AN4228 datasheet(28/90 Pages) STMICROELECTRONICS

28 / 90 page

Peripheral migration

AN4228

28/90

DocID024110 Rev 5

The I/O pins are connected to on-chip peripherals/modules through a multiplexer that allows

only one peripheral alternate function to be connected to an I/O pin at a time. In this way,

there can be no conflict between peripherals sharing the same I/O pin. Each I/O pin has a

multiplexer with 16 alternate function inputs (AF0 to AF15) that can be configured through

the GPIOx_AFRL and GPIOx_AFRH registers: the peripheral alternate functions are

mapped by configuring AF0 to AF15.

In addition to this flexible I/O multiplexing architecture, each peripheral has alternate

functions mapped on different I/O pins to optimize the number of peripheral I/O functions for

different device packages. For example, the USART2_RX pin can be mapped on PA3 or

PA15 pin.

Note:

Please refer to the “Alternate function mapping” table in the STM32F3x datasheet for the

detailed mapping of the system and the peripheral alternate function I/O pins.

Configuration procedure

–

Configure the desired I/O as an alternate function in the GPIOx_MODER register

–

Select the type, pull-up/pull-down and output speed via the GPIOx_OTYPER,

GPIOx_PUPDR and GPIOx_OSPEEDER registers, respectively

–

Connect the I/O to the desired AFx in the GPIOx_AFRL or GPIOx_AFRH register

3.8

EXTI source selection

In STM32F1 devices, the selection of the EXTI line source is performed through EXTIx bits

in AFIO_EXTICRx registers, while in STM32F3 series this selection is done through EXTIx

bits in SYSCFG_EXTICRx registers.

Only the mapping of the EXTICRx registers has been changed, without any changes to the

meaning of the EXTIx bits. However, the maximum range of EXTIx bit values is 0b0101 as

the last PORT is F (in STM32F1 series, the maximum value is 0b0110).

3.9

FLASH interface

The table below presents the difference between the FLASH interface of STM32F1 series

and STM32F3 series.

Table 15. FLASH differences between STM32F1 and STM32F3 series

Feature

STM32F1 series

STM32F3 series

Main/Program memory granularity

Page size = 2 Kbytes

except for Low and Medium

density page size = 1 Kbyte

Page size = 2 Kbytes

System memory

Start Address 0x1FFF F000

0x1FFF D800

End Address

0x1FFF F7FF

Flash interface programming

procedure

Same for all product lines

Same as STM32F1 series for

Flash program and erase

operations. Different from

STM32F1 series for Option

byte programming

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