JP6102785B2 - Physical quantity sensor - Google Patents

Description

  The present invention relates to a physical quantity sensor that transmits transmission data corresponding to a sensor waveform indicating a temporal change of a physical quantity to a transmission destination device.

  2. Description of the Related Art Conventionally, there is a data communication system that includes a physical quantity sensor that functions as a slave and a transmission destination device that functions as a master, and the physical quantity sensor transmits transmission data corresponding to a sensor waveform indicating a temporal change in physical quantity to the transmission destination device. It is provided. For example, in a data communication system of DSI (Distributed Systems Interface) 3 or PSI (Peripheral Sensor Interface) 5, the cycle (communication cycle) at which the physical quantity sensor transmits transmission data depends on the communication protocol specification. On the other hand, the period (sampling period) at which the physical quantity sensor acquires digital data depends on circuit factors such as sensor elements and AD converters. For these reasons, the communication period and the sampling period are determined independently of each other. Therefore, for example, it is difficult to set the communication cycle to an integer multiple of the sampling cycle, and it is difficult to make the communication cycle and the sampling cycle follow.

  If the sampling period and the communication period do not follow in this way, the time difference from the timing for acquiring the digital data to the timing for transmitting the transmission data will vary. As a result, transmission data that cannot accurately reproduce the sensor waveform (raw waveform) is transmitted, and there is a problem that erroneous determination occurs in the transmission destination device. To deal with such a problem, for example, Patent Document 1 discloses a method of transmitting data including sampling period information before transmitting transmission data in a physical quantity sensor.

Japanese Patent No. 4880273

  However, in the above-described data communication system such as DSI3 or PSI5, not only the communication cycle but also the data format depends on the communication protocol specification. For this reason, it is difficult to increase the amount of data transmitted by the physical quantity sensor, and it is difficult to transmit data including information on the sampling period.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a transmission that can accurately reproduce a sensor waveform indicating a temporal change in a physical quantity without increasing the amount of data to be transmitted to a transmission destination device. An object of the present invention is to provide a physical quantity sensor that can transmit data to a transmission destination device and can prevent an erroneous determination in the transmission destination device.

  According to the first aspect of the present invention, the sensor element outputs a sensor waveform indicating a change in physical quantity with time. The digital data output means holds and outputs digital data corresponding to the sensor waveform. The oscillation means outputs an internal clock. The timing control means outputs data acquisition timing and data transmission timing. The estimated data acquisition means acquires estimated data corresponding to the data acquisition timing based on a plurality of digital data continuously output from the digital data output means. The transmission means transmits the estimated data to the transmission destination apparatus as transmission data according to the data transmission timing.

  Here, the timing control means controls the data acquisition timing and the data transmission timing output based on the internal clock so that the period from the data acquisition timing output to the data transmission timing output is constant. Thereby, the data acquisition timing for acquiring estimated data from the sensor waveform and the data transmission timing for transmitting the estimated data as transmission data can be tracked, and the time difference from the data acquisition timing to the data transmission timing is made constant. be able to. That is, for example, even when the external reference clock is not received from the transmission destination device but the transmission data transmission cycle (transmission cycle) is defined by the specification of the transmission destination device, the cycle (sampling cycle) follows the transmission cycle. Data corresponding to the sensor waveform can be acquired and transmitted. As a result, it is possible to transmit transmission data that can accurately reproduce a sensor waveform indicating a change in physical quantity over time to a transmission destination apparatus, and prevent an erroneous determination from occurring in the transmission destination apparatus. At this time, the amount of data to be transmitted to the transmission destination device is not increased.

  According to the second aspect of the present invention, the sensor element outputs a sensor waveform indicating a change in physical quantity with time. The digital data output means holds and outputs digital data corresponding to the sensor waveform. The receiving unit receives an external reference clock from the transmission destination device. The oscillation means outputs an internal clock. The timing control means outputs data acquisition timing and data transmission timing. The estimated data acquisition means acquires estimated data corresponding to the data acquisition timing based on a plurality of digital data continuously output from the digital data output means. The transmission means transmits the estimated data to the transmission destination apparatus as transmission data according to the data transmission timing.

