JPH07181273A - Clock signal generator and method and system for measuring packet transmission time - Google Patents

Abstract

PURPOSE:To improve the clocking accuracy of a clock driven by a crystal oscillator. CONSTITUTION:Time data where a GPS receiver 20 outputs the oscillation frequency (the number of clock pulses: wave number) of a crystal oscillator 11 are stored at a count start time register 13 and an end time register 14 and the wave number of clock pulses oscillated by the oscillator 11 is counted by a frequency counter 17 of these start time and end time. The difference between the count value and a target wave number (the wave number when the oscillator 11 oscillated at a rated frequency) which is calculated based on the start time and the end time is calculated and a compensation value so that a compensation value operation part 16 cancels the difference is calculated and is output to a clock 10. Therefore, even if the GPS receiver 20 cannot receive a position-measurement signal constantly (even if time data cannot be output), an accurate time (clock signal) can always be output since the clock 10 is calibrated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a clock signal generator capable of always holding the frequency of an output clock signal accurately, and in particular, an oscillator with a certain degree of accuracy such as a crystal oscillator, based on GPS time data. The present invention relates to a clock signal generator that is calibrated to maintain accuracy.

The present invention also relates to a packet transmission time measuring method and a measuring system capable of accurately measuring a packet transmission rate in a packet communication network using the clock signal generating device.

[0003]

2. Description of the Related Art In a packet communication network, when communication becomes congested, packet transmission in a router may cause a very long transmission time. Depending on the packet communication network, a packet that does not reach the destination station after a certain period of time may be rejected by the router. Therefore, if the transmission time becomes long, the transmitted packet may not reach the destination station. Therefore, it becomes necessary to know the packet transmission time on the packet switching network.

When measuring the packet transmission time from a certain point (transmission point) to a certain point (reception point), accurate data cannot be obtained unless the transmission time is measured with an accuracy of about 100 μs. Further, in the packet communication network, since the transmission time differs between the forward path and the return path, it is not possible to make the packet reciprocate and determine one transmission time from the transmission time. Further, when the transmission time is measured by reciprocating the packet in this manner, the processing time of the device on the loopback side is included in the time, so that an error occurs. Therefore, in order to accurately measure the time required for transmission from the transmission point to the reception point, an accurate clock that is completely synchronized between the transmission side and the reception side is required.

In addition to this, there are various situations where such an accurate clock is required, such as the case where the lightning occurrence point is determined based on the electromagnetic wave reception times at a plurality of points.

[0006]

However, the oscillator that can be generally used for ordinary applications is a crystal oscillator, and even this crystal oscillator has an accuracy of about 10 ^-4 to 10 ^-6 . Therefore, if another clock is driven without being synchronized with the two oscillators, an error gradually occurs over time, and the times at the two points are different, which is not sufficient for the above application.

Further, since a high-precision oscillator such as an atomic clock is very expensive and difficult to handle, it has a drawback that it cannot be applied to general purposes.

On the other hand, in recent years, a GPS receiver has been put into practical use as a device capable of calculating an accurate time with a relatively simple device. However, the GPS receiver can output accurate time data only when receiving the positioning signals of the GPS satellites, and is otherwise unreliable and cannot always be used.

An object of the present invention is to provide a clock signal generator capable of maintaining a relatively simple and high clock accuracy by calibrating an oscillator using time data output from a GPS receiver. .

A further object of the present invention is to provide a packet transmission time measuring device which can accurately measure the transmission time of a packet communication network using this clock signal generator.

[0011]

The invention according to claim 1 of this application is to provide a clock signal generating means, a GPS receiver, and the G receiver.
When the PS receiver outputs the time data by receiving the positioning signal of the GPS satellite, the PS receiver comprises a calibration means for calibrating the clock frequency of the clock signal generation means based on the time data. And

According to a second aspect of the present invention, the clock signal generating means is a clock circuit driven by a pulse signal output from a crystal oscillator, and the calibrating means is a step of the clock signal with respect to the pulse signal of the clock circuit. It is characterized in that it is a means for correcting the amount.

