The INLVLx register controls the input voltage threshold for each of the available PORTx input pins. A selection between the Schmitt Trigger CMOS or the TTL compatible thresholds is available. If that feature is enabled, the input threshold is important in determining the value of a read of the PORTx register and also all other peripherals which are connected to the input. Refer to the I/O Ports table in the “Electrical Specifications” chapter for more details on threshold levels.