mc908jl16 Freescale Semiconductor, Inc, mc908jl16 Datasheet - Page 63

• Manufacturer Part Number: mc908jl16
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Chapter 5
Oscillator (OSC)
5.1 Introduction
The oscillator module provides the reference clocks for the MCU system and bus. Two oscillators are
running on the device:
Selectable oscillator — for bus clock
The selected oscillator is used to drive the bus clock, the SIM, and other modules on the MCU. The
oscillator type is selected by programming a bit FLASH memory. The RC and crystal oscillator cannot run
concurrently; one is disabled while the other is selected; because the RC and XTAL circuits share the
same OSC1 pin.
Non-selectable oscillator — for COP
This internal oscillator is used to drive the computer operating properly (COP) module and the SIM. The
internal oscillator runs continuously after a POR or reset, and is always available.
5.2 Oscillator Selection
The oscillator type is selected by programming a bit in a FLASH memory location; the mask option register
(MOR), at $FFD0. (See
Freescale Semiconductor
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Crystal oscillator (XTAL) — built-in oscillator that requires an external crystal or ceramic-resonator.
This option also allows an external clock that can be driven directly into OSC1.
RC oscillator (RC) — built-in oscillator that requires an external resistor-capacitor connection only.
Internal oscillator — built-in RC oscillator that requires no external components.
On the ROM device, the oscillator is selected by a ROM-mask layer at
factory.
3.5 Mask Option Register
MC68HC908JL16 Data Sheet, Rev. 1.1
NOTE
(MOR).)
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