2021-10-26 06:28 AM
When STM32F439 power supply is dropping from 3.3V to 0V what will be state of GPIO which is configured as Mode output pp, pull up and speed_fast whether it will hold to value mentioned in GPIOx_ODR
2021-10-26 06:40 AM
As the supply drops to 0V, at some point it crosses the BOR level (around 1.8V but it varies) at which the chip will enter a reset state and the GPIO pin will be set to default (typically input, no pull).
The chip can't output a high level on a pin with no power.