In the invention of claim 3 of this application, the clock signal generating means is a clock circuit driven by a pulse signal output from a crystal oscillator, and the calibrating means is means for correcting the oscillation frequency of the crystal oscillator. It is characterized by

According to a fourth aspect of the present invention, the calibration means includes a frequency detecting means for periodically detecting the clock frequency of the clock signal generating means, and the frequency detecting means detects the clock frequency based on the detected value. It is characterized in that it is constituted by a characteristic detecting means for determining a periodic or secular change characteristic and a correcting means for correcting the clock frequency by a correction amount for canceling the change characteristic calculated by the characteristic detecting means.

According to the invention of claim 5 of this application, a packet including transmission time data is created on the transmitting side, the transmission time is detected by using the clock signal generator, and the packet is transmitted at the timing of the transmission time. When a packet is transmitted and the receiving side receives the packet, the reception time is detected using the clock signal generator, and the packet is detected from the difference between the reception time and the transmission time data written in the packet. It is characterized in that the transmission time of is calculated.

The invention of claim 6 of this application comprises a transmitting side device and a receiving side device, and the transmitting side device, the clock signal generating device, means for creating a packet including transmission time data, and the clock. The clock signal generating device includes: means for detecting the timing of the transmission time based on the output of the signal generating device; and means for transmitting the packet to the receiving device at the timing. And a means for calculating a reception time based on the output of the clock signal generator when the packet is received, and a transmission time of the packet from a difference between the reception time and the transmission time data written in the packet. And means.

According to the invention of claim 7 of this application, the transmission side device transmits a packet including the transmission time data, and the transmission side device transmits the packet based on the reception time when the packet is received and the transmission time data. A packet transmission time measuring system for measuring a packet transmission time between a side device and a reception side device, the clock signal generating device according to claim 1, means for creating a packet including transmission time data, and the clock signal generating device. Means for detecting the timing of the transmission time on the basis of the output of, and means for transmitting the packet to the receiving side device at the timing.

According to the invention of claim 8 of this application, the transmission side device transmits a packet including the transmission time data, and the transmission side device transmits the packet based on the reception time when the packet is received and the transmission time data. A packet transmission time measuring system for measuring a transmission time of a packet between a side device and a receiving side device, wherein the clock signal generating device according to claim 1 and, based on an output of the clock signal generating device when the packet is received. It is characterized in that a means for calculating the reception time and a means for calculating the transmission time of the packet from the difference between the reception time and the transmission time data written in the packet are provided.

[0019]

The clock signal generating device of this application has a clock signal generating means such as a clock circuit driven by a crystal oscillator, and outputs a clock signal at constant time intervals and data representing time. For example, a crystal oscillator is 10 ^-4 to 10
^Although the accuracy is about ^-6 , this device is equipped with a GPS receiver, and this GPS receiver receives positioning signals from GPS satellites and outputs accurate time data (accuracy of 0.1 μs). At this time, the clock frequency of the clock signal generating means is calibrated based on this time data. This allows
An accurate clock signal can be generated even when the GPS receiver cannot always receive the positioning signal.

When the clock signal generating means is a clock circuit driven by a pulse signal output from a crystal oscillator, the object to be calibrated based on the time data of the GPS receiver is the clock signal corresponding to the pulse signal of the clock circuit. It can be a step amount. In this case, since the crystal oscillator continues to oscillate under the same conditions, changes over time become clear, and it becomes easy to determine periodic fluctuations and changes over time and calculate a correction value for them. .

In the above case, the object to be calibrated based on the time data of the GPS receiver may be the oscillation frequency of the crystal oscillator. In this case, since the pulse signal serving as the reference of the clock signal can be kept constant, the clock circuit only needs to perform a simple counting operation, and the configuration can be simplified.

Further, in the invention of claim 4, the clock frequency of the clock signal generating means is periodically detected to determine the periodic or secular change characteristic of the clock frequency.
Based on this, the change characteristic is corrected with a correction amount that cancels out. As a result, it becomes possible to determine in advance and cancel periodic and aging frequency fluctuations.

