Z8 Encore! XP® 4K Series
Product Specification
190
Internal Precision Oscillator
Overview
The internal precision oscillator (IPO) is designed for use without external components.
The user can either manually trim the oscillator for a non-standard frequency or use the
automatic factory-trimmed version to achieve a 5.53 MHz frequency. IPO features
include:
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•
•
•
On-chip RC oscillator that does not require external components
Output frequency of either 5.53 MHz or 32.8 KHz (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 accu-
racy 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 the user 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 will be optimal.
If not used, the IPO can be disabled by the Oscillator Control Register (page 183).
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 Trim Bit Address Space on page 153.
Select one of two frequencies for the oscillator: 5.53 MHz and 32.8 KHz, using the OSC-
SEL bits in the Oscillator Control on page 180.
PS022815-0206
Internal Precision Oscillator
ZILOG [ ZILOG, INC. ]
