Flashing fails on STM32WL5MOC6HTR when PB8 is set high (STSAFE power pin on “S” variant)
Hello ST team,
We are using the STM32WL5MOC6HTR module, which does not include the STSAFE-A110 secure element.
However, in the STM32WL5MOC6HS variant, the PB8 pin is used to power the STSAFE chip (VDD_STSAFE).
In our setup (with the HTR module), when we set PB8 high during testing, the flashing process (using ST-Link / STM32CubeProgrammer) fails or hangs.
When PB8 is left floating or configured as input, flashing works normally.
I want to understand:
Why does driving PB8 high prevent flashing on the STM32WL5MOC6HTR module?
Is PB8 internally connected or reserved for STSAFE even on the non-S variant?
Should PB8 be kept floating or pulled low when STSAFE is not populated?
Any hardware or reference design explanation would be very helpful.
Thank you!
Module: STM32WL5MOC6HTR
Observed Behavior: Flashing fails when PB8 is driven high.