JP2972556B2 - Time synchronization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time synchronization system, and more particularly to a time synchronization system in a system including a plurality of devices connected via a network.

[0002]

2. Description of the Related Art Referring to FIG. 4 in which FIG. 1 of FIG. 1 of Japanese Patent Application Laid-Open No. 63-52089, which is a first prior art of a time synchronization system in a conventional network, is referred to as a "network The time synchronization method ”includes a clock mechanism 40 that creates time, a detection mechanism 41 that detects the time from when a time reading request is issued to the slave station to when a response is received from the slave station, and a detection mechanism 41 that detects the time. Simulator 4 for simulating transmission time of communication line 5 from master station to slave station
2, a correction mechanism 43 that corrects the actual time to be detected by the slave station with respect to the set time of the master station based on the pseudo transmission time created by the simulation mechanism 42 based on the time read from the slave station. A comparison mechanism 44 that compares the created pseudo time of the slave station with the set time of the master station and detects the time difference.
And data for information exchange between the slave station and the slave station.
Transmitting / receiving mechanism 45 for transmitting to or receiving from communication line 5
And a control mechanism 4 for interfacing with the operator console 100 and software for real time control
6; a clock mechanism 60 having a function of creating time; a time adjustment mechanism 61 for adjusting the time of the clock mechanism 60 based on time adjustment information from the master station; Transmission / reception mechanism 62 for transmitting and receiving data for information exchange between the communication line 5 to the communication line 5 and a control mechanism 63 for interfacing with the time setting mechanism 61 and the transmission / reception mechanism 62 for the actual time control. And a slave central processing unit 6 having:

With this configuration, the master station detects the transmission time of the communication line 5 at the time of reading the time of the slave station, and corrects the time read from the slave station by this detection time, thereby detecting the set time of the master station and the detection of the slave station. This is achieved by eliminating the delay due to the transmission time of the communication line 5 at the time.

[0004] In other words, to detect the transmission time of the communication line, the master station monitors the time from the transmission of the time reading command to the slave station until the response is received, and uses half of the time as correction data. At this time, in order to make the transmission data and the reception data length the same, half of the monitoring time is equal to the one-way transmission time. Therefore, by adding the detected transmission time to the time read from the slave station, it is possible to simulate the time of the slave station when the master station issues the time read command.

[0005] Next, Japanese Patent Application Laid-Open No. Hei 5-314030, which is a second prior art of the time synchronization system in the conventional network.
Referring to FIG. 5 in which FIG. 1 of the above publication is transcribed, a “time setting method via a communication line” of a time synchronization method according to a second related art is described with respect to a setting device 7-1 and a set device 7-2. Are connected via a communication line 8-1 and a communication line 8-2,
Memory 70 for storing programs and various data
A transmission buffer 71 for storing a transmission message, a reception buffer 72 for storing a reception message, an internal clock 73 for measuring the current time, and a communication line 8-1 and a communication line for transmitting data from the own device to the opposite device. Transmission unit 7 for transmitting to 8-2
4 and a receiving unit 7 for receiving data from an opposite device input through the communication line 8-1 and the communication line 8-2.
5 and a central processing unit 76 for performing calculations associated with various operation controls and processes in the own device.

With this configuration, the setting device 7-1 notifies the current time indicated by the internal clock to the device to be set 7-2 via the communication line 8-1, and the internal clock 73 of the device to be set 7-2 and the setting device 7-2. Difference between the current time notified by the setting device 7-1 to the device to be set 7-2 and the notification reception time at which the device to be set 7-2 has received the notification, when the time is synchronized with the internal clock 73 of -1. Is returned to the setting device 7-1, and the setting device 7-
Reference numeral 1 denotes an internal clock 73 of the set device 7-2 and its own internal clock 7 based on the content of the response and the response reception time at which the response was received.
3, the error is again notified to the set device 7-2, and the internal clock 73 of the setting device 7-1 and the set device 7-
2 is matched with the current time of the internal clock 73. That is, the setting device 7-1 and the setting device 7-2 in consideration of the time required for communication between the setting device 7-1 and the setting device 7-2.
The setting device 7-1 instructs the set device 7-2 to eliminate the error.

