the synchronization point and can synchronize. .
As in the first embodiment, a correction completion frame, an update frame, and a synchronization frame are also transmitted / received.
Regarding the update frame, in order to confirm that the update frame has been received by each slave device, a response frame of the update frame is defined in advance, and the slave device 1 responds to the master device after the update frame is transmitted. May be returned.
More specifically, the correction completion frame is included in the upstream communication frame and transmitted from the slave device 3 to the master device, and the update frame and the synchronization frame are included in the downstream communication frame and transmitted from the master device to each slave device. The
Note that the processing not particularly described in the present embodiment is the same as that described in the first embodiment.
Also, a configuration example of the master device according to the present embodiment is as shown in FIG. 2, and a configuration example of the slave device according to the present embodiment is as shown in FIG.

As described above, in the present embodiment, the master device transmits the measurement frame, the correction frame, the update frame, and the synchronization frame at the transmission timing of the downlink communication frame.
Further, the slave device receives the measurement frame, the correction frame, the update frame, and the synchronization frame transmitted at the transmission timing of the downlink communication frame, and performs a process corresponding to each frame.
Further, the slave device transmits a measurement frame and a correction frame to the slave device in the next transfer order at the transmission timing of the downlink communication frame.
Further, the slave device transmits the measurement response frame and the correction completion frame at the transmission timing of the uplink communication frame.
In addition, the master device receives the measurement response frame and the correction completion frame transmitted at the transmission timing of the uplink communication frame, and performs processing corresponding to each frame.

  As described above, according to the present embodiment, since the frame for synchronization correction is transmitted together with the communication of user data, there is no need to provide a special phase for transmission / reception of the frame for synchronization correction. Communication efficiency can be improved.

As described above, in the present embodiment, the master device and the slave device transmit a measurement frame, a measurement response frame, a correction frame, an update frame, and the like when the network is operating during system operation, and explain a synchronization system that corrects a synchronization shift. did.
At this time, the synchronization correction shift is simultaneously performed in the entire system to prevent the synchronization shift accumulation.

Finally, a hardware configuration example of the master device 100 and the slave device 200 described in the first and second embodiments will be described.
FIG. 13 is a diagram illustrating an example of hardware resources of the master device 100 and the slave device 200 illustrated in the first and second embodiments.
The configuration in FIG. 13 is merely an example of the hardware configuration of the master device 100 and the slave device 200, and the hardware configuration of the master device 100 and the slave device 200 is not limited to the configuration described in FIG. Other configurations may be used.
Further, the master device 100 and the slave device 200 may have different hardware configurations.

In FIG. 13, the master device 100 and the slave device 200 include a CPU 911 (also referred to as a central processing unit, a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, and a processor) that executes a program.
The CPU 911 is connected to, for example, a ROM (Read Only Memory) 913, a RAM (Random Access Memory) 914, a communication board 915, a display device 901, a keyboard 902, a mouse 903, and a magnetic disk device 920 via a bus 912. Control hardware devices.
Further, the CPU 911 may be connected to an FDD 904 (Flexible Disk Drive), a compact disk device 905 (CDD), a printer device 906, and a scanner device 907. Further, instead of the magnetic disk device 920, a storage device such as an optical disk device or a memory card (registered trademark) read / write device may be used.
The RAM 914 is an example of a volatile memory. The storage media of the ROM 913, the FDD 904, the CDD 905, and the magnetic disk device 920 are an example of a nonvolatile memory. These are examples of the storage device.
The “synchronization point storage unit 102”, “first storage unit 203”, and “second storage unit 204” described in the first and second embodiments are realized by the RAM 914, the magnetic disk device 920, and the like.
A communication board 915, a keyboard 902, a mouse 903, a scanner device 907, an FDD 904, and the like are examples of input devices.
The communication board 915, the display device 901, the printer device 906, and the like are examples of output devices.

  As shown in FIG. 1, the communication board 915 is connected to a network. For example, the communication board 915 may be connected to a LAN (local area network), the Internet, a WAN (wide area network), a SAN (storage area network), or the like.

