GD32F20x User Manual
73
4.
Backup registers (BKP)
4.1.
Overview
The Backup registers are located in the Backup domain that remains powered-on by V
BAT
even if V
DD
power is shut down. The Backup registers have forty two 16-bit (84 bytes) registers
that can be used to store and protect user application data. Wake-up action from Standby
mode or system reset do not affect these registers.
In addition, the BKP registers can be used to implement the tamper detection, RTC calibration
function and waveform detection.
After reset, any writing access to the registers in Backup domain is disabled, that is, the
Backup registers and RTC cannot be written to access. In order to enable access to the
Backup registers and RTC, the Power and Backup interface clocks should be enabled firstly
by setting the PMUEN and BKPIEN bits in the RCU_APB1EN register, and writing access to
the registers in Backup domain should be enabled by setting the BKPWEN bit in the
PMU_CTL register.
4.2.
Characteristics
84 bytes Backup registers which can keep data under power saving mode. If tamper
event is detected, Backup registers will be reset
The active level of Tamper source (PC13 and PI8) can be configured
RTC Clock Calibration register provides RTC alarm and second output selection, and
sets the calibration value
Tamper control and status register (BKP_TPCS) can control tamper detection and
waveform dectection with interrupt or event capability
Two square waveform detection on PC13->PI8 or PC14->PC15
4.3.
Function overview
4.3.1.
RTC clock calibration
In order to improve the RTC clock accuracy, the MCU provides clock output calibration
function. The RTC clock, or a clock with the frequency is f
RTCCLK
/64, can be output on the
PC13. It is enabled by setting the COEN bit in the BKP_OCTL register.
The calibration value is set by RCCV[6:0] in the BKP_OCTL register, and the calibration
function can slow down the RTC clock by steps of 1000000/2^20 ppm.
Содержание GD32F20 Series
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Страница 325: ...GD32F20x User Manual 325 15 0 ALRM 15 0 RTC alarm value low ...
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Страница 523: ...GD32F20x User Manual 523 clears AERR bit by writing 0 to it ...