Z8F021ASH020SC datasheet(199/276 Pages) ZILOG

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PS022815-0206

Oscillator Control

Z8 Encore! XP® 4K Series

Product Specification

180

Oscillator Control

Overview

The Z8 Encore! XP® 4K Series devices uses five possible clocking schemes, each user-

selectable:

• Internal precision trimmed RC oscillator (IPO)

• On-chip oscillator using off-chip crystal or resonator

• On-chip oscillator using external RC network

• External clock drive

• On-chip low precision Watch-Dog Timer oscillator

In addition, Z8 Encore! XP® 4K Series devices contain clock failure detection and recov-

ery circuitry, allowing continued operation despite a failure of the system clock oscillator.

Operation

This chapter discusses the logic used to select the system clock and handle primary oscil-

lator failures. A description of the specific operation of each oscillator is outlined else-

where in this document. The detailed description of the Watch-Dog Timer Oscillator starts

on page 83, the Internal Precision Oscillator description begins on page 190, and the chap-

ter outlining the Crystal Oscillator begins on page 185 of this document.

System Clock Selection

The oscillator control block selects from the available clocks. Table 111 details each clock

source and its usage.

Z8F021ASH020SC 数据表(PDF) 199 Page - Zilog, Inc.