JP2003185465A - Inertia equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide inertia equipment by which an inertia data synchronized with an external clock signal can be supplied to external apparatuses, even if the period of the external clock signal varies. <P>SOLUTION: An external clock period measuring circuit 5 measures the cycle period of the external clock signal 102, and supplies the external clock period data to an arithmetic processing portion 4. On the basis of the external clock period data, the processing portion 4 finds the error of the cycle period of the external clock 102, produces an internal clock which is a frequency- divided signal of the external clock 102. The period of the internal clock is corrected by the error, and an internal clock whose period has been corrected is produced. The processing portion 4 receives the output data of an inertia sensor 2 via an updown counter 3 by a period on the external clock 102, integrates the output data of the inertia sensor 2 by the corrected period of the internal clock, and computes a precise inertia data from which the influence of the error of the cycle period of the external signal 102 has been excluded. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mounted on an aircraft, a rocket or other moving body, detects an angular velocity and acceleration of the moving body by an inertial sensor composed of a gyro and an accelerometer, and detects the angular velocity and acceleration of the moving body based on the angular velocity and the acceleration. Posture angle of
The present invention relates to an inertial device that calculates inertial data such as speed and position, and more particularly to an inertial device that can receive an external clock signal supplied from an external device such as an autopilot and output the inertial data to the external device in synchronization with the external clock signal. .

[0002]

2. Description of the Related Art Generally, an inertial device is mounted on an aircraft, a rocket or other moving body, has an inertial sensor and an arithmetic processing unit, and generates an attitude angle, a velocity and a position of the moving body.
The attitude angle, velocity and position of the moving body are referred to as inertial data of the moving body. The inertial sensor includes a gyro that detects the angular velocity of the moving body with respect to the three orthogonal X, Y and Z axes, and an accelerometer that detects the acceleration of the moving body with respect to the three orthogonal axes. The angular velocity and acceleration detected by the inertial sensor are
Here, it is referred to as a sensor output. The arithmetic processing unit calculates the attitude angle, speed and position of the moving body, that is, inertial data, based on the sensor output. A calculation for obtaining inertial data (attitude angle, speed and position) of a moving body based on sensor outputs (angular velocity and acceleration) is called inertial calculation. In the inertia calculation, an integral calculation is performed on the sensor output to obtain the angle and speed of the moving body with respect to the three orthogonal axes X, Y and Z, and the data of the angle and speed are processed to determine the posture, speed and position of the moving body. Is an operation for obtaining. The inertial data is provided to, for example, an autopilot device (autopilot device) of the mobile body, and is used as control system control data of the mobile body. FIG. 4 and FIG. 5 are diagrams respectively showing a configuration of a conventionally known inertial device.
The autopilot device is an example of an external device.

The inertial device 41 (first conventional example) shown in FIG.
The inertial sensor 2, the up / down counter 3, the arithmetic processing unit 44, and the external connection circuit 6 are provided, and the inertial data is supplied to the external device 16 via the data bus 14. The inertial sensor 2 is a gyro that detects angular acceleration and an accelerometer that detects acceleration. The inertial sensor 2 outputs angular velocity and acceleration about three orthogonal axes of X, Y, and Z as a sensor output 101. Then, the inertial sensor 2 outputs the sensor output 1
01 has an up terminal and a down terminal corresponding to each data (angular velocity or acceleration about three orthogonal axes of X, Y and Z), and when the data is a positive value,
The number of pulses representing the size of the data is output from the up terminal, and when the data has a negative value, the number of pulses representing the size of the data is output from the down terminal.

The up-down counter 3 has an up-count input terminal and a down-count input terminal corresponding to the up terminal and the down terminal of the inertial sensor 2, respectively. The up terminal of the inertial sensor 2 is connected to the up count input terminal, and the down terminal of the inertial sensor 2 is connected to the down count input terminal. The up-down counter 3 adds the count value by the number of pulses input to the up-count input terminal at the timing of the clock signal 402 supplied from the arithmetic processing unit 44 (count-up).
Then, the count value is subtracted (counted down) by the number of pulses input to the down count input terminal. Up Down·
This counting process in the counter 3 is called an up / down counting process. The up / down count process is a kind of integration process because the sensor output 101 is counted in the cycle of the clock signal 402. The cycle of the clock signal 402 is, for example, about 1 msec. The up / down count processing output 103 of the up / down counter 3 is sent to the arithmetic processing unit 44. Arithmetic processing unit 44
Performs inertia calculation on the up / down count processing output 103 to generate inertia data 144. The inertia calculation in the calculation processing section 44 includes an integral calculation of the up / down count processing output 103. Inertial data 144
Is supplied to the external device 16 via the external connection circuit 6 and the data bus 14.

