STMicroelectronics STM32F05 series User Manual

Real-time clock (RTC) RM0091
538/742 Doc ID 018940 Rev 1
24.3.3 Clock and prescalers
The RTC clock source (RTCCLK) is selected through the clock controller among the LSE
clock, the LSI oscillator clock, and the HSE clock. For more information on the RTC clock
source configuration, refer to the Reset and clock control (RCC) section.
A programmable prescaler stage generates a 1 Hz clock which is used to update the
calendar. To minimize power consumption, the prescaler is split into 2 programmable
prescalers (see Figure 227: RTC block diagram):
● A 7-bit asynchronous prescaler configured through the PREDIV_A bits of the
RTC_PRER register.
● A 15-bit synchronous prescaler configured through the PREDIV_S bits of the
RTC_PRER register.
Note: When both prescalers are used, it is recommended to configure the asynchronous prescaler
to a high value to minimize consumption.
Table 78. LSE pin PC14 configuration
(1)
Pin configuration and
function
LSEON bit in
RCC_BDCR register
LSEBYP bit in
RCC_BDCR register
PC14MODE
bit
PC14VALUE
bit
LSE oscillator 1 0 Don’t care Don’t care
LSE bypass 1 1 Don’t care Don’t care
Output PP forced 0 Don’t care 1
PC14 output data
value
Standard GPIO 0 Don’t care 0 Don’t care
1. OD: open drain; PP: push-pull.
Table 79. LSE pin PC15 configuration
(1)
Pin configuration and
function
LSEON bit in
RCC_BDCR register
LSEBYP bit in
RCC_BDCR register
PC15MODE
bit
PC15VALUE
bit
LSE oscillator 1 0 Don’t care Don’t care
Output PP forced
11
1
PC15 output data
value
0 Don’t care
Standard GPIO 0 Don’t care 0 Don’t care
1. OD: open drain; PP: push-pull.

STMicroelectronics STM32F05 series Specifications

General

Brand	STMicroelectronics
Model	STM32F05 series
Category	Microcontrollers
Language	English