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Behavior of PB15 During First Boot: CC2 Dead-Battery vs. SPI2_MOSI (STM32G071CBU6)

HKet
Associate

Hi,

On STM32G071CBU6, when PB15 is used as CC2 with DBCC2 shorted to CC2, does the ROM bootloader ever drive PB15 as SPI2_MOSI, or does the CC/dead-battery own the CC2 pin and that path always takes priority?

This detail is critical for our design because the device is bus-powered and relies on the dead-battery path to manage initial power-up. If the bootloader were to override PB15 and drive it as SPI2_MOSI while the flash is blank, it could cause a power drop when the ROM bootloader starts.

I checked the datasheet, reference manual, programming manual, and bootloader manual, and none of them explicitly state how the ROM bootloader handles SPI2_MOSI when that pad is also CC2 with DBCC shorted.

Could you please clarify?

Thanks

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