Datasheet

DocID025409 Rev 8 25/121
STM32F334x4 STM32F334x6 STM32F334x8 Functional overview
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3.14.7 SysTick timer
This timer is dedicated to real-time operating systems, but could also be used as a standard
down counter. It features:
• A 24-bit down counter
• Auto reload capability
• Maskable system interrupt generation when the counter reaches 0.
• Programmable clock source
3.15 Real-time clock (RTC) and backup registers
The RTC and the 5 backup registers are supplied through a switch that takes power from
either the V
DD
supply when present or the VBAT pin. The backup registers are five 32-bit
registers used to store 20 bytes of user application data when V
DD
power is not present.
They are not reset by a system or power reset, or when the device wakes up from Standby
mode.
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.
• Reference clock detection: a more precise second source clock (50 or 60 Hz) can be
used to enhance the calendar precision.
• Automatic correction for 28, 29 (leap year), 30, and 31 days of the month.
• Two programmable alarms with wakeup from Stop and Standby 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.
• Two anti-tamper detection pins with programmable filter. The MCU can be woken up
from Stop and Standby modes 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 and Standby modes on timestamp event detection.
• 17-bit Auto-reload counter for periodic interrupt with wakeup from STOP/STANDBY
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.
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