[0007] The notification by the setting device 7-1 and the reply by the set device 7-2 are repeated a plurality of times to repeat the communication line 8
-1 and the communication time generated when notifying the current time through the communication line 8-2 are averaged, and the setting device 7-1 determines the setting target device 7 based on the averaged response content and the response reception time when the response was received. -2 internal clock 73 and setting device 7-
1 and an error from the internal clock 73 is obtained, and this error is notified to the set device 7-2, and the current time of the internal clock 73 of the setting device 7-1 matches the current time of the internal clock 73 of the set device 7-2. Let it. That is, when the communication time is not constant, the notification and the reply are repeatedly performed to calculate a highly accurate transmission time, and then an error is obtained.
-2 is instructed to eliminate the error.

[0008]

In the first prior art "system time synchronization method", the communication time and the master time when the master device as the master station reads the time of the slave device as the slave station are determined. The communication time when the device notifies the slave device of the new time is the same, but this communication time depends on the line status at the time of communication, the operation status of the master device, the status of the slave device, and the like. Therefore, there is a disadvantage that the error between the master device and the slave device changes depending on the communication timing.

In the second prior art "time setting method via a communication line" of the time synchronization method, a report does not reach a set device due to a failure of a transmission line or the like, or a reset of the set device occurs. When the clock of the device to be set is reset due to start-up (power on again), the average value of the averaged communication time is increased, so that the accuracy of time synchronization between the setting device and the device to be set is reduced. Had the disadvantage of doing so.

[0010]

According to the time synchronization method of the present invention, a master device and a slave device are connected by a network line, and the slave device is connected to its own station.
Measure the time and use the time information as slave-side time information.
And output the data of the own station based on the time setting information.
First clock means for setting the current time latest;
First time inquiry to collect time information of remote device
The request signal is output multiple times at a predetermined
The first clock hand stores the slave-side time information for each power hour.
From the stage as the first slave side time information
Corresponding to each of the plurality of first time inquiry request signals
Time inquiry returned from the master side device
Each of the response signals
The first clock means transfers the slave-side time information to a second clock.
Read as the slave side time information, the first slave side
From the time information and the second slave-side time information,
The first time after sending the time inquiry request signal
One cycle until an inquiry response signal is returned and input
The communication time is measured within a predetermined value.
In this case, the communication time is output as first communication time information.
And average communication obtained by averaging the plurality of communication times
And comparing the time with the latest first communication time information.
When the time difference is within a predetermined value, the latest first time is required.
From the first communication time information at the time of sending the request signal,
The time obtained by subtracting half of the communication time is used as the time setting information.
And outputs it to the first clock means and supplies it to the slave side.
Said first time management means for setting the latest time;
The first time inquiry request signal from the first time management means;
The master facing the network through the network line
To the first device and the first time inquiry request
Facing through the network line corresponding to the signal
A second time inquiry response returned from the master device
Receiving the response signal and inputting the first time inquiry response signal
And supplies it to the first time management means.
Transmission / reception management means, and
Each of the plurality of times of the first communication time information is stored.
And storing the stored first communication time information.
The communication time for the specified number of reports is added and the average of the added values
Calculating the first time management value as the average communication time.
Time statistical processing means for supplying to the means,
-Side device measures the current time of its own station and
Second clock means for outputting as master-side time information;
The slave side facing through the network line
Receiving the first time inquiry request signal transmitted from the device;
And outputs it as a second time inquiry request signal.
Together with the third time inquiry response signal,
A second time inquiry response signal is output as the network
To the opposite device on the slave side
Second transmission / reception management means, and the second transmission / reception management means
When the second time inquiry request signal is input from the
Reading the first master-side time information from the second clock means.
Before outputting as the third time inquiry response signal described above.
Second time management means for supplying to the second transmission / reception management means
And

[0011]

[0012]

