JP4423827B2 - FM tone generation circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an FM tone generation circuit that forms a tone signal by FM (frequency modulation).
[0002]
[Prior art]
Various methods for generating musical tone signals of synthesizers and electronic organs are known, and one of them is the FM method. This FM tone generation circuit is configured by combining two to six sine wave generators called operators. FIG. 4 is a block diagram showing the configuration of the operator OP. In this figure, reference numeral 1 denotes a phase generator, the details of which are shown in FIG. In FIG. 5, FN is a frequency number that indicates a note of a digital musical tone signal generated by the operator OP, and BL is octave data that indicates an octave. Reference numeral 2 denotes a shifter, which shifts the frequency number FN by the number of bits indicated by the octave data BL and outputs it as frequency data FD. As is well known, the frequency number on the M octave is obtained by multiplying the frequency number FN by 2 ^M , that is, by shifting the frequency number upward by M bits.
[0003]
The shift & adder 3 is a circuit that multiplies the frequency data FD output from the shifter 2 by the next magnification corresponding to the 4-bit control data Mult.
Data Mult: 0 1 2 3 4 5 6 7 8 9 9,11 12,13 14,15
Magnification: 1/2 1 2 3 4 5 6 7 8 9 10 12 15
In other words, the shift & adder 3 includes a shifter that shifts the frequency data FD by a predetermined number of bits and a circuit that adds the frequency data FD to the shifted data one or more times. In the case of “3”, the frequency data FD is doubled by shifting by 1 bit, and then the frequency data FD is added once to the shifted data to be tripled. Similarly, when the control data Mult is “6”, the frequency data FD is shifted by 2 bits and added twice to make 6 times. The accumulator 4 is a circuit that repeatedly accumulates the output of the shift & adder 3, and accumulates again from the minimum value when the accumulated value overflows. The output of the accumulator 4 is output to the adder 7 (FIG. 4) as phase data ωct. The output of the accumulator 4 is data that changes in a sawtooth shape.
[0004]
The adder 7 adds the phase data ωct described above and data Dp from another operator or the like, and outputs the addition result to the sine table 8. The sine table 8 is a memory in which each instantaneous value of the sine waveform is stored. When the output of the adder 7 is applied to its address terminal, each instantaneous value of the sine waveform is sequentially read and output to the multiplier 9. Is done. That is, the output of the sign table 8 is
sin (ωct + Dp)
It becomes.
[0005]
An envelope generator 10 generates envelope data A (t) and outputs it to the multiplier 9. The multiplier 9 multiplies the output of the envelope generator 10 and the output of the sine table 8 and outputs the result. That is, the output of this multiplier (output of the operator OP) is
A (t) sin (ωct + Dp)
A sine wave represented by the following formula.
[0006]
FIG. 6 is a block diagram showing a configuration of a tone generation circuit in which the above-described operators are connected in series. Now, the output of operator OP1
A1 (t) sinωmt
When the output of the operator OP1 is applied as data Dp to the operator OP2, the output of the operator OP2 is
A (t) sin {ωct + A1 (t) sinωmt}
It becomes. That is, an FM modulation waveform is obtained.
[0007]
As described above, the FM-based musical tone forming circuit forms a musical tone waveform rich in change by combining various operators OP in various ways.
[0008]
[Problems to be solved by the invention]
By the way, the above-described conventional FM tone generation circuit has a restriction that the control data Mult = 4 bits. Therefore, the shift & adder 3 reduces the basic frequency data FD to 1/2 times, 1 time, 2 times,・ ・ Although it is possible to create frequency data with a limited simple magnification, there is a drawback that it is not possible to create frequency data with complex magnifications such as 1.5 times, 2.5 times, 2.25 times, and 21 times.
[0009]
The present invention has been made in consideration of such circumstances, and its object is to form a high-order or decimal tone / harmonic tone signal that could not be produced by a conventional tone-forming circuit. It is to provide an FM sound source operator that can be used.
[0010]
[Means for Solving the Problems]
The present invention has been made to solve the above problems, and the invention according to claim 1 is characterized in that one of the first frequency data indicating the frequency of the generated musical sound and the second frequency data supplied from the outside is used. A selector that selects and outputs based on first control data supplied from outside, a data changing means that changes output data of the selector at a magnification based on second control data supplied from outside, and the data change An FM musical tone forming circuit comprising first to nth operators, comprising accumulating means for accumulating outputs of the means and musical tone signal forming means for forming musical tone signals based on the output of the accumulating means. The output of the data changing means of the kth (k = 1, 2,..., N−1) operator is applied as second frequency data to the selector of the (k + 1) th operator. A FM tone formation circuit.
[0011]
Further, the invention according to claim 2 is the FM musical tone forming circuit according to claim 1, wherein a 1/2 circuit for halving the output data of the data changing means is provided at the rear of the data changing means, The output of the 1/2 circuit is supplied to the accumulating means and the selector of the next-stage operator instead of the output of the data changing means.
