JP6475128B2 - Total value calculation circuit and moving average circuit including the same - Google Patents

Description

  The technology disclosed in this specification relates to a total value calculation circuit that calculates a total value for N times of a time-series digital signal. The technology disclosed in the present specification further relates to a moving average circuit including the total value calculation circuit.

  Non-Patent Document 1 discloses a moving average method for smoothing a time-series signal. In the moving average method, for example, when obtaining a moving average value for N times of a time series digital signal, a total value is calculated by adding all N time series digital signals, and the total value is divided by N. This is a method for obtaining a moving average value. In such a moving average method, when the data acquisition period is long, that is, when N is large, the calculation amount for calculating the total value of N times of the time series digital signal becomes enormous.

  In view of this, Non-Patent Document 1 discloses that the difference between the latest time-series digital signal and the N-time previous time-series digital signal is the previous one in order to simplify the calculation of the N-time total value of the time-series digital signal. A moving average method is proposed in which the total value of N times of the latest time series digital signal is calculated by adding to the total value of N times of the series digital signal. With this simplified moving average method, it is possible to greatly reduce the amount of calculation for calculating the total value of N times of the time series digital signal.

“Beginners Digital Filter” written by Shogo Nakamura, Tokyo Denki University Press

  A shift register that sequentially stores time series digital signals in order to obtain the latest time series digital signal and the Nth previous time series digital signal when the above-described simplified moving average method is realized by a moving average circuit. Can be considered. However, such a shift register has a problem that the circuit scale becomes large when the number of bits of the time-series digital signal is large. It is an object of the present specification to provide a technique for reducing the circuit scale of a total value calculation circuit that calculates a total value for N times of a time-series digital signal.

  One embodiment of the total value calculation circuit disclosed in the present specification is configured to calculate a total value for N times of a multi-bit time-series digital signal. The total value calculation circuit includes a shift register, a correction value adjustment circuit, a calculation circuit, and a total value register. The shift register is configured to sequentially store change components corresponding to changes in the time-series digital signal and to output the change component N times before. The correction value adjustment circuit adjusts a correction value corresponding to the difference between the latest time-series digital signal and the N-time previous time-series digital signal based on the latest change component of the time-series digital signal and the N-time previous change component. Is configured to do. The calculation circuit is configured to add the correction value to the total value of N times of the previous time series digital signal to calculate the total value of N times of the latest time series digital signal. The total value register is configured to store the latest total value generated by the calculation circuit.

  The total value calculation circuit is a circuit for realizing the simplified moving average method. The total value calculation circuit uses a change component of the time-series digital signal to adjust a correction value corresponding to the difference between the latest time-series digital signal and the N-time previous time-series digital signal. For this reason, since the shift register of the total value arithmetic circuit only needs to be configured to store the change component of the time-series digital signal, as compared with the shift register that stores N-time digital signal, The circuit scale is greatly reduced.

FIG. 1 shows a circuit configuration of a moving average circuit according to the embodiment. FIG. 2 shows an outline of the algorithm of the operation performed by the moving average circuit of the embodiment. FIG. 3 shows an outline of an algorithm for calculation performed by the moving average circuit of the comparative example. FIG. 4 shows a circuit configuration of a moving average circuit according to a first modification of the embodiment. FIG. 5 shows an outline of an algorithm of calculation performed by the moving average circuit of the first modification of the embodiment. FIG. 6 shows a circuit configuration of a moving average circuit according to a second modification of the embodiment. FIG. 7 shows an outline of an algorithm of calculation performed by the moving average circuit of the second modification example of the embodiment.

  The technical features disclosed in this specification will be summarized below. The items described below have technical usefulness independently.