The magnetic disk device 920 stores an operating system 921 (OS), a window system 922, a program group 923, and a file group 924.
The programs in the program group 923 are executed by the CPU 911 using the operating system 921 and the window system 922.

The RAM 914 temporarily stores at least part of the operating system 921 program and application programs to be executed by the CPU 911.
The RAM 914 stores various data necessary for processing by the CPU 911.

The ROM 913 stores a BIOS (Basic Input Output System) program, and the magnetic disk device 920 stores a boot program.
When the master device 100 and the slave device 200 are activated, the BIOS program in the ROM 913 and the boot program in the magnetic disk device 920 are executed, and the operating system 921 is activated by the BIOS program and the boot program.

  The program group 923 includes “˜ unit” (“synchronization point storage unit 102”, “first storage unit 203”, and “second storage unit 204”) in the description of the first and second embodiments. The program which performs the function demonstrated as) is memorize | stored. The program is read and executed by the CPU 911.

In the file group 924, in the description of the first and second embodiments, “determination of”, “calculation of”, “calculation of”, “derivation of”, “generation of”, “comparison of” ”,“ Update of ”,“ setting of ”,“ registration of ”,“ selection of ”, etc. It is stored as each item of "~ file" and "~ database".
The “˜file” and “˜database” are stored in a recording medium such as a disk or a memory. Information, data, signal values, variable values, and parameters stored in a storage medium such as a disk or memory are read out to the main memory or cache memory by the CPU 911 via a read / write circuit, and extracted, searched, referenced, compared, and calculated. Used for CPU operations such as calculation, processing, editing, output, printing, and display.
Information, data, signal values, variable values, and parameters are stored in the main memory, registers, cache memory, and buffers during the CPU operations of extraction, search, reference, comparison, calculation, processing, editing, output, printing, and display. It is temporarily stored in a memory or the like.
In addition, the arrows in the flowcharts described in the first and second embodiments mainly indicate input / output of data and signals, and the data and signal values are the RAM 914 memory, the FDD 904 flexible disk, the CDD 905 compact disk, and the magnetic field. Recording is performed on a recording medium such as a magnetic disk of the disk device 920, other optical disks, mini disks, DVDs, and the like. Data and signals are transmitted online via a bus 912, signal lines, cables, or other transmission media.

In addition, what is described as “˜unit” in the description of the first and second embodiments may be “˜circuit”, “˜device”, “˜device”, and “˜step”, It may be “˜procedure” or “˜processing”.
That is, the “time synchronization method” according to the present invention can be realized by the steps, procedures, and processes shown in the flowcharts described in the first and second embodiments.
Further, what is described as “˜unit” may be realized by firmware stored in the ROM 913. Alternatively, it may be implemented only by software, or only by hardware such as elements, devices, substrates, and wirings, by a combination of software and hardware, or by a combination of firmware. Firmware and software are stored as programs in a recording medium such as a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, and a DVD. The program is read by the CPU 911 and executed by the CPU 911. That is, the program causes the computer to function as “to part” in the first and second embodiments. Alternatively, the computer executes the procedure and method of “to unit” in the first and second embodiments.

  As described above, the master device 100 and the slave device 200 described in the first and second embodiments are displayed as output devices such as a CPU as a processing device, a memory as a storage device, a magnetic disk, a keyboard as an input device, a mouse, a communication board, and the like. A computer including a device, a communication board, and the like, and implements the functions indicated as “˜units” using the processing device, the storage device, the input device, and the output device as described above.

  100 master device, 101 synchronization point setting unit, 102 synchronization point storage unit, 103 correction value generation unit, 104 propagation delay measurement unit, 105 frame processing unit, 106 synchronization processing unit, 200 slave device, 201 frame processing unit, 202 offset time Calculation unit, 203 first storage unit, 204 second storage unit, 205 effective offset time selection unit, 206 propagation delay measurement unit, 207 correction value generation unit, 208 synchronization point calculation unit.

