MC68HC705K1 Datasheet, PDF (21/140 Pages) Freescale Semiconductor, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
General Description
Pin Assignments
NOTE:
Use an AT-cut crystal and not a strip or tuning fork crystal. The MCU may
overdrive or have the wrong characteristic impedance for a strip or
tuning fork crystal.
To use the crystal-driven oscillator, the RC and PIN3 bits in the mask
option register must be clear. See 9.6 Mask Option Register. Clearing
the RC bit connects an internal 2-MΩ startup resistor between OSC1
and OSC2.
1.6.2.2 Ceramic Resonator
To reduce cost, use a ceramic resonator in place of the crystal. Use the
circuit in Figure 1-5 for a 2-pin ceramic resonator or Figure 1-6 for a
3-pin ceramic resonator, and follow the resonator manufacturer’s
recommendations. The resonator parameters determine the external
component values required for maximum stability and reliable starting.
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
2 MΩ
C3
27 pF
CERAMIC
RESONATOR
C4
27 pF
V_SS
OSC1
OSC2
CER.
RES.
V_SS
C1 C2
V_DD
Figure 1-5. 2-Pin Ceramic Resonator Connections
MC68HC705K1 — Rev. 2.0
General Description
For More Information On This Product,
Go to: www.freescale.com
Technical Data