Freescale Semiconductor, Inc.
Ge ne ra l De sc rip tion
MCU
MCU
R
MCU
2 MΩ
OSC1
OSC2
OSC1
OSC2
OSC1
OSC2
UNCONNECTED
EXTERNAL CLOCK
(a) Crystal or
(b) RC Oscillator
Connections
(c) External
Clock Source
Connection
Ceramic Resonator
Connections
Figure 1-3. EPO Oscillator Connections
1.7.1 Crysta l Osc illa tor
The circuit in Figure 1-3 (a) shows a typical oscillator circuit for an AT-
cut, parallel resonant crystal. The crystal manufacturer’s
recommendations should be followed, as 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 MΩ can be provided between OSC1 and
OSC2 for the crystal type oscillator by use of the OSCRES bit in the
MOR.
NOTE: In general, a 32-kHz crystal is not recommended for use with the
MC68HC705JJ7/MC68HC705JP7 unless specifically indicated by the
crystal manufacturer.
1.7.2 Ce ra m ic Re sona tor Osc illa tor
In cost-sensitive applications, a ceramic resonator can be used in place
of the crystal. The circuit in Figure 1-3 (a) can be used for a ceramic
resonator. The resonator manufacturer’s recommendations should be
followed, as the resonator parameters determine the external
component values required for maximum stability and reliable starting.
General Release Specification
MC68HC705JJ7/MC68HC705JP7 — Rev. 3.0
General Description
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