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K22 RTC Clock Source

Question asked by LALUQUE Thibaut on Mar 15, 2017
Latest reply on Mar 30, 2017 by EARL GOODRICH


For one of our application, we have to share a same reference clock for RTC module between multiple K22FN512VLH12  to keep the same reference time between all MCU.


According to datasheet and reference manual of the K22, the RTC can only take the XTAL32 oscillator as clock source. This oscillator is only defined as "analog oscillator" for 32k crystal and seems not to accept digital clock (no configuration available to switch working mode from crystal to digital oscillator). The problem is that a 32k crystal can't be share between multiple MCU...


My question is the following : Is that possible to replace the 32k crystal by a digital clock by connecting only the EXTAL32 to the digital clock ? And sharing it with multiple MCU ?


We made test on the FRDM-K22F board by replacing the 32k oscillator by a digital clock, it seems to work but we don't know if this result is repeatable and reliable. We won't take any risk hence my question !


in advance, thank you for your return.