  The total value calculation circuit disclosed in this specification is configured to calculate a total value for N times of a multi-bit time-series digital signal. The total value calculation circuit only needs to be configured to calculate at least the total value of N times of the time series digital signal, and is configured to calculate a plurality of total values of the time series digital signal as necessary. It may be. The total value calculation circuit may include a shift register, a correction value adjustment circuit, a calculation circuit, and a total value register. The shift register is configured to sequentially store change components corresponding to changes in the time-series digital signal and to output the change component N times before. The “change component” here may be a signal that can directly or indirectly derive a change in a time-series digital signal. For example, the change component may be a 1-bit instruction signal that instructs increase / decrease of the time-series digital signal. The correction value adjustment circuit adjusts a correction value corresponding to the difference between the latest time-series digital signal and the N-time previous time-series digital signal based on the latest change component of the time-series digital signal and the N-time previous change component. Is configured to do. Here, “adjusting the correction value” means adjusting the signal necessary for calculating the difference between the latest time-series digital signal and the N-time previous time-series digital signal. A signal corresponding to the difference between the signal and the N-time previous time-series digital signal may be adjusted. The calculation circuit is configured to add the correction value to the total value of N times of the previous time series digital signal to calculate the total value of N times of the latest time series digital signal. The total value register is configured to store the latest total value generated by the calculation circuit.

  One embodiment of the correction value adjustment circuit may include a first counter and a second counter. The first counter is configured to update the latest time-series digital signal based on the latest change component. The second counter is configured to update the time-series digital signal N times before based on the change component N times before. In this case, the difference between the output signal of the first counter and the output signal of the second counter corresponds to the correction value.

  Another embodiment of the correction value adjustment circuit may include a third counter. The third counter is configured to update and adjust the correction value based on the combination of the latest change component and the change component N times before. In this case, the output signal of the third counter corresponds to the correction value.

The total value calculation circuit may be used in a moving average circuit. In particular, when N is a power of 2 (N = 2 ⁿ , n is a positive natural number), this total value calculation circuit operates as a moving average circuit that outputs a moving average value without requiring a division circuit. Can do.

  First, before starting to describe a specific moving average circuit, a simplified moving average method used by the moving average circuit of this embodiment will be described. The simplified moving average method can simplify the calculation of the total value of the N time series digital signals when obtaining the moving average value of the N time series digital signals.

  The total value SUM (T-1) for N times of the time-series digital signal DA at the time point T-1 is expressed by the following Equation 1.

  A total value SUM (T) of N time-series digital signals at the next time T is expressed by the following Equation 2.

  The underlined portions of Equation 1 and Equation 2 match. Therefore, Formula 2 is expressed by the following Formula 3 using Formula 1.

  As described above, the total value SUM (T) at the time point T is obtained by adding the latest time series digital signal DA (T) to the total value SUM (T-1) at the time point T-1 and N times before. It is obtained by subtracting the series digital signal DA (TN). In other words, the total value SUM (T) at the time point T is the sum of the difference between the latest time-series digital signal DA (T) and the N-time previous time-series digital signal DA (T−N) at the time point T−1. It is obtained by adding to the value SUM (T-1). This simplified moving average method has the advantage that the amount of calculation is greatly reduced as compared with the case where the total value is obtained by adding all N time-series digital signals. The moving average circuit of the present embodiment is characterized by using the above-described simplified moving average method.

  The moving average circuit described below is configured to directly output a total value of N times of the time series digital signal, and at this point, outputs a total value of N times of the time series digital signal. It can be evaluated as a total value calculation circuit. On the other hand, as will be described later, this moving average circuit is configured to output a moving average value (SUM / N) if the decimal point position of the total value is shifted because N is a power of 2. In this respect, it can be evaluated as a moving average circuit that outputs a moving average value for N times of a time-series digital signal.

  As shown in FIG. 1, the moving average circuit 1 includes a shift register 11, a correction value adjustment circuit 12 having a first up / down counter 12A and a second up / down counter 12B, an addition / subtraction circuit 13 and a SUM register 14. In addition, the moving average circuit 1 includes a first terminal T1 to which an instruction signal CA for instructing increase / decrease of the time series digital signal DA is input, a second terminal T2 to which a clock signal CK is input, and a third terminal T3 to which a reset signal RES is input. And a fourth terminal T4 for outputting the total value SUM.

  The shift register 11 is configured to sequentially store the instruction signal CA in synchronization with the clock signal CK and output the instruction signal CB N times before. The shift register 11 is composed of 16 stages of D-type flip-flops, and is a serial input serial output type. The instruction signals CA and CB are 1-bit digital signals “1” or “0”.