According to another aspect of the packet transmission time measuring method of the present invention, a packet including transmission time data is created on the transmitting side, an accurate timing of the transmission time is detected by the clock signal generator, and the timing of the transmission time is detected. The packet is transmitted. As a result, this packet is accurately transmitted at the timing of the transmission time data written in its own packet. When the packet is received, the receiving side detects the reception time using the clock signal generator. By using the clock signal generator, it is possible to know the exact reception time. The transmission time of the packet is calculated from the difference between the reception time and the transmission time data written in the packet. Since the sending and receiving times are accurate,
The transmission time calculated based on this is also very accurate.

In the packet transmission time measuring system of this application, the transmitting side device creates a packet containing the transmission time data, and the packet of the transmission time data determined based on the output of the clock signal generating device is used. It transmits to the receiving side device at the timing. When the receiving side device receives this packet, the receiving side device determines the reception time based on the output of the clock signal generating device. Since the times of both clock signal generators are accurately calibrated as described above, the accurate transmission time of this packet can be determined from the difference between the reception time and the transmission time data written in the packet.

[0025]

1 is a block diagram of a timepiece device according to an embodiment of the present invention. The clock 10 is 100 μs (HH, MM,
SS. (XXXX) scale timekeeping function,
It has a function of counting dates (YY, MM, DD). This timepiece 10 operates by clock pulses of an oscillator 11. The oscillator 11 is a crystal oscillator, and the accuracy during free-running oscillation is about 10 ⁻⁶ to 10 ⁻⁴ . Therefore,
The oscillation frequency is 100p depending on the surrounding environment such as temperature.
It varies in the range of about pm. On the other hand, this timepiece device 1 is G
When the GPS receiver 20 is provided with the PS receiver 20 and receives the positioning signal of the GPS satellite, the timepiece 10 is calibrated based on the time data of 0.1 μs accuracy calculated from the positioning signal. To do. The time data is the time display data output every 1s, the hourly pulse and 100μ.
It consists of timing pulses output every s. The time display data is numerical data (SS) that displays the time (second) with a two-digit value, and is output before the time (hour pulse). The hourly pulse and the timing pulse are output at the exact timing when the rising edges coincide with each other at that time.

The calibration method is as follows. GPS
The start time and the end time are set based on the accurate clock of the receiver 20, and the number of clock pulses (wave number) output from the time oscillator 11 between the start time and the end time is counted.
The wave number (target wave number) when the oscillator 11 is oscillating at the rated frequency is calculated based on the start time and the end time,
The actual count value is compared with the target wave number to determine the error ratio. A correction value for canceling this error ratio is output to the timepiece 10. That is, in this embodiment, the oscillation frequency of the oscillator 11 is not corrected, and the time progress is corrected on the clock 10 side with respect to the clock pulse of the oscillator 11.
This is for facilitating the time-series aggregation of changes in the oscillation frequency of the oscillator 11 and the calculation of the corresponding correction value. Of course, a method of correcting the oscillation frequency of the oscillator 11 may be adopted, and even in this case, it is possible to grasp the long-term fluctuation and make a correction to cancel it.

The configuration of the timepiece device 1 for this purpose is as follows. The start time register 13 and the end time register 14 are connected to the GPS receiver 20. These registers store time data of the GPS receiver 20 according to an instruction from the control unit 12. A wave number counter 17 is connected to the control unit 12. The wave number counter counts the number of clock pulses generated by the oscillator 11. The control unit 12 starts the wave number counter 17 at the same time as outputting the time storage trigger to the start time register 13, and outputs the time storage trigger to the end time register 14 at the same time as the counting operation of the wave number counter 17. Stop.

