MC68HC705K1 Datasheet, PDF (20/140 Pages) Freescale Semiconductor, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
General Description
1.6.2 OSC1 and OSC2
The OSC1, OSC2, and PB1/OSC3 pins are the control connections for
the 2-pin or 3-pin on-chip oscillator. The oscillator can be driven by any
of these:
• Crystal
• Ceramic resonator
• Resistor-capacitor network
• External clock signal
The frequency of the internal oscillator is f_OSC. The MCU divides the
internal oscillator output by two to produce the internal clock with a
frequency of f_OP.
1.6.2.1 Crystal
The circuit in Figure 1-4 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 start-up 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
2 MΩ
XTAL
C3
27 pF
C4
27 pF
V_SS
OSC1
XTAL
OSC2
V_SS
C1 C2
V_DD
Figure 1-4. Crystal Connections
Technical Data
General Description
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MC68HC705K1 — Rev. 2.0