Byte-lane clock (DBC and QBC) input pin pairs are dedicated clock inputs directly driving source synchronous clocks to the bit slices in the I/O banks. In memory applications, these are also known as DQS. When not used for I/O byte clocking these pin have other functions such as general purpose I/Os. For more information, consult the UltraScale Architecture SelectIO Resources User Guide (UG571) [Ref 3] .