JPH02216511A - Sine wave generation circuit - Google Patents

Abstract

PURPOSE:To shorten an operation time by generating square wave data having the same frequency as an output sine wave from saw wave data obtained by means of integrating input data deciding the frequency of output sine wave data and multiplying square wave data and waveform data which function ROM outputs so as to obtain sine wave data. CONSTITUTION:A square waveform generation means 37 generating square waveform data (i) having the same frequency as the output sine wave from saw wave data (a) obtained by integrating input data deciding the frequency of output sine wave data and a multiplication means 39 which multiplies the square wave data (i) and waveform data (e) which function ROM 24 outputs to obtains sine wave data, generate in parallel an address reading and controlling function ROM 24 and square wave data (i) which obtains output sine wave data by an operation based on the output of function ROM 24. A condition branching instruction such as polarity decision does not exist. Consequently, a program as a whole can be proceeded by using idle steps in respective programs.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a sine wave generation circuit that generates a sine wave using a function ROM. It is designed to shorten the .

(Prior Art) For example, there is a sine wave generation circuit that uses a function ROM in which SIN curve data is written and generates a sine wave through address control.

FIG. 3 is a waveform diagram showing the operation of such a sine wave generating circuit.

First, the frequency of the output sine wave data is determined by the period 1]fH of the sawtooth wave data shown in FIG. 4a, that is, the inclination angle of the slope. This sawtooth wave data is obtained by integrating constant value data at sampling intervals. Taking the absolute values of the positive and negative values of this sawtooth wave data, the fourth
The triangular wave shown in the figure is obtained. Further, the triangular wave shown in FIG. 4C is obtained by shifting the reference level of the triangular wave shown in FIG. 4b to the negative side. Next, the triangular wave shown in FIG. 4C is converted into an absolute value in the same way as the sawtooth wave. As a result, as shown in FIG. 4d, a triangular wave whose frequency is twice that of the initial sawtooth wave data is obtained. For a triangular wave with such a frequency, one triangular wave section is equal to half the period of the output sine wave shown in Fig. Function ROM for one round of minutes
It can be read more easily. After reading out this 1/4 cycle, the address signal is saturated, so next,
By decreasing the address in accordance with the slope of the latter half of the triangular wave shown in Figure 4d, the output sine wave can be divided by half.
Data for a period can be read. The waveform obtained from the function ROM is shown in FIG. 4e. The waveform shown in Fig. 4e is an inversion of the negative half cycle of the output sine wave, and by determining the polarity of the sine wave shown in Fig. 4e output from the function ROM and assigning a sign, the output sine wave is can be generated.

FIG. 5 shows a circuit for outputting a sine waveform in the manner shown in FIG. This circuit is actually constructed when each component of the digital signal processor is operated based on a waveform generation program.

In FIG. 5, adder circuit 41. Working register (
(hereinafter simply referred to as register) 42 and RAM (#1) 43
returns the frequency determination data input to the adder circuit 41 to the adder circuit 41 via the register 42 and the RAM 43;
This is an integrating means for generating the sawtooth wave data a shown in FIG. 4A from the register 42.

Absolute value circuit 44 downstream of this integrating means. register 4
5. Addition circuit 46. Coefficient ROM 47. Register 48° Absolute value circuit 49. Register 51 and address register 5
2 is means for creating the address of the function ROM 54, the output of the register 45 is the triangular wave data shown in FIG. 4, the output of the register 48 is the triangular wave data shown in FIG. This results in the triangular wave data shown in Figure 4 d. Further, the coefficient ROM 47 generates a coefficient +0°5 for downshifting the triangular wave data b by the half width.

Therefore, the address register 52 converts the triangular wave data d from the register 51 into a digital value matching the address system of the function ROM 54 and holds it, and furthermore, the adder 53
Set the SIN data to an address suitable for generating a sine wave.

