14.4.5 Input Threshold Control
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. The input threshold is important in determining the value of a read of the PORTx register and also the level at which an interrupt-on-change occurs, if that feature is enabled.
Important: Changing the input threshold selection may be
performed while all peripheral modules are disabled. Changing the threshold level during
the time a module is active may inadvertently generate a transition associated with an
input pin, regardless of the actual voltage level on that pin.