•
SB142 and SB145 OFF (PH0/PH1 not connected to CN11 as I/O)
•
SB143 (MCO) OFF
•
SB6 and SB7 ON (connected to external HSE)
MCO from ST-LINK (Default: not connected):
MCO, the output of ST-LINK MCU, is used as an input clock. This frequency cannot be changed. It is fixed at 8
MHz, and connected to PH0 OSC_IN of STM32 microcontroller. The following configuration is needed:
•
SB142 OFF and SB145 ON (Only PH1 connected to CN11 as I/O)
•
SB143 ON: MCO connected to PH0
•
SB6 and SB7 OFF (not connected to external HSE)
External oscillator to PH0 input (Default: not connected)
The input clock comes from an external oscillator through pin 29 of the CN11 connector. The following
configuration is needed:
•
SB142 ON and SB145 ON (PH0/PH1 connected to CN11)
•
SB143 OFF: MCO not connected to PH0
•
SB6 and SB7 OFF (not connected to external HSE)
HSE not used (Default configuration)
PH0 and PH1 are used as GPIOs instead of clocks. The following configuration is needed:
•
SB142 and SB145 ON (PH0/PH1 connected to CN11 as I/O)
•
SB143 OFF: MCO not connected to PH0
•
SB6 and SB7 OFF (External HSE)
6.10
Reset sources
The reset signal of Nucleo board is active LOW and the reset sources include:
•
The RESET button B2
•
The embedded ST-LINK/V2-1
•
The ARDUINO
®
-included Zio connector CN8 pin 5
•
The ST morpho connector CN11 pin 14
6.11
RSS/bootloader
The bootloader is located in the system memory, programmed by ST during production. It is used to reprogram
the Flash memory via USART, I
2
C, SPI, CAN FD or USB FS in device mode through the DFU (device firmware
upgrade). The bootloader is available on all devices. Refer to the
STM32 microcontroller system memory boot
mode
application note 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 third party. The RSS is available on all devices,
after enabling the TrustZone
®
through TZEN option bit.
The bootloader version can be identified by reading the bootloader ID at the address
0x0BF97FFE
.
6.11.1
RSS limitation
The STM32L5 part soldered on NUCLEO-L552ZE-Q with the Finish Good (FG) NUL552ZEQ$AU1 (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:
UM2581
Reset sources
UM2581
-
Rev 2
page 25/48