  Here, the timing control means controls the output of the data acquisition timing and the data transmission timing based on the external reference clock and the internal clock so that the period from the output of the data acquisition timing to the output of the data transmission timing is constant. I made it. Thus, in this case as well, the data acquisition timing for acquiring the estimated data from the sensor waveform and the data transmission timing for transmitting the estimated data as transmission data can be tracked, and the time difference from the data acquisition timing to the data transmission timing Can be made constant. That is, for example, even when a cycle (transmission cycle) for transmitting transmission data is defined by an external reference clock received from the transmission destination device, data corresponding to the sensor waveform is acquired at a cycle (sampling cycle) following the transmission cycle. Can be acquired and sent. As a result, it is possible to transmit transmission data that can accurately reproduce a sensor waveform indicating a change in physical quantity over time to a transmission destination apparatus, and prevent an erroneous determination from occurring in the transmission destination apparatus. Also at this time, the amount of data to be transmitted to the transmission destination device is not increased.

Functional block diagram showing a first embodiment of the present invention Diagram showing the relationship between data acquisition timing and data transmission timing Time chart (part 1) Diagram showing interpolated values Functional block diagram showing a second embodiment of the present invention Time chart (part 2) Diagram showing extrapolated values Functional block diagram showing a third embodiment of the present invention Time chart (part 3) Time chart (part 4) Functional block diagram showing a fourth embodiment of the present invention Functional block diagram showing a fifth embodiment of the present invention Functional block diagram showing a sixth embodiment of the present invention Functional block diagram showing a seventh embodiment of the present invention Diagram showing the relationship between the ideal number of clocks and the actual number of clocks Time chart (part 5) Functional block diagram showing an eighth embodiment of the present invention

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, a physical quantity sensor 1 includes a sensor element 2, a CR oscillation circuit 3 (oscillation means), an AD converter 4, a digital filter 5 (digital data output means), and a timing control circuit 6 (timing control). Means), an interpolation calculation circuit 7 (estimated data acquisition means, interpolation calculation means), and a transmission circuit 8 (transmission means). The physical quantity sensor 1 is connected to a host 9 (transmission destination apparatus) via a data communication line (data transmission path). The physical quantity sensor 1 functions as a slave, and the host 9 functions as a master.

  The sensor element 2 detects a physical quantity (sensor value) that acts on the detection target, and outputs a sensor waveform (analog signal) indicating a change over time of the detected physical quantity to the AD converter 4. For example, if the physical quantity sensor 1 is an acceleration sensor mounted on an automobile, the sensor element 2 outputs a sensor waveform indicating a change over time in acceleration acting on the automobile to the AD converter 4. The CR oscillation circuit 3 generates an internal clock from an oscillation signal having a predetermined oscillation frequency, and outputs the generated internal clock to the AD converter 4, the digital filter 5, the timing control circuit 6, the interpolation calculation circuit 7, and the transmission circuit 8. To do. The frequency of the internal clock output from the CR oscillation circuit 3 to the AD converter 4, the digital filter 5, the timing control circuit 6, the interpolation calculation circuit 7, and the transmission circuit 8 may be the same or different.

  The AD converter 4 operates using the internal clock input from the CR oscillation circuit 3 as an operation clock. When the sensor waveform is input from the sensor element 2, the input sensor waveform is voltage-amplified. Then, the AD converter 4 converts the sensor waveform after voltage amplification from an analog signal to a digital signal to generate digital data, and outputs the generated digital data to the digital filter 5.

  The digital filter 5 is, for example, an IIR (Infinite Impulse Response) filter. The digital filter 5 operates using the internal clock input from the CR oscillation circuit 3 as an operation clock. When digital data is input from the AD converter 4, the digital filter 5 performs a filtering process on the input digital data and performs the filtering process. The digital data is output to the interpolation calculation circuit 7. The digital filter 5 can hold at least the latest data (the latest data) subjected to the filtering process and the previous data (the previous data).