[0012]
According to a third aspect of the present invention, one of the first frequency data indicating the frequency of the generated musical sound or the second frequency data supplied from the outside is based on the first control data supplied from the outside. A selector for selecting and outputting; data changing means for changing output data of the selector at a magnification based on second control data supplied from the outside; accumulating means for accumulating outputs of the data changing means; A musical tone signal forming means for forming a musical tone signal based on the output of the accumulating means, and a delay circuit for delaying the output data of the data changing means by a time width of time-division driving and applying it to the selector as the second frequency data An FM musical tone forming circuit, wherein the data changing means, the accumulating means, and the musical tone signal forming means are time-division driven based on the time width. That.
[0013]
According to a fourth aspect of the present invention, in the FM musical tone forming circuit according to the third aspect, a 1/2 circuit for halving the output data of the data changing means is provided at the rear of the data changing means, The output of the 1/2 circuit is supplied to the accumulating means and the delay circuit in place of the output of the data changing means.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an FM musical tone signal forming circuit according to the first embodiment of the present invention, and the FM musical tone signal forming circuit shown in FIG. 1 includes four operators 11-14. Each of the operators 11 to 14 is configured in substantially the same manner as the conventional operator OP shown in FIGS. 4 and 5 described above, and the same components are denoted by the same reference numerals. Further, the frequency number FN and the octave data BL are applied to the operators 11 to 14 in common. Furthermore, the output of each operator 11-14 is applied to the output mixer (not shown) or the adder 7 of the other operators 11-14.
[0015]
The operators 11 to 14 are different from the conventional operator OP in the following two points.
(1) Selectors 16 to 19 are inserted between the shifter 2 and the shift & adder 3 of each operator 11 to 14. The selection operations of the selectors 16 to 19 are controlled by 1-bit control data SLC1 to SLC4, respectively. That is, when the control data SLC1 to SLC4 are “0”, the data of the first input terminals of the selectors 16 to 19 are output from the selectors 16 to 19, and when the control data SLC1 to SLC4 is “1”, the second data of the selectors 16 to 19 is output. Data at the input end is output from the selectors 16-19.
(2) The output of the shift & adder 3 of the operator 11 is applied to the first input terminal of the selector 17 of the operator 12, and the output of the shift & adder 3 of the operator 12 is applied to the first input terminal of the selector 18 of the operator 13. The output of the shift & adder 3 of the operator 13 is applied to the first input terminal of the selector 19 of the operator 14.
[0016]
In such a configuration, when the control data SLC1 is set to “0” and the control data SLC2 to SLC4 are set to “1”, the output of the shift & adder 3 of the operator 11 is sent to the shift & adder 3 of the operator 12 via the selector 17. The output of the shift & adder 3 of the operator 12 is applied to the shift & adder 3 of the operator 13 via the selector 18, and the output of the shift & adder 3 of the operator 13 is shifted to the shift & adder 3 of the operator 14 via the selector 19. Applied to adder 3.
[0017]
Thus, for example, if the control data Mult1 to Mult4 to be applied to the shift & adder 3 are “0”, “3”, “5” and “3”, respectively, the operators of the frequency data FD from the operators 12 to 14 respectively. 12 ... 0.5x3 = 1.5 times operator 13 ... 0.5x3x5 = 7.5 times operator 14 ... Sine wave signal corresponding to 0.5x3x5x3 = 22.5 times frequency data is output The
[0018]
For example, the control data SLC1 and SLC3 are set to “0”, the control data SLC2 and SLC4 are set to “1”, and the control data Mult1 to Mult4 are set to “0”, “3”, “0”, and “5”, respectively. Then, a sine wave signal corresponding to the frequency data of the operator 12... 0.5 × 3 = 1.5 times the operator 14... 0.5 × 5 = 2.5 times of the frequency data FD is output from the operators 12 and 14, respectively.
[0019]
As described above, by selecting the control data SLC1 to SLC4 and the control data Mult1 to Mult4 in various ways, it is possible to form a sine wave signal having a variety of pitches. 1 may be used as separate sound generation channels, or may be used as a plurality of slots of the same sound generation channel.
[0020]
In the above embodiment, the frequency number FN and the octave data BL are commonly applied to each operator. However, different frequency numbers FN and octave data BL may be applied to each operator.
Further, the outputs of the shift & adder 3 of other operators as well as the preceding operator may be applied to the selectors 17 to 19.
[0021]
FIG. 2 is a block diagram showing the configuration of the second embodiment of the present invention. The embodiment shown in this figure uses each component of the circuit in a time-sharing manner, and operates as two operators. That is, this circuit operates as a separate operator in the first and second time zones that are alternately repeated, and in the first time zone, the control data SLC = "1" is applied to the selector 21, As a result, the frequency data FD output from the shifter 2 is applied to the shift & adder 3 via the selector 21, the multiplication according to the control data Mult is multiplied in the shift & adder 3, and output to the accumulator 4. .
