Honored Contributor
Honored ContributorNo that's all you have to do. Vref pins are only used for I/O standards that require a reference voltage for input. SSTL is one such example. DDR memory interfaces use the reference voltage.
The real answer to your question lies in the Cyclone III handbook. See Table 6-4 on page 6-12 of the following document: http://www.altera.com/literature/hb/cyc3/cyc3_ciii5v1_02.pdf If it doesn't say "Voltage-referenced" in the Type column, you don't need a reference voltage. More details can be found in the Cylcone III datasheet: http://www.altera.com/literature/hb/cyc3/cyc3_ciii52001.pdf Jake
