JP7565882B2 - Time measuring device and time measuring method - Google Patents

Description

The present invention relates to a time measurement device and a time measurement method.

A known time measurement device measures the length of a target period from the start of measurement to the end of measurement by combining a low-speed clock with a reference period and a high-speed clock with a period shorter than the reference period and counting the number of pulses from these (see Patent Document 1). This time measurement device measures the outline period from the start of measurement to the measurement elapsed time point that is synchronized with the reference period that arrives after the measurement end point using the low-speed clock, measures the excess period from the measurement end point to the measurement elapsed time point using the high-speed clock, and subtracts the excess period from the outline period to measure the length of the target period.

In general, the period of a high-speed clock is not stable when it starts to be generated, and the period changes over time. For this reason, the time measurement device described above sets a reference clock number that is the intermediate number of pulses between the number of pulses of the high-speed clock for the first reference period and the number of pulses of the high-speed clock for the next reference period adjacent to the first reference period, and calculates the number of pulses of the low-speed clock corresponding to the overage period based on this reference clock number, the number of pulses of the high-speed clock in the overage period, and the time length of the reference period, thereby reducing measurement errors.

JP 2020-204472 A

The length of the overrun period varies depending on the length of the target period and the length of the reference period. However, the time measurement device described above measures the same regardless of the length of the overrun period. Therefore, depending on the selection of the reference clock count and the length of the overrun period, there may be variations in measurement accuracy, and further improvements in measurement accuracy are needed.

The present invention aims to solve the above problems and provide a time measurement device and a time measurement method that can improve measurement accuracy.

The time measurement device according to the present invention is a time measurement device that measures the length of a target period from a measurement start point to a measurement end point, and includes a low-speed clock generation unit that generates low-speed clock pulses at a reference period, a high-speed clock generation unit that generates high-speed clock pulses having a period shorter than that of the low-speed clock pulses in a first reference period from a first point in time until a first multiple of the reference period has elapsed, a second reference period from a second point in time until a second multiple of the reference period that is different from the first multiple has elapsed, and an overrun period from the measurement end point to an overrun point that is synchronized with the reference period after the measurement end point, a low-speed clock counter that counts the number of pulses of the low-speed clock pulses generated by the low-speed clock generation unit in the period from the measurement start point to the overrun point, and a pulse counter that counts the number of pulses of the high-speed clock pulses generated by the high-speed clock generation unit. The device is characterized by comprising: a high-speed clock counter that counts the number of pulses in a period of the same time length as the first reference period, the second reference period, and the overtime period; a reference selection unit that acquires a first reference pulse number, which is the number of pulses of the high-speed clock pulse counted in the first reference period, and a second reference pulse number, which is the number of pulses of the high-speed clock pulse counted in the second reference period, and selects one of the first reference pulse number and the second reference pulse number as the reference pulse number according to the length of the overtime period; and a time calculation unit that calculates the length of the target period based on the reference pulse number, the length of the period during which the reference pulse number was counted, the count number of the high-speed clock counter during the period of the same time length as the overtime period, the time length of the reference period, and the count number of the low-speed clock counter.

According to the present invention, either the first reference pulse number or the second reference pulse number, which have different time lengths, are selected as the reference pulse depending on the length of the overrun period, and the length of the target period is calculated based on this reference pulse number, the time length of the reference period, the count number of the low-speed clock counter, and the count number of the high-speed clock counter during the overrun period. Therefore, for example, even if the period of the high-speed clock pulse changes over time from the start of generation, it is possible to measure the length of the overrun period with high accuracy, and the measurement accuracy of the length of the target period can be improved.

2 is a block diagram showing a part of the hardware configuration of the time measurement device according to the first embodiment; 5 is a flowchart showing a process performed by a control unit according to the first embodiment. 11 is a timing chart in the case where the length of an overrun period is close to one reference period when the control unit according to the first embodiment measures time. 11 is a timing chart in which the length of an overrun period is close to two reference periods when the control unit according to the first embodiment measures time. 11 is a timing chart in which the length of an overrun period is close to 1.5 reference cycles when the control unit according to the first embodiment measures time. 4 is a block diagram showing a calculation process of a process performed by the time measurement device according to the first embodiment; 13 is a flowchart showing a process performed by a control unit according to the second embodiment. 13 is a timing chart in the case where the length of an overrun period is close to one reference period when the control unit according to the second embodiment measures time. 13 is a timing chart showing a case where the length of an overrun period is close to two reference periods when the control unit according to the second embodiment measures time. 13 is a timing chart in the case where the length of an overrun period is close to one reference period when the control unit according to the third embodiment measures time. 13 is a timing chart in the case where the length of an overrun period is close to two reference periods when the control unit according to the third embodiment measures time.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in
Embodiment 1.
First, the configuration of a time measurement device 100 according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a block diagram showing a part of the hardware configuration of the time measurement device 100. The time measurement device 100 according to the first embodiment is a device that is mounted on, for example, an ultrasonic flowmeter (not shown) and measures the time length of a target period Tm, which is a period between two signals input at different times, by using a low-speed clock pulse and a high-speed clock pulse.

The ultrasonic flowmeter has, for example, an output vibrator that oscillates when a voltage is applied to it, thereby outputting a drive pulse at a substantially constant period, and an input vibrator that is disposed at a distance from the output vibrator, vibrates when a drive pulse is input, and converts the vibration into an electrical signal. The ultrasonic flowmeter outputs a start pulse Pstart to the time measurement device 100 in response to the output of the drive pulse, and outputs a stop pulse Pstop to the time measurement device 100 when the input vibrator detects the drive pulse. For example, the ultrasonic flowmeter determines that the point at which the amplitude of the vibration input to the input vibrator exceeds a predetermined threshold and then becomes 0 is the point at which the drive pulse was detected (zero cross point), and outputs a stop pulse Pstop to the time measurement device 100.

When a start pulse Pstart and a stop pulse Pstop are input from the ultrasonic flowmeter or the like at different times, the time measurement device 100 according to the first embodiment calculates and outputs the length of the target period Tm, which is the period between these two signals. In other words, the time measurement device 100 calculates and outputs the length of the target period Tm from the measurement start point, which is the time when the start pulse Pstart is input, to the measurement end point, which is the time when the stop pulse Pstop is input, i.e., the time difference between the times when these two signals are input.

The time measurement device 100 includes an input unit 10 to which a signal is input, a low-speed clock generation unit 11A that generates a low-speed clock pulse CL, a high-speed clock generation unit 11B that generates a high-speed clock pulse, a low-speed clock counter 13A that counts the number of pulses of the low-speed clock pulse generated by the low-speed clock generation unit 11A, a high-speed clock counter 13B that counts the number of pulses of the high-speed clock pulse generated by the high-speed clock generation unit 11B, an enable signal generation unit 14 that generates an enable signal EN for controlling the generation period of the high-speed clock pulse by the high-speed clock generation unit 11B, a reference selection unit 15, a storage unit 16 that stores various information for calculating the time length of the target period Tm, a time calculation unit 17 that calculates the time length of the target period Tm, and a control unit 12 that controls each component of the time measurement device 100. The reference selection unit 15 will be described later.

