JP2001292031A - One-chip microcomputer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems of a conventional one-chip microcomputer that has increased the cost because mechanical adjustment of an external damping resistor requires time and man-hours where the mechanical adjustment for each oscillator is used to eliminate harmonic noise and cannot execute harmonic correction including dispersion in the oscillation characteristic of each LSI. SOLUTION: This one-chip microcomputer, in which, a variable damping resistor with built in chip is connected to an output terminal of an oscillation inverter of the microcomputer having a self-excited oscillation function, is provided with a harmonic noise detection section that detects undesired radiation noise with an oscillation frequency, a correction value generating circuit, and a harmonic correction discrimination circuit that self-discriminates whether or not the correction value automatically calculated by the hardware is correctly set, is characterized in that it has a function of optimizing the resistance of the variable damping resistor with respect to the harmonic noise.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to reduction of unnecessary radiation noise by correcting harmonic noise due to self-excited oscillation in a MOS type one-chip microcomputer.

[0002]

2. Description of the Related Art In recent years, MOS-type one-chip microcomputers often have a self-excited oscillation configuration on the assumption that a crystal oscillator and a ceramic lock oscillator are externally provided as a system clock source.

FIG. 2 shows a block diagram of a conventional CERALOCK self-excited oscillation circuit.

In FIG. 2, reference numeral 9 denotes a MOS type one-chip microcomputer. The external capacitance 1 (Cin) and the external capacitance 2 (Cout), and the external damping resistor 6 are connected to the oscillation input terminal 3 at both ends of the ceramic lock oscillator 5 and the oscillation. Connected to the output terminal 4 and the oscillation input terminal 3 and the oscillation output terminal 4
Has a feedback resistor 8 and an oscillation inverter 7 connected in parallel to form an oscillation portion. The microcomputer unit 9 other than the oscillation unit receives the system clock 1 from the oscillation unit.
1 is operating.

[0005] The operation of the Ceralock oscillation circuit configured as described above will be described below.

The external capacitance 1 (Cin) and the external capacitance 2 (Cou
t), and manually adjusting the resistance value of the damping resistor to manually set the optimum load capacity and damping resistance value that match the resonance frequency of the external CERALOCK, and the CERALOCK oscillator 5 and the oscillation input at both ends. Feedback resistor 8 connected in parallel with terminal 3 and oscillation output terminal 4
And the oscillation inverter 7, a self-excited oscillation operation can be performed.

[0007] The basic configuration of the oscillation circuit is a configuration in which an amplification system and a feedback system are combined, and converts externally applied electric energy into an oscillation waveform close to a sine wave of a specific frequency. As an element of the damping resistor, it is used to oscillate with an oscillation element having a gain over a wide band inserted for the purpose of lowering the loop gain, and has an effect of suppressing abnormal oscillation at a spurious frequency.

Since the oscillation phenomenon cannot be a perfect sine wave due to the use of the non-linear region of the transistor, harmonic distortion of 2, 3, 4,... N times the fundamental frequency is generated.

[0009]

In the above-mentioned conventional configuration, the damping resistance is adjusted for each CERALOCK oscillator to be used by the impedance of the CERALOCK oscillator itself, and the beat is mixed into another frequency band to form a beat. It was necessary to remove harmonic distortion.

Therefore, in an actual production line, in order to set an appropriate external damping resistance, the above-mentioned disadvantage is adjusted by mechanical adjustment. In the adjustment of frequency bands represented by TV and radio (especially FM bands), beat noise in the frequency band of a key station must be pinpointed for harmonic noise correction to reduce the beat noise.

[0011] However, this mechanical adjustment requires time and manpower to increase the cost, and it is not possible to perform harmonic correction including variations in the oscillation characteristics of individual LSIs. However, there is a drawback in that, when there is a variation in manufacturing, beat noise is put on the frequency band of the key station, and noise is generated.

An object of the present invention is to solve the above-mentioned conventional problems, and to provide an accurate and efficient harmonic correction for each LSI and to reduce unnecessary radiation noise.

[0013]

In order to achieve this object, a one-chip microcomputer according to the first aspect of the present invention is provided with an output terminal of an oscillation inverter of a microcomputer having a self-excited oscillation function. The chip has a built-in variable damping resistor, and has a register that stores a correction value automatically calculated by hardware using a harmonic noise detection unit and a correction value generation circuit that generates unwanted radiation noise at the oscillation frequency. A function that can self-determine whether the correction value is set correctly by the wave correction judgment circuit and control the multi-value data of the trimming register to optimize the resistance value of the variable damping resistor against harmonic noise. have.

[0014] With this configuration, even if the oscillation characteristics vary among the individual LSIs, the harmonic noise correction can be absorbed by making it possible to perform self-determination, and further, there is no mechanical adjustment on the production line of the set, and the production line can be eliminated. It is easy to digitize and can greatly improve efficiency.

