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Issue with writing to addresses using system Bootloader of STM32U5

Associate II

Hello ST Community,

I've been troubleshooting an issue with writing to address using system Bootloader on the STM32U5A9J-DK. According to AN3155 Application Note, the data to be written during the 'Write to Memory Command' should be a multiple of 4 bytes. However, during debugging I noticed for the above mentioned device, the data must be a multiple of 16 bytes to be successfully written.

This has raised the question: Is there a way to write to the addresses which are multiple of four?

Any insights or recommendations on how to handle this would be greatly appreciated.

Thank you for your assistance in advance!


Flash on the STM32U5 must be programmed 128-bits at a time, per the reference manual. This is because it contains ECC bits.


You can write these in 4x32 bit operations.

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