This address controls the function ROM54 and
Read the sine wave data stored in 4. The read data is as shown in FIG. 4e, and is stored in the RAM (#3) 56 via the register 55.

On the other hand, triangular wave data C from RAM (#2>50) is input to the polarity determination circuit 57 via the register 58. Waveform data e from RAM (#3) 5G is also input to the polarity determination circuit 57. As a result, the polarity determination circuit 51 outputs the positive half-cycle sine wave data and the negative half-cycle sine wave data whose polarities have been determined.Among these data, the positive half-cycle 1 stop sinusoidal wave data is as follows. The data from the coefficient ROM that outputs +1 is multiplied by the multiplier 61, and the multiplication result is output as the positive half period of the output sine wave.In addition, -1 is output for the negative side single period sine wave data. It is multiplied by the data from the coefficient ROM 60, and the multiplication result is output as a negative half period of the output sine wave.

In the above-described sine wave generation circuit, specified registers and arithmetic circuits are operated in a digital signal processor based on a predetermined instruction to obtain various waveform data.

FIG. 6 shows a flowchart showing a sine wave generation program using the circuit of FIG. 861 to S81 indicate each instruction step, and the resulting waveform data is shown on the right side. In this flowchart, steps 863.64 use the results of step 362 in step 865, so that
This is an empty step that is set to generate 1ifil wave data a which is the result of 862.
S67, BIN; L, empty step for adding the output of the coefficient ROM 47 and the triangular wave data b. Similarly, steps 370 to 71 are empty steps for step S69, step 375 is an empty step when transferring the contents of 8M50 to register 58, and step 880
, 881 is an empty step for the output operation.

Such an empty step takes some time to execute an instruction and produce a result due to differences in the characteristics of multipliers and adder circuits, so the program is delayed and the previous step is It waits for the calculation result.

Therefore, such empty steps can be effectively used to perform other calculations. However, in the case of the circuit of FIG. 5, as in step 877, the polarity determination circuit 5
There is a conditional branch instruction in 7.

If you use a conditional branch instruction like the one above in the middle of a program, the number of empty steps for polarity determination such as steps 80.81 may change, and steps 863.8
64. Empty steps such as 867 and 868 cannot be used effectively.

(Problem to be solved by the invention) As mentioned above, using a digital signal processor,
In a function generating circuit that generates a sine wave according to a program, depending on the characteristics of the arithmetic unit and the type of operation, the arithmetic processing instructions of the program are executed, and several empty steps may occur before a result is produced. Therefore, it is possible to effectively utilize such empty steps to perform other calculations, but if a conditional branch instruction such as polarity judgment is included,
Since the number of empty steps in this conditional branch instruction changes, the empty steps cannot be used effectively, resulting in a disadvantage that the calculation time becomes longer.

It is an object of the present invention to provide a sine wave generation circuit which can eliminate the above-mentioned problems, generate a sine wave without using conditional branch instructions, and make effective use of empty steps.

[Structure of the Invention] (Means for Solving Problem 'Ii) The present invention includes an integrating means for integrating input data that determines the frequency of output sine wave data and generating sawtooth wave data having a predetermined slope angle; address generating means for generating address data corresponding to twice the frequency of the output sine wave data from the sawtooth wave data; and a waveform in which an access operation is performed based on the address data and a half cycle of the sine waveform is shifted to one polarity. a function ROM that generates the output sine wave, and a square wave generating means that generates square wave data having the same frequency as the output sine wave from the recorded sawtooth wave data; A multiplication means is provided for multiplying the output waveform data to obtain sine wave data.

(Function) According to such a sine wave generation circuit, generation of an address for reading and controlling the function ROM and generation of square wave data for obtaining output sine wave data by calculation based on the output of the function ROM are performed in parallel. In addition, there are no conditional branch instructions such as polarity judgment.This allows the program as a whole to proceed by using empty steps in each program, reducing the number of steps in the sine wave generation program. Computation time can be reduced.

