5.9.6 Managing I/Os in a Designer Block Component

If you use I/Os in your Designer Block, use the following rules:

• If the I/O is placed in the block, placement and VCCI of the I/O cannot be changed in the <top> design.
• The register combining option cannot be changed in the <top> design.
• Attributes and Vref pins can be changed if the values are legal (the I/O will not be unplaced).