STM32F103x8, STM32F103xB
Description
2.3.13
DMA
The flexible 7-channel general-purpose DMA is able to manage memory-to-memory,
peripheral-to-memory and memory-to-peripheral transfers. The DMA controller supports
circular buffer management avoiding the generation of interrupts when the controller
reaches the end of the buffer.
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.
2.3.14
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.
2.3.15
Timers and watchdogs
The medium-density STM32F103xx performance line devices include an advanced-control
timer, three general-purpose timers, two watchdog timers and a SysTick timer.
compares the features of the advanced-control and general-purpose timers.
Table 4.
Timer
Timer feature comparison
Counter
resolution
16-bit
Counter
type
Up,
down,
up/down
Up,
down,
up/down
Prescaler
factor
Any integer
between 1
and 65536
Any integer
between 1
and 65536
DMA request Capture/compare Complementary
generation
channels
outputs
Yes
4
Yes
TIM1
TIM2,
TIM3,
TIM4
16-bit
Yes
4
No
Advanced-control timer (TIM1)
The advanced-control timer (TIM1) can be seen as a three-phase PWM multiplexed on 6
channels. It has complementary PWM outputs with programmable inserted dead-times. It
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