Are input configuration pins of a Virtex-II Pro device 2.5V and 3.3V-tolerant?
Virtex-II Pro dedicated configuration pins can be driven with either 2.5V or 3.3V signals under the following guidelines:
The configuration pins on the Virtex-II Pro device can be driven at 2.5V under the recommended operating conditions for 2.5V inputs in the Virtex-II Pro Data Sheet.
The dedicated configuration pins are powered by Vccaux at 2.5V.
When a 3.3 V signal is driving a dedicated pin, there will be a reverse current from the pin to the VCCAUX via a parasitic diode in the circuitry of the pin. The reverse current can be up to 25 mA. This will not damage the pins, but precaution should be taken to make sure that the regulator can handle this current. To further limit the current, a 100 ohm series resistor can be added between the 3.3V signal and the dedicated pins.