◆ ViL——when I/O port is input mode, the input voltage changes from 0 to VDD, once MCU reads the value of the change from 0 to 1, its corresponding input voltage is ViL, the input low.
◆ ViH——when I/O port is input mode, the input voltage changes from VDD to 0,once MCU reads the value of the change from 1 to 0, its corresponding input voltage is ViH, the input high.

※ Note: When the input voltage ranges between ViL and ViH, such as ViL / ViH is 0.3VDD/0.7VDD, when the input voltage is 0.5VDD, MCU I/O port level is uncertain, user should take measures to avoid this situation.