Claims (21)

A master device that manages a plurality of slave devices provided with a frame transfer order,
A synchronization point setting unit that sets a time point after a predetermined time from the transmission time of the synchronization frame as a synchronization point for synchronizing the time in the plurality of slave devices;
A measurement frame processing unit that transmits a measurement frame for delay measurement to a start point slave device that is a start point of a transfer order, and receives a measurement response frame that is a response to the measurement frame from the start point slave device;
Based on the time from transmission of the measurement frame to reception of the measurement response frame, a delay time that occurs when the frame is transmitted from the master device to the start slave device is calculated, and the calculated delay time is subtracted from the predetermined time. A correction value generation unit for generating correction values
A correction frame processing unit that transmits a correction frame including the correction value to the start point slave device;
The start-point slave device receives the correction frame, and based on a time from reception of the measurement frame to transmission of the measurement response frame in the start-point slave device and the correction value included in the correction frame, the start-point slave Calculating an offset time from the reception time of the synchronization frame to the synchronization point in a device, transmitting a measurement frame to a slave device in the next transfer order and receiving a measurement response frame from the slave device in the next transfer order, Based on the time from the transmission of the measurement frame to the reception of the measurement response frame, the delay time that occurs when the frame is transmitted from the start slave device to the slave device in the next transfer order is calculated, and the calculated delay time is the offset A correction value is generated by subtracting from the time, and a correction frame that includes the correction value is generated. The over-time after sending to the slave device of the next transfer sequence, the plurality of slave devices at later similar procedure to calculate each offset time according to the transfer order,
A synchronization frame whose reception time in each slave device is a starting point of the offset time of each slave device is transmitted to the start slave device, the synchronization frame is transferred between the plurality of slave devices according to a transfer order, and the slave device in each slave device A synchronization frame processing unit that causes each slave device to derive the synchronization point by adding the synchronization frame reception time and the offset time calculated by each slave device, and synchronizes the time of each slave device at the synchronization point; A master device characterized by The master device is
The synchronization processing session is performed every predetermined period from transmission of the measurement frame by the measurement frame processing unit to time synchronization in each slave device after transmission of the synchronization frame by the synchronization frame processing unit. The master device according to 1. The master device is
Manage multiple slave devices that store multiple offset times calculated in multiple synchronization sessions,
The correction frame processing unit
After transmitting the correction frame, from the start slave device, receiving a correction completion frame notifying that the offset time has been calculated in the plurality of slave devices,
The master device further includes:
After the correction completion frame is received by the correction frame processing unit, an update frame for instructing each slave device to select the offset time calculated in the current synchronization processing session and derive the synchronization point is used as the start slave device. An update frame processing unit that transmits the update frame according to a transfer order between the plurality of slave devices,
The synchronization frame processing unit
The master device according to claim 2, wherein the synchronization frame is transmitted to the start slave device after the update frame is transmitted by the update frame processing unit. The master device is
Managing a plurality of slave devices that store a plurality of offset times calculated in a plurality of synchronization processing sessions in association with a session ID representing each synchronization processing session;
The update frame processing unit
The master device according to claim 3, wherein after the correction completion frame is received by the correction frame processing unit, an update frame in which a session ID representing a current synchronization processing session is described is transmitted. The synchronization frame processing unit
In the n (n ≧ 1) synchronization processing session, after each slave device synchronizes the time at the synchronization point and before the (n + 1) th synchronization processing session starts,
Each slave device transmits a resynchronization frame whose reception time at each slave device is a starting point of the offset time of each slave device to the start slave device, and transfers the resynchronization frame between the plurality of slave devices according to a transfer order. In each slave device, the synchronization point is derived again by adding the reception time of the resynchronization frame and the offset time calculated in the n-th synchronization processing session in each slave device, and the time of each slave device is determined at the synchronization point. 5. The master device according to claim 2, wherein the master device is synchronized again. The synchronization frame processing unit
