Manuals / Freescale Semiconductor / Computer Equipment / Network Card

Freescale Semiconductor M68HC08, MC68HC908QT2 manual Design Considerations, 2.Switch Circuitry

Models: M68HC08

1 30

Download 30 pages 41.27 Kb

Page 22

Design Considerations

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

Design Considerations

A logic 1 from port A, bit 0 will turn the NPN transistor on, driving its collector low. The low level applied to the base of the PNP transistor, Q2, will drive its emitter to collector into conduction, illuminating the two LEDs. Resistor R5 is in place to guarantee that Q1 is biased off during initial power on and before the microcontroller’s program has configured port A, bit 1 to behave as a digital output.

5.4 Switch Circuitry

A simple circuit is used to give the ability of reading several switches into an A/D port. Figure 5-2shows the circuit. This circuit has the advantage of using only one I/O pin for the six switches. Using a switch matrix and the keyboard interrupt pins is an alternative approach, but in this case would require a microcontroller with more I/O pins.

Vdd

2

2	JP3
1	SW_DISC

1

	R9
	3.3K
	POWER
PTA1_ATD1	SW1
	SW1
		R11
	PLAY	4.7K
	SW2
		R12
	FWD	2.2k
	SW3
		R15
	REV	1k
	SW6
		R14
	PAUSE	470
	SW5
		R13
	STOP	220
	SW4

Figure 5-2. Switch Circuitry

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

22	Design Considerations	MOTOROLA

For More Information On This Product,

Go to: www.freescale.com

Image 22

Freescale Semiconductor M68HC08, MC68HC908QT2 Design Considerations, 2.Switch Circuitry, Freescale Semiconductor, Inc

Contents

Using the ASB520 MC68HC908QT2 Based Infrared Freescale Semiconductor, IncFreescale Semiconductor, Inc Remote Control Reference PC BoardFreescale Semiconductor, Inc Freescale Semiconductor, IncFor More Information On This Product Infrared Remote Control Reference PC Board Reference DesignUsing the ASB520 MC68HC908QT2 Based Freescale Semiconductor, IncFreescale Semiconductor, Inc Revision HistoryRevision History Freescale Semiconductor, IncSection 4. Schematic and Parts List Table of ContentsSection 1. Introduction and Setup Section 6. System TestingFreescale Semiconductor, Inc Table of ContentsFreescale Semiconductor, Inc DRM0451.2 About this Manual Section 1. Introduction and Setup1.1 Introduction Freescale Semiconductor, IncFreescale Semiconductor, Inc Introduction and Setup1.3 Setup Guide Freescale Semiconductor, IncFreescale Semiconductor, Inc Introduction and Setup Setup GuideIntroduction and Setup Freescale Semiconductor, IncFreescale Semiconductor, Inc Introduction and SetupFreescale Semiconductor, Inc DRM0452.1 Introduction 2.3.1 Red Activity Indicator LEDSection 2. Operational Description 2.2 Push ButtonsFreescale Semiconductor, Inc Operational DescriptionFigure 2-1.PC Board JP1 JP2 JP3 JP4Freescale Semiconductor, Inc 2.4 Header and Jumpers BlocksFreescale Semiconductor, Inc Freescale Semiconductor, Inc 2.5 Microcontroller Current Monitor Jumper BlockFreescale Semiconductor, Inc Operational Description3.1 Introduction 3.2 16-PinConnector J1Section 3. Pin Description Table 3-1.MON08 Pin AssignmentsFreescale Semiconductor, Inc Pin DescriptionFreescale Semiconductor, Inc DRM0454.1 Introduction Section 4. Schematic and Parts List4.2 Schematic Freescale Semiconductor, IncSemiconductor, Inc Schematic and Parts ListBoard Schematic Figure 4-1.ASB520 PCSchematic and Parts List Parts List 4.3 Parts ListTable 4-1.Reference PC Board Parts List Freescale Semiconductor, IncFreescale Semiconductor, Inc Schematic and Parts ListFreescale Semiconductor, Inc DRM0455.1 Introduction FreescaleSection 5. Design Considerations 5.2 GroundingDesign Considerations 5.4 Switch CircuitryFigure 5-2.Switch Circuitry Freescale Semiconductor, IncSwitch Table 5-1.Switch Input A/D ValuesDesign Considerations Switch Circuitry Freescale Semiconductor, IncDesign Considerations Freescale Semiconductor, IncFreescale Semiconductor, Inc DRM0456.1 Introduction Section 6. System Testing6.2 Hardware/Software Testing Summary 6.3FLASH ProgrammingFreescale 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, IncFreescale Semiconductor, Inc Freescale Semiconductor, IncFor More Information On This Product Freescale Semiconductor, Inc HOW TO REACH USFreescale Semiconductor, Inc For More Information On This Product