We know a micro can be powered up using its GPIO. If you didn't know - Link
I have an STM32F0103 which will be in OFF state (VCC = 0 V) and another uC which will be connected to it through SPI. The second uC can initiate an SPI transaction - call chip select, send SCK etc, but the STM is still in its OFF state. So my question is
1.Will this cause the STM to get powered for a brief duration (when the pin is high)? I know it won't get enough current (the second uC GPIO pin won't supply enough), but will this flickering power cycle cause problems?
2.What should I do to prevent this if it happens?