  The timing control circuit 6 operates using the internal clock input from the CR oscillation circuit 3 as an operation clock, and outputs the data acquisition timing to the interpolation calculation circuit 7 by measuring (counting) the number of clocks of the internal clock. The data transmission timing is output to the transmission circuit 8. More specifically, when the timing control circuit 6 starts measuring the number of clocks of the internal clock, the timing control circuit 6 outputs the data transmission timing when the number of clocks reaches a preset first set value, Resume counting. The timing control circuit 6 outputs the data transmission timing to the transmission circuit 8 at a constant cycle (a constant number of clocks) by repeating measurement of the number of clocks. Further, when the timing control circuit 6 starts measuring the number of clocks of the internal clock, the timing control circuit 6 outputs a data acquisition timing when the number of clocks reaches a second set value smaller than the first set value.

  That is, as shown in FIG. 2, the timing control circuit 6 sets the data acquisition timing at a time before a certain period (a certain number of clocks) before the time (t2, t4, t6) at which the data transmission timing is output to the transmission circuit 8. It outputs to the interpolation calculation circuit 7 (t1, t3, t5). In this way, the timing control circuit 6 makes the period (t1 to t2, t3 to t4, t5 to t6) from the output of the data acquisition timing to the output of the data transmission timing constant.

The interpolation calculation circuit 7 operates using the internal clock input from the CR oscillation circuit 3 as an operation clock. When the latest data and the previous data are input from the digital filter 5, the interpolation calculation circuit 7 receives the data acquisition timing input from the timing control circuit 6. An estimated value of the corresponding estimated data is calculated by interpolation (estimated and acquired). That is, as shown in FIGS. 3 and 4, the interpolation calculation circuit 7 obtains data from the time when the digital filter 5 outputs the digital data as “T” and starts the cycle (when the counter is reset). Assuming that the period until the timing is input is “ΔT”, the data value of the latest data at the time of inputting the data acquisition timing is “X _N ”, and the data value of the previous data is “X _N-1 ”, Based on the digital data of the next cycle when the data acquisition timing is input, the estimated value is calculated by the following calculation formula.
Estimated value = X _N + {ΔT × (X _{N + 1} −X _N ) / T}

  Then, the interpolation calculation circuit 7 outputs estimated data indicating the estimated value calculated in this way to the transmission circuit 8. The interpolation calculation circuit 7 may be provided as a dedicated circuit, or may be provided as software by a CPU (Central Processing Unit). The transmission circuit 8 operates using the internal clock input from the CR oscillation circuit 3 as an operation clock. When the estimation data is input from the interpolation calculation circuit 7, the input estimation data is input to the data transmission timing input from the timing control circuit 6. To transmit as transmission data.

  When the host 9 receives the transmission data transmitted from the physical quantity sensor 1 through the data communication line in this way, the temporal change of the physical quantity detected by the sensor element 2 is performed by signal-processing the temporal change of the transmission data. Determine. The host 9 is, for example, an electronic control unit (ECU: Electronic Control Unit) mounted on an automobile. If the physical quantity sensor 1 is an acceleration sensor, the host 9 receives transmission data transmitted from the acceleration sensor via a data communication line. Then, an event such as a vehicle collision is determined by performing signal processing on the temporal change of the transmission data.

  As described above, according to the first embodiment, in the physical quantity sensor 1, the period from the output of the data acquisition timing to the output of the data transmission timing is made constant based on the internal clock. Then, in the physical quantity sensor 1, the estimated value is calculated using the latest data and the previous data output from the digital filter 5 according to the output of the data acquisition timing. Thereby, the data acquisition timing which acquires estimated data from a sensor waveform, and the data transmission timing which transmits the estimated data as transmission data can be made to follow. As a result, it is possible to transmit transmission data that can accurately reproduce a sensor waveform indicating a change in physical quantity over time to the host 9, thereby preventing an erroneous determination in the host 9. At this time, the amount of data transmitted from the physical quantity sensor 1 to the host 9 is not increased. In addition, when the estimated value is calculated using the interpolated value, the estimated value is calculated using data located before and after the sensor waveform, so the upper and lower limits indicated by the data located before and after the estimated value are calculated. An estimate can be calculated within the range.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. In addition, description is abbreviate | omitted about the same part as above-mentioned 1st Embodiment, and a different part is demonstrated. In the first embodiment, the estimated value of the estimated data is calculated using an interpolated value. In the second embodiment, the estimated value of the estimated data is calculated using an extrapolated value.

