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.
PS022815-0206
Oscillator Control
ZILOG [ ZILOG, INC. ]
