Datasheet
DocID16554 Rev 4 19/136
STM32F103xF, STM32F103xG Description
132
The DMA can be used with the main peripherals: SPI, I
2
C, USART, general-purpose, basic
and advanced-control timers TIMx, DAC, I
2
S, SDIO and ADC.
2.3.17 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 forty-two 16-bit
registers used to store 84 bytes of user application data when V
DD
power is not present.
They are not reset by a system or power reset, and they are not reset when the device
wakes up from the Standby mode.
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-speed RC has a typical frequency of 40 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.
2.3.18 Timers and watchdogs
The XL-density STM32F103xF/G performance line devices include up to two advanced-
control timers, up to ten general-purpose timers, two basic timers, two watchdog timers and
a SysTick timer.
Tabl e 4 compares the features of the advanced-control, general-purpose and basic timers.
Table 4. STM32F103xF and STM32F103xG timer feature comparison
Timer
Counter
resolution
Counter
type
Prescaler factor
DMA request
generation
Capture/compare
channels
Complementary
outputs
TIM1, TIM8 16-bit
Up,
down,
up/down
Any integer between
1 and 65536
Yes 4 Yes
TIM2, TIM3,
TIM4, TIM5
16-bit
Up,
down,
up/down
Any integer between
1 and 65536
Yes 4 No
TIM9, TIM12 16-bit Up
Any integer between
1 and 65536
No 2 No
TIM10, TIM11
TIM13, TIM14
16-bit Up
Any integer between
1 and 65536
No 1 No
TIM6, TIM7 16-bit Up
Any integer between
1 and 65536
Yes 0 No
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