Additional Information
In page 4 of the Specification Sheet it's mentioned:
Digital I/O
Input logic levels
Input low voltage = VIL 0.0 V min; 0.8 V max
Input high voltage = VIH 2.0 V min; 5.25 V max
While it is not specified as the maximum allowed voltage, the Logic Level shows the hardware's capability in these terminals, thus establishing the Maximum Allowed Voltage, too.