Z8F0113HJ005EG Datasheet, PDF (184/245 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F0823 Series
Product Specification
169
Oscillator Control
Z8 Encore! XP F0823 Series devices uses three possible clocking schemes, each user-
selectable. These three schemes are:
• On-chip precision trimmed RC oscillator
• External clock drive
• On-chip low power Watchdog Timer oscillator
In addition, F0823 Series devices contain clock failure detection and recovery circuitry,
which allow continued operation despite a failure of the primary 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.
System Clock Selection
The oscillator control block selects from the available clocks. Table 104 details each clock
source and its usage.
Table 104. Oscillator Configuration and Selection
Clock Source
Internal Precision
RC Oscillator
External Clock
Drive
Internal Watchdog
Timer Oscillator
Characteristics
Required Setup
• 32.8kHz or 5.53MHz
• ± 4% accuracy when trimmed
• No external components required
• Unlock and write Oscillator Control
Register (OSCCTL) to enable and
select oscillator at either 5.53 MHz or
32.8 kHz
• 0 to 20MHz
• Write GPIO registers to configure PB3
• Accuracy dependent on external clock pin for external clock function
source
• Unlock and write OSCCTL to select
external system clock
• Apply external clock signal to GPIO
• 10kHz nominal
• ± 40% accuracy; no external compo-
nents required
• Very Low power consumption
• Enable WDT if not enabled and wait
until WDT Oscillator is operating.
• Unlock and write Oscillator Control
Register (OSCCTL) to enable and
select oscillator
PS024315-1011
PRELIMINARY
Oscillator Control