Next, the present invention will be described with reference to the drawings. Referring to FIG. 1 showing an embodiment of the present invention, the time synchronization system employs a system configuration in which a master device 1 and a slave device 3 are connected via a network line 2. Here, the slave-side device 3 measures the current time of its own station in real time, outputs the time information, that is, the slave-side time information, and outputs the master-side device 1.
A clock unit 30 for resetting the current time of the own station by the time setting information set based on the average communication time information between the master unit 1 and the master unit 1
A first time inquiry request signal is output a plurality of times at predetermined fixed time intervals in order to collect the real time information of the first time, and the real time slave side time information for each output time is output from the clock unit 30 to the first slave side. The first information read as time information and returned from the master device 1 corresponding to each of the plurality of first time inquiry request signals.
, The real-time slave-side time information is read from the clock unit 30 as the second slave-side time information from the clock unit 30 at each time of the input, and the first slave-side time information and the second slave-side time information are read. From the time information, the communication time for each cycle from the transmission of the first time inquiry request signal to the return input of the first time inquiry response signal is measured. Outputs the communication time as the first communication time information, compares the average communication time obtained by averaging the plurality of communication times with the latest first communication time information, and determines that the time difference is within a predetermined value. Outputs the time obtained by subtracting half of the average communication time from the first communication time information at the time of sending the latest first time request signal as time setting information and supplies it to the clock unit 30 to supply the time on the slave side. And time management unit 31 for the latest set,
A first time inquiry request signal from the time management unit 31 is transmitted to the opposing master device 1 via the network line 2, and the same master side device that opposes through the network line 2 in response to the first time inquiry request signal. A transmission / reception management unit 32 that receives and inputs a second time inquiry response signal returned from the device 1, outputs the second time inquiry response signal as a first time inquiry response signal, and supplies the first time inquiry response signal to the time management unit 31. The first communication time information of each time is stored, and a predetermined number of communication times of the stored plurality of first communication time information are added to calculate an average value of the added value. The master-side device 1 measures the current time of its own station and supplies the time information to the time statistics processing unit 33 which supplies the time information to the time management unit 31 as average communication time information. A clock unit 10 that outputs as star-side time information, and a first time inquiry request signal transmitted from the opposing slave device 3 through the network line 2 are received and input and output as a second time inquiry request signal. 3; a transmission / reception management unit 12 which receives the time inquiry response signal of No. 3 and outputs it as the above-mentioned second time inquiry response signal and sends it out to the opposing slave device 3 via the network line 2; When an inquiry request signal is input, the time management unit 11 reads the master-side time information from the clock unit 10, outputs it as the third time inquiry response signal, and supplies the third time inquiry response signal to the transmission / reception management unit 12.

Next, the operation will be described with reference to FIG. 2 and FIG. FIG. 2 shows an example of a format in a time inquiry request RQ and a time inquiry response RS when performing bidirectional communication of time information between the master device 1 and the slave device 3.

The time management unit 31 of the slave device 3 stores a time inquiry request identification (ID) in the command field CF1 of the time inquiry request RQ at a fixed time interval, for example, at t _1.
The sequence number M is written in the number and sequence field SF1, output as the first time inquiry request signal, and supplied to the transmission / reception management unit 32. Then, the transmission / reception management unit 32 outputs the time inquiry request RQ from the time management unit 31 as the above-described second time inquiry request signal, and sends the signal to the master-side device 1 through the network line 2.

The transmission / reception management unit 12 of the master-side device 1
The time inquiry request RQ input from the slave device 3 through the network line 2 is supplied to the time management unit 11 as the third time inquiry request signal. Each time the time inquiry request RQ is input from the transmission / reception management unit 12, the time management unit 11 reads the master-side time from the clock unit 10 in real time, and
The time read from the clock unit 10 is written in the time field TF, and the time inquiry response identification (ID) number is written in the command field CF2, and the sequence number M written in the time inquiry request RQ is written in the sequence field SF2. The transmission / reception management unit 12 receives the third
As a time inquiry response signal. by this,
The transmission / reception management unit 12 outputs the time inquiry response RS supplied from the time management unit 11 as the above-described second time inquiry response signal, and sends it to the slave device 3 through the network line 2.

