68HC805K3 datasheet(21/119 Pages) FREESCALE

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General Release Specification

Functional Pin Description

MC68HC805K3 — Rev. 1.0

General Description

1.7.2.1 2-Pin Crystal Oscillator

The circuit in Figure 1-3(a) shows a typical 2-pin oscillator circuit for an

AT-cut, parallel resonant crystal. The crystal manufacturer’s

recommendations should be followed, since 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 is provided between OSC1 and OSC2

when the crystal/ceramic resonator oscillator option is used.

Figure 1-3. Oscillator Connections

MCU

36 pF*

(a) 2-Pin Crystal or

Ceramic Resonator

Connections

OSC1

OSC2

36 pF*

2 M

Ω (MASK OPTION)

UNCONNECTED

EXTERNAL CLOCK

(b) 2-Pin

RC Oscillator

Connections

(d) External

Clock Source

Connection

RC Oscillator

Connections

OSC1

OSC2

MCU

OSC1

OSC2

MCU

OSC1

OSC2

MCU

PB1/OSC3

* Starting value only. Follow crystal

supplier’s recommendations

regarding component values that

will provide reliable startup and

maximum stability.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

68HC805K3 Datasheet(PDF) 21 Page - Freescale Semiconductor, Inc

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