Chapter 18 Real-Time Counter With Calendar (RTCV2)
S12ZVHY/S12ZVHL Family Reference Manual Rev. 1.05
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Freescale Semiconductor
the variation in the RTC clock output and determine the correct calibration point. Refer to Device spec for
more information on timer channel connection.
18.6.2 RTC compensation
To reach the high precision RTC clock, the compensation need following steps.
•
Characterization of the OSCCLK or OSCCLK_32K crystal, get the lookup table for the crystal
frequency versus to temperature. This step is just required one time per crystal type.
•
Perform the RTC calibration at production for each device, get the base frequency offset.
•
Perform the RTC compensation periodically after enabling the RTC.
— Measure the external temperature
— Lookup compensation value in lookup table
— Load the compensation value into RTC