The transmission / reception manager 32 of the slave device 3
The time inquiry response RS from the master device 1 input through the network line 2 is output as the above-described first time inquiry response signal and supplied to the time management unit 31. In this time management unit 31, the transmission / reception management unit 32
After transmitting the time inquiry request RQ as the time inquiry request signal of
And measuring the communication time until receiving the S, in which case the communication time of for example, within the communication time threshold t ₂ predetermined measured, the first communication time information that communication time mentioned above Is supplied to the time statistical processing unit 33. Also,
If the communication time exceeds t ₂ ,
It is considered that some abnormality has occurred in any of the time information transmitting means in the above-described steps, and the supply of the communication time to the time statistical processing unit 33 is stopped. Excluded from being added to the average communication time. Then, the time statistic processing unit 33 stores the past n-1 communication times in an internal memory, and adds each of the n communication times together with the latest communication time received most recently. The average value is calculated, and the calculation result is supplied to the time management unit 31 as the above-described average communication time information. Accordingly, when the time management unit 31 is supplied with the average communication time information from the time statistics processing unit 33, the time management unit 31 compares the average communication time with the n-th latest communication time, and determines the time difference as the threshold T. _In case of less than ₂ , master-side device 1
Supplies a value obtained by subtracting half of the average communication time from the time written in the time field TF of the latest time inquiry response RS sent from the mobile station to the time unit 30 as time setting information of the own station. As a result, the clock unit 30 sets the current time of the own station to match the time according to the time setting information. This completes one step of time setting.

Subsequently, after transmitting the time inquiry request RQ of the sequence number M, the slave side device 3 sets the sequence number to M + 1 and transmits the next time inquiry request RQ at time t ₁ . Hereinafter, the same operation as described above is repeated.

As described above, in order to keep the time error between the master-side device 1 and the slave-side device 3 within a predetermined time t ₀ seconds, the average communication time T of a predetermined number of times in the past and the most recently obtained communication time T Compared with time t, the time difference is t
If there is more than ₀ seconds, the time is not set. In other words, the response from the master device 1 to the request from the slave device is delayed or not returned due to an abnormality in the transmission / reception function in the two devices or a failure in the network line 2. This is because it is conceivable that a "deviation" occurs between the request and the response. Since such a “shift” is generally longer than the communication time t, if the average communication time includes the time corresponding to the “shift”, the average communication time T becomes longer than the original value. hand,
The result is “shift” even before the time set based on this. That is, since the communication time between the master device and the slave device connected to the network in advance is almost fixed, if the communication time exceeds the communication time by a predetermined time or more, it is regarded as a communication error, and by not adding the communication time t to calculate the average communication time T, and the error of the mean communication time T in t less than ₀ seconds, all slaves even when a plurality of slave devices are connected to the network The time error of the side device can be less than t ₀ seconds.

Subsequently, referring to FIG.
The exchange of time information between the slave-side device 3 and the calculation of the average communication time and the time setting in the slave-side device 3 will be described for five cases.
Here, the average communication time T is 2 seconds (s), the communication interval t ₁ is 10 minutes, the time error t ₀ is 2 seconds (s), the communication time threshold t ₂ is 2 seconds (s), and the communication time. Is defined as t.

In the first exchange, the slave device 3 issues a request sequence No. 1 sends a time inquiry request RQ to the master device 1, and the master device 1 responds to the request with a response sequence No. 1. 1 shows an example in which the time inquiry response RS is returned to the slave device 3, and it is an example in which one exchange requires a communication time of 3 seconds (s). Communication time t = 3 in this case
s is a communication time threshold value t ₂ not included in the average communication time.
= 1 minute (60 s), the communication time t =
3s is added to the average communication time. Furthermore, since the value obtained by subtracting the average communication time T = 2 s from the communication time t = 3 s is smaller than the predetermined time error t ₀ = 2 s, the time of the slave device 3 is set to the response sequence NO. 1 is set according to the time information of the time inquiry response RS.

