KR20010009551A - An apparatus of noise removal for microcomputer - Google Patents

Abstract

PURPOSE: An apparatus for removing a noise of a micom is provided to restrain the generation of the noise and prevent an error operation of the micom by using a digital filter designed for changing a reference clock signal according to a period of an interrupt signal in each interrupt input unit. CONSTITUTION: A switching unit has a switch(SW) for changing an operation/sleep mode of a washing machine, the first resistor(R1) and the first condenser(C1). The switching unit generates the first interrupt signal. A zero point detecting unit has a comparator(11) connected with reference resistors(R3,R4) at one input terminal and connected with an AC power and the fifth resistor(R5) at the other input terminal, a full-up resistor(R2) and the second condenser(C2). The zero point detecting unit detects a zero point in the AC power and performs a soft switching without an occurrence of an external noise for generating the second interrupt signal to restrain the occurrence of a noise. A frequency measuring unit counts a frequency of a sensing signal through a sensor(12) and generates a time measuring signal(TC1) for grasping a state of a current system. First to third digital filters(21-23) receive first and second interrupt signals and the time measuring signal(TC1) and removes a noise of each signal for preventing an error operation of a micom(M). A frequency generating unit(30) changes a frequency of a reference clock signal of first to third digital filters(21-23) according to a period of each interrupt signal. A microprocessor(40) performs an operation and a control for processing signals transmitted from the frequency generating unit(30) or first to third digital filters(21-23).

Description

An apparatus of noise removal for microcomputer

The present invention relates to a noise reduction device of a microcomputer applied to all devices using a microcomputer, and in particular, to prevent the congestion of the microcomputer by strong external noise in a product driving a motor or a heater using a large power. The present invention relates to a noise canceling device of a microcomputer, which is designed to change a frequency of a clock signal and prevents malfunction of the microcomputer as well as noise cancellation.

First, a microcomputer refers to a microcomputer, and refers to a microcomputer system centered on a CPU microprocessor configured as one or several LSIs. Next, the microcomputer's structure is usually composed of CPU, memory (ROM, RAM), input / output interface circuit (I / O section), input / output device, auxiliary memory device and control circuit, and they are called data (BUS). It is assembled by connecting with line and control signal line.

In order to improve the noise resistance of the microcomputer, as shown in FIG. 1, a RC low pass filter using a first resistor R1 and a first capacitor C1 outside the microcomputer M is used. LPF) is attached to block external high frequency noise. Reference numeral R2, which is not described in FIG. 1, refers to the second resistor.

That is, in the mechanical switch SW, as shown in (a) of FIG. 2, the chattering is forced to generate a severe signal. The chattering is a fine closed movement several times before the contact is closed in the electrical circuit. In the case of repeating will be generated in a swinging form. If a signal such as (a) of FIG. 2 generated by the switch (SW) passes the RC low pass filter composed of the first resistor (R1) and the first condenser (C1), noise as shown in (b) of FIG. After transformed into the removed signal is transmitted to the input terminal of the microcomputer (M).

At this time, the interrupt signal INTØ input through the RC low pass filter to the microcomputer M is a signal input to the interrupt port of the microcomputer M, and the analog RC filter having the frequency characteristic of FIG. When passing through, all periods above a specific frequency f _cut are cut off to remove noise. In particular, the RC filter should have appropriate R and C values depending on the magnitude of the signal or the period of the noise.

However, in order to remove noise from a signal input to the general port of the microcomputer M, chattering is detected through a software timer. As shown in FIG. 4, external input is prevented due to chattering by a software timer. Noise is removed from the pin data.

That is, as shown in (b) of FIG. 4, the software timer determines the sampling time by setting a constant value with internal software time, and then interrupt sampling of the software time is the same for the input signal of FIG. External noise may be removed by recognizing high only when the level is maintained ('ga' in FIG. 4B) or low.

However, in the conventional case, since the analog RC filter is used, there is a problem in that the precision and signal or noise cannot be detected accurately. In particular, since the accuracy of the capacity of the first condenser C1 is inferior, there is a problem that the configuration of the RC filter itself is difficult.

In addition, the microcomputer M may remove noise from the external input pin data by software, but the interrupt processing pin among the external input pins is a hardware device that cannot be processed by software. Therefore, when noise is generated in the interrupt processing pin data by external high frequency noise, a high frequency interrupt is automatically generated by hardware, which causes a malfunction of software. Therefore, anti-noise measures are urgently required for the pin data for interrupt processing of the microcomputer M.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof is to additionally use a digital filter designed to change a reference clock signal according to a cycle of an interrupt signal when each product is applied to each interrupt input of the microcomputer. Therefore, it is possible to suppress the occurrence of noise and at the same time provide a noise removing device of the microcomputer to prevent the malfunction of the microcomputer.