The time measurement device 100 has a processing circuit with a CPU, ROM, RAM, I/O ports, etc. (not shown), and the processing circuit realizes the functions of the input unit 10, low-speed clock generation unit 11A, high-speed clock generation unit 11B, low-speed clock counter 13A, high-speed clock counter 13B, enable signal generation unit 14, reference selection unit 15, memory unit 16, time calculation unit 17, and control unit 12.

The input unit 10 receives a signal from a device to which the time measurement device 100 is connected. For example, a start pulse Pstart and a stop pulse Pstop are input from the ultrasonic flowmeter described above. When the input unit 10 receives a signal, it outputs the signal to the low-speed clock generating unit 11A and the high-speed clock generating unit 11B.

The low-speed clock generating unit 11A generates a low-speed clock pulse CL at a reference period that is a substantially constant period during a predetermined period. For example, the low-speed clock generating unit 11A has an oscillator that oscillates when a voltage is applied to it, and generates a low-speed clock pulse CL such as a square wave. Also, for example, the low-speed clock counter 13A starts generating a low-speed clock pulse CL based on a signal being input from the input unit 10. The low-speed clock pulse CL generated by the low-speed clock generating unit 11A is output to the low-speed clock counter 13A.

The high-speed clock generating unit 11B generates high-speed clock pulses CH at a period shorter than the reference period. For example, the high-speed clock generating unit 11B is configured with a high-frequency type clock pulse generating circuit such as a ring oscillator, and generates high-speed clock pulses CH that are rectangular waves. Also, for example, the high-speed clock generating unit 11B starts generating high-speed clock pulses CH based on the input of a stop pulse Pstop to the time measurement device 100. The high-speed clock pulses CH generated by the high-speed clock generating unit 11B are output to the high-speed clock counter 13B.

The low-speed clock counter 13A counts and accumulates the number of low-speed clock pulses CL output by the low-speed clock generating unit 11A during a predetermined period. For example, the low-speed clock counter 13A starts counting the low-speed clock pulses CL based on the start pulse Pstart being input to the time measurement device 100.

The high-speed clock counter 13B counts and accumulates the number of pulses of the high-speed clock pulse CH output by the high-speed clock generating unit 11B during a predetermined period. For example, the high-speed clock counter 13B starts counting the high-speed clock pulse CH based on the input of a stop pulse Pstop to the time measurement device 100.

In general, when the length of a target period Tm from the measurement start point to the measurement end point is measured by a time measurement device, the time measurement device measures the time by combining a low-speed clock pulse and a high-speed clock pulse.
For example, the time measurement device first counts the number of pulses of the low-speed clock pulse CL generated in the reference period during a measurement period T that is a period from the measurement start time when generation of the low-speed clock pulse CL starts to the overrun time after the measurement end time when the time measurement device synchronizes with the reference period. In other words, the time measurement device first counts the number of pulses of the low-speed clock pulse CL generated in the reference period during a measurement period T that is a period from the measurement start time to the overrun time after the measurement end time when the elapsed time from the measurement start time becomes an integer multiple of the reference period.
In addition, the time measurement device converts the count of the number of pulses of high-speed clock pulses CH generated during the overrun period, which is the period from the end of measurement to the overrun point, into the number of pulses of low-speed clock pulses CL generated during this period, based on the reference period and the period of the high-speed clock pulse.

Next, the time measurement device subtracts the conversion value of the low-speed clock pulse CL in the overage period from the count number of the low-speed clock pulse CL in the measurement period. In this way, the time measurement device obtains the pulse number of the low-speed clock pulse CL in the target period Tm, and calculates the time length of the target period Tm by multiplying this pulse number by the reference period, which is the period of the low-speed clock pulse CL.

When a high-frequency clock pulse generating circuit such as a ring oscillator is used as the high-speed clock pulse generating unit, the power consumption required to generate a high-speed clock pulse is greater than that of a low-speed clock. Therefore, it is desirable to suppress power consumption by generating a high-speed clock pulse only during the period required for time measurement, for example, during an overage period, rather than generating a high-speed clock pulse from the start to end of measurement. However, the period of such a high-speed clock pulse does not stabilize until a sufficient amount of time has passed since the clock pulse was generated, and the period may change over time.

Therefore, in the first embodiment, the time measurement device 100 causes the high-speed clock generating unit 11B to generate high-speed clock pulses CH for a time length that is an integer multiple of the reference period, and calculates the number of pulses of low-speed clock pulses CL generated in the overtime period based on the count number of high-speed clock pulses CH at that time and the count number of high-speed clock pulses CH in the overtime period. For example, the number of pulses of low-speed clock pulses CL generated in the overtime period can be calculated by dividing the count number of high-speed clock pulses CH generated in the overtime period by the count number of high-speed clock pulses CH generated in the time length of one reference period.
As a result, even if the period of the high-speed clock pulse CH changes while the high-speed clock pulse CH is being counted, the number of low-speed clock pulses CL generated during the overrun period can be calculated.

In addition, when generating high-speed clock pulses, depending on the circuit configuration, the period may expand over time until a sufficient amount of time has passed since the generation of the clock pulse, or the period may contract over time. In such cases, even if an attempt is made to calculate the number of pulses of low-speed clock pulses CL generated in the overage period based on the count number of high-speed clock pulses CH generated with a time length that is an integer multiple of the reference period and the count number of high-speed clock pulses CH in the overage period, sufficient accuracy may not be obtained depending on the difference between the time length that is an integer multiple of the reference period for generating the high-speed clock pulses CH and the time length of the overage period.

For this reason, in the first embodiment, high-speed clock pulses CH are generated in multiple periods of different time lengths, and the number of counts of the resulting multiple high-speed clock pulses CH and the number of counts of the high-speed clock pulses CH generated in the overage period are used to calculate the number of pulses of the low-speed clock pulses CL generated in the overage period with higher accuracy.

In the time measurement device 100 according to the first embodiment, the high-speed clock counter 13B counts the number of high-speed clock pulses CH generated in a first reference period from a first point in time until a time length that is a first multiple of the reference period has elapsed as a first reference pulse number, and counts the number of high-speed clock pulses CH generated in a second reference period from a second point in time until a time length that is a second multiple of the reference period that is different from the first number has elapsed as a second reference pulse number, and the reference selection unit 15 selects either the first reference pulse number or the second reference pulse number as the reference pulse number depending on the time length of the overage period, and calculates the number of pulses of the low-speed clock pulses CL generated in the overage period based on this reference pulse number and the count number of high-speed clock pulses CH generated in a period of the same time length as the overage period.

