Datasheet

Oscillator (OSC)
Data Sheet MC68HC908LJ24/LK24 — Rev. 2.1
104 Oscillator (OSC) Freescale Semiconductor
The reference clock for the CGM, real time clock module (RTC) and
other MCU sub-systems is driven by the crystal oscillator. The COP
module is always driven by internal RC clock.
The internal RC oscillator runs continuously after a POR or reset and is
always available in run and wait modes. In stop mode, it can be disabled
by setting the STOP_IRCDIS bit in CONFIG2 register.
Figure 7-1. shows the block diagram of the oscillator module.
Figure 7-1. Oscillator Module Block Diagram
C
1
C
2
R
B
X
1
R
S
*
*R
S
can be zero (shorted) when used with higher-frequency crystals.
MCU
Refer to manufacturer’s data.
OSC2OSC1
See Section 24. for component value requirements.
STOP_XCLKEN
CONFIG2
CGMXCLK
To RTC, ADC, LCD,
INTERNAL RC
EN
SIMOSCEN
STOP_IRCDIS
CONFIG2
ICLK
From SIM
To SIM, COP
CGMRCLK
CGM Clock Selection MUX
OSCILLATOR
To CGM PLL
CRYSTAL OSCILLATOR
INTERNAL RC OSCILLATOR
32.768kHz
(typical)