The USB OTG controller functions as both AHB master and AHB slave on the AMBA interconnect. The AHB master interface is used by the DMA engine, which is built into the USB OTG controller, for data transfer between memory in the USB OTG controller and the system memory. The AHB slave interface is used by other masters, such as the processor or Fabric masters in the FPGA fabric, to configure registers in the USB OTG controller.