M68HC08 datasheet(19/188 Pages) FREESCALE

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General Description

Pin Assignments

MC68HC908RF2 — Rev. 4.0

Data Sheet

MOTOROLA

General Description

Figure 1-3. Power Supply Bypassing

1.4.2 Oscillator Pins (OSC1 and OSC2)

The OSC1 and OSC2 pins are the connections to an external clock source or

crystal/ceramic resonator.

1.4.3 External Reset (RST)

A logic 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.

The RST pin contains an internal pullup resistor.

For additional information, see Section 10. System Integration Module (SIM).

1.4.4 External Interrupt Pin (IRQ)

IRQ is an asynchronous external interrupt pin.

The IRQ pin contains an internal pullup resistor.

1.4.5 Port A Input/Output Pins (PTA7, PTA6/KBD6–PTA1/KBD1, and PTA0)

Port A is an 8-bit special function port that shares its pins with the keyboard

interrupt.

Six port A pins (PTA6–PTA1) can be programmed to serve as an external interrupt.

Once enabled, that pin will contain an internal pullup resistor.

All port A pins are high-current sink pins.

1.4.6 Port B Input/Output Pins (PTB3/TCLK, PTB2/TCH0, PTB1, and PTB0/MCLK)

Port B is a 4-bit, general-purpose, bidirectional I/O port, with some of its pins

shared with the timer (TIM) module.

MCU

VDD

CBulk

VSS

VDD

Note: Component values shown represent typical applications.

CBypass

0.1

µF

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