1 is a view showing the configuration of a noise removing device of the microcomputer according to the prior art,

FIG. 2 is a diagram illustrating signal waveforms at V1 and V2 of FIG. 1;

3 is a diagram illustrating frequency characteristics of an RC low pass filter, which is a component of FIG. 1;

4 is a diagram illustrating a method of removing noise through a software timer for an interrupt processing pin of a microcomputer according to the prior art;

5 is a block diagram showing a noise removing device of the microcomputer according to the present invention;

FIG. 6 is a diagram illustrating in detail a digital filter which is a part of FIG. 5;

7 is a view illustrating waveforms of signals input and output to the digital filter.

<Explanation of symbols about main part of drawing>

11: comparator 12: sensor

21, 22, 23: first to third digital filter 30: frequency generator

40: microprocessor M: microcomputer

SW: switch R1 to R5: resistance

C1, C2: capacitors D1 to D4: D-flip flop

NA1 to NA4: NAND GATE TC1: Time measurement signal

INTØ, INT1: First and second interrupt signal

According to a first aspect of the apparatus for removing noise of a microcomputer according to the present invention for solving the above problems, a switching unit for generating and outputting a first interrupt signal by performing a switching operation to change a mode of a system; A zero point detection unit for detecting a zero point of commercial power supplied from the outside and generating and outputting a second interrupt signal to prevent generation of noise; A frequency measuring unit generating and outputting a time measurement signal to count the frequency of the detection signal transmitted through the sensor so as to determine the current state of the system; At least one digital filter unit designed to change a reference clock signal according to a period of each signal to prevent a malfunction of a microcomputer by blocking noise generated from the first and second interrupt signals and a time measurement signal; A microprocessor that executes operations and controls to process signals transmitted through the digital filter unit; It includes.

In addition, according to the second aspect of the present invention, the digital filter unit is designed such that the reference clock signal is fixed in hardware during an initial ROM mask so that the reference clock signal does not change during program processing.

According to a third aspect of the invention, the digital filter unit includes a frequency generator for changing the reference clock signal to remove noise according to the period of the first and second interrupt signal and the time measurement signal when each product is applied. .

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, FIG. 5 is a block diagram illustrating an apparatus for removing noise of a microcomputer according to the present invention, and FIG. 6 is a block diagram showing in detail a digital filter that is a part of FIG. 5. And, Figure 7 is a diagram showing the waveform of the signal input and output to the digital filter, (a) is a waveform of the input signal input to the digital filter, (b) is the output signal of the digital filter Waveform (c) shows the waveform of the reference clock signal input to the digital filter, respectively.

Next, the microcomputer (M) of the present invention is applied to all devices, but to be described with reference to FIGS. 5 to 7 with reference to the application example in the washing machine for easy description, the washing machine operation / sleep mode (sleep mode) is changed A switching unit configured to generate a first interrupt signal INTØ, the switch SW being configured to include a first switch R1 and a first capacitor C1;

One input signal is fixed by the reference resistors R3 and R4 while the other input signal is a comparator 11 connected to a commercial power supply line AC line and a fifth resistor R5, and a full-up. The second interrupt signal consisting of a resistor R2 and a second capacitor C2 detects a zero point on a commercial power supply (for example, a sine wave) and softly switches without generating external noise to suppress noise generation. A zero detection unit for generating and outputting INT1);

A frequency measuring unit generating and outputting a time measurement signal TC1 so as to count the frequency of the detection signal (usually 30-40 kHz) through the sensor 12 so as to grasp the state of the current system; First to third digital filters (21, 22, and 23) connected to the first and second interrupt signals and a time measurement signal, respectively, to remove noise of each signal to prevent a malfunction of the microcomputer M;

When the frequency of the reference clock signal of the first to third digital filters (21, 22, 23) to other products when the frequency generator 30 for varying variously to remove the noise in accordance with the cycle of each interrupt signal and ; A microprocessor (40) which executes operations and controls to process signals transmitted from the frequency generator (30) or first to third digital filters (21, 22, 23); It is configured to include.

In particular, the operation of the washing machine in the switch (SW) refers to a process of performing washing, rinsing, and dehydration by putting laundry, and the sleep mode refers to a state in which the user only makes a reservation and the like. It means the mode to keep.

Here, the minimum power for saving only the microcomputer M is standby power, and this standby power has become a major issue in terms of energy saving in recent years. Therefore, when the microcomputer M is changed from the sleep mode to the wake-up mode by the operation of the switch SW, the software operates normally. Such a switch SW can remove a noise signal only by hardware processing.

Therefore, the first digital filter 21 is installed while the first interrupt signal is transmitted to the microprocessor 40, so that noise generated from the first interrupt signal is removed, and the first digital filter 21 removes the noise. The first interrupted signal from which the noise is removed is transmitted to the microprocessor 40.