  The first up / down counter 12A of the correction value adjusting circuit 12 is configured to update the counter value of the latest time-series digital signal DA in synchronization with the clock signal CK based on the latest instruction signal CA. For example, the first up / down counter 12A increases (+1) the latest time-series digital signal DA in synchronization with the clock signal CK when the latest instruction signal CA is “1”. On the other hand, when the latest instruction signal CA is “0”, the first up / down counter 12A decrements (−1) the latest time-series digital signal DA in synchronization with the clock signal CK. Therefore, the time-series digital signal DA (T) output from the first up / down counter 12A at the time T is expressed by the following Equation 4. The first up / down counter 12A is reset to an initial value by a reset signal RES.

  The second up / down counter 12B of the correction value adjusting circuit 12 is configured to update the counter value of the time-series digital signal DB N times before in synchronization with the clock signal CK based on the instruction signal CB N times before. Has been. For example, when the instruction signal CB N times before is “1”, the second up / down counter 12B increases (+1) the time series digital signal DB N times before in synchronization with the clock signal CK. On the other hand, when the instruction signal CB N times before is “0”, the second up / down counter 12B decreases (−1) the time series digital signal DB N times before in synchronization with the clock signal CK. Therefore, the N-time previous time-series digital signal DB (T) output from the second up / down counter 12B at the time point T is expressed by the following Equation 5. The second up / down counter 12B is reset to an initial value by a reset signal RES.

  The adder / subtractor circuit 13 adds the latest time-series digital signal DA output from the first up / down counter 12A, the N-time previous time-series digital signal DB output from the second up / down counter 12B, and the SUM register 14. The stored total value SUM of N times of the previous time-series digital signal is inputted. The addition / subtraction circuit 13 is configured to add the latest time series digital signal DA to the total value SUM one time before and subtract the time series digital signal DB N times before. In other words, the addition / subtraction circuit 13 is configured to add a correction value corresponding to the difference between the latest time-series digital signal DA and the N-time previous time-series digital signal DB to the previous total value SUM.

  The SUM register 14 is configured to capture the output of the adder / subtractor circuit 13 in synchronization with the clock signal CK and store it in the memory. That is, the SUM register 14 updates the total value SUM for N times of the time-series digital signal in synchronization with the clock signal CK.

  The moving average circuit 1 outputs the total value SUM stored in the SUM register 14 to the fourth terminal T4. In this example, N is a power of 2 (4, 8, 16, 32, 64, etc.), and the total value SUM is a binary digital value. Therefore, for example, when N = 16, the moving average circuit 1 outputs the moving average value SUM / N to the fourth terminal T4 if the decimal point position of the total value SUM is shifted four digits to the left. It can be evaluated that it is configured as follows.

  FIG. 2 shows an outline of a calculation algorithm of the moving average circuit 1. In this example, the time-series digital signal is 8 bits and N = 16. FIG. 2 shows a state in which each data is updated in synchronization with the clock signal CK at time T. As shown in FIG. 2, the moving average circuit 1 generates the latest time-series digital signal DA (T) based on the latest instruction signal CA (T) at the time point T, and the instruction 16 times before. Based on the signal CB (T), the time series digital signal DB (T) 16 times before is generated. The instruction signals for 16 times are sequentially stored in a 16-stage shift register. The instruction signal is a digital signal “1” or “0”, and a 1-bit memory is sufficient for each stage of the shift register. The moving average circuit 1 adds the latest time-series digital signal DA (T) to the total value SUM of the time-series digital signals at the time point T−1 and subtracts the previous 16-time time-series digital signal DB (T). Thus, the total value SUM of the time-series digital signals at time T is calculated.

  Here, FIG. 3 shows an outline of a calculation algorithm of the moving average circuit of the comparative example. The moving average circuit of this comparative example also has the same calculation algorithm, and adds the latest time-series digital signal DA (T) to the total value SUM of the time-series digital signals at the time point T−1 and 16 times before. By subtracting the time series digital signal DB (T), the total value SUM of the time series digital signals at the time point T is calculated. The moving average circuit of this comparative example is characterized in that a shift register is configured to sequentially store 16-bit 8-bit time-series digital signals. Thus, in the moving average circuit of this comparative example, it is necessary to store all 16-bit time series digital signals for 16 times, and the circuit scale of the shift register is large.

  On the other hand, in the moving average circuit 1 of the present embodiment, the shift register is configured so as to sequentially store only the 1-bit instruction signal CA, and based on the instruction signal CB (T) 16 times before, A time series digital signal DB (T) 16 times before is calculated. For this reason, the moving average circuit 1 of the present embodiment only needs to store 16-bit instruction signals CA for 16 times, and the circuit scale is greatly reduced as compared with the shift register of the moving average circuit of the comparative example.

