JP5541113B2 - DA converter using delta-sigma type modulation circuit, DA conversion method, and program - Google Patents

Description

  The present invention relates to a DA converter using a delta-sigma modulation circuit, a DA conversion method, and a program.

  Circuit elements (transistors, capacitors, resistors, etc.) on LSI (Large Scale Integration) vary in characteristics due to size variations due to processes. Especially in an analog circuit, characteristic deterioration due to this variation is a serious problem. For example, in a DA converter using a delta-sigma type modulation circuit, feedback noise potentially possessed by the delta-sigma type modulation circuit is amplified non-linearly due to element variations, which causes a problem in hearing in audio signal processing. May appear in the output. Conventionally, a method of applying a dither signal has been used to solve this problem.

  FIG. 6 is a diagram showing a circuit configuration of a DA converter using a conventional delta-sigma modulation circuit. As shown in FIG. 6, a conventional DA converter using a delta-sigma modulation circuit includes an adder 67 for adding a digital input signal A and a DC dither signal E, a delta-sigma modulation circuit 61, and the delta The D / A converter analog circuit 62 is connected to the subsequent stage of the sigma modulation circuit 61.

  In the DA converter using the conventional digital sigma type modulation circuit, the digital input signal A and the DC dither signal are added by the adder 67, and the added signal is input to the delta sigma type modulation circuit 61. The signal modulated by the delta-sigma modulation circuit 61 is input to a D / A converter analog circuit 62, and the digital input signal A is converted into an analog output signal B and output.

  Here, the DA converter using the delta sigma type modulation circuit has a delta sigma type modulation circuit when the input signal transitions from a state where the input signal is not zero (no signal) to a state where the input signal is zero (no signal). There is a problem that a residual signal is generated in 61 and a signal is output even though the input signal is no signal, which becomes noise.

  As a countermeasure against this noise, conventionally, the DC dither signal E is added to the digital input signal A of the D / A converter using the delta-sigma type modulation circuit, and the noise due to this residual signal is out of the use frequency band. The method of moving was taken.

  That is, in the DA converter using this digital sigma type modulation circuit, the DC dither signal E is added to the digital input signal A by the adder 67 provided in the preceding stage of the delta sigma type modulation circuit 61. This signal is converted into a 1-bit (or multiple-bit) PDM (Pulse Density Modulation) signal by a delta-sigma modulation circuit 61, and a D / A converter analog circuit 62 (analog low-pass filter). ) Is output as an analog output signal B.

  Here, the DC dither signal E is a kind of noise that is generated from pseudo noise, and is an erroneous signal / data that is intentionally added to the sample data in order to minimize the quantization error. This signal is commonly used when processing digital acoustic data.

  However, in the circuit configuration of the DA converter using the above-described conventional digital sigma modulation circuit, the DC dither signal E is added to the digital input signal A, so that there is a problem that a DC offset voltage is generated in the analog output signal B. It was.

  Therefore, the present invention has been made in view of the above problems. Even when the digital input signal A becomes zero (no signal), the delta-sigma modulation circuit 61 uses an AC dither signal with a biased amplitude. DA converter using a delta-sigma type modulation circuit capable of suppressing noise generated due to element variations in the output delta-sigma type modulation circuit 61 by reducing the residual signal in the signal, a DA conversion method, and The purpose is to provide a program.

  In order to solve the above problems, a DA converter using a delta-sigma modulation circuit according to the present invention is a DA converter using a delta-sigma modulation circuit, and an input signal to an input stage of the delta-sigma modulation circuit Input signal detecting means for detecting the presence or absence of the signal, first potential information detecting means for detecting the potential information of the output signal output from the output stage of the delta-sigma modulation circuit, and the first potential information detecting means First potential information output means for outputting first potential information of the output signal based on detected potential information, dither signal output means for outputting two types of dither signals, and output by the dither signal output means Selecting means for selectively selecting one of the two types of dither signals from the two types of dither signals. The selecting means is provided by the input signal detecting means. When it is detected that the input signal is in a no-signal state, either one of the two types of dither signals is selectively selected according to the output result of the first potential information. And the alternatively selected dither signal is applied to the input stage.

