68HC05CL48 datasheet(18/145 Pages) MOTOROLA

18 / 145 page

GENERAL RELEASE SPECIFICATION

June 11, 1997

MOTOROLA

GENERAL DESCRIPTION

MC68HC05CL48

1-6

REV 2.0

1.4.4 IRQ0, IRQ1, IRQ2

These three pins provide additional sources of interrupt. They are all edge-

triggered only. IRQ0 and IRQ1 are both negative-edge triggered only and IRQ2

can be triggered on both rising and falling edges. Refer to Section 4.3.2. The

IRQ0, IRQ1 and IRQ2 pins contain internal Schmitt trigger as part of its input to

improve noise immunity.

1.4.5 OSC1, OSC2

These pins provide control input for an on-chip clock oscillator circuit. A crystal, a

ceramic resonator or an external signal to these pins provides the clock to the on

chip PLL.

The OSC1 and OSC2 pins can accept the following:

A crystal as shown in Figure 1-4(a)

A ceramic resonator as shown in Figure 1-4(a)

An external clock signal as shown in Figure 1-4(b)

The system clock can either be the 32kHz external clock or a higher frequency

clock from the PLL. See Section 13.

1.4.5.1

Crystal with no Internal Components

The circuit in Figure 1-4(a) shows a typical oscillator circuit for an AT-cut, parallel

resonant crystal. Follow the crystal manufacturer’s recommendations, as the

crystal parameters determine the external component values required to provide

maximum stability and reliable start-up. The load capacitance values used in the

oscillator circuit design should include all stray capacitance. Mount the crystal and

components as close as possible to the pins for start-up stabilization and to

minimize output distortion.

1.4.5.2

Ceramic Resonator

In cost-sensitive applications, use a ceramic resonator in place of a crystal. Use

the circuit in Figure 1-4(a) for a ceramic resonator and follow the resonator

manufacturer’s recommendations, as 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 capacitance. Mount the resonator and components as close as possible to

the pins for start-up stabilization and to minimize output distortion

68HC05CL48 Datasheet(PDF) 18 Page - Motorola, Inc