In the conventional example of FIG. 4, the up / down count processing in the up / down counter 3 and the inertial calculation processing in the calculation processing section 44 are performed by the external device 1
It is performed at a unique timing irrelevant to the clock signal of 6, that is, asynchronously with the processing operation in the external device 16. Therefore, it is unavoidable that the processing timing between the inertial device 41 and the external device 16 is deviated, and when the external device 16 receives the inertial data 144, the mobile unit acquired at the moment when the inertial data 144 is acquired. The external device 16 cannot accurately know whether or not the physical movement state of Therefore, in the inertial device of FIG. 4, an error between the inertial data 144 and the physical motion state of the moving body is inevitable.

The inertial device 51 (second conventional example) shown in FIG.
This is a conventional example intended to eliminate this drawback, and each component is the same as that in the device of FIG. The inertial device 51 of FIG. 5 differs from the inertial device 41 of FIG. 4 in that
External clock signal 102 output from the external device 16
Is that it is introduced into the inertial device 51. The frequency of the external clock signal 102 is, for example, 1 kHz.

In FIG. 5, the sensor output 101 of the inertial sensor 2 is input to the up / down counter 3 and subjected to up / down counting processing at a timing based on the external clock signal 102. Up-down counter 3
The up-down count processing output 103 of is sent to the arithmetic processing unit 44. The arithmetic processing unit 44 performs inertia calculation processing on the up / down count processing output 103 at the timing of the external clock signal 102, and outputs the inertia data 14
4 is generated. This inertia calculation includes integration calculation similar to the calculation in FIG. In the inertial device 51 of FIG. 5, the external clock signal 1 is used to start and end the integration period of the integration operation.
It is the timing of 02. This inertial data 144 is supplied to the external device 16 via the external connection circuit 6 and the data bus 14 as in the case of the conventional example of FIG.

As described with respect to the up / down counter 3 in the inertial device 41 of FIG. 4, the counting processing in the up / down counter 3 is a kind of integration processing, and the calculation processing section 44 also performs the integration processing. The counting processing in the up / down counter 3 is a short-time counting of about 1 msec, and the integration processing in the arithmetic processing unit 44 is up / down counting processing output 1 for a longer time.
This is done by integrating 03. Arithmetic processing unit 44
Receives the external clock signal 102, generates an internal clock signal obtained by dividing the frequency of the external clock signal 102,
Integration processing is performed at the timing of the internal clock signal.

In the conventional example shown in FIG.
Since the processing operations of the counter 3 and the arithmetic processing unit 44 are synchronized with the external clock signal 102 of the external device 16, the inertia data 144 is supplied to the external device 16 at the standby timing of the upper external device 16. Therefore, in the inertial device 51 (second conventional example) of FIG.
The drawbacks of the inertial device 41 (first conventional example) are temporarily avoided.

[0010]

In the case of the second conventional example proposed to compensate for the drawbacks of the first conventional example in the above-mentioned conventional example, the up / down counter 3 in the inertial device 51 is provided. The processing operation of the arithmetic processing unit 44 is performed in synchronization with the external clock signal 102 of the external device 16, and the time difference between the inertial data 144 of the output of the inertial device 51 and the data reception timing of the external device 16 is performed. Is temporarily avoided, and the external device 16 can accurately know at what point the inertial data 144 represents the physical motion state of the mobile body acquired. However, the inertial calculation process in the calculation processing unit 44 includes an integral calculation, and the time interval from the start to the end of the integral calculation is defined by the external clock signal 102. Therefore, if the cycle of the external clock signal 102 varies, There is a drawback that it becomes an error in the integration time section of the integration calculation, and the error in the integration time section directly leads to deterioration in accuracy of the inertia data 144 (posture angle, speed and position) due to the inertia calculation in the calculation processing unit 44.

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks and to provide inertial data synchronized with an external clock signal to an external device with high accuracy even if the cycle of the external clock signal varies. To provide.

[0012]

In order to solve the above problems, the present invention provides the following means.