In the n (n ≧ 1) synchronization processing session, each slave device synchronizes time at the synchronization point, and in the n + 1 synchronization processing session, each slave device calculates a new offset time. , Before an update frame is transmitted by the update frame processing unit,
Each slave device transmits a resynchronization frame whose reception time at each slave device is a starting point of the offset time of each slave device to the start slave device, and transfers the resynchronization frame between the plurality of slave devices according to a transfer order. In each slave device, the synchronization point is derived again by adding the reception time of the resynchronization frame and the offset time calculated in the n-th synchronization processing session in each slave device, and the time of each slave device is determined at the synchronization point. The master device according to claim 3 or 4, wherein the master device is synchronized again. The master device is
Managing a plurality of slave devices that store a plurality of offset times calculated in a plurality of synchronization processing sessions in association with a session ID representing each synchronization processing session;
The synchronization frame processing unit
A resynchronization frame in which a session ID representing the n-th synchronization processing session is described is transmitted to the start-point slave device. Based on the session ID, the reception time of the resynchronization frame in each slave device and each slave device 7. The master device according to claim 5, wherein the offset time calculated in the n-th synchronization processing session is added. The master device further includes:
8. The system according to claim 1, further comprising: a synchronization processing unit configured to synchronize a time of the own device with times of the plurality of slave devices at the synchronization point after transmission of the synchronization frame by the synchronization frame processing unit. The master device described. The master device is
Periodically repeating the transmission of the downlink communication frame to the start point slave device and the reception of the uplink communication frame from the start point slave device,
The measurement frame processing unit
Transmitting the measurement frame at the transmission timing of the downlink communication frame, receiving the measurement response frame at the reception timing of the uplink communication frame,
The correction frame processing unit
Transmitting the correction frame at the transmission timing of the downlink communication frame;
The synchronization frame processing unit
The master device according to claim 1, wherein the synchronization frame is transmitted at a transmission timing of a downlink communication frame. A slave device included in a communication system having a plurality of slave devices provided with a frame transfer order and a master device that transmits a frame,
A first measurement frame processing unit that receives a measurement frame for delay measurement from the master device or a slave device in the previous transfer order, and transmits a measurement response frame that is a response to the measurement frame to a transmission source of the measurement frame; ,
A first correction frame processing unit that receives a correction frame including a correction value calculated based on the delay measured by the measurement frame and the measurement response frame from the master device or the slave device of the previous transfer order;
Timing to synchronize the time with the other slave devices and the master device from the reception time of the synchronization frame based on the time from reception of the measurement frame to transmission of the measurement response frame and the correction value included in the correction frame An offset time calculation unit that calculates an offset time to a synchronization point,
A second measurement frame processing unit that transmits a measurement frame for delay measurement to a slave device in the next transfer order and receives a measurement response frame that is a response to the measurement frame from the slave device in the next transfer order;
Based on the time from the transmission of the measurement frame to the reception of the measurement response frame, the delay time generated when the frame is transmitted from the slave device to the slave device in the next order is calculated, and the offset in the slave device in the next order is calculated. A correction value generation unit that generates a correction value used for time calculation by subtracting the delay time from the offset time calculated by the offset time calculation unit;
A second correction frame processing unit that transmits a correction frame including the correction value generated by the correction value generation unit to a slave device in the next transfer order;
A synchronization frame processing unit that receives a synchronization frame from the master device or a slave device in a previous transfer order, and transmits the received synchronization frame to a slave device in a next transfer order;
The synchronization point is derived by adding the offset time calculated by the offset time calculation unit to the reception time of the synchronization frame, and the time is synchronized with other slave devices and the master device at the derived synchronization point. And a synchronization processing unit. The slave device is
11. The slave device according to claim 10, wherein a synchronization processing session is performed every predetermined period from reception of a measurement frame by the first measurement frame processing unit to time synchronization by the synchronization processing unit. The slave device further includes:
A storage unit for storing a plurality of offset times calculated in a plurality of synchronization processing sessions;