For example, in the time measurement device 100 according to the first embodiment, when the overrun time point is determined to be the first time point synchronized with the reference period after the measurement end time point, the high-speed clock counter 13B counts the number of high-speed clock pulses CH generated in a first reference period from the measurement start time to the time length of one reference period elapses as the first reference pulse number, and counts the number of high-speed clock pulses CH generated in a second reference period that is after the first reference period and from a second time point in the target period to the time length of two reference periods elapses as the second reference pulse number, and the reference selection unit 15 selects either the first reference pulse number or the second reference pulse number, whichever is closer to the time length of the overrun time point, as the reference pulse number, and calculates the number of pulses of low-speed clock pulses CL generated in the overrun time period based on the ratio between the count number of high-speed clock pulses CH generated in the overrun time period and the reference pulse number.
The reference selection unit 15 may be configured to select one of three or more pulse numbers as the reference pulse number.

As a result, the time measurement device 100 according to the first embodiment calculates the number of pulses of the low-speed clock pulse CL generated in the overrun period based on the ratio between the reference pulse number, which is the count number of the high-speed clock counter 13B in either the first or second reference period that is closest to the length of the overrun period, and the count number of the high-speed clock counter in the overrun period. Therefore, even if, for example, the period of the high-speed clock pulse expands or contracts over time from the start of generation, it is possible to measure the length of the overrun period with high accuracy, thereby improving the measurement accuracy of the length of the target period.

The process performed by the control unit 12 of the time measurement device 100 according to the first embodiment will be described in detail below. FIG. 2 is a flowchart showing the process performed by the control unit 12 according to the first embodiment. FIG. 3 is a timing chart showing the case where the time length of the overage period ΔT is close to one reference period (same time length as the reference period Ts) when the time measurement device according to the first embodiment measures time. FIG. 4 is a timing chart showing the case where the time length of the overage period ΔT is close to two reference periods (twice the time length of the reference period Ts) when the time measurement device according to the first embodiment measures time. FIG. 5 is a timing chart showing the case where the time length of the overage period ΔT is close to 1.5 reference periods (1.5 times the time length of the reference period Ts) when the time measurement device according to the first embodiment measures time.

The control unit 12 first judges whether or not a start pulse Pstart has been input to the input unit 10 (step ST1). In this process, the control unit 12 judges whether or not a target period Tm, which is a target for calculating a time length, has started by judging whether or not a start pulse Pstart, which is an input signal from an ultrasonic flowmeter or the like, has been input to the input unit 10. The start pulse Pstart constitutes a first signal indicating the measurement start time point.
In the process of step ST1, if the start pulse Pstart is not input (NO in step ST1), the control unit 12 determines that the target period Tm has not yet started, and waits for the subsequent processes.

When a start pulse Pstart is input in the processing of step ST1 (YES in step ST1), the control unit 12 determines that the target period Tm, for which the time length is to be calculated, has started, and starts counting the low-speed clock pulses CL by the low-speed clock generating unit 11A at the measurement start time t0, which is the time when the target period Tm started (step ST2). In addition, the control unit 12 causes the enable signal generating unit 14 to output an enable signal EN at the measurement start time t0, and causes the high-speed clock generating unit 11B to start generating high-speed clock pulses CH for obtaining the first reference pulse number.

When time t1 is reached, which is the time equivalent to one reference period from measurement start time t0, the control unit 12 causes the high-speed clock generating unit 11B to end the generation of the high-speed clock pulses CH, and stores the count number of the high-speed clock pulses CH in the first reference period P1 from measurement start time t0 until the time equivalent to one reference period, i.e., one time equivalent to the reference period Ts, as the first reference pulse number in the memory unit 16 (step ST3). In this process, the control unit 12 stores the first reference pulse number, which is the number of pulses of the high-speed clock pulses CH generated in the time length of one reference period, in the memory unit 16 as the reference pulse number when the time length of the excess period is close to the time length of one reference period.

After performing the process of step ST3, the control unit 12 judges whether or not a predetermined period has elapsed since the generation of the high-speed clock pulse CH was started in the first reference period P1 (step ST4). In this process, the predetermined period is a period that is an integer multiple of a predetermined reference cycle Ts, and is, for example, a period in which the generation of the high-speed clock pulse CH in the first reference period P1 has no effect on the cycle of the high-speed clock pulse CH when the generation of the high-speed clock pulse CH is started after this predetermined period, or the effect is so small that it can be ignored.
In the process of step ST4, if a predetermined period has not elapsed since the generation of the high-speed clock pulse CH was started in the first reference period P1 (NO in step ST4), the control section 12 waits for the subsequent process.

In the processing of step ST4, if a time t4 is reached at which a predetermined period has elapsed since the generation of high-speed clock pulses CH was started in the first reference period P1 (YES in step ST4), the control unit 12 causes the enable signal generating unit 14 to output an enable signal EN, and causes the high-speed clock generating unit 11B to start generating high-speed clock pulses CH to obtain the second reference pulse number (step ST6).

When time t5 is reached, which is the time equivalent to two reference periods from measurement start time t0, the control unit 12 causes the high-speed clock generating unit 11B to end generation of the high-speed clock pulses CH, and stores the count number of the high-speed clock pulses CH in the second reference period P2 from measurement start time t4 until the time equivalent to two reference periods, i.e., twice the time equivalent to the reference period Ts, as the second reference pulse number in the memory unit 16 (step ST7). In this process, the control unit 12 stores the second reference pulse number, which is the number of pulses of the high-speed clock pulses CH generated in the time length of two reference periods, in the memory unit 16 as the reference pulse number when the time length of the excess period is close to the time length of two reference periods.

After performing the process of step ST7, the control unit 12 calculates a third reference pulse number, which is the average value of the first reference pulse number and half the value of the second reference pulse number, based on the first reference pulse number and the second reference pulse number, and stores it in the memory unit 16 (step ST8). In this process, the control unit 12 calculates a third reference pulse number, which is the average value of the first reference pulse number and half the value of the second reference pulse number, as the reference pulse number when the time length of the excess period ΔT is close to the time length of 1.5 reference periods, and stores it in the memory unit 16. The control unit 12 calculates the average value of the first reference pulse number and the value obtained by dividing the second reference pulse number by 2, based on the fact that the time length of the second reference period is twice the reference period Ts.

After performing the process of step ST8, the control unit 12 determines whether or not a stop pulse Pstop has been input (step ST9). In this process, the control unit 12 determines whether or not a stop pulse Pstop, which is an input signal from, for example, an ultrasonic flowmeter, has been input to the input unit 10, thereby determining whether or not the target period Tm, for which the time length is to be calculated, has ended. In the process of step ST9, if a stop pulse Pstop has not been input (NO in step ST9), the control unit 12 determines that the target period Tm has not yet ended, and waits for subsequent processes. Note that in the first embodiment, the stop pulse Pstop constitutes a second signal indicating the end of measurement.

In the process of step ST9, if a stop pulse Pstop is input (YES in step ST9), the control unit 12 determines that the target period Tm for which the time length is to be calculated has ended, and causes the high-speed clock generating unit 11B to start generating high-speed clock pulses CH at the measurement end time t8, which is the time when the stop pulse Pstop was input (step ST11). In this process, the control unit 12 causes the high-speed clock generating unit 11B to start generating high-speed clock pulses CH in the overage period ΔT from the measurement end time t8 to the overage time t9 that is synchronized with the reference period Ts after the measurement end time t8, in order to calculate the number of pulses of the low-speed clock pulses CL generated in the overage period ΔT.