  FIG. 4 shows the moving average circuit 2 of the first modification. In contrast to the moving average circuit 1 shown in FIG. 1, the moving average circuit 2 is characterized in that the correction value adjusting circuit 12 is composed of one third up / down counter 12C.

  The third up / down counter 12C is configured to update and adjust the correction value counter value DC in synchronization with the clock signal CK based on the combination of the latest instruction signal CA and the instruction signal CB N times before. ing. The correction value counter value DC corresponds to the difference between the latest time-series digital signal and the N-time previous time-series digital signal. For example, the third up / down counter 12C increases the correction value counter value DC in synchronization with the clock signal CK when the latest instruction signal CA is “1” and the instruction signal CB N times before is “0”. (+2). The third up / down counter 12C decreases the correction value counter value DC in synchronization with the clock signal CK when the latest instruction signal CA is “0” and the instruction signal CB N times before is “1” (− 2) Do. Further, the third up / down counter 12C maintains the correction value counter value DC in synchronization with the clock signal CK when the latest instruction signal CA matches the instruction signal CB N times before. Therefore, the correction value counter value DC (T) output from the third up / down counter 12C at time T is expressed by the following Equation 6. The third up / down counter 12C is reset to an initial value by a reset signal RES.

  The addition circuit 15 inputs the correction value counter value DC output from the third up / down counter 12C and the total value SUM for N times of the previous time-series digital signal stored in the SUM register 14. Is configured to do. The addition circuit 15 is configured to add the correction value counter value DC to the previous total value SUM.

  FIG. 5 shows an outline of a calculation algorithm of the moving average circuit 1. In this example, the time-series digital signal is 8 bits and N = 16. FIG. 5 shows a state in which each data is updated in synchronization with the clock signal CK at time T. As shown in FIG. 5, the moving average circuit 2 calculates the correction value counter value DC (T (T) at the time T based on the combination of the latest instruction signal CA (T) and the 16th instruction signal CB (T). ) To calculate the total value SUM of the time-series digital signals at the time point T, by adding the correction value counter value DC (T) to the total value SUM of the time-series digital signals at the time point T−1. To do.

  In the moving average circuit 2 shown in FIG. 4, the correction value adjusting circuit 12 is composed of one counter circuit as compared with the moving average circuit 1 shown in FIG.

  FIG. 6 shows the moving average circuit 3 of the second modification. The moving average circuit 3 is configured to output a plurality of moving average values. Compared with the moving average circuit 1 shown in FIG. 1, the moving average circuit 3 further includes an addition / subtraction circuit 16 and a SUM ′ register 17, and the correction value adjustment circuit 12 additionally includes a fourth up / down counter 12D. It is characterized by. The moving average circuit 3 includes a fifth terminal T5 that outputs a total value SUM '.

  In the moving average circuit 3, as compared with the moving average circuit 1 shown in FIG. The shift register 11 is configured to sequentially store the instruction signal CA in synchronization with the clock signal CK, to output the instruction signal CB N times before, and to output the instruction signal CD M times before. M> N. The shift register 11 is composed of 64 stages of D-type flip-flops and is a serial input serial output type.

  The fourth up / down counter 12D of the correction value adjustment circuit 12 is configured to update the counter value of the time-series digital signal DD M times before in synchronization with the clock signal CK based on the instruction signal CD M times before. Has been. For example, when the instruction signal CD M times before is “1”, the fourth up / down counter 12D increases (+1) the time series digital signal DD before M times in synchronization with the clock signal CK. On the other hand, when the instruction signal CD M times before is “0”, the fourth up / down counter 12D decrements (−1) the time-series digital signal DD before M times in synchronization with the clock signal CK. Therefore, the time series digital signal DD (T) before M times output from the fourth up / down counter 12D at time T is expressed by the following Equation 7. The fourth up / down counter 12D is reset to an initial value by a reset signal RES.