An update frame is received from the master device or a slave device in the previous transfer order to select an offset time calculated in the current synchronization processing session and instruct to derive the synchronization point, and the received update frame is An update frame processing unit for transmitting to the slave device in the transfer order,
The synchronization processing unit
According to the update frame, the offset time calculated in the current synchronization processing session is extracted from the storage unit, and the synchronization point is derived by adding the extracted offset time to the reception time of the synchronization frame. The slave device according to claim 11. The storage unit
A plurality of offset times calculated in a plurality of synchronization processing sessions are stored in association with a session ID representing each synchronization processing session,
The update frame processing unit
Receiving an update frame in which a session ID representing the current synchronization processing session is described;
The synchronization processing unit
The slave device according to claim 12, wherein an offset time associated with a session ID described in the update frame is extracted from the storage unit. The slave device further includes:
A storage unit that stores a plurality of offset times calculated in a plurality of synchronization processing sessions;
The synchronization frame processing unit
In the n (n ≧ 1) synchronization processing session, after the synchronization processing unit synchronizes the time at the synchronization point and before the (n + 1) th synchronization processing session starts, the master device or the previous transfer Receiving the resynchronization frame from the slave device in the order, and transmitting the received resynchronization frame to the slave device in the next transfer order;
The synchronization processing unit
The offset time calculated in the nth synchronization processing session is extracted from the storage unit, and the offset time calculated in the nth synchronization processing session is added to the reception time of the resynchronization frame to re-establish the synchronization point. The slave device according to any one of claims 11 to 13, wherein the slave device is derived and the time is synchronized again with another slave device and the master device at the derived synchronization point. The slave device further includes:
A storage unit that stores a plurality of offset times calculated in a plurality of synchronization processing sessions;
The synchronization frame processing unit
In the n (n ≧ 1) -th synchronization processing session, the synchronization processing unit synchronizes the time at the synchronization point, and in the n + 1-th synchronization processing session, the offset time calculation unit calculates a new offset time. And before the update frame processing unit receives the update frame, the master frame or the slave device in the previous transfer order is received from the master device or the slave device in the previous transfer order. To the slave device,
The synchronization processing unit
The offset time calculated in the nth synchronization processing session is extracted from the storage unit, and the offset time calculated in the nth synchronization processing session is added to the reception time of the resynchronization frame to re-establish the synchronization point. 14. The slave device according to claim 12, wherein the slave device is derived and the time is synchronized again with another slave device and the master device at the derived synchronization point. The storage unit
A plurality of offset times calculated in a plurality of synchronization processing sessions are stored in association with a session ID representing each synchronization processing session,
The synchronization frame processing unit
Receiving a resynchronization frame in which a session ID representing the n-th synchronization processing session is described;
The synchronization processing unit
The offset time associated with the session ID described in the resynchronization frame is extracted from the storage unit, and the synchronization point is derived again by adding the extracted offset time to the reception time of the resynchronization frame. The slave device according to claim 14 or 15, characterized in that The slave device is
Receiving the downlink communication frame from the master device or the slave device in the previous transfer order, transmitting the downlink communication frame to the slave device in the next transfer order, receiving the uplink communication frame from the slave device in the next transfer order, and Periodically repeating the transmission of upstream communication frames to the master device or the slave device in the previous transfer order,
The first measurement frame processing unit includes:
The measurement frame is received from the master device or the slave device in the previous transfer order at the reception timing of the downlink communication frame, and the measurement response frame is received from the master device or the slave device in the previous transfer order at the transmission timing of the uplink communication frame. Send
The first correction frame processing unit includes:
The correction frame is received from the master device or the slave device in the previous transfer order at the reception timing of the downlink communication frame,
The second measurement frame processing unit includes:
Sending the measurement frame to the slave device of the next transfer order at the transmission timing of the downlink communication frame, receiving the measurement response frame from the slave device of the next transfer order at the reception timing of the uplink communication frame,
The second correction frame processing unit includes:
Send the correction frame to the slave device of the next transfer order at the transmission timing of the downlink communication frame,
The synchronization frame processing unit
