The interrupt controller is made up of three blocks – the Main Interrupt Controller (MIC), the Sub1 Interrupt Controller (SIC1), and the Sub 2 Interrupt Controller (SIC2). The output of the interrupt controller drives IRQ and FIQ to the main CPU. Interrupt priority is fixed and is in direct correspondence to the way the peripherals are connected to the controller. As an example, the Ethernet interrupt is connected to the MIC whereas the USB interrupts are connected to the SIC1. When an interrupt occurs, the application has to go through the MIC, SIC1, and/or SIC2 status registers and search for the source of the interrupt. Also, as a note, the interrupt controller does not operate in STOP mode. The start sources connected to the START controller will help the device to exit STOP mode.