In both (UG576) and (UG578), the port TXPIPPMEN is declared to be Asynchronous.
How should I handle this signal?
This signal is re-synchronized internally, however it is still recommended that TXPIPPMEN be treated as a synchronous signal on the TXUSRCLK domain.
TXPIPPMEN should be pulsed for two TXUSRCLK cycles in order to move TXPIPPMSTEPSIZE[3:0] of the PI controller in the direction of TXPIPPMSTEPSIZE[4].