AN4661 datasheet(19/33 Pages) STMICROELECTRONICS

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AN4661

Boot configuration

4.1

Boot mode selection

In the STM32F746xx/STM32F756xx devices, two different boot spaces can be selected

through the BOOT pin and the boot base address programmed in the BOOT_ADD0 or

BOOT_ADD1 option bytes as shown in the Table 3.

The BOOT_ADD0 and BOOT_ADD1 address option bytes allow to program any boot

memory address from 0x0000 0000 to 0x2004 FFFF which include:

•

All Flash memory address space mapped on ITCM or AXIM interface.

•

All RAM address space: ITCM, DTCM RAMs and SRAMs mapped on AXIM interface.

•

The system memory bootloader.

The BOOT_ADD0 / BOOT_ADD1 option bytes can be modified after reset in order to boot

from any other boot address after next reset.

If the programmed boot memory address is out of the memory mapped area or a reserved

area, the default boot fetch address is programmed as follows:

•

Boot address 0: ITCM-FLASH at 0x0020 0000

•

Boot address 1: ITCM-RAM at 0x0000 0000

When flash level 2 protection is enabled, only boot from Flash memory (on ITCM or AXIM

interface) or system bootloader will be available. If the already programmed boot address in

the BOOT_ADD0 and/or BOOT_ADD1 option bytes is out of the memory range or RAM

address (on ITCM or AXIM) the default fetch will be forced from Flash memory on ITCM

interface at address 0x00200000.

Table 3. Boot modes

STM32F746xx/STM32F756xx

Boot mode selection

Boot space

BOOT pin

Boot address

option bytes

BOOT_ADD0 [15:0]

– Boot address defined by user option byte BOOT_ADD0[15:0]

- ST programmed value: Flash on ITCM at 0x0020 0000

BOOT_ADD1 [15:0]

– Boot address defined by user option byte BOOT_ADD1[15:0]

- ST programmed value: System bootloader at 0x0010 0000

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