(Example) The present invention will be explained below with reference to illustrated embodiments.

FIG. 1 is a circuit diagram showing an embodiment of a sine wave generating circuit according to the present invention.

In FIG. 1, adder circuit 11. Register 12. RAM
(#1) 13. Absolute value circuit 14. register 15
．． Addition circuit 16. Coefficient ROM 17. Register 18. Absolute value circuit 19. Register 21. The address register 22 and the adder circuit 23 have the same configuration as the conventional one, and generate triangular wave data having twice the frequency of the output sine wave.

That is, the adder circuit 11. Register 12. RAM (#
1) 13 integrates the input data to determine the frequency,
An integrating means for creating sawtooth wave data a is configured.

The absolute value circuit 14 and register 15 at the next stage convert sawtooth wave data a into absolute values to create triangular wave data b.

This triangular wave data b is the coefficient -0 from the coefficient ROM 17.
, 5, and store it in the register 18 to obtain the triangular wave data C.
becomes. The absolute value circuit 19 takes the absolute value of the triangular wave data C and stores it in the register 21. The output of the register 21 is sent to the adder circuit 23 via the address register 22 to the SI
It is added to the N data and becomes the address for reading the function ROM 24.

On the other hand, the sawtooth wave data a output from the register 12 is input to the other side of the adder circuit 31, which inputs the coefficient +0.5 from the coefficient ROM 32 to one side. +0 to sawtooth wave data a.
By adding 5, sawtooth wave data Q whose phase is shifted by half a cycle from the sawtooth wave data a is obtained.

The output of the adder circuit 31 is sent to the adder circuit 3 via the register 33.
Enter it in one of 4. The other side of the adder circuit 34 has a coefficient RO.
The coefficient +1 from M35 is input, and as a result, sawtooth wave data 1) obtained by shifting the sawtooth wave data b by a half period in the same direction is obtained from the boost circuit 34. This sawtooth wave data h enters the other side of the adder circuit 37 into which the sawtooth wave data q is input.

The adder circuit 31 outputs waveform data i obtained by adding (synthesizing) the sawtooth wave data q and h. This waveform data i is square wave data and is held in the register 38.

Therefore, the waveform data e read from the function ROM 24
is multiplied by the square wave data i by the n multiplier 39. As a result, the multiplier 39 outputs sine wave data according to the frequency specified by the input data.

FIG. 2 is a waveform diagram illustrating the operation of the above configuration.

In Figure 2, waveforms (a), (0), (h)
, m.

(e) and m correspond to the operation waveform data of each part shown in FIG. 1, respectively. Note that triangular wave data b, triangular wave data C0, and triangular wave data d are omitted because they have the same waveforms as in FIG. 4, respectively.

According to FIGS. 2(a), (b), and (c), the sawtooth wave data 90 converts the sawtooth wave data a into (1/2) fH
It becomes a sawtooth wave that is advanced by Similarly, the sawtooth wave data h is a sawtooth wave obtained by advancing the sawtooth wave data 9 by (1/2) flll. Then, the adder circuit 31
q is added to the mm-shaped wave data. This can be considered to correspond to waveform synthesis of analog waveforms, and when both waveform data are added, square wave data as shown in FIG. 2m is obtained. This square wave data is the same frequency as the output sine wave.

Next, from the function ROM 24, as in the conventional case, a waveform in which a half cycle of the sine waveform is shifted to the positive side is obtained. The desired sine wave as shown in Figure 2 () can be obtained.In other words, the two levels of the square wave data i can be considered as digital fixed coefficients (for example, +1 and -1), For each half-period sine wave shifted to the positive side,
This means that the polarity has been changed. In this way, the multiplier 39 outputs square sine wave data.

According to such a configuration, waveform data a-d, q, h
1 and the means for obtaining the square wave data and the output of the function ROM 24 are all composed of arithmetic means and do not include a conditional branch instruction for determining polarity, unlike conventional circuits.

