If the uC is not powered via VCC, then voltage on any IO pin will put current thru the clamp protection diodes and power the device. At the least this may damage the clamp diodes, at the worst this may cause other damage.
If the uC is not powered via VCC, then voltage on any IO pin will put current thru the clamp protection diodes and power the device. At the least this may damage the clamp diodes, at the worst this may cause other damage.