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.