JPS59211092A - Electronic tone generation circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic sound generation circuit that adds an envelope to a digital melody waveform signal. This invention relates to an electronic sound generation circuit.

In recent years, it has been proposed to add envelopes to these electronic sounds using various envelope generation circuits in order to obtain more natural sounds when generating electronic sounds such as melody, ticking sounds, chime sounds, etc. ing.

Conventional circuits for generating envelopes can be roughly divided into analog circuits that use capacitors and resistors and use the capacitor's charging/discharging waveforms, and digital circuits that can be incorporated inside an IC. .

An example of these conventional examples and their drawbacks will be explained below.

An example of this is a method in which envelope information from a waveform ROM that stores desired envelope information is multiplied by a melody signal in a multiplier, and the multiplied signal is converted into an analog signal by a DA converter.

When a multiplier is used as in the above example, the processing speed of the multiplier is slow, making it difficult to keep up with high frequencies.

In addition, the circuit itself becomes large-scale, which increases the area it occupies.Furthermore, in order to generate the minimum attenuation sound, the number of bits in the DA converter must be increased, and the It was difficult to drive with voltage.

On the other hand, there were some that added an envelope by controlling the gain etc. of the amplifier externally connected to the C by changing the value of the resistor built into the IC, but the difference between the resistor inside the IC and the amplifier was It is difficult to match the envelopes, and furthermore, when the number of stages of the envelope is large, it is necessary to increase the number of resistors built into the IC.

Furthermore, a method has been proposed in which an envelope is added by changing the reference voltage of the DA converter in order to eliminate the drawbacks of the above method. An example of this will be explained using FIG.

The DA converter 2 in FIG.
corresponds to each bit of waveform ROM 4.

Further, an envelope generating circuit 6 is connected to a reference input of the DA converter 2.

This occurs when the DA converter 2 outputs a waveform signal based on the waveform stored value in the waveform ROMJ.
is controlled by an envelope signal from an envelope generating circuit 6 to add an envelope to the waveform signal.

However, if an OR time constant circuit consisting of a capacitor 8, a resistor 1, and a transistor 12 is used as the envelope generating circuit 6, as shown in FIG. This results in high costs (8).

In addition, since such an OR time constant circuit can only obtain one attenuation waveform, it is not possible to cope with complicated volume changes such as musical instrument sounds. If the OR time constant circuit is used as the envelope generation circuit 6 in this way, various problems will occur, so the envelope generation circuit 6 is also integrated as a combination of a ROM and a DA converter, and It has also been proposed to set and configure data such that it can accommodate complex volume changes.

However, in this way, the envelope generation circuit 6 is
When configured with multiple OM and DA converters.

The envelope generation circuit 6 The linearity of the output of the DA converter inside the device was lost, causing a problem in that the volume could not be varied in accordance with the data.

(4) In order to provide the envelope generating circuit 6 which is not affected by the input resistance value of the A converter 2 and can be further integrated, a problem arises in that an extremely complicated circuit configuration is required.

The present invention uses a voltage division ladder resistance type DA converter as a DA converter that converts a digital signal from a volume ROM that stores melody volume, that is, envelope information, into an analog signal. By using a current addition ladder resistance type DA converter as a DA converter that converts a digital signal into an analog signal, the drawbacks and problems of the conventional example can be solved, it can be easily integrated, and complicated The purpose is to provide an electronic sound generation circuit that can also respond to melodies and their envelopes.

An embodiment of the present invention will be described below based on the drawings.

FIG. 3 is a diagram showing a case where an embodiment of the electronic sound generating circuit of the present invention is applied to the ticking sound of an electronic clock.

First, the configuration of the electronic sound generation circuit portion of the present invention and the functions and characteristics of its constituent elements will be explained.

14 is a melody waveform ROM in which predetermined melody waveform data is stored as a digital signal.

Reference numeral 16 denotes a melody address counter for reading data stored in the melody waveform ROM, and is driven by a clock signal output from a scale frequency divider circuit to be described later.

18 is a melody volume ROM in which melody volume data, that is, envelope data is stored as a digital signal.

Reference numeral 20 denotes an envelope address counter for reading data stored in the melody volume ROM 18, and is driven by a clock signal output from an envelope frequency dividing circuit to be described later.

