MC68HC705J1AC データシートの表示（PDF） - Freescale Semiconductor

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MC68HC705J1AC

Microcontrollers

Freescale Semiconductor 

General Description

Pin Assignments

1.5.2 OSC1 and OSC2

The OSC1 and OSC2 pins are the connections for the on-chip oscillator.

The oscillator can be driven by any of these:

1. Crystal (See Figure 1-4 and Figure 1-5.)

2. Ceramic resonator (See Figure 1-6 and Figure 1-7.)

3. Resistor/capacitor (RC) oscillator (Refer to Appendix A.

MC68HRC705J1A and Appendix C. MC68HSR705J1A.)

4. External clock signal (See Figure 1-8.)

The frequency, fosc, of the oscillator or external clock source is divided

by two to produce the internal operating frequency, fop.

1.5.2.1 Crystal Oscillator

Figure 1-4 and Figure 1-5 show a typical crystal oscillator circuit for an

AT-cut, parallel resonant crystal. Follow the crystal supplier’s

recommendations, as the crystal parameters determine the external

component values required to provide reliable startup and maximum

stability. The load capacitance values used in the oscillator circuit design

should include all stray layout capacitances.

To minimize output distortion, mount the crystal and capacitors as close

as possible to the pins. An internal startup resistor of approximately

2 MΩ is provided between OSC1 and OSC2 for the crystal oscillator as

a programmable mask option.

NOTE: Use an AT-cut crystal and not an AT-strip crystal because the MCU can

overdrive an AT-strip crystal.

MC68HC705J1A — Rev. 4.0

MOTOROLA

General Description

Technical Data

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