The physical quantity sensor 11 has an extrapolation calculation circuit 12 (estimated data acquisition means, extrapolation calculation means) instead of the interpolation calculation circuit 7 described in the first embodiment. The extrapolation calculation circuit 12 operates using the internal clock input from the CR oscillation circuit 3 as an operation clock. When the latest data and the previous data are input from the digital filter 5, the extrapolation calculation circuit 12 receives the data acquisition timing input from the timing control circuit 6. The estimated value of the corresponding estimated data is calculated by extrapolation (estimated and acquired). That is, as shown in FIGS. 6 and 7, the extrapolation calculation circuit 12 calculates an estimated value by the following calculation formula based on the digital data of the cycle at the time when the data acquisition timing is input.
Estimated value = X _N + {ΔT × (X _N −X _N−1 ) / T}

  Then, the extrapolation calculation circuit 12 outputs estimated data indicating the estimated value calculated in this way to the transmission circuit 8. Note that the extrapolation calculation circuit 12 may also be provided as a dedicated circuit, or may be provided as software by the CPU. The transmission circuit 8 operates using the internal clock input from the CR oscillation circuit 3 as an operation clock. When the estimation data is input from the extrapolation calculation circuit 12, the input estimation data is input to the data transmission timing input from the timing control circuit 6. To transmit as transmission data.

  As described above, according to the second embodiment, the same operational effects as those of the first embodiment can be obtained. That is, the data acquisition timing for acquiring the estimated data from the sensor waveform and the data transmission timing for transmitting the estimated data as transmission data can be made to follow. As a result, it is possible to transmit transmission data that can accurately reproduce a sensor waveform indicating a change in physical quantity over time to the host 9, thereby preventing an erroneous determination in the host 9. Further, when the estimated value is calculated by extrapolation value, the estimated value is calculated using already determined data on the sensor waveform, so that the estimated value can be calculated reliably.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIGS. In addition, description is abbreviate | omitted about the same part as above-mentioned 1st Embodiment, and a different part is demonstrated. The first embodiment is configured to control the output of the data acquisition timing and the data transmission timing based on the internal clock output from the CR oscillation circuit 3, but the third embodiment is an external reference received from the host 25. In this configuration, output of data acquisition timing and data transmission timing is controlled based on a clock.

  The physical quantity sensor 21 includes a receiving circuit 22 (receiving means) in addition to the configuration described in the first embodiment, and a timing control circuit 23 (timing control) instead of the timing control circuit 6 described in the first embodiment. And a CR oscillation circuit 24 (oscillation means) instead of the CR oscillation circuit 3. The physical quantity sensor 21 is connected to the host 25 (transmission destination device) via a data communication line and a clock communication line (clock transmission path). In this case, the data communication line and the clock communication line may be shared like DSI3 or PSI5.

  The host 25 includes, for example, a crystal resonator or a ceramic resonator, generates an external reference clock from an oscillation signal having a predetermined oscillation frequency oscillated by the crystal resonator or the ceramic resonator, and performs clock communication with the generated external reference clock. It transmits to the physical quantity sensor 21 via a line. The external reference clock has a characteristic of higher frequency accuracy (smaller jitter) than the internal clock.

