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STM32H755 Security settings

immortal2113
Associate

‎2025-08-26 2:58 AM - last edited on ‎2025-08-26 3:05 AM by

Hello, I have an STM32H755 nucleo board and I want to use the secure memory area features but I need to clarify my understanding of the reference manual "rm0399" and some follow up questions.

My understanding is that:

  1. From my normal code (non-secure) in standard mode you enable secure access mode.
  2. Then an MCU reset is triggered.
  3. Then from my normal code in secure access mode I call RSS_resetAndInitializeSecureAreas that is mentioned in page 258 in the reference manual with the memory area I need to setup to be my secure code and this request triggers a reset.
  4. After reset the MCU enters the RSS ROM instead of my normal boot code and then it jumps to my secure code that won't exit it until the API RSS_exitSecureArea.

Q1: If I don't call the RSS_exitSecureArea can I keep the secure code running on CM7, Can I run a normal non-secure application on CM4?

Q2: Does the RSS have a feature to authenticate a bootloader code and if the answer is yes, where is that documented?

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Jocelyn RICARD
ST Employee

‎2025-12-04 2:31 AM

Hello @immortal2113 ,

After creating the secure areas, it is not mandatory to call the exitSecureArea. Now, in such case, why creating this secure area if you don't use it ?

The RSS is not a secure boot. Reference Manual is a bit misleading on this point. There is no authentication done at this stage, just checking that your boot address is inside the secure area.

Best regards

Jocelyn

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