MC9S12HZ256 Datasheet, PDF (203/692 Pages) Freescale Semiconductor, Inc – HCS12 Microcontrollers

Chapter 6
Oscillator (OSCV2)
6.1 Introduction
The OSC module provides two alternative oscillator concepts:
• A low noise and low power Colpitts oscillator with amplitude limitation control (ALC)
• A robust full swing Pierce oscillator with the possibility to feed in an external square wave
6.1.1 Features
The Colpitts OSC option provides the following features:
• Amplitude limitation control (ALC) loop:
— Low power consumption and low current induced RF emission
— Sinusoidal waveform with low RF emission
— Low crystal stress (an external damping resistor is not required)
— Normal and low amplitude mode for further reduction of power and emission
• An external biasing resistor is not required
The Pierce OSC option provides the following features:
• Wider high frequency operation range
• No DC voltage applied across the crystal
• Full rail-to-rail (2.5 V nominal) swing oscillation with low EM susceptibility
• Fast start up
Common features:
• Clock monitor (CM)
• Operation from the V_DDPLL 2.5 V (nominal) supply rail
6.1.2 Modes of Operation
Two modes of operation exist:
• Amplitude limitation controlled Colpitts oscillator mode suitable for power and emission critical
applications
• Full swing Pierce oscillator mode that can also be used to feed in an externally generated square
wave suitable for high frequency operation and harsh environments
MC9S12HZ256 Data Sheet, Rev. 2.04
Freescale Semiconductor
203