In the first embodiment, the overrun time t9 is the time when the clock first synchronizes with the reference period Ts after one reference period Ts or more has elapsed since the measurement end time t8, for example, when the rising edge of the low-speed clock pulse is detected. As a result, in the first embodiment, the length of the overrun period ΔT is one reference period or more and less than two reference periods.

When the time reaches the overrun time t9 after the high-speed clock generating unit 11B starts generating the high-speed clock pulse CH, the control unit 12 causes the reference selecting unit 15 to determine whether the time length of the overrun period ΔT from the measurement end time t8 to the overrun time t9 is close to the time length of the first reference period P1, i.e., the time length of one reference period (step ST12). In other words, the control unit 12 causes the reference selecting unit 15 to determine whether the time length of the overrun period ΔT is within a range that is determined to be close to the time length of the first reference period P1.
For example, the control unit 12 causes the reference selection unit 15 to determine whether the time length of the overrun period ΔT is in a range of one reference period or more and less than 4/3 reference periods (a time length 4/3 times the reference period Ts). In this process, the control unit 12 causes the reference selection unit 15 to compare the time length of the overrun period ΔT with the time length of the first reference period P1, and to determine whether the first reference pulse number should be selected as the reference pulse number.

In the process of step ST12, if the length of the excess period ΔT is close to the length of the first reference period P1 (YES in step ST12), the control unit 12 causes the reference selection unit 15 to select the first reference number of pulses as the reference pulse number from the first reference number of pulses, the second reference number of pulses, and the third reference number of pulses (step ST13). In this process, the control unit 12 causes the reference selection unit 15 to select the first reference number of pulses as the reference pulse number based on the fact that the length of the excess period ΔT is close to the length of the first reference period P1.

In the process of step ST12, if the time length of the excess period ΔT is not close to the time length of the first reference period P1 (NO in step ST12), the control unit 12 causes the reference selection unit 15 to determine whether the time length of the excess period ΔT is close to the time length of the second reference period P2, i.e., the time length of two reference periods (step ST14). In other words, the control unit 12 causes the reference selection unit 15 to determine whether the time length of the excess period ΔT is within a range that is determined to be close to the time length of the second reference period P2. For example, the control unit 12 causes the reference selection unit 15 to determine whether the time length of the excess period ΔT is in a range of 5/3 reference periods (a time length 5/3 times the reference period Ts) or more and less than two reference periods. In this process, the control unit 12 causes the reference selection unit 15 to compare the time length of the excess period ΔT with the time length of the second reference period P2 and determine whether the second reference pulse number should be selected as the reference pulse number.

In the process of step ST14, if the length of the excess period ΔT is close to the length of the second reference period P2 (YES in step ST14), the control unit 12 causes the reference selection unit 15 to select the second reference pulse number as the reference pulse number from among the first reference pulse number, the second reference pulse number, and the third reference pulse number (step ST16). In this process, the control unit 12 causes the reference selection unit 15 to select the second reference pulse number as the reference pulse number based on the fact that the length of the excess period ΔT is close to the length of the second reference period P2.

In this way, in the first embodiment, the control unit 12 causes the reference selection unit 15 to select either the first reference period P1 or the second reference period P2 as the reference pulse when the time length of the overage period ΔT is within a predetermined range. Specifically, the control unit 12 causes the reference selection unit 15 to select, as the reference pulse, one of the first reference period P1 and the second reference period P2 whose time length is closer to the overage period ΔT when the time length of the overage period ΔT is within a predetermined range. More specifically, the control unit 12 causes the reference selection unit 15 to select, as the reference pulse, one of the first reference period P1 and the second reference period P2 whose time length is closer to the overage period ΔT when the time length of the overage period ΔT is within a range of 1 reference period or more and less than 4/3 reference periods, and 5/3 reference periods or more and less than 2 reference periods.

In the process of step ST14, if the time length of the excess period ΔT is not close to the time length of the second reference period P2 (NO in step ST14), the control unit 12 causes the reference selection unit 15 to select the third reference pulse number from the first reference pulse number, the second reference pulse number, and the third reference pulse number as the reference pulse number (step ST17). For example, if the time length of the excess period ΔT is less than 5/3 of the reference period, the control unit 12 causes the reference selection unit 15 to select the third reference pulse number from the first reference pulse number, the second reference pulse number, and the third reference pulse number as the reference pulse number. In this process, the control unit 12 causes the reference selection unit 15 to select the third reference pulse number as the reference pulse number based on the fact that the time length of the excess period ΔT is close to the time length of 1.5 reference periods, for example, the time length of the excess period ΔT is equal to or greater than 4/3 of the reference period and less than 5/3 of the reference period.

After performing the processing of step ST13, step ST16 or step ST17, the control unit 12 causes the time calculation unit 17 to calculate the number of pulses of the low-speed clock pulses CL generated in the overrun period ΔT based on the reference pulse number, the time length of the period during which the reference pulse number was counted, and the count number of the high-speed clock pulses CH in the overrun period ΔT (step ST18).

6 is a block diagram showing the calculation process of the process performed by the time measurement device according to the first embodiment. When the first reference pulse number is selected as the reference pulse number, for example, the control unit 12 causes the time calculation unit 17 to calculate the number of pulses of the low-speed clock pulse CL generated in the overage period ΔT by dividing the count number of the high-speed clock pulse CH in the overage period ΔT by the first reference pulse number. In this process, the control unit 12 causes the time calculation unit 17 to calculate the number of pulses of the low-speed clock pulse CL generated in the overage period ΔT (how many times the time length of the overage period ΔT is one reference period) by dividing the count number of the high-speed clock pulse CH in the overage period ΔT by the first reference pulse number.
When the second reference pulse number is selected as the reference pulse number, for example, the control unit 12 causes the time calculation unit 17 to calculate the number of pulses of the low-speed clock pulse CL generated in the overrun period ΔT by dividing the count number of the high-speed clock pulse CH in the overrun period ΔT by the second reference pulse number, and dividing the obtained value by 2. In this process, the control unit 12 causes the time calculation unit 17 to calculate the number of pulses of the low-speed clock pulse CL generated in the overrun period ΔT (how many times the time length of the overrun period ΔT is one reference period) by dividing the value obtained by dividing the count number of the high-speed clock pulse CH in the overrun period ΔT by the second reference pulse number by 2 based on the fact that the time length of the period during which the reference pulse number is counted is two reference periods.
In addition, when the above-mentioned third reference pulse number (not shown) is selected as the reference pulse number, for example, the control unit 12 causes the time calculation unit 17 to calculate the number of pulses of the low-speed clock pulse CL generated in the overage period ΔT by dividing the count number of the high-speed clock pulse CH in the overage period ΔT by the third reference pulse number. In this case, the control unit 12 also causes the time calculation unit 17 to calculate the number of pulses of the low-speed clock pulse CL generated in the overage period ΔT (how many times the time length of the overage period ΔT is one reference period) by dividing the count number of the high-speed clock pulse CH in the overage period ΔT by the first reference pulse number. In addition, the number of pulses of the low-speed clock pulse CL generated in the overage period ΔT constitutes the number of excess pulses.