FIG. 3 does not show the sine wave generation program according to this embodiment.

Step 811 is a process of supplying input data to the addition circuit 11. Step S12 includes the addition circuit 11.
This is an integration process performed by the register 12 and the RAM (#1) 13, whereby the register 12 generates sawtooth wave data a. The next step, step 313, is an empty step for the above integration process. Integral processing normally requires two steps, but in this case, sawtooth wave data q is calculated in step 814 (see step 64 in FIG. 6), which corresponds to the second step.

Subsequently, in step 815, triangular wave data b is created, and further, in step 316, triangular wave data C is created.

This step 816 also requires two empty steps (see steps $67 and 888) in FIG. 6), but in this embodiment, steps 817 and 318"?-1 sawtooth corresponding to these empty steps It is possible to create wave-shaped waves.

Furthermore, in step S19, triangular wave data d is created. In the case of this step S19, originally, the following step S20. S21 is an empty step, but in the case of the embodiment, these steps 320 and 321 contain square wave data i.
is being created.

Steps S22 and 823 are processes for reading waveform data e from the function ROM 24. Then, the next step 82
4 is a process performed by the multiplier 39, which multiplies the output data e of the function ROM 24 and the square wave data i.

In this manner, the present invention does not require determination processing for polarizing the output data e of the function ROM 24, and can be performed entirely by addition and multiplication processing.

In particular, step S, in which polarity determination was conventionally performed.
The process corresponding to step 77 is performed in the multiplication process of step 824. Such multiplication processing does not change the number of empty steps like polarity determination, and for example, step 825.8
26, always step 8 after two empty steps.
You can go back to 11.

Therefore, in empty steps such as ζ steps 812, 816, 819, steps 814° 81 for creating square wave data.
7, 818, and S 20.21, allowing effective use of empty steps. For this reason, 70
The number of steps in the gram can be reduced, and the calculation processing time of the digital signal processor can be shortened.

By providing such a digital signal processor in, for example, a Videotex receiving terminal equipped with an electronic sound generating device, the time required for audio processing can be shortened, and more time can be taken for other processing.

[Effects of the Invention] As explained above, according to the present invention, the empty steps of the waveform generation program in the digital signal processor can be effectively used, and the calculation program can be shortened.

4. Drawing 1! ! ll11 Description FIG. 1 is a circuit diagram showing an embodiment of the sine wave generating circuit according to the present invention, FIG. 2 is an operation waveform diagram explaining the operation of the embodiment shown in FIG. 1, and FIG. 3 is a diagram showing the operation of the embodiment shown in FIG. Flowchart showing an example of a program to realize the embodiment, FIG. 4 is an operation waveform diagram explaining the conventional sine wave generation method, and FIG. A circuit diagram showing the circuit, and FIG. 6 is a flowchart explaining a conventional sine wave generation program.

It, 23.34.37...Addition circuit, 12.15
．． 18.21°23, 36.38...Register, 13
...RAM, 14.19...Absolute value circuit, 17.
32.35... Coefficient ROM, 22... Address register, 24... Function ROM, 39... Multiplier, aW
A: Tooth wave data, d: Triangular wave data (address data), e: Function ROM data, Q, h: Sawtooth wave data, i: Square wave data, f: Output sine wave.

Figure 2

Claims (1)

[Scope of Claims] Integrating means for integrating input data that determines the frequency of output sine wave data to generate sawtooth wave data with a predetermined slope angle; address generation means for generating address data corresponding to twice the frequency of the wave data; a function ROM that performs an access operation based on the address data and generates a waveform in which a half period of a sine waveform is shifted to one polarity; and the sawtooth. square wave creating means for creating square wave data having the same frequency as the output sine wave from the shape wave data; and multiplying the square wave data output from the square wave creating means by the waveform data output from the function ROM. A sine wave generation circuit comprising multiplication means for obtaining sine wave data.