STM32F103XC datasheet(14/118 Pages) STMICROELECTRONICS

14 / 118 page

Description

STM32F103xC, STM32F103xD, STM32F103xE

14/118

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Standby mode

The Standby mode is used to achieve the lowest power consumption. The internal

voltage regulator is switched off so that the entire 1.8 V domain is powered off. The

PLL, the HSI RC and the HSE crystal oscillators are also switched off. After entering

Standby mode, SRAM and register contents are lost except for registers in the Backup

domain and Standby circuitry.

The device exits Standby mode when an external reset (NRST pin), an IWDG reset, a

rising edge on the WKUP pin, or an RTC alarm occurs.

Note:

The RTC, the IWDG, and the corresponding clock sources are not stopped by entering Stop

or Standby mode.

DMA

The flexible 12-channel general-purpose DMAs (7 channels for DMA1 and 5 channels for

DMA2) are able to manage memory-to-memory, peripheral-to-memory and memory-to-

peripheral transfers. The two DMA controllers support circular buffer management,

removing the need for user code intervention 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, basic

and advanced control timers TIMx, DAC, I2S, SDIO 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

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

registers used to store 84 bytes of user application data. 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.

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 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 timeout

management. It is hardware or software configurable through the option bytes. The counter

can be frozen in debug mode.

STM32F103XC Datasheet(PDF) 14 Page - STMicroelectronics

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