After performing the process of step ST18, the control unit 12 causes the time calculation unit 17 to calculate the time length of the target period Tm based on the number of pulses of the low-speed clock pulses CL generated in the overage period ΔT, the number of pulses of the low-speed clock pulses CL generated in the measurement period T, and the reference period Ts (step ST19). For example, the control unit 12 causes the time calculation unit 17 to calculate the time length of the target period Tm by multiplying the value obtained by subtracting the number of pulses of the low-speed clock pulses CL generated in the overage period ΔT from the number of pulses of the low-speed clock pulses CL generated in the measurement period T by the reference period Ts.
After performing the process of step ST19, the control section 12 outputs the time length of the target period Tm calculated by the time calculation section 17 (step ST20).

In this way, the time measurement device 100 according to the first embodiment selects as a reference pulse either one of the first and second reference pulse numbers, which have different time lengths, depending on the length of the overrun period ΔT, and calculates the length of the target period Tm based on this reference pulse number, the length of the reference period Ts, the count number of the low-speed clock counter, and the count number of the high-speed clock counter during the overrun period ΔT. Therefore, for example, even if the period of the high-speed clock pulse changes over time from the start of generation, it is possible to measure the length of the overrun period with high accuracy, and the measurement accuracy of the length of the target period Tm can be improved.

In addition, in the time measurement device 100 according to the first embodiment, the high-speed clock generating unit 11B generates a high-speed clock pulse CH for measuring the number of reference pulses in a first reference period P1 that starts from a first point in the target period Tm, and in a second reference period that starts from a second point in the target period Tm. In general, the period of the high-speed clock pulse CH may be affected by environmental conditions such as the temperature of the device, and an error may occur for each measurement. However, by simultaneously measuring the number of reference pulses during the measurement of the target period Tm in this manner, the number of reference pulses can be measured under the environmental conditions when the length of the target period Tm is measured, and the measurement accuracy of the length of the target period Tm can be improved. In addition, the time required for the entire process can be shortened compared to measuring the number of reference pulses before the start of the target period Tm and then starting to calculate the length of the target period Tm.

In the first embodiment, the control unit 12 causes the time calculation unit 17 to calculate the number of pulses of the low-speed clock pulse CL generated in the overage period ΔT based on the reference pulse number, the count number of the high-speed clock pulse CH in the overage period ΔT, and the time length of the reference period Ts. However, the control unit only needs to calculate the number of pulses of the low-speed clock pulse CL generated in the overage period ΔT based on at least the reference pulse number, the count number of the high-speed clock pulse CH in the overage period ΔT, and the time length of the reference period Ts, and may calculate the number of pulses of the low-speed clock pulse CL generated in the overage period ΔT based on other numerical values in addition to the above numerical values.

For example, the control unit may cause the time calculation unit to calculate the number of pulses of the low-speed clock pulse CL generated in the overage period ΔT based on the reference pulse number, the count number of the high-speed clock pulse CH in the overage period ΔT, the time length of the reference period Ts, and the count number of the high-speed clock pulse CH in the additional measurement period from the time when the stop pulse Pstop is input, which is the measurement end time t8, that is, the time when a half period Td of the drive pulse has elapsed since the measurement end time t8, to the time when the next stop pulse Pstop is input and the same length of time as the overage period ΔT has elapsed.

Specifically, the control unit may cause the time calculation unit to calculate the number of pulses of the low-speed clock pulse CL generated in the overage period ΔT based on the reference pulse number, the average value of the count number of the high-speed clock pulse CH in the overage period ΔT and the count number of the high-speed clock pulse CH in the additional measurement period, and the time length of the reference period Ts. This improves the accuracy of the count number of the high-speed clock pulse CH generated in the overage period ΔT compared to the case where the number of pulses of the low-speed clock pulse CL generated in the overage period ΔT is calculated based on the count number of the high-speed clock pulse CH in one overage period ΔT, the reference pulse number, and the reference period Ts, and therefore improves the measurement accuracy of the time length of the target period Tm.

In addition, in the first embodiment, the time measurement device 100 is configured to calculate the length of the target period based on the reference pulse number, the time length of the period in which the reference pulse number is counted, the time length of the reference period, the count number of the low-speed clock counter, and the count number of the high-speed clock counter in the overrun period, but is not limited to this. The time measurement device only needs to be configured to calculate the length of the target period based on the reference pulse number, the time length of the period in which the reference pulse number is counted, the time length of the reference period, the count number of the low-speed clock counter, and the count number of the high-speed clock counter in a period of the same length as the overrun period, and the period of the same length as the overrun period may be the overrun period itself, or may be a period different from the overrun period that has the same length as the overrun period.

Next, a second embodiment of the present invention will be described in detail with reference to the drawings.
Embodiment 2.
Fig. 7 is a flowchart showing the processing performed by the control unit 212 according to the second embodiment. Fig. 8 is a timing chart showing a case where the length of the overage period ΔT is close to one reference period when the time measurement device 200 according to the second embodiment measures time. Fig. 9 is a timing chart showing a case where the length of the overage period ΔT is close to two reference periods when the time measurement device 200 according to the second embodiment measures time.
The second embodiment is different from the first embodiment in the procedure for measuring the reference pulse number and the procedure for calculating the number of pulses of low-speed clock pulses CL generated in the overrun period ΔT. However, other configurations and other processes are the same, and the same reference symbols are used for the contents similar to those of the first embodiment, and the description thereof will be omitted.

In order to improve the measurement accuracy of the time length of the target period Tm, the control unit 212 according to the second embodiment generates high-speed clock pulses CH multiple times in accordance with the period of the drive pulse when measuring the reference pulse number and calculating the number of pulses of the low-speed clock pulses CL generated in the overrun period ΔT.

For example, as in the first embodiment, the control unit 212 causes the high-speed clock generating unit 11B to generate high-speed clock pulses CH in a first reference period P1 from the first point in time t2 to time t3 when a time equivalent to a reference period has elapsed, and in a second reference period P2 from the second point in time t6 to time t7 when a time equivalent to two reference periods has elapsed. In addition, the control unit 212 also causes the high-speed clock generating unit 11B to generate high-speed clock pulses CH in a third reference period P3 from a point in time half a drive pulse before the first point in time t2, that is, before the input period of the stop pulse Pstop, to a point in time t1 when a time length equal to the first reference period P1 has elapsed, and in a fourth reference period P4 from a point in time t4 half a drive pulse before the second point in time t6 to a point in time when a time length equal to the second reference period P2 has elapsed.
In the second embodiment, the start point of the third reference period P3, which is a half cycle of the drive pulse before the first point in time t2, is set as the measurement start point in time t0.