  The addition / subtraction circuit 16 includes the latest time-series digital signal DA output from the first up / down counter 12A, the M-time previous time-series digital signal DD output from the fourth up / down counter 12D, and the SUM ′ register 17. The total value SUM ′ for M times of the previous time-series digital signal stored in is stored. The addition / subtraction circuit 16 is configured to add the latest time series digital signal DA to the total value SUM 'one time before and subtract the time series digital signal DD M times before. In other words, the addition / subtraction circuit 16 is configured to add a correction value corresponding to the difference between the latest time-series digital signal DA and the M-time previous time-series digital signal DD to the previous total value SUM ′. .

  The SUM 'register 17 is configured to capture the output of the adder / subtractor circuit 16 in synchronization with the clock signal CK and store it in the memory. That is, the SUM 'register 17 updates the total value SUM' for M times of the time-series digital signal in synchronization with the clock signal CK.

  The moving average circuit 3 outputs the total value SUM 'stored in the SUM' register 17 to the fifth terminal T5. In this example, M is a power of 2 (4, 8, 16, 32, 64, etc.), and the total value SUM 'is a binary digital value. Therefore, for example, when M = 64, the moving average circuit 3 supplies the moving average value SUM ′ / M to the fifth terminal T5 if the decimal point position of the total value SUM ′ is shifted six digits to the left. It can be evaluated that it is configured to output.

  FIG. 7 shows an outline of a calculation algorithm of the moving average circuit 3. In this example, the time-series digital signal is 8 bits, N = 16, and M = 64. FIG. 7 shows a state in which each data is updated in synchronization with the clock signal CK at time T. As shown in FIG. 7, the moving average circuit 3 generates the latest time-series digital signal DA (T) based on the latest instruction signal CA (T) at the time T, and the instruction signal 16 times before A time series digital signal DB (T) 16 times before is generated based on CB (T), and further, a time series digital signal DD (64 times before is indicated based on the instruction signal CD (T) 64 times before. T). The instruction signals for 64 times are sequentially stored in a 64-stage shift register. The instruction signal is a digital signal “1” or “0”, and a 1-bit memory is sufficient for each stage of the shift register. The moving average circuit 3 adds the latest time-series digital signal DA (T) to the total value SUM of the time-series digital signals at the time point T-1, and subtracts the previous 16-time time-series digital signal DB (T). Thus, the total value SUM of 16 times of the time series digital signal at the time point T is calculated, and the latest time series digital signal DA (T) is further added to the total value SUM ′ of the time series digital signal at the time point T−1. And 64 times previous time-series digital signal DD (T) is subtracted to calculate a total value SUM ′ for 64 times of the time-series digital signal at time T.

  Thus, the moving average circuit 3 is configured to output a moving average value for 16 times and a moving average value for 64 times. The moving average circuit 3 is characterized in that the shift register 11 and the first up / down counter 12A are used in combination for calculating the plurality of moving average values. For this reason, the moving average circuit 3 can output a plurality of moving average values with a small circuit scale.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

1: moving average circuit 11: shift register 12: correction value adjustment circuit 12A: first up / down counter 12B: second up / down counter 13: addition / subtraction circuit 14: SUM register 15: division circuit

Claims (5)

A total value calculation circuit for calculating a total value of N times of a multi-bit time series digital signal,
A shift register configured to sequentially store change components corresponding to changes in the time-series digital signal and output the change component N times before;
Based on the latest change component of the time-series digital signal and the change component N times before, a correction value corresponding to the difference between the latest time-series digital signal and the time-series digital signal N times before is adjusted. A configured correction value adjustment circuit;
A calculation circuit configured to add the correction value to a total value of N times of the previous time series digital signal to calculate a total value of N times of the latest time series digital signal;
And a total value register configured to store the latest total value calculated by the calculation circuit.   The total value calculation circuit according to claim 1, wherein the change component is a 1-bit instruction signal that instructs increase / decrease of the time-series digital signal. The correction value adjustment circuit includes:
A first counter configured to update the latest time-series digital signal based on the latest change component;
A second counter configured to update the time-series digital signal N times before based on the change component N times before,
The total value calculation circuit according to claim 1, wherein a difference between an output signal of the first counter and an output signal of the second counter corresponds to the correction value. The correction value adjustment circuit includes:
A third counter configured to update and adjust the correction value based on a combination of the latest change component and the change component N times before,
The total value calculation circuit according to claim 1, wherein an output signal of the third counter corresponds to the correction value. A total value arithmetic circuit according to any one of claims 1 to 4 is provided,
A moving average circuit, where N is a power of two.

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