MC68HC05RC8 Datasheet, PDF (24/122 Pages) Freescale Semiconductor, Inc – General Release Specification

Freescale Semiconductor, Inc.
General Description
1.5.3 OSC1 and OSC2
These pins provide control input for an on-chip clock oscillator circuit. A
crystal, a ceramic resonator, or an external signal connects to these pins
to provide a system clock. The oscillator frequency is two times the
internal bus rate.
Figure 1-5 shows the recommended circuit when using a crystal. The
crystal and components should be mounted as close as possible to the
input pins to minimize output distortion and startup stabilization time.
A ceramic resonator may be used in place of the crystal in cost-sensitive
applications. Figure 1-5 (a) shows the recommended circuit for using a
ceramic resonator. The manufacturer of the particular ceramic resonator
being considered should be consulted for specific information.
An external clock should be applied to the OSC1 input with the OSC2 pin
not connected (see Figure 1-5 (b)). This setup can be used if the user
does not want to run the CPU with a crystal.
OSC1
MCU
OSC2
10 MΩ
30 pF
30 pF
MCU
OSC1
OSC2
UNCONNECTED
< EXTERNAL CLOCK
(a) Crystal/Ceramic Resonator
Oscillator Connections
(b) External Clock Source
Connections
Figure 1-5. Oscillator Connections
General Release Specification
MC68HC05RC16 — Rev. 3.0
General Description
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