15.15.6.5 VREF

A voltage referenced I/O input (VREF) requires an input referenced voltage. You must assign VREF pins to IGLOOe, Fusion, ProASIC3L (A3PE3000L only), ProASIC3E, and Axcelerator devices before running Layout.

Note: You cannot assign VREF pins in IGLOO or ProASIC3 low-cost devices.