Description
Yes, there is a longer delay on VREF pins when used as an I/O pin compared to a general purpose I/O pin in Cyclone®-series devices that support dual-purpose VREF pins.
The pin capacitance is higher on VREF pins than general purpose I/O pins, thus you should avoid placing fast edge rate signals such as clocks on these pins, and avoid using these pins in buses since the I/O timing will not be consistent with the rest of the bus.