In the one-chip microcomputer according to the second aspect of the present invention, a variable damping resistor built in the chip is connected to an output terminal of an oscillation inverter of the microcomputer having a self-excited oscillation function, and the oscillation frequency is controlled. A register that stores the correction value automatically calculated by hardware by the harmonic noise detection unit and the correction value generation circuit that becomes unnecessary radiation noise, and that the correction value is set correctly by the harmonic correction determination circuit The CPU has a function of performing wait control on the CPU to prevent a malfunction if a non-coincidence determination occurs after a self-determination and a once-coincidence determination.

[0016]

(Embodiment 1) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a simplified one-chip microcomputer according to the first embodiment of the present invention, and, similarly to the conventional embodiment, an external capacitor 1 (Cin) and an external capacitor 1 (Cin). A capacitor 2 (Cout) is connected to the oscillation input terminal 3 and the oscillation output terminal 4 at both ends of the ceramic lock oscillator 5. The oscillation input terminal 3 and the oscillation output terminal 4 at both ends are provided with an oscillation circuit including a feedback resistor 8 and an oscillation inverter 7 connected in parallel.

In this case, the one-chip microcomputer determines the frequency of the source oscillation, determines a harmonic noise band generated at n times the source oscillation, and stores a plurality of the excluded frequency bands stored in advance. A harmonic component detection correction value generating circuit 26 that outputs harmonic correction data for harmonic noise with respect to the frequency and a harmonic correction register 20, between the oscillation output terminal 4 and the output of the oscillation inverter 7. Register 18 for trimming the variable damping resistor 13 connected in series to the
Is connected to

At this time, the one-chip microcomputer sends a μ-CO
From M9, while the correction determination enable signal 16 is connected as an input, the oscillation output signal 15, the system clock 1
1 as an input, outputs the trimming timing control signal 22 to the trimming register 18 as an output, outputs an n-bit counter value as a comparison value with the value of the harmonic correction register 20. The correction value coincidence signal 21 here is connected as an input to the trimming register 18.

The built-in variable damping resistor Rdn 13 is a block in which a plurality of built-in elements having a plurality of resistance values are prepared, and is a circuit that can set an arbitrary resistance value by the trimming signal 23.

Next, the operation of the one-chip microcomputer according to the first embodiment will be described. for that reason,
Determination of the frequency of the source oscillation of the oscillation output signal over a wide range is performed as shown in FIG.

First, an enable area section is created by using the detection start signal 25, and the time of the judgment voltage C is calculated by using the edge of the system clock 11, and the frequency detection signal which is a delay signal of the judgment voltage D prepared in advance is used. 0 to
The data decoded up to n is converted into a logical signal as a source oscillation frequency. Immediately, in the harmonic noise band generated by n times, it is checked whether or not the frequency coincides with a plurality of frequencies in the exclusion frequency band stored in advance. Transfer to the wave correction register 20. If they do not match, the default correction data is transferred with no correction.

Next, the correction value is transferred to the trimming register. Here, the operation of the harmonic correction determination circuit 19 is started by the correction determination enable signal 16. As for a specific operation sequence, as shown in FIG. 4, in the enable section of the correction determination enable signal 16, the initial value of the trimming signal 23 for two cycles of the system clock 11 is set to 0, and the built-in variable damping resistor Rdn13 is set. Is turned off, and the operation is started without damping resistance. Then, at this time, for example, the trimming is activated two cycles later like the trimming timing control signal 22, and the variable damping resistor is set to an arbitrary value according to the set value. At this time, a plurality of analog counter signals having different delay values are provided, and the analog counter signals 1 to n hit by the judgment voltage B are converted into logic signals as the counter values. That is, by changing the impedance itself of the Ceralock oscillator due to a change in the damping resistance due to the correction data, it is possible to determine whether or not the resonance frequency has been shifted. Next, when the value of the harmonic correction determination counter matches the value of the harmonic correction register, the value of the trimming register is held and the damping resistance value is determined.

The trimming data is retained until the one-chip microcomputer 24 is initialized again, so that the damping resistance of the damping resistor Rdn13 is kept constant. This is because the built-in variable damping resistor Rdn13 having an arbitrary resistance value is connected to the oscillation input terminal 3 and the oscillation output terminal 4, so that the oscillation input terminal 3 and the oscillation output terminal 4 are optimally damped by harmonic correction. This means that the resistance has been set and the resonance frequency has been changed, and a shift in the peak frequency due to the peak current factor has occurred, and beat noise can be avoided.

(Embodiment 2) In FIG. 5 of a one-chip microcomputer according to Embodiment 2, an abnormal oscillation weight control circuit 27 and a CPU weight control signal 28 are added to FIG. Is the same as FIG.

The operation of the one-chip microcomputer different from the first embodiment will be described.

