The length of time for which data that feeds a register via its data or enable input(s) must be present at an input pin before the clock signal that clocks the register is asserted at the clock pin.

In the Quartus^® II software, you can specify a required t_SU for the entire project and/or for any input pin, bidirectional pin, input register, or clock. You can also specify a point-to-point t_SU requirement between an input pin and a register.

The Timing Analyzer calculates t_SU using the following equation:

t_SU = <pin to register delay> + <micro setup delay> - <clock to destination register delay>