After the above count start operation and count end operation, the stored contents of the start time register 13 and the end time register 14 are input to the target wave number calculating section 15. The target wave number calculator 15 calculates a count time based on these times, and the count time and the oscillator 11
The target wave number of the count number is calculated from the rated oscillation frequency of. The calculated target wave number is output to the correction value calculation unit 16. On the other hand, the count value of the wave number counter 17 is also output to the correction value calculation unit 16. The correction value calculation unit 16 calculates an error ratio based on the target wave number and the count value, and outputs a correction value for correcting this error to the timepiece 10. As described above, when the correction value calculation unit 16 calculates the error, it outputs the correction value for canceling the error to the timepiece 10. The output of the correction value and the result of the wave number counting operation are shown in FIG. Is stored in the counting history table shown in FIG. 2 and is used as data for calculating a correction value for previously correcting the fluctuation of the periodic error.

Further, the timepiece 10 may be driven by the time data output by the GPS receiver 20 while the GPS receiver 20 is receiving the positioning signals of the GPS satellites. That is, as shown in FIG. 1, the GPS receiver 20 is connected to the timepiece 10 via the reset circuit 19, and 100 μ
The count value of the timepiece 10 may be incremented by inputting a timing pulse every s. In this case, while the GPS positioning signal is being received, the oscillator 11 is disconnected from the clock and only calibration is performed. Further, even when the timepiece is not driven by this timing pulse, the digit of less than 1 second of the timepiece 10 may be reset by the hour pulse every hour.

FIG. 2 shows various tables set in the correction value calculator 16. The figure (A) is a counting history table. This table stores the start time, end time, target wave number, count value, and error ratio (difference) each time the above-described wave number counting operation is executed. This counting history is accumulated and stored for a long period of time. Based on this counting history data, the daily change correction table (FIG. (B)), the annual change correction table (FIG. (C)), and the secular change function (same) of FIGS. Figure (D)) is determined.

FIG. 3 is a diagram showing an example of the wave number counting operation timing and the daily change curve. Further, FIG. 4 is a diagram showing the relationship among the daily change curve, the annual change curve and the secular change function. In this example, in order to simplify the explanation, it is assumed that the change in the oscillation frequency (count value) mainly follows the change in the temperature. Various factors other than the temperature can be considered as factors for changing the oscillation frequency, and in actual operation, a change curve including all of these factors is included, but the correction value is also automatically calculated in accordance with this.

In FIG. 3, the oscillation frequency is low when the temperature is high and high when the temperature is low. For this reason, the oscillation frequency shows the change as shown in FIG. In the example shown in the figure, the oscillation frequency of the oscillator 11 is slightly higher than the rated oscillation frequency (target value). The control unit 12 is GP
The S receiver 20 is outputting the time data, and the wave number counting operation is executed at an arbitrary timing, and the error ratio (ppm) between the actual count value and the target value is caused by this wave number counting operation. It is calculated. The correction value calculation unit 16 calculates a correction value for canceling this error ratio and outputs it to the timepiece 10, and stores the content of the counting operation in the counting history table. In the example of FIG.
The wave number counting operation is executed 10 times a day, and the diurnal change curve in the figure is determined by plotting the detected value (error ratio) of each wave number counting operation. The average day difference is calculated by integrating this change curve. The average daily difference is the average value of the error ratios in this day, and the daily change is corrected based on this average daily difference. That is, the day change correction table of FIG. 2B stores a value obtained by subtracting the average day difference from the value of the day change curve at each time (every 10 minutes from 0:00), and the average day difference is shown in FIG. It is stored in the column of the month and day of the annual change correction table in (C). By reading these correction values and calculating the correction value by adding the daily change correction value to the daily annual change correction value (average day difference) as shown in FIG. Also, a correct correction value can be calculated.

On the other hand, by continuously observing daily changes and yearly changes, it is possible to determine changes over time in the crystal oscillator 11. By approximating the degree of change over time with a constant function,
The secular change function is stored in the secular change function storage area in FIG. When calculating the correction value, the operation time is input as a variable to this secular change function, the change amount is calculated, and this is added. When this process is performed, the annual change curve changes as shown in FIG. In this example, the secular change acts on the tendency that the oscillation frequency rises.

