FAQ
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FAQ
In the M451 series, why the read RTC_TIME and RTC_CAL values are incorrect after VDD is powered on when VBAT and VDD are powered independently? Issue Date：2016-06-27
Since VBAT and VDD are powered independently, the across power domain and synchronization issue exists. If RTC_TIME and RTC_CAL registers are read immediately after power on, the RTC_TIME and RTC_CAL values may be incorrect.
This is because both the RTC_TIME and RTC_CAL registers are triggered and updated by the RTC Counter. Please refer to the following figure. The RTC Counter is updated once per second.
Thus, to solve the power-on synchronization issue, wait a second, until the RTC Counter updates RTC_TIME and RTC_CAL, and then read the value of the register.
| Products: | Microcontrollers ,Arm Cortex-M4 MCUs ,M451 Base Series ,M452 USB Series ,M453 CAN Series |
|---|---|
| Applications: | |
| Function: | Peripherals,Timer and PWM,RTC |