As described in the first embodiment, the resistance value of the damping resistor Rdn13 is constant after the one-chip microcomputer at this time performs the harmonic correction determination. At this time, the value of the harmonic correction register 20 and the value converted into a logical signal by the harmonic correction determination circuit 19 match.

However, when an abnormal oscillation frequency, which is unnecessary radiation noise from the outside, enters the self-excited oscillation circuit,
The one-chip microcomputer itself malfunctions due to interference of the abnormal oscillation frequency.

According to the configuration of the second embodiment, when an abnormal oscillation frequency enters the self-excited oscillation circuit, the value of the harmonic correction register 20 and the value converted into a logical signal by the harmonic correction determination circuit 19 are used. Are not the same.

Therefore, when the value of the harmonic correction register 20 and the value converted into a logical signal by the harmonic correction determination circuit 19 after the harmonic correction match, a mismatch occurs, which is called abnormal oscillation interference. A determination is made, a CPU wait control signal 28 is input from the abnormal oscillation wait control circuit 27 to the CPU, and the CPU is shifted to a wait state. When abnormal oscillation frequency noise is input, the operation is performed by a non-operation instruction. , The wait state is set, and the μ-COM 9 prevents malfunction due to interference of the abnormal oscillation frequency. afterwards,
Again, until the value of the harmonic correction register 20 and the value converted into a logical signal by the harmonic correction determination circuit 19 match, μ-
COM9 is kept in the wait state.

That is, it is detected whether or not interference such as abnormal oscillation due to extraneous noise is occurring,
By preventing malfunction due to abnormal oscillation frequency interference,
A one-chip microcomputer with extremely high operation reliability can be provided.

[0032]

As described above, the LSI is provided with the function of automatically performing the harmonic correction by hardware and having the self-determination of the harmonic correction determination whether the set value is correctly corrected. The accuracy of individual harmonic correction can be improved and efficient correction can be performed, harmonic distortion in a specific frequency band can be suppressed, beat noise can be prevented from entering, and noise prevention can be compensated.

This compensates for variations in harmonic distortion due to delicate oscillation characteristics of each set and each microcomputer, and achieves high reliability of the set and achieves program adjustment in the production line, deviating from conventional complicated mechanical adjustment. This makes it possible to realize a one-chip microcomputer capable of achieving a very excellent oscillation frequency.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a microcomputer according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a conventional microcomputer.

FIG. 3 is a timing chart for detecting a reference frequency for harmonic noise detection.

FIG. 4 is an operation timing chart of a harmonic correction determination.

FIG. 5 is a schematic configuration diagram of a microcomputer according to a second embodiment of the present invention.

[Explanation of symbols]

1 External capacitance (Cin) 2 External capacitance (Cout) 3 Oscillation input terminal 4 Oscillation output terminal 5 Ceralock oscillator 6 External damping resistor 7 Oscillation inverter 8 Oscillation feedback resistor 9 Microcomputer other than oscillation 10 Conventional one-chip microcomputer 11 System Clock 12 Oscillation buffer 13 Variable damping resistor 14 Harmonic correction data 15 Oscillation output signal 16 Correction judgment enable signal 17 Harmonic detection data 18 Rimming register 19 Harmonic correction judgment circuit 20 Harmonic correction register 21 Correction value coincidence signal 22 Trimming timing Control signal 23 Trimming signal 24 One-chip microcomputer with built-in harmonic correction determination circuit 25 Detection start signal 26 Harmonic component detection correction value generation circuit 27 Abnormal oscillation wait control circuit 28 CPU Ito control signal

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5B062 CC01 DD10 HH01 JJ06 5J079 AA04 AA05 BA35 BA47 FA14 FA21 FA22 FB03 FB32 FB40 FB47 GA04 GA09 GA13 KA01

Claims (2)

[Claims] An output terminal of an oscillation inverter of a microcomputer having a self-excited oscillation function is connected to a built-in variable damping resistor, and a harmonic noise detector for generating unnecessary radiation noise of an oscillation frequency and a correction value generator. The circuit has a register that stores the correction value automatically calculated by hardware, and the harmonic correction judgment circuit determines whether the correction value is set correctly and controls the multi-value data of the trimming register. A one-chip microcomputer having a function of optimizing the resistance value of the variable damping resistor and enabling self-determination of harmonic noise correction. 2. A harmonic noise detector for generating unnecessary radiation noise of an oscillation frequency, wherein a variable damping resistor built in a chip is connected to an output terminal of an oscillation inverter of a microcomputer having a self-excited oscillation function, and a correction value is generated. The circuit has a register to store the correction value, and the harmonic correction determination circuit makes a self-determination as to whether the correction value is set correctly, and controls the multi-value data of the trimming register to control the variable damping resistor. The resistance value is optimized, and when the judgment does not match the optimized correction value once, it is immediately recognized as the entry of abnormal oscillation noise, and the CPU
A one-chip microcomputer having a function of performing a weight control on a microcomputer to prevent malfunction due to abnormal oscillation noise from other devices.