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Freescale Semiconductor MC68HC908QT2 1.Switch Input A/D Values, Freescale Semiconductor, Inc

Models: M68HC08

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Design Considerations

Switch Circuitry

The spreadsheet in Table 5-1gives the decimal values seen by the A/D, based on which switch is depressed. Because the voltage from the switches is ratiometric to VDD, power supply variation will have no effect on A/D readings.

Table 5-1. Switch Input A/D Values

Switch	Ideal Value	Minus 6%	Plus 6%

No switch	255	239.7	255

Power	170.5	160.3	180.7

Play	127.7	120	153.3

Forward	79.9	75.1	84.7

Reverse	40.8	38.4	43.3

Pause	14.8	13.9	15.6

Stop	0	0	0

The ±6% values in Table 5-1indicate worst case values, as the resistors used in the design are ±5%. The software uses the minimum values from the table to decode the switches.

Using the ASB520 MC68HC908QT2 Based Infrared Remote Control Reference PC Board		DRM045

MOTOROLA	Design Considerations	23
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Freescale Semiconductor MC68HC908QT2 1.Switch Input A/D Values, Freescale Semiconductor, Inc, DRM045, Ideal Value, Plus 6%

Contents

Remote Control Reference PC Board Freescale Semiconductor, IncFreescale Semiconductor, Inc Using the ASB520 MC68HC908QT2 Based InfraredFor More Information On This Product Freescale Semiconductor, IncFreescale Semiconductor, Inc Freescale Semiconductor, Inc Reference DesignUsing the ASB520 MC68HC908QT2 Based Infrared Remote Control Reference PC BoardFreescale Semiconductor, Inc Revision HistoryRevision History Freescale Semiconductor, IncSection 6. System Testing Table of ContentsSection 1. Introduction and Setup Section 4. Schematic and Parts ListDRM045 Table of ContentsFreescale Semiconductor, Inc Freescale Semiconductor, IncFreescale Semiconductor, Inc Section 1. Introduction and Setup1.1 Introduction 1.2 About this ManualFreescale Semiconductor, Inc Introduction and Setup1.3 Setup Guide Freescale Semiconductor, IncFreescale Semiconductor, Inc Introduction and Setup Setup GuideIntroduction and Setup Freescale Semiconductor, IncDRM045 Introduction and SetupFreescale Semiconductor, Inc Freescale Semiconductor, Inc2.2 Push Buttons 2.3.1 Red Activity Indicator LEDSection 2. Operational Description 2.1 IntroductionJP1 JP2 JP3 JP4 Operational DescriptionFigure 2-1.PC Board Freescale Semiconductor, IncFreescale Semiconductor, Inc 2.4 Header and Jumpers BlocksFreescale Semiconductor, Inc Operational Description 2.5 Microcontroller Current Monitor Jumper BlockFreescale Semiconductor, Inc Freescale Semiconductor, IncTable 3-1.MON08 Pin Assignments 3.2 16-PinConnector J1Section 3. Pin Description 3.1 IntroductionDRM045 Pin DescriptionFreescale Semiconductor, Inc Freescale Semiconductor, IncFreescale Semiconductor, Inc Section 4. Schematic and Parts List4.2 Schematic 4.1 IntroductionFigure 4-1.ASB520 PC Schematic and Parts ListBoard Schematic Semiconductor, IncFreescale Semiconductor, Inc 4.3 Parts ListTable 4-1.Reference PC Board Parts List Schematic and Parts List Parts ListDRM045 Schematic and Parts ListFreescale Semiconductor, Inc Freescale Semiconductor, Inc5.2 Grounding FreescaleSection 5. Design Considerations 5.1 IntroductionFreescale Semiconductor, Inc 5.4 Switch CircuitryFigure 5-2.Switch Circuitry Design ConsiderationsFreescale Semiconductor, Inc Table 5-1.Switch Input A/D ValuesDesign Considerations Switch Circuitry SwitchDRM045 Freescale Semiconductor, IncFreescale Semiconductor, Inc Design Considerations6.3FLASH Programming Section 6. System Testing6.2 Hardware/Software Testing Summary 6.1 IntroductionFreescale Semiconductor, Inc System Testing6.4 LED and Push Button Test Code Freescale Semiconductor, IncFreescale Semiconductor, Inc 6.5 DVD Player Control TestFreescale Semiconductor, Inc Freescale Semiconductor, Inc System TestingSystem Testing Freescale Semiconductor, IncFor More Information On This Product Freescale Semiconductor, IncFreescale Semiconductor, Inc For More Information On This Product HOW TO REACH USFreescale Semiconductor, Inc Freescale Semiconductor, Inc