MC68HC908GR8BMFA View Datasheet(PDF) - Freescale Semiconductor

Part Name

Description

Manufacturer

MC68HC908GR8BMFA

M68HC08 Microcontrollers

Freescale Semiconductor 

1.5 Pin Functions

Descriptions of the pin functions are provided here.

Pin Functions

1.5.1 Power Supply Pins (VDD and VSS)

VDD and VSS are the power supply and ground pins. The MCU operates from a single power supply.

Fast signal transitions on MCU pins place high, short-duration current demands on the power supply. To

prevent noise problems, take special care to provide power supply bypassing at the MCU as Figure 1-4

shows. Place the C1 bypass capacitor as close to the MCU as possible. Use a high-frequency-response

ceramic capacitor for C1. C2 is an optional bulk current bypass capacitor for use in applications that

require the port pins to source high current levels.

MCU

VDD

VSS

C1

0.1 μF

+

C2

VDD

Note: Component values shown represent typical applications.

Figure 1-4. Power Supply Bypassing

1.5.2 Oscillator Pins (OSC1 and OSC2)

OSC1 and OSC2 are the connections for an external crystal, resonator, or clock circuit. See Chapter 4

Clock Generator Module (CGM).

1.5.3 External Reset Pin (RST)

A 0 on the RST pin forces the MCU to a known startup state. RST is bidirectional, allowing a reset of the

entire system. It is driven low when any internal reset source is asserted. This pin contains an internal

pullup resistor. See Chapter 14 System Integration Module (SIM).

1.5.4 External Interrupt Pin (IRQ)

IRQ is an asynchronous external interrupt pin. This pin contains an internal pullup resistor. See

Chapter 8 External Interrupt (IRQ).

MC68HC908GR8B Data Sheet, Rev. 3.0

Freescale Semiconductor

21

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