These two GPIO bits are connected to the U42 MSP430 system controller for general purpose signaling or communications between the Zynq UltraScale+ RFSoC device and the MSP430 system controller. These signals are level-shifted by TSX0108E U41. The connections between the U42 system controller and the XCZU28DR RFSoC are listed in Table: System Controller U42 GPIO Connections to XCZU28DR U1 .