  In the DA converter using the delta-sigma modulation circuit according to the present invention, the two types of dither signals are signals having an amplitude having a bias on a positive electrode side or a negative electrode side, and the selecting means includes the first converter If the potential information of 1 is a positive potential, a signal having an amplitude having a bias on the negative electrode side is obtained, and if the first potential information is a negative potential, a signal having an amplitude having a bias on the positive electrode side is obtained. Each is selected alternatively.

  Further, the DA converter using the delta sigma type modulation circuit in the present invention is a DA converter using the delta sigma type modulation circuit, and the output stage of the delta sigma type modulation circuit includes a D / A converter circuit. An input stage is connected, input signal detection means for detecting the presence or absence of an input signal to the input stage of the delta-sigma modulation circuit, and potential information of the output signal output from the output stage of the D / A converter circuit A second potential information detecting means for detecting; a comparing means for comparing the potential information detected by the second potential information detecting means with a zero reference potential; and a second comparison result of the comparing means. Second potential information output means for outputting potential information, dither signal output means for outputting two types of dither signals, and the two types of dither signal output means output by the dither signal output means Selecting means for selectively selecting one of the dither signals from the dither signal, and the selecting means detects that the input signal is in a no-signal state by the input signal detecting means. Then, in response to the output result of the second potential information, either one of the two types of dither signals is alternatively selected, and the one selected alternatively A dither signal is applied to the input stage.

  In the DA converter using the delta-sigma modulation circuit according to the present invention, the two types of dither signals are signals having an amplitude having a bias on a positive electrode side or a negative electrode side, and the selecting means includes the first converter If the potential information of 2 is a positive potential, a signal having an amplitude having a bias on the negative electrode side is obtained. If the second potential information is a negative potential, a signal having an amplitude having a bias on the positive electrode side is obtained. Each is selected alternatively.

  The DA conversion method using the delta sigma type modulation circuit in the present invention is a DA conversion method using the delta sigma type modulation circuit, and detects the presence or absence of an input signal to the input stage of the delta sigma type modulation circuit. A step of detecting potential information of an output signal output from an output stage of the delta-sigma modulation circuit; and a first of the output signals based on the potential information detected by the step of detecting the potential information. One of the two types of dither signals output by the step of outputting the potential information, the step of outputting the two types of dither signals, and the step of outputting the dither signals is selected. A step of selecting the input signal when the input signal is detected to be in a no-signal state by the step of detecting the presence or absence of the input signal. Corresponding to the output result of the step of outputting the first potential information, one of the two types of dither signals is alternatively selected, and the one of the two types is selected. Applying a dither signal to the input stage.

  Further, the DA conversion method using the delta sigma type modulation circuit in the present invention is a DA conversion method using the delta sigma type modulation circuit, and a D / A converter circuit is provided at the output stage of the delta sigma type modulation circuit. A step of detecting presence / absence of an input signal to an input stage of the delta-sigma modulation circuit, a step of detecting potential information of an output signal output from the output stage of the D / A converter circuit; A step of comparing the potential information detected by the step of detecting potential information with a zero reference potential; a step of outputting second potential information as a comparison result of the step of performing the comparison; and two types of dithers One of the dither signals is alternatively selected from the two types of dither signals output by the signal output step and the dither signal output step. And the step of selecting outputs the second potential information when the input signal is detected to be in the no-signal state by detecting the presence or absence of the input signal. Corresponding to the result, either one of the two types of dither signals is alternatively selected, and the alternatively selected dither signal is applied to the input stage. And a process.

  A program for causing a computer that controls a DA converter using a delta-sigma modulation circuit to perform DA conversion using the delta-sigma modulation circuit determines whether or not there is an input signal to the input stage of the delta-sigma modulation circuit. A detection process; a process for detecting potential information of an output signal output from an output stage of the delta-sigma modulation circuit; and a process for detecting the potential information based on the potential information detected by the process for detecting the potential information. One of the two types of dither signals output from the processing of outputting the first potential information, the processing of outputting the two types of dither signals, and the processing of outputting the dither signals. Alternatively, the input signal is in a non-signal state by the process of detecting the presence or absence of the input signal. When detected, one of the two types of dither signals is alternatively selected from the two types of dither signals in accordance with the output result of the process of outputting the first potential information. And applying a selected dither signal to the input stage.

