Toggle rate (%) is the rate at which the output of a synchronous logic element switches with respect to a given clock input. It is modeled as a percentage between 0 - 100%. A toggle rate of 100% means that on average the output toggles once during every clock cycle. As an example, If a signal changes at every four clock cycles with respect to a clock of any frequency, then the Toggle Rate is: (1/4)*100 = 25%.
For asynchronous elements such as nets and logic that are not synchronized with a clock, the toggle rate cannot be computed. The Vivado® power tools expect the use of Signal Rate for these kinds of elements.
By default the primary inputs of the design are not associated with a
specific clock. Use the set_input_delay constraint
to associate a clock with the primary inputs. If you do not associate a clock, the
power tools compute the toggle rate with respect to either the capturing clock or
the fastest clock in the design.