In addition, in the second embodiment, a stop pulse Pstop is input to the input unit 10 each time the amplitude of the vibration input to the input vibrator exceeds a predetermined threshold and the amplitude becomes 0. That is, in the second embodiment, the stop pulse Pstop is repeatedly input to the input unit 10 multiple times with an input period that is the same as the half period Td of the drive pulse. In the second embodiment, the stop pulse Pstop includes a signal indicating the measurement end point, and constitutes a second signal that is repeated multiple times with the input period.

As in the first embodiment, the control unit 212 causes the high-speed clock generating unit 11B to generate a high-speed clock pulse CH in the overage period ΔT from the measurement end time t8, i.e., the time when the stop pulse Pstop is input, to the overage time t9 that is synchronized with the reference period Ts after the measurement end time t8. In addition, the control unit 212 causes the high-speed clock pulse CH to be generated in an additional measurement period ΔT1 from time t10, which is a half period Td of the drive pulse after the measurement end time t8, i.e., from the time when the stop pulse Pstop, which is the measurement end time t8, is input, to time t11, which is a time the same as the overage period ΔT has elapsed since the next stop pulse Pstop is input. Note that in the second embodiment, the additional measurement period ΔT1 constitutes a period of the same length as the overage period ΔT.

The control unit 212 causes the reference selection unit 15 to select, as the reference pulse number, either the first reference pulse number, which is the count number of high-speed clock pulses CH generated in the first reference period P1, or the second reference pulse number, which is the count number of high-speed clock pulses CH generated in the second reference period P2, depending on the time length of the excess period ΔT, and calculates the excess pulse number, which is the pulse number of low-speed clock pulses CL in the excess period ΔT, based on the reference pulse number selected by the reference selection unit 15, the time length of the period during which the reference pulse number was counted, and the count number of the high-speed clock counter in the additional measurement period ΔT1.

In FIG. 7, the control section 212 first determines whether or not a start pulse Pstart has been input to the input section 10 (step ST1).
In the process of step ST1, if the start pulse Pstart is input (YES in step ST1), the control unit 212 determines that the target period Tm, the time length of which is to be calculated, has started, and causes the low-speed clock generating unit 11A to start generating the low-speed clock pulse CL at the measurement start time t0, which is the time when the start pulse Pstart is input (step ST2). The control unit 12 also causes the enable signal generating unit 14 to output the enable signal EN, and causes the high-speed clock generating unit 11B to start generating the high-speed clock pulse CH at the measurement start time t0, which is the start time of the third reference period P3, which is a preparation period for enabling the generation of high-speed clock pulses at a stable cycle in the first reference period P1.
When the time reaches time t1, which is the time equivalent to one reference period from the measurement start time t0, the control unit 212 determines that the third reference period P3 has ended, and causes the high-speed clock generating unit 11B to end the generation of the high-speed clock pulse CH.

After performing the process of step ST2, the control unit 212 judges whether or not a time equivalent to four reference periods (four times the reference period Ts) has elapsed since the generation of the high-speed clock pulse CH was started at t0 (step ST33). In this process, the control unit 212 judges whether or not the time t2 has been reached, which is the time when the generation of the high-speed clock pulse CH is started in the first reference period P1 after the generation of the high-speed clock pulse CH has been started and the time equivalent to a half period Td of the drive pulse has elapsed.
In the process of step ST33, if a time period equivalent to four reference periods has not elapsed since the generation of the high-speed clock pulse CH started at t0 (NO in step ST33), the control section 212 waits for the subsequent process.

In the processing of step ST33, if a time equivalent to four reference periods has elapsed since the generation of the high-speed clock pulse CH was started at t0 (YES in step ST33), the high-speed clock generating unit 11B is made to start generating the high-speed clock pulse CH to obtain the first reference pulse number (step ST34).

When time t3 is reached, which is the time equivalent to one reference period from time t2, the control unit 212 causes the high-speed clock generating unit 11B to end the generation of the high-speed clock pulses CH, and stores the count number of the high-speed clock pulses CH in the first reference period P1 from time t2 until the time equivalent to one reference period, i.e., one time equivalent to the reference period Ts, as the first reference pulse number in the memory unit 16 (step ST36). In this process, the control unit 212 stores the first reference pulse number, which is the number of pulses of the high-speed clock pulses CH generated in the time length of one reference period, in the memory unit 16 as the reference pulse number when the time length of the excess period is close to the time length of one reference period.

After performing the process of step ST36, the control unit 12 judges whether or not a predetermined period has elapsed since the generation of the high-speed clock pulse CH was started in the first reference period P1 (step ST37). In this process, the predetermined period is a period that is an integer multiple of a predetermined reference period Ts, and is, for example, a period in which the generation of the high-speed clock pulse CH in the first reference period P1 has no effect on the period of the high-speed clock pulse CH when the generation of the high-speed clock pulse CH is started after this predetermined period, or the effect is so small that it can be ignored.
In the process of step ST37, if a predetermined period has not elapsed since the generation of high-speed clock pulses CH was started in the first reference period P1 (NO in step ST37), the control section 212 waits for the subsequent process.

In the processing of step ST37, if the time t4 has been reached after a predetermined period of time has elapsed since the generation of high-speed clock pulses CH was started in the first reference period P1 (YES in step ST37), the control unit 12 causes the enable signal generating unit 14 to output the enable signal EN, and causes the high-speed clock generating unit 11B to start generating high-speed clock pulses CH at the measurement start time t4, which is the start of the fourth reference period P4, which serves as a preparation period to enable the generation of high-speed clock pulses at a stable cycle in the second reference period P2 (step ST38).
When time t5 is reached, which is two reference periods after measurement start time t4, the control unit 212 determines that the fourth reference period P4 has ended, and causes the high-speed clock generating unit 11B to end the generation of the high-speed clock pulse CH.

After performing the process of step ST38, the control unit 212 judges whether or not a time equivalent to four reference periods has elapsed since the generation of the high-speed clock pulse CH was started at t4 (step ST39). In this process, the control unit 212 judges whether or not the time t6 has been reached at which a time equivalent to a half period Td of the drive pulse has elapsed since the generation of the high-speed clock pulse CH was started, which is the time when the generation of the high-speed clock pulse CH is started in the second reference period P2.
In the process of step ST39, if a time period equivalent to four reference cycles has not elapsed since the generation of the high-speed clock pulse CH started at t4 (NO in step ST39), the control section 212 waits for the subsequent process.

In the processing of step ST39, if a time equivalent to four reference periods has elapsed since the generation of the high-speed clock pulse CH was started at t4 (YES in step ST39), the high-speed clock generating unit 11B is made to start generating the high-speed clock pulse CH to obtain the second reference pulse number (step ST41).

When time t7 is reached, which is two reference cycles after time t6, the control unit 212 causes the high-speed clock generating unit 11B to end the generation of the high-speed clock pulses CH, and stores the count number of the high-speed clock pulses CH in the second reference period P2 from time t6 until two reference cycles, i.e., twice the reference period Ts, has elapsed as the second reference pulse number in the memory unit 16 (step ST42). In this process, the control unit 212 stores the second reference pulse number, which is the number of pulses of the high-speed clock pulses CH generated in the time length of two reference cycles, in the memory unit 16 as the reference pulse number when the time length of the excess period is close to the time length of two reference cycles.