In the second exchange, the request sequence No. 2 sends a time inquiry request RQ to the master device 1, and the master device 1 responds to the request with a response sequence NO. 2 shows an example in which the time inquiry response RS is returned to the slave device 3, and this is an example in which the second exchange requires a communication time of 5 s. Communication time t = 5 in this case
Since s is also smaller than t ₂ = 1 minute (60 s), this communication time t = 5 s is also added to the average communication time. Further, since the value obtained by subtracting the average communication time T = 2 s from the communication time t = 5 s is larger than the time error t ₀ = 2 s, the time of the slave device 1 is not changed and new setting is not performed. Response sequence NO. 2 is the slave device 3
Discard at

In the third exchange, the slave device 3 sends a request sequence No. 3 shows an example in which a response is not sent back from the master device 1 when the time inquiry request RQ is sent to the master device 1 according to No. 3, and there is no response within t ₁ = 10 minutes of the time inquiry cycle. Is the next request sequence from the slave side device 3, that is, the request sequence No. Time inquiry request RQ by 4
Is sent to the master device 1.

In the fourth exchange, the slave device 3 issues a request sequence No. When the time inquiry request RQ is transmitted to the master side device 1 according to the response sequence NO. 4 before the time inquiry response RS is returned. Time inquiry response R by 3
S, that is, the request sequence No. at the time of the third exchange described above. 3 shows an example in which the time inquiry response RS corresponding to No. 3 is returned at this time. In this case, since the slave side device 3 always compares and verifies the request sequence number and the response sequence number, If a response with a different sequence number is returned for the requested sequence number, the time information from the time inquiry response RS with the different response sequence number is discarded.
Therefore, the response sequence NO. 3 is discarded and the response sequence No. 3 is discarded.
4 is received by the time inquiry response RS. In the fourth operation, the request sequence No. 4 is transmitted, and then the response sequence No. A communication time of t = 6 s is required until 4 is returned. Therefore, the communication time t = 6 s is smaller than t ₂ = 1 minute (60 s), as in the case of the second exchange, so that the communication time t = 6 s is also added to the average communication time. . Then, from the communication time t = 6s to the average communication time T
= 2 s is larger than the time error t ₀ = 2 s, so that the time of the slave device 3 is set to the response sequence number from the master device 1. 4 Time inquiry response RS
Set according to the time information of.

In the fifth exchange, the slave device 3 sends a request sequence No. 5, when the time inquiry request RQ is sent to the master device 1, the response sequence No. 5 is sent to the request after t = 62s from the master device 1. 5 shows an example in which the time inquiry response RS is returned to the slave device 3 and the communication time t
Is not counted in the average communication time T, the communication time threshold t ₂ =
This is an example in which one minute (60 s) is exceeded. In this case, the communication time t = 62 s is equal to the communication time threshold t ₂ = 60.
Since the communication time is larger than s, the communication time t = 62 s is not added to the average communication time.

In the above description, if the communication time t = 62 s exceeding the communication time threshold t ₂ = 60 s is included in the average communication time calculation, the average communication time from the first time to the fourth time is calculated. T is 3s + 5s + 6s = 14s / 3 ≒
The average communication time T from the first time to the fifth time is 4.7 s, whereas the average communication time T is 3 s + 5 s + 6 s + 62 s = 76 s /
4 = 19 s, which is set to a time with a “shift” of about 14 s. The value obtained by subtracting the average communication time T = 2 s from the communication time t = 62 s is the time error t ₀ = 2 s.
Therefore, the new time is not set while the time of the slave device 3 is kept as it is, and the response sequence No. The time information of the time inquiry response RS according to 5 is discarded in the slave device 3.

As described above, the communication time threshold value t ₂ is set to prevent the time setting from being “shifted” due to an abnormality in the transmission / reception function inside the master device 1 and the slave device 3 or a failure in the network line 2. By setting in advance and excluding the communication time t exceeding this from the calculation of the average communication time T, the error of the average communication time T is reduced to less than t ₀ seconds, and the communication time of the slave device 3 connected to the network is reduced. The time error can be less than t ₀ seconds.