(1) An inertial sensor for detecting the angular velocity and acceleration of a moving body, and an arithmetic means for receiving the output of the inertial sensor are provided, and the external clock signal output from an external device is received by the arithmetic means, In an inertial device that obtains inertial data of the moving object by performing integral calculation processing on the inertial sensor output with respect to time based on the repetition period of the clock signal, and transmits the inertial data to the external device, An external clock cycle measuring circuit for measuring a repeating cycle and generating external clock cycle data representing the repeating cycle, wherein the calculating means receives the external clock cycle data and repeats the external clock cycle data represented by the external clock cycle data. The difference between the cycle and the reference value is calculated as the external clock cycle error, and the external clock cycle error is calculated based on the external clock cycle error. Of the inertia of the moving body by generating a corrected external clock having a corrected repeating cycle by performing the integral calculation processing on the output of the inertial sensor with respect to the time based on the repeating cycle of the corrected external clock. An inertial device characterized by obtaining data and transmitting the inertial data to the external device.

(2) The inertial sensor includes a gyro for detecting the angular velocity and an accelerometer for detecting the acceleration, and the calculating means counts up and down in the inertial sensor output at the timing of the external clock signal. An up-down counter for performing processing to generate an up-down count processing output, and an operation processing section for generating the inertial data by performing integral operation processing on the up-down count processing output. Supplies a control signal for controlling the operation of the external clock cycle measuring circuit and a reference clock signal to the external clock cycle measuring circuit, and the repetition frequency of the reference clock signal is
The external clock signal is greater than the repetition frequency of the external clock signal, the external clock cycle measurement circuit generates an external clock signal repetition cycle detection means for generating a pulse signal having a pulse width of the repetition cycle of the external clock signal, and the time of the pulse width. The external clock signal has a counting unit that counts with a reference clock signal, and a unit that takes out the count value output from the counting unit and sends the count value to the arithmetic processing unit as the external clock cycle data. The repetition period detection means generates first and second pulse signals respectively representing continuous first and second repetition cycles of the external clock signal, and the counting means comprises the first
First and second counters for counting the pulse widths of the first and second pulse signals with the reference clock signal, respectively, and the sending means for taking out the count values of the first and second counters, respectively. And a second buffer, and a data bus for guiding the count values of the first and second counters fetched by the first and second buffers to the arithmetic processing unit as the external clock cycle data. The signal controls the counting period in the counting means and the timing for taking out the count values of the first and second counters by the first and second buffers, the inertial device according to the above (1).

(3) The external clock signal repetition cycle detecting means latches the external clock signal, synchronizes with the external clock signal, and alternately switches to a high level and a low level for each cycle of the external clock signal. A latch that generates a pulse signal as the first pulse signal, and a polarity of the first pulse signal that is inverted
The inertial device according to (2) above, which comprises an inverter that generates the pulse signal of

(4) The corrected external clock is a clock obtained by correcting a repeating cycle of an internal clock obtained by dividing the external clock based on the external clock cycle error, (1) to (3). Inertial device according to.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the inertial device of the present invention will be described more specifically with reference to the embodiments of the present invention.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. As shown in FIG. 1, the inertial device 1 of the present embodiment includes an inertial sensor 2, an up / down counter 3, an arithmetic processing unit 4, an external clock cycle measuring circuit 5, and an external connection circuit 6. Consists of 2 is a diagram showing an internal configuration of an embodiment of the external clock cycle measuring circuit 5, and FIGS. 3 (a), 3 (b), 3 (c),
(D), (e), (f), (g), (h), (i),
(J) and (k) are timing charts of signals of respective parts in the external clock cycle measuring circuit 5. As shown in FIG. 2, the external clock cycle measuring circuit 5 corresponds to the arithmetic processing unit 4 and includes a latch 7, an inverter 8, a counter 9, and
10 and buffers 11 and 12 are provided.

In FIG. 1, the sensor output 101 detected by the inertial sensor 2 (corresponding to the inertial sensor output described above) is input to the up / down counter 3 and the timing of the external clock signal 102 supplied from the external device 16 is supplied. Up / down count processing is performed. The operation of the inertial sensor 2 and the up / down counter 3 is similar to that described with reference to FIG. Up-down counter 3
Up / down count processing output 103 output from
Is input to the arithmetic processing unit 4. In the calculation processing unit 4, the inertia calculation processing is performed on the up / down count processing output 103, as in the conventional inertial device shown in FIGS. 4 and 5. In the inertial device 1 of the present embodiment, the external clock cycle measurement circuit 5 measures the repetition cycle of the external clock signal 102, and the repetition cycle of the external clock signal 102 is used as external clock cycle data via the data bus 13 to perform an arithmetic processing unit. It is characterized by supplying to No. 4.