  When receiving the external reference clock transmitted from the host 25 via the clock communication line, the receiving circuit 22 outputs the external reference clock to the timing control circuit 23. The timing control circuit 23 outputs the data acquisition timing to the interpolation calculation circuit 7 by transmitting the data transmission timing by measuring the number of clocks of the internal clock from the rising edge of the external reference clock input from the reception circuit 22 as a base point. Output to the circuit 8. More specifically, after detecting the rising edge of the external reference clock, the timing control circuit 23 outputs the data transmission timing when the number of internal clocks reaches a preset first setting value. The timing control circuit 23 repeats the measurement of the number of clocks to output the data transmission timing to the transmission circuit 8 at a constant period (a constant number of clocks). In addition, when the timing control circuit 23 starts measuring the number of clocks of the internal clock, the timing control circuit 23 outputs a data acquisition timing when the number of clocks reaches a second set value smaller than the first set value.

  That is, as shown in FIG. 9, if the second set value is “0”, the timing control circuit 23 outputs the data acquisition timing to the interpolation calculation circuit 7 when the external reference clock is input (t11). , T13, t15), the data transmission timing is output to the transmission circuit 8 at a time after a certain period (a certain number of clocks, the first certain period) from that time (t12, t14, t16). In this way, the timing control circuit 23 makes the period (t11 to t12, t13 to t14, t15 to t16) from the output of the data acquisition timing to the output of the data transmission timing constant.

  In addition, as shown in FIG. 10, the timing control circuit 23, if the second set value is not “0”, has a fixed period (a fixed number of clocks, from the time (t21, t24, t27) when the external reference clock is input. The data acquisition timing is output to the interpolation calculation circuit 7 at a time after the second fixed period) (t22, t25, t28). Further, the timing control circuit 23 outputs the data transmission timing to the transmission circuit 8 at a time after a certain period (a certain number of clocks, a third certain period longer than the second certain period) from the time when the external reference clock is input. (T23, t26, t29). In this way, the timing control circuit 23 makes the period (t22 to t23, t25 to t26, t28 to t29) from the output of the data acquisition timing to the output of the data transmission timing constant.

  As described above, according to the third embodiment, in the physical quantity sensor 21, the period from the output of the data acquisition timing to the output of the data transmission timing is made constant based on the external reference clock and the internal clock. . Then, in the physical quantity sensor 21, an estimated value is calculated using the latest data and the previous data output from the digital filter 5 according to the output of the data acquisition timing. Thereby, similarly to 1st Embodiment, the data acquisition timing which acquires estimated data from a sensor waveform, and the data transmission timing which transmits the estimated data as transmission data can be tracked. As a result, transmission data capable of accurately reproducing the sensor waveform indicating the change in physical quantity with time can be transmitted to the host 25, and an erroneous determination in the host 25 can be prevented. At this time, the amount of data transmitted from the physical quantity sensor 21 to the host 25 is not increased. Further, by shortening the time difference between the data acquisition timing and the data transmission timing, it is possible to transmit (newer) transmission data that more accurately reflects the sensor waveform.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to FIG. The change part from 3rd Embodiment in 4th Embodiment is the same as the change part from 1st Embodiment in 2nd Embodiment. That is, the fourth embodiment is configured to calculate an estimated value of estimated data by extrapolation values. The physical quantity sensor 31 includes an extrapolation calculation circuit 12 instead of the interpolation calculation circuit 7 described in the first embodiment. Also in the fourth embodiment, the same operational effects as in the third embodiment can be obtained.

(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described with reference to FIG. In addition, description is abbreviate | omitted about the same part as above-mentioned 3rd Embodiment, and a different part is demonstrated. In the fifth embodiment, the internal clock output from the CR oscillation circuit 24 is corrected (adjusted) according to the external reference clock.