Further, the daily change curve can be calculated every day based on the result (error ratio) of the wave number counting operation for one day. Although various methods of updating the daily change correction table are possible, the following methods are available, for example. ■ Method of updating the daily change correction table every day Considering that the same day change as the previous day is performed on the current day, the method of updating the daily change correction table daily with the value of the day change curve of the previous day There is the value of the day change curve of the previous day Percentage (eg 60%),
The value of the day change correction table of the previous day is set to a certain ratio (for example, 40
%) Method to calculate the daily change correction table for the current day ■ Method to update the daily change correction table every predetermined period Update method when the daily change curve is significantly different from the content of the daily change correction table Fixed period A method in which a day change curve for one month (for example, one month) is stored, an average value of the day change curve is calculated after the lapse of the certain period, and updated as contents of a new day change correction table. There is one type of daily change correction table, but you can set multiple types depending on the season and installation conditions.
If one of them is selected according to the situation, a more accurate correction value can be calculated.

The above is the method of updating the daily change correction table, but the same applies to the annual change correction table.

Although the correction value (regular correction value) is calculated on the basis of the daily change correction table, the annual change correction table and the secular change function, it is optional even when the periodic correction is performed. The wave number counting operation is executed at the timing of, and the error ratio of the oscillator 11 is calculated based on the accurate time data of the GPS receiver 20. In this case,
A correction value (temporary correction value) for canceling the error ratio calculated by the wave number counting operation is output to the timepiece 10 regardless of the periodic correction value. Further, the difference between the temporary correction value and the periodic correction value is stored in the correction error storage area,
In the subsequent regular correction operation, the correction error is added to the calculated regular correction value to follow the fluctuation of the day.

In FIG. 1, each function of the timepiece device is described as a functional block, but in an actual device,
It is preferable to configure the control unit 12, the start time register 13, the end time register 14, the target wave number calculation unit 15, and the correction value calculation unit 16 by a microcomputer in order to simplify the configuration of the device.

FIG. 5 is a flow chart showing the operation of the microcomputer when the timepiece device 1 has a microcomputer configuration. The figure (A) has shown the wave number count operation. GP
This operation is executed at an arbitrary timing, provided that the S receiver 20 is outputting time data. First, the start of wave number counting is instructed (n1). Specifically, this operation is an operation of storing the start time in the start time register and simultaneously outputting a count start trigger to the wave number counter 17. After that, after waiting for a predetermined time, a count end instruction is given (n2). Specifically, the count end instruction is an operation of storing the count end time in the register and simultaneously outputting a count stop trigger to the wave number counter 17. After that, the stored start time and end time are read (n3), the target wave number is calculated (n4), the count value is read from the wave number counter 17 (n5), and the error ratio of the count value to the target wave number is calculated. (N6). The result of the wave number counting operation is stored in the counting history table (FIG. 2A) (n7), and the correction value (temporary correction value) for canceling this error is output to the timepiece 10 (n8). .. Further, the difference between the temporary correction value and the regular correction value calculated by the operation of FIG. 7B is stored in the correction error storage area (n9).

FIG. 6B is a flow chart showing the regular correction operation. This operation is an operation executed every 10 minutes from 0:00. First, the correction value is read from each correction table (n11). That is, the daily difference correction value at that time is read from the daily difference correction table, the yearly difference correction value (average day difference) is read from the yearly difference correction table, and the aged correction value is further calculated based on the secular change function. calculate.
These values are added to calculate a combined correction value (regular correction value) (n12). Further, a correction error detected by the immediately preceding wave number counting operation is added to this value to calculate a final correction value (n13), and this correction value is output to the timepiece 10.

FIG. 6 is a block diagram of a transmission time measuring device using the timepiece device 1. This device is for measuring the accurate transmission time from a point (sending point) to a certain point (reception point) connected to a packet communication network that seems to be unable to perform prompt transmission due to a failure. Is. Therefore, this device operates by connecting two units, one at the transmission point and one at the reception point of the packet communication network.

FIG. 7 shows an example of a local area network (LAN) to which the transmission time measuring device 30 is connected. In this network, one server 41, a plurality of workstations 40, and a printer 42 are connected on a plurality of cables connected by a router 45. The transmission time measuring device 30 is connected to any two points of such a network, and the accurate transmission time between the two points is measured. As described above, this example is a small-scale personal computer LAN, but it is of course possible to apply it to a larger-scale LAN network or a nationwide packet communication network.