After performing the process of step ST42, the control section 212 determines whether or not a first stop pulse Pstop has been input (step ST9).
In the process of step ST9, if the stop pulse Pstop is not input (NO in step ST9), the control section 212 determines that the target period Tm has not yet ended, and waits for the subsequent processes.

In the process of step ST9, if the first stop pulse Pstop is input (YES in step ST9), the control unit 212 determines that the target period Tm for which the time length is to be calculated has ended, and causes the high-speed clock generating unit 11B to start generating high-speed clock pulses CH at the measurement end time t8, which is the time when the stop pulse Pstop was input (step ST44). In this process, the control unit 12 causes the high-speed clock generating unit 11B to start generating high-speed clock pulses CH in the overage period ΔT from the measurement end time t8 to the overage time t9 that is synchronized with the reference period Ts after the measurement end time t8, in order to generate high-speed clock pulses CH with a stable period during the additional measurement period ΔT1 for calculating the number of pulses of the low-speed clock pulses CL generated during the overage period ΔT.

After performing the process of step ST44, the control unit 212 judges whether or not a second stop pulse Pstop has been input (step ST46). In this process, the control unit 212 judges whether or not it has reached time t10 at which the additional measurement period ΔT1 starts, which is the time when four reference periods have elapsed since the generation of the high-speed clock pulse CH started at the measurement end time t8.
In the process of step ST46, if the second stop pulse Pstop is not input (NO in step ST46), the control section 212 waits for the subsequent processes.

In the process of step ST46, when the first stop pulse Pstop is input (YES in step ST46), the control unit 212 determines that the additional measurement period ΔT1 has started, and causes the high-speed clock generating unit 11B to start generating high-speed clock pulses CH at the measurement end time t10, which is the time when the stop pulse Pstop is input (step ST47). In this process, the control unit 12 causes the high-speed clock generating unit 11B to start generating high-speed clock pulses CH in the additional measurement period ΔT1 for calculating the number of pulses of the low-speed clock pulses CL generated in the overage period ΔT.
After starting the generation of the high-speed clock pulse CH in the additional measurement period ΔT1, when the time for one reference period has elapsed and the time t11 is reached at which the high-speed clock pulse CH is first synchronized with the reference period Ts, the control unit 212 causes the high-speed clock generating unit 11 to end the generation of the high-speed clock pulse CH. In other words, when the time equal to the excess period ΔT has elapsed since starting the generation of the high-speed clock pulse CH in the additional measurement period ΔT1, the control unit 212 causes the high-speed clock generating unit 11 to end the generation of the high-speed clock pulse CH.

After processing step ST47, the control unit 212 causes the reference selection unit 15 to determine whether the length of the excess period ΔT from the measurement end time t8 to the excess time t9 is close to the length of the first reference period P1, i.e., the length of one reference cycle (step ST12).
In the processing of step ST12, if the length of the excess period ΔT is close to the length of the first reference period P1 (YES in step ST12), the control unit 12 causes the reference selection unit 15 to select the first reference pulse number as the reference pulse number from the first reference pulse number, the second reference pulse number, and the third reference pulse number (step ST13).

In the process of step ST12, if the length of the excess period ΔT is not close to the length of the first reference period P1 (NO in step ST12), the control unit 212 causes the reference selection unit 15 to select the second reference pulse number as the reference pulse number from the first reference pulse number and the second reference pulse number (step ST51). In this process, the control unit 12 causes the reference selection unit 15 to select the second reference pulse number as the reference pulse number based on the fact that the length of the excess period ΔT is close to the length of the second reference period P2.

After performing the processing of step ST13 or step ST51, the control unit 212 causes the time calculation unit 17 to calculate the number of pulses of the low-speed clock pulses CL generated in the excess period ΔT based on the reference pulse number, the time length of the period during which the reference pulse number was counted, and the count number of the high-speed clock pulses CH in the additional measurement period ΔT1 (step ST52).

For example, the control unit 212 causes the time calculation unit 17 to calculate the number of pulses of the low-speed clock pulses CL generated in the overage period ΔT by dividing the count number of the high-speed clock pulses CH in the additional measurement period ΔT1 by the first reference pulse number. In this process, the control unit 12 causes the time calculation unit 17 to calculate the number of pulses of the low-speed clock pulses CL generated in the overage period ΔT by dividing the count number of the high-speed clock pulses CH in the additional measurement period ΔT1, which is a period of the same time length as the overage period ΔT, by the first reference pulse number.
When the second reference pulse number is selected as the reference pulse number, for example, the control unit 212 causes the time calculation unit 17 to calculate the number of pulses of low-speed clock pulses CL generated in the overage period ΔT by dividing the count number of high-speed clock pulses CH in the additional measurement period ΔT1 by the second reference pulse number and dividing the obtained value by 2. In this process, the control unit 212 causes the time calculation unit 17 to calculate the number of pulses of low-speed clock pulses CL generated in the overage period ΔT by dividing the value obtained by dividing the count number of high-speed clock pulses CH in the additional measurement period ΔT1, which is a period of the same time length as the overage period ΔT, by the second reference pulse number, based on the fact that the time length of the period during which the reference pulse number is counted is two reference cycles.
After performing the process of step ST52, the control unit 212 causes the time calculation unit 17 to calculate the time length of the target period Tm based on the number of pulses of the low-speed clock pulses CL generated in the overage period ΔT, the number of pulses of the low-speed clock pulses CL generated in the measurement period T, and the reference period Ts (step ST53).

The high-speed clock pulses CH generated in the first reference period P1, the second reference period P2, and the additional measurement period ΔT1 have a more stable period than the high-speed clock pulses CH generated in the immediately preceding periods, the third reference period P3, the fourth reference period P4, and the overage period ΔT. Therefore, the time measurement device 200 according to the second embodiment can calculate the number of pulses of the low-speed clock pulses CL generated in the overage period ΔT based on the count number of the high-speed clock pulses CH in a state in which the period is more stable than the reference pulse number and the count number of the high-speed clock pulses CH in the overage period ΔT generated in the first embodiment, thereby improving the measurement accuracy of the time length of the target period Tm.

In the second embodiment, the control unit 212 is configured to cause the reference selection unit 15 to select either the first reference pulse number or the second reference pulse number as the reference pulse number regardless of the length of the overrun period ΔT, but is not limited to this. The control unit may be configured to cause the reference selection unit to select either the first reference pulse number or the second reference pulse number as the reference pulse number depending on the length of the overrun period ΔT. For example, as in the first embodiment, the control unit may be configured to cause the reference selection unit to select either the first reference pulse number or the second reference pulse number as the reference pulse number when the length of the overrun period ΔT is within a predetermined range.

