we're trying to use 32kHz crystal for RTC clock instead of internal oscillator. According to Fig.59-2 in Chapter 59.4.1 of reference manual, internal oscillator should be disconnected by automatic mux when correct signal is detected on RTC_XTALI/O pins. Then bit RTC_XTAL_SOURCE in reg. XTALOSC24M_MISC0 should reads 1.
We're facing problem, that although we have correct signals on RTC_XTALI/O pins, we're still running on internal oscillator. We checked both power consumption and pin value.
So the question is, what important setting are we missing. And if switching to crystal means that internal oscillator is turned off, or whether continues ticking into void.
Thanks in advance
Hello Jiri Luznicky,
I would recommend looking at the latest revision of the Reference Manual (link below) as this information is now on Chapter 58.
If I understand correctly you’re not seeing the XTALOSC24M_MISC0 [RTC_XTAL_SOURCE] switching from zero to one. I would
recommend reviewing that the connection matches one of the three suggested forms in section 58.4.2 and that the voltage is set as 1.1V.
Which of the three configurations are you using? Have you measured the voltage on the ball to make sure there are no problems like voltage dropping down?
I rechecked XTALOSC24M_MISC0, and I have to admit, that I misread the address of register in reference manual. So RTC_XTAL_SOURCE is set 1, therefor correctly.
The reaming problem is, that power consumption is circa 48uA instead of expected 15uA. We've checked tamper pins, and found them set to disabled in fuses. We're now looking for leakages.