In FIG. 6, the transmission time measuring device 30 is
Microcomputer 3 for controlling the operation of the device
1. It has a LAN connection board 32 for sending and receiving packets to and from a packet communication network, and further has a timepiece device 1, a selector 34 and a counter 33 for calculating an accurate time. The clock device 1 outputs time data. The time data is composed of time display data output every 1 s, an hour pulse, and a timing pulse output every 100 μs. Selector 34 is G
When the PS receiver 20 is outputting time data, this time data is output to the microcomputer 31 and the counter 33, and when the GPS receiver 20 is not outputting time data, the time data output by the clock 10 is output. Output to the microcomputer 31 and the counter 33. Counter 33
Is a counter that counts the timing pulse of 100 μs, and continues counting while being reset by the hour pulse. Therefore, the count value of the counter 33 represents the elapsed time in 100 μs units from every 0 seconds. Further, the counter 33 suspends its count when a STOP pulse is input from the microcomputer 31. The microcomputer 31 is input with time display data every 1 s and an hourly pulse indicating the exact timing of this time. The operation of the transmission time measuring device will be described with reference to the following flowchart.

FIG. 8 is a flowchart showing the operation of the transmission time measuring device. FIG. 7A is a flowchart showing the operation of the transmitting side device. When the transmission side device enters the transmission operation, first, the time display data transmitted from the timepiece device 1 is read, and the reception side device is designated as the address, and the time (H
H. MM. A packet in which SS) is written as transmission time data is created (n21). As described above, since the hour pulse indicating the correct timing of the time display data is input after the time display data, the process waits at n22 until the hour pulse is input. When the hourly pulse is input, the above-mentioned time-stamped packet is transmitted to the receiving side device (n23).

On the other hand, the receiving side device stands by until the packet is sent from the transmitting side device, and when the packet is received, the operation of FIG. First, a STOP signal is output to the counter 33 to stop counting. As a result, a numerical value in units of 100 μs, which is a digit less than seconds in the packet reception time, is fixed. Next, the time display data sent from the timepiece device 1 is read, and further, the count value of the counter 33 is read. Based on these data, the packet reception time is calculated in units of 100 μs, and the required transmission time is calculated from the difference between this reception time and the transmission time (n3).
3). This required transmission time is displayed on the display (not shown) of the device (n34). This transmission required time is formed into a packet (n35) and returned to the transmitting side device (n
36).

Based on the required transmission time measured in this way, a staff member can analyze the network and take action such as eliminating the neck portion.

The transmission time measuring device 30 may be a device that is temporarily connected to the network or a device that is always connected to the network. Further, it may be integrated with a so-called LAN analyzer. Also, this function may be incorporated in a normal workstation. When it is installed in a workstation or configured as a device that is always connected to the network, it can be configured to automatically execute the operation shown in FIG. 8 when it is detected that the packet transmission time is getting longer. Good.

As a device using the timepiece device 1,
Not only the above-mentioned transmission time measuring device, but also all fields that require a clock accurately synchronized at a plurality of points can be applied. For example, it can be applied to a system in which an event that occurs at one point is observed at a plurality of points and the occurrence position is calculated based on the difference between the observation times. In particular,
It is an earthquake epicenter detection system, a lightning point detection system, and a wind share (air spot near the ground surface) detection system.

[0048]

As described above, according to the present invention, the clock signal generating means is calibrated on the basis of the time data of the GPS receiver, so that even if the GPS receiver does not output the time data, the accurate data can be obtained. A clock signal can be output. Further, by performing this calibration on the clock circuit, the crystal oscillator can be continuously operated under a constant condition, and the change over time can be easily detected. Furthermore, by performing this calibration on the crystal oscillator, the oscillation frequency can be kept constant, the operation of the clock circuit can be simplified, and the calibration can be simplified. In addition, the clock frequency
By detecting a temporal change and canceling it, it is possible to detect the change in advance and cancel the change.