In the above description, a method of communicating time information and setting time in a point-to-point system by one master device 1 and one slave device 3 has been described. In a multi-point system using the device 3 and one master device 1, the same operation can be performed by, for example, performing polling communication.

[0028]

As described above, according to the present invention, a threshold value for the communication time between the master device and the slave device is set, and the communication time exceeding the threshold value is reduced to the average communication time. , The average communication time error is reduced to less than a predetermined time, and each time error of all the slave devices connected to the network is within the allowable time error of each device. Can be suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a time synchronization method according to an embodiment of the present invention.

FIG. 2 is a format of a time inquiry request and a time inquiry response of a time synchronization method in the embodiment.

FIG. 3 is a sequence diagram showing exchange of time information between a master-side device and a slave-side device using a time synchronization method in the embodiment.

FIG. 4 is a block diagram showing a first conventional example.

FIG. 5 is a block diagram showing a second conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Master side apparatus 2 Network line 3 Slave side apparatus 10 Clock section 11 Time management section 12 Transmission / reception management section 30 Clock section 31 Time management section 32 Transmission / reception management section 33 Time statistics management section

Continuing on the front page (72) Inventor Hideki Shibasaki 1-403 Kosugi-cho, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture In-house NEC Corporation (72) Inventor Hiroyuki Fukuda 1-403 Kosugi-cho, Nakahara-ku, Kawasaki-shi, Kanagawa Japan In-house (56) References JP-A-7-131853 (JP, A) JP-A-3-264890 (JP, A) JP-A-5-336574 (JP, A) JP-A-63-63238 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) H04L 7/00

Claims (1)

(57) [Claims] 1. A master device and a slave device are connected by a network line. The slave device measures the current time of its own station, outputs the time information as slave time information, and sets time setting information. First clock means for setting the current time of the own station latest based on the first time inquiry request signal for collecting the time information of the master side apparatus a plurality of times in a predetermined cycle and outputting the same. The slave-side time information for each hour is read from the first clock means as first slave-side time information, and is returned from the master-side device in response to each of the plurality of first time inquiry request signals. First
Each time of the time inquiry response signal, and reads the slave-side time information from the first clock means as second slave-side time information at each input time. And measuring the communication time for each cycle from the transmission of the first time inquiry request signal to the return input of the first time inquiry response signal from the slave side time information and the communication time. Is less than or equal to a predetermined value, the communication time is output as first communication time information, and the average communication time obtained by averaging the plurality of communication times is compared with the latest first communication time information. If the time difference is within a predetermined value, a time obtained by subtracting half of the average communication time from the first communication time information at the time of sending the latest first time request signal is output as the time setting information. A first time management unit that supplies the first clock unit with the latest time setting of the slave-side time, and transmits the first time inquiry request signal from the first time management unit through the network line A second time inquiry response signal transmitted from the opposite master side device through the network line in response to the first time inquiry request signal is transmitted to the opposite master side device and received and input. A first transmission / reception management unit that outputs the first time inquiry response signal and supplies it to the first time management unit; and a plurality of times of the first communication time information supplied from the first time management unit. Each of them is stored, and a predetermined number of communication times of the stored first communication time information are added to calculate an average value of the added values. A time statistical processing means for supplying the time as the time to the first time management means; wherein the master device measures the current time of its own station and outputs the time information as master time information. A clock unit; receiving and inputting the first time inquiry request signal transmitted from the slave device facing the device through the network line, outputting the second time inquiry request signal and outputting a third time inquiry response signal; A second transmission / reception management means which is inputted and outputted as the above-mentioned third time inquiry response signal, and is transmitted to the opposing slave side device through the network line; and the second time inquiry from the second transmission / reception management means. When a request signal is input, the first clock is sent from the second clock means.
A second time management means for reading out the master-side time information, outputting the third time inquiry response signal, and supplying the third time inquiry response signal to the second transmission / reception management means.