HC05 datasheet(37/232 Pages) MOTOROLA

37 / 232 page

MC68HC05X16

Rev. 1

MOTOROLA

2-13

MODES OF OPERATION AND PIN DESCRIPTIONS

2.3.11

SCLK

The SCLK pin is the clock output pin of the SCI transmitter.

2.3.12

OSC1, OSC2

These pins provide control input for an on-chip oscillator circuit. A crystal, ceramic resonator or

external clock signal connected to these pins supplies the oscillator clock. The oscillator frequency

(fOSC) is divided by two, four, eight or ten to give the internal bus frequency (fOP). There is also a

software option which introduces an additional divide by 16 into the oscillator clock, giving an

internal bus frequency of fOSC/32, /64, /128 or /160.

2.3.12.1

Crystal

The circuit shown in Figure 2-6(a) is recommended when using either a crystal or a ceramic

resonator. An internal feedback resistor is provided on-chip between OSC1 and OSC2.

Figure 2-6(d) lists the recommended capacitance values. The internal oscillator is designed to

interface with an AT-cut parallel-resonant quartz crystal resonator in the frequency range speciﬁed

for fOSC (see Section 12.4). Use of an external CMOS oscillator is recommended when crystals

outside the speciﬁed ranges are to be used. The crystal and associated components should be

mounted as close as possible to the input pins to minimise output distortion and start-up

stabilization time. The manufacturer of the particular crystal being considered should be consulted

for speciﬁc information.

2.3.12.2

Ceramic resonator

A ceramic resonator may be used instead of a crystal in cost sensitive applications for frequencies up

to 8MHz external. The circuit shown in Figure 2-6(a) is recommended when using either a crystal or a

ceramic resonator. Figure 2-6(d) lists the recommended capacitance and feedback resistance values.

The manufacturer of the particular ceramic resonator being considered should be consulted for speciﬁc

information. This option is recommended only for applications that operate at an external clock

frequency of 8MHz or less. Any application requiring an external operating frequency greater that

8MHz should use either a crystal oscillator or an external CMOS compatible clock source.

2.3.12.3

External clock

When using an external clock the OSC1 and OSC2 pins should be driven in antiphase, as shown

in Figure 2-6(c). The tOXOV or tILCH speciﬁcations (see Section 12.4) do not apply when using an

external clock input. The equivalent speciﬁcation of the external clock source should be used in

lieu of tOXOV or tILCH.

HC05 Datasheet(PDF) 37 Page - Motorola, Inc