The arithmetic processing unit 4 makes an error (corresponding to the above-mentioned external clock cycle error) by an amount of deviation of the integration time section indicated by the external clock cycle data from a predetermined external clock cycle (corresponding to the above-mentioned reference value). And external clock signal 1
The period of the internal clock obtained by dividing 02 is corrected based on the error, and accurate inertial data excluding the influence of the frequency fluctuation of the external clock signal 102 can be obtained.

For the external clock cycle measuring circuit 5,
The external clock signal 102 is input, the reference clock signal 104 and the counter (9) are supplied from the arithmetic processing unit 4.
Clear signal 107, counter (10) clear signal 10
8, the buffer (11) enable signal 111 and the buffer (12) enable signal 112 are input. The signals 107, 108, 111 and 112 correspond to the control signals mentioned above. From the external clock cycle measuring circuit 5, the external clock cycle data [the data constituted by alternately selecting the counter (9) count data 109 and the counter (10) count data 110] representing the repetition cycle of the external clock signal 102 is data. It is output to the arithmetic processing unit 4 via the bus 13.

In the arithmetic processing unit 4, as described above,
According to the external clock cycle data, the external clock signal 10
Knowing the repetition cycle of 2, the amount of time that the actual repetition cycle of the external clock signal 102 deviates from the reference repetition cycle of the external clock signal 102 is determined as the external clock signal (102) repetition cycle error. Then, the arithmetic processing unit 4 determines the repetition cycle of the internal clock obtained by dividing the external clock signal 102 by the external clock signal (102).
A correction external clock is generated by performing correction based on the repetition cycle error, and an up / down count processing output 103 is generated at a time based on the repetition cycle of the correction external clock.
Inertial data is generated by time integration of. The inertial data obtained by the time integration of the up / down count processing output 103 is almost the same as the inertial data obtained by integrating at the repetition cycle of the reference value when the repetition cycle of the external clock signal 102 is the reference value. It is precision. This inertial data is input to the external connection circuit 6 via the data bus 14 and further transmitted to the external device 16 via the data bus 15.

As described above, in the inertial calculation in the arithmetic processing unit 4, the error of the repetition cycle of the external clock signal 102 can be obtained to improve the calculation accuracy of the inertial data. In the following, with reference to FIGS. 1, 2, and 3, the present embodiment will be described focusing on the operation content of one example of the external clock period measurement circuit 5.

As shown in FIG. 1, the external clock signal 102 output from the external device 16 (see FIG. 3B).
Is input to the up / down counter 3 and also to the arithmetic processing unit 4 and the external clock cycle measuring circuit 5 as described above. For the external clock cycle measuring circuit 5, the reference clock signal 104 (see FIG.
(See (a)) is supplied from the arithmetic processing unit 4, and as a control signal, a counter (9) clear signal 107 (see FIG. 3).
(G)), counter (10) clear signal 108 (see FIG. 3 (h)), buffer (11) enable signal 11
1 (see FIG. 3 (i)) and the buffer (12) enable signal 112 (see FIG. 3 (j)) are supplied from the arithmetic processing unit 4. The frequency of the external clock signal 102 is 1k
Hz. The reference clock signal 104 is supplied to the arithmetic processing unit 4
It is a signal with a stable frequency of 10 MHz generated by an internal oscillator and is asynchronous with the external clock signal 102.

In FIG. 2, the external clock signal 102 from the external device 16 is input to the latch 7, and from the latch 7, the counter enable signal 105 (corresponding to the above-mentioned first pulse signal. FIG. 3C). Is output to the counter 9 and is inverted by the inverter 8 to be inverted counter enable signal 106 (corresponding to the second pulse signal described above; see FIG. 3D).
It is input to the counter 10.

The counter 9 (corresponding to the above-mentioned first counter) receives the counter enable signal 105 and the reference clock signal 104 and, as shown in FIG. 3 (e), during the period from the timing T1 to the timing T2. At, the reference clock signal 104 is counted. The count value of the counter 9 is held as counter (9) count data 109 in the time zone after the timing T2. The counter (9) count data 109 is the external clock signal 102.
Represents the cycle of. Similarly, the counter 10 (corresponding to the above-mentioned second counter) has an inverted counter enable signal 1
06 and the reference clock signal 104,
As shown in (f), the reference clock signal 104 is counted between the timings T2 and T5.
The count value of the counter 10 is held as counter (10) count data 110 in the time period after the timing T5. Counter (10) Count data 110
Represents the cycle of the external clock signal 102, like the count data 109 of the counter (9). The counter (9) count data 109 and the counter (10) count data 110 are
Each represents an alternate repetition period in the external clock signal 102.

