Other Parts Discussed in Thread: OMAP5912
There is an internal RTC in OMAP5912 processor. CPU pins configured as follow:
DVDDRTC - to 2.6 V battery
CVDDRTC - to 1.6 V battery
RTC_ON_OFF - to 3.3 V main power with a resistor
After power on the register RTC_CTRL_REG = 0x00000000, the register RTC_STATUS_REG = 0x00000080. This look like the RTC was frozen, there is no increment of second's register. If I start RTC by writing to the RTC_CTRL_REG register a value 0x00000001 then the RTC_STATUS_REG become 0x000082 that mean the RTC in a work mode. Now the RTC working properly.
But I just turn off the main power. The 32 kHz oscillator works properly (I saw it on oscilloscope), battery power is ok. Then I turn on the main power and make connect to the ARM processor. I look to the RTC registers and... I see registers have a default state (RTC_CTRL_REG = 0x00000000, RTC_STATUS_REG = 0x00000080). POWER_UP flag in RTC_STATUS_REG indicates that a reset occured. Current time is zero.
I think RTC was reset with the processor on power-on reset stage. But why?