s908ey8ad4cfjer Freescale Semiconductor, Inc, s908ey8ad4cfjer Datasheet - Page 77

• Manufacturer Part Number: s908ey8ad4cfjer
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 8
Internal Clock Generator (ICG) Module
8.1 Introduction
The internal clock generator (ICG) module is used to create a stable clock source for the microcontroller
without using any external components. The ICG generates the oscillator output clock (CGMXCLK),
which is used by the computer operating properly (COP), low-voltage inhibit (LVI), and other modules.
The ICG also generates the clock generator output (CGMOUT), which is fed to the system integration
module (SIM) to create the bus clocks. The bus frequency will be one-fourth the frequency of CGMXCLK
and one-half the frequency of CGMOUT. Finally, the ICG generates the timebase clock (TBMCLK), which
is used in the timebase module (TBM).
8.2 Features
The ICG has these features:
8.3 Functional Description
The ICG, shown in
Freescale Semiconductor
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Selectable external clock generator, either 1-pin external source or 2-pin crystal, multiplexed with
port pins
Internal clock generator with programmable frequency output in integer multiples of a nominal
frequency (307.2 kHz ± 25 percent)
Internal oscillator trimmed accuracy of ±3.5 percent
Bus clock software selectable from either internal or external clock (bus frequency range from 76.8
kHz ± 25 percent to 9.75 MHz ± 25 percent in 76.8-kHz increments)
Timebase clock automatically selected from external clock if external clock is available
Clock monitor for both internal and external clocks
Clock enable circuit
Internal clock generator
External clock generator
Clock monitor circuit
Clock selection circuit
For the MC68HC908EY16, do not exceed the maximum bus frequency of
8 MHz at 5.0 V.
Figure
8-2, contains these major submodules:
MC68HC908EY16 • MC68HC908EY8 Data Sheet, Rev. 10
NOTE
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