  The physical quantity sensor 41 includes a clock correction circuit 42 (clock correction means) in addition to the configuration described in the third embodiment. When receiving the external reference clock transmitted from the host 25 via the clock communication line, the receiving circuit 22 adds the external reference clock to the timing control circuit 23 and also outputs it to the clock correction circuit 42. The CR oscillation circuit 24 outputs the internal clock to the clock correction circuit 42 in addition to the AD converter 4, the digital filter 5, the interpolation calculation circuit 7, the transmission circuit 8 and the timing control circuit 23. When the internal clock is input from the CR oscillation circuit 24 and the external reference clock is input from the reception circuit 22, the clock correction circuit 42 measures the number of internal clocks between the external reference clocks. When the clock correction circuit 42 determines that the number of internal clocks between the external reference clocks is equal to or greater than the first threshold value, the clock correction circuit 42 outputs a correction command for instructing a decrease in the oscillation frequency to the CR oscillation circuit 24. When the CR oscillation circuit 24 receives a correction command for instructing a decrease in the oscillation frequency from the clock correction circuit 42, the CR oscillation circuit 24 decreases the oscillation frequency at that time. On the other hand, when the clock correction circuit 42 determines that the number of internal clocks between the external reference clocks is equal to or smaller than the second threshold value, the clock correction circuit 42 outputs a correction command for instructing an increase in the oscillation frequency to the CR oscillation circuit 24. When the CR oscillation circuit 24 receives a correction command for instructing an increase in the oscillation frequency from the clock correction circuit 42, the CR oscillation circuit 24 increases the oscillation frequency at that time.

  As described above, according to the fifth embodiment, as in the third embodiment, data acquisition timing for acquiring estimated data from a sensor waveform, and data transmission timing for transmitting the estimated data as transmission data, Can be made to follow. As a result, transmission data capable of accurately reproducing the sensor waveform indicating the change in physical quantity with time can be transmitted to the host 25, and an erroneous determination in the host 25 can be prevented. Further, by having a clock correction circuit 42 that corrects the oscillation frequency of the CR oscillation circuit 24 based on the external reference clock, the corrected internal clock corrected based on the external reference clock is converted into the AD converter 4, the digital filter 5, and the internal filter. The data can be output to the insertion calculation circuit 7, the transmission circuit 8, the timing control circuit 23, and the like.

(Sixth embodiment)
Next, a sixth embodiment of the present invention will be described with reference to FIG. The change part from 5th Embodiment in 6th Embodiment is the same as the change part from 1st Embodiment in 2nd Embodiment. That is, the sixth embodiment is configured to calculate the estimated value of the estimated data using the extrapolated value. The physical quantity sensor 51 includes an extrapolation calculation circuit 12 instead of the interpolation calculation circuit 7 described in the first embodiment. In the sixth embodiment, the same function and effect as in the fifth embodiment can be obtained.

(Seventh embodiment)
Next, a seventh embodiment of the present invention will be described with reference to FIGS. In addition, description is abbreviate | omitted about the same part as above-mentioned 3rd Embodiment, and a different part is demonstrated. In the seventh embodiment, an error of the internal clock output from the CR oscillation circuit 24 is calculated, and the output of the data acquisition timing is corrected (adjusted) based on the calculated error.

  The physical quantity sensor 61 includes a clock measurement circuit 62 (clock measurement means) in addition to the configuration described in the third embodiment. When receiving the external reference clock transmitted from the host 25 via the clock communication line, the receiving circuit 22 adds the external reference clock to the timing control circuit 23 and also outputs it to the clock measurement circuit 62. The CR oscillation circuit 24 outputs the internal clock to the clock measurement circuit 62 in addition to the AD converter 4, the digital filter 5, the interpolation calculation circuit 7, the transmission circuit 8 and the timing control circuit 23. When the internal clock is input from the CR oscillation circuit 24 and the external reference clock is input from the reception circuit 22, the clock measurement circuit 62 measures the number of internal clocks between the external reference clocks. Then, the clock correction circuit 42 outputs correction information indicating the number of internal clocks between the measured external reference clocks to the timing control circuit 23.

