JPH01128100A - Envelope generator - Google Patents

Abstract

PURPOSE: To precisely convert digital envelope data into an analog envelope signal by integrating output pulses of a tone generator which outputs the pulses of constant width in repetitive cycles corresponding to digital envelope data. CONSTITUTION: A digital envelope data generating means 1 outputs digital data representing the momentary value (n) of an envelope according to constant algorithm. The tone generator 2 outputs the pulses of constant width in cycles corresponding to the digital data representing the momentary value (n) and the output pulses of the tone generator 2 are integrated by an integrator 3. Consequently, the digital data on the envelope can correctly be converted into the analog envelope signal in spite of simple constitution using general circuit components.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to the digitization of envelope generators in electronic musical instruments.

(Conventional technology) Even in electronic musical instruments that traditionally used analog methods,
There was a movement to digitize each part.

It can be said that the envelope generator is also a part where digital processing can be easily introduced and its effects can be fully demonstrated. In this case, digital envelope data must ultimately be converted into an analog signal. VOA
(Voltage Controlled Amplif
ier: voltage controlled amplifier) and V OF (Voltg
This is to use it as a control signal for an electronic control filter (voltage control filter) or the like. At this time, a DA converter is used to convert digital data into an analog signal. The most commonly used DA converter is one realized with a resistor network circuit called R, -2R. Since there are only two types of resistance values, it is easy to manufacture and suitable for integration. In fact, devices that are integrated into ICs and are easy to use are becoming available.

(Problems to be Solved by the Invention) Now, in order to obtain a smooth envelope, linear quantization requires a resolution of 10 to 12 bits or more. However, the current situation is that high resolution and high precision make manufacturing difficult and expensive. One way to inexpensively convert digital data into analog signals using general-purpose circuit components is to charge a capacitor every sampling period and output the terminal voltage when the capacitor is discharged for a time corresponding to the digital data. .

In this case, the envelope data generation algorithm can be simplified because it exhibits exponential conversion characteristics. but,
There is a drawback that the magnitude relationship between the digital data and the analog signal does not match, and that 101 cannot be expressed in principle.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method that can accurately convert envelope digital data into an analog envelope signal with a simple configuration using general-purpose circuit components.

(Means for Solving the Problems) In order to achieve the above object, the present invention generates a pulse with a constant width at a period corresponding to the digital data of the envelope, and integrates the pulse to generate an analog envelope signal. A digital envelope data generating means, a rate generator that outputs a pulse of a constant width at a repetition period corresponding to the digital envelope data generated by the digital envelope data generating means, and an output pulse of the rate generator. An integration means for integration is constructed.

(Example) An example will be explained below. FIG. 1 is the most basic block diagram showing the present invention. The digital envelope data generating means 1 outputs digital data representing the instantaneous value n of the envelope according to a certain algorithm. Examples of algorithms include exponential conversion of a straight line obtained by accumulating constant values, and a method using an exponential curve obtained by accumulating constant values. Any explanation of this algorithm will be omitted here, as any algorithm may be used. Now, the rate generator 2 outputs a - constant width pulse at a period corresponding to the digital data representing the instantaneous value n of the envelope outputted from the digital envelope data generating means 1.

The output pulses of the rate generator 2 are integrated by an integrator 3. The relationship between the instantaneous value n of the envelope and the integrated output voltage is as follows. As shown in Fig. 2, the frame period is TC8], and the width τ [S] and the peak value e [■
] is assumed to fit n pulses. The output voltage Ea (V:1) obtained by integrating this is as follows. Since e, τ and T are constants, Ea is proportional to n.

FIG. 3 schematically shows how digital envelope data is converted into an analog signal every period T (s). In the initial state, the digital envelope data is 101. The highest voltage is then obtained as the integrator output. The following digital data 181, 151
．． . . . is applied in response to '01.

The basic principle has been explained above, and this is for outputting an envelope signal for one channel. In order to output envelope signals for multiple channels, it is sufficient to time-division multiplex the frame periods and output them in parallel using an analog demultiplexer.

Now, when actually configuring an electronic musical instrument, MPU (Micro Processor) is generally used for system control.
Unjt) is used. Therefore, when the envelope generator of the present invention is installed, the function of the digital envelope data generation means 1 is realized by a program and the MP
When built into the U, externally there is a PIT+ (Programmable
Interval Timer) and operate it in rate generator mode. later,
An envelope generator can be constructed with only a few components such as an integrating circuit and an analog demultiplexer for multi-channeling, making it ideal as a sound source for electronic musical instruments.

(Effects of the Invention) As described above, according to the present invention, digital envelope data can be correctly converted into an analog envelope signal with a simple circuit configuration using general-purpose circuit components.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a waveform diagram showing how n pulses are contained within one frame. FIG. 3 is a waveform diagram showing the relationship between digital envelope data and analog envelope signals. l...Digital envelope data generation means. 2...Rate generator, 3...Integrator. Figure 1 Figure 2 Figure 8 Flea 1 verse [S1

Claims (1)

[Claims] In an electronic musical instrument, a digital envelope data generating means, a rate generator that outputs a pulse of a constant width at a repetition period corresponding to the digital envelope data generated by the digital envelope data generating means, and an output pulse of the rate generator are integrated. An envelope generator comprising: an integrating means, wherein a signal output from the integrating means is an analog envelope signal corresponding to the digital envelope data.