mc68hc908qf4 Freescale Semiconductor, Inc, mc68hc908qf4 Datasheet - Page 91

• Manufacturer Part Number: mc68hc908qf4
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

11.1 Introduction
11.2 Features
11.3 Functional Description
11.3.1 Internal Oscillator
MC68HC908QF4 — Rev. 1.0
MOTOROLA
Data Sheet — MC68HC908QF4
The oscillator module is used to provide a stable clock source for the
microcontroller system and bus. The oscillator module generates two output
clocks, BUSCLKX2 and BUSCLKX4. The BUSCLKX4 clock is used by the system
integration module (SIM) and the computer operating properly module (COP). The
BUSCLKX2 clock is divided by two in the SIM to be used as the bus clock for the
microcontroller. Therefore the bus frequency will be one forth of the BUSCLKX4
frequency.
The oscillator has these four clock source options available:
The oscillator contains these major subsystems:
The internal oscillator circuit is designed for use with no external components to
provide a clock source with tolerance less than ±25% untrimmed. An 8-bit trimming
register allows adjustment to a tolerance of less than ±5%.
The internal oscillator will generate a clock of 4.0 MHz typical (INTCLK) resulting
in a bus speed (internal clock ÷ 4) of 1.0 MHz.
1. Internal oscillator: An internally generated, fixed frequency clock, trimmable
2. External oscillator: An external clock that can be driven directly into OSC1.
3. External RC: A built-in oscillator module (RC oscillator) that requires an
4. External crystal: A built-in oscillator module (XTAL oscillator) that requires
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to ±5%. This is the default option out of reset.
external R connection only. The capacitor is internal to the chip.
an external crystal or ceramic-resonator.
Internal oscillator circuit
Internal or external clock switch control
External clock circuit
External crystal circuit
External RC clock circuit
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Oscillator Module (OSC)
Section 11. Oscillator Module (OSC)
Data Sheet
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