[0022]
Next, at the second time zone, the control data SLC = “0” is applied to the selector 21, whereby the output of the delay circuit 22 is applied to the shift & adder 3 via the selector 21. Here, the delay time of the delay circuit 22 is equal to the time width of the first time zone (= second time zone). Therefore, in the second time zone, shift & adder is performed in the first time zone. The frequency data output from 3 is applied to the shift & adder 3 via the selector 21. Then, the shift & adder 3 multiplies the magnification according to the control data Mult at this time and outputs the result to the accumulator 4.
[0023]
Thus, the second embodiment described above has the same function as the combination of the operators 11 and 12 in FIG.
Note that the embodiment shown in FIG. 2 may be time-division driven so as to achieve the functions of the four operators shown in FIG.
[0024]
FIG. 3 is a block diagram showing the configuration of the third embodiment of the present invention. The embodiment shown in this figure is different from that shown in FIG. 2 in that a 1/2 shifter 24 is provided at the rear of the shift & adder 3. The output data of the 1/2 shifter 24 is provided to the delay circuit 22. When the control data 1 / 2Mu is “0”, the 1/2 shifter 24 passes through the output of the shift & adder 3 as it is, but when the control data 1 / 2Mu is “1”, the output of the shift & adder 3 is 1 in the lower direction. Bit shift and output. That is, the output of the shift & adder 3 is halved and output.
[0025]
Thus, for example, both in the first and second time zones
Mult = 3, 1 / 2Mu = "1"
Then, 3 × 0.5 × 3 × 0.5 × FD = 2.25 × FD in the second time zone
The following frequency data FD is obtained. That is, it is possible to form a sine wave signal having a finer pitch than the first and second embodiments described above.
Of course, even if a 1/2 shifter is inserted in the rear part of each shift & adder 3 in the circuit of FIG. 1, the same effect as the circuit of FIG. 3 can be obtained.
[0026]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a high-order or decimal tone / overtone tone signal that cannot be produced by a conventional tone generation circuit with a simple configuration. .
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an FM tone generation circuit according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of an FM musical tone forming circuit according to a second embodiment of the present invention.
FIG. 3 is a block diagram showing a configuration of an FM tone generation circuit according to a third embodiment of the present invention.
FIG. 4 is a block diagram showing a configuration of a conventional operator.
5 is a block diagram showing a configuration of a phase generator 1 in the operator shown in FIG.
6 is a block diagram showing a configuration of a tone generation circuit configured using two operators shown in FIG. 4; FIG.
[Explanation of symbols]
2 ... Shifter, 3 ... Shift & Adder, 4 ... Accumulator, 7 ... Adder, 8 ... Sine table, 9 ... Multiplier, 10 ... Envelope generator, 11-14 ... Operator, 22 ... Delay circuit, 24 ... 1 / 2 shifter.

Claims (4)

A selector that selects and outputs one of first frequency data indicating the frequency of the generated musical sound or second frequency data supplied from outside based on first control data supplied from outside;
Data changing means for changing the output data of the selector at a magnification based on second control data supplied from the outside;
Accumulating means for accumulating the output of the data changing means;
Musical tone signal forming means for forming a musical tone signal based on the output of the accumulation means;
An FM musical tone forming circuit comprising first to nth operators comprising:
The output of the data changing means of the kth (k = 1, 2,..., N−1) operator is applied as second frequency data to the selector of the (k + 1) th operator. Music generation circuit. A ½ circuit that halves the output data of the data changing unit is provided at the rear of the data changing unit, and the output of the 1/2 circuit is replaced with the output of the data changing unit, and the accumulating unit and the next 2. The FM tone generation circuit according to claim 1, wherein the FM tone generation circuit is supplied to the selector of a stage operator. A selector that selects and outputs one of first frequency data indicating the frequency of the generated musical sound or second frequency data supplied from outside based on first control data supplied from outside;
Data changing means for changing the output data of the selector at a magnification based on second control data supplied from the outside;
Accumulating means for accumulating the output of the data changing means;
Musical tone signal forming means for forming a musical tone signal based on the output of the accumulation means;
A delay circuit that delays the output data of the data changing means by a time width of time-division driving and applies the second frequency data to the selector;
And the data changing means, the accumulating means and the tone signal forming means are time-division driven based on the time width. A ½ circuit that halves the output data of the data changing unit is provided at the rear of the data changing unit, and the output of the 1/2 circuit is replaced with the output of the data changing unit, and the accumulating unit and the 4. The FM tone generation circuit according to claim 3, wherein the FM tone generation circuit is supplied to a delay circuit.

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