MC68HC908KX8 Datasheet, PDF (127/310 Pages) Motorola, Inc – Microcontrollers

Internal Clock Generator Module (ICG)
CONFIG or MOR Options
7.7 CONFIG or MOR Options
Four CONFIG or MOR options affect the functionality of the ICG. These
options are:
1. EXTCLKEN, external clock enable
2. EXTXTALEN, external crystal enable
3. EXTSLOW, slow external clock
4. OSCENINSTOP, oscillator enable in stop
All CONFIG or MOR options will have a default setting. Refer to
Section 9. Configuration Register (CONFIG) on how the CONFIG or
MOR is used.
7.7.1 External Clock Enable (EXTCLKEN)
External clock enable (EXTCLKEN), when set, enables the ECGON bit
to be set. ECGON turns on the external clock input path through the
PTB6/(OSC1) pin. When EXTCLKEN is clear, ECGON cannot be set
and PTB6/(OSC1) will always perform the PTB6 function.
The default state for this option is clear.
7.7.2 External Crystal Enable (EXTXTALEN)
External crystal enable (EXTXTALEN), when set, will enable an amplifier
to drive the PTB7/(OSC2) pin from the PTB6/(OSC1) pin. The amplifier
will drive only if the external clock enable (EXTCLKEN) bit and the
ECGON bit are also set. If EXTCLKEN or ECGON are clear,
PTB7/(OSC2) will perform the PTB7 function. When EXTXTALEN is
clear, PTB7/(OSC2) will always perform the PTB7 function.
EXTXTALEN, when set, also configures the clock monitor to expect an
external clock source in the valid range of crystals (30 kHz to 100 kHz or
1 MHz to 8 MHz). When EXTXTALEN is clear, the clock 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).
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 — Rev. 1.0
MOTOROLA
Internal Clock Generator Module (ICG)
Technical Data
127