A method is provided for operating an interface between a first unit and a second unit supplying its data. The method includes switching control between LSSD_B and LSSD_C clocks and system clock (CLK) to provide a test mode of operation and a functional mode of operation to optimize setup and hold times depending on conditions under which the unit is operating. In the test mode, data is launched by the LSSD_C clock. In the functional mode, the data is launched by the system clock (CLK) to RAM. A method is also provided to determine which memory inputs should use a circuit that provides adequate setup and hold margins.