AN4088 datasheet(41/71 Pages) STMICROELECTRONICS

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AN4088

Firmware migration using the library

used to configure the microcontroller system at start-up and before branching to the

main() program.

Note:

For STM32F0xx, you can use the clock configuration tool,

STM32F0xx_Clock_Configuration.xls, to generate a customized SystemInit() function

depending on your application requirements. For more information, refer to AN4055 “Clock

configuration tool for STM32F0xx microcontrollers”.

Peripheral access configuration: as presented in section 3.4: Reset and clock controller

(RCC) interface, you need to call different functions to [enable/disable] or [enter/exit]

the peripheral [clock] or [from reset mode]. For example, GPIOA is mapped on AHB

bus on STM32F0 series (APB2 bus on STM32F1 series). To enable its clock, you have

to use the RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);

function instead of:

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

in the STM32F1 series.

Refer to Table 8 for the peripheral bus mapping changes between STM32F0 and

STM32F1 series.

Peripheral clock configuration

Some STM32F0xx peripherals support dual clock features. The table below summarizes the

clock sources for those IPs in comparison with STM32F10xx peripherals.

Table 20. STM32F10x and STM32F0xx source clock API correspondence

Peripherals

Source clock in STM32F10xx

device

Source clock in STM32F0xx device

ADC

APB2 clock with prescaler

– HSI14: by default

– APB2 clock/2

– APB2 clock/4

CEC

APB1 clock with prescaler

HSI/244: by default

LSE

APB clock: Clock for the digital interface

(used for register read/write access). This

clock is equal to the APB2 clock.

I2C

APB1 clock

I2C1can be clocked with:

– System clock

–HSI

I2C2 can be only clocked with:

–HSI

SPI/I2S

System clock

USART

USART1 can be clocked with

– PCLK2 (72 MHz Max)

Other USARTs can be clocked with

– PCLK1 (36 MHz Max)

USART1, USART2 and USART3 can be

clocked with:

– system clock

– LSE clock

– HSI clock

– APB clock (PCLK)

For STM32F051 devices, USART2 can be

only clocked with system clock

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