Z8F082ASH020SC datasheet(187/244 Pages) ZILOG

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PS024705-0405

P R E L I M I N A R Y

Internal Precision Oscillator

Z8 Encore! XP® F08xA Series

Product Specification

169

Internal Precision Oscillator

Overview

The Internal Precision Oscillator (IPO) is designed for use without external components.

The user can either manually trim the oscillator for a non-standard frequency or use the

automatic factory-trimmed version to achieve a 5.53MHz frequency. IPO features include:

• On-chip RC oscillator that does not require external components

• Output frequency of either 5.53MHz or 32.8KHz (contains both a fast and a slow mode)

• Trimming possible through Flash option bits with user override

• Elimination of crystals or ceramic resonators in applications where high timing accuracy

is not required.

Operation

The internal oscillator is an RC relaxation oscillator that has had its sensitivity to power

supply variation minimized. By using ratio tracking thresholds, the effect of power supply

voltage is cancelled out. The dominant source of oscillator error is the absolute variance of

chip level fabricated components, such as capacitors. An 8-bit trimming register, incorpo-

rated into the design, compensates for absolute variation of oscillator frequency. Once

trimmed the oscillator frequency is stable and does not require subsequent calibration.

Trimming was performed during manufacturing and is not necessary for the user to repeat

unless a frequency other than 5.53MHz (fast mode) or 32.8kHz (slow mode) is required.

Power down this block for minimum system power.

By default, the oscillator is configured through the Flash Option bits. However, the user

code can override these trim values as described in “Trim Bit Address Space” on

page 142.

Select one of two frequencies for the oscillator: 5.53MHz and 32.8KHz, using the OSC-

SEL bits in the “Oscillator Control” on page 160.

Z8F082ASH020SC Datasheet(PDF) 187 Page - Zilog, Inc.