STM32F103CBU6TR datasheet(17/96 Pages) STMICROELECTRONICS

17 / 96 page

STM32F103x8, STM32F103xB

Description

Doc ID 13587 Rev 12

17/96

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, I2C, 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

VDD supply when present or through the VBAT pin. The backup registers are ten 16-bit

registers used to store 20 bytes of user application data when VDD 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.

Table 4 compares the features of the advanced-control and general-purpose timers.

Table 4.

Timer feature comparison

Timer

Counter

resolution

Counter

type

Prescaler

factor

DMA request

generation

Capture/compare

channels

Complementary

outputs

TIM1

16-bit

Up,

down,

up/down

Any integer

between 1

and 65536

Yes

TIM2,

TIM3,

TIM4

16-bit

Up,

down,

up/down

Any integer

between 1

and 65536

Yes

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