Furthermore, in the packet transmission time measuring method and system of the present invention, since the clock signal generating circuit which is accurately calibrated is used for both the transmitting side device and the receiving side device, transmission is performed between these transmitting side device and receiving side device. It is possible to detect the accurate transmission time of the packet and to grasp the correct state of the packet communication network.

[Brief description of drawings]

FIG. 1 is a block diagram of a timepiece device that is an embodiment of the present invention.

FIG. 2 is a memory configuration diagram of the same timepiece device.

FIG. 3 is a diagram showing a daily change of an oscillator of the same timepiece device.

FIG. 4 is a diagram for explaining a method of combining correction values of the timepiece device.

FIG. 5 is a flowchart showing the operation of the timepiece device.

FIG. 6 is a block diagram of a transmission time measuring device according to another embodiment of the present invention.

FIG. 7 is a diagram showing an example of a local area network to which the transmission time measuring device is connected.

FIG. 8 is a flowchart showing the operation of the transmission time measuring device.

[Explanation of symbols]

Claims (8)

[Claims] 1. A clock signal generating means, a GPS receiver, and when the GPS receiver outputs time data by receiving a positioning signal of a GPS satellite, the clock signal generation is based on the time data. A clock signal generator, comprising: a calibration unit that calibrates a clock frequency of the unit. 2. The clock signal generating means is a clock circuit driven by a pulse signal output from a crystal oscillator, and the calibrating means corrects a step amount of the clock signal with respect to the pulse signal of the clock circuit. Claim 1
The clock signal generator described. 3. The clock signal generating means is a clock circuit driven by a pulse signal output from a crystal oscillator, and the calibrating means is means for correcting the oscillation frequency of the crystal oscillator. Clock signal generator. 4. The calibrating means includes a frequency detecting means for periodically detecting a clock frequency of the clock signal generating means, and a periodic or secular change characteristic of the clock frequency based on the detected value of the frequency detecting means. 2. The clock signal generator according to claim 1, further comprising: a characteristic detecting unit that determines the clock frequency and a correcting unit that corrects the clock frequency by a correction amount that cancels the change characteristic determined by the characteristic detecting unit. 5. The transmission side creates a packet including transmission time data, detects the transmission time by using the clock signal generator according to claim 1, and transmits the packet at the timing of the transmission time. When the packet is received on the receiving side, the reception time is detected by using the clock signal generator according to claim 1, and the packet is detected from the difference between the reception time and the transmission time data written in the packet. A packet transmission time measuring method characterized in that the transmission time of the packet is calculated. 6. A clock signal generator according to claim 1, comprising a transmitting side device and a receiving side device, and a means for creating a packet containing transmission time data.
The reception side device comprises: means for detecting the timing of the transmission time based on the output of the clock signal generation device; and means for transmitting the packet to the reception side device at the timing. 1. A clock signal generator according to claim 1, and means for calculating a reception time based on the output of the clock signal generator when the packet is received,
Means for determining the transmission time of the packet from the difference between the reception time and the transmission time data written in the packet,
A packet transmission time measuring system comprising: 7. A transmission side device transmits a packet including transmission time data, and when the reception side device receives the packet, the transmission side device is based on the reception time of the packet and the transmission time data. A packet transmission time measuring system for measuring a packet transmission time between receiving side devices, wherein the clock signal generating device according to claim 1, means for creating a packet including transmission time data, and an output of the clock signal generating device. A transmitting side device of a packet transmission time measuring system, comprising: a means for detecting the timing of the transmission time based on the transmission time; and a means for transmitting the packet to the receiving side device at the timing. 8. A transmission side device transmits a packet including transmission time data, and when the reception side device receives the packet, the transmission side device is based on the reception time of the packet and the transmission time data. A packet transmission time measuring system for measuring a packet transmission time between receiving side devices, wherein the clock signal generating device according to claim 1 and a reception time based on an output of the clock signal generating device when the packet is received. A device on the receiving side of a packet transmission time measuring system, comprising: means for calculating; and means for calculating the transmission time of the packet from the difference between the reception time and the transmission time data written in the packet.