Feedback selection is only available when phase alignment is selected. When phase alignment is not selected, the output feedback is directly connected to the input feedback.
For designs with phase alignment, choose automatic control on-chip if you
want the feedback path to match the insertion delay for CLK_OUT1. You can also select user-controlled feedback if the feedback is
in external code. If the path is completely on the FPGA, select on-chip; otherwise,
select off-chip. For designs that require external feedback and related I/O logic,
choose automatic control off-chip feedback. You can choose either single-ended or
differential feedback in this mode.
The wizard generates the core logic and logic required to route the feedback signals to the I/O.