When the correction information is input from the clock measurement circuit 62, the timing control circuit 23 corrects the output of the data acquisition timing according to the correction information. That is, as shown in FIG. 15, the timing control circuit 23 sets the ideal internal clock number between external reference clocks to “N”, and the actual internal clock number between external reference clocks to “N ′”. Assuming that the ideal clock number from the reception of the external reference clock to the data acquisition timing is “n”, and the corrected clock number is “n ′”, the corrected clock number is calculated by the following formula.
n ′ = n × N ′ / N

  Then, as shown in FIG. 16, the timing control circuit 23 corrects the data acquisition timing according to the number of clocks after correction, so that the constant after correction from the time (t31, t34, t37) when the external reference clock is input. Data acquisition timing is output to the interpolation calculation circuit 7 at a time point after the period (a constant number of clocks, a fourth constant period) (t32, t35, t38). Furthermore, the timing control circuit 23 outputs the data transmission timing to the transmission circuit 8 at a time after a fixed period (a fixed number of clocks) from the time when the external reference clock is input (t33, t36, t39).

Note that the relationship shown in FIG. 15 may be applied when the interpolation calculation circuit 7 calculates the estimated value instead of the timing control circuit 23 correcting the data acquisition timing according to the corrected number of clocks. . In other words, the interpolation calculation circuit 7 calculates the difference between the corrected clock number and the ideal clock number by the following calculation formula.
Δn = n′−n = n (N ′ / N−1)
In this case, the interpolation calculation circuit 7 calculates the estimated value by the following calculation formula.
Estimated value = X _N + {(ΔT + Δn) × (X _{N + 1} −X _N ) / T}

  As described above, according to the seventh embodiment, as in the third embodiment, data acquisition timing for acquiring estimated data from a sensor waveform, and data transmission timing for transmitting the estimated data as transmission data, Can be made to follow. As a result, transmission data capable of accurately reproducing the sensor waveform indicating the change in physical quantity with time can be transmitted to the host 25, and an erroneous determination in the host 25 can be prevented. In addition, by including the clock measurement circuit 62 that measures the number of internal clocks between the external reference clocks, the output of the data acquisition timing can be controlled by reflecting the error of the internal clock output from the CR oscillation circuit 24. it can.

(Eighth embodiment)
Next, an eighth embodiment of the present invention will be described with reference to FIG. The changed portion from the seventh embodiment in the eighth embodiment is the same as the changed portion from the first embodiment in the second embodiment. That is, the eighth embodiment is configured to calculate the estimated value of the estimated data using the extrapolated value. The physical quantity sensor 71 includes an extrapolation calculation circuit 12 instead of the interpolation calculation circuit 7 described in the first embodiment. The extrapolation calculation circuit 12 may calculate the estimated value by the following calculation formula.
Estimated value = X _N + {(ΔT + Δn) × (X _N −X _N−1 ) / T}
In the eighth embodiment, the same function and effect as in the seventh embodiment can be obtained.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and can be modified or expanded as follows. A plurality of modified examples may be combined.
For example, the present invention may be applied to an acceleration sensor of a two-wheeled vehicle as an application other than that of an automobile. Further, the present invention is not limited to the acceleration sensor, and may be applied to various sensors such as a temperature sensor that detects temperature and a humidity sensor that detects humidity.
The configuration for calculating the estimated value (interpolated value and extrapolated value) using two points of digital data has been described. However, if the problem that the calculation formula becomes complicated is solved, three or more points of digital data are obtained. A configuration may be used in which the estimated value is calculated.

  In the drawings, 1, 11, 21, 31, 41, 51, 61, 71 are physical quantity sensors, 2 is a sensor element, 3, 24 is a CR oscillation circuit (oscillation means), 5 is a digital filter (digital data output means), 6, 23 are timing control circuits (timing control means), 7 is an interpolation calculation circuit (estimated data acquisition means, interpolation calculation means), 8 is a transmission circuit (transmission means), and 9 and 25 are hosts (destination devices). , 12 is an extrapolation calculation circuit (estimated data acquisition means, extrapolation calculation means), 22 is a reception circuit (reception means), 42 is a clock correction circuit (clock correction means), and 62 is a clock measurement circuit (clock measurement means). is there.