22 is a voltage division ladder resistance type DA converter (hereinafter abbreviated as voltage ladder) in which resistors having resistance values of Re and 2Re are connected in a ladder shape, and a melody volume ROM 18
It converts the digital signal from the computer into an analog signal.

This voltage ladder 22 is arranged as shown in FIG.
7'+ switch S. -8n-1 respectively correspond to this switch S. -Sn is connected to ground when the bit signal is 101, and to the reference voltage V when it is 111.

It operates to connect to.

This voltage ladder 22 has a resistance value R8 constant as viewed from the output side, regardless of the bit pattern of the melody volume ROM 18.

Therefore, the equivalent circuit becomes as shown in FIG. 5, and assuming that the load connected to the output terminal of this voltage ladder 22 is RL, the voltage V applied to this load. ut becomes as follows.

It will vary from 0 to 0.

In addition, each switch S. Since the resistance value when viewed from the -8n-1 side changes depending on the bit pattern, the reference voltage v8 in this embodiment is connected to the constant voltage source vDD so as not to be influenced by it.

(R) In Fig. 3, 24 is a current addition ladder resistance type DA converter (hereinafter abbreviated as current ladder) in which 2Rm resistors with different resistance values are connected in a ladder shape, and the melody waveform ROM
This converts the digital signal from 14 into an analog signal.

This current ladder 24 receives each bit of the melody waveform ROM 14 as shown in FIG. -bn-1 and each switch S. , 5n-1 are set to correspond to each other, and this switch S. -"11-1 has a bit signal of 101
It is set to be connected to the ground when it is , and to be connected to the resistor 26 for current-voltage conversion when it is III.

This current ladder 24 is set so that the resistance value as seen from the reference voltage TgNflV remains constant regardless of the bit pattern of the melody waveform ROM 14.

Therefore, the summed current output is:

bt=c)ohi1 (j=Q, 1.'', n1) In this embodiment, the reference voltage input of the current ladder 24 is as follows:
The output of the voltage ladder 22 mentioned above is connected.

The current ladder 24 has a constant resistance υ when viewed from the reference voltage input, and the voltage ladder 22 has a constant resistance R8 when viewed from the output side, so they are connected as shown in Figure 3. Then, it can be represented by an equivalent circuit as shown in FIG.

The circuit shown in FIG. 7 is the same as the circuit shown in FIG. 5 except that the load resistance RL is negative.

It can be expressed as

According to the above formula, the voltage VEV is (RTnZRm+R8)v
The switch S of the current ladder 24 changes only depending on the information in the melody volume ROM 18 in the range from DD to 00. -8n-1° It is not affected by ON and OFF'F states.

On the other hand, since the current ladder 24 is given VEL as a stable reference voltage, the linearity of the DA converter is not lost.

Therefore, the current ladder 24 and the voltage ladder 22 connected to this reference input operate effectively only as envelope additions without adversely affecting each other.

Furthermore, by setting the resistance values of the current ladder 24 and voltage ladder 22 so that -))R,
Since the value of m Re approaches 1, the range of the voltage ηN can be increased as the resistance value of the current ladder 24 increases.

The above-mentioned melody waveform ROM 14, melody address counter 16, melody volume ROM 1B, envelope 7゛dress counter 20, voltage ladder 22, and current ladder 24 are the constituent elements of the electronic sound generation circuit of this embodiment. The ladder 22 and the current ladder 24 output data communication output signals without affecting each other's outputs at all.

Next, using FIG. 3 again, each component of the above embodiment is shown in FIG. 3, 28 is a reference signal generator such as a crystal oscillator, 60
62 is a waveform shaping circuit that shapes the signal from the frequency dividing circuit 30; 64 is a drive circuit that drives the motor 66;
38 is a wheel train driven by the motor 66.

Reference numeral 40 denotes a reference mechanism, which turns on when the hour is on the hour due to the movement of the wheel train 38.

Reference numeral 42 designates a timing control circuit which, when the reference mechanism 40 is turned on, enables the above-mentioned melody address counter 16 and envelope address counter 20, and also activates the envelope frequency dividing circuit 44 and the scale frequency dividing circuit 46. It is something.