Next, a third embodiment of the present invention will be described in detail with reference to the drawings.
Embodiment 3.
Fig. 10 is a timing chart showing a case where the length of the overrun period ΔT is close to one reference period when the time measurement device according to the third embodiment measures time. Fig. 11 is a timing chart showing a case where the length of the overrun period ΔT is close to two reference periods when the time measurement device according to the third embodiment measures time.
The third embodiment is different from the second embodiment in the procedure for measuring the reference pulse number and the procedure for calculating the number of pulses of low-speed clock pulses CL generated in the overrun period ΔT. However, other configurations and other processes are the same, and the same reference symbols are used for the contents similar to those of the first embodiment, and the description thereof will be omitted.

The control unit 312 of the time measurement device 300 according to the third embodiment calculates the average value of the count number of the high-speed clock pulse CH generated in a plurality of periods having the same time length as the overage period ΔT after the measurement end time t8, and calculates the pulse number of the low-speed clock pulse CL in the overage period ΔT based on the average value, the reference pulse number, and the reference period Ts. This improves the accuracy of the count number of the high-speed clock pulse CH generated in the overage period ΔT compared to the case of calculating the pulse number of the low-speed clock pulse CL generated in the overage period ΔT based on the count number of the high-speed clock pulse CH in one overage period ΔT or one additional measurement period ΔT1, the reference pulse number, and the reference period Ts as in the first and second embodiments, thereby improving the measurement accuracy of the time length of the target period Tm.

In any of the above-described embodiments, various calculation procedures can be considered for calculating the target period Tm, and the above-described calculation procedures include mathematically equivalent procedures. For example, in the above-described embodiments, the time measurement device 100 calculates the length of the target period Tm by multiplying the value obtained by subtracting the number of pulses of the low-speed clock pulse CL generated in the overage period ΔT from the number of pulses of the low-speed clock pulse CL generated in the measurement period T by the reference period Ts, but the length of the target period Tm may be calculated by subtracting the length of the overage period ΔT obtained by multiplying the number of pulses of the low-speed clock pulse CL generated in the overage period ΔT by the reference period Ts from the length of the measurement period T obtained by multiplying the number of pulses of the low-speed clock pulse CL generated in the measurement period T by the reference period Ts.

11A Low-speed clock generating unit 11B High-speed clock generating unit 13A Low-speed clock counter 13B High-speed clock counter 15 Reference selecting unit 17 Time calculating unit 100, 200, 300 Time measuring device P1 First reference period P2 Second reference period P3 Third reference period P4 Fourth reference period t0 Measurement start time point (first time point)
t4 Second time point t8 Measurement end time point Ts Reference period Tm Target period ΔT Excess period ΔT1 Additional measurement period

Claims (7)

A time measurement device that measures a time length of a target period from a measurement start point to a measurement end point,
a low-speed clock generating unit that generates a low-speed clock pulse at a reference period;
a high-speed clock generating unit that generates a high-speed clock pulse having a shorter period than the low-speed clock pulse during a first reference period from a first point in time until a first multiple of the reference period has elapsed, a second reference period from a second point in time until a second multiple of the reference period, the second multiple being different from the first multiple, and an overrun period from the measurement end point to an overrun point after the measurement end point that is synchronized with the reference period;
a low-speed clock counter that counts the number of low-speed clock pulses generated by the low-speed clock generating unit during a period from the measurement start time to the exceeding time;
a high-speed clock counter that counts the number of high-speed clock pulses generated by the high-speed clock generating unit during a period having the same time length as the first reference period, the second reference period, and the overtime period;
a reference selection unit that acquires a first reference pulse number, which is the number of pulses of a high-speed clock pulse counted in the first reference period, and a second reference pulse number, which is the number of pulses of a high-speed clock pulse counted in the second reference period, and selects one of the first reference pulse number and the second reference pulse number as a reference pulse number according to a time length of the excess period;
and a time calculation unit that calculates the length of the target period based on the reference pulse number, the length of the period during which the reference pulse number is counted, the length of the reference period, the count number of the low-speed clock counter, and the count number of the high-speed clock counter during a period of the same length as the overrun period. 2. The time measurement device according to claim 1, wherein the reference selection section selects, as the reference pulse number, one of the first reference period and the second reference period, the one whose time length is closer to the overtime period. 3. The time measurement device according to claim 1, wherein the time calculation unit calculates the number of excess pulses of low-speed clock pulses that can be generated by the low-speed clock generating unit during the overrun period based on the reference pulse number, the time length of the period during which the reference pulse number was counted, the time length of the reference period, and the count number of the high-speed clock counter during a period of the same time length as the overrun period, and calculates the time length of the target period based on the number of excess pulses, the time length of the reference period, and the count number of the low-speed clock counter. 4. The time measurement device according to claim 1, wherein the high-speed clock generating unit generates a high-speed clock pulse in the first reference period starting from the first time point within the target period and in the second reference period starting from the second time point within the target period. an input unit for receiving a first signal indicating a measurement start point and a second signal including a signal indicating a measurement end point and repeated multiple times in an input period;
the high-speed clock generating unit generates the high-speed clock pulse during an additional measurement period from a point when the input period has elapsed since the measurement end point until a point when a time length equal to the excess period has elapsed;
the high-speed clock counter counts the number of high-speed clock pulses generated by the high-speed clock generating unit during the additional measurement period;
The time measurement device according to any one of claims 1 to 4, characterized in that the time calculation unit calculates the length of the target period based on the reference pulse number, the length of the period during which the reference pulse number was counted, the count number of the high-speed clock counter during the excess period, the length of the reference period, and the count number of the low-speed clock counter. the high-speed clock generating unit generates the high-speed clock during a third reference period from a time point that is the input cycle before the first time point until a time period that is the same as the first reference period has elapsed, and during a fourth reference period from a time point that is the input cycle before the second time point until a time period that is the same as the second reference period has elapsed.
6. The time measurement device according to claim 5. A time measurement method for measuring a time length of a target period from a measurement start point to a measurement end point, comprising:
A low-speed clock generating unit generates a low-speed clock pulse at a reference period;
a high-speed clock generating unit generating a high-speed clock pulse having a shorter period than the low-speed clock pulse in a first reference period from a first point in time until a first multiple of the reference period has elapsed, a second reference period from a second point in time until a second multiple of the reference period has elapsed, the second multiple being different from the first multiple, and an overrun period from the measurement end point in time to an overrun point in time that is synchronized with the reference period after the measurement end point;
a step of counting the number of low-speed clock pulses generated by the low-speed clock generating unit during a period from the measurement start time to the exceeding time by a low-speed clock counter;
A high-speed clock counter counts the number of high-speed clock pulses generated by the high-speed clock generating unit during a period having the same time length as the first reference period, the second reference period, and the excess period;
a reference selection unit acquiring a first reference pulse number, which is the number of pulses of a high-speed clock pulse counted in the first reference period, and a second reference pulse number, which is the number of pulses of a high-speed clock pulse counted in the second reference period, and selecting one of the first reference pulse number and the second reference pulse number as a reference pulse number according to a time length of the excess period;
a step of a time calculation unit calculating the time length of the target period based on the reference pulse number, the time length of the period during which the reference pulse number was counted, the time length of the reference period, the count number of the low-speed clock counter, and the count number of the high-speed clock counter during a period of the same time length as the overrun period.

Images