In IMX6DQRM Revision 2, 71.1 it said Automatically switch to the external oscillation source when sensed on the RTC_XTAL bumps(contacts) (32 kHz specific feature). Is it means i.MX6 sensed it by checking XTALOSC_RTC_XTALI & XTALOSC_RTC_XTALO pin contact with external oscillator or not?
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You are correct. In case the i.MX6 detects that an external oscillator has been connected to the XTALOSC_RTC_XTALI & XTALOSC_RTC_XTALO pins this external oscillator is used. In the absence of an external RTC oscillator the i.MX6 switches to the internal ring oscillator.
More details on this on-chip oscillator can be found on Section 4.1.4 of the i.MX6DQ Datasheet. I recommend reviewing these as the on-chip oscillator is not as precise as a 32 kHz crystal.
You are correct. In case the i.MX6 detects that an external oscillator has been connected to the XTALOSC_RTC_XTALI & XTALOSC_RTC_XTALO pins this external oscillator is used. In the absence of an external RTC oscillator the i.MX6 switches to the internal ring oscillator.
More details on this on-chip oscillator can be found on Section 4.1.4 of the i.MX6DQ Datasheet. I recommend reviewing these as the on-chip oscillator is not as precise as a 32 kHz crystal.
So, if an external RTC oscillator is not use, the i.MX6 will switches to the internal ring oscillator, but when I didn't use an external RTC, few boards sometime will not boot and reboot, it just stop and cannot see message from UART debug port. I assert POR signal, iMX6 still not work.
But when I connect RTC_XTALI with 4.7k to ground, the symptom was never happen again. Is it any problem with software or hardware setting?
Hello Chen Jasper,
This is normal HW behavior. In order to engage the internal on-chip loose-tolerance ring oscillator you need to tie RTC_XTALI to GND and leave RTC_XTALO floated.