NXP Semiconductors
UM10789
USB-I²C-bus dongle OM13518 with a GUI
UM10789
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© NXP B.V. 2014. All rights reserved.
User manual
Rev. 1 — 19 May 2014
15 of 19
4. Enable the watchdog for a repeat every 2 seconds for example (see Fig 18).
Fig 18. Enable the watchdog for a repeat every 2 seconds
5. Observe the LED flashing every 2 seconds!!!
5.3.3 Interactive quartz frequency offset correction:
The quartz crystals come with a tolerance of typical ± 20 ppm. To correct the actual
offset of the quartz in use, take the following steps:
1. Measure the frequency at CLKout pin, e.g. 32 768.51 Hz
2. Write the measured frequency in the entry field, it automatically calculates the offset
and the needed correction value. 15.19 ppm or 7 correction pulses.
3. By activating
SET BYTE
the offset value is programmed in to the RTCs offset
register.
Note
: The offset calibration operates at the time counter level and will not result in any
observable change in frequency.
Fig 19. Offset correction
