z8f083a ZiLOG Semiconductor, z8f083a Datasheet - Page 158

• Manufacturer Part Number: z8f083a
• Description: High-performance 8-bit Microcontrollers
• Manufacturer: ZiLOG Semiconductor

Table 94. Oscillator Configuration and Selection
PS026308-1207
Clock Source
Internal precision
RC oscillator
External crystal/
resonator
External RC
oscillator
External clock drive • 0 to 20 MHz
Internal Watchdog
Timer Oscillator
Caution:
OSC Control Register Unlocking/Locking
To write the oscillator control register, unlock it by making two writes to the OSCCTL
register with the values
changes the value of the actual register and returns the register to a Locked state. Any
other sequence of oscillator control register writes has no effect. The values written to
unlock the register must be ordered correctly, but are not necessarily consecutive. It is
possible to write to or read from other registers within the unlocking/locking operation.
Unintentional accesses to the oscillator control register actually stops the chip by
switching to a non-functioning oscillator. To prevent this condition, the oscillator
control block employs a register unlocking/locking scheme.
Characteristics
• 119 kHz or 20 MHz
• ± 4% accuracy when trimmed
• No external components required
• 32 kHz to 20 MHz
• Very high accuracy (dependent on
• Requires external components
• 32 kHz to 4 MHz
• Accuracy dependent on external
• Accuracy dependent on external clock
• 10 kHz nominal
• ± 40% accuracy; no external
• Low power consumption
crystal or resonator used)
components
source
components required
E7H
followed by
18H
. A third write to the OSCCTL register
Required Setup
• Unlock and write oscillator control
• Configure Flash option bits for correct
• Unlock and write OSCCTL to enable
• Configure Flash option bits for correct
• Unlock and write OSCCTL to enable
• Write GPIO registers to configure PB3
• Unlock and write OSCCTL to select
• Apply external clock signal to GPIO
• Enable WDT if not enabled and wait
• Unlock and write oscillator control
register (OSCCTL) to enable and select
oscillator at either 20 MHz or
119 kHz
external OSCILLATOR mode
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 OSCILLATOR mode
crystal oscillator and select as system
clock
pin for external clock function
external system clock
until WDT oscillator is operating.
register (OSCCTL) to enable and select
oscillator
Z8 Encore!
Product Specification
®
F083A Series
Oscillator Control
146