MC68HC908LJ24 Datasheet, PDF (104/464 Pages) Motorola, Inc – Microcontrollers

Oscillator (OSC)
Freescale Semiconductor, Inc.
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.
From SIM
CONFIG2
STOP_IRCDIS
CONFIG2
STOP_XCLKEN
MCU
EN
INTERNAL RC
OSCILLATOR
INTERNAL RC OSCILLATOR
CRYSTAL OSCILLATOR
OSC1
R_B
ICLK
To SIM, COP
CGMRCLK
To CGM PLL
CGMXCLK
To RTC, ADC, LCD,
CGM Clock Selection MUX
OSC2
R_S*
*R_S can be zero (shorted) when used with higher-frequency crystals.
X₁
Refer to manufacturer’s data.
See Section 24. for component value requirements.
C₁
32.768 kHz
(typical)
C₂
Figure 7-1. Oscillator Module Block Diagram
Data Sheet
104
MC68HC908LJ24/LK24 — Rev. 2
Oscillator (OSC)
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