MC68HC705C8A Datasheet, PDF (28/222 Pages) Motorola, Inc – HCMOS Microcontroller Unit

General Description
1.7.2.1 Crystal Resonator
The circuit in Figure 1-8 shows a
crystal oscillator circuit for an AT-cut,
parallel resonant crystal. Follow the
crystal supplier’s recommendations,
because 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
account for all stray layout
capacitances. To minimize output
distortion, mount the crystal and
capacitors as close as possible to the
pins.
MCU
OSC1
10 MΩ∗
OSC2
22 pF^∗
XTAL
2 MHz
22 pF^∗
∗_{Starting value only. Follow crystal supplier’s}
recommendations regarding component
values that will provide reliable startup and
maximum stability.
Figure 1-8. Crystal
Connections
NOTE:
Use an AT-cut crystal and not a strip or tuning fork crystal. The MCU
might overdrive or have the incorrect characteristic impedance for a strip
or tuning fork crystal.
1.7.2.2 Ceramic Resonator
To reduce cost, use a ceramic
resonator instead of a crystal. Use the
circuit shown in Figure 1-9 for a 2-pin
ceramic resonator or the circuit shown
in Figure 1-10 for a 3-pin ceramic
resonator, and follow the resonator
manufacturer’s recommendations.
MCU
OSC1
R
OSC2
CERAMIC
C
RESONATOR
C
The external component values
required for maximum stability and
reliable starting depend upon the
Figure 1-9. 2-Pin Ceramic
resonator parameters. The load
Resonator Connections
.
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.
Technical Data
28
General Description
MC68HC705C8A — Rev. 2.0
MOTOROLA