  A program for causing a computer that controls a DA converter using a delta-sigma modulation circuit to perform DA conversion using the delta-sigma modulation circuit is a D / A converter at the output stage of the delta-sigma modulation circuit. A circuit is connected, a process for detecting the presence or absence of an input signal to the input stage of the delta-sigma modulation circuit, and a process for detecting potential information of an output signal output from the output stage of the D / A converter circuit A process for comparing the potential information detected by the process for detecting the potential information with a zero reference potential; a process for outputting second potential information as a comparison result of the process for performing the comparison; and two types Any one of the two types of dither signals output by the process of outputting the dither signal and the process of outputting the dither signal. And selecting the second potential information when the input signal is detected to be non-signaled by the process of detecting the presence or absence of the input signal. Corresponding to the output result of the processing to be output, either one of the two types of dither signals is selectively selected, and the alternatively selected dither signal is selected as the input stage. And a process to be applied to.

  According to the present invention, it is possible to suppress the output noise of the delta sigma modulation circuit when there is no signal, and the offset voltage of the output of the D / A converter analog circuit using the delta sigma modulation circuit when there is no signal Can be suppressed.

It is a figure which shows the circuit structure of the DA converter using the delta-sigma type | mold modulation circuit in embodiment of this invention. It is a figure which shows the circuit structure of the DA converter using the delta-sigma type | mold modulation circuit in other embodiment of this invention. It is a figure which shows the example of a waveform of the deflection | deviation AC dither signal in this invention. It is a flowchart explaining operation | movement of the DA converter using the delta-sigma type | mold modulation circuit in embodiment of this invention. It is a flowchart explaining operation | movement of the DA converter using the delta-sigma type | mold modulation circuit in other embodiment of this invention. It is a figure which shows the circuit structure of the DA converter using the conventional delta-sigma type | mold modulation circuit.

  Next, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified thru | or abbreviate | omitted suitably. The present invention reduces the residual signal in the delta-sigma modulation circuit by using an AC dither signal whose amplitude is biased to one potential even when the digital input signal becomes zero (no signal). It is characterized by suppressing feedback noise in the output delta-sigma modulation circuit.

  FIG. 1 shows a circuit configuration of a DA converter using a delta-sigma modulation circuit according to an embodiment of the present invention. In FIG. 1, a DA converter using a delta-sigma modulation circuit is connected to an output stage of a no-signal detector 15, an adder 17, a delta-sigma modulation circuit 11, and a delta-sigma modulation circuit 11. The D / A converter analog circuit 12, the integrating circuit 13, the selector 14, and the AND circuit 16 are configured, and the digital signal A input from the input stage of the delta-sigma modulation circuit 11 is converted into a D / A converter. By converting from the output stage of the analog circuit to the analog output signal B, a D / A converter using a delta-sigma modulation circuit is configured.

  The no-signal detection circuit 15 outputs an “H (High)” signal when detecting that the digital signal A inputted from the input stage of the delta-sigma modulation circuit 11 becomes zero (no signal). The integrating circuit 13 integrates the output signal of the delta-sigma modulation circuit 11, detects potential information (positive electrode or negative electrode) of the output signal, and integrates the detected potential information, specifically. The sign information indicating whether the detected potential is on the positive electrode side or the negative electrode side is transmitted to the selector 14.

  The selector 14 has a signal C (hereinafter also referred to as a “negative deflection AC dither signal”) having an amplitude with a bias on the negative side and a signal D (hereinafter referred to as “positive deflection” with a bias on the positive side). 2 types of signals are also input, and one of the signals is selected in accordance with the code information transmitted from the integrating circuit 13. When one of the signals is selected, the selected deflection AC dither signal is output, and at the same time, the “H (High)” signal is output.

  The AND circuit 16 outputs the deflection AC dither signal selected by the selector 14 to the adder 17 only when the output of the no-signal detection circuit 15 is “H” and the output of the selector 14 is “H”. Output.

  The adder 17 adds the digital input signal A and the deflection AC dither signal output from the AND circuit 16 and inputs the addition result to the delta sigma modulation circuit 11.

