Datasheet

STM32F313xx Functional overview
Doc ID 023636 Rev 1 21/58
3.17 Real-time clock (RTC) and backup registers
The RTC and the 16 backup registers are supplied through a switch that takes power from
either the V
DD
supply when present or the V
BAT
pin. The backup registers are sixteen 32-bit
registers used to store 64 bytes of user application data when V
DD
power is not present.
They are not reset by a system or power reset.
The RTC is an independent BCD timer/counter. It supports the following features:
● Calendar with subsecond, seconds, minutes, hours (12 or 24 format), week day, date,
month, year, in BCD (binary-coded decimal) format.
● Automatic correction for 28, 29 (leap year), 30 and 31 days of the month.
● Two programmable alarms with wake up from Stop mode capability.
● On-the-fly correction from 1 to 32767 RTC clock pulses. This can be used to
synchronize it with a master clock.
● Digital calibration circuit with 1 ppm resolution, to compensate for quartz crystal
inaccuracy.
● Three anti-tamper detection pins with programmable filter. The MCU can be woken up
from Stop mode on tamper event detection.
● Timestamp feature which can be used to save the calendar content. This function can
be triggered by an event on the timestamp pin, or by a tamper event. The MCU can be
woken up from Stop mode on timestamp event detection.
● 17-bit Auto-reload counter for periodic interrupt with wakeup from STOP capability.
The RTC clock sources can be:
● A 32.768 kHz external crystal
● A resonator or oscillator
● The internal low-power RC oscillator (typical frequency of 40 kHz)
● The high-speed external clock divided by 32.
3.18 I
2
C bus
Up to two I
2
C bus interfaces can operate in multimaster and slave modes. They can support
standard (up to 100 KHz), fast (up to 400 KHz) and fast mode + (up to 1 MHz) modes.
Both support 7-bit and 10-bit addressing modes, multiple 7-bit slave addresses
(2 addresses, 1 with configurable mask). They also include programmable analog and
digital noise filters.