how to set PCROP Protection to default STM32H755

[Domy_ST]

hello ST Community,

I'm trying to protect sector 0 of the flash drive from mass erasure using the PCCOP Protection option on the NUCLEO-H755ZI-Q.

After tinkering around a bit to understand its functions, I can no longer reset its protection to its default state. Currently, it looks like the one in the photo:

When I try to set these values

PROT_AREA_START1 = 0x0801FF00

PROT_AREA_END1 = 0x080100FF

which i believe are their default values, both in the RDP=0xAA and RDP=0xBB states, I get this error.

How can I fix this? Is there a way to reset PCROP Protection to its default mode?

Thanks for the support.

[Bubbles]

Hello @Domy_ST ,

no, there is no such setting. But let me ask, what is the use case here? You don't seem to be too concerned with security (just my impression) so what use is to you the RDP1?

If you describe the goal, we can help you find the correct means.

BR,

J

[Domy_ST]

hello @Bubbles,

My goal is to load two pieces of software into the flash area: in sector 0, only the Bootloader SW, and the rest of the sectors are the Application SW, which must be protected at RDP level 1 for security.

But I also need to be able to update the Application SW (reprogramming) from the Bootloader SW in sector 0. To do this, I have to reset the RDP level to 0, which involves a mass erasure, including the Bootloader SW, and I cannot reprogram.

I know that the STM32 factory bootloader exists, with BOOT0 = 1, and this is fine for updating only the Bootloader SW in sector 0 but not the Application SW. I can update the Application SW only from the Bootloader SW in sector 0, and after the update, it must be protected at level 1 for security.

This is my goal. Is there a way, like in my case, to avoid the mass erasure of just sector 0 during RDP regression?

Thanks

[Bubbles · Accepted solution]

Hello @Domy_ST,

what you describe to me looks like SBSFU application. You definitely do not need to perform RDP regression to update the Application SW. It should even work in RDP2 without any problem. Unless modification of OB is involved, of course.

Please have a look at X-CUBE-SBSFU | Product - STMicroelectronics examples, which you can use as inspiration and starting point.

It's well tested to provide security to Application SW while retaining the flexibility of secure firmware update.

BR,

J

[Domy_ST]

hello @Bubbles,

Ok, thanks for the help. I'll take a look at the examples you provided.

[Onizuka09]

Hello @Domy_ST 

your current question which is : 

are the examples still compatible with this STM32H755 series?

Is different from your initial question :

Is there a way to reset PCROP Protection to its default mode?

for to moderation purposes , we are going to split this thread, you can find the new thread here.
B.R