STM32H743 RDP Level 1

[bgi95]

Hi

i dont fully get what is possible under RDP Level1 on STM32H743. I have a application which loads credentials into SRAM2. AN5156 writes that debug accesses to SRAM2 are forbidden. As it seems i can still read SRAM2 via STM32CubeProgrammer but the data is 0. Then i tried to run my application from flash while the debugger is attached to see if i could then read the credentials from sram2 but i cant get the fw running while the debugger is connected.
Is that a protection feature or am i doing something wrong?
Is there a way to externally access SRAM2 after the fw has run for a while?
Are there other security implications for using rdp level 1 and i should use rdp level 2?

Thanks

[STea]

Hello @bgi95and Welcome to the ST Community!

In RDP level 1, the debug accesses to SRAM2 and flash memory depends on the boot configuration. While booting from SRAM or system memory bootloader any read request to a protected area will generate a bus error. Booting from flash memory, accesses to both flash memory and to SRAM2 (from user code) are allowed. 

here is a summary of the options available for debug access in RDP Level 1:

Readout protection Level 1

If boot mode = user Flash and no debugger access is detected then

• R/W/Erase possible on Flash memory, SRAM* and Backup registers*.
• Option bytes change possible

If boot mode ≠ user Flash or debugger access is detected then

• R/W/Erase to Flash memory, SRAM* (family dependent), and Backup registers are blocked (hard fault generated).
• Option bytes change possible.

for more details about the RDP protection mechanism i recommend you visit our mooc section dedicated for RDP as well as the LAB which can be ported to the STM32H743 MCU .

and i really don't recommend trying the RDP Level 2 you wont be able to connect to the board and it will be locked with no way to do a regression .

best regards

Hichem