Claims (9)

A sensor element (2) for outputting a sensor waveform indicating a change in physical quantity with time;
Digital data output means (5) for holding and outputting digital data corresponding to the sensor waveform;
Oscillation means (3) for outputting an internal clock;
Timing control means (6) for outputting data acquisition timing and data transmission timing;
Estimated data acquisition means (7, 12) for acquiring estimated data corresponding to the data acquisition timing based on a plurality of digital data continuously output from the digital data output means;
Transmission means (8) for transmitting the estimated data acquired by the estimated data acquisition means as transmission data to the transmission destination device (9) according to the data transmission timing,
The timing control means controls the output of the data acquisition timing and the data transmission timing based on the internal clock so that a period from the output of the data acquisition timing to the output of the data transmission timing is constant. Physical quantity sensors (1, 11). A sensor element (2) for outputting a sensor waveform indicating a change in physical quantity with time;
Digital data output means (5) for holding and outputting digital data corresponding to the sensor waveform;
Receiving means (22) for receiving an external reference clock from the transmission destination device (25);
Oscillating means (24) for outputting an internal clock;
Timing control means (23) for outputting data acquisition timing and data transmission timing;
Estimated data acquisition means (7, 12) for acquiring estimated data corresponding to the data acquisition timing based on a plurality of digital data continuously output from the digital data output means;
Transmission means (8) for transmitting the estimated data acquired by the estimated data acquisition means as transmission data to the transmission destination device according to the data transmission timing,
The timing control means outputs the data acquisition timing and the data transmission timing based on the external reference clock and the internal clock so that a period from the output of the data acquisition timing to the output of the data transmission timing is constant. A physical quantity sensor (21, 31, 41, 51, 61, 71) characterized by controlling. The physical quantity sensor according to claim 2,
The timing control means outputs the data acquisition timing when the external reference clock is input from the receiving means, and outputs the data transmission timing after a lapse of a first fixed period from the time when the data acquisition timing is output. A physical quantity sensor (21, 31) characterized by: The physical quantity sensor according to claim 2,
The timing control means outputs the data acquisition timing after the elapse of a second fixed period from the time when the external reference clock is input from the reception means, and the time from the time when the external reference clock is input from the reception means. 2. The physical quantity sensor (21, 31) characterized in that the data transmission timing is output after a lapse of a third fixed period longer than a fixed period of 2. The physical quantity sensor according to claim 2,
A physical quantity sensor (41, 51) comprising clock correction means (42) for correcting the internal clock according to the external reference clock. The physical quantity sensor according to claim 2,
Clock measuring means (62) for measuring the number of internal clocks between external reference clocks according to the internal clock and the external reference clock;
The timing control means calculates an error of the internal clock based on the number of internal clocks between the external reference clocks, sets a period reflecting the calculated error as a fourth constant period, and receives the external clock from the reception means. The physical quantity sensor (61, 71), wherein the data acquisition timing is output after the fourth fixed period has elapsed from the time when the reference clock is input. The physical quantity sensor according to claim 2,
Clock measuring means (62) for measuring the number of internal clocks between external reference clocks according to the internal clock and the external reference clock;
The timing control means calculates an internal clock error based on the number of internal clocks between the external reference clocks,
The physical quantity sensor (61, 71) characterized in that the estimated data acquisition means acquires estimated data corresponding to the data acquisition timing by reflecting the error. In the physical quantity sensor according to any one of claims 1 to 7,
The estimated data acquisition means uses the plurality of digital data continuously output from the digital data output means in the next cycle after the data acquisition timing is input from the timing control means, thereby storing the estimated data. A physical quantity sensor (1, 21, 41, 61) characterized by having an interpolation calculation means (7) for calculating by an insertion value. In the physical quantity sensor according to any one of claims 1 to 7,
The estimated data acquisition means uses the plurality of digital data continuously output from the digital data output means at a period when the data acquisition timing is input from the timing control means, thereby extrapolating the estimated data. A physical quantity sensor (11, 31, 51, 71) characterized by having extrapolation calculation means (12) for calculating by

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