MC68HC705P9 Datasheet, PDF (16/156 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Pin Descriptions _{Pin Functions}
Crystal
Connections
The circuit in Figure 3 shows a
typical crystal oscillator circuit
for an AT-cut, parallel resonant
crystal. Follow the crystal
supplier’s recommendations, as
the crystal parameters
determine the external
component values required to
provide reliable startup and
maximum stability. The load
capacitance values used in the
oscillator circuit design should
include all stray layout
capacitances. To minimize
output distortion, mount the
crystal and capacitors as close
as possible to the pins.
MCU
10 MΩ
XTAL
27 pF
27 pF
Figure 3. Crystal Connections
NOTE:
Use an AT-cut crystal. Do not use a strip or tuning fork crystal. The MCU
may overdrive or have the incorrect characteristic impedance for a strip
or tuning fork crystal.
Ceramic
Resonator
Connections
To reduce cost, use a ceramic
resonator in place of the crystal.
Figure 4 shows a ceramic
resonator circuit. For the values
of any external components,
follow the recommendations of
the resonator manufacturer. The
load capacitance values used in
the oscillator circuit design
should include all stray layout
capacitances. To minimize
output distortion, mount the
resonator and capacitors as
close as possible to the pins.
MCU
CERAMIC
RESONATOR
Figure 4. Ceramic Resonator
Connections
4-mc68hc705p9
16
Pin Descriptions
MOTOROLA