MC68HC05P18 Datasheet, PDF (22/144 Pages) Freescale Semiconductor, Inc – Advance Information

Freescale Semiconductor, Inc.
General Description
The frequency, f_OSC, of the oscillator or external clock source is divided
by two to produce the internal PH2 bus clock operating frequency, f_OP.
The oscillator cannot be turned off by software if the stop-to-halt
conversion is enabled via mask option for the MC68HC05P18 and mask
option register 1 for the MC68HC805P18. Refer to 8.5 Mask Option
Registers.
1.5.3 Crystal
The circuit in Figure 1-3(a) shows a typical oscillator circuit for an
AT-cut, parallel resonant crystal. Follow the crystal manufacturer’s
recommendations, 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.
NOTE: Mount the crystal and components as close as possible to the pins for
startup stabilization and to minimize output distortion.
1.5.3.1 Ceramic Resonator
In cost-sensitive applications, use a ceramic resonator instead of a
crystal. Use the circuit in Figure 1-3(a) for a ceramic resonator and
follow the resonator manufacturer’s recommendations, as 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 capacitances.
Mount the resonator and components as close as possible to the pins for
startup stabilization and to minimize output distortion.
1.5.3.2 External Clock
An external clock from another CMOS-compatible device can be
connected to the OSC1 input, with the OSC2 input not connected, as
shown in Figure 1-3(b).
Advance Information
22
MC68HC(8)05P18 — Rev. 2.0
General Description
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