HC805K3GRSSLASHD datasheet(22/119 Pages) NXP

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General Release Speciﬁcation

Functional Pin Description

MC68HC805K3 — Rev. 1.0

General Description

1.7.2.2 2-Pin Ceramic Resonator Oscillator

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

of the crystal. The circuit in Figure 1-3(a) is for a ceramic resonator also.

The resonator manufacturer’s recommendations should be followed,

since the resonator parameters determine the external component

values required for maximum stability and reliable starting. The load

capacitance values used in the oscillator circuit design should include all

stray capacitances. The ceramic resonator 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 for the crystal/ceramic

resonator oscillator mask option register bit.

1.7.2.3 2-Pin RC Oscillators

The 2-pin RC oscillator configuration can be used for very low-cost

applications. With this option, a resistor must be connected between the

two oscillator pins and a capacitor must be connected from the OSC1 pin

to VSS, as shown in Figure 1-3(b). The signal on the OSC2 pin is a

square wave and the signal on the OSC1 pin approximates a triangular

wave.

The 2-pin RC oscillator is selected by programming bit 5 ("RC") of the

mask option register located at $0012. Bit 6 ("Pin 3") should NOT be

programmed when using the 2-pin oscillator.

The 2-pin RC oscillator is optimized for operation at 500 kHz. This

oscillator can be used at higher or lower frequencies with degraded

accuracy over temperature, supply voltage, and/or device processing

variations. The internal startup resistor of approximately 2 M

Ω is not

connected between OSC1 and OSC2 when the 2-pin RC oscillator mask

option register bit is selected.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

HC805K3GRS/D Datasheet(PDF) 22 Page - NXP Semiconductors