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| 型号： | DM164120-1 |
| 厂商： | Microchip Technology |
| 文件页数： | 27/42页 |
| 文件大小： | 0K |
| 描述： | BOARD DEMO PICKIT 2 LP COUNT |
| 标准包装： | 1 |
| 系列： | PICkit™ |
| 类型： | MCU |
| 适用于相关产品： | 28 引脚 PIC16C、16F、18C、18F |
| 所含物品： | 3 个板（1 个装有元件的板，2 个裸板） |
| 产品目录页面： | 659 (CN2011-ZH PDF) |
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LPC Demo Board Lessons
3.2.6
Lesson 6: Switch Debouncing
Mechanical switches play an important and extensive role in practically every
computer, microprocessor and microcontroller application. Mechanical switches are
inexpensive, simple and reliable. In addition, switches can be very noisy. The apparent
noise is caused by the closing and opening action that seldom results in a clean
electrical transition. The connection makes and breaks several, perhaps even
hundreds, of times before the final switch state settles.
The problem is known as switch bounce. Some of the intermittent activity is due to the
switch contacts actually bouncing off each other. Imagine slapping two billiard balls
together. The hard non-resilient material doesn’t absorb the kinetic energy of motion.
Instead, the energy dissipates over time and friction in the bouncing action against the
forces push the billiard balls together. Hard metal switch contacts react in much the
same way. Also, switch contacts are not perfectly smooth. As the contacts move
against each other, the imperfections and impurities on the surfaces cause the
electrical connection to be interrupted. The result is switch bounce.
The consequences of uncorrected switch bounce can range from being just annoying
to catastrophic. For example, imagine advancing the TV channel, but instead of getting
the next channel, the selection skips one or two. This is a situation a designer should
strive to avoid.
Switch bounce has been a problem even before the earliest computers. The classic
solution involved filtering, such as through a resistor-capacitor circuit, or through
re-settable shift registers (see Figures 3-4 and 3-5). These methods are still effective
but they involve additional cost in material, installation and board real estate. Why
suffer the additional expense when software is free and program memory is abundant.
FIGURE 3-4:
FILTERING DEBOUNCE SOLUTION
+V
R2
R1
Filtered
Switch
SW
C 1
Output
FIGURE 3-5:
SHIFT REGISTER DEBOUNCE SOLUTION
+V
R1
D
Qn
Filtered
Switch
SW
CLK
CLR
Output
Debounce
Clock
? 2005 Microchip Technology Inc.
DS51556A-page 23
相关PDF资料 |
PDF描述 |
|---|---|
| DM164120-3 | BOARD DEMO PICKIT2 28-PIN |
| DM164120-5 | BOARD DEMO PICKIT 2 64/80-PIN |
| DM164123 | KIT MANAGEMENT SYSTEM PICDEM |
| DM180021 | KIT STARTER MPLAB FOR PIC18F MCU |
| DM183022 | BOARD DEMO PIC18FXX22 64/80TQFP |
相关代理商/技术参数 |
参数描述 |
|---|---|
| DM164120-1 | 制造商:Microchip Technology Inc 功能描述:DEVELOPMENT TOOLS - PICKIT 2 LOW PIN COU |
| DM164120-2 | 功能描述:开发板和工具包 - PIC / DSPIC PICkit 2 44-Pin Count Demo Brd RoHS:否 制造商:Microchip Technology 产品:Starter Kits 工具用于评估:chipKIT 核心:Uno32 接口类型: 工作电源电压: |
| DM164120-3 | 功能描述:开发板和工具包 - PIC / DSPIC PICkit 2 Count Demo Board RoHS:否 制造商:Microchip Technology 产品:Starter Kits 工具用于评估:chipKIT 核心:Uno32 接口类型: 工作电源电压: |
| DM164120-4 | 功能描述:开发板和工具包 - PIC / DSPIC PICkit 2 1 Dem Board RoHS:否 制造商:Microchip Technology 产品:Starter Kits 工具用于评估:chipKIT 核心:Uno32 接口类型: 工作电源电压: |
| DM164120-4 | 制造商:Microchip Technology Inc 功能描述:PICkit 2 18-Pin Demo Board |
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