When the second interrupt signal is transmitted to the microcomputer M in the zero detection unit, the microcomputer M stops the process in progress in hardware and performs the process by the second interrupt signal. Therefore, the second interrupt signal serves to interrupt program execution by a hardware device that cannot remove noise by software.

When the external high frequency noise occurs in the second interrupt signal or noise occurs in the input sine wave signal, various problems occur. In order to prevent such a problem, the second interrupt signal is transmitted to the microprocessor 40. The second digital filter 22 is disposed on the way to remove noise generated in the second interrupt signal.

On the other hand, the frequency of the detection signal is changed in the frequency measuring unit is a detection method currently used a lot because the frequency well reflects the state of the sensing object regardless of the magnitude of the voltage applied to the microcomputer (M). However, when high frequency noise is generated in the frequency measuring unit and transmitted to the time measurement signal, the microcomputer M may incorrectly determine a current state of the system and cause a malfunction of the system.

However, since the third digital filter 23 is provided in the time measurement signal as well as the first and second interrupt signals, noise that may be generated in the time measurement signal is removed beforehand. Since the microprocessor 40 is transferred to the microprocessor 40, the microcomputer M may accurately determine the current state of the system.

In the above, the digital filters 21, 22, 23 for removing noise of the first and second interrupt signals and the time measurement signal are shown in FIG. 6, wherein the digital filters 21, 22, 23 are divided into four. D-flip flop (D1, D2, D3, D4) and four NAND GATE (NA1, NA2, NA3, NA4).

The digital filters 21, 22, and 23 configured as described above have no signal change at the input terminal while four reference clock signals are inputted to the clock terminal CLK by the reference clock signal as shown in FIG. As shown in (c) of FIG. 7, the output terminal signal is 'low', and when the reference clock signal is input, if a severe chattering signal is input to the input terminal as shown in FIG. Ignored, the output will be '0'.

However, when the normal signal as shown in FIG. 7B is maintained for a predetermined time, that is, while four or more reference clock signals are input, the output signal is 'high'.

On the other hand, the frequency of the reference clock signal of the digital filter (21, 22, 23) is fixed in hardware when masking the ROM of the microcomputer (M), so that the clock value does not change during the program processing, the microcomputer (M) Since the data of the ROM is different from product to product, the frequency data of the reference clock signal is input at a specific address of the ROM to fix the clock value of the reference clock signal input to each digital filter 21, 22, 23 in hardware. Can be.

As described above, the digital filters 21, 22, and 23 perform strong hardware by performing a portion that cannot be executed in software for noise cancellation of interrupt signals such as first and second interrupt signals and time measurement signals. The runaway of the microcomputer M due to external noise can be prevented in advance. In addition, the first to third digital filters 21, 22, and 23 may cut off the frequency of the normal signal input to the interrupt port of the microcomputer M unconditionally according to each product to prevent the microcomputer M from malfunctioning. do.

Thus, the present invention generates a variety of signals and noise frequencies according to each product using the microcomputer (M), the digital filter (21, 22, 23) to remove the noise while meeting the various frequency characteristics of each product And the frequency of the reference clock signal of the digital filters 21, 22, and 23 can be changed so that the noise resistance of the microcomputer M can be improved and the microcomputer M can be prevented from malfunctioning. It becomes possible.

The noise reduction device of the microcomputer according to the present invention configured as described above suppresses the occurrence of noise by using a digital filter designed to change the reference clock signal according to the cycle of the interrupt signal when each product is applied to each interrupt input of the microcomputer. At the same time, the malfunction of the microcomputer can be prevented. Accordingly, the system can be operated smoothly, and the overheating state of the heater and the overdriving state of the load due to the microcomputer malfunction can be prevented in advance.

Claims (3)

A switching unit configured to generate a first interrupt signal by performing a switching operation to change a mode of the system; A zero point detection unit for detecting a zero point of commercial power supplied from the outside and generating and outputting a second interrupt signal to prevent generation of noise; A frequency measuring unit generating and outputting a time measurement signal to count the frequency of the detection signal transmitted through the sensor so as to determine the current state of the system; At least one digital filter unit designed to change a reference clock signal according to a period of each signal to prevent a malfunction of a microcomputer by blocking noise generated from the first and second interrupt signals and a time measurement signal; A microprocessor that executes operations and controls to process signals transmitted through the digital filter unit; Noise reduction device of the microcomputer, characterized in that it comprises a. The method of claim 1, And the digital filter unit is designed such that the reference clock signal is fixed in hardware during an initial ROM mask so that the reference clock signal does not change during program processing. The method of claim 1, The digital filter unit includes a frequency generator for changing the reference clock signal to remove the noise according to the period of the first and second interrupt signal and the time measurement signal when each product is applied .