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Using an external 32 KHz clock in 5606B

Question asked by Gilad Barzilay on Nov 25, 2015
Latest reply on Nov 27, 2015 by Petr Stancik

Hi there,


I am trying to use an external 32KHz clock on the EXTAL pin as the clock reference for the internal RTC in the 5606B chip.


I am working according to this table from the reference manual:


My OSC32_EXTAL pin is connected to a 32KHz clock (which is ticking correctly, verified with a scope), and OSC32_XTAL is grounded.


When I am setting the bypass bit in the SXOSC_CTL register (as per line 2) the RTC clock does not tick at all, and the API interrupt is never called, and when I set is to enable, and I am supposedly at line 4 of the table, the interrupt is called instead of every second, every ~1.3 seconds.


I measured the internal 32KHz clock using the CMU, and got a result of ~24KHz, which is consistent with the RTC behavior.


Tried on another board and replicated the results.


Any ideas on what I am doing wrong?


Thanks in advance.