Rss/Bootloader; Rss Limitation; Figure 16. Vdd_Mcu Power Selection - ST STM32L562E-DK User Manual

6.4

RSS/bootloader

The bootloader is located in the system memory, programmed by ST during production. It is used to reprogram
the Flash memory by using USART, I
firmware upgrade). The bootloader is available on all devices. Refer to the application note STM32 microcontroller
system memory boot mode (AN2606) for more details.
The Root Secure Services (RSS) are embedded in a flash area named Secure information block, programmed
during ST production. For example, it enables Secure Firmware Installation (SFI) thanks to the RSS extension
firmware (RSSe SFI). This feature allows customers to protect the confidentiality of the FW to be provisioned into
the STM32 when production is sub-contracted to an untrusted 3rd party. The RSS is available on all devices, after
enabling the TrustZone
The bootloader version can be identified by reading the bootloader ID at the address 0x0BF97FFE.
6.4.1

RSS limitation

The STM32L5 part soldered on STM32L562E-DK with the finished good (FG) DK32L562E$AT1 (sticker available
on the top side of the board) embeds bootloader V9.0 affected by the limitations to be worked around, as
described hereunder. The bootloader ID of the bootloader V9.0 is 0x90.
The following limitations exist in the bootloader V9.0:
Issue observed:
Option Byte programming in RDP level 0.5: The user can not program non-secure option bytes in RDP level
0.5 through the bootloader.
Proposed workaround:
The user can program option bytes thanks to STM32CubeProgrammer GUI or command-line interfaces through
JTAG. To know how to program option bytes through STM32CubeProgrammer, refer to the user manual
STM32CubeProgrammer software description (UM2237).
Issue observed:
Impossible to set TZEN option bit: The user can not set the TZEN option bit through Bootloader interfaces.
Proposed workaround:
Instead of the bootloader interface, the user can use JTAG to set the TZEN option bit.
UM2617 - Rev 2
Figure 16. VDD_MCU power selection
2
C, SPI, CAN FD or USB FS in device mode through the DFU (device
®
through TZEN option bit.
UM2617
RSS/bootloader
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