The synchronization frame is received from the master device or the slave device in the previous transfer order at the reception timing of the downlink communication frame, and the synchronization frame is transmitted to the slave device in the next transfer order at the transmission timing of the downlink communication frame. The slave device according to claim 10. A time synchronization method performed by a master device that manages a plurality of slave devices provided with a frame transfer order,
A synchronization point setting step in which the master device sets a time point after a predetermined time from the transmission time of the synchronization frame as a synchronization point for synchronizing the time with the plurality of slave devices;
A measurement frame processing step in which the master device transmits a measurement frame for delay measurement to a start point slave device that is a start point of a transfer order, and receives a measurement response frame that is a response to the measurement frame from the start point slave device;
Based on the time from the transmission of the measurement frame to the reception of the measurement response frame, the master device calculates a delay time that occurs when the master device transmits a frame to the start slave device, and calculates the calculated delay time. A correction value generation step of generating a correction value by subtracting from the predetermined time ;
A correction frame processing step in which the master device transmits a correction frame including the correction value to the start-point slave device; and
The start-point slave device receives the correction frame, and based on a time from reception of the measurement frame to transmission of the measurement response frame in the start-point slave device and the correction value included in the correction frame, the start-point slave Calculating an offset time from the reception time of the synchronization frame to the synchronization point in a device, transmitting a measurement frame to a slave device in the next transfer order and receiving a measurement response frame from the slave device in the next transfer order, Based on the time from the transmission of the measurement frame to the reception of the measurement response frame, the delay time that occurs when the frame is transmitted from the start slave device to the slave device in the next transfer order is calculated, and the calculated delay time is the offset A correction value is generated by subtracting from the time, and a correction frame that includes the correction value is generated. The over-time after sending to the slave device of the next transfer sequence, the plurality of slave devices at later similar procedure to calculate each offset time according to the transfer order,
The master device transmits a synchronization frame whose reception time at each slave device is a starting point of the offset time of each slave device to the start slave device, and transfers the synchronization frame according to a transfer order between the plurality of slave devices, Synchronization frame processing for causing each slave device to derive the synchronization point by adding the reception time of the synchronization frame in each slave device and the offset time calculated in each slave device, and synchronizing the time of each slave device at the synchronization point And a time synchronization method. A time synchronization method performed by a slave device included in a communication system having a plurality of slave devices provided with a frame transfer order and a master device that transmits a frame,
The slave device receives a measurement frame for delay measurement from the master device or a slave device in the previous transfer order, and transmits a measurement response frame that is a response to the measurement frame to a transmission source of the measurement frame. A measurement frame processing step;
A first correction in which the slave device receives a correction frame including a correction value calculated based on the delay measured by the measurement frame and the measurement response frame from the master device or a slave device in a previous transfer order. A frame processing step;
Based on the time from the reception of the measurement frame to the transmission of the measurement response frame and the correction value included in the correction frame, the slave device, from the reception time of the synchronization frame, to other slave devices and the master device An offset time calculating step for calculating an offset time to a synchronization point which is a timing for synchronizing the time;
Second measurement frame processing in which the slave device transmits a measurement frame for delay measurement to a slave device in the next transfer order, and receives a measurement response frame that is a response to the measurement frame from the slave device in the next transfer order Steps,
Based on the time from the transmission of the measurement frame to the reception of the measurement response frame, the slave device calculates a delay time that occurs when the slave device transmits a frame to the slave device in the next order. A correction value generating step for generating a correction value used for calculation of the offset time in the slave device by subtracting the delay time from the offset time calculated by the offset time calculating step;
A second correction frame processing step in which the slave device transmits a correction frame including the correction value generated in the correction value generation step to the slave device in the next transfer order;
A synchronization frame processing step in which the slave device receives a synchronization frame from the master device or a slave device in a previous transfer order, and transmits the received synchronization frame to a slave device in a next transfer order;
