MCU IO port outputs high level by default. Will it recover after low level trigger

Restore high level after canceling external low level

The IO port of the single chip microcomputer has read operation and write operation, which are connected by different MOS tubes respectively, and the IO port is connected with a latch, which is not directly connected with each bit of the IO register. In other words, the circuit passed by the IO port when writing is different from that when reading. The IO port reads the value of the latch when reading, and the latch is weak pull-up in the standard state, which can be pulled down by the external level. When the external low level is cancelled, the high level is restored.