  Here, the deflection AC dither signal will be described. FIG. 3 is a diagram showing a waveform example of the deflection AC dither signal in the present invention. In FIG. 3, a rectangular wave will be described as an example, but it is needless to say that not only a rectangular wave but also other waveforms such as a sine wave, a triangular wave, and a pulse wave may be used.

  In FIG. 3, (a) shows a negative deflection AC dither signal having an amplitude with a bias on the negative side, and (b) shows a positive deflection AC dither signal with an amplitude with a bias on the positive side. The deflection AC dither signal is a signal in which the positive-side amplitude and the negative-side amplitude are asymmetric with respect to the time axis.

  For example, (a) in the case of a negative deflection AC dither signal, the amplitude on the positive side is asymmetric with +10 and the amplitude on the negative side is -11, and as this signal is successively input, −1, − 2, −3,..., −n (where n is a natural number), and so on. Is input to the input signal, it works to bring the input signal closer to the negative electrode side.

  Conversely, for (b) a positive deflection AC dither signal, the absolute value of the amplitude difference (in this case, “1”), such as +1, +2, +3,..., + N (where n is a natural number). ) Are accumulated and increased one after another, and when this signal is input to the input signal, it works to bring the input signal closer to the positive electrode side.

  Next, the operation of the DA converter using the delta-sigma modulation circuit in the embodiment of the present invention will be described. FIG. 4 is a flowchart for explaining the operation of the DA converter using the delta-sigma modulation circuit in the embodiment of the present invention. When the DA conversion using the delta-sigma modulation circuit is started, the no-signal detection circuit 15 determines whether or not the digital input signal A is in the no-signal state (step (hereinafter simply referred to as “S”). .) 41).

  In S41, if the digital input signal A is in the no signal state (S41: Y), the process proceeds to S42. If the digital input signal A is not in the no signal state (S41: N), the digital input signal A is in the no signal state. Wait until The no-signal detection circuit 15 outputs an “H” signal to the AND circuit 16 when detecting that the digital input signal A is in the no-signal state.

  In S42, the integration circuit 13 integrates the output signal of the delta-sigma modulation circuit 11, and detects the potential information of this output signal. Then, it is determined whether or not the potential of the output signal of the delta-sigma modulation circuit 11 is a positive potential.

  In S42, when the output potential of the delta-sigma modulation circuit 11 is a positive potential (S42: Y), the process proceeds to S44, and when it is not a positive potential, that is, when it is a negative potential (S42: N), S43 Migrate to

  When sign information indicating whether the output potential of the delta-sigma modulation circuit 11 is a positive potential or a negative potential is transmitted to the selector 14, if the sign information is a positive polarity, the selector 14 is connected to the negative deflection AC dither. The signal C is selected (S44), and if it is negative, the selector 14 selects the positive deflection AC dither signal D (S45).

  The selector 14 outputs an “H” signal and also outputs the selected negative deflection AC dither signal C or positive deflection AC dither signal D to the AND circuit 16. In the AND circuit 16, the no-signal detection circuit 15 Since the “H” signal is input, a negative deflection AC dither signal or a positive deflection AC dither signal is input to the adder 17 (S46, S47).

  Finally, the digital input signal A and the negative deflection AC dither signal C or the positive deflection AC dither signal D are added in the adder 17 and the added signal is input to the delta-sigma modulation circuit 11 (S48). ), The output of the delta-sigma modulation circuit 11 is operated to approach zero, and the output noise is suppressed.

Next, another embodiment of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified thru | or abbreviate | omitted suitably.
FIG. 2 is a diagram showing a circuit configuration of a DA converter using a delta-sigma modulation circuit according to another embodiment of the present invention.

  1 differs from the embodiment of FIG. 1 in that the potential of the analog output signal B, which is the output signal of the D / A converter analog circuit 12 connected to the output stage of the delta-sigma modulation circuit 11, and the zero output reference potential E The comparator 18 compares the potential of the analog output signal B, which is the output signal of the D / A converter analog circuit 12, with the zero output reference potential E, and is either a positive potential or a negative potential. The code information, such as whether or not there is, is transmitted to the selector 14, and the circuit configuration of the other parts is the same as that of the embodiment in FIG.

