STM32F103xx
Description
RTC (real-time clock) and backup registers
The RTC and the backup registers are supplied through a switch that takes power either on
V
DD
supply when present or through the V
BAT
pin. The backup registers (ten 16-bit
registers) can be used to store data when V
DD
power is not present.
The real-time clock provides a set of continuously running counters which can be used with
suitable software to provide a clock calendar function, and provides an alarm interrupt and a
periodic interrupt. It is clocked by an external 32.768 kHz oscillator, the internal low power
RC oscillator or the High Speed External clock divided by 128. The internal low power RC
has a typical frequency of 32 kHz. The RTC can be calibrated using an external 512 Hz
output to compensate for any natural quartz deviation. The RTC features a 32-bit
programmable counter for long term measurement using the Compare register to generate
an alarm. A 20-bit prescaler is used for the time base clock and is by default configured to
generate a time base of 1 second from a clock at 32.768 kHz.
Independent watchdog
The independent watchdog is based on a 12-bit downcounter and 8-bit prescaler. It is
clocked from an independent 32 kHz internal RC and as it operates independently from the
main clock, it can operate in Stop and Standby modes. It can be used either as a watchdog
to reset the device when a problem occurs, or as a free running timer for application time out
management. It is hardware or software configurable through the option bytes. The counter
can be frozen in debug mode.
Window watchdog
The window watchdog is based on a 7-bit downcounter that can be set as free running. It
can be used as a watchdog to reset the device when a problem occurs. It is clocked from the
main clock. It has an early warning interrupt capability and the counter can be frozen in
debug mode.
SysTick timer
This timer is dedicated for OS, but could also be used as a standard down counter. It
features:
●
●
●
●
A 24-bit down counter
Autoreload capability
Maskable system interrupt generation when the counter reaches 0.
Programmable clock source
General purpose timers (TIMx)
There are up to 3 synchronizable standard timers embedded in the STM32F103xx
performance line devices. These timers are based on a 16-bit auto-reload up/down counter,
a 16-bit prescaler and feature 4 independent channels each for input capture/output
compare, PWM or one pulse mode output. This gives up to 12 input captures / output
compares / PWMs on the largest packages. They can work together with the Advanced
Control Timer via the Timer Link feature for synchronization or event chaining.
The counter can be frozen in debug mode.
Any of the standard timers can be used to generate PWM outputs. Each of the timers has
independent DMA request generations.
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