Datasheet

STM32F103x8, STM32F103xB Description
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Each channel is connected to dedicated hardware DMA requests, with support for software
trigger on each channel. Configuration is made by software and transfer sizes between
source and destination are independent.
The DMA can be used with the main peripherals: SPI, I
2
C, USART, general-purpose and
advanced-control timers TIMx and ADC.
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 are ten 16-bit
registers used to store 20 bytes of user application 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 a 32.768 kHz external crystal, resonator or 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 40 kHz. The RTC can be calibrated using
an external 512 Hz output to compensate for any natural crystal 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 40 kHz internal RC and as it operates independently of 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 timeout
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 downcounter. It
features:
● A 24-bit downcounter
● Autoreload capability
● Maskable system interrupt generation when the counter reaches 0
● Programmable clock source
General-purpose timers (TIMx)
There are up to three synchronizable general-purpose 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.