The slave device derives the synchronization point by adding the offset time calculated in the offset time calculation step to the reception time of the synchronization frame, and another slave device and the master at the derived synchronization point. A time synchronization method comprising a synchronization processing step for synchronizing time with an apparatus. To a master device that is a computer that manages a plurality of slave devices provided with a frame transfer order,
A synchronization point setting step in which a time point after a predetermined time from the transmission time of the synchronization frame is set as a synchronization point for synchronizing the time in the plurality of slave devices;
A measurement frame processing step of transmitting a measurement frame for delay measurement to a start point slave device that is a start point of a transfer order, and receiving a measurement response frame that is a response to the measurement frame from the start point slave device;
Based on the time from transmission of the measurement frame to reception of the measurement response frame, a delay time that occurs when the frame is transmitted from the master device to the start slave device is calculated, and the calculated delay time is subtracted from the predetermined time. A correction value generation step for generating a correction value by
A correction frame processing step in which the master device transmits a correction frame including the correction value to the start-point slave device; and
The start-point slave device receives the correction frame, and based on a time from reception of the measurement frame to transmission of the measurement response frame in the start-point slave device and the correction value included in the correction frame, the start-point slave Calculating an offset time from the reception time of the synchronization frame to the synchronization point in a device, transmitting a measurement frame to a slave device in the next transfer order and receiving a measurement response frame from the slave device in the next transfer order, Based on the time from the transmission of the measurement frame to the reception of the measurement response frame, the delay time that occurs when the frame is transmitted from the start slave device to the slave device in the next transfer order is calculated, and the calculated delay time is the offset A correction value is generated by subtracting from the time, and a correction frame that includes the correction value is generated. The over-time after sending to the slave device of the next transfer sequence, the plurality of slave devices at later similar procedure to calculate each offset time according to the transfer order,
A synchronization frame whose reception time in each slave device is a starting point of the offset time of each slave device is transmitted to the start slave device, the synchronization frame is transferred between the plurality of slave devices according to a transfer order, and the slave device in each slave device A synchronization frame processing step of causing each slave device to derive the synchronization point by adding the synchronization frame reception time and the offset time calculated by each slave device and synchronizing the time of each slave device at the synchronization point is executed. A program characterized by that. To a slave device that is a computer included in a communication system having a plurality of slave devices provided with a frame transfer order and a master device that transmits frames,
A first measurement frame processing step of receiving a measurement frame for delay measurement from the master device or a slave device in the previous transfer order, and transmitting a measurement response frame that is a response to the measurement frame to a transmission source of the measurement frame; ,
A first correction frame processing step of receiving a correction frame including a correction value calculated based on the delay measured by the measurement frame and the measurement response frame from the master device or the slave device of the previous transfer order;
Timing to synchronize the time with the other slave devices and the master device from the reception time of the synchronization frame based on the time from reception of the measurement frame to transmission of the measurement response frame and the correction value included in the correction frame An offset time calculating step for calculating an offset time to a synchronization point,
A second measurement frame processing step of transmitting a measurement frame for delay measurement to a slave device in the next transfer order and receiving a measurement response frame that is a response to the measurement frame from the slave device in the next transfer order;
Based on the time from the transmission of the measurement frame to the reception of the measurement response frame, the delay time generated when the frame is transmitted from the slave device to the slave device in the next order is calculated, and the offset in the slave device in the next order is calculated. A correction value generating step for generating a correction value used for time calculation by subtracting the delay time from the offset time calculated by the offset time calculating step;
A second correction frame processing step of transmitting a correction frame including the correction value generated by the correction value generation step to a slave device of the next transfer order;
A synchronization frame processing step of receiving a synchronization frame from the master device or a slave device of the previous transfer order, and transmitting the received synchronization frame to the slave device of the next transfer order;
The synchronization point is derived by adding the offset time calculated by the offset time calculation step to the reception time of the synchronization frame, and the time is synchronized with other slave devices and the master device at the derived synchronization point. A program for executing a synchronization processing step.

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