Z8F0830HH020SG Datasheet, PDF (170/257 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore!^® F0830 Series
Product Specification
152
Table 98. Oscillator Configuration and Selection
Clock Source
Characteristics
Required Setup
Internal precision
RC oscillator
• 32.8 kHz or 5.53MHz
• ± 4% accuracy when trimmed
• No external components required
• Unlock and write to the Oscillator Con-
trol Register (OSCCTL) to enable and
select oscillator at either 5.53 MHz or
32.8 kHz
External crystal/res- • 32 kHz to 20MHz
onator
• Very high accuracy (dependent on
crystal or resonator used)
• Requires external components
• Configure Flash option bits for correct
external OSCILLATOR Mode
• Unlock and write OSCCTL to enable
crystal oscillator, wait for it to stabilize
and select as system clock (if the
XTLDIS option bit has been
de-asserted, no waiting is required)
External RC oscilla- • 32 kHz to 4MHz
tor
• Accuracy dependent on
nal components
• Configure Flash option bits for correct
exter- external OSCILLATOR Mode
• Unlock and write OSCCTL to enable
crystal oscillator and select as system
clock
External clock drive • 0 to 20MHz
• Accuracy dependent on
nal clock source
• Write GPIO registers to configure PB3
exter- pin for external clock function
• Unlock and write OSCCTL to select
external system clock
• Apply external clock signal to GPIO
Internal Watchdog
Timer Oscillator
• 10 kHz nominal
• ± 40% accuracy; no external compo-
nents required
• Low power consumption
• Enable WDT if not enabled and wait
until WDT oscillator is operating.
• Unlock and write to the Oscillator Con-
trol Register (OSCCTL) to enable and
select oscillator
Caution: Unintentional accesses to the Oscillator Control Register can actually stop the chip by
switching to a nonfunctioning oscillator. To prevent this condition, the oscillator control
block employs a register unlocking/locking scheme.
OSC Control Register Unlocking/Locking
To write the Oscillator Control Register, unlock it by making two writes to the OSCCTL
Register with the values E7H followed by 18H. A third write to the OSCCTL Register
changes the value of the actual register and returns the register to a Locked state. Any
other sequence of Oscillator Control Register writes have no effect. The values written to
unlock the register must be ordered correctly, but are not necessarily consecutive. It is pos-
sible to write to or read from other registers within the unlocking/locking operation.
PS025113-1212
Operation