The buffer 11 (corresponding to the above-mentioned first buffer) has a timing T3 as shown in FIG. 3 (i).
In the buffer (1
1) Upon receiving the enable signal 111, the counter (9) which holds data in the counter 9 after the timing T2
The count data 109 is taken in. The counter (9) count data 109 is transmitted to the arithmetic processing unit 4 via the buffer 11 and the data bus 13. At timing T4 after the transfer of the counter (9) count data 109, the counter (9) clear signal 107 is input from the arithmetic processing unit 4 to the counter 9 to count the counter (9) held in the counter 9. The data 109 is cleared.

These series of linked operations relating to the counter 9 and the buffer 11 are performed by the counter 10 and the buffer 12.
The same applies to (corresponding to the above-mentioned second buffer). As shown in FIG. 3 (j), the buffer 12 receives the buffer (12) enable signal 112 output from the arithmetic processing unit 4 at the timing T6 and holds the data in the counter 10 after the timing T5. The counter (10) count data 110 is fetched, and the counter (10) count data 110 is transmitted to the arithmetic processing unit 4 via the buffer 12 and the data bus 13. The counter (10) clear signal 108 is input from the arithmetic processing unit 4 to the counter 10 at a timing T7 after the transfer of the count data 110 of the counter (10), and the counter (1
0) The count data 110 is cleared.

FIG. 3K shows the counter (9) count data 109 and the counter (10) count data 110 of the data bus 13 when they are transmitted to the external device 16 via the data bus 13, respectively. It is the figure which showed the utilization time zone notionally. Buffer (11) enable signal 111
And the counter count data 10 in the transmission time zone 13a corresponding to the buffer (12) enable signal 112.
Reference numerals 9 and 110 denote arithmetic processing units 4 via the data bus 13.
To the counter (9) counting data 1
09 and the counter (10) count data 110 are alternately output to the arithmetic processing unit 4 via the data bus 13 in synchronization with the external clock signal 102. The counter count data 109 and 110 are stored in the data bus 1 as described above.
When the data is alternately supplied to the arithmetic processing unit 4 via the data processing unit 3, the arithmetic processing unit 4 recognizes the data 109 and 110 as integrated data which is the external clock cycle data. See also FIG.
The period indicated by reference numeral 13b in (k) indicates a time zone in which the data bus 13 is in a high impedance state, and indicates a transmission time zone that can be used for transmission of data signals other than the counter count data 109 and 110. ing.

Thus, the external clock cycle measuring circuit 5 of FIG. 2 supplies the external clock cycle data composed of the counter count data 109 and 110 to the arithmetic processing section 4,
The arithmetic processing unit 4 calculates the error of the repeating cycle of the external clock signal 102 (external clock cycle error) based on the external clock cycle data, corrects the repeating cycle of the external clock signal 102 based on the external clock cycle error, and corrects the external A clock is generated, and time integration of the up / down count processing output 103 is performed with a time based on the repetition cycle of the corrected external clock. Since the time data in the time integration is accurate, the arithmetic processing unit 4 can calculate the accurate inertial data excluding the influence of the error of the repetition period of the external clock signal 102. However, since the reference clock signal 104 is asynchronous with the external clock signal 102, the repetition cycle of the external clock signal 102 measured by the external clock cycle measurement circuit 5 has an error of maximum two cycles of the reference clock signal 104. There is. However, in this embodiment, since the reference clock signal 104 has a frequency of 10 MHz, the error for these two cycles is 200 nanoseconds (ns), resulting in a fluctuation of several tens of microseconds that can occur in the repetition cycle of the external clock signal 102. In comparison, the size is negligible.

Further, the error of the repeating period of the external clock signal 102 is due to the jitter of the repeating period of the external clock signal 102, and even if the jitter is a relatively large value, in the present embodiment, the external clock signal is not generated. Signal 1
Since the repeat cycle of 02 is measured for each cycle,
Even if the inertial data obtained by calculation in accordance with the repetition cycle of the external clock signal 102 has an error due to the jitter, accurate inertial data with the error corrected can be output. The external clock period measurement circuit uses the external clock signal 1
If the average value of a plurality of repeating cycles in 02 is measured, the error of the integrated value based on individual jitter cannot be corrected, but in the present embodiment, as described above, the repeating cycle of the external clock signal 102 is one cycle. Since the measurement is performed for each, it is possible to correct the error based on the jitter for each repeating cycle.

