MC908JL8CDWE Datasheet, PDF (81/212 Pages) Freescale Semiconductor, Inc – Microcontrollers

Internal Oscillator
6.2.2 RC Oscillator
The RC oscillator circuit is designed for use with external resistor and capacitor 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:
• C_EXT
• R_EXT
From SIM
To SIM
To SIM
2OSCOUT
OSCOUT
SIMOSCEN
EN
EXT-RC
OSCILLATOR
RCCLK
÷2
MCU
OSC1
0
1
PTA6
I/O
RCCLK/PTA6 (OSC2)
PTA6
PTA6EN
V_DD
R_EXT
C_EXT
See Chapter 17 for component value requirements.
Figure 6-3. RC Oscillator External Connections
6.3 Internal Oscillator
The internal oscillator clock (ICLK) is a free running 50-kHz clock that requires no external components.
It is used as the reference clock input to the computer operating properly (COP) module and the SIM.
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_ICLKDIS bit before executing the STOP instruction.
Figure 6-4 shows the logical representation of components of the internal oscillator circuitry.
From SIM
To SIM and COP
SIMOSCEN
ICLK
CONFIG2
STOP_ICLKDIS
EN
INTERNAL
OSCILLATOR
Figure 6-4. Internal Oscillator
MC68HC908JL8/JK8 • MC68HC08JL8/JK8 • MC68HC908KL8 Data Sheet, Rev. 3.1
Freescale Semiconductor
81