The platform management unit (PMU) in the Zynq UltraScale+ MPSoC is responsible for handling the primary pre-boot tasks.
PMU ROM will execute from a ROM during boot to configure a default power state for the device, initialize RAMs, and test memories and registers. After the PMU performs these tasks and relinquishes system control to the configuration security unit (CSU), it enters a service mode. In this mode, the PMU responds to interrupt requests made by system software through the register interface or by hardware through the dedicated I/O to perform platform management services.