Due to a fitter report bug, an I/O standard assignment will affect the VCCIO voltage of its adjacent unused banks in Stratix® V devices under all of following conditions:
- The default I/O standard is 3.3V
- The I/O standard requiring the VCCPD of 2.5V is assigned to an I/O bank
- The above I/O bank shares the VCCPD with its adjacent I/O bank
- The above adjacent I/O bank is unused
In this case, the VCCIO voltage of the unused adjacent I/O bank unexpectedly shows 1.2V in the fitter report.
For example, if you assign 2.5V I/O standard to the I/O banks 7A and 7B, when the default I/O standard is 3.3V and the I/O banks 7C and 7D is unused, the VCCIO voltage of 7C and 7D shows 1.2V in the fitter report.
Since this is only the fitter report bug, you can ignore the report and supply proper desired voltage.
This problem is fixed in the Quartus® II software version 13.0.