Z8F042AHJ020SG Datasheet, PDF (220/282 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F082A Series
Product Specification
203
Internal Precision Oscillator
The internal precision oscillator (IPO) is designed for use without external components.
You can either manually trim the oscillator for a nonstandard frequency or use the auto-
matic factory-trimmed version to achieve a 5.53 MHz frequency. IPO features include:
• On-chip RC oscillator that does not require external components
• Output frequency of either 5.53MHz or 32.8kHz (contains both a fast and a slow mode)
• Trimmed through Flash option bits with user override
• Elimination of crystals or ceramic resonators in applications where very high timing
accuracy is not required
Operation
An 8-bit trimming register, incorporated into the design, compensates for absolute varia-
tion of oscillator frequency. Once trimmed the oscillator frequency is stable and does not
require subsequent calibration. Trimming is performed during manufacturing and is not
necessary for you to repeat unless a frequency other than 5.53 MHz (fast mode) or
32.8 kHz (slow mode) is required. This trimming is done at +30ºC and a supply voltage of
3.3 V, so accuracy of this operating point is optimal.
If not used, the IPO can be disabled by the Oscillator Control Register (see the Oscillator
Control Register Definitions section on page 196).
By default, the oscillator frequency is set by the factory trim value stored in the write-pro-
tected Flash information page. However, the user code can override these trim values as
described in the Trim Bit Address Space section on page 165.
Select one of two frequencies for the oscillator (5.53 MHz and 32.8 kHz) using the OSC-
SEL bits in the the Oscillator Control chapter on page 193.
PS022827-1212
PRELIMINARY
Internal Precision Oscillator