[0032]

As described above, according to the present invention, an inertial device capable of supplying inertial data synchronized with an external clock signal to an external device with high accuracy even if the cycle of the external clock signal varies. Can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing an example of an external clock cycle measurement circuit in the embodiment of FIG.

FIG. 3 is a timing diagram showing signals of various parts in the external clock cycle measurement circuit of FIG.

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

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

[Explanation of symbols]

1, 41, 51 Inertial device 2 Inertial sensor 3 Up-down counter 4,44 Arithmetic processing unit 5 External clock cycle measuring circuit 6 External connection circuit 7 Latch 8 Inverter 9, 10 Counter 11, 12 Buffer 13, 14, 15 Data bus 16 external device 101 sensor output 102 external clock signal 103 up / down counter 3 up / down
Count processing output 104 Reference clock signal 105 Counter enable signal 106 Inverse counter enable signal 107 Counter (9) clear signal 108 Counter (10) Clear signal 109 Counter (9) Count data 110 Counter (10) Count data 111 Buffer (11 ) Enable signal 112 Buffer (12) Enable signal 144 Inertial data 402 Clock signal

Claims (4)

[Claims] 1. An inertial sensor for detecting an angular velocity and an acceleration of a moving body, and an arithmetic means for receiving an output of the inertial sensor. The external clock signal output from an external device is received by the arithmetic means, and the external clock is supplied. In an inertial device that obtains inertial data of the moving object by performing integral calculation processing on the inertial sensor output with respect to time based on a signal repetition period, and repeats the external clock signal in an inertial device that transmits the inertial data to the external device. An external clock cycle measuring circuit for measuring a cycle and generating external clock cycle data representing the repeating cycle, wherein the calculating means receives the external clock cycle data,
The difference between the repeating cycle represented by the external clock cycle data and the reference value is obtained as an external clock cycle error, and the cycle of the external clock is corrected based on the external clock cycle error, thereby correcting the repeating cycle. A corrected external clock is generated, and inertial data of the moving body is obtained by performing integral calculation processing on the inertial sensor output with respect to the time based on the repetition cycle of the corrected external clock, and the inertial data is transmitted to the external device. An inertial device characterized by the above. 2. The inertial sensor includes a gyro for detecting the angular velocity and an accelerometer for detecting the acceleration, and the computing means performs up / down count processing on the inertial sensor output at the timing of the external clock signal. And an arithmetic processing unit that generates the inertia data by performing integral arithmetic processing on the output of the up-down count processing, and the arithmetic processing unit, A control signal for controlling the operation of the external clock cycle measuring circuit and a reference clock signal are supplied to the external clock cycle measuring circuit, and the repeating frequency of the reference clock signal is higher than the repeating frequency of the external clock signal, The clock cycle measuring circuit is a circuit for measuring the repetition cycle of the external clock signal. External clock signal repetition period detecting means for generating a pulse signal of a pulse width, counting means for counting the time of the pulse width with the reference clock signal, and a count value output from the counting means, and the count value is obtained. Means for sending to the arithmetic processing unit as the external clock cycle data, the external clock signal repetition cycle detection means having a first first cycle and a second repetition cycle each representing a continuous first and second repetition cycle in the external clock signal. And a second pulse signal, wherein the counting means includes first and second counters that respectively count the pulse widths of the first and second pulse signals with the reference clock signal, and the sending means. Are first and second buffers for respectively taking out the count values of the first and second counters, and the first and second buffers.
And a data bus for guiding the count values of the first and second counters fetched to the second buffer to the arithmetic processing section as the external clock cycle data, and the control signal is used for the counting period in the counting means and The inertial device according to claim 1, wherein the timings for taking out the count values of the first and second counters by the first and second buffers are controlled. 3. The external clock signal repetition cycle detecting means latches the external clock signal, synchronizes with the external clock signal, and alternately switches to a high level and a low level for each cycle of the external clock signal. A latch for generating a signal as the first pulse signal;
The inertial device according to claim 2, further comprising an inverter that inverts the polarity of the first pulse signal to generate the second pulse signal. 4. The inertia according to claim 1, wherein the corrected external clock is a clock obtained by correcting a repeating cycle of an internal clock obtained by dividing the external clock based on the external clock cycle error. apparatus.