Freescale Semiconductor Demonstration Board for Freescale MC9S12XHY256 Microcontroller DEMO9S12XHY256 DEMO9S12XHY256 Manual De Usuario

Freescale Semiconductor

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The Pierce oscillator (XOSC) module provides a robust, low-noise and low-power clock source. The
module will be operated from the V

DDPLL

supply rail (1.8 V nominal) and require the minimum number

of external components. It is designed for optimal start-up margin with typical crystal oscillators.

The XOSC will contain circuitry to dynamically control current gain in the output amplitude. This ensures
a signal with low harmonic distortion, low power and good noise immunity.

•

High noise immunity due to input hysteresis

•

Low RF emissions with peak-to-peak swing limited dynamically

•

Transconductance (gm) sized for optimum start-up margin for typical oscillators

•

Dynamic gain control eliminates the need for external current limiting resistor

•

Integrated resistor eliminates the need for external bias resistor in loop controlled Pierce mode.

•

Low power consumption:

— Operates from 1.8 V (nominal) supply

— Amplitude control limits power

•

Clock monitor

Two modes of operation exist:

1. Loop controlled Pierce (LCP) oscillator

2. External square wave mode featuring also full swing Pierce (FSP) without internal bias resistor

The oscillator mode selection is described in the Device Overview section, subsection Oscillator
Configuration.

V01.05

19 Jul 2006

- All xclks info was removed

V02.00

04 Aug 2006

- Incremented revision to match the design system spec revision