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.