68HC705SP7 datasheet(26/230 Pages) FREESCALE

26 / 230 page

General Description

General Release Specification

MC68HC705JJ7/MC68HC705JP7 — Rev. 3.0

General Description

Figure 1-3. EPO Oscillator Connections

1.7.1 Crystal Oscillator

The circuit in Figure 1-3 (a) shows a typical oscillator circuit for an AT-

cut, parallel resonant crystal. The crystal manufacturer’s

recommendations should be followed, as the crystal parameters

determine the external component values required to provide maximum

stability and reliable startup. The load capacitance values used in the

oscillator circuit design should include all stray capacitances. The crystal

and components should be mounted as close as possible to the pins for

startup stabilization and to minimize output distortion. An internal startup

resistor of approximately 2 M

Ω can be provided between OSC1 and

OSC2 for the crystal type oscillator by use of the OSCRES bit in the

MOR.

NOTE:

In general, a 32-kHz crystal is not recommended for use with the

MC68HC705JJ7/MC68HC705JP7 unless specifically indicated by the

crystal manufacturer.

1.7.2 Ceramic Resonator Oscillator

In cost-sensitive applications, a ceramic resonator can be used in place

of the crystal. The circuit in Figure 1-3 (a) can be used for a ceramic

resonator. The resonator manufacturer’s recommendations should be

followed, as the resonator parameters determine the external

component values required for maximum stability and reliable starting.

MCU

(a) Crystal or

Ceramic Resonator

Connections

OSC1

OSC2

2 M

Ω

UNCONNECTED

EXTERNAL CLOCK

(b) RC Oscillator

Connections

Clock Source

Connection

OSC1

OSC2

MCU

OSC1

OSC2

MCU

Freescale Semiconductor, Inc.

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