MC68HC908GT16 Datasheet, PDF (149/412 Pages) Motorola, Inc – Microcontrollers

Configuration Register (CONFIG)
Functional Description
monitor will expect an external clock source in the valid range for
externally generated clocks when using the clock monitor (60 Hz to
32 MHz).
EXTXTALEN, when set, also configures the external clock
stabilization divider in the clock monitor for a 4096-cycle timeout to
allow the proper stabilization time for a crystal. When EXTXTALEN is
clear, the stabilization divider is configured to 16 cycles since an
external clock source does not need a startup time.
1 = Allows PTE3/OSC2 to be an external crystal connection.
0 = PTE3/OSC2 functions as an I/O port pin (default).
EXTSLOW — Slow External Crystal Enable Bit
The EXTSLOW bit has two functions. It configures the ICG module for
a fast (1 MHz to 8 MHz) or slow (30 kHz to 100 kHz) speed crystal.
The option also configures the clock monitor operation in the ICG
module to expect an external frequency higher (307.2 kHz to 32 MHz)
or lower (60 Hz to 307.2 kHz) than the base frequency of the internal
oscillator. See Section 7. Internal Clock Generator (ICG) Module.
1 = ICG set for slow external crystal operation
0 = ICG set for fast external crystal operation
127( This bit does not function without setting the EXTCLKEN bit also.
EXTCLKEN — External Clock Enable Bit
EXTCLKEN enables an external clock source or crystal/ceramic
resonator to be used as a clock input. Setting this bit enables
PTE4/OSC1 pin to be a clock input pin. Clearing this bit (default
setting) allows the PTE4/OSC1 and PTE3/OSC2 pins to function as
a general-purpose input/output (I/O) pin. Refer to Table 8-1 for
configuration options for the external source. See Section 7. Internal
Clock Generator (ICG) Module for a more detailed description of the
external clock operation.
1 = Allows PTE4/OSC1 to be an external clock connection
0 = PTE4/OSC1 and PTE3/OSC2 function as I/O port pins
(default).
MC68HC908GT16 • MC68HC908GT8 — Rev. 2
MOTOROLA
Configuration Register (CONFIG)
Technical Data
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