
Oscillator (OSC)
Data Sheet
MC68HC908SR12MC68HC08SR12 — Rev. 5.0
106
Oscillator (OSC)
Freescale Semiconductor
The internal oscillator by default is always available and is free running
after POR or reset. It can be stopped in Stop mode by setting the
STOP_ICLKEN bit before executing the STOP instruction.
Figure 7-4 shows the logical representation of components of the
internal oscillator circuitry.
Figure 7-4. Internal Oscillator
7.5 RC Oscillator
The RC oscillator circuit is designed for use with external R and C to
provide a clock source with tolerance less than 10%.
In its typical configuration, the RC oscillator requires two external
components, one R and one C. Component values should have a
tolerance of 1% or less, to obtain a clock source with less than 10%
tolerance. The oscillator configuration uses two components:
CEXT
REXT
INTERNAL OSCILLATOR
EN
SIMOSCEN
STOP_ICLKEN
CONFIG2
ICLK
MCU
From SIM
To Clock Selection MUX
BUS CLOCK
From SIM
OSC2
and COP