In this way, the envelope frequency divider circuit 44 and the scale frequency divider circuit 4
6 is activated, the envelope address counter 20 and melody address counter 16 are activated and read envelope data and waveform data from the melody volume ROM 18 and melody waveform ROM 14, respectively.

(''l) The data read out from the melody volume ROM 18 is converted into a stain pressure output by the voltage ladder 22, and when the switch Sn, which is turned ON when adding an envelope, is turned ON, the voltage ladder is changed to the current ladder 24. 22, a reference voltage is applied.

Further, the data read from the melody waveform ROM 14 is applied to the current ladder 24 to which the reference voltage from the voltage ladder 22 is applied. , is converted to

Electric construction output from this current ladder 24. , is resistance 26
The current-voltage is converted through the amplifier 48 and applied to the amplifier 48,
This amplifier 48 drives a speaker 50 to generate a hitting sound when an empress is applied. Such reading of data from the melody volume ROM 18 is performed for each time-beating operation, and each time a reading is performed, a nox signal is sent from the envelope address counter 20 to the number-of-strokes counter 52. Output.

The number of strokes counter 52 is the envelope address counter 2.
Signals from 0 are counted, and this count (12) value is compared with the count value of the counting counter 54 in a matching circuit 56.

The contents of the counting counter 54 are determined in advance by operating the counting control circuit 58 in response to the operation of the counting switch 60.

When the coincidence circuit 56 outputs a coincidence signal, the timing control circuit 4
2 stops all of the melody address counter 16, envelope address counter 20, envelope frequency division circuit 44, and scale frequency division circuit 46. The time control circuit 42 then outputs a pulse signal to the counting control circuit 58,
In response to this signal, the counting control circuit 58 adds 1 to the contents of the counting counter 54 in preparation for the next hour on the hour, and the counting operation ends.

The death beat sound obtained in this way is a melody waveform ROM.
Melody waveform stored in 14 and melody volume ROM
18, and it is possible to obtain a tone that is very close to natural. Note that the application to an electronic clock is just one example, and the electronic sound generation of the present invention The circuit can also be used in musical instruments and the like.

According to the present invention, since the envelope can be added to the melody inside the IC, no parts are required externally to the IC, and the area occupied by the circuit can be reduced, and the number of parts can be reduced. It is also possible to reduce the system cost by improving assembly workability.In addition, since the envelope generating section in the present invention is composed only of a combination of a resistor network and a switch element, it can be used at a voltage as low as 1.5 V. Therefore, it can be widely used in small portable devices.

Furthermore, the shape of the envelope can be freely changed simply by changing the stored contents of the memory, and a wide range of sounds from the natural world, such as bird calls and the sound of waves, to the sounds of musical instruments such as the piano, can be generated using the same circuit. I can do it.

What's more, the rise of the sound can be made steeper than with the CR method, and the feel of the hitting sound can be particularly improved.

In this way, the present invention is based on two ODA projects.
5) To provide an electronic sound generation circuit configured so that the following do not adversely affect each other.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a device using a conventional envelope addition method, FIG. 2 is a diagram showing a conventional example of the envelope generating circuit shown in FIG. 1, and FIG. Figure 4 is a diagram showing the characteristics of the voltage division ladder resistance type DA converter shown in Figure 3. Figure 5 is a diagram showing the equivalent circuit of the DA converter shown in Figure 4.
This figure is a characteristic explanatory diagram of the current adding ladder resistance type DA converter shown in FIG. 3, and FIG. 7 is a diagram showing an equivalent circuit of the DA converter shown in FIG. 3. 14...Melody waveform ROM. 16...Melody address counter, 18...Melody volume ROM. 20...Envelope address counter, 22...
Voltage division ladder resistance type DA converter, 24... Current addition ladder resistance type DA converter. 6 () 2, ``three

Claims (1)

[Scope of Claims] A melody waveform ROM in which melody waveform data is stored as a digital signal; A melody volume ROM in which melody volume data is stored in a digital signal; An address counter for reading data from both ROMs; a first ODA converter that converts data from the volume ROM into an analog signal; a second ODA converter that uses the signal from the first ODA converter as a reference input and converts data from the melody waveform ROM into an analog signal; and an output of the second ODA converter. 1. An electronic sound generation circuit comprising: a sound generation circuit that generates a sound; and a second ODA converter comprising a ladder resistance type DA converter with a constant input resistance.