Differences Between XDC and UCF Constraints - 2022.2 English - UG911

ISE to Vivado Design Suite Migration Guide (UG911)

Document ID
UG911
Release Date
2022-10-19
Version
2022.2 English

The fundamental differences between XDC and UCF constraints are:

XDC is a sequential language, with clear precedence rules.

UCF constraints are typically applied to nets: XDC constraints are typically applied to pins, ports, and cell objects.

UCF PERIOD constraints and XDC create_clock command are not always equivalent and can lead to different timing results.

UCF by default does not time between asynchronous clock groups, while in XDC, all clocks are considered related and timed unless otherwise constrained ( set_clock_groups ).

In XDC, multiple clocks can exist on the same object.