I'm trying to get the SPI connection working for the AD-DRF3-EBZ board.  I'm not sure how to drive FMC_SPI_EN.  Is this an active high or active low signal?  And does it need to be set before I assert CS to the individual chips?  Looks like I need to tristate the FMC_SPI_EN when I want to drive it high as it is going straight into the PIC, but also want to make sure on that as well.