Rtc Functional Description; Overview; Figure 179. Rtc Simplified Block Diagram - ST STM32F101 series Reference Manual

Real-time clock (RTC)
18.3

RTC functional description

18.3.1

Overview

The RTC consists of two main units (see
Interface) is used to interface with the APB1 bus. This unit also contains a set of 16-bit
registers accessible from the APB1 bus in read or write mode (for more information refer to
Section 18.4: RTC registers on page
clock in order to interface with the APB1 bus.
The other unit (RTC Core) consists of a chain of programmable counters made of two main
blocks. The first block is the RTC prescaler block, which generates the RTC time base
TR_CLK that can be programmed to have a period of up to 1 second. It includes a 20-bit
programmable divider (RTC Prescaler). Every TR_CLK period, the RTC generates an
interrupt (Second Interrupt) if it is enabled in the RTC_CR register. The second block is a
32-bit programmable counter that can be initialized to the current system time. The system
time is incremented at the TR_CLK rate and compared with a programmable date (stored in
the RTC_ALR register) in order to generate an alarm interrupt, if enabled in the RTC_CR
control register.
PCLK1
RTCCLK
475/1128

Figure 179. RTC simplified block diagram

Backup domain
RTC_PRL
32-bit programmable
Reload
TR_CLK
RTC_DIV
rising
edge
RTC prescaler
powered in Standby
powered in Standby
WKUP pin
DocID13902 Rev 15
Figure 179 on page
478). The APB1 interface is clocked by the APB1 bus
APB1 bus
APB1 interface
RTC_Second
counter
RTC_Overflow
RTC_CNT
RTC_Alarm
=
RTC_ALR
RTC_Alarm
WKP_STDBY
475). The first one (APB1
not powered in Standby
RTC_CR
SECF
SECIE
OWF
OWIE
ALRF
ALRIE
not powered in Standby
NVIC interrupt
controller
not powered in Standby
exit
Standby mode
powered in Standby
RM0008
ai14969b