  Next, the operation of the DA converter using the delta-sigma modulation circuit according to another embodiment of the present invention will be described. FIG. 5 is a flowchart for explaining the operation of a DA converter using a delta-sigma modulation circuit according to another embodiment of the present invention. When the DA conversion using the delta-sigma modulation circuit is started, the no-signal detection circuit 15 determines whether or not the digital input signal A is in the no-signal state (S51). This is the same as the operation (S41).

  In S52, the output potential of the analog output signal B, which is the output signal of the D / A converter analog circuit 12, is acquired. In S53, the comparator 18 acquires the output voltage of the acquired analog output signal B and zero output. Comparison with the reference voltage E is performed.

  In S54, it is determined whether or not the output potential of the D / A converter analog circuit 12 is a positive potential. In S54, if the output potential of the D / A converter analog circuit 12 is a positive potential, that is, if the output of the comparator 18 is a positive potential (S54: Y), the process proceeds to S56, and if it is not a positive potential, When the potential is negative (S54: N), the process proceeds to S55.

  When sign information indicating whether the output potential of the D / A converter analog circuit 12 is a positive potential or a negative potential is transmitted from the comparator 18 to the selector 14, if the sign information is positive, the selector 14 The negative deflection AC dither signal C is selected (S56). If it is negative, the selector 14 selects the positive deflection AC dither signal D (S57). Hereinafter, the processing of S58 to S60 is the same as the processing of S46 to S48 in FIG. By performing each processing described above, the output of the D / A converter analog circuit 12 is operated so as to be close to zero, so that the DC offset voltage of the output of the D / A converter analog circuit 12 can be suppressed. It becomes.

  Each process of the operation of the DA converter using the delta sigma type modulation circuit shown in FIG. 4 and FIG. 5 described in the operation of the embodiment described above and the operation of the other embodiment is performed as a delta sigma type modulation circuit. A control unit (CPU (Central Processing Unit)) (not shown) that controls the operation of the DA converter using a computer is converted into a computer-readable program stored in a ROM (Read Only Memory), a RAM (Random Access Memory), or the like. It is configured to control based on.

  The present invention has been described above by the preferred embodiments of the present invention. While the invention has been described with reference to specific embodiments thereof, various modifications and changes can be made to these embodiments without departing from the broader spirit and scope of the invention as defined in the claims. is there.

11 Delta-sigma modulation circuit 12 DA converter analog circuit 13 Integration circuit 14 Selector 15 No signal detection circuit 16 AND circuit 17 Adder 18 Comparator A Digital input signal B Analog output signal C Negative deflection AC dither signal D Positive deflection AC dither signal E Zero output reference voltage

JP 2009-182899 A

Claims (8)

A DA converter using a delta-sigma modulation circuit,
Input signal detection means for detecting the presence or absence of an input signal to the input stage of the delta-sigma modulation circuit;
First potential information detection means for detecting potential information of an output signal output from an output stage of the delta-sigma modulation circuit;
First potential information output means for outputting first potential information of the output signal based on potential information detected by the first potential information detection means;
Dither signal output means for outputting two types of dither signals;
Selecting means for alternatively selecting any one of the two types of dither signals output by the dither signal output means;
When the input signal detecting means detects that the input signal is in a no-signal state, the selecting means selects one of the two types of dither signals in accordance with the output result of the first potential information. A D / A conversion using a delta-sigma modulation circuit, wherein any one type of dither signal is selectively selected, and the alternatively selected dither signal is applied to the input stage vessel.   The two types of dither signals are signals having an amplitude with a bias on the positive electrode side or the negative electrode side, and the selection means has a bias on the negative electrode side if the first potential information is a positive potential. 2. The signal having an amplitude is alternatively selected when the first potential information is a negative potential and the signal having an amplitude biased toward the positive electrode is selected. DA converter using delta-sigma type modulation circuit. A DA converter using a delta-sigma modulation circuit,
The input stage of the D / A converter circuit is connected to the output stage of the delta-sigma modulation circuit,
Input signal detection means for detecting the presence or absence of an input signal to the input stage of the delta-sigma modulation circuit;
Second potential information detecting means for detecting potential information of an output signal output from the output stage of the D / A converter circuit;
Comparison means for comparing the potential information detected by the second potential information detection means with a zero reference potential;
Second potential information output means for outputting second potential information as a comparison result of the comparison means;
Dither signal output means for outputting two types of dither signals;
Selecting means for alternatively selecting any one of the two types of dither signals output by the dither signal output means;
When the input signal detecting means detects that the input signal is in the no-signal state, the selecting means selects one of the two types of dither signals in accordance with the output result of the second potential information. A D / A conversion using a delta-sigma modulation circuit, wherein any one type of dither signal is selectively selected, and the alternatively selected dither signal is applied to the input stage vessel.   The two types of dither signals are signals having an amplitude with a bias on the positive electrode side or the negative electrode side, and the selection means has a bias on the negative electrode side if the second potential information is a positive potential. 4. The signal having an amplitude is alternatively selected when the second potential information is a negative potential, and a signal having an amplitude having a bias on the positive electrode side is selected. 5. DA converter using delta-sigma type modulation circuit. A DA conversion method using a delta-sigma modulation circuit,
Detecting the presence or absence of an input signal to the input stage of the delta-sigma modulation circuit;
Detecting potential information of an output signal output from an output stage of the delta-sigma modulation circuit;
Outputting first potential information of the output signal based on the potential information detected by the step of detecting the potential information;
Outputting two types of dither signals;
Selectively selecting any one type of dither signal from the two types of dither signals output in the step of outputting the dither signal,
The selecting step corresponds to the output result of the step of outputting the first potential information when it is detected that the input signal is in the no-signal state by detecting the presence or absence of the input signal, Alternatively selecting any one of the two types of dither signals and applying the alternatively selected dither signal to the input stage. A DA conversion method using a characteristic delta-sigma modulation circuit. A DA conversion method using a delta-sigma modulation circuit,
A D / A converter circuit is connected to the output stage of the delta-sigma modulation circuit,
Detecting the presence or absence of an input signal to the input stage of the delta-sigma modulation circuit;
Detecting potential information of an output signal output from an output stage of the D / A converter circuit;
Comparing the potential information detected by the step of detecting the potential information with a zero reference potential;
Outputting second potential information that is a comparison result of the step of performing the comparison;
Outputting two types of dither signals;
Selectively selecting any one type of dither signal from the two types of dither signals output in the step of outputting the dither signal,
The selecting step corresponds to the output result of the step of outputting the second potential information when it is detected that the input signal is in a no-signal state by detecting the presence or absence of the input signal. Alternatively selecting any one of the two types of dither signals and applying the alternatively selected dither signal to the input stage. A DA conversion method using a characteristic delta-sigma modulation circuit. A program for causing a computer that controls a DA converter using a delta-sigma modulation circuit to perform DA conversion using a delta-sigma modulation circuit,
A process for detecting the presence or absence of an input signal to the input stage of the delta-sigma modulation circuit;
Processing for detecting potential information of an output signal output from an output stage of the delta-sigma modulation circuit;
Processing for outputting first potential information of the output signal based on the potential information detected by the processing for detecting the potential information;
Processing to output two types of dither signals;
A process of alternatively selecting one of the two types of dither signals output by the process of outputting the dither signal,
The selecting process corresponds to the output result of the process of outputting the first potential information when the input signal is detected to be in a no-signal state by the process of detecting the presence or absence of the input signal, A process of alternatively selecting any one of the two types of dither signals and applying the alternatively selected dither signal to the input stage. A featured program. A program for causing a computer that controls a DA converter using a delta-sigma modulation circuit to perform DA conversion using a delta-sigma modulation circuit,
A D / A converter circuit is connected to the output stage of the delta-sigma modulation circuit,
A process for detecting the presence or absence of an input signal to the input stage of the delta-sigma modulation circuit;
Processing for detecting potential information of an output signal output from the output stage of the D / A converter circuit;
A process of comparing the potential information detected by the process of detecting the potential information with a zero reference potential;
A process of outputting second potential information that is a comparison result of the process of performing the comparison;
Processing to output two types of dither signals;
A process of alternatively selecting one of the two types of dither signals output by the process of outputting the dither signal,
The selecting process corresponds to an output result of the process of outputting the second potential information when it is detected that the input signal is in a no-signal state by the process of detecting the presence or absence of the input signal. A process of alternatively selecting any one of the two types of dither signals and applying the alternatively selected dither signal to the input stage. A featured program.

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