Hi NXP Engineer:
In my design，MCU powers off earlier than power.Before MCU shutdown i will Pull PTC3 high，but if i shutdown the mcu，and then turn off the power the led will Flash once times。that mean it was low。
How to check the status of IO (pull-up, pull-down, floating) under power-off?Configure the output attributes of the IO port so that the hardware connection cannot be changed（We are as PWM output）.
The pins are as follows：
Circuit design as shown：
It is not necessary to use the pull-up function when the MCU is powered down. It is not clear what the state of the IO is when the MCU is powered off, because the datasheet does not describe this.
Hi,
So, without power there is no pull up/pull down functionality. So, external resistor can solve your issue.
Jiri
When the MCU is powered off, is it in a floating state or an open-drain output state? Is there a corresponding document description?
Hi,
you can find more details in this application note:
https://www.nxp.com/docs/en/application-note/AN12130.pdf
Jiri
if I understand it correctly,applying voltages to I/O pins when the processor is not powered is not allowed.Regardless of whether the state is input or output.
Hi,
if I understand it correctly - you like to use pull up for a while without MCU Power? I'm afraid that this is not possible. You need to use external resistor for that.
Jiri