Can the STM32H7x M4 core boot from SDRAM or not ?

[Ibrahim Abdalkader]

According to the STM32H7's datasheet, the M4 core shouldn't be able to boot from an SDRAM memory address (because it's outside of the range 0x00000000 to 0x3FFF0000):

However, I found out that I can actually boot the M4 core from SDRAM, if I used the alias address at 0x70000000 (which is also outside of the range) instead of 0xC0000000. So I'm wondering if this is a documentation error, or an undocumented feature/bug that we shouldn't count on ?

Thanks!

[FBL · Accepted solution]

Hello @Ibrahim Abdalkader 

The answer is next sentence. The BOOT_ADD0 / BOOT_ADD1 / BCM4_ADD0 / BCM4_ADD1 option bytes can be modified after reset in order to boot from any other boot address after next reset.

[Ibrahim Abdalkader]

Hi @FBL Thank you very much for clarifying that! But I still don't understand why it can't boot from 0xC0000000 ? I tried but I can only boot from 0x70000000 after reset.

[FBL]

According to Table 6. Memory map and default device memory area attributes, you can remap to 0xD0000000 as it is considered for FMC SDRAM bank 2 in case of FMC remap. 0xC0000000 is linked to bank 1.

[Ibrahim Abdalkader]

Yes but this table seems to suggest that 0x70000000 and 0xC0000000 are both the same address for SDRAM bank1 with the default mapping.

Anyway, I I checked the table you mentioned and noticed 0xC0000000 has different default memory attributes, specifically Never Execute! Maybe that's why I couldn't boot from it. I will try to make it executable with the MPU later. Thanks a lot @FBL I think all my questions are answered.