The HPIO_VREF primitive is only supported in HP I/O banks (see the following figure). This UltraScale architecture specific primitive provides access to the VREF scan feature that is available in HP I/O banks. The VREF scan feature is accessed using the HPIO_VREF primitive with either the IBUFE3 or IOBUFE3 primitives.
Figure 1. HPIO_VREF Primitive—VREF Scan Feature (HP
I/O Banks Only)
The XP5IO_VREF primitive is similar to